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E2F1 promotes angiogenesis through the VEGF-C/VEGFR-3 axis in a feedback loop for cooperative induction of PDGF-B Free
David Engelmann1,†, Deborah Mayoli-Nüssle1,†, Christian Mayrhofer2, Katharina Fürst1, Vijay Alla1, Anja Stoll1, Alf Spitschak1, Kerstin Abshagen2, Brigitte Vollmar2, Sophia Ran3, and Brigitte M. Pützer1,*
1Institute of Experimental Gene Therapy and Cancer Research, Rostock University Medical Center, 18057 Rostock, Germany
2Institute for Experimental Surgery, Rostock University Medical Center, 18057 Rostock, Germany
3Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62794-9626, USA *Correspondence to:Brigitte M. Pützer, E-mail: brigitte.puetzer@med.uni-rostock.de
J Mol Cell Biol, Volume 5, Issue 6, December 2013, 391-403,  https://doi.org/10.1093/jmcb/mjt035
Keyword: E2F1, hypoxia, neovascularization, PDGF-B, VEGFR-3, VEGF-C, regulatory feedback loop

Angiogenesis is essential for primary tumor growth and metastatic dissemination. E2F1, frequently upregulated in advanced cancers, was recently shown to drive malignant progression. In an attempt to decipher the molecular events underlying this behavior, we demonstrate that the tumor cell-associated vascular endothelial growth factor-C/receptor-3 (VEGF-C/VEGFR-3) axis is controlled by E2F1. Activation or forced expression of E2F1 in cancer cells leads to the upregulation of VEGFR-3 and its ligand VEGF-C, whereas E2F1 depletion prevents their expression. E2F1-dependent receptor induction is crucial for tumor cells to enhance formation of capillary tubes and neovascularization in mice. We further provide evidence for a positive feedback loop between E2F1 and VEGFR-3 signaling to stimulate pro-angiogenic platelet-derived growth factor B (PDGF-B). E2F1 or VEGFR-3 knockdown results in reduced PDGF-B levels, while the coexpression synergistically upregulates promoter activity and endogenous protein expression of PDGF-B. Our findings delineate an as yet unrecognized function of E2F1 as enhancer of angiogenesis via regulation of VEGF-C/VEGFR-3 signaling in tumors to cooperatively activate PDGF-B expression. Targeting this pathway might be reasonable to complement standard anti-angiogenic treatment of cancers with deregulated E2F1.