A molecular interactome of the glioblastoma perivascular niche reveals integrin binding sialoprotein as a mediator of tumor cell migration.

Glioblastoma (GBM) is characterized by extensive microvascular hyperproliferation. In addition to supplying blood to the tumor, GBM vessels also provide trophic support to glioma cells and serve as conduits for migration into the surrounding brain, promoting recurrence. Here, we enrich CD31-expressing glioma vascular cells (GVCs) and A2B5-expressing glioma tumor cells (GTCs) from primary GBM and use RNA sequencing to create a comprehensive molecular interaction map of the secreted and extracellular factors elaborated by GVCs that can interact with receptors and membrane molecules on GTCs. To validate our findings, we utilize functional assays, including a hydrogel-based migration assay and in vivo mouse models to demonstrate that one identified factor, the little-studied integrin binding sialoprotein (IBSP), enhances tumor growth and promotes the migration of GTCs along the vasculature. This perivascular niche interactome will serve as a resource to the research community in defining the potential functions of the GBM vasculature.

Long-term outcomes after gene therapy for adenosine deaminase severe combined immune deficiency.

Patients lacking functional adenosine deaminase activity have severe combined immunodeficiency (ADA SCID), which can be treated with ADA enzyme replacement therapy (ERT), allogeneic hematopoietic stem cell transplantation (HSCT), or autologous HSCT with gene-corrected cells (gene therapy [GT]). A cohort of 10 ADA SCID patients, aged 3 months to 15 years, underwent GT in a phase 2 clinical trial between 2009 and 2012. Autologous bone marrow CD34+ cells were transduced ex vivo with the MND (myeloproliferative sarcoma virus, negative control region deleted, dl587rev primer binding site)-ADA gammaretroviral vector (gRV) and infused following busulfan reduced-intensity conditioning. These patients were monitored in a long-term follow-up protocol over 8 to 11 years. Nine of 10 patients have sufficient immune reconstitution to protect against serious infections and have not needed to resume ERT or proceed to secondary allogeneic HSCT. ERT was restarted 6 months after GT in the oldest patient who had no evidence of benefit from GT. Four of 9 evaluable patients with the highest gene marking and B-cell numbers remain off immunoglobulin replacement therapy and responded to vaccines. There were broad ranges of responses in normalization of ADA enzyme activity and adenine metabolites in blood cells and levels of cellular and humoral immune reconstitution. Outcomes were generally better in younger patients and those receiving higher doses of gene-marked CD34+ cells. No patient experienced a leukoproliferative event after GT, despite persisting prominent clones with vector integrations adjacent to proto-oncogenes. These long-term findings demonstrate enduring efficacy of GT for ADA SCID but also highlight risks of genotoxicity with gRVs. This trial was registered at www.clinicaltrials.gov as #NCT00794508.

CD38 is methylated in prostate cancer and regulates extracellular NAD.

BACKGROUND: Cancer cell metabolism requires sustained pools of intracellular nicotinamide adenine dinucleotide (NAD+) which is maintained by a balance of NAD+ hydrolase activity and NAD+ salvage activity. We recently reported that human prostate cancer can be initiated following oncogene expression in progenitor-like luminal cells marked by low expression of the NAD+-consuming enzyme CD38. CD38 expression is reduced in prostate cancer compared to benign prostate, suggesting that tumor cells may reduce CD38 expression in order to enhance pools of NAD+. However, little is known about how CD38 expression is repressed in advanced prostate cancer and whether CD38 plays a role in regulating NAD+ levels in prostate epithelial cells. METHODS: CD38 expression, its association with recurrence after prostatectomy for clinically localized prostate cancer, and DNA methylation of the CD38 promoter were evaluated in human prostate tissues representing various stages of disease progression. CD38 was inducibly over-expressed in benign and malignant human prostate cell lines in order to determine the effects on cell proliferation and levels of NAD+ and NADH. NAD+ and NADH were also measured in urogenital tissues from wild-type and CD38 knockout mice. RESULTS: CD38 mRNA expression was reduced in metastatic castration-resistant prostate cancer compared to localized prostate cancer. In a large cohort of men undergoing radical prostatectomy, CD38 protein expression was inversely correlated with recurrence. We identified methylation of the CD38 promoter in primary and metastatic prostate cancer. Over-expression of wild-type CD38, but not an NAD+ hydrolase-deficient mutant, depleted extracellular NAD+ levels in benign and malignant prostate cell lines. However, expression of CD38 did not significantly alter intracellular NAD+ levels in human prostate cell lines grown in vitro and in urogenital tissues isolated from wild-type and CD38 knockout mice. CONCLUSIONS: CD38 protein expression in prostate cancer is associated with risk of recurrence. Methylation results suggest that CD38 is epigenetically regulated in localized and metastatic prostate cancer tissues. Our study provides support for CD38 as a regulator of extracellular, but not intracellular, NAD+ in epithelial cells. These findings suggest that repression of CD38 by methylation may serve to increase the availability of extracellular NAD+ in prostate cancer tissues.

