Expression and distribution of a human colon-carcinoma-associated antigen in normal and diseased liver tissue

Expression and distribution of 17-1A, a human colon-carcinoma-associated antigen as defined by a monoclonal antibody (17-1A mAb), were evaluated in liver tissues from normal subjects and patients with inflammatory and noninflammatory liver diseases. The antigen recognized by 17-1A mAb is a 41-kD protein that does not belong to the proteins of the cytoskeleton. Using a streptavidin-biotin-peroxidase method on frozen sections of liver tissue, it was located in the cytoplasm of bile duct epithelial cells in normal livers, whereas the hepatocytes were completely unreactive. When diseased liver tissue was examined, a strong 17-1A Ag expression was demonstrable in the epithelium of typical and atypical bile ductules in portal areas. In addition, periportal or periseptal hepatocytes revealed variable staining for 17-1A Ag directly related to acute and chronic inflammatory changes. 17-1A Ag expression in hepatocytes reached the highest frequency in acute hepatitis (5/5) and chronic active hepatitis (17/19). These results indicate that periportal hepatocytes are capable of acquiring antigen expression common to bile ductular cells in inflammatory liver diseases, further supporting the view that these ductules represent transformed hepatocytes. Furthermore, two distinct pictures were found in primary liver malignancies. Neoplastic bile duct epithelium did not maintain 17-1A Ag expression in cholangiocarcinoma, whereas neoplastic liver cells acquired cytoplasmic 17-1A Ag expression in clustered areas in hepatocellular carcinoma and the intensity of staining and antigen distribution were inversely related to the grade of tumor differentiation.