Deletion of histo-blood group A and B antigens and expression of incompatible A antigen in ovarian cancer.

Expression of histo-blood group ABH antigens in 53 cases of ovarian cancer was examined by immunoperoxidase staining of Formalin-fixed as well as frozen histological sections with various monoclonal antibodies, including those defining type 1, 2, 3, and 4 chain A. Findings of major interest were (a) deletion of A and B determinants in tumors from histo-blood group A and B individuals, and a high incidence of H antigen deletion in tumors from group O individuals were observed and (b) strong expression of incompatible A antigen in two of 10 samples from group B patients and in two of nine samples from group O patients was demonstrated. A antigen expression was defined by monoclonal antibody AH21, which reacts with monofucosyl type 1 chain A (ALed), but not by other types of anti-A antibodies directed to difucosyl type 1 chain A (ALeb), mono- or difucosyl type 2 chain A, or type 3 or type 4 chain A. The reactivity of monoclonal antibody AH21 was abolished by alpha-N-acetylgalactosaminidase from chicken liver. These findings clearly identified the specific expression of incompatible A antigen with the structure monofucosyl type 1 chain A (ALed) in tumors from histo-blood group B and O individuals.