Characterization of plasminogen activators from normal human breast and colon and from breast and colon carcinomas

Triton X-100 and NaSCN extracts of 18 normal breast and colon tissues and of 20 breast and colon carcinomas were fractionated by SDS-PAGE and plasminogen activators (PA) revealed by a zymographic method. Four different lysis bands, corresponding to MWs of 54,000, 68,000, 95,000 and 110,000 were observed. Using immunoadsorption with specific antisera against urokinase (UK) and tissue PA (t-PA), we found that all normal tissue extracts contained free t-PA (68 kd). Some of these revealed, in addition, a complex (110 kd) of t-PA with a 40-kd component. The latter presumably represents the fast-acting specific inhibitor of t-PA and UK. Most carcinoma extracts contained, in addition to the two t-PA-related lysis bands, the UK-related 54 kd PA, and some a 95 kd complex of UK with the 40 kd component. For each extractant, mean total fibrinolytic activity of normal and tumor tissue was comparable when measured on conventional fibrin plates, but breast and colon carcinomas contained higher concentrations of UK-related PA. PA activity was higher in normal and carcinoma NaSCN extracts than in the corresponding Triton X-100 extracts. In general, Triton X-100 but not NaSCN extracts of malignant tissue contained a high concentration of fibrinolytic inhibitors. Mixing experiments revealed that the inhibitory activity was mainly directed against UK. It was abolished by acidification of the carcinoma extracts. The anti-UK inhibitory activity was absent in extracts of normal breast or colon and appears to be different from the 40 kd fast-acting PA inhibitor. These studies show that malignant transformation of breast and colon is accompanied by important changes of the production of a UK-related PA and of an inhibitory activity directed against UK.