The extracellular matrix niche microenvironment of neural and cancer stem cells in the brain

Accepted Manuscript Title: The extracellular matrix niche microenvironment of neural and cancer stem cells in the brain Author: Jacqueline Reinhard Nicole Br¨osicke Ursula Theocharidis Andreas Faissner PII: DOI: Reference:

S1357-2725(16)30107-8 http://dx.doi.org/doi:10.1016/j.biocel.2016.05.002 BC 4847

To appear in:

The International Journal of Biochemistry & Cell Biology

Received date: Revised date: Accepted date:

2-9-2015 25-3-2016 4-5-2016

Please cite this article as: Reinhard, Jacqueline., Brddotosicke, Nicole., Theocharidis, Ursula., & Faissner, Andreas., The extracellular matrix niche microenvironment of neural and cancer stem cells in the brain.International Journal of Biochemistry and Cell Biology http://dx.doi.org/10.1016/j.biocel.2016.05.002 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.

The extracellular matrix niche microenvironment of neural and cancer stem cells in the brain

Jacqueline Reinhard*, Nicole Brösicke*, Ursula Theocharidis and Andreas Faissner

Department of Cell Morphology & Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Universitätsstraße 150, 44870 Bochum, Germany

* These authors contributed equally and should be regarded as equivalent authors # This article is part of a Directed Issue entitled: “Stem Cells and Matrix”

Corresponding author: Prof. Dr. Andreas Faissner, Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany, Phone: +49 234 32 23851, Fax: +49 234 32 14313, e-mail: [email protected]

List of potential referees (in alphabetical order): 

Ruth

Chiquet-Ehrismann,

Research,

Maulbeerstrasse

Friedrich 66,

Miescher

CH-4058

Institute

Basel,

for

Biomedical

Switzerland;

e-mail:

[email protected] 

Reinhard Fässler, MPI of Biochemistry, Martinsried, Germany, e-mail: [email protected]



James Fawcett, John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, United Kingdom¸ e-mail: [email protected] 1



Charles ffrench-Constant, MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh BioQuarter, Edinburgh, United Kingdom; e-mail: [email protected]



Magdalena Götz, Helmholtz Zentrum München German Research Center for Environmental Health, Institute for Stem Cell Research, Ludwig-MaximiliansUniversität,

Munich,

Germany,

e-mail:

magdalena.goetz@helmholtz-

muenchen.de 

Christel Herold-Mende, Division of Neurosurgical Research, Department of Neurosurgery, University of Heidelberg, Heidelberg, Germany, e-mail: [email protected]



Wieland Huttner, Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany, e-mail: [email protected]



Sanjay Kumar, Department of Bioengineering, University of California, Berkeley, Berkeley, California, USA, e-mail: [email protected]



Kim Midwood, Kennedy Institute of Rheumatology, University of Oxford; email: [email protected]



James Thomas Rutka, Department of Surgery, University of Toronto, Canada, e-mail: [email protected]



Björn

Scheffler,

Stem

Cell

Pathologies,

Institute

of

Reconstructive

Neurobiology, University of Bonn Medical Center; e-mail: [email protected]

2

Highlights: 

Neural and cancer stem cells (NSCs/CSCs) share a comparable extracellular niche compartment.



Extracellular matrix (ECM) constituents and complementary receptors contribute to NSC/CSC behavior and brain tumor progression.



Tenascin-C and the DSD-1-PG are major functional and supportive niche components of NSCs/CSCs.

Abstract Numerous studies demonstrated that neural stem cells and cancer stem cells (NSCs/CSCs) share several overlapping characteristics such as self-renewal, multipotency and a comparable molecular repertoire. In addition to the intrinsic cellular properties, NSCs/CSCs favor a similar environment to acquire and maintain their characteristics. In the present review, we highlight the shared properties of NSCs and CSCs in regard to their extracellular microenvironment called the NSC/CSC niche. Moreover, we point out that extracellular matrix (ECM) molecules and their complementary receptors influence the behavior of NSCs/CSCs as well as brain tumor progression. Here, we focus on the expression profile and functional importance of the ECM glycoprotein tenascin-C, the chondroitin sulfate proteoglycan DSD-1-PG/phosphacan but also on other important glycoprotein/proteoglycan constituents. Within this review, we specifically concentrate on glioblastoma multiforme (GBM). GBM is the most common malignant brain tumor in adults and is associated with poor prognosis despite intense and aggressive surgical and therapeutic treatment. 3

Recent studies indicate that GBM onset is driven by a subpopulation of CSCs that display self-renewal and recapitulate tumor heterogeneity. Based on the CSC hypothesis the cancer arises just from a small subpopulation of self-sustaining cancer cells with the exclusive ability to self-renew and maintain the tumor. Besides the fundamental stem cell properties of self-renewal and multipotency, GBM stem cells share further molecular characteristics with NSCs, which we would like to review in this article. Keywords: Brain tumor, Chondroitinsulfate proteoglycans, Extracellular matrix, Glioblastoma multiforme, Neural stem cells, Cancer stem cells, Phosphacan, Stem cell niche, Tenascin-C

Contents 1. Introduction Building up tissues during development and maintaining a homeostasis of tissue compartments by replacing cells are main features of stem cells in normal physiological processes. But if these processes are disturbed by pathological influences and cells lose specific control mechanisms tumors can arise that lead to fatal consequences for the organism. In the last decades both fields have been studied intensively. The most obvious similarity of a neural stem cell (NSC) and a cancer stem cell (CSC) is self-renewal. Both cell types achieve a common purpose, which is the production of a huge number of daughter cells. The molecular repertoire inherited in the respective cell popukations reflects these efforts. Several studies reported largely on the intrinsic signaling of stem cells and CSCs. Indeed, stem cells and CSCs share an overlapping collection of growth factor receptors, cell cycle progression genes and transcription factors (Chen et al., 2012, Denysenko et al., 2010, Rebetz et al., 2008).

4

Also, the influence of epigenetic factors in cancer initiation and progression is well established and resembles what is known from stem cells in the developing tissue (Baylin, 2011, Baylin and Jones, 2011, Imamura et al., 2014, MuhChyi et al., 2013, Pujadas and Feinberg, 2012). Glioblastoma multiforme (GBM) represents the most common malignancy of the brain and is associated with a devastating prognosis despite intense and aggressive surgical and therapeutical treatment. It has been shown that the onset of GBM is driven by a subpopulation of cells that display self-renewal and recapitulate tumor heterogeneity: the so-called CSCs (Galli et al., 2004, Singh et al., 2004). Besides the fundamental stem cell properties of self-renewal and multipotency, GBM stem cells share further molecular characteristics with NSCs. In addition to the intrinsic cellular properties, NSCs/CSCs favor a similar environment to acquire and maintain their characteristics. Similarities and differences of NSCs/CSCs in regard to their extracellular microenvironment, called the NSC/CSC niche have also been reported. Extracellular matrix (ECM) molecules as well as their complementary receptors contribute to cell behavior and brain tumor progression. For instance, CD133 (also known as prominin-1) - a marker for NSCs and neural progenitor cells - is the classical glycoprotein for cell sorting to obtain pure CSC cultures from GBM. Additionally, it is known that the expression of CD133 inhibits the differentiation of neuroblastoma cells (Takenobu et al., 2011). Similar to stem cells, CSCs are supported by the tumor microenvironment, which contributes to tumor development and cell behavior (reviewed by) (Filatova et al., 2013). The ECM represents one major part of this “niche”. Basically, the stem cell niche comprises the stem cell itself, its progeny, a variety of supporting cells, the vascular supply, and surrounding ECM components (for review see) (Kazanis and ffrench-Constant, 2011, Rojas-Rios and Gonzalez-Reyes, 2014, Scadden, 2006).

5

Tumor cells exhibit an extensive overexpression of various matrix components to design their own ECM. This matrix in consequence supports the CSCs and tumor cells in their behavior but it is also known that the ECM is involved in alterating the diffusion of therapeutic drugs and other neuroactive molecules. The latter property counts for one of the huge problems in the therapy of glioma (Zamecnik, 2005).