Metabolic characterization of isocitrate dehydrogenase (IDH) mutant and IDH wildtype gliomaspheres uncovers cell type-specific vulnerabilities.

BACKGROUND: There is considerable interest in defining the metabolic abnormalities of IDH mutant tumors to exploit for therapy. While most studies have attempted to discern function by using cell lines transduced with exogenous IDH mutant enzyme, in this study, we perform unbiased metabolomics to discover metabolic differences between a cohort of patient-derived IDH1 mutant and IDH wildtype gliomaspheres. METHODS: Using both our own microarray and the TCGA datasets, we performed KEGG analysis to define pathways differentially enriched in IDH1 mutant and IDH wildtype cells and tumors. Liquid chromatography coupled to mass spectrometry analysis with labeled glucose and deoxycytidine tracers was used to determine differences in overall cellular metabolism and nucleotide synthesis. Radiation-induced DNA damage and repair capacity was assessed using a comet assay. Differences between endogenous IDH1 mutant metabolism and that of IDH wildtype cells transduced with the IDH1 (R132H) mutation were also investigated. RESULTS: Our KEGG analysis revealed that IDH wildtype cells were enriched for pathways involved in de novo nucleotide synthesis, while IDH1 mutant cells were enriched for pathways involved in DNA repair. LC-MS analysis with fully labeled 13C-glucose revealed distinct labeling patterns between IDH1 mutant and wildtype cells. Additional LC-MS tracing experiments confirmed increased de novo nucleotide synthesis in IDH wildtype cells relative to IDH1 mutant cells. Endogenous IDH1 mutant cultures incurred less DNA damage than IDH wildtype cultures and sustained better overall growth following X-ray radiation. Overexpression of mutant IDH1 in a wildtype line did not reproduce the range of metabolic differences observed in lines expressing endogenous mutations, but resulted in depletion of glutamine and TCA cycle intermediates, an increase in DNA damage following radiation, and a rise in intracellular ROS. CONCLUSIONS: These results demonstrate that IDH1 mutant and IDH wildtype cells are easily distinguishable metabolically by analyzing expression profiles and glucose consumption. Our results also highlight important differences in nucleotide synthesis utilization and DNA repair capacity that could be exploited for therapy. Altogether, this study demonstrates that IDH1 mutant gliomas are a distinct subclass of glioma with a less malignant, but also therapy-resistant, metabolic profile that will likely require distinct modes of therapy.

Microtubins: a novel class of small synthetic microtubule targeting drugs that inhibit cancer cell proliferation.

Microtubule targeting drugs like taxanes, vinca alkaloids, and epothilones are widely-used and effective chemotherapeutic agents that target the dynamic instability of microtubules and inhibit spindle functioning. However, these drugs have limitations associated with their production, solubility, efficacy and unwanted toxicities, thus driving the need to identify novel antimitotic drugs that can be used as anticancer agents. We have discovered and characterized the Microtubins (Microtubule inhibitors), a novel class of small synthetic compounds, which target tubulin to inhibit microtubule polymerization, arrest cancer cells predominantly in mitosis, activate the spindle assembly checkpoint and trigger an apoptotic cell death. Importantly, the Microtubins do not compete for the known vinca or colchicine binding sites. Additionally, through chemical synthesis and structure-activity relationship studies, we have determined that specific modifications to the Microtubin phenyl ring can activate or inhibit its bioactivity. Combined, these data define the Microtubins as a novel class of compounds that inhibit cancer cell proliferation by perturbing microtubule polymerization and they could be used to develop novel cancer therapeutics.

