Expression of urokinase-type plasminogen activator receptor in hepatocellular carcinoma

It is well known that a urokinase-type plasminogen activator receptor (uPAR) is a key protein in the plasminogen activation system, which plays a proteolytically important role in the invasion and metastasis of various cancer cells. To assess the expression of uPAR in hepatocellular carcinoma (HCC), we analyzed the expression of uPAR messenger RNA (mRNA) and the protein in 31 pair-samples of solitary HCC and nontumorous liver tissues from the same patients. Fifteen samples exhibited no histological potential of recurrence, such as portal involvement or intrahepatic metastasis (group A), and 16 samples exhibited such histological features (group B). Seventy one percent of the cases showed uPAR signals, and these signals were mainly localized at the cytoplasm of the tumor cells and tended to be at the front of invasive foci. 87.5% of the cases in group B showed uPAR signals against 53.3% of the cases in group A (P < .05). The rate of recurrence in the uPAR positive/negative cases in group A was 75.0% and 14.3%, respectively (P < .05). In non-neoplastic cases, e.g., chronic active hepatitis and cirrhosis, weak uPAR mRNA and protein signals were detected in hepatocytes neighboring the portal tracts, suggesting that this protein plays some role in such cases. The present study indicates that uPAR plays an important role at least in its initial stage in invasion and metastasis of HCC, and that uPAR expression can be a candidate predictor of these factors.