IN-VITRO ACTIVATION OF PRO-CATHEPSIN-B BY 3 SERINE PROTEINASES - LEUKOCYTE ELASTASE, CATHEPSIN-G, AND THE UROKINASE-TYPE PLASMINOGEN-ACTIVATOR

In vitro activation of pro-cathepsin B purified from ascitic fluid of ovarian carcinomas by serine proteinases was studied. Both elastase an d cathepsin G from human leucocytes were found to be activators, on th e basis of generation of cathepsin B activity and processing of the pr ecursor. These results represent a new cooperative pathway between can cer cells and host cells. The urokinase-type plasminogen activator act ivated pro-cathepsin B faster than leucocyte proteinases. A new relati onship is emerging between the cysteine proteinases and the plasmin-ac tivation system. Both pathways suggest an important role of cathepsin B in the proteolytic cascade associated with tumour invasion.