Low CD38 Identifies Progenitor-like Inflammation-Associated Luminal Cells that Can Initiate Human Prostate Cancer and Predict Poor Outcome.

Inflammation is a risk factor for prostate cancer, but the mechanisms by which inflammation increases that risk are poorly understood. Here, we demonstrate that low expression of CD38 identifies a progenitor-like subset of luminal cells in the human prostate. CD38lo luminal cells are enriched in glands adjacent to inflammatory cells and exhibit epithelial nuclear factor κB (NF-κB) signaling. In response to oncogenic transformation, CD38lo luminal cells can initiate human prostate cancer in an in vivo tissue-regeneration assay. Finally, the CD38lo luminal phenotype and gene signature are associated with disease progression and poor outcome in prostate cancer. Our results suggest that prostate inflammation expands the pool of progenitor-like target cells susceptible to tumorigenesis.

Large-scale assessment of the gliomasphere model system.

BACKGROUND: Gliomasphere cultures are widely utilized for the study of glioblastoma (GBM). However, this model system is not well characterized, and the utility of current classification methods is not clear. METHODS: We used 71 gliomasphere cultures from 68 individuals. Using gene expression-based classification, we performed unsupervised clustering and associated gene expression with gliomasphere phenotypes and patient survival. RESULTS: Some aspects of the gene expression-based classification method were robust because the gliomasphere cultures retained their classification over many passages, and IDH1 mutant gliomaspheres were all proneural. While gene expression of a subset of gliomasphere cultures was more like the parent tumor than any other tumor, gliomaspheres did not always harbor the same classification as their parent tumor. Classification was not associated with whether a sphere culture was derived from primary or recurrent GBM or associated with the presence of EGFR amplification or rearrangement. Unsupervised clustering of gliomasphere gene expression distinguished 2 general categories (mesenchymal and nonmesenchymal), while multidimensional scaling distinguished 3 main groups and a fourth minor group. Unbiased approaches revealed that PI3Kinase, protein kinase A, mTOR, ERK, Integrin, and beta-catenin pathways were associated with in vitro measures of proliferation and sphere formation. Associating gene expression with gliomasphere phenotypes and patient outcome, we identified genes not previously associated with GBM: PTGR1, which suppresses proliferation, and EFEMP2 and LGALS8, which promote cell proliferation. CONCLUSIONS: This comprehensive assessment reveals advantages and limitations of using gliomaspheres to model GBM biology, and provides a novel strategy for selecting genes for future study.

Targeted therapy resistance mediated by dynamic regulation of extrachromosomal mutant EGFR DNA.

Intratumoral heterogeneity contributes to cancer drug resistance, but the underlying mechanisms are not understood. Single-cell analyses of patient-derived models and clinical samples from glioblastoma patients treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) demonstrate that tumor cells reversibly up-regulate or suppress mutant EGFR expression, conferring distinct cellular phenotypes to reach an optimal equilibrium for growth. Resistance to EGFR TKIs is shown to occur by elimination of mutant EGFR from extrachromosomal DNA. After drug withdrawal, reemergence of clonal EGFR mutations on extrachromosomal DNA follows. These results indicate a highly specific, dynamic, and adaptive route by which cancers can evade therapies that target oncogenes maintained on extrachromosomal DNA.

Identification of retinol binding protein 1 promoter hypermethylation in isocitrate dehydrogenase 1 and 2 mutant gliomas.

