Differentiation antigens include the melanoma antigens Melan A/MART-1 (10, 11), gp100 (12), tyrosinase (13), the prostate antigen prostate specific antigen (PSA) (14, 15) and the colon antigen carcinoembryonic antigen (CEA) (16, 17). This evidence concerns the gene KLK3 and melanoma.