Conversely, CDKN2A/p16INK4A, CDKN2B and CDKN2C, inhibit the different CDKs and are frequently inactivated in GBM (homozygously deleted or mutated in 50–52%, homozygously deleted in 47%, homozygously deleted in 2%, respectively) [6,7]. The gene discussed is CDKN2A; the disease is glioblastoma.