Evaluation of clinical significance of isoferritin by development of new monoclonal antibodies specific for acidic isoferritin.

We produced monoclonal antibodies (MAbs) against acidic isoferritin (AIF) of primary hepatic carcinoma (PHC) and human placental tissues. Competitive enzyme-linked immunosorbent assay (ELISA) revealed that each MAb bound to different antigenic determinants of AIF, but there is the same epitope between PHC AIF and placental AIF. Sandwich-type ELISA was developed to measure the concentration of serum AIF in the patients with PHC, chronic hepatitis, and cirrhosis. In most of cases of PHC, serum AIF levels were found to be significantly elevated, but were in low levels in almost all of the patients with chronic hepatitis and cirrhosis. On the other hand, we have studied the expression of AIF in liver tissue. Immunohistochemical study using MAb4c9 specific for PHC AIF and MAb7a9 specific for placental AIF has shown that AIF positive staining rates of hepatocytes with liver tissues of PHC, nonmalignant live diseases and normal control were 81.6, 6.7, 0%, and 73.7, 10, 0%, respectively. We also studied the p53 protein expression in those liver tissues (47.4, 0, 0% in PHC, nonmalignant liver diseases and normal liver, respectively). Our data indicated that there was significant correlation between AIF and p53 expression in liver tissues of PHC. Taken together, the results suggested that AIF is probably synthesized and secreted by the tumor cells of PHC and its production may reflect carcinogenesis of hepatocytes. Anti-PHC AIF MAb was clearly superior in diagnosis of PHC to antiplacental AIF MAb, and has potential application of immunotherapy.