Metabolic regulation of the glioblastoma stem cell epitranscriptome by malate dehydrogenase 2 (MDH2)

Glioblastoma (GBM) ranks among the most lethal of human cancers with current therapies offering only palliation. GBM displays striking intratumoral heterogeneity with diversity of cell state, metabolism, and molecular regulation. Here, we demonstrate that stem-like tumor cells, designated GBM stem cells (GSCs), display higher activity of the malate aspartate shuttle (MAS) through increased expression of malate dehydrogenase 2 (MDH2). Genetic and pharmacologic targeting of MDH2 reduced GSC proliferation, self-renewal, and in vivo tumor growth. MDH2 targeting induced accumulation of alpha-ketoglutarate (aKG), a critical enzymatic co-factor. Mechanistically, MDH2 regulated post-transcriptional regulation of mRNA, specifically N6-Methyladenosine (m6A) with platelet-derived growth factor receptor-? (PDGFR?) as a regulated transcript. Leveraging these observations, targeting MDH2 and PDGFR? displayed combinatorial efficacy against GSCs. Collectively, these results suggest that stem-like tumor cells reprogram their metabolism to induce changes in their epitranscriptomes that reveal possible therapeutic paradigms. Overall design: RNA-seq: TRIzol reagent (Sigma Aldrich) was used to isolate total cellular RNA from cell pellets according to the manufacturer's instructions. RNA was purified from 387 GSCs, transduced either with a nontargeting or two independent, non-overlapping shRNAs targeting MDH2 and were subjected to RNA-seq. The experiment was performed in biological duplicates. MeRIP-seq: GSCs were tranduced either with a nontargeting or two independent, non-overlapping shRNAs targeting MDH2 and were subjected to m6A-seq. The experiment was performed in biological duplicates.