Cancer stem cells in the mammalian central nervous system

CD57 defines a novel cancer stem cell that drive invasion of diffuse pediatric-type high grade gliomas

BACKGROUND

Diffuse invasion remains a primary cause of treatment failure in pediatric high-grade glioma (pHGG). Identifying cellular driver(s) of pHGG invasion is needed for anti-invasion therapies.

METHODS

Ten highly invasive patient-derived orthotopic xenograft (PDOX) models of pHGG were subjected to isolation of matching pairs of invasive (HGGINV) and tumor core (HGGTC) cells.

RESULTS

pHGGINV cells were intrinsically more invasive than their matching pHGGTC cells. CSC profiling revealed co-positivity of CD133 and CD57 and identified CD57+CD133- cells as the most abundant CSCs in the invasive front. In addition to discovering a new order of self-renewal capacities, i.e., CD57+CD133- > CD57+CD133+ > CD57-CD133+ > CD57-CD133- cells, we showed that CSC hierarchy was impacted by their spatial locations, and the highest self-renewal capacities were found in CD57+CD133- cells in the HGGINV front (HGGINV/CD57+CD133- cells) mediated by NANOG and SHH over-expression. Direct implantation of CD57+ (CD57+/CD133- and CD57+/CD133+) cells into mouse brains reconstituted diffusely invasion, while depleting CD57+ cells (i.e., CD57-CD133+) abrogated pHGG invasion.

CONCLUSION

We revealed significantly increased invasive capacities in HGGINV cells, confirmed CD57 as a novel glioma stem cell marker, identified CD57+CD133- and CD57+CD133+ cells as a new cellular driver of pHGG invasion and suggested a new dual-mode hierarchy of HGG stem cells.

The Subventricular Zone in Glioblastoma: Genesis, Maintenance, and Modeling

Glioblastoma (GBM) is a malignant tumor with a median survival rate of 15-16 months with standard care; however, cases of successful treatment offer hope that an enhanced understanding of the pathology will improve the prognosis. The cell of origin in GBM remains controversial. Recent evidence has implicated stem cells as cells of origin in many cancers. Neural stem/precursor cells (NSCs) are being evaluated as potential initiators of GBM tumorigenesis. The NSCs in the subventricular zone (SVZ) have demonstrated similar molecular profiles and share several distinctive characteristics to proliferative glioblastoma stem cells (GSCs) in GBM. Genomic and proteomic studies comparing the SVZ and GBM support the hypothesis that the tumor cells and SVZ cells are related. Animal models corroborate this connection, demonstrating migratory patterns from the SVZ to the tumor. Along with laboratory and animal research, clinical studies have demonstrated improved progression-free survival in patients with GBM after radiation to the ipsilateral SVZ. Additionally, key genetic mutations in GBM for the most part carry regulatory roles in the SVZ as well. An exciting avenue towards SVZ modeling and determining its role in gliomagenesis in the human context is human brain organoids. Here we comprehensively discuss and review the role of the SVZ in GBM genesis, maintenance, and modeling.

PDGFRα depletion attenuates glioblastoma stem cells features by modulation of STAT3, RB1 and multiple oncogenic signals

Platelet derived growth factor receptors (PDGFRs) play an important role in tumor pathogenesis, and they are frequently overexpressed in glioblastoma (GBM). Earlier we have shown a higher protein expression of PDGFR isoforms (α and β) in peritumoral-tissue derived cancer stem cells (p-CSC) than in tumor core (c-CSC) of several GBM affected patients. In the current study, in order to assess the activity of PDGFRα/PDGF-AA signaling axis, we performed time course experiments to monitor the effects of exogenous PDGF-AA on the expression of downstream target genes in c-CSC vs p-CSC. Interestingly, in p-CSC we detected the upregulation of Y705-phosphorylated Stat3, concurrent with a decrement of Rb1 protein in its active state, within minutes of PDGF-AA addition. This finding prompted us to elucidate the role of PDGFRα in self-renewal, invasion and differentiation in p-CSC by using short hairpin RNA depletion of PDGFRα expression. Notably, in PDGFRα-depleted cells, protein analysis revealed attenuation of stemness-related and glial markers expression, alongside early activation of the neuronal marker MAP2a/b that correlated with the induction of tumor suppressor Rb1. The in vitro reduction of the invasive capacity of PDGFRα-depleted CSC as compared to parental cells correlated with the downmodulation of markers of epithelial-mesenchymal transition phenotype and angiogenesis. Surprisingly, we observed the induction of anti-apoptotic proteins and compensatory oncogenic signals such as EDN1, EDNRB, PRKCB1, PDGF-C and PDGF-D. To conclude, we hypothesize that the newly discovered PDGFRα/Stat3/Rb1 regulatory axis might represent a potential therapeutic target for GBM treatment.

Functional expression of calcium-permeable canonical transient receptor potential 4-containing channels promotes migration of medulloblastoma cells

KEY POINTS

The proton sensing ovarian cancer G protein coupled receptor 1 (OGR1, aka GPR68) promotes expression of the canonical transient receptor potential channel subunit TRPC4 in normal and transformed cerebellar granule precursor (DAOY) cells. OGR1 and TRPC4 are prominently expressed in healthy cerebellar tissue throughout postnatal development and in primary cerebellar medulloblastoma tissues. Activation of TRPC4-containing channels in DAOY cells, but not non-transformed granule precursor cells, results in prominent increases in [Ca2+ ]i and promotes cell motility in wound healing and transwell migration assays. Medulloblastoma cells not arising from granule precursor cells show neither prominent rises in [Ca2+ ]i nor enhanced motility in response to TRPC4 activation unless they overexpressTRPC4. Our results suggest that OGR1 enhances expression of TRPC4-containing channels that contribute to enhanced invasion and metastasis of granule precursor-derived human medulloblastoma.

ABSTRACT

Aberrant intracellular Ca2+ signalling contributes to the formation and progression of a range of distinct pathologies including cancers. Rises in intracellular Ca2+ concentration occur in response to Ca2+ influx through plasma membrane channels and Ca2+ release from intracellular Ca2+ stores, which can be mobilized in response to activation of cell surface receptors. Ovarian cancer G protein coupled receptor 1 (OGR1, aka GPR68) is a proton-sensing Gq -coupled receptor that is most highly expressed in cerebellum. Medulloblastoma (MB) is the most common paediatric brain tumour that arises from cerebellar precursor cells. We found that nine distinct human MB samples all expressed OGR1. In both normal granule cells and the transformed human cerebellar granule cell line DAOY, OGR1 promoted expression of the proton-potentiated member of the canonical transient receptor potential (TRPC) channel family, TRPC4. Consistent with a role for TRPC4 in MB, we found that all MB samples also expressed TRPC4. In DAOY cells, activation of TRPC4-containing channels resulted in large Ca2+ influx and enhanced migration, while in normal cerebellar granule (precursor) cells and MB cells not derived from granule precursors, only small levels of Ca2+ influx and no enhanced migration were observed. Our results suggest that OGR1-dependent increases in TRPC4 expression may favour formation of highly Ca2+ -permeable TRPC4-containing channels that promote transformed granule cell migration. Increased motility of cancer cells is a prerequisite for cancer invasion and metastasis, and our findings may point towards a key role for TRPC4 in progression of certain types of MB.

