- Email: [email protected]
Functional and mechanistic analysis of telomerase: An antitumor drug target
Functional and mechanistic analysis of telomerase: An anti-tumor drug target Yinnan Chen, Yanmin Zhang PII: DOI: Reference:
S0163-7258(16)30039-0 doi: 10.1016/j.pharmthera.2016.03.017 JPT 6890
To appear in:
Pharmacology and Therapeutics
Please cite this article as: Chen, Y. & Zhang, Y., Functional and mechanistic analysis of telomerase: An anti-tumor drug target, Pharmacology and Therapeutics (2016), doi: 10.1016/j.pharmthera.2016.03.017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT P&T 22937
Title Page
School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province,
SC
a
RI
Yinnan Chenb, Yanmin Zhanga*
710061, P.R. China
School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
MA
NU
b
PT
Functional and mechanistic analysis of telomerase: an anti-tumor drug target
D
*Correspondence to:
TE
Dr Yanmin Zhang, Address: School of Pharmacy, Health Science Center, Xi’an Jiaotong University, No. 76, Yanta West Street, #54, Xi’an, Shaanxi Province 710061,
AC CE P
P.R. China
E-mail: [email protected] (YM. Zhang)
1
ACCEPTED MANUSCRIPT
Functional and mechanistic analysis of telomerase: an anti-tumor drug target Yinnan Chenb, Yanmin Zhanga∗ School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province,
PT
a
School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
SC
b
RI
710061, P.R. China
NU
ABSTRACT
The current research on anticancer drugs focuses on exploiting particular traits or
MA
hallmarks unique to cancer cells. Telomerase, a special reverse transcriptase, has been recognized as a common factor in most tumor cells, and in turn a distinctive
TE
D
characteristic with respect to non-malignant cells. This feature has made telomerase a preferred target for anticancer drug development and cancer therapy. This review aims
AC CE P
to analyze the pharmacological function and mechanism and role of telomerase in oncogenesis; to provide fundamental knowledge for research on the structure, function and working mechanism of telomerase; to expound the role that telomerase plays in the initiation and development of tumor and its relationship with tumor cell growth, proliferation, apoptosis and related pathway molecules; and to display potential targets of anti-tumor drug for inhibiting the expression, reconstitution and trafficking of the enzyme. We therefore summarize recent advances in potential telomerase inhibitors for anti-tumor including natural products, synthetic small molecules, peptides and proteins, which indicate that optimizing the delivery method and drug combination could be of help in a combinatorial drug treatment for tumor.
∗
Corresponding author at: School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province, 710061, P.R. China. Tel.: +86 29 8265 6264; fax: +86 29 8265 5451. E-mail address: [email protected] (Y.M. Zhang) 2
ACCEPTED MANUSCRIPT More extensive understanding of the structure, biogenesis and mechanism of telomerase will provide invaluable information for increasing the efficiency of
PT
rational anti-tumor drug design.
AC CE P
TE
D
MA
NU
SC
RI
Keywords: Function; Mechanism; Telomerase; Drug Target; Tumor inhibitors
3
ACCEPTED MANUSCRIPT
Contents
PT
1. Introduction………………………………………………………………………6 2. Biological aspects of telomerase…………………………………………………8
RI
3. Role of telomerase in oncogenesis……………………………………………….15
SC
4. Potential biological aspects of telomerase as anti-tumor drug targets…………..19 5. Tumor inhibitors targeting telomerase…………………………………………...25
NU
6. Conclusions and perspectives……………………………………………………47
MA
Conflict of interest……………………………………………………………….….49 Acknowledgements……………………………………………………………….…49
AC CE P
TE
D
References……………………………………………………………………….…..50
4
ACCEPTED MANUSCRIPT
Abbreviations: TERT, telomerase reverse transcriptase; hTERT, human telomerase
PT
reverse transcriptase; RT, reverse transcriptase; TR, telomerase RNA; hTR, human
RI
telomerase RNA; RNP, ribonucleoprotein; TEN, essential N-terminal domain; TRBD,
SC
telomerase RNA binding domain; CTE, C-terminal extension domain; CR4/5, conserved region 4 and 5; TBE, template boundary element; ROS, reactive oxygen
growth
factor;
bFGF,
basic
fibroblast
growth
factor;
EMT,
MA
epidermal
NU
specie; G4, G-quadruplexes; ALT, alternative lengthening of telomeres; EGF,
epithelial-mesenchymal transition; TERRA, telomeric repeat-containing RNA; PKC,
protein
90;
ODN,
Antisense
oligodeoxynucleotides;
TE
shock
D
protein kinase C; HDAC, Histone deacetylases; MM, multiple myeloma; Hsp90, heat TAA,
Human
AC CE P
tumour-associated-antigens; CTL, cytotoxCLLic T lymphocytes; VCA, Viscum album L. coloratum agglutinin; CLL, lymphocytic leukemia; NSCLC, non-small cell lung cancer; mTOR, ammalian target of rapamycin; TRF1, telomeric repeat-binding factor 1; POT1, protection of telomeres; TNKS1, TRF1-interacting ankyrin-related ADP-ribose
polymerase
1;
DOX,
Doxorubicin;
RHPS4,
3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acri-dinium methosulfate; DNA-PK, DNA-dependent protein kinase; IR, immune response; Sp1, specificity protein 1; ER, estrogen receptor; GKN1, Gastrokine 1.
5
ACCEPTED MANUSCRIPT
1. Introduction
PT
Telomerase is a special reverse transcriptase enzyme that adds DNA repeats to the ends of chromosome to offset the loss (Greider & Blackburn, 1987). For the past
RI
few decades, since the discovery of telomerase, progress has been made in the
SC
identification of core components from evolutionary groups of species across eukaryotes, the catalytic telomerase reverse transcriptase (TERT) and telomerase
NU
RNA (TR). TERT contains the catalytic site for DNA synthesis and TR provides the
MA
template (Greider & Blackburn, 1989; Shippen-Lentz & Blackburn, 1990). A variety of accessory proteins, while dispensable for enzyme activity in vitro, play important
D
roles in regulation, biogenesis and localization (Egan & Collins, 2010; Podlevsky,
TE
Bley, Omana, Qi, & Chen, 2008).
Tumor cell growth is a complicated progression, which is regulated by multiple
AC CE P
factors including proliferation, cell cycle and apoptosis (Y. Zhang, et al., 2014). An increase in telomerase activity is often directly correlated with uncontrolled growth of cells, a known hallmark of cancer (Ruden & Puri, 2013). According to the Hanahan-Weinberg model of the hallmarks of cancer, to successfully achieve oncogenesis cancer cells have to: sustain proliferative signaling, evade growth suppressors, avoid immune destruction, enable replicative immortality, promote inflammation, activate invasion and metastasis, induce angiogenesis, establish genome instability, resist cell death and deregulate cellular energetics (Hanahan & Weinberg, 2011). The hallmark enabling replicative immortality demonstrates the ability to grow endlessly, synonymous with reactivation of TERT. Telomerase, and specifically its catalytic subunit TERT, is overactive in 85-90% of cancers and has become a widely acceptable tumor marker and a popular target for anticancer 6
ACCEPTED MANUSCRIPT therapeutics (Ruden & Puri, 2013). The discovery of the relationship between telomerase, telomeres, aging and tumors has broadened the avenue in tumor biology
PT
research (Calado & Young, 2009; Low & Tergaonkar, 2013). In humans, telomerase is inactive in most of the somatic cells, which stop division when their telomeres are
RI
critically short. This is known as replicative senescence. Most of the human cells
SC
cannot overcome the senescence and crisis, which restricts cell growth and protects against oncogenesis (Martinez & Blasco, 2011). Many human cells remain in the
NU
crisis period, as balance between cell growth and death, unless occasionally acquiring
MA
a mechanism such as up-regulation of telomerase. Cells that escape crisis can grow continuously and are usually characterized with telomere stability and telomerase activity (Feldser & Greider, 2007). This is believed to be a pivotal step in
TE
D
carcinogenesis (Mocellin, Pooley, & Nitti, 2013). Cancer cells that develop chromosomal aberrations show activation or re-activation of telomerase upon
AC CE P
exposure to a DNA damage signal, thereby bypassing cell cycle checkpoints and leading to uncontrolled growth and proliferation (Rankin, Faller, & Spanjaard, 2008; Tian, Chen, & Liu, 2010). In addition to the canonical role of maintaining telomere length in malignant cells, telomerase has also been recognized to take part in tumor promoting pathways. Telomerase activity is prominent in highly proliferative cells such as stem cells, germ line cells, as well as 90% of human cancers (N. W. Kim, et al., 1994), which makes it as a main target for cancer treatment. There are two general strategies of targeting telomerase in cancer treatment. One directly inhibits telomerase catalytic
activity
leading
to
telomere
shortening.
The
other
strategy
is
down-regulating the expression of the telomerase subunits or blocking the access of telomerase to its substrates. The current trend in research on anticancer drugs is to exploit particular traits 7
ACCEPTED MANUSCRIPT or hallmarks unique to cancer cells (Olaussen, et al., 2006). The ideal cancer treatment would target specifically at cancer cells but have a minimal adverse effect on the
PT
normal cells. This review highlights recent advances in our understanding of mammalian telomere biology, analyzing the functional and mechanism of telomerase
RI
and how it relates to cancer. Meanwhile, we discuss the current approaches that
2. Biological aspects of telomerase
NU
2.1. Structural and components of telomerase
SC
exploit this knowledge to develop novel anti-tumor drugs targeting telomerase.
MA
Telomerase is unique reverse transcriptase (RT) by functioning as a ribonucleoprotein (RNP). The catalytic core of telomerase is minimally composed of TERT and TR (Collins, 2006; Weinrich, et al., 1997). Between the two essential
TE
D
components of telomerase RNP complex, the catalytic TERT protein is highly conserved among all eukaryotes, while the TR is extremely divergent, suggesting that
AC CE P
telomerase initially emerges as a protein enzyme and acquires an integral RNA component during the early evolution of eukaryotes (Lingner, et al., 1997; Peng, Mian, & Lue, 2001; Podlevsky, et al., 2008). TERT is the catalytic component of the enzyme that comprises four conserved structural domains: the telomerase essential N-terminal domain (TEN), the telomerase RNA binding domain (TRBD), the RT domain and the C-terminal extension domain (CTE) (Fig. 1A) (Lingner, et al., 1997). The catalytic domains of TERT and other reverse transcriptases have the common and highly conserved motifs that form the active site for RNA-dependent DNA polymerization. The tertiary structure of TERT, similar to HIV RT, consists of the finger, palm and thumb domains (Lingner, et al., 1997; Peng, et al., 2001). The finger domain is composed of motifs 1 and 2, believed to bind incoming nucleotides. The palm domain is composed of motif A-E and forms the catalytic site. Between them there is motif 3, 8
ACCEPTED MANUSCRIPT unique to TERT, closely related to the property of the enzyme (Xie, Podlevsky, Qi, Bley, & Chen, 2010). Mutational analysis of the Asp residues from motifs A and C is
PT
evidence that the telomerase employs acidic metal-coordination by the aspartic acid for DNA polymerization, which is common to conventional RTs (Haering, Nakamura,
RI
Baumann, & Cech, 2000; Lingner, et al., 1997). The CTE in TERT binds to the RNA
SC
template/DNA primer duplex, sharing functionality with the HIV RT-C terminus referred to as the thumb domain (Peng, et al., 2001). The TEN and TRBD domains are
NU
telomerase specific and unique to TERT protein. The TEN domain contains anchor
MA
sites that bind to single strand telomeric DNA. Mutational analysis has identified it as related to the repeat addition processivity, which is the characteristic of telomerase, but not to nucleotide addition processivity (Sealey, et al., 2010; Zaug, Podell, & Cech,
TE
D
2008). According to the recently resolved the co-crystal structure of the TRBD with conserved regions 4 and 5 (CR4/5) of TR in teleost fish Oryzias latipes, as well as
AC CE P
crosslink data, TRBD contains RNA interacting domain which has a high affinity binding site for TR (Bley, et al., 2011; J. Huang, et al., 2014). The structure of TERT protein from Tribolium castaneum was solved in 2008 by Emmanuel Skordelakes et al (Gillis, Schuller, & Skordalakes, 2008). The challenge to get the crystal structure of human TERT (hTERT) is to determine how to purify highly concentrated protein. The crystal structure of hTERT could offer insight into research on the enzyme function, which provides a novel opportunity for rational drug design. Unlike conventional reverse transcriptase, telomerase contains its own template provided by the integral RNA component within the telomerase catalytic core (Feng, et al., 1995). The size, structure and sequence of TR are quite diverse among different species, however they all contain two conserved domains: the template/pseudoknot domain and CR4/5 domain (or three way junction/stem-terminus elements) (Fig. 1B). 9
ACCEPTED MANUSCRIPT These two domains are essential for telomerase activity. In fact, an active telomerase enzyme reconstituted in vitro only requires the TERT protein and these two excised
PT
elements from TR (Mitchell & Collins, 2000). The secondary structure of TR has implications for telomerase function (J. L. Chen, Blasco, & Greider, 2000). The
RI
template/pseudoknot domain contains template boundary element (TBE), the template
SC
region and pseudoknot.
TBE that is conserved across eukaryotes defines the template boundary physically.
NU
The hTR template region promotes base pairing with telomeric DNA, primer to each
MA
cycle of the DNA synthesis as well as contains pause signal for each round of repeats by a recent study (A. F. Brown, et al., 2014). The pseudoknot with a triple helix and part of it binds to the TERT protein (Fig. 1 B). The TR template/pseudoknot domain is
TE
D
a remarkably complex structure and its detailed mechanistic function remains unknown. The functional assay together with NMR structure analysis demonstrates
AC CE P
that the special triple helix and contained residues are essential for telomerase activity (N. K. Kim, et al., 2008; Theimer, Blois, & Feigon, 2005). It also indicates the interaction between the TERT protein and pseudoknot domain was crucial for the integrity of the enzyme (Jiang, et al., 2015; Wu & Collins, 2014). Further studies are required to analyze the detailed binding of this region with certain motifs in TERT and to understand how it contributes to the activity of telomerase. The other domain required for enzymatic activity is the CR4/5 domain in humans. CR4/5 is a major TERT binding site located far away from template/pseudoknot domain in the primary sequence as well as the secondary structure (Blackburn & Collins, 2011). It is a three way junction of stem-loops that has been shown interaction with TRBD domain of the TERT protein by UV-crosslinking analysis, as well as crystal structure in Oryzias latipes (medaka) (Bley, et al., 2011; J. Huang, et al., 2014). This secondary essential 10
ACCEPTED MANUSCRIPT TERT-binding element, despite structural variation, is retained throughout all eukaryotes and is essential or stimulatory for telomerase activity (X. D. Qi, et al.,
PT
2013). The homology model of the medaka telomerase RNP structure based on Tribolium castaneum TERT protein structure, which indicates that the stem-loop in
RI
CR4/5 is very close to the CTE domain in hTERT (Gillis, et al., 2008). However, the
SC
mechanism of regulation of the CR4/5 domain to the conformational change of the protein and activation of telomerase function has yet to be further studied. While the 5’
NU
of TR provides a defined template and stable assembly with the TERT protein, the 3’
MA
of the RNA has a variety of functions for TR biogenesis. H/ACA domain is a conserved region located at the 3’ end of TR in vertebrates (Mitchell, Cheng, & Collins, 1999). This domain contains two stem-loops separated by the box H/ACA
TE
D
moieties. The accessory proteins of telomerase such as dyskerin, NOP10, NHP2 and GAR1 bind to this region (Egan & Collins, 2010). Mutations in the H/ACA moieties
AC CE P
can abolish 3’ end processing of human telomerase RNA (hTR) and cause accumulation in nucleoli instead of Cajal bodies (Mitchell, Wood, & Collins, 1999; Venteicher, et al., 2009). In short, the H/ACA domain is important for biogenesis and localization of telomerase in vivo. TR is a highly complex non-coding RNA with special structural domains to adapt, incorporate distinct and unique mechanisms necessary and sufficient for assembly with the catalytic subunit TERT protein, and to regulate and impart telomerase enzymatic activity. Further research could elucidate the detailed mechanism of how TR and TERT interact with each other to maintain a functional and intrinsic component of the telomerase enzyme. 2.2. Functional aspects and working mechanism of telomerase Unlike conventional reverse transcriptases, telomerase reaction produces a long tract of telomeric DNA repeats from a single short RNA template in TR (Shippenlentz 11
ACCEPTED MANUSCRIPT & Blackburn, 1990). In brief, the telomerase catalytic cycle involves two major phases (Fig. 2). The first phase is nucleotide addition: the synthesis of a single
PT
telomeric DNA repeat to the 3’ end of telomeric primer base paired with template on TR. This process is similar to DNA polymerase. The second phase is repeat addition:
RI
the regeneration of the template of the synthesis of additional repeats. The processive
SC
synthesis of multiple telomere repeats from the same template to a given primer is unique for a polymerase and requires a special mechanism for the template
NU
regeneration. For human telomerase, the telomerase reaction initiates by forming
MA
RNA/DNA duplex before coming in the active site (X. D. Qi, et al., 2012). After six nucleotides 5’-GGTTAG-3’ are added on to the 3’ end of the DNA primer from the RNA template in the active site, nucleotide addition arrests waiting for next repeat
TE
D
synthesis or disassociation of the DNA product (W. Yang & Lee, 2015). Processive repeat addition requires the translocation of the RNA template after each cycle to
AC CE P
regenerate the template. This is a complicated multi-step process that is poorly understood. Several models have been set up to explain how telomerase works. For instance, Qi et al has proposed that the duplex dissociates from the active site when reaching the end of RNA template. Then the DNA primer realigns to the anchor site for template realignment or releasing the product. Parks & Stone hypothesized the favorable conformational rearrangements when reaching the template boundary and has tested it by single molecular fluorescence resonance energy transfer (Parks & Stone, 2014; X. D. Qi, et al., 2012). Most recently, Yang & Lee propose a DNA-hairpin model for telomeric-repeat addition, which explains that the telomeric DNA participates in repeat addition processivity and its conserved sequence throughout evolution (W. Yang & Lee, 2015). Some experiments like protein cross-linking, site directed mutagenesis and single molecular fluorescence resonance 12
ACCEPTED MANUSCRIPT energy transfer (FRET) within TERT or with TR can be designed to test and validate the predictions for each model for further deciphering the special working mechanism
PT
of the telomerase. 2.3. The expression of telomerase and RNP biogenesis
RI
For the past decades, intensive studies of telomerase in human cells have shown
SC
novel perspectives on the regulation of hTERT gene expression. Some evidence suggests that only hTERT is needed to restore the telomerase activity in
NU
telomerase-negative normal cells (Artandi, et al., 2002; Gonzalez-Suarez, et al., 2001;
MA
D. L. Qi, et al., 2011). The transcriptional control of hTERT is supposed to play a crucial role in the complex regulation of telomerase activity (Hahn, et al., 1999). The hTERT gene consists of 15 introns and 16 exons and over 40 kb in length. The 5’
TE
D
regulatory region contains numerous binding sites for a plenty of transcription factors from various signal pathways, such as TGF-b, PI3K/Akt, NF-κB, ErbB, MAPK, cell
AC CE P
cycle, among others (Daniel, Peek, & Tollefsbol, 2012; Gladych, Wojtyla, & Rubis, 2011). Activators of hTERT include some oncogenic transcription factors and hormones, which promote cell proliferation. Repressors of hTERT include tumor suppressors and some transcription factors that induce the senescence or apoptosis for the somatic cells. Meanwhile, epigenetic control and modulation of the hTERT promoter via methylation and acetylation, even with contradictory results, also play an essential role in regulation of hTERT, but further research is required to elucidate this mechanism (Daniel, et al., 2012). Splice variants of hTERT, whichassociated with risk of cancer, may be expressed in normal, pre-crisis and ALT cells with undetectable telomerase activity (Bojesen, et al., 2013; Ulaner, Hu, Vu, Giudice, & Hoffman, 1998). Post-transcriptional regulation of telomerase activity can occur via reversible phosphorylation of hTERT catalytic subunit at specific residues, such as 13
ACCEPTED MANUSCRIPT serine/threonine/tyrosine (D. L. M. Gomez, Farina, & Gomez, 2013). Some of the phosphorylation sites within hTERT protein influence telomerase activity (Haendeler,
PT
Hoffmann, Rahman, Zeiher, & Dimmeler, 2003; Selvam, et al., 2015). In short, the hTERT expression is regulated at both transcriptional and post-transcriptional levels
RI
with the alternative splicing of hTERT in the control of telomerase activity.
SC
It was previously believed that though hTERT is tightly regulated during the cellular differentiation and expressed at very low levels in normal somatic cells, hTR
NU
is widely express in the majority of cell types including those with negative
MA
telomerase activity. However, in some types of tumors, the hTR expression is more closely correlated to tumor grade and is a potential marker for prognosis (Soder, et al., 1997; Yashima, et al., 1997). The role of hTR has also been well studied in mouse
TE
D
models (Cairney & Keith, 2008). According to a recent paper from Linghe et al, overexpression of either hTR or hTERT could increase telomerase activity in vivo,
AC CE P
which indicates that their assembling into active telomerase is an equilibrium process (Xi & Cech, 2014). It can also explain that hTR levels are increased in tumor cells compared to normal cells, although hTR expression is detected in some tissue where hTERT is not. Transcription of hTR can be activated by Sp1 and HIF-1 and repressed by Sp3, which integrates cues from the MAPK signal cascade to silence the hTR promoter (Cifuentes-Rojas & Shippen, 2012). Furthermore, hTR transcription appears to be subjected to epigenetic control similar to hTERT. hTR begins as a precursor RNA polymerase II transcript capped by trimethyl-guanosine (TMG) (Feng, et al., 1995). The RNA helicase associated with AU-rich element resolves the G-quadruplexes (G4) at the 5’ end and other proteins to the 3’ end for trimming and modifying RNA to produce mature hTR (Lattmann, Stadler, Vaughn, Akman, & Nagamine, 2011). The initial binding of dyskerin to the hTR, other H/ACA snoRNA 14
ACCEPTED MANUSCRIPT species relies on the sequential binding of snoRNA H/ACA family quantitative accumulation 1 (SHQ1), followed by nuclear assembly factor 1 (NAF1) to dyskerin
PT
(Grozdanov, Roy, Kittur, & Meier, 2009). NAR1 is exchanged for GAR1 and SHQ1 is lost prior to the localization of mature hTR to Cajal bodies. TCAB1, together with
RI
other protein components, is thought to direct mature hTR to Cajal bodies (Kiss,
SC
Fayet-Lebaron, & Jady, 2010; Tomlinson, Li, Culp, Terns, & Terns, 2010). The detailed process and mechanism of the hTR accumulation remains unclear.
NU
Telomerase assembly could take place during S phase and it is probably
MA
disassembled during M phase (Wojtyla, Gladych, & Rubis, 2011). Throughout most of the cell cycle, TR is present in Cajal bodies; TERT, however, is located in distinct nucleoplasmic foci. Therefore, the two main subunits of telomerase are separated
TE
D
during the whole cell cycle. The CAB box and H/ACA motif within TR have been identified to influence the TR translocation of Cajal bodies and nucleoli. Similarly,
AC CE P
hTERT contains both nuclear localization signal and nuclear export signal for nuclear-cytoplasmic shuttling. Several studies have demonstrated that hTERT is associated with chaperone proteins heat shock protein 90 (Hsp90) and p23 for incorporation into an enzymatically active RNP containing hTERT in nucleus (Holt, et al., 1999). While the intricate details of telomerase RNP assembly have yet to be fully elucidated, much progress has been made to uncover the function of each component for assembling into an active ribonucleoprotein enzyme. Telomerase localizes to Cajal bodies for most of the cell cycle and factors involved in this process have been well studied and reviewed (Schmidt & Cech, 2015). Further studies need focus on understanding the physiological process of how hTR and hTERT accumulate to Cajal bodies, and elucidating the mechanism of Cajal bodies for telomerase trafficking. 3. Telomerase role in oncogenesis 15
ACCEPTED MANUSCRIPT 3.1. Potential for replication and integration of the genome Cancer is a disease of impaired genome stability (Hanahan & Weinberg, 2011). In
PT
theory, the molecular forces that maintain genome integrity should suppress the initiation of carcinogenesis. Telomerase extends telomeres to prevent replicative
RI
senescence by promoting genome stability and keeps the telomere from erosion. As
SC
previously discussed, telomerase may act preferentially on short telomeres (Hug & Lingner, 2006), which reduces their risk for acquiring a dysfunctional structure. Thus
NU
activation of telomerase might be protective and prevents telomere dysfunction. With
MA
tightly controlled expression in stem cells, telomerase can retard or prevent age-related pathology, including cancer, acting as a suppressor by ensuring genome stability and inhibiting mutations. Moreover, hTERT can regulate DNA damage signal
TE
D
by keeping histones from modification and decreasing mitochondrial reactive oxygen species (ROS) production, all of which may result in genome instability (Masutomi, et
AC CE P
al., 2005; Singhapol, et al., 2013). However, maintaining genome stability can be oncogenic as well. The telomere shortening can lead to apoptosis through the p53 dependent pathway (Artandi & DePinho, 2010). During tumor development, a wide range of studies show that genomes keep relative stability after telomerase is up-regulated. The up-regulation of serves to enhance proliferation of cancer cells by maintaining telomere sequences that ensure genome stability during cell division and prevent the cellular senescence or apoptosis induced by genomic instability. It could be the role of telomerase for cancer cells genome instability: suppression on the initiation and promotion on the development of carcinogenesis. 3.2. Non-canonical function of telomerase components It is believed that each hallmark of cancer is independently driven. Although elongation of telomeres is thought to be the prime function of reactivated telomerase 16
ACCEPTED MANUSCRIPT reverse transcriptase, there are other non-canonical functions of telomerase such as increasing cell proliferation, resistance to apoptosis and promotion of invasion (Low
PT
& Tergaonkar, 2013). Concomitant with telomerase activity, the component TERT is reactivated in cancer cells related closely to other hallmarks of cancer. Overexpression
RI
of TERT increases proliferation of mammary carcinomas and epidermal tumors
SC
without affecting telomere length (Broccoli, Godley, Donehower, Varmus, & deLange,
substitute for the telomerase function.
NU
1996). In humans, an ALT which could also maintain telomere length cannot fully
MA
3.2.1. Resistance to apoptosis and antigrowth signals TERT has been shown to be localized in mitochondria and inhibit caspase mediated apoptosis in cancer cells (Singhapol, et al., 2013). Meanwhile TERT can
TE
D
increase intracellular reduced glutathione/oxidized gultathine ratios, thus reducing intracellular ROS-induced apoptosis (Indran, Hande, & Pervaiz, 2011). Many studies
AC CE P
also demonstrate that hTERT could activate NF-κb for resistance of death-inducing stimuli (Low & Tergaonkar, 2013). Ectopic expression of TERT in mouse embryonic fibroblasts antagonized transforming growth factor (TGF)-β, which is a cytokine that inhibits growth of epithelial cells (Geserick, Tejera, Gonzalez-Suarez, Klatt, & Blasco, 2006). This indicates TERT may help cancer bypass antigrowth signals. Additionally, TERT has been shown to cause cells to bypass differentiation as a strategy for cancer cells proliferation. Another transcription factor Myc also contributes to the anti-growth signal in cancer cells. Not only is hTERT the transciption target of Myc but it can also activate the Myc induced tumorigenesis in vivo (Flores, Evan, & Blasco, 2006). Similar to oncogenic Wnt/β-catenin signaling, which hTERT positively regulated, overexpression of hTERT is able to help cell bypass differentiation (Y. Zhang, Toh, Lau, & Wang, 2012). 17
ACCEPTED MANUSCRIPT 3.2.2. Regulation of cell growth and proliferation TERT can stimulate proliferation of human epithelial cells by EGFR signaling
PT
(Smith, Coller, & Roberts, 2003). Epiregulin can be regulated by IL-1b and TNF-α, and neutralization of epiregulin compromise the growth of the cells, which indicates
RI
TERT might be a consequence of the NF-κb signal pathway. Meanwhile, it has been
SC
shown that the TERT could promote epithelial proliferation in hair follicles and skin cells through the Wnt and Myc signaling pathways. Human fibroblasts immortalized
NU
by overexpression of TERT, secrete epiregulin, which belongs to the epidermal
MA
growth factor (EGF) family (Lindvall, et al., 2003). The expression of an activity-deficient form of TERT also promotes cancer progression by up-regulation of EGFR in glioblastoma multiforme (Beck, et al., 2011). At the same time, studies show
TE
D
that the EGFR signal pathway could upregulate the expression of TERT by transcription factor Ets-2 in lung cancer cells (Hsu, et al., 2015). Overexpression of an
AC CE P
enzymatically inactive TERT has been demonstrated to inhibit differentiation and induce proliferation of glioma cells through upregulation of EGFR and basic fibroblast growth factor (bFGF), which is independent of its enzyme activity. In short, TERT seems to favor tumor growth by inhibiting anti-growth signals and suppressing differentiation.
3.2.3. Other effects of TERT on regulating hallmarks of cancer Studies show TERT could regulate NF-κb gene expression by recruiting a subset of transcription factors to the promoter that lead to cancer progression, and the blocking of NF-κb signal can inhibit telomerase overexpression (Ghosh, et al., 2012). The link between TERT and NF-κb is feed-forward regulation that is critical for inflammation and cancer. TERT has been reported to modulate angiogenesis as well. Xenografted 18
ACCEPTED MANUSCRIPT glioblastoma cells transfected with siRNA against TERT show that it reduces formation of microvessels and production of pro-angiogenic factor of vascular
PT
endothelial growth factor (VEGF) and bFGF (Falchetti, et al., 2008; L. L. Zhou, Zheng, Wang, & Cong, 2009). Further studies also indicate the TERT promoter can be
RI
activated by VEGF and bFGF via phosphoinositide 3-kinase pathway (Zaccagnini, et
SC
al., 2005). It has been hypothesized that TERT and VEGF potentially regulate the expression of each other, such as TERT could be a potential VEFG enhancer to
NU
promote angiogenesis (Hartwig, et al., 2012).
MA
The hTERT overexpression has been found promoting epithelial-mesenchymal transition, which is also regulated by Wnt/b-catenin signaling pathway (T. D. Zhao, Hu, Qiao, Chen, & Tao, 2015). Further studies show evidence for hTERT involvement
TE
D
in invasion and metastasis through activation of NF-κb signaling, which up-regulates matrix metalloproteinase (MMP)-9 and is critical for epithelial-mesenchymal
AC CE P
transition (EMT) (Fukuyama, et al., 2007). In short, telomerase plays a crucial role not only in maintaining telomere homeostasis that is an essential property for sustenance and progression of cancer, but its catalytic subunit hTERT has the cross-talk with signal cascade involved in proliferation, apoptosis, and differentiation in cancer cells. Some of the factors have a feed-forward regulatory loop mechanism with TERT, which makes it hard to interpret, but further investigation of the new interaction of TERT and other key factors of cancer may help to discover new targets for anti-cancer therapy, and provide useful information for rational drug combination therapy. 4. Potential biological aspects of telomerase as anti-tumor drug targets As a common factor in most tumor cells and in turn a distinctive characteristic with respect to somatic cells, telomerase is a promising target for cancer therapy. The 19
ACCEPTED MANUSCRIPT holoenzyme consists of TERT, TR and a six-protein complex known as shelterin protein complex. So the target of telomerase inhibitors can be classified according to
PT
biogenesis of the active enzyme as well as its components (Fig. 3). 4.1. Catalytic subunit of telomerase
RI
Targeting the hTERT catalytic subunit as anticancer therapy is theoretically
SC
tumor-specific and moderately toxic because of the expression in tumor and highly proliferating cells compared to other somatic cells. Since hTERT can act as cofactor
NU
to regulate NF-κB, Wnt and β-catenin signaling pathways, it provides therapeutic
MA
implications for the design of inhibitors. However, it is not clear how the activation of hTERT, which not only induces telomerase activity but influences other signaling cascades, may directly or indirectly regulate all hallmarks of cancer.
TE
D
The expression of TERT can be regulated by ontogenetic transcription factors so in theory any inhibitors of those factors or blocking certain signal pathways should be
AC CE P
able to decrease the expression of TERT (Daniel, et al., 2012). There are already some inhibitors targeting transcription factors to regulate the hTERT expression. Recently, DNA methyltransferase inhibitors, which can change chromatin structure of the hTERT gene promotor region, have been tested for down-regulation of the hTERT expression and induce telomere dysfunction exerting anti-tumor activity (X. Zhang, Li, de Jonge, Bjorkholm, & Xu, 2015). The messenger RNA of hTERT has been well studied as the target for the hTERT expression. The degradation of hTERT mRNA can be implied by antisense technology such as standard oligonucleotide as well as peptide nucleic acids (Folini, et al., 2007; Folini, et al., 2003). RNAi has been employed to degrade mRNA of hTERT recently (H. Xu, et al., 2015; W. Zhang & Xing, 2013). Ribozymes that are antisense RNAs possessing endoribonuclease activity are able to cleave target RNA 20
ACCEPTED MANUSCRIPT sequences. They have also been used to degrade mRNA of hTERT (J. Kim, et al., 2015).
PT
The post-translation modification of hTERT could also be the potential target for regulation of telomerase activity. The dominant negative hTERT can induce
RI
catalytically inactive enzyme and it has been demonstrated to decrease telomerase
SC
activity (Nguyen, Elmore, & Holt, 2009). Some antibiotics that suppress the chaperone proteins are able to impair maturation of hTERT and assembly of the
NU
holoenzyme. Furthermore, the phosphorylation of hTERT, a common type of
MA
post-translation modification, can regulate the distribution of TERT in cancer cells by some kinases (Ale-Agha, Dyballa-Rukes, Jakob, Altschmied, & Haendeler, 2014)). The mutations in hTERT nuclear localization signal have shown effects on telomerase
TE
D
activity, which confirmed the essential role of localization of the hTERT for the active enzyme (J. Chung, Khadka, & Chung, 2012). Therefore the trafficking of hTERT
AC CE P
from cytoplasm to nucleus could be a potential target for drug design even though the nuclear export signal on telomerase function has yet to be investigated. To inhibit the catalytic function of the hTERT subunit (loss of function), several inhibitors for RTs have been tested, such as nucleoside analogs 3’ azido-3’deoxythymidine and its derivatives (J. Wang, Wang, Chen, & Kwon, 2014), and enzyme inhibitors including FJ 5002 and BIBR1532 (Bryan, et al., 2015; S. H. Naasani I, Yamori T, Tsuruo T., 1999). hTERT can also be an attractive target for cancer immunotherapy, and the specificity expression in cancer cells enables it to become a target for this type of therapy (K. P. Patel & Vonderheide, 2004). In short, it is crucial to note that the role of TERT in carcinogenesis should not be viewed as either canonical or non-canonical. As the catalytic subunit of the enzyme, it keeps the length of telomeres, and takes part in the signal cascade related to the 21
ACCEPTED MANUSCRIPT proliferation, spreading and invasion of the cancer cells. All these reasons indicate hTERT is promising as a target of cancer therapy.
PT
4.2. Telomerase RNA Targeting the RNA component of telomerase is another effective strategy to
RI
repress the telomerase activity. hTR provides the template for the enzyme which is
SC
close to the active site of the enzyme and available for the incoming substrate. Recently Brown et al. shows the hTR template contains important information for
NU
regulating activity and fidelity of the enzyme (A. F. Brown, et al., 2014). Some
MA
previous studies have already shown that the mutations of the template region of hTR have great influence for the enzyme activity and behavior (Drosopoulos, Direnzo, & Prasad, 2005). Therefore, hTR template region is a promising target for inhibiting
TE
D
enzyme function in carcinogenesis. N3’ -> P5’ thio-phosphoramidate (NPS) oligonucleotides has been designed as telomerase template antagonists to form stable
AC CE P
duplex with template RNA (Asai, et al., 2003), and imetelstat as a type of NPS has been tested in clinical phase for non-small cell lung cancer (NSCLC) (Chiappori, et al., 2015). Antisense technology can be used for the degradation of hTR to inhibit telomerase activity, thus enhancing the anti-tumor effect (C. Yu, et al., 2015). Other methods such as siRNA, ribozyme could also be used to degrade or instablize hTR. Meanwhile, peptide nucleic acids as well as other alternative oligonucleotides have been used for targeting at TR (H. Chen, Li, & Tollefsbol, 2009). Another potential target is telomeric repeat-containing RNA (TERRA). Telomeres do not encode protein and are considered to be transcriptionally silent, but the transcription of these regions gives rise to this G-rich RNA. TERRA has been proposed to interact with telomerase through their complementary sequences to the template of human telomerase RNA. Oligonucleotides that are mimicked TERRA have shown repressing telomerase 22
ACCEPTED MANUSCRIPT activity in vitro (Redon, Reichenbach, & Lingner, 2010). Recently it has been proposed that TERRA can modulate cellular phenotype by regulating gene expression
PT
in genome wide manner (Hirashima & Seimiya, 2015). The detailed functions of TERRA in carcinogenesis, as well as its biological significance, remain elusive.
RI
4.3. Shelterin protein complex and substrate
SC
Telomere is G-rich single stranded DNA with accessory proteins. In vitro it has been proven that G-rich strand can fold back to form a G4 structure, which is poor
NU
substrate for telomerase. It has been hypothesized that G4 can sequester telomerase
MA
and prevent it from being extended by telomerase in human somatic cells. Although the structure of telomere remains unknown in vivo, some models have been proposed, such as T-loop structures, G-quadruplexes or others (Sekhri, 2014). In fact, a number
TE
D
of G-quartet stabilizing agents are under investigation. These agents can keep G-quadruplexes structure in order to block telomerase to recognize its substrate with
AC CE P
the principle that telomerase is negatively regulated by G4 formation at telomeric end (D. J. Patel, Phan, & Kuryavyi, 2007). Actually the processivity of telomerase decreases with the increasing concentration of potassium chloride, which can be explained by the fact that K+ stabilizes G4 (Ambrus, et al., 2006). Interestingly, according to a recent study by Moye et al., telomerase is able to localize to G4 and partially resolve the structure for extending telomere DNA substrate (Moye, et al., 2015). One possibility could be that telomerase tends to bind to the G4 structure of DNA which is its own substrate. However, it can only partially dissociate it. So the G-quartet stabilizing agents are able to inhibit cancer by suppressing telomerase activity. Targeting telomere associated proteins, shelterin complex, can also lead to de-regulation of telomerase and its maintaining function of the length of the telomere. 23
ACCEPTED MANUSCRIPT The subunits of shelterin TRF1, TRF2 and POT1 directly recognize TTAGGG repeats and bind to the telomere. TPP1, TIN2 and Rapl can form a complex to distinguish
PT
telomere from DNA damage signal (de Lange, 2005). TRF1 has been proposed as a cis inhibitor of telomerase activity and it could be a potential target for anticancer
RI
drug development. Also, the dominant negative of TRF2 can result in telomere
SC
shortening and rapid p53-dependent apoptosis (Karlseder, Broccoli, Dai, Hardy, & de Lange, 1999). A number of studies have found that the TPP1 and POT1 complex
NU
could increase the processivity of telomerase. This implies that the complex is
MA
important for the catalytic enzyme (F. Wang, et al., 2007). Therefore the expression of each subunit of the shelterin complex could be the potential way for inhibiting the recruitment or function of telomerase.
TE
D
4.4. Assembling and trafficking of the holoenzyme The assembly of the active enzyme in cells is complicated and the detailed
AC CE P
mechanism is unclear. There are many factors involved in this process, including the accumulation of hTR and hTERT to Cajal bodies, the translocation of hTERT from cytoplasm to nucleoplasm, as well as the chaperons necessary for assembling the holoenzyme, which could also be a potential strategy for telomerase inhibitors. Dyskerin protein, which binds to the H/ACA box of human telomerase RNA, is a core telomerase subunit for RNP biogenesis in vivo (Kannan, Nelson, & Shippen, 2008). The protein complex TCAB1/WDR-79 associates with CAB-box of hTR to drive it to Cajal bodies. Similarly, there are many factors involved in the process of accumulation of hTR in Cajal bodies (Schmidt & Cech, 2015). The chaperones HSP90 and p23 play a role in translocation for the TERT protein to nucleus for assembly of the core enzyme (Holt, et al., 1999). The direct or indirect repressing of dyskerin or other proteins could potentially inhibit maximal telomerase activity, 24
ACCEPTED MANUSCRIPT leading to decrease telomere length. Some strategies have already been investigated aiming at these targets (Ruden & Puri, 2013). However, the challenge is to find out
PT
the factors that are not only essential but also specific for the telomerase biogenesis pathway.
RI
5. Tumor inhibitors targeting telomerase
SC
There has been a vast increase in telomerase research over the past several years with many different pre-clinical approaches being tested for inhibiting the activity of
NU
this enzyme as a novel therapeutic modality to treat malignancy (Laura K. White,
MA
2001). Many of the synthetic and natural compounds have been screened for telomerase inhibitory activity. Telomerase inhibitors, based on the targets, have been reviewed before by Olaussen et al. (Olaussen, et al., 2006) and White et al. (Laura K.
TE
D
White, 2001). In this review, we mainly focus on the telomerase inhibitors from the origins of drugs in recent 20 years. The main targets and regulatory effect of inhibitors
AC CE P
for telomerase include hTERT, hTR and the telomerase substrate and associated proteins (Kiran, Palaniswamy, & Angayarkanni, 2015; Olaussen, et al., 2006). 5.1. Telomerase inhibitors from Natural products Natural products with extensive structural diversity have been a major source of currently available anticancer drugs. A number of plant derived natural products have been described as potential telomerase inhibitors. Here, we review these natural chemical entities and anti-tumor herbal extracts. 5.1.1. Natural compounds derived from plants These telomerase inhibitors derived from plant sources encompass a wide range of molecular structures, including alkaloids, xanthones, sesquiterpene lactones, terpenoids and various polyphenols (J. L.-Y. Chen, Sperry, Ip, & Brimble, 2011). Boldine, a natural aporphine alkaloid found abundantly in Peumus boldus, inhibits 25
ACCEPTED MANUSCRIPT telomerase in cells treated with sub-cytotoxic concentrations. A recent study had also reported anti-tumor effects of boldine by stimulation of apoptosis in vitro and its
PT
feasible application by intraperitoneal injection (50 or 100 mg/kg) in an animal model of breast cancer (Paydar, et al., 2014). Boldine has also shown anti-proliferative effect
RI
on glioma cell lines by G2/M arrest and beneficial antitumor properties against glioma
SC
in mouse model via down-regulation of hTERT. Meanwhile, boldine could change the splicing variants of hTERT towards shorter non-functional transcripts (Kazemi
NU
Noureini & Tanavar, 2015).
MA
Berberine is an isoquinoline alkaloid, isolated from the roots and stem-bark of many plants, including Berberis vulgaris chinensis (Coptis or goldenthread). It has a decorated history in Chinese, Indian and Middle Eastern traditional medicine for a
TE
D
wide range of indications (Imanshahidi & Hosseinzadeh, 2008). Berberine-induced apoptosis of human leukemia HL-60 cells is associated with down-regulation of
AC CE P
nucleophosmin/b23 and telomerase activity. Telomerase activity was repressed to about 70% and 40% after treatment with 25µg/ml berberine for 24 and 48 h, respectively (Wu HL, 1999) against U937 human leukemia cells (S. H. Naasani I, Yamori T, Tsuruo T., 1999). The anti-telomerase activity of berberine lies in its preference for binding G4 over duplex DNA to stabilize G4 (Franceschin, et al., 2006). Further studies by Gu et al. have shown that C9-substituted derivatives containing amino121 or aza-aromatic groups significantly increase the binding affinity of these compounds with G4, resulting in increased anti-telomerase activity (Ma, et al., 2009; W. J. Zhang, et al., 2007). Ji et al. investigated the interaction of berberine and 9 other natural alkaloids with G4 formed by telomeric DNA and C-Myc22 sequences (Ji, et al., 2012). Ligands that facilitate the formation and increase the stabilization of G4 can halt tumor cell proliferation and have been regarded as potential anti-cancer drugs. 26
ACCEPTED MANUSCRIPT A large number of promising G4 interacting ligands have now been reported. Berberine, palmatine and sanguinarine could induce the formation of G4 as well as
PT
increase the stabilization of G4 to induce cell differentiation or quiescence. The stabilization ability was in the following order: sanguinarine > palmatine > berberine.
RI
Daurisoline, O-methyldauricine, O-diacetyldaurisoline, daurinoline, dauricinoline,
SC
N,N’-dimethyldauricine iodide and N,N’-dimethyldaurisoline iodide show similar stabilization ability. The unsaturated ring C, N+ positively charged centers, and
NU
conjugated aromatic rings are key factors to increase the stabilization ability of
MA
sanguinarine, palmatine and berberine (Ji, et al., 2012). Gambogic acid belongs to a family of caged xanthones and is isolated from the gamboge resin of the Garcinia hurburyi tree in Southeast Asia. Gambogic acid has
TE
D
been used as a coloring material and folk medicines due to its unique color and broad spectrum of cytotoxic activities. It has shown promising in vitro and in vivo activity
AC CE P
against a number of different cancer cell lines, including human leukemia, gastric carcinoma, lung carcinoma, breast cancer, hepatoma and pancreatic cancer. Both the crude extract gamboge and gambogic acid have been tested in clinical trials against cancer in China (Guo, et al., 2006; Han QB, 2009). Studies of Guo et al. research group have shown that the induction of apoptosis by gambogic acid may depend on the reduction in telomerase activity. hTERT activity was reduced by both the down-regulation of hTERT transcription via inhibition of the transcription activator c-Myc, and inhibition of the phosphorylation of Akt which down-regulated the activity of hTERT in a post-translational manner (Guo, et al., 2006; J. Yu, et al., 2006; Q. Zhao, et al., 2008). Resveratrol, a representative compound from plants, is isolated from a variety of biological sources including white hellbore (Veratrum grandiflorum O. Loes), peanuts 27
ACCEPTED MANUSCRIPT (Arachis hypogeal), legumes (Cassia sp.) and grapes (Vitis vinifera) (Aggarwal BB, 2004). It has been demonstrated to interact with a large variety of molecular targets
PT
and shown to be beneficial for a wide range of ailments including inhibiting different cancer in vivo and in vitro (Tan, et al., 2015; Y. Zhu, et al., 2015). Resveratrol has a inhibitory
effect
on
MCF-7
breast
cancer
cells,
RI
direct
HT-29
and
SC
WiDr human colon cancer cell proliferation. The growth-inhibitory effect is mainly due to its ability to induce S phase arrest and apoptosis in association with reduced
NU
levels of telomerase activity (Fuggetta MP, 2006; Lanzilli G, 2006). In particular,
MA
resveratrol down-regulates the telomerase activity of target cells and the nuclear levels of hTERT (Lanzilli G, 2006). Pterostilbene is a naturally occurring dimethyl ether analog of resveratrol in several plant species. Molecular docking studies indicate good
H-460
cancer
TE
D
interaction between pterostilbene and the active site of telomerase. MCF7 and NCI cell
lines
treated
with pterostilbene exhibite
AC CE P
significant telomerase inhibition after 72 h (Tippani R, 2014). Others compounds from plants also show good inhibition on telomerase activity for anti-cancer, such as CFP -2, a novel lichenin from Cladonia furcate (X. Lin, et al., 2003), silymarin from Silybum marianum (Faezizadeh Z, 2012; Yurtcu E, 2015), etc. The various natural anti-tumor compound targeting telomerase from plants are listed in Table 1. Some extracts also exert telomerase inhibitory activity. Ethyl acetate extract of Pleurotus ostreatus, ethyl acetate and water extracts of Lasiosphaera fenzlii, hexane extract of Strobilomyces floccopus, water extract of Sarcodon aspratus, and hexane, ethyl acetate and water extracts from Umbilicaria esculenta show positive telomerase inhibitory activity in gastric cell line SNU-1 (Xu B, 2014). 5.1.2. Herbal medicine extracts Herbal extracts have recently captured the attention for tumor therapy. Many 28
ACCEPTED MANUSCRIPT herbal extracts targeting telomerase indicate obvious inhibition on tumor. Hedyotis diffusa is a kind of herb used in traditional Chinese medicine. Wild Hedyotis
PT
diffusa can be found in China, Japan, and Nepal. The effects of aqueous extracts from Hedyotis diffusa in vitro have been studied showing that it could inhibit telomerase
RI
activity, induce cell apoptosis and arrest of cell cycle in S phase (Gao C, 2010).
SC
Bupleuri radix, a traditional Chinese herb, has been widely used in various herbal mixtures to treat liver diseases such as hepatitis and cirrhosis. Acetone extract of
NU
Bupleurum scorzonerifolium is found to inhibit proliferation of A549 human lung
MA
cancer cells via inducing apoptosis and suppressing telomerase activity (Cheng, et al., 2003). Cordyceps militaris, a well-known traditional medicinal mushroom, is a potentially interesting candidate in cancer treatment. The water extract of C. militaris
TE
D
(WECM) inhibits the growth and induced apoptosis in A549 cells, which is associated with activation of caspases, down-regulation of anti-apoptotic Bcl-2 expression, and
AC CE P
up-regulation of pro-apoptotic Bax protein. It is also concluded that apoptotic events due to WECM exerted a dose-dependent inhibition on telomerase activity via down-regulation of hTERT, c-Myc and Sp1 expression (S. E. Park, et al., 2009). Special herbal complex (Fufang of traditional Chinese medicine) is used widely in clinic in China. Other countries also use the herbal complex for tumor therapy. Juzen-taiho-to (which contained Hoelen, Angelicae radix and Glycyrrhizae radix) has been used for patients taking anti-cancer drugs in Japan, for protection from the deleterious effects of anti-cancer drugs and irradiation (Lian, et al., 2003; Sugiyama K, 1995). Lian et al. reportes a special herbal complex, which is composed of Hoelen, Angelicae radix, Scutellariae radix and Glycyrrhizae radix, which decreases cell viability
and
induced
apoptosis
to
endocrine-resistant
AN3CA
and
adriamycin-resistant MCF7/ADR carcinoma cells. It could decrease expression of 29
ACCEPTED MANUSCRIPT apoptosis-related genes, Bcl-2, c-Myc and hTERT. The effect is via suppressing telomerase activity involved in cellular apoptosis in endocrine-resistant AN3CA cells
PT
(Lian, et al., 2003). Shugansanjie Tang of traditional Chinese medication, whose active component is
RI
Akebia Trifoliate Koidz., possesses potential anti-tumor and immunostimulatory
SC
effects especially for breast cancer. Shugansanjie Tang could inhibit the growth of breast cancer cells by apoptosis and lower the level of certain matrix
NU
metalloproteinases and activity of hTERT in breast cancer (Loo, Chen, Chow, & Chou,
MA
2007). Traditional Chinese medicine kang ai fang comprising Curcuma zedoaria, Portulaca grandiflora, Bupleurum chinense DC., Scutellaria baicalensis and Codonopsis pilosula, shows good inhibition of telomerase activity on human colon
TE
D
cancer cell line in vitro. Traditional Chinese medicine Janpi liqi fang, encompassing 10 kinds of Chinese herbal medicines including Rhizoma Atractylodis Macrocephalae,
AC CE P
Codonopsis pilosula, fructus aurantii, Wolfiporia extensa, etc., indicates obvious down-regulation of telomerase activity on human liver cancer cell line in vitro and tumor-bearing mice in vivo. Other traditional Chinese medicine, zhenggan fang (Astragalus membranaceus, Salvia miltiorrhiza, Glossy Privet Fruit, Turtle shell, Ligusticum chuanxiong, Portulaca grandiflora, Lycium chinense Miller and Hedyotis diffusa), qingjin desheng tablet (Anax quinquefolius, Gynostemma pentaphylla, Ophiopogon japonicas, Cortex Phellodendri, Asarum sagittarioides and Asiatic toad), yiqi jiedu fang (Berberine hydrochloride, Rosa banksiae, Tetradium ruticarpum and Paeonia lactiflora) and fuzheng yiliu fang (Scutellaria baicalensis, Angelica sinensis, Curcuma zedoaria and Patrinia heterophylla) also show good inhibition on tumor for liver cancer, lung cancer, gastric cancer and nasopharynx cancer by inhibiting telomerase activity (Fan YX, 2008; Li GX, 2011). 30
ACCEPTED MANUSCRIPT 5.1.3. Inhibitors from microbial sources Natural compounds isolated from microbes also provide a new scope of screening
PT
for telomerase inhibitors of anti-tumor. Telomerase inhibitors have been isolated from various fungal, bacterial and actinomycetes sources. Most of these compounds have
RI
only been isolated in the last two decades; however, their anti-telomerase activity has
SC
just identified and demonstrated following the discovery of telomerase as a biological target (J. L.-Y. Chen, et al., 2011). Some of them are chemically modified to increase
NU
the potency (Kiran, et al., 2015).
MA
Elaboration of telomerase inhibitors is based on their target. Quinine antibiotics isolated from Actinomycetes sp., the most widely explored microorganism, are potential inhibitors of telomerase (Kiran, et al., 2015). Rubromycin is one of the
TE
D
widely studied compounds among quinine antibiotics, which were basically a red colour pigments isolated from Actinomycetes namely Streptomyces collinus by
AC CE P
Brockmann and Renneberg in 1950s (J. L.-Y. Chen, et al., 2011). They are primarily aromatic naphthoquinone and isocoumarin ring systems, which competitively interacte with the hTERT and/or hTR subunits of telomerase enzyme. Studies prove that spiroketal moiety of rubromycin is the key pharmacophore for telomerase inhibitory action (Ueno T, 2000). Chrolactomycin, another novel anticancer compound isolated from Streptomyces sp., shows telomerase inhibitory activity. The exo-methylene group of chrolactomycin acts as a michael acceptor and forms a covalent bond with sulfhydryl group of a cysteine residue near the active site of the telomerase enzyme, which causes the irreversible inhibition of telomerase (Nakai R, 2001). Many fungi are the sources of telomerase inhibitors as well. Thelavin A and B were isolated from a fungus Thielavia terricola, and thelavin B showed telomerase inhibitory activity (Kitahara N, 1981; Togashi, Ko, Ahn, & Osada, 2001). 31
ACCEPTED MANUSCRIPT Diazaphilonic acid, isolated from a fungus Talaromyces flavus, is a fungal metabolite that could inhibit the telomerase activity at 50 µM completely (Tabata Y, 1999).
PT
CRM646-A, a phenol glucuronide, was initially isolated from a soil fungus Acremonium sp. MT70646. It inhibits the reverse transcriptase of molony murine
RI
leukemia virus in vitro. Therefore, it could be considered as universal inhibitors for
SC
RNA dependent DNA polymerases (Kiran, et al., 2015).
Targeting hTERT gene transcriptional and post-transcriptional regulation,
NU
docosahexanoic acid, eicosapentanoic acid and rapamycin show good activities.
MA
Docosahexanoic acid was from a marine micro alga Crypthecodinium cohnii (Ratledge C, 2001) and eicosapentanoic acid was from a marine bacteria Shewanella pneumatophore (Hirota, Nodasaka, Orikasa, Okuyama, & Yumoto, 2005). They
TE
D
inhibit telomerase directly by binding to functional enzyme and reducing the expression level of c-Myc gene and hTERT expression. This has been achieved
AC CE P
through inhibition of protein kinase C (PKC) activity in a cell culture experiment (Eitsuka, Nakagawa, Suzuki, & Miyazawa, 2005). Histone deacetylases (HDAC) are known to regulate gene transcription and oncogenesis through remodeling of chromatin structure, canonically resulting in the repression of target genes (Rahman, et al., 2010). This makes HDAC inhibitors as promising anticancer agents (Kiran, et al., 2015). Trichostatin A isolated from the culture broth of Streptomyces platensis (Tsuji N, 1976) is a well-known HDAC inhibitor which inhibited HDAC at nano molar concentrations. Trichostatin-A usually elicits Smad3 and Mad1 which are repressors of hTERT gene to decrease the expression hTERT (Rahman, et al., 2010). In addition, Hsp90 is required for the assembly and activation of telomerase in human cells (Villa R, 2003). Over-expression of Hsp90 induces the activation of telomerase by readily folding hTERT protein. Studies have shown that inhibition of 32
ACCEPTED MANUSCRIPT Hsp90 can elicit nitric oxide synthase dependent free radical production and telomere shortening. So compounds which target the integration of Hsp90 and hTERT complex
PT
is an attractive target for cancer chemotherapy (Qin HL, 2008). Geldanamycin was originally isolated from Streptomyces hygroscopicus in 1970 (DeBoer C, 1970) and
RI
exerted a significant reduction of telomerase activity (Kiran, et al., 2015). Radicicol
SC
from fungal species Pochonia chlamydosporia and Neocosmospora tenuicristata directly binds with the amino-terminal ATP binding pocket of Hsp90 and inhibited
NU
ATP hydrolysis, and could elicit nitric oxide synthase dependent free radical
Jackson-Cook, & Holt, 2006).
