Joshua D. Frenster

Notch signaling regulates metabolic heterogeneity in glioblastoma stem cells

Glioblastoma (GBM) stem cells (GSCs) reside in both hypoxic and vascular microenvironments within tumors. The molecular mechanisms that allow GSCs to occupy such contrasting niches are not understood. We used patient-derived GBM cultures to identify GSC subtypes with differential activation of Notch signaling, which co-exist in tumors but occupy distinct niches and match their metabolism accordingly. Multipotent GSCs with Notch pathway activation reside in perivascular niches, and are unable to entrain anaerobic glycolysis during hypoxia. In contrast, most CD133-expressing GSCs do not depend on canonical Notch signaling, populate tumors regardless of local vascularity and selectively utilize anaerobic glycolysis to expand in hypoxia. Ectopic activation of Notch signaling in CD133-expressing GSCs is sufficient to suppress anaerobic glycolysis and resistance to hypoxia. These findings demonstrate a novel role for Notch signaling in regulating GSC metabolism and suggest intratumoral GSC heterogeneity ensures metabolic adaptations to support tumor growth in diverse tumor microenvironments.Glioblastoma (GBM) stem cells (GSCs) reside in both hypoxic and vascular microenvironments within tumors. The molecular mechanisms that allow GSCs to occupy such contrasting niches are not understood. We used patient-derived GBM cultures to identify GSC subtypes with differential activation of Notch signaling, which co-exist in tumors but occupy distinct niches and match their metabolism accordingly. Multipotent GSCs with Notch pathway activation reside in perivascular niches, and are unable to entrain anaerobic glycolysis during hypoxia. In contrast, most CD133-expressing GSCs do not depend on canonical Notch signaling, populate tumors regardless of local vascularity and selectively utilize anaerobic glycolysis to expand in hypoxia. Ectopic activation of Notch signaling in CD133-expressing GSCs is sufficient to suppress anaerobic glycolysis and resistance to hypoxia. These findings demonstrate a novel role for Notch signaling in regulating GSC metabolism and suggest intratumoral GSC heterogeneity ensures metabolic adaptations to support tumor growth in diverse tumor microenvironments.

GPR133 (ADGRD1), an adhesion G-protein-coupled receptor, is necessary for glioblastoma growth.

Glioblastoma (GBM) is a deadly primary brain malignancy with extensive intratumoral hypoxia. Hypoxic regions of GBM contain stem-like cells and are associated with tumor growth and angiogenesis. The molecular mechanisms that regulate tumor growth in hypoxic conditions are incompletely understood. Here, we use primary human tumor biospecimens and cultures to identify GPR133 (ADGRD1), an orphan member of the adhesion family of G-protein-coupled receptors, as a critical regulator of the response to hypoxia and tumor growth in GBM. GPR133 is selectively expressed in CD133+ GBM stem cells (GSCs) and within the hypoxic areas of PPN in human biospecimens. GPR133 mRNA is transcriptionally upregulated by hypoxia in hypoxia-inducible factor 1α (Hif1α)-dependent manner. Genetic inhibition of GPR133 with short hairpin RNA reduces the prevalence of CD133+ GSCs, tumor cell proliferation and tumorsphere formation in vitro. Forskolin rescues the GPR133 knockdown phenotype, suggesting that GPR133 signaling is mediated by cAMP. Implantation of GBM cells with short hairpin RNA-mediated knockdown of GPR133 in the mouse brain markedly reduces tumor xenograft formation and increases host survival. Analysis of the TCGA data shows that GPR133 expression levels are inversely correlated with patient survival. These findings indicate that GPR133 is an important mediator of the hypoxic response in GBM and has significant protumorigenic functions. We propose that GPR133 represents a novel molecular target in GBM and possibly other malignancies where hypoxia is fundamental to pathogenesis.

Adult Primary Spinal Epidural Extraosseous Ewing’s Sarcoma: A Case Report and Review of the Literature

Background. Extraosseous Ewings sarcoma in the spinal epidural space is a rare malignancy, especially in adults. Case Presentation. A 40-year-old male presented with back pain and urinary hesitancy. MRI revealed a thoracic extradural mass with no osseous involvement. He underwent surgery for gross total resection of the mass, which was diagnosed as Ewings sarcoma. He was subsequently treated with chemoradiotherapy. He remains disease-free 1 year after surgery. Review of the literature indicated only 45 previously reported cases of spinal epidural extraosseous Ewings sarcoma in adults. Conclusions. Extraosseous Ewings sarcoma in the spinal epidural space is a rare clinical entity that should be included in the differential for spinal epidural masses. Its treatment is multidisciplinary but frequently requires surgical intervention due to compressive neurologic symptoms. Gross total resection appears to correlate with improved outcomes.