Transmembrane protein CD9 is glioblastoma biomarker, relevant for maintenance of glioblastoma stem cells

The cancer stem cell model suggests that glioblastomas contain a subpopulation of stem-like tumor cells that reproduce themselves to sustain tumor growth. Targeting these cells thus represents a novel treatment strategy and therefore more specific markers that characterize glioblastoma stem cells need to be identified. In the present study, we performed transcriptomic analysis of glioblastoma tissues compared to normal brain tissues revealing sensible up-regulation of CD9 gene. CD9 encodes the transmembrane protein tetraspanin which is involved in tumor cell invasion, apoptosis and resistance to chemotherapy. Using the public REMBRANDT database for brain tumors, we confirmed the prognostic value of CD9, whereby a more than two fold up-regulation correlates with shorter patient survival. We validated CD9 gene and protein expression showing selective up-regulation in glioblastoma stem cells isolated from primary biopsies and in primary organotypic glioblastoma spheroids as well as in U87-MG and U373 glioblastoma cell lines. In contrast, no or low CD9 gene expression was observed in normal human astrocytes, normal brain tissue and neural stem cells. CD9 silencing in three CD133+ glioblastoma cell lines (NCH644, NCH421k and NCH660h) led to decreased cell proliferation, survival, invasion, and self-renewal ability, and altered expression of the stem-cell markers CD133, nestin and SOX2. Moreover, CD9-silenced glioblastoma stem cells showed altered activation patterns of the Akt, MapK and Stat3 signaling transducers. Orthotopic xenotransplantation of CD9-silenced glioblastoma stem cells into nude rats promoted prolonged survival. Therefore, CD9 should be further evaluated as a target for glioblastoma treatment.

Inhibition of PI3K Signalling Selectively Affects Medulloblastoma Cancer Stem Cells

Medulloblastoma is the most common malignant brain tumor of childhood. Although survival has slowly increased in the past years, the prognosis of these patients remains unfavourable. In this context, it has been recently shown that the intracellular signaling pathways activated during embryonic cerebellar development are deregulated in MDB. One of the most important is PI3K/AKT/mTOR, implicated in cell proliferation, survival, growth, and protein synthesis. Moreover, a fraction of MDB cells has been shown to posses stemlike features, to express typical neuronal precursor markers (Nestin and CD133), and to be maintained by the hypoxic cerebellar microenvironment. This subpopulation of MDB cells is considered to be responsible for treatment resistance and recurrence. In this study, we evaluated the effects of PI3K/AKT pathway inhibition on primary cultures of MDB and particularly on the cancer stem cell (CSC) population (CD133⁺). PI3K inhibition was able to counteract MDB cell growth and to promote differentiation of stemlike MDB cells. Moreover, PI3K/AKT pathway suppression induced dramatic cell death through activation of the mitochondrial proapoptotic cascade. Finally, analysis on the stem cells fraction revealed that the MDB CSC population is more sensitive to PI3K targeting compared to the whole cancerous population and its nonstem cell counterpart.

Cell-specific in vivo functions of glycosphingolipids: lessons from genetic deletions of enzymes involved in glycosphingolipid synthesis

Glycosphingolipids (GSLs) are believed to be involved in many cellular events including trafficking, signaling and cellular interactions. Over the past decade considerable progress was made elucidating the function of GSLs by generating and exploring animal models with GSL-deficiency. Initial studies focused on exploring the role of complex sialic acid containing GSLs (gangliosides) in neuronal tissue. Although complex gangliosides were absent, surprisingly, the phenotype observed was rather mild. In subsequent studies, several mouse models with combinations of gene-deletions encoding GSL-synthesizing enzymes were developed. The results indicated that reduction of GSL-complexity correlated with severity of phenotypes. However, in these mice, accumulation of precursor GSLs or neobiosynthesized GSL-series seemed to partly compensate the loss of GSLs. Thus, UDP-glucose:ceramide glucosyltransferase (Ugcg), catalyzing the basic step of the glucosylceramide-based GSL-biosynthesis, was genetically disrupted. A total systemic deletion of Ugcg caused early embryonic lethality. Therefore, Ugcg was eliminated in a cell-specific manner using the cre/loxP-system. New insights into the cellular function of GSLs were gained. It was demonstrated that neurons require GSLs for differentiation and maintenance. In keratinocytes, preservation of the skin barrier depends on GSL synthesis and in enterocytes of the small intestine GSLs are involved in endocytosis and vesicular transport.

Malignant behaviorial characteristics of CD133(+/-) glioblastoma cells from a Northern Chinese population

Following emergence of the tumor stem cell theory, the increasing number of related studies demonstrates the theory’s growing importance in cancer research and its potential for clinical applications. Few studies have addressed the in vitro or in vivo properties of glioma stem cells from a Han Chinese population. In the present study, surgically obtained glioblastoma tissue was classified into two subtypes, CD133⁺ and CD133⁻. The hierarchy, invasiveness, growth tolerance under low nutrient conditions and colony forming abilities of the tissue samples were analyzed. Additionally, the characteristics of tumor cells transplanted subcutaneously or re-transplanted into nude mice were observed. The results demonstrated that CD133⁺ glioblastoma cells derived from Han Chinese glioma specimens were more prone to primitive cell differentiation and more invasive than CD133⁻ glioblastoma cells, leading to increased tumor malignancy compared with CD133⁻ cells. The tumor formation rates of CD133⁺ and CD133⁻ cells in mice were 26/30 and 2/30, respectively. A comparison of tumor subtypes demonstrated that CD133⁺ glioblastoma cells had a lower incidence of cell apoptosis in the tumor tissue and higher protein expression levels of Oct4, Sox2, PCNA, EGFR, Ang2, MMP2 and MMP9 compared with CD133⁻ cells. Flow cytometry revealed that in the CD133⁺ and CD133⁻ glioblastoma cell-induced tumors, the percentage of CD133⁺ cells was 2.47±0.67 and 0.44±0.14%, respectively. The tumor formation rates following the re-transplantation of CD133⁺ or CD133⁻ tumors into nude mice were 10/10 and 4/10, respectively. These findings suggest that the CD133⁺ glioblastoma cell subpopulation has a stronger malignant cell phenotype than the CD133⁻ subpopulation and that its recurrence rate is increased compared with the primitive tumorigenic rate following in vivo transplantation.

