Cell proliferation assay

The effects of the given drugs on cell proliferation were measured as previously described [26]. Briefly, cells were trypsinized and seeded into six-well plates at 1000 cells/well density and then treated with indicated concentration of BKM120, combination (BKM120 plus Olaparib at the respective concentrations) or DMSO control. Cell culture medium containing drug or vehicle control was renewed every 3 days. The cells were incubated for about 10 days until colonies were large enough to be clearly discerned. Cells were fixed with cold methanol, stained with crystal violet (Sigma–Aldrich) and subsequently extracted with 10% glacial acetic acid. The optical density (OD) was measured at 570 nm by EnSpire^® Multimode Plate Readers (PerkinElmer).