KRAS and malignant colon neoplasm: To confirm this possibility, we used human colon cancer PDX models with cell line 52, which expresses wild-type KRAS and PIK3CA, and cell line 87, which expresses wild-type KRAS and mutant PIK3CA. When the tumours reached ~100 mm3 in volume, MEK inhibitor (GSK112012) was orally administered to mice carrying these PDXs.