Nonlesions, unusual cell types, and postmortem artifacts in the central nervous system of domestic animals

In the central nervous system (CNS) of domestic animals, numerous specialized normal structures, unusual cell types, findings of uncertain or no significance, artifacts, and various postmortem alterations can be observed. They may cause confusion for inexperienced pathologists and those not specialized in neuropathology, leading to misinterpretations and wrong diagnoses. Alternatively, changes may mask underlying neuropathological processes. "Specialized structures" comprising the hippocampus and the circumventricular organs, including the vascular organ of the lamina terminalis, subfornical organ, subcommissural organ, pineal gland, median eminence/neurohypophyseal complex, choroid plexus, and area postrema, are displayed. Unusual cell types, including cerebellar external germinal cells, CNS progenitor cells, and Kolmer cells, are presented. In addition, some newly recognized cell types as of yet incompletely understood significance and functionality, such as synantocytes and aldynoglia, are introduced and described. Unusual reactive astrocytes in cats, central chromatolysis, neuronal vacuolation, spheroids, spongiosis, satellitosis, melanosis, neuromelanin, lipofuscin, polyglucosan bodies, and psammoma bodies may represent incidental findings of uncertain or no significance and should not be confused with significant microscopic changes. Auto- and heterolysis as well as handling and histotechnological processing may cause postmortem morphological changes of the CNS, including vacuolization, cerebellar conglutination, dark neurons, Buscaino bodies, freezing, and shrinkage artifacts, all of which have to be differentiated from genuine lesions. Postmortem invasion of micro-organisms should not be confused with intravital infections. Awareness of these different changes and their recognition are a prerequisite for identifying genuine lesions and may help to formulate a professional morphological and etiological diagnosis.

A Prominin-1-Rich Pediatric Glioblastoma: Biologic Behavior Is Determined by Oxygen Tension-Modulated CD133 Expression but Not Accompanied by Underlying Molecular Profiles

Few studies on the biologic and molecular properties of pediatric glioblastoma have been performed. Until now, differential genomic analysis of CD133(+)ve and CD133(-)ve fractions has not been described in pediatric glioma. We hypothesize not only that the presence of CD133 could be the source of tumor resistance but also that maintenance of this molecule by hypoxia dictates cellular and molecular behavior. From a series of human glioblastoma biopsies investigated, only one, IN699 (from a pediatric glioblastoma), generated greater than 4% of the total cell volume as CD133(+)ve cells. Using this pediatric glioblastoma, containing unprecedented high levels of the putative brain tumor stem cell marker CD133, as a study model, we report biologic and molecular characteristics of the parent culture and of CD133(+)ve and CD133(-)ve populations derived therefrom under atmospheric and hypoxic culture conditions. Immunocytochemistry and flow cytometry were performed with antigenic markers known to characterize neural stem cells and associated glioma behavior. Behavioral analysis was carried out using proliferation, adhesion, migration, and invasion assays. Cell cycle analysis and array comparative genomic hybridization were used to assess copy number profiles for parental cells and CD133(+)ve and CD133(-)ve fractions, respectively. With regard to invasion and proliferation, CD133(+)ve and CD133(-)ve fractions were inversely proportional, with a significant increase in invasive propensity within the CD133(-)ve cells (P < .005) and a significant increase in proliferation within CD133(+)ve cells (P < .005). Our observations indicate identical genomic imbalances between CD133(+)ve and CD133(-)ve fractions. Furthermore, our research documents a direct link between decreasing oxygen tension and CD133 expression.

Regulation of glioblastoma multiforme stem-like cells by inhibitor of DNA binding proteins and oligodendroglial lineage-associated transcription factors

Tumor-initiating stem cells (also referred to as cancer stem cells, CSCs) are a subpopulation of cancer cells that play unique roles in tumor propagation, therapeutic resistance and tumor recurrence. It is increasingly important to understand how molecular signaling regulates the self-renewal and differentiation of CSCs. Basic helix-loop-helix (bHLH) transcription factors are critical for the differentiation of normal stem cells, yet their roles in neoplastic stem cells are not well understood. In glioblastoma neurosphere cultures that contain cancer stem cells (GBM-CSCs), the bHLH family member inhibitors of DNA binding protein 2 and 4 (Id2 and Id4) were found to be upregulated during the differentiation of GBM-CSCs in response to histone deacetylase inhibitors. In this study, we examined the functions of Id2 and Id4 in GBM neurosphere cells and identified Id proteins as efficient differentiation regulators of GBM-CSCs. Overexpression of Id2 and Id4 promoted the lineage-specific differentiation of GBM neurosphere cells as evidenced by the induction of neuronal/astroglial differentiation markers Tuj1 and GFAP and the inhibition of the oligodendroglial marker GalC. Id protein overexpression also reduced both stem cell marker expression and neurosphere formation potential, a biological marker of cancer cell "stemness." We further showed that Id2 and Id4 regulated GBM neurosphere differentiation through downregulating of another bHLH family member, the oligodendroglial lineage-associated transcription factors (Olig) 1 and 2. Our results provide evidence for distinct functions of Id proteins in neoplastic stem cells, which supports Id proteins and their downstream targets as potential candidates for differentiation therapy in CSCs.

Receptors for hyaluronic acid and poliovirus: a combinatorial role in glioma invasion?

Background

CD44 has long been associated with glioma invasion while, more recently, CD155 has been implicated in playing a similar role. Notably, these two receptors have been shown closely positioned on monocytes.

Methods and Findings

In this study, an up-regulation of CD44 and CD155 was demonstrated in established and early-passage cultures of glioblastoma. Total internal reflected fluorescence (TIRF) microscopy revealed close proximity of CD44 and CD155. CD44 antibody blocking and gene silencing (via siRNA) resulted in greater inhibition of invasion than that for CD155. Combined interference resulted in 86% inhibition of invasion, although in these investigations no obvious evidence of synergy between CD44 and CD155 in curbing invasion was shown. Both siRNA-CD44 and siRNA-CD155 treated cells lacked processes and were rounder, while live cell imaging showed reduced motility rate compared to wild type cells. Adhesion assay demonstrated that wild type cells adhered most efficiently to laminin, whereas siRNA-treated cells (p<0.0001 for both CD44 and CD155 expression) showed decreased adhesion on several ECMs investigated. BrdU assay showed a higher proliferation of siRNA-CD44 and siRNA-CD155 cells, inversely correlated with reduced invasion. Confocal microscopy revealed overlapping of CD155 and integrins (β₁, α_vβ₁ and α_vβ₃) on glioblastoma cell processes whereas siRNA-transfected cells showed consequent reduction in integrin expression with no specific staining patterns. Reduced expression of Rho GTPases, Cdc42, Rac1/2/3, RhoA and RhoB, was seen in siRNA-CD44 and siRNA-CD155 cells. In contrast to CD44-knockdown and ‘double’-knockdown cells, no obvious decrease in RhoC expression was observed in CD155-knockdown cells.

