MGMT and central nervous system cancer: MGMT (O6-methylguanine DNA methyltransferase) promoter methylation is inversely correlated with MGMT expression and patients’ response to the alkylating agent temozolomide (Esteller et al., 2000) with approximately 50% of grade IV glioma (usually glioblastoma, GBM) exhibiting MGMT promoter methylation (Wick et al., 2014).