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-3α,17β-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, −155G/A, in the proximal promoter of the UGT2B17 gene. This polymorphism modulates UGT2B17 promoter activity, because luciferase-gene reporter constructs containing the −155A allele were 13-fold more active than those containing the −155G allele in prostate cancer LNCaP cells. The −155G/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 −155G allele compared with the −155A allele. Consonant with its capacity to be stimulated by FOXA1, the UGT2B17 −155A allele, compared with the −155G allele, is associated with higher levels of circulating androstane-3α,17β-diol glucuronide. Although the initial phases of prostate cancer are androgen-dependent and UGT2B17 inactivates androgens, there was no association of the UGT2B17 −155G/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.
Footnotes
The work was supported by funding from the National Health and Medical Research Council of Australia [Grant 426705].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.065953.
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ABBREVIATIONS:
- AR
- androgen receptor
- UGT
- UDP-glucuronosyltransferase
- LNCaP
- lymph node carcinoma of the prostate
- DHT
- dihydrotestosterone
- R1881
- methyltrienolone
- FOXA1
- Forkhead Box A1
- SNP
- single-nucleotide polymorphisms
- PCR
- polymerase chain reaction
- VCaP
- vertebral cancer of the prostate
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- bp
- base pair(s)
- EMSA
- electrophoretic mobility shift assay
- PSA
- prostate-specific antigen
- ChIP
- chromatin immunoprecipitation
- qPCR
- quantitative real-time PCR
- siRNA
- small interfering RNA
- RT
- reverse transcription
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- T/E
- testosterone glucuronide/epitestosterone glucuronide
- HNF
- hepatocyte nuclear factor
- Pbx
- pre-B-cell homeobox
- FXR
- farnesoid X receptor.
- Received April 28, 2010.
- Accepted July 13, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
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