MA
production and telomere shortening by inhibition of Hsp90 (Compton, Elmore, Haydu,
Compounds interacting with G4 DNA also show good inhibition on telomerase
TE
D
activity. Telomestatin from Streptomyces anulatus 3533-SV4 could inhibit telomerase activity at nanomolar concentrations. Telomestatin binds preferentially to the
AC CE P
basket-type G4 structure, d[T2AG3]4 with a 2:1 stoichiometry and with high selectivity for intramolecular over intermolecular binding and for G4 structures over duplex DNA. (Rezler EM, 2005; Shin-ya K, 2001). Some tumor inhibitors targeting telomerase from microbial sources are in Table 2. 5.2. Synthetic inhibitors for telomerase 5.2.1. Small molecule inhibitors Small molecule inhibitors are a rapidly emerging area for discovering potential candidates of telomerase inhibitors (Laura K. White, 2001). Rapid screening of small molecules by large-scale screening models, targeted synthesis of telomerase inhibitors and the derivatives of natural products provide a lot of promising sources. 5.2.1.1. Laboratorial or preclinical studies of synthetic inhibitors Many studies on synthesis of the pyrazole derivatives have been described. 33
ACCEPTED MANUSCRIPT Certain pyrazole derivatives exhibit pharmacological activities and have proved to be useful templates in drug research. The series of novel inhibitors were designed by
PT
replacing the central ring of acridine with the pyrazole ring (Kalathiya U, 2014). Kalathiya et al. used the three docking programs CDOCKER, ligandfit docking
RI
(Scoring Functions) and AutoDock to evaluate the dibenzopyrrole derivatives. The
SC
studies show hydrogen bond interaction, and Pi interactions between the dibenzopyrrole group of inhibitors and enzyme active site may be one of the key
NU
factors for the combination of ligands with TERT. Compounds designed with electron
MA
donating groups, CH3 and OCH3 (C_9g and C_9k) and hydroxyl group OH (C_9l) at R 3 position were the best by all three docking methods (Kalathiya U, 2014). Wong et al. developed a surrogate yeast high-throughput assay to identify human telomerase
TE
D
inhibitors. SEW05920, SPB03924, and CD11359 three heteroaromatic small molecules compounds exhibited specific inhibition of both purified recombinant
AC CE P
human telomerase and telomerase activity in crude HeLa cell extracts in vitro. These compounds represent probes into human telomerase function, and potential entry points for development of lead compounds against telomerase-positive cancers (Wong, et al., 2013).
BIBR1532, synthetic non-peptidic, non-nucleosidic small molecule inhibitor, is one of the most potent specific inhibitors of hTERT. It could bind to a site in the telomerase, which is distinct from those for deoxyribonucleotides and the DNA primer, and act as a chain terminator during nucleotide polymerization, leading to inhibition of the catalytic activity of telomerase in a dose-dependent manner (Damm K, 2001; Pascolo, et al., 2002). Bryan et al. presented the crystal structure of BIBR1532 bound to Tribolium castaneum catalytic subunit of telomerase (tcTERT). BIBR1532 binds to a conserved hydrophobic pocket (FVYL motif) on the outer 34
ACCEPTED MANUSCRIPT surface of the thumb domain. The FVYL motif is near TRBD residues that bind to the activation domain (CR4/5) of hTR. hTERT thumb domain binds to the P6.1 stem loop
PT
of CR4/5 in vitro (Bryan, et al., 2015). BIBR1532 suppress telomerase in human cancer cells of different histological origin leading to progressive shortening of
RI
telomeres and inhibition of cell proliferation in vitro and in vivo. Moreover, a direct
SC
short-term cytotoxic activity of the compound is also observed in leukemic cells from chronic lymphocytic leukemia (CLL) and acute myeloid leukemia. Time dependent
NU
individual telomere erosion is observed, which is associated with loss of telomeric
MA
repeat binding factor 2 (TRF2) and increased phosphorylation of p53 (Bashash, Ghaffari, Mirzaee, Alimoghaddam, & Ghavamzadeh, 2013; Pascolo, et al., 2002). This compound leads to progressive telomere shortening, consecutive telomere
TE
D
dysfunction, and finally, growth arrest after a lag period that is largely dependent on initial telomere length in hematopoietic cancer cell lines and chondrosarcoma cell
AC CE P
lines (El Daly & Martens, 2007; Parsch, Brassat, Brummendorf, & Fellenberg, 2008). BIBR1532 might impede cell proliferation and restrict telomerase activity through suppressing activation of c-Myc and hTERT expression in Nalm-6 cells and acute promyelocytic leukemia NB4 cells (Bashash, et al., 2012). Subsequent decreased telomerase activity and probable telomere dysfunction due to the hTERT down-regulation is a probable mechanism that causes rapid cell death upon exposure of pre-B ALL cells to high doses of BIBR1532 (Bashash, et al., 2013). In addition, BIBR1532 is in combination with carboplatin and TEL patch (a specific surface of the TPP1 protein) mutations to inhibit the ovarian cancer ES2, SKOV3, and TOV112D cells as well as cervical cancer, HeLa cell, growth by inhibition of the telomerase enzyme (Meng, Taylor, Ray, Shevde, & Rocconi, 2012; Nakashima, Nandakumar, Sullivan, Espinosa, & Cech, 2013). 35
ACCEPTED MANUSCRIPT Natural products provide sources for leading compounds and many synthetic inhibitors
derivatived
from
natural
products
have
been
reported.
PT
Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a synthetic derivative of oleanolic acid, a triterpene, with apoptosis-inducing activity in a wide
RI
range of cancer cells (Honda T, 2000). Telomerase is a potential target of CDDO-Me.
SC
CDDO-Me could attenuate hTERT mRNA, telomerase activity and hTERT regulatory proteins (e.g., c-Myc, Sp1, NF-κB and p-Akt) (Deeb, et al., 2012). Inhibition of cell
NU
proliferation and induction of apoptosis by CDDO-Me in pancreatic cancer cells is
MA
associated with the repression of hTERT expression and telomerase activity. Inhibition of telomerase activity by CDDO-Me is also mediated through a ROS-dependent mechanism. Blocking ROS generation prevents the inhibition of
TE
D
hTERT gene expression, hTERT protein production and expression of a number of hTERT regulatory proteins by CDDO-Me (Deeb, et al., 2013; Y. Liu, Gao, Deeb,
AC CE P
Arbab, & Gautam, 2012).
Liriodenine is a representative oxoaporphine alkaloid mainly occurring in the families of Rutaceae, Annonaceae, Magnoliaceae, etc. cis-[PtCl2(L)(DMSO)] (Complex 1) is a synthesis product of the platinum(II) and liriodenine (L) complex (Z. F. Chen, et al., 2009). Complex 1 has a significant growth inhibition against BEL-7404 human hepatoma cell and could induce its apoptosis via the mitochondrial pathway as well as caused both the G2/M phase and S phase cell cycle arrest. It significantly induces the formation and stabilization of the telomeric G4 DNA by intercalative binding mode via π-π stacking and exterior electrostatic attraction between the positively charged platinum(II) and G4 DNA. It indicates Complex 1 inhibited the telomerase activity based on the G4 DNA stabilization (Y. L. Li, Qin, Liu, Chen, & Liang, 2014). 36
ACCEPTED MANUSCRIPT The development of G4 DNA binding small molecules has become an important strategy for selectively targeting cancer cells (W. J. Chung, et al., 2013; Maji, Kumar,
PT
Muniyappa, & Bhattacharya, 2015). So far, the structural information on complexes between human telomeric DNA and ligands is limited to the parallel G4 conformation,
RI
despite the high structural polymorphism of human telomeric G4. No structure has yet
SC
been resolved for the complex with telomestatin. Chung, et al. presented high-resolution structure of the complex between an intramolecular (3+1) human
NU
telomeric G4 and a telomestatin derivative, the macrocyclic hexaoxazole
MA
L2H2-6M(2)OTD, which interacts with G4 by π-stacking and electrostatic interactions (W. J. Chung, et al., 2013). The bifunctional complex represents an intriguing example of ligand design and suggests new possibilities for achieving
TE
D
complementary biological activity. Roe et al. synthesized and screened bifunctional ligand of hybrid acridine-Hsp90 ligand SR374, SR375, SR361 and SR362 using a
AC CE P
click-chemistry approach based on a G4 binder-geldanamycin conjugate. The conjugates also demonstrate significant cyctotoxity against a number of cancer cell lines in the sub-µM range (Roe, et al., 2015). In addition, chemical structure modifications of small molecule inhibitors also increase telomerase inhibition activity. Maji, et al. reported the design and evolution of a new kind of carbazole-based benzimidazole dimers (six carbazole based symmetric benzimidazole derivatives including two monomers M1 and M2 and four corresponding dimeric ligands having different types of linkers) for their efficient telomerase inhibition activity. Spectroscopic and electrophoretic mobility analyses revealed the higher affinity and excellent selectivity of ligands toward G4 DNA over duplex DNA. Each of the ligands induce topological transformation of the K
+
-stabilized mixed-hybrid G4
DNA to a thermodynamically more stable parallel G4 DNA structure. The ligands M2, 37
ACCEPTED MANUSCRIPT D2, D3 and D4 show complete telomerase inhibition with IC 50 values in the sub-µM concentration range. The ligands induce significant apoptotic response and
PT
anti-proliferative activity toward cancer cells when compared to the normal cells (Maji, et al., 2015). The various synthesized tumor inhibitors targeting telomerase are
RI
listed in Table 3.
SC
Some inhibitors show reversible telomerase inhibitory effects. Continual exposure of cancer cells to telomerase inhibitor leads to population of cells, which
NU
displays resistance to telomerase inhibition-mediated cell arrest. MST-312, a
MA
chemically modified derivative of epigallocatechin gallate, shows strong binding affinity to DNA and displayed reversible telomerase inhibitory effects in brain tumor cells (Gurung RL, 2014). DNA-PKcs (one of DNA-dependent protein kinase,
TE
D
DNA-PK) activation is observed in telomerase-inhibited cells presumably as a response to DNA damage. Combined inhibition of DNA-PKcs and telomerase results
AC CE P
in an increase in telomere signal-free chromosomal ends in brain tumor cells as well. DNA-PKcs ablation in these cells confers higher cell sensitivity to telomerase inhibition, inducing cell death (Gurung RL, 2014). It indicates telomerase inhibitors combined with other reagents could play better suppressive role. 5.2.1.2. Synthetic telomerase inhibitors of anti-tumor in clinical trials or in clinic Many drugs in clinical trials or in clinic show inhibition for telomerase (Table. 4). Perifosine, an AKT inhibitor in clinical trials, inhibits telomerase activity and induced telomere shortening in a wide variety of cell lines in vitro. Perifosine reduces primary breast cancer orthotopic xenograft tumor size. However, perifosine reduces telomerase activity in four of six CLL patients evaluated. Two of the patients were treated for four to six months and shortening of the shortest telomeres occurred in both patients’ cells (Holohan B, 2015). 38
ACCEPTED MANUSCRIPT Bortezomib, a proteasome inhibitor with pleiotropic activities, shows activity in mantle cell lymphoma and is currently implemented in therapeutic combinations for
PT
this disease. Bortezomib exerts inhibition on mantle cell lymphoma HBL-2 cells and NCEB cells, and multiple myeloma (MM) ARP-1 and CAG cancer cell (Uziel, Cohen,
RI
Beery, Nordenberg, & Lahav, 2014; Weiss, et al., 2012). Bortezomib downregulates
SC
telomerase activity in MM cells both transcriptionally and post-translationally. ARP-1 cells are more sensitive to differential phosphorylation of hTERT by PKCα than that
NU
of CAG cells. Transcription of hTERT is similarly inhibited in both lines by decreased
MA
binding of SP1. But, methylation of hTERT promoter is not affected (Weiss, et al., 2012). Inhibition of telomerase activity in mantle cell lymphoma is operated by two separate mechanisms: reduction of the hTERT mRNA expression and reduction in
TE
D
phosphorylation of the catalytic subunit of hTERT by its kinases, AKT and PKCα (Uziel, et al., 2014). In addition, the bortezomib treatment of leukemic and BGC-823
AC CE P
gastric cancer cells results in significant inhibition of hTERT expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggers telomere dysfunction and DNA damage. It reveals a profound impact of bortezomib on telomere homeostasis/function, which may have important clinical implications (Ci X, 2015).
Doxorubicin (DOX) is derived by chemical semisynthesis from a bacterial species and used in cancer chemotherapy. It is an anthracycline antitumor antibiotic and it works by intercalating DNA (Tacar, Sriamornsak, & Dass, 2013). In BEL-7404 human hepatoma cells, telomerase activity was inhibited in a dose and time-dependent manner in cells treated with DOX, which was correlated with the inhibition of cell growth. The mRNA of three telomerase subunits (hTERT, hTR and TP1) did not affect after exposure for 72 h with indicated concentrations. The telomerase inhibition 39
ACCEPTED MANUSCRIPT and telomere shortening by DOX may contribute to its efficiency in treatment in hepatocellular carcinoma (Zhang RG, 2002). Kato et al. found that TRF1, POT1 and
PT
TNKS1 mRNAs decreased in HeLa and U-2 OS cells treated with doxorubicin, while an increased TRF2-interacting telomeric protein, RAP1, mRNA level was observed in
RI
U-2OS cells (Kato, Nakayama, Agata, & Yoshida, 2013). In most instances, DOX
SC
combined with other reagents plays the inhibition role. DOX combined with RHPS4 inhibits the Hsp90 heat shock protein, and confers enhanced sensitivity in RHPS4
NU
treated MCF-7 cells. DOX combined with GRN163L increases DOX sensitivity to
MA
hepatoma cell Hep3B by inhibiting telomerase activity (Cookson, et al., 2005; Djojosubroto, et al., 2005). DOX combined with sodium butyrate (histone deacetylase inhibitors) inhibits proliferation of uterine cancer cell. Growth inhibition is
TE
D
accompanied by caspase-dependent apoptosis with reduced telomerase activity and decreased the hTERT mRNA expression (M. Yu, et al., 2014).
AC CE P
Mammalian target of rapamycin (mTOR) inhibitors such as rapamycin exert their anti-proliferative effects through inhibition of the serine/threonine kinase mTOR, by forming a complex with one of the immunophilin family of FK506 binding proteins, FKBP12 (Bae-Jump, et al., 2010). Zhou et al. showed that rapamycin rapidly inhibited telomerase activity by decreasing the mRNA level of hTERT in Ishikawa, Hec-1B and ECC-1 cells of endometrial cancer cells (Zhou C, 2003), and in both rapamycin-sensitive and -resistant cell (Bae-Jump, Zhou, Gehrig, Whang, & Boggess, 2006). Rapamycin also displayed a potent anti-leukemic effect on the human T-cell leukemia cell Jurkat through G1 cell cycle arrest and suppression of telomerase activity (reducing hTERT expression) (Y. M. Zhao, Zhou, Xu, Lai, & Huang, 2008). The related synergistic inhibition of telomerase activity has been reported. For instance, a combination of bortezomib and rapamycin induced synergistic inhibition 40
ACCEPTED MANUSCRIPT of telomerase activity in HBL-2 cells, the combined treatment decreased telomerase activity by 80% compared to the expected value (40%) and a similar trend was
PT
observed for NCEB cells (Uziel, et al., 2014). Many tyrosine kinase inhibitors show good inhibition on telomerase activity
RI
including nilotinib, dasatinib, gefitinib (Shapira, et al., 2012), etc., which are listed
SC
with other synthetic tumor inhibitors targeting telomerase in clinical trials or in clinic together in Table. 4.
NU
5.2.2. Oligonucleotide
MA
Antisense oligodeoxynucleotides (ODN) are an area of heightened interest in the field of telomerase inhibition. These drugs consist of short stretches of DNA that are complementary to a target RNA. The mechanism of action for most applications is to
TE
D
hybridize to their complementary RNA by Watson-Crick base pairing and inhibit the translation of the RNA by a passive and/or active mechanism. The passive inhibition
AC CE P
occurs simply by the competitive binding of the ODN to the RNA, whereas the active mechanism recruits RNaseH to degrade the mRNA once the RNA-ODN hybridization occurs (Laura K. White, 2001). Different approaches have been used: antisense technology, RNA interference, aptamers, anti-microRNAs, CRISPR, etc. The main problems associated with using oligonucleotides as therapeutic agents are caused by their low stability in vivo and difficulties in their selective delivery into tissues and cells. Chemically modified oligonucleotides are significantly more stable and can penetrate into cells more effectively while retaining their biological activity. Addition of different ligands allows researchers to obtain specific delivery of conjugates into particular cells due to receptor mediated endocytosis (Juliano, Carver, Cao, & Ming, 2013; Zvereva, et al., 2015). Main targets are: processes associated with transcription of the hTERT and hTR genes, a disturbance in the telomerase complex assembly, 41
ACCEPTED MANUSCRIPT inhibition of enzymatic activity of the assembled telomerase complex, loss by telomere ends of availability for interaction with telomerase, and inhibition of activity
PT
of telomerase complex interacting with telomeres (Zvereva, et al., 2015). A variety of studies, reported the inhibition of telomerase using antisense
RI
approaches, direct both at the template and non-template regions of hTR. Azhibek et
SC
al, synthesized chimeric oligonucleotides containing two target sites that could simultaneously interact with two functional domains of hTR. The chimeric
NU
bifunctional oligonucleotides that contain two oligonucleotide parts complementary
MA
to the functional domains of telomerase RNA connected with non-nucleotide linkers in different orientations (5'-3', 5'-5' or 3'-3'), within which chimeras significantly influenced the inhibitory activity. The functional parts of chimeric oligonucleotides
TE
D
are complementary to either the template or single-stranded parts of a pseudoknot or the CR4/CR5 domain. Such chimeras inhibited telomerase in vitro in the nM range,
effect
AC CE P
but were effective in vivo in sub-nM concentrations, predominantly due to their on
telomerase
assembly
and
dimerization.
Chimeric
bifunctional
oligonucleotides could be considered a basis for the development of new, safe anti-cancer drugs (Azhibek, Zvereva, Zatsepin, Rubtsova, & Dontsova, 2014). Imetelstat (GRN163L) is the first telomerase inhibitor to advance to clinical development. Imetelstat as a short, modified oligonucleotide is a lipid-conjugated 13-mer oligonucleotide sequence that is complementary to and binds with high affinity to the RNA template of telomerase, thereby directly inhibiting telomerase activity. The compound has a proprietary thio-phosphoramidate backbone, which is designed to provide resistance to the effect of cellular nucleases, thus conferring improved stability in plasma and tissues, as well as significantly improves binding affinity to its target (Hochreiter, et al., 2006; Lin CP, 2007). Imetelstat has shown 42
ACCEPTED MANUSCRIPT hopeful results in multiple preclinical studies. It has been moved into six stage I and stage I/II clinical trials targeting patients with chronic lympho-proliferative diseases,
PT
refractory and relapsed solid tumor malignancies, refractory and relapsed MM, locally recurrent or metastatic breast cancer, and advanced and metastatic NSCLC. In
RI
addition, GRN163L is in combination with paclitaxel and bevacizumab in patients
SC
with locally recurrent or metastatic breast cancer (Ruden & Puri, 2013). Following intravenous administration of imetelstat using tolerable dosing regimens, clinically
NU
relevant and significant inhibition of telomerase activity is observed in various types
MA
of tissue in which telomerase activity was measurable, including normal bone marrow hematopoietic cells, malignant plasma cells, hair follicle cells, and peripheral blood mononuclear cells (Hu, Bobb, Lu, He, & Dome, 2014; Joseph, et al., 2010; Thompson,
TE
D
et al., 2013). In addition, preliminary information on the therapeutic activity and safety of imetelstat in patients has been obtained. Clinic reports in 2015 indicated that
AC CE P
imetelstat was found to be active in patients with myelofibrosis, but it was potential to cause clinically significant myelosuppression. The rapid and durable hematologic and molecular responses were observed in patients with essential thrombocythemia (Baerlocher, et al., 2015; Tefferi, et al., 2015). The application of oligonucleotide inhibitors of telomerase as antitumor preparations is associated with high price and difficult synthesis of modified oligonucleotides. However, an increase in the efficiency of telomerase activity by antisense oligonucleotides concurrently influencing hTR and hTERT and an increased influence on tumor stem cells suggest that oligonucleotide inhibitors of telomerase can be promising in combined antitumor therapy, but not as a universal preparation (Zvereva, et al., 2015). 5.3. Peptide and Protein 43
ACCEPTED MANUSCRIPT 5.3.1. Peptide In recent years, there have been studies about telomerase inhibitors of different
PT
peptides and proteins for anti-tumor. Since telomerase is present in most cancers, its peptides are universal telomerase-associated antigens. They are capable of producing
RI
strong immune response by eliciting both CD4+ and CD8+, T-cell responses and
SC
stimulating the hTERT peptide-specific CTL activity, potentially leading to tumor cell lysis (Beatty & Vonderheide, 2008; Vonderheide, 2008). Several strategies are
MA
and eliminate the issue of self-tolerance.
NU
employed in the development of vaccines that may induce hTERT’s immunogenicity
GV1001, hTERT peptide-based vaccine, is a 16 amino acid MHC class II-restricted hTERT peptide vaccine, which consists of amino acids 611-626
TE
D
(EARPALLTSRLRFIPK) of the hTERT active site. GV1001 was used in conjunction with an adjuvant, such as granulocyte-monocyte colony-stimulating factor or Toll-like
AC CE P
receptor-7 agonist (Kyte, 2009; Ruden & Puri, 2013; Shaw, et al., 2010). It was administered as an MHC class-II peptide, which was endogenously processed to yield a MHC class-I peptide producing both CD4+and CD8+ responses, thus leading to a robust CTL signaling cascade and a maximum immune response. The hTERT-positive B-CLL patients treated with GV1001 peptide-loaded dendritic cells showed positive CD4+ and CD8+ T-cell responses without a negative effect on normal cells or autoimmunity (Kokhaei, et al., 2007), which suggests that GV1001 may be an effective for treatment of patients with B-CLL. GV1001 had successfully completed several phase I and II clinical trials conducted in patients with advanced stage melanoma, NSCLC, hepatocellular carcinoma and pancreatic cancer (Ruden & Puri, 2013). The phase III clinical trial has been carried out. Vx-001, cryptic peptide-based vaccine, is a new peptide based anticancer therapy 44
ACCEPTED MANUSCRIPT vaccine. Vx-001 consists of a low affinity cryptic peptide hTERT572 (RLFFYRKSV) (Ruden & Puri, 2013). Vx-001 had shown good antitumor efficacy evidenced by
PT
inhibition of tumor growth in vivo in HHD transgenic mice and in phase I and II clinical trials in patients with various types of tumors. Vx-001 had completed a large
RI
phase I/II clinical trial with different types of advanced stage cancers, including
SC
patients with NSCLC, breast cancer, melanoma and cholangiocarcinoma (Mavroudis, et al., 2006; Menez-Jamet & Kosmatopoulos, 2009).
NU
5.3.2. Protein
MA
Korean Mistletoe Lectin, a galactose- and N-acetyI-D-galactosamine-specific lectin (Viscum album L. coloratum agglutinin, VCA), was reported in 2002. VCA has anti-tumor potential and induced apoptosis in both SK-Hep-1 (p53-positive) and
TE
D
Hep3B (p53-negative) cells, which was associated with inhibition of telomerase via mitochondrial controlled pathway independent of p53 (Lyu SY, 2002). In addition,
AC CE P
VCA induced apoptotic cell death through activation of caspase-3 and the inhibition of telomerase activity through transcriptional down-regulation of hTERT in the VCA-treated A253 cells, which also resulted from dephosphorylation of Akt in the survival signaling pathways (S. H. Choi, Lyu, & Park, 2004). Fungal immunomodulatory protein, FIP-gts, was isolated from Ganoderma tsugae. Recombinant fungal immunomodulatory protein reFIP-gts in E. coli was expressed and purified. reFIP-gts significantly and selectively inhibited the growth of A549 cancer cells and suppressed telomerase activity in concentration-dependent manner via c-Myc-responsive element-dependent down-regulation of the hTERT (Liao CH, 2006). reFIP-gts entered the cell and its localization in the endoplasmic reticulum (ER) could result in ER stress, thereby increasing ER stress markers (CHOP/GADD153) and intracellular calcium release in A549 cells. ER stress induced intracellular 45
ACCEPTED MANUSCRIPT calcium release and resulted in inhibition of telomerase activity (Liao, et al., 2007). PinX1, Pin2/TRF1-interacting proteins, was reported in 2001 (L. K. Zhou XZ,
PT
2001). PinX1 can inhibit telomerase activity and affect tumorigenicity. PinX1 and its small TID domain bind to the hTERT, potently inhibiting its activity. Overexpression
RI
of PinX1 or its TID domain inhibits telomerase activity, shortens telomeres, and
SC
induces crisis, whereas depletion of endogenous PinX1 increases telomerase activity and elongated telomeres. Depletion of PinX1 also increase tumorigenicity in nude
NU
mice, consistent with its chromosome localization at 8p23, a region with frequent loss
MA
of heterozygosity in a number of human cancers (L. K. Zhou XZ, 2001; Lai XF, 2012). The continuous research indicates PinX1 is a major haplo-insufficient tumor suppressor, essential for maintaining telomerase activity and chromosome stability
TE
D
and therefore it is essential for cancer initiation (H. P. Zhou XZ, Shi R, Lee TH, Lu G, Zhang Z, Bronson R, Lu KP., 2011). Telomere elongation by human telomerase is
AC CE P
inhibited in cis by the telomeric protein TRF1 and its associated proteins. However, the link between TRF1 and inhibition of telomerase elongation of telomeres remains elusive because TRF1 has no direct effect on telomerase activity. The telomerase inhibitor PinX1 is recruited to telomeres by TRF1. It provides a critical link between TRF1 and telomerase inhibition to prevent telomere elongation and help to maintain telomere homeostasis (Soohoo, et al., 2011). Gastrokine 1 (GKN1) is a novel autocrine/paracrine protein that is specifically expressed in gastric mucosa and is isolated from the gastric mucosa cells of several mammalian species including rats (Yoon, et al., 2013). GKN1 had a tumor suppressor function through inhibition of cell proliferation and induction of apoptosis in gastric cancer cells (Yoon JH, 2014). Yoon et al. reported that GKN1 significantly decreased hTERT expression, telomerase activity, and telomere length in AGSGKN1 and MKN1GKN1 cells (both stable 46
ACCEPTED MANUSCRIPT overexpressed GKN1 gastric cancer cell lines). It could also directly bind to c-Myc and downregulate its expression as well as inhibit its binding to the TRF1 protein.
PT
GKN1 may be a potential chemotherapeutic candidate for gastric cancer treatment (Yoon JH, 2014).
RI
In addition, there are other reports about the telomerase inhibition of proteins.
SC
Protein phosphatase 2A inhibits nuclear telomerase activity in human breast cancer cells (Li H, 1997). Interferon-alpha induces a repression of hTERT and telomerase
NU
activity in human malignant and nonmalignant hematopoietic cells (D. Xu, et al.,
in
the
IL-6-dependent
MM
MA
2000). Interferon-alpha and interferon-gamma could downregulate telomerase activity cell
line
U266-1970
(Lindkvist,
Ivarsson,
Jernberg-Wiklund, & Paulsson-Karlsson, 2006). Bone Morphogenetic Protein-7
TE
D
inhibits cervical tumor growth by inhibiting telomerase activity and telomere maintenance (Cassar, et al., 2008). Activin, a pleiotropic cytokine, inhibits telomerase
AC CE P
activity and induces repression of hTERT gene in breast and cervical cancer cells (Katik, et al., 2009). Sohn et al. constructed zinc finger protein transcription factor. It derives from the human genome which bound to a 12-bp recognition sequence within the promoter of the hTERT gene and fused them with a KRAB repressor domain to create a potent transcriptional repressor. It could decrease mRNA level and telomerase activity together result in shortening of telomere length (Sohn, et al., 2010). 6. Conclusions and perspectives Telomerase is a promising target for cancer therapy. In this review, we emphasize the recent advances of function and mechanism of telomerase as an anti-tumor drug target in our understanding of telomere biology and its relation to cancer. In spite of development inhibitors targeting telomerase, practice has proven to be more difficult than what drug companies expected, but a new wave of clinical trials testing novel 47
ACCEPTED MANUSCRIPT combinations of drugs and new patient populations is finally providing evidence that telomerase inhibitors might be an effective cancer treatment, at least when it comes to
PT
some tumor types (Williams, 2013).
RI
But there are some concerns for using this strategy. Delay in efficacy for the
SC
therapy becomes phenotypically manifest because telomere shortening requires certain divisions of cells. And the lag phase between the time when telomerase of
NU
cancer cells has been inhibited and the shortening of their telomere length may allow
MA
cells to develop other alternative mechanism to overcome the crisis, such as ALT. About 85%-90% of human cancers achieve through increased activity of telomerase;
D
of the remaining 10%-15%, most are able to maintain their telomere lengths in
TE
absence of telomerase by one or more mechanisms referred to as ALT that occurs in
AC CE P
some common types of cancers. The reasons for this association are unclear. But it could be a potential alternative way for cancer cells escaping from anti-telomerase therapy.
Targeting of the non-canonical function of hTERT in combination with inhibiting telomerase catalytic activity could be a therapeutic approach, which could not only prevent the persistent activation of oncogenic signaling pathways, but concurrently induce senescence in proliferating tumor cells as a result of critical telomere shortening. The challenge is to explore the non-canonical function of hTERT by
cross-talking
with
complicated
signal
pathways.
Adverse
effects
of
telomerase-targeted treatment on normal cells need to be evaluated. With further understanding the action mechanism of telomerase component, it is more likely for
48
ACCEPTED MANUSCRIPT rational design of effective therapeutic interventions against telomerase active cancers.
PT
An interesting study shows that even though telomerase accumulates at Cajal
RI
bodies, it is not necessary for telomerase assembly, trafficking and extension in Cajal
SC
bodies of human cells (Y. Chen, et al., 2015). And mutations in dyskerin results in dyskerotosis congenita, a complex syndrome characterized by bone marrow failure
NU
(Zaug, Crary, Jesse Fioravanti, Campbell, & Cech, 2013). With more extensive
MA
understanding of the structure, biogenesis and mechanism of the enzyme, it will provide invaluable information for increasing the efficiency of rational drug design. In
D
addition, most treatments have shown to be more effective when used in combination
TE
with standard therapies. Optimizing the delivery methods and drug combinations
AC CE P
could be helpful in drug treatment because these would target many hallmarks of cancer at once.
Conflict of interest
The authors declare that there are no conflicts of interest. Acknowledgements
This work was supported by the National Natural Science Foundation of China (Grant no. 81370088), the Fundamental Research Funds for the Central Universities of Zhuizong, the Project of Shaanxi Star of Science and Technology (Grant no. 2012Kjxx-06), and the Supporting Plan of Education Ministry's New Century Excellent Talents (Grant no. NCET-13-0467). References Adler, S., Rashid, G., & Klein, A. (2011). Indole-3-carbinol inhibits telomerase activity and gene 49
ACCEPTED MANUSCRIPT expression in prostate cancer cell lines. Anticancer Res, 31, 3733-3737. Agatsuma T, A. T., Nara S, Matsumiya S, Nakai R, Ogawa H, Otaki S, Ikeda S, Saitoh Y, Kanda Y. (2002). UCS1025A and B, new antitumor antibiotics from the fungus Acremonium species.
PT
Org Lett, 4, 4387-4390. Aggarwal BB, B. A., Aggarwal RS, Seeram NP, Shishodia S, Takada Y. (2004). Role of resveratrol in
RI
prevention and therapy of cancer: preclinical and clinical studies. Anticancer Res, 24,
SC
2783-2840.
Ale-Agha, N., Dyballa-Rukes, N., Jakob, S., Altschmied, J., & Haendeler, J. (2014). Cellular functions
NU
of the dual-targeted catalytic subunit of telomerase, telomerase reverse transcriptase--potential role in senescence and aging. Experimental Gerontology, 56, 189-193.
MA
Ambrus, A., Chen, D., Dai, J., Bialis, T., Jones, R. A., & Yang, D. (2006). Human telomeric sequence forms a hybrid-type intramolecular G-quadruplex structure with mixed parallel/antiparallel strands in potassium solution. Nucleic Acids Research, 34, 2723-2735.
D
Artandi, S. E., Alson, S., Tietze, M. K., Sharpless, N. E., Ye, S., Greenberg, R. A., Castrillon, D. H.,
TE
Horner, J. W., Weiler, S. R., Carrasco, R. D., & DePinho, R. A. (2002). Constitutive telomerase expression promotes mammary carcinomas in aging mice. Proc Natl Acad Sci U S
AC CE P
A, 99, 8191-8196.
Artandi, S. E., & DePinho, R. A. (2010). Telomeres and telomerase in cancer. Carcinogenesis, 31, 9-18. Asai, A., Oshima, Y., Yamamoto, Y., Uochi, T. A., Kusaka, H., Akinaga, S., Yamashita, Y., Pongracz, K., Pruzan, R., Wunder, E., Piatyszek, M., Li, S., Chin, A. C., Harley, C. B., & Gryaznov, S. (2003). A novel telomerase template antagonist (GRN163) as a potential anticancer agent. Cancer Res, 63, 3931-3939. Azhibek, D., Zvereva, M., Zatsepin, T., Rubtsova, M., & Dontsova, O. (2014). Chimeric bifunctional oligonucleotides as a novel tool to invade telomerase assembly. Nucleic Acids Res, 42, 9531-9542. Bae-Jump, V. L., Zhou, C., Boggess, J. F., Whang, Y. E., Barroilhet, L., & Gehrig, P. A. (2010). Rapamycin inhibits cell proliferation in type I and type II endometrial carcinomas: a search for biomarkers of sensitivity to treatment. Gynecol Oncol, 119, 579-585. Bae-Jump, V. L., Zhou, C., Gehrig, P. A., Whang, Y. E., & Boggess, J. F. (2006). Rapamycin inhibits hTERT telomerase mRNA expression, independent of cell cycle arrest. Gynecol Oncol, 100, 50
ACCEPTED MANUSCRIPT 487-494. Baerlocher, G. M., Oppliger Leibundgut, E., Ottmann, O. G., Spitzer, G., Odenike, O., McDevitt, M. A., Roth, A., Daskalakis, M., Burington, B., Stuart, M., & Snyder, D. S. (2015). Telomerase
PT
Inhibitor Imetelstat in Patients with Essential Thrombocythemia. N Engl J Med, 373, 920-928. Bai, L. P., Hagihara, M., Jiang, Z. H., & Nakatani, K. (2008). Ligand binding to tandem G
RI
quadruplexes from human telomeric DNA. Chembiochem, 9, 2583-2587.
SC
Baoping, Y., Guoyong, H., Jieping, Y., Zongxue, R., & Hesheng, L. (2004). Cyclooxygenase-2 inhibitor nimesulide suppresses telomerase activity by blocking Akt/PKB activation in gastric cancer
NU
cell line. Dig Dis Sci, 49, 948-953.
Bashash, D., Ghaffari, S. H., Mirzaee, R., Alimoghaddam, K., & Ghavamzadeh, A. (2013). Telomerase
MA
inhibition by non-nucleosidic compound BIBR1532 causes rapid cell death in pre-B acute lymphoblastic leukemia cells. Leuk Lymphoma, 54, 561-568. Bashash, D., Ghaffari, S. H., Zaker, F., Hezave, K., Kazerani, M., Ghavamzadeh, A., Alimoghaddam,
D
K., Mosavi, S. A., Gharehbaghian, A., & Vossough, P. (2012). Direct short-term cytotoxic
TE
effects of BIBR 1532 on acute promyelocytic leukemia cells through induction of p21 coupled with downregulation of c-Myc and hTERT transcription. Cancer Invest, 30, 57-64.
AC CE P
Beatty, G. L., & Vonderheide, R. H. (2008). Telomerase as a universal tumor antigen for cancer vaccines. Expert Rev Vaccines, 7, 881-887.
Beck, S., Jin, X., Sohn, Y. W., Kim, J. K., Kim, S. H., Yin, J., Pian, X., Kim, S. C., Nam, D. H., Choi, Y. J., & Kim, H. (2011). Telomerase activity-independent function of TERT allows glioma cells to attain cancer stem cell characteristics by inducing EGFR expression. Mol Cells, 31, 9-15.
Bermudez, Y., Ahmadi, S., Lowell, N. E., & Kruk, P. A. (2007). Vitamin E suppresses telomerase activity in ovarian cancer cells. Cancer Detect Prev, 31, 119-128. Blackburn, E. H., & Collins, K. (2011). Telomerase: an RNP enzyme synthesizes DNA. Cold Spring Harb Perspect Biol, 3. Bley, C. J., Qi, X. D., Rand, D. P., Borges, C. R., Nelson, R. W., & Chen, J. J. L. (2011). RNA-protein binding interface in the telomerase ribonucleoprotein. Proc Natl Acad Sci U S A, 108, 20333-20338. Bojesen, S. E., Pooley, K. A., Johnatty, S. E., Beesley, J., Michailidou, K., Tyrer, J. P., et al. (2013). Multiple independent variants at the TERT locus are associated with telomere length and risks 51
ACCEPTED MANUSCRIPT of breast and ovarian cancer. Nat Genet, 45, 371-384. Brandt, S., Heller, H., Schuster, K. D., & Grote, J. (2005). The tamoxifen-induced suppression of telomerase activity in the human hepatoblastoma cell line HepG2: a result of post-translational
PT
regulation. J Cancer Res Clin Oncol, 131, 120-128. Broccoli, D., Godley, I. A., Donehower, L. A., Varmus, H. E., & deLange, T. (1996). Telomerase
RI
activation in mouse mammary tumors: Lack of detectable telomere shortening and evidence
SC
for regulation of telomerase RNA with cell. Mol Cell Biol, 16, 3765-3772. Brown, A. F., Podlevsky, J. D., Qi, X., Chen, Y., Xie, M., & Chen, J. J. (2014). A self-regulating
NU
template in human telomerase. Proc Natl Acad Sci U S A, 111, 11311-11316. Brown, T., Sigurdson, E., Rogatko, A., & Broccoli, D. (2003). Telomerase inhibition using
MA
azidothymidine in the HT-29 colon cancer cell line. Ann Surg Oncol, 10, 910-915. Bryan, C., Rice, C., Hoffman, H., Harkisheimer, M., Sweeney, M., & Skordalakes, E. (2015). Structural Basis of Telomerase Inhibition by the Highly Specific BIBR1532. Structure, 23,
D
1934-1942.
TE
Burger, A. M., Dai, F., Schultes, C. M., Reszka, A. P., Moore, M. J., Double, J. A., & Neidle, S. (2005). The G-quadruplex-interactive molecule BRACO-19 inhibits tumor growth, consistent with
AC CE P
telomere targeting and interference with telomerase function. Cancer Res, 65, 1489-1496.
Burger AM, D. J., Newell DR. (1997). Inhibition of telomerase activity by cisplatin in human testicular cancer cells. Eur J Cancer, 33, 638-644.
Cairney, C. J., & Keith, W. N. (2008). Telomerase redefined: Integrated regulation of hTR and hTERT for telomere maintenance and telomerase activity. Biochimie, 90, 13-23.
Calado, R. T., & Young, N. S. (2009). Mechanisms of Disease: Telomere Diseases. New England Journal of Medicine, 361, 2353-2365. Cassar, L., Li, H., Pinto, A. R., Nicholls, C., Bayne, S., & Liu, J. P. (2008). Bone morphogenetic protein-7 inhibits telomerase activity, telomere maintenance, and cervical tumor growth. Cancer Res, 68, 9157-9166. Chakrabarti, M., Banik, N. L., & Ray, S. K. (2013). Sequential hTERT knockdown and apigenin treatment inhibited invasion and proliferation and induced apoptosis in human malignant neuroblastoma SK-N-DZ and SK-N-BE2 cells. J Mol Neurosci, 51, 187-198. Chen, C. L., Chang, D. M., Chen, T. C., Lee, C. C., Hsieh, H. H., Huang, F. C., Huang, K. F., Guh, J. H., 52
ACCEPTED MANUSCRIPT Lin, J. J., & Huang, H. S. (2013). Structure-based design, synthesis and evaluation of novel anthra[1,2-d]imidazole-6,11-dione derivatives as telomerase inhibitors and potential for cancer polypharmacology. Eur J Med Chem, 60, 29-41.
PT
Chen, H., Li, Y., & Tollefsbol, T. O. (2009). Strategies targeting telomerase inhibition. Mol Biotechnol, 41, 194-199.
RI
Chen, J. L.-Y., Sperry, J., Ip, N. Y., & Brimble, M. A. (2011). Natural products targeting telomere
SC
maintenance. MedChemComm, 2, 229.
Chen, J. L., Blasco, M. A., & Greider, C. W. (2000). Secondary structure of vertebrate telomerase RNA.
NU
Cell, 100, 503-514.
Chen, Y., Deng, Z., Jiang, S., Hu, Q., Liu, H., Songyang, Z., Ma, W., Chen, S., & Zhao, Y. (2015).
MA
Human cells lacking coilin and Cajal bodies are proficient in telomerase assembly, trafficking and telomere maintenance. Nucleic Acids Res, 43, 385-395. Chen, Y. J., Sheng, W. Y., Huang, P. R., & Wang, T. C. (2006). Potent inhibition of human telomerase
D
by U-73122. J Biomed Sci, 13, 667-674.
TE
Chen, Z. F., Liu, Y. C., Liu, L. M., Wang, H. S., Qin, S. H., Wang, B. L., Bian, H. D., Yang, B., Fun, H. K., Liu, H. G., Liang, H., & Orvig, C. (2009). Potential new inorganic antitumour agents from
AC CE P
combining the anticancer traditional Chinese medicine (TCM) liriodenine with metal ions, and DNA binding studies. Dalton Trans, 262-272.
Chen, Z. F., Qin, Q. P., Qin, J. L., Liu, Y. C., Huang, K. B., Li, Y. L., Meng, T., Zhang, G. H., Peng, Y., Luo, X. J., & Liang, H. (2015). Stabilization of G-quadruplex DNA, inhibition of telomerase activity, and tumor cell apoptosis by organoplatinum(II) complexes with oxoisoaporphine. J Med Chem, 58, 2159-2179. Chen, Z. F., Qin, Q. P., Qin, J. L., Zhou, J., Li, Y. L., Li, N., Liu, Y. C., & Liang, H. (2015). Water-Soluble Ruthenium(II) Complexes with Chiral 4-(2,3-Dihydroxypropyl)-formamide Oxoaporphine (FOA): In Vitro and in Vivo Anticancer Activity by Stabilization of G-Quadruplex DNA, Inhibition of Telomerase Activity, and Induction of Tumor Cell Apoptosis. J Med Chem, 58, 4771-4789. Cheng, Y.-L., Chang, W.-L., Lee, S.-C., Liu, Y.-G., Lin, H.-C., Chen, C.-J., Yen, C.-Y., Yu, D.-S., Lin, S.-Z., & Harn, H.-J. (2003). Acetone extract of Bupleurum scorzonerifolium inhibits proliferation of A549 human lung cancer cells via inducing apoptosis and suppressing 53
ACCEPTED MANUSCRIPT telomerase activity. Life Sci, 73, 2383-2394. Chiappori, A. A., Kolevska, T., Spigel, D. R., Hager, S., Rarick, M., Gadgeel, S., Blais, N., Von Pawel, J., Hart, L., Reck, M., Bassett, E., Burington, B., & Schiller, J. H. (2015). A randomized phase
non-small-cell lung cancer. Annals of Oncology, 26, 354-362.
PT
II study of the telomerase inhibitor imetelstat as maintenance therapy for advanced
RI
Chiu, W. T., Shen, S. C., Yang, L. Y., Chow, J. M., Wu, C. Y., & Chen, Y. C. (2011). Inhibition of
endothelial cells. J Cell Physiol, 226, 2041-2051.
SC
HSP90-dependent telomerase activity in amyloid beta-induced apoptosis of cerebral
NU
Choi, J. H., Min, N. Y., Park, J., Kim, J. H., Park, S. H., Ko, Y. J., Kang, Y., Moon, Y. J., Rhee, S., Ham, S. W., Park, A. J., & Lee, K. H. (2010). TSA-induced DNMT1 down-regulation represses
MA
hTERT expression via recruiting CTCF into demethylated core promoter region of hTERT in HCT116. Biochem Biophys Res Commun, 391, 449-454. Choi, S. H., Im, E., Kang, H. K., Lee, J. H., Kwak, H. S., Bae, Y. T., Park, H. J., & Kim, N. D. (2005).
D
Inhibitory effects of costunolide on the telomerase activity in human breast carcinoma cells.
TE
Cancer Lett, 227, 153-162.
Choi, S. H., Lyu, S. Y., & Park, W. B. (2004). Mistletoe lectin induces apoptosis and telomerase
AC CE P
inhibition in human A253 cancer cells through dephosphorylation of Akt. Arch Pharm Res, 27, 68-76.
Chung, J., Khadka, P., & Chung, I. K. (2012). Nuclear import of hTERT requires a bipartite nuclear localization signal and Akt-mediated phosphorylation. Journal of Cell Science, 125,
2684-2697.
Chung, W. J., Heddi, B., Tera, M., Iida, K., Nagasawa, K., & Phan, A. T. (2013). Solution structure of an intramolecular (3 + 1) human telomeric G-quadruplex bound to a telomestatin derivative. J Am Chem Soc, 135, 13495-13501. Ci X, L. B., Ma X, Kong F, Zheng C, Björkholm M, Jia J, Xu D. (2015). Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells. Oncotarget, 6, 38079-38092. Cifuentes-Rojas, C., & Shippen, D. E. (2012). Telomerase regulation. Mutat Res, 730, 20-27. Clark GR, P. P., Squire CJ, Neidle S. (2003). Structure of the first parallel DNA quadruplex-drug complex. J Am Chem Soc, 125, 4066-4067. 54
ACCEPTED MANUSCRIPT Cocco MJ, H. L., Huber MD, Maizels N. (2003). Specific interactions of distamycin with G-quadruplex DNA. Nucleic Acids Res, 31, 2944-2951. Collins, K. (2006). The biogenesis and regulation of telomerase holoenzymes. Nature Reviews
PT
Molecular Cell Biology, 7, 484-494. Compton, S. A., Elmore, L. W., Haydu, K., Jackson-Cook, C. K., & Holt, S. E. (2006). Induction of
SC
human tumor cells. Mol Cell Biol, 26, 1452-1462.
RI
nitric oxide synthase-dependent telomere shortening after functional inhibition of Hsp90 in
Cookson, J. C., Dai, F., Smith, V., Heald, R. A., Laughton, C. A., Stevens, M. F., & Burger, A. M. Pharmacodynamics
of
the
G-quadruplex-stabilizing
telomerase
inhibitor
NU
(2005).
3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acridinium methosulfate (RHPS4) in vitro:
MA
activity in human tumor cells correlates with telomere length and can be enhanced, or antagonized, with cytotoxic agents. Mol Pharmacol, 68, 1551-1558. D'Ambrosio, D., Reichenbach, P., Micheli, E., Alvino, A., Franceschin, M., Savino, M., & Lingner, J.
D
(2012). Specific binding of telomeric G-quadruplexes by hydrosoluble perylene derivatives
TE
inhibits repeat addition processivity of human telomerase. Biochimie, 94, 854-863. Damm K, H. U., Garin-Chesa P, Hauel N, Kauffmann I, Priepke H, Niestroj C, Daiber C, Enenkel B,
AC CE P
Guilliard B, Lauritsch I, Müller E, Pascolo E, Sauter G, Pantic M, Martens UM, Wenz C, Lingner J, Kraut N, Rettig WJ, Schnapp A. (2001). A highly selective telomerase inhibitor limiting human cancer cell proliferation. EMBO J, 20, 6958-6968.
Daniel, M., Peek, G. W., & Tollefsbol, T. O. (2012). Regulation of the human catalytic subunit of telomerase (hTERT). Gene, 498, 135-146.
de Lange, T. (2005). Shelterin: the protein complex that shapes and safeguards human telomeres. Genes Dev, 19, 2100-2110. DeBoer C, M. P., Wnuk RJ, Peterson DH. (1970). Geldanamycin, a new antibiotic. J Antibiot, 23, 442-447. Debray, J., Zeghida, W., Jourdan, M., Monchaud, D., Dheu-Andries, M. L., Dumy, P., Teulade-Fichou, M. P., & Demeunynck, M. (2009). Synthesis and evaluation of fused bispyrimidinoacridines as novel pentacyclic analogues of quadruplex-binder BRACO-19. Org Biomol Chem, 7, 5219-5228. Deeb, D., Gao, X., Liu, Y., Kim, S. H., Pindolia, K. R., Arbab, A. S., & Gautam, S. C. (2012). 55
ACCEPTED MANUSCRIPT Inhibition of cell proliferation and induction of apoptosis by oleanane triterpenoid (CDDO-Me) in pancreatic cancer cells is associated with the suppression of hTERT gene expression and its telomerase activity. Biochem Biophys Res Commun, 422, 561-567.
PT
Deeb, D., Gao, X., Liu, Y., Varma, N. R., Arbab, A. S., & Gautam, S. C. (2013). Inhibition of telomerase activity by oleanane triterpenoid CDDO-Me in pancreatic cancer cells is
RI
ROS-dependent. Molecules, 18, 3250-3265.
SC
Djojosubroto, M. W., Chin, A. C., Go, N., Schaetzlein, S., Manns, M. P., Gryaznov, S., Harley, C. B., & Rudolph, K. L. (2005). Telomerase antagonists GRN163 and GRN163L inhibit tumor growth
NU
and increase chemosensitivity of human hepatoma. Hepatology, 42, 1127-1136. Draisci, R., Lucentini, L., Giannetti, L., Boria, P., & Poletti, R. (1996). First report of pectenotoxin-2
MA
(PTX-2) in algae (Dinophysis fortii) related to seafood poisoning in Europe. Toxicon, 34, 923-935.
Drosopoulos, W. C., Direnzo, R., & Prasad, V. R. (2005). Human telomerase RNA template sequence is
D
a determinant of telomere repeat extension rate. J Biol Chem, 280, 32801-32810.
TE
Duan, W., Rangan, A., Vankayalapati, H., Kim, M. Y., Zeng, Q., Sun, D., Han, H., Fedoroff, O. Y., Nishioka, D., Rha, S. Y., Izbicka, E., Von Hoff, D. D., & Hurley, L. H. (2001). Design and
AC CE P
synthesis of fluoroquinophenoxazines that interact with human telomeric G-quadruplexes and their biological effects. Mol Cancer Ther, 1, 103-120.
Egan, E. D., & Collins, K. (2010). Specificity and stoichiometry of subunit interactions in the human telomerase holoenzyme assembled in vivo. Mol Cell Biol, 30, 2775-2786.
Eitsuka, T., Nakagawa, K., Suzuki, T., & Miyazawa, T. (2005). Polyunsaturated fatty acids inhibit telomerase activity in DLD-1 human colorectal adenocarcinoma cells: a dual mechanism approach. Biochim Biophys Acta, 1737, 1-10. El Daly, H., & Martens, U. M. (2007). Telomerase inhibition and telomere targeting in hematopoietic cancer cell lines with small non-nucleosidic synthetic compounds (BIBR1532). Methods Mol Biol, 405, 47-60. Faezizadeh Z, M.-N. S., Allameh A. (2012). The effect of silymarin on telomerase activity in the human leukemia cell line K562. Planta Med, 78, 899-902. Falchetti, M. L., Mongiardi, M. P., Fiorenzo, P., Petrucci, G., Pierconti, F., D'Agnano, I., D'Alessandris, G., Alessandri, G., Gelati, M., Ricci-Vitiani, L., Maira, G., Larocca, L. M., Levi, A., & Pallini, 56
ACCEPTED MANUSCRIPT R. (2008). Inhibition of telomerase in the endothelial cells disrupts tumor angiogenesis in glioblastoma xenografts. International Journal of Cancer, 122, 1236-1242. Fan YX, W. Z., Cheng JR, Gao N, Chen JM. (2008). Research progress of Chinese Traditional
PT
Medicine on the inhibiting of telomerase activity. Chinese Traditonal patent Medicine, 30, 1346-1350.
RI
Feldser, D. M., & Greider, C. W. (2007). Short telomeres limit tumor progression in vivo by inducing
SC
senescence. Cancer Cell, 11, 461-469.
Feng, J. L., Funk, W. D., Wang, S. S., Weinrich, S. L., Avilion, A. A., Chiu, C. P., Adams, R. R., Chang,
NU
E., Allsopp, R. C., Yu, J. H., Le, S. Y., West, M. D., Harley, C. B., Andrews, W. H., Greider, C. W., & Villeponteau, B. (1995). The Rna Component of Human Telomerase. Science, 269,
MA
1236-1241.
Flores, I., Evan, G., & Blasco, M. A. (2006). Genetic analysis of myc and telomerase interactions in vivo. Mol Cell Biol, 26, 6130-6138.
D
Folini, M., Bandiera, R., Millo, E., Gandellini, P., Sozzi, G., Gasparini, P., Longoni, N., Binda, M.,
TE
Daidone, M. G., Berg, K., & Zaffaroni, N. (2007). Photochemically enhanced delivery of a cell-penetrating peptide nucleic acid conjugate targeting human telomerase reverse
AC CE P
transcriptase: effects on telomere status and proliferative potential of human prostate cancer cells. Cell Prolif, 40, 905-920.
Folini, M., Berg, K., Millo, E., Villa, R., Prasmickaite, L., Daidone, M. G., Benatti, U., & Zaffaroni, N. (2003). Photochemical internalization of a peptide nucleic acid targeting the catalytic subunit of human telomerase. Cancer Res, 63, 3490-3494.
Franceschin, M., Rossetti, L., D'Ambrosio, A., Schirripa, S., Bianco, A., Ortaggi, G., Savino, M., Schultes, C., & Neidle, S. (2006). Natural and synthetic G-quadruplex interactive berberine derivatives. Bioorg Med Chem Lett, 16, 1707-1711. Francis J. Schmitz, F. S. D., M. Bilayet Hossain, Dick Van der Helm. (1991). Cytotoxic aromatic alkaloids from the ascidian Amphicarpa meridiana and Leptoclinides sp.: meridine and 11-hydroxyascididemin. J. Org. Chem, 56, 804-808. Fuggetta MP, L. G., Tricarico M, Cottarelli A, Falchetti R, Ravagnan G, Bonmassar E. (2006). Effect of resveratrol on proliferation and telomerase activity of human colon cancer cells in vitro. J Exp Clin Cancer Res, 25, 189-193. 57
ACCEPTED MANUSCRIPT Fujimori, J., Matsuo, T., Shimose, S., Kubo, T., Ishikawa, M., Yasunaga, Y., & Ochi, M. (2011). Antitumor effects of telomerase inhibitor TMPyP4 in osteosarcoma cell lines. J Orthop Res, 29, 1707-1711.
PT
Fukuyama, R., Ng, K. P., Cicek, M., Kelleher, C., Niculaita, R., Casey, G., & Sizemore, N. (2007). Role of IKK and oscillatory NF kappa B kinetics in MMP-9 gene expression and
RI
chemoresistance to 5-fluorouracil in RKO colorectal cancer cells. Mol Carcinog, 46, 402-413.
SC
Gan, Y., Lu, J., Yeung, B. Z., Cottage, C. T., Wientjes, M. G., & Au, J. L. (2015). Pharmacodynamics of telomerase inhibition and telomere shortening by noncytotoxic suramin. AAPS J, 17, 268-276.
NU
Gao C, L. Y., Cai XM, Hao XZ. (2010). The effect of Hedyotis diffusais on telomerase activity, cell apoptosis and cell cycle. Acta academiae medicinae Xuzhou, 30, 466-468.
MA
Gao, S., Yu, B. P., Li, Y., Dong, W. G., & Luo, H. S. (2003). Antiproliferative effect of octreotide on gastric cancer cells mediated by inhibition of Akt/PKB and telomerase. World J Gastroenterol, 9, 2362-2365.
D
Geserick, C., Tejera, A., Gonzalez-Suarez, E., Klatt, P., & Blasco, M. A. (2006). Expression of mTert in
TE
primary murine cells links the growth-promoting effects of telomerase to transforming growth factor-beta signaling. Oncogene, 25, 4310-4319.
AC CE P
Ghosh, A., Saginc, G., Leow, S. C., Khattar, E., Shin, E. M., Yan, T. D., Wong, M., Zhang, Z. Z., Li, G. L., Sung, W. K., Zhou, J. B., Chng, W. J., Li, S., Liu, E., & Tergaonkar, V. (2012). Telomerase directly regulates NF-kappa B-dependent transcription. Nature Cell Biology, 14, 1270-+.
Gillis, A. J., Schuller, A. P., & Skordalakes, E. (2008). Structure of the Tribolium castaneum telomerase catalytic subunit TERT. Nature, 455, 633-U636.
Giridharan, P., Somasundaram, S. T., Perumal, K., Vishwakarma, R. A., Karthikeyan, N. P., Velmurugan, R., & Balakrishnan, A. (2002). Novel substituted methylenedioxy lignan suppresses proliferation of cancer cells by inhibiting telomerase and activation of c-myc and caspases leading to apoptosis. Br J Cancer, 87, 98-105. Gladych, M., Wojtyla, A., & Rubis, B. (2011). Human telomerase expression regulation. Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire, 89, 359-376. Gomez, D., O'Donohue, M. F., Wenner, T., Douarre, C., Macadre, J., Koebel, P., Giraud-Panis, M. J., Kaplan, H., Kolkes, A., Shin-ya, K., & Riou, J. F. (2006). The G-quadruplex ligand telomestatin inhibits POT1 binding to telomeric sequences in vitro and induces GFP-POT1 58
ACCEPTED MANUSCRIPT dissociation from telomeres in human cells. Cancer Res, 66, 6908-6912. Gomez, D. L. M., Farina, H. G., & Gomez, D. E. (2013). Telomerase regulation: A key to inhibition? (Review). International Journal of Oncology, 43, 1351-1356.
