Methionine and Kynurenine Activate Oncogenic Kinases in Glioblastoma, and Methionine Deprivation Compromises Proliferation

Abstract

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.

Nicotinamide metabolism regulates glioblastoma stem cell maintenance

“…These results could suggest that a tumor evolves to create regions of stress that favor the maintenance of GSCs through metabolic and epigenetic reprogramming. A recent report using mostly established cell lines suggested that methionine deprivation compromises proliferation, but the authors used complete removal of methionine, rather than a gradient as we examined (Nota bene we found that complete removal of methionine decreased proliferation) (65). Restriction of methionine and other epigenetic cofactors may promote reduction of available methyl donors and inhibit DNMT expression to shift the DNA methylation toward a more aggressive phenotype.…”

“…SAM is a major methyl donor, and its de novo synthesis pathways are recycled by methionine and homocysteine pathways. These metabolites have been implicated in various biological significances, including human diseases (65,76,77). SAM, popularly called SAMe, has been used in complementary and holistic medicine as a potential therapy for numerous conditions, including cancer, suggesting that it is safe.…”

NNMT Silencing Activates Tumor Suppressor PP2A, Inactivates Oncogenic STKs, and Inhibits Tumor Forming Ability

“…The metabolic profiling protocol used has been outlined previously (21). Briefly, mass spectral profiling was done using Accurate Mass Q-TOF LC/MS instrument.…”

Targeting Cancer Metabolism: Dietary and Pharmacologic Interventions

“…On the contrary, several tumor cell lines, including colon, breast and prostate ones, cannot proliferate and survive in the absence of methionine (35). Methionine contributes to activating oncogenic pathways in GBM, and methionine deprivation negatively impacts on tumor cell proliferation (36). Coherently with in vitro data, lowering dietary intake of methionine inhibits tumor growth in in vivo mouse and rat models, and also reduces tumor size synergistically with cytotoxic treatments (37).…”