Therapeutic potential of nitric oxide in cancer

Drug Resistance Updates 9 (2006) 157–173

Therapeutic potential of nitric oxide in cancer Benjamin Bonavida a,∗ , Soraya Khineche a , Sara Huerta-Yepez b , Hermes Garb´an c a

c

Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, 10833 Le Conte Avenue, A2-060 CHS, Los Angeles, CA, 90095-1747, USA b Unidad de Investigation Medica en Immunologia e Infectologia, Hospital de Infectologia, Centro Medico Nacional La Raza, Instituto Mexicano del Seguro Social, Mexico City, M´exico Department of Surgery, Division of Surgical Oncology, David Geffen School of Medicine, Johnson Comprehensive Cancer Center, University of California at Los Angeles, Los Angeles, CA 90095, USA Received 12 April 2006; received in revised form 25 May 2006; accepted 30 May 2006

Abstract In recent years, several novel approaches have been developed to overcome tumor cell resistance to conventional therapeutics. Such approaches include genetic manipulations, vaccine development and exploitation of the anti-tumor host immune response. The overall development of tumor cell resistance to therapeutics is, in large part, the result of the ability of tumor cells to develop specific mechanisms to overcome cell death or apoptosis. Therefore, the possibility to interfere selectively in the regulation of the apoptotic signaling pathways may result in either the direct induction of cell death and/or sensitization of the cells to cytotoxic stimuli. A novel approach based on modifying gene products that regulate resistance to apoptosis involves nitric oxide (NO). NO is a ubiquitous molecule with diverse cellular effects that depend on the source, concentration, latency, cell type and phenotype. This review describes the role played by NO in cancer including carcinogenesis, pathogenesis, angiogenesis, chemoprevention and as a novel therapeutic to overcome resistance when used alone or as a sensitizing agent used in combination with other therapeutics. © 2006 Elsevier Ltd. All rights reserved. Keywords: Nitric oxide sensitization; cGMP; NO donors; S-nitrosation; S-nitrosylation; NO-based therapy; Cancer therapy; Apoptosis

1. Introduction Cancer is a complex disease consisting of several hundred diseases entities with both common and unique features. The incidence of cancer is only second to heart disease. Treatment of cancer remains one of the biggest challenges, particularly in view of increase in average life span, at least in developed countries; cancer is largely a disease of older individuals. Significant progress has been made in the development of novel therapeutics and the treatment of a large number of cancers. Hence, current therapeutics (chemotherapy, radiation, hormonal, and immune therapy) have resulted in significant clinical responses and prolongation of life, albeit with little complete remission. One of the major problems in the treatment of cancer is the acquisition/development of resis∗

Corresponding author. Tel.: +1 310 825 2233; fax: +1 310 206 2791. E-mail address: [email protected] (B. Bonavida).

1368-7646/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.drup.2006.05.003

tance and refractoriness to conventional therapeutics. It is clear that most cytotoxic therapeutics exert their anti-tumor effect by inducing cell death by apoptosis. In addition to the development of new cancer therapeutics, several areas of investigation also search for cancer preventive agents and novel diagnostic/prognostic markers for early detection and follow-up. Among the novel agents that have recently emerged are agents that induce NO or NO donors. Nitric oxide is a ubiquitous molecule that exerts many biological effects. It has been used clinically in cardiovascular diseases. In addition, evidence is accumulating for the role of NO as a new oncopreventive agent and more recently as a novel therapeutic to overcome tumor cell resistance. This review will focus on the role of NO in cancer and will describe its clinical potential as a novel therapeutic when used as a single agent or when used in combination as a sensitizing agent with chemotherapeutics or immunotherapeutics.

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Fig. 1. Peroxynitrite formation and activity. NO reacts with reactive oxygen species (ROS) such as superoxide (O2 − ) to form the reactive nitrogen species (RNI), peroxynitrite (OONO− ). Peroxynitrite is highly oxidative and nitrating, and is involved in regulation of several protein oxidation reactions.

2. Chemistry of nitric oxide Nitric oxide (NO) is a highly reactive free radical capable of mediating a multitude of reactions (Blaise et al., 2005). The free radical, NO, is an uncharged molecule containing an unpaired electron in its outermost orbital, allowing it to undergo several reactions functioning either as a weak oxidant (electron donor) or as an anti-oxidant (electron acceptor). NO is able to react with other inorganic molecules (i.e. oxygen, superoxide or transition metals), structures in DNA (pyrimidine bases), prosthetic groups (i.e. heme) or with proteins (leading to S-nitrosylation of thiol groups, nitration of tyrosine residues or disruption of metal-sulfide clusters such as zinc-finger domains or iron-sulfide complexes) (Bogdan, 2001). In addition, NO can function as an anti-oxidant against reactive oxygen species (ROS) such as hydrogen peroxide (H2 O2 ) and superoxide (O2 − ) by diffusing and concentrating into the hydrophobic core of low-density lipoprotein (LDL) (Benz et al., 2002). It can react with several ROS, such as superoxide to form peroxynitrite (ONOO− ), a highly oxidizing and nitrating reactive nitrogen species (RNS) responsible for mediating protein oxidation reactions under physiological conditions (Tuteja et al., 2004) (see Fig. 1). Another mechanism of NO-related reactivity is through the addition of an NO group to the thiol side chain of cysteine residues within proteins and peptides, termed S-nitrosylation, which plays a significant role in the ubiquitous influence of NO on cellular signal transduction (Hess et al., 2005). NO or NO+ ion is capable of forming S-nitrosothiols (RSNO; product of Snitrosylation), which function as potent platelet aggregation inhibitors and vasorelaxant compounds (Myers et al., 1990) (see Fig. 2). l-Arginine is the amino acid essential for the biosynthesis of NO. The oxidation of l-arginine is catalyzed via a family of enzymes called nitric oxide synthases (NOSs) which, in

effect, yield both NO and l-citrulline using NADPH and O2 as co-substrates. This reaction is carried out via the NOSmediated five-electron oxidation of the terminal guanidino nitrogen of l-arginine to produce NO and l-citrulline (Stuehr, 2004) (see Fig. 3). NO-mediated physiological effects are carried out primarily by 3 ,5 -cyclic guanylate monophosphate, more commonly known as cyclic GMP (cGMP). cGMP is a principal molecular messenger responsible for smooth muscle relaxation, platelet aggregation and neurotransmission. In its cGMP-dependent mechanism, NO binds and activates the enzyme guanylate cyclase (GC), which, in turn, catalyzes the synthesis of cGMP from guanosine triphosphate (GTP). cGMP is then converted to guanylic acid using the enzyme

Fig. 2. Relevant biological/chemical reactivity of NO• . NO can rapidly react with susceptible chemical moieties in relevant biological proteins: (a) metals: nitrosation; (b) thiols: S-nitrosylation; and (c) tyrosine residues: nitration.

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Fig. 3. Synthesis of NO from l-arginine. Two-step, five-electron oxidation of the guanidino nitrogen of l-arginine leads to production of l-citrulline and nitric oxide via NOS mediated catalysis.

Fig. 4. cGMP-dependent cell signaling. NO is converted from arginine via NOS and binds and activates the enzyme soluble guanylate cyclase (sGC), which, in turn, catalyzes the synthesis of cGMP from guanosine triphosphate (GTP). cGMP is then converted to guanylic acid using the enzyme cGMP phosphodiesterase. This conversion allows for the appointment of a variety of downstream targets including protein kinases, phosphodiesterases and ion channels, which modify cell functions.

cGMP phosphodiesterase. This conversion allows for the appointment of a variety of downstream targets including protein kinases, phosphodiesterases and ion channels, which modify cell functions (Koesling et al., 2004) (Fig. 4).

3. Cellular source of nitric oxide Nitric oxide synthase (NOS), the enzyme responsible for the catalytic conversion of l-arginine to NO, is expressed in three major isoforms: inducible nitric oxide synthase (NOS II/iNOS), endothelial nitric oxide synthase (NOS III/eNOS), and neuronal nitric oxide synthase (NOS I/nNOS). Both NOS I and NOS III are constitutively expressed and are important for the production and maintenance of a low basal level of NO synthesis in neural cells and endothelial cells. These constitutive NOS isoforms are Ca2+ /CaM-dependent and

require several cofactors for their enzymatic activity (Haynes et al., 2004). NOS III, the only membrane-associated isoform, is constitutively expressed in endothelial cells, cardiac myocytes, and hippocampal pyramidal cells and is involved in suppressing platelet aggregation, maintaining vascular tone, inhibiting smooth muscle cell proliferation, and prompting angiogenesis. NOS III also mediates penile erection in males by diffusing NO to smooth muscle through the elevation of cGMP levels, which in turn, reduce cytoplasmic Ca2+ thus triggering relaxation of the corpora cavernosa (erectile bodies) (Drew and Leeuwenburgh, 2002). NOS I, constitutively expressed in neurons, skeletal muscle and lung epithelium, is responsible for relaxation of vascular and nonvascular smooth muscle and acts as a neurotransmitter. NOS I is directly involved in the contraction of skeletal muscle and is responsible for producing large amounts of NO during contractile activity (Drew and Leeuwenburgh, 2002) (Fig. 5). The Ca2+ /CaM-independent inducible isoform (NOS II/iNOS) is found in various cell types including macrophages, dendritic cells, fibroblasts, chondrocytes, osteoclasts, astrocytes, epithelial cells, and a variety of cancer cells. NOS II is stimulated and upregulated via induction by cytokines and/or microbial agents such as lipopolysaccharides (LPS) and is responsible for generating large amounts of NO sustained over long periods of time for host defense against pathogens (Blaise et al., 2005). Regulation of NOS II predominantly occurs at the level of synthesis and stability of mRNA and protein. In fact, it was observed in human cells that, although there was no detectable NOS II mRNA in non-induced AKN hepatocytes or DLD1 cells, significant basal activity of the human NOS II promoter was induced 2–5-fold by cytokines in these cells (de Vera et al., 1996; Rodriguez-Pascual et al., 2000). Furthermore, human primary cardiomyocytes in cell culture were found to express NOS II mRNA but no NOS II protein. Thus, a connection can be made between the incapability of translation of NOS II mRNA and the presence of the 5 or 3 UTR of the human NOS II mRNA (Luss et al., 1997) (Fig. 5). The human NOS II promoter contains a TATA box of ∼30 bp from the transcription initiation site to which all mammalian promoters can bind. Additionally, at ∼900 bp

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Fig. 5. Pathways of NO signaling. Schematic representation of the two predominant type of NOS isoform kinetics (constitutive and inducible) and subsequent NO signaling.

position, rat, murine and human promoters contain binding sites for transcription factors induced by IFN-␥: ␥-interferon activated site, GAS; ␥interferon responsible element, ␥IRE; interferon stimulated response element, ISRE (Kleinert et al., 2004). NOS II expression is regulated by transcription factors such as NF␬B, activator protein 1 (AP-1), signal transducer and activator of transcription 1␣ (STAT-1␣), interferon regulatory factor 1 (IRF-1), nuclear factor interleukin-6 (NFIL-6) and high-motility group I (Y) protein (Lin et al., 1996; Kleinert et al., 2004). Induction of NOS II expression by LPS, IL-1␤, TNF-␣ and oxidative stress has been demonstrated in various cell types through NF-␬B activation (Ghosh et al., 1998). As a confirmation that the transcription factor NF␬B regulates NOS II activity, inhibition of NOS II expression by various agents including glucocorticoids and transforming growth factor-␤1 (TGF␤1) was found to be an effect of the inhibition of NF-␬B from direct capture by protein–protein interactions, inhibition of nuclear translocation of NF␬B, inhibition of NF␬B trans-activation activity or from enhancement of the expression of the specific inhibitor of NF-␬B, I-␬B (Mukaida et al., 1994; Kleinert et al., 2004).

