Both genes are involved in cell-cycle control by regulating pRB and p53 signaling.118CDKN2Aencodes both p16INK4aand p14ARFby alternative splicing, which were found to be inactivated in 52 and 49% of glioblastoma tumors, respectively.119In classical glioblastoma, 94% of samples showed homozygous deletion ofCDKN2Ain co-occurrence with amplification ofEGFR. This evidence concerns the gene RB1 and glioblastoma.