NAB2, a Corepressor of EGR-1, Inhibits Vascular Endothelial Growth Factor-mediated Gene Induction and Angiogenic Responses of Endothelial Cells

Abstract

In this study we have investigated the role of a specific corepressor of EGR-1, NAB2, to down-regulate vascular endothelial growth factor (VEGF)-induced gene expression in endothelial cells and to inhibit angiogenesis. Firstly, we show a reciprocal regulation of EGR-1 and NAB2 following VEGF treatment. During the initial phase EGR-1 is rapidly induced and NAB2 levels are down-regulated. This is followed by a reduction of EGR-1 and a concomitant increase of NAB2. Secondly, using the tissue factor gene as a readout for VEGFinduced and EGR-1-regulated gene expression we demonstrate that NAB2 can completely block VEGF-induced tissue factor reporter gene activity. Thirdly, by adenovirus-mediated expression we show that NAB2 inhibits up-regulation of tissue factor, VEGF receptor-1, and urokinase plasminogen activator mRNAs even when a combination of VEGF and bFGF is used for induction. In addition, NAB2 overexpression significantly reduced tubule and sprout formation in two different in vitro angiogenesis assays and largely prevented the invasion of cells and formation of vessel-like structures in the murine Matrigel model. These data suggest that NAB2 regulation represents a mechanism to guarantee transient EGR-1 activity following exposure of endothelial cells to VEGF and that NAB2 overexpression could be used to inhibit signals involved in the early phase of angiogenesis.

Modulation of the oncogene-dependent tissue factor expression by kinase suppressor of ras 1

“…and NFAT) [27][28][29][30]. In cancer cells, the effects of oncogenic EGFR on TF are mediated through an NFκB dependent mechanism [10], as well as by processes involving AP-1 and c-Jun Nterminal kinase (JNK) activation [12].…”

Early Growth Response-1 Induces and Enhances Vascular Endothelial Growth Factor-A Expression in Lung Cancer Cells

“…23 It has also been reported that EGR-1 and NAB-2 play pivotal roles in vascular biology, especially in VEGF-A-mediated angiogenesis. 53,54 However, obtaining evidence that EGR-1 directly regulates VEGF-A expression has heretofore been intractable because EGR-1 is immediately and transiently induced by various kinds of signals, and because conventional expression vector systems that result in sustained EGR-1 expression/overexpression reduce cell growth. 24,55 We therefore established EGR-1-inducible lung cancer cells to allow strict examination of the alterations caused by EGR-1 up-regulation, and we could successfully provide direct evidence that EGR-1 activates VEGF-A in lung cancer cells in a HIF-1␣-independent manner.…”

A therapeutic aptamer inhibits angiogenesis by specifically targeting the heparin binding domain of VEGF 165

“…A VEGF-induced TF expression assay in HUVEC was used to demonstrate the direct binding of the aptamer to the HBD in vivo (16). HUVEC up-regulate the expression of TF in response to VEGF 165 , and this up-regulation can be suppressed by the aptamer (Fig.…”