PT
Gonzalez-Suarez, E., Samper, E., Ramirez, A., Flores, J. M., Martin-Caballero, J., Jorcano, J. L., & Blasco, M. A. (2001). Increased epidermal tumors and increased skin wound healing in
RI
transgenic mice overexpressing the catalytic subunit of telomerase, mTERT, in basal
SC
keratinocytes. Embo Journal, 20, 2619-2630.
Greider, C. W., & Blackburn, E. H. (1987). The Telomere Terminal Transferase of Tetrahymena Is a
NU
Ribonucleoprotein Enzyme with 2 Kinds of Primer Specificity. Cell, 51, 887-898. Greider, C. W., & Blackburn, E. H. (1989). A telomeric sequence in the RNA of Tetrahymena
MA
telomerase required for telomere repeat synthesis. Nature, 337, 331-337. Grozdanov, P. N., Roy, S., Kittur, N., & Meier, U. T. (2009). SHQ1 is required prior to NAF1 for
Society, 15, 1188-1197.
D
assembly of H/ACA small nucleolar and telomerase RNPs. Rna-a Publication of the Rna
TE
Guittat, L., Alberti, P., Rosu, F., Van Miert, S., Thetiot, E., Pieters, L., Gabelica, V., De Pauw, E., Ottaviani, A., Riou, J.-F., & Mergny, J.-L. (2003). Interactions of cryptolepine and
AC CE P
neocryptolepine with unusual DNA structures. Biochimie, 85, 535-547.
Guo, Q. L., Lin, S. S., You, Q. D., Gu, H. Y., Yu, J., Zhao, L., Qi, Q., Liang, F., Tan, Z., & Wang, X. (2006). Inhibition of human telomerase reverse transcriptase gene expression by gambogic acid in human hepatoma SMMC-7721 cells. Life Sci, 78, 1238-1245.
Gurung RL, L. H., Venkatesan S, Lee PS, Hande MP. (2014). Targeting DNA-PKcs and telomerase in brain tumour cells. Mol Cancer, 13, 232. Haendeler, J., Hoffmann, J., Rahman, S., Zeiher, A. M., & Dimmeler, S. (2003). Regulation of telomerase activity and anti-apoptotic function by protein-protein interaction and phosphorylation. Febs Letters, 536, 180-186. Haering, C. H., Nakamura, T. M., Baumann, P., & Cech, T. R. (2000). Analysis of telomerase catalytic subunit mutants in vivo and in vitro in Schizosaccharomyces pombe. Proc Natl Acad Sci U S A, 97, 6367-6372. Hahn, W. C., Counter, C. M., Lundberg, A. S., Beijersbergen, R. L., Brooks, M. W., & Weinberg, R. A. (1999). Creation of human tumour cells with defined genetic elements. Nature, 400, 464-468. 59
ACCEPTED MANUSCRIPT Han, M. H., Kim, G. Y., Moon, S. K., Kim, W. J., Nam, T. J., & Choi, Y. H. (2011). Apoptosis induction by glycoprotein isolated from Laminaria japonica is associated with down-regulation of telomerase activity and prostaglandin E2 synthesis in AGS human gastric cancer cells. Int J
PT
Oncol, 38, 577-584. Han QB, X. H. (2009). Caged Garcinia xanthones: development since 1937. Curr Med Chem, 16,
RI
3775-3796.
SC
Hanahan, D., & Weinberg, R. A. (2011). Hallmarks of Cancer: The Next Generation. Cell, 144, 646-674.
NU
Hartwig, F. P., Nedel, F., Collares, T. V., Tarquinio, S. B. C., Nor, J. E., & Demarco, F. F. (2012). Telomeres and Tissue Engineering: The Potential Roles of TERT in VEGF-mediated
MA
Angiogenesis. Stem Cell Reviews and Reports, 8, 1275-1281. Hayakawa, N., Nozawa, K., Ogawa, A., Kato, N., Yoshida, K., Akamatsu, K., Tsuchiya, M., Nagasaka, A., & Yoshida, S. (1999). Isothiazolone derivatives selectively inhibit telomerase from human
D
and rat cancer cells in vitro. biochemistry, 38, 11501-11507.
TE
He, H., Xia, H. H., Wang, J. D., Gu, Q., Lin, M. C., Zou, B., Lam, S. K., Chan, A. O., Yuen, M. F., Kung, H. F., & Wong, B. C. (2006). Inhibition of human telomerase reverse transcriptase by
AC CE P
nonsteroidal antiinflammatory drugs in colon carcinoma. Cancer, 106, 1243-1249.
Herz, C., Hertrampf, A., Zimmermann, S., Stetter, N., Wagner, M., Kleinhans, C., Erlacher, M., Schuler, J., Platz, S., Rohn, S., Mersch-Sundermann, V., & Lamy, E. (2014). The isothiocyanate erucin abrogates telomerase in hepatocellular carcinoma cells in vitro and in an orthotopic xenograft tumour model of HCC. J Cell Mol Med, 18, 2393-2403.
Hirashima, K., & Seimiya, H. (2015). Telomeric repeat-containing RNA/G-quadruplex-forming sequences cause genome-wide alteration of gene expression in human cancer cells in vivo. Nucleic Acids Research, 43, 2022-2032. Hirota, K., Nodasaka, Y., Orikasa, Y., Okuyama, H., & Yumoto, I. (2005). Shewanella pneumatophori sp. nov., an eicosapentaenoic acid-producing marine bacterium isolated from the intestines of Pacific mackerel (Pneumatophorus japonicus). Int J Syst Evol Microbiol, 55, 2355-2359. Hochreiter, A. E., Xiao, H., Goldblatt, E. M., Gryaznov, S. M., Miller, K. D., Badve, S., Sledge, G. W., & Herbert, B. S. (2006). Telomerase template antagonist GRN163L disrupts telomere maintenance, tumor growth, and metastasis of breast cancer. Clin Cancer Res, 12, 3184-3192. 60
ACCEPTED MANUSCRIPT Holohan B, H. M., Lai TP, Huang E, Friedman DR, Wright WE, Shay JW. (2015). Perifosine as a potential novel anti-telomerase therapy. Oncotarget, 6, 21816-21826. Holt, S. E., Aisner, D. L., Baur, J., Tesmer, V. M., Dy, M., Ouellette, M., Trager, J. B., Morin, G. B.,
and Hsp90 in telomerase complexes. Genes Dev, 13, 817-826.
PT
Toft, D. O., Shay, J. W., Wright, W. E., & White, M. A. (1999). Functional requirement of p23
RI
Honda T, R. B., Bore L, Finlay HJ, Favaloro FG Jr, Suh N, Wang Y, Sporn MB, Gribble GW. (2000).
SC
Synthetic oleanane and ursane triterpenoids with modified rings A and C: a series of highly active inhibitors of nitric oxide production in mouse macrophages. J. Med. Chem, 43,
NU
4233-4246.
Hsu, C. P., Lee, L. W., Tang, S. C., Hsin, I. L., Lin, Y. W., & Ko, J. L. (2015). Epidermal growth factor
MA
activates telomerase activity by direct binding of Ets-2 to hTERT promoter in lung cancer cells. Tumor Biology, 36, 5389-5398.
Hu, Y., Bobb, D., Lu, Y., He, J., & Dome, J. S. (2014). Effect of telomerase inhibition on preclinical
D
models of malignant rhabdoid tumor. Cancer Genet, 207, 403-411.
TE
Huang, F. C., Chang, C. C., Wang, J. M., Chang, T. C., & Lin, J. J. (2012). Induction of senescence in cancer cells by the G-quadruplex stabilizer, BMVC4, is independent of its telomerase
AC CE P
inhibitory activity. Br J Pharmacol, 167, 393-406.
Huang, F. C., Huang, K. F., Chen, R. H., Wu, J. E., Chen, T. C., Chen, C. L., Lee, C. C., Chen, J. Y., Lin, J. J., & Huang, H. S. (2012). Synthesis, telomerase evaluation and anti-proliferative studies on various series of diaminoanthraquinone-linked aminoacyl residue derivatives. Arch Pharm
(Weinheim), 345, 101-111.
Huang, J., Brown, A. F., Wu, J., Xue, J., Bley, C. J., Rand, D. P., Wu, L. J., Zhang, R. G., Chen, J. J. L., & Lei, M. (2014). Structural basis for protein-RNA recognition in telomerase. Nature Structural & Molecular Biology, 21, 507-512. Huang, P. R., Yeh, Y. M., Pao, C. C., Chen, C. Y., & Wang, T. C. (2012). N-(1-Pyrenyl) maleimide inhibits telomerase activity in a cell free system and induces apoptosis in Jurkat cells. Mol Biol Rep, 39, 8899-8905. Huang, S. T., Wang, C. Y., Yang, R. C., Chu, C. J., Wu, H. T., & Pang, J. H. (2010). Wogonin, an active compound in Scutellaria baicalensis, induces apoptosis and reduces telomerase activity in the HL-60 leukemia cells. Phytomedicine, 17, 47-54. 61
ACCEPTED MANUSCRIPT Hug, N., & Lingner, J. (2006). Telomere length homeostasis. Chromosoma, 115, 413-425. Ilyinsky, N. S., Shchyolkina, A. K., Borisova, O. F., Mamaeva, O. K., Zvereva, M. I., Azhibek, D. M., Livshits, M. A., Mitkevich, V. A., Balzarini, J., Sinkevich, Y. B., Luzikov, Y. N., Dezhenkova,
PT
L. G., Kolotova, E. S., Shtil, A. A., Shchekotikhin, A. E., & Kaluzhny, D. N. (2014). Novel multi-targeting anthra[2,3-b]thiophene-5,10-diones with guanidine-containing side chains:
SC
cytotoxic properties. Eur J Med Chem, 85, 605-614.
RI
interaction with telomeric G-quadruplex, inhibition of telomerase and topoisomerase I and
Imanshahidi, M., & Hosseinzadeh, H. (2008). Pharmacological and therapeutic effects of Berberis
NU
vulgaris and its active constituent, berberine. Phytother Res, 22, 999-1012. Indran, I. R., Hande, M. P., & Pervaiz, S. (2011). hTERT overexpression alleviates intracellular ROS
cells. Cancer Res, 71, 266-276.
MA
production, improves mitochondrial function, and inhibits ROS-mediated apoptosis in cancer
Jagadeesh, S., Kyo, S., & Banerjee, P. P. (2006). Genistein represses telomerase activity via both
TE
66, 2107-2115.
D
transcriptional and posttranslational mechanisms in human prostate cancer cells. Cancer Res,
Jayasooriya, R. G., Kang, S. H., Kang, C. H., Choi, Y. H., Moon, D. O., Hyun, J. W., Chang, W. Y., &
AC CE P
Kim, G. Y. (2012). Apigenin decreases cell viability and telomerase activity in human leukemia cell lines. Food Chem Toxicol, 50, 2605-2611.
Ji, X., Sun, H., Zhou, H., Xiang, J., Tang, Y., & Zhao, C. (2012). The interaction of telomeric DNA and C-myc22 G-quadruplex with 11 natural alkaloids. Nucleic Acid Ther, 22, 127-136.
Ji ZN, Y. W., Liu GQ, Huang Y. (2002). Inhibition of telomerase activity and bcl-2 expression in berbamine-induced apoptosis in HL-60 cells. Planta Med, 68, 596-600. Jiang, J., Chan, H., Cash, D. D., Miracco, E. J., Ogorzalek Loo, R. R., Upton, H. E., Cascio, D., O'Brien Johnson, R., Collins, K., Loo, J. A., Zhou, Z. H., & Feigon, J. (2015). Structure of Tetrahymena telomerase reveals previously unknown subunits, functions, and interactions. Science, 350, aab4070. Joseph, I., Tressler, R., Bassett, E., Harley, C., Buseman, C. M., Pattamatta, P., Wright, W. E., Shay, J. W., & Go, N. F. (2010). The telomerase inhibitor imetelstat depletes cancer stem cells in breast and pancreatic cancer cell lines. Cancer Res, 70, 9494-9504. Juliano, R. L., Carver, K., Cao, C., & Ming, X. (2013). Receptors, endocytosis, and trafficking: the 62
ACCEPTED MANUSCRIPT biological basis of targeted delivery of antisense and siRNA oligonucleotides. J Drug Target, 21, 27-43. Jun'ichi Kobayash, J.-f. C., Hideshi Nakamura, Yasushi Ohizumi. (1988). Ascididemin, a novel
PT
pentacyclic aromatic alkaloid with potent antileukemic activity from the okinawan tunicate Didemnum sp. Tetrahedron Letters, 29, 1177-1180.
RI
Kakiuchi, Y., Sasaki, N., Satoh-Masuoka, M., Murofushi, H., & Murakami-Murofushi, K. (2004). A
SC
novel pyrazolone, 4,4-dichloro-1-(2,4-dichlorophenyl)-3-methyl-5-pyrazolone, as a potent catalytic inhibitor of human telomerase. Biochem Biophys Res Commun, 320, 1351-1358.
NU
Kalathiya U, P. M., Baginski M. (2014). Molecular Modeling and Evaluation of Novel Dibenzopyrrole Derivatives as Telomerase Inhibitors and Potential Drug for Cancer Therapy. IEEE/ACM
MA
Trans Comput Biol Bioinform, 11, 1196-1120.
Kang, S.-S. L., Seung-Eun. (1998). Growth and Telomerase Inhibition of SK-MEL 28 Melanoma Cell Line by a Plant Flavonoid, Apigenin. BMB Reports, 31, 339-344.
D
Kannan, K., Nelson, A. D., & Shippen, D. E. (2008). Dyskerin is a component of the Arabidopsis
TE
telomerase RNP required for telomere maintenance. Mol Cell Biol, 28, 2332-2341. Kanno S, K. Y., Kakuta M, Osanai Y, Kurauchi K, Ujibe M, Ishikawa M. (2008). Costunolide-induced
AC CE P
apoptosis is caused by receptor-mediated pathway and inhibition of telomerase activity in NALM-6 cells. Biol Pharm Bull, 31, 1024-1028.
Kanzawa, T., Germano, I. M., Kondo, Y., Ito, H., Kyo, S., & Kondo, S. (2003). Inhibition of telomerase activity in malignant glioma cells correlates with their sensitivity to temozolomide. Br J Cancer, 89, 922-929.
Karlseder, J., Broccoli, D., Dai, Y., Hardy, S., & de Lange, T. (1999). p53- and ATM-dependent apoptosis induced by telomeres lacking TRF2. Science, 283, 1321-1325. Kasiappan, R., Shen, Z., Tse, A. K., Jinwal, U., Tang, J., Lungchukiet, P., Sun, Y., Kruk, P., Nicosia, S. V., Zhang, X., & Bai, W. (2012). 1,25-Dihydroxyvitamin D3 suppresses telomerase expression and human cancer growth through microRNA-498. J Biol Chem, 287, 41297-41309. Katik, I., Mackenzie-Kludas, C., Nicholls, C., Jiang, F. X., Zhou, S., Li, H., & Liu, J. P. (2009). Activin inhibits telomerase activity in cancer. Biochem Biophys Res Commun, 389, 668-672. Kato, M., Nakayama, M., Agata, M., & Yoshida, K. (2013). Gene expression levels of human shelterin complex and shelterin-associated factors regulated by the topoisomerase II inhibitors 63
ACCEPTED MANUSCRIPT doxorubicin and etoposide in human cultured cells. Tumour Biol, 34, 723-733. Kazemi Noureini, S., & Tanavar, F. (2015). Boldine, a natural aporphine alkaloid, inhibits telomerase at non-toxic concentrations. Chem Biol Interact, 231, 27-34.
PT
Khorramizadeh, M. R., Saadat, F., Vaezzadeh, F., Safavifar, F., Bashiri, H., & Jahanshiri, Z. (2007). Suppression of telomerase activity by pyrimethamine: implication to cancer. Iran Biomed J, 11,
RI
223-228.
SC
Killedar, A., Stutz, M. D., Sobinoff, A. P., Tomlinson, C. G., Bryan, T. M., Beesley, J., Chenevix-Trench, G., Reddel, R. R., & Pickett, H. A. (2015). A Common Cancer
Telomerase. PLoS Genet, 11, e1005286.
NU
Risk-Associated Allele in the hTERT Locus Encodes a Dominant Negative Inhibitor of
MA
Kim, J., Won, R., Ban, G., Ju, M. H., Cho, K. S., Young Han, S., Jeong, J. S., & Lee, S. W. (2015). Targeted Regression of Hepatocellular Carcinoma by Cancer-Specific RNA Replacement through MicroRNA Regulation. Sci Rep, 5, 12315.
D
Kim, J. H., Lee, G. E., Kim, S. W., & Chung, I. K. (2003). Identification of a quinoxaline derivative
TE
that is a potent telomerase inhibitor leading to cellular senescence of human cancer cells. Biochem J, 373, 523-529.
AC CE P
Kim, J. H., Lee, G. E., Lee, J. E., & Chung, I. K. (2003). Potent inhibition of human telomerase by nitrostyrene derivatives. Mol Pharmacol, 63, 1117-1124.
Kim, M. O., Moon, D. O., Kang, S. H., Heo, M. S., Choi, Y. H., Jung, J. H., Lee, J. D., & Kim, G. Y. (2008). Pectenotoxin-2 represses telomerase activity in human leukemia cells through suppression of hTERT gene expression and Akt-dependent hTERT phosphorylation. FEBS Lett, 582, 3263-3269. Kim, N.-H., Park, H. J., Oh, M.-K., & Kim, I.-S. (2013). Antiproliferative effect of gold(I) compound auranofin through inhibition of STAT3 and telomerase activity in MDA-MB 231 human breast cancer cells. BMB Reports, 46, 59-64. Kim, N. K., Zhang, Q., Zhou, J., Theimer, C. A., Peterson, R. D., & Feigon, J. (2008). Solution structure and dynamics of the wild-type pseudoknot of human telomerase RNA. J Mol Biol, 384, 1249-1261. Kim, N. W., Piatyszek, M. A., Prowse, K. R., Harley, C. B., West, M. D., Ho, P. L. C., Coviello, G. M., Wright, W. E., Weinrich, S. L., & Shay, J. W. (1994). Specific Association of Human 64
ACCEPTED MANUSCRIPT Telomerase Activity with Immortal Cells and Cancer. Science, 266, 2011-2015. Kim, Y. J., Kwon, H. C., Ko, H., Park, J. H., Kim, H. Y., Yoo, J. H., & Yang, H. O. (2008). Anti-tumor activity of the ginsenoside Rk1 in human hepatocellular carcinoma cells through inhibition of
PT
telomerase activity and induction of apoptosis. Biol Pharm Bull, 31, 826-830. Kiran, K. G., Palaniswamy, M., & Angayarkanni, J. (2015). Human telomerase inhibitors from
RI
microbial source. World J Microbiol Biotechnol, 31, 1329-1341.
SC
Kiss, T., Fayet-Lebaron, E., & Jady, B. E. (2010). Box H/ACA Small Ribonucleoproteins. Molecular Cell, 37, 597-606.
NU
Kitahara N, E. A., Furuya K, Takahashi S. (1981). Thielavin A and B, new inhibitors of prostaglandin biosynthesis produced by Thielavia terricola. J Antibiot, 34, 1562-1568.
MA
Kokhaei, P., Palma, M., Hansson, L., Osterborg, A., Mellstedt, H., & Choudhury, A. (2007). Telomerase (hTERT 611-626) serves as a tumor antigen in B-cell chronic lymphocytic leukemia and generates spontaneously antileukemic, cytotoxic T cells. Exp Hematol, 35,
D
297-304.
18, 687-694.
TE
Kyte, J. A. (2009). Cancer vaccination with telomerase peptide GV1001. Expert Opin Investig Drugs,
AC CE P
Lai XF, S. C., Wen Z, Qian YH, Yu CS, Wang JQ, Zhong PN, Wang HL. (2012). PinX1 regulation of telomerase activity and apoptosis in nasopharyngeal carcinoma cells. J Exp Clin Cancer Res,
31, 12.
Lanzilli G, F. M., Tricarico M, Cottarelli A, Serafino A, Falchetti R, Ravagnan G, Turriziani M, Adamo R, Franzese O, Bonmassar E. (2006). Resveratrol down-regulates the growth and telomerase activity of breast cancer cells in vitro. Int J Oncol, 28, 641-648. Lattmann, S., Stadler, M. B., Vaughn, J. P., Akman, S. A., & Nagamine, Y. (2011). The DEAH-box RNA helicase RHAU binds an intramolecular RNA G-quadruplex in TERC and associates with telomerase holoenzyme. Nucleic Acids Research, 39, 9390-9404. Laura K. White, W. E. W., Jerry W. Shay. (2001). Telomerase inhibitors. TRENDS in Biotechnology, 19, 114-120. Leon-Blanco, M. M., Guerrero, J. M., Reiter, R. J., Calvo, J. R., & Pozo, D. (2003). Melatonin inhibits telomerase activity in the MCF-7 tumor cell line both in vivo and in vitro. J Pineal Res, 35, 204-211. 65
ACCEPTED MANUSCRIPT Li, C. T., Hsiao, Y. M., Wu, T. C., Lin, Y. W., Yeh, K. T., & Ko, J. L. (2011). Vorinostat, SAHA, represses telomerase activity via epigenetic regulation of telomerase reverse transcriptase in non-small cell lung cancer cells. J Cell Biochem, 112, 3044-3053.
PT
Li GX, W. M., Gao SL. (2011). Research progress of anti-aging and anti-tumor TCM drugs on telomere andtelomerase. Liaoning Journal of Traditional Chinese Medicine, 38, 2293-2295.
RI
Li H, Z. L., Funder JW, Liu JP. (1997). Protein phosphatase 2A inhibits nuclear telomerase activity in
SC
human breast cancer cells. J Biol Chem, 272, 16729-16732.
Li, Q., Zhang, J., Yang, L., Yu, Q., Chen, Q., Qin, X., Le, F., Zhang, Q., & Liu, J. (2014). Stabilization
NU
of G-quadruplex DNA and inhibition of telomerase activity studies of ruthenium(II) complexes. J Inorg Biochem, 130, 122-129.
MA
Li, W., Zhang, M., Zhang, J. L., Li, H. Q., Zhang, X. C., Sun, Q., & Qiu, C. M. (2006). Interactions of daidzin with intramolecular G-quadruplex. FEBS Lett, 580, 4905-4910. Li, Y., Liu, L., Andrews, L. G., & Tollefsbol, T. O. (2009). Genistein depletes telomerase activity
D
through cross-talk between genetic and epigenetic mechanisms. Int J Cancer, 125, 286-296.
TE
Li, Y. L., Qin, Q. P., Liu, Y. C., Chen, Z. F., & Liang, H. (2014). A platinum(II) complex of liriodenine from traditional Chinese medicine (TCM): Cell cycle arrest, cell apoptosis induction and
AC CE P
telomerase inhibition activity via G-quadruplex DNA stabilization. J Inorg Biochem, 137, 12-21.
Lian, Z., Niwa, K., Gao, J., Tagami, K., Mori, H., & Tamaya, T. (2003). Association of cellular apoptosis with anti-tumor effects of the Chinese herbal complex in endocrine-resistant cancer cell line. Cancer Detection and Prevention, 27, 147-154.
Liao, C. H., Hsiao, Y. M., Sheu, G. T., Chang, J. T., Wang, P. H., Wu, M. F., Shieh, G. J., Hsu, C. P., & Ko, J. L. (2007). Nuclear translocation of telomerase reverse transcriptase and calcium signaling in repression of telomerase activity in human lung cancer cells by fungal immunomodulatory protein from Ganoderma tsugae. Biochem Pharmacol, 74, 1541-1554. Liao CH, H. Y., Hsu CP, Lin MY, Wang JC, Huang YL, Ko JL. (2006). Transcriptionally mediated inhibition of telomerase of fungal immunomodulatory protein from Ganoderma tsugae in A549 human lung adenocarcinoma cell line. Mol Carcinog, 45, 220-229. Lin CP, L. J., Chow JM, Liu CR, Liu HE. (2007). Small-molecule c-Myc inhibitor, 10058-F4, inhibits proliferation, downregulates human telomerase reverse transcriptase and enhances 66
ACCEPTED MANUSCRIPT chemosensitivity in human hepatocellular carcinoma cells. Anticancer Drugs, 18, 161-170. Lin, P. C., Lin, S. Z., Chen, Y. L., Chang, J. S., Ho, L. I., Liu, P. Y., Chang, L. F., Harn, Y. C., Chen, S. P., Sun, L. Y., Huang, P. C., Chein, J. T., Tsai, C. H., Chou, C. W., Harn, H. J., & Chiou, T. W.
PT
(2011). Butylidenephthalide suppresses human telomerase reverse transcriptase (TERT) in human glioblastomas. Ann Surg Oncol, 18, 3514-3527.
RI
Lin, S. C., Li, W. C., Shih, J. W., Hong, K. F., Pan, Y. R., & Lin, J. J. (2006). The tea polyphenols
SC
EGCG and EGC repress mRNA expression of human telomerase reverse transcriptase (hTERT) in carcinoma cells. Cancer Lett, 236, 80-88.
NU
Lin, X., Cai, Y.-J., Li, Z.-X., Chen, Q., Liu, Z.-L., & Wang, R. (2003). Structure determination, apoptosis induction, and telomerase inhibition of CFP-2, a novel lichenin from Cladonia
MA
furcata. Biochimica et Biophysica Acta (BBA) - General Subjects, 1622, 99-108. Lindkvist, A., Ivarsson, K., Jernberg-Wiklund, H., & Paulsson-Karlsson, Y. (2006). Interferon-induced sensitization to apoptosis is associated with repressed transcriptional activity of the hTERT
D
promoter in multiple myeloma. Biochem Biophys Res Commun, 341, 1141-1148.
TE
Lindvall, C., Hou, M., Komurasaki, T., Zheng, C. Y., Henriksson, M., Sedivy, J. M., Bjorkholm, M., Teh, B. T., Nordenskjold, M., & Xu, D. W. (2003). Molecular characterization of human
AC CE P
telomerase reverse transcriptase-immortalized human fibroblasts by gene expression profiling: Activation of the Epiregulin gene. Cancer Research, 63, 1743-1747.
Lingner, J., Hughes, T. R., Shevchenko, A., Mann, M., Lundblad, V., & Cech, T. R. (1997). Reverse transcriptase motifs in the catalytic subunit of telomerase. Science, 276, 561-567.
Liu, J., Guo, L., Yin, F., Zheng, X., Chen, G., & Wang, Y. (2008). Characterization and antitumor activity of triethylene tetramine, a novel telomerase inhibitor. Biomed Pharmacother, 62, 480-485. Liu, Q., Mao, X., Zeng, F., Jin, S., & Yang, X. (2012). Effect of daurisoline on HERG channel electrophysiological function and protein expression. J Nat Prod, 75, 1539-1545. Liu, W. J., Zhang, Y. W., Shen, Y., Jiang, J. F., Miao, Z. H., & Ding, J. (2004). Telomerase inhibition is a specific early event in salvicine-treated human lung adenocarcinoma A549 cells. Biochem Biophys Res Commun, 323, 660-667. Liu, X. D., Fan, R. F., Zhang, Y., Yang, H. Z., Fang, Z. G., Guan, W. B., Lin, D. J., Xiao, R. Z., Huang, R. W., Huang, H. Q., Liu, P. Q., & Liu, J. J. (2010). Down-regulation of telomerase activity 67
ACCEPTED MANUSCRIPT and activation of caspase-3 are responsible for Tanshinone I-induced apoptosis in monocyte leukemia cells in vitro. Int J Mol Sci, 11, 2267-2280. Liu, Y., Gao, X., Deeb, D., Arbab, A. S., & Gautam, S. C. (2012). Telomerase reverse transcriptase
PT
(TERT) is a therapeutic target of oleanane triterpenoid CDDO-Me in prostate cancer. Molecules, 17, 14795-14809.
RI
Long, C., Wang, J., Guo, W., Wang, H., Wang, C., Liu, Y., & Sun, X. (2015). Triptolide inhibits
SC
transcription of hTERT through down-regulation of transcription factor specificity protein 1 in primary effusion lymphoma cells. Biochem Biophys Res Commun.
NU
Loo, W. T., Chen, J. P., Chow, L. W., & Chou, J. W. (2007). Effects of Shugansanjie Tang on matrix metalloproteinases 1, 3 and 9 and telomerase reverse transcriptase expression in human breast
MA
cells in vitro. Biomed Pharmacother, 61, 601-605.
Low, K. C., & Tergaonkar, V. (2013). Telomerase: central regulator of all of the hallmarks of cancer. Trends Biochem Sci, 38, 426-434.
D
Lu Q, L. W., Ding J, Cai J, Duan W. (2002). Shikonin derivatives: synthesis and inhibition of human
TE
telomerase. Bioorg Med Chem Lett, 12, 1375-1378. Lu Y, G. J., Jin D, Gao Y, Yuan M. (2011). Inhibition of telomerase activity by HDV ribozyme in
AC CE P
cancers. J Exp Clin Cancer Res, 30, 1.
Luo, Y., Zhang, S., Qiu, K. M., Liu, Z. J., Yang, Y. S., Fu, J., Zhong, W. Q., & Zhu, H. L. (2013). Synthesis, biological evaluation, 3D-QSAR studies of novel aryl-2H-pyrazole derivatives as telomerase inhibitors. Bioorg Med Chem Lett, 23, 1091-1095.
Lyu SY, C. S., Park WB. (2002). Korean mistletoe lectin-induced apoptosis in hepatocarcinoma cells is associated with inhibition of telomerase via mitochondrial controlled pathway independent of p53. Arch Pharm Res, 25, 93-101. Ma, Y., Ou, T. M., Tan, J. H., Hou, J. Q., Huang, S. L., Gu, L. Q., & Huang, Z. S. (2009). Synthesis and evaluation of 9-O-substituted berberine derivatives containing aza-aromatic terminal group as highly selective telomeric G-quadruplex stabilizing ligands. Bioorg Med Chem Lett, 19, 3414-3417. Maji, B., Kumar, K., Muniyappa, K., & Bhattacharya, S. (2015). New dimeric carbazole-benzimidazole mixed ligands for the stabilization of human telomeric G-quadruplex DNA and as telomerase inhibitors. A remarkable influence of the spacer. Org Biomol Chem, 13, 8335-8348. 68
ACCEPTED MANUSCRIPT Martinez, P., & Blasco, M. A. (2011). Telomeric and extra-telomeric roles for telomerase and the telomere-binding proteins. Nature Reviews Cancer, 11, 161-176. Masutomi, K., Possemato, R., Wong, J. M., Currier, J. L., Tothova, Z., Manola, J. B., Ganesan, S.,
PT
Lansdorp, P. M., Collins, K., & Hahn, W. C. (2005). The telomerase reverse transcriptase regulates chromatin state and DNA damage responses. Proc Natl Acad Sci U S A, 102,
RI
8222-8227.
SC
Mavroudis, D., Bolonakis, I., Cornet, S., Myllaki, G., Kanellou, P., Kotsakis, A., Galanis, A., Nikoloudi, I., Spyropoulou, M., Menez, J., Miconnet, I., Niniraki, M., Cordopatis, P., Kosmatopoulos, K.,
NU
& Georgoulias, V. (2006). A phase I study of the optimized cryptic peptide TERT(572y) in patients with advanced malignancies. Oncology, 70, 306-314.
MA
Menez-Jamet, J., & Kosmatopoulos, K. (2009). Development of optimized cryptic peptides for immunotherapy. IDrugs, 12, 98-102.
Meng, E., Taylor, B., Ray, A., Shevde, L. A., & Rocconi, R. P. (2012). Targeted inhibition of telomerase
D
activity combined with chemotherapy demonstrates synergy in eliminating ovarian cancer
TE
spheroid-forming cells. Gynecol Oncol, 124, 598-605. Mitchell, J. R., Cheng, J., & Collins, K. (1999). A box H/ACA small nucleolar RNA-like domain at the
AC CE P
human telomerase RNA 3 ' end. Mol Cell Biol, 19, 567-576.
Mitchell, J. R., & Collins, K. (2000). Human telomerase activation requires two independent interactions between telomerase RNA and telomerase reverse transcriptase. Molecular Cell, 6,
361-371.
Mitchell, J. R., Wood, E., & Collins, K. (1999). A telomerase component is defective in the human disease dyskeratosis congenita. Nature, 402, 551-555. Mizushina, Y., Takeuchi, T., Sugawara, F., & Yoshida, H. (2012). Anti-cancer targeting telomerase inhibitors: beta-rubromycin and oleic acid. Mini Rev Med Chem, 12, 1135-1143. Mocellin, S., Pooley, K. A., & Nitti, D. (2013). Telomerase and the search for the end of cancer. Trends Mol Med, 19, 125-133. Moon, D. O., Kang, S. H., Kim, K. C., Kim, M. O., Choi, Y. H., & Kim, G. Y. (2010). Sulforaphane decreases viability and telomerase activity in hepatocellular carcinoma Hep3B cells through the reactive oxygen species-dependent pathway. Cancer Lett, 295, 260-266. Moon, D. O., Kim, M. O., Choi, Y. H., Lee, H. G., Kim, N. D., & Kim, G. Y. (2008). Gossypol 69
ACCEPTED MANUSCRIPT suppresses telomerase activity in human leukemia cells via regulating hTERT. FEBS Lett, 582, 3367-3373. Moon, D. O., Kim, M. O., Heo, M. S., Lee, J. D., Choi, Y. H., & Kim, G. Y. (2009). Gefitinib induces
PT
apoptosis and decreases telomerase activity in MDA-MB-231 human breast cancer cells. Arch Pharm Res, 32, 1351-1360.
RI
Mor-Tzuntz, R., Uziel, O., Shpilberg, O., Lahav, J., Raanani, P., Bakhanashvili, M., Rabizadeh, E.,
SC
Zimra, Y., Lahav, M., & Granot, G. (2010). Effect of imatinib on the signal transduction cascade regulating telomerase activity in K562 (BCR-ABL-positive) cells sensitive and
NU
resistant to imatinib. Exp Hematol, 38, 27-37.
Moriai, M., Tsuji, N., Kobayashi, D., Kuribayashi, K., & Watanabe, N. (2009). Down-regulation of
MA
hTERT expression plays an important role in 15-deoxy-Delta12,14-prostaglandin J2-induced apoptosis in cancer cells. Int J Oncol, 34, 1363-1372. Moye, A. L., Porter, K. C., Cohen, S. B., Phan, T., Zyner, K. G., Sasaki, N., Lovrecz, G. O., Beck, J. L.,
D
& Bryan, T. M. (2015). Telomeric G-quadruplexes are a substrate and site of localization for
TE
human telomerase. Nature Communications, 6, 7643. Mukherjee Nee Chakraborty, S., Ghosh, U., Bhattacharyya, N. P., Bhattacharya, R. K., Dey, S., & Roy,
AC CE P
M. (2007). Curcumin-induced apoptosis in human leukemia cell HL-60 is associated with inhibition of telomerase activity. Mol Cell Biochem, 297, 31-39.
Mukherjee, S., Bhattacharya, R. K., & Roy, M. (2009). Targeting protein kinase C (PKC) and telomerase
by
phenethyl
isothiocyanate
(PEITC)
sensitizes
PC-3
cells
towards
chemotherapeutic drug-induced apoptosis. J Environ Pathol Toxicol Oncol, 28, 269-282.
Murakami, J., Asaumi, J., Kawai, N., Tsujigiwa, H., Yanagi, Y., Nagatsuka, H., Inoue, T., Kokeguchi, S., Kawasaki, S., Kuroda, M., Tanaka, N., Matsubara, N., & Kishi, K. (2005). Effects of histone deacetylase inhibitor FR901228 on the expression level of telomerase reverse transcriptase in oral cancer. Cancer Chemother Pharmacol, 56, 22-28. Naasani I, S. H., Tsuruo T. (1998). Telomerase Inhibition, Telomere Shortening, and Senescence of Cancer Cells by Tea Catechins. Biochem Biophys Res Commun, 249, 391-396. Naasani I, S. H., Yamori T, Tsuruo T. (1999). FJ5002: a potent telomerase inhibitor identified by exploiting the disease-oriented screening program with COMPARE analysis. Cancer Res, 59, 4004-4011. 70
ACCEPTED MANUSCRIPT Nagle, D. G., Ferreira, D., & Zhou, Y. D. (2006). Epigallocatechin-3-gallate (EGCG): chemical and biomedical perspectives. Phytochemistry, 67, 1849-1855. Nakai, R., Ishida, H., Asai, A., Ogawa, H., Yamamoto, Y., Kawasaki, H., Akinaga, S., Mizukami, T., &
PT
Yamashita, Y. (2006). Telomerase inhibitors identified by a forward chemical genetics approach using a yeast strain with shortened telomere length. Chem Biol, 13, 183-190.
RI
Nakai R, K. S., Asai A, Chiba S, Akinaga S, Mizukami T, Yamashita Y. (2001). Chrolactomycin, a
SC
novel antitumor antibiotic produced by Streptomyces sp. J Antibiot, 54, 836-839. Nakashima, M., Nandakumar, J., Sullivan, K. D., Espinosa, J. M., & Cech, T. R. (2013). Inhibition of
NU
telomerase recruitment and cancer cell death. J Biol Chem, 288, 33171-33180. Nguyen, B. N., Elmore, L. W., & Holt, S. E. (2009). Mechanism of dominant-negative telomerase
MA
function. Cell Cycle, 8, 3227-3233.
Noureini, S. K., & Wink, M. (2012). Antiproliferative effects of crocin in HepG2 cells by telomerase inhibition and hTERT down-regulation. Asian Pac J Cancer Prev, 13, 2305-2309.
D
Noureini, S. K., & Wink, M. (2014). Antiproliferative effect of the isoquinoline alkaloid papaverine in
TE
hepatocarcinoma HepG-2 cells--inhibition of telomerase and induction of senescence. Molecules, 19, 11846-11859.
AC CE P
Olaussen, K. A., Dubrana, K., Domont, J., Spano, J.-P., Sabatier, L., & Soria, J.-C. (2006). Telomeres and telomerase as targets for anticancer drug development. Critical Reviews in Oncology/Hematology, 57, 191-214.
Paeschke, K., Bochman, M. L., Garcia, P. D., Cejka, P., Friedman, K. L., Kowalczykowski, S. C., & Zakian, V. A. (2013). Pif1 family helicases suppress genome instability at G-quadruplex motifs. Nature, 497, 458-462. Pan X, H. C., Zeng F, Zhang S, Xu J. (1998). Isolation and identification of alkaloids form Menispermum dauricum growing in Xianning. Zhong Yao Cai, 21, 456-458. Park, C., Jung, J. H., Kim, N. D., & Choi, Y. H. (2007). Inhibition of cyclooxygenase-2 and telomerase activities in human leukemia cells by dideoxypetrosynol A, a polyacetylene from the marine sponge Petrosia sp. Int J Oncol, 30, 291-298. Park, C., Kim, G. Y., Kim, W. I., Hong, S. H., Park, D. I., Kim, N. D., Bae, S. J., Jung, J. H., & Choi, Y. H. (2007). Induction of apoptosis by (Z)-stellettic acid C, an acetylenic acid from the sponge Stelletta sp., is associated with inhibition of telomerase activity in human leukemic U937 cells. 71
ACCEPTED MANUSCRIPT Chemotherapy, 53, 160-168. Park, S. E., Yoo, H. S., Jin, C.-Y., Hong, S. H., Lee, Y.-W., Kim, B. W., Lee, S. H., Kim, W.-J., Cho, C. K., & Choi, Y. H. (2009). Induction of apoptosis and inhibition of telomerase activity in
PT
human lung carcinoma cells by the water extract of Cordyceps militaris. Food and Chemical Toxicology, 47, 1667-1675.
RI
Parks, J. W., & Stone, M. D. (2014). Coordinated DNA dynamics during the human telomerase
SC
catalytic cycle. Nature Communications, 5.
Parsch, D., Brassat, U., Brummendorf, T. H., & Fellenberg, J. (2008). Consequences of telomerase
NU
inhibition by BIBR1532 on proliferation and chemosensitivity of chondrosarcoma cell lines. Cancer Invest, 26, 590-596.
MA
Pascolo, E., Wenz, C., Lingner, J., Hauel, N., Priepke, H., Kauffmann, I., Garin-Chesa, P., Rettig, W. J., Damm, K., & Schnapp, A. (2002). Mechanism of human telomerase inhibition by BIBR1532, a synthetic, non-nucleosidic drug candidate. J Biol Chem, 277, 15566-15572.
D
Patel, D. J., Phan, A. T., & Kuryavyi, V. (2007). Human telomere, oncogenic promoter and 5'-UTR
TE
G-quadruplexes: diverse higher order DNA and RNA targets for cancer therapeutics. Nucleic Acids Research, 35, 7429-7455.
AC CE P
Patel, K. P., & Vonderheide, R. H. (2004). Telomerase as a tumor-associated antigen for cancer immunotherapy. Cytotechnology, 45, 91-99.
Paydar, M., Kamalidehghan, B., Wong, Y. L., Wong, W. F., Looi, C. Y., & Mustafa, M. R. (2014). Evaluation of cytotoxic and chemotherapeutic properties of boldine in breast cancer using in vitro and in vivo models. Drug Des Devel Ther, 8, 719-733.
Peng, Y., Mian, I. S., & Lue, N. F. (2001). Analysis of telomerase processivity: Mechanistic similarity to HIV-1 reverse transcriptase and role in telomere maintenance. Molecular Cell, 7, 1201-1211. Phatak, P., Cookson, J. C., Dai, F., Smith, V., Gartenhaus, R. B., Stevens, M. F., & Burger, A. M. (2007). Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism. Br J Cancer, 96, 1223-1233. Phipps, S. M., Love, W. K., White, T., Andrews, L. G., & Tollefsbol, T. O. (2009). Retinoid-induced histone deacetylation inhibits telomerase activity in estrogen receptor-negative breast cancer 72
ACCEPTED MANUSCRIPT cells. Anticancer Res, 29, 4959-4964. Pizzimenti, S., Menegatti, E., Berardi, D., Toaldo, C., Pettazzoni, P., Minelli, R., Giglioni, B., Cerbone, A., Dianzani, M. U., Ferretti, C., & Barrera, G. (2010). 4-hydroxynonenal, a lipid peroxidation
PT
product of dietary polyunsaturated fatty acids, has anticarcinogenic properties in colon carcinoma cell lines through the inhibition of telomerase activity. J Nutr Biochem, 21,
RI
818-826.
SC
Podlevsky, J. D., Bley, C. J., Omana, R. V., Qi, X., & Chen, J. J. (2008). The telomerase database. Nucleic Acids Research, 36, D339-343.
NU
Qi, D. L., Ohhira, T., Fujisaki, C., Inoue, T., Ohta, T., Osaki, M., Ohshiro, E., Seko, T., Aoki, S., Oshimura, M., & Kugoh, H. (2011). Identification of PITX1 as a TERT Suppressor Gene
MA
Located on Human Chromosome 5. Mol Cell Biol, 31, 1624-1636. Qi, X. D., Li, Y., Honda, S., Hoffmann, S., Marz, M., Mosig, A., Podlevsky, J. D., Stadler, P. F., Selker, E. U., & Chen, J. L. J. L. (2013). The common ancestral core of vertebrate and fungal
D
telomerase RNAs. Nucleic Acids Research, 41, 450-462.
TE
Qi, X. D., Xie, M. Y., Brown, A. F., Bley, C. J., Podlevsky, J. D., & Chen, J. J. L. (2012). RNA/DNA hybrid binding affinity determines telomerase template-translocation efficiency. Embo Journal,
AC CE P
31, 150-161.
Qin HL, P. J. (2008). Total synthesis of the Hsp90 inhibitor geldanamycin. Org Lett, 10, 2477-2479. Rabi, T., & Banerjee, S. (2009). Novel semisynthetic triterpenoid AMR-Me inhibits telomerase activity in human leukemic CEM cells and exhibits in vivo antitumor activity against Dalton's lymphoma ascites tumor. Cancer Lett, 278, 156-163.
Rafii, F. (2015). The role of colonic bacteria in the metabolism of the natural isoflavone daidzin to equol. Metabolites, 5, 56-73. Rahman, R., Osteso-Ibanez, T., Hirst, R. A., Levesley, J., Kilday, J. P., Quinn, S., Peet, A., O'Callaghan, C., Coyle, B., & Grundy, R. G. (2010). Histone deacetylase inhibition attenuates cell growth with associated telomerase inhibition in high-grade childhood brain tumor cells. Mol Cancer Ther, 9, 2568-2581. Rangarajan, S., & Friedman, S. H. (2007). Design, synthesis, and evaluation of phenanthridine derivatives targeting the telomerase RNA/DNA heteroduplex. Bioorg Med Chem Lett, 17, 2267-2273. 73
ACCEPTED MANUSCRIPT Rankin, A. M., Faller, D. V., & Spanjaard, R. A. (2008). Telomerase inhibitors and 'T-oligo' as cancer therapeutics: contrasting molecular mechanisms of cytotoxicity. Anticancer Drugs, 19, 329-338.
PT
Rao, Y., Xiong, W., Liu, H., Jia, C., Zhang, H., Cui, Z., Zhang, Y., & Cui, J. (2014). Inhibition of telomerase activity by dominant-negative hTERT retards the growth of breast cancer cells.
RI
Breast Cancer.
SC
Rao, Y. K., Kao, T. Y., Wu, M. F., Ko, J. L., & Tzeng, Y. M. (2010). Identification of small molecule inhibitors of telomerase activity through transcriptional regulation of hTERT and calcium
NU
induction pathway in human lung adenocarcinoma A549 cells. Bioorg Med Chem, 18, 6987-6994.
Troglitazone
suppresses
MA
Rashid-Kolvear, F., Taboski, M. A., Nguyen, J., Wang, D. Y., Harrington, L. A., & Done, S. J. (2010). telomerase
activity
independently
of
PPARgamma
in
estrogen-receptor negative breast cancer cells. BMC Cancer, 10, 390.
D
Ratledge C, K. K., Anderson AJ, Grantham DJ, Stephenson JC. (2001). Production of docosahexaenoic
TE
acid by Crypthecodinium cohnii grown in a pH-auxostat culture with acetic acid as principal carbon source. Lipids, 36, 1241-1246.
AC CE P
Redon, S., Reichenbach, P., & Lingner, J. (2010). The non-coding RNA TERRA is a natural ligand and direct inhibitor of human telomerase. Nucleic Acids Research, 38, 5797-5806.
Rezler, E. M., Seenisamy, J., Bashyam, S., Kim, M. Y., White, E., Wilson, W. D., & Hurley, L. H. (2005). Telomestatin and diseleno sapphyrin bind selectively to two different forms of the human telomeric G-quadruplex structure. J Am Chem Soc, 127, 9439-9447.
Rezler EM, S. J., Bashyam S, Kim MY, White E, Wilson WD, Hurley LH. (2005). Telomestatin and diseleno sapphyrin bind selectively to two different forms of the human telomeric G-quadruplex structure. J Am Chem Soc, 127, 9439-9447. Roe, S., Gunaratnam, M., Spiteri, C., Sharma, P., Alharthy, R. D., Neidle, S., & Moses, J. E. (2015). Synthesis and biological evaluation of hybrid acridine-HSP90 ligand conjugates as telomerase inhibitors. Org Biomol Chem, 13, 8500-8504. Ruden, M., & Puri, N. (2013). Novel anticancer therapeutics targeting telomerase. Cancer Treatment Reviews, 39, 444-456. Sato, N., Mizumoto, K., Kusumoto, M., Niiyama, H., Maehara, N., Ogawa, T., & Tanaka, M. (1998). 74
ACCEPTED MANUSCRIPT 9-Hydroxyellipticine inhibits telomerase activity in human pancreatic cancer cells. FEBS Lett, 441, 318-321. Schmidt, J. C., & Cech, T. R. (2015). Human telomerase: biogenesis, trafficking, recruitment, and
PT
activation. Genes & Development, 29, 1095-1105. Sealey, D. C. F., Zheng, L., Taboski, M. A. S., Cruickshank, J., Ikura, M., & Harrington, L. A. (2010).
RI
The N-terminus of hTERT contains a DNA-binding domain and is required for telomerase
SC
activity and cellular immortalization. Nucleic Acids Research, 38, 2019-2035. Sekhri, K. (2014). Telomeres and telomerase: understanding basic structure and potential new
NU
therapeutic strategies targeting it in the treatment of cancer. Journal of Postgraduate Medicine, 60, 303-308.
MA
Selvam, S. P., De Palma, R. M., Oaks, J. J., Oleinik, N., Peterson, Y. K., Stahelin, R. V., Skordalakes, E., Ponnusamy, S., Garrett-Mayer, E., Smith, C. D., & Ogretmen, B. (2015). Binding of the sphingolipid S1P to hTERT stabilizes telomerase at the nuclear periphery by allosterically
D
mimicking protein phosphorylation. Science Signaling, 8.
TE
Serrano, D., Bleau, A. M., Fernandez-Garcia, I., Fernandez-Marcelo, T., Iniesta, P., Ortiz-de-Solorzano, C., & Calvo, A. (2011). Inhibition of telomerase activity preferentially targets aldehyde
AC CE P
dehydrogenase-positive cancer stem-like cells in lung cancer. Mol Cancer, 10, 96.
Shapira, S., Granot, G., Mor-Tzuntz, R., Raanani, P., Uziel, O., Lahav, M., & Shpilberg, O. (2012). Second-generation tyrosine kinase inhibitors reduce telomerase activity in K562 cells. Cancer Lett, 323, 223-231.
Sharma, V., Koul, N., Joseph, C., Dixit, D., Ghosh, S., & Sen, E. (2010). HDAC inhibitor, scriptaid, induces glioma cell apoptosis through JNK activation and inhibits telomerase activity. J Cell Mol Med, 14, 2151-2161. Shaw, V. E., Naisbitt, D. J., Costello, E., Greenhalf, W., Park, B. K., Neoptolemos, J. P., & Middleton, G. W. (2010). Current status of GV1001 and other telomerase vaccination strategies in the treatment of cancer. Expert Rev Vaccines, 9, 1007-1016. Shi, S., Gao, S., Cao, T., Liu, J., Gao, X., Hao, J., Lv, C., Huang, H., Xu, J., & Yao, T. (2013). Targeting human telomeric G-quadruplex DNA and inhibition of telomerase activity with [(dmb)2Ru(obip)Ru(dmb)2](4+). PLoS One, 8, e84419. Shin-ya K, W. K., Matsuo K, Ohtani T, Yamada Y, Furihata K, Hayakawa Y, Seto H. (2001). 75
ACCEPTED MANUSCRIPT Telomestatin, a novel telomerase inhibitor from Streptomyces anulatus. J Am Chem Soc, 123, 1262-1263. Shippen-Lentz, D., & Blackburn, E. H. (1990). Functional evidence for an RNA template in telomerase.
PT
Science, 247, 546-552. Shippenlentz, D., & Blackburn, E. H. (1990). Functional Evidence for an Rna Template in Telomerase.
RI
Science, 247, 546-552.
SC
Singh, M., & Singh, N. (2009). Molecular mechanism of curcumin induced cytotoxicity in human cervical carcinoma cells. Mol Cell Biochem, 325, 107-119.
NU
Singhapol, C., Pal, D., Czapiewski, R., Porika, M., Nelson, G., & Saretzki, G. C. (2013). Mitochondrial telomerase protects cancer cells from nuclear DNA damage and apoptosis. PLoS One, 8,
MA
e52989.
Smith, L. L., Coller, H. A., & Roberts, J. M. (2003). Telomerase modulates expression of growth-controlling genes and enhances cell proliferation. Nature Cell Biology, 5, 474-479.
D
Soder, A. I., Hoare, S. F., Muir, S., Going, J. J., Parkinson, E. K., & Keith, W. N. (1997). Amplification,
TE
increased dosage and in situ expression of the telomerase RNA gene in human cancer. Oncogene, 14, 1013-1021.
AC CE P
Sohn, J. H., Yeh, B. I., Choi, J. W., Yoon, J., Namkung, J., Park, K. K., & Kim, H. W. (2010). Repression of human telomerase reverse transcriptase using artificial zinc finger transcription factors. Mol Cancer Res, 8, 246-253.
Song, Y. Y., S.L.; Yang, Y.M.; Wang, X.J.; Huang, G.Q. (2005). Alteration of activities of telomerase in tanshinone IIA inducing apoptosis of the leukemia cells. China journal of chinese meteria medica, 30, 207-211. Soohoo, C. Y., Shi, R., Lee, T. H., Huang, P., Lu, K. P., & Zhou, X. Z. (2011). Telomerase inhibitor PinX1 provides a link between TRF1 and telomerase to prevent telomere elongation. J Biol Chem, 286, 3894-3906. Sugiyama K, U. H., Ichio Y. (1995). Protective effect of juzen-taiho-to against carboplatin-induced toxic side effects in mice. Biol Pharm Bull, 18, 544-548. Sun CC, X. H., Yuan Y, Gao ZH, Lou HX, Qu XJ. (2014). Riccardin D, a macrocyclic bisbibenzy, inhibits human breast cancer growth through the suppression of telomerase activity. Basic Clin Pharmacol Toxicol, 115, 488-498. 76
ACCEPTED MANUSCRIPT Sun, H., Xiang, J., Li, Q., Liu, Y., Li, L., Shang, Q., Xu, G., & Tang, Y. (2012). Recognize three different human telomeric G-quadruplex conformations by quinacrine. Analyst, 137, 862-867. Sun L, W. X. (2003). Effects of allicin on both telomerase activity and apoptosis in gastric cancer
PT
SGC-7901 cells. World J Gastroenterol, 9, 1930-1934. Sundin, T., Peffley, D. M., & Hentosh, P. (2013). Disruption of an hTERT-mTOR-RAPTOR protein
RI
complex by a phytochemical perillyl alcohol and rapamycin. Mol Cell Biochem, 375, 97-104.
SC
Tabata Y, I. S., Yaguchi T, Sasaki T, Hoshiko S, Sakuma S, Shin-Ya K, Seto H. (1999). Diazaphilonic acid, a new azaphilone with telomerase inhibitory activity. J Antibiot, 52, 412-414.
NU
Tacar, O., Sriamornsak, P., & Dass, C. R. (2013). Doxorubicin: an update on anticancer molecular action, toxicity and novel drug delivery systems. J Pharm Pharmacol, 65, 157-170.
MA
Tan, L., Wang, W., He, G., Kuick, R. D., Gossner, G., Kueck, A. S., Wahl, H., Opipari, A. W., & Liu, J. R. (2015). Resveratrol inhibits ovarian tumor growth in an in vivo mouse model. Cancer. Tao, S. F., Zhang, C. S., Guo, X. L., Xu, Y., Zhang, S. S., Song, J. R., Li, R., Wu, M. C., & Wei, L. X.
D
(2012). Anti-tumor effect of 5-aza-2'-deoxycytidine by inhibiting telomerase activity in
TE
hepatocellular carcinoma cells. World J Gastroenterol, 18, 2334-2343. Tauchi, T., Shin-Ya, K., Sashida, G., Sumi, M., Nakajima, A., Shimamoto, T., Ohyashiki, J. H., &
AC CE P
Ohyashiki, K. (2003). Activity of a novel G-quadruplex-interactive telomerase inhibitor, telomestatin (SOT-095), against human leukemia cells: involvement of ATM-dependent DNA damage response pathways. Oncogene, 22, 5338-5347.
Tefferi, A., Lasho, T. L., Begna, K. H., Patnaik, M. M., Zblewski, D. L., Finke, C. M., Laborde, R. R., Wassie, E., Schimek, L., Hanson, C. A., Gangat, N., Wang, X., & Pardanani, A. (2015). A Pilot Study of the Telomerase Inhibitor Imetelstat for Myelofibrosis. N Engl J Med, 373, 908-919. Theimer, C. A., Blois, C. A., & Feigon, J. (2005). Structure of the human telomerase RNA pseudoknot reveals conserved tertiary interactions essential for function. Molecular Cell, 17, 671-682. Thelen, P., Wuttke, W., Jarry, H., Grzmil, M., & Ringert, R. H. (2004). Inhibition of telomerase activity and secretion of prostate specific antigen by silibinin in prostate cancer cells. J Urol, 171, 1934-1938. Thompson, P. A., Drissi, R., Muscal, J. A., Panditharatna, E., Fouladi, M., Ingle, A. M., Ahern, C. H., Reid, J. M., Lin, T., Weigel, B. J., & Blaney, S. M. (2013). A phase I trial of imetelstat in children with refractory or recurrent solid tumors: a Children's Oncology Group Phase I 77
ACCEPTED MANUSCRIPT Consortium Study (ADVL1112). Clin Cancer Res, 19, 6578-6584. Tian, X., Chen, B., & Liu, X. (2010). Telomere and telomerase as targets for cancer therapy. Appl Biochem Biotechnol, 160, 1460-1472.
