Angiogenesis in microvascular endothelial cells induced by glioma cells and inhibited by tumor necrosis factor in vitro

Neovascularization is a prerequisite for glioma growth, so inhibition of angiogenesis may achieve control of glioma growth. We examined whether glioma cells induce angiogenesis and proliferation in microvascular endothelial cells from Fisher 344 rat brains by co-culture in a physical separation system with rat C6 glioma cells or rat T9 gliosarcoma cells. Endothelial cells cultured on type 1 collagen formed capillary-like structures. C6 glioma cells co-cultured with endothelial cells promoted the formation of these capillary-like structures. However, conditioned medium from C6 cells inhibited the proliferation of endothelial cells. T9 cells had little effect on the formation of capillary-like structures and no effect on the proliferation of endothelial cells. We also examined the effects of human tumor necrosis factor (TNF)-alpha on the formation of the capillary-like structures and on the proliferation of endothelial cells. Human TNF-alpha inhibited the formation of capillary-like structures induced by C6 glioma cells at a concentration of 100 U/ml, as well as the proliferation of endothelial cells at a concentration of 1000 U/ml. These results indicate that induction of angiogenesis varies with glioma cell lines and angiogenesis does not correspond with proliferation of endothelial cells. TNF-alpha can inhibit angiogenesis in gliomas in vitro.