Conclusions

This investigation has enhanced our understanding of cell invasion and confirmed CD44 to play a more significant role in this biological process than CD155. Joint CD44/CD155 approaches may, however, merit further study in therapeutic targeting of infiltrating glioma cells.

Exposure to N-ethyl-N-nitrosourea in adult mice alters structural and functional integrity of neurogenic sites

Background

Previous studies have shown that prenatal exposure to the mutagen N-ethyl-N-nitrosourea (ENU), a N-nitroso compound (NOC) found in the environment, disrupts developmental neurogenesis and alters memory formation. Previously, we showed that postnatal ENU treatment induced lasting deficits in proliferation of neural progenitors in the subventricular zone (SVZ), the main neurogenic region in the adult mouse brain. The present study is aimed to examine, in mice exposed to ENU, both the structural features of adult neurogenic sites, incorporating the dentate gyrus (DG), and the behavioral performance in tasks sensitive to manipulations of adult neurogenesis.

Methodology/Principal Findings

2-month old mice received 5 doses of ENU and were sacrificed 45 days after treatment. Then, an ultrastructural analysis of the SVZ and DG was performed to determine cellular composition in these regions, confirming a significant alteration. After bromodeoxyuridine injections, an S-phase exogenous marker, the immunohistochemical analysis revealed a deficit in proliferation and a decreased recruitment of newly generated cells in neurogenic areas of ENU-treated animals. Behavioral effects were also detected after ENU-exposure, observing impairment in odor discrimination task (habituation-dishabituation test) and a deficit in spatial memory (Barnes maze performance), two functions primarily related to the SVZ and the DG regions, respectively.

Conclusions/Significance

The results demonstrate that postnatal exposure to ENU produces severe disruption of adult neurogenesis in the SVZ and DG, as well as strong behavioral impairments. These findings highlight the potential risk of environmental NOC-exposure for the development of neural and behavioral deficits.

Hereditary inclusion-body myopathy with sparing of the quadriceps: the many tiles of an incomplete puzzle

The hereditary inclusion-body myopathies encompass several syndromes with autosomal recessive or dominant inheritance. Despite a different clinical presentation they all have a progressive course leading to severe disability and share similar pathologic findings at the muscle biopsy. Quadriceps-sparing autosomal recessive hereditary inclusion-body myopathy (h-IBM) is the commonest form and is tied to mutations of the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) that codes for a rate-limiting enzyme in the sialic acid biosynthetic pathway. Despite the identification of the causative gene defect, it has not been clarified how mutations of the GNE gene impair muscle homeostasis. Although several lines of evidence argue in favor of an abnormal sialylation of muscle glycoproteins playing a key role in h-IBM pathogenesis, others studies have demonstrated new functions of the GNE gene, outside the sialic acid biosynthetic pathway, that may also be relevant. This review illustrates the clinical and pathologic characteristics of h-IBM and the main clues available to date concerning the possible pathogenic mechanisms of this disorder. Understanding the molecular mechanism underlying h-IBM pathology is a fundamental requisite to plan a future attempt to therapy.

CD133/prominin1 is prognostic for GBM patient's survival, but inversely correlated with cysteine cathepsins' expression in glioblastoma derived spheroids

Introduction

CD133 is a marker for a population of glioblastoma (GBM) and normal neural stem cells (NNSC). We aimed to reveal whether the migratory potential and differentiation of these stem cells is associated with CD133 expression and with cathepsin proteases (Cats).

Materials and methods.

The invasiveness of normal NNSC, GBM/CD133+ cell lines and GBM spheroids was evaluated in 3D collagen, as well as of U87-MG and normal astrocytes (NHA) grown in monolayers in 2D Matrigel. Expression of Cats B, L and S was measured at mRNA and activity levels and their relation to invasiveness, to CD133 mRNA in 26 gliomas, and to the survival of these patients.

Results

The average yield of CD133+ cells from GBM samples was 9.6 %. Survival of patients with higher CD133 mRNA expression was significantly shorter (p< 0.005). Invasion, associated with proteolytic degradation of matrix, was higher in normal stem cells and GBM spheroids and cells than in isolated GBM CD133+ cells. In glioma samples, there was no correlation between CD133 mRNA expression and Cat mRNAs, but there was an inverse correlation with Cat activities.

Conclusions

The study confirms CD133 as a prognostic marker for the survival of GBM patients. We demonstrated that NNSC have higher invasion potential and invade the collagen matrix in a mode different from that of GBM, initiating stem cell spheres. This result could have implications for the design of new therapeutics, including protease inhibitors that specifically target invasive tumour stem cells. Increased activity of cathepsins in CD133– cells suggests their role in the invasive behaviour of GBM.

A cancer stem cell origin for human endometrial carcinoma?

Endometrial cancer (EC) is the most common gynaecological malignancy affecting women in the western world. Cancer stem cells (CSCs) are defined as a subset of tumour cells with the capacity to self-renew and give rise to the differentiated cells that comprise the bulk of the tumour. Given that a rare population of epithelial stem/progenitor cells has been identified in human endometrium, it is possible that these cells or their progeny may be the source of the putative CSCs that may initiate and maintain EC. Studies have shown that some cells within EC have the capacity to initiate clones that undergo self-renewing cell division and form tumoursin vivothat can be serially passaged, demonstrating self-renewal, proliferation and differentiation abilities of the potential EC stem cells (ECSCs). These potential ECSCs may be located within the tumour cell population expressing CD133 and/or within the side population. With the discovery of markers for ECSCs, it is hoped that ECSCs can be isolated and characterised, and that their role in the development of human EC will be further investigated. This knowledge opens the way for the development of new treatment modalities that target the CSCs, but spares normal endometrial stem/progenitor cells and other cells. Such treatments will be particularly useful for early-stage and pre-menopausal EC candidates where the uterus may be conserved, and for late-stage cases where hysterectomy is not curative and current treatments target the bulk tumour cells rather than CSCs.

Ganglioside GM3 levels are altered in a mouse model of HIBM: GM3 as a cellular marker of the disease

Objective

HIBM (Hereditary Inclusion Body Myopathy) is a recessive hereditary disease characterized by adult-onset, slowly progressive muscle weakness sparing the quadriceps. It is caused by a single missense mutation of each allele of the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, a bifunctional enzyme catalyzing the first two steps of sialic acid synthesis in mammals. However, the mechanisms and cellular pathways affected by the GNE mutation and causing the muscle weakness could not be identified so far. Based on recent evidence in literature, we investigated a new hypothesis, i.e. the involvement in the disease of the GM3 ganglioside, a specific glycolipid implicated in muscle cell proliferation and differentiation.

Methods

qRT-PCR analysis of St3gal5 (GM3 synthase) gene expression and HPLC quantification of GM3 ganglioside were conducted on muscle tissue from a mouse model of HIBM harboring the M712T mutation of GNE (Gne^M712T/M712T mouse) vs control mice (Gne^+/+ mouse).

