Introduction

The steroid 5-[alpha] reductase type 2 (SRD5A2) is critical for prostatic development and growth. One-third of men are resistant to 5ARI therapies. We previously showed that expression of SRD5A2 is not static. Here we wished to identify whether absence of prostatic SRD5A2, when androgenic pathways are blocked, leads to modification of alternate hormonal pathways.

Methods

Prostatic samples were obtained from patients with symptomatic BPH undergoing transurethral resection of prostate (TURP) surgery. Methylation of SRD5A2 promoter was assessed using Methylated CpG Island Recovery Assay (MIRA). RNA was extracted for whole-transcriptome profiling analysis by Illumina Human BeadChip Arrays. Prostatic protein expression of SRD5A2, androgen receptor (AR), estrogen receptor (ER) subunits, and aromatase were determined in a panel of six BPH patients by Western blot, immunohistochemistry (IHC), and ELISA assays. Prostatic levels of testosterone (T), dihydrotestosterone (DHT), estradiol (E) were measured by HPLC-MS. In in vitro study, primary prostatic stroma cells and epithelial cell line, BPH-1, were cultured and treated with TNF-[alpha] and IL-6, and mRNA levels were determined by qPCR.

Results

In prostate specimens that were methylated at the SRD5A2 promoter locus, estrogen response genes were identified as one of the most significantly upregulated gene family members as determined by gene expression analysis. The levels of T, E and aromatase were significantly upregulated, while DHT was significantly decreased. Absence of SRD5A2 significantly upregulated the phosphorylation of ER? (pER?), but did not significantly affect the levels of total ER?, total ER? or pER?. In primary prostatic stromal cells, administration of TNF-?, but not IL-6, suppressed the level of SRD5A2 and upregulated aromatase activity and ER? expression. However, treatment of prostatic epithelial cells with TNF-? or IL-6 did not change the androgenic or estrogenic signalling, suggesting that stromal cells regulate the androgenic to estrogenic switch when SRD5A2 is absent.

Conclusions

Our study demonstrates for the first time that there is an androgenic to estrogenic switch when SRD5A2 is absent in the prostate gland. Somatic epigenetic silencing of SRD5A2 changes the prostatic hormonal milieu, and may modulate prostatic homeostasis and growth. Targeting the aromatase-estrogen-ER axis may serve as an effective treatment strategy in BPH patients who lack SRD5A2 expression.

Funding

NIH/R01 DK091353