MGMT and glioblastoma: In glioblastoma, CpG promoter hypermethylation occurs at genes with diverse functions related to tumorigenesis and tumor progression, including cell cycle regulation (CDK2A-p16INK4a and CDK2B-p15INK4b) tumor suppression (RB1, VHL, EMP3, RASSF1A, and BLU), DNA repair [methylguanine DNA methyltransferase (MGMT) and MLH1], inhibition of apoptosis (DAPK1, TIMP3, CDH1), and genes associated with angiogenesis, regulation of tumor invasion, and drug resistance (53).