PIK3CA and cancer: This study used three colorectal cancer cell lines, HT29, DLD1, and Caco2, harboring different statuses of the microsatellite instability (MSI) and the mutations of cancer critical genes: HT29 has microsatellite stable (MSS) and mutant BRAF and PIK3CA; DLD1 has MSI and mutant KRAS and PIK3CA; and Caco2 has MSS and wild-type KRAS, BRAF, and PIK3CA [23].