Abstract
Background: The etiology of benign prostatic hyperplasia (BPH) has not been well established. The preferred medical treatment for many men with symptomatic benign prostatic hyperplasia is either an α-adrenergic receptor antagonist (α-blocker), or a 5α-reductase inhibitor. Single nucleotide polymorphism (SNP) is a powerful tool for successful implementation of individualized treatment.
Methods: Eighteen SNPs associated with drug efficacy in a Chinese population were genotyped in 790 BPH cases (330 aggressive and 460 non-aggressive BPH cases) and 1008 controls. All BPH patients were treated with α-adrenergic blockers for at least 9 months. We tested the associations between tagging single nucleotide polymorphism and BPH risk/aggressiveness, clinical characteristics at baseline, including the International Prostate Symptom Score (IPSS) and total prostate volume, and changes in clinical characteristics after treatment.
Results: There were nine SNPs associated with BPH risk, clinical progression and therapeutic effect. (1) There were nine tSNPs been chosen in CYP3A4, CYP3A5 and RANBP3L genes. (2) The SNP, rs16902947 in RANBP3L at 5p13.2 (p = .01), was significantly associated with BPH. (3) We found two SNPs, rs16902947 in RANBP3L at 5p13.2 (p = .0388) and rs4646437 in CYP3A4 at 7q21.1 (p = .0325), associated with drug effect. (4) Allele “G” for rs16902947 was found to be risk alleles for BPH risk (OR= 2.357, 95%CI 1.01–1.48). The “A” allele of rs4646437 was associated with lower IPSS at baseline (β= −0.4232, p= .03255).
Conclusions: rs16902947, rs16902947 and rs4646437 single nucleotide polymorphisms are significantly associated with the clinical characteristics of benign prostatic hyperplasia and the efficacy of benign prostatic hyperplasia treatment.
Introduction
Benign prostatic hyperplasia (BPH) is the most prevalent benign disease in the aging male [Citation1]. The etiology of BPH has not been well established yet; however, age, race/ethnicity and genetics are considered as risk factors for developing BPH. The incidence is higher in Caucasians and African descendants, compared with East Asians [Citation2]. The symptoms of BPH can be broadly divided into obstructive and irritative components. The former symptoms include a weakened urinary stream, hesitancy and the need to push or strain to initiate micturition. Irritative symptoms can be much more bothersome for many men and include frequency, nocturia and urgency [Citation3]. These symptoms may adversely affect the quality of life and interfere with activities of daily living [Citation4–6].
BPH itself is actually only a histological diagnosis, which in itself is without much clinical significance. However, it becomes a clinical entity when associated with bothersome lower urinary tract symptoms (LUTS), significant prostatic enlargement and/or bladder outlet obstruction (BOO). Aging and metabolic syndrome are common risk factors of BPH [Citation7–9]. Among all men over the age of 40 years, in an age-dependent manner, approximately 50% will develop histological hyperplasia or BPH [Citation6]; of those, 30–50% will have bothersome LUTS, which may also be caused by other conditions [Citation10–13]; some will develop a significant enlargement of the prostate, which can only exist in men with histological BPH; some will develop BOO, which may also exist because of causes other than BPH and enlargement of the prostate.
The role of α1-adrenergic receptors (α1-adrenoceptors) in the causes of BPH has been expanded [Citation14]; these receptors seem to not only increase the tone of prostatic smooth muscle but may also modify prostatic growth [Citation15–17] and contribute to LUTS by effects on the bladder and the spinal cord [Citation18]. Three α1-adrenoceptor subtypes have been identified so far, i.e. subtypes α1a, α1b and α1d [Citation19]. α1a-adrenoceptors, which are predominantly situated in the prostatic smooth muscle [Citation20], presumably have a direct effect on voiding symptoms. α1d-adrenoceptors, which are mainly located in the bladder wall and spinal cord, may contribute to storage symptoms [Citation21].