144 GPR133 Promotes Glioblastoma Growth in Hypoxia.

INTRODUCTION Microenvironmental diversity in glioblastoma (GBM) is exemplified by normoxic hypervascular areas and hypoxic necrotic regions. GBM stem cells (GSCs) play a central role in tumor growth and therapy resistance. How GSCs adapt to diverse GBM microenvironments remains an important and unanswered question. METHODS Using primary human GBM cultures, we discovered that CD133+ GSCs are metabolically adept at expanding in hypoxic conditions. Transcriptional analysis indicated that CD133+ GSCs have 17.8 ± 8.8-fold enriched expression of GPR133 (n = 3 biospecimens), a member of the adhesion family of G-protein-coupled receptors. We used genetic, biochemical, and computational assays to interrogate the role of GPR133 in GBM. RESULTS Immunostaining of 12 human GBM biospecimens revealed that GPR133 expression is restricted to hypoxic regions of GBM and not present in normal brain. To test whether GPR133 expression is regulated by oxygen tension, we subjected GBM cultures to 1% O2 and found that GPR133 transcript was consistently upregulated (n = 5 cultures) in HIF1a-dependent manner. To elucidate GPR133s role in tumor growth, we used small hairpin RNA-mediated knockdown. GPR133 knockdown depleted CD133+ GSCs and inhibited tumor sphere formation under both normoxic and hypoxic conditions (P < .05). GPR133 knockdown also prevented in vivo tumor formation and increased survival of implanted mice (n = 4/group). CD133+ GSCs have 26.2% ± 12.53% higher cAMP levels than CD133- GBM cells (n = 3). GPR133 knockdown downregulated cAMP levels to 47.25% ± 27.27% of control (n = 3). Forskolin, which activates adenylate cyclase and boosts cAMP production, rescued the knockdown phenotype. These findings suggest that GPR133 canonical signaling is mediated by cAMP. Kaplan-Meier survival analysis of 160 The Cancer Genome Atlas (TCGA) patients indicated that increased GPR133 mRNA in GBM tumors correlated with poor survival (P = .002). CONCLUSION Our results suggest that GPR133 acts promotes GBM growth in hypoxia. We propose that GPR133 represents an attractive novel therapeutic target in GBM.

Lentiviral Transduction of Primary Human Glioblastoma Cultures

This chapter provides detailed step-by-step instructions for the production of lentiviral particles and the transduction of primary human glioblastoma cultures. Lentiviruses stably transduce both dividing and non-dividing cells, such as quiescent cancer stem cell populations. The viral envelope is pseudotyped with the vesicular stomatitis virus envelope glycoprotein G (VSV-G), which renders the lentiviral particles pantropic, so that they can infect theoretically all cell types. The third generation packaging system used in this protocol produces lentiviruses with important safety features, including replication incompetence and self-inactivation (SIN). The protocol we describe here leads to transduction of primary human glioblastoma cultures with efficiencies of up to 90%.

Isolation of Glioblastoma Stem Cells with Flow Cytometry

This chapter describes a straightforward method for isolating glioblastoma stem cells (GSCs) from in vitro tissue cultures via fluorescence-activated cell sorting (FACS) using CD133 as a surface marker. The use of a directly conjugated antibody to an APC fluorophore against the CD133 molecule provides sufficient and clear detection of positive cells from the rest of the population. This strategy avoids an unnecessary secondary antibody incubation step thereby minimizing loss and increasing yield. The same protocol can be applied to other GSC surface markers. The described method allows for quick and efficient purification of GSCs, which can then be used in several downstream applications.

Bioluminescent In Vivo Imaging of Orthotopic Glioblastoma Xenografts in Mice

Orthotopic rodent xenografts are an essential tool for studying glioblastoma in vivo. Xenograft growth as a function of time can only be monitored by noninvasive imaging. This chapter describes in detail how to assess xenograft size and growth using bioluminescent imaging with IVIS (in vivo imaging system). This form of imaging (a) can be performed without the help of a trained technician, (b) is a very quick procedure, allowing simultaneous imaging of up to five animals at a total experimental duration of 15 min, and (c) is cheaper than the alternatives (small animal MRI or CT). This technique relies on the stable expression of luciferase by the xenografted GBM cells. Luciferin, the substrate of luciferase, which is injected into host mice intraperitoneally, distributes throughout the mouse body and crosses the blood brain barrier. Luciferase expressed by the xenografted cells uses this substrate in a catalytic reaction, leading to the emission of visible light, which is detected by the CCD camera of the IVIS imaging system. The intensity of this emitted light correlates to the size of a given xenograft and allows comparisons of xenograft size across different animals, as well as within the same animal across different time points.

Establishing Primary Human Glioblastoma Tumorsphere Cultures from Operative Specimens

In vitro propagation of patient-derived glioblastoma (GBM) cells can be achieved either by adherent monolayer culture, already described in Chapter 3 , or by tumorsphere culture in suspension. Here, we provide a detailed protocol for establishing patient-derived tumorsphere cultures. Such cultures are enriched for GBM stem cells (GSCs) and can be used to generate orthotopic tumor xenografts in the brain of immunocompromised mice. We also point out nuances in the protocol that can increase the yield of successful cultures from operative specimens.