The major goal of this project is to define the functional role of hepatitis B virus (HBV) in human liver cancer. There is strong evidence associating persistent infection of HBV with the development of primary hepatocellular carcinoma (PHC), a cancer that is a major public health problem worldwide. It is of utmost importance to establish whether HBV is involved as a complete transforming virus carrying its own transforming gene, or whether it acts indirectly, perhaps activating the expression of a cellular oncogene. We have designed a comprehensive approach to address this topic, integrating biological, molecular, and immunological investigations, predicated on the principal features of both DNA and RNA tumor virus systems. The first aim is to determine the ability of HBV to immortalize or transform normal human liver cells in vitro, either alone or in the presence of tumor promoters. Human hepatocytes will be cultured on collagen gels to permit retention of architecture and physiology exhibited in vivo. Secondly, we will analyze the status and expression of HBV markers in PHC tumor tissue obtained from several geographical areas of the world. Third, the transforming activity of DNA from PHC cells will be examined to detect activated cellular oncogenes. Both the standard NIH-3T3 cells and normal human hepatocytes will be used as indicator cells in transfection experiments. The fourth aim is to search for putative HBV transforming protein(s), using antisera prepared against synthetic peptides homologous to regions of the predicted amino acid sequence encoded by an open reading frame in the HBV genome. Hepatoma patients' sera will also be utilized in the search for a transforming protein. Finally, we will determine if a particular idiotype may serve as a genetic marker for HBV-associated PHC. THis project will provide insights into the oncogenic potential of HBV and its role in the development of liver cancer.