PT
Tippani R, P. L., Porika M, Sirisha K, Abbagani S, Thammidala C. (2014). Pterostilbene as a potential novel telomerase inhibitor: molecular docking studies and its in vitro evaluation. Curr Pharm
RI
Biotechnol, 14, 1027-1035.
SC
Togashi, K., Ko, H. R., Ahn, J. S., & Osada, H. (2001). Inhibition of telomerase activity by fungus metabolites, CRM646-A and thielavin B. Biosci Biotechnol Biochem, 65, 651-653.
NU
Tomlinson, R. L., Li, J. A., Culp, B. R., Terns, R. M., & Terns, M. P. (2010). A Cajal body-independent pathway for telomerase trafficking in mice. Exp Cell Res, 316, 2797-2809.
MA
Toshikatsu Okuno, I. N., Ko Sawai, Kenzo Sawamura, Akio Furusakia, Takeshi Matsumoto. (1983). Structure of antifungal and phytotoxic pigments produced by alternaria sps Tetrahedron Letters, 24, 5653-5656.
TE
J Antibiot, 29, 1-6.
D
Tsuji N, K. M., Nagashima K, Wakisaka Y, Koizumi K. (1976). A new antifungal antibiotic, trichostatin.
Ueno, T., Takahashi, H., Oda, M., Mizunuma, M., Yokoyama, A., Goto, Y., Mizushina, Y., Sakaguchi,
AC CE P
K., & Hayashi, H. (2000). Inhibition of human telomerase by rubromycins: implication of spiroketal system of the compounds as an active moiety. biochemistry, 39, 5995-6002.
Ueno T, T. H., Oda M, Mizunuma M, Yokoyama A, Goto Y, Mizushina Y, Sakaguchi K, Hayashi H. (2000). Inhibition of human telomerase by rubromycins: implication of spiroketal system of the compounds as an active moiety biochemistry, 39, 5995-6002.
Ulaner, G. A., Hu, J. F., Vu, T. H., Giudice, L. C., & Hoffman, A. R. (1998). Telomerase activity in human development is regulated by human telomerase reverse transcriptase (hTERT) transcription and by alternate splicing of hTERT transcripts. Cancer Research, 58, 4168-4172. Uziel, O., Cohen, O., Beery, E., Nordenberg, J., & Lahav, M. (2014). The effect of Bortezomib and Rapamycin on Telomerase Activity in Mantle Cell Lymphoma. Transl Oncol, 7, 741-751. Uziel, O., Fenig, E., Nordenberg, J., Beery, E., Reshef, H., Sandbank, J., Birenbaum, M., Bakhanashvili, M., Yerushalmi, R., Luria, D., & Lahav, M. (2005). Imatinib mesylate (Gleevec) downregulates telomerase activity and inhibits proliferation in telomerase-expressing cell lines. Br J Cancer, 92, 1881-1891. 78
ACCEPTED MANUSCRIPT Venteicher, A. S., Abreu, E. B., Meng, Z. J., McCann, K. E., Terns, R. M., Veenstra, T. D., Terns, M. P., & Artandi, S. E. (2009). A Human Telomerase Holoenzyme Protein Required for Cajal Body Localization and Telomere Synthesis. Science, 323, 644-648.
PT
Verma, A. K., & Pratap, R. (2010). The biological potential of flavones. Nat Prod Rep, 27, 1571-1593. Verma, V., Sharma, V., Singh, V., Sharma, S., Bishnoi, A. K., Chandra, V., Maikhuri, J. P., Dwivedi, A.,
RI
Kumar, A., & Gupta, G. (2014). Designed modulation of sex steroid signaling inhibits
SC
telomerase activity and proliferation of human prostate cancer cells. Toxicol Appl Pharmacol, 280, 323-334.
NU
Villa R, F. M., Porta CD, Valentini A, Pennati M, Daidone MG, Zaffaroni N. (2003). Inhibition of telomerase activity by geldanamycin and 17-allylamino, 17-demethoxygeldanamycin in
MA
human melanoma cells. Carcinogenesis, 24, 851-859.
Villa, R., Folini, M., Porta, C. D., Valentini, A., Pennati, M., Daidone, M. G., & Zaffaroni, N. (2003). Inhibition
of
telomerase
activity
by
geldanamycin
and
17-allylamino,
D
17-demethoxygeldanamycin in human melanoma cells. Carcinogenesis, 24, 851-859.
TE
Vonderheide, R. H. (2008). Prospects and challenges of building a cancer vaccine targeting telomerase. Biochimie, 90, 173-180.
AC CE P
Wang, F., Podell, E. R., Zaug, A. J., Yang, Y., Baciu, P., Cech, T. R., & Lei, M. (2007). The POT1-TPP1 telomere complex is a telomerase processivity factor. Nature, 445, 506-510.
Wang, J., Wang, Y. J., Chen, Z. S., & Kwon, C. H. (2014). Synthesis and evaluation of sulfonylethyl-containing phosphotriesters of 3'-azido-3'-deoxythymidine as anticancer prodrugs. Bioorg Med Chem, 22, 5747-5756.
Warabi K, H. T., Nakao Y, Matsunaga S, Hirota H, van Soest RW, Fusetani N. (2005). Axinelloside A, an unprecedented highly sulfated lipopolysaccharide inhibiting telomerase, from the marine sponge, Axinella infundibula. J Am Chem Soc, 127, 13262-13270. Warabi K, M. S., van Soest RW, Fusetani N. (2003). Dictyodendrins A-E, the first telomerase-inhibitory marine natural products from the sponge Dictyodendrilla verongiformis. J Org Chem, 68, 2765-2670. Wei, C., Wen, Y., & Wang, J. (2013). Novel platinum complexes as efficient G-quadruplex DNA binders and telomerase inhibitors. Int J Biol Macromol, 55, 185-192. Weinrich, S. L., Pruzan, R., Ma, L. B., Ouellette, M., Tesmer, V. M., Holt, S. E., Bodnar, A. G., 79
ACCEPTED MANUSCRIPT Lichtsteiner, S., Kim, N. W., Trager, J. B., Taylor, R. D., Carlos, R., Andrews, W. H., Wright, W. E., Shay, J. W., Harley, C. B., & Morin, G. B. (1997). Reconstitution of human telomerase with the template RNA component hTR and the catalytic protein subunit hTRT. Nat Genet, 17,
PT
498-502. Weiss, C., Uziel, O., Wolach, O., Nordenberg, J., Beery, E., Bulvick, S., Kanfer, G., Cohen, O., Ram,
RI
R., Bakhanashvili, M., Magen-Nativ, H., Shilo, N., & Lahav, M. (2012). Differential
SC
downregulation of telomerase activity by bortezomib in multiple myeloma cells-multiple regulatory pathways in vitro and ex vivo. Br J Cancer, 107, 1844-1852.
NU
Williams, S. C. (2013). No end in sight for telomerase-targeted cancer drugs. Nat Med, 19, 6. Wojtyla, A., Gladych, M., & Rubis, B. (2011). Human telomerase activity regulation. Molecular
MA
Biology Reports, 38, 3339-3349.
Wong, L. H., Unciti-Broceta, A., Spitzer, M., White, R., Tyers, M., & Harrington, L. (2013). A yeast chemical genetic screen identifies inhibitors of human telomerase. Chem Biol, 20, 333-340.
D
Woo, H. J., & Choi, Y. H. (2005). Growth inhibition of A549 human lung carcinoma cells by
TE
beta-lapachone through induction of apoptosis and inhibition of telomerase activity. Int J Oncol, 26, 1017-1023.
AC CE P
Wu HL, H. C., Liu WH, Yung BY. (1999). Berberine-induced apoptosis of human leukemia HL-60 cells is associated with down-regulation of nucleophosmin/B23 and telomerase activity. Int J Cancer, 81, 923-929.
Wu, R. A., & Collins, K. (2014). Human telomerase specialization for repeat synthesis by unique handling of primer-template duplex. Embo Journal, 33, 921-935.
Xi, L. H., & Cech, T. R. (2014). Inventory of telomerase components in human cells reveals multiple subpopulations of hTR and hTERT. Nucleic Acids Research, 42, 8565-8577. Xiao, N., Chen, S., Ma, Y., Qiu, J., Tan, J. H., Ou, T. M., Gu, L. Q., Huang, Z. S., & Li, D. (2012). Interaction of Berberine derivative with protein POT1 affect telomere function in cancer cells. Biochem Biophys Res Commun, 419, 567-572. Xie, M. Y., Podlevsky, J. D., Qi, X. D., Bley, C. J., & Chen, J. J. L. (2010). A novel motif in telomerase reverse transcriptase regulates telomere repeat addition rate and processivity. Nucleic Acids Research, 38, 1982-1996. Xu B, L. C., Sung C. (2014). Telomerase inhibitory effects of medicinal mushrooms and lichens, and 80
ACCEPTED MANUSCRIPT their anticancer activity. Int J Med Mushrooms, 16, 17-28. Xu, D., Erickson, S., Szeps, M., Gruber, A., Sangfelt, O., Einhorn, S., Pisa, P., & Grander, D. (2000). Interferon alpha down-regulates telomerase reverse transcriptase and telomerase activity in
PT
human malignant and nonmalignant hematopoietic cells. Blood, 96, 4313-4318. Xu, H., Gong, X., Zhang, H. H., Zhang, Q., Zhao, D., & Peng, J. X. (2015). Targeting Human
RI
Telomerase Reverse Transcriptase by a Simple siRNA Expression Cassette in HepG2 Cells.
SC
Hepat Mon, 15, e24343.
Yamakuchi, M., Nakata, M., Kawahara, K., Kitajima, I., & Maruyama, I. (1997). New quinolones,
NU
ofloxacin and levofloxacin, inhibit telomerase activity in transitional cell carcinoma cell lines. Cancer Lett, 119, 213-219.
MA
Yang, D. Y., Chang, T. C., & Sheu, S. Y. (2007). Interaction between human telomere and a carbazole derivative: a molecular dynamics simulation of a quadruplex stabilizer and telomerase inhibitor. J Phys Chem A, 111, 9224-9232.
D
Yang, W., & Lee, Y. S. (2015). A DNA-hairpin model for repeat-addition processivity in telomere
TE
synthesis. Nature Structural & Molecular Biology, 22, 844-847. Yashima, K., Piatyszek, M. A., Saboorian, H. M., Virmani, A. K., Brown, D., Shay, J. W., & Gazdar, A.
AC CE P
F. (1997). Telomerase activity and in situ telomerase RNA expression in malignant and non-malignant lymph nodes. Journal of Clinical Pathology, 50, 110-117.
Ye Y, Y. H., Wu J, Li M, Min JM, Cui JR. (2005). Z-ajoene causes cell cycle arrest at G2/M and decrease of telomerase activity in HL-60 cells. Chinese journal of oncology, 27, 516-520.
Yoon, J. H., Choi, Y. J., Choi, W. S., Ashktorab, H., Smoot, D. T., Nam, S. W., Lee, J. Y., & Park, W. S. (2013). GKN1-miR-185-DNMT1 axis suppresses gastric carcinogenesis through regulation of epigenetic alteration and cell cycle. Clin Cancer Res, 19, 4599-4610. Yoon JH, S. H., Choi WS, Kim O, Nam SW, Lee JY, Park WS. (2014). Gastrokine 1 induces senescence and apoptosis through regulating telomere length in gastric cancer. Oncotarget,, 5, 11695-11708. Yu, C., Yu, Y., Xu, Z., Li, H., Yang, D., Xiang, M., Zuo, Y., Li, S., Chen, Z., & Yu, Z. (2015). Antisense oligonucleotides targeting human telomerase mRNA increases the radiosensitivity of nasopharyngeal carcinoma cells. Mol Med Rep, 11, 2825-2830. Yu, J., Guo, Q. L., You, Q. D., Lin, S. S., Li, Z., Gu, H. Y., Zhang, H. W., Tan, Z., & Wang, X. (2006). 81
ACCEPTED MANUSCRIPT Repression of telomerase reverse transcriptase mRNA and hTERT promoter by gambogic acid in human gastric carcinoma cells. Cancer Chemother Pharmacol, 58, 434-443. Yu, M., Kong, H., Zhao, Y., Sun, X., Zheng, Z., Yang, C., & Zhu, Y. (2014). Enhancement of
PT
adriamycin cytotoxicity by sodium butyrate involves hTERT downmodulation-mediated apoptosis in human uterine cancer cells. Mol Carcinog, 53, 505-513.
RI
Yu Q, L. Y., Wang C, Sun D, Yang X, Liu Y, Liu J. (2012). Chiral ruthenium(II) polypyridyl complexes:
SC
stabilization of g-quadruplex DNA, inhibition of telomerase activity and cellular uptake. PLoS One, 7, e50902.
NU
Yurtcu E, D. I. O., Iffet Sahin F. (2015). Effects of silymarin and silymarin-doxorubicin applications on telomerase activity of human hepatocellularcarcinoma cell line HepG2. J BUON, 20, 555-561.
MA
Zaccagnini, G., Gaetano, C., Della Pietra, L., Nanni, S., Grasselli, A., Mangoni, A., Benvenuto, R., Fabrizi, M., Truffa, S., Germani, A., Moretti, F., Pontecorvi, A., Sacchi, A., Bacchetti, S., Capogrossi, M. C., & Farsetti, A. (2005). Telomerase mediates vascular endothelial growth
D
factor-dependent responsiveness in a rat model of hind limb ischemia. Journal of Biological
TE
Chemistry, 280, 14790-14798.
Zaffaroni N, L. S., Villa R, Bellarosa D, Cermele C, Felicetti P, Rossi C, Orlandi L, Daidone MG.
AC CE P
(2002). Inhibition of telomerase activity by a distamycin derivative: effects on cell proliferation and induction of apoptosis in human cancer cells. Eur J Cancer, 38, 1792-1801.
Zaug, A. J., Crary, S. M., Jesse Fioravanti, M., Campbell, K., & Cech, T. R. (2013). Many disease-associated variants of hTERT retain high telomerase enzymatic activity. Nucleic Acids Res, 41, 8969-8978.
Zaug, A. J., Podell, E. R., & Cech, T. R. (2008). Mutation in TERT separates processivity from anchor-site function. Nature Structural & Molecular Biology, 15, 871-872. Zhang, B., Qian, D., Ma, H. H., Jin, R., Yang, P. X., Cai, M. Y., Liu, Y. H., Liao, Y. J., Deng, H. X., Mai, S. J., Zhang, H., Zeng, Y. X., Lin, M. C., Kung, H. F., Xie, D., & Huang, J. J. (2012). Anthracyclines disrupt telomere maintenance by telomerase through inducing PinX1 ubiquitination and degradation. Oncogene, 31, 1-12. Zhang RG, G. L., Wang XW, Xie H. (2002). Telomerase inhibition and telomere loss in BEL-7404 human hepatoma cells treated with doxorubicin. World J Gastroenterol, 8, 827-831. Zhang, W., Tong, Q., Li, S., Wang, X., & Wang, Q. (2008). MG-132 inhibits telomerase activity, 82
ACCEPTED MANUSCRIPT induces apoptosis and G(1) arrest associated with upregulated p27kip1 expression and downregulated survivin expression in gastric carcinoma cells. Cancer Invest, 26, 1032-1036. Zhang, W., & Xing, L. (2013). RNAi gene therapy of SiHa cells via targeting human TERT induces
PT
growth inhibition and enhances radiosensitivity. International Journal of Oncology, 43, 1228-1234.
RI
Zhang, W. J., Ou, T. M., Lu, Y. J., Huang, Y. Y., Wu, W. B., Huang, Z. S., Zhou, J. L., Wong, K. Y., &
SC
Gu, L. Q. (2007). 9-Substituted berberine derivatives as G-quadruplex stabilizing ligands in telomeric DNA. Bioorg Med Chem, 15, 5493-5501.
NU
Zhang X, L. B., de Jonge N, Björkholm M, Xu D. (2015). The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase
MA
over-expression. Oncotarget, 6, 4888-4900.
Zhang, X., Li, B., de Jonge, N., Bjorkholm, M., & Xu, D. (2015). The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase
D
over-expression. Oncotarget, 6, 4888-4900.
TE
Zhang, Y., Sun, M., Shi, W., Yang, Q., Chen, C., Wang, Z., & Zhou, X. (2015). Arsenic trioxide suppresses transcription of hTERT through down-regulation of multiple transcription factors
AC CE P
in HL-60 leukemia cells. Toxicol Lett, 232, 481-489.
Zhang, Y., Toh, L., Lau, P., & Wang, X. (2012). Human telomerase reverse transcriptase (hTERT) is a novel target of the Wnt/beta-catenin pathway in human cancer. J Biol Chem, 287,
32494-32511.
Zhang, Y., Zhan, Y., Zhang, D., Dai, B., Ma, W., Qi, J., Liu, R., & He, L. (2014). Eupolyphaga sinensis walker displays inhibition on hepatocellular carcinoma through regulating cell growth and metastasis signaling. Sci Rep, 4, 5518. Zhao, Q., Yang, Y., Yu, J., You, Q. D., Zeng, S., Gu, H. Y., Lu, N., Qi, Q., Liu, W., Wang, X. T., & Guo, Q. L. (2008). Posttranscriptional regulation of the telomerase hTERT by gambogic acid in human gastric carcinoma 823 cells. Cancer Lett, 262, 223-231. Zhao, T. D., Hu, F. C., Qiao, B., Chen, Z. F., & Tao, Q. (2015). Telomerase reverse transcriptase potentially promotes the progression of oral squamous cell carcinoma through induction of epithelial-mesenchymal transition. International Journal of Oncology, 46, 2205-2215. Zhao, Y.-Q., Feng, H.-W., Jia, T., Chen, X.-M., Zhang, H., Xu, A.-T., Zhang, H.-L., & Fan, X.-L. 83
ACCEPTED MANUSCRIPT (2014). Antiproliferative Effects of Celecoxib in Hep-2 Cells through Telomerase Inhibition and Induction of Apoptosis. Asian Pacific Journal of Cancer Prevention, 15, 4919-4923. Zhao, Y. M., Zhou, Q., Xu, Y., Lai, X. Y., & Huang, H. (2008). Antiproliferative effect of rapamycin on
PT
human T-cell leukemia cell line Jurkat by cell cycle arrest and telomerase inhibition. Acta Pharmacol Sin, 29, 481-488.
RI
Zhou C, G. P., Whang YE, Boggess JF. (2003). Rapamycin inhibits telomerase activity by decreasing
SC
the hTERT mRNA level in endometrial cancer cells. Mol Cancer Ther, 2, 789-795. Zhou, J. M., Zhu, X. F., Lu, Y. J., Deng, R., Huang, Z. S., Mei, Y. P., Wang, Y., Huang, W. L., Liu, Z. C.,
NU
Gu, L. Q., & Zeng, Y. X. (2006). Senescence and telomere shortening induced by novel potent G-quadruplex interactive agents, quindoline derivatives, in human cancer cell lines. Oncogene,
MA
25, 503-511.
Zhou, L. L., Zheng, D. H., Wang, M., & Cong, Y. S. (2009). Telomerase reverse transcriptase activates the expression of vascular endothelial growth factor independent of telomerase activity.
D
Biochem Biophys Res Commun, 386, 739-743.
TE
Zhou, Q., Li, L., Xiang, J., Tang, Y., Zhang, H., Yang, S., Li, Q., Yang, Q., & Xu, G. (2008). Screening potential antitumor agents from natural plant extracts by G-quadruplex recognition and NMR
AC CE P
methods. Angew Chem Int Ed Engl, 47, 5590-5592.
Zhou XZ, H. P., Shi R, Lee TH, Lu G, Zhang Z, Bronson R, Lu KP. (2011). The telomerase inhibitor PinX1 is a major haploinsufficient tumor suppressor essential for chromosome stability in mice. J Clin Invest, 121, 1266-1282.
Zhou XZ, L. K. (2001). The Pin2/TRF1-interacting protein PinX1 is a potent telomerase inhibitor. Cell, 107, 347-359. Zhu, S., Rousseau, P., Lauzon, C., Gandin, V., Topisirovic, I., & Autexier, C. (2014). Inactive C-terminal telomerase reverse transcriptase insertion splicing variants are dominant-negative inhibitors of telomerase. Biochimie, 101, 93-103. Zhu, Y., He, W., Gao, X., Li, B., Mei, C., Xu, R., & Chen, H. (2015). Resveratrol overcomes gefitinib resistance by increasing the intracellular gefitinib concentration and triggering apoptosis, autophagy and senescence in PC9/G NSCLC cells. Sci Rep, 5, 17730. Zvereva, M. I., Zatsepin, T. S., Azhibek, D. M., Shubernetskaya, O. S., Shpanchenko, O. V., & Dontsova, O. A. (2015). Oligonucleotide inhibitors of telomerase: prospects for anticancer 84
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
therapy and diagnostics. Biochemistry (Mosc), 80, 251-259.
85
ACCEPTED MANUSCRIPT
PT
Figure Legends
RI
Fig. 1. Schematic representation of functional domains of hTERT and hTR. (A) Four
SC
functional domains of hTERT. The telomerase N-terminal (TEN) domain participates in catalysis and drives telomerase localization to telomeres. The TR-binding domain
NU
(TRBD) interacts with hTR. The reverse transcriptase (RT) domain and C-terminal extension (CTE) domain form the catalytic core of telomerase. The RT domain is
MA
similar to fingers domain (1-2) and palm domain (A-E), and the CTE is similar structure to thumb domain of conventional RTs. Motif 3 and IFD are telomerase
D
specific motifs. (B) Secondary structure of the hTR. hTR is composed of three
TE
functional domains. The template/pseudoknot and conserved region CR4/5 domains
AC CE P
bind to TERT and are essential for enzymatic activity. TBE composes of helix structure located upstream of the template. The H/ACA domain is dispensable for activity, it is essential for in vivo biogenesis, accumulation and RNP assembly. Fig. 2. A schematic drawing of telomerase catalytic cycle for processive repeat addition. The human telomerase enzyme binds to the telomeric DNA substrate and adds DNA repeats (GGTTAG)n to the DNA primer by copying the template sequence (5’-CUAACCCUAAC-3’) from the intrinsic hTR component. After reaching the end of the template, the DNA substrate reanneals the alignment region to regenerate the template for next round of extension. Until now, the process is complex and unclear, only a few models try to explain the mechanism of the template translocation process. Model 1. RNA/DNA duplex binding to telomerase active site determines the template translocation efficiency; model 2. DNA conformational rearrangement during telomerase catalytic cycle; model 3. DNA hairpin model for telomeric repeat addition. 86
ACCEPTED MANUSCRIPT Fig. 3. A model of telomerase RNP biogenesis and potential targets of telomerase for anti-tumor drugs. hTERT protein expression follows the canonical eukaryotic
PT
transcription, RNA maturation and nuclear export to the cytoplasm for translation. The hTERT protein is imported back into the nucleus and localizes to the nucleolus
RI
prior to assembly with the hTR. The hTR precursor, synthesized by RNA polymerase
SC
II and TMG capped, is bound by two copies of the protein complex for localization of the mature hTR to Cajal bodies. hTERT localizes to Cajal bodies for assembly with
NU
the hTR, aiding by the chaperone proteins hsp90 and p23. The fully assembled active
MA
telomerase complex localizes to the telomere. The potential targets are mainly as followed: ① inhibition of the hTERT gene transcription; ② degradation of primary
D
transcript form of hTERT mRNA; ③ dominant negative hTERT or post-translation
TE
modification of hTERT; ④ inhibition the nuclear localization of hTERT; ⑤
AC CE P
inhibition of hTR gene transcription; ⑥ degradation of the primary transcript and affecting the maturation of the hTR primary transcript; ⑦ disturbance of telomerase complex assembly; ⑧ blocking enzymatic activity of assembled telomerase complex; ⑨ repression of the expression of the shelterin protein or inhibition the interaction of the telomerase with the complex; ⑩ inhibition of telomerase complex interacting with telomeres and decreased availability of telomere ends for telomerase.
87
Fig. 1
AC CE P
TE
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
88
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
Fig. 2
89
Fig. 3
AC CE P
TE
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
90
PT
ACCEPTED MANUSCRIPT
Table 1. Overreview of natural anti-tumor compounds targeting telomerase from plants
Compounds
RI
Target location Plant source
Mechanism of action
NU
Targeting hTERT Inhibition of the Epigallocatechin Camellia sinensis
Binding competitively at the active site of hTERT
MA
catalytic function gallate
Boldine
Peumus boldus
(S. C. Lin, et al., 2006; S. H. Naasani I, Tsuruo T., 1998; Nagle, Ferreira, & Zhou, 2006) (Kazemi Noureini & Tanavar,
PT ED
Suppression of
Inhibition of hTERT expression
transcriptional
2015)
Inhibition of transcription of hTERT through
Triptolide
CE
and post transcriptional
Ref.
SC
of telomerase
Tripterygium wilfordii
AC
regulation
down-regulation of transcription factor specificity
(Long, et al., 2015)
protein 1 (Chakrabarti, Banik, & Ray, 2013;
Common fruits and
Down-regulation of telomerase activity by
vegetables
suppression of c-Myc-mediated hTERT expression
Apigenin
Jayasooriya, et al., 2012; Kang, 1998) Down-regulation of telomerase activity and hTERT
Papaverine
Papaveraceae
(Noureini & Wink, 2014) expression
91
Crocus sativus L.
Down-regulation of hTERT expression
Cephalotaxus
Asian coniferous evergreen
alkaloids
trees Cephalotaxus sp.
RI
Crocin
PT
ACCEPTED MANUSCRIPT
SC
Down-regulation of hTERT transcription
(Noureini & Wink, 2012)
(J. L.-Y. Chen, et al., 2011)
Down-regulation of the telomerase activity and
Butylidenephthal
NU
Angelica sinensis ide
(P. C. Lin, et al., 2011)
hTERT expression
Cruciferous vegetables
MA
Down-regulation of the telomerase activity and Indole-3-carbinol
(Adler, Rashid, & Klein, 2011)
Glycoprotein Laminaria japonica LJPG
CE
The flavonoid family,
PT ED
hTERT mRNA expression
Down-regulation of hTERT expression
(Han, et al., 2011)
including commonly ingested fruits and
AC
Quercetin
(J. L.-Y. Chen, et al., 2011; A. K. Down-regulation of hTERT gene expression Verma & Pratap, 2010)
vegetables such as red onion and also tea and red wine Tanshinone I
Salvia miltiorrhiza
Helenalin
Arnica montana
Down-regulation of hTERT expression
(X. D. Liu, et al., 2010)
Down-regulation of hTERT transcription through (J. L.-Y. Chen, et al., 2011) inhibition of NF-kB
92
PT
ACCEPTED MANUSCRIPT
Inhibition of hTERT, human telomerase-associated Scutellaria baicalensis
protein 1 (hTP1) and c-myc messenger ribonucleic
RI
Wogonin
(S. T. Huang, et al., 2010)
SC
acid (m-RNA) expression
NU
Down-regulation of hTERT transcription via inhibition of the transcription activator c-myc, and Garcinia hurburyi tree
by the inhibition of the phosphorylation of Akt;
MA
Gambogic acid
(Han QB, 2009; J. Yu, et al., 2006)
downregulates the activity of hTERT in a
Secondary plant metabolites
Curcumin
AC
CE
Genistein
PT ED
post-translational manner (Jagadeesh, Kyo, & Banerjee, 2006;
Down-regulation of hTERT expression
Y. Li, Liu, Andrews, & Tollefsbol, 2009)
Inhibition of telomerase activity and hTERT
(Mukherjee Nee Chakraborty, et al.,
expression
2007; Singh & Singh, 2009)
Curcuma longa
Inhibition of telomerase activity, reduction of
Costunolide
hTERT mRNA and protein levels, decreasing the
(S. H. Choi, et al., 2005; Kanno S,
bindings of transcription factors in hTERT
2008)
Magnolia sieboldii
promoters
93
PT
ACCEPTED MANUSCRIPT
Inhibition of telomerase activity with (Draisci, Lucentini, Giannetti,
Pectenotoxin-2
RI
down-regulation of hTERT expression, attenuating Dinophysis fortii
Boria, & Poletti, 1996; M. O. Kim,
SC
the binding of c-Myc and Sp1 to the regulatory et al., 2008)
NU
regions of hTERT
Inhibition telomerase activity with down-regulation Ginsenoside Rk1
Sun Ginseng
(Y. J. Kim, et al., 2008)
(Z)-Stellettic
MA
of levels of hTERT and c-Myc mRNA Down-regulation of the telomerase activity and the Marine sponge Stelletta sp.
Dideoxypetrosyn
Down-regulation of the telomerase activity and the
Marine sponge Petrosia sp.
Reduction of hTERT mRNA levels
(Sun L, 2003; Ye Y, 2005)
AC
Garlic (Allium sativum) ajoene
(C. Park, Jung, Kim, & Choi, 2007)
hTERT expression
CE
ol A Allicin and
(C. Park, Kim, et al., 2007)
hTERT expression
PT ED
acid C
Hellbore (Veratrum
grandiflorum O. Loes), Down-regulation of the telomerase activity and the Resveratrol
peanuts (Arachis hypogeal),
(Aggarwal BB, 2004) nuclear levels of hTERT
legumes (Cassia sp.) and grapes (Vitis vinifera)
94
PT
ACCEPTED MANUSCRIPT
Silybum marianum (L.)
Down-regulation of the telomerase activity and the
(Thelen, Wuttke, Jarry, Grzmil, &
Gaertn
mRNA levels of hTERT
Ringert, 2004)
RI
Silibinin
Inhibition of telomerase activity with translocation Gossypol
SC
Translocation Cottonseed
(Moon, et al., 2008)
(Draisci, et al., 1996; M. O. Kim, et
phosphorylation and nuclear translocation of hTERT
al., 2008)
Secondary plant metabolites
Disturbance in the translocation of hTERT to the
(Jagadeesh, et al., 2006; Y. Li, et
nucleus
al., 2009)
MA
Genistein
Inhibition of telomerase activity with reducing the Dinophysis fortii
PT ED
Pectenotoxin-2
NU
into the nucleus
Post translational
Inhibition of telomerase activity with
Gossypol
Cottonseed
(Moon, et al., 2008)
down-regulation of hTERT phosphorylation
Inhibition of Silymarin
Inhibition of telomerase activity and
Broccoli and cauliflower
AC
Sulforaphane
CE
modification
Silybum marianum
(Moon, et al., 2010) posttranslational modification of hTERT (Faezizadeh Z, 2012; Yurtcu E, Inhibition of telomerase activity
telomerase
2015)
activity
Metabolites of sulforaphane MTBITC(erucin)
(Mechanism is unclear)
Inhibition of telomerase activity
(Herz, et al., 2014)
Inhibition of telomerase activity
(H. T. Warabi K, Nakao Y,
from broccoli Axinelloside A
marine sponge Axinella
95
PT
ACCEPTED MANUSCRIPT
Salvia miltiorrhiza
Inhibition of telomerase activity
SC
Tanshinone IIA
RI
infundibula
Dictyodendrins
NU
Marine sponge Dictyodendrilla
Matsunaga S, Hirota H, van Soest RW, Fusetani N., 2005) (Song, 2005)
(M. S. Warabi K, van Soest RW,
Inhibition of telomerase activity
MA
verongiformis
Fusetani N., 2003)
Cladonia furcate
Inhibition of telomerase activity
(X. Lin, et al., 2003)
Berbamine
Berberis vulgaris
Inhibition of telomerase activity
(Ji ZN, 2002)
Inhibition of telomerase activity
(Giridharan, et al., 2002)
7'-hydroxy-3',4',5 ,9,9'-pentametho
CE
Phyllanthus urinaria
Targeting hTR Transcriptional
AC
xy-3,4-methylen e dioxy lignan
PT ED
Lichenin CFP -2
Tabebuia avellanedae
Inhibition of telomerase activity, down-regulation of
(Lapacho tree)
the levels of hTR and c-myc expression
Beta-Lapachone level
(Woo & Choi, 2005)
Targeting the telomerase substrate and associated protein Competitor for
Epigallocatechin
Camellia sinensis
Binding competitively with respect to the RNA
96
(S. C. Lin, et al., 2006; S. H.
substrate primer
RI
gallate
G4
Naasani I, Tsuruo T., 1998; Nagle, et al., 2006)
Inhibition of telomerase activity and interaction with Daidzin
SC
substrate
PT
ACCEPTED MANUSCRIPT
Soybeans G4
NU
DNA-interactive compounds Coptidis rhizoma
North American herb bloodroot (Sanguinaria canadensis) Daurisoline,
CE
Menispermum dauricum and dauricinoline and
AC
Rhizoma Menispermi daurinoline
2008)
(Bai, Hagihara, Jiang, & Nakatani,
Formation of C-myc22 G4 and Hum24 G4
PT ED
Sanguinarine
(Ji, et al., 2012; Q. Zhou, et al.,
Formation of C-myc22 G4 and Hum24 G4
MA
Palmatine
(W. Li, et al., 2006; Rafii, 2015)
2008; Ji, et al., 2012)
Induction the formation of G4 as well as increase the
(Ji, et al., 2012; Q. Liu, Mao, Zeng,
stabilization of G4
Jin, & Yang, 2012; Pan X, 1998)
Berberis vulgaris chinensis
Interaction with G4 preference for G4 over duplex
(Coptis or goldenthread)
DNA
Cryptolepine
Cryptolepis triangularis
Interaction with G4
(Guittat, et al., 2003)
Shikonin and its
Boraginaceae family Interaction with G4
(Lu Q, 2002)
derivatives
(mainly in the genus of
Berberine
(Franceschin, et al., 2006)
97
PT
ACCEPTED MANUSCRIPT
RI
Alkanna,Lithospermum) Okinawan tunicate Didenum
Stabilization of G4 and inhibition of telomerase
sp.
activity
Ascidian Amphicarpa
Inhibition of telomerase activity and stabilization of
meridian
G4
NU
AC
CE
PT ED
MA
Meridine
(Jun'ichi Kobayash, 1988)
SC
Ascididemin
98
(Francis J. Schmitz, 1991)
PT
ACCEPTED MANUSCRIPT
Compounds
SC
Target location of Microbial source
Mechanism of action
Ref.
NU
telomerase Targeting hTERT
An unwinder of DNA/RNA duplex formed by mtelomerase Pif1 helicase
Saccharomyces cerevisiae
(Paeschke, et al., 2013)
RNA and telomeric DNA
Wortmannin
transcriptional and
Penicillium funiculosum Streptomyces
Rapamycin hygroscopicus
regulation Trichostatin A
AC
post transcriptional
Competitive interact ion with the hTERT and subunits of
(Kiran, et al., 2015; Ueno T,
telomerase enzyme
2000)
Down-regulation of hTERT expression
(Kiran, et al., 2015)
Streptomyces collinus
CE
Rubromycins
PT ED
catalytic function
MA
Inhibition of the
Suppression of
RI
Table 2. Overreview of tumor inhibitors targeting telomerase from microbial sources
Inhibition of telomerase enzyme and down-regulation of (Sundin, Peffley, & Hentosh, hTERT mRNA level
2013)
Eliciting Smad3, Mad1 gene expression and leading to the
Streptomyces platensis
(Rahman, et al., 2010) down-regulation of hTERT
Chromobacterium FR901228
Down-regulation of hTERT expression
(Murakami, et al., 2005)
violaceum Eicosapentanoic
Shewanella
Inhibition of telomerase enzyme; reducing the expression of (Eitsuka, et al., 2005; Hirota,
99
pneumatophore
c-myc gene and hTERT expression
Docosahexanoic Crypthecodinium cohnii
Hsp90 ligand conjugates, inhibition of telomerase catalytic
(DeBoer C, 1970; Roe, et al.,
hygroscopicus
activity
NU
MA
and Neocosmospora
2015; Villa, et al., 2003)
(Chiu, et al., 2011; Compton,
Hsp90 activity inhibitor and inhibition of telomerase enzyme
PT ED
tenuicristata Inhibition of
2005;
Streptomyces
Pochonia chlamydosporia Radicicol
al.,
Ratledge C, 2001)
Geldanamycin of hTERT protein
et
c-myc gene and hTERT expression
SC
acid Molecular folding
et al., 2005)
Inhibition of telomerase enzyme; reducing the expression of (Eitsuka,
RI
acid
PT
ACCEPTED MANUSCRIPT
Griseorhodins A Streptomyces californicus
et al., 2006)
(Kiran, et al., 2015; Ueno, et
Inhibition of telomerase enzyme
and C
(Mechanism is
and Streptomyces griseus Actinoplanes
Purpuromycin ianthinogenes
Alterperylenol
AC
unclear)
CE
telomerase activity
Alternaria sp.
al., 2000) (Kiran, et al., 2015; Ueno T,
Inhibition of telomerase enzyme 2000) (Kiran,
et
al.,
2015;
Inhibition of telomerase enzyme Toshikatsu Okuno, 1983) (Nakai, et al., 2006; Nakai R,
Chrolactomycin
Streptomyces sp.
Inhibition of telomerase enzyme 2001)
UCS1025A
Fungus Acremonium sp.
Inhibition of telomerase enzyme
100
(Agatsuma T, 2002; Nakai, et
Talaromyces flavus
Inhibition of telomerase enzyme
Streptomyces anulatus
Inhibition of telomerase enzyme and stabilization of G4
(Rezler, et al., 2005; Shin-ya
3533-SV4
DNA
K, 2001)
Inhibition of telomerase enzyme by G4 binding
(Clark GR, 2003)
Interaction of G4
(Cocco MJ, 2003)
Telomestatin
Streptomyces peucetius
Distamycin A
Streptomyces distallicus
Rubromycins
Streptomyces collinus
AC
telomere-associated
CE
Daunomycin
Target
(Togashi, et al., 2001)
(Tabata Y, 1999)
MA PT ED
Targeting hTR
compounds
et al., 2001)
Inhibition of telomerase enzyme
acid
interactive
(Kitahara N, 1981; Togashi,
Acremonium sp.
Diazaphilonic
G4 DNA
al., 2006)
Inhibition of telomerase enzyme
SC
CRM646-A
Thielavia terricola
NU
Thelavin B
RI
PT
ACCEPTED MANUSCRIPT
Competitive interact ion with the hTR subunits of telomerase (Kiran, et al., 2015; Ueno T, enzyme
2000)
proteins
(D. Gomez, et al., 2006; Inducing dissociation of TRF2 and POT1 proteins by Telomestatin
Streptomyces anulatus 3
Rezler, et al., 2005; Shin-ya initiating the DNA damage response K, 2001; Tauchi, et al., 2003)
101
AC
CE
PT ED
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
102
PT
ACCEPTED MANUSCRIPT
RI
Table 3. Summary of laboratorial or preclinical studies of synthetic tumor inhibitors targeting telomerase
SC
Target location of Compounds
Mechanism of action
NU
telomerase Targeting hTERT BIBR1532
Inhibition of telomerase function by disrupting TERT-RNA binding
MA
Inhibition of the catalytic function
Ref.
(Bryan, et al., 2015)
Binding well with the telomerase active site and inhibitory activity
PT ED
Aryl-2H-pyrazole, 16A
(Luo, et al., 2013)
for telomerase
TELIN
2007)
Inhibiting the capping and catalytic functions of telomerase.
AC
BRACO-19
(Rangarajan & Friedman,
Inhibition of telomerase by targeting RNA/DNA heteroduplex
CE
5-benzylic acid ethidium derivative
(Burger, et al., 2005) (Kakiuchi, Sasaki,
A Specific potent catalytic blocker of telomerase and Inhibiting
Satoh-Masuoka, Murofushi,
telomerase activity
& Murakami-Murofushi, 2004)
Suppression of
Riccardin D
Inhibition of telomerase activity and down-regulation of hTERT
103
(Sun CC, 2014)
DIMA
Inhibition of telomerase activity and hTERT transcript levels
post transcriptional
Anthra[1,2-d]imidazole-6,11-dione
regulation
derivatives: 16, 39, and 40
RI
transcriptional and
PT
ACCEPTED MANUSCRIPT
SC
Down-regulation of hTERT expression
Inhibition of telomerase activity, hTERT mRNA expression and
NU
CDDO-Me
MA
hTERT regulatory proteins (c-Myc, Sp1, NF-κB and p-Akt)
BIBR1532
(V. Verma, et al., 2014)
(C. L. Chen, et al., 2013)
(Deeb, et al., 2013; Y. Liu, et al., 2012) (Bashash, et al., 2013; El
Down-regulation of c-Myc and hTERT expression Daly & Martens, 2007)
Down-regulation of hTERT mRNA expression
(Kasiappan, et al., 2012)
2'-hydroxy-2,3,4',6'-tetramethoxych
Inhibition of telomerase activity and the expression of hTERT, and
(Y. K. Rao, Kao, Wu, Ko, &
alcone
decrease of the hTERT promoter
Tzeng, 2010)
Trichostatin A
CE
Scriptaid
AC
4-hydroxynonenal
PT ED
1,25-dihydroxyvitamin D3
Inhibition of telomerase activity and hTERT expression
(Pizzimenti, et al., 2010)
Inhibition of telomerase activity
(Sharma, et al., 2010)
Repression of hTERT via recruitment of CTCF to the promoter
(J. H. Choi, et al., 2010)
Inhibition of telomerase activity by decreasing the hTERT expression
(Rabi & Banerjee, 2009)
Decrease of telomerase activity associated with a rapid decrease in
(Phipps, Love, White,
histone H3-lysine 9 acetylation (H3-K9-Ac) of the hTERT promoter
Andrews, & Tollefsbol,
Methyl-25-hydroxy-3-oxoolean-12en-28-oate
All-trans retinoic acid
104
RI
PT
ACCEPTED MANUSCRIPT
2009) (Moriai, Tsuji, Kobayashi,
Down-regulation of hTERT mRNA expression, repression the
SC
15d-PGJ2
Kuribayashi, & Watanabe,
NU
DNA-binding of c-Myc, Sp1 and ER to the hTERT gene promoter 2009)
Inhibition of telomerase activity involved in decreasing the Triethylene tetramine
(J. Liu, et al., 2008)
MA
expression of hTERT
Down-regulation of hTERT transcriptional level
(Lin CP, 2007)
Down-regulation of hTERT-mRNA transcript levels and reduction of
(Bermudez, Ahmadi, Lowell,
hTERT promoter activity
& Kruk, 2007)
PT ED
10058-F4
Vitamin E
CE
Inhibition of telomerase activity, down-regulation of hTERT mRNA
1,25-dihydroxyvitamin D3
and protein expression through suppression of hTERT transcriptional
AC
SC-236
(He, et al., 2006)
activity Decrease of the stability of hTERT mRNA
(Olaussen, et al., 2006)
BRACO-19
Reduction in hTERT expression and telomere dysfunction
(Burger, et al., 2005)
SR374, SR375, SR361and SR362
Hsp90 ligand conjugates, inhibition of telomerase catalytic activity
(Roe, et al., 2015)
INS1b, INS3 and INS4
Decreasing telomerase activity, telomere shortening, and an
(Killedar, et al., 2015; S.
Molecular folding of hTERT protein
105
PT
ACCEPTED MANUSCRIPT
increasing telomere-specific DNA damage response (DDR) Inhibition of telomerase activity and reduction of telomere length by DN-hTERT dominant-negative hTERT
SC
hTERT
RI
Dominant negative
Zhu, et al., 2014)
(Y. Rao, et al., 2014)
Translocation
NU
Displacement of hTERT from the nucleus, induction of RHPS4
(Phatak, et al., 2007;
Telomere-initiated DNA-damage signalling and chromosome fusions, Cookson, et al., 2005)
Inhibition of
MA
reduction in telomere length 4-methylthiobutyl isothiocyanate
Inhibition of telomerase activity
MST-312
Inhibition of telomerase activity
(Mechanism is SEW05920, SPB03924 and
(Serrano, et al., 2011)
CE
Inhibition of telomerase activity CD11359
(Wong, et al., 2013)
(F. C. Huang, K. F. Huang, et
Diaminoanthraquinone-linkedamin
AC
unclear)
(Gurung RL, 2014);
PT ED
telomerase activity
(Herz, et al., 2014)
Inhibition of telomerase activity
oacyl residue derivatives, B11
al., 2012) (Mizushina, Takeuchi,
β-Rubromycin
Inhibition of telomerase activity Sugawara, & Yoshida, 2012) (P. R. Huang, Yeh, Pao,
N-(1-Pyrenyl) maleimide
Inhibition of telomerase activity Chen, & Wang, 2012)
106
Inhibition of telomerase activity
Phenethyl isothiocyanate
Inhibition of telomerase activity
SC
RI
5-aza-2'-deoxycitidine
PT
ACCEPTED MANUSCRIPT
(Mukherjee, Bhattacharya, & Roy, 2009) (W. Zhang, Tong, Li, Wang,
Inhibition of telomerase activity
MA
NU
MG-132
(Tao, et al., 2012)
U-73122
& Wang, 2008) (Y. J. Chen, Sheng, Huang,
Inhibition of telomerase activity
Inhibition of telomerase activity and telomere erosion
PT ED
Salvcine
& Wang, 2006) (W. J. Liu, et al., 2004)
Inhibition of telomerase activity, telomere erosion followed by an (J. H. Kim, Lee, Kim, &
increased incidence of chromosome abnormalities and induction of Chung, 2003)
CE
2,3,7-trichloro-5-nitroquinoxaline
the senescence phenotype
Inhibition of telomerase activity, telomere erosion followed by the
(J. H. Kim, Lee, Lee, &
ne
induction of senescence phenotype
Chung, 2003)
Distamycin derivative, MEN 10716
Inhibition of telomerase activity
(Zaffaroni N, 2002)
Rhodacyanine derivative, FJ5002
Inhibition of telomerase activity by telomere shortening
AC
3-(3,5-dichlorophenoxy)-nitrostyre
(S. H. Naasani I, Yamori T, Tsuruo T., 1999) 2-[3-(trifluoromethyl)phenyl]isothia
Inhibition of telomerase activity
107
(Hayakawa, et al., 1999)
zolin-3-one Inhibition of telomerase activity
RI
9-hydroxyellipticine
PT
ACCEPTED MANUSCRIPT
SC
Targeting hTR Degradation/instabil
(Sato, et al., 1998)
Inhibition of telomerase activity and specific cleavage activity against
ity
NU
HDV ribozyme (g.RZ57)
(Lu Y, 2011)
the telomerase RNA
MA
Targeting the telomerase substrate and associated protein Carbazole-based benzimidazole
Higher affinity and excellent selectivity of ligands toward G4 DNA
compounds
dimers M2, D2, D3 and D4
over duplex DNA
Ruthenium(II) complexes:4
PT ED
G4 DNA-interactive
(Maji, et al., 2015)
Binding affinity to G4-DNA in telomere, effective stabilizers of
(Z. F. Chen, Q. P. Qin, J. L.
telomeric and G4-DNA in promoter of c-myc
Qin, J. Zhou, et al., 2015)
Inhibition of telomerase activity and interaction with telomeric,
(Z. F. Chen, Q. P. Qin, J. L.
with Oxoisoaporphine: Pt1 and Pt2
c-myc, and bcl-2 G4
Qin, Y. C. Liu, et al., 2015)
RHPS4
G4 interacting ligands
(Roe, et al., 2015)
Inhibition of telomerase activity and interaction with telomeric G4
(Ilyinsky, et al., 2014)
(S-enantiomer)
AC
Organoplatinum(II) Complexes
CE
(racemate), 5 (R-enantiomer) and 6
11-(3-aminopropylamino)-4-(2-gua nidinoethylamino)anthra[2,3-b]thio phene-5,10-dione, 13
108
Platinum(II) complex of liriodenine
PT
ACCEPTED MANUSCRIPT
G4 DNA stabilization
RI
Ruthenium(II) complexes: [Ru(IP)2
Induction of the stabilization of G4 DNA
SC
(PIP)](ClO4) 2 ·2H2O, [Ru(PIP) 2
NU
(IP)](ClO4) 2 ·2H2O (2) [(dmb)2Ru(obip)Ru(dmb)2]4+
Promote the formation and stabilization of G4 DNA
MA
Macrocyclic hexaoxazole
Interaction with G4 by π-stacking and electrostatic interactions L2H2-6 M(2)OTD
PT ED
Platinum(II) complexes: [PtL1(II)en](PF6)2,
Stabilizing h-telo,c-kit2, and c-myc G4, higher binding affinities to
[PtL2(II)en](PF6)2,
G4
BMVC4
Perylene diimides
(Q. Li, et al., 2014)
(Shi, et al., 2013)
(W. J. Chung, et al., 2013)
(Wei, et al., 2013)
CE AC
[PtL3(II)en](PF6)2
(Y. L. Li, et al., 2014)
(F. C. Huang, Chang, Wang,
G4 stabilizer Chang, & Lin, 2012) Telomerase inhibition and binding to G4 DNA
(D'Ambrosio, et al., 2012)
Inhibition of telomerase activity and stabilization of G4 DNA
(Yu Q, 2012)
Chiral Ruthenium(II) Polypyridyl Complexes: Λ-[Ru(phen)2 (p-HPIP)]2+ and∆-[Ru(phen)
109
2(p-HPIP)]
PT
ACCEPTED MANUSCRIPT
2+
Including telomere dysfunction through G4 stabilization
BRACO-19
High selectivity and affinity for G4 DNA
NU
SC
RI
TMPyP4
3,6-bis(1-methyl-4-vinylpyridinium
(Fujimori, et al., 2011) (Burger, et al., 2005; Debray, et al., 2009) (D. Y. Yang, Chang, & Sheu,
Inhibition of telomerase activity and stabilization of G4 DNA
MA
iodine) carbazole
2007)
Interaction with G4 and telomere shortening
(J. M. Zhou, et al., 2006)
Fluoroquinophenoxazine
Interaction with the telomeric G4 structure
(Duan, et al., 2001)
PT ED
SYUIQ-5
Targeting
POT1-binding ligand, interfering with the binding between Berberine derivative, Sysu-00692
(Xiao, et al., 2012)
human POT1 and the telomeric DNA
BIBR1532
(Bashash, et al., 2013;
Loss of telomeric repeat binding factor 2 (TRF2) Pascolo, et al., 2002)
AC
proteins
CE
telomere-associated
110
RI
Table 4. Summary of synthetic tumor inhibitors targeting telomerase in clinical trials or in clinic
Compounds
SC
Target location of Mechanism of action
Pharmacodynamic effects in Ref. clinic
NU
telomerase Targeting hTERT
5-azacytidine
MA
Inducing DNA damage and telomere dysfunction; Target S phase of the cycle
diminishing telomerase reverse transcriptase
PT ED
Inhibition of the
(Zhang X, 2015) specially
expression, reduction in telomere length Activating peroxisome
Inhibition of telomerase activity and Troglitazone
(Rashid-Kolvear, et al., proliferator-activated receptors
Arsenic trioxide
CE
down-regulation of mRNA hTERT expression
2010) (PPARs)
Reduction of hTERT at mRNA and protein levels
AC
catalytic function
PT
ACCEPTED MANUSCRIPT
Cytotoxic drugs
(Y. Zhang, et al., 2015)
Effective chemosensitizer
(Gan, et al., 2015)
Inhibition of telomerase activity and reduction in Suramin
telomere length Inhibition of telomerase activity and
Ubiquitin/proteasome pathway
down-regulation of hTERT expression; reduction in
inhibitor and NF-κB inhibition
Bortezomib
(Ci X, 2015)
111
telomere length; reduction in phosphorylation of the
PKCα Romidepsin
NU
Down-regulation of hTERT expression
MA
(FR901228)
Celecoxib
SC
RI
catalytic subunit of hTERT by its kinases, AKT and
PT
ACCEPTED MANUSCRIPT
(Kiran, et al., 2015; Histone deacetylase inhibitor Murakami, et al., 2005) COX-2 selective nonsteroidal
Down-regulation of hTERT mRNA level
(Y.-Q. Zhao, et al., 2014) anti-inflammatory drug
Nilotinib
PT ED
Down-regulation of hTERT gene transcription, Selective Bcr-Abl kinase
reduction of hTERT nuclear expression and
(Shapira, et al., 2012) inhibitor
Down-regulation of hTERT gene transcription,
Bcr-Abl tyrosine kinase
reduction of hTERT nuclear expression and
inhibitor and Src family tyrosine
inhibition of telomerase activity
kinase inhibitor
AC
Dasatinib
CE
inhibition of telomerase activity
(Shapira, et al., 2012)
Histone deacetylase inhibitors Inhibition of telomerase activity and by reducing the Vorinostat
for treatment of cutaneous T cell
(C. T. Li, et al., 2011)
expression of hTERT lymphoma Imatinib
Inhibition of telomerase activity caused mainly
112
Tyrosine kinase inhibitor
(Mor-Tzuntz, et al., 2010;
mesylate
PT
ACCEPTED MANUSCRIPT
downregulation of hTERT transcription by
selective for BCR-ABL
RI
post-translational
Uziel, et al., 2005)
SC
Modifications
down-regulation of the hTERT
MA
Inhibition of telomerase activity and
NU
Inhibition of telomerase activity and Gefitinib
Rapamycin
EGFR tyrosine kinase inhibitor
(Moon, et al., 2009)
(Y. M. Zhao, et al., 2008; m-TOR pathway inhibitor
down-regulation of hTERT mRNA level
Zhou C, 2003)
Aspirin
PT ED
Inhibition of telomerase activity, down-regulation of Non-steroidal anti-inflammatory
hTERT mRNA and protein expression through
(He, et al., 2006) drug
CE
suppression of hTERT transcriptional activity Inhibition of telomerase activity, down-regulation of Non-steroidal anti-inflammatory
hTERT mRNA and protein expression through
AC
Indomethacin
(He, et al., 2006) drug
suppression of hTERT transcriptional activity Involving in the circadian Inhibition of telomerase activity and
(Leon-Blanco, Guerrero,
Melatonin
rhythms of physiological down-regulation of TERT mRNA expression
Reiter, Calvo, & Pozo, 2003) functions
Temozolomide
Inhibition of telomerase activity and
Chemotherapy drug that
113
(Kanzawa, et al., 2003)
PT
ACCEPTED MANUSCRIPT
interfering with transcription factor Sp1 binding
Inhibition of telomerase activity by post translational
tumor cells (Brandt, Heller, Schuster, &
mediating via suppression of PKC-activity
modulator
Grote, 2005)
Perifosine
Inhibition of telomerase activity
AKT inhibitor
(Holohan B, 2015)
Treatment for rheumatoid
(N.-H. Kim, Park, Oh, &
Auranofin
Inhibition of telomerase activity
arthritis
Kim, 2013)
MA
medication Inhibition of
DNA and triggers the death of
Selective estrogen-receptor
Tamoxifen
telomerase activity
PT ED
(Mechanism is unclear)
Inhibiting the enzyme (Khorramizadeh, et al.,
Inhibition of telomerase activity
dihydrofolate reductase, 2007)
CE
Pyrimethamine
NU
Posttranslational
SC
sites of the hTERT core promoter
methylation caused damages the
RI
down-regulation of hTERT gene expression by
treatment for antimalarial drug
AC
Selective COX-2 inhibitor for
Inhibition of telomerase activity associated with the Nimesulide
(Baoping, Guoyong, Jieping, non-steroidal anti-inflammatory
attenuation of Akt/PKB activity
Zongxue, & Hesheng, 2004) drug (T. Brown, Sigurdson,
Azidothymidine
Inhibition of telomerase activity
Antiretroviral medication Rogatko, & Broccoli, 2003)
Octreotide
Inhibition of telomerase activity
Treatment of growth hormone
114
(Gao, Yu, Li, Dong, & Luo,
PT
ACCEPTED MANUSCRIPT
SC
Inhibition of telomerase activity
NU
levofloxacin
functions by inhibiting DNA
Kawahara, Kitajima, &
gyrase
Maruyama, 1997)
the levels of hTR and c-myc expression
inhibitor
(Woo & Choi, 2005)
PT ED
Involving in the circadian
Down-regulation of TR mRNA expression
rhythms of physiological
(Leon-Blanco, et al., 2003)
functions
CE
Melatonin
(Yamakuchi, Nakata,
Selective DNA topoisomerase I
Beta-Lapachone level
Broad-spectrum antibiotic that
Inhibition of telomerase activity, down-regulation of
MA
Transcriptional
2003)
RI
Ofloxacin and
Targeting hTR
producing tumors
Inhibition of telomerase activity, disabling Causing crosslinking of DNA
transcription of the telomerase-RNA encoding gene region
AC
Cisplatin
(Burger AM, 1997) and triggers apoptosis
Targeting the telomerase substrate and associated protein G4 DNA-interactive compounds
An antiprotozoal, antirheumatic Quinacrine
Binding affinity to G4-DNA
and an intrapleural sclerosing agent
115
(Sun, et al., 2012)
PT
ACCEPTED MANUSCRIPT
Targeting
Ubiquitin/proteasome pathway
Bortezomib
Dysregulation of shelterin protein expression
(Ci X, 2015)
inhibitor and NF-κB inhibition
RI
telomere-associated
NU
PT ED
MA
mRNAs reduction in TRF1, POT1, and TNKS1
CE
Doxorubicin
Topoisomerase inhibitor of
mRNAs reduction in TRF1, POT1, and TNKS1
AC
Etoposide
SC
proteins
116
(Kato, et al., 2013) cytotoxic anticancer drug An anthracycline antitumor (Kato, et al., 2013; B. Zhang, antibiotic with et al., 2012) intercalating DNA
S0163-7258(16)30039-0 doi: 10.1016/j.pharmthera.2016.03.017 JPT 6890
To appear in:
Pharmacology and Therapeutics
Please cite this article as: Chen, Y. & Zhang, Y., Functional and mechanistic analysis of telomerase: An anti-tumor drug target, Pharmacology and Therapeutics (2016), doi: 10.1016/j.pharmthera.2016.03.017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT P&T 22937
Title Page
School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province,
SC
a
RI
Yinnan Chenb, Yanmin Zhanga*
710061, P.R. China
School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
MA
NU
b
PT
Functional and mechanistic analysis of telomerase: an anti-tumor drug target
D
*Correspondence to:
TE
Dr Yanmin Zhang, Address: School of Pharmacy, Health Science Center, Xi’an Jiaotong University, No. 76, Yanta West Street, #54, Xi’an, Shaanxi Province 710061,
AC CE P
P.R. China
E-mail: [email protected] (YM. Zhang)
1
ACCEPTED MANUSCRIPT
Functional and mechanistic analysis of telomerase: an anti-tumor drug target Yinnan Chenb, Yanmin Zhanga∗ School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province,
PT
a
School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
SC
b
RI
710061, P.R. China
NU
ABSTRACT
The current research on anticancer drugs focuses on exploiting particular traits or
MA
hallmarks unique to cancer cells. Telomerase, a special reverse transcriptase, has been recognized as a common factor in most tumor cells, and in turn a distinctive
TE
D
characteristic with respect to non-malignant cells. This feature has made telomerase a preferred target for anticancer drug development and cancer therapy. This review aims
AC CE P
to analyze the pharmacological function and mechanism and role of telomerase in oncogenesis; to provide fundamental knowledge for research on the structure, function and working mechanism of telomerase; to expound the role that telomerase plays in the initiation and development of tumor and its relationship with tumor cell growth, proliferation, apoptosis and related pathway molecules; and to display potential targets of anti-tumor drug for inhibiting the expression, reconstitution and trafficking of the enzyme. We therefore summarize recent advances in potential telomerase inhibitors for anti-tumor including natural products, synthetic small molecules, peptides and proteins, which indicate that optimizing the delivery method and drug combination could be of help in a combinatorial drug treatment for tumor.
