To determine if TMZ resistance conferred by IDH1 mutation is mediated by D2HG production, we evaluated TMZ sensitivity in IDH1 mutant and parental NHA treated with D2HG, which has been shown to rapidly enter cells [29], at a concentration (5mM) within the range of what has been reported in IDH1 mutant gliomas [6, 30]. Here, IDH1 is linked to central nervous system cancer.