PIK3CA and cancer: PIK3CA-mutant cancer cells used in this study have different types of PIK3CA mutation; mutations of glutamic acid to lysine at 545 amino acid (E545K) in PIK3CA in Caski, ME-180 and MCF7 cells, histidine to arginine at 1047 amino acid (H1047R) in T47D and A2780 cells, and arginine to glutamine at 88 amino acid (R88Q) in C33A.