Elevation of tissue cathepsin B and L activities in gastric cancer.

Cathepsin B and L activities were determined with 7-amino-4-methyl-coumarin conjugates as substrates using small tissue specimens of gastric cancer and benign gastric ulcer. Both cathepsin B and L activities were higher in homogenates of gastric cancer tissue than in regenerative mucosa of benign gastric ulcer. Cathepsin B activity was much higher in cancer tissue than in tissue surrounding the tumor. In contrast, the activity in regenerative mucosa of benign gastric ulcer was not elevated as compared with the tissue surrounding the ulcer. Similar results were obtained with cathepsin L activity. These results indicate that cathepsin B and L are related to proliferation and evolvement of gastric cancer.