Expression of immunoreactive matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in human normal livers and primary liver tumors

Matrix metalloproteinases (MMPs) play an important role in cancer cell invasion by degrading extracellular matrix proteins. However, little is known about the in situ expression of MMP in human normal livers and primary liver tumors. In this study, we therefore examined the in situ expression of immunoreactive MMP and tissue inhibitors of MMP (TIMP) in 10 normal livers, 11 surgically resected intrahepatic cholangiocarcinomas (CCs), and 6 surgically resected hepatocellular carcinomas (HCCs). In normal livers, MMP and TIMP were infrequently and faintly expressed in bile ducts, but were not expressed in hepatocytes. In the 11 CCs, MMP-1, MMP-2, MMP3, MMP-9, TIMP-1, and TIMP-2 were expressed in tumor cells and/or tumor stroma in 11 (100%), 5 (45%), 8 (73%), 3 (27%), 9 (82%), and 9 (82%), respectively. The expression of MMP and TIMP in tumor cells was located in the cytoplasm with a diffuse or granular pattern; that in the tumor stroma was situated in fibroblasts, leukocytes, and extracellular matrix. Their expression was stronger in CC cases with severe invasion than in CC cases with mild invasion. In contrast, MMP and TIMP were not expressed in any cases of HCC. These results show that intrahepatic bile duct cells may neoexpress or overexpress MMP and TIMP after malignant transformation but that hepatocytes do not, and suggest that MMP and TIMP play an important role in CC cell invasion by degrading extracellular matrix proteins.