Cancer of the liver has a high mortality rate. The disease is most often detected at a later stage when resection of the tumors is impossible. Early diagnosis and the ability to localize the presence of hepatocellular carcinoma would save thousands of lives annually. Monoclonal antibodies supplied by the Shanghai Institute of Cell Biology will be evaluated for their specific binding to hepatocellular carcinoma. In Phase I of this proposal, the potential utility of selected monoclonal antibodies as reagents for the early diagnosis of subclinical hepatocellular carcinoma will be established. The antibodies will be tested as immunohistochemical reagents, and the suitability of high binding antibodies for localization of human hepatocellular carcinoma xenograft tumors will be investigated in the nude mouse. The molecular nature of antigens detected will be determined. Phase II activities include production and testing of additional monoclonal antibodies to hepatocellular carcinoma, development of an in vitro serological assay for subclinical hepatocellular carcinoma, full molecular characterization of tumor-associated antigens, and initial clinical evaluation of selected monoclonal antibodies.