4. Post-translational modification of proteins by NO and derivatives NO is involved in the regulation of fundamental physiologic processes such as vasodilation, neurotransmission, inflammation and cell death via post-translational modification of proteins. NO affects most of these processes by binding to soluble guanylyl cyclase (sGC)-coupled cytosolic receptors; an action resulting in conformational changes that trigger sGC activity and the consequent generation of cyclic

GMP from GTP which activates various downstream targets (i.e. protein kinases, phosphodiesterases and ion channels) which modify cell functions such as smooth muscle relaxation, platelet disaggregation and synaptic plasticity (Blaise et al., 2005; Krumenacker et al., 2004) (see Fig. 4). This activation mechanism is carried out by the binding of NO to the heme-binding domain of sGC (N-terminal region), a fivemembered nitrogen-containing ring structure with a central ferrous iron. Subsequent to NO binding, the bond is broken between a histidine in the ␤1 subunit (His105 ) and the iron of sGC, generating a nitrosyl-heme complex (Krumenacker et al., 2004). Both the ␤1 and ␤1 subunit of sGC must dimerize in order for NO-mediated sGC activity to take place. In parallel, both subunits are required for the binding of heme to the heterodimeric complex (Krumenacker et al., 2004). These processes, in effect, lead to the production of cGMP and the consequent activation of downstream targets and soon after, protein modification. NO can also modify proteins through direct chemical reactions, rather than using enzymatic mechanisms. NO has the ability to oxidize nitrate or nitrosylate proteins (Mannick and Schonhoff, 2002). Nitration can be classified as the binding of an NO2 group to a tyrosine or occasionally, a tryptophan residue. Nitrosylation, as previously mentioned, refers to the attachment of an NO group to a transition metal or a thiol, usually a cysteine residue (S-nitrosylation). In a number of studies, evidence clearly suggests that nitration modifies proteins in an irreversible fashion and may be responsible for some of the toxic effects of NO, while S-nitrosylation is a reversible modification involved in cell signaling (Mannick and Schonhoff, 2002). S-nitrosylation can be viewed as a cellular signaling process, which can regulate both cellular homeostasis

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and pathogenesis of disease. S-nitrosylation can be mediated by various NO derivatives such as nitrosylated transition metals, NO carriers (i.e. nitrosothiols), or by direct interaction with NO in the presence of electron acceptors (Tuteja et al., 2004). Similarly to phosphorylation, S-nitrosylation is a rapidly reversible and specifically targeted modification, that allows cells to respond rapidly and precisely to physiological stimuli. S-nitrosylation is pivotal in the posttranslational modification of ion channels and allows NO to regulate electrical activity without the stimulation of cGMP production (Gow et al., 2004). Recently, S-nitrosylation has been shown to regulate the function of many intracellular proteins in a manner analogous to that of phosphorylation in signal transduction regulation (Mannick and Schonhoff, 2002). For example, it has been shown that NO inhibits ornithine decarboxylase (ODC), the primary (rate-limiting) enzyme in the polyamine biosynthetic pathway required for cell growth in mammalian cells, via S-nitrosylation. NO inhibits ODC enzyme activity via the S-nitrosylation of 4 cysteine residues, including cysteine 360, the active site for enzymatic activity (Bauer et al., 2001). Other examples of gene regulation by NO will be discussed in the following sections.

5. Cell signaling by NO: cGMP-dependent and CGMP-independent signaling NO is a pluripotent molecule that can mediate a variety of cell signaling functions. It can act as an intracellular messenger, an autacoid, a paracrine substance, a neurotransmitter, or as a diffusible hormone. NO signaling can be cGMPdependent or cGMP-independent (Fig. 5). The former occurs when NO readily binds to certain transition metal ions (i.e. Fe2+ heme groups in GC) (Fig. 4) and to Fe-S clusters of metalloenzymes. Aconitase, a key enzyme in the TCA cycle, as well as complex IV, the cytochrome oxidase, in the inner membrane of mitochondria, are two metalloenzymes inactivated by NO. NO inhibits their oxidative phosphorylating activity through its blockade of the electron transport chain as well as regulating citrate levels in the Krebs cycle by inhibiting the oxidative breakdown of acetyl-CoA. Following the binding of NO to Fe2+ , GC is activated increasing the production of cGMP from GTP. This, in turn, reduces intracellular Ca2+ levels via Ca2+ release from intracellular stores, Ca2+ uptake mediated by calcium adenosine 5 -triphosphatase of the endoplasmic reticulum (ER) and Ca2+ influx (Birschmann and Walter, 2004). These actions thereby stimulate muscle relaxation, vessel dilation and decrease in blood pressure through cellular targeting of downstream effectors. An example of specific downstream targets of cGMP is the family of cGMP-dependent protein serine/threonine kinases (cGKs) (Lucas et al., 2000). In the cGMP-bound, active form, cGKs can act on various substrates such as the IP3 receptor, phospholamban, vimentin, the phosphatase inhibitor G substrate, and subunits of myosin light chain phosphatase (Endo et

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al., 1999; Komalavilas and Lincoln, 1994; Eggermont et al., 1990; Rapoport and Murad, 1983; Krumenacker et al., 2004). Ruth (1999) demonstrated that the deletion of cGK I and cGK II in mice resulted in decrease in smooth muscle relaxation and increase in blood pressure, confirming the vasorelaxant role of cGMP via cGK activity (Fig. 5). cGMP-independent cell signaling, occurs via reactions with molecular oxygen, superoxide (O2 − ), thiols, and transition metals (Fig. 5). When NO interacts with oxygen species, O2 and O2 − , nitrosylation and nitration can occur, respectively (Krumenacker et al., 2004). With respect to nitrosylation, NO can interact with O2 , electron acceptors or metals to produce NO+ , which can subsequently interact with thiols such as cysteine residues in proteins (Brune, 2005). Snitrosylation of the thiol is a chemical reaction that has been demonstrated to affect the function of numerous proteins such as transcription factors and/or signaling molecules (Brune, 2005). For example, NO can interact with O2 − to form peroxynitrite (ONOO− ). Once peroxynitrite is generated, tyrosine nitration, the addition of a NO2 group to the phenol ring in tyrosine, can occur. An example of S-nitrosylation-mediated protein modification involves the oncoprotein p21Ras . Using pure recombinant p21Ras , Lander et al. (1995) and Hess et al. (2005), demonstrated that NO induces a profound conformational change in p21Ras associated with the formation of one nitrosothiol per molecule.

6. NO-mediated regulation of mitochondria and apoptosis NO is known to regulate mitochondrial respiration through binding to cytochrome c oxidase, the terminal enzyme in the mitochondrial electron transport chain (Moncada and Erusalimsky, 2002). NO binds with high affinity to the ferrous iron of heme a3 in the binuclear site of cytochrome c oxidase, thereby inhibiting the binding of molecular oxygen and its subsequent reduction to water (Giuffre et al., 2000). This NO-mediated inhibition is dependent on low oxygen tension as well as elevated electron pressure through the mitochondrial respiratory chain, represented by the ferrocytochrome c concentration (Shiva et al., 2001). In addition to its role in inhibiting cytochrome c oxidase, NO plays a role in programmed cell death (apoptosis). Sustained production of NO acts as a pro-apoptotic modulator by activating caspases, whereas low or physiological concentrations of NO prevent cells from apoptosis (Brune, 2003) (Fig. 6). NO can directly induce cytochrome c release through mitochondrial membrane potential (
Ψ m ) loss where cytochrome c activates the caspase-dependent apoptotic signaling cascade. NO binds to cytochrome c oxidase (complex IV) in mitochondrial transfer chains (Poderoso et al., 1996) and superoxide interacts with NO to form peroxynitrite which induces mitochondrial dysfunction and cytochrome c release. NO has also been found to upregulate the p53 tumor suppressor gene, and results in increasing the ratio of Bax to Bcl-XL (regulatory-

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Fig. 6. NO-mediated protein modifications. NO is involved in a variety of signaling mechanism which result in the alteration of proteins. These modifications are concentration-dependent and include: direct binding to heme centers, nitrosylation of thiol and amine groups, nitration of tyrosine, tryptophan, amine, carboxylic acid, and phenylanaline groups, oxidation of thiols, and binding of sGC and transcription factors.

apoptotic molecules involved in the intrinsic apoptotic pathway) (Messmer and Brune, 1996). Superoxide radicals are normally produced during mitochondrial respiration. At low concentrations, NO reversibly inhibits cytochrome oxidase (complex IV), which may shift the electron transport chain to a more reduced state, a condition that favors O2 − formation. Specifically, superoxide dismutase (SOD) catalyzes the conversion of superoxide radicals to H2 O2 and allows assorted adaptation of the oxidative metabolism of the cell. Decreased SOD activity can result in the kinetically favorable side-reaction of triplet NO− with O2 − . This reaction generates ONOO radical that is damaging to cells. ONOO− will oxidize free thiols in the cytosol and form disulfide linkages, potentially affecting protein functions in cells (Nelson et al., 2003). Additionally, at respiration-inhibiting concentrations, NO can cause glutamate release from synaptosomes and neurons which is directly associated with inhibition of mitochondrial respiration, followed by reversal of glutamate uptake (Meffert et al., 1994). Apoptosis occurs by two separate pathways: caspasedependent and caspase-independent. Caspase-dependent pathways are either intrinsic or extrinsic in nature. The intrinsic death receptor-independent pathway is stimulated by apoptotic stimuli, including irradiation, or RNI leading to the loss of the mitochondrial membrane potential and release of cytochrome c into the cytosol. Cytochrome c along with ATP, Apaf-1, and procaspase-9 direct the activation of the initiator caspase-9 followed by the processing of procaspase-3 and its activation (Brune, 2005; Mashima and Tsuruo, 2005). Thus, apoptosis occurs downstream of active caspase-3. Secondly, the extrinsic pathway is induced by death receptor activation by death ligands such as the Fas

ligand. Procaspase-3 is cleaved and activated by caspase-8 and thereby induces apoptosis. Depending on its concentration, NO can have pro- or anti-apoptotic properties. High NO concentrations promote apoptosis in most cases, while low NO concentrations can result in resistance to apoptosis. In the latter case, NO counteracts the reactive oxygen species (ROS) generated by pro-apoptotic ceramides and, in turn, inhibits the assembly of Apaf-1 and pro-caspase-9, which are essential for apoptosis (Zech et al., 2003). Through a cGMPindependent mechanism, NO can directly inhibit the activity of downstream caspase-3 by S-nitrosylation of the enzyme, resulting in suppression of apoptotic activity. In the case of apoptosis promotion, NO produces peroxynitrite (ONOO− ) in response to a rapid reaction with superoxide (O2 − ), a powerful oxidant with sufficient stability to diffuse through cells to react with targets (Blaise et al., 2005). Increased concentrations of NO enhance the formation of ONOO− which induces DNA damage. In response to DNA damage, p53, a key player in the caspase-independent pathway, is upregulated and thereby activates the DNA repair enzyme poly-ADP ribose polymerase (PARP). The amount of energy necessary for DNA repair may stimulate the cell to initiate apoptosis (Borst and Rottenberg, 2004). NO oxidative products (NO2 , ONOO− ions, HNO2 , ‘NOx ’) may deaminate, crosslink and oxidize DNA bases. In NO-induced apoptosis, NO donors induce the up-regulation of CD95 (APO-1/Fas) ligand, TRAIL/APO-2 ligand and p53 gene expression in addition to caspase activation that cleaves nuclear proteins such as PARP (Brune, 2005). For example, experiments in thymocytes from mutant p53 human lymphoblastoid cells revealed that the cells were resistant and/or less sensitive to NO-induced apoptosis, indicating that p53 promotes an RNS-dependent apoptotic response (Gordon et al., 2001; Li

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et al., 2002; Brune, 2005) NO also regulates the concentration of mRNA coding for a variety of transcription factors and other gene products. The regulation of central signalresponsive transcription factors, such as NF-␬B, zinc fingertranscription factors, and AP-1 by NO, have been associated with NO-induced apoptosis (Bogdan, 2001 and Pfeilschifter et al., 2001). A study by Taimor et al. (2001), describes the role of NO in apoptotic regulation via activation of AP-1. In this study, binding activity of AP-1 in nuclear extracts from cardiomyocytes was analyzed in retardation assays using a radioactive labeled oligonucleotide, which contained the specific binding motif of AP-1 (TRE) (Taimor et al., 2001). AP-1 binding activity was activated by SNAP (photoactivatable NO donor), leading to induction of apoptosis and indicating that NO plays yet another role in apoptotic regulation, via activation of transcription factors (Fig. 6).

