KRAS and malignant colon neoplasm: To determine the sensitivity of the different cell lines to MEK inhibitors, we first exposed a panel of eight human colon cancer cell lines with KRAS mutations, i.e., three PIK3CA wild-type cell lines and five mutant cell lines, to a variety of selective MEK inhibitors, i.e., AZD6244, AS703026, BAY 86–9766, and GSK112012.6,14 These cells were treated with these four MEK inhibitors at the indicated concentrations.