PIK3R1 and glioblastoma: In this study, several genetic alterations related to EGFR, TP53, NF1, P13KCA/PIK3R1, PTEN, PDGFRA, and IDH1 were identified in GBM, which were subsequently used to classify GBM tumors into the four genetically defined subtypes, namely classic, neural, pro-neural, and mesenchymal, with the last being the worst (reviewed in [51]).