∗
Corresponding author at: School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi’an, Shaanxi Province, 710061, P.R. China. Tel.: +86 29 8265 6264; fax: +86 29 8265 5451. E-mail address: [email protected] (Y.M. Zhang) 2
ACCEPTED MANUSCRIPT More extensive understanding of the structure, biogenesis and mechanism of telomerase will provide invaluable information for increasing the efficiency of
PT
rational anti-tumor drug design.
AC CE P
TE
D
MA
NU
SC
RI
Keywords: Function; Mechanism; Telomerase; Drug Target; Tumor inhibitors
3
ACCEPTED MANUSCRIPT
Contents
PT
1. Introduction………………………………………………………………………6 2. Biological aspects of telomerase…………………………………………………8
RI
3. Role of telomerase in oncogenesis……………………………………………….15
SC
4. Potential biological aspects of telomerase as anti-tumor drug targets…………..19 5. Tumor inhibitors targeting telomerase…………………………………………...25
NU
6. Conclusions and perspectives……………………………………………………47
MA
Conflict of interest……………………………………………………………….….49 Acknowledgements……………………………………………………………….…49
AC CE P
TE
D
References……………………………………………………………………….…..50
4
ACCEPTED MANUSCRIPT
Abbreviations: TERT, telomerase reverse transcriptase; hTERT, human telomerase
PT
reverse transcriptase; RT, reverse transcriptase; TR, telomerase RNA; hTR, human
RI
telomerase RNA; RNP, ribonucleoprotein; TEN, essential N-terminal domain; TRBD,
SC
telomerase RNA binding domain; CTE, C-terminal extension domain; CR4/5, conserved region 4 and 5; TBE, template boundary element; ROS, reactive oxygen
growth
factor;
bFGF,
basic
fibroblast
growth
factor;
EMT,
MA
epidermal
NU
specie; G4, G-quadruplexes; ALT, alternative lengthening of telomeres; EGF,
epithelial-mesenchymal transition; TERRA, telomeric repeat-containing RNA; PKC,
protein
90;
ODN,
Antisense
oligodeoxynucleotides;
TE
shock
D
protein kinase C; HDAC, Histone deacetylases; MM, multiple myeloma; Hsp90, heat TAA,
Human
AC CE P
tumour-associated-antigens; CTL, cytotoxCLLic T lymphocytes; VCA, Viscum album L. coloratum agglutinin; CLL, lymphocytic leukemia; NSCLC, non-small cell lung cancer; mTOR, ammalian target of rapamycin; TRF1, telomeric repeat-binding factor 1; POT1, protection of telomeres; TNKS1, TRF1-interacting ankyrin-related ADP-ribose
polymerase
1;
DOX,
Doxorubicin;
RHPS4,
3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acri-dinium methosulfate; DNA-PK, DNA-dependent protein kinase; IR, immune response; Sp1, specificity protein 1; ER, estrogen receptor; GKN1, Gastrokine 1.
5
ACCEPTED MANUSCRIPT
1. Introduction
PT
Telomerase is a special reverse transcriptase enzyme that adds DNA repeats to the ends of chromosome to offset the loss (Greider & Blackburn, 1987). For the past
RI
few decades, since the discovery of telomerase, progress has been made in the
SC
identification of core components from evolutionary groups of species across eukaryotes, the catalytic telomerase reverse transcriptase (TERT) and telomerase
NU
RNA (TR). TERT contains the catalytic site for DNA synthesis and TR provides the
MA
template (Greider & Blackburn, 1989; Shippen-Lentz & Blackburn, 1990). A variety of accessory proteins, while dispensable for enzyme activity in vitro, play important
D
roles in regulation, biogenesis and localization (Egan & Collins, 2010; Podlevsky,
TE
Bley, Omana, Qi, & Chen, 2008).
Tumor cell growth is a complicated progression, which is regulated by multiple
AC CE P
factors including proliferation, cell cycle and apoptosis (Y. Zhang, et al., 2014). An increase in telomerase activity is often directly correlated with uncontrolled growth of cells, a known hallmark of cancer (Ruden & Puri, 2013). According to the Hanahan-Weinberg model of the hallmarks of cancer, to successfully achieve oncogenesis cancer cells have to: sustain proliferative signaling, evade growth suppressors, avoid immune destruction, enable replicative immortality, promote inflammation, activate invasion and metastasis, induce angiogenesis, establish genome instability, resist cell death and deregulate cellular energetics (Hanahan & Weinberg, 2011). The hallmark enabling replicative immortality demonstrates the ability to grow endlessly, synonymous with reactivation of TERT. Telomerase, and specifically its catalytic subunit TERT, is overactive in 85-90% of cancers and has become a widely acceptable tumor marker and a popular target for anticancer 6
ACCEPTED MANUSCRIPT therapeutics (Ruden & Puri, 2013). The discovery of the relationship between telomerase, telomeres, aging and tumors has broadened the avenue in tumor biology
PT
research (Calado & Young, 2009; Low & Tergaonkar, 2013). In humans, telomerase is inactive in most of the somatic cells, which stop division when their telomeres are
RI
critically short. This is known as replicative senescence. Most of the human cells
SC
cannot overcome the senescence and crisis, which restricts cell growth and protects against oncogenesis (Martinez & Blasco, 2011). Many human cells remain in the
NU
crisis period, as balance between cell growth and death, unless occasionally acquiring
MA
a mechanism such as up-regulation of telomerase. Cells that escape crisis can grow continuously and are usually characterized with telomere stability and telomerase activity (Feldser & Greider, 2007). This is believed to be a pivotal step in
TE
D
carcinogenesis (Mocellin, Pooley, & Nitti, 2013). Cancer cells that develop chromosomal aberrations show activation or re-activation of telomerase upon
AC CE P
exposure to a DNA damage signal, thereby bypassing cell cycle checkpoints and leading to uncontrolled growth and proliferation (Rankin, Faller, & Spanjaard, 2008; Tian, Chen, & Liu, 2010). In addition to the canonical role of maintaining telomere length in malignant cells, telomerase has also been recognized to take part in tumor promoting pathways. Telomerase activity is prominent in highly proliferative cells such as stem cells, germ line cells, as well as 90% of human cancers (N. W. Kim, et al., 1994), which makes it as a main target for cancer treatment. There are two general strategies of targeting telomerase in cancer treatment. One directly inhibits telomerase catalytic
activity
leading
to
telomere
shortening.
The
other
strategy
is
down-regulating the expression of the telomerase subunits or blocking the access of telomerase to its substrates. The current trend in research on anticancer drugs is to exploit particular traits 7
ACCEPTED MANUSCRIPT or hallmarks unique to cancer cells (Olaussen, et al., 2006). The ideal cancer treatment would target specifically at cancer cells but have a minimal adverse effect on the
PT
normal cells. This review highlights recent advances in our understanding of mammalian telomere biology, analyzing the functional and mechanism of telomerase
RI
and how it relates to cancer. Meanwhile, we discuss the current approaches that
2. Biological aspects of telomerase
NU
2.1. Structural and components of telomerase
SC
exploit this knowledge to develop novel anti-tumor drugs targeting telomerase.
MA
Telomerase is unique reverse transcriptase (RT) by functioning as a ribonucleoprotein (RNP). The catalytic core of telomerase is minimally composed of TERT and TR (Collins, 2006; Weinrich, et al., 1997). Between the two essential
TE
D
components of telomerase RNP complex, the catalytic TERT protein is highly conserved among all eukaryotes, while the TR is extremely divergent, suggesting that
AC CE P
telomerase initially emerges as a protein enzyme and acquires an integral RNA component during the early evolution of eukaryotes (Lingner, et al., 1997; Peng, Mian, & Lue, 2001; Podlevsky, et al., 2008). TERT is the catalytic component of the enzyme that comprises four conserved structural domains: the telomerase essential N-terminal domain (TEN), the telomerase RNA binding domain (TRBD), the RT domain and the C-terminal extension domain (CTE) (Fig. 1A) (Lingner, et al., 1997). The catalytic domains of TERT and other reverse transcriptases have the common and highly conserved motifs that form the active site for RNA-dependent DNA polymerization. The tertiary structure of TERT, similar to HIV RT, consists of the finger, palm and thumb domains (Lingner, et al., 1997; Peng, et al., 2001). The finger domain is composed of motifs 1 and 2, believed to bind incoming nucleotides. The palm domain is composed of motif A-E and forms the catalytic site. Between them there is motif 3, 8
ACCEPTED MANUSCRIPT unique to TERT, closely related to the property of the enzyme (Xie, Podlevsky, Qi, Bley, & Chen, 2010). Mutational analysis of the Asp residues from motifs A and C is
PT
evidence that the telomerase employs acidic metal-coordination by the aspartic acid for DNA polymerization, which is common to conventional RTs (Haering, Nakamura,
RI
Baumann, & Cech, 2000; Lingner, et al., 1997). The CTE in TERT binds to the RNA
SC
template/DNA primer duplex, sharing functionality with the HIV RT-C terminus referred to as the thumb domain (Peng, et al., 2001). The TEN and TRBD domains are
NU
telomerase specific and unique to TERT protein. The TEN domain contains anchor
MA
sites that bind to single strand telomeric DNA. Mutational analysis has identified it as related to the repeat addition processivity, which is the characteristic of telomerase, but not to nucleotide addition processivity (Sealey, et al., 2010; Zaug, Podell, & Cech,
TE
D
2008). According to the recently resolved the co-crystal structure of the TRBD with conserved regions 4 and 5 (CR4/5) of TR in teleost fish Oryzias latipes, as well as
AC CE P
crosslink data, TRBD contains RNA interacting domain which has a high affinity binding site for TR (Bley, et al., 2011; J. Huang, et al., 2014). The structure of TERT protein from Tribolium castaneum was solved in 2008 by Emmanuel Skordelakes et al (Gillis, Schuller, & Skordalakes, 2008). The challenge to get the crystal structure of human TERT (hTERT) is to determine how to purify highly concentrated protein. The crystal structure of hTERT could offer insight into research on the enzyme function, which provides a novel opportunity for rational drug design. Unlike conventional reverse transcriptase, telomerase contains its own template provided by the integral RNA component within the telomerase catalytic core (Feng, et al., 1995). The size, structure and sequence of TR are quite diverse among different species, however they all contain two conserved domains: the template/pseudoknot domain and CR4/5 domain (or three way junction/stem-terminus elements) (Fig. 1B). 9
ACCEPTED MANUSCRIPT These two domains are essential for telomerase activity. In fact, an active telomerase enzyme reconstituted in vitro only requires the TERT protein and these two excised
PT
elements from TR (Mitchell & Collins, 2000). The secondary structure of TR has implications for telomerase function (J. L. Chen, Blasco, & Greider, 2000). The
RI
template/pseudoknot domain contains template boundary element (TBE), the template
SC
region and pseudoknot.
TBE that is conserved across eukaryotes defines the template boundary physically.
NU
The hTR template region promotes base pairing with telomeric DNA, primer to each
MA
cycle of the DNA synthesis as well as contains pause signal for each round of repeats by a recent study (A. F. Brown, et al., 2014). The pseudoknot with a triple helix and part of it binds to the TERT protein (Fig. 1 B). The TR template/pseudoknot domain is
TE
D
a remarkably complex structure and its detailed mechanistic function remains unknown. The functional assay together with NMR structure analysis demonstrates
AC CE P
that the special triple helix and contained residues are essential for telomerase activity (N. K. Kim, et al., 2008; Theimer, Blois, & Feigon, 2005). It also indicates the interaction between the TERT protein and pseudoknot domain was crucial for the integrity of the enzyme (Jiang, et al., 2015; Wu & Collins, 2014). Further studies are required to analyze the detailed binding of this region with certain motifs in TERT and to understand how it contributes to the activity of telomerase. The other domain required for enzymatic activity is the CR4/5 domain in humans. CR4/5 is a major TERT binding site located far away from template/pseudoknot domain in the primary sequence as well as the secondary structure (Blackburn & Collins, 2011). It is a three way junction of stem-loops that has been shown interaction with TRBD domain of the TERT protein by UV-crosslinking analysis, as well as crystal structure in Oryzias latipes (medaka) (Bley, et al., 2011; J. Huang, et al., 2014). This secondary essential 10
ACCEPTED MANUSCRIPT TERT-binding element, despite structural variation, is retained throughout all eukaryotes and is essential or stimulatory for telomerase activity (X. D. Qi, et al.,
PT
2013). The homology model of the medaka telomerase RNP structure based on Tribolium castaneum TERT protein structure, which indicates that the stem-loop in
RI
CR4/5 is very close to the CTE domain in hTERT (Gillis, et al., 2008). However, the
SC
mechanism of regulation of the CR4/5 domain to the conformational change of the protein and activation of telomerase function has yet to be further studied. While the 5’
NU
of TR provides a defined template and stable assembly with the TERT protein, the 3’
MA
of the RNA has a variety of functions for TR biogenesis. H/ACA domain is a conserved region located at the 3’ end of TR in vertebrates (Mitchell, Cheng, & Collins, 1999). This domain contains two stem-loops separated by the box H/ACA
TE
D
moieties. The accessory proteins of telomerase such as dyskerin, NOP10, NHP2 and GAR1 bind to this region (Egan & Collins, 2010). Mutations in the H/ACA moieties
AC CE P
can abolish 3’ end processing of human telomerase RNA (hTR) and cause accumulation in nucleoli instead of Cajal bodies (Mitchell, Wood, & Collins, 1999; Venteicher, et al., 2009). In short, the H/ACA domain is important for biogenesis and localization of telomerase in vivo. TR is a highly complex non-coding RNA with special structural domains to adapt, incorporate distinct and unique mechanisms necessary and sufficient for assembly with the catalytic subunit TERT protein, and to regulate and impart telomerase enzymatic activity. Further research could elucidate the detailed mechanism of how TR and TERT interact with each other to maintain a functional and intrinsic component of the telomerase enzyme. 2.2. Functional aspects and working mechanism of telomerase Unlike conventional reverse transcriptases, telomerase reaction produces a long tract of telomeric DNA repeats from a single short RNA template in TR (Shippenlentz 11
ACCEPTED MANUSCRIPT & Blackburn, 1990). In brief, the telomerase catalytic cycle involves two major phases (Fig. 2). The first phase is nucleotide addition: the synthesis of a single
PT
telomeric DNA repeat to the 3’ end of telomeric primer base paired with template on TR. This process is similar to DNA polymerase. The second phase is repeat addition:
RI
the regeneration of the template of the synthesis of additional repeats. The processive
SC
synthesis of multiple telomere repeats from the same template to a given primer is unique for a polymerase and requires a special mechanism for the template
NU
regeneration. For human telomerase, the telomerase reaction initiates by forming
MA
RNA/DNA duplex before coming in the active site (X. D. Qi, et al., 2012). After six nucleotides 5’-GGTTAG-3’ are added on to the 3’ end of the DNA primer from the RNA template in the active site, nucleotide addition arrests waiting for next repeat
TE
D
synthesis or disassociation of the DNA product (W. Yang & Lee, 2015). Processive repeat addition requires the translocation of the RNA template after each cycle to
AC CE P
regenerate the template. This is a complicated multi-step process that is poorly understood. Several models have been set up to explain how telomerase works. For instance, Qi et al has proposed that the duplex dissociates from the active site when reaching the end of RNA template. Then the DNA primer realigns to the anchor site for template realignment or releasing the product. Parks & Stone hypothesized the favorable conformational rearrangements when reaching the template boundary and has tested it by single molecular fluorescence resonance energy transfer (Parks & Stone, 2014; X. D. Qi, et al., 2012). Most recently, Yang & Lee propose a DNA-hairpin model for telomeric-repeat addition, which explains that the telomeric DNA participates in repeat addition processivity and its conserved sequence throughout evolution (W. Yang & Lee, 2015). Some experiments like protein cross-linking, site directed mutagenesis and single molecular fluorescence resonance 12
ACCEPTED MANUSCRIPT energy transfer (FRET) within TERT or with TR can be designed to test and validate the predictions for each model for further deciphering the special working mechanism
PT
of the telomerase. 2.3. The expression of telomerase and RNP biogenesis
RI
For the past decades, intensive studies of telomerase in human cells have shown
SC
novel perspectives on the regulation of hTERT gene expression. Some evidence suggests that only hTERT is needed to restore the telomerase activity in
NU
telomerase-negative normal cells (Artandi, et al., 2002; Gonzalez-Suarez, et al., 2001;
MA
D. L. Qi, et al., 2011). The transcriptional control of hTERT is supposed to play a crucial role in the complex regulation of telomerase activity (Hahn, et al., 1999). The hTERT gene consists of 15 introns and 16 exons and over 40 kb in length. The 5’
TE
D
regulatory region contains numerous binding sites for a plenty of transcription factors from various signal pathways, such as TGF-b, PI3K/Akt, NF-κB, ErbB, MAPK, cell
AC CE P
cycle, among others (Daniel, Peek, & Tollefsbol, 2012; Gladych, Wojtyla, & Rubis, 2011). Activators of hTERT include some oncogenic transcription factors and hormones, which promote cell proliferation. Repressors of hTERT include tumor suppressors and some transcription factors that induce the senescence or apoptosis for the somatic cells. Meanwhile, epigenetic control and modulation of the hTERT promoter via methylation and acetylation, even with contradictory results, also play an essential role in regulation of hTERT, but further research is required to elucidate this mechanism (Daniel, et al., 2012). Splice variants of hTERT, whichassociated with risk of cancer, may be expressed in normal, pre-crisis and ALT cells with undetectable telomerase activity (Bojesen, et al., 2013; Ulaner, Hu, Vu, Giudice, & Hoffman, 1998). Post-transcriptional regulation of telomerase activity can occur via reversible phosphorylation of hTERT catalytic subunit at specific residues, such as 13
ACCEPTED MANUSCRIPT serine/threonine/tyrosine (D. L. M. Gomez, Farina, & Gomez, 2013). Some of the phosphorylation sites within hTERT protein influence telomerase activity (Haendeler,
PT
Hoffmann, Rahman, Zeiher, & Dimmeler, 2003; Selvam, et al., 2015). In short, the hTERT expression is regulated at both transcriptional and post-transcriptional levels
RI
with the alternative splicing of hTERT in the control of telomerase activity.
SC
It was previously believed that though hTERT is tightly regulated during the cellular differentiation and expressed at very low levels in normal somatic cells, hTR
NU
is widely express in the majority of cell types including those with negative
MA
telomerase activity. However, in some types of tumors, the hTR expression is more closely correlated to tumor grade and is a potential marker for prognosis (Soder, et al., 1997; Yashima, et al., 1997). The role of hTR has also been well studied in mouse
TE
D
models (Cairney & Keith, 2008). According to a recent paper from Linghe et al, overexpression of either hTR or hTERT could increase telomerase activity in vivo,
AC CE P
which indicates that their assembling into active telomerase is an equilibrium process (Xi & Cech, 2014). It can also explain that hTR levels are increased in tumor cells compared to normal cells, although hTR expression is detected in some tissue where hTERT is not. Transcription of hTR can be activated by Sp1 and HIF-1 and repressed by Sp3, which integrates cues from the MAPK signal cascade to silence the hTR promoter (Cifuentes-Rojas & Shippen, 2012). Furthermore, hTR transcription appears to be subjected to epigenetic control similar to hTERT. hTR begins as a precursor RNA polymerase II transcript capped by trimethyl-guanosine (TMG) (Feng, et al., 1995). The RNA helicase associated with AU-rich element resolves the G-quadruplexes (G4) at the 5’ end and other proteins to the 3’ end for trimming and modifying RNA to produce mature hTR (Lattmann, Stadler, Vaughn, Akman, & Nagamine, 2011). The initial binding of dyskerin to the hTR, other H/ACA snoRNA 14
ACCEPTED MANUSCRIPT species relies on the sequential binding of snoRNA H/ACA family quantitative accumulation 1 (SHQ1), followed by nuclear assembly factor 1 (NAF1) to dyskerin
PT
(Grozdanov, Roy, Kittur, & Meier, 2009). NAR1 is exchanged for GAR1 and SHQ1 is lost prior to the localization of mature hTR to Cajal bodies. TCAB1, together with
RI
other protein components, is thought to direct mature hTR to Cajal bodies (Kiss,
SC
Fayet-Lebaron, & Jady, 2010; Tomlinson, Li, Culp, Terns, & Terns, 2010). The detailed process and mechanism of the hTR accumulation remains unclear.
NU
Telomerase assembly could take place during S phase and it is probably
MA
disassembled during M phase (Wojtyla, Gladych, & Rubis, 2011). Throughout most of the cell cycle, TR is present in Cajal bodies; TERT, however, is located in distinct nucleoplasmic foci. Therefore, the two main subunits of telomerase are separated
TE
D
during the whole cell cycle. The CAB box and H/ACA motif within TR have been identified to influence the TR translocation of Cajal bodies and nucleoli. Similarly,
AC CE P
hTERT contains both nuclear localization signal and nuclear export signal for nuclear-cytoplasmic shuttling. Several studies have demonstrated that hTERT is associated with chaperone proteins heat shock protein 90 (Hsp90) and p23 for incorporation into an enzymatically active RNP containing hTERT in nucleus (Holt, et al., 1999). While the intricate details of telomerase RNP assembly have yet to be fully elucidated, much progress has been made to uncover the function of each component for assembling into an active ribonucleoprotein enzyme. Telomerase localizes to Cajal bodies for most of the cell cycle and factors involved in this process have been well studied and reviewed (Schmidt & Cech, 2015). Further studies need focus on understanding the physiological process of how hTR and hTERT accumulate to Cajal bodies, and elucidating the mechanism of Cajal bodies for telomerase trafficking. 3. Telomerase role in oncogenesis 15
ACCEPTED MANUSCRIPT 3.1. Potential for replication and integration of the genome Cancer is a disease of impaired genome stability (Hanahan & Weinberg, 2011). In
PT
theory, the molecular forces that maintain genome integrity should suppress the initiation of carcinogenesis. Telomerase extends telomeres to prevent replicative
RI
senescence by promoting genome stability and keeps the telomere from erosion. As
SC
previously discussed, telomerase may act preferentially on short telomeres (Hug & Lingner, 2006), which reduces their risk for acquiring a dysfunctional structure. Thus
NU
activation of telomerase might be protective and prevents telomere dysfunction. With
MA
tightly controlled expression in stem cells, telomerase can retard or prevent age-related pathology, including cancer, acting as a suppressor by ensuring genome stability and inhibiting mutations. Moreover, hTERT can regulate DNA damage signal
TE
D
by keeping histones from modification and decreasing mitochondrial reactive oxygen species (ROS) production, all of which may result in genome instability (Masutomi, et
AC CE P
al., 2005; Singhapol, et al., 2013). However, maintaining genome stability can be oncogenic as well. The telomere shortening can lead to apoptosis through the p53 dependent pathway (Artandi & DePinho, 2010). During tumor development, a wide range of studies show that genomes keep relative stability after telomerase is up-regulated. The up-regulation of serves to enhance proliferation of cancer cells by maintaining telomere sequences that ensure genome stability during cell division and prevent the cellular senescence or apoptosis induced by genomic instability. It could be the role of telomerase for cancer cells genome instability: suppression on the initiation and promotion on the development of carcinogenesis. 3.2. Non-canonical function of telomerase components It is believed that each hallmark of cancer is independently driven. Although elongation of telomeres is thought to be the prime function of reactivated telomerase 16
ACCEPTED MANUSCRIPT reverse transcriptase, there are other non-canonical functions of telomerase such as increasing cell proliferation, resistance to apoptosis and promotion of invasion (Low
PT
& Tergaonkar, 2013). Concomitant with telomerase activity, the component TERT is reactivated in cancer cells related closely to other hallmarks of cancer. Overexpression
RI
of TERT increases proliferation of mammary carcinomas and epidermal tumors
SC
without affecting telomere length (Broccoli, Godley, Donehower, Varmus, & deLange,
substitute for the telomerase function.
NU
1996). In humans, an ALT which could also maintain telomere length cannot fully
MA
3.2.1. Resistance to apoptosis and antigrowth signals TERT has been shown to be localized in mitochondria and inhibit caspase mediated apoptosis in cancer cells (Singhapol, et al., 2013). Meanwhile TERT can
TE
D
increase intracellular reduced glutathione/oxidized gultathine ratios, thus reducing intracellular ROS-induced apoptosis (Indran, Hande, & Pervaiz, 2011). Many studies
AC CE P
also demonstrate that hTERT could activate NF-κb for resistance of death-inducing stimuli (Low & Tergaonkar, 2013). Ectopic expression of TERT in mouse embryonic fibroblasts antagonized transforming growth factor (TGF)-β, which is a cytokine that inhibits growth of epithelial cells (Geserick, Tejera, Gonzalez-Suarez, Klatt, & Blasco, 2006). This indicates TERT may help cancer bypass antigrowth signals. Additionally, TERT has been shown to cause cells to bypass differentiation as a strategy for cancer cells proliferation. Another transcription factor Myc also contributes to the anti-growth signal in cancer cells. Not only is hTERT the transciption target of Myc but it can also activate the Myc induced tumorigenesis in vivo (Flores, Evan, & Blasco, 2006). Similar to oncogenic Wnt/β-catenin signaling, which hTERT positively regulated, overexpression of hTERT is able to help cell bypass differentiation (Y. Zhang, Toh, Lau, & Wang, 2012). 17
ACCEPTED MANUSCRIPT 3.2.2. Regulation of cell growth and proliferation TERT can stimulate proliferation of human epithelial cells by EGFR signaling
PT
(Smith, Coller, & Roberts, 2003). Epiregulin can be regulated by IL-1b and TNF-α, and neutralization of epiregulin compromise the growth of the cells, which indicates
RI
TERT might be a consequence of the NF-κb signal pathway. Meanwhile, it has been
SC
shown that the TERT could promote epithelial proliferation in hair follicles and skin cells through the Wnt and Myc signaling pathways. Human fibroblasts immortalized
NU
by overexpression of TERT, secrete epiregulin, which belongs to the epidermal
MA
growth factor (EGF) family (Lindvall, et al., 2003). The expression of an activity-deficient form of TERT also promotes cancer progression by up-regulation of EGFR in glioblastoma multiforme (Beck, et al., 2011). At the same time, studies show
TE
D
that the EGFR signal pathway could upregulate the expression of TERT by transcription factor Ets-2 in lung cancer cells (Hsu, et al., 2015). Overexpression of an
AC CE P
enzymatically inactive TERT has been demonstrated to inhibit differentiation and induce proliferation of glioma cells through upregulation of EGFR and basic fibroblast growth factor (bFGF), which is independent of its enzyme activity. In short, TERT seems to favor tumor growth by inhibiting anti-growth signals and suppressing differentiation.
3.2.3. Other effects of TERT on regulating hallmarks of cancer Studies show TERT could regulate NF-κb gene expression by recruiting a subset of transcription factors to the promoter that lead to cancer progression, and the blocking of NF-κb signal can inhibit telomerase overexpression (Ghosh, et al., 2012). The link between TERT and NF-κb is feed-forward regulation that is critical for inflammation and cancer. TERT has been reported to modulate angiogenesis as well. Xenografted 18
ACCEPTED MANUSCRIPT glioblastoma cells transfected with siRNA against TERT show that it reduces formation of microvessels and production of pro-angiogenic factor of vascular
PT
endothelial growth factor (VEGF) and bFGF (Falchetti, et al., 2008; L. L. Zhou, Zheng, Wang, & Cong, 2009). Further studies also indicate the TERT promoter can be
RI
activated by VEGF and bFGF via phosphoinositide 3-kinase pathway (Zaccagnini, et
SC
al., 2005). It has been hypothesized that TERT and VEGF potentially regulate the expression of each other, such as TERT could be a potential VEFG enhancer to
NU
promote angiogenesis (Hartwig, et al., 2012).
MA
The hTERT overexpression has been found promoting epithelial-mesenchymal transition, which is also regulated by Wnt/b-catenin signaling pathway (T. D. Zhao, Hu, Qiao, Chen, & Tao, 2015). Further studies show evidence for hTERT involvement
TE
D
in invasion and metastasis through activation of NF-κb signaling, which up-regulates matrix metalloproteinase (MMP)-9 and is critical for epithelial-mesenchymal
AC CE P
transition (EMT) (Fukuyama, et al., 2007). In short, telomerase plays a crucial role not only in maintaining telomere homeostasis that is an essential property for sustenance and progression of cancer, but its catalytic subunit hTERT has the cross-talk with signal cascade involved in proliferation, apoptosis, and differentiation in cancer cells. Some of the factors have a feed-forward regulatory loop mechanism with TERT, which makes it hard to interpret, but further investigation of the new interaction of TERT and other key factors of cancer may help to discover new targets for anti-cancer therapy, and provide useful information for rational drug combination therapy. 4. Potential biological aspects of telomerase as anti-tumor drug targets As a common factor in most tumor cells and in turn a distinctive characteristic with respect to somatic cells, telomerase is a promising target for cancer therapy. The 19
ACCEPTED MANUSCRIPT holoenzyme consists of TERT, TR and a six-protein complex known as shelterin protein complex. So the target of telomerase inhibitors can be classified according to
PT
biogenesis of the active enzyme as well as its components (Fig. 3). 4.1. Catalytic subunit of telomerase
RI
Targeting the hTERT catalytic subunit as anticancer therapy is theoretically
SC
tumor-specific and moderately toxic because of the expression in tumor and highly proliferating cells compared to other somatic cells. Since hTERT can act as cofactor
NU
to regulate NF-κB, Wnt and β-catenin signaling pathways, it provides therapeutic
MA
implications for the design of inhibitors. However, it is not clear how the activation of hTERT, which not only induces telomerase activity but influences other signaling cascades, may directly or indirectly regulate all hallmarks of cancer.
TE
D
The expression of TERT can be regulated by ontogenetic transcription factors so in theory any inhibitors of those factors or blocking certain signal pathways should be
AC CE P
able to decrease the expression of TERT (Daniel, et al., 2012). There are already some inhibitors targeting transcription factors to regulate the hTERT expression. Recently, DNA methyltransferase inhibitors, which can change chromatin structure of the hTERT gene promotor region, have been tested for down-regulation of the hTERT expression and induce telomere dysfunction exerting anti-tumor activity (X. Zhang, Li, de Jonge, Bjorkholm, & Xu, 2015). The messenger RNA of hTERT has been well studied as the target for the hTERT expression. The degradation of hTERT mRNA can be implied by antisense technology such as standard oligonucleotide as well as peptide nucleic acids (Folini, et al., 2007; Folini, et al., 2003). RNAi has been employed to degrade mRNA of hTERT recently (H. Xu, et al., 2015; W. Zhang & Xing, 2013). Ribozymes that are antisense RNAs possessing endoribonuclease activity are able to cleave target RNA 20
ACCEPTED MANUSCRIPT sequences. They have also been used to degrade mRNA of hTERT (J. Kim, et al., 2015).
PT
The post-translation modification of hTERT could also be the potential target for regulation of telomerase activity. The dominant negative hTERT can induce
RI
catalytically inactive enzyme and it has been demonstrated to decrease telomerase
SC
activity (Nguyen, Elmore, & Holt, 2009). Some antibiotics that suppress the chaperone proteins are able to impair maturation of hTERT and assembly of the
NU
holoenzyme. Furthermore, the phosphorylation of hTERT, a common type of
MA
post-translation modification, can regulate the distribution of TERT in cancer cells by some kinases (Ale-Agha, Dyballa-Rukes, Jakob, Altschmied, & Haendeler, 2014)). The mutations in hTERT nuclear localization signal have shown effects on telomerase
TE
D
activity, which confirmed the essential role of localization of the hTERT for the active enzyme (J. Chung, Khadka, & Chung, 2012). Therefore the trafficking of hTERT
AC CE P
from cytoplasm to nucleus could be a potential target for drug design even though the nuclear export signal on telomerase function has yet to be investigated. To inhibit the catalytic function of the hTERT subunit (loss of function), several inhibitors for RTs have been tested, such as nucleoside analogs 3’ azido-3’deoxythymidine and its derivatives (J. Wang, Wang, Chen, & Kwon, 2014), and enzyme inhibitors including FJ 5002 and BIBR1532 (Bryan, et al., 2015; S. H. Naasani I, Yamori T, Tsuruo T., 1999). hTERT can also be an attractive target for cancer immunotherapy, and the specificity expression in cancer cells enables it to become a target for this type of therapy (K. P. Patel & Vonderheide, 2004). In short, it is crucial to note that the role of TERT in carcinogenesis should not be viewed as either canonical or non-canonical. As the catalytic subunit of the enzyme, it keeps the length of telomeres, and takes part in the signal cascade related to the 21
ACCEPTED MANUSCRIPT proliferation, spreading and invasion of the cancer cells. All these reasons indicate hTERT is promising as a target of cancer therapy.
PT
4.2. Telomerase RNA Targeting the RNA component of telomerase is another effective strategy to
RI
repress the telomerase activity. hTR provides the template for the enzyme which is
SC
close to the active site of the enzyme and available for the incoming substrate. Recently Brown et al. shows the hTR template contains important information for
NU
regulating activity and fidelity of the enzyme (A. F. Brown, et al., 2014). Some
MA
previous studies have already shown that the mutations of the template region of hTR have great influence for the enzyme activity and behavior (Drosopoulos, Direnzo, & Prasad, 2005). Therefore, hTR template region is a promising target for inhibiting
TE
D
enzyme function in carcinogenesis. N3’ -> P5’ thio-phosphoramidate (NPS) oligonucleotides has been designed as telomerase template antagonists to form stable
AC CE P
duplex with template RNA (Asai, et al., 2003), and imetelstat as a type of NPS has been tested in clinical phase for non-small cell lung cancer (NSCLC) (Chiappori, et al., 2015). Antisense technology can be used for the degradation of hTR to inhibit telomerase activity, thus enhancing the anti-tumor effect (C. Yu, et al., 2015). Other methods such as siRNA, ribozyme could also be used to degrade or instablize hTR. Meanwhile, peptide nucleic acids as well as other alternative oligonucleotides have been used for targeting at TR (H. Chen, Li, & Tollefsbol, 2009). Another potential target is telomeric repeat-containing RNA (TERRA). Telomeres do not encode protein and are considered to be transcriptionally silent, but the transcription of these regions gives rise to this G-rich RNA. TERRA has been proposed to interact with telomerase through their complementary sequences to the template of human telomerase RNA. Oligonucleotides that are mimicked TERRA have shown repressing telomerase 22
ACCEPTED MANUSCRIPT activity in vitro (Redon, Reichenbach, & Lingner, 2010). Recently it has been proposed that TERRA can modulate cellular phenotype by regulating gene expression
PT
in genome wide manner (Hirashima & Seimiya, 2015). The detailed functions of TERRA in carcinogenesis, as well as its biological significance, remain elusive.
RI
4.3. Shelterin protein complex and substrate
SC
Telomere is G-rich single stranded DNA with accessory proteins. In vitro it has been proven that G-rich strand can fold back to form a G4 structure, which is poor
NU
substrate for telomerase. It has been hypothesized that G4 can sequester telomerase
MA
and prevent it from being extended by telomerase in human somatic cells. Although the structure of telomere remains unknown in vivo, some models have been proposed, such as T-loop structures, G-quadruplexes or others (Sekhri, 2014). In fact, a number
TE
D
of G-quartet stabilizing agents are under investigation. These agents can keep G-quadruplexes structure in order to block telomerase to recognize its substrate with
AC CE P
the principle that telomerase is negatively regulated by G4 formation at telomeric end (D. J. Patel, Phan, & Kuryavyi, 2007). Actually the processivity of telomerase decreases with the increasing concentration of potassium chloride, which can be explained by the fact that K+ stabilizes G4 (Ambrus, et al., 2006). Interestingly, according to a recent study by Moye et al., telomerase is able to localize to G4 and partially resolve the structure for extending telomere DNA substrate (Moye, et al., 2015). One possibility could be that telomerase tends to bind to the G4 structure of DNA which is its own substrate. However, it can only partially dissociate it. So the G-quartet stabilizing agents are able to inhibit cancer by suppressing telomerase activity. Targeting telomere associated proteins, shelterin complex, can also lead to de-regulation of telomerase and its maintaining function of the length of the telomere. 23
ACCEPTED MANUSCRIPT The subunits of shelterin TRF1, TRF2 and POT1 directly recognize TTAGGG repeats and bind to the telomere. TPP1, TIN2 and Rapl can form a complex to distinguish
PT
telomere from DNA damage signal (de Lange, 2005). TRF1 has been proposed as a cis inhibitor of telomerase activity and it could be a potential target for anticancer
RI
drug development. Also, the dominant negative of TRF2 can result in telomere
SC
shortening and rapid p53-dependent apoptosis (Karlseder, Broccoli, Dai, Hardy, & de Lange, 1999). A number of studies have found that the TPP1 and POT1 complex
NU
could increase the processivity of telomerase. This implies that the complex is
MA
important for the catalytic enzyme (F. Wang, et al., 2007). Therefore the expression of each subunit of the shelterin complex could be the potential way for inhibiting the recruitment or function of telomerase.
TE
D
4.4. Assembling and trafficking of the holoenzyme The assembly of the active enzyme in cells is complicated and the detailed
AC CE P
mechanism is unclear. There are many factors involved in this process, including the accumulation of hTR and hTERT to Cajal bodies, the translocation of hTERT from cytoplasm to nucleoplasm, as well as the chaperons necessary for assembling the holoenzyme, which could also be a potential strategy for telomerase inhibitors. Dyskerin protein, which binds to the H/ACA box of human telomerase RNA, is a core telomerase subunit for RNP biogenesis in vivo (Kannan, Nelson, & Shippen, 2008). The protein complex TCAB1/WDR-79 associates with CAB-box of hTR to drive it to Cajal bodies. Similarly, there are many factors involved in the process of accumulation of hTR in Cajal bodies (Schmidt & Cech, 2015). The chaperones HSP90 and p23 play a role in translocation for the TERT protein to nucleus for assembly of the core enzyme (Holt, et al., 1999). The direct or indirect repressing of dyskerin or other proteins could potentially inhibit maximal telomerase activity, 24
ACCEPTED MANUSCRIPT leading to decrease telomere length. Some strategies have already been investigated aiming at these targets (Ruden & Puri, 2013). However, the challenge is to find out
PT
the factors that are not only essential but also specific for the telomerase biogenesis pathway.
RI
5. Tumor inhibitors targeting telomerase
SC
There has been a vast increase in telomerase research over the past several years with many different pre-clinical approaches being tested for inhibiting the activity of
NU
this enzyme as a novel therapeutic modality to treat malignancy (Laura K. White,
MA
2001). Many of the synthetic and natural compounds have been screened for telomerase inhibitory activity. Telomerase inhibitors, based on the targets, have been reviewed before by Olaussen et al. (Olaussen, et al., 2006) and White et al. (Laura K.
TE
D
White, 2001). In this review, we mainly focus on the telomerase inhibitors from the origins of drugs in recent 20 years. The main targets and regulatory effect of inhibitors
AC CE P
for telomerase include hTERT, hTR and the telomerase substrate and associated proteins (Kiran, Palaniswamy, & Angayarkanni, 2015; Olaussen, et al., 2006). 5.1. Telomerase inhibitors from Natural products Natural products with extensive structural diversity have been a major source of currently available anticancer drugs. A number of plant derived natural products have been described as potential telomerase inhibitors. Here, we review these natural chemical entities and anti-tumor herbal extracts. 5.1.1. Natural compounds derived from plants These telomerase inhibitors derived from plant sources encompass a wide range of molecular structures, including alkaloids, xanthones, sesquiterpene lactones, terpenoids and various polyphenols (J. L.-Y. Chen, Sperry, Ip, & Brimble, 2011). Boldine, a natural aporphine alkaloid found abundantly in Peumus boldus, inhibits 25
ACCEPTED MANUSCRIPT telomerase in cells treated with sub-cytotoxic concentrations. A recent study had also reported anti-tumor effects of boldine by stimulation of apoptosis in vitro and its
PT
feasible application by intraperitoneal injection (50 or 100 mg/kg) in an animal model of breast cancer (Paydar, et al., 2014). Boldine has also shown anti-proliferative effect
RI
on glioma cell lines by G2/M arrest and beneficial antitumor properties against glioma
SC
in mouse model via down-regulation of hTERT. Meanwhile, boldine could change the splicing variants of hTERT towards shorter non-functional transcripts (Kazemi
NU
Noureini & Tanavar, 2015).
MA
Berberine is an isoquinoline alkaloid, isolated from the roots and stem-bark of many plants, including Berberis vulgaris chinensis (Coptis or goldenthread). It has a decorated history in Chinese, Indian and Middle Eastern traditional medicine for a
TE
D
wide range of indications (Imanshahidi & Hosseinzadeh, 2008). Berberine-induced apoptosis of human leukemia HL-60 cells is associated with down-regulation of
AC CE P
nucleophosmin/b23 and telomerase activity. Telomerase activity was repressed to about 70% and 40% after treatment with 25µg/ml berberine for 24 and 48 h, respectively (Wu HL, 1999) against U937 human leukemia cells (S. H. Naasani I, Yamori T, Tsuruo T., 1999). The anti-telomerase activity of berberine lies in its preference for binding G4 over duplex DNA to stabilize G4 (Franceschin, et al., 2006). Further studies by Gu et al. have shown that C9-substituted derivatives containing amino121 or aza-aromatic groups significantly increase the binding affinity of these compounds with G4, resulting in increased anti-telomerase activity (Ma, et al., 2009; W. J. Zhang, et al., 2007). Ji et al. investigated the interaction of berberine and 9 other natural alkaloids with G4 formed by telomeric DNA and C-Myc22 sequences (Ji, et al., 2012). Ligands that facilitate the formation and increase the stabilization of G4 can halt tumor cell proliferation and have been regarded as potential anti-cancer drugs. 26
ACCEPTED MANUSCRIPT A large number of promising G4 interacting ligands have now been reported. Berberine, palmatine and sanguinarine could induce the formation of G4 as well as
PT
increase the stabilization of G4 to induce cell differentiation or quiescence. The stabilization ability was in the following order: sanguinarine > palmatine > berberine.
RI
Daurisoline, O-methyldauricine, O-diacetyldaurisoline, daurinoline, dauricinoline,
SC
N,N’-dimethyldauricine iodide and N,N’-dimethyldaurisoline iodide show similar stabilization ability. The unsaturated ring C, N+ positively charged centers, and
NU
conjugated aromatic rings are key factors to increase the stabilization ability of
MA
sanguinarine, palmatine and berberine (Ji, et al., 2012). Gambogic acid belongs to a family of caged xanthones and is isolated from the gamboge resin of the Garcinia hurburyi tree in Southeast Asia. Gambogic acid has
TE
D
been used as a coloring material and folk medicines due to its unique color and broad spectrum of cytotoxic activities. It has shown promising in vitro and in vivo activity
AC CE P
against a number of different cancer cell lines, including human leukemia, gastric carcinoma, lung carcinoma, breast cancer, hepatoma and pancreatic cancer. Both the crude extract gamboge and gambogic acid have been tested in clinical trials against cancer in China (Guo, et al., 2006; Han QB, 2009). Studies of Guo et al. research group have shown that the induction of apoptosis by gambogic acid may depend on the reduction in telomerase activity. hTERT activity was reduced by both the down-regulation of hTERT transcription via inhibition of the transcription activator c-Myc, and inhibition of the phosphorylation of Akt which down-regulated the activity of hTERT in a post-translational manner (Guo, et al., 2006; J. Yu, et al., 2006; Q. Zhao, et al., 2008). Resveratrol, a representative compound from plants, is isolated from a variety of biological sources including white hellbore (Veratrum grandiflorum O. Loes), peanuts 27
ACCEPTED MANUSCRIPT (Arachis hypogeal), legumes (Cassia sp.) and grapes (Vitis vinifera) (Aggarwal BB, 2004). It has been demonstrated to interact with a large variety of molecular targets
PT
and shown to be beneficial for a wide range of ailments including inhibiting different cancer in vivo and in vitro (Tan, et al., 2015; Y. Zhu, et al., 2015). Resveratrol has a inhibitory
effect
on
MCF-7
breast
cancer
cells,
RI
direct
HT-29
and
SC
WiDr human colon cancer cell proliferation. The growth-inhibitory effect is mainly due to its ability to induce S phase arrest and apoptosis in association with reduced
NU
levels of telomerase activity (Fuggetta MP, 2006; Lanzilli G, 2006). In particular,
MA
resveratrol down-regulates the telomerase activity of target cells and the nuclear levels of hTERT (Lanzilli G, 2006). Pterostilbene is a naturally occurring dimethyl ether analog of resveratrol in several plant species. Molecular docking studies indicate good
H-460
cancer
TE
D
interaction between pterostilbene and the active site of telomerase. MCF7 and NCI cell
lines
treated
with pterostilbene exhibite
AC CE P
significant telomerase inhibition after 72 h (Tippani R, 2014). Others compounds from plants also show good inhibition on telomerase activity for anti-cancer, such as CFP -2, a novel lichenin from Cladonia furcate (X. Lin, et al., 2003), silymarin from Silybum marianum (Faezizadeh Z, 2012; Yurtcu E, 2015), etc. The various natural anti-tumor compound targeting telomerase from plants are listed in Table 1. Some extracts also exert telomerase inhibitory activity. Ethyl acetate extract of Pleurotus ostreatus, ethyl acetate and water extracts of Lasiosphaera fenzlii, hexane extract of Strobilomyces floccopus, water extract of Sarcodon aspratus, and hexane, ethyl acetate and water extracts from Umbilicaria esculenta show positive telomerase inhibitory activity in gastric cell line SNU-1 (Xu B, 2014). 5.1.2. Herbal medicine extracts Herbal extracts have recently captured the attention for tumor therapy. Many 28
ACCEPTED MANUSCRIPT herbal extracts targeting telomerase indicate obvious inhibition on tumor. Hedyotis diffusa is a kind of herb used in traditional Chinese medicine. Wild Hedyotis
PT
diffusa can be found in China, Japan, and Nepal. The effects of aqueous extracts from Hedyotis diffusa in vitro have been studied showing that it could inhibit telomerase
RI
activity, induce cell apoptosis and arrest of cell cycle in S phase (Gao C, 2010).
SC
Bupleuri radix, a traditional Chinese herb, has been widely used in various herbal mixtures to treat liver diseases such as hepatitis and cirrhosis. Acetone extract of
NU
Bupleurum scorzonerifolium is found to inhibit proliferation of A549 human lung
MA
cancer cells via inducing apoptosis and suppressing telomerase activity (Cheng, et al., 2003). Cordyceps militaris, a well-known traditional medicinal mushroom, is a potentially interesting candidate in cancer treatment. The water extract of C. militaris
TE
D
(WECM) inhibits the growth and induced apoptosis in A549 cells, which is associated with activation of caspases, down-regulation of anti-apoptotic Bcl-2 expression, and
AC CE P
up-regulation of pro-apoptotic Bax protein. It is also concluded that apoptotic events due to WECM exerted a dose-dependent inhibition on telomerase activity via down-regulation of hTERT, c-Myc and Sp1 expression (S. E. Park, et al., 2009). Special herbal complex (Fufang of traditional Chinese medicine) is used widely in clinic in China. Other countries also use the herbal complex for tumor therapy. Juzen-taiho-to (which contained Hoelen, Angelicae radix and Glycyrrhizae radix) has been used for patients taking anti-cancer drugs in Japan, for protection from the deleterious effects of anti-cancer drugs and irradiation (Lian, et al., 2003; Sugiyama K, 1995). Lian et al. reportes a special herbal complex, which is composed of Hoelen, Angelicae radix, Scutellariae radix and Glycyrrhizae radix, which decreases cell viability
and
induced
apoptosis
to
endocrine-resistant
AN3CA
and
adriamycin-resistant MCF7/ADR carcinoma cells. It could decrease expression of 29
ACCEPTED MANUSCRIPT apoptosis-related genes, Bcl-2, c-Myc and hTERT. The effect is via suppressing telomerase activity involved in cellular apoptosis in endocrine-resistant AN3CA cells
PT
(Lian, et al., 2003). Shugansanjie Tang of traditional Chinese medication, whose active component is
RI
Akebia Trifoliate Koidz., possesses potential anti-tumor and immunostimulatory
SC
effects especially for breast cancer. Shugansanjie Tang could inhibit the growth of breast cancer cells by apoptosis and lower the level of certain matrix
NU
metalloproteinases and activity of hTERT in breast cancer (Loo, Chen, Chow, & Chou,
MA
2007). Traditional Chinese medicine kang ai fang comprising Curcuma zedoaria, Portulaca grandiflora, Bupleurum chinense DC., Scutellaria baicalensis and Codonopsis pilosula, shows good inhibition of telomerase activity on human colon
TE
D
cancer cell line in vitro. Traditional Chinese medicine Janpi liqi fang, encompassing 10 kinds of Chinese herbal medicines including Rhizoma Atractylodis Macrocephalae,
AC CE P
Codonopsis pilosula, fructus aurantii, Wolfiporia extensa, etc., indicates obvious down-regulation of telomerase activity on human liver cancer cell line in vitro and tumor-bearing mice in vivo. Other traditional Chinese medicine, zhenggan fang (Astragalus membranaceus, Salvia miltiorrhiza, Glossy Privet Fruit, Turtle shell, Ligusticum chuanxiong, Portulaca grandiflora, Lycium chinense Miller and Hedyotis diffusa), qingjin desheng tablet (Anax quinquefolius, Gynostemma pentaphylla, Ophiopogon japonicas, Cortex Phellodendri, Asarum sagittarioides and Asiatic toad), yiqi jiedu fang (Berberine hydrochloride, Rosa banksiae, Tetradium ruticarpum and Paeonia lactiflora) and fuzheng yiliu fang (Scutellaria baicalensis, Angelica sinensis, Curcuma zedoaria and Patrinia heterophylla) also show good inhibition on tumor for liver cancer, lung cancer, gastric cancer and nasopharynx cancer by inhibiting telomerase activity (Fan YX, 2008; Li GX, 2011). 30
ACCEPTED MANUSCRIPT 5.1.3. Inhibitors from microbial sources Natural compounds isolated from microbes also provide a new scope of screening
PT
for telomerase inhibitors of anti-tumor. Telomerase inhibitors have been isolated from various fungal, bacterial and actinomycetes sources. Most of these compounds have
RI
only been isolated in the last two decades; however, their anti-telomerase activity has
SC
just identified and demonstrated following the discovery of telomerase as a biological target (J. L.-Y. Chen, et al., 2011). Some of them are chemically modified to increase
NU
the potency (Kiran, et al., 2015).
MA
Elaboration of telomerase inhibitors is based on their target. Quinine antibiotics isolated from Actinomycetes sp., the most widely explored microorganism, are potential inhibitors of telomerase (Kiran, et al., 2015). Rubromycin is one of the
TE
D
widely studied compounds among quinine antibiotics, which were basically a red colour pigments isolated from Actinomycetes namely Streptomyces collinus by
AC CE P
Brockmann and Renneberg in 1950s (J. L.-Y. Chen, et al., 2011). They are primarily aromatic naphthoquinone and isocoumarin ring systems, which competitively interacte with the hTERT and/or hTR subunits of telomerase enzyme. Studies prove that spiroketal moiety of rubromycin is the key pharmacophore for telomerase inhibitory action (Ueno T, 2000). Chrolactomycin, another novel anticancer compound isolated from Streptomyces sp., shows telomerase inhibitory activity. The exo-methylene group of chrolactomycin acts as a michael acceptor and forms a covalent bond with sulfhydryl group of a cysteine residue near the active site of the telomerase enzyme, which causes the irreversible inhibition of telomerase (Nakai R, 2001). Many fungi are the sources of telomerase inhibitors as well. Thelavin A and B were isolated from a fungus Thielavia terricola, and thelavin B showed telomerase inhibitory activity (Kitahara N, 1981; Togashi, Ko, Ahn, & Osada, 2001). 31
ACCEPTED MANUSCRIPT Diazaphilonic acid, isolated from a fungus Talaromyces flavus, is a fungal metabolite that could inhibit the telomerase activity at 50 µM completely (Tabata Y, 1999).
PT
CRM646-A, a phenol glucuronide, was initially isolated from a soil fungus Acremonium sp. MT70646. It inhibits the reverse transcriptase of molony murine
RI
leukemia virus in vitro. Therefore, it could be considered as universal inhibitors for
SC
RNA dependent DNA polymerases (Kiran, et al., 2015).
Targeting hTERT gene transcriptional and post-transcriptional regulation,
NU
docosahexanoic acid, eicosapentanoic acid and rapamycin show good activities.
MA
Docosahexanoic acid was from a marine micro alga Crypthecodinium cohnii (Ratledge C, 2001) and eicosapentanoic acid was from a marine bacteria Shewanella pneumatophore (Hirota, Nodasaka, Orikasa, Okuyama, & Yumoto, 2005). They
TE
D
inhibit telomerase directly by binding to functional enzyme and reducing the expression level of c-Myc gene and hTERT expression. This has been achieved
AC CE P
through inhibition of protein kinase C (PKC) activity in a cell culture experiment (Eitsuka, Nakagawa, Suzuki, & Miyazawa, 2005). Histone deacetylases (HDAC) are known to regulate gene transcription and oncogenesis through remodeling of chromatin structure, canonically resulting in the repression of target genes (Rahman, et al., 2010). This makes HDAC inhibitors as promising anticancer agents (Kiran, et al., 2015). Trichostatin A isolated from the culture broth of Streptomyces platensis (Tsuji N, 1976) is a well-known HDAC inhibitor which inhibited HDAC at nano molar concentrations. Trichostatin-A usually elicits Smad3 and Mad1 which are repressors of hTERT gene to decrease the expression hTERT (Rahman, et al., 2010). In addition, Hsp90 is required for the assembly and activation of telomerase in human cells (Villa R, 2003). Over-expression of Hsp90 induces the activation of telomerase by readily folding hTERT protein. Studies have shown that inhibition of 32
ACCEPTED MANUSCRIPT Hsp90 can elicit nitric oxide synthase dependent free radical production and telomere shortening. So compounds which target the integration of Hsp90 and hTERT complex
PT
is an attractive target for cancer chemotherapy (Qin HL, 2008). Geldanamycin was originally isolated from Streptomyces hygroscopicus in 1970 (DeBoer C, 1970) and
RI
exerted a significant reduction of telomerase activity (Kiran, et al., 2015). Radicicol
SC
from fungal species Pochonia chlamydosporia and Neocosmospora tenuicristata directly binds with the amino-terminal ATP binding pocket of Hsp90 and inhibited
NU
ATP hydrolysis, and could elicit nitric oxide synthase dependent free radical
Jackson-Cook, & Holt, 2006).
