title: Inhibition of vascular endothelial growth factor receptor signaling leads to reversal of tumor resistance to radiotherapy.
abstract: Certain refractory neoplasms, such as glioblastoma multiforme (GBM) and melanoma, demonstrate a resistant tumor phenotype in vivo. We observed that these refractory tumor models (GBM and melanoma) contain blood vessels that are relatively resistant to radiotherapy. To determine whether the vascular endothelial growth factor receptor-2 (Flk-1/KDR) may be a therapeutic target to improve the effects of radiotherapy, we used the soluble extracellular component of Flk-1 (ExFlk), which blocks vascular endothelial growth factor binding to Flk-1 receptor expressed on the tumor endothelium. Both sFlk-1 and the Flk-1-specifc inhibitor SU5416 eliminated the resistance phenotype in GBM and melanoma microvasculature as determined by both the vascular window and Doppler blood flow methods. Human microendothelial cells and human umbilical vein endothelial cells showed minimal radiation-induced apoptosis. The Flk-1 antagonists sFlk-1 and SU5416 reverted these cell models to apoptosis-prone phenotype. Flk-1 antagonists also reverted GBM and melanoma tumor models to radiation-sensitive phenotype after treatment with 3 Gy. These findings demonstrate that the tumor microenvironment including the survival of tumor-associated endothelial cells contributes to tumor blood vessel resistance to therapy.
authors: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors: L
authors: L
authors: Geng
authors: E
authors: E
authors: Donnelly
authors: G
authors: G
authors: McMahon
authors: P C
authors: PC
authors: Lin
authors: E
authors: E
authors: Sierra-Rivera
authors: H
authors: H
authors: Oshinka
authors: D E
authors: DE
authors: Hallahan
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D016228:Endothelial Growth Factors / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005909:Glioblastoma / Q000098:blood supply / Q000532:radiotherapy*; D007211:Indoles / Q000494:pharmacology; D008222:Lymphokines / Q000378:metabolism; D008546:Melanoma, Experimental / Q000098:blood supply / Q000532:radiotherapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000532:radiotherapy; D011758:Pyrroles / Q000494:pharmacology; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D017978:Receptors, Growth Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D040262:Receptors, Vascular Endothelial Growth Factor; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D020533:Angiogenesis Inhibitors; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D007211:Indoles; D008222:Lymphokines; D011758:Pyrroles; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C116890:Semaxinib; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor