RB1 and glioblastoma: The molecular profiling of brain tumors correlates clinical features with the disruption of specific signaling pathways during the development and progression of glial tumors, including the epidermal growth factor receptor (EGFR) gene, p53 (85% of GBM patients), retinoblastoma (Rb) (78% of GBM patients), and phosphatase and tensin homolog (PTEN) (30%–40% of GBM) [5, 6, 7].