Conditional switching of vascular endothelial growth factor (VEGF) expression in tumors: induction of endothelial cell shedding and regression of hemangioblastoma …

LE Benjamin, E Keshet - Proceedings of the National …, 1997 - National Acad Sciences
LE Benjamin, E Keshet
Proceedings of the National Academy of Sciences, 1997National Acad Sciences
We have recently shown that VEGF functions as a survival factor for newly formed vessels
during developmental neovascularization, but is not required for maintenance of mature
vessels. Reasoning that expanding tumors contain a significant fraction of newly formed and
remodeling vessels, we examined whether abrupt withdrawal of VEGF will result in
regression of preformed tumor vessels. Using a tetracycline-regulated VEGF expression
system in xenografted C6 glioma cells, we showed that shutting off VEGF production leads …
We have recently shown that VEGF functions as a survival factor for newly formed vessels during developmental neovascularization, but is not required for maintenance of mature vessels. Reasoning that expanding tumors contain a significant fraction of newly formed and remodeling vessels, we examined whether abrupt withdrawal of VEGF will result in regression of preformed tumor vessels. Using a tetracycline-regulated VEGF expression system in xenografted C6 glioma cells, we showed that shutting off VEGF production leads to detachment of endothelial cells from the walls of preformed vessels and their subsequent death by apoptosis. Vascular collapse then leads to hemorrhages and extensive tumor necrosis. These results suggest that enforced withdrawal of vascular survival factors can be applied to target preformed tumor vasculature in established tumors. The system was also used to examine phenotypes resulting from over-expression of VEGF. When expression of the transfected VEGF cDNA was continuously “on,” tumors became hyper-vascularized with abnormally large vessels, presumably arising from excessive fusions. Tumors were significantly less necrotic, suggesting that necrosis in these tumors is the result of insufficient angiogenesis.
National Acad Sciences