KRAS and colonic neoplasm: These apparently paradoxical effects may be explained by the fact that the studies by Weinberg et al. 126 and Baracca et al. 132 used healthy cells transfected with a construct coding for mutant KRAS, while Chun et al.134 used KRAS-mutated colon cancer cells (HCT116) in which mutated KRAS was removed by knockout.