Strikingly, we observed that some of the cell lines that exhibited resistance to the single agents but were synergistically inhibited by the combination also had an activating mutation in either KRAS (SW480, SW837, DLD1, HCT116, HCT15) or loss-of-function mutations in NF1 (LOXIMVI, HCT116, RKO, MeWo; Fig. 5A; ref. 24).