Mutant IDH1 Enhances Temozolomide Sensitivity via Regulation of the ATM/CHK2 Pathway in Glioma

PURPOSE: Isocitrate dehydrogenase 1 (IDH1) mutations are the most common genetic abnormalities in low-grade gliomas and secondary glioblastomas. Glioma patients with these mutations had better clinical outcomes. However, the effect of IDH1 mutation on drug sensitivity is still under debate. MATERIALS AND METHODS: IDH1-R132H mutant cells were established by lentivirus. IDH1-R132H protein expression was confirmed by western blot. The expression of ataxia telangiectasia mutated (ATM) signaling pathway and apoptosis-related proteins were detected by immunofluorescence and western blot. Temozolomide (TMZ) induced cell apoptosis was detected by flow cytometry. Tumor cell proliferation was detected by Cell Counting Kit-8. In vivo nude mice were used to confirm the in vitro roles of IDH1 mutation. RESULTS: We established glioma cell lines that expressed IDH1-R132H mutation stably. We found that TMZ inhibited glioma cells proliferation more significantly in IDH1 mutant cells compared to wild type. The IC(50) of TMZ in IDH1-R132H mutant group was less than half that of wild-type group (p < 0.01). TMZ significantly induced more DNA damage (quantification of γH2AX expression in IDH1 mutation vs. wild type, p < 0.05) and apoptosis (quantification of AnnexinV(+)propidium iodide(−) cells in IDH1 mutation versus wild type, p < 0.01) in IDH1 mutant gliomas compared to wild-type gliomas. The ATM-associated DNA repair signal was impaired in IDH1 mutant cells. Inhibiting the ATM/checkpoint kinase 2DNA repair pathway further sensitized IDH1 mutant glioma cells to chemotherapy. We found that IDH1 mutation significantly inhibited tumor growth in vivo (the tumor size was analyzed statistically, p < 0.05). Moreover, we confirmed that gliomas with IDH1 mutation were more sensitive to TMZ in vivo compared to wild type significantly and the results were consistent with the in vitro experiment. CONCLUSION: These results provide evidence that combination of TMZ and ATM inhibitor enhances the antitumor effect in IDH1 mutant gliomas.