BackgroundVascular Endothelial Growth Factor (VEGF) is regulated by a number of different factors, but the mechanism(s) behind androgen-mediated regulation of VEGF in prostate cancer are poorly understood.ResultsThree novel androgen receptor (AR) binding sites were discovered in the VEGF promoter and in vivo binding of AR to these sites was demonstrated by chromatin immunoprecipitation. Mutation of these sites attenuated activation of the VEGF promoter by the androgen analog, R1881 in prostate cancer cells. The transcription factors AR and Sp1 were shown to form a nuclear complex and both bound the VEGF core promoter in chromatin of hormone treated CWR22Rv1 prostate cancer cells. The importance of the Sp1 binding site in hormone mediated activation of VEGF expression was demonstrated by site directed mutagenesis. Mutation of a critical Sp1 binding site (Sp1.4) in the VEGF core promoter region prevented activation by androgen. Similarly, suppression of Sp1 binding by Mithramycin A treatment significantly reduced VEGF expression.ConclusionsOur mechanistic study of androgen mediated induction of VEGF expression in prostate cancer cells revealed for the first time that this induction is mediated through the core promoter region and is dependent upon a critical Sp1 binding site. The importance of Sp1 binding suggests that therapy targeting the AR-Sp1 complex may dampen VEGF induced angiogenesis and, thereby, block prostate cancer progression, helping to maintain the indolent form of prostate cancer.

Background: Gene expression analyses have led to a better understanding of growth control of prostate cancer cells. We and others have identified the presence of several zinc finger transcription factors in the neoplastic prostate, suggesting a potential role for these genes in the regulation of the prostate cancer transcriptome. One of the transcription factors (TFs) identified in the prostate cancer epithelial cells was the Wilms tumor gene (WT1). To rapidly identify coordinately expressed prostate cancer growth control genes that may be regulated by WT1, we used an in silico approach.

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Licence: This open access article is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Users are allowed to share (copy and redistribute the material in any medium or format) and adapt (remix, transform, and build upon the material for any purpose, even commercially), as long as the authors and the publisher are explicitly identified and properly acknowledged as the original source. AbstractAlthough initial discoveries of Wilms tumor 1 (WT1) expression in extrarenal disease generated controversy, we and others have examined WT1 expression in non-Wilms cancers and have demonstrated that the WT1(A) isoform, lacking the lysine-threonine-serine tripeptide (KTS) insertion, transcriptionally regulates the expression of growth control genes in other cancer types. Here, we review our evidence that WT1 is expressed in prostate cancer (PC) epithelial cells and regulates PC critical genes. That WT1 may promote metastatic disease is consistent with previous findings that WT1 suppressed E-cadherin and enhanced motility of PC cells with low migratory and metastatic potential. Recent findings led us to askFraizer et al. 236whether WT1 acts as an angiogenic switch in PC. Although vascular endothelial growth factor (VEGF) is regulated at several levels and by a number of different factors, a mechanistic understanding of WT1-mediated transcriptional regulation in PC cells was previously lacking. Here, we discuss the evidence of WT1-and androgen receptor (AR)-binding sites in the VEGF promoter and show the potential for cooperation between hormone and WT1. These findings revealed that in AR-intact PC cells, WT1 was sufficient to upregulate VEGF transcription, and WT1 expression enhanced the hormone activation of VEGF expression. This notion that WT1 can activate an angiogenic switch in PC cells, to enhance tumor growth and progression to metastatic disease, is consistent with our understanding of the oncogenic nature of WT1 overexpression in inappropriate tissues or at inappropriate times. The potential for WT1 to promote both tumor angiogenesis and PC cell migration suggests that WT1 regulates genes that promote PC progression to lethal metastatic disease. Therapies targeting WT1 in PC may reduce metastatic spread and increase overall survival.