GBM has also been associated with aberration in signaling through the mitogen-activated protein kinase (RAS/MAPK), phosphatase inosine 3 kinase/protein kinase B (also known as AKT)/mammalian target of rapamycin (PI3K/AKT/mTOR), cell cycle-regulating retinoblastoma (RB) tumor suppressor related pathways, tumor protein p53 (TP53) [11], promoter methylation of O-6-methylguanine-DNA methyltransferase (MGMT), isocitrate dehydrogenase (IDH) mutation, and altered expression of cyclin dependent kinase (CDK) genes [12]. Here, MGMT is linked to glioblastoma.