Results

St3gal5 mRNA levels were significantly lower in Gne^M712T/M712T mouse muscles vs Gne^+/+ mouse muscles (64.41%±10% of Gne^+/+ levels). GM3 ganglioside levels showed also a significant decrease in Gne^M712T/M712T mouse muscle compared to Gne^+/+ mouse muscle (18.09%±5.33% of Gne^+/+ levels). Although these Gne^M712T/M712T mice were described to suffer severe glomerular proteinuria, no GM3 alterations were noted in kidneys, highlighting a tissue specific alteration of gangliosides.

Conclusion

The M712T mutation of GNE hampers the muscle ability to synthesize normal levels of GM3. This is the first time that a mutation of GNE can be related to the molecular pathological mechanism of HIBM.

Beyond glycosylation: sialic acid precursors act as signaling molecules and are involved in cellular control of differentiation of PC12 cells

Sialic acids represent a family of 9-carbon acidic amino sugars expressed mainly as terminal monosaccharides on most mammalian glycoconjugates. Sialic acids play an outstanding role during cellular processes, such as development and regeneration, as they are involved in a variety of molecular interactions. Sialic acids are synthesized in the cytosol starting from UDP-N-acetylglucosamine by the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine-kinase (GNE), which is the key enzyme in the biosynthesis of sialic acid that catalyzes the generation of N-acetylmannosamine, which in turn is an intermediate of the sialic acid pathway that represents the natural molecular precursor of all sialic acids. Of increasing interest are the influence of the sialic acid precursor N-acetylmannosamine (or related N-acylmannosamines), GNE, and sialic acids themselves on cellular processes such as proliferation, gene expression, or cell differentiation. Here, we present recent data and review indications that N-acylmannosamines (the direct precursors of all sialic acids) may act as signaling molecules, and that the key enzyme of the sialic acid metabolism is directly involved in the regulation of cell proliferation and cell differentiation.

In vivo investigation of CD133 as a putative marker of cancer stem cells in Hep-2 cell line

BACKGROUND

Mounting evidence suggests that most tumors consist of a heterogeneous population of cells with a subset population that has the exclusive tumorigenic ability. They are called cancer stem cells (CSCs). CSCs can self-renew to generate additional CSCs and also differentiate to generate phenotypically diverse cancer cells with limited proliferative potential. They have been identified in a variety of tumors. In this study, we identify the marker of CSCs in the established human laryngeal tumor Hep-2 cell line in vivo. Our in vitro experiment shown as CD133, a 5-transmembrane glycoprotein expressed in Hep-2 cell line. CD133 was supposed as a candidate of CSC in laryngeal carcinoma. In this study, the expression of CD133 was detected in a Hep-2 cell line. Applying the magnetic cell sorting (MACS) technology, we reported the results of purifying CD133 positive cells from a Hep-2 cell line. Three-type cells' tumor-forming ability was examined in vivo to identify the marker of CSCs in Hep-2 cell line.

METHODS

CD133 was selected as a putative marker of CSC in laryngeal carcinoma, Hep-2 cell lines. Flow cytometry was used to detect the expression of CD133 in the Hep-2 cell line. Immunomagnetic beads were applied to purify CD133-positive cells. CD133(+), CD133(-) tumor cells, and unsorted Hep-2 cells were injected into severe combined immune deficiency (SCID) mice individually to observe tumor-forming ability.

RESULTS

Only a small proportion (3.15% +/- 0.83%) of cells in the Hep-2 cell line express the CD133 marker. In comparison with CD133(-) tumor cells and unsorted cells, CD133(+) cells possess a marked capacity for tumor formation in vivo (p <.05).

CONCLUSION

CD133 is 1 of the markers for CSCs in human laryngeal tumors of the Hep-2 cell line. Work on the characterization of these cells provides a powerful tool to investigate the tumorigenic process in the larynx and to develop therapies targeting the CSC.

Allergies: their role in cancer prevention

The nature of the biological relationships between cancers and allergies has intrigued researchers and health care providers for five decades. Three hypotheses have been proposed: antigenic stimulation predicts positive associations between cancers and allergies (i.e., allergy sufferers are more likely to get cancer), whereas immunosurveillance and prophylaxis predict inverse associations (i.e., allergy sufferers are less likely to get cancer). Immunosurveillance predicts inverse associations for cancers of all tissues and organ systems, and prophylaxis predicts inverse associations specifically for cancers of tissues and organ systems that interface with the external environment. To comparatively evaluate these hypotheses, we comprehensively reviewed the literature on cancer and allergies. We located 148 papers published from 1955 through 2006 that reported results of 463 studies of relationships between patients' histories of 11 specific allergies and cancers of 19 tissues and organ systems, and 183 studies of patients' histories of multiple allergies in relation to various types/sites of cancers. Analyses of these studies revealed that (1) frequencies of positive, inverse, and null allergy-cancer associations differed considerably among cancers of different tissues and organ systems; (2) more than twice as many studies reported inverse allergy-cancer associations as reported positive associations; (3) inverse associations were particularly common for cancers of the mouth and throat, brain glia, colon and rectum, pancreas, skin, and cervix but (4) particularly rare for cancers of the breast, prostate, and brain meninges, and for myeloma, non-Hodgkin's lymphoma, and myelocytic leukemia; (5) lung cancer was positively associated with asthma but inversely associated with other allergies; (6) inverse associations with allergies were more than twice as common for cancers of nine tissues and organ systems that interface with the external environment compared to cancers of nine tissues and organ systems that do not interface with the external environment; and (7) eczema, hives, and allergies to animal dander and food were most frequently inversely associated with cancers of tissues that interface with the external environment. Taken together, these results are more consistent with the prophylaxis hypothesis than the two alternatives. IgE is a widespread and ancient immunoglobulin isotype in mammals, occurring among all known marsupials, monotremes, and eutherians. The IgE system and its associated allergy symptoms may serve a common protective function: the rapid expulsion of pathogens, dangerous natural toxins, and other carcinogenic antigens before they can trigger malignant neoplasia in exposed tissues.

Identification of cancer stem cells in dog glioblastoma

There is increasing evidence in some malignancies that the tumor clone is heterogeneous in regard to proliferation and differentiation. The cancer stem cell hypothesis implies that not all the cells in the tumor have the same capacity to proliferate and maintain the growth of the tumor. Only a relatively small fraction of cells in the tumor, termed cancer stem cells (CSCs), possess the ability to proliferate and self-renew extensively. In the past decade, several groups have reported the existence of a CSC population in different human brain tumors from both children and adults. We report here the identification of a CSC population from a Boxer dog with glioblastoma multiforme (GBM) that possesses a great capacity for proliferation, self-renewal, and differentiation. This cloned cell line is aneuploid, forms neurospheres in culture, possesses CSC markers, and reproduces the original dog GBM when inoculated into the nude mouse brain.

