Tumor antigens, including differentiation antigens, such as gp100 and MART-1 for malignant melanoma; cancer/testis antigens, such as MAGE3 and NY-ESO-1; and overexpressed antigens, such as carcinoembryonic antigen (CEA) for colon cancer, are self-antigens that are expressed by normal cells. The gene discussed is CEACAM5; the disease is cancer.