Despite intense research efforts in the past five decades to elucidate the underlying etiology of prostatic growth in older men, cause-and-effect relationships have not been established. Recently, some novel medical treatments have shown considerable effect on LUTS [Citation22–25]. But the preferred medical treatment for many men with symptomatic benign prostatic hyperplasia is either an α-adrenergic receptor antagonist (α-blocker) which reduces smooth muscle tone in the prostate and bladder neck, or a 5α-reductase inhibitor, which reduces prostate volume by inducing epithelial atrophy [Citation14–16]. Multiple randomized, double-blind, multicenter, placebo-controlled studies have demonstrated the efficacy and safety of α-blockers for BPH [Citation18]. The importance of this dynamic obstruction was supported by morphometric studies, demonstrating that smooth muscle is one of the dominant cellular constituents of BPH, accounting for 40% of the area density of the hyperplastic prostate [Citation19]. The Medical Therapy of Prostatic Symptoms (MTOPS) study was designed to determine whether therapy with the α-blocker would delay or prevent clinical progression of benign prostatic hyperplasia.
Methods
Study subjects
All subjects included in this study were of Chinese Han descent, including 790 BPH cases and 1008 controls. Cases were recruited at Xinhua Hospital (Shanghai Jiao Tong University School of Medicine) in Shanghai, during the period of July 2014 to July 2015. This study was approved by the Institutional Ethic Review Board at Xinhua Hospital and written informed consent was obtained from each individual prior to qualifying study inclusion criteria. All participants gave informed consent and the study was approved by Xinhua’s Ethics Committee prior to involvement in this study.
Study inclusion criteria were as follows: (1) BPH with lower urine tract symptoms, (2) age greater than 45 years, (3) prostate gland size greater than 30 ml, (4) IPSS 7 or greater, and (5) post-void residual urine volume 150 ml or less. Exclusion criteria were as follows: (1) a history of urinary tract infection, (2) previous lower tract surgery, and (3) neurogenic bladder dysfunction.
Eligible subjects were treated with combined therapy of 4 mg α-adrenergic blockers (doxazosin) once daily. Patients were classified into “aggressive” group if they suffered from a significant increase in the IPSS score, continuous decrease in maximum urinary flow rate or BPH related complications (acute urinary retention, bladder stone or recurrent hematuria, etc.), or underwent an operation after the combined medication therapy. In contrast, patients with stable disease and without indications to receive invasive treatments were assigned to the non-aggressive group. Thus, 330 aggressive and 460 non-aggressive BPH cases were defined.
SNP selection and genotyping
A total of 18 SNPs with a minor allele frequency of greater than 0.05 were cataloged based on HapMap 3 data from the CHB population, release 27 (http://hapmap.ncbi.nlm.nih.gov). We selected tSNPs using Haploview software 15 with aggressive 2- and 3-marker tagging methods.
We genotyped these SNPs on the MassARRAY iPLEX platform (Sequenom, Inc., San Diego, CA) in a study population from Fudan University in Shanghai, China. Two duplicates and two water samples were included in each 96-well plate as polymerase chain reaction-negative controls. All assays were performed in a blinded fashion. The overall genotyping rate was 98.5%. The average concordance rate between samples was 100% among the duplicated quality control samples.
Statistical analysis
Genotype distributions for the SNP were tested for Hardy–Weinberg equilibrium (HWE). Logistic regression was used to estimate the association between SNPs and BPH risk, assuming an additive model and adjusting for age. The association of tSNPs with quantitative clinical traits, including IPSS, TPV, Qmax and QoL, was analyzed using linear models with adjustment for age. An additive model of inheritance was used for all of these analyses. For SNPs that were significant at a nominal p = .05, dominant and recessive models were also tested. All above statistical analysis were conducted using PLINK software [Citation26]. p-Values were two-tailed. An α of 0.05 was used to claim statistical significance. Results are expressed as odds ratio (OR) and 95% confidence intervals (CI).
Results and discussion
Demographic and clinical information
Phenotype data were available on 790 cases and 1008 controls. Briefly, age distribution was significantly different between cases and controls (p < .05). Therefore, all subsequent statistical analyses were age-adjusted. No significant differences in clinical characteristics were found between the aggressive and non-aggressive groups ().
Table 1. Clinical and demographic characteristics of all subjects.
Genetic association results
Genotype distributions for the SNP were in Hardy–Weinberg equilibrium (HWE) in both case and control groups (p > .05, data not shown). Three CYP3A4 SNPs (rs6945984, rs4646437 and rs2246709), two CYP3A5 SNPs (rs4646447 and rs28365067) and four SNPs (rs16902947, rs35681285, rs7779057 and rs2122469) associated with α-adrenergic blockers (doxazosin or tamsulosin hydrochloride) were selected as tSNPs and included in our study.