2. The specialized extracellular matrix compartment of the embryonic and adult neural stem cell niche Neuroepithelial cells of the developing neural tube represent veritable neural stem cells (Merkle and Alvarez-Buylla, 2006). They divide symmetrically to expand the number of cells in the early phase of neural development. At the onset of forebrain neurogenesis the neuroepithelial cells are replaced by radial glia cells (RGCs) (Gotz and Huttner, 2005, Kriegstein and Alvarez-Buylla, 2009). RGCs display long processes that stretch the entire thickness of the cortical tissue extending from the ventricular zone (VZ) towards the pial surface. In gyrencephalic primates, so-called outer radial glia cells have been discovered in the outer subventricular zone and are considered responsible for the expansion and folding of the cortex (Fietz et al., 2010, Hansen et al., 2010). In contrast to RGCs, these extend solely a basal process towards the surface of the cortex (Taverna et al., 2014). Neuroepithelial cells and RGCs share common characteristics like the expression of the intermediate filament nestin. However, RGCs express additional glial markers such as the brain lipid binding protein (BLBP), the glutamate aspartate transporter (GLAST), S100 and vimentin (Mori et al., 2005). RGCs mainly divide asymmetrically, undergo selfrenewal and generate a differentiated progeny, namely a neuron or a glia cell. Moreover, RGCs give rise to intermediate progenitor cells of the subventricular zone (SVZ). These divide symmetrically to generate two daughter neurons or two novel

6

intermediate progenitors. This transit amplifying precursor mode increases the number of daughter cells and leads to high cell numbers in a short time frame. The progenitor cells in the developing brain also differentiate into glial cells. In general, oligodendrocytes and astrocytes originate from distinct intermediate progenitor cells. Later during development, RGCs detach from the ventricle, migrate into the cortical plate and convert into glial cells. A minor fraction of RGCs keeps contact with the ventricular surface and leads to neurogenic astrocytes, called type B cells and ependymal cells that constitute the adult SVZ, which represents the adult neural stem cell niche of the brain. Restricted neurogenic regions, where stem cells have been localized during adult stages, share several characteristics with stem cell compartments in the developing tissue. The adult NSC niche consists of slowly dividing astrocytes/type B cells – the late RGC descendants, leptomeningeal cells, blood vessel-forming endothelial cells and the cerebrospinal fluid (Ihrie and AlvarezBuylla, 2011, Riquelme et al., 2008). Slowly dividing type B cells produce transient amplifying type C precursor cells. These type C cells rapidly proliferate and increase the number of descendent lineage cells by the generation of neuroblasts. It is well accepted that the ECM creates a niche compartment for NSCs (reviewed in) (Faissner and Reinhard, 2015, Kazanis and ffrench-Constant, 2011, Theocharidis et al., 2014, Wiese and Faissner, 2015). Here, environmental micro-heterogeneity, termed environmental asymmetry, enforces self-renewal or differentiation properties of NSCs. The interaction of the stem cell itself with surrounding molecules and other cells is integrated via membrane receptors and their consecutive signaling cascades. A variation of interaction partners can result in different lineage decisions of daughter cells arising from a cell division. It is evident that proliferation, differentiation, and migration processes are not only cell-intrinsic decisions but often crucially determined by the cells` environment.

7

Indeed, systematic comparative screenings for a variety of ECM components enriched in the human inner and outer SVZ revealed major expression differences, which suggest that the matrix is crucial for NSC proliferation and maintenance (Fietz et al., 2012, Pollen et al., 2015). Collagens, glycoproteins and proteoglycans as well as integrins interacting with specific growth factors and morphogens keep the stem cells in their proliferative and self-renewing state, or drive them to lineage progression and differentiation. In general, the neural ECM forms a complex interactive network of glycoproteins and proteoglycans. ECM constituents are structural components of the neurogenic stem cell niche as initially reported by Gates and Steindler for the glycoprotein tenascin-C and its complementary ligand and chondroitin sulfate proteoglycan (CSPG) DSD-1PG, called phosphacan (Garwood et al., 1999, Gates et al., 1995, Steindler et al., 1996). Both molecules interact with each other, form regulatory networks with other ECM proteins and play a pivotal role during neural development, plasticity, and regeneration (Garcion et al., 2001, Sirko et al., 2010a, von Holst et al., 2006). During the neurogenic and gliogenic phases of embryonic neural development the glycoprotein tenascin-C and phosphacan are detectable in RGCs in vivo (Garcion, Faissner, 2001, Garcion et al., 2004, Sirko, Akita, 2010a, von Holst, Sirko, 2006) (Figure 1 A-H). Neurospheres generated from embryonic brain tissue express the mRNA of at least 20 tenascin-C isoforms, which are generated by alternative splicing Interestingly, overexpression of the transcription factor and radial glia determinant Pax6 induces the expression of large tenascin-C isoforms (Joester and Faissner, 1999, von Holst et al., 2007). Also on protein level, tenascin-C is detectable in proliferative cortical neurospheres (Figure 1 I-L). The functional importance of tenascin-C in the telencephalic NSC niche is well documented as reviewed recently (Faissner and Reinhard, 2015, Theocharidis, Long, 2014, Wiese and Faissner, 2015)

8

and has also been confirmed for spinal cord NSCs (Karus et al., 2011). Garcion verified that proliferation of NSCs and oligodendrocyte precursors is diminished in the lateral ventricle of tenascin-C knockout mice (Garcion, Faissner, 2001, Garcion, Halilagic, 2004). In a gene trap-based screen it was reported that tenascin-C can regulate proliferation of NSCs via downregulation of the RNA binding protein SAM68 (Moritz et al., 2008). In the adult stem cell niche tenascin-C is expressed by type B cells and localizes in the ependymal layer. Interestingly, an increased proliferation of transit amplifying precursor cells upon epidermal growth factor injection into the lateral ventricle is accompanied by an increased tenascin-C expression (Doetsch et al., 2002). Tenascin-C is not restricted to the NSC niche but also detectable in stem cell niches of other tissues and therefore seems to be a fundamental constituent of various stem cell compartments. Moreover, tenascin-C is also prominently up-regulated in the microenvironment of several tumors (Brosicke and Faissner, 2015, Brosicke et al., 2013, Chiquet-Ehrismann et al., 2014, Midwood and Orend, 2009, Orend and Chiquet-Ehrismann, 2006). Many proteoglycans of the heparan sulfate, chondroitin sulfate, dermatan sulfate or keratan sulfate types are present in the developing and mature neural tissue where they interact with other ECM components as well as with cell surface receptors (Bandtlow and Zimmermann, 2000, Faissner et al., 2006, Gates, Thomas, 1995, Maeda, 2015, Sarrazin et al., 2011). The presentation of morphogens and growth factors is influenced by their interaction with the core proteins or O- or N-linked carbohydrates of the proteoglycans (Iozzo and Schaefer, 2015). They play a role in the regulation of cell motility and axon growth and guidance. In particular, CSPGs of the lectican family such as aggrecan, brevican, neurocan and versican are expressed by neurons, glia cells and NSCs (Abaskharoun et al., 2010, Quirico-Santos et al.,

9

2010). The CSPGs DSD-1-PG/phosphacan and its membrane-bound receptor isoform RPTPβ/ζ were intensively studied with regard to their functional influence on NSC proliferation and differentiation characteristics mediated by a specific carbohydrate motif (Akita et al., 2008, Sirko, Akita, 2010a, Sirko et al., 2007, von Holst, Sirko, 2006). The in vitro culture of NSCs, either growing as free-floating neurospheres or adherently growing on the culture substrate, was used to uncover many functional details of ECM components acting on the cells (Hall et al., 2008, Moritz, Lehmann, 2008, Pollard et al., 2006, Sirko, Akita, 2010a, Sirko, von Holst, 2007, von Holst, Egbers, 2007, von Holst, Sirko, 2006). The crucial importance of ECM molecules in NSC behavior becomes obvious in regard to a variety of genetic modifications. Several ECM components, ECM receptors and their associated downstream signaling molecules were found to be essential for cortical development. In the embryonic as well as in the adult NSC niches high levels of laminin proteins can be found with a variety of isoforms. They represent a huge family of hetero-trimeric ECM glycoproteins that are composed of an α-, β- and γ-subunit and play a major functional role during development. Disruption of laminin expression during development leads to severe malformations or is even lethal (reviewed in) (Theocharidis, Long, 2014, Yurchenco, 2011, Yurchenco and Patton, 2009). For instance, mice lacking both, the laminin β2 and the γ3 chain, exhibit hallmarks of human cobblestone lissencephaly, which includes laminar disruption of the cortex, midline fusion, perturbation of Cajal-Retzius cell distribution, altered RGC morphology and ectopic germinal zones (Radner et al., 2013). Integrins are transmembrane adhesion proteins composed of an α- and a β-subunit functioning as the main receptor family for ECM constituents (D'Abaco and Kaye, 2007, Hynes, 2002). Via a short intracellular domain the signal from the ECM protein

10

bound to the extracellular domain is delivered through the plasma membrane influencing actin cytoskeleton dynamics, proliferation and gene transcription (Bosman and Stamenkovic, 2003, Calderwood, 2004). Disruption of regular integrin signaling influences stem cell homeostasis e.g. enhanced integrin αν/β3 signaling leads to stimulation of basal progenitor proliferation (Stenzel et al., 2014). Cortical lamination defects, which include aberrant anatomical changes such as RGC detachment or basement membrane disruption, were reported in close association with the laminin receptor dystroglycan, perlecan, the laminin γ1 chain, or integrin β1 (Costell et al., 1999, Graus-Porta et al., 2001, Halfter et al., 2002, Moore et al., 2002).

