In addition, while Phe-Arg-Trp-Gly-NH2 showed an antagonistic activity, Ac-Phe-Arg-Trp-Gly-NH2 rather potentiated the α-MSH-induced increase of TYR activity in murine melanoma cells, and did not show agonistic or antagonistic activity [61]. This evidence concerns the gene TYR and melanoma.