As shown in , rs16902947 on chromosome 5p13.2 was significantly associated with aggressive BPH compared to non-aggressive BPH (p = .01). The major alleles of the SNPs, “G” allele for rs16902947, were found to be risk alleles for BPH risk (OR =2.357, 95%CI 1.01–1.48). We also evaluated the effects of these SNPs on baseline clinical traits related to BPH (). We found that the “A” allele of rs4646437 at 7q21.1 was associated with lower IPSS at baseline (β= −0.4232, p = .03255). However, no SNP showed significant association with baseline PV. We further investigated the associations between SNPs and change of clinical traits after treatment (). The SNPs associated with aggressive BPH risk were observed to be also significantly associated with IPSS change, with p-Values of .03388 for rs16902947. None of the other SNPs were significantly associated with change of PV (all p > .05).
Table 2. Associations between SNPs and benign prostatic hyperplasia (BPH)/aggressiveness risk.
Table 3. Associations between SNPs and baseline clinical traits in BPH patients.
Table 4. Associations between SNPs and change of clinical traits after treatment in BPH patients.
Interestingly, there was a significant improvement in perceived QoL, but such improvement was not reflected in the other eight SNPs. QoL is a very subjective variable; other factors than treatment success can affect QoL. Therefore, this variable seems to be less reliable for comparing the other SNPs, which are more objective. That there seems to be an effect of the rs28365067 polymorphism on QoL, but not on the other variables, suggests that the former is caused by factors indirectly related to treatment response.
However, the rs16902947 polymorphism had had a clinically relevant effect on Qmax, and this would have been apparent even in the presence of considerable within-patient variability in these measures. This was confirmed, as in the longer term, there was no significant difference in the risk of BPH-related invasive therapy among the three genotypes.
Discussion
The prevalence of BPH increases along with age. The prevalence of pathological BPH ranges from 8 to 80% between the fourth and ninth decades of life [Citation27]. The age-adjusted prevalence of BPH among all hospitalizations increases from 4.3 to 8% from 1998 to 2008 in the USA [Citation28]. Many studies show that the risk of BPH progression is only partially decreased in men treated with 5α-reductase inhibitors or α-adrenergic receptor antagonists [Citation29–31]. To our knowledge, this is the first study to show associations between 5p13.2 and 7q21.2 SNPs and the drug efficacy of the α-adrenergic receptor antagonists as BPH treatment.
In this study, we show associations between CYP3A4, CYP3A5 or RANBP3L variants and the drug efficacy of the combination of α-adrenergic receptor antagonists as BPH treatment. Three CYP3A4 SNPs (rs6945984, rs4646437 and rs2246709), two CYP3A5 SNPs (rs4646447 and rs28365067) and four SNPs (rs16902947, rs35681285, rs7779057 and rs2122469) associated with α-adrenergic blockers (doxazosin or tamsulosin hydrochloride) were selected as tSNPs and included in our study. The SNP rs16902947 was significantly associated with BPH. rs16902947 and rs4646437 were associated with drug effect.
SNP rs16902947 is located at 7 kb upstream of RANBP3L, which encodes a paralog of RANBP3. RANBP3 functions as a negative regulator of transforming growth factor-β signaling through the interaction with the R-SMAD proteins [Citation32]. In addition, transforming growth factor-β was shown to induce uridine diphosphate glucose dehydrogenase [Citation33], which acts as a substrate for glucuronosyltransferase and regulates glucuronidation. Because glucuronidation is a key step of tamsulosin metabolism, RANBP3L may also regulate glucuronidation and, subsequently, alter tamsulosin metabolism. As tamsulosin hydrochloride is widely used for the treatment of BPH because of its better tolerability than other type of α1AR antagonists [Citation34,Citation35], prediction of drug efficacy and toxicity would contribute to better treatment of BPH patients. And one study is the first such large-scale TGF-β signaling network proposed as a mechanism for epithelial dysplasia associated with an adrenergic cause of BPH [Citation36], while RANBP3 has a definitive role in terminating TGF-β signaling [Citation32].