7. Role of NO in health and non-malignant diseases NO affects many aspects of inflammation and immune regulation. A variety of cell types such as fibroblasts, endothelial and epithelial cells, keratinocytes, chondrocytes, monocytes, macrophages, antigen-presenting cells (APC), and natural killer cells (NK) express NO (Coleman, 2001). NO can act as a toxic agent towards infectious organisms as well as regulate the induction or suppression of apoptosis. At low concentrations, NO displays its pro-inflammatory effects by inducing vasodilatation and recruitment of neutrophils. Furthermore, low concentrations of NO produced by the constitutive NOS I and NOS III isoforms inhibit expression of adhesion molecules, cytokine and chemokine synthesis and leukocyte adhesion/transmigration (Bogdan, 2001). Also at low concentrations, NO can inhibit T cell proliferation and act as a regulator for T cell growth. At high concentrations, however, NO downregulates adhesion molecules, suppresses activation, and stimulates apoptosis of inflammatory cells. NO can act as an anti-inflammatory/immunosuppressive agent via its apoptotic effects on inflammatory cells. Also, NO and ONOO– can both mediate immunoregulatory effects through interaction with cell signaling systems such as cyclic AMP (cAMP), cGMP, Janus kinase/signal transducer and activator of transcription (JAK/STAT), G-protein, NF-␬B/I␬B or MAPK-dependent signal transduction pathways. This leads to modification of transcription factor activity and, as a result, modulates the expression of numerous additional mediators of inflammation (Coleman, 2001). NO is involved in various mechanisms of cardiovascular regulation such as vascular tone (vasodilation), vascular structure (inhibition of smooth muscle cell proliferation), and cell–cell interactions in blood vessels (inhibition of platelet adhesion and aggregation; inhibition of monocyte adhesion) (Cannon, 1998). NO is involved in the regulation of basal systemic, coronary, and pulmonary vascular tone through high levels of cGMP in smooth muscle, inhibition of vasoconstric-

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tor peptide endothelin-1, and inhibition of norepinephrine release from sympathetic nerve terminals (Cannon, 1998). Through activation of soluble guanylyl cyclase and subsequent generation of cGMP, NO regulates the cardiovascular system by inhibiting the activity of growth factors, released from cells within the vessel wall and from platelets on the endothelial surface (McNamara et al., 1993; Dubey et al., 1995). NO production is also shown to significantly contribute to the growth-promoting effect of vasodilating peptides and VEGF in acquiring the angiogenic phenotype by microvascular endothelium in response to GC signaling (Ziche and Morbidelli, 2000). NO is ubiquitous in the peripheral nervous system and encompasses several roles in the regulation of the CNS. NO is most well known for acting as a neurotransmitter in the periphery. It can also serve as a chemical messenger in the nervous system mediating the complex machinery of synaptic transmission and plasticity (Bicker, 2005). Furthermore, NO promotes the enhancement of retinotectal projections as well as synaptic suppression at developing neuromuscular synapses (Bicker, 2005). Another important aspect of NO signaling is the regulation of cell proliferation and differentiation of neural precursor cells in vertebrate and insect nervous systems (Champlin and Truman, 2000). NO signaling also mediates growth-cone extension, suggesting that the effect of NO on synaptic connectivity could be due, in part, by cell motility. NO has been found to play a significant role in a variety of diseases of the immune system including chronic asthma, rheumatoid arthritis, and autoimmunity. Normal NO production in the lungs regulates basic airway events such as modification of airway tone, regulation of pulmonary vascular tone and stimulation of mucous secretion via its binding to sGC and the subsequent formation of cGMP (van der Vliet et al., 2000). Asthma affects the respiratory system, particularly the lungs, and is characterized by chronic airway inflammation and subsequent cough, tightness of the chest, and expired breath due to increased levels of NO and its intermediates (Dweik et al., 2001). NO functions as a pro-inflammatory mediator of rheumatoid arthritis (RA), an autoimmune disease dealing with hyperproliferation of the synovial membrane and the accumulation of activated T-cells and macrophages which subsequently leads to progressive joint destruction (Stichtenoth and Frolich, 1998). Loss of function, swelling and stiffness are all effects of this NOmediated disease. High levels of NO are associated with RA disease (Bhatia et al., 2004). NO also plays a role in the pathogenesis of autoimmunity, acting as a cytotoxic factor responsible for tissue destruction via NOS II expression in inflamed tissue (Kolb and Kolb-Bachofen, 1998; Bogdan, 2001; Marshall et al., 2000). NO plays a primary role in the pathogenesis of atherosclerosis through its roles in vasoconstriction, platelet aggregation, increased muscle proliferation and enhanced leukocyte adhesion (Cooke and Dzau, 1997; Herman and Moncada, 2005). Diabetes mellitus often leads to severe cardiovascu-

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lar diseases such as stroke (Li and Forstermann, 2000) and NO inactivation by ROS contributes to the abnormal vascular reactivity observed in diabetes (Brune, 2005; Klahr and Morrissey, 2004). Nitric oxide plays several vital roles in both the neurotoxicity and neuroprotection of neurological diseases including Alzheimer’s disease and multiple sclerosis (Markesbery, 1997; Butterfield et al., 1999; Mattson et al., 1991; Dokmeci, 2004). Multiple sclerosis (MS) is a disabling and progressive disease of the CNS, which is a result of the destruction of the myelin sheath surrounding neurons and the consequent formation of plaques (Mitrovic et al., 1994; Bo et al., 1994; Smith and Lassmann, 2002). NO is a molecule essential to penile erection, yet can also be less beneficial in its role in erectile dysfunction (ED). Both constitutive NOS isoforms are involved in mediating ED (Ghalayini, 2004).

8. Role of NO in cancer 8.1. Role of NO in carcinogenesis Both NO and its derivatives, produced in response to increased oxygen uptake followed by the release of free radicals such as NO from leukocytes (i.e. activated macrophages), induce damage to typically healthy adjacent epithelial and stromal cells, thereby contributing to carcinogenesis. NO can induce DNA damage, alone or through its interaction with oxygen and superoxide, and subsequently carcinogenesis. (Lala, 1998). NO can induce DNA damage via the formation of ONOO− and N2 O3 from the interaction of NO and superoxide (Xu et al., 2002). The accumulation of DNA modifications induced by NO-mediated deamination can lead to various types of carcinogenic mutations (Nguyen et al., 1992). Nguyen et al. (1992), after exposing NO to either TK6 cells or naked DNA in the presence of oxygen, demonstrated that both xanthine and hypoxanthine resulted from the deamination of guanine and adenine in all cases, thus mutating the TK6 cells. Also, according to a study exposing NO to Salmonella typhimurium, it was found that the highest occurrence of mutations resulting from NO-mediated deamination are the G:C to A:T modifications (Zhuang et al., 2000; Tamir et al., 1996). Oxidation of guanine at the C8 position produces the G:T transversions that are widely found in mutated oncogenes and tumor suppressor genes (Klaunig and Kamendulis, 2004). The generation of DNA single-strand breaks takes place in response to the formation of NO-mediated abasic sites (a result of DNA deamination), and/or via the direct effects of peroxynitrite (Tamir et al., 1996). Single strand breaks in DNA activate the nuclear enzyme PARP, acting as an “off” switch for DNA replication until base excision repair is completed by DNA repair enzymes (Felley-Bosco, 1998). In genotoxic situations, however, NO has been found to cause irreversible damage to DNA repair enzymes including the zinc finger-containing DNA repair enzyme formamidopy-

rimidine DNA glycosylase (Fpg protein) (Wink and Laval, 1994). NO also causes DNA damage indirectly via the interaction of its reactive species with other molecules such as amines, thiols and lipids. The reaction of N2 O3 with secondary and tertiary amines is responsible for the generation of nitrosamines (prominent chemical carcinogens), which are metabolized to strong alkylating electrophiles which react with DNA at various nucleophilic sites such as the N-7 and O-6 positions of guanine and the N-3 position of adenine (Felley-Bosco, 1998). It has been found that the O6 substitution is the most mutagenic and induce G:A transitions during DNA replication (Marnett and Burcham, 1993). Another form of indirect DNA damage by NO is through the formation of S-nitrosothiols (Davis et al., 2001). A study conducted by Kim et al. (1997), demonstrated that hepatocytes incubated with NO donors such as SNAP or V-PYRRO/NO inhibited caspase-3-like activity in the cytosol. NO-mediated caspase inhibition has also been found to affect caspase-9 and caspase-8 (Brune, 2005). It has also been shown in a study by Calmels et al. (1997), that mammalian cells incubated with excess NO, accumulate the p53 tumor-suppressor protein, yet at the same time, p53 loses its capacity for binding to its DNA consensus sequence. This mutation of the p53 protein by NO generated via S-nitrosylation and/or tyrosine residue nitration demonstrates the carcinogenic effects of NO through its inhibition of the tumor suppressor function of p53 and transcription of proto-oncogenes such as c-FOS, c-JUN and c-MYC, which can be carcinogenic due to their highly proliferative activity (Hussain et al., 2003). NO also indirectly causes lipid peroxidation through radical-mediated damage to cellular membranes. This process forms several products such as reactive electrophiles, namely, epoxides and aldehydes (Janero, 1990). A highly electrophilic and nucleophilic tautomer, Malondialdehyde (MDA), is a derivative of lipid degradation, and has been found to be carcinogenic (Spalding, 1988; Stone et al., 1990; Klaunig and Kamendulis, 2004). 8.2. NO in tumor progression Solid tumor progression involves a stepwise series of genetic alterations to tumor cells, resulting in growth, invasion, metastasis, and ability to induce angiogenesis, all of which can be influenced by NO signaling. A solid tumor is composed of both tumor cells and host-derived cells, including tumor-infiltrating leukocytes and cells of the tumor vasculature (Lala and Chakraborty, 2001). Each of these various tumor components may express any of the active NOS isoforms. In one of the preliminary experimental studies on human primary breast cancers, Thomsen and Miles (1998) showed that NOS activity was higher in malignant compared to benign tissue, and a parallel was found between the level of tumor progression and NOS activity. Various experimental tumor models have offered substantial evidence for a direct role of NO stimulation of

