RB1 and glioblastoma: Further studies have identified known oncogenic pathways in GBM such as RB, p53, RTK/RAS/P13K (16); a putative attempt at linking GBM molecular subtypes to cell types of the central nervous system (CNS) has also been suggested based on gene expression signature: PN subtype—oligondendrocytic, CL subtype-astrocytic and MSC subtype–astrocytic (cultured cells) (22, 50).