SNP rs4646437 lies within intron 7 of CYP3A4 (cytochrome P450, family 3, subfamily A, polypeptide 4) [Citation37], which plays an important role in drug metabolism [Citation31,Citation38]. Human CYP3A4 is the major CYP enzyme for testosterone deactivation [Citation37,Citation39]. CYP3A4 has also been shown to be involved in the regulation of cell proliferation and differentiation in prostate cells. Therefore, it is possible that rs4646437 contributes to BPH aggressiveness by regulating cell proliferation in BPH tissue. One study shows that a constitutive CYP3A4 SNP is associated with a group of men with BPH that are at an increased risk of PCa (prostatic cancer) and may be a useful component of a polygenic prediction strategy for this disease [Citation40]. Although PCa and BPH form in different areas of the prostate and present in two distinct pathogenetic pathways, studies have suggested several common characteristics between PCa and BPH, including incidence and prevalence rise with increased age, and both conditions are hormone dependent and both diseases are associated with prostatic inflammation [Citation41–44].
The primary objective of medical therapy is to improve LUTS and improve the quality of life index. Side effects that are bothersome, especially in the elderly, are dizziness and orthostatic hypotension. The results of the MTOPS trial in one study suggest that the combination of doxazosin and finasteride exerts a clinically relevant, positive effect on rates of disease progression. Men who received combination therapy were significantly less likely to experience BPH progression than those receiving either monotherapy or placebo, with risk reduction rates of 39% for doxazosin, 34% for finasteride and 67% for combination therapy compared with placebo [Citation45]. In population studies of elderly men, the presence of moderate and severe LUTS independently increased the 1-year risk of falls, and there was a modest increase in risk associated with exposure to α-adrenergic blockers [Citation46]. Thus, caution should be taken in elderly men before starting α-blockers. These findings may be useful for making future clinical decisions about using therapy in clinical practice for patients with BPH.
Some study limitations need to be noted regarding the present study. Firstly, the statistical power may not be enough for SNPs with small effect size due to the relatively small sample size, especially for association studies conducted in BPH cases only. In addition, none of the associations remain significant after Bonferroni correction. However, Bonferroni correction might be too stringent, because SNPs included in this study may have potential biological effect on BPH. Additional replication studies are warranted to further confirm our results.
Conclusion
In conclusion, we successfully identified significant association of rs16902947 on 5p13.2 and aggressiveness of BPH and associations between genetic variants of rs16902947 and rs4646437 and the drug efficacy of therapy of α-adrenergic receptor antagonists.
Ethical standards and informed consent
The research ethics was approved by Xinhua Hospital.
All the patients gave written informed consent before participation in this study.
Disclosure statement
There is no conflict of interest in the body of this manuscript.
Additional information
Funding
References
- Issa MM, Regan TS. Medical therapy for benign prostatic hyperplasia–present and future impact. Am J Manag Care. 2007;13:S4–S9.
- Ziada A, Rosenblum M, Crawford ED. Benign prostatic hyperplasia: an overview. Urology. 1999;53:1–6.
- Barry MJ. Evaluation of symptoms and quality of life in men with benign prostatic hyperplasia. Urology. 2001;58:25–32; discussion 32.
- Welch G, Weinger K, Barry MJ. Quality-of-life impact of lower urinary tract symptom severity: results from the Health Professionals Follow-up Study. Urology. 2002;59:245–250.
- Girman CJ, Jacobsen SJ, Tsukamoto T, et al. Health-related quality of life associated with lower urinary tract symptoms in four countries. Urology. 1998;51:428–436.
- Bushman W. Etiology, epidemiology, and natural history of benign prostatic hyperplasia. Urol Clin North Am. 2009;36:403–415.
- Park SG, Yeo JK, Cho DY, et al. Impact of metabolic status on the association of serum vitamin D with hypogonadism and lower urinary tract symptoms/benign prostatic hyperplasia. Aging Male. 2017 DOI:10.1080/13685538.2017.1311857
- Besiroglu H, Dursun M, Otunctemur A, et al. The association between triglyceride high density lipoprotein cholesterol ratio and benign prostate hyperplasia in non-diabetic patients: a cross-sectional study. Aging Male. 2017;23:1–7.
- Asiedu B, Anang Y, Nyarko A, et al. The role of sex steroid hormones in benign prostatic hyperplasia. Aging Male. 2017;20:17–22.
- Girman CJ. Natural history and epidemiology of benign prostatic hyperplasia: relationship among urologic measures. Urology. 1998;51:8–12.
- Girman CJ, Epstein RS, Jacobsen SJ, et al. Natural history