IMMUNOHISTOCHEMICAL LOCALIZATION OF PLASMINOGEN-ACTIVATOR INHIBITOR TYPE-1 IN HUMAN BRAIN-TUMORS

We investigated the immunohistochemical localization of plasminogen ac tivator inhibitor type 1 (PAI-1) in surgical specimens of 41 human int racranial tumors. Malignant tumors (7 glioblastoma multiforme, 5 anapl astic gliomas, 4 malignant meningiomas, and 9 metastatic tumors) showe d consistently stronger PAI-I immunohistoreactivity than benign or low -grade tumors (5 low-grade gliomas, 8 benign meningiomas, and 3 Schwan nomas). Strong PAI-1 positivity was confined to glomeruloid-shaped pro liferative vessels seen in high-grade gliomas and metastatic tumors. B lood vessels near necrotic foci and some zones of necrosis also showed strong PAI-1 positivity. PAI-1 localizes in the vascular basement mem brane and perivascular connective tissue, while endothelial cells them selves show weak positivity. None of the specimens showed PAI-1 reacti vity within the tumor cells per se. Localization of PAI-1 in prolifera ting vessels suggests that PAI-1 may be involved in angiogenesis.