PIK3CA and cancer: The PI3K/Akt/mTOR signaling pathway is frequently hyperactivated in most human cancers, and inactivation of tumor suppressors such as PTEN, LKB1, and TSC1/2, which antagonize the PI3K/AKT/mTORC1 pathway, may drive tumorigenesis (Fonseca et al., 2016; Proud, 2018; Roux and Topisirovic, 2018).