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tumor growth and metastasis (Lala and Chakraborty, 2001). Jenkins et al. (1995) showed that introduction of functional NOS II into a human colonic adenocarcinoma cell line led to increased growth and vascularity of the tumors when transplanted in nude mice. Furthermore, a selective NOS II inhibitor (1400 W) was shown to inhibit tumor growth rate of a genetically engineered cell line (iNOS-19) and of constitutively iNOS expressing EMT6 tumors, indicating a direct role of NO in tumor progression and vascularity (Thomsen et al., 1997). A murine mammary adenocarcinoma model, using C3H/HeJ spontaneous mammary tumors and their clonal derivatives, revealed that the metastatic clonal derivatives possessed a significant amount of NOS III activity, indicative of the role of NO in metastasis (Lala, 1998; Orucevic et al., 1999) found in NOS III-expressing C3-L5 cells, that constitutively produced NO stimulated tumor cell invasiveness in vitro through its down-regulation of TIMP 2 and TIMP 3. Additionally, it was found that MMP-2 was upregulated after IFN-gamma and LPS-mediated induction of endogenous NO, suggesting a NO-mediated tumor invasiveness mechanism depending on the modification of the MMP-2/TIMP2 and TIMP3 systems (Orucevic et al., 1999). 8.3. NO and tumor angiogenesis NO has been shown to stimulate angiogenesis during tumor growth through its stimulation of proliferative and migratory function of endothelial cells (Jenkins et al., 1995; Ambs et al., 1998). Active NOS III is a necessary factor for the migration of endothelial cells via its stimulation by VEGF. NOS III can be induced by VEGF either through upregulation of NOS III mRNA/protein, increased association with HSP90, activation of PI3 kinase, or activation of MAPK/PLC-␥ (Lala and Chakraborty, 2001). In summary, NO generation by NOS leads to tumor angiogenesis. 8.4. Role of NO in cancer chemoprevention NOS II inhibitors have been found to reduce inflammation, tumor promotion, and metastases (Orucevic and Lala, 1996; Jenkins et al., 1995). Also, a more recent study was conducted using NOS II-selective inhibitors (SC-51, AG) alone and in conjunction with a Cox-2 inhibitor (celecoxib) in male F344 rats with AOM (azoxymethane)-induced colonic carcinogenesis (Rao et al., 2002). These inhibitors reduce AOM-induced colonic abberant crypt formation (ACF; colon cancer marker) in colon cancer and an even further decreased occurrence of ACF was found with the concomitant use of both SC-51 and celecoxib (Rao et al., 2002). Aside from direct inhibition of NOS II in cancer chemoprevention, the NF␬B pathway, which is necessary for NOS II induction, may be targeted in order to indirectly inhibit NOS II (Hofseth et al., 2003; Yamamoto and Gaynor, 2001). Curcumin (diferuloylmethane) is a yellow spice composed of turmeric and curry and is involved in suppression

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of tumorigenesis. Curcumin acts as a potent inhibitor of PKC, EGF-receptor tyrosine kinase, and IkB kinase, which are involved in NO regulation (Lin and Lin-Shiau, 2001). Curcumin may also act as an inhibitor of COX-2 and lipoxygenase (LOX), which have both been implicated in inflammation and subsequent tumorigenesis (Lin and Lin-Shiau, 2001). Thus, because it blocks the activation of several NOmediated signaling pathways, curcumin should be considered as a possible therapeutic agent in cancer chemoprevention. Resveratrol (trans-3,4 ,5-trihydroxystibene) is a phytopolyphenol found in the seeds and skins of grapes. Tsai et al. (1999), examining the effects of resveratrol on NOS induction in RAW 264.7 cells activated with LPS, found that it potently inhibited NO production in activated macrophages and was responsible for the reduction of NOS II protein. Also, LPS-induced activation of NF␬B was inhibited by resveratrol (Tsai et al., 1999). Mutoh et al. (2000) examined the effects of resveratrol on a human colon adenocarcinoma cell line. And it was found to suppress COX-2 promoter activity. Through its inhibition of NO, NF␬B, and COX-2, resveratrol, may be a potent chemopreventive agent in cancer (Pervaiz, 2004). Epigallocatechin gallate (EGCG) a green tea polyphenol has antioxidative and chemopreventive properties in various in vitro and animal models (Surh et al., 2001). Lin and Lin (1997) showed that EGCG suppressed NOS II induction by down-regulating the activity of NF␬B stimulated by LPS in vitro. Treatment with EGCG in this study reduced the enzymatic activity of NOS II resulting in the decreased production of NO. Also EGCG inhibited the binding activity of NF-␬B by preventing degradation of I␬B (Lin and Lin, 1997). EGCG also induced apoptosis and cell cycle arrest in human carcinoma cells (Ahmad et al., 2000) and inhibited peroxynitrite-mediated tyrosine nitration, preventing DNA damage and subsequent carcinogenesis (Pannala et al., 1997). The inhibitory function of EGCG on NO activity may represent a new method of chemoprevention of cancer. Nitric-oxide-donating non-steroidal anti-inflammatory drugs (NO-NSAIDs), comprised of a known non-steroidal anti-inflammatory drug and an NO releasing group may have an important role in the chemoprevention of cancer. Kashfi et al. (2002) demonstrated that NO-NSAIDs inhibit the growth of pancreatic, colon, prostate, lung, and tongue cancer cell lines. NO-NSAIDs can also suppress the cytokine production of IL-1␤, IL-18 and IFN-␥ through the S-nitrosylation and subsequent inhibition of caspase-1, an action resulting in the inhibition of NOS II production (Fiorucci et al., 2001). Also, more specifically, Williams et al. (2003) demonstrated that NO-releasing aspirin (ASA) (specific NO-NSAID) inhibited the growth of human colon cancer cells both via NF␬B binding, and NOS II expression. 8.5. NO-mediated effects on tumorigenesis It has been reported that NO can induce both cytotoxic and anti-apoptotic effects on tumor cells (Yim et

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al., 1995; Xie et al., 2003; Rutschman et al., 2001). The balance between NO-mediated cellular proliferation or apoptosis will dictate the fate of the tumor. High, but physiologically relevant, concentrations of NO can induce apoptosis whereas lower concentrations can be anti-apoptotic and this relationship is a function of the tumor cell type and its sensitivity to NO (Hussain et al., 2003). In tumor cells NO is produced by NOSII and NOSII is induced by various inflammatory cytokines, such as TNF␣ and IL-1␤. The tumor suppressor p53 governs NO production by transcriptionally regulating NOSII. Lymphoma developed more readily in p53−/− NOSII−/− or in p53−/− NOSII+/− than in p53−/− NOSII+/+ . Compared to the double knockout mice, p53−/− NOSII+/+ mice exhibited a higher apoptotic index, and a decreased proliferation index with an increased expression of death receptor ligands, Fas ligand and TRAIL, in the spleen and thymus before tumor development (Hussain et al., 2004). A study in NOSII−/− mice revealed that tumors grew faster than in mice with wild-type NOSII+/+ (Wei et al., 2003). This study suggests an important role of NO in the suppression of tumorigenesis. Another study showed that the IL-13-induced anti-tumor effect is mediated by NO. Receptors for IL-13 are upregulated in several types of solid cancers, including glioblastoma, renal cell carcinoma, AIDS Kaposi’s sarcoma, and head and neck cancer. Pre-treatment of mice with an NO inhibitor significantly inhibited the IL-13-mediated anti-tumor effect (Kashiwagi et al., 2005). The cellular origin and local NO production by tumor cells appear to be critical in the metastatic process. Two clones of breast cancer cells producing different levels of NOSII and NO had different lung metastatic potential. Administration of aminoguadine (AG) and NOSII inhibitor into the mice significantly decreased tumor formation by both clones (Gauthier et al., 2004). The in vivo use of NO or NO-generating drugs has been shown to increase the anti-cancer efficacy of dendritic cells (Perrotta et al., 2004). Dendritic cells treated ex vivo with NO, released by the NO donor (DETA/NONOate), significantly reduced tumor growth, with cure of 37% of animals. DETA/NONOate-treated DC became resistant to tumorinduced apoptosis, showed increased anti-tumor cytotoxicity and increased ability to trigger T-lymphocyte proliferation. All of these effects by DETA/NONOate were mediated by the generation of cGMP. Recent studies reported the role of NOSII-induced NO in the formation of estrogen-dependent mammary adenocarcinoma following radiation (Inano and Onoda, 2005). Rats exposed to whole-body radiation immediately after weaning and then treated with the estrogen diethylstilbestrol. The tumor incidence increased 7.6-fold (85%) in comparison with that of the non-eradiated mice (11.1%) and declined to 25.6% in the rats injected i.p. with an inhibitor of NOSII.

9. Role of NO in chemosensitization and immunosensitization of cancer to induction of apoptosis 9.1. Anti-tumor effects of NO NO influences downstream events in carcinogenesis that promote anti-tumor effects, in particular apoptosis, via high levels of NOS II expression. A study by Xie et al. (1995) demonstrated, that NOS II-overexpressing murine melanoma cells displayed poor tumor growth and survival because of NO-induced apoptosis in vitro and consequently lost their ability for metastasis in vivo. It has also been demonstrated that NOS II knockout mice have been found to promote intestinal tumorigenesis in the Apc (Min/+) colon cancer mouse model (Scott et al., 2001). In addition, NO-mediated DNA damage can trigger p53 accumulation and subsequent cell cycle arrest and apoptosis of tumor cells. In response to increased transcriptional activity/post-transcriptional regulation of p53, NOS II activity increases in tumor cells and elevates NO concentration, thereby leading to p53mediated growth arrest and apoptosis (Ambs et al., 1997; Xu et al., 2002). Furthermore, the wild-type p53-induced transrepression of NOS II, which has been demonstrated both in vitro and in vivo, serves as a safeguard against DNA damage thereby decreasing the likelihood of NO-induced DNA damage (Forrester et al., 1996). It is important to note that the activation of cyclo-oxygenase (COX)-2 presents resistance to NO-mediated tumor progression. In two separate studies, NO-sensitive cells were either transfected with a COX-2 expression vector or pretreated with low amounts of NO to stimulate COX-2 through the activation of NF␬B or AP-1, resulting in cellular resistance to high levels of NO (von Knethen et al., 1999). Unusually high levels of NO production generated over long periods of time by NOS II may result in tumor cell cytotoxicity through several apoptotic mechanisms. Mechanisms of NO-mediated apoptosis include accumulation of p53, inhibition of mitochondrial respiration, alterations to Bcl-2 family member expression, activation of caspase signaling, and DNA damage (Umansky and Schirrmacher, 2001). 9.2. Role of NO in chemosensitization NO has been found to be a pivotal factor in the chemosensitization of tumor cells to various chemotherapeutic drugs. Hypoxia has been implicated in the induction of drug resistance to cancer cells (Matthews et al., 2001; Wouters et al., 2004). In a study using human breast carcinoma (MDA-MB231) and mouse melanoma (B16F10) cells pre-exposed to O2 , treatment with an NO inhibitor followed by chemotherapeutic agents was examined for drug resistance and NO inhibition enhanced hypoxia-induced chemoresistance, suggesting that hypoxia-mediated drug resistance is likely a result of suppression of endogenous NO production and that NO functions as a chemosensitizer in tumor cells (Matthews

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et al., 2001). Another study demonstrated that co-incubation of human PC-3 and mouse TRAMP-C2 prostatic adenocarcinoma cells with glyceryl trinitrate (GTN) (low concentration of NO) inhibited hypoxia-induced resistance to doxorubicin (Frederiksen et al., 2003). Moreover, NO-mediated chemosensitization was demonstrated in a study by Evig et al. (2004) which exposed MCF-7 human breast cancer cells to an aqueous solution of NO delivered (as a bolus) previous to doxorubicin. They found cell survival of 40% with doxorubicin and of only 5% with the combination of NO and doxorubicin. A separate study showed an analogous role for NO in chemosensitization through the use of a doxorubicinresistant epithelial colon cell line (HT29-dx). Administration of various NO donors such as SNAP, GSNO, and SNP as well as inducers of NO synthesis (i.e. atorvastatin) the resistance of HT29-dx cells to doxorubicin was partly reversed (Riganti et al., 2005). Both an increased doxorubicin accumulation and an increase in NOS activity were observed. Further, kinetic data suggested that NO (through the use of SNAP) triggered tyrosine nitration of multi-drug resistant-associated proteins and also inhibited the efflux of doxorubicin, decreasing the resistance of the cell to the drug by reducing the number of active transporters (P-glycoprotein) through an unknown mechanism (Riganti et al., 2005). Konovalova et al. (2003) showed that in P388 leukemic mice co-injection of cyclophosphamide (CPA) and NO donor significantly increased CPA activity. Also the NO donor increased the tumor’s sensitivity to cisplatin and doxorubicin. In addition, it was demonstrated in melanoma B16 carrying mice, that the co-injection of NO donor and CPA inhibited metastasis. We have treated athymic nude mice bearing subcutaneous human prostate carcinoma (PC-3) xenografts with the NO donor DETA/NONOate, cisplatin or the combination, which resulted in significant inhibition of tumor growth compared to mice treated with either DETA/NONOate or cisplatin alone (Huerta-Yepez et al., 2006). In conclusion, chemosensitizing agents such as NO may enhance the anti-tumor effect of chemotherapeutic drugs. However, further investigation is crucial for the complete mechanistic interpretation of these anti-tumor effects. The dual role of NO and RNS in pathophysiology divides the literature in half with opposite results. Although the antiapoptotic role of NO has been extensively reported (Boyd and Cadenas, 2002; Brune et al., 1999; Chung et al., 2001) a unifying concept is still missing. Depending on the cellular context, source, molecular interaction and relative amount generated, the specific roles of NO and RNS regulating cellular protection comprise immediate effects such as: (a) caspase inhibition, (b) cGMP-mediated protection, (c) radical-radical interference, and (d) expression of anti-apoptotic genes. In a recent study, Sebens-Muerkoster et al. (2006) have suggested an increased chemoresistance in pancreatic carcinoma cells apparently by etoposide-mediated generation of IL-1␤ and consequent production of NO resulting in further inactivation of caspases.

