METABOLOGENOMIC CHARACTERIZATION UNCOVERS HETEROGENEITY AMONG IDH MUTANT GLIOMAS

Mutations in isocitrate dehydrogenase (IDH) enzymes are recognised to drive the molecular footprint of diffuse gliomas, and patients with IDH-mutant gliomas have overall favorable outcomes compared to patients with IDH wildtype tumors. Nonetheless, survival can vary widely even amongst patients with IDH-mutant tumors. A comprehensive metabologenomic characterization of IDH-mutant gliomas has not been performed to date. METHOD: Glioma samples from a cohort of 154 patients that underwent surgery at the UHN in Toronto, ON, underwent multiplatform molecular analysis, including metabolomic studies, genome- wide DNA methylation profiling and bulk RNA sequencing. A comprehensive, integrative analysis was performed, and validated through the use of an independent cohort derived from The Cancer Genome Atlas. RESULTS: We discovered a group of IDH-mutant gliomas with globally altered metabolism that highly resembled IDH wildtype tumors. Notably, these IDH-mutant gliomas with dysregulated metabolism were distinguished from their IDH-mutant counterparts by significantly shorter overall survival. The prognostic relevance of dysregulated metabolism complements, but was not wholly explained by canonically recognized prognostic classifications in IDH-mutant gliomas including 1p/19q codeletion, glioma CpG Island Hypermethylator (GCIMP) status and CDKN2A homozygous deletion. IDH-mutant tumors with dysregulated metabolism harbored distinct epigenetic alterations that converged to drive proliferative and stem-like transcriptional profiles. CONCLUSION: Utilizing a cross-platform analysis we have uncovered a novel subtyping of IDH-mutant gliomas with dysregulated cellular metabolism with similar survival to IDH-wildtype tumors. The metabolic profile provides unique information on glioma phenotypes, which may can facilitate a more comprehensive understanding of glioma biology, and provide a window to target novel dependencies.