We have been investigating the antigenic characteristics of primary human hepatocellular carcinoma (HCC) cells. Employing monoclonal antibodies (MAbs) important cell surface antigenic changes associated with transformed hepatocytes have been identified. We will pursue investigations that explore antigenic differences displayed on the cell surface during hepatocyte transformation to the malignant phenotype. We have now defined 10 antigens of interest (XF-4, XF-8, AF-5, AF-20, AF-10, SF-25, SF-17, SF-32, SF-90 and FB-50). We plan to: 1) examine antigen expression in various liver diseases such as adenomas, cirrhosis, regenerating nodules, and chronic active hepatitis compared to HCC and other normal tissues. 2) determine some of the biochemical and physical properties of these antigens. 3) perform cDNA cloning in lambda GT10 as well as lambda GT11 and CDM8 expression vectors. 4) obtain primary sequence information on the cDNAs of interest. 5) study gene expression at the protein and mRNA level in HCC and adjacent uninvolved liver, in various liver diseases, other tumors and normal tissues. Since MAbs XF-8, AF-20 and SF-25 may have sufficient sensitivity and tissue specificity to be strongly considered as immunotargeting agents in man, we plan to perform experiments with radiolabeled, drug and toxin antibody conjugates to determine their effects either alone or in combination on the growth rate of HCCs in a new animal model system. These tumors produce both hepatitis B surface antigen (HBsAG) and alphafetoprotein (AFP) which will be used as another independent marker of tumor cell growth and viability. The cDNA of some of these antigens have been cloned. These investigations have led to the development of novel reagents for nuclear imaging and potential immunotherapy. In HCC we have observed the existence of low level hepatitis B virus (HBV) or variant viral infection. These agents need to be characterized at the molecular level. We plan to perform studies on HBsAG negative HCC patients with and without serologic markers of past HBV infection. From serum we will first capture on a solid phase support, HBV or variants with different high affinity monoclonal anti-HBsAG antibodies that recognize all known subtypes of HBV. We will employ the polymerase chain reaction (PCR) to subsequently detect and amplify HBV or variant DNA sequences in serum, lymphocytes, tumor tissue and adjacent uninvolved liver. We expect that the studies outlined in the present application will help to define the molecular events associated with human hepatocyte transformation and will result in novel reagents for immunodiagnosis and therapy.
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