MGMT and glioblastoma: Epigenetic inactivation of the O6-methylguanine-DNA methyltransferase (MGMT) gene in GBM is detected to be present with a heterogeneous pattern where MGMT expression is detected in distinct areas of positive tumor cells surrounded by negative cells [23] and its inactivation by promoter hypermethylation is associated with better response to alkylating agents such as temozolomide.