Plasminogen activators in human xenografted oro-pharyngeal squamous cell carcinomas

Specimens of squamous cell carcinomas of the head and neck established as xenografted tumour lines on nude mice were examined by the fibrin slide method for the presence of plasminogen activator(s). The fibrinolytic activity was partly quenched by antibodies against the vessel-related tissue plasminogen activator and partly by antibodies against urokinase. The results indicate that inactive pre-urokinase in tumour tissue is to some degree activated when the tumour tissue is transplanted to the nude mice. In organ culture of the tumours, urokinase of both low and high molecular form was secreted into the medium, but only traces of tissue plasminogen activator. Inhibition of urokinase activity might be an approach to hinder tumour growth.