Tissue cathepsin B activity and serum inhibitory factor　of cathepsin B activity in patients with liver cancer

Liver tissue cathepsin B (EC 3.4.22.1) activity was measured with N-benzyloxy-carbonyl-L-arginyl-L-arginine-4-methyl-7-coumarilamide (Z-Arg-Arg-MCA) as the substrate in order to clarify the role of this enzyme in tumor invasion or metastasis of liver cancer. Serum inhibitory factor of cathepsin B activity was also determined in cirrhotic patients with hepatocellular carcinoma and in patients with other liver diseases.Cathepsin B activity of liver cancer tissues in patients with lung metastasis was higher than that in non-cancerous tissue sourrounding the main tumor. The levels of serum inhibitory factor of cathepsin B activity in patients with hepatocellular carcinoma were lower than those in healthy subjects or non-malignant chronic liver diseases. Furthemore, in hepatocellular carcinoma patients with portal invasion, serum levels of inhibitory factor of cathepsin B activity were much lower than those with no portal invasion.The results suggest that cathepsin B activity participates in tumor invasion and metastasis of liver cancer due to imbalance of enzyme-inhibitor relationship.