Naturally soluble tumor antigens from guinea pig hepatomas: isolation and partial characterization

Naturally soluble tumor antigens were detected in the ascites fluid of guinea pigs bearing as ascites tumor and from exhausted tissue culture media of cultured tumor cells. Two antigenically distinct cell lines of diethylnitrosamine induced strain 2 guinea pig hepatomas (line 10 and line 1) served as the source of tumor antigens. Tumor antigen activity was detected by 4 different techniques: immunodiffusion, inhibition of complement mediated cytotoxicity, inhibition of membrane immunofluorescence, and delayed cutaneous hypersensitivity. With syngeneic tumor specific antiserum, line 10 guinea pig tumor antigens were detected by immunofluorescence in the concentrated ascites and tissue culture fluids. With a xenogeneic antiserum, demonstrated to be tumor specific, line 10 tumor antigens were detected not only in the concentrated ascites and tissue culture fluids but also in two of the partially purified fractions of these fluids. When the line 10 concentrated ascites and its fraction I were subjected to ultracentrifugation at 3000,000 x G for 1 hr, the antigen activity was retained in the supernatant and thus by this criterion the tumor antigens detected in these samples are soluble. Immunodiffusion data indicate that more than one antigen is present in the line 10 system since 3 lines of precipitation were detected when line 10 concentrated ascites was reacted with the line 10 tumor specific antiserum. In contrast to this, the line 10 concentrated tissue culture fluid displayed only one line of precipitation. Although tumor antigens could not be demonstrated in the other antigenically distinct tumor cell line, line 1, by immunodiffusion or inhibition of membrane immunofluorescence, inhibition of complement mediated cytotoxicity was able to detect tumor antigens in the line 1 concentrated ascites and tissue culture fluids.