Brain tumors and plasmin inhibitors

Four different intracranial neoplasms inhibited purified plasmin in an in vitro assay. The greatest inhibition (80%) was observed with extracts of a parasagittal meningioma that had invaded and completely occluded the sinus. Significant inhibition (greater than 40%) was also observed with extracts prepared from a glioma surgically removed from a patient who had suffered three thromboembolic episodes during the preceding several months. Lesser (less than 30%) inhibition was obtained with extracts from two other patients who had no evidence of thromboembolic complications. This report constitutes the first demonstration of plasmin inhibition activity in association with brain tumors. Further studies will be required to test the hypothesis that certain intracranial tumors may escape host antitumor fibrinolytic activity by producing plasmin inhibitors and that plasmin inhibitors may play a role in the thromboembolic complications frequently seen in patients with intracranial neoplasms.