Nestin expression in osteosarcomas and derivation of nestin/CD133 positive osteosarcoma cell lines

Background

Nestin was originally identified as a class VI intermediate filament protein that is expressed in stem cells and progenitor cells in the mammalian CNS during development. This protein is replaced in the adult organism by other intermediate filament proteins; however, nestin may be re-expressed under certain pathological conditions such as ischemia, inflammation, brain injury, and neoplastic transformation. Nestin has been detected in many kinds of tumors, especially in tumors derived from the CNS. Co-expression of nestin and the CD133 surface molecule is considered to be a marker for cancer stem cells in neurogenic tumors. Our work was aimed at a detailed study of nestin expression in osteosarcomas and osteosarcoma-derived cell lines.

Methods

Using immunodetection methods, we examined nestin in tumor tissue samples from 18 patients with osteosarcomas. We also successfully established permanent cell lines from the tumor tissue of 4 patients and immunodetection of nestin and CD133 was performed on these cell lines.

Results

Nestin-positive tumor cells were immunohistochemically detected in all of the examined osteosarcomas, but the proportion of these cells that were positively stained as well as the intensity of staining varied. Nestin-positive cells were rarely observed in 2 tumor samples, and the remaining 16 tumor samples showed various nestin expression patterns ranging from very sporadic occurrence to an overwhelming proportion of cells with strong positive staining. Three of the established osteosarcoma cell lines were demonstrated to be nestin-positive, and only one cell line showed no expression of nestin; this finding corresponds with the rare occurrence of nestin-positive cells in the respective tumor sample. Moreover, three of these osteosarcoma cell lines were undoubtedly proven to be Nes+/CD133+.

Conclusion

Our results represent the first evidence of nestin expression in osteosarcomas and suggest the possible occurrence of cells with a stem-like phenotype in these tumors.

The key enzyme of sialic acid biosynthesis (GNE) promotes neurite outgrowth of PC12 cells

Axonal outgrowth is a prerequisite for the development of the most complex organ, the brain. It depends partially on the attachment of sialic acid on glycans of (sialo)-glycoproteins expressed on the plasma membrane. In our study, we showed that nerve growth factor-induced neurite outgrowth of PC12-cells enhances the expression of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine-kinase (GNE), the key enzyme for the biosynthesis of sialic acid. Furthermore, we could show that overexpression of GNE induces neurite outgrowth in PC12 cells. The neurite-outgrowth promoting activity of overexpressed GNE, however, does not lead to an increased biosynthesis of sialic acid. These data suggest a novel role of GNE during neurite outgrowth, which is independent to its specific enzymatic activity.

Up-regulation of NG2 proteoglycan and interferon-induced transmembrane proteins 1 and 3 in mouse astrocytoma: a membrane proteomics approach

Although brain tumors are classified as if their lineage were well understood, the relationship between the molecular events that specify neural cell lineage and brain tumors remains enigmatic. Traditionally, cell surface membrane antigens have served as biomarkers that distinguish brain tumor origin and malignancy. In this study, membrane proteins were identified from a terminally differentiated mouse astrocyte (AC) and CT-2A astrocytoma (CT-2A) cell line using liquid-chromatography coupled with tandem mass spectrometry (LC-MS/MS). A total of 321 and 297 protein groups with at least one unique peptide were identified in the AC and CT-2A cells. Using a label-free quantitative MS approach, 25 plasma membrane proteins in CT-2A were found significantly up- or down-regulated compared with those in AC. Three of the up-regulated proteins, chondroitin sulfate proteoglycan-4 (Cspg4), interferon-induced transmembrane protein-2 (IFITM2) and -3 (IFITM3) were further validated by semi-quantitative RT-PCR analysis. In addition, a third member of the IFITM family, interferon-induced transmembrane protein-1 (IFITM1) was also analyzed. Expression of Cspg4, IFITM1 and IFITM3 was significantly greater in the CT-2A cells than that in the AC cells. Interestingly, Cspg4, also known as neuronal/glial 2 (NG2) proteoglycan in human, is an oligodendrocyte progenitor marker. Therefore, our data suggest that the CT-2A tumor may be derived from NG2 glia rather than from fully differentiated astrocytes. Moreover, the CT-2A cells also express a series of interferon-induced signature proteins that may be specific to this tumor. These data highlight the utility of LC-MS/MS for the identification of brain tumor membrane biomarkers.

Approaches to mitochondrially mediated cancer therapy

For some malignant cancers even combined surgical, radiotherapeutic and chemotherapeutic approaches are not curative, indeed, in certain tumour types even a modest survival benefit is difficult to achieve. There are various biological reasons which underlie this profound resistance but the propensity of cancer cells to repair breaks caused by DNA-damaging radiation and cytotoxic drugs is of major significance in this context. Such highly resistant tumours include the malignant gliomas which are intrinsic to and directly affect the brain and spinal cord. In evaluating approaches which do not elicit tumour cell death directly by DNA damage, it is intriguing to consider mitochondrially mediated apoptosis as a potentially effective alternative. Since the mitochondrial membrane potentials in cancer cells are frequently reduced in comparison with those of non-neoplastic cells this allows a window of opportunity for small molecule agents to enter the tumour cell mitochondria and reduce oxygen consumption with subsequent release of cytochrome c and activation of a caspase pathway to apoptosis which is cancer cell specific. In the quest for agents which can selectively destroy neoplastic cells in this manner, whilst leaving normal adjacent cells intact, various tricyclic drugs have come under scrutiny. In a range of laboratory assays we, and others, have established that certain cancers and, in particular, malignant glioma, are intrinsically sensitive to this approach. We have also established the cellular, molecular and biochemical mechanisms underlying this process. While such archival tricyclics as the antidepressants, clomipramine and amitriptyline, have been used in these experiments their commercial development in cancer therapy has not been forthcoming and their clinical use in glioma has been confined to anecdotal cases. In addition, the dose-dependant role of agents such as anticonvulsants and steroids commonly used in glioma patients in modulating efficacy of the tricyclics is a matter for continued investigation. Other ways of targeting the mitochondrion for cancer therapy include exploitation of the 18kDa translocator protein (peripheral-type benzodiazepine receptor) within the mitochondrial permeability transition pore and enzymatic or molecular modification of a species of ganglioside (GD3/GD3(A)) expressed on the surface of neoplastic cells which are determinants of mitochondrially mediated apoptosis. It is hoped that such approaches may lead to clinical programmes which will improve the prognosis for patients suffering from highly resistant neoplasms.

