Purinergic regulation of vascular endothelial growth factor signaling in angiogenesis

Abstract

P2Y purine nucleotide receptors (P2YRs) promote endothelial cell tubulogenesis through breast cancer cell-secreted nucleoside diphosphate kinase (NDPK). We tested the hypothesis that activated P2Y 1 receptors transactivate vascular endothelial growth factor receptor (VEGFR-2) in angiogenic signaling. P2Y 1 R stimulation (10 M 2-methyl-thio-ATP (2MS-ATP)) of angiogenesis is suppressed by the VEGFR-2 tyrosine kinase inhibitor, SU1498 (1 M). Phosphorylation of VEGFR-2 by 0.0262 or 2.62 nM VEGF was comparable with 0.01 or 10 M 2MS-ATP stimulation of the P2Y 1 R. 2MS-ATP, and VEGF stimulation increased tyrosine phosphorylation at tyr1175. 2MS-ATP (0.1-10 M) also stimulated EC tubulogenesis in a dose-dependent manner. The addition of sub-maximal VEGF (70 pM) in the presence of increasing concentrations of 2MS-ATP yielded additive effects at 2MS-ATP concentrations 3 M, whereas producing saturated and less than additive effects at 3 M. We propose that the VEGF receptor can be activated in the absence of VEGF, and that the P2YR-VEGFR2 interaction and resulting signal transduction is a critical determinant of vascular homoeostasis and tumour-mediated angiogenesis.© 2009 Cancer Research UK.