3. Glioma cells under the influence of the extracellular matrix In the field of human brain cancer, glioma is the most frequently diagnosed tumor type, with a median survival time varying from 15 months to 3 years depending on the World Health Organization (WHO) grade (Adamson et al., 2009, Grier and Batchelor, 2006, Krex et al., 2007, Wen and Kesari, 2008). The severest and prevalently detected subtype of glioma is described as GBM (Louis et al., 2007). With max 5 % of patients surviving 3 years after diagnosis this tumor type is the so-called malignant endpoint of glioma diseases (Adamson, Kanu, 2009). The high migratory activity of glioblastoma cells accompanied with a strong invasion rate into surrounding brain areas renders these tumors hardly treatable and dramatically reduces the lifespan of glioma patients (Claes et al., 2007, Lim et al., 2011, Wen and Kesari, 2008). As previously described for non-cancerous tissues, the ECM surrounds also tumor cells, which produce relevant molecules themselves to obtain an appropriate environment. The glioma cells modulate and degrade this matrix to

11

provide favorable preconditions for the migration process (Brosicke and Faissner, 2015). Besides the contribution to migration the ECM plays also an important role in processes like proliferation, survival, polarity and differentiation of cells not only in the embryonic development but also in pathological conditions like tumor growth (Chintala et al., 1996, Rutka et al., 1987a). One of the highly upregulated ECM components in tumor cells and tissues that is strongly associated with stem cell biology is tenascin-C (Brellier and Chiquet-Ehrismann, 2012, Brellier et al., 2009, Brosicke and Faissner, 2015, Brosicke, van Landeghem, 2013, Midwood et al., 2011). It is expressed in tumor cells as well as in tumor blood vessels (Figure 2) with a notable correlation between the amount of tenascin-C and the malignancy of the tumor (Brosicke, van Landeghem, 2013, Kim et al., 2000). Regarding parallels between stem cells and a group of tumor cells that share classical stem cell properties lead to the CSC theory (Rutka et al., 1987b). Even though it has been demonstrated that ECM proteins like tenascin-C, collagens, fibronectin, and laminins are involved in the behavior of cancer cells, especially in the field of tumor angiogenesis defined pathways showing the influence on CSCs similar to stem cells could not be obviously recognized until today (Brosicke, van Landeghem, 2013, Chintala, Gokaslan, 1996, Giordana et al., 1995, Rutka et al., 1987c).

4. The concept of cancer stem cells Tumors consist of a heterogeneous composition of cells. This leads to different areas within the tumor: the stroma, the tumorous vascular system and inflammatory cells (Li et al., 2009). During the last years a small subpopulation of cells attracts increasing interest based on their exclusive ability to maintain the tumor (Galli, Binda, 2004, Singh, Hawkins, 2004). These cells seem to play a pivotal role for the

12

formation and progression of tumors. Based on their similarities of expression patterns and cellular properties to stem cell populations these cells were termed CSCs (Dalerba et al., 2007, Soltysova et al., 2005). They are characterized by their ability to self-renew via symmetric or asymmetric division, the capacity to differentiate into all cell types of the tumor, a high migration potential and their capability to form a tumor phenotypically identical to the tumor of origin (Altaner, 2008, Soltysova, Altanerova, 2005). In 1985, first hints were obtained that cells in acute myeloblastic leukemia, initially considered to be clonogenic, show some heterogeneity (Griffin and Lowenberg, 1986, Sabbath et al., 1985, Sabbath and Griffin, 1985). Subsequently, cells with stem cell-like properties could be described in many other cancer types (Li, Wang, 2009). CSCs found in GBM are thought to be responsible for the main features of astrocytic tumors: insensitivity for mitogens, aneuploidy, dysregulation of the cell cycle, hyperplasia as well as deficiencies in anoikis and contact inhibition (Altaner, 2008). NSCs of the adult SVZ are considered as cells of origin for astrocytomas sharing the characteristics of glioblastoma tumors mentioned before (Lee et al., 2006, Walton et al., 2009). Interestingly, the SVZ is known for a high expression level of the ECM protein tenascin-C, which plays an important role in NSC proliferation and fate restriction (Garcion, Halilagic, 2004, Garwood et al., 2004) as well as in glioma angiogenesis (Brosicke, van Landeghem, 2013, Kim, Bak, 2000) and glioma cell migration (Deryugina and Bourdon, 1996, Hirata et al., 2009). Here, the tenascinC/RPTPβ/ζ receptor system represents an important adhesion system of glial tumor cells (Adamsky et al., 2001). CSCs derived from GBM show a high expression of tenascin-C (Fig. 3), which represents a further similarity to stem cells from the SVZ. Tenascin-C is well known for its influence in stem cell as well as in glioma biology. An additional shared feature is the high expression of the cell surface glycoprotein

13

CD133/prominin-1 in normal stem cells as well as glioma derived CSCs (Brescia et al., 2013). In the adult NSC niche, CD133/GFAP (glial fibrillary acidic protein)-positive cells represent quiescent NSCs. These can be distinguished from activated NSCs by the additional expression of the EGFR (epidermal growth factor)-receptor (Codega et al., 2014). Similarly, CD15 (LewisX) – a marker for pluripotency in embryonic and adult stem cells (Capela and Temple, 2002, 2006, Hennen et al., 2011, Hennen and Faissner, 2012) – could be found in elevated levels in brain CSCs besides CD44, a cell surface protein functioning as a marker for astrocyte-restricted precursor cells (Lu et al., 2012). Additionally the induction of proliferation of NSCs through the transcription factor OLIG2 is also possible in stem cells of glioma origin (Ligon et al., 2007). The identification of CSCs in glioma in this context and the fatal resistance of glioma cells against chemo- and radiotherapy raise a ray of hope to include the population of CSCs into new therapeutic approaches to improve the prognosis and quality of life for glioma patients. To keep their specific characteristics, every type of stem cell needs a particular microenvironment, the so-called niche. One of the most prominent niches of stem cells is the vascular niche (Shen et al., 2008). Tumors have the capacity to build up their own vascular system by generating new blood vessels (Brosicke, van Landeghem, 2013). CSCs often reside in perivascular areas, which indicates that glioma stem cells utilize the vascular niche to remain quiescent and maintain their proliferative capacity (Calabrese et al., 2007). The ECM of various stem cell niches contains the glycoprotein tenascin-C, whose expression level could be directly correlated to the grade of malignancy of glioma and to patients’ prognosis (Chiquet-Ehrismann, Orend, 2014, Kim, Bak, 2000). On the other hand, vascular endothelial growth factor (VEGF) is also highly overexpressed

14

in GBM (Plate et al., 1992). The expression of both proteins is strongly correlated in perivascular zones and the expression as well as the action of VEGF might be regulated by tenascin-C (Behrem et al., 2005, Tanaka et al., 2004). Interestingly, elevated VEGF levels in the adult hippocampal neurogenic niche are accompanied with an increased blood vessel density, an enhanced neurogenesis and increased memory performance (Licht et al., 2011).

5. Molecular similarities of NSCs and CSCs Numerous studies in the last years pointed out that CSCs share molecular similarities with the normal stem cells from their tissue of origin. Besides the already mentioned proteins tenascin-C, nestin, CD133 or CD15, additional factors such as CD34 are expressed by epidermal stem cells and induced squamous cell carcinoma cells (Brescia, Ortensi, 2013, Jin et al., 2013, Ligon, Huillard, 2007, Lu, Chang, 2012, Malanchi et al., 2008). A specific profile of a CD34-positive/CD38-negative cell population was found in acute myeloid leukemia- and hematopoietic stem cells (Civin et al., 1984, Lapidot et al., 1994). Interestingly in this context, both stem cells and CSCs share RNA-binding proteins of the Musashi-family that confer protection to various populations of stem cells and seem involved in oncogenesis, including GBM (Fox et al., 2015). The LewisX carbohydrate/CD15 or stage-specific embryonic antigen 1 (SSEA-1), represents a glycan specifically localized on neural stem/progenitor cells (Capela and Temple, 2002, 2006, Hennen, Czopka, 2011, Hennen and Faissner, 2012, Karus et al., 2013, Solter and Knowles, 1978). In addition, LewisX is also expressed during spinal cord development and even in the adult central nervous system (Karus, Hennen, 2013, Nishihara et al., 2003). This carbohydrate epitope is also described as potential enrichment marker for tumor-initiating cells in glioblastoma (Son et al., 15

2009, Stieber et al., 2014), although very recent findings indicate that CD15-positive and -negative cells generate mixed populations of glioblastoma cells in vitro and the expression of CD15 does not identify a phenotypically or genetically distinct glioblastoma population (Kenney-Herbert et al., 2015). Especially microarray analysis revealed considerable overlap between the gene expression signatures of GBM cells and progenitors of the developing forebrain as well as of adult NSCs (Phillips et al., 2006, Sandberg et al., 2013). Indeed, similarities in the cellular gene expression profile suggest that common signaling pathways act in normal, healthy and malignant NSCs. For instance, Olig2 promotes the proliferation of both neural stem/progenitor cells and GBM cells possibly via the repression of the tumor suppressor p21 (Ligon, Huillard, 2007). Regarding ECM glycoproteins, members of the laminin family were also found within the NSC/CSC niche (Lathia et al., 2007). Laminins are enriched in fractones, specialized ECM structures that contact NSCs (Kerever et al., 2007, Mercier et al., 2002). Laminin supports self-renewal of hippocampal neural stem/progenitor cells (Imbeault et al., 2009). The interaction of laminin and integrin α6 could be shown to be important for the maintenance of NSCs/CSCs (Sun et al., 2008). Interestingly, Lathia et al. could show that the respective laminin α2 is not produced by the glioma stem cell itself but by the non-stem tumor cells (Lathia et al., 2012). CSPGs are highly expressed in the developing embryonic and adult brain as well as in glioma tissue. They have influence on cell motility and axon growth and guidance (Maeda, 2015). Interestingly, in the adult healthy brain, CSPGs exhibit inhibitory effects on stem cell migration. However, in glioma tissue upregulated CSPGs were reported to stimulate stem cell migration (Kearns et al., 2003, Sim et al., 2009). Here, especially chondroitin sulfates were found to be necessary for the fibroblast growth factor-2 induced proliferation and maintenance of NSCs, for epidermal growth factor-

16

dependent migration of their progeny as well as for their differentiation behavior (Purushothaman et al., 2012, Sirko, Akita, 2010a, Sirko et al., 2010b). In the context of CSPGs, sulfotransferase enzymes were identified in RGCs as well as in the adult neurogenic niche and the inhibition of sulfation by chlorate is accompanied with an altered cell cycle progression of spinal cord-derived NSCs (Akita, von Holst, 2008, Karus et al., 2012). The CSPGs brevican and versican also display a prominent expression in glioma. Both molecules form networks with mesenchymal gliomaspecific matrix molecules, which are not detectable in the healthy brain tissue. Brevican is enriched in astrocytoma and in GBM. Recently, it was shown that brevican knockdown contributes to a reduction of late stage glioma tumor aggressiveness (Dwyer et al., 2014). Elevated expression of the CSPG neurocan was observed in glioma cells (Rauch, 2004, Varga et al., 2012). Also, other ECM components e.g. hyaluronic acid, the adhesion molecule CD44 as well as tenascins interact with versican and stimulate brain tumor invasion. The CSPG family member and oligodendrocyte progenitor cell marker neuroglia protein 2 (NG2) was also overexpressed in glioma (Schrappe et al., 1991, Wiranowska et al., 2006). In the healthy brain, mainly progenitor cells express NG2. Within glioma tissue NG2 is associated with other molecules such as collagen VI and CD44. Interestingly, migratory glioma cells express high levels of NG2 in vivo and in vitro whereas nonmigratory cells express low NG2 levels (Galli, Binda, 2004, Lin et al., 1996, Nishiyama et al., 2009, Stallcup and Huang, 2008, Trotter et al., 2010, Wiranowska, Ladd, 2006). In addition, pericytes express high levels of NG2. Based on these findings it was supposed that NG2 might play a functional role in the formation of the glioma microvasculature as well as in glioma progression (Stallcup and Huang, 2008).

17

Heparan sulfate proteoglycans (HSPGs) seem to represent also main constituents of the NSC/CSC niche. The HSPGs perlecan and agrin are also main fractone constituents within the adult neurogenic SVZ niche (Kerever, Schnack, 2007). HSPGs preferentially bind to the basal lamina of blood vessels, to ependymal and endothelial surfaces or to astroglial cells and function as storage/disposal sites for various cytokines and growth factors. For syndecan-2 it was demonstrated that its expression levels increases in brain tumor tissue whereas syndecan expression was not reported in NSCs. Glypican-1 was found to stimulate S-phase entry and DNA replication in human glioma cells and normal astrocytes (Qiao et al., 2013, Theocharis et al., 2010). HSPGs are involved in many processes during development and pathological conditions as well as in homeostasis of cells and tissue. The sulfation pattern of HSPGs is critically regulated and failures in this regulation lead to severe defects, for example in developing organisms. For NSCs it is well known that numerous processes for maintaining the stem cell status (e.g. proliferation, inhibition of differentiation) are mediated by factors that are heparan sulfate-dependent (e.g. fibroblast growth factor and notch) (Xiong et al., 2014). The alteration of HSPGexpression profiles in glial tumors (Su et al., 2006, Watanabe et al., 2006) raises the possibility that the regulation of the CSC features functions in a similar manner indicated above for NSCs. In line with this hypothesis, glypican-1 is frequently overexpressed in human gliomas and enhances cellular FGF-2 signaling (Su, Meyer, 2006). The most important membrane receptors integrating extracellular signals to the intracellular signaling cascade are integrins (Gardiner, 2011). In 2013 Niibori-Nambu et al. detected an increased expression of various integrin subunits during the differentiation process of glioma stem cells. Specifically, ECM-integrin αν-signaling was found to be important for the differentiation of glioma-initiating cells (Niibori-

18

Nambu et al., 2013). The integrin subunit α3 plays a potential role for the motility of glioma stem cells mediated by the ERK1/2-pathway (Nakada et al., 2013). Also integrin α6 seems to be involved in the invasion of glioma stem cells via N-Cadherin and ERK1/2 (Velpula et al., 2012). Integrins are also crucial regulators of the embryonic and adult NSC niche (Porcheri et al., 2014, Stenzel, Wilsch-Brauninger, 2014).

6. Conclusions In the present review we summarized the current knowledge regarding the overlapping functional ECM compartment of NSCs/CSCs (Figure 4). We showed that NSCs/CSCs share several characteristics regarding their molecular repertoire and the interaction with their microenvironment. Nevertheless, it is not clear at which transition step these similarities cease and differences occur because of open questions regarding e.g. their development and cellular origin as well as their proliferation and lineage progression. Future studies should focus on the detailed molecular differences of the NSCs/CSCs niches. Several therapies such as chemotherapy, radiotherapy or surgery target brain tumor tissue and proliferating cancer cells. However, these therapeutic strategies or even combined treatments do not selectively destroy the quiescent CSC population within the nutritive and supportive tumor niche microenvironment. As a consequence CSCs proliferate and lead to tumor recurrence (Denysenko, Gennero, 2010). As reviewed by Wiranowska and Rojiani and as indicated by the review article at hand the targeting of NSC/CSC-enriched regulatory ECM constituents might represent a promising therapeutic approach in future cancer therapy (Wiranowska, 2011). In addition, ECM components might act as useful prognostic marker molecules.

19

Various growth factors, such as the pro-angiogenic factor VEGF, were found to promote the survival of NSCs and are released in the niche of CSCs. The potential benefit of VEGF-blockade in glioma has been comprehensively reviewed (Wiranowska, 2011). Anti-VEGF-therapy restores the abnormal tumor vasculature, reduces vascular permeability and promotes tumor regression (Curry et al., 2015, Field et al., 2015). However, it was reported that CSCs generate endothelial cells, which form new blood vessels that do not respond to the anti-VEGF treatment (RicciVitiani et al., 2010, Wang et al., 2010). Moreover, it was demonstrated that antiVEGF-treated tumor tissue still contains nestin-immunoreactive CSCs despite tumor vascularization was narrowed down (di Tomaso et al., 2011). In line with these findings, further clinical studies unfortunately verified that anti-VEGF treatment failed to improve the overall survival of GBM patients because it is accompanied by an increased tumor infiltration rate (Lai et al., 2011, Takano et al., 2010). In sum, there is an urgent need for the development of new alternative therapeutic strategies that might target the ECM niche compartment of CSCs. Furthermore, the development of new therapeutic strategies regarding ECM constituents might also help to improve stem cell transplantation therapies (Roll and Faissner, 2014, Roll et al., 2012).

Conflict of interest The authors declare that they have no competing financial or personal interests.

Acknowledgements The work of the laboratory gratefully acknowledges funding by the Stem Cell Network North-Rhine Westphalia, the German Research Foundation (DFG: SPP 1109; Fa 159/16-1; SFB 642; SPP 1757, Fa 159/21-1; GRK 736; GSC 98/1), the German

20

Ministry of Education, Research and Technology (BMBF 01GN0503) and the RuhrUniversity (President’s special program call 2008). In addition, we thank Sabine Kindermann, Sandra Lata, Marion Voelzkow and Anke Mommsen for excellent technical assistance. We thank Björn Scheffler for providing the glioma tissue samples.

21

References Abaskharoun M, Bellemare M, Lau E, Margolis RU. Expression of hyaluronan and the hyaluronan-binding proteoglycans neurocan, aggrecan, and versican by neural stem cells and neural cells derived from embryonic stem cells. Brain Res. 2010;1327:6-15. Adamsky K, Schilling J, Garwood J, Faissner A, Peles E. Glial tumor cell adhesion is mediated by binding of the FNIII domain of receptor protein tyrosine phosphatase beta (RPTPbeta) to tenascin C. Oncogene. 2001;20:609-18. Adamson C, Kanu OO, Mehta AI, Di C, Lin N, Mattox AK, et al. Glioblastoma multiforme: a review of where we have been and where we are going. Expert Opin Investig Drugs. 2009;18:1061-83. Akita K, von Holst A, Furukawa Y, Mikami T, Sugahara K, Faissner A. Expression of multiple chondroitin/dermatan sulfotransferases in the neurogenic regions of the embryonic and adult central nervous system implies that complex chondroitin sulfates have a role in neural stem cell maintenance. Stem Cells. 2008;26:798-809. Altaner C. Glioblastoma and stem cells. Neoplasma. 2008;55:369-74. Bandtlow CE, Zimmermann DR. Proteoglycans in the developing brain: new conceptual insights for old proteins. Physiol Rev. 2000;80:1267-90. Baylin SB. Resistance, epigenetics and the cancer ecosystem. Nat Med. 2011;17:288-9. Baylin SB, Jones PA. A decade of exploring the cancer epigenome - biological and translational implications. Nat Rev Cancer. 2011;11:726-34.