MA
production and telomere shortening by inhibition of Hsp90 (Compton, Elmore, Haydu,
Compounds interacting with G4 DNA also show good inhibition on telomerase
TE
D
activity. Telomestatin from Streptomyces anulatus 3533-SV4 could inhibit telomerase activity at nanomolar concentrations. Telomestatin binds preferentially to the
AC CE P
basket-type G4 structure, d[T2AG3]4 with a 2:1 stoichiometry and with high selectivity for intramolecular over intermolecular binding and for G4 structures over duplex DNA. (Rezler EM, 2005; Shin-ya K, 2001). Some tumor inhibitors targeting telomerase from microbial sources are in Table 2. 5.2. Synthetic inhibitors for telomerase 5.2.1. Small molecule inhibitors Small molecule inhibitors are a rapidly emerging area for discovering potential candidates of telomerase inhibitors (Laura K. White, 2001). Rapid screening of small molecules by large-scale screening models, targeted synthesis of telomerase inhibitors and the derivatives of natural products provide a lot of promising sources. 5.2.1.1. Laboratorial or preclinical studies of synthetic inhibitors Many studies on synthesis of the pyrazole derivatives have been described. 33
ACCEPTED MANUSCRIPT Certain pyrazole derivatives exhibit pharmacological activities and have proved to be useful templates in drug research. The series of novel inhibitors were designed by
PT
replacing the central ring of acridine with the pyrazole ring (Kalathiya U, 2014). Kalathiya et al. used the three docking programs CDOCKER, ligandfit docking
RI
(Scoring Functions) and AutoDock to evaluate the dibenzopyrrole derivatives. The
SC
studies show hydrogen bond interaction, and Pi interactions between the dibenzopyrrole group of inhibitors and enzyme active site may be one of the key
NU
factors for the combination of ligands with TERT. Compounds designed with electron
MA
donating groups, CH3 and OCH3 (C_9g and C_9k) and hydroxyl group OH (C_9l) at R 3 position were the best by all three docking methods (Kalathiya U, 2014). Wong et al. developed a surrogate yeast high-throughput assay to identify human telomerase
TE
D
inhibitors. SEW05920, SPB03924, and CD11359 three heteroaromatic small molecules compounds exhibited specific inhibition of both purified recombinant
AC CE P
human telomerase and telomerase activity in crude HeLa cell extracts in vitro. These compounds represent probes into human telomerase function, and potential entry points for development of lead compounds against telomerase-positive cancers (Wong, et al., 2013).
BIBR1532, synthetic non-peptidic, non-nucleosidic small molecule inhibitor, is one of the most potent specific inhibitors of hTERT. It could bind to a site in the telomerase, which is distinct from those for deoxyribonucleotides and the DNA primer, and act as a chain terminator during nucleotide polymerization, leading to inhibition of the catalytic activity of telomerase in a dose-dependent manner (Damm K, 2001; Pascolo, et al., 2002). Bryan et al. presented the crystal structure of BIBR1532 bound to Tribolium castaneum catalytic subunit of telomerase (tcTERT). BIBR1532 binds to a conserved hydrophobic pocket (FVYL motif) on the outer 34
ACCEPTED MANUSCRIPT surface of the thumb domain. The FVYL motif is near TRBD residues that bind to the activation domain (CR4/5) of hTR. hTERT thumb domain binds to the P6.1 stem loop
PT
of CR4/5 in vitro (Bryan, et al., 2015). BIBR1532 suppress telomerase in human cancer cells of different histological origin leading to progressive shortening of
RI
telomeres and inhibition of cell proliferation in vitro and in vivo. Moreover, a direct
SC
short-term cytotoxic activity of the compound is also observed in leukemic cells from chronic lymphocytic leukemia (CLL) and acute myeloid leukemia. Time dependent
NU
individual telomere erosion is observed, which is associated with loss of telomeric
MA
repeat binding factor 2 (TRF2) and increased phosphorylation of p53 (Bashash, Ghaffari, Mirzaee, Alimoghaddam, & Ghavamzadeh, 2013; Pascolo, et al., 2002). This compound leads to progressive telomere shortening, consecutive telomere
TE
D
dysfunction, and finally, growth arrest after a lag period that is largely dependent on initial telomere length in hematopoietic cancer cell lines and chondrosarcoma cell
AC CE P
lines (El Daly & Martens, 2007; Parsch, Brassat, Brummendorf, & Fellenberg, 2008). BIBR1532 might impede cell proliferation and restrict telomerase activity through suppressing activation of c-Myc and hTERT expression in Nalm-6 cells and acute promyelocytic leukemia NB4 cells (Bashash, et al., 2012). Subsequent decreased telomerase activity and probable telomere dysfunction due to the hTERT down-regulation is a probable mechanism that causes rapid cell death upon exposure of pre-B ALL cells to high doses of BIBR1532 (Bashash, et al., 2013). In addition, BIBR1532 is in combination with carboplatin and TEL patch (a specific surface of the TPP1 protein) mutations to inhibit the ovarian cancer ES2, SKOV3, and TOV112D cells as well as cervical cancer, HeLa cell, growth by inhibition of the telomerase enzyme (Meng, Taylor, Ray, Shevde, & Rocconi, 2012; Nakashima, Nandakumar, Sullivan, Espinosa, & Cech, 2013). 35
ACCEPTED MANUSCRIPT Natural products provide sources for leading compounds and many synthetic inhibitors
derivatived
from
natural
products
have
been
reported.
PT
Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a synthetic derivative of oleanolic acid, a triterpene, with apoptosis-inducing activity in a wide
RI
range of cancer cells (Honda T, 2000). Telomerase is a potential target of CDDO-Me.
SC
CDDO-Me could attenuate hTERT mRNA, telomerase activity and hTERT regulatory proteins (e.g., c-Myc, Sp1, NF-κB and p-Akt) (Deeb, et al., 2012). Inhibition of cell
NU
proliferation and induction of apoptosis by CDDO-Me in pancreatic cancer cells is
MA
associated with the repression of hTERT expression and telomerase activity. Inhibition of telomerase activity by CDDO-Me is also mediated through a ROS-dependent mechanism. Blocking ROS generation prevents the inhibition of
TE
D
hTERT gene expression, hTERT protein production and expression of a number of hTERT regulatory proteins by CDDO-Me (Deeb, et al., 2013; Y. Liu, Gao, Deeb,
AC CE P
Arbab, & Gautam, 2012).
Liriodenine is a representative oxoaporphine alkaloid mainly occurring in the families of Rutaceae, Annonaceae, Magnoliaceae, etc. cis-[PtCl2(L)(DMSO)] (Complex 1) is a synthesis product of the platinum(II) and liriodenine (L) complex (Z. F. Chen, et al., 2009). Complex 1 has a significant growth inhibition against BEL-7404 human hepatoma cell and could induce its apoptosis via the mitochondrial pathway as well as caused both the G2/M phase and S phase cell cycle arrest. It significantly induces the formation and stabilization of the telomeric G4 DNA by intercalative binding mode via π-π stacking and exterior electrostatic attraction between the positively charged platinum(II) and G4 DNA. It indicates Complex 1 inhibited the telomerase activity based on the G4 DNA stabilization (Y. L. Li, Qin, Liu, Chen, & Liang, 2014). 36
ACCEPTED MANUSCRIPT The development of G4 DNA binding small molecules has become an important strategy for selectively targeting cancer cells (W. J. Chung, et al., 2013; Maji, Kumar,
PT
Muniyappa, & Bhattacharya, 2015). So far, the structural information on complexes between human telomeric DNA and ligands is limited to the parallel G4 conformation,
RI
despite the high structural polymorphism of human telomeric G4. No structure has yet
SC
been resolved for the complex with telomestatin. Chung, et al. presented high-resolution structure of the complex between an intramolecular (3+1) human
NU
telomeric G4 and a telomestatin derivative, the macrocyclic hexaoxazole
MA
L2H2-6M(2)OTD, which interacts with G4 by π-stacking and electrostatic interactions (W. J. Chung, et al., 2013). The bifunctional complex represents an intriguing example of ligand design and suggests new possibilities for achieving
TE
D
complementary biological activity. Roe et al. synthesized and screened bifunctional ligand of hybrid acridine-Hsp90 ligand SR374, SR375, SR361 and SR362 using a
AC CE P
click-chemistry approach based on a G4 binder-geldanamycin conjugate. The conjugates also demonstrate significant cyctotoxity against a number of cancer cell lines in the sub-µM range (Roe, et al., 2015). In addition, chemical structure modifications of small molecule inhibitors also increase telomerase inhibition activity. Maji, et al. reported the design and evolution of a new kind of carbazole-based benzimidazole dimers (six carbazole based symmetric benzimidazole derivatives including two monomers M1 and M2 and four corresponding dimeric ligands having different types of linkers) for their efficient telomerase inhibition activity. Spectroscopic and electrophoretic mobility analyses revealed the higher affinity and excellent selectivity of ligands toward G4 DNA over duplex DNA. Each of the ligands induce topological transformation of the K
+
-stabilized mixed-hybrid G4
DNA to a thermodynamically more stable parallel G4 DNA structure. The ligands M2, 37
ACCEPTED MANUSCRIPT D2, D3 and D4 show complete telomerase inhibition with IC 50 values in the sub-µM concentration range. The ligands induce significant apoptotic response and
PT
anti-proliferative activity toward cancer cells when compared to the normal cells (Maji, et al., 2015). The various synthesized tumor inhibitors targeting telomerase are
RI
listed in Table 3.
SC
Some inhibitors show reversible telomerase inhibitory effects. Continual exposure of cancer cells to telomerase inhibitor leads to population of cells, which
NU
displays resistance to telomerase inhibition-mediated cell arrest. MST-312, a
MA
chemically modified derivative of epigallocatechin gallate, shows strong binding affinity to DNA and displayed reversible telomerase inhibitory effects in brain tumor cells (Gurung RL, 2014). DNA-PKcs (one of DNA-dependent protein kinase,
TE
D
DNA-PK) activation is observed in telomerase-inhibited cells presumably as a response to DNA damage. Combined inhibition of DNA-PKcs and telomerase results
AC CE P
in an increase in telomere signal-free chromosomal ends in brain tumor cells as well. DNA-PKcs ablation in these cells confers higher cell sensitivity to telomerase inhibition, inducing cell death (Gurung RL, 2014). It indicates telomerase inhibitors combined with other reagents could play better suppressive role. 5.2.1.2. Synthetic telomerase inhibitors of anti-tumor in clinical trials or in clinic Many drugs in clinical trials or in clinic show inhibition for telomerase (Table. 4). Perifosine, an AKT inhibitor in clinical trials, inhibits telomerase activity and induced telomere shortening in a wide variety of cell lines in vitro. Perifosine reduces primary breast cancer orthotopic xenograft tumor size. However, perifosine reduces telomerase activity in four of six CLL patients evaluated. Two of the patients were treated for four to six months and shortening of the shortest telomeres occurred in both patients’ cells (Holohan B, 2015). 38
ACCEPTED MANUSCRIPT Bortezomib, a proteasome inhibitor with pleiotropic activities, shows activity in mantle cell lymphoma and is currently implemented in therapeutic combinations for
PT
this disease. Bortezomib exerts inhibition on mantle cell lymphoma HBL-2 cells and NCEB cells, and multiple myeloma (MM) ARP-1 and CAG cancer cell (Uziel, Cohen,
RI
Beery, Nordenberg, & Lahav, 2014; Weiss, et al., 2012). Bortezomib downregulates
SC
telomerase activity in MM cells both transcriptionally and post-translationally. ARP-1 cells are more sensitive to differential phosphorylation of hTERT by PKCα than that
NU
of CAG cells. Transcription of hTERT is similarly inhibited in both lines by decreased
MA
binding of SP1. But, methylation of hTERT promoter is not affected (Weiss, et al., 2012). Inhibition of telomerase activity in mantle cell lymphoma is operated by two separate mechanisms: reduction of the hTERT mRNA expression and reduction in
TE
D
phosphorylation of the catalytic subunit of hTERT by its kinases, AKT and PKCα (Uziel, et al., 2014). In addition, the bortezomib treatment of leukemic and BGC-823
AC CE P
gastric cancer cells results in significant inhibition of hTERT expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggers telomere dysfunction and DNA damage. It reveals a profound impact of bortezomib on telomere homeostasis/function, which may have important clinical implications (Ci X, 2015).
Doxorubicin (DOX) is derived by chemical semisynthesis from a bacterial species and used in cancer chemotherapy. It is an anthracycline antitumor antibiotic and it works by intercalating DNA (Tacar, Sriamornsak, & Dass, 2013). In BEL-7404 human hepatoma cells, telomerase activity was inhibited in a dose and time-dependent manner in cells treated with DOX, which was correlated with the inhibition of cell growth. The mRNA of three telomerase subunits (hTERT, hTR and TP1) did not affect after exposure for 72 h with indicated concentrations. The telomerase inhibition 39
ACCEPTED MANUSCRIPT and telomere shortening by DOX may contribute to its efficiency in treatment in hepatocellular carcinoma (Zhang RG, 2002). Kato et al. found that TRF1, POT1 and
PT
TNKS1 mRNAs decreased in HeLa and U-2 OS cells treated with doxorubicin, while an increased TRF2-interacting telomeric protein, RAP1, mRNA level was observed in
RI
U-2OS cells (Kato, Nakayama, Agata, & Yoshida, 2013). In most instances, DOX
SC
combined with other reagents plays the inhibition role. DOX combined with RHPS4 inhibits the Hsp90 heat shock protein, and confers enhanced sensitivity in RHPS4
NU
treated MCF-7 cells. DOX combined with GRN163L increases DOX sensitivity to
MA
hepatoma cell Hep3B by inhibiting telomerase activity (Cookson, et al., 2005; Djojosubroto, et al., 2005). DOX combined with sodium butyrate (histone deacetylase inhibitors) inhibits proliferation of uterine cancer cell. Growth inhibition is
TE
D
accompanied by caspase-dependent apoptosis with reduced telomerase activity and decreased the hTERT mRNA expression (M. Yu, et al., 2014).
AC CE P
Mammalian target of rapamycin (mTOR) inhibitors such as rapamycin exert their anti-proliferative effects through inhibition of the serine/threonine kinase mTOR, by forming a complex with one of the immunophilin family of FK506 binding proteins, FKBP12 (Bae-Jump, et al., 2010). Zhou et al. showed that rapamycin rapidly inhibited telomerase activity by decreasing the mRNA level of hTERT in Ishikawa, Hec-1B and ECC-1 cells of endometrial cancer cells (Zhou C, 2003), and in both rapamycin-sensitive and -resistant cell (Bae-Jump, Zhou, Gehrig, Whang, & Boggess, 2006). Rapamycin also displayed a potent anti-leukemic effect on the human T-cell leukemia cell Jurkat through G1 cell cycle arrest and suppression of telomerase activity (reducing hTERT expression) (Y. M. Zhao, Zhou, Xu, Lai, & Huang, 2008). The related synergistic inhibition of telomerase activity has been reported. For instance, a combination of bortezomib and rapamycin induced synergistic inhibition 40
ACCEPTED MANUSCRIPT of telomerase activity in HBL-2 cells, the combined treatment decreased telomerase activity by 80% compared to the expected value (40%) and a similar trend was
PT
observed for NCEB cells (Uziel, et al., 2014). Many tyrosine kinase inhibitors show good inhibition on telomerase activity
RI
including nilotinib, dasatinib, gefitinib (Shapira, et al., 2012), etc., which are listed
SC
with other synthetic tumor inhibitors targeting telomerase in clinical trials or in clinic together in Table. 4.
NU
5.2.2. Oligonucleotide
MA
Antisense oligodeoxynucleotides (ODN) are an area of heightened interest in the field of telomerase inhibition. These drugs consist of short stretches of DNA that are complementary to a target RNA. The mechanism of action for most applications is to
TE
D
hybridize to their complementary RNA by Watson-Crick base pairing and inhibit the translation of the RNA by a passive and/or active mechanism. The passive inhibition
AC CE P
occurs simply by the competitive binding of the ODN to the RNA, whereas the active mechanism recruits RNaseH to degrade the mRNA once the RNA-ODN hybridization occurs (Laura K. White, 2001). Different approaches have been used: antisense technology, RNA interference, aptamers, anti-microRNAs, CRISPR, etc. The main problems associated with using oligonucleotides as therapeutic agents are caused by their low stability in vivo and difficulties in their selective delivery into tissues and cells. Chemically modified oligonucleotides are significantly more stable and can penetrate into cells more effectively while retaining their biological activity. Addition of different ligands allows researchers to obtain specific delivery of conjugates into particular cells due to receptor mediated endocytosis (Juliano, Carver, Cao, & Ming, 2013; Zvereva, et al., 2015). Main targets are: processes associated with transcription of the hTERT and hTR genes, a disturbance in the telomerase complex assembly, 41
ACCEPTED MANUSCRIPT inhibition of enzymatic activity of the assembled telomerase complex, loss by telomere ends of availability for interaction with telomerase, and inhibition of activity
PT
of telomerase complex interacting with telomeres (Zvereva, et al., 2015). A variety of studies, reported the inhibition of telomerase using antisense
RI
approaches, direct both at the template and non-template regions of hTR. Azhibek et
SC
al, synthesized chimeric oligonucleotides containing two target sites that could simultaneously interact with two functional domains of hTR. The chimeric
NU
bifunctional oligonucleotides that contain two oligonucleotide parts complementary
MA
to the functional domains of telomerase RNA connected with non-nucleotide linkers in different orientations (5'-3', 5'-5' or 3'-3'), within which chimeras significantly influenced the inhibitory activity. The functional parts of chimeric oligonucleotides
TE
D
are complementary to either the template or single-stranded parts of a pseudoknot or the CR4/CR5 domain. Such chimeras inhibited telomerase in vitro in the nM range,
effect
AC CE P
but were effective in vivo in sub-nM concentrations, predominantly due to their on
telomerase
assembly
and
dimerization.
Chimeric
bifunctional
oligonucleotides could be considered a basis for the development of new, safe anti-cancer drugs (Azhibek, Zvereva, Zatsepin, Rubtsova, & Dontsova, 2014). Imetelstat (GRN163L) is the first telomerase inhibitor to advance to clinical development. Imetelstat as a short, modified oligonucleotide is a lipid-conjugated 13-mer oligonucleotide sequence that is complementary to and binds with high affinity to the RNA template of telomerase, thereby directly inhibiting telomerase activity. The compound has a proprietary thio-phosphoramidate backbone, which is designed to provide resistance to the effect of cellular nucleases, thus conferring improved stability in plasma and tissues, as well as significantly improves binding affinity to its target (Hochreiter, et al., 2006; Lin CP, 2007). Imetelstat has shown 42
ACCEPTED MANUSCRIPT hopeful results in multiple preclinical studies. It has been moved into six stage I and stage I/II clinical trials targeting patients with chronic lympho-proliferative diseases,
PT
refractory and relapsed solid tumor malignancies, refractory and relapsed MM, locally recurrent or metastatic breast cancer, and advanced and metastatic NSCLC. In
RI
addition, GRN163L is in combination with paclitaxel and bevacizumab in patients
SC
with locally recurrent or metastatic breast cancer (Ruden & Puri, 2013). Following intravenous administration of imetelstat using tolerable dosing regimens, clinically
NU
relevant and significant inhibition of telomerase activity is observed in various types
MA
of tissue in which telomerase activity was measurable, including normal bone marrow hematopoietic cells, malignant plasma cells, hair follicle cells, and peripheral blood mononuclear cells (Hu, Bobb, Lu, He, & Dome, 2014; Joseph, et al., 2010; Thompson,
TE
D
et al., 2013). In addition, preliminary information on the therapeutic activity and safety of imetelstat in patients has been obtained. Clinic reports in 2015 indicated that
AC CE P
imetelstat was found to be active in patients with myelofibrosis, but it was potential to cause clinically significant myelosuppression. The rapid and durable hematologic and molecular responses were observed in patients with essential thrombocythemia (Baerlocher, et al., 2015; Tefferi, et al., 2015). The application of oligonucleotide inhibitors of telomerase as antitumor preparations is associated with high price and difficult synthesis of modified oligonucleotides. However, an increase in the efficiency of telomerase activity by antisense oligonucleotides concurrently influencing hTR and hTERT and an increased influence on tumor stem cells suggest that oligonucleotide inhibitors of telomerase can be promising in combined antitumor therapy, but not as a universal preparation (Zvereva, et al., 2015). 5.3. Peptide and Protein 43
ACCEPTED MANUSCRIPT 5.3.1. Peptide In recent years, there have been studies about telomerase inhibitors of different
PT
peptides and proteins for anti-tumor. Since telomerase is present in most cancers, its peptides are universal telomerase-associated antigens. They are capable of producing
RI
strong immune response by eliciting both CD4+ and CD8+, T-cell responses and
SC
stimulating the hTERT peptide-specific CTL activity, potentially leading to tumor cell lysis (Beatty & Vonderheide, 2008; Vonderheide, 2008). Several strategies are
MA
and eliminate the issue of self-tolerance.
NU
employed in the development of vaccines that may induce hTERT’s immunogenicity
GV1001, hTERT peptide-based vaccine, is a 16 amino acid MHC class II-restricted hTERT peptide vaccine, which consists of amino acids 611-626
TE
D
(EARPALLTSRLRFIPK) of the hTERT active site. GV1001 was used in conjunction with an adjuvant, such as granulocyte-monocyte colony-stimulating factor or Toll-like
AC CE P
receptor-7 agonist (Kyte, 2009; Ruden & Puri, 2013; Shaw, et al., 2010). It was administered as an MHC class-II peptide, which was endogenously processed to yield a MHC class-I peptide producing both CD4+and CD8+ responses, thus leading to a robust CTL signaling cascade and a maximum immune response. The hTERT-positive B-CLL patients treated with GV1001 peptide-loaded dendritic cells showed positive CD4+ and CD8+ T-cell responses without a negative effect on normal cells or autoimmunity (Kokhaei, et al., 2007), which suggests that GV1001 may be an effective for treatment of patients with B-CLL. GV1001 had successfully completed several phase I and II clinical trials conducted in patients with advanced stage melanoma, NSCLC, hepatocellular carcinoma and pancreatic cancer (Ruden & Puri, 2013). The phase III clinical trial has been carried out. Vx-001, cryptic peptide-based vaccine, is a new peptide based anticancer therapy 44
ACCEPTED MANUSCRIPT vaccine. Vx-001 consists of a low affinity cryptic peptide hTERT572 (RLFFYRKSV) (Ruden & Puri, 2013). Vx-001 had shown good antitumor efficacy evidenced by
PT
inhibition of tumor growth in vivo in HHD transgenic mice and in phase I and II clinical trials in patients with various types of tumors. Vx-001 had completed a large
RI
phase I/II clinical trial with different types of advanced stage cancers, including
SC
patients with NSCLC, breast cancer, melanoma and cholangiocarcinoma (Mavroudis, et al., 2006; Menez-Jamet & Kosmatopoulos, 2009).
NU
5.3.2. Protein
MA
Korean Mistletoe Lectin, a galactose- and N-acetyI-D-galactosamine-specific lectin (Viscum album L. coloratum agglutinin, VCA), was reported in 2002. VCA has anti-tumor potential and induced apoptosis in both SK-Hep-1 (p53-positive) and
TE
D
Hep3B (p53-negative) cells, which was associated with inhibition of telomerase via mitochondrial controlled pathway independent of p53 (Lyu SY, 2002). In addition,
AC CE P
VCA induced apoptotic cell death through activation of caspase-3 and the inhibition of telomerase activity through transcriptional down-regulation of hTERT in the VCA-treated A253 cells, which also resulted from dephosphorylation of Akt in the survival signaling pathways (S. H. Choi, Lyu, & Park, 2004). Fungal immunomodulatory protein, FIP-gts, was isolated from Ganoderma tsugae. Recombinant fungal immunomodulatory protein reFIP-gts in E. coli was expressed and purified. reFIP-gts significantly and selectively inhibited the growth of A549 cancer cells and suppressed telomerase activity in concentration-dependent manner via c-Myc-responsive element-dependent down-regulation of the hTERT (Liao CH, 2006). reFIP-gts entered the cell and its localization in the endoplasmic reticulum (ER) could result in ER stress, thereby increasing ER stress markers (CHOP/GADD153) and intracellular calcium release in A549 cells. ER stress induced intracellular 45
ACCEPTED MANUSCRIPT calcium release and resulted in inhibition of telomerase activity (Liao, et al., 2007). PinX1, Pin2/TRF1-interacting proteins, was reported in 2001 (L. K. Zhou XZ,
PT
2001). PinX1 can inhibit telomerase activity and affect tumorigenicity. PinX1 and its small TID domain bind to the hTERT, potently inhibiting its activity. Overexpression
RI
of PinX1 or its TID domain inhibits telomerase activity, shortens telomeres, and
SC
induces crisis, whereas depletion of endogenous PinX1 increases telomerase activity and elongated telomeres. Depletion of PinX1 also increase tumorigenicity in nude
NU
mice, consistent with its chromosome localization at 8p23, a region with frequent loss
MA
of heterozygosity in a number of human cancers (L. K. Zhou XZ, 2001; Lai XF, 2012). The continuous research indicates PinX1 is a major haplo-insufficient tumor suppressor, essential for maintaining telomerase activity and chromosome stability
TE
D
and therefore it is essential for cancer initiation (H. P. Zhou XZ, Shi R, Lee TH, Lu G, Zhang Z, Bronson R, Lu KP., 2011). Telomere elongation by human telomerase is
AC CE P
inhibited in cis by the telomeric protein TRF1 and its associated proteins. However, the link between TRF1 and inhibition of telomerase elongation of telomeres remains elusive because TRF1 has no direct effect on telomerase activity. The telomerase inhibitor PinX1 is recruited to telomeres by TRF1. It provides a critical link between TRF1 and telomerase inhibition to prevent telomere elongation and help to maintain telomere homeostasis (Soohoo, et al., 2011). Gastrokine 1 (GKN1) is a novel autocrine/paracrine protein that is specifically expressed in gastric mucosa and is isolated from the gastric mucosa cells of several mammalian species including rats (Yoon, et al., 2013). GKN1 had a tumor suppressor function through inhibition of cell proliferation and induction of apoptosis in gastric cancer cells (Yoon JH, 2014). Yoon et al. reported that GKN1 significantly decreased hTERT expression, telomerase activity, and telomere length in AGSGKN1 and MKN1GKN1 cells (both stable 46
ACCEPTED MANUSCRIPT overexpressed GKN1 gastric cancer cell lines). It could also directly bind to c-Myc and downregulate its expression as well as inhibit its binding to the TRF1 protein.
PT
GKN1 may be a potential chemotherapeutic candidate for gastric cancer treatment (Yoon JH, 2014).
RI
In addition, there are other reports about the telomerase inhibition of proteins.
SC
Protein phosphatase 2A inhibits nuclear telomerase activity in human breast cancer cells (Li H, 1997). Interferon-alpha induces a repression of hTERT and telomerase
NU
activity in human malignant and nonmalignant hematopoietic cells (D. Xu, et al.,
in
the
IL-6-dependent
MM
MA
2000). Interferon-alpha and interferon-gamma could downregulate telomerase activity cell
line
U266-1970
(Lindkvist,
Ivarsson,
Jernberg-Wiklund, & Paulsson-Karlsson, 2006). Bone Morphogenetic Protein-7
TE
D
inhibits cervical tumor growth by inhibiting telomerase activity and telomere maintenance (Cassar, et al., 2008). Activin, a pleiotropic cytokine, inhibits telomerase
AC CE P
activity and induces repression of hTERT gene in breast and cervical cancer cells (Katik, et al., 2009). Sohn et al. constructed zinc finger protein transcription factor. It derives from the human genome which bound to a 12-bp recognition sequence within the promoter of the hTERT gene and fused them with a KRAB repressor domain to create a potent transcriptional repressor. It could decrease mRNA level and telomerase activity together result in shortening of telomere length (Sohn, et al., 2010). 6. Conclusions and perspectives Telomerase is a promising target for cancer therapy. In this review, we emphasize the recent advances of function and mechanism of telomerase as an anti-tumor drug target in our understanding of telomere biology and its relation to cancer. In spite of development inhibitors targeting telomerase, practice has proven to be more difficult than what drug companies expected, but a new wave of clinical trials testing novel 47
ACCEPTED MANUSCRIPT combinations of drugs and new patient populations is finally providing evidence that telomerase inhibitors might be an effective cancer treatment, at least when it comes to
PT
some tumor types (Williams, 2013).
RI
But there are some concerns for using this strategy. Delay in efficacy for the
SC
therapy becomes phenotypically manifest because telomere shortening requires certain divisions of cells. And the lag phase between the time when telomerase of
NU
cancer cells has been inhibited and the shortening of their telomere length may allow
MA
cells to develop other alternative mechanism to overcome the crisis, such as ALT. About 85%-90% of human cancers achieve through increased activity of telomerase;
D
of the remaining 10%-15%, most are able to maintain their telomere lengths in
TE
absence of telomerase by one or more mechanisms referred to as ALT that occurs in
AC CE P
some common types of cancers. The reasons for this association are unclear. But it could be a potential alternative way for cancer cells escaping from anti-telomerase therapy.
Targeting of the non-canonical function of hTERT in combination with inhibiting telomerase catalytic activity could be a therapeutic approach, which could not only prevent the persistent activation of oncogenic signaling pathways, but concurrently induce senescence in proliferating tumor cells as a result of critical telomere shortening. The challenge is to explore the non-canonical function of hTERT by
cross-talking
with
complicated
signal
pathways.
Adverse
effects
of
telomerase-targeted treatment on normal cells need to be evaluated. With further understanding the action mechanism of telomerase component, it is more likely for
48
ACCEPTED MANUSCRIPT rational design of effective therapeutic interventions against telomerase active cancers.
PT
An interesting study shows that even though telomerase accumulates at Cajal
RI
bodies, it is not necessary for telomerase assembly, trafficking and extension in Cajal
SC
bodies of human cells (Y. Chen, et al., 2015). And mutations in dyskerin results in dyskerotosis congenita, a complex syndrome characterized by bone marrow failure
NU
(Zaug, Crary, Jesse Fioravanti, Campbell, & Cech, 2013). With more extensive
MA
understanding of the structure, biogenesis and mechanism of the enzyme, it will provide invaluable information for increasing the efficiency of rational drug design. In
D
addition, most treatments have shown to be more effective when used in combination
TE
with standard therapies. Optimizing the delivery methods and drug combinations
AC CE P
could be helpful in drug treatment because these would target many hallmarks of cancer at once.
Conflict of interest
The authors declare that there are no conflicts of interest. Acknowledgements
This work was supported by the National Natural Science Foundation of China (Grant no. 81370088), the Fundamental Research Funds for the Central Universities of Zhuizong, the Project of Shaanxi Star of Science and Technology (Grant no. 2012Kjxx-06), and the Supporting Plan of Education Ministry's New Century Excellent Talents (Grant no. NCET-13-0467). References Adler, S., Rashid, G., & Klein, A. (2011). Indole-3-carbinol inhibits telomerase activity and gene 49
ACCEPTED MANUSCRIPT expression in prostate cancer cell lines. Anticancer Res, 31, 3733-3737. Agatsuma T, A. T., Nara S, Matsumiya S, Nakai R, Ogawa H, Otaki S, Ikeda S, Saitoh Y, Kanda Y. (2002). UCS1025A and B, new antitumor antibiotics from the fungus Acremonium species.
PT
Org Lett, 4, 4387-4390. Aggarwal BB, B. A., Aggarwal RS, Seeram NP, Shishodia S, Takada Y. (2004). Role of resveratrol in
RI
prevention and therapy of cancer: preclinical and clinical studies. Anticancer Res, 24,
SC
2783-2840.
Ale-Agha, N., Dyballa-Rukes, N., Jakob, S., Altschmied, J., & Haendeler, J. (2014). Cellular functions
NU
of the dual-targeted catalytic subunit of telomerase, telomerase reverse transcriptase--potential role in senescence and aging. Experimental Gerontology, 56, 189-193.
MA
Ambrus, A., Chen, D., Dai, J., Bialis, T., Jones, R. A., & Yang, D. (2006). Human telomeric sequence forms a hybrid-type intramolecular G-quadruplex structure with mixed parallel/antiparallel strands in potassium solution. Nucleic Acids Research, 34, 2723-2735.
D
Artandi, S. E., Alson, S., Tietze, M. K., Sharpless, N. E., Ye, S., Greenberg, R. A., Castrillon, D. H.,
TE
Horner, J. W., Weiler, S. R., Carrasco, R. D., & DePinho, R. A. (2002). Constitutive telomerase expression promotes mammary carcinomas in aging mice. Proc Natl Acad Sci U S
AC CE P
A, 99, 8191-8196.
Artandi, S. E., & DePinho, R. A. (2010). Telomeres and telomerase in cancer. Carcinogenesis, 31, 9-18. Asai, A., Oshima, Y., Yamamoto, Y., Uochi, T. A., Kusaka, H., Akinaga, S., Yamashita, Y., Pongracz, K., Pruzan, R., Wunder, E., Piatyszek, M., Li, S., Chin, A. C., Harley, C. B., & Gryaznov, S. (2003). A novel telomerase template antagonist (GRN163) as a potential anticancer agent. Cancer Res, 63, 3931-3939. Azhibek, D., Zvereva, M., Zatsepin, T., Rubtsova, M., & Dontsova, O. (2014). Chimeric bifunctional oligonucleotides as a novel tool to invade telomerase assembly. Nucleic Acids Res, 42, 9531-9542. Bae-Jump, V. L., Zhou, C., Boggess, J. F., Whang, Y. E., Barroilhet, L., & Gehrig, P. A. (2010). Rapamycin inhibits cell proliferation in type I and type II endometrial carcinomas: a search for biomarkers of sensitivity to treatment. Gynecol Oncol, 119, 579-585. Bae-Jump, V. L., Zhou, C., Gehrig, P. A., Whang, Y. E., & Boggess, J. F. (2006). Rapamycin inhibits hTERT telomerase mRNA expression, independent of cell cycle arrest. Gynecol Oncol, 100, 50
ACCEPTED MANUSCRIPT 487-494. Baerlocher, G. M., Oppliger Leibundgut, E., Ottmann, O. G., Spitzer, G., Odenike, O., McDevitt, M. A., Roth, A., Daskalakis, M., Burington, B., Stuart, M., & Snyder, D. S. (2015). Telomerase
PT
Inhibitor Imetelstat in Patients with Essential Thrombocythemia. N Engl J Med, 373, 920-928. Bai, L. P., Hagihara, M., Jiang, Z. H., & Nakatani, K. (2008). Ligand binding to tandem G
RI
quadruplexes from human telomeric DNA. Chembiochem, 9, 2583-2587.
SC
Baoping, Y., Guoyong, H., Jieping, Y., Zongxue, R., & Hesheng, L. (2004). Cyclooxygenase-2 inhibitor nimesulide suppresses telomerase activity by blocking Akt/PKB activation in gastric cancer
NU
cell line. Dig Dis Sci, 49, 948-953.
Bashash, D., Ghaffari, S. H., Mirzaee, R., Alimoghaddam, K., & Ghavamzadeh, A. (2013). Telomerase
MA
inhibition by non-nucleosidic compound BIBR1532 causes rapid cell death in pre-B acute lymphoblastic leukemia cells. Leuk Lymphoma, 54, 561-568. Bashash, D., Ghaffari, S. H., Zaker, F., Hezave, K., Kazerani, M., Ghavamzadeh, A., Alimoghaddam,
D
K., Mosavi, S. A., Gharehbaghian, A., & Vossough, P. (2012). Direct short-term cytotoxic
TE
effects of BIBR 1532 on acute promyelocytic leukemia cells through induction of p21 coupled with downregulation of c-Myc and hTERT transcription. Cancer Invest, 30, 57-64.
AC CE P
Beatty, G. L., & Vonderheide, R. H. (2008). Telomerase as a universal tumor antigen for cancer vaccines. Expert Rev Vaccines, 7, 881-887.
Beck, S., Jin, X., Sohn, Y. W., Kim, J. K., Kim, S. H., Yin, J., Pian, X., Kim, S. C., Nam, D. H., Choi, Y. J., & Kim, H. (2011). Telomerase activity-independent function of TERT allows glioma cells to attain cancer stem cell characteristics by inducing EGFR expression. Mol Cells, 31, 9-15.
Bermudez, Y., Ahmadi, S., Lowell, N. E., & Kruk, P. A. (2007). Vitamin E suppresses telomerase activity in ovarian cancer cells. Cancer Detect Prev, 31, 119-128. Blackburn, E. H., & Collins, K. (2011). Telomerase: an RNP enzyme synthesizes DNA. Cold Spring Harb Perspect Biol, 3. Bley, C. J., Qi, X. D., Rand, D. P., Borges, C. R., Nelson, R. W., & Chen, J. J. L. (2011). RNA-protein binding interface in the telomerase ribonucleoprotein. Proc Natl Acad Sci U S A, 108, 20333-20338. Bojesen, S. E., Pooley, K. A., Johnatty, S. E., Beesley, J., Michailidou, K., Tyrer, J. P., et al. (2013). Multiple independent variants at the TERT locus are associated with telomere length and risks 51
ACCEPTED MANUSCRIPT of breast and ovarian cancer. Nat Genet, 45, 371-384. Brandt, S., Heller, H., Schuster, K. D., & Grote, J. (2005). The tamoxifen-induced suppression of telomerase activity in the human hepatoblastoma cell line HepG2: a result of post-translational
PT
regulation. J Cancer Res Clin Oncol, 131, 120-128. Broccoli, D., Godley, I. A., Donehower, L. A., Varmus, H. E., & deLange, T. (1996). Telomerase
RI
activation in mouse mammary tumors: Lack of detectable telomere shortening and evidence
SC
for regulation of telomerase RNA with cell. Mol Cell Biol, 16, 3765-3772. Brown, A. F., Podlevsky, J. D., Qi, X., Chen, Y., Xie, M., & Chen, J. J. (2014). A self-regulating
NU
template in human telomerase. Proc Natl Acad Sci U S A, 111, 11311-11316. Brown, T., Sigurdson, E., Rogatko, A., & Broccoli, D. (2003). Telomerase inhibition using
MA
azidothymidine in the HT-29 colon cancer cell line. Ann Surg Oncol, 10, 910-915. Bryan, C., Rice, C., Hoffman, H., Harkisheimer, M., Sweeney, M., & Skordalakes, E. (2015). Structural Basis of Telomerase Inhibition by the Highly Specific BIBR1532. Structure, 23,
D
1934-1942.
TE
Burger, A. M., Dai, F., Schultes, C. M., Reszka, A. P., Moore, M. J., Double, J. A., & Neidle, S. (2005). The G-quadruplex-interactive molecule BRACO-19 inhibits tumor growth, consistent with
AC CE P
telomere targeting and interference with telomerase function. Cancer Res, 65, 1489-1496.
Burger AM, D. J., Newell DR. (1997). Inhibition of telomerase activity by cisplatin in human testicular cancer cells. Eur J Cancer, 33, 638-644.
Cairney, C. J., & Keith, W. N. (2008). Telomerase redefined: Integrated regulation of hTR and hTERT for telomere maintenance and telomerase activity. Biochimie, 90, 13-23.
Calado, R. T., & Young, N. S. (2009). Mechanisms of Disease: Telomere Diseases. New England Journal of Medicine, 361, 2353-2365. Cassar, L., Li, H., Pinto, A. R., Nicholls, C., Bayne, S., & Liu, J. P. (2008). Bone morphogenetic protein-7 inhibits telomerase activity, telomere maintenance, and cervical tumor growth. Cancer Res, 68, 9157-9166. Chakrabarti, M., Banik, N. L., & Ray, S. K. (2013). Sequential hTERT knockdown and apigenin treatment inhibited invasion and proliferation and induced apoptosis in human malignant neuroblastoma SK-N-DZ and SK-N-BE2 cells. J Mol Neurosci, 51, 187-198. Chen, C. L., Chang, D. M., Chen, T. C., Lee, C. C., Hsieh, H. H., Huang, F. C., Huang, K. F., Guh, J. H., 52
ACCEPTED MANUSCRIPT Lin, J. J., & Huang, H. S. (2013). Structure-based design, synthesis and evaluation of novel anthra[1,2-d]imidazole-6,11-dione derivatives as telomerase inhibitors and potential for cancer polypharmacology. Eur J Med Chem, 60, 29-41.
PT
Chen, H., Li, Y., & Tollefsbol, T. O. (2009). Strategies targeting telomerase inhibition. Mol Biotechnol, 41, 194-199.
RI
Chen, J. L.-Y., Sperry, J., Ip, N. Y., & Brimble, M. A. (2011). Natural products targeting telomere
SC
maintenance. MedChemComm, 2, 229.
Chen, J. L., Blasco, M. A., & Greider, C. W. (2000). Secondary structure of vertebrate telomerase RNA.
NU
Cell, 100, 503-514.
Chen, Y., Deng, Z., Jiang, S., Hu, Q., Liu, H., Songyang, Z., Ma, W., Chen, S., & Zhao, Y. (2015).
MA
Human cells lacking coilin and Cajal bodies are proficient in telomerase assembly, trafficking and telomere maintenance. Nucleic Acids Res, 43, 385-395. Chen, Y. J., Sheng, W. Y., Huang, P. R., & Wang, T. C. (2006). Potent inhibition of human telomerase
D
by U-73122. J Biomed Sci, 13, 667-674.
TE
Chen, Z. F., Liu, Y. C., Liu, L. M., Wang, H. S., Qin, S. H., Wang, B. L., Bian, H. D., Yang, B., Fun, H. K., Liu, H. G., Liang, H., & Orvig, C. (2009). Potential new inorganic antitumour agents from
AC CE P
combining the anticancer traditional Chinese medicine (TCM) liriodenine with metal ions, and DNA binding studies. Dalton Trans, 262-272.
Chen, Z. F., Qin, Q. P., Qin, J. L., Liu, Y. C., Huang, K. B., Li, Y. L., Meng, T., Zhang, G. H., Peng, Y., Luo, X. J., & Liang, H. (2015). Stabilization of G-quadruplex DNA, inhibition of telomerase activity, and tumor cell apoptosis by organoplatinum(II) complexes with oxoisoaporphine. J Med Chem, 58, 2159-2179. Chen, Z. F., Qin, Q. P., Qin, J. L., Zhou, J., Li, Y. L., Li, N., Liu, Y. C., & Liang, H. (2015). Water-Soluble Ruthenium(II) Complexes with Chiral 4-(2,3-Dihydroxypropyl)-formamide Oxoaporphine (FOA): In Vitro and in Vivo Anticancer Activity by Stabilization of G-Quadruplex DNA, Inhibition of Telomerase Activity, and Induction of Tumor Cell Apoptosis. J Med Chem, 58, 4771-4789. Cheng, Y.-L., Chang, W.-L., Lee, S.-C., Liu, Y.-G., Lin, H.-C., Chen, C.-J., Yen, C.-Y., Yu, D.-S., Lin, S.-Z., & Harn, H.-J. (2003). Acetone extract of Bupleurum scorzonerifolium inhibits proliferation of A549 human lung cancer cells via inducing apoptosis and suppressing 53
ACCEPTED MANUSCRIPT telomerase activity. Life Sci, 73, 2383-2394. Chiappori, A. A., Kolevska, T., Spigel, D. R., Hager, S., Rarick, M., Gadgeel, S., Blais, N., Von Pawel, J., Hart, L., Reck, M., Bassett, E., Burington, B., & Schiller, J. H. (2015). A randomized phase
non-small-cell lung cancer. Annals of Oncology, 26, 354-362.
PT
II study of the telomerase inhibitor imetelstat as maintenance therapy for advanced
RI
Chiu, W. T., Shen, S. C., Yang, L. Y., Chow, J. M., Wu, C. Y., & Chen, Y. C. (2011). Inhibition of
endothelial cells. J Cell Physiol, 226, 2041-2051.
SC
HSP90-dependent telomerase activity in amyloid beta-induced apoptosis of cerebral
NU
Choi, J. H., Min, N. Y., Park, J., Kim, J. H., Park, S. H., Ko, Y. J., Kang, Y., Moon, Y. J., Rhee, S., Ham, S. W., Park, A. J., & Lee, K. H. (2010). TSA-induced DNMT1 down-regulation represses
MA
hTERT expression via recruiting CTCF into demethylated core promoter region of hTERT in HCT116. Biochem Biophys Res Commun, 391, 449-454. Choi, S. H., Im, E., Kang, H. K., Lee, J. H., Kwak, H. S., Bae, Y. T., Park, H. J., & Kim, N. D. (2005).
D
Inhibitory effects of costunolide on the telomerase activity in human breast carcinoma cells.
TE
Cancer Lett, 227, 153-162.
Choi, S. H., Lyu, S. Y., & Park, W. B. (2004). Mistletoe lectin induces apoptosis and telomerase
AC CE P
inhibition in human A253 cancer cells through dephosphorylation of Akt. Arch Pharm Res, 27, 68-76.
Chung, J., Khadka, P., & Chung, I. K. (2012). Nuclear import of hTERT requires a bipartite nuclear localization signal and Akt-mediated phosphorylation. Journal of Cell Science, 125,
2684-2697.
Chung, W. J., Heddi, B., Tera, M., Iida, K., Nagasawa, K., & Phan, A. T. (2013). Solution structure of an intramolecular (3 + 1) human telomeric G-quadruplex bound to a telomestatin derivative. J Am Chem Soc, 135, 13495-13501. Ci X, L. B., Ma X, Kong F, Zheng C, Björkholm M, Jia J, Xu D. (2015). Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells. Oncotarget, 6, 38079-38092. Cifuentes-Rojas, C., & Shippen, D. E. (2012). Telomerase regulation. Mutat Res, 730, 20-27. Clark GR, P. P., Squire CJ, Neidle S. (2003). Structure of the first parallel DNA quadruplex-drug complex. J Am Chem Soc, 125, 4066-4067. 54
ACCEPTED MANUSCRIPT Cocco MJ, H. L., Huber MD, Maizels N. (2003). Specific interactions of distamycin with G-quadruplex DNA. Nucleic Acids Res, 31, 2944-2951. Collins, K. (2006). The biogenesis and regulation of telomerase holoenzymes. Nature Reviews
PT
Molecular Cell Biology, 7, 484-494. Compton, S. A., Elmore, L. W., Haydu, K., Jackson-Cook, C. K., & Holt, S. E. (2006). Induction of
SC
human tumor cells. Mol Cell Biol, 26, 1452-1462.
RI
nitric oxide synthase-dependent telomere shortening after functional inhibition of Hsp90 in
Cookson, J. C., Dai, F., Smith, V., Heald, R. A., Laughton, C. A., Stevens, M. F., & Burger, A. M. Pharmacodynamics
of
the
G-quadruplex-stabilizing
telomerase
inhibitor
NU
(2005).
3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acridinium methosulfate (RHPS4) in vitro:
MA
activity in human tumor cells correlates with telomere length and can be enhanced, or antagonized, with cytotoxic agents. Mol Pharmacol, 68, 1551-1558. D'Ambrosio, D., Reichenbach, P., Micheli, E., Alvino, A., Franceschin, M., Savino, M., & Lingner, J.
D
(2012). Specific binding of telomeric G-quadruplexes by hydrosoluble perylene derivatives
TE
inhibits repeat addition processivity of human telomerase. Biochimie, 94, 854-863. Damm K, H. U., Garin-Chesa P, Hauel N, Kauffmann I, Priepke H, Niestroj C, Daiber C, Enenkel B,
AC CE P
Guilliard B, Lauritsch I, Müller E, Pascolo E, Sauter G, Pantic M, Martens UM, Wenz C, Lingner J, Kraut N, Rettig WJ, Schnapp A. (2001). A highly selective telomerase inhibitor limiting human cancer cell proliferation. EMBO J, 20, 6958-6968.
Daniel, M., Peek, G. W., & Tollefsbol, T. O. (2012). Regulation of the human catalytic subunit of telomerase (hTERT). Gene, 498, 135-146.
de Lange, T. (2005). Shelterin: the protein complex that shapes and safeguards human telomeres. Genes Dev, 19, 2100-2110. DeBoer C, M. P., Wnuk RJ, Peterson DH. (1970). Geldanamycin, a new antibiotic. J Antibiot, 23, 442-447. Debray, J., Zeghida, W., Jourdan, M., Monchaud, D., Dheu-Andries, M. L., Dumy, P., Teulade-Fichou, M. P., & Demeunynck, M. (2009). Synthesis and evaluation of fused bispyrimidinoacridines as novel pentacyclic analogues of quadruplex-binder BRACO-19. Org Biomol Chem, 7, 5219-5228. Deeb, D., Gao, X., Liu, Y., Kim, S. H., Pindolia, K. R., Arbab, A. S., & Gautam, S. C. (2012). 55
ACCEPTED MANUSCRIPT Inhibition of cell proliferation and induction of apoptosis by oleanane triterpenoid (CDDO-Me) in pancreatic cancer cells is associated with the suppression of hTERT gene expression and its telomerase activity. Biochem Biophys Res Commun, 422, 561-567.
PT
Deeb, D., Gao, X., Liu, Y., Varma, N. R., Arbab, A. S., & Gautam, S. C. (2013). Inhibition of telomerase activity by oleanane triterpenoid CDDO-Me in pancreatic cancer cells is
RI
ROS-dependent. Molecules, 18, 3250-3265.
SC
Djojosubroto, M. W., Chin, A. C., Go, N., Schaetzlein, S., Manns, M. P., Gryaznov, S., Harley, C. B., & Rudolph, K. L. (2005). Telomerase antagonists GRN163 and GRN163L inhibit tumor growth
NU
and increase chemosensitivity of human hepatoma. Hepatology, 42, 1127-1136. Draisci, R., Lucentini, L., Giannetti, L., Boria, P., & Poletti, R. (1996). First report of pectenotoxin-2
MA
(PTX-2) in algae (Dinophysis fortii) related to seafood poisoning in Europe. Toxicon, 34, 923-935.
Drosopoulos, W. C., Direnzo, R., & Prasad, V. R. (2005). Human telomerase RNA template sequence is
D
a determinant of telomere repeat extension rate. J Biol Chem, 280, 32801-32810.
TE
Duan, W., Rangan, A., Vankayalapati, H., Kim, M. Y., Zeng, Q., Sun, D., Han, H., Fedoroff, O. Y., Nishioka, D., Rha, S. Y., Izbicka, E., Von Hoff, D. D., & Hurley, L. H. (2001). Design and
AC CE P
synthesis of fluoroquinophenoxazines that interact with human telomeric G-quadruplexes and their biological effects. Mol Cancer Ther, 1, 103-120.
Egan, E. D., & Collins, K. (2010). Specificity and stoichiometry of subunit interactions in the human telomerase holoenzyme assembled in vivo. Mol Cell Biol, 30, 2775-2786.
Eitsuka, T., Nakagawa, K., Suzuki, T., & Miyazawa, T. (2005). Polyunsaturated fatty acids inhibit telomerase activity in DLD-1 human colorectal adenocarcinoma cells: a dual mechanism approach. Biochim Biophys Acta, 1737, 1-10. El Daly, H., & Martens, U. M. (2007). Telomerase inhibition and telomere targeting in hematopoietic cancer cell lines with small non-nucleosidic synthetic compounds (BIBR1532). Methods Mol Biol, 405, 47-60. Faezizadeh Z, M.-N. S., Allameh A. (2012). The effect of silymarin on telomerase activity in the human leukemia cell line K562. Planta Med, 78, 899-902. Falchetti, M. L., Mongiardi, M. P., Fiorenzo, P., Petrucci, G., Pierconti, F., D'Agnano, I., D'Alessandris, G., Alessandri, G., Gelati, M., Ricci-Vitiani, L., Maira, G., Larocca, L. M., Levi, A., & Pallini, 56
ACCEPTED MANUSCRIPT R. (2008). Inhibition of telomerase in the endothelial cells disrupts tumor angiogenesis in glioblastoma xenografts. International Journal of Cancer, 122, 1236-1242. Fan YX, W. Z., Cheng JR, Gao N, Chen JM. (2008). Research progress of Chinese Traditional
PT
Medicine on the inhibiting of telomerase activity. Chinese Traditonal patent Medicine, 30, 1346-1350.
RI
Feldser, D. M., & Greider, C. W. (2007). Short telomeres limit tumor progression in vivo by inducing
SC
senescence. Cancer Cell, 11, 461-469.
Feng, J. L., Funk, W. D., Wang, S. S., Weinrich, S. L., Avilion, A. A., Chiu, C. P., Adams, R. R., Chang,
NU
E., Allsopp, R. C., Yu, J. H., Le, S. Y., West, M. D., Harley, C. B., Andrews, W. H., Greider, C. W., & Villeponteau, B. (1995). The Rna Component of Human Telomerase. Science, 269,
MA
1236-1241.
Flores, I., Evan, G., & Blasco, M. A. (2006). Genetic analysis of myc and telomerase interactions in vivo. Mol Cell Biol, 26, 6130-6138.
D
Folini, M., Bandiera, R., Millo, E., Gandellini, P., Sozzi, G., Gasparini, P., Longoni, N., Binda, M.,
TE
Daidone, M. G., Berg, K., & Zaffaroni, N. (2007). Photochemically enhanced delivery of a cell-penetrating peptide nucleic acid conjugate targeting human telomerase reverse
AC CE P
transcriptase: effects on telomere status and proliferative potential of human prostate cancer cells. Cell Prolif, 40, 905-920.
Folini, M., Berg, K., Millo, E., Villa, R., Prasmickaite, L., Daidone, M. G., Benatti, U., & Zaffaroni, N. (2003). Photochemical internalization of a peptide nucleic acid targeting the catalytic subunit of human telomerase. Cancer Res, 63, 3490-3494.
Franceschin, M., Rossetti, L., D'Ambrosio, A., Schirripa, S., Bianco, A., Ortaggi, G., Savino, M., Schultes, C., & Neidle, S. (2006). Natural and synthetic G-quadruplex interactive berberine derivatives. Bioorg Med Chem Lett, 16, 1707-1711. Francis J. Schmitz, F. S. D., M. Bilayet Hossain, Dick Van der Helm. (1991). Cytotoxic aromatic alkaloids from the ascidian Amphicarpa meridiana and Leptoclinides sp.: meridine and 11-hydroxyascididemin. J. Org. Chem, 56, 804-808. Fuggetta MP, L. G., Tricarico M, Cottarelli A, Falchetti R, Ravagnan G, Bonmassar E. (2006). Effect of resveratrol on proliferation and telomerase activity of human colon cancer cells in vitro. J Exp Clin Cancer Res, 25, 189-193. 57
ACCEPTED MANUSCRIPT Fujimori, J., Matsuo, T., Shimose, S., Kubo, T., Ishikawa, M., Yasunaga, Y., & Ochi, M. (2011). Antitumor effects of telomerase inhibitor TMPyP4 in osteosarcoma cell lines. J Orthop Res, 29, 1707-1711.
PT
Fukuyama, R., Ng, K. P., Cicek, M., Kelleher, C., Niculaita, R., Casey, G., & Sizemore, N. (2007). Role of IKK and oscillatory NF kappa B kinetics in MMP-9 gene expression and
RI
chemoresistance to 5-fluorouracil in RKO colorectal cancer cells. Mol Carcinog, 46, 402-413.
SC
Gan, Y., Lu, J., Yeung, B. Z., Cottage, C. T., Wientjes, M. G., & Au, J. L. (2015). Pharmacodynamics of telomerase inhibition and telomere shortening by noncytotoxic suramin. AAPS J, 17, 268-276.
NU
Gao C, L. Y., Cai XM, Hao XZ. (2010). The effect of Hedyotis diffusais on telomerase activity, cell apoptosis and cell cycle. Acta academiae medicinae Xuzhou, 30, 466-468.
MA
Gao, S., Yu, B. P., Li, Y., Dong, W. G., & Luo, H. S. (2003). Antiproliferative effect of octreotide on gastric cancer cells mediated by inhibition of Akt/PKB and telomerase. World J Gastroenterol, 9, 2362-2365.
D
Geserick, C., Tejera, A., Gonzalez-Suarez, E., Klatt, P., & Blasco, M. A. (2006). Expression of mTert in
TE
primary murine cells links the growth-promoting effects of telomerase to transforming growth factor-beta signaling. Oncogene, 25, 4310-4319.
AC CE P
Ghosh, A., Saginc, G., Leow, S. C., Khattar, E., Shin, E. M., Yan, T. D., Wong, M., Zhang, Z. Z., Li, G. L., Sung, W. K., Zhou, J. B., Chng, W. J., Li, S., Liu, E., & Tergaonkar, V. (2012). Telomerase directly regulates NF-kappa B-dependent transcription. Nature Cell Biology, 14, 1270-+.
Gillis, A. J., Schuller, A. P., & Skordalakes, E. (2008). Structure of the Tribolium castaneum telomerase catalytic subunit TERT. Nature, 455, 633-U636.
Giridharan, P., Somasundaram, S. T., Perumal, K., Vishwakarma, R. A., Karthikeyan, N. P., Velmurugan, R., & Balakrishnan, A. (2002). Novel substituted methylenedioxy lignan suppresses proliferation of cancer cells by inhibiting telomerase and activation of c-myc and caspases leading to apoptosis. Br J Cancer, 87, 98-105. Gladych, M., Wojtyla, A., & Rubis, B. (2011). Human telomerase expression regulation. Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire, 89, 359-376. Gomez, D., O'Donohue, M. F., Wenner, T., Douarre, C., Macadre, J., Koebel, P., Giraud-Panis, M. J., Kaplan, H., Kolkes, A., Shin-ya, K., & Riou, J. F. (2006). The G-quadruplex ligand telomestatin inhibits POT1 binding to telomeric sequences in vitro and induces GFP-POT1 58
ACCEPTED MANUSCRIPT dissociation from telomeres in human cells. Cancer Res, 66, 6908-6912. Gomez, D. L. M., Farina, H. G., & Gomez, D. E. (2013). Telomerase regulation: A key to inhibition? (Review). International Journal of Oncology, 43, 1351-1356.
