Abstract 1052: Variable expression of 5-alpha reductase 2 in the aging adult prostate is regulated by DNA methylation
Authors: Rongbin Ge , Wang Zongwei , Bechis Seth , Otsetov Alexander , Hua Shengyu , Wu Shulin , Wu Chin-Lee , Tabatabaei Shahin , Olumi Aria 
Published: August 2015

BACKGROUND:

5-alpha reductase type 2 (SRD5A2), an enzyme that is critical for prostatic development and growth, is utilized as an inhibitory target by finasteride for patients with bladder outlet obstrution secondary to BPH. However, we have found that many aging benign prostate tissues do not express the enzyme. Since the SRD5A2 promoter contains a CpG island, we hypothesized that somatic methylation of the promoter would be regulated by DNA methyltransferases leading to suppression of SRD5A2.

METHODS:

Benign prostatic tissues from wild-type mice at 3, 6 and 12 months of age were used. In addition, 96 prostate samples from human male patients who were treated by TURP for bladder outlet obstruction secondary to BPH were used. Methylation of SRD5A2 promoter was assessed using Methylated CpG Island Recovery Assay (MIRA). DNMT1 siRNA and 5-AZA-C were used to determine the methylation status of SRD5A2 in benign prostatic cell line, BPH-1. To determine the effect of CpG methylation, SRD5A2 promoter-luciferase constructs were methylated in vitro using M.SssI methylase. Statistical analyses were performed with JMP Pro version 11 (SAS Institute Inc., Cary, NC).

RESULTS:

We analyzed 96 human BPH samples from transurethral resection of prostate (TURP) surgeries and found that absence of SRD5A2 was closely associated with hypermethylation of the SRD5A2 promoter region. We found that methylation of SRD5A2 was regulated by DNA methytransferase 1 (DNMT1) and the cytokines, TNF-alpha, NF-κB and IL-6, regulated DNMT1protein expression and thereby indirectly affected SRD5A2 promoter methylation and gene expression. Suppression of cytokines inhibited activity of DNMT1, while over-expression of p65 or treatment with TNF-alpha or IL-6 up-regulated DNMT1. In addition, we found that methylation of the SRD5A2 promoter and concomitant decrease in protein expression were closely associated with patient's increasing age (P&lt;0.05). Finally, in murine prostate tissues, cytokine levels, DNMT1 and global methylation were all increased in older mice. Induction of inflammation with lipopolysaccharide (LPS) stimulated the TNFR1/NF-κB/IL-6/DNMT1 pathway, leading to hypermethylation of the SRD5A2 promoter and silencing of SRD5A2, while treatment with both LPS and TNF-alpha inhibitor reversed this pathway and reactivated SRD5A2.

CONCLUSIONS:

Expression of SRD5A2 is not static and ubiquitous in benign adult prostate tissues.

We show that SRD5A2 expression is lacking in many benign human adult prostate tissues. Methylation of SRD5A2 promoter region, which is regulated by DNMT1, accounts for absence of SRD5A2 expression in many adult human prostate tissues. Methylation and expression of SRD5A2 may be used as a gene signature to tailor therapies for more effective treatment of prostatic diseases.

Citation Format: Ge Rongbin, Zongwei Wang, Seth Bechis, Alexander Otsetov, Shengyu Hua, Shulin Wu, Chin-Lee Wu, Shahin Tabatabaei, Aria Olumi. Variable expression of 5-alpha reductase 2 in the aging adult prostate is regulated by DNA methylation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1052. doi:10.1158/1538-7445.AM2015-1052