CDK4 and glioblastoma: Around 78% of glioblastomas have disruptions in RB signalling and frequently show alterations in RB1, CDK4, CDK6, CCND2, and the cyclin-dependent kinase inhibitor 2 (CDKN2) family.63,67,69RTK/RAS/PI3K activation is observed in approximately 88% of tumours, typically affecting known hereditary (NF1) and non-hereditary (PIK3R1, and PIK3CA) genes.70–72