CAR-3, a Monoclonal Antibody-defined Antigen Expressed on Human Carcinomas

Several monoclonal antibodies were raised against the human epidermoid carcinoma line A 431. The antibody produced by clone AR-3, when tested in enzyme-linked immunosorbent assay, was found to react with the cell line used as immunogen, the human gastric carcinoma line KATO III, the colon carcinoma line HT29, and the ovarian carcinoma line SW626. This monoclonal antibody was found unreactive when tested on human peripheral blood leukocytes or on a number of normal or neoplastic cell lines. The antibody precipitated a high-molecular-weight glycosylated component. When tested on paraffin sections by the avidinbiotin peroxidase method, the AR-3 antibody stained pancreatic (6:7) gastric (11:14), ovarian (5:6), colon (4:8), endometrial (4:6), anc cervical (4:7) carcinomas. A small minority of carcinomas of othei organs was also stained. Sarcomas, lymphomas, and othei tumors of nonepithelial origin were constantly negative. Staininc of some normal epithelial cells was also observed. Among the fetal tissue tested, the antibody reacted with pancreatic ducts and the small intestine. The antibody recognized metastatic carcinoma cells in peritoneal effusions. On the basis of its tissue distribution, the antigenic determinant defined by the AR-3 mono clonal antibody was called CAR-3. The monoclonal AR-3 did not cross-react with partially purified preparations of carcinoem-bryonic antigen, gastrointestinal carcinoma antigen, or the hu-man milk fat globule antigen. The AR-3 MAb appear, thus, to broaden the number of avail- able reagents for histopathological diagnosis of carcinomas.