Abstract 377: The role of VEGFR-2 in leptin induction of Notch and angiogenic features of endothelial cells.
Authors: Lanier Viola , Gillespie Corey , Leffers Merle , Elhassey Muna , Waltenberger Johannes , Gonzalez-Perez Ruben R. 
Published: August 2014

Abstract
We have previously shown that leptin is a pro-survival factor for breast cancer (BC) cells that reduces the effects of chemotherapeutics. We have also found that leptin is a pro-angiogenic, pro-inflammatory and mitogenic factor that induces the expression of Notch and VEGF/VEGFR-2 in BC and transactivates/phosphorylates VEGFR-2 in endothelial cells (EC). We hypothesize that leptin-induced transactivation of VEGFR-2 and upregulation of Notch are essential for the development of angiogenic features in EC. To assess the role of VEGFR-2 in these leptin-induced effects we used porcine aortic endothelial cells (PAEC) and human umbilical vein endothelial cells (HUVEC). PAEC wild type (do not express VEGFR-2), PAEC-expressing VEGFR-2, PAEC-expressing VEGFR-1 (negative control) and HUVEC (VEGFR-2+) were challenged with leptin. Phosphorylation/transactivation of VEGFR-2 and VEGF expression were determined by ELISA. Leptin-induced formation of EC tubules was determined using a Matrigel Assay. In a series of experiments, inhibitors of leptin (leptin peptide receptor antagonist 2, LPrA2), VEGFR-2 (kinase inhibitor, SU5416) and Notch signaling (g-secretase inhibitor, DAPT) were added to PAEC and HUVEC cultures. Leptin-dose and time-course effects on expression of Notch (receptors: Notch1, Notch2, Notch3 and Notch4); ligands: JAG1, DLL-4 and target: Survivin were determined by Western blot and Real-Time RT-PCR. In addition, siRNA VEGFR-2 and siRNA Notch 1 and 3 were used to further determine the role of VEGFR-2 transactivation and leptin-induced Notch in the development of EC angiogenic features. Our studies reinforce the idea that leptin is a potent inducer of EC angiogenic transformation via VEGFR-2 transactivation and Notch expression. Moreover, we show that an intact Leptin-VEGFR-2/Notch crosstalk is essential for leptin pro-angiogenic actions. Data generated from the present investigations suggest that leptin secreted either by adipose tissue or BC cells could be an important factor contributing to tumor angiogenesis by acting directly on cancer cells inducing VEGF secretion or through EC inducing VEGFR-2/Notch crosstalk. Combinatory therapies targeting both Notch and leptin signaling could be a new strategy for Breast Cancer treatment. Funding: This work was supported by NIH/NCI 5SC1CA138658-04 and the Georgia Cancer Coalition Distinguished Cancer Scholar Award (to RRGP), NIH/2G12RR003034-26 and U54 MSM/TU/UAB Cancer Center Partnership. This research was also supported by facilities and support services at Morehouse School of Medicine (NIH 1C06 RR18386) and by the University of Muenster, Germany.
Citation Format: Viola Lanier, Corey Gillespie, Merle Leffers, Muna Elhassey, Johannes Waltenberger, Ruben R. Gonzalez-Perez. The role of VEGFR-2 in leptin induction of Notch and angiogenic features of endothelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 377. doi:10.1158/1538-7445.AM2013-377