Moreover, the significance of hypermethylation of CpG island of gene promoters in GBM is highlighted by the observation of epigenetic-mediated inactivation of a wide variety of genes associated with tumor suppression (RB1, VHL, EMP3, RASSF1A, BLU), cell cycle regulation (CDKN2A/CDKN2B), DNA repair (MGMT, hMLH1), and tumor invasion and apoptosis (DAPK1, TIMP3, CDH1, the protocadherin family member PCDH-gamma-A11, TMS1/ASC) [25–31]. Here, RB1 is linked to glioblastoma.