We have examined the relationship between the procoagulant activity of F3II mouse mammary carcinoma cells and the production of urokinase, a profibrinolytic serine protease involved in tumor invasion and hematogenous metastasis. F3II cells were capable of inducing the conversion of purified fibrinogen to fibrin in the presence of calcium and plasma traces. Immunocytochemical examination of semi-confluent monolayers demonstrated that F3II cells also synthesized high levels of urokinase. Although fibrinogen did not modify profibrinolytic activity produced by F3II monolayers, fibrin formation increased tumor-derived urokinase activity by two-fold. The present data provide new insights into the cooperative role of coagulation and fibrinolysis facilitating and perpetuating tumor invasion.

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