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Since 1997 an extensive body of evidence has been established supporting the idea of inactivation of caspases activity by S-nitrosation of key reactive cysteine residues inherent to all caspase-family members (Dimmeler et al., 1997; Kim et al., 1997; Mannick et al., 1997; Melino et al., 1997; Mohr et al., 1997; Ogura et al., 1997; Tenneti et al., 1997). However, it is difficult to explain these results in light of caspases activation in association with the pro-apoptotic role of NO (review in Brune, 2005). 9.3. Role of NO in immuno-sensitization Immunosensitization is the process by which cells are made sensitive to immune-mediated cytotoxicity. Molecular mechanisms of immuno-sensitization such as transciptional up-regulation of pro-apoptotic proteins and down-regulation of anti-apoptotic proteins have been proposed to induce apoptosis. Interestingly, NO has been found to be involved in the sensitization of tumor cells to various apoptotic stimuli such as FasL (APO-1/CD95), TRAIL, and TNF-␣. One mechanism responsible for the eradication of tumor cells by cytotoxic immune lymphocytes is Fas-mediated apoptosis and Fukuo et al. (1996) found that NO caused an increased expression of the Fas receptor in aortic vascular smooth muscle cells and increased sensitivity to FasL-mediated apoptosis. IFN-␥, together with many other pro-inflammatory cytokines (TNF␣, IL-1␤, LPS, etc.), can stimulate the induction of NOS II and the subsequent generation of NO. Through treatment with IFN-␥ and NO donor SNAP (alone or in combination), we have shown that human ovarian carcinoma cell lines (A2780 and AD10) were sensitized to FasL-mediated apoptosis by IFN-␥, partly due to NOS II induction and the consequent upregulation of Fas gene expression by RNS (Garban and Bonavida, 1999, 2001a). These findings demonstrate that NO and reactive nitrogen species can regulate the sensitivity of tumor cells to FasL-mediated cytotoxic immune lymphocytes. A similar study by Park et al. (2003) using ionizing radiation (IR) in combination with SNAP, showed sensitization to FasL-induced apoptotic cell death of HeLa human cervical cancer cells parallel to our findings with regard to the role of NO as an immuno-sensitizer. We have also previously reported, using a Fas promoterdriven luciferase reporter system, that the transcription factor Yin Yang 1 (YY1) (which normally represses Fas expression by binding to a cis-element clustered at the silencer region of the Fas promoter) negatively regulates Fas expression through its interaction with the silencer region of the Fas promoter (Garban and Bonavida, 2001a). NO-mediated inhibition of YY1 resulted in up-regulation of Fas expression and sensitization of ovarian carcinoma cells to FasL-induced apoptosis (Garban and Bonavida, 2001a). Recently, we have found that the treatment of the B non-hodgkin’s lymphoma cell line (B-NHL), Ramos, with rituximab (chimeric antiCD20 Ab) or with specific NF-␬B inhibitors (e.g., Bay 117085 and DHMEQ) and/or inhibition of YY1 (through the use of the NO donor, DETA/NONOate), resulted in sensitization

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Fig. 7. Schematic representation of the effect of NO regulating NF-␬B-mediated apoptosis related gene expression. Cellular exposure to either endogenous or exogenous sources of NO will inhibit, at different levels, the transcriptional activity of NF-␬B and further decreasing expression of anti-apoptotic genes and hence, chemosensitization to drug-induced apoptosis. Furthermore, inhibition of the transcriptional repressor YY1 results in the upregulation of the Fas receptor and the TRAIL pro-apoptotic receptor DR5, leading to immunosensitization to immune-mediated cytotoxicity and apoptosis. Thus, NO will promote overall chemo/immune sensitization of tumor cells to apoptosis.

to FasL-induced apoptosis (Vega et al., 2005). Noteworthy, the NO-mediated inhibition of YY1 activity (in the absence of rituximab) again resulted in significant up-regulation of surface Fas expression and sensitized Ramos cells to CH-11 (Fas agonist mAb)-induced apoptosis. Until now, the mechanism of YY1 inhibition by NO was unclear. However, Hongo et al. (2005) demonstrated that treatment of prostate cancer (PC3) cells with DETA/NONOate resulted in the S-nitrosation of YY1, thereby up-regulating Fas expression and sensitizing tumor cells to FasL-induced apoptosis through a direct NO-mediated mechanism. In the past few years, the significance of the role of NF-B in cancer has been well documented (Dolcet et al., 2005; Viatour et al., 2005; Karin et al., 2002; Ravi and Bedi, 2004). It is established that the improper activation of NF-␬B leads to the up-regulation of a variety of genes. Of particular interest associated with NO, improper activation of NF-␬B leads to the up-regulation of inflammatory cytokines such as TNF-␣. TNF-␣ can have a profound cytotoxic effect, nevertheless, tumor cells can acquire resistance to TNF-␣-mediated apoptosis. Han et al. (2000) suggested that regulation of NF-␬B activity may sensitize colon cancer cells to TNF-␣-induced cell death. We have observed that IFN-␥ sensitizes human ovarian carcinoma cell lines to TNF-␣-mediated apoptosis as well as mediates NO production (Garban and Bonavida, 2001b). We have examined the role of NO in the sensitization of the ovarian carcinoma cell line AD10 to TNF-␣-mediated cytotoxicity through use of the NOS inhibitor L-NMA, and NO donors (SNAP). We found that L-NAME blocked and NO donors sensitized these cells to the TNF-mediated cytotoxicity. Further, we found that inhibition of NF-␬B nuclear translocation by NO donors was linked directly with the intracellular concentration of the reactive oxygen species, H2 O2 , and was reversed by the addition of exogenous H2 O2 . Our findings demonstrate that NO-mediated disruption of NF-␬B activation results in the

eradication of anti-apoptotic/resistance signals, thus sensitizing tumor cells to cytotoxic cytokines like TNF-␣ (Garban and Bonavida, 2001b). Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytotoxic molecule that has been shown to exert, selectively, anti-tumor cytotoxic effects both in vitro and in vivo with minimal toxicity to normal tissues (Ashkenazi and Dixit, 1999; Ashkenazi et al., 1999; Huerta-Yepez et al., 2004). Various sensitizing agents like chemotherapeutic drugs (Zisman et al., 2001; Munshi et al., 2002), cytokines, and inhibitors are able to reverse TRAIL-resistance. Treatment of prostate cancer (CaP) cell lines (DU145, PC-3, CL-1, and LNCaP) with the NO donor DETA/NONOate sensitized CaP cells to TRAIL-induced apoptosis. Recent studies examining the mechanism by which DETA/NONOate mediated this sensitization, found that NF-␬B (p50) was S-nitrosylated by DETA/NONOate, thereby inhibiting NF-␬B activity. Further, DETA/NONOate was found to inhibit YY1 and resulted in upregulation of TRAIL death receptor DR5 (Huerta-Yepez et al., 2005). Altogether, the role of NO in the sensitization of cancer cells to immune-mediated cytotoxicity may have considerable therapeutic potential. The use of NO-based therapies may be a significant factor used to control tumor cell death via chemo- and immune apoptosis-mediated mechanisms (see schematic diagram in Fig. 7).

10. Concluding remarks NO plays several roles in cells and its effects vary depending on its concentration and its selective modification of various gene products. Its ultimate manifestation results from a complex set of interactions depending on the type of cells studied. It is also clear from recent findings that NO can play a significant role as a chemo-preventive agent in cancer development and in cancer therapeutics. The application

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of NO donors as cancer therapeutics is a new venue that has not been appreciated in the past as NO was primarily used for the treatment of blood vessel-related diseases and other non-cancer related applications. The demonstration of NO-mediated cytotoxicity directly on cancer cells and/or indirectly in the tumor microenvironment through its anti-proliferative and chemo-sensitizing roles, presents new challenges for its optimal use in cancer therapy. The data suggest that NO can be used as a chemo-sensitizing as well as an immuno-sensitizing agent, and thus, one may consider its clinical application using combination treatment of NO donors and chemotherapy or immunotherapy resulting in synergistic activity in the treatment of cancer. It is also conceivable that one might use NO donors complexed with chemotherapeutic drugs or other cytotoxic agents. One may also consider using agents that can activate endogenous NO production via NOS II. Clearly, apart from the direct effects of NO on tumor cells, NO donors would also be functioning as vasodilators and thus have an even enhanced therapeutic potential. Possibly, novel NO donors may be administered orally and thus be more applicable to treatment. For certain tumors, it is also possible to administer NO donors intratumorally and thus reducing the systemic toxic effects that may arise from its route of administration. We expect that the application of NO donors in cancer therapy will be added to the armamentarium of cancer therapeutics in the future.

Acknowledgments This work was supported in part by the Department of Defense (DOD)/US Army DAMD 17-02-1-0023 and the Fogarty International Center Fellowship (D43 TW00013-14) (S.H.-Y., M.V., and U.C. MEXUS-Conacyt (S.H.-Y.), Research Supplement for Minorities from the PHS/NIH/NCI/CMBB ROI CA79976 to H.G. and a philanthropic contribution from the Ann C. Rosenfield Fund, under the direction of David Leveton. We also acknowledge the assistance of Christine Yue, Alina Katsman, Mardjan Nafissi, Amy Wu and Samuel Olson in the preparation of this manuscript.

References Ahmad, N., Gupta, S., Mukhtar, H., 2000. Green tea polyphenol epigallocatechin-3-gallate differentially modulates nuclear factor kappaB in cancer cells versus normal cells. Arch. Biochem. Biophys. 376, 338–346. Ambs, S., Hussain, S.P., Harris, C.C., 1997. Interactive effects of nitric oxide and the p53 tumor suppressor gene in carcinogenesis and tumor progression. FASEB J. 11, 443–448. Ambs, S., Merriam, W.G., Ogunfusika, M.O., Bennett, W.P., Ishibe, N., Hussain, S.P., Tzeng, E.E., Geller, D.A., Billiar, T.R., Harris, C.C., 1998. p53 and vascular endothelial growth factor regulate tumor growth of NOS2-expressing human carcinoma cells. Nat. Med. 4, 1371–1376.

