Evaluation of changes in the activity of proteolytic enzymes and their inhibitors in the processes that accompany the growth of gastric cancer

Abstract

Many investigators have observed a correlation between the aggressiveness of malignant tumor growth and the levels of cysteine peptidases and their autogenous inhibitors. Cathepsins B and L are activated by pepsin in an acidic pH. This fact encouraged us to measure the activity of these enzymes in tissue samples of gastric cancer.We measured the activities of cathepsins B and L, and their precursors and inhibitors, in homogenates of tissue samples obtained from operations for gastric cancer. We compared the results for the homogenates of tissues from three different sites: the tumor center, the zone of cancer invasion (border of the tumor), and healthy tissue.The highest activities of free cysteine peptidases and those in complexes with their inhibitors, as well as their precursors, were observed in the border of the tumor, while the activities in healthy tissue were significantly lower.The local activities of cysteine peptidases and their inhibitors reflect the topographical differences between the center of the tumor, the zone of invasion, and healthy tissues in gastric cancer patients. In addition, the results for the pattern of changes in the activity of cysteine peptidases according to the degree of tissue infiltration were not dependent on the method of measurement (colorimetry vs spectrofluorometry).