Distribution of Novikoff ascites hepatoma antigens p39 and p49 in various tumorigenic cell lines.

This study investigates the specificity of two antigenic proteins with molecular weights of 39,000 and 49,000, respectively (p39 and p49), present in Novikoff ascites hepatoma. Chromatins and cytosol fractions were assayed from a number of tumorigenic cell lines by identifying antigenic species immunologically on nitrocellulose transfers containing proteins separated electrophoretically. Immunoreactivity was confirmed with complement-fixation. Although the p49 antigen was present only in Novikoff ascites hepatoma and a tissue culture line derived from these ascites cells, the p39 antigen was found in every carcinoma cell line examined. In contrast, neither antigen was present in a representative sarcoma, fibrosarcoma, or Walker 256 carcinosarcoma. These results suggest that the p39 antigen is a protein specific for malignant cells derived from the epithelium. The overall expression of the p39 antigen by the various cell lines examined did not appear to be influenced by in vivo or in vitro growth of homologous cell lines. This latter feature suggests that the p39 antigen is a stable, possibly structural component of neoplastic cells.