Characteristics of fibrinolysin secreted by cultured rat breast carcinoma cells

Abstract

Summary Fibrinolysin secreted by cultured R2426 rat breast carcinoma cells has been purified and partially characterized. Three methods of assay were used: the hydrolysis of [ 125 I]fibrinogen and N-p -tosyl- l -arginine methyl ester (TAME), and clearing of fibrin-agar plates (heated and unheated). Two types of fibrinolytic activity were identified: a plasminogen activator and a direct fibrinolysin. The fibrinolysin had direct hydrolytic action on plasminogen-free fibrinogen, fibrin, and TAME. The products of fibrinogen hydrolysis by the tumor cell fibrinolysin differed from those of human plasmin. It was heat stable (60°C, 12 h), and was inhibited by e-aminocaproic acid and soybean trypsin inhibitor. Ethylenediaminetetraacetate (EDTA) inhibited the action of the tumor cell enzyme on TAME, but not on human fibrinogen. The direct fibrinolytic activity could be separated from plasminogen activator activity by gel filtration on Sephadex G-200, and the molecular weight was estimated to be approx. 110 000 D.