169

Ashkenazi, A., Dixit, V.M., 1999. Apoptosis control by death and decoy receptors. Curr. Opin. Cell. Biol. 11, 255–260. Ashkenazi, A., Pai, R.C., Fong, S., Leung, S., Lawrence, D.A., Marsters, S.A., et al., 1999. Safety and antitumor activity of recombinant soluble Apo2 ligand. J. Clin. Invest. 104, 155–162. Bauer, P.M., Buga, G.M., Fukuto, J.M., Pegg, A.E., Ignarro, L.J., 2001. Nitric oxide inhibits ornithine decarboxylase via S-nitrosylation of cysteine 360 in the active site of the enzyme. J. Biol. Chem. 276, 34458–34464. Benz, D., Cadet, P., Mantione, K., Zhu, W., Stefano, G., 2002. Tonal nitric oxide and health—a free radical and a scavenger of free radicals. Med. Sci. Monit. 8, RA1–RA4. Bhatia, G.S., Sosin, M.D., Connolly, D.L., Davis, R.C., 2004. Statins and rheumatoid arthritis. Lancet 364, 1853, author reply 1855. Bicker, G., 2005. STOP and GO with NO: nitric oxide as a regulator of cell motility in simple brains. Bioessays 27, 495–505. Birschmann, I., Walter, U., 2004. Physiology and pathophysiology of vascular signaling controlled by guanosine 3 ,5 -cyclic monophosphatedependent protein kinase. Acta Biochim. Pol. 51, 397–404. Blaise, G.A., Gauvin, D., Gangal, M., Authier, S., 2005. Nitric oxide, cell signaling and cell death. Toxicology 208, 177–192. Bo, L., Dawson, T.M., Wesselingh, S., Mork, S., Choi, S., Kong, P.A., Hanley, D., Trapp, B.D., 1994. Induction of nitric oxide synthase in demyelinating regions of multiple sclerosis brains. Ann. Neurol. 36, 778–786. Bogdan, C., 2001. Nitric oxide and the regulation of gene expression. Trends Cell Biol. 11, 66–75. Boyd, C.S., Cadenas, E., 2002. Nitric oxide and cell signaling pathways in mitochondrial-dependent apoptosis. Biol. Chem. 383, 411– 423. Borst, P., Rottenberg, S., 2004. Cancer cell death by programmed necrosis? Drug Resist. Update 7, 321–324. Brune, B., 2003. Nitric oxide: NO apoptosis or turning it ON? Cell Death Differ. 10, 864–869. Brune, B., 2005. The intimate relation between nitric oxide and superoxide in apoptosis and cell survival. Antioxid. Redox Signal. 7, 497–507. Brune, B., von Knethen, A., Sandau, K.B., 1999. Nitric oxide (NO): an effector of apoptosis. Cell Death Differ. 6, 969–975. Butterfield, D.A., Yatin, S.M., Link, C.D., 1999. In vitro and in vivo protein oxidation induced by Alzheimer’s disease amyloid beta-peptide (1–42). Ann. N.Y. Acad. Sci. 893, 265–268. Calmels, S., Hainaut, P., Ohshima, H., 1997. Nitric oxide induces conformational and functional modifications of wild-type p53 tumor suppressor protein. Cancer Res. 57, 3365–3369. Cannon III, R.O., 1998. Role of nitric oxide in cardiovascular disease: focus on the endothelium. Clin. Chem. 44, 1809–1819. Champlin, D.T., Truman, J.W., 2000. Ecdysteroid coordinates optic lobe neurogenesis via a nitric oxide signaling pathway. Development 127, 3543–3551. Chung, H.T., Pae, H.O., Choi, B.M., Billiar, T.R., Kim, Y.M., 2001. Nitric oxide as a bioregulator of apoptosis. Biochem. Biophys. Res. Commun. 282, 1075–1079. Coleman, J.W., 2001. Nitric oxide in immunity and inflammation. Int. Immunopharmacol. 1, 1397–1406. Cooke, J.P., Dzau, V.J., 1997. Nitric oxide synthase: role in the genesis of vascular disease. Annu. Rev. Med. 48, 489–509. Davis, K.L., Martin, E., Turko, I.V., Murad, F., 2001. Novel effects of nitric oxide. Annu. Rev. Pharmacol. Toxicol. 41, 203–236. de Vera, M.E., Shapiro, R.A., Nussler, A.K., Mudgett, J.S., Simmons, R.L., Morris Jr., S.M., et al., 1996. Transcriptional regulation of human inducible nitric oxide synthase (NOS2) gene by cytokines: initial analysis of the human NOS2 promoter. Proc. Natl. Acad. Sci. (USA) 93, 1054–1059. Dimmeler, S., Haendeler, J., Nehls, M., Zeiher, A.M., 1997. Suppression of apoptosis by nitric oxide via inhibition of interleukin-1beta-converting enzyme (ICE)-like and cysteine protease protein (CPP)-32-like proteases. J. Exp. Med. 185, 601–607.

170

B. Bonavida et al. / Drug Resistance Updates 9 (2006) 157–173

Dokmeci, D., 2004. Ibuprofen and Alzheimer’s disease. Folia Med. (Plovdiv) 46, 5–10. Dolcet, X., Llobet, D., Pallares, J., Matias-Guiu, X., 2005. NF-kB in development and progression of human cancer. Virchows Arch. 446, 475–482. Drew, B., Leeuwenburgh, C., 2002. Aging and the role of reactive nitrogen species. Ann. N.Y. Acad. Sci. 959, 66–81. Dubey, R.K., Jackson, E.K., Luscher, T.F., 1995. Nitric oxide inhibits angiotensin II-induced migration of rat aortic smooth muscle cell. Role of cyclic-nucleotides and angiotensin1 receptors. J. Clin. Invest. 96, 141–149. Dweik, R.A., Comhair, S.A., Gaston, B., Thunnissen, F.B., Farver, C., Thomassen, M.J., et al., 2001. NO chemical events in the human airway during the immediate and late antigen-induced asthmatic response. Proc. Natl. Acad. Sci. (USA) 98, 2622–2627. Eggermont, J.A., Wuytack, F., Verbist, J., Casteels, R., 1990. Expression of endoplasmic-reticulum Ca2(+)-pump isoforms and of phospholamban in pig smooth-muscle tissues. Biochem. J. 271, 649–653. Endo, S., Suzuki, M., Sumi, M., Nairn, A.C., Morita, R., Yamakawa, K., et al., 1999. Molecular identification of human G-substrate, a possible downstream component of the cGMP-dependent protein kinase cascade in cerebellar Purkinje cells. Proc. Natl. Acad. Sci. (USA) 96, 2467–2472. Evig, C.B., Kelley, E.E., Weydert, C.J., Chu, Y., Buettner, G.R., Burns, C.P., 2004. Endogenous production and exogenous exposure to nitric oxide augment doxorubicin cytotoxicity for breast cancer cells but not cardiac myoblasts. Nitric Oxide 10, 119–129. Felley-Bosco, E., 1998. Role of nitric oxide in genotoxicity: implication for carcinogenesis. Cancer Metastasis Rev. 17, 25–37. Fiorucci, S., Antonelli, E., Burgaud, J.L., Morelli, A., 2001. Nitric oxidereleasing NSAIDs: a review of their current status. Drug Safety 24, 801–811. Forrester, K., Ambs, S., Lupold, S.E., Kapust, R.B., Spillare, E.A., Weinberg, W.S., et al., 1996. Nitric oxide-induced p53 accumulation and regulation of inducible nitric oxide synthase expression by wild-type p53. Proc. Natl. Acad. Sci. (USA) 93, 2442–2447. Frederiksen, L.J., Siemens, D.R., Heaton, J.P., Maxwell, L.R., Adams, M.A., Graham, C.H., 2003. Hypoxia induced resistance to doxorubicin in prostate cancer cells is inhibited by low concentrations of glyceryl trinitrate. J. Urol. 170, 1003–1007. Fukuo, K., Hata, S., Suhara, T., Nakahashi, T., Shinto, Y., Tsujimoto, Y., Morimoto, S., Ogihara, T., 1996. Nitric oxide induces upregulation of Fas and apoptosis in vascular smooth muscle. Hypertension 27, 823–826. Garban, H.J., Bonavida, B., 1999. Nitric oxide sensitizes ovarian tumor cells to Fas-induced apoptosis. Gynecol. Oncol. 73, 257–264. Garban, H.J., Bonavida, B., 2001a. Nitric oxide inhibits the transcription repressor Yin-Yang 1 binding activity at the silencer region of the Fas promoter: a pivotal role for nitric oxide in the up-regulation of Fas gene expression in human tumor cells. J. Immunol. 167, 75–81. Garban, H.J., Bonavida, B., 2001b. Nitric oxide disrupts H2 O2 -dependent activation of nuclear factor kappa B. Role in sensitization of human tumor cells to tumor necrosis factor-alpha -induced cytotoxicity. J. Biol. Chem. 276, 8918–8923. Gauthier, N., Lohm, S., Touzery, C., Chantome, A., Perette, B., Reveneau, S., et al., 2004. Tumour-derived and host-derived nitric oxide differentially regulate breast carcinoma metastasis to the lungs. Carcinogenesis 25, 1559–1565. Ghalayini, I.F., 2004. Nitric oxide-cyclic GMP pathway with some emphasis on cavernosal contractility. Int. J. Impot. Res. 16, 459–469. Ghosh, S., May, M.J., Kopp, E.B., 1998. NF-kappa B and Rel proteins: evolutionarily conserved mediators of immune responses. Annu. Rev. Immunol. 16, 225–260. Giuffre, A., Barone, M.C., Mastronicola, D., D’Itri, E., Sarti, P., Brunori, M., 2000. Reaction of nitric oxide with the turnover intermediates of cytochrome c oxidase: reaction pathway and functional effects. Biochemistry 39, 15446–15453.

