PIK3CA and malignant colon neoplasm: Most colon cancer cells used in this study were not sensitive to cetuximab owing to the mutations in RAS (DLD1, HCT-116, SW620), BRAF (HT-29), or the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (DLD1, HCT116, HT-29)31 (Fig. 1A).