To determine whether MC1R signaling was active in the breast cancer cell lines, T-47d and MCF7, we treated the cells with the MC1R agonist and α-MSH analog, Nle4-D-Phe7-α-MSH (NDP-MSH), or the MC1R antagonist, MSG-60629–31, and evaluated the changes in intracellular cAMP levels. Here, MC1R is linked to breast cancer.