[A study on cathepsin B-like substance in cancer of the urinary tract]

Cathepsin B, a cysteine proteinase, has been shown to be increased in tumor tissue and to be responsible for the process of invasion and metastasis. To study the biochemical characteristics of cathepsin B-like substance in the tissue of a non-cancerous kidney and some urologic cancer tissues, we extracted cathepsin B-like substances from a non-cancerous human kidney tissue, human renal tumor, human renal pelvic tumor and human bladder tumor. The cathepsin B-like substance extracted from the non-neoplastic human kidney has a molecular weight of approximately 28,000. On the result of western blotting with anti-human liver cathepsin B antibody, two types of protein were observed in the fraction extracted from urologic cancer tissues. The molecular weights of them were 28,000 and 35,000, respectively. Both types of cathepsin B-like substances had the same activities for benzyloxy-carbonyl-L-arginine-L-arginine-4-methyl-7-coumarylamide, and both activities were inhibited by (L-3-transcarboxyoxiran-2-carbonyl)-L-leucyl-agmatin. These findings suggest that both cancer cells of the renal parenchyma and urothelium secrete cathepsin B-like protease which express not only a normal cathepsin B but also a higher molecular weight of cathepsin B-like protease and that a higher one plays an important role in a process of invasion.