PIK3CB and glioblastoma: PI3K catalyzes the formation of PIP3 from PIP2, and the lipid phosphatase PTEN antagonizes PI3K by dephosphorylating PIP3 into PIP2.[19] Interestingly, the expression of PTEN protein was not affected by STELB in PTEN wild‐type GBM cells, SF268 and LN229[20] (Figure S4C, Supporting Information).