22

Behrem S, Zarkovic K, Eskinja N, Jonjic N. Distribution pattern of tenascin-C in glioblastoma: correlation with angiogenesis and tumor cell proliferation. Pathol Oncol Res. 2005;11:229-35. Bosman FT, Stamenkovic I. Functional structure and composition of the extracellular matrix. J Pathol. 2003;200:423-8. Brellier F, Chiquet-Ehrismann R. How do tenascins influence the birth and life of a malignant cell? J Cell Mol Med. 2012;16:32-40. Brellier F, Tucker RP, Chiquet-Ehrismann R. Tenascins and their implications in diseases and tissue mechanics. Scand J Med Sci Sports. 2009;19:511-9. Brescia P, Ortensi B, Fornasari L, Levi D, Broggi G, Pelicci G. CD133 is essential for glioblastoma stem cell maintenance. Stem Cells. 2013;31:857-69. Brosicke N, Faissner A. Role of tenascins in the ECM of gliomas. Cell Adh Migr. 2015;9:131-40. Brosicke N, van Landeghem FK, Scheffler B, Faissner A. Tenascin-C is expressed by human glioma in vivo and shows a strong association with tumor blood vessels. Cell Tissue Res. 2013;354:409-30. Calabrese C, Poppleton H, Kocak M, Hogg TL, Fuller C, Hamner B, et al. A perivascular niche for brain tumor stem cells. Cancer cell. 2007;11:69-82. Calderwood DA. Integrin activation. J Cell Sci. 2004;117:657-66. Campos B, Wan F, Farhadi M, Ernst A, Zeppernick F, Tagscherer KE, et al. Differentiation therapy exerts antitumor effects on stem-like glioma cells. Clin Cancer Res. 2010;16:2715-28.

23

Capela A, Temple S. LeX/ssea-1 is expressed by adult mouse CNS stem cells, identifying them as nonependymal. Neuron. 2002;35:865-75. Capela A, Temple S. LeX is expressed by principle progenitor cells in the embryonic nervous system, is secreted into their environment and binds Wnt-1. Dev Biol. 2006;291:300-13. Chen J, McKay RM, Parada LF. Malignant glioma: lessons from genomics, mouse models, and stem cells. Cell. 2012;149:36-47. Chintala SK, Gokaslan ZL, Go Y, Sawaya R, Nicolson GL, Rao JS. Role of extracellular matrix proteins in regulation of human glioma cell invasion in vitro. Clin Exp Metastasis. 1996;14:358-66. Chiquet-Ehrismann R, Orend G, Chiquet M, Tucker RP, Midwood KS. Tenascins in stem cell niches. Matrix Biol. 2014;37:112-23. Civin CI, Strauss LC, Brovall C, Fackler MJ, Schwartz JF, Shaper JH. Antigenic analysis of hematopoiesis. III. A hematopoietic progenitor cell surface antigen defined by a monoclonal antibody raised against KG-1a cells. J Immunol. 1984;133:157-65. Claes A, Idema AJ, Wesseling P. Diffuse glioma growth: a guerilla war. Acta Neuropathol. 2007;114:443-58. Codega P, Silva-Vargas V, Paul A, Maldonado-Soto AR, Deleo AM, Pastrana E, et al. Prospective identification and purification of quiescent adult neural stem cells from their in vivo niche. Neuron. 2014;82:545-59.

24

Costell M, Gustafsson E, Aszodi A, Morgelin M, Bloch W, Hunziker E, et al. Perlecan maintains the integrity of cartilage and some basement membranes. J Cell Biol. 1999;147:1109-22. Curry RC, Dahiya S, Alva Venur V, Raizer JJ, Ahluwalia MS. Bevacizumab in highgrade gliomas: past, present, and future. Expert Rev Anticancer Ther. 2015;15:38797. D'Abaco GM, Kaye AH. Integrins: molecular determinants of glioma invasion. J Clin Neurosci. 2007;14:1041-8. Dalerba P, Cho RW, Clarke MF. Cancer stem cells: models and concepts. Annu Rev Med. 2007;58:267-84. Denysenko T, Gennero L, Roos MA, Melcarne A, Juenemann C, Faccani G, et al. Glioblastoma cancer stem cells: heterogeneity, microenvironment and related therapeutic strategies. Cell Biochem Funct. 2010;28:343-51. Deryugina EI, Bourdon MA. Tenascin mediates human glioma cell migration and modulates cell migration on fibronectin. J Cell Sci. 1996;109 ( Pt 3):643-52. di Tomaso E, Snuderl M, Kamoun WS, Duda DG, Auluck PK, Fazlollahi L, et al. Glioblastoma recurrence after cediranib therapy in patients: lack of "rebound" revascularization as mode of escape. Cancer Res. 2011;71:19-28. Doetsch F, Petreanu L, Caille I, Garcia-Verdugo JM, Alvarez-Buylla A. EGF converts transit-amplifying neurogenic precursors in the adult brain into multipotent stem cells. Neuron. 2002;36:1021-34. Dwyer CA, Bi WL, Viapiano MS, Matthews RT. Brevican knockdown reduces latestage glioma tumor aggressiveness. Journal of neuro-oncology. 2014;120:63-72. 25

Faissner A, Clement A, Lochter A, Streit A, Mandl C, Schachner M. Isolation of a neural chondroitin sulfate proteoglycan with neurite outgrowth promoting properties. J Cell Biol. 1994;126:783-99. Faissner A, Heck N, Dobbertin A, Garwood J. DSD-1-Proteoglycan/Phosphacan and receptor protein tyrosine phosphatase-beta isoforms during development and regeneration of neural tissues. Adv Exp Med Biol. 2006;557:25-53. Faissner A, Kruse J. J1/tenascin is a repulsive substrate for central nervous system neurons. Neuron. 1990;5:627-37. Faissner A, Reinhard J. The extracellular matrix compartment of neural stem and glial progenitor cells. Glia. 2015;63:1330-49. Field KM, Jordan JT, Wen PY, Rosenthal MA, Reardon DA. Bevacizumab and glioblastoma: scientific review, newly reported updates, and ongoing controversies. Cancer. 2015;121:997-1007. Fietz SA, Kelava I, Vogt J, Wilsch-Brauninger M, Stenzel D, Fish JL, et al. OSVZ progenitors of human and ferret neocortex are epithelial-like and expand by integrin signaling. Nature neuroscience. 2010;13:690-9. Fietz SA, Lachmann R, Brandl H, Kircher M, Samusik N, Schroder R, et al. Transcriptomes of germinal zones of human and mouse fetal neocortex suggest a role of extracellular matrix in progenitor self-renewal. Proc Natl Acad Sci U S A. 2012;109:11836-41. Filatova A, Acker T, Garvalov BK. The cancer stem cell niche(s): the crosstalk between glioma stem cells and their microenvironment. Biochim Biophys Acta. 2013;1830:2496-508.

26

Fox RG, Park FD, Koechlein CS, Kritzik M, Reya T. Musashi Signaling in Stem Cells and Cancer. Annu Rev Cell Dev Biol. 2015;31:249-67. Galli R, Binda E, Orfanelli U, Cipelletti B, Gritti A, De Vitis S, et al. Isolation and characterization

of

tumorigenic,

stem-like

neural

precursors

from

human

glioblastoma. Cancer Res. 2004;64:7011-21. Garcion E, Faissner A, ffrench-Constant C. Knockout mice reveal a contribution of the extracellular matrix molecule tenascin-C to neural precursor proliferation and migration. Development. 2001;128:2485-96. Garcion E, Halilagic A, Faissner A, ffrench-Constant C. Generation of an environmental niche for neural stem cell development by the extracellular matrix molecule tenascin C. Development. 2004;131:3423-32. Gardiner NJ. Integrins and the extracellular matrix: key mediators of development and regeneration of the sensory nervous system. Dev Neurobiol. 2011;71:1054-72. Garwood J, Garcion E, Dobbertin A, Heck N, Calco V, ffrench-Constant C, et al. The extracellular matrix glycoprotein Tenascin-C is expressed by oligodendrocyte precursor cells and required for the regulation of maturation rate, survival and responsiveness to platelet-derived growth factor. Eur J Neurosci. 2004;20:2524-40. Garwood J, Schnadelbach O, Clement A, Schutte K, Bach A, Faissner A. DSD-1proteoglycan is the mouse homolog of phosphacan and displays opposing effects on neurite outgrowth dependent on neuronal lineage. J Neurosci. 1999;19:3888-99. Gates MA, Thomas LB, Howard EM, Laywell ED, Sajin B, Faissner A, et al. Cell and molecular analysis of the developing and adult mouse subventricular zone of the cerebral hemispheres. J Comp Neurol. 1995;361:249-66.

27

Giordana MT, Bradac GB, Pagni CA, Marino S, Attanasio A. Primary diffuse leptomeningeal gliomatosis with anaplastic features. Acta Neurochir (Wien). 1995;132:154-9. Gotz M, Huttner WB. The cell biology of neurogenesis. Nat Rev Mol Cell Biol. 2005;6:777-88. Graus-Porta D, Blaess S, Senften M, Littlewood-Evans A, Damsky C, Huang Z, et al. Beta1-class integrins regulate the development of laminae and folia in the cerebral and cerebellar cortex. Neuron. 2001;31:367-79. Grier JT, Batchelor T. Low-grade gliomas in adults. Oncologist. 2006;11:681-93. Griffin JD, Lowenberg B. Clonogenic cells in acute myeloblastic leukemia. Blood. 1986;68:1185-95. Halfter W, Dong S, Yip YP, Willem M, Mayer U. A critical function of the pial basement membrane in cortical histogenesis. J Neurosci. 2002;22:6029-40. Hall PE, Lathia JD, Caldwell MA, Ffrench-Constant C. Laminin enhances the growth of human neural stem cells in defined culture media. BMC Neurosci. 2008;9:71. Hansen DV, Lui JH, Parker PR, Kriegstein AR. Neurogenic radial glia in the outer subventricular zone of human neocortex. Nature. 2010;464:554-61. Hennen E, Czopka T, Faissner A. Structurally distinct LewisX glycans distinguish subpopulations of neural stem/progenitor cells. J Biol Chem. 2011;286:16321-31. Hennen E, Faissner A. LewisX: a neural stem cell specific glycan? Int J Biochem Cell Biol. 2012;44:830-3.

28

Hirata E, Arakawa Y, Shirahata M, Yamaguchi M, Kishi Y, Okada T, et al. Endogenous tenascin-C enhances glioblastoma invasion with reactive change of surrounding brain tissue. Cancer Sci. 2009;100:1451-9. Hynes RO. Integrins: bidirectional, allosteric signaling machines. Cell. 2002;110:67387. Ihrie RA, Alvarez-Buylla A. Lake-front property: a unique germinal niche by the lateral ventricles of the adult brain. Neuron. 2011;70:674-86. Imamura T, Uesaka M, Nakashima K. Epigenetic setting and reprogramming for neural cell fate determination and differentiation. Philos Trans R Soc Lond B Biol Sci. 2014;369. Imbeault S, Gauvin LG, Toeg HD, Pettit A, Sorbara CD, Migahed L, et al. The extracellular matrix controls gap junction protein expression and function in postnatal hippocampal neural progenitor cells. BMC Neurosci. 2009;10:13. Iozzo RV, Schaefer L. Proteoglycan form and function: A comprehensive nomenclature of proteoglycans. Matrix Biol. 2015. Jin X, Jung JE, Beck S, Kim H. Cell surface Nestin is a biomarker for glioma stem cells. Biochem Biophys Res Commun. 2013;433:496-501. Joester A, Faissner A. Evidence for combinatorial variability of tenascin-C isoforms and developmental regulation in the mouse central nervous system. J Biol Chem. 1999;274:17144-51. Karus M, Denecke B, ffrench-Constant C, Wiese S, Faissner A. The extracellular matrix molecule tenascin C modulates expression levels and territories of key

29

patterning

genes

during

spinal

cord

astrocyte

specification.

Development.

2011;138:5321-31. Karus M, Hennen E, Safina D, Klausmeyer A, Wiese S, Faissner A. Differential expression

of

micro-heterogeneous LewisX-type

glycans in

the

stem

cell

compartment of the developing mouse spinal cord. Neurochemical research. 2013;38:1285-94. Karus M, Samtleben S, Busse C, Tsai T, Dietzel ID, Faissner A, et al. Normal sulfation levels regulate spinal cord neural precursor cell proliferation and differentiation. Neural development. 2012;7:20. Kazanis I, ffrench-Constant C. Extracellular matrix and the neural stem cell niche. Dev Neurobiol. 2011;71:1006-17. Kearns SM, Laywell ED, Kukekov VK, Steindler DA. Extracellular matrix effects on neurosphere cell motility. Exp Neurol. 2003;182:240-4. Kenney-Herbert E, Al-Mayhani T, Piccirillo SG, Fowler J, Spiteri I, Jones P, et al. CD15 Expression Does Not Identify a Phenotypically or Genetically Distinct Glioblastoma Population. Stem Cells Transl Med. 2015;4:822-31. Kerever A, Schnack J, Vellinga D, Ichikawa N, Moon C, Arikawa-Hirasawa E, et al. Novel extracellular matrix structures in the neural stem cell niche capture the neurogenic factor fibroblast growth factor 2 from the extracellular milieu. Stem Cells. 2007;25:2146-57. Kim CH, Bak KH, Kim YS, Kim JM, Ko Y, Oh SJ, et al. Expression of tenascin-C in astrocytic tumors: its relevance to proliferation and angiogenesis. Surg Neurol. 2000;54:235-40.

30

Krex D, Klink B, Hartmann C, von Deimling A, Pietsch T, Simon M, et al. Long-term survival with glioblastoma multiforme. Brain. 2007;130:2596-606. Kriegstein A, Alvarez-Buylla A. The glial nature of embryonic and adult neural stem cells. Annu Rev Neurosci. 2009;32:149-84. Lai A, Tran A, Nghiemphu PL, Pope WB, Solis OE, Selch M, et al. Phase II study of bevacizumab plus temozolomide during and after radiation therapy for patients with newly diagnosed glioblastoma multiforme. J Clin Oncol. 2011;29:142-8. Lapidot T, Sirard C, Vormoor J, Murdoch B, Hoang T, Caceres-Cortes J, et al. A cell initiating human acute myeloid leukaemia after transplantation into SCID mice. Nature. 1994;367:645-8. Lathia JD, Li M, Hall PE, Gallagher J, Hale JS, Wu Q, et al. Laminin alpha 2 enables glioblastoma stem cell growth. Annals of neurology. 2012;72:766-78. Lathia JD, Patton B, Eckley DM, Magnus T, Mughal MR, Sasaki T, et al. Patterns of laminins and integrins in the embryonic ventricular zone of the CNS. J Comp Neurol. 2007;505:630-43. Lee J, Kotliarova S, Kotliarov Y, Li A, Su Q, Donin NM, et al. Tumor stem cells derived from glioblastomas cultured in bFGF and EGF more closely mirror the phenotype and genotype of primary tumors than do serum-cultured cell lines. Cancer Cell. 2006;9:391-403. Li Z, Wang H, Eyler CE, Hjelmeland AB, Rich JN. Turning cancer stem cells inside out: an exploration of glioma stem cell signaling pathways. J Biol Chem. 2009;284:16705-9.

31

Licht T, Goshen I, Avital A, Kreisel T, Zubedat S, Eavri R, et al. Reversible modulations of neuronal plasticity by VEGF. Proc Natl Acad Sci U S A. 2011;108:5081-6. Ligon KL, Huillard E, Mehta S, Kesari S, Liu H, Alberta JA, et al. Olig2-regulated lineage-restricted pathway controls replication competence in neural stem cells and malignant glioma. Neuron. 2007;53:503-17. Lim SK, Llaguno SR, McKay RM, Parada LF. Glioblastoma multiforme: a perspective on recent findings in human cancer and mouse models. BMB Rep. 2011;44:158-64. Lin XH, Grako KA, Burg MA, Stallcup WB. NG2 proteoglycan and the actin-binding protein fascin define separate populations of actin-containing filopodia and lamellipodia during cell spreading and migration. Mol Biol Cell. 1996;7:1977-93. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK, Burger PC, Jouvet A, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol. 2007;114:97-109. Lu KV, Chang JP, Parachoniak CA, Pandika MM, Aghi MK, Meyronet D, et al. VEGF inhibits tumor cell invasion and mesenchymal transition through a MET/VEGFR2 complex. Cancer cell. 2012;22:21-35. Maeda N. Proteoglycans and neuronal migration in the cerebral cortex during development and disease. Frontiers in neuroscience. 2015;9:98. Malanchi I, Peinado H, Kassen D, Hussenet T, Metzger D, Chambon P, et al. Cutaneous cancer stem cell maintenance is dependent on beta-catenin signalling. Nature. 2008;452:650-3.

