To determine whether PI3K inhibition by BKM120 differently affects the phosphorylation of FOXO3a depending on PIK3CA-mutant cancer cell type, we examined the phosphorylation status of FOXO3a at the S253 residue because the S253 site is more selective and preferential phosphorylation site by Akt compared with other two Akt phosphorylation sites of FOXO3a and an antibody against phospho-S253 of FOXO3a is commercially available. This evidence concerns the gene AKT1 and cancer.