A tumor-associated melanocytic differentiation antigen. Vaccination with MART-1 antigen may stimulate a host cytotoxic T-cell response against tumor cells expressing the melanocytic differentiation antigen, resulting in tumor cell lysis. Or A protein found on normal melanocytes (cells that make the pigment melanin) in the skin and in the retina. It is also found on most melanomas (cancers that begin in melanocytes). Vaccines using pieces of the MART-1 antigen are being studied for their ability to boost the immune response to cancer cells in patients with melanoma. Also called Melan-A protein and Melanoma Antigen Recognized by T cells 1.