PIK3CA and cancer: A key feature of human cancers is intrinsic or acquired resistance to apoptosis, including upregulation of anti-apoptotic proteins (e.g., Bcl-2, Bcl-xL, IAPs) and pro-survival signaling pathways (e.g., PI3K/Akt, NF-kB) and/or downregulation of pro-apoptotic proteins (e.g., Bax, Bad, Bim).