Abstract 1247: Transcriptional regulation of VEGF by WT1 and AR in prostate cancer

Abstract

Abstract Identifying molecular mechanisms that influence prostate cancer progression is central to understanding how this disease develops. Angiogenesis is key for cancer development and growth as tumors require new blood vessels for nutrients and oxygen. Vascular endothelial growth factor (VEGF) is the most important signaling protein involved in angiogenesis and is up-regulated by oncogene expression among other things. Previous studies have shown that the zinc finger transcription factor WT1 (Wilms tumor 1) transcriptionally regulated VEGF in multiple cell lines. Additionally, WT1 activation of VEGF required an intact zinc finger domain and was mediated by DNA binding. Potential WT1 binding sites were identified in the VEGF promoter using in silico approaches and shown to bind WT1 protein using electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays. Luciferase reporter assays showed increased activation of the VEGF promoter by over-expression of WT1. Additional factors known to induce VEGF expression are growth factors, hypoxia and hormones. How androgen regulates VEGF transcription is unknown, but we have identified two potential androgen receptor (AR) binding sites within 2kb of the transcriptional start site and demonstrated reporter activation by R1881 treatment of transfected LNCaP cells. This study examined the effect of mutating selected WT1 and AR binding sites in the VEGF promoter to determine whether they were responsible for activation of VEGF transcription. Mutating these binding sites by site-directed mutagenesis significantly decreased activation of the VEGF promoter by WT1 and the androgen analog R1881 in LNCaP cells. As predicted, treatment with the anti-androgen casodex similarly eliminated hormone response of the VEGF promoter, suggesting that androgens are functioning via androgen signaling. This was confirmed in vivo by both western blot analysis of VEGF protein and quantitative real-time PCR measurement of VEGF mRNA in cells treated with casodex. This is important because androgen signaling is vital to normal prostate development and malignant prostate growth. Overall these results show that both WT1 and AR transcriptionally regulate VEGF expression in prostate cancer cells and these factors directly bind and activate the promoter in vivo. Understanding how angiogenesis is regulated will lead to improved therapy and prevention of prostate cancer progression. This work was supported by NIHR15CA11360 (GF), Sigma Xi GIAR220034 (KE), and GSSKSU (KE) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1247.