Gordon, S.A., Abou-Jaoude, W., Hoffman, R.A., McCarthy, S.A., Kim, Y.M., Zhou, X., et al., 2001. Nitric oxide induces murine thymocyte apoptosis by oxidative injury and a p53-dependent mechanism. J. Leukoc. Biol. 70, 87–95. Gow, A.J., Farkouh, C.R., Munson, D.A., Posencheg, M.A., Ischiropoulos, H., 2004. Biological significance of nitric oxide-mediated protein modifications. Am. J. Physiol. Lung Cell. Mol. Physiol. 287, L262–L268. Han, S.Y., Choung, S.Y., Paik, I.S., Kang, H.J., Choi, Y.H., Kim, S.J., Lee, M.O., 2000. Activation of NF-kappaB determines the sensitivity of human colon cancer cells to TNFalpha-induced apoptosis. Biol. Pharm. Bull. 23, 420–426. Haynes, V., Elfering, S., Traaseth, N., Giulivi, C., 2004. Mitochondrial nitricoxide synthase: enzyme expression, characterization, and regulation. J. Bioenerg. Biomembr. 36, 341–346. Herman, A.G., Moncada, S., 2005. Therapeutic potential of nitric oxide donors in the prevention and treatment of atherosclerosis. Eur. Heart J. 26, 1945–1955. Hess, D.T., Matsumoto, A., Kim, S.O., Marshall, H.E., Stamler, J.S., 2005. Protein S-nitrosylation: purview and parameters. Nat. Rev. Mol. Cell. Biol. 6, 150–166. Hofseth, L.J., Hussain, S.P., Wogan, G.N., Harris, C.C., 2003. Nitric oxide in cancer and chemoprevention. Free Radic. Biol. Med. 34, 955– 968. Hongo, F., Garban, H., Huerta-Yepez, S., Vega, M., Jazirehi, A.R., Mizutani, Y., et al., 2005. Inhibition of the transcription factor Yin Yang 1 activity by S-nitrosation. Biochem. Biophys. Res. Commun. 336, 692– 701. Huerta-Yepez, S., Vega, M., Jazirehi, A., Garban, H., Hongo, F., Cheng, G., Bonavida, B., 2004. Nitric oxide sensitizes prostate carcinoma cell lines to TRAIL-mediated apoptosis via inactivation of NFkappa B and inhibition of Bcl-xl expression. Oncogene 23, 4993– 5003. Huerta-Yepez, S., Vega, M.I., Escoto-Chavez, S.E., Murdock, B., Garban, H., Sakai, T., Bonavida, B., 2005. Regulation of the TRAIL receptor DR5 expression by the transcription represor Yin Yang 1 (YY1). Proc. Amer. Assoc. Cancer Res. 46 [Abstract #6032]. Huerta-Yepez, S., Baritaki, S., Vega, M., Baay-Guzman, G., HernandezPando, R., Gonzalez-Pando, R., Gonzalez-Bonilla, C., Bonavida, B., 2006. Inhibition of PC-3 protstate tumor cell growth in nude mice following treatment with combination of the NO donor DETANONoate and CDDP. Proc. Amer. Assoc. Cancer. Res. 47 [Abstract #5480]. Hussain, S.P., Hofseth, L.J., Harris, C.C., 2003. Radical causes of cancer. Nat. Rev. Cancer 3, 276–285. Hussain, S.P., Trivers, G.E., Hofseth, L.J., He, P., Shaikh, I., Mechanic, L.E., et al., 2004. Nitric oxide, a mediator of inflammation, suppresses tumorigenesis. Cancer Res 64, 6849–6853. Inano, H., Onoda, M., 2005. Nitric oxide produced by inducible nitric oxide synthase is associated with mammary tumorigenesis in irradiated rats. Nitric Oxide 12, 15–20. Janero, D.R., 1990. Malondialdehyde and thiobarbituric acid-reactivity as diagnostic indices of lipid peroxidation and peroxidative tissue injury. Free Radic. Biol. Med. 9, 515–540. Jenkins, D.C., Charles, I.G., Thomsen, L.L., Moss, D.W., Holmes, L.S., Baylis, S.A., et al., 1995. Roles of nitric oxide in tumor growth. Proc. Natl. Acad. Sci. (USA) 92, 4392–4396. Karin, M., Cao, Y., Greten, F.R., Li, Z.W., 2002. NF-kappaB in cancer: from innocent bystander to major culprit. Nat. Rev. Cancer 2, 301–310. Kashfi, K., Ryan, Y., Qiao, L.L., Williams, J.L., Chen, J., Del Soldato, P., Traganos, F., Rigas, B., 2002. Nitric oxide-donating nonsteroidal antiinflammatory drugs inhibit the growth of various cultured human cancer cells: evidence of a tissue type-independent effect. J. Pharmacol. Exp. Ther. 303, 1273–1282. Kashiwagi, S., Izumi, Y., Gohongi, T., Demou, Z.N., Xu, L., Huang, P.L., et al., 2005. NO mediates mural cell recruitment and vessel morphogenesis in murine melanomas and tissue-engineered blood vessels. J. Clin. Invest. 115, 1816–1827.

B. Bonavida et al. / Drug Resistance Updates 9 (2006) 157–173 Kim, Y.M., Talanian, R.V., Billiar, T.R., 1997. Nitric oxide inhibits apoptosis by preventing increases in caspase-3-like activity via two distinct mechanisms. J. Biol. Chem. 272, 31138–31148. Klahr, S., Morrissey, J., 2004. l-Arginine as a therapeutic tool in kidney disease. Semin. Nephrol. 24, 389–394. Klaunig, J.E., Kamendulis, L.M., 2004. The role of oxidative stress in carcinogenesis. Annu. Rev. Pharmacol. Toxicol. 44, 239–267. Kleinert, H., Pautz, A., Linker, K., Schwarz, P.M., 2004. Regulation of the expression of inducible nitric oxide synthase. Eur. J. Pharmacol. 500, 255–266. Koesling, D., Russwurm, M., Mergia, E., Mullershausen, F., Friebe, A., 2004. Nitric oxide-sensitive guanylyl cyclase: structure and regulation. Neurochem. Int. 45, 813–819. Kolb, H., Kolb-Bachofen, V., 1998. Nitric oxide in autoimmune disease: cytotoxic or regulatory mediator? Immunol. Today 19, 556–561. Komalavilas, P., Lincoln, T.M., 1994. Phosphorylation of the inositol 1,4,5trisphosphate receptor by cyclic GMP-dependent protein kinase. J. Biol. Chem. 269, 8701–8707. Konovalova, N.P., Goncharova, S.A., Volkova, L.M., Rajewskaya, T.A., Eremenko, L.T., Korolev, A.M., 2003. Nitric oxide donor increases the efficiency of cytostatic therapy and retards the development of drug resistance. Nitric Oxide 8, 59–64. Krumenacker, J.S., Hanafy, K.A., Murad, F., 2004. Regulation of nitric oxide and soluble guanylyl cyclase. Brain Res. Bull. 62, 505–515. Lala, P.K., 1998. Significance of nitric oxide in carcinogenesis, tumor progression and cancer therapy. Cancer Metastasis Rev. 17, 1–6. Lala, P.K., Chakraborty, C., 2001. Role of nitric oxide in carcinogenesis and tumour progression. Lancet Oncol. 2, 149–156. Lander, H.M., Ogiste, J.S., Pearce, S.F., Levi, R., Novogrodsky, A., 1995. Nitric oxide-stimulated guanine nucleotide exchange on p21ras. J. Biol. Chem. 270, 7017–7020. Li, C.Q., Trudel, L.J., Wogan, G.N., 2002. Nitric oxide-induced genotoxicity, mitochondrial damage, and apoptosis in human lymphoblastoid cells expressing wild-type and mutant p53. Proc. Natl. Acad. Sci. (USA) 99, 10364–10369. Li, H., Forstermann, U., 2000. Nitric oxide in the pathogenesis of vascular disease. J. Pathol. 190, 244–254. Lin, A.W., Chang, C.C., McCormick, C.C., 1996. Molecular cloning and expression of an avian macrophage nitric-oxide synthase cDNA and the analysis of the genomic 5 -flanking region. J. Biol. Chem. 271, 11911–11919. Lin, J.K., Lin-Shiau, S.Y., 2001. Mechanisms of cancer chemoprevention by curcumin. Proc. Natl. Sci. Counc. Rep. Chin. B 25, 59–66. Lin, Y.L., Lin, J.K., 1997. (−)-Epigallocatechin-3-gallate blocks the induction of nitric oxide synthase by down-regulating lipopolysaccharideinduced activity of transcription factor nuclear factor-kappaB. Mol. Pharmacol. 52, 465–472. Lucas, K.A., Pitari, G.M., Kazerounian, S., Ruiz-Stewart, I., Park, J., Schulz, S., et al., 2000. Guanylyl cyclases and signaling by cyclic GMP. Pharmacol. Rev. 52, 375–414. Luss, H., Li, R.K., Shapiro, R.A., Tzeng, E., McGowan, F.X., Yoneyama, T., et al., 1997. Dedifferentiated human ventricular cardiac myocytes express inducible nitric oxide synthase mRNA but not protein in response to IL-1, TNF, IFNgamma, and LPS. J. Mol. Cell. Cardiol. 29, 1153– 1165. Mannick, J.B., Miao, X.Q., Stamler, J.S., 1997. Nitric oxide inhibits Fasinduced apoptosis. J. Biol. Chem. 272, 24125–24128. Mannick, J.B., Schonhoff, C.M., 2002. Nitrosylation: the next phosphorylation? Arch. Biochem. Biophys. 408, 1–6. Markesbery, W.R., 1997. Oxidative stress hypothesis in Alzheimer’s disease. Free Radic. Biol. Med. 23, 134–147. Marnett, L.J., Burcham, P.C., 1993. Endogenous DNA adducts: potential and paradox. Chem. Res. Toxicol. 6, 771–785. Marshall, H.E., Merchant, K., Stamler, J.S., 2000. Nitrosation and oxidation in the regulation of gene expression. FASEB J. 14, 1889–1900. Mashima, T., Tsuruo, T., 2005. Defects of the apoptotic pathway as therapeutic target against cancer. Drug Resist. Update 8, 339–343.

171

Matthews, N.E., Adams, M.A., Maxwell, L.R., Gofton, T.E., Graham, C.H., 2001. Nitric oxide-mediated regulation of chemosensitivity in cancer cells. J. Natl. Cancer Inst. 93, 1879–1885. Mattson, M.P., Rychlik, B., Chu, C., Christakos, S., 1991. Evidence for calcium-reducing and excito-protective roles for the calcium-binding protein calbindin-D28k in cultured hippocampal neurons. Neuron 6, 41–51. McNamara, D.B., Bedi, B., Aurora, H., Tena, L., Ignarro, L.J., Kadowitz, P.J., Akers, D.L., 1993. l-Arginine inhibits balloon catheter-induced intimal hyperplasia. Biochem. Biophys. Res. Commun. 193, 291– 296. Meffert, M.K., Premack, B.A., Schulman, H., 1994. Nitric oxide stimulates Ca(2+)-independent synaptic vesicle release. Neuron 12, 1235– 1244. Melino, G., Bernassola, F., Knight, R.A., Corasaniti, M.T., Nistico, G., Finazzi-Agro, A., 1997. S-nitrosylation regulates apoptosis. Nature 388, 432–433. Messmer, U.K., Brune, B., 1996. Nitric oxide-induced apoptosis: p53dependent and p53-independent signalling pathways. Biochem. J. 319 (Pt 1), 299–305. Mitrovic, B., Ignarro, L.J., Montestruque, S., Smoll, A., Merrill, J.E., 1994. Nitric oxide as a potential pathological mechanism in demyelination: its differential effects on primary glial cells in vitro. Neuroscience 61, 575–585. Mohr, S., Zech, B., Lapetina, E.G., Brune, B., 1997. Inhibition of caspase-3 by S-nitrosation and oxidation caused by nitric oxide. Biochem. Biophys. Res. Commun. 238, 387–391. Moncada, S., Erusalimsky, J.D., 2002. Does nitric oxide modulate mitochondrial energy generation and apoptosis? Nat. Rev. Mol. Cell. Biol. 3, 214–220. Mukaida, N., Morita, M., Ishikawa, Y., Rice, N., Okamoto, S., Kasahara, T., Matsushima, K., 1994. Novel mechanism of glucocorticoidmediated gene repression. Nuclear factor-kappa B is target for glucocorticoid-mediated interleukin 8 gene repression. J. Biol. Chem. 269, 13289–13295. Munshi, A., McDonnell, T.J., Meyn, R.E., 2002. Chemotherapeutic agents enhance TRAIL-induced apoptosis in prostate cancer cells. Cancer Chemother. Pharmacol. 50, 46–52. Mutoh, M., Takahashi, M., Fukuda, K., Matsushima-Hibiya, Y., Mutoh, H., Sugimura, T., Wakabayashi, K., 2000. Suppression of cyclooxygenase2 promoter-dependent transcriptional activity in colon cancer cells by chemopreventive agents with a resorcin-type structure. Carcinogenesis 21, 959–963. Myers, P.R., Minor Jr., R.L., Guerra Jr., R., Bates, J.N., Harrison, D.G., 1990. Vasorelaxant properties of the endothelium-derived relaxing factor more closely resemble S-nitrosocysteine than nitric oxide. Nature 345, 161–163. Nelson, E.J., Connolly, J., McArthur, P., 2003. Nitric oxide and Snitrosylation: excitotoxic and cell signaling mechanism. Biol. Cell 95, 3–8. Nguyen, T., Brunson, D., Crespi, C.L., Penman, B.W., Wishnok, J.S., Tannenbaum, S.R., 1992. DNA damage and mutation in human cells exposed to nitric oxide in vitro. Proc. Natl. Acad. Sci. (USA) 89, 3030–3034. Ogura, T., Tatemichi, M., Esumi, H., 1997. Nitric oxide inhibits CPP32-like activity under redox regulation. Biochem. Biophys. Res. Commun. 236, 365–369. Orucevic, A., Bechberger, J., Green, A.M., Shapiro, R.A., Billiar, T.R., Lala, P.K., 1999. Nitric-oxide production by murine mammary adenocarcinoma cells promotes tumor-cell invasiveness. Int. J. Cancer 81, 889– 896. Orucevic, A., Lala, P.K., 1996. Effects of N(g)-methyl-l-arginine, an inhibitor of nitric oxide synthesis, on interleukin-2-induced capillary leakage and antitumor responses in healthy and tumor-bearing mice. Cancer Immunol. Immunother. 42, 38–46. Pannala, A.S., Rice-Evans, C.A., Halliwell, B., Singh, S., 1997. Inhibition of peroxynitrite-mediated tyrosine nitration by catechin polyphenols. Biochem. Biophys. Res. Commun. 232, 164–168.

