PIK3CB and glioblastoma: Since PI3K p110α-specific inhibitors have been shown to possess greater activity against tumor cell lines with a PIK3CA mutated background [40], we analyzed cell proliferation in the two PIK3CA mutated GBM cell lines SK-MG-17 (V344G) and SK-MG-26 (H1047Y) in the presence of either one of the three PI3K p110α-specific inhibitors YM024, PIK75, or A66 (Figure S3).