BACKGROUND: Mutations in isocitrate dehydrogenase 1 (IDH1) and associated CpG island hypermethylation represent early events in the development of low-grade gliomas and secondary glioblastomas. To identify candidate tumor suppressor genes whose promoter methylation may contribute to gliomagenesis, we compared methylation profiles of IDH1 mutant (MUT) and IDH1 wild-type (WT) tumors using massively parallel reduced representation bisulfite sequencing. METHODS: Reduced representation bisulfite sequencing was performed on ten pathologically matched WT and MUT glioma samples and compared with data from a methylation-sensitive restriction enzyme technique and data from The Cancer Genome Atlas (TCGA). Methylation in the gene retinol-binding protein 1 (RBP1) was identified in IDH1 mutant tumors and further analyzed with primer-based bisulfite sequencing. Correlation between IDH1/IDH2 mutation status and RBP1 methylation was evaluated with Spearman correlation. Survival data were collected retrospectively and analyzed with Kaplan-Meier and Cox proportional hazards analysis. All statistical tests were two-sided. RESULTS: Methylome analysis identified coordinated CpG island hypermethylation in IDH1 MUT gliomas, consistent with previous reports. RBP1, important in retinoic acid metabolism, was found to be hypermethylated in 76 of 79 IDH1 MUT, 3 of 3 IDH2 MUT, and 0 of 116 IDH1/IDH2 WT tumors. IDH1/IDH2 mutation was highly correlated with RBP1 hypermethylation (n = 198; Spearman R = 0.94, 95% confidence interval = 0.92 to 0.95, P < .001). The Cancer Genome Atlas showed IDH1 MUT tumors (n = 23) to be RBP1-hypermethylated with decreased RBP1 expression compared with WT tumors (n = 124). Among patients with primary glioblastoma, patients with RBP1-unmethylated tumors (n = 102) had decreased median overall survival compared with patients with RBP1-methylated tumors (n = 22) (20.3 months vs 36.8 months, respectively; hazard ratio of death = 2.48, 95% confidence interval = 1.30 to 4.75, P = .006). CONCLUSION: RBP1 promoter hypermethylation is found in nearly all IDH1 and IDH2 mutant gliomas and is associated with improved patient survival. Because RBP1 is involved in retinoic acid synthesis, our results suggest that dysregulation of retinoic acid metabolism may contribute to glioma formation along the IDH1/IDH2-mutant pathway.

A molecular screening approach to identify and characterize inhibitors of glioblastoma stem cells.

Glioblastoma (GBM) is among the most lethal of all cancers. GBM consist of a heterogeneous population of tumor cells among which a tumor-initiating and treatment-resistant subpopulation, here termed GBM stem cells, have been identified as primary therapeutic targets. Here, we describe a high-throughput small molecule screening approach that enables the identification and characterization of chemical compounds that are effective against GBM stem cells. The paradigm uses a tissue culture model to enrich for GBM stem cells derived from human GBM resections and combines a phenotype-based screen with gene target-specific screens for compound identification. We used 31,624 small molecules from 7 chemical libraries that we characterized and ranked based on their effect on a panel of GBM stem cell-enriched cultures and their effect on the expression of a module of genes whose expression negatively correlates with clinical outcome: MELK, ASPM, TOP2A, and FOXM1b. Of the 11 compounds meeting criteria for exerting differential effects across cell types used, 4 compounds showed selectivity by inhibiting multiple GBM stem cells-enriched cultures compared with nonenriched cultures: emetine, n-arachidonoyl dopamine, n-oleoyldopamine (OLDA), and n-palmitoyl dopamine. ChemBridge compounds #5560509 and #5256360 inhibited the expression of the 4 mitotic module genes. OLDA, emetine, and compounds #5560509 and #5256360 were chosen for more detailed study and inhibited GBM stem cells in self-renewal assays in vitro and in a xenograft model in vivo. These studies show that our screening strategy provides potential candidates and a blueprint for lead compound identification in larger scale screens or screens involving other cancer types.

Proliferative neural stem cells have high endogenous ROS levels that regulate self-renewal and neurogenesis in a PI3K/Akt-dependant manner.

The majority of research on reactive oxygen species (ROS) has focused on their cellular toxicities. Stem cells generally have been thought to maintain low levels of ROS as a protection against these processes. However, recent studies suggest that ROS can also play roles as second messengers, activating normal cellular processes. Here, we investigated ROS function in primary brain-derived neural progenitors. Somewhat surprisingly, we found that proliferative, self-renewing multipotent neural progenitors with the phenotypic characteristics of neural stem cells (NSC) maintained a high ROS status and were highly responsive to ROS stimulation. ROS-mediated enhancements in self-renewal and neurogenesis were dependent on PI3K/Akt signaling. Pharmacological or genetic manipulations that diminished cellular ROS levels also interfered with normal NSC and/or multipotent progenitor function both in vitro and in vivo. This study has identified a redox-mediated regulatory mechanism of NSC function that may have significant implications for brain injury, disease, and repair.

