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. This evidence concerns the gene KRAS and colonic neoplasm.