Correlation of endothelin-1 and transforming growth factor β1 with malignancy and vascularity in human gliomas

Because the prominent neovascularization characteristic of high grade primary brain tumors is composed mostly of vascular smooth muscle cells (VSMC), we studied the expression of the potent smooth muscle mitogen endothelin-1 (ET-1) and one of its secretagogues, transforming growth factor β1 (TGF-β1) in a series of astrocytic tumors. TGF-β1 is also of interest due to its known activity as an angiogenic factor. Using immunohistochemical methods, we examined 30 surgical cases: 10 glioblastoma multiforme, 10 anaplastic astrocytomas, and 10 low-grade astrocytomas. Using a monoclonal antibody to TGF-β1 and a polyclonal antibody to ET-1, we detected both growth factors in all cases of glioblastoma examined. In cases of anaplastic astrocytoma, 4 tumors were positive for both factors; 2 contained only ET-1: 2 contained only TGF-β1; and 2 exhibited no tumor cell immunoreactivity for either factor. In low-grade astrocytoma, 4 of 10 tumors showed weak ET-1 immunoreactivity; 2 of those contained TGF-β1 immunopositive tumor astrocytes; 6 tumors were negative for both factors. In all tumors that expressed both factors, serial sections showed that regions of ET-1 immunopositivity also tended to be positive for TGF-β1. Endothelial cells within all tumors were positive for ET-1. ET-1 and TGF-β1 are present in human astrocytomas and their expression correlates with tumor vascularity and malignancy. These results suggest roles for both ET-1 and TGF-β1 in the growth and progressive angiogenesis of the human glioma.