Monoclonal antibodies against antigens expressed on human hepatocellular carcinoma cells

Monoclonal antibodies with selectivity for human hepatoma cell lines were produced by immunizing BALB/c mice with human hepatoma cell lines, HA22T/VGH or Hep 3B, and fusing sensitized mouse spleen cells with mouse myeloma cells. Two monoclonal antibodies recognizing antigens present only on human hepatoma cell lines were investigated. The monoclonal antibody IB1 was found to react with 3 of 9 hepatoma cell lines. Monoclonal antibody 9B2 reacted with all nine hepatoma cell lines. None of the other 20 cell lines tested was bound by IB1 and 9B2. The immunoperoxidase staining of monoclonal antibodies on frozen sections of paired hepatoma and normal liver tissues from the same individuals were studied. Antibody IB1 reacted with 3 of 13 hepatoma tissues, but with none of the normal liver and other tissues, and antibody 9B2 was reactive with antigens appearing on the bile canalicular domain of hepatoma and normal liver tissues. The antibody 9B2 stained no normal tissues with the exception of proximal tubules of kidney. Radioimmunoprecipitation tests identified two antigens reacting with 9B2. The major antigen had an apparent molecular weight of 140,000 and a minor one of 130,000. Therefore, antibody IB1 seems to be specific for antigens present on a group of human hepatoma cells and may be useful for classification and diagnosis of human hepatomas. Antibody 9B2 is quite specific to human liver cells and may be used to provide clues for the characterization of tumor cell lines, identification of metastatic tumors with hepatocytic origin, and study of the structure and function of bile canaliculi.