Abstract 4164: uPA modulates angiogenesis through transcriptional regulation of vascular endothelial growth factor (VEGF) receptors VEGFR1 and VEGFR2
Authors: Stepanova Victoria , Jayaraman Padma Sheela , Zaitsev Sergei V. , Lebedeva Tatiana , Kershaw Rachael M. , Cines Douglas B. 
Published: August 2015

Abstract
The urokinase-type plasminogen activator (uPA) system has multifunctional roles in neoplastic grows and metastasis, affecting cancer cell proliferation, adhesion, migration and survival, and tumor angiogenesis. uPA mediates tumor angiogenesis and vascular permeability through proteolytic degradation of extracellular matrix proteins, activation of release of growth factors and by intracellular signaling initiated upon its binding to the uPA receptor (CD87) and others. In accord with this, we observed that VEGF-induced endothelial cell (EC) proliferation is dependent on uPA; ECs isolated from uPA knockout mice (uPA-/- ECs) show less proliferation in response to VEGF than their wild type counterparts or than uPA-/- ECs in which expression of wild type uPA has been restored using lentiviral transfection.
We reported previously that uPA is transported from cell surface to nuclei through a mechanism that requires its kringle domain, and that intranuclear uPA modulates gene transcription by binding to a subset of transcription factors (1, 2). Here, we show that uPA regulates angiogenesis in part through this novel mechanism. Wild type single-chain uPA (WT-scuPA) translocates to the nuclei of ECs, but not a kringle-deficient uPA variant (ΔK-scuPA) incapable of nuclear transport(1). Translocation of uPA is accompanied by increased expression of cell surface VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2), whereas
ΔK-scuPA had no effect on expression of either receptor.
We used a transcription factor protein-protein microarray to identify the intranuclear target responsible for regulating receptor expression. We report that uPA binds hematopoietically expressed homeobox transcription factor (HHEX), also referred to as proline-rich homeobox TF (PRH), which has been identified by us previously as a transcriptional repressor of vegf, vegfr1 and vegfr2 promoters(3). uPA directly binds to HHEX/PRH, interferes with its binding to the target DNA sequence, and de-represses transcription of vegfr1 and vegfr2 genes.
These studies identify a novel mechanism underlying the pro-angiogenic effects of VEGF through uPA binding to HHEX/PRH leading to de-repression of vegfr1 and vegfr2 gene transcription and thereby suggest that interruption of this pathway might provide a new approach to mitigate tumor angiogenesis.
References.
1. Stepanova V, Lebedeva T, Kuo A, Yarovoi S, Tkachuk S, Zaitsev S, Bdeir Kh, Dumler I, Marks M.S., Parfyonova Ye, Tkachuk VA, Higazi A.-A., Cines D.B. (2008) Blood 112(1): 100-110.
2. Asuthkar S, Stepanova V, Lebedeva T, Holterman AL, Estes N, Cines DB, Rao JS, Gondi CS. (2013) Mol Biol Cell. 24(17):2620-32.
3. Noy P, Williams H, Sawasdichai A, Gaston K, Jayaraman PS. Mol Cell Biol. (2010) 30(9):2120-34.
Note: This abstract was not presented at the meeting.
Citation Format: Victoria Stepanova, Padma Sheela Jayaraman, Sergei V. Zaitsev, Tatiana Lebedeva, Rachael M. Kershaw, Douglas B. Cines. uPA modulates angiogenesis through transcriptional regulation of vascular endothelial growth factor (VEGF) receptors VEGFR1 and VEGFR2. [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 4164. doi:10.1158/1538-7445.AM2015-4164