PT
Gonzalez-Suarez, E., Samper, E., Ramirez, A., Flores, J. M., Martin-Caballero, J., Jorcano, J. L., & Blasco, M. A. (2001). Increased epidermal tumors and increased skin wound healing in
RI
transgenic mice overexpressing the catalytic subunit of telomerase, mTERT, in basal
SC
keratinocytes. Embo Journal, 20, 2619-2630.
Greider, C. W., & Blackburn, E. H. (1987). The Telomere Terminal Transferase of Tetrahymena Is a
NU
Ribonucleoprotein Enzyme with 2 Kinds of Primer Specificity. Cell, 51, 887-898. Greider, C. W., & Blackburn, E. H. (1989). A telomeric sequence in the RNA of Tetrahymena
MA
telomerase required for telomere repeat synthesis. Nature, 337, 331-337. Grozdanov, P. N., Roy, S., Kittur, N., & Meier, U. T. (2009). SHQ1 is required prior to NAF1 for
Society, 15, 1188-1197.
D
assembly of H/ACA small nucleolar and telomerase RNPs. Rna-a Publication of the Rna
TE
Guittat, L., Alberti, P., Rosu, F., Van Miert, S., Thetiot, E., Pieters, L., Gabelica, V., De Pauw, E., Ottaviani, A., Riou, J.-F., & Mergny, J.-L. (2003). Interactions of cryptolepine and
AC CE P
neocryptolepine with unusual DNA structures. Biochimie, 85, 535-547.
Guo, Q. L., Lin, S. S., You, Q. D., Gu, H. Y., Yu, J., Zhao, L., Qi, Q., Liang, F., Tan, Z., & Wang, X. (2006). Inhibition of human telomerase reverse transcriptase gene expression by gambogic acid in human hepatoma SMMC-7721 cells. Life Sci, 78, 1238-1245.
Gurung RL, L. H., Venkatesan S, Lee PS, Hande MP. (2014). Targeting DNA-PKcs and telomerase in brain tumour cells. Mol Cancer, 13, 232. Haendeler, J., Hoffmann, J., Rahman, S., Zeiher, A. M., & Dimmeler, S. (2003). Regulation of telomerase activity and anti-apoptotic function by protein-protein interaction and phosphorylation. Febs Letters, 536, 180-186. Haering, C. H., Nakamura, T. M., Baumann, P., & Cech, T. R. (2000). Analysis of telomerase catalytic subunit mutants in vivo and in vitro in Schizosaccharomyces pombe. Proc Natl Acad Sci U S A, 97, 6367-6372. Hahn, W. C., Counter, C. M., Lundberg, A. S., Beijersbergen, R. L., Brooks, M. W., & Weinberg, R. A. (1999). Creation of human tumour cells with defined genetic elements. Nature, 400, 464-468. 59
ACCEPTED MANUSCRIPT Han, M. H., Kim, G. Y., Moon, S. K., Kim, W. J., Nam, T. J., & Choi, Y. H. (2011). Apoptosis induction by glycoprotein isolated from Laminaria japonica is associated with down-regulation of telomerase activity and prostaglandin E2 synthesis in AGS human gastric cancer cells. Int J
PT
Oncol, 38, 577-584. Han QB, X. H. (2009). Caged Garcinia xanthones: development since 1937. Curr Med Chem, 16,
RI
3775-3796.
SC
Hanahan, D., & Weinberg, R. A. (2011). Hallmarks of Cancer: The Next Generation. Cell, 144, 646-674.
NU
Hartwig, F. P., Nedel, F., Collares, T. V., Tarquinio, S. B. C., Nor, J. E., & Demarco, F. F. (2012). Telomeres and Tissue Engineering: The Potential Roles of TERT in VEGF-mediated
MA
Angiogenesis. Stem Cell Reviews and Reports, 8, 1275-1281. Hayakawa, N., Nozawa, K., Ogawa, A., Kato, N., Yoshida, K., Akamatsu, K., Tsuchiya, M., Nagasaka, A., & Yoshida, S. (1999). Isothiazolone derivatives selectively inhibit telomerase from human
D
and rat cancer cells in vitro. biochemistry, 38, 11501-11507.
TE
He, H., Xia, H. H., Wang, J. D., Gu, Q., Lin, M. C., Zou, B., Lam, S. K., Chan, A. O., Yuen, M. F., Kung, H. F., & Wong, B. C. (2006). Inhibition of human telomerase reverse transcriptase by
AC CE P
nonsteroidal antiinflammatory drugs in colon carcinoma. Cancer, 106, 1243-1249.
Herz, C., Hertrampf, A., Zimmermann, S., Stetter, N., Wagner, M., Kleinhans, C., Erlacher, M., Schuler, J., Platz, S., Rohn, S., Mersch-Sundermann, V., & Lamy, E. (2014). The isothiocyanate erucin abrogates telomerase in hepatocellular carcinoma cells in vitro and in an orthotopic xenograft tumour model of HCC. J Cell Mol Med, 18, 2393-2403.
Hirashima, K., & Seimiya, H. (2015). Telomeric repeat-containing RNA/G-quadruplex-forming sequences cause genome-wide alteration of gene expression in human cancer cells in vivo. Nucleic Acids Research, 43, 2022-2032. Hirota, K., Nodasaka, Y., Orikasa, Y., Okuyama, H., & Yumoto, I. (2005). Shewanella pneumatophori sp. nov., an eicosapentaenoic acid-producing marine bacterium isolated from the intestines of Pacific mackerel (Pneumatophorus japonicus). Int J Syst Evol Microbiol, 55, 2355-2359. Hochreiter, A. E., Xiao, H., Goldblatt, E. M., Gryaznov, S. M., Miller, K. D., Badve, S., Sledge, G. W., & Herbert, B. S. (2006). Telomerase template antagonist GRN163L disrupts telomere maintenance, tumor growth, and metastasis of breast cancer. Clin Cancer Res, 12, 3184-3192. 60
ACCEPTED MANUSCRIPT Holohan B, H. M., Lai TP, Huang E, Friedman DR, Wright WE, Shay JW. (2015). Perifosine as a potential novel anti-telomerase therapy. Oncotarget, 6, 21816-21826. Holt, S. E., Aisner, D. L., Baur, J., Tesmer, V. M., Dy, M., Ouellette, M., Trager, J. B., Morin, G. B.,
and Hsp90 in telomerase complexes. Genes Dev, 13, 817-826.
PT
Toft, D. O., Shay, J. W., Wright, W. E., & White, M. A. (1999). Functional requirement of p23
RI
Honda T, R. B., Bore L, Finlay HJ, Favaloro FG Jr, Suh N, Wang Y, Sporn MB, Gribble GW. (2000).
SC
Synthetic oleanane and ursane triterpenoids with modified rings A and C: a series of highly active inhibitors of nitric oxide production in mouse macrophages. J. Med. Chem, 43,
NU
4233-4246.
Hsu, C. P., Lee, L. W., Tang, S. C., Hsin, I. L., Lin, Y. W., & Ko, J. L. (2015). Epidermal growth factor
MA
activates telomerase activity by direct binding of Ets-2 to hTERT promoter in lung cancer cells. Tumor Biology, 36, 5389-5398.
Hu, Y., Bobb, D., Lu, Y., He, J., & Dome, J. S. (2014). Effect of telomerase inhibition on preclinical
D
models of malignant rhabdoid tumor. Cancer Genet, 207, 403-411.
TE
Huang, F. C., Chang, C. C., Wang, J. M., Chang, T. C., & Lin, J. J. (2012). Induction of senescence in cancer cells by the G-quadruplex stabilizer, BMVC4, is independent of its telomerase
AC CE P
inhibitory activity. Br J Pharmacol, 167, 393-406.
Huang, F. C., Huang, K. F., Chen, R. H., Wu, J. E., Chen, T. C., Chen, C. L., Lee, C. C., Chen, J. Y., Lin, J. J., & Huang, H. S. (2012). Synthesis, telomerase evaluation and anti-proliferative studies on various series of diaminoanthraquinone-linked aminoacyl residue derivatives. Arch Pharm
(Weinheim), 345, 101-111.
Huang, J., Brown, A. F., Wu, J., Xue, J., Bley, C. J., Rand, D. P., Wu, L. J., Zhang, R. G., Chen, J. J. L., & Lei, M. (2014). Structural basis for protein-RNA recognition in telomerase. Nature Structural & Molecular Biology, 21, 507-512. Huang, P. R., Yeh, Y. M., Pao, C. C., Chen, C. Y., & Wang, T. C. (2012). N-(1-Pyrenyl) maleimide inhibits telomerase activity in a cell free system and induces apoptosis in Jurkat cells. Mol Biol Rep, 39, 8899-8905. Huang, S. T., Wang, C. Y., Yang, R. C., Chu, C. J., Wu, H. T., & Pang, J. H. (2010). Wogonin, an active compound in Scutellaria baicalensis, induces apoptosis and reduces telomerase activity in the HL-60 leukemia cells. Phytomedicine, 17, 47-54. 61
ACCEPTED MANUSCRIPT Hug, N., & Lingner, J. (2006). Telomere length homeostasis. Chromosoma, 115, 413-425. Ilyinsky, N. S., Shchyolkina, A. K., Borisova, O. F., Mamaeva, O. K., Zvereva, M. I., Azhibek, D. M., Livshits, M. A., Mitkevich, V. A., Balzarini, J., Sinkevich, Y. B., Luzikov, Y. N., Dezhenkova,
PT
L. G., Kolotova, E. S., Shtil, A. A., Shchekotikhin, A. E., & Kaluzhny, D. N. (2014). Novel multi-targeting anthra[2,3-b]thiophene-5,10-diones with guanidine-containing side chains:
SC
cytotoxic properties. Eur J Med Chem, 85, 605-614.
RI
interaction with telomeric G-quadruplex, inhibition of telomerase and topoisomerase I and
Imanshahidi, M., & Hosseinzadeh, H. (2008). Pharmacological and therapeutic effects of Berberis
NU
vulgaris and its active constituent, berberine. Phytother Res, 22, 999-1012. Indran, I. R., Hande, M. P., & Pervaiz, S. (2011). hTERT overexpression alleviates intracellular ROS
cells. Cancer Res, 71, 266-276.
MA
production, improves mitochondrial function, and inhibits ROS-mediated apoptosis in cancer
Jagadeesh, S., Kyo, S., & Banerjee, P. P. (2006). Genistein represses telomerase activity via both
TE
66, 2107-2115.
D
transcriptional and posttranslational mechanisms in human prostate cancer cells. Cancer Res,
Jayasooriya, R. G., Kang, S. H., Kang, C. H., Choi, Y. H., Moon, D. O., Hyun, J. W., Chang, W. Y., &
AC CE P
Kim, G. Y. (2012). Apigenin decreases cell viability and telomerase activity in human leukemia cell lines. Food Chem Toxicol, 50, 2605-2611.
Ji, X., Sun, H., Zhou, H., Xiang, J., Tang, Y., & Zhao, C. (2012). The interaction of telomeric DNA and C-myc22 G-quadruplex with 11 natural alkaloids. Nucleic Acid Ther, 22, 127-136.
Ji ZN, Y. W., Liu GQ, Huang Y. (2002). Inhibition of telomerase activity and bcl-2 expression in berbamine-induced apoptosis in HL-60 cells. Planta Med, 68, 596-600. Jiang, J., Chan, H., Cash, D. D., Miracco, E. J., Ogorzalek Loo, R. R., Upton, H. E., Cascio, D., O'Brien Johnson, R., Collins, K., Loo, J. A., Zhou, Z. H., & Feigon, J. (2015). Structure of Tetrahymena telomerase reveals previously unknown subunits, functions, and interactions. Science, 350, aab4070. Joseph, I., Tressler, R., Bassett, E., Harley, C., Buseman, C. M., Pattamatta, P., Wright, W. E., Shay, J. W., & Go, N. F. (2010). The telomerase inhibitor imetelstat depletes cancer stem cells in breast and pancreatic cancer cell lines. Cancer Res, 70, 9494-9504. Juliano, R. L., Carver, K., Cao, C., & Ming, X. (2013). Receptors, endocytosis, and trafficking: the 62
ACCEPTED MANUSCRIPT biological basis of targeted delivery of antisense and siRNA oligonucleotides. J Drug Target, 21, 27-43. Jun'ichi Kobayash, J.-f. C., Hideshi Nakamura, Yasushi Ohizumi. (1988). Ascididemin, a novel
PT
pentacyclic aromatic alkaloid with potent antileukemic activity from the okinawan tunicate Didemnum sp. Tetrahedron Letters, 29, 1177-1180.
RI
Kakiuchi, Y., Sasaki, N., Satoh-Masuoka, M., Murofushi, H., & Murakami-Murofushi, K. (2004). A
SC
novel pyrazolone, 4,4-dichloro-1-(2,4-dichlorophenyl)-3-methyl-5-pyrazolone, as a potent catalytic inhibitor of human telomerase. Biochem Biophys Res Commun, 320, 1351-1358.
NU
Kalathiya U, P. M., Baginski M. (2014). Molecular Modeling and Evaluation of Novel Dibenzopyrrole Derivatives as Telomerase Inhibitors and Potential Drug for Cancer Therapy. IEEE/ACM
MA
Trans Comput Biol Bioinform, 11, 1196-1120.
Kang, S.-S. L., Seung-Eun. (1998). Growth and Telomerase Inhibition of SK-MEL 28 Melanoma Cell Line by a Plant Flavonoid, Apigenin. BMB Reports, 31, 339-344.
D
Kannan, K., Nelson, A. D., & Shippen, D. E. (2008). Dyskerin is a component of the Arabidopsis
TE
telomerase RNP required for telomere maintenance. Mol Cell Biol, 28, 2332-2341. Kanno S, K. Y., Kakuta M, Osanai Y, Kurauchi K, Ujibe M, Ishikawa M. (2008). Costunolide-induced
AC CE P
apoptosis is caused by receptor-mediated pathway and inhibition of telomerase activity in NALM-6 cells. Biol Pharm Bull, 31, 1024-1028.
Kanzawa, T., Germano, I. M., Kondo, Y., Ito, H., Kyo, S., & Kondo, S. (2003). Inhibition of telomerase activity in malignant glioma cells correlates with their sensitivity to temozolomide. Br J Cancer, 89, 922-929.
Karlseder, J., Broccoli, D., Dai, Y., Hardy, S., & de Lange, T. (1999). p53- and ATM-dependent apoptosis induced by telomeres lacking TRF2. Science, 283, 1321-1325. Kasiappan, R., Shen, Z., Tse, A. K., Jinwal, U., Tang, J., Lungchukiet, P., Sun, Y., Kruk, P., Nicosia, S. V., Zhang, X., & Bai, W. (2012). 1,25-Dihydroxyvitamin D3 suppresses telomerase expression and human cancer growth through microRNA-498. J Biol Chem, 287, 41297-41309. Katik, I., Mackenzie-Kludas, C., Nicholls, C., Jiang, F. X., Zhou, S., Li, H., & Liu, J. P. (2009). Activin inhibits telomerase activity in cancer. Biochem Biophys Res Commun, 389, 668-672. Kato, M., Nakayama, M., Agata, M., & Yoshida, K. (2013). Gene expression levels of human shelterin complex and shelterin-associated factors regulated by the topoisomerase II inhibitors 63
ACCEPTED MANUSCRIPT doxorubicin and etoposide in human cultured cells. Tumour Biol, 34, 723-733. Kazemi Noureini, S., & Tanavar, F. (2015). Boldine, a natural aporphine alkaloid, inhibits telomerase at non-toxic concentrations. Chem Biol Interact, 231, 27-34.
PT
Khorramizadeh, M. R., Saadat, F., Vaezzadeh, F., Safavifar, F., Bashiri, H., & Jahanshiri, Z. (2007). Suppression of telomerase activity by pyrimethamine: implication to cancer. Iran Biomed J, 11,
RI
223-228.
SC
Killedar, A., Stutz, M. D., Sobinoff, A. P., Tomlinson, C. G., Bryan, T. M., Beesley, J., Chenevix-Trench, G., Reddel, R. R., & Pickett, H. A. (2015). A Common Cancer
Telomerase. PLoS Genet, 11, e1005286.
NU
Risk-Associated Allele in the hTERT Locus Encodes a Dominant Negative Inhibitor of
MA
Kim, J., Won, R., Ban, G., Ju, M. H., Cho, K. S., Young Han, S., Jeong, J. S., & Lee, S. W. (2015). Targeted Regression of Hepatocellular Carcinoma by Cancer-Specific RNA Replacement through MicroRNA Regulation. Sci Rep, 5, 12315.
D
Kim, J. H., Lee, G. E., Kim, S. W., & Chung, I. K. (2003). Identification of a quinoxaline derivative
TE
that is a potent telomerase inhibitor leading to cellular senescence of human cancer cells. Biochem J, 373, 523-529.
AC CE P
Kim, J. H., Lee, G. E., Lee, J. E., & Chung, I. K. (2003). Potent inhibition of human telomerase by nitrostyrene derivatives. Mol Pharmacol, 63, 1117-1124.
Kim, M. O., Moon, D. O., Kang, S. H., Heo, M. S., Choi, Y. H., Jung, J. H., Lee, J. D., & Kim, G. Y. (2008). Pectenotoxin-2 represses telomerase activity in human leukemia cells through suppression of hTERT gene expression and Akt-dependent hTERT phosphorylation. FEBS Lett, 582, 3263-3269. Kim, N.-H., Park, H. J., Oh, M.-K., & Kim, I.-S. (2013). Antiproliferative effect of gold(I) compound auranofin through inhibition of STAT3 and telomerase activity in MDA-MB 231 human breast cancer cells. BMB Reports, 46, 59-64. Kim, N. K., Zhang, Q., Zhou, J., Theimer, C. A., Peterson, R. D., & Feigon, J. (2008). Solution structure and dynamics of the wild-type pseudoknot of human telomerase RNA. J Mol Biol, 384, 1249-1261. Kim, N. W., Piatyszek, M. A., Prowse, K. R., Harley, C. B., West, M. D., Ho, P. L. C., Coviello, G. M., Wright, W. E., Weinrich, S. L., & Shay, J. W. (1994). Specific Association of Human 64
ACCEPTED MANUSCRIPT Telomerase Activity with Immortal Cells and Cancer. Science, 266, 2011-2015. Kim, Y. J., Kwon, H. C., Ko, H., Park, J. H., Kim, H. Y., Yoo, J. H., & Yang, H. O. (2008). Anti-tumor activity of the ginsenoside Rk1 in human hepatocellular carcinoma cells through inhibition of
PT
telomerase activity and induction of apoptosis. Biol Pharm Bull, 31, 826-830. Kiran, K. G., Palaniswamy, M., & Angayarkanni, J. (2015). Human telomerase inhibitors from
RI
microbial source. World J Microbiol Biotechnol, 31, 1329-1341.
SC
Kiss, T., Fayet-Lebaron, E., & Jady, B. E. (2010). Box H/ACA Small Ribonucleoproteins. Molecular Cell, 37, 597-606.
NU
Kitahara N, E. A., Furuya K, Takahashi S. (1981). Thielavin A and B, new inhibitors of prostaglandin biosynthesis produced by Thielavia terricola. J Antibiot, 34, 1562-1568.
MA
Kokhaei, P., Palma, M., Hansson, L., Osterborg, A., Mellstedt, H., & Choudhury, A. (2007). Telomerase (hTERT 611-626) serves as a tumor antigen in B-cell chronic lymphocytic leukemia and generates spontaneously antileukemic, cytotoxic T cells. Exp Hematol, 35,
D
297-304.
18, 687-694.
TE
Kyte, J. A. (2009). Cancer vaccination with telomerase peptide GV1001. Expert Opin Investig Drugs,
AC CE P
Lai XF, S. C., Wen Z, Qian YH, Yu CS, Wang JQ, Zhong PN, Wang HL. (2012). PinX1 regulation of telomerase activity and apoptosis in nasopharyngeal carcinoma cells. J Exp Clin Cancer Res,
31, 12.
Lanzilli G, F. M., Tricarico M, Cottarelli A, Serafino A, Falchetti R, Ravagnan G, Turriziani M, Adamo R, Franzese O, Bonmassar E. (2006). Resveratrol down-regulates the growth and telomerase activity of breast cancer cells in vitro. Int J Oncol, 28, 641-648. Lattmann, S., Stadler, M. B., Vaughn, J. P., Akman, S. A., & Nagamine, Y. (2011). The DEAH-box RNA helicase RHAU binds an intramolecular RNA G-quadruplex in TERC and associates with telomerase holoenzyme. Nucleic Acids Research, 39, 9390-9404. Laura K. White, W. E. W., Jerry W. Shay. (2001). Telomerase inhibitors. TRENDS in Biotechnology, 19, 114-120. Leon-Blanco, M. M., Guerrero, J. M., Reiter, R. J., Calvo, J. R., & Pozo, D. (2003). Melatonin inhibits telomerase activity in the MCF-7 tumor cell line both in vivo and in vitro. J Pineal Res, 35, 204-211. 65
ACCEPTED MANUSCRIPT Li, C. T., Hsiao, Y. M., Wu, T. C., Lin, Y. W., Yeh, K. T., & Ko, J. L. (2011). Vorinostat, SAHA, represses telomerase activity via epigenetic regulation of telomerase reverse transcriptase in non-small cell lung cancer cells. J Cell Biochem, 112, 3044-3053.
PT
Li GX, W. M., Gao SL. (2011). Research progress of anti-aging and anti-tumor TCM drugs on telomere andtelomerase. Liaoning Journal of Traditional Chinese Medicine, 38, 2293-2295.
RI
Li H, Z. L., Funder JW, Liu JP. (1997). Protein phosphatase 2A inhibits nuclear telomerase activity in
SC
human breast cancer cells. J Biol Chem, 272, 16729-16732.
Li, Q., Zhang, J., Yang, L., Yu, Q., Chen, Q., Qin, X., Le, F., Zhang, Q., & Liu, J. (2014). Stabilization
NU
of G-quadruplex DNA and inhibition of telomerase activity studies of ruthenium(II) complexes. J Inorg Biochem, 130, 122-129.
MA
Li, W., Zhang, M., Zhang, J. L., Li, H. Q., Zhang, X. C., Sun, Q., & Qiu, C. M. (2006). Interactions of daidzin with intramolecular G-quadruplex. FEBS Lett, 580, 4905-4910. Li, Y., Liu, L., Andrews, L. G., & Tollefsbol, T. O. (2009). Genistein depletes telomerase activity
D
through cross-talk between genetic and epigenetic mechanisms. Int J Cancer, 125, 286-296.
TE
Li, Y. L., Qin, Q. P., Liu, Y. C., Chen, Z. F., & Liang, H. (2014). A platinum(II) complex of liriodenine from traditional Chinese medicine (TCM): Cell cycle arrest, cell apoptosis induction and
AC CE P
telomerase inhibition activity via G-quadruplex DNA stabilization. J Inorg Biochem, 137, 12-21.
Lian, Z., Niwa, K., Gao, J., Tagami, K., Mori, H., & Tamaya, T. (2003). Association of cellular apoptosis with anti-tumor effects of the Chinese herbal complex in endocrine-resistant cancer cell line. Cancer Detection and Prevention, 27, 147-154.
Liao, C. H., Hsiao, Y. M., Sheu, G. T., Chang, J. T., Wang, P. H., Wu, M. F., Shieh, G. J., Hsu, C. P., & Ko, J. L. (2007). Nuclear translocation of telomerase reverse transcriptase and calcium signaling in repression of telomerase activity in human lung cancer cells by fungal immunomodulatory protein from Ganoderma tsugae. Biochem Pharmacol, 74, 1541-1554. Liao CH, H. Y., Hsu CP, Lin MY, Wang JC, Huang YL, Ko JL. (2006). Transcriptionally mediated inhibition of telomerase of fungal immunomodulatory protein from Ganoderma tsugae in A549 human lung adenocarcinoma cell line. Mol Carcinog, 45, 220-229. Lin CP, L. J., Chow JM, Liu CR, Liu HE. (2007). Small-molecule c-Myc inhibitor, 10058-F4, inhibits proliferation, downregulates human telomerase reverse transcriptase and enhances 66
ACCEPTED MANUSCRIPT chemosensitivity in human hepatocellular carcinoma cells. Anticancer Drugs, 18, 161-170. Lin, P. C., Lin, S. Z., Chen, Y. L., Chang, J. S., Ho, L. I., Liu, P. Y., Chang, L. F., Harn, Y. C., Chen, S. P., Sun, L. Y., Huang, P. C., Chein, J. T., Tsai, C. H., Chou, C. W., Harn, H. J., & Chiou, T. W.
PT
(2011). Butylidenephthalide suppresses human telomerase reverse transcriptase (TERT) in human glioblastomas. Ann Surg Oncol, 18, 3514-3527.
RI
Lin, S. C., Li, W. C., Shih, J. W., Hong, K. F., Pan, Y. R., & Lin, J. J. (2006). The tea polyphenols
SC
EGCG and EGC repress mRNA expression of human telomerase reverse transcriptase (hTERT) in carcinoma cells. Cancer Lett, 236, 80-88.
NU
Lin, X., Cai, Y.-J., Li, Z.-X., Chen, Q., Liu, Z.-L., & Wang, R. (2003). Structure determination, apoptosis induction, and telomerase inhibition of CFP-2, a novel lichenin from Cladonia
MA
furcata. Biochimica et Biophysica Acta (BBA) - General Subjects, 1622, 99-108. Lindkvist, A., Ivarsson, K., Jernberg-Wiklund, H., & Paulsson-Karlsson, Y. (2006). Interferon-induced sensitization to apoptosis is associated with repressed transcriptional activity of the hTERT
D
promoter in multiple myeloma. Biochem Biophys Res Commun, 341, 1141-1148.
TE
Lindvall, C., Hou, M., Komurasaki, T., Zheng, C. Y., Henriksson, M., Sedivy, J. M., Bjorkholm, M., Teh, B. T., Nordenskjold, M., & Xu, D. W. (2003). Molecular characterization of human
AC CE P
telomerase reverse transcriptase-immortalized human fibroblasts by gene expression profiling: Activation of the Epiregulin gene. Cancer Research, 63, 1743-1747.
Lingner, J., Hughes, T. R., Shevchenko, A., Mann, M., Lundblad, V., & Cech, T. R. (1997). Reverse transcriptase motifs in the catalytic subunit of telomerase. Science, 276, 561-567.
Liu, J., Guo, L., Yin, F., Zheng, X., Chen, G., & Wang, Y. (2008). Characterization and antitumor activity of triethylene tetramine, a novel telomerase inhibitor. Biomed Pharmacother, 62, 480-485. Liu, Q., Mao, X., Zeng, F., Jin, S., & Yang, X. (2012). Effect of daurisoline on HERG channel electrophysiological function and protein expression. J Nat Prod, 75, 1539-1545. Liu, W. J., Zhang, Y. W., Shen, Y., Jiang, J. F., Miao, Z. H., & Ding, J. (2004). Telomerase inhibition is a specific early event in salvicine-treated human lung adenocarcinoma A549 cells. Biochem Biophys Res Commun, 323, 660-667. Liu, X. D., Fan, R. F., Zhang, Y., Yang, H. Z., Fang, Z. G., Guan, W. B., Lin, D. J., Xiao, R. Z., Huang, R. W., Huang, H. Q., Liu, P. Q., & Liu, J. J. (2010). Down-regulation of telomerase activity 67
ACCEPTED MANUSCRIPT and activation of caspase-3 are responsible for Tanshinone I-induced apoptosis in monocyte leukemia cells in vitro. Int J Mol Sci, 11, 2267-2280. Liu, Y., Gao, X., Deeb, D., Arbab, A. S., & Gautam, S. C. (2012). Telomerase reverse transcriptase
PT
(TERT) is a therapeutic target of oleanane triterpenoid CDDO-Me in prostate cancer. Molecules, 17, 14795-14809.
RI
Long, C., Wang, J., Guo, W., Wang, H., Wang, C., Liu, Y., & Sun, X. (2015). Triptolide inhibits
SC
transcription of hTERT through down-regulation of transcription factor specificity protein 1 in primary effusion lymphoma cells. Biochem Biophys Res Commun.
NU
Loo, W. T., Chen, J. P., Chow, L. W., & Chou, J. W. (2007). Effects of Shugansanjie Tang on matrix metalloproteinases 1, 3 and 9 and telomerase reverse transcriptase expression in human breast
MA
cells in vitro. Biomed Pharmacother, 61, 601-605.
Low, K. C., & Tergaonkar, V. (2013). Telomerase: central regulator of all of the hallmarks of cancer. Trends Biochem Sci, 38, 426-434.
D
Lu Q, L. W., Ding J, Cai J, Duan W. (2002). Shikonin derivatives: synthesis and inhibition of human
TE
telomerase. Bioorg Med Chem Lett, 12, 1375-1378. Lu Y, G. J., Jin D, Gao Y, Yuan M. (2011). Inhibition of telomerase activity by HDV ribozyme in
AC CE P
cancers. J Exp Clin Cancer Res, 30, 1.
Luo, Y., Zhang, S., Qiu, K. M., Liu, Z. J., Yang, Y. S., Fu, J., Zhong, W. Q., & Zhu, H. L. (2013). Synthesis, biological evaluation, 3D-QSAR studies of novel aryl-2H-pyrazole derivatives as telomerase inhibitors. Bioorg Med Chem Lett, 23, 1091-1095.
Lyu SY, C. S., Park WB. (2002). Korean mistletoe lectin-induced apoptosis in hepatocarcinoma cells is associated with inhibition of telomerase via mitochondrial controlled pathway independent of p53. Arch Pharm Res, 25, 93-101. Ma, Y., Ou, T. M., Tan, J. H., Hou, J. Q., Huang, S. L., Gu, L. Q., & Huang, Z. S. (2009). Synthesis and evaluation of 9-O-substituted berberine derivatives containing aza-aromatic terminal group as highly selective telomeric G-quadruplex stabilizing ligands. Bioorg Med Chem Lett, 19, 3414-3417. Maji, B., Kumar, K., Muniyappa, K., & Bhattacharya, S. (2015). New dimeric carbazole-benzimidazole mixed ligands for the stabilization of human telomeric G-quadruplex DNA and as telomerase inhibitors. A remarkable influence of the spacer. Org Biomol Chem, 13, 8335-8348. 68
ACCEPTED MANUSCRIPT Martinez, P., & Blasco, M. A. (2011). Telomeric and extra-telomeric roles for telomerase and the telomere-binding proteins. Nature Reviews Cancer, 11, 161-176. Masutomi, K., Possemato, R., Wong, J. M., Currier, J. L., Tothova, Z., Manola, J. B., Ganesan, S.,
PT
Lansdorp, P. M., Collins, K., & Hahn, W. C. (2005). The telomerase reverse transcriptase regulates chromatin state and DNA damage responses. Proc Natl Acad Sci U S A, 102,
RI
8222-8227.
SC
Mavroudis, D., Bolonakis, I., Cornet, S., Myllaki, G., Kanellou, P., Kotsakis, A., Galanis, A., Nikoloudi, I., Spyropoulou, M., Menez, J., Miconnet, I., Niniraki, M., Cordopatis, P., Kosmatopoulos, K.,
NU
& Georgoulias, V. (2006). A phase I study of the optimized cryptic peptide TERT(572y) in patients with advanced malignancies. Oncology, 70, 306-314.
MA
Menez-Jamet, J., & Kosmatopoulos, K. (2009). Development of optimized cryptic peptides for immunotherapy. IDrugs, 12, 98-102.
Meng, E., Taylor, B., Ray, A., Shevde, L. A., & Rocconi, R. P. (2012). Targeted inhibition of telomerase
D
activity combined with chemotherapy demonstrates synergy in eliminating ovarian cancer
TE
spheroid-forming cells. Gynecol Oncol, 124, 598-605. Mitchell, J. R., Cheng, J., & Collins, K. (1999). A box H/ACA small nucleolar RNA-like domain at the
AC CE P
human telomerase RNA 3 ' end. Mol Cell Biol, 19, 567-576.
Mitchell, J. R., & Collins, K. (2000). Human telomerase activation requires two independent interactions between telomerase RNA and telomerase reverse transcriptase. Molecular Cell, 6,
361-371.
Mitchell, J. R., Wood, E., & Collins, K. (1999). A telomerase component is defective in the human disease dyskeratosis congenita. Nature, 402, 551-555. Mizushina, Y., Takeuchi, T., Sugawara, F., & Yoshida, H. (2012). Anti-cancer targeting telomerase inhibitors: beta-rubromycin and oleic acid. Mini Rev Med Chem, 12, 1135-1143. Mocellin, S., Pooley, K. A., & Nitti, D. (2013). Telomerase and the search for the end of cancer. Trends Mol Med, 19, 125-133. Moon, D. O., Kang, S. H., Kim, K. C., Kim, M. O., Choi, Y. H., & Kim, G. Y. (2010). Sulforaphane decreases viability and telomerase activity in hepatocellular carcinoma Hep3B cells through the reactive oxygen species-dependent pathway. Cancer Lett, 295, 260-266. Moon, D. O., Kim, M. O., Choi, Y. H., Lee, H. G., Kim, N. D., & Kim, G. Y. (2008). Gossypol 69
ACCEPTED MANUSCRIPT suppresses telomerase activity in human leukemia cells via regulating hTERT. FEBS Lett, 582, 3367-3373. Moon, D. O., Kim, M. O., Heo, M. S., Lee, J. D., Choi, Y. H., & Kim, G. Y. (2009). Gefitinib induces
PT
apoptosis and decreases telomerase activity in MDA-MB-231 human breast cancer cells. Arch Pharm Res, 32, 1351-1360.
RI
Mor-Tzuntz, R., Uziel, O., Shpilberg, O., Lahav, J., Raanani, P., Bakhanashvili, M., Rabizadeh, E.,
SC
Zimra, Y., Lahav, M., & Granot, G. (2010). Effect of imatinib on the signal transduction cascade regulating telomerase activity in K562 (BCR-ABL-positive) cells sensitive and
NU
resistant to imatinib. Exp Hematol, 38, 27-37.
Moriai, M., Tsuji, N., Kobayashi, D., Kuribayashi, K., & Watanabe, N. (2009). Down-regulation of
MA
hTERT expression plays an important role in 15-deoxy-Delta12,14-prostaglandin J2-induced apoptosis in cancer cells. Int J Oncol, 34, 1363-1372. Moye, A. L., Porter, K. C., Cohen, S. B., Phan, T., Zyner, K. G., Sasaki, N., Lovrecz, G. O., Beck, J. L.,
D
& Bryan, T. M. (2015). Telomeric G-quadruplexes are a substrate and site of localization for
TE
human telomerase. Nature Communications, 6, 7643. Mukherjee Nee Chakraborty, S., Ghosh, U., Bhattacharyya, N. P., Bhattacharya, R. K., Dey, S., & Roy,
AC CE P
M. (2007). Curcumin-induced apoptosis in human leukemia cell HL-60 is associated with inhibition of telomerase activity. Mol Cell Biochem, 297, 31-39.
Mukherjee, S., Bhattacharya, R. K., & Roy, M. (2009). Targeting protein kinase C (PKC) and telomerase
by
phenethyl
isothiocyanate
(PEITC)
sensitizes
PC-3
cells
towards
chemotherapeutic drug-induced apoptosis. J Environ Pathol Toxicol Oncol, 28, 269-282.
Murakami, J., Asaumi, J., Kawai, N., Tsujigiwa, H., Yanagi, Y., Nagatsuka, H., Inoue, T., Kokeguchi, S., Kawasaki, S., Kuroda, M., Tanaka, N., Matsubara, N., & Kishi, K. (2005). Effects of histone deacetylase inhibitor FR901228 on the expression level of telomerase reverse transcriptase in oral cancer. Cancer Chemother Pharmacol, 56, 22-28. Naasani I, S. H., Tsuruo T. (1998). Telomerase Inhibition, Telomere Shortening, and Senescence of Cancer Cells by Tea Catechins. Biochem Biophys Res Commun, 249, 391-396. Naasani I, S. H., Yamori T, Tsuruo T. (1999). FJ5002: a potent telomerase inhibitor identified by exploiting the disease-oriented screening program with COMPARE analysis. Cancer Res, 59, 4004-4011. 70
ACCEPTED MANUSCRIPT Nagle, D. G., Ferreira, D., & Zhou, Y. D. (2006). Epigallocatechin-3-gallate (EGCG): chemical and biomedical perspectives. Phytochemistry, 67, 1849-1855. Nakai, R., Ishida, H., Asai, A., Ogawa, H., Yamamoto, Y., Kawasaki, H., Akinaga, S., Mizukami, T., &
PT
Yamashita, Y. (2006). Telomerase inhibitors identified by a forward chemical genetics approach using a yeast strain with shortened telomere length. Chem Biol, 13, 183-190.
RI
Nakai R, K. S., Asai A, Chiba S, Akinaga S, Mizukami T, Yamashita Y. (2001). Chrolactomycin, a
SC
novel antitumor antibiotic produced by Streptomyces sp. J Antibiot, 54, 836-839. Nakashima, M., Nandakumar, J., Sullivan, K. D., Espinosa, J. M., & Cech, T. R. (2013). Inhibition of
NU
telomerase recruitment and cancer cell death. J Biol Chem, 288, 33171-33180. Nguyen, B. N., Elmore, L. W., & Holt, S. E. (2009). Mechanism of dominant-negative telomerase
MA
function. Cell Cycle, 8, 3227-3233.
Noureini, S. K., & Wink, M. (2012). Antiproliferative effects of crocin in HepG2 cells by telomerase inhibition and hTERT down-regulation. Asian Pac J Cancer Prev, 13, 2305-2309.
D
Noureini, S. K., & Wink, M. (2014). Antiproliferative effect of the isoquinoline alkaloid papaverine in
TE
hepatocarcinoma HepG-2 cells--inhibition of telomerase and induction of senescence. Molecules, 19, 11846-11859.
AC CE P
Olaussen, K. A., Dubrana, K., Domont, J., Spano, J.-P., Sabatier, L., & Soria, J.-C. (2006). Telomeres and telomerase as targets for anticancer drug development. Critical Reviews in Oncology/Hematology, 57, 191-214.
Paeschke, K., Bochman, M. L., Garcia, P. D., Cejka, P., Friedman, K. L., Kowalczykowski, S. C., & Zakian, V. A. (2013). Pif1 family helicases suppress genome instability at G-quadruplex motifs. Nature, 497, 458-462. Pan X, H. C., Zeng F, Zhang S, Xu J. (1998). Isolation and identification of alkaloids form Menispermum dauricum growing in Xianning. Zhong Yao Cai, 21, 456-458. Park, C., Jung, J. H., Kim, N. D., & Choi, Y. H. (2007). Inhibition of cyclooxygenase-2 and telomerase activities in human leukemia cells by dideoxypetrosynol A, a polyacetylene from the marine sponge Petrosia sp. Int J Oncol, 30, 291-298. Park, C., Kim, G. Y., Kim, W. I., Hong, S. H., Park, D. I., Kim, N. D., Bae, S. J., Jung, J. H., & Choi, Y. H. (2007). Induction of apoptosis by (Z)-stellettic acid C, an acetylenic acid from the sponge Stelletta sp., is associated with inhibition of telomerase activity in human leukemic U937 cells. 71
ACCEPTED MANUSCRIPT Chemotherapy, 53, 160-168. Park, S. E., Yoo, H. S., Jin, C.-Y., Hong, S. H., Lee, Y.-W., Kim, B. W., Lee, S. H., Kim, W.-J., Cho, C. K., & Choi, Y. H. (2009). Induction of apoptosis and inhibition of telomerase activity in
PT
human lung carcinoma cells by the water extract of Cordyceps militaris. Food and Chemical Toxicology, 47, 1667-1675.
RI
Parks, J. W., & Stone, M. D. (2014). Coordinated DNA dynamics during the human telomerase
SC
catalytic cycle. Nature Communications, 5.
Parsch, D., Brassat, U., Brummendorf, T. H., & Fellenberg, J. (2008). Consequences of telomerase
NU
inhibition by BIBR1532 on proliferation and chemosensitivity of chondrosarcoma cell lines. Cancer Invest, 26, 590-596.
MA
Pascolo, E., Wenz, C., Lingner, J., Hauel, N., Priepke, H., Kauffmann, I., Garin-Chesa, P., Rettig, W. J., Damm, K., & Schnapp, A. (2002). Mechanism of human telomerase inhibition by BIBR1532, a synthetic, non-nucleosidic drug candidate. J Biol Chem, 277, 15566-15572.
D
Patel, D. J., Phan, A. T., & Kuryavyi, V. (2007). Human telomere, oncogenic promoter and 5'-UTR
TE
G-quadruplexes: diverse higher order DNA and RNA targets for cancer therapeutics. Nucleic Acids Research, 35, 7429-7455.
AC CE P
Patel, K. P., & Vonderheide, R. H. (2004). Telomerase as a tumor-associated antigen for cancer immunotherapy. Cytotechnology, 45, 91-99.
Paydar, M., Kamalidehghan, B., Wong, Y. L., Wong, W. F., Looi, C. Y., & Mustafa, M. R. (2014). Evaluation of cytotoxic and chemotherapeutic properties of boldine in breast cancer using in vitro and in vivo models. Drug Des Devel Ther, 8, 719-733.
Peng, Y., Mian, I. S., & Lue, N. F. (2001). Analysis of telomerase processivity: Mechanistic similarity to HIV-1 reverse transcriptase and role in telomere maintenance. Molecular Cell, 7, 1201-1211. Phatak, P., Cookson, J. C., Dai, F., Smith, V., Gartenhaus, R. B., Stevens, M. F., & Burger, A. M. (2007). Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism. Br J Cancer, 96, 1223-1233. Phipps, S. M., Love, W. K., White, T., Andrews, L. G., & Tollefsbol, T. O. (2009). Retinoid-induced histone deacetylation inhibits telomerase activity in estrogen receptor-negative breast cancer 72
ACCEPTED MANUSCRIPT cells. Anticancer Res, 29, 4959-4964. Pizzimenti, S., Menegatti, E., Berardi, D., Toaldo, C., Pettazzoni, P., Minelli, R., Giglioni, B., Cerbone, A., Dianzani, M. U., Ferretti, C., & Barrera, G. (2010). 4-hydroxynonenal, a lipid peroxidation
PT
product of dietary polyunsaturated fatty acids, has anticarcinogenic properties in colon carcinoma cell lines through the inhibition of telomerase activity. J Nutr Biochem, 21,
RI
818-826.
SC
Podlevsky, J. D., Bley, C. J., Omana, R. V., Qi, X., & Chen, J. J. (2008). The telomerase database. Nucleic Acids Research, 36, D339-343.
NU
Qi, D. L., Ohhira, T., Fujisaki, C., Inoue, T., Ohta, T., Osaki, M., Ohshiro, E., Seko, T., Aoki, S., Oshimura, M., & Kugoh, H. (2011). Identification of PITX1 as a TERT Suppressor Gene
MA
Located on Human Chromosome 5. Mol Cell Biol, 31, 1624-1636. Qi, X. D., Li, Y., Honda, S., Hoffmann, S., Marz, M., Mosig, A., Podlevsky, J. D., Stadler, P. F., Selker, E. U., & Chen, J. L. J. L. (2013). The common ancestral core of vertebrate and fungal
D
telomerase RNAs. Nucleic Acids Research, 41, 450-462.
TE
Qi, X. D., Xie, M. Y., Brown, A. F., Bley, C. J., Podlevsky, J. D., & Chen, J. J. L. (2012). RNA/DNA hybrid binding affinity determines telomerase template-translocation efficiency. Embo Journal,
AC CE P
31, 150-161.
Qin HL, P. J. (2008). Total synthesis of the Hsp90 inhibitor geldanamycin. Org Lett, 10, 2477-2479. Rabi, T., & Banerjee, S. (2009). Novel semisynthetic triterpenoid AMR-Me inhibits telomerase activity in human leukemic CEM cells and exhibits in vivo antitumor activity against Dalton's lymphoma ascites tumor. Cancer Lett, 278, 156-163.
Rafii, F. (2015). The role of colonic bacteria in the metabolism of the natural isoflavone daidzin to equol. Metabolites, 5, 56-73. Rahman, R., Osteso-Ibanez, T., Hirst, R. A., Levesley, J., Kilday, J. P., Quinn, S., Peet, A., O'Callaghan, C., Coyle, B., & Grundy, R. G. (2010). Histone deacetylase inhibition attenuates cell growth with associated telomerase inhibition in high-grade childhood brain tumor cells. Mol Cancer Ther, 9, 2568-2581. Rangarajan, S., & Friedman, S. H. (2007). Design, synthesis, and evaluation of phenanthridine derivatives targeting the telomerase RNA/DNA heteroduplex. Bioorg Med Chem Lett, 17, 2267-2273. 73
ACCEPTED MANUSCRIPT Rankin, A. M., Faller, D. V., & Spanjaard, R. A. (2008). Telomerase inhibitors and 'T-oligo' as cancer therapeutics: contrasting molecular mechanisms of cytotoxicity. Anticancer Drugs, 19, 329-338.
PT
Rao, Y., Xiong, W., Liu, H., Jia, C., Zhang, H., Cui, Z., Zhang, Y., & Cui, J. (2014). Inhibition of telomerase activity by dominant-negative hTERT retards the growth of breast cancer cells.
RI
Breast Cancer.
SC
Rao, Y. K., Kao, T. Y., Wu, M. F., Ko, J. L., & Tzeng, Y. M. (2010). Identification of small molecule inhibitors of telomerase activity through transcriptional regulation of hTERT and calcium
NU
induction pathway in human lung adenocarcinoma A549 cells. Bioorg Med Chem, 18, 6987-6994.
Troglitazone
suppresses
MA
Rashid-Kolvear, F., Taboski, M. A., Nguyen, J., Wang, D. Y., Harrington, L. A., & Done, S. J. (2010). telomerase
activity
independently
of
PPARgamma
in
estrogen-receptor negative breast cancer cells. BMC Cancer, 10, 390.
D
Ratledge C, K. K., Anderson AJ, Grantham DJ, Stephenson JC. (2001). Production of docosahexaenoic
TE
acid by Crypthecodinium cohnii grown in a pH-auxostat culture with acetic acid as principal carbon source. Lipids, 36, 1241-1246.
AC CE P
Redon, S., Reichenbach, P., & Lingner, J. (2010). The non-coding RNA TERRA is a natural ligand and direct inhibitor of human telomerase. Nucleic Acids Research, 38, 5797-5806.
Rezler, E. M., Seenisamy, J., Bashyam, S., Kim, M. Y., White, E., Wilson, W. D., & Hurley, L. H. (2005). Telomestatin and diseleno sapphyrin bind selectively to two different forms of the human telomeric G-quadruplex structure. J Am Chem Soc, 127, 9439-9447.
Rezler EM, S. J., Bashyam S, Kim MY, White E, Wilson WD, Hurley LH. (2005). Telomestatin and diseleno sapphyrin bind selectively to two different forms of the human telomeric G-quadruplex structure. J Am Chem Soc, 127, 9439-9447. Roe, S., Gunaratnam, M., Spiteri, C., Sharma, P., Alharthy, R. D., Neidle, S., & Moses, J. E. (2015). Synthesis and biological evaluation of hybrid acridine-HSP90 ligand conjugates as telomerase inhibitors. Org Biomol Chem, 13, 8500-8504. Ruden, M., & Puri, N. (2013). Novel anticancer therapeutics targeting telomerase. Cancer Treatment Reviews, 39, 444-456. Sato, N., Mizumoto, K., Kusumoto, M., Niiyama, H., Maehara, N., Ogawa, T., & Tanaka, M. (1998). 74
ACCEPTED MANUSCRIPT 9-Hydroxyellipticine inhibits telomerase activity in human pancreatic cancer cells. FEBS Lett, 441, 318-321. Schmidt, J. C., & Cech, T. R. (2015). Human telomerase: biogenesis, trafficking, recruitment, and
PT
activation. Genes & Development, 29, 1095-1105. Sealey, D. C. F., Zheng, L., Taboski, M. A. S., Cruickshank, J., Ikura, M., & Harrington, L. A. (2010).
RI
The N-terminus of hTERT contains a DNA-binding domain and is required for telomerase
SC
activity and cellular immortalization. Nucleic Acids Research, 38, 2019-2035. Sekhri, K. (2014). Telomeres and telomerase: understanding basic structure and potential new
NU
therapeutic strategies targeting it in the treatment of cancer. Journal of Postgraduate Medicine, 60, 303-308.
MA
Selvam, S. P., De Palma, R. M., Oaks, J. J., Oleinik, N., Peterson, Y. K., Stahelin, R. V., Skordalakes, E., Ponnusamy, S., Garrett-Mayer, E., Smith, C. D., & Ogretmen, B. (2015). Binding of the sphingolipid S1P to hTERT stabilizes telomerase at the nuclear periphery by allosterically
D
mimicking protein phosphorylation. Science Signaling, 8.
TE
Serrano, D., Bleau, A. M., Fernandez-Garcia, I., Fernandez-Marcelo, T., Iniesta, P., Ortiz-de-Solorzano, C., & Calvo, A. (2011). Inhibition of telomerase activity preferentially targets aldehyde
AC CE P
dehydrogenase-positive cancer stem-like cells in lung cancer. Mol Cancer, 10, 96.
Shapira, S., Granot, G., Mor-Tzuntz, R., Raanani, P., Uziel, O., Lahav, M., & Shpilberg, O. (2012). Second-generation tyrosine kinase inhibitors reduce telomerase activity in K562 cells. Cancer Lett, 323, 223-231.
Sharma, V., Koul, N., Joseph, C., Dixit, D., Ghosh, S., & Sen, E. (2010). HDAC inhibitor, scriptaid, induces glioma cell apoptosis through JNK activation and inhibits telomerase activity. J Cell Mol Med, 14, 2151-2161. Shaw, V. E., Naisbitt, D. J., Costello, E., Greenhalf, W., Park, B. K., Neoptolemos, J. P., & Middleton, G. W. (2010). Current status of GV1001 and other telomerase vaccination strategies in the treatment of cancer. Expert Rev Vaccines, 9, 1007-1016. Shi, S., Gao, S., Cao, T., Liu, J., Gao, X., Hao, J., Lv, C., Huang, H., Xu, J., & Yao, T. (2013). Targeting human telomeric G-quadruplex DNA and inhibition of telomerase activity with [(dmb)2Ru(obip)Ru(dmb)2](4+). PLoS One, 8, e84419. Shin-ya K, W. K., Matsuo K, Ohtani T, Yamada Y, Furihata K, Hayakawa Y, Seto H. (2001). 75
ACCEPTED MANUSCRIPT Telomestatin, a novel telomerase inhibitor from Streptomyces anulatus. J Am Chem Soc, 123, 1262-1263. Shippen-Lentz, D., & Blackburn, E. H. (1990). Functional evidence for an RNA template in telomerase.
PT
Science, 247, 546-552. Shippenlentz, D., & Blackburn, E. H. (1990). Functional Evidence for an Rna Template in Telomerase.
RI
Science, 247, 546-552.
SC
Singh, M., & Singh, N. (2009). Molecular mechanism of curcumin induced cytotoxicity in human cervical carcinoma cells. Mol Cell Biochem, 325, 107-119.
NU
Singhapol, C., Pal, D., Czapiewski, R., Porika, M., Nelson, G., & Saretzki, G. C. (2013). Mitochondrial telomerase protects cancer cells from nuclear DNA damage and apoptosis. PLoS One, 8,
MA
e52989.
Smith, L. L., Coller, H. A., & Roberts, J. M. (2003). Telomerase modulates expression of growth-controlling genes and enhances cell proliferation. Nature Cell Biology, 5, 474-479.
D
Soder, A. I., Hoare, S. F., Muir, S., Going, J. J., Parkinson, E. K., & Keith, W. N. (1997). Amplification,
TE
increased dosage and in situ expression of the telomerase RNA gene in human cancer. Oncogene, 14, 1013-1021.
AC CE P
Sohn, J. H., Yeh, B. I., Choi, J. W., Yoon, J., Namkung, J., Park, K. K., & Kim, H. W. (2010). Repression of human telomerase reverse transcriptase using artificial zinc finger transcription factors. Mol Cancer Res, 8, 246-253.
Song, Y. Y., S.L.; Yang, Y.M.; Wang, X.J.; Huang, G.Q. (2005). Alteration of activities of telomerase in tanshinone IIA inducing apoptosis of the leukemia cells. China journal of chinese meteria medica, 30, 207-211. Soohoo, C. Y., Shi, R., Lee, T. H., Huang, P., Lu, K. P., & Zhou, X. Z. (2011). Telomerase inhibitor PinX1 provides a link between TRF1 and telomerase to prevent telomere elongation. J Biol Chem, 286, 3894-3906. Sugiyama K, U. H., Ichio Y. (1995). Protective effect of juzen-taiho-to against carboplatin-induced toxic side effects in mice. Biol Pharm Bull, 18, 544-548. Sun CC, X. H., Yuan Y, Gao ZH, Lou HX, Qu XJ. (2014). Riccardin D, a macrocyclic bisbibenzy, inhibits human breast cancer growth through the suppression of telomerase activity. Basic Clin Pharmacol Toxicol, 115, 488-498. 76
ACCEPTED MANUSCRIPT Sun, H., Xiang, J., Li, Q., Liu, Y., Li, L., Shang, Q., Xu, G., & Tang, Y. (2012). Recognize three different human telomeric G-quadruplex conformations by quinacrine. Analyst, 137, 862-867. Sun L, W. X. (2003). Effects of allicin on both telomerase activity and apoptosis in gastric cancer
PT
SGC-7901 cells. World J Gastroenterol, 9, 1930-1934. Sundin, T., Peffley, D. M., & Hentosh, P. (2013). Disruption of an hTERT-mTOR-RAPTOR protein
RI
complex by a phytochemical perillyl alcohol and rapamycin. Mol Cell Biochem, 375, 97-104.
SC
Tabata Y, I. S., Yaguchi T, Sasaki T, Hoshiko S, Sakuma S, Shin-Ya K, Seto H. (1999). Diazaphilonic acid, a new azaphilone with telomerase inhibitory activity. J Antibiot, 52, 412-414.
NU
Tacar, O., Sriamornsak, P., & Dass, C. R. (2013). Doxorubicin: an update on anticancer molecular action, toxicity and novel drug delivery systems. J Pharm Pharmacol, 65, 157-170.
MA
Tan, L., Wang, W., He, G., Kuick, R. D., Gossner, G., Kueck, A. S., Wahl, H., Opipari, A. W., & Liu, J. R. (2015). Resveratrol inhibits ovarian tumor growth in an in vivo mouse model. Cancer. Tao, S. F., Zhang, C. S., Guo, X. L., Xu, Y., Zhang, S. S., Song, J. R., Li, R., Wu, M. C., & Wei, L. X.
D
(2012). Anti-tumor effect of 5-aza-2'-deoxycytidine by inhibiting telomerase activity in
TE
hepatocellular carcinoma cells. World J Gastroenterol, 18, 2334-2343. Tauchi, T., Shin-Ya, K., Sashida, G., Sumi, M., Nakajima, A., Shimamoto, T., Ohyashiki, J. H., &
AC CE P
Ohyashiki, K. (2003). Activity of a novel G-quadruplex-interactive telomerase inhibitor, telomestatin (SOT-095), against human leukemia cells: involvement of ATM-dependent DNA damage response pathways. Oncogene, 22, 5338-5347.
Tefferi, A., Lasho, T. L., Begna, K. H., Patnaik, M. M., Zblewski, D. L., Finke, C. M., Laborde, R. R., Wassie, E., Schimek, L., Hanson, C. A., Gangat, N., Wang, X., & Pardanani, A. (2015). A Pilot Study of the Telomerase Inhibitor Imetelstat for Myelofibrosis. N Engl J Med, 373, 908-919. Theimer, C. A., Blois, C. A., & Feigon, J. (2005). Structure of the human telomerase RNA pseudoknot reveals conserved tertiary interactions essential for function. Molecular Cell, 17, 671-682. Thelen, P., Wuttke, W., Jarry, H., Grzmil, M., & Ringert, R. H. (2004). Inhibition of telomerase activity and secretion of prostate specific antigen by silibinin in prostate cancer cells. J Urol, 171, 1934-1938. Thompson, P. A., Drissi, R., Muscal, J. A., Panditharatna, E., Fouladi, M., Ingle, A. M., Ahern, C. H., Reid, J. M., Lin, T., Weigel, B. J., & Blaney, S. M. (2013). A phase I trial of imetelstat in children with refractory or recurrent solid tumors: a Children's Oncology Group Phase I 77
ACCEPTED MANUSCRIPT Consortium Study (ADVL1112). Clin Cancer Res, 19, 6578-6584. Tian, X., Chen, B., & Liu, X. (2010). Telomere and telomerase as targets for cancer therapy. Appl Biochem Biotechnol, 160, 1460-1472.
PT
Tippani R, P. L., Porika M, Sirisha K, Abbagani S, Thammidala C. (2014). Pterostilbene as a potential novel telomerase inhibitor: molecular docking studies and its in vitro evaluation. Curr Pharm
RI
Biotechnol, 14, 1027-1035.