32

Mercier F, Kitasako JT, Hatton GI. Anatomy of the brain neurogenic zones revisited: fractones and the fibroblast/macrophage network. J Comp Neurol. 2002;451:170-88. Merkle FT, Alvarez-Buylla A. Neural stem cells in mammalian development. Curr Opin Cell Biol. 2006;18:704-9. Midwood KS, Hussenet T, Langlois B, Orend G. Advances in tenascin-C biology. Cell Mol Life Sci. 2011;68:3175-99. Midwood KS, Orend G. The role of tenascin-C in tissue injury and tumorigenesis. J Cell Commun Signal. 2009;3:287-310. Moore SA, Saito F, Chen J, Michele DE, Henry MD, Messing A, et al. Deletion of brain dystroglycan recapitulates aspects of congenital muscular dystrophy. Nature. 2002;418:422-5. Mori T, Buffo A, Gotz M. The novel roles of glial cells revisited: the contribution of radial glia and astrocytes to neurogenesis. Curr Top Dev Biol. 2005;69:67-99. Moritz S, Lehmann S, Faissner A, von Holst A. An induction gene trap screen in neural stem cells reveals an instructive function of the niche and identifies the splicing regulator sam68 as a tenascin-C-regulated target gene. Stem Cells. 2008;26:2321-31. MuhChyi C, Juliandi B, Matsuda T, Nakashima K. Epigenetic regulation of neural stem cell fate during corticogenesis. Int J Dev Neurosci. 2013;31:424-33. Nakada M, Nambu E, Furuyama N, Yoshida Y, Takino T, Hayashi Y, et al. Integrin alpha3 is overexpressed in glioma stem-like cells and promotes invasion. British journal of cancer. 2013;108:2516-24.

33

Niibori-Nambu A, Midorikawa U, Mizuguchi S, Hide T, Nagai M, Komohara Y, et al. Glioma initiating cells form a differentiation niche via the induction of extracellular matrices and integrin alphaV. PLoS One. 2013;8:e59558. Nishihara S, Iwasaki H, Nakajima K, Togayachi A, Ikehara Y, Kudo T, et al. Alpha1,3fucosyltransferase IX (Fut9) determines Lewis X expression in brain. Glycobiology. 2003;13:445-55. Nishiyama A, Komitova M, Suzuki R, Zhu X. Polydendrocytes (NG2 cells): multifunctional cells with lineage plasticity. Nat Rev Neurosci. 2009;10:9-22. Orend G, Chiquet-Ehrismann R. Tenascin-C induced signaling in cancer. Cancer Lett. 2006;244:143-63. Phillips HS, Kharbanda S, Chen R, Forrest WF, Soriano RH, Wu TD, et al. Molecular subclasses of high-grade glioma predict prognosis, delineate a pattern of disease progression, and resemble stages in neurogenesis. Cancer Cell. 2006;9:157-73. Plate KH, Breier G, Weich HA, Risau W. Vascular endothelial growth factor is a potential

tumour

angiogenesis

factor

in

human

gliomas

in

vivo.

Nature.

1992;359:845-8. Pollard SM, Conti L, Sun Y, Goffredo D, Smith A. Adherent neural stem (NS) cells from fetal and adult forebrain. Cereb Cortex. 2006;16 Suppl 1:i112-20. Pollen AA, Nowakowski TJ, Chen J, Retallack H, Sandoval-Espinosa C, Nicholas CR, et al. Molecular identity of human outer radial glia during cortical development. Cell. 2015;163:55-67. Porcheri C, Suter U, Jessberger S. Dissecting integrin-dependent regulation of neural stem cell proliferation in the adult brain. J Neurosci. 2014;34:5222-32. 34

Pujadas E, Feinberg AP. Regulated noise in the epigenetic landscape of development and disease. Cell. 2012;148:1123-31. Purushothaman A, Sugahara K, Faissner A. Chondroitin sulfate "wobble motifs" modulate maintenance and differentiation of neural stem cells and their progeny. J Biol Chem. 2012;287:2935-42. Qiao D, Meyer K, Friedl A. Glypican 1 stimulates S phase entry and DNA replication in human glioma cells and normal astrocytes. Mol Cell Biol. 2013;33:4408-21. Quirico-Santos T, Fonseca CO, Lagrota-Candido J. Brain sweet brain: importance of sugars

for

the

cerebral

microenvironment

and

tumor

development.

Arq

Neuropsiquiatr. 2010;68:799-803. Radner S, Banos C, Bachay G, Li YN, Hunter DD, Brunken WJ, et al. beta2 and gamma3 laminins are critical cortical basement membrane components: ablation of Lamb2 and Lamc3 genes disrupts cortical lamination and produces dysplasia. Dev Neurobiol. 2013;73:209-29. Rauch U. Extracellular matrix components associated with remodeling processes in brain. Cell Mol Life Sci. 2004;61:2031-45. Rebetz J, Tian D, Persson A, Widegren B, Salford LG, Englund E, et al. Glial progenitor-like phenotype in low-grade glioma and enhanced CD133-expression and neuronal lineage differentiation potential in high-grade glioma. PLoS One. 2008;3:e1936. Ricci-Vitiani L, Pallini R, Biffoni M, Todaro M, Invernici G, Cenci T, et al. Tumour vascularization via endothelial differentiation of glioblastoma stem-like cells. Nature. 2010;468:824-8.

35

Riquelme PA, Drapeau E, Doetsch F. Brain micro-ecologies: neural stem cell niches in the adult mammalian brain. Philos Trans R Soc Lond B Biol Sci. 2008;363:123-37. Rojas-Rios P, Gonzalez-Reyes A. Concise review: The plasticity of stem cell niches: a general property behind tissue homeostasis and repair. Stem Cells. 2014;32:852-9. Roll L, Faissner A. Influence of the extracellular matrix on endogenous and transplanted stem cells after brain damage. Front Cell Neurosci. 2014;8:219. Roll L, Mittmann T, Eysel UT, Faissner A. The laser lesion of the mouse visual cortex as a model to study neural extracellular matrix remodeling during degeneration, regeneration and plasticity of the CNS. Cell Tissue Res. 2012;349:133-45. Rutka JT, Dougherty DV, Giblin JR, Edwards MS, McCulloch JR, Rosenblum ML. Growth of a medulloblastoma on normal leptomeningeal cells in culture: interaction of tumor cells and normal cells. Neurosurgery. 1987a;21:872-8. Rutka JT, Giblin JR, Apodaca G, DeArmond SJ, Stern R, Rosenblum ML. Inhibition of growth and induction of differentiation in a malignant human glioma cell line by normal leptomeningeal extracellular matrix proteins. Cancer Res. 1987b;47:3515-22. Rutka JT, Myatt CA, Giblin JR, Davis RL, Rosenblum ML. Distribution of extracellular matrix proteins in primary human brain tumours: an immunohistochemical analysis. Can J Neurol Sci. 1987c;14:25-30. Sabbath KD, Ball ED, Larcom P, Davis RB, Griffin JD. Heterogeneity of clonogenic cells in acute myeloblastic leukemia. J Clin Invest. 1985;75:746-53. Sabbath KD, Griffin JD. Clonogenic cells in acute myeloblastic leukaemia. Scand J Haematol. 1985;35:251-6.

36

Sandberg CJ, Altschuler G, Jeong J, Stromme KK, Stangeland B, Murrell W, et al. Comparison of glioma stem cells to neural stem cells from the adult human brain identifies dysregulated Wnt- signaling and a fingerprint associated with clinical outcome. Exp Cell Res. 2013;319:2230-43. Sarrazin S, Lamanna WC, Esko JD. Heparan sulfate proteoglycans. Cold Spring Harb Perspect Biol. 2011;3. Scadden DT. The stem-cell niche as an entity of action. Nature. 2006;441:1075-9. Schrappe M, Klier FG, Spiro RC, Waltz TA, Reisfeld RA, Gladson CL. Correlation of chondroitin sulfate proteoglycan expression on proliferating brain capillary endothelial cells with the malignant phenotype of astroglial cells. Cancer Res. 1991;51:4986-93. Shen Q, Wang Y, Kokovay E, Lin G, Chuang SM, Goderie SK, et al. Adult SVZ stem cells lie in a vascular niche: a quantitative analysis of niche cell-cell interactions. Cell Stem Cell. 2008;3:289-300. Sim H, Hu B, Viapiano MS. Reduced expression of the hyaluronan and proteoglycan link proteins in malignant gliomas. J Biol Chem. 2009;284:26547-56. Singh SK, Hawkins C, Clarke ID, Squire JA, Bayani J, Hide T, et al. Identification of human brain tumour initiating cells. Nature. 2004;432:396-401. Sirko S, Akita K, Von Holst A, Faissner A. Structural and functional analysis of chondroitin sulfate proteoglycans in the neural stem cell niche. Methods Enzymol. 2010a;479:37-71. Sirko S, von Holst A, Weber A, Wizenmann A, Theocharidis U, Gotz M, et al. Chondroitin

sulfates

are

required

for

37

fibroblast

growth

factor-2-dependent

proliferation and maintenance in neural stem cells and for epidermal growth factordependent migration of their progeny. Stem Cells. 2010b;28:775-87. Sirko S, von Holst A, Wizenmann A, Gotz M, Faissner A. Chondroitin sulfate glycosaminoglycans

control

proliferation,

radial

glia

cell

differentiation

and

neurogenesis in neural stem/progenitor cells. Development. 2007;134:2727-38. Solter D, Knowles BB. Monoclonal antibody defining a stage-specific mouse embryonic antigen (SSEA-1). Proc Natl Acad Sci U S A. 1978;75:5565-9. Soltysova A, Altanerova V, Altaner C. Cancer stem cells. Neoplasma. 2005;52:43540. Son MJ, Woolard K, Nam DH, Lee J, Fine HA. SSEA-1 is an enrichment marker for tumor-initiating cells in human glioblastoma. Cell Stem Cell. 2009;4:440-52. Stallcup WB, Huang FJ. A role for the NG2 proteoglycan in glioma progression. Cell Adh Migr. 2008;2:192-201. Steindler DA, Kadrie T, Fillmore H, Thomas LB. The subependymal zone: "brain marrow". Prog Brain Res. 1996;108:349-63. Stenzel D, Wilsch-Brauninger M, Wong FK, Heuer H, Huttner WB. Integrin alphavbeta3 and thyroid hormones promote expansion of progenitors in embryonic neocortex. Development. 2014;141:795-806. Stieber D, Golebiewska A, Evers L, Lenkiewicz E, Brons NH, Nicot N, et al. Glioblastomas are composed of

genetically divergent

clones with

distinct

tumourigenic potential and variable stem cell-associated phenotypes. Acta Neuropathol. 2014;127:203-19.

