Plasminogen activator inhibitor in stomach and colorectal carcinomas.

The content of PAI was measured in carcinoma tissues from the stomach and colorectum divided macroscopically into three portions: the central part of the carcinoma, the marginal part of the carcinoma containing some normal mucosa, and the normal mucosa. The PAI-1 antigen was highest in the central part of the carcinoma. On the other hand, no PAI-1 antigen or activity was observed in the normal mucosa. The PAI-1 in the carcinoma tissues showed a nonlytic zone with a molecular weight of 54 kd by reverse fibrin autography, and this 54 kd band reacted with anti-PAI-1 immunoglobulin G (IgG) on an immunoblotted nitrocellulose membrane. The contents of PAI-2 in the carcinoma tissues were not significantly different from those in the normal mucosa of the stomach and colorectum, respectively. In both the stomach and colorectal carcinomas, the highest value of u-PA/total PA (sum of u-PA and t-PA) was observed in the central part of the carcinoma, followed by the marginal part of the carcinoma, and was lowest in the normal mucosa. We conclude that increased levels of PAI-1 in malignant tissue of the stomach and colorectal tract may serve to modulate extracellular proteolysis by u-PA.