TP53 and glioblastoma: Genetic alterations in signal transduction routes and processes induced by growth factors which control cell cycle progression, such as receptor tyrosine kinases (RTKs)/RAS/phosphatidylinositol 3-kinase (PI-3K), the p53 tumor suppressor pathway, and retinoblastoma (RB) protein signaling pathways, are found in majority of GBM tumors.