Thus, this analysis confirmed the frequent mutations in glioblastomas of PTEN, TP53, EGFR, PI3KCA, PIK3R1, NF1, RB1, IDH1, and PDGFRA. Analysis of the mostly frequently mutated genes or with frequent copy number alterations in glioblastoma showed that various gene sets are very frequently altered in these tumors in a pattern of mutual exclusivity [16]. Here, PIK3R1 is linked to glioblastoma.