PTEN and glioblastoma: The important signaling pathways that change in glioblastoma include overexpression of EGFR and PDGFR, and activation of Rat sarcoma (RAS), PI3K/PTEN/AKT, RB/CDK N2A-p16INK4a, and TP53/MDM2/MDM4/CDKN2A-p14ARF pathways.