To investigate the efficacy of the combination of MK-5108 and trametinib, we examined the antitumor effect using WST-8 assay in colon cancer cell lines: HCT116 cells harboring wild-type (wt) TP53 and mutant-type (mt) KRAS, DLD1 harboring mt TP53 and mt KRAS, and HT29 harboring mt TP53 and mt BRAF (Fig. 1A–C). The gene discussed is KRAS; the disease is colonic neoplasm.