PIK3R1 and glioblastoma: The occurrence of glioblastoma is frequently associated with activation of PI3K/Akt pathway.16 Increased level of phosphorylated Akt has been reported to associate with poor prognosis for glioblastoma patients.17, 18 EGFR amplification or overexpression, which leads to activation of PI3K/Akt signalling pathway, occurs in 40%‐50% of glioblastoma.19 Activating mutations in PIK3CA and PIK3R1, coding for subunits of PI3K, have been identified in approximate 10% of glioblastoma.20 Other stimulators of Akt activity, such as PDK1 and mTOR, were also upregulated in glioblastoma.