HUMAN GASTRIC CANCER-ASSOCIATED ANTIGENS AND CARCINOEMBRYONIC ANTIGEN DETECTED BY MONOCLONAL ANTIBODIES

The serologic and molecular characterization of four monoclonal antibodies to human gastric cancer cells and to CEA were described and the immunohistologic patterns of reactions with freshly obtained gastrointestinal tissues were examined. Monoclonal antibody YK004, which was secreted by the hybridoma constructed with the gastric carcinoma cell line KATO III, reacted with an antigenic determinant preferentially expressed on human gastric and colonic carcinoma cells, but it failed to bind any nonmalignant tissues tested except the stomach. Although this antibody reacted with fetal digestive tract tissues, it failed to immunoprecipitate CEA. Monoclonal antibodies YK013 and YK024 prepared in the same manner by immunizing with the gastric carcinoma cell line KATO III reacted with antigenic determinants on CEA, but not on NCA or NCA2. The antigenic profiles recognized by these two antibodies were found to be identical by sequential immunoprecipitation experiments. However, the antigenic determinant recognized by antibody YK013 may be different from that recognized by antibody YK024, since the immunohistologic reactivity patterns in carcinoma tissue sections were clearly different. Monoclonal antibody AS001, which was secreted by the hybridomas constructed with purified CEA as immunogen, immunoprecipitated CEA molecule with a single antigenic structure of 200 Kd, which was different from the antigenic profile detected by two other monoclonal antibodies, YK013 and YK024. The unique distribution of the antigenic determinants recognized by our monoclonal antibodies on cancerous tissues suggests that antibodies might be able to detect the unique determinants of the circulating CEA molecule or CEA-related molecules in the serum of cancer patients.