172

B. Bonavida et al. / Drug Resistance Updates 9 (2006) 157–173

Park, I.C., Woo, S.H., Park, M.J., Lee, H.C., Lee, S.J., Hong, Y.J., et al., 2003. Ionizing radiation and nitric oxide donor sensitize Fas-induced apoptosis via up-regulation of Fas in human cervical cancer cells. Oncol. Rep. 10, 629–633. Perrotta, C., Falcone, S., Capobianco, A., Camporeale, A., Sciorati, C., De Palma, C., Pisconti, A., et al., 2004. Nitric oxide confers therapeutic activity to dendritic cells in a mouse model of melanoma. Cancer Res. 64, 3767–3771. Pervaiz, S., 2004. Chemotherapeutic potential of the chemopreventive phytoalexin resveratrol. Drug Resist. Update 7, 333–344. Pfeilschifter, J., Eberhardt, W., Beck, K.F., 2001. Regulation of gene expression by nitric oxide. Pflugers Arch. 442, 479–486. Poderoso, J.J., Carreras, M.C., Lisdero, C., Riobo, N., Schopfer, F., Boveris, A., 1996. Nitric oxide inhibits electron transfer and increases superoxide radical production in rat heart mitochondria and submitochondrial particles. Arch. Biochem. Biophys. 328, 85–92. Rao, C.V., Indranie, C., Simi, B., Manning, P.T., Connor, J.R., Reddy, B.S., 2002. Chemopreventive properties of a selective inducible nitric oxide synthase inhibitor in colon carcinogenesis, administered alone or in combination with celecoxib, a selective cyclooxygenase-2 inhibitor. Cancer Res. 62, 165–170. Rapoport, R.M., Murad, F., 1983. Endothelium-dependent and nitrovasodilator-induced relaxation of vascular smooth muscle: role of cyclic GMP. J. Cycl. Nucl. Protein Phosphor. Res. 9, 281–296. Ravi, R., Bedi, A., 2004. NF-␬B in cancer—a friend turned foe. Drug Resist. Update 7, 53–67. Riganti, C., Miraglia, E., Viarisio, D., Costamagna, C., Pescarmona, G., Ghigo, D., Bosia, A., 2005. Nitric oxide reverts the resistance to doxorubicin in human colon cancer cells by inhibiting the drug efflux. Cancer Res. 65, 516–525. Rodriguez-Pascual, F., Hausding, M., Ihrig-Biedert, I., Furneaux, H., Levy, A.P., Forstermann, U., Kleinert, H., 2000. Complex contribution of the 3 -untranslated region to the expressional regulation of the human inducible nitric-oxide synthase gene. Involvement of the RNA-binding protein HuR. J. Biol. Chem. 275, 26040–26049. Ruth, P., 1999. Cyclic GMP-dependent protein kinases: understanding in vivo functions by gene targeting. Pharmacol. Ther. 82, 355–372. Rutschman, R., Lang, R., Hesse, M., Ihle, J.N., Wynn, T.A., Murray, P.J., 2001. Cutting edge: Stat6-dependent substrate depletion regulates nitric oxide production. J. Immunol. 166, 2173–2177. Scott, D.J., Hull, M.A., Cartwright, E.J., Lam, W.K., Tisbury, A., Poulsom, R., et al., 2001. Lack of inducible nitric oxide synthase promotes intestinal tumorigenesis in the Apc(Min/+) mouse. Gastroenterology 121, 889–899. Sebens-Muerkoster, S., Lust, J., Arlt, A., Hasler, R., Witt, M., Sebens, T., et al., 2006. Acquired chemoresistance in pancreatic carcinoma cells: induced secretion of IL-1beta and NO lead to inactivation of caspases. Oncogene 25, 3973–3981. Shiva, S., Brookes, P.S., Patel, R.P., Anderson, P.G., Darley-Usmar, V.M., 2001. Nitric oxide partitioning into mitochondrial membranes and the control of respiration at cytochrome c oxidase. Proc. Natl. Acad. Sci. (USA) 98, 7212–7217. Smith, K.J., Lassmann, H., 2002. The role of nitric oxide in multiple sclerosis. Lancet Neurol. 1, 232–241. Spalding, J., 1988. NTP toxicology and carcinogenesis studies of malonaldehyde, sodium salt (3-hydroxy-2-propenal, sodium salt) (CAS No. 24382-04-5) in F344/N rats and B6C3F1 mice (Gavage studies). Natl. Toxicol. Program Tech. Rep. Ser. 331, 1–182. Stichtenoth, D.O., Frolich, J.C., 1998. Nitric oxide and inflammatory joint diseases. Br. J. Rheumatol. 37, 246–257. Stone, K., Ksebati, M.B., Marnett, L.J., 1990. Investigation of the adducts formed by reaction of malondialdehyde with adenosine. Chem. Res. Toxicol. 3, 33–38. Stuehr, D.J., 2004. Enzymes of the l-arginine to nitric oxide pathway. J. Nutr. 134, 2748S–2751S, discussion 2765S-2767S. Surh, Y.J., Chun, K.S., Cha, H.H., Han, S.S., Keum, Y.S., Park, K.K., Lee, S.S., 2001. Molecular mechanisms underlying chemopreventive activ-

ities of anti-inflammatory phytochemicals: down-regulation of COX-2 and iNOS through suppression of NF-kappa B activation. Mutat. Res. 480–481, 243–268. Taimor, G., Rakow, A., Piper, H.M., 2001. Transcription activator protein 1 (AP-1) mediates NO-induced apoptosis of adult cardiomyocytes. FASEB J. 15, 2518–2520. Tamir, S., Burney, S., Tannenbaum, S.R., 1996. DNA damage by nitric oxide. Chem. Res. Toxicol. 9, 821–827. Tenneti, L., D’Emilia, D.M., Lipton, S.A., 1997. Suppression of neuronal apoptosis by S-nitrosylation of caspases. Neurosci. Lett. 236, 139– 142. Thomsen, L.L., Miles, D.W., 1998. Role of nitric oxide in tumour progression: lessons from human tumours. Cancer Metastasis Rev. 17, 107–118. Thomsen, L.L., Scott, J.M., Topley, P., Knowles, R.G., Keerie, A.J., Frend, A.J., 1997. Selective inhibition of inducible nitric oxide synthase inhibits tumor growth in vivo: studies with 1400W, a novel inhibitor. Cancer Res. 57, 3300–3304. Tsai, S.H., Lin-Shiau, S.Y., Lin, J.K., 1999. Suppression of nitric oxide synthase and the down-regulation of the activation of NFkappaB in macrophages by resveratrol. Br. J. Pharmacol. 126, 673–680. Tuteja, N., Chandra, M., Tuteja, R., Misra, M.K., 2004. Nitric oxide as a unique bioactive signaling messenger in physiology and pathophysiology. J. Biomed. Biotechnol., 227–237. Umansky, V., Schirrmacher, V., 2001. Nitric oxide-induced apoptosis in tumor cells. Adv. Cancer Res. 82, 107–131. van der Vliet, A., Eiserich, J.P., Cross, C.E., 2000. Nitric oxide: a proinflammatory mediator in lung disease? Respir. Res. 1, 67–72. Vega, M.I., Jazirehi, A.R., Huerta-Yepez, S., Bonavida, B., 2005. Rituximabinduced inhibition of YY1 and Bcl-xL expression in Ramos nonHodgkin’s lymphoma cell line via inhibition of NF-kappa B activity: role of YY1 and Bcl-xL in Fas resistance and chemoresistance, respectively. J. Immunol. 175, 2174–2183. Viatour, P., Merville, M.P., Bours, V., Chariot, A., 2005. Phosphorylation of NF-kappaB and IkappaB proteins: implications in cancer and inflammation. Trends Biochem. Sci. 30, 43–52. von Knethen, A., Callsen, D., Brune, B., 1999. Superoxide attenuates macrophage apoptosis by NF-kappa B and AP-1 activation that promotes cyclooxygenase-2 expression. J. Immunol. 163, 2858–2866. Wei, D., Richardson, E.L., Zhu, K., Wang, L., Le, X., He, Y., Huang, S., Xie, K., 2003. Direct demonstration of negative regulation of tumor growth and metastasis by host-inducible nitric oxide synthase. Cancer Res. 63, 3855–3859. Williams, J.L., Nath, N., Chen, J., Hundley, T.R., Gao, J., Kopelovich, L., et al., 2003. Growth inhibition of human colon cancer cells by nitric oxide (NO)-donating aspirin is associated with cyclooxygenase-2 induction and beta-catenin/T-cell factor signaling, nuclear factor-kappaB, and NO synthase 2 inhibition: implications for chemoprevention. Cancer Res. 63, 7613–7618. Wink, D.A., Laval, J., 1994. The Fpg protein, a DNA repair enzyme, is inhibited by the biomediator nitric oxide in vitro and in vivo. Carcinogenesis 15, 2125–2129. Wouters, B.G., van den Beucken, T., Magagnin, M.G., Lambin, P., Koumenis, C., 2004. Targeting hypoxia tolerance in cancer. Drug Resist. Update 7, 25–40. Xie, K., Huang, S., Dong, Z., Juang, S.H., Gutman, M., Xie, Q.W., et al., 1995. Transfection with the inducible nitric oxide synthase gene suppresses tumorigenicity and abrogates metastasis by K-1735 murine melanoma cells. J. Exp. Med. 181, 1333–1343. Xu, W., Liu, L.Z., Loizidou, M., Ahmed, M., Charles, I.G., 2002. The role of nitric oxide in cancer. Cell Res. 12, 311–320. Yamamoto, Y., Gaynor, R.B., 2001. Therapeutic potential of inhibition of the NF-kappaB pathway in the treatment of inflammation and cancer. J. Clin. Invest. 107, 135–142. Yim, C.Y., McGregor, J.R., Kwon, O.D., Bastian, N.R., Rees, M., Mori, M., et al., 1995. Nitric oxide synthesis contributes to IL-2-induced antitumor responses against intraperitoneal Meth A tumor. J. Immunol. 155, 4382–4390.

B. Bonavida et al. / Drug Resistance Updates 9 (2006) 157–173 Zech, B., Kohl, R., von Knethen, A., Brune, B., 2003. Nitric oxide donors inhibit formation of the Apaf-1/caspase-9 apoptosome and activation of caspases. Biochem. J. 371, 1055–1064. Zhuang, J.C., Wright, T.L., deRojas-Walker, T., Tannenbaum, S.R., Wogan, G.N., 2000. Nitric oxide-induced mutations in the HPRT gene of human lymphoblastoid TK6 cells and in Salmonella typhimurium. Environ. Mol. Mutagen. 35, 39–47.

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Ziche, M., Morbidelli, L., 2000. Nitric oxide and angiogenesis. J. Neurooncol. 50, 139–148. Zisman, A., Ng, C.P., Pantuck, A.J., Bonavida, B., Belldegrun, A.S., 2001. Actinomycin D and gemcitabine synergistically sensitize androgenindependent prostate cancer cells to Apo2L/TRAIL-mediated apoptosis. J. Immunother. 24, 459–471.