Clinical outcome in pediatric glial and embryonal brain tumors correlates with in vitro multi-passageable neurosphere formation.

BACKGROUND: Cultured brain tumors can form neurospheres harboring tumorigenic cells with self renewal and differentiation capacities. Renewable neurosphere formation has clinical predictive value in adult malignant gliomas, yet its prognostic role for pediatric brain tumors is unknown. METHODS: Established neurosphere conditions were used for culturing samples from glial, embryonal and mixed glioneuronal tumors from 56 pediatric patients. Potential associations between neurosphere formation and clinical outcome were analyzed retrospectively. RESULTS: Thirty-seven percent of all samples formed renewable neurospheres. Analysis of available clinical outcome data from 51 patients demonstrated significantly increased hazard ratios (HR) for both disease progression (HR = 9.9, P < 0.001) and death (HR = 16.6, P < 0.01) in the neurosphere forming group. Furthermore, neurosphere formation correlated with adverse progression free survival (PFS) in glial and embryonal tumors, but not in mixed glioneuronal tumors. Overall survival (OS) was significantly worse for neurosphere-forming patients with embryonal tumors, as a group and amongst the subgroup with medulloblastoma, but not in the glial group. Multivariate analysis showed that neurosphere formation was associated with diminished PFS and OS independent of age, gender, or treatment. Neurosphere formation was an independent predictor of diminished PFS of glial tumors after adjusting for grade. Multivariate analysis, adjusting for both Ki67 staining and neurosphere formation, demonstrated that neurosphere formation remained predictive of progression whereas Ki67 did not. CONCLUSIONS: Neurosphere formation is more predictive of pediatric brain tumor progression than semi-quantitative Ki67 staining. Pediatric brain tumor derived neurospheres may provide a predictive model for preclinical explorations.

A microfluidic platform for systems pathology: multiparameter single-cell signaling measurements of clinical brain tumor specimens.

The clinical practice of oncology is being transformed by molecular diagnostics that will enable predictive and personalized medicine. Current technologies for quantitation of the cancer proteome are either qualitative (e.g., immunohistochemistry) or require large sample sizes (e.g., flow cytometry). Here, we report a microfluidic platform-microfluidic image cytometry (MIC)-capable of quantitative, single-cell proteomic analysis of multiple signaling molecules using only 1,000 to 2,800 cells. Using cultured cell lines, we show simultaneous measurement of four critical signaling proteins (EGFR, PTEN, phospho-Akt, and phospho-S6) within the oncogenic phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway. To show the clinical application of the MIC platform to solid tumors, we analyzed a panel of 19 human brain tumor biopsies, including glioblastomas. Our MIC measurements were validated by clinical immunohistochemistry and confirmed the striking intertumoral and intratumoral heterogeneity characteristic of glioblastoma. To interpret the multiparameter, single-cell MIC measurements, we adapted bioinformatic methods including self-organizing maps that stratify patients into clusters that predict tumor progression and patient survival. Together with bioinformatic analysis, the MIC platform represents a robust, enabling in vitro molecular diagnostic technology for systems pathology analysis and personalized medicine.

Developmental expression of glial fibrillary acidic protein mRNA in mouse forebrain germinal zones--implications for stem cell biology.

Postnatal neural stem cells (NSCs) express the "traditional" astrocyte marker, glial fibrillary acidic protein (GFAP). Here, we analyze the ontogeny of GFAP mRNA in mouse forebrain germinal zones (GZ). On embryonic day 15, mRNA distribution is highly restricted. Subsequently, expression expands to include many cells in the GZ regions adjacent to the cortex and septum but not to the striatum. Double immunostaining for GFAP and nestin did not demonstrate extensive overlap in the GZ of adult rats, suggesting that either few of the GFAP-expressing cells are stem cells, or that nestin is not a reliable marker for stem cells in the adult rat brain. The current findings indicate that while some GFAP-expressing cells in the GZ may be NSCs, most are not likely to function in a neurogenic capacity.