Similarly, just as melanocortin‐1 receptor (MC1R) plays an important role in regulating skin pigmentation and melanoma growth in humans and expression of agouti‐signalling protein (ASIP), a known MC1R antagonist, slows melanoma growth and increases survival times in mice [109], grey horses carrying a loss‐of‐function mutation in ASIP have a higher incidence of melanoma [106], suggesting that increased MC1R signalling promotes melanoma development in grey horses, as it does in humans. This evidence concerns the gene MC1R and melanoma.