AKT1 and glioblastoma: Alpelisib inhibited PI3Kα signalling in a dose dependent manner, as reflected by the reduced phosphorylation of AKT on Ser-473 in U87 (Supplementary Fig. S1A), LN18 (Supplementary Fig. S1B) and LN443 (Supplementary Fig. S1C) GBM cells.