38

Su G, Meyer K, Nandini CD, Qiao D, Salamat S, Friedl A. Glypican-1 is frequently overexpressed in human gliomas and enhances FGF-2 signaling in glioma cells. Am J Pathol. 2006;168:2014-26. Sun Y, Pollard S, Conti L, Toselli M, Biella G, Parkin G, et al. Long-term tripotent differentiation capacity of human neural stem (NS) cells in adherent culture. Mol Cell Neurosci. 2008;38:245-58. Takano S, Mashiko R, Osuka S, Ishikawa E, Ohneda O, Matsumura A. Detection of failure of bevacizumab treatment for malignant glioma based on urinary matrix metalloproteinase activity. Brain Tumor Pathol. 2010;27:89-94. Takenobu H, Shimozato O, Nakamura T, Ochiai H, Yamaguchi Y, Ohira M, et al. CD133

suppresses

neuroblastoma

cell

differentiation

via

signal

pathway

modification. Oncogene. 2011;30:97-105. Tanaka K, Hiraiwa N, Hashimoto H, Yamazaki Y, Kusakabe M. Tenascin-C regulates angiogenesis in tumor through the regulation of vascular endothelial growth factor expression. Int J Cancer. 2004;108:31-40. Taverna E, Gotz M, Huttner WB. The cell biology of neurogenesis: toward an understanding of the development and evolution of the neocortex. Annu Rev Cell Dev Biol. 2014;30:465-502. Theocharidis U, Long K, ffrench-Constant C, Faissner A. Regulation of the neural stem cell compartment by extracellular matrix constituents. Prog Brain Res. 2014;214:3-28.

39

Theocharis AD, Skandalis SS, Tzanakakis GN, Karamanos NK. Proteoglycans in health and disease: novel roles for proteoglycans in malignancy and their pharmacological targeting. The FEBS journal. 2010;277:3904-23. Trotter J, Karram K, Nishiyama A. NG2 cells: Properties, progeny and origin. Brain research reviews. 2010;63:72-82. Varga I, Hutoczki G, Szemcsak CD, Zahuczky G, Toth J, Adamecz Z, et al. Brevican, neurocan, tenascin-C and versican are mainly responsible for the invasiveness of low-grade astrocytoma. Pathol Oncol Res. 2012;18:413-20. Velpula KK, Rehman AA, Chelluboina B, Dasari VR, Gondi CS, Rao JS, et al. Glioma stem cell invasion through regulation of the interconnected ERK, integrin alpha6 and N-cadherin signaling pathway. Cellular signalling. 2012;24:2076-84. von Holst A, Egbers U, Prochiantz A, Faissner A. Neural stem/progenitor cells express 20 tenascin C isoforms that are differentially regulated by Pax6. J Biol Chem. 2007;282:9172-81. von Holst A, Sirko S, Faissner A. The unique 473HD-Chondroitinsulfate epitope is expressed by radial glia and involved in neural precursor cell proliferation. J Neurosci. 2006;26:4082-94. Walton NM, Snyder GE, Park D, Kobeissy F, Scheffler B, Steindler DA. Gliotypic neural

stem

cells

transiently

adopt

tumorigenic

properties

during

normal

differentiation. Stem Cells. 2009;27:280-9. Wang R, Chadalavada K, Wilshire J, Kowalik U, Hovinga KE, Geber A, et al. Glioblastoma stem-like cells give rise to tumour endothelium. Nature. 2010;468:82933.

40

Watanabe A, Mabuchi T, Satoh E, Furuya K, Zhang L, Maeda S, et al. Expression of syndecans, a heparan sulfate proteoglycan, in malignant gliomas: participation of nuclear factor-kappaB in upregulation of syndecan-1 expression. Journal of neurooncology. 2006;77:25-32. Wen PY, Kesari S. Malignant gliomas in adults. N Engl J Med. 2008;359:492-507. Wiese S, Faissner A. The role of extracellular matrix in spinal cord development. Exp Neurol. 2015. Wiranowska M, Ladd S, Smith SR, Gottschall PE. CD44 adhesion molecule and neuro-glial proteoglycan NG2 as invasive markers of glioma. Brain Cell Biol. 2006;35:159-72. Wiranowska MR, M.V. Extracellular Matrix Microenvironment in Glioma Progression. In: Ghosh DA, editor. Glioma - Exploring Its Biology and Practical Relevance: InTech; 2011. Xiong A, Kundu S, Forsberg-Nilsson K. Heparan sulfate in the regulation of neural differentiation and glioma development. The FEBS journal. 2014;281:4993-5008. Yurchenco PD. Basement membranes: cell scaffoldings and signaling platforms. Cold Spring Harb Perspect Biol. 2011;3. Yurchenco PD, Patton BL. Developmental and pathogenic mechanisms of basement membrane assembly. Curr Pharm Des. 2009;15:1277-94. Zamecnik J. The extracellular space and matrix of gliomas. Acta Neuropathol. 2005;110:435-42.

41

Figure Legends Figure 1: Immunohistochemical detection of the ECM glycoprotein Tenascin-C in the embryonic cortical stem cell niche. A) and E) TN-C expression (green channel), as detected by the pAbKaf14, is co-localized with Nestin-immunoreactive radial glia cells (red channel; B) and F)) in the E15 mouse cortex and GE as shown in the merged figures (D) and H)). Moreover, as shown in I), TN-C is detectable in proliferative BrdU-positive (J)) cortical mouse neurospheres. L) Merge of I) and J). Nuclear TO-PRO-3 staining is shown in C), G) and K). The polyclonal antibodies have been described elsewhere (Faissner and Kruse, 1990). Abbreviations: CP = cortical plate; GE = ganglionic eminence; TN-C = Tenascin-C; pAb = polyclonal antibody; SP = subplate; SVZ = subventricular zone; VZ = ventricular zone. Scale bars: D) and H) = 50 μm; L) = 100 μm.

Figure 2: Human species of Glioblastoma multiforme immunohistochemically stained for the ECM glycoprotein Tenascin-C by using various specific antibodies. A) and B) The distribution of TN-C in highly vascularized tumor tissue was visualized using the pAbKaf14. C) and D) TN-C encompassing tumor BVs stained with the mAb19H12TN-C and the mAb608TN-C, respectively. Single cells within tumor tissue express high levels of TN-C as demonstrated by the mAb606TNC E) and the mAb20A1TN-C F). The mAbs have been recently characterized (Brosicke, van Landeghem, 2013). Abbreviations: BVs = blood vessels; TN-C = Tenascin-C; mAb = monoclonal antibody; pAb = polyclonal antibody. Scale bars: A) and B) = 500 μm; C) - F) = 50 μm.

Figure 3: Immunocytochemical detection of Tenascin-C and the DSD-1 epitope in the glioma stem cell line NCH421k. A) and B) TN-C expression in the glioma

42

stem cell line NCH421k was verified by the pAbKaf14 (green channel) and the mAb608TN-C (red channel). The NCH421k cell line has been described (Campos et al., 2010). Co-localization of both TN-C antibodies is depicted in C). The DSD-1 chondroitin sulfate epitope recognized by the mAb 473HD (D; green channel) is also highly expressed by pluripotent Oct3/4-immunoreactive NCH421k glioma stem cells (E; red channel). A description of the mAb 473HD has been published (Faissner et al., 1994). F) Merge of D) and E). The blue channel represents nuclear TO-PRO-3 staining. Abbreviations: TN-C = Tenascin-C; mAb = monoclonal antibody; pAb = polyclonal antibody. Scale bars: C) and F) = 100 μm.

Figure 4: The extracellular matrisome of neural and cancer stem cells. The scheme depicts the shared (white ellipses) versus exclusive (red ellipses) extracellular matrisome and the corresponding receptors expressed by NSCs/CSCs. Most ECM molecules are part of the neural as well as of the cancerous stem cell niche. Only few ECM constituents have uniquely been reported either in NSCs or CSCs (e.g. aggrecan and syndecan).

43

Fig 1

Fig 2

44

Fig 3

45

Fig 4

46