MC1R and melanoma: Other signaling intermediates reported to be activated by MSH/MC1R in melanocytes or melanoma cells include protein kinase C, nitric oxide, p38MAPK and p42/p44MAPK, with the first three reported to stimulate melanogenesis/differentiation, but in each case there was evidence that the effect was dependent on cAMP signaling (Buffey et al., 1992; Englaro et al., 1995; Park et al., 2006; Smalley and Eisen, 2000; Tsatmali et al., 2000).