PIK3CA and cancer: A prominent feature of many cancers are mutations that lead to activation of PI3K (phosphatidylinositol-3-kinase)/PKB (protein kinase B) and the Ras (rat sarcoma)/MAPK (mitogen-activated protein kinase) pathways, including loss-of-function mutations of PTEN and gain-of-function mutations of PI3K and genes in the Ras/mitogen-activated protein kinase MAPK pathway [15,16,17,18,19,20].