Expression and cellular localization of the urokinase-type plasminogen activator and its receptor in human hepatocellular carcinoma.

The urokinase-type plasminogen activator (uPA) and its receptor (uPAR) play an important role in tumour invasion. Previous studies have shown by RT-PCR that uPA and uPAR mRNAs are expressed in human hepatocellular carcinoma (HCC). Here, in situ hybridization, immunohistochemistry, and double immunofluorescence were used to identify the cells expressing uPA and uPAR in 26 HCCs. The results indicate that uPA and uPAR were expressed in every case, almost exclusively in stromal cells, mostly myofibroblasts and macrophages, except for rare tumoural hepatocytes expressing cytokeratin 7. These results show the important role of stromal cells of HCC in the pericellular proteolysis which facilitates cancer cell invasion.