IDENTIFICATION OF HEPATOCELLULAR CARCINOMA-ASSOCIATED ANTIGENS USING MONOCLONAL ANTIBODIES

Abstract

Three monoclonal antibodies ( 11KV5, 38KV225 and 38KV236) produced by immunizing mice with HCC cell lines were used to identify and characterize previously unreported antigens of HCC cells. All 3 mAbs are of IgG1 subtype. Both 11KVS and 38KV225 identified surface membrane antigens whereas 38KV236 identified a cytoplasmic antigen. Immunofluorescence studies showed : (1) 11KV5 antibody stained 10/14 HCC cell lines, MCF-7 ( breast carcinoma cell line), FS4 ( human fibroblast cell line) and normal human thyroid tissue, (2) 38KV225 antibody stained 5/14 HCC cell lines, MCF-7, normal kidney and breast tissues, (3) 38KV236 antibody stained 8/14 HCC cell lines. The 11KV5 and 38KV225 antigens are formalin-sensitive whereas the 38KV236 antigen is not affected by the formalin fixative. Immunoperoxidase staining of formalin-fixed tissues revealed that the 38KV236 antigen was found in 6/10 HCC tumors and some non-HCC tumors. The antigen was also present in a small number of cells of normal thyroid, stomach, normal colon and kidney tissues. The mAb 11KV5 recognized 2 antigens ( 52kD and 45kD ), mAb 38KV225 recognized 1 antigen ( 42kD) and mAb 38KV236 recognized 2 antigens ( 52kD and 22kD ). Nuclear imaging studies with mAb 38KV225 showed sharp visualization of tumor and demonstrated that this antibody has sufficient specificity and affinity to be considered as an immunotargeting agent.