SC
Togashi, K., Ko, H. R., Ahn, J. S., & Osada, H. (2001). Inhibition of telomerase activity by fungus metabolites, CRM646-A and thielavin B. Biosci Biotechnol Biochem, 65, 651-653.
NU
Tomlinson, R. L., Li, J. A., Culp, B. R., Terns, R. M., & Terns, M. P. (2010). A Cajal body-independent pathway for telomerase trafficking in mice. Exp Cell Res, 316, 2797-2809.
MA
Toshikatsu Okuno, I. N., Ko Sawai, Kenzo Sawamura, Akio Furusakia, Takeshi Matsumoto. (1983). Structure of antifungal and phytotoxic pigments produced by alternaria sps Tetrahedron Letters, 24, 5653-5656.
TE
J Antibiot, 29, 1-6.
D
Tsuji N, K. M., Nagashima K, Wakisaka Y, Koizumi K. (1976). A new antifungal antibiotic, trichostatin.
Ueno, T., Takahashi, H., Oda, M., Mizunuma, M., Yokoyama, A., Goto, Y., Mizushina, Y., Sakaguchi,
AC CE P
K., & Hayashi, H. (2000). Inhibition of human telomerase by rubromycins: implication of spiroketal system of the compounds as an active moiety. biochemistry, 39, 5995-6002.
Ueno T, T. H., Oda M, Mizunuma M, Yokoyama A, Goto Y, Mizushina Y, Sakaguchi K, Hayashi H. (2000). Inhibition of human telomerase by rubromycins: implication of spiroketal system of the compounds as an active moiety biochemistry, 39, 5995-6002.
Ulaner, G. A., Hu, J. F., Vu, T. H., Giudice, L. C., & Hoffman, A. R. (1998). Telomerase activity in human development is regulated by human telomerase reverse transcriptase (hTERT) transcription and by alternate splicing of hTERT transcripts. Cancer Research, 58, 4168-4172. Uziel, O., Cohen, O., Beery, E., Nordenberg, J., & Lahav, M. (2014). The effect of Bortezomib and Rapamycin on Telomerase Activity in Mantle Cell Lymphoma. Transl Oncol, 7, 741-751. Uziel, O., Fenig, E., Nordenberg, J., Beery, E., Reshef, H., Sandbank, J., Birenbaum, M., Bakhanashvili, M., Yerushalmi, R., Luria, D., & Lahav, M. (2005). Imatinib mesylate (Gleevec) downregulates telomerase activity and inhibits proliferation in telomerase-expressing cell lines. Br J Cancer, 92, 1881-1891. 78
ACCEPTED MANUSCRIPT Venteicher, A. S., Abreu, E. B., Meng, Z. J., McCann, K. E., Terns, R. M., Veenstra, T. D., Terns, M. P., & Artandi, S. E. (2009). A Human Telomerase Holoenzyme Protein Required for Cajal Body Localization and Telomere Synthesis. Science, 323, 644-648.
PT
Verma, A. K., & Pratap, R. (2010). The biological potential of flavones. Nat Prod Rep, 27, 1571-1593. Verma, V., Sharma, V., Singh, V., Sharma, S., Bishnoi, A. K., Chandra, V., Maikhuri, J. P., Dwivedi, A.,
RI
Kumar, A., & Gupta, G. (2014). Designed modulation of sex steroid signaling inhibits
SC
telomerase activity and proliferation of human prostate cancer cells. Toxicol Appl Pharmacol, 280, 323-334.
NU
Villa R, F. M., Porta CD, Valentini A, Pennati M, Daidone MG, Zaffaroni N. (2003). Inhibition of telomerase activity by geldanamycin and 17-allylamino, 17-demethoxygeldanamycin in
MA
human melanoma cells. Carcinogenesis, 24, 851-859.
Villa, R., Folini, M., Porta, C. D., Valentini, A., Pennati, M., Daidone, M. G., & Zaffaroni, N. (2003). Inhibition
of
telomerase
activity
by
geldanamycin
and
17-allylamino,
D
17-demethoxygeldanamycin in human melanoma cells. Carcinogenesis, 24, 851-859.
TE
Vonderheide, R. H. (2008). Prospects and challenges of building a cancer vaccine targeting telomerase. Biochimie, 90, 173-180.
AC CE P
Wang, F., Podell, E. R., Zaug, A. J., Yang, Y., Baciu, P., Cech, T. R., & Lei, M. (2007). The POT1-TPP1 telomere complex is a telomerase processivity factor. Nature, 445, 506-510.
Wang, J., Wang, Y. J., Chen, Z. S., & Kwon, C. H. (2014). Synthesis and evaluation of sulfonylethyl-containing phosphotriesters of 3'-azido-3'-deoxythymidine as anticancer prodrugs. Bioorg Med Chem, 22, 5747-5756.
Warabi K, H. T., Nakao Y, Matsunaga S, Hirota H, van Soest RW, Fusetani N. (2005). Axinelloside A, an unprecedented highly sulfated lipopolysaccharide inhibiting telomerase, from the marine sponge, Axinella infundibula. J Am Chem Soc, 127, 13262-13270. Warabi K, M. S., van Soest RW, Fusetani N. (2003). Dictyodendrins A-E, the first telomerase-inhibitory marine natural products from the sponge Dictyodendrilla verongiformis. J Org Chem, 68, 2765-2670. Wei, C., Wen, Y., & Wang, J. (2013). Novel platinum complexes as efficient G-quadruplex DNA binders and telomerase inhibitors. Int J Biol Macromol, 55, 185-192. Weinrich, S. L., Pruzan, R., Ma, L. B., Ouellette, M., Tesmer, V. M., Holt, S. E., Bodnar, A. G., 79
ACCEPTED MANUSCRIPT Lichtsteiner, S., Kim, N. W., Trager, J. B., Taylor, R. D., Carlos, R., Andrews, W. H., Wright, W. E., Shay, J. W., Harley, C. B., & Morin, G. B. (1997). Reconstitution of human telomerase with the template RNA component hTR and the catalytic protein subunit hTRT. Nat Genet, 17,
PT
498-502. Weiss, C., Uziel, O., Wolach, O., Nordenberg, J., Beery, E., Bulvick, S., Kanfer, G., Cohen, O., Ram,
RI
R., Bakhanashvili, M., Magen-Nativ, H., Shilo, N., & Lahav, M. (2012). Differential
SC
downregulation of telomerase activity by bortezomib in multiple myeloma cells-multiple regulatory pathways in vitro and ex vivo. Br J Cancer, 107, 1844-1852.
NU
Williams, S. C. (2013). No end in sight for telomerase-targeted cancer drugs. Nat Med, 19, 6. Wojtyla, A., Gladych, M., & Rubis, B. (2011). Human telomerase activity regulation. Molecular
MA
Biology Reports, 38, 3339-3349.
Wong, L. H., Unciti-Broceta, A., Spitzer, M., White, R., Tyers, M., & Harrington, L. (2013). A yeast chemical genetic screen identifies inhibitors of human telomerase. Chem Biol, 20, 333-340.
D
Woo, H. J., & Choi, Y. H. (2005). Growth inhibition of A549 human lung carcinoma cells by
TE
beta-lapachone through induction of apoptosis and inhibition of telomerase activity. Int J Oncol, 26, 1017-1023.
AC CE P
Wu HL, H. C., Liu WH, Yung BY. (1999). Berberine-induced apoptosis of human leukemia HL-60 cells is associated with down-regulation of nucleophosmin/B23 and telomerase activity. Int J Cancer, 81, 923-929.
Wu, R. A., & Collins, K. (2014). Human telomerase specialization for repeat synthesis by unique handling of primer-template duplex. Embo Journal, 33, 921-935.
Xi, L. H., & Cech, T. R. (2014). Inventory of telomerase components in human cells reveals multiple subpopulations of hTR and hTERT. Nucleic Acids Research, 42, 8565-8577. Xiao, N., Chen, S., Ma, Y., Qiu, J., Tan, J. H., Ou, T. M., Gu, L. Q., Huang, Z. S., & Li, D. (2012). Interaction of Berberine derivative with protein POT1 affect telomere function in cancer cells. Biochem Biophys Res Commun, 419, 567-572. Xie, M. Y., Podlevsky, J. D., Qi, X. D., Bley, C. J., & Chen, J. J. L. (2010). A novel motif in telomerase reverse transcriptase regulates telomere repeat addition rate and processivity. Nucleic Acids Research, 38, 1982-1996. Xu B, L. C., Sung C. (2014). Telomerase inhibitory effects of medicinal mushrooms and lichens, and 80
ACCEPTED MANUSCRIPT their anticancer activity. Int J Med Mushrooms, 16, 17-28. Xu, D., Erickson, S., Szeps, M., Gruber, A., Sangfelt, O., Einhorn, S., Pisa, P., & Grander, D. (2000). Interferon alpha down-regulates telomerase reverse transcriptase and telomerase activity in
PT
human malignant and nonmalignant hematopoietic cells. Blood, 96, 4313-4318. Xu, H., Gong, X., Zhang, H. H., Zhang, Q., Zhao, D., & Peng, J. X. (2015). Targeting Human
RI
Telomerase Reverse Transcriptase by a Simple siRNA Expression Cassette in HepG2 Cells.
SC
Hepat Mon, 15, e24343.
Yamakuchi, M., Nakata, M., Kawahara, K., Kitajima, I., & Maruyama, I. (1997). New quinolones,
NU
ofloxacin and levofloxacin, inhibit telomerase activity in transitional cell carcinoma cell lines. Cancer Lett, 119, 213-219.
MA
Yang, D. Y., Chang, T. C., & Sheu, S. Y. (2007). Interaction between human telomere and a carbazole derivative: a molecular dynamics simulation of a quadruplex stabilizer and telomerase inhibitor. J Phys Chem A, 111, 9224-9232.
D
Yang, W., & Lee, Y. S. (2015). A DNA-hairpin model for repeat-addition processivity in telomere
TE
synthesis. Nature Structural & Molecular Biology, 22, 844-847. Yashima, K., Piatyszek, M. A., Saboorian, H. M., Virmani, A. K., Brown, D., Shay, J. W., & Gazdar, A.
AC CE P
F. (1997). Telomerase activity and in situ telomerase RNA expression in malignant and non-malignant lymph nodes. Journal of Clinical Pathology, 50, 110-117.
Ye Y, Y. H., Wu J, Li M, Min JM, Cui JR. (2005). Z-ajoene causes cell cycle arrest at G2/M and decrease of telomerase activity in HL-60 cells. Chinese journal of oncology, 27, 516-520.
Yoon, J. H., Choi, Y. J., Choi, W. S., Ashktorab, H., Smoot, D. T., Nam, S. W., Lee, J. Y., & Park, W. S. (2013). GKN1-miR-185-DNMT1 axis suppresses gastric carcinogenesis through regulation of epigenetic alteration and cell cycle. Clin Cancer Res, 19, 4599-4610. Yoon JH, S. H., Choi WS, Kim O, Nam SW, Lee JY, Park WS. (2014). Gastrokine 1 induces senescence and apoptosis through regulating telomere length in gastric cancer. Oncotarget,, 5, 11695-11708. Yu, C., Yu, Y., Xu, Z., Li, H., Yang, D., Xiang, M., Zuo, Y., Li, S., Chen, Z., & Yu, Z. (2015). Antisense oligonucleotides targeting human telomerase mRNA increases the radiosensitivity of nasopharyngeal carcinoma cells. Mol Med Rep, 11, 2825-2830. Yu, J., Guo, Q. L., You, Q. D., Lin, S. S., Li, Z., Gu, H. Y., Zhang, H. W., Tan, Z., & Wang, X. (2006). 81
ACCEPTED MANUSCRIPT Repression of telomerase reverse transcriptase mRNA and hTERT promoter by gambogic acid in human gastric carcinoma cells. Cancer Chemother Pharmacol, 58, 434-443. Yu, M., Kong, H., Zhao, Y., Sun, X., Zheng, Z., Yang, C., & Zhu, Y. (2014). Enhancement of
PT
adriamycin cytotoxicity by sodium butyrate involves hTERT downmodulation-mediated apoptosis in human uterine cancer cells. Mol Carcinog, 53, 505-513.
RI
Yu Q, L. Y., Wang C, Sun D, Yang X, Liu Y, Liu J. (2012). Chiral ruthenium(II) polypyridyl complexes:
SC
stabilization of g-quadruplex DNA, inhibition of telomerase activity and cellular uptake. PLoS One, 7, e50902.
NU
Yurtcu E, D. I. O., Iffet Sahin F. (2015). Effects of silymarin and silymarin-doxorubicin applications on telomerase activity of human hepatocellularcarcinoma cell line HepG2. J BUON, 20, 555-561.
MA
Zaccagnini, G., Gaetano, C., Della Pietra, L., Nanni, S., Grasselli, A., Mangoni, A., Benvenuto, R., Fabrizi, M., Truffa, S., Germani, A., Moretti, F., Pontecorvi, A., Sacchi, A., Bacchetti, S., Capogrossi, M. C., & Farsetti, A. (2005). Telomerase mediates vascular endothelial growth
D
factor-dependent responsiveness in a rat model of hind limb ischemia. Journal of Biological
TE
Chemistry, 280, 14790-14798.
Zaffaroni N, L. S., Villa R, Bellarosa D, Cermele C, Felicetti P, Rossi C, Orlandi L, Daidone MG.
AC CE P
(2002). Inhibition of telomerase activity by a distamycin derivative: effects on cell proliferation and induction of apoptosis in human cancer cells. Eur J Cancer, 38, 1792-1801.
Zaug, A. J., Crary, S. M., Jesse Fioravanti, M., Campbell, K., & Cech, T. R. (2013). Many disease-associated variants of hTERT retain high telomerase enzymatic activity. Nucleic Acids Res, 41, 8969-8978.
Zaug, A. J., Podell, E. R., & Cech, T. R. (2008). Mutation in TERT separates processivity from anchor-site function. Nature Structural & Molecular Biology, 15, 871-872. Zhang, B., Qian, D., Ma, H. H., Jin, R., Yang, P. X., Cai, M. Y., Liu, Y. H., Liao, Y. J., Deng, H. X., Mai, S. J., Zhang, H., Zeng, Y. X., Lin, M. C., Kung, H. F., Xie, D., & Huang, J. J. (2012). Anthracyclines disrupt telomere maintenance by telomerase through inducing PinX1 ubiquitination and degradation. Oncogene, 31, 1-12. Zhang RG, G. L., Wang XW, Xie H. (2002). Telomerase inhibition and telomere loss in BEL-7404 human hepatoma cells treated with doxorubicin. World J Gastroenterol, 8, 827-831. Zhang, W., Tong, Q., Li, S., Wang, X., & Wang, Q. (2008). MG-132 inhibits telomerase activity, 82
ACCEPTED MANUSCRIPT induces apoptosis and G(1) arrest associated with upregulated p27kip1 expression and downregulated survivin expression in gastric carcinoma cells. Cancer Invest, 26, 1032-1036. Zhang, W., & Xing, L. (2013). RNAi gene therapy of SiHa cells via targeting human TERT induces
PT
growth inhibition and enhances radiosensitivity. International Journal of Oncology, 43, 1228-1234.
RI
Zhang, W. J., Ou, T. M., Lu, Y. J., Huang, Y. Y., Wu, W. B., Huang, Z. S., Zhou, J. L., Wong, K. Y., &
SC
Gu, L. Q. (2007). 9-Substituted berberine derivatives as G-quadruplex stabilizing ligands in telomeric DNA. Bioorg Med Chem, 15, 5493-5501.
NU
Zhang X, L. B., de Jonge N, Björkholm M, Xu D. (2015). The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase
MA
over-expression. Oncotarget, 6, 4888-4900.
Zhang, X., Li, B., de Jonge, N., Bjorkholm, M., & Xu, D. (2015). The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase
D
over-expression. Oncotarget, 6, 4888-4900.
TE
Zhang, Y., Sun, M., Shi, W., Yang, Q., Chen, C., Wang, Z., & Zhou, X. (2015). Arsenic trioxide suppresses transcription of hTERT through down-regulation of multiple transcription factors
AC CE P
in HL-60 leukemia cells. Toxicol Lett, 232, 481-489.
Zhang, Y., Toh, L., Lau, P., & Wang, X. (2012). Human telomerase reverse transcriptase (hTERT) is a novel target of the Wnt/beta-catenin pathway in human cancer. J Biol Chem, 287,
32494-32511.
Zhang, Y., Zhan, Y., Zhang, D., Dai, B., Ma, W., Qi, J., Liu, R., & He, L. (2014). Eupolyphaga sinensis walker displays inhibition on hepatocellular carcinoma through regulating cell growth and metastasis signaling. Sci Rep, 4, 5518. Zhao, Q., Yang, Y., Yu, J., You, Q. D., Zeng, S., Gu, H. Y., Lu, N., Qi, Q., Liu, W., Wang, X. T., & Guo, Q. L. (2008). Posttranscriptional regulation of the telomerase hTERT by gambogic acid in human gastric carcinoma 823 cells. Cancer Lett, 262, 223-231. Zhao, T. D., Hu, F. C., Qiao, B., Chen, Z. F., & Tao, Q. (2015). Telomerase reverse transcriptase potentially promotes the progression of oral squamous cell carcinoma through induction of epithelial-mesenchymal transition. International Journal of Oncology, 46, 2205-2215. Zhao, Y.-Q., Feng, H.-W., Jia, T., Chen, X.-M., Zhang, H., Xu, A.-T., Zhang, H.-L., & Fan, X.-L. 83
ACCEPTED MANUSCRIPT (2014). Antiproliferative Effects of Celecoxib in Hep-2 Cells through Telomerase Inhibition and Induction of Apoptosis. Asian Pacific Journal of Cancer Prevention, 15, 4919-4923. Zhao, Y. M., Zhou, Q., Xu, Y., Lai, X. Y., & Huang, H. (2008). Antiproliferative effect of rapamycin on
PT
human T-cell leukemia cell line Jurkat by cell cycle arrest and telomerase inhibition. Acta Pharmacol Sin, 29, 481-488.
RI
Zhou C, G. P., Whang YE, Boggess JF. (2003). Rapamycin inhibits telomerase activity by decreasing
SC
the hTERT mRNA level in endometrial cancer cells. Mol Cancer Ther, 2, 789-795. Zhou, J. M., Zhu, X. F., Lu, Y. J., Deng, R., Huang, Z. S., Mei, Y. P., Wang, Y., Huang, W. L., Liu, Z. C.,
NU
Gu, L. Q., & Zeng, Y. X. (2006). Senescence and telomere shortening induced by novel potent G-quadruplex interactive agents, quindoline derivatives, in human cancer cell lines. Oncogene,
MA
25, 503-511.
Zhou, L. L., Zheng, D. H., Wang, M., & Cong, Y. S. (2009). Telomerase reverse transcriptase activates the expression of vascular endothelial growth factor independent of telomerase activity.
D
Biochem Biophys Res Commun, 386, 739-743.
TE
Zhou, Q., Li, L., Xiang, J., Tang, Y., Zhang, H., Yang, S., Li, Q., Yang, Q., & Xu, G. (2008). Screening potential antitumor agents from natural plant extracts by G-quadruplex recognition and NMR
AC CE P
methods. Angew Chem Int Ed Engl, 47, 5590-5592.
Zhou XZ, H. P., Shi R, Lee TH, Lu G, Zhang Z, Bronson R, Lu KP. (2011). The telomerase inhibitor PinX1 is a major haploinsufficient tumor suppressor essential for chromosome stability in mice. J Clin Invest, 121, 1266-1282.
Zhou XZ, L. K. (2001). The Pin2/TRF1-interacting protein PinX1 is a potent telomerase inhibitor. Cell, 107, 347-359. Zhu, S., Rousseau, P., Lauzon, C., Gandin, V., Topisirovic, I., & Autexier, C. (2014). Inactive C-terminal telomerase reverse transcriptase insertion splicing variants are dominant-negative inhibitors of telomerase. Biochimie, 101, 93-103. Zhu, Y., He, W., Gao, X., Li, B., Mei, C., Xu, R., & Chen, H. (2015). Resveratrol overcomes gefitinib resistance by increasing the intracellular gefitinib concentration and triggering apoptosis, autophagy and senescence in PC9/G NSCLC cells. Sci Rep, 5, 17730. Zvereva, M. I., Zatsepin, T. S., Azhibek, D. M., Shubernetskaya, O. S., Shpanchenko, O. V., & Dontsova, O. A. (2015). Oligonucleotide inhibitors of telomerase: prospects for anticancer 84
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
NU
SC
RI
PT
therapy and diagnostics. Biochemistry (Mosc), 80, 251-259.
85
ACCEPTED MANUSCRIPT
PT
Figure Legends
RI
Fig. 1. Schematic representation of functional domains of hTERT and hTR. (A) Four
SC
functional domains of hTERT. The telomerase N-terminal (TEN) domain participates in catalysis and drives telomerase localization to telomeres. The TR-binding domain
NU
(TRBD) interacts with hTR. The reverse transcriptase (RT) domain and C-terminal extension (CTE) domain form the catalytic core of telomerase. The RT domain is
MA
similar to fingers domain (1-2) and palm domain (A-E), and the CTE is similar structure to thumb domain of conventional RTs. Motif 3 and IFD are telomerase
D
specific motifs. (B) Secondary structure of the hTR. hTR is composed of three
TE
functional domains. The template/pseudoknot and conserved region CR4/5 domains
AC CE P
bind to TERT and are essential for enzymatic activity. TBE composes of helix structure located upstream of the template. The H/ACA domain is dispensable for activity, it is essential for in vivo biogenesis, accumulation and RNP assembly. Fig. 2. A schematic drawing of telomerase catalytic cycle for processive repeat addition. The human telomerase enzyme binds to the telomeric DNA substrate and adds DNA repeats (GGTTAG)n to the DNA primer by copying the template sequence (5’-CUAACCCUAAC-3’) from the intrinsic hTR component. After reaching the end of the template, the DNA substrate reanneals the alignment region to regenerate the template for next round of extension. Until now, the process is complex and unclear, only a few models try to explain the mechanism of the template translocation process. Model 1. RNA/DNA duplex binding to telomerase active site determines the template translocation efficiency; model 2. DNA conformational rearrangement during telomerase catalytic cycle; model 3. DNA hairpin model for telomeric repeat addition. 86
ACCEPTED MANUSCRIPT Fig. 3. A model of telomerase RNP biogenesis and potential targets of telomerase for anti-tumor drugs. hTERT protein expression follows the canonical eukaryotic
PT
transcription, RNA maturation and nuclear export to the cytoplasm for translation. The hTERT protein is imported back into the nucleus and localizes to the nucleolus
RI
prior to assembly with the hTR. The hTR precursor, synthesized by RNA polymerase
SC
II and TMG capped, is bound by two copies of the protein complex for localization of the mature hTR to Cajal bodies. hTERT localizes to Cajal bodies for assembly with
NU
the hTR, aiding by the chaperone proteins hsp90 and p23. The fully assembled active
MA
telomerase complex localizes to the telomere. The potential targets are mainly as followed: ① inhibition of the hTERT gene transcription; ② degradation of primary
D
transcript form of hTERT mRNA; ③ dominant negative hTERT or post-translation
TE
modification of hTERT; ④ inhibition the nuclear localization of hTERT; ⑤
AC CE P
inhibition of hTR gene transcription; ⑥ degradation of the primary transcript and affecting the maturation of the hTR primary transcript; ⑦ disturbance of telomerase complex assembly; ⑧ blocking enzymatic activity of assembled telomerase complex; ⑨ repression of the expression of the shelterin protein or inhibition the interaction of the telomerase with the complex; ⑩ inhibition of telomerase complex interacting with telomeres and decreased availability of telomere ends for telomerase.
87
Fig. 1
AC CE P
TE
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
88
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
AC CE P
TE
D
MA
Fig. 2
89
Fig. 3
AC CE P
TE
D
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
90
PT
ACCEPTED MANUSCRIPT
Table 1. Overreview of natural anti-tumor compounds targeting telomerase from plants
Compounds
RI
Target location Plant source
Mechanism of action
NU
Targeting hTERT Inhibition of the Epigallocatechin Camellia sinensis
Binding competitively at the active site of hTERT
MA
catalytic function gallate
Boldine
Peumus boldus
(S. C. Lin, et al., 2006; S. H. Naasani I, Tsuruo T., 1998; Nagle, Ferreira, & Zhou, 2006) (Kazemi Noureini & Tanavar,
PT ED
Suppression of
Inhibition of hTERT expression
transcriptional
2015)
Inhibition of transcription of hTERT through
Triptolide
CE
and post transcriptional
Ref.
SC
of telomerase
Tripterygium wilfordii
AC
regulation
down-regulation of transcription factor specificity
(Long, et al., 2015)
protein 1 (Chakrabarti, Banik, & Ray, 2013;
Common fruits and
Down-regulation of telomerase activity by
vegetables
suppression of c-Myc-mediated hTERT expression
Apigenin
Jayasooriya, et al., 2012; Kang, 1998) Down-regulation of telomerase activity and hTERT
Papaverine
Papaveraceae
(Noureini & Wink, 2014) expression
91
Crocus sativus L.
Down-regulation of hTERT expression
Cephalotaxus
Asian coniferous evergreen
alkaloids
trees Cephalotaxus sp.
RI
Crocin
PT
ACCEPTED MANUSCRIPT
SC
Down-regulation of hTERT transcription
(Noureini & Wink, 2012)
(J. L.-Y. Chen, et al., 2011)
Down-regulation of the telomerase activity and
Butylidenephthal
NU
Angelica sinensis ide
(P. C. Lin, et al., 2011)
hTERT expression
Cruciferous vegetables
MA
Down-regulation of the telomerase activity and Indole-3-carbinol
(Adler, Rashid, & Klein, 2011)
Glycoprotein Laminaria japonica LJPG
CE
The flavonoid family,
PT ED
hTERT mRNA expression
Down-regulation of hTERT expression
(Han, et al., 2011)
including commonly ingested fruits and
AC
Quercetin
(J. L.-Y. Chen, et al., 2011; A. K. Down-regulation of hTERT gene expression Verma & Pratap, 2010)
vegetables such as red onion and also tea and red wine Tanshinone I
Salvia miltiorrhiza
Helenalin
Arnica montana
Down-regulation of hTERT expression
(X. D. Liu, et al., 2010)
Down-regulation of hTERT transcription through (J. L.-Y. Chen, et al., 2011) inhibition of NF-kB
92
PT
ACCEPTED MANUSCRIPT
Inhibition of hTERT, human telomerase-associated Scutellaria baicalensis
protein 1 (hTP1) and c-myc messenger ribonucleic
RI
Wogonin
(S. T. Huang, et al., 2010)
SC
acid (m-RNA) expression
NU
Down-regulation of hTERT transcription via inhibition of the transcription activator c-myc, and Garcinia hurburyi tree
by the inhibition of the phosphorylation of Akt;
MA
Gambogic acid
(Han QB, 2009; J. Yu, et al., 2006)
downregulates the activity of hTERT in a
Secondary plant metabolites
Curcumin
AC
CE
Genistein
PT ED
post-translational manner (Jagadeesh, Kyo, & Banerjee, 2006;
Down-regulation of hTERT expression
Y. Li, Liu, Andrews, & Tollefsbol, 2009)
Inhibition of telomerase activity and hTERT
(Mukherjee Nee Chakraborty, et al.,
expression
2007; Singh & Singh, 2009)
Curcuma longa
Inhibition of telomerase activity, reduction of
Costunolide
hTERT mRNA and protein levels, decreasing the
(S. H. Choi, et al., 2005; Kanno S,
bindings of transcription factors in hTERT
2008)
Magnolia sieboldii
promoters
93
PT
ACCEPTED MANUSCRIPT
Inhibition of telomerase activity with (Draisci, Lucentini, Giannetti,
Pectenotoxin-2
RI
down-regulation of hTERT expression, attenuating Dinophysis fortii
Boria, & Poletti, 1996; M. O. Kim,
SC
the binding of c-Myc and Sp1 to the regulatory et al., 2008)
NU
regions of hTERT
Inhibition telomerase activity with down-regulation Ginsenoside Rk1
Sun Ginseng
(Y. J. Kim, et al., 2008)
(Z)-Stellettic
MA
of levels of hTERT and c-Myc mRNA Down-regulation of the telomerase activity and the Marine sponge Stelletta sp.
Dideoxypetrosyn
Down-regulation of the telomerase activity and the
Marine sponge Petrosia sp.
Reduction of hTERT mRNA levels
(Sun L, 2003; Ye Y, 2005)
AC
Garlic (Allium sativum) ajoene
(C. Park, Jung, Kim, & Choi, 2007)
hTERT expression
CE
ol A Allicin and
(C. Park, Kim, et al., 2007)
hTERT expression
PT ED
acid C
Hellbore (Veratrum
grandiflorum O. Loes), Down-regulation of the telomerase activity and the Resveratrol
peanuts (Arachis hypogeal),
(Aggarwal BB, 2004) nuclear levels of hTERT
legumes (Cassia sp.) and grapes (Vitis vinifera)
94
PT
ACCEPTED MANUSCRIPT
Silybum marianum (L.)
Down-regulation of the telomerase activity and the
(Thelen, Wuttke, Jarry, Grzmil, &
Gaertn
mRNA levels of hTERT
Ringert, 2004)
RI
Silibinin
Inhibition of telomerase activity with translocation Gossypol
SC
Translocation Cottonseed
(Moon, et al., 2008)
(Draisci, et al., 1996; M. O. Kim, et
phosphorylation and nuclear translocation of hTERT
al., 2008)
Secondary plant metabolites
Disturbance in the translocation of hTERT to the
(Jagadeesh, et al., 2006; Y. Li, et
nucleus
al., 2009)
MA
Genistein
Inhibition of telomerase activity with reducing the Dinophysis fortii
PT ED
Pectenotoxin-2
NU
into the nucleus
Post translational
Inhibition of telomerase activity with
Gossypol
Cottonseed
(Moon, et al., 2008)
down-regulation of hTERT phosphorylation
Inhibition of Silymarin
Inhibition of telomerase activity and
Broccoli and cauliflower
AC
Sulforaphane
CE
modification
Silybum marianum
(Moon, et al., 2010) posttranslational modification of hTERT (Faezizadeh Z, 2012; Yurtcu E, Inhibition of telomerase activity
telomerase
2015)
activity
Metabolites of sulforaphane MTBITC(erucin)
(Mechanism is unclear)
Inhibition of telomerase activity
(Herz, et al., 2014)
Inhibition of telomerase activity
(H. T. Warabi K, Nakao Y,
from broccoli Axinelloside A
marine sponge Axinella
95
PT
ACCEPTED MANUSCRIPT
Salvia miltiorrhiza
Inhibition of telomerase activity
SC
Tanshinone IIA
RI
infundibula
Dictyodendrins
NU
Marine sponge Dictyodendrilla
Matsunaga S, Hirota H, van Soest RW, Fusetani N., 2005) (Song, 2005)
(M. S. Warabi K, van Soest RW,
Inhibition of telomerase activity
MA
verongiformis
Fusetani N., 2003)
Cladonia furcate
Inhibition of telomerase activity
(X. Lin, et al., 2003)
Berbamine
Berberis vulgaris
Inhibition of telomerase activity
(Ji ZN, 2002)
Inhibition of telomerase activity
(Giridharan, et al., 2002)
7'-hydroxy-3',4',5 ,9,9'-pentametho
CE
Phyllanthus urinaria
Targeting hTR Transcriptional
AC
xy-3,4-methylen e dioxy lignan
PT ED
Lichenin CFP -2
Tabebuia avellanedae
Inhibition of telomerase activity, down-regulation of
(Lapacho tree)
the levels of hTR and c-myc expression
Beta-Lapachone level
(Woo & Choi, 2005)
Targeting the telomerase substrate and associated protein Competitor for
Epigallocatechin
Camellia sinensis
Binding competitively with respect to the RNA
96
(S. C. Lin, et al., 2006; S. H.
substrate primer
RI
gallate
G4
Naasani I, Tsuruo T., 1998; Nagle, et al., 2006)
Inhibition of telomerase activity and interaction with Daidzin
SC
substrate
PT
ACCEPTED MANUSCRIPT
Soybeans G4
NU
DNA-interactive compounds Coptidis rhizoma
North American herb bloodroot (Sanguinaria canadensis) Daurisoline,
CE
Menispermum dauricum and dauricinoline and
AC
Rhizoma Menispermi daurinoline
2008)
(Bai, Hagihara, Jiang, & Nakatani,
Formation of C-myc22 G4 and Hum24 G4
PT ED
Sanguinarine
(Ji, et al., 2012; Q. Zhou, et al.,
Formation of C-myc22 G4 and Hum24 G4
MA
Palmatine
(W. Li, et al., 2006; Rafii, 2015)
2008; Ji, et al., 2012)
Induction the formation of G4 as well as increase the
(Ji, et al., 2012; Q. Liu, Mao, Zeng,
stabilization of G4
Jin, & Yang, 2012; Pan X, 1998)
Berberis vulgaris chinensis
Interaction with G4 preference for G4 over duplex
(Coptis or goldenthread)
DNA
Cryptolepine
Cryptolepis triangularis
Interaction with G4
(Guittat, et al., 2003)
Shikonin and its
Boraginaceae family Interaction with G4
(Lu Q, 2002)
derivatives
(mainly in the genus of
Berberine
(Franceschin, et al., 2006)
97
PT
ACCEPTED MANUSCRIPT
RI
Alkanna,Lithospermum) Okinawan tunicate Didenum
Stabilization of G4 and inhibition of telomerase
sp.
activity
Ascidian Amphicarpa
Inhibition of telomerase activity and stabilization of
meridian
G4
NU
AC
CE
PT ED
MA
Meridine
(Jun'ichi Kobayash, 1988)
SC
Ascididemin
98
(Francis J. Schmitz, 1991)
PT
ACCEPTED MANUSCRIPT
Compounds
SC
Target location of Microbial source
Mechanism of action
Ref.
NU
telomerase Targeting hTERT
An unwinder of DNA/RNA duplex formed by mtelomerase Pif1 helicase
Saccharomyces cerevisiae
(Paeschke, et al., 2013)
RNA and telomeric DNA
Wortmannin
transcriptional and
Penicillium funiculosum Streptomyces
Rapamycin hygroscopicus
regulation Trichostatin A
AC
post transcriptional
Competitive interact ion with the hTERT and subunits of
(Kiran, et al., 2015; Ueno T,
telomerase enzyme
2000)
Down-regulation of hTERT expression
(Kiran, et al., 2015)
Streptomyces collinus
CE
Rubromycins
PT ED
catalytic function
MA
Inhibition of the
Suppression of
RI
Table 2. Overreview of tumor inhibitors targeting telomerase from microbial sources
Inhibition of telomerase enzyme and down-regulation of (Sundin, Peffley, & Hentosh, hTERT mRNA level
2013)
Eliciting Smad3, Mad1 gene expression and leading to the
Streptomyces platensis
(Rahman, et al., 2010) down-regulation of hTERT
Chromobacterium FR901228
Down-regulation of hTERT expression
(Murakami, et al., 2005)
violaceum Eicosapentanoic
Shewanella
Inhibition of telomerase enzyme; reducing the expression of (Eitsuka, et al., 2005; Hirota,
99
pneumatophore
c-myc gene and hTERT expression
Docosahexanoic Crypthecodinium cohnii
Hsp90 ligand conjugates, inhibition of telomerase catalytic
(DeBoer C, 1970; Roe, et al.,
hygroscopicus
activity
NU
MA
and Neocosmospora
2015; Villa, et al., 2003)
(Chiu, et al., 2011; Compton,
Hsp90 activity inhibitor and inhibition of telomerase enzyme
PT ED
tenuicristata Inhibition of
2005;
Streptomyces
Pochonia chlamydosporia Radicicol
al.,
Ratledge C, 2001)
Geldanamycin of hTERT protein
et
c-myc gene and hTERT expression
SC
acid Molecular folding
et al., 2005)
Inhibition of telomerase enzyme; reducing the expression of (Eitsuka,
RI
acid
PT
ACCEPTED MANUSCRIPT
Griseorhodins A Streptomyces californicus
et al., 2006)
(Kiran, et al., 2015; Ueno, et
Inhibition of telomerase enzyme
and C
(Mechanism is
and Streptomyces griseus Actinoplanes
Purpuromycin ianthinogenes
Alterperylenol
AC
unclear)
CE
telomerase activity
Alternaria sp.
al., 2000) (Kiran, et al., 2015; Ueno T,
Inhibition of telomerase enzyme 2000) (Kiran,
et
al.,
2015;
Inhibition of telomerase enzyme Toshikatsu Okuno, 1983) (Nakai, et al., 2006; Nakai R,
Chrolactomycin
Streptomyces sp.
Inhibition of telomerase enzyme 2001)
UCS1025A
Fungus Acremonium sp.
Inhibition of telomerase enzyme
100
(Agatsuma T, 2002; Nakai, et
Talaromyces flavus
Inhibition of telomerase enzyme
Streptomyces anulatus
Inhibition of telomerase enzyme and stabilization of G4
(Rezler, et al., 2005; Shin-ya
3533-SV4
DNA
K, 2001)
Inhibition of telomerase enzyme by G4 binding
(Clark GR, 2003)
Interaction of G4
(Cocco MJ, 2003)
Telomestatin
Streptomyces peucetius
Distamycin A
Streptomyces distallicus
Rubromycins
Streptomyces collinus
AC
telomere-associated
CE
Daunomycin
Target
(Togashi, et al., 2001)
(Tabata Y, 1999)
MA PT ED
Targeting hTR
compounds
et al., 2001)
Inhibition of telomerase enzyme
acid
interactive
(Kitahara N, 1981; Togashi,
Acremonium sp.
Diazaphilonic
G4 DNA
al., 2006)
Inhibition of telomerase enzyme
SC
CRM646-A
Thielavia terricola
NU
Thelavin B
RI
PT
ACCEPTED MANUSCRIPT
Competitive interact ion with the hTR subunits of telomerase (Kiran, et al., 2015; Ueno T, enzyme
2000)
proteins
(D. Gomez, et al., 2006; Inducing dissociation of TRF2 and POT1 proteins by Telomestatin
Streptomyces anulatus 3
Rezler, et al., 2005; Shin-ya initiating the DNA damage response K, 2001; Tauchi, et al., 2003)
101
AC
CE
PT ED
MA
NU
SC
RI
PT
ACCEPTED MANUSCRIPT
102
PT
ACCEPTED MANUSCRIPT
RI
Table 3. Summary of laboratorial or preclinical studies of synthetic tumor inhibitors targeting telomerase
SC
Target location of Compounds
Mechanism of action
NU
telomerase Targeting hTERT BIBR1532
Inhibition of telomerase function by disrupting TERT-RNA binding
MA
Inhibition of the catalytic function
Ref.
(Bryan, et al., 2015)
Binding well with the telomerase active site and inhibitory activity
PT ED
Aryl-2H-pyrazole, 16A
(Luo, et al., 2013)
for telomerase
TELIN
2007)
Inhibiting the capping and catalytic functions of telomerase.
AC
BRACO-19
(Rangarajan & Friedman,
Inhibition of telomerase by targeting RNA/DNA heteroduplex
CE
5-benzylic acid ethidium derivative
(Burger, et al., 2005) (Kakiuchi, Sasaki,
A Specific potent catalytic blocker of telomerase and Inhibiting
Satoh-Masuoka, Murofushi,
telomerase activity
& Murakami-Murofushi, 2004)
Suppression of
Riccardin D
Inhibition of telomerase activity and down-regulation of hTERT
103
(Sun CC, 2014)
DIMA
Inhibition of telomerase activity and hTERT transcript levels
post transcriptional
Anthra[1,2-d]imidazole-6,11-dione
regulation
derivatives: 16, 39, and 40
RI
transcriptional and
PT
ACCEPTED MANUSCRIPT
SC
Down-regulation of hTERT expression
Inhibition of telomerase activity, hTERT mRNA expression and
NU
CDDO-Me
MA
hTERT regulatory proteins (c-Myc, Sp1, NF-κB and p-Akt)
BIBR1532
(V. Verma, et al., 2014)
(C. L. Chen, et al., 2013)
(Deeb, et al., 2013; Y. Liu, et al., 2012) (Bashash, et al., 2013; El
Down-regulation of c-Myc and hTERT expression Daly & Martens, 2007)
Down-regulation of hTERT mRNA expression
(Kasiappan, et al., 2012)
2'-hydroxy-2,3,4',6'-tetramethoxych
Inhibition of telomerase activity and the expression of hTERT, and
(Y. K. Rao, Kao, Wu, Ko, &
alcone
decrease of the hTERT promoter
Tzeng, 2010)
Trichostatin A
CE
Scriptaid
AC
4-hydroxynonenal
PT ED
1,25-dihydroxyvitamin D3
Inhibition of telomerase activity and hTERT expression
(Pizzimenti, et al., 2010)
Inhibition of telomerase activity
(Sharma, et al., 2010)
Repression of hTERT via recruitment of CTCF to the promoter
(J. H. Choi, et al., 2010)
Inhibition of telomerase activity by decreasing the hTERT expression
(Rabi & Banerjee, 2009)
Decrease of telomerase activity associated with a rapid decrease in
(Phipps, Love, White,
histone H3-lysine 9 acetylation (H3-K9-Ac) of the hTERT promoter
Andrews, & Tollefsbol,
Methyl-25-hydroxy-3-oxoolean-12en-28-oate
All-trans retinoic acid
104
RI
PT
ACCEPTED MANUSCRIPT
2009) (Moriai, Tsuji, Kobayashi,
Down-regulation of hTERT mRNA expression, repression the
SC
15d-PGJ2
Kuribayashi, & Watanabe,
NU
DNA-binding of c-Myc, Sp1 and ER to the hTERT gene promoter 2009)
Inhibition of telomerase activity involved in decreasing the Triethylene tetramine
(J. Liu, et al., 2008)
MA
expression of hTERT
Down-regulation of hTERT transcriptional level
(Lin CP, 2007)
Down-regulation of hTERT-mRNA transcript levels and reduction of
(Bermudez, Ahmadi, Lowell,
hTERT promoter activity
& Kruk, 2007)
PT ED
10058-F4
Vitamin E
CE
Inhibition of telomerase activity, down-regulation of hTERT mRNA
1,25-dihydroxyvitamin D3
and protein expression through suppression of hTERT transcriptional
AC
SC-236
(He, et al., 2006)
activity Decrease of the stability of hTERT mRNA
(Olaussen, et al., 2006)
BRACO-19
Reduction in hTERT expression and telomere dysfunction
(Burger, et al., 2005)
SR374, SR375, SR361and SR362
Hsp90 ligand conjugates, inhibition of telomerase catalytic activity
(Roe, et al., 2015)
INS1b, INS3 and INS4
Decreasing telomerase activity, telomere shortening, and an
(Killedar, et al., 2015; S.
Molecular folding of hTERT protein
105
PT
ACCEPTED MANUSCRIPT
increasing telomere-specific DNA damage response (DDR) Inhibition of telomerase activity and reduction of telomere length by DN-hTERT dominant-negative hTERT
SC
hTERT
RI
Dominant negative
Zhu, et al., 2014)
(Y. Rao, et al., 2014)
Translocation
NU
Displacement of hTERT from the nucleus, induction of RHPS4
(Phatak, et al., 2007;
Telomere-initiated DNA-damage signalling and chromosome fusions, Cookson, et al., 2005)
Inhibition of
MA
reduction in telomere length 4-methylthiobutyl isothiocyanate
Inhibition of telomerase activity
MST-312
Inhibition of telomerase activity
(Mechanism is SEW05920, SPB03924 and
(Serrano, et al., 2011)
CE
Inhibition of telomerase activity CD11359
(Wong, et al., 2013)
(F. C. Huang, K. F. Huang, et
Diaminoanthraquinone-linkedamin
AC
unclear)
(Gurung RL, 2014);
PT ED
telomerase activity
(Herz, et al., 2014)
Inhibition of telomerase activity
oacyl residue derivatives, B11
al., 2012) (Mizushina, Takeuchi,
β-Rubromycin
Inhibition of telomerase activity Sugawara, & Yoshida, 2012) (P. R. Huang, Yeh, Pao,
N-(1-Pyrenyl) maleimide
Inhibition of telomerase activity Chen, & Wang, 2012)
106
Inhibition of telomerase activity
Phenethyl isothiocyanate
Inhibition of telomerase activity
SC
RI
5-aza-2'-deoxycitidine
PT
ACCEPTED MANUSCRIPT
(Mukherjee, Bhattacharya, & Roy, 2009) (W. Zhang, Tong, Li, Wang,
Inhibition of telomerase activity
MA
NU
MG-132
(Tao, et al., 2012)
U-73122
& Wang, 2008) (Y. J. Chen, Sheng, Huang,
Inhibition of telomerase activity
Inhibition of telomerase activity and telomere erosion
PT ED
Salvcine
& Wang, 2006) (W. J. Liu, et al., 2004)
Inhibition of telomerase activity, telomere erosion followed by an (J. H. Kim, Lee, Kim, &
increased incidence of chromosome abnormalities and induction of Chung, 2003)
CE
2,3,7-trichloro-5-nitroquinoxaline
the senescence phenotype
Inhibition of telomerase activity, telomere erosion followed by the
(J. H. Kim, Lee, Lee, &
ne
induction of senescence phenotype
Chung, 2003)
Distamycin derivative, MEN 10716
Inhibition of telomerase activity
(Zaffaroni N, 2002)
Rhodacyanine derivative, FJ5002
Inhibition of telomerase activity by telomere shortening
AC
3-(3,5-dichlorophenoxy)-nitrostyre
(S. H. Naasani I, Yamori T, Tsuruo T., 1999) 2-[3-(trifluoromethyl)phenyl]isothia
Inhibition of telomerase activity
107
(Hayakawa, et al., 1999)
zolin-3-one Inhibition of telomerase activity
RI
9-hydroxyellipticine
PT
ACCEPTED MANUSCRIPT
SC
Targeting hTR Degradation/instabil
(Sato, et al., 1998)
Inhibition of telomerase activity and specific cleavage activity against
ity
NU
HDV ribozyme (g.RZ57)
(Lu Y, 2011)
the telomerase RNA
MA
Targeting the telomerase substrate and associated protein Carbazole-based benzimidazole
Higher affinity and excellent selectivity of ligands toward G4 DNA
compounds
dimers M2, D2, D3 and D4
over duplex DNA
Ruthenium(II) complexes:4
PT ED
G4 DNA-interactive
(Maji, et al., 2015)
Binding affinity to G4-DNA in telomere, effective stabilizers of
(Z. F. Chen, Q. P. Qin, J. L.
telomeric and G4-DNA in promoter of c-myc
Qin, J. Zhou, et al., 2015)
Inhibition of telomerase activity and interaction with telomeric,
(Z. F. Chen, Q. P. Qin, J. L.
with Oxoisoaporphine: Pt1 and Pt2
c-myc, and bcl-2 G4
Qin, Y. C. Liu, et al., 2015)
RHPS4
G4 interacting ligands
(Roe, et al., 2015)
Inhibition of telomerase activity and interaction with telomeric G4
(Ilyinsky, et al., 2014)
(S-enantiomer)
AC
Organoplatinum(II) Complexes
CE
(racemate), 5 (R-enantiomer) and 6
11-(3-aminopropylamino)-4-(2-gua nidinoethylamino)anthra[2,3-b]thio phene-5,10-dione, 13
108
Platinum(II) complex of liriodenine
PT
ACCEPTED MANUSCRIPT
G4 DNA stabilization
RI
Ruthenium(II) complexes: [Ru(IP)2
Induction of the stabilization of G4 DNA
SC
(PIP)](ClO4) 2 ·2H2O, [Ru(PIP) 2
NU
(IP)](ClO4) 2 ·2H2O (2) [(dmb)2Ru(obip)Ru(dmb)2]4+
Promote the formation and stabilization of G4 DNA
MA
Macrocyclic hexaoxazole
Interaction with G4 by π-stacking and electrostatic interactions L2H2-6 M(2)OTD
PT ED
Platinum(II) complexes: [PtL1(II)en](PF6)2,
Stabilizing h-telo,c-kit2, and c-myc G4, higher binding affinities to
[PtL2(II)en](PF6)2,
G4
BMVC4
Perylene diimides
(Q. Li, et al., 2014)
(Shi, et al., 2013)
(W. J. Chung, et al., 2013)
(Wei, et al., 2013)
CE AC
[PtL3(II)en](PF6)2
(Y. L. Li, et al., 2014)
(F. C. Huang, Chang, Wang,
G4 stabilizer Chang, & Lin, 2012) Telomerase inhibition and binding to G4 DNA
(D'Ambrosio, et al., 2012)
Inhibition of telomerase activity and stabilization of G4 DNA
(Yu Q, 2012)
Chiral Ruthenium(II) Polypyridyl Complexes: Λ-[Ru(phen)2 (p-HPIP)]2+ and∆-[Ru(phen)
109
2(p-HPIP)]
PT
ACCEPTED MANUSCRIPT
2+
Including telomere dysfunction through G4 stabilization
BRACO-19
High selectivity and affinity for G4 DNA
NU
SC
RI
TMPyP4
3,6-bis(1-methyl-4-vinylpyridinium
(Fujimori, et al., 2011) (Burger, et al., 2005; Debray, et al., 2009) (D. Y. Yang, Chang, & Sheu,
Inhibition of telomerase activity and stabilization of G4 DNA
MA
iodine) carbazole
2007)
Interaction with G4 and telomere shortening
(J. M. Zhou, et al., 2006)
Fluoroquinophenoxazine
Interaction with the telomeric G4 structure
(Duan, et al., 2001)
PT ED
SYUIQ-5
Targeting
POT1-binding ligand, interfering with the binding between Berberine derivative, Sysu-00692
(Xiao, et al., 2012)
human POT1 and the telomeric DNA
BIBR1532
(Bashash, et al., 2013;
Loss of telomeric repeat binding factor 2 (TRF2) Pascolo, et al., 2002)
AC
proteins
CE
telomere-associated
110
RI
Table 4. Summary of synthetic tumor inhibitors targeting telomerase in clinical trials or in clinic
Compounds
SC
Target location of Mechanism of action
Pharmacodynamic effects in Ref. clinic
NU
telomerase Targeting hTERT
5-azacytidine
MA
Inducing DNA damage and telomere dysfunction; Target S phase of the cycle
diminishing telomerase reverse transcriptase
PT ED
Inhibition of the
(Zhang X, 2015) specially
expression, reduction in telomere length Activating peroxisome
Inhibition of telomerase activity and Troglitazone
(Rashid-Kolvear, et al., proliferator-activated receptors
Arsenic trioxide
CE
down-regulation of mRNA hTERT expression
2010) (PPARs)
Reduction of hTERT at mRNA and protein levels
AC
catalytic function
PT
ACCEPTED MANUSCRIPT
Cytotoxic drugs
(Y. Zhang, et al., 2015)
Effective chemosensitizer
(Gan, et al., 2015)
Inhibition of telomerase activity and reduction in Suramin
telomere length Inhibition of telomerase activity and
Ubiquitin/proteasome pathway
down-regulation of hTERT expression; reduction in
inhibitor and NF-κB inhibition
Bortezomib
(Ci X, 2015)
111
telomere length; reduction in phosphorylation of the
PKCα Romidepsin
NU
Down-regulation of hTERT expression
MA
(FR901228)
Celecoxib
SC
RI
catalytic subunit of hTERT by its kinases, AKT and
PT
ACCEPTED MANUSCRIPT
(Kiran, et al., 2015; Histone deacetylase inhibitor Murakami, et al., 2005) COX-2 selective nonsteroidal
Down-regulation of hTERT mRNA level
(Y.-Q. Zhao, et al., 2014) anti-inflammatory drug
Nilotinib
PT ED
Down-regulation of hTERT gene transcription, Selective Bcr-Abl kinase
reduction of hTERT nuclear expression and
(Shapira, et al., 2012) inhibitor
Down-regulation of hTERT gene transcription,
Bcr-Abl tyrosine kinase
reduction of hTERT nuclear expression and
inhibitor and Src family tyrosine
inhibition of telomerase activity
kinase inhibitor
AC
Dasatinib
CE
inhibition of telomerase activity
(Shapira, et al., 2012)
Histone deacetylase inhibitors Inhibition of telomerase activity and by reducing the Vorinostat
for treatment of cutaneous T cell
(C. T. Li, et al., 2011)
expression of hTERT lymphoma Imatinib
Inhibition of telomerase activity caused mainly
112
Tyrosine kinase inhibitor
(Mor-Tzuntz, et al., 2010;
mesylate
PT
ACCEPTED MANUSCRIPT
downregulation of hTERT transcription by
selective for BCR-ABL
RI
post-translational
Uziel, et al., 2005)
SC
Modifications
down-regulation of the hTERT
MA
Inhibition of telomerase activity and
NU
Inhibition of telomerase activity and Gefitinib
Rapamycin
EGFR tyrosine kinase inhibitor
(Moon, et al., 2009)
(Y. M. Zhao, et al., 2008; m-TOR pathway inhibitor
down-regulation of hTERT mRNA level
Zhou C, 2003)
Aspirin
PT ED
Inhibition of telomerase activity, down-regulation of Non-steroidal anti-inflammatory
hTERT mRNA and protein expression through
(He, et al., 2006) drug
CE
suppression of hTERT transcriptional activity Inhibition of telomerase activity, down-regulation of Non-steroidal anti-inflammatory
hTERT mRNA and protein expression through
AC
Indomethacin
(He, et al., 2006) drug
suppression of hTERT transcriptional activity Involving in the circadian Inhibition of telomerase activity and
(Leon-Blanco, Guerrero,
Melatonin
rhythms of physiological down-regulation of TERT mRNA expression
Reiter, Calvo, & Pozo, 2003) functions
Temozolomide
Inhibition of telomerase activity and
Chemotherapy drug that
113
(Kanzawa, et al., 2003)
PT
ACCEPTED MANUSCRIPT
interfering with transcription factor Sp1 binding
Inhibition of telomerase activity by post translational
tumor cells (Brandt, Heller, Schuster, &
mediating via suppression of PKC-activity
modulator
Grote, 2005)
Perifosine
Inhibition of telomerase activity
AKT inhibitor
(Holohan B, 2015)
Treatment for rheumatoid
(N.-H. Kim, Park, Oh, &
Auranofin
Inhibition of telomerase activity
arthritis
Kim, 2013)
MA
medication Inhibition of
DNA and triggers the death of
Selective estrogen-receptor
Tamoxifen
telomerase activity
PT ED
(Mechanism is unclear)
Inhibiting the enzyme (Khorramizadeh, et al.,
Inhibition of telomerase activity
dihydrofolate reductase, 2007)
CE
Pyrimethamine
NU
Posttranslational
SC
sites of the hTERT core promoter
methylation caused damages the
RI
down-regulation of hTERT gene expression by
treatment for antimalarial drug
AC
Selective COX-2 inhibitor for
Inhibition of telomerase activity associated with the Nimesulide
(Baoping, Guoyong, Jieping, non-steroidal anti-inflammatory
attenuation of Akt/PKB activity
Zongxue, & Hesheng, 2004) drug (T. Brown, Sigurdson,
Azidothymidine
Inhibition of telomerase activity
Antiretroviral medication Rogatko, & Broccoli, 2003)
Octreotide
Inhibition of telomerase activity
Treatment of growth hormone
114
(Gao, Yu, Li, Dong, & Luo,
PT
ACCEPTED MANUSCRIPT
SC
Inhibition of telomerase activity
NU
levofloxacin
functions by inhibiting DNA
Kawahara, Kitajima, &
gyrase
Maruyama, 1997)
the levels of hTR and c-myc expression
inhibitor
(Woo & Choi, 2005)
PT ED
Involving in the circadian
Down-regulation of TR mRNA expression
rhythms of physiological
(Leon-Blanco, et al., 2003)
functions
CE
Melatonin
(Yamakuchi, Nakata,
Selective DNA topoisomerase I
Beta-Lapachone level
Broad-spectrum antibiotic that
Inhibition of telomerase activity, down-regulation of
MA
Transcriptional
2003)
RI
Ofloxacin and
Targeting hTR
producing tumors
Inhibition of telomerase activity, disabling Causing crosslinking of DNA
transcription of the telomerase-RNA encoding gene region
AC
Cisplatin
(Burger AM, 1997) and triggers apoptosis
Targeting the telomerase substrate and associated protein G4 DNA-interactive compounds
An antiprotozoal, antirheumatic Quinacrine
Binding affinity to G4-DNA
and an intrapleural sclerosing agent
115
(Sun, et al., 2012)
PT
ACCEPTED MANUSCRIPT
Targeting
Ubiquitin/proteasome pathway
Bortezomib
Dysregulation of shelterin protein expression
(Ci X, 2015)
inhibitor and NF-κB inhibition
RI
telomere-associated
NU
PT ED
MA
mRNAs reduction in TRF1, POT1, and TNKS1
CE
Doxorubicin
Topoisomerase inhibitor of
mRNAs reduction in TRF1, POT1, and TNKS1
AC
Etoposide
SC
proteins
116
(Kato, et al., 2013) cytotoxic anticancer drug An anthracycline antitumor (Kato, et al., 2013; B. Zhang, antibiotic with et al., 2012) intercalating DNA