Abstract 1363: VEGF reduction facilitates angiogenesis by CXCR2

Abstract PURPOSE: With multiple pathways for angiogeneis, the purpose of the study is to quantify the expression of angiogenic tyrosine kinase receptors during endothelial tubule formation while inhibiting a G-protein linked CXCR2 receptor that binds angiogenic CXC chemokines. METHODS: Using endothelial tubule formation assays on Matrigel and Growth Factor Reduced (GFR) Matrigel, and without added VEGF, human umbilical vascular endothelial cells (HUVEC) were treated with a selective small molecule non-peptide inhibitor of CXCR2 called SB225002 (N-(2-hydroxy-4-nitrophenyl)-N9-(2-bromophenyl)urea compared with control. Previous dose-inhibition curves established optimal dosing of SB225002. After 6 hours of incubation, endothelial tubule formation was quantified by counting tubule length in four random microscopic fields using the microscope camera software NIS-Elements AR 3.10 in triplicate and compared to control. In parallel, endothelial cells were collected from the Matrigel under the same conditions for quantification of angiogenesis receptors and growth factors by RT-PCR in triplicate. RESULTS: There was significant inhibition of endothelial tubule formation on Matrigel (and GFR Matrigel) by the addition of SB225002 (40-58% of inhibition) under conditions of no added VEGF when compared to control. The expression of mRNA in HUVEC cells harvested from Matrigel was not different for VEGFR1-3, FGFR1-3, and PDGFRA,B with or without the inhibitor. Under conditions of no added VEGF, the expression of CXCR2 mRNA was the same with or without the inhibitor, but the endothelial tubule formation was significantly inhibited. CONCLUSION: Under growth factor reduced conditions, including no added VEGF, the endothelial tubule formation and angiogenenic tyrosine kinase receptor expression was similar to standard matrigel. However, when a selective non-peptide inhibitor of CXCR2 (SB225002) was added, endothelial tubule formation was inhibited without change in expression of other angiogenesis receptors from HUVEC cells retrieved from the matrigel. Therefore, tubule formation continues with the chemokine/CXCR2 axis and may be an additional pathway that circumvents other attempts at angiogenesis inhibition targeting tyrosine kinase inhibitors. Citation Format: Mary A. Kosir, Donghong Ju. VEGF reduction facilitates angiogenesis by CXCR2. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1363. doi:10.1158/1538-7445.AM2015-1363