CEACAM5 and cancer: In non-virus-induced cancers, the transformed cells can produce antigens to which the host is tolerant (tumor-associated self-antigens), as in the case of antigens either expressed during fetal development (oncofetal antigens), e.g., Carcinoembryonic antigen (CEA), or overexpressed in specific tissues, e.g., human epidermal growth factor receptor 2 (HER2) in mammary glands.