EXPRESSION OF THROMBOMODULIN IN ASTROCYTOMAS OF VARIOUS MALIGNANCY AND IN GLIOTIC AND NORMAL BRAINS

A total of 22 surgical specimens, 16 astrocytomas with various maligna ncy, 3 brains adjacent to tumor and 3 brains with non-neoplastic lesio n, was investigated immunohistochemically for the expression of thromb omodulin (TM). This membrane protein is localized on the vascular endo thelium of nearly every human tissue and plays a crucial role in the m aintenance of antithrombotic property of the endothelial cells. Althou gh the normal cerebral vessels were negative for TM, the tumor vessels were positive for TM. The increased expression of TM was, however, de monstrated not only in glioblastomas but also in low-grade astrocytoma s. Furthermore, the vessels in the brains adjacent to tumor and glioti c brains were also positive for TM. Those observations suggested that the tendency of intratumoral bleeding, which is rather characteristic of glioblastomas, is not simply explained by the altered expression of vascular endothelial TM. In two cases of glioblastoma, not only the b lood vessels but also the tumor cells were positive. Considering the m itogenic activity of thrombin, a ligand for TM, the increased expressi on of TM might be related to the tumor neovascularization and also the tumor growth.