Purpose To identify potential molecular hubs that regulate oncogenic kinases and target them to improve treatment outcomes for glioblastoma (GBM) patients. Experimental Design Data mining of The Cancer Genome Atlas (TCGA) datasets identified Nicotinamide-N-methyl transferase (NNMT) as a prognostic marker for GBM, an enzyme linked to the reorganization of the methylome. We tested our hypothesis that NNMT plays a crucial role by modulating protein methylation leading to inactivation of tumor suppressors and activation of oncogenes. Further experiments were performed to understand the underlying biochemical mechanisms using GBM patient samples, established, primary, and isogenic cells. Results We demonstrate that NNMT outcompetes leucine carboxyl methyl transferase 1 (LCMT1) for methyl transfer from principal methyl donor SAM in biological systems. Inhibiting NNMT increased the availability of methyl groups for LCMT1 to methylate PP2A, resulting in the inhibition of oncogenic serine/threonine kinases (STKs). Further, NNMT inhibition retained the radiosensitizer nicotinamide and enhanced radiation sensitivity. We have provided the biochemical rationale of how NNMT plays a vital role in inhibiting tumor suppressor PP2A while concomitantly activating STKs. Conclusion We report the intricate novel mechanism in which NNMT inhibits tumor suppressor PP2A by reorganizing the methylome both at epigenome and proteome levels and concomitantly activating pro-survival STKs. In GBM tumors with NNMT expression, activation of PP2A can be accomplished by FDA approved perphenazine (PPZ) which is currently used to treat mood disorders such as schizophrenia, bipolar disorder, etc. This study forms a foundation for further GBM clinical trials using PPZ with standard of care treatment.

Purpose We employed a metabolomics-based approach with the goal to better understand the molecular signatures of glioblastoma (GBM) cells and tissues, with an aim towards identifying potential targetable biomarkers for developing more effective and novel therapies. Experimental Design We used liquid chromatography coupled with mass spectrometry (LC-MS/Q-TOF and LC-MS/QQQ) for the discovery and validation of metabolites from primary and established GBM cells, GBM tissues, and normal human astrocytes. Results We identified tryptophan, methionine, kynurenine, and 5-methylthioadenosine as differentially regulated metabolites (DRMs) in GBM cells compared to normal human astrocytes (NHAs). Unlike NHAs, GBM cells depend on dietary methionine for proliferation, colony formation, survival, and to maintain a deregulated methylome (SAM:SAH ratio). In methylthioadenosine phosphorylase (MTAP) deficient GBM cells, expression of MTAP transgene did not alter methionine dependency, but compromised tumor growth in vivo. We discovered that a lack of the kynurenine metabolizing enzymes kynurenine monooxygenase and/or kynureninase promotes the accumulation of kynurenine, which triggers immune evasion in GBM cells. Insilico analysis of the identified DRMs mapped the activation of key oncogenic kinases that promotes tumorigenesis in GBM. We validated this result by demonstrating that the exogenous addition of DRMs to GBM cells in vitro, results in oncogene activation as well as the simultaneous downregulation of Ser/Thr phosphatase PP2A. Conclusion We have connected a four-metabolite signature, implicated in the methionine and kynurenine pathways, to the promotion and maintenance of GBM. Together, our data suggest that these metabolites and their respective metabolic pathways serve as potential therapeutic targets for GBM.

BackgroundThe goal of this study is to identify and characterize treatment resistant tumor initiating cells (TRTICs) using orthotopic xenografts.MethodsTRTICs were enriched from GBM cell lines using mouse xenografts treated with fractionated doses of radiation and temozolomide. TRTICs were characterized by neurosphere clonogenicity and self-renewal, serial xenotransplantation, differentiation potential, and mRNA & miRNA transcriptomic profiling. We use an unbiased approach to identify antigens encoding TRTIC and glioma stem cells (GSC) populations. Co-culture experiments of TRTIC and differentiated cells were conducted to evaluate the reliance of TRTIC differentiation on the secretome of differentiated cells.FindingsTRTICs acquire stem-like gene expression signatures and increased side population staining resulting from the activation of multi-drug resistance genes. Genetic and functional characterization of TRTICs shows a striking resemblance with GSCs. TRTICs can differentiate towards specific progeny in the neural stem cell lineage. TRTIC-derived tumors display all the histological hallmarks of glioblastoma (GBM) and exhibit a miRNA-transcript and mRNA-transcriptomic profile associated with aggressiveness. We report that CD24+/CD44+ antigens are expressed in TRTICs and patient-derived GSCs. Double positive CD24+/CD44+ exhibit treatment resistance and enhanced tumorigenicity. Interestingly, co-culture experiments with TRTICs and differentiated cells indicated that the regulation of TRTIC differentiation could rely on the secretome in the tumor niche.InterpretationRadiation and temozolomide treatment enriches a population of cells that have increased iPSC gene expression. As few as 500 cells produced aggressive intracranial tumors resembling patient GBM. CD24+/CD44+ antigens are increased in TRTICs and patient-derived GSCs. The enrichment for TRTICs may result in part from the secretome of differentiated cells.FundNIH/NCI 1RC2CA148190, 1R01CA108633, 1R01CA188228, and The Ohio State University Comprehensive Cancer Center.