Plasminogen activators in human colorectal neoplasia.

A crucial step in the transition from adenomatous polyp to invasive colorectal cancer is the degradation of the epithelial basement membrane. Plasminogen activators may play a part in regulating the extracellular protease environment necessary for this to occur. Both functional and antigenic activity of the two principal activators of plasminogen, tissue plasminogen activator and urokinase, were measured in 30 colorectal cancers, matched samples of mucosa, and eight adenomatous polyps. Both polyps (p less than 0.01) and carcinomas (p less than 0.001) had raised urokinase activities compared with normal mucosa, the activity being highest in the carcinomas. Activity of tissue plasminogen activator, however, was diminished in both polyps (p less than 0.01) and carcinomas (p less than 0.001) compared with normal mucosa, the values being lowest in carcinomas. Plasmin generation by urokinase--in contrast with tissue plasminogen activator--is fibrin independent and thus less subject to physiological control.