Inhibition of vascular endothelial growth factor receptor signaling leads to reversal of tumor resistance to radiotherapy.

Geng L, Donnelly E, McMahon G, Lin PC, Sierra-Rivera E, Oshinka H, Hallahan DE
Cancer Res. 2001 61 (6): 2413-9

PMID: 11289107

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.

MeSH Terms (22)

Angiogenesis Inhibitors Animals Cell Survival Dose-Response Relationship, Radiation Endothelial Growth Factors Endothelium, Vascular Enzyme Inhibitors Glioblastoma Indoles Lymphokines Melanoma, Experimental Mice Mice, Inbred C57BL Neovascularization, Pathologic Pyrroles Radiation Tolerance Receptor Protein-Tyrosine Kinases Receptors, Growth Factor Receptors, Vascular Endothelial Growth Factor Signal Transduction Vascular Endothelial Growth Factor A Vascular Endothelial Growth Factors

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