Interestingly, inoculation of C57BL/6Je/e mice with 25,000 or 12,500 tumor cells still resulted in progressive tumor growth whereas we did not observe solid tumors in wt mice after injection of these cell numbers (Figure 4C) indicating that α-MSH/MC-1R signaling plays an important role for anti-tumoral immune responses in vivo by inducing/up-regulating cytotoxic activity in CD8+ T cells. Here, MC1R is linked to neoplasm.