PIK3CA and colorectal carcinoma: Several studies have examined the role of the PI3K/AKT/mTOR pathway in CRC, but most of these have focused on upstream regulators, such as phosphatase and tensin homolog (PTEN) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), with few studies focused on mTOR itself.