A striking feature of 249C is the selectivity for KRAS mutants, which we established using three separate systems: (1) a panel of 53 established cancer cell lines (Fig. 1d,c); (2) MEFs expressing specific KRAS alleles (Fig. 5a) and; (3) four SW48 colon cancer cells/xenografts that differ in KRAS mutation status but are otherwise genetically matched (isogenic) (in vitro (Fig. 6d,e) and in vivo (Fig. 6f–i)). Here, KRAS is linked to cancer.