Increased urokinase activity to antigen ratio in human renal‐cell carcinoma

Eighteen patients with renal‐cell carcinoma have been investigated in an attempt to elucidate the ratio of active urokinase enzyme to urokinase antigen in the tumor and adjacent normal kidney. The tumor itself exhibited a significantly increased total fibrinolytic activity, an increase in the relative contribution of anti‐urokinase IgG‐inhibitable plasminogen activator activity and increased levels of urokinase antigen when compared to normal renal tissue. In tumor‐adjacent tissue total fibrinolytic activity was also, but not significantly, increased, this increase being completely due to tissue‐type plasminogen activator. Correlation of active urokinase‐type plasminogen activator with urokinase antigen revealed that in tumor tissue the enzyme was present to more than 70% in its active form whereas in tumor‐adjacent tissue and normal renal tissue only half of the enzyme appeared to be active. No correlation was obtained between urokinase antigen present in one of the 3 tissues investigated and plasma urokinase antigen.