Glioblastoma-derived stem cell-enriched cultures form distinct subgroups according to molecular and phenotypic criteria

Tumor cells with stem cell-like properties can be cultured from human glioblastomas by using conditions that select for the expansion of neural stem cells. We generated cell lines from glioblastoma specimens with the goal to obtain model systems for glioma stem cell biology. Unsupervised analysis of the expression profiles of nine cell lines established under neural stem cell conditions yielded two distinct clusters. Four cell lines were characterized by the expression of neurodevelopmental genes. They showed a multipotent differentiation profile along neuronal, astroglial and oligodendroglial lineages, grew spherically in vitro, expressed CD133 and formed highly invasive tumors in vivo. The other five cell lines shared expression signatures enriched for extracellular matrix-related genes, had a more restricted differentiation capacity, contained no or fewer CD133+ cells, grew semiadherent or adherent in vitro and displayed reduced tumorigenicity and invasion in vivo. Our findings show that stable, multipotent glioblastoma cell lines with a full stem-like phenotype express neurodevelopmental genes as a distinctive feature, which may offer therapeutic targeting opportunities. The generation of another distinct cluster of cell lines showing similarly homogeneous profiling but restricted stem cell properties suggests that different phenotypes exist, each of which may lead to the typical appearance of glioblastoma.

Successful isolation and long-term establishment of a cell line with stem cell-like features from an anaplastic medulloblastoma

AIMS

Herein we report on the successful isolation and establishment of a novel, long-term, primary, neurosphere-like cell line called 1603-MED from a 5-year-old boy affected by a highly aggressive anaplastic medulloblastoma.

METHODS

Elaboration of the new protocol for neurosphere assay is extensively discussed, together with a complete immuno-histochemical and cytogenetic characterization of 1603-MED.

RESULTS

Clinical course and histopathology are briefly discussed. The 1603-MED possesses a high capacity for proliferation, CD133 expression, self-renewal and differentiation, thus indicating that anaplastic medulloblastoma contains a subpopulation of cancer stem cells as observed in classic medulloblastoma.

CONCLUSIONS

1603-MED provides us with the first in vitro model of anaplastic medulloblastoma that may be suitable for studying both tumour progression and the genetic mechanisms related to therapy resistance, and may lead to the development and testing of chemosensitivity and new therapeutic targets.

Medulloblastomas expressing IL13Ralpha2 are targets for IL13-zetakine+ cytolytic T cells

Central nervous system loco-regional disease relapse is a common etiology of treatment failure for medulloblastoma (MB)/primitive neuroectodermal tumors. Therapeutic targeting of primary disease and the adjacent craniospinal cerebral spinal fluid pathways should decrease relapse rates and allow for the curtailed use of radiation therapy. The adoptive transfer of tumor-specific cytolytic T cells (CTLs) to the tumor bed and cerebral spinal fluid is an attractive strategy, but limited in its clinical application owing to the paucity of defined antigens consistently expressed by these tumors and their potential to escape T-cell recognition by expressing low level surface human leukocyte antigen. Here, we describe the human leukocyte antigen-independent recognition of MB cell-surface IL13Ralpha2 by genetically modified CTLs expressing an IL13-zetakine chimeric immunoreceptor. We found that IL13-zetakine+ CTLs exhibit potent cytolytic activity toward IL13Ralpha2 Daoy cells, and are activated to secrete proinflammatory cytokines such as interferon-gamma. By employing an orthotopic NOD-scid murine model in which intraventricularly seeded Daoy cells form tumors on leptomeningeal surfaces, regression of established ffLuc+ Daoy xenografts in response to intraventricularly delivered IL13-zetakine+ CD8+ CTLs was observed using biophotonic imaging. These studies support the rationale for exploring the clinical utility of targeted immunotherapy using adoptively transferred IL13-zetakine redirected CTLs as a therapeutic component for treating IL13Ralpha2+ MB/primitive neuroectodermal tumors.

Diverse actions of retinoid receptors in cancer prevention and treatment

Retinoids (retinol [vitamin A] and its biologically active metabolites) are essential signaling molecules that control various developmental pathways and influence the proliferation and differentiation of a variety of cell types. The physiological actions of retinoids are mediated primarily by the retinoic acid receptors alpha, beta, and gamma (RARs) and rexinoid receptors alpha, beta, and gamma. Although mutations in RARalpha, via the PML-RARalpha fusion proteins, result in acute promyelocytic leukemia, RARs have generally not been reported to be mutated or part of fusion proteins in carcinomas. However, the retinoid signaling pathway is often compromised in carcinomas. Altered retinol metabolism, including low levels of lecithin:retinol acyl trasferase and retinaldehyde dehydrogenase 2, and higher levels of CYP26A1, has been observed in various tumors. RARbeta(2) expression is also reduced or is absent in many types of cancer. A greater understanding of the molecular mechanisms by which retinoids induce cell differentiation, and in particular stem cell differentiation, is required in order to solve the issue of retinoid resistance in tumors, and thereby to utilize RA and synthetic retinoids more effectively in combination therapies for human cancer.

Spindle orientation, asymmetric division and tumour suppression in Drosophila stem cells

Recent genetic studies in flies have added further support to an increasing body of evidence that suggests that stem cells might be the cell-of-origin of certain tumours. Malfunction of the mechanisms that control the division of stem cells and the developmental fate of the two resulting daughters could be one of the initial events that steers cells into malignant transformation. These studies suggest a role for controlled spindle orientation in suppressing stem-cell overgrowth. In parallel, the machinery that drives asymmetry in stem cells has been further characterized, identifying new components and uncovering the unique, highly sophisticated behaviour of centrosomes in these cells.

Expression of nestin and vimentin in gliomatosis cerebri

Gliomatosis cerebri (GC) is a rare form of CNS neoplasia in which there is diffuse involvement of the nervous tissue with or without the presence of tumor mass. The origin of the tumor is unknown, nor whether it represents a disease with diffuse onset or infiltration from a neoplastic focus. Here we studied the histopathologic characteristics of 6 cases with a diagnosis of GC and performed an immunohistochemical analysis using glial fibrillary acidic protein (GFAP), synaptophysin, nestin and vimentin. Most tumor cells were negative for GFAP, even though there were foci of positivity for this marker in all cases. We detected the presence of many positive cells for nestin and vimentin in all studied samples. The presence of these cells may indicate origin of the tumor from undifferentiated cells with a high degree of mobility.

CD133, One of the Markers of Cancer Stem Cells in Hep-2 Cell Line

OBJECTIVE

In recent years, a growing body of evidence has been reported that a tumor clone is organized as a hierarchy that originates from rare stem cells. CD133, a cell surface antigen, was identified as a stem cell maker for human leukemia, brain tumors, and prostate cancer. The purpose of this study was to detect the expression of CD133, a putative marker of cancer stem cells in the Hep-2 cell line, and isolate CD133 positive cells to observe their proliferation and differentiation ability in vitro.

METHOD

Immunocytochemical staining technology and flow cytometry were used to detect the expression of the putative stem cell marker CD133 in a Hep-2 cell line. The immunomagnetic beads were applied to purify CD133 positive cells. CD133+ tumor cells were cultured in vitro to observe their ability to proliferate and differentiate.

RESULTS

Only a small proportion (<5%) of cells in the Hep-2 cell line expressed CD133. CD133+ cells possess a marked capacity for self renewal, extensive proliferation, and mutilineal differentiation potency in vitro.

CONCLUSION

CD133 is one of the markers for cancer stem cells in human laryngeal tumors, the Hep-2 cell line.

Tumour-initiating cells vs. cancer 'stem' cells and CD133: what's in the name?

Recent evidence suggests that a subset of cells within a tumour have 'stem-like' characteristics. These tumour-initiating cells, distinct from non-malignant stem cells, show low proliferative rates, high self-renewing capacity, propensity to differentiate into actively proliferating tumour cells, resistance to chemotherapy or radiation, and they are often characterised by elevated expression of the stem cell surface marker CD133. Understanding the molecular biology of the CD133(+) cancer cells is now essential for developing more effective cancer treatments. These may include drugs targeting organelles, such as mitochondria or lysosomes, using highly efficient and selective inducers of apoptosis. Alternatively, agents or treatment regimens that enhance sensitivity of these therapy-resistant "tumour stem cells" to the current or emerging anti-tumour drugs would be of interest as well.

Inducible functional expression of Bcl-2 in human astrocytes derived from NTera-2 cells

Astrocytes provide structural support for neurons and may also play important roles in both neuroprotection and neurodegeneration. We, here report that human astrocytes derived from on NTera-2 (NT2) cell line expressing a functional anti-apoptotic protein bcl-2 under the control of a tetracycline responsive promoter using the Tet-On and Tet-Off expression systems. NT2 cells were transfected with the Tet On or Tet Off vectors followed by pTRE carrying human bcl-2. Drug resistant cells were differentiated into astrocytes under retinoic acid exposure. These astrocyte lines were found to express astrocyte specific markers such glial fibrillary acidic protein and chemokine receptors (CCR5, CXCR4) but not CCR3 and CD4. Furthermore, NT2 astrocytes expressing bcl-2 showed rapid response to doxycycline presence in the Tet On and Tet off system. The inducible expression of bcl-2 was found to be tightly regulated by doxycycline concentration in the NT2 astrocytes. We also showed that the induction of bcl-2 expression prevented NT2 astrocytes from camptothecin-induced cellular damage. These results indicate that this system may be useful for the study of specific effects of bcl-2 gene expression on astrocyte function(s) and cellular damage.

Therapeutic value of glycosaminoglycans in cancer

Glycosaminoglycans are unbranched polysaccharides composed of repeating units of alternating uronic acids and amino sugars. Most glycosaminoglycans are covalently attached to core proteins to form proteoglycans. Posttranslational modifications result in specific motifs that bind to a large variety of ligands, thus regulating growth factor signaling, cellular behavior, inflammation, angiogenesis, and the proteolytic environment. Dysregulated expression of glycosaminoglycans is present in cancer and reported to correlate with clinical prognosis in several malignant neoplasms. Recent knowledge on the biological roles of these molecules in cancer biology, tumor angiogenesis, and metastasis has promoted the development of drugs targeting them. Pharmaceutical approaches include the use of chemically modified heparins and glycosaminoglycans with defined structures, combination of inhibitors of glycosaminoglycan biosynthesis and polyamine depletion, and biologically active glycosaminoglycan-binding peptides. In addition, glycosaminoglycans are used as tumor-specific delivery and targeting vehicles for toxins and chemotherapeutics. Encouraging results in animal studies and clinical trials show the clinical relevance of glycosaminoglycan-based drugs and the use of glycosaminoglycans as therapeutic targets.

Some speculation on the origin of glioblastoma

Glioblastoma, the most common primary brain tumor, is also the most deadly, with median survival of about one year, which is little improved over the last five decades. Its pathogenesis is a vexing problem. Despite extensive basic and clinical scientific research, little is known regarding the cause of this disease, the genetic factors which drive its course, or any strategies which may result in effective treatment. This persistent resistance to understanding suggests to the authors that some of the fundamental assumptions regarding the disease are likely to be flawed, and that a new paradigm must be sought to replace them. This manuscript is a review of some of what is known regarding this disease, and then presents a series of hypotheses which compromise an alternative view of glioblastoma.

Roles for UDP-GlcNAc 2-epimerase/ManNAc 6-kinase outside of sialic acid biosynthesis: modulation of sialyltransferase and BiP expression, GM3 and GD3 biosynthesis, proliferation, and apoptosis, and ERK1/2 phosphorylation

Roles for UDP-GlcNAc 2-epimerase/ManNAc 6-kinase (GNE) beyond controlling flux into the sialic acid biosynthetic pathway by converting UDP-GlcNAc to N-acetylmannosamine are described in this report. Overexpression of recombinant GNE in human embryonic kidney (HEK AD293) cells led to an increase in mRNA levels for ST3Gal5 (GM3 synthase) and ST8Sia1 (GD3 synthase) as well as the biosynthetic products of these sialyltransferases, the GM3 and GD3 gangliosides. Conversely, down-regulation of GNE by RNA interference methods had the opposite, but consistent, effect of lowering ST3Gal5 and ST8Sia1 mRNAs and reducing GM3 and GD3 levels. Control experiments ensured that GNE-mediated changes in sialyltransferase expression and ganglioside biosynthesis were not the result of altered flux through the sialic acid pathway. Interestingly, exogenous GM3 and GD3 also changed the expression of GNE and led to reduced ST3Gal5 and ST8Sia1 mRNA levels, demonstrating a reciprocating feedback mechanism where gangliosides regulate upstream biosynthetic enzymes. Cellular responses to the GNE-mediated changes in ST3Gal5 and ST8Sia1 expression and GM3 and GD3 levels were investigated next. Conditions that led to reduced ganglioside production (e.g. short hairpin RNA exposure) stimulated proliferation, whereas conditions that resulted in increased ganglioside levels (e.g. recombinant GNE and exogenous gangliosides) led to reduced proliferation with a concomitant increase in apoptosis. Finally, changes to BiP expression and ERK1/2 phosphorylation consistent with apoptosis and proliferation, respectively, were observed. These results provide examples of specific biochemical pathways, other than sialic acid metabolism, that are influenced by GNE.

Brain tumor stem cells: new targets for clinical treatments?

✓ The observation of similarities between the self-renewal mechanisms of stem cells and cancer cells has led to the new concept of the cancer stem cell. In cases of leukemia, multiple myeloma, and breast cancer, cells with a high self-renewal potential have been identified. Furthermore, investigators have shown these cells' ability to drive the formation and growth of the tumor. Brain tumors have also been reported to possess a subpopulation of cancer stemlike cells that have the ability to proliferate, self-renew, and be multipotent. When grafted into mice, these cells are also able to generate a tumor that recapitulates that of the patient from whom the cells were derived. The identification and characterization of this new category of cells call for new therapies capable of selectively targeting and killing these multifaceted cells.