Cartilage oligomeric matrix protein expression in hepatocellular carcinoma and the cirrhotic liver

Background: Cartilage oligomeric matrix protein (COMP) is the fifth member of the thrombospondin family of extracellular, calcium-binding proteins. It was initially isolated and characterized in cartilage tissue, where it is thought to contribute to the extracellular matrix composition and cell-extracellular matrix interaction. In the present study the expression of COMP was investigated in normal liver (n = 19), liver cirrhosis (n = 14) and hepatocellular carcinoma (HCC; n = 16) tissues, both at the mRNA and protein level. Methods and Results: By northern blot and western blot analysis, COMP was absent or rarely expressed in the normal liver and liver cirrhosis tissues, but significantly overexpressed in HCC tissue samples. The COMP mRNA overexpression in HCC was not related to the clinical stage or tumor grade. By in situ hybridization and immunohistochemistry analysis, COMP mRNA and protein expression were localized within the cytoplasm of the tumor cells, Conclusion: COMP is highly expressed within the tumor cells of HCC, suggesting that COMP might play a role in the pathophysiology of this disease.