PIK3CA and colonic neoplasm: To ascertain the effect of MEK inhibition on β-catenin status in PIK3CA mutant colon cancer cells, we used two special colon cancer cell lines: DLD-1–PIK3CA wt (cell line 351), which has the mutant allele knocked out, and DLD-1–PIK3CA mt (cell line 353), which has the wt allele knocked out.