MAP2K7 and melanoma: To assess whether digitoxin plus MEK inhibitor is preferentially toxic to cancer cells we transplanted mice with gelatin sponges containing either human melanoma cells (M214) or immortalized human melanocytes (hiMEL) (one of each type of sponge per mouse, implanted subcutaneously on different flanks) then treated the mice with digitoxin plus MEK inhibitor (Fig. 3c).