TP53 and glioblastoma: Alterations in cell cycle regulatory signaling pathways, for example, CDK signaling (especially mutation of CDK4, CDK6, and CDKN2A followed by E2F1 transcription factor dysregulation), and inactivation of TP53 (either dependent or independent of MDM2 mutation), have also been extensively targeted in GBM [8, 24].