Differential Expression of Promyelocytic Leukemia Protein in Autoimmune Liver Diseases

ABSTRACT

BACKGROUND: Promyelocytic leukemia protein (PML) is a primary biliary cirrhosis (PBC)-specific autoantigen. Anti-PML antibody is analyzed using cultured cells with patient sera, however, PML expression has rarely been examined in liver tissues. METHODS: In the present study, PML expression was examined immunohistochemically in paraffin embedded liver needle biopsy specimens obtained from 20 cases of PBC, 10 cases of autoimmune cholangitis, 36 cases of autoimmune hepatitis and from 5 cases of noninflammatory livers. RESULTS: Variable PML immunopositivity was detected in the bile duct epithelial cells of 18 (90.0%) of 20 PBC cases and in all 10 cases (100.0%) of autoimmune cholangitis, whereas it was only present in 6 (16.7%) of 36 cases of autoimmune hepatitis (p<0.001). In contrast, hepatocyte PML immunopositivity was higher in autoimmune hepatitis (33/36 cases, 90.8%), than in PBC (10/20 cases, 50.0%) or autoimmune cholangitis (3/10 cases, 30.0%) (p<0.05). CONCLUSION: Our data indicate that the differential expression of PML is closely related to autoimmune liver diseases type, and suggest that the overexpression of PML protein in bile duct cells is associated with the development of autoantibodies in patients with PBC or autoimmune cholangitis. Furthermore, PML immunoreactivity may be useful for the diagnosis of autoimmune cholangitis and overlap syndrome.