A Novel Polymorphism in a Forkhead Box A1 (FOXA1) Binding Site of the Human UDP Glucuronosyltransferase 2B17 Gene Modulates Promoter Activity and Is Associated with Altered Levels of Circulating Androstane-3α,17β-diol Glucuronide

Abstract

UDP glucuronosyltransferase 2B17 is present in the prostate, where it catalyzes the addition of glucuronic acid to testosterone and dihydrotestosterone and their metabolites androsterone and androstane-3␣,17␤-diol. Hence, changes in UGT2B17 gene expression may affect the capacity of the prostate to inactivate and eliminate male sex hormones. In this work, we identify a prevalent polymorphism, Ϫ155G/A, in the proximal promoter of the UGT2B17 gene. This polymorphism modulates UGT2B17 promoter activity, because luciferasegene reporter constructs containing the Ϫ155A allele were 13-fold more active than those containing the Ϫ155G allele in prostate cancer LNCaP cells. The Ϫ155G/A polymorphism is contained within a putative binding site for the transcription factor Forkhead Box A1 (FOXA1). Using gene reporter, electromobility shift, and chromatin immunoprecipitation analyses, we show that FOXA1 binds to this site and stimulates the UGT2B17 promoter. Furthermore, down-regulation of FOXA1 in LNCaP cells substantially reduces UGT2B17 mRNA levels. The binding of FOXA1 and subsequent stimulation of the UGT2B17 promoter is greatly reduced in the presence of the Ϫ155G allele compared with the Ϫ155A allele. Consonant with its capacity to be stimulated by FOXA1, the UGT2B17 Ϫ155A allele, compared with the Ϫ155G allele, is associated with higher levels of circulating androstane-3␣,17␤-diol glucuronide. Although the initial phases of prostate cancer are androgen-dependent and UGT2B17 inactivates androgens, there was no association of the UGT2B17 Ϫ155G/A polymorphism with prostate cancer risk. In summary, this work identifies FOXA1 as an important regulator of UGT2B17 expression in prostate cancer LNCaP cells and identifies a polymorphism that alters this regulation.

Forkhead Box Protein A1 Regulates UDP-Glucuronosyltransferase 2B15 Gene Transcription in LNCaP Prostate Cancer Cells

“…Hence, our results show for the first time that FOXA1, a pioneering transcription factor (Lupien et al, 2008), plays a crucial role in controlling basal expression of UGT2B15 in prostate cancer cells. Together with our previous demonstration of the importance of FOXA1 in regulating basal UGT2B17 gene expression (Hu et al, 2010), these findings provide new insights into our understanding of the molecular mechanisms that determine androgen glucuronidation capacity and hence androgen homeostasis and signaling in the prostate. Because UGT2B15 and UGT2B17 are the major enzymes inactivating and eliminating active androgens by glucuronidation, the control of UGT2B15 gene expression by FOXA1 would be of particular significance for individuals homozygous for the UGT2B17 deletion, where UGT2B15 is the only enzyme in the prostate with the capacity to effectively glucuronidate active androgens (McCarroll et al, 2006).…”

“…We recently reported that FOXA1 is a major regulator of the basal expression of UGT2B17 gene in prostate cancer cell lines (Hu et al, 2010). In this study, we report that FOXA1 is also essential for the basal transcriptional activity of the UGT2B15 gene in LNCaP cells.…”

“…1), so it is likely that they are regulated by some of the same transcription factors. We have recently shown that FOXA1 regulates the basal activity of the UGT2B17 promoter in LNCaP cells (Hu et al, 2010). We have also shown that a single base change (the A/G SNP at Ϫ155 bp) within the UGT2B17 FOXA1 site can alter promoter activity up to 13-fold.…”

Association of Uridine Diphosphate-Glucuronosyltransferase 2B Gene Variants with Serum Glucuronide Levels and Prostate Cancer Risk

“…A common genetic polymorphism in the UGT2B17 gene is gene deletion, and evidence shows that individuals who have two deleted UGT2B17 alleles secrete little-to-no urinary testosterone compared to individuals with at least one copy of the gene ( Jakobsson et al, 2006). In addition, a polymorphism in the regulatory region of the UGT2B17 gene has been associated with altered levels of AAG (Hu et al, 2010). While both the UGT2B17 and UGT2B15 polymorphisms are significantly associated with AAG levels in European populations, no observations have been made in individuals of African descent (Hsing, 2001;Swanson et al, 2007;Olsson et al, 2011).…”

UGT2B17 status and risk of prostate cancer: A meta-analysis

“…A total of 69 published records up to December 15, 2012 were identified, of which 9 were considered potentially eligible for inclusion in this meta-analysis and were retrieved in full texts. Among these, 3 studies were excluded because they had insufficient data on OR calculation [34][35][36]. Finally, 6 articles were included in the meta-analysis.…”