Given that the G-CIMP is highly enriched in IDH1-mutant proneural GBM [139], as well as the positive association between MGMT methylation and G-CIMP in GBM tumours [41], the role of IDH1 mutations in MGMT silencing may be related to IDH-mutant-induced histone methylation. Here, MGMT is linked to glioblastoma.