Expression of heterophil Forssman antigen on cultured malignant cell lines

By means of indirect immunofluorescence (IIF) tests with rabbit antiserum against Forssman (F) antigen, F-antigen was demonstrated on 5 of 7 cultured cell lines originating from various cancer tissues. Results of cytotoxicity tests with normal human sera with F-antibodies confirmed the presence of F-antigen on these "IIF-positive" cell lines. In contrast, F-antigen could not be detected under the same experimental conditions on B-cell lines established from lymphoma or leukemia patients or on lymphoblastoid cell lines established from normal individuals. The expression of F-antigen was also studied on transformed rat cell lines derived from an F-negative normal cell line, 3y1. Transformation of the 3y1 line by whole DNA or by the EcoRI-C fragment (0-16 map unit) but not by the Accl-H fragment (0-4.7 map unit) of adenovirus type 12 resulted in expression of F-antigen on the cell surface. The transformed cells with F-antigen showed an in vitro growth pattern characteristic of that seen in malignant cells; this observation indicates that F-antigen expression is closely associated with malignant transformation of the cells.