Characterization of a family of glycoproteins associated with the bile canalicular membrane of normal hepatocytes but not expressed by two transplantable rat hepatocellular carcinomas.

Xenoantisera were used to investigate the expression of normal cell-surface components on transplantable rat hepatocellular carcinoma (253 and 311c) cells. Cell-surface components, immunoprecipitated from non-ionic detergent extracts of 125I-labeled hepatocytes by xenoantisera raised against rat hepatocytes, 253 cells, or 311c cells, were analyzed by 2-dimensional polyacrylamide gel electrophoresis. Comparison of the gel patterns revealed that anti-hepatocyte antiserum was reactive with a component having an apparent molecular weight of 105,000 (gp105) that was not recognized by xenoantisera against 253 or 311c cells. This component was isolated by affinity adsorption to Sepharose-conjugated wheat germ agglutinin, reconstituted in liposomes, and used to immunize a rabbit. The resulting antiserum, anti-gp105, was reactive with a family of glycoproteins that had an apparent molecular weight of 105,000 but differed in isoelectric points. Immunohistochemical techniques revealed that gp105 was localized in the bile canalicular domain of the hepatocyte plasma membrane. Immunodepletion analysis, blocking of immunoprecipitation by extracts of tumor cells, and labeling of cells by immunohistochemical techniques indicated that gp105 was not expressed at the surface of 253 or 311c cells. These studies suggest that the altered expression of gp105 on 253 and 311c hepatocellular carcinoma cells may be associated with the abnormal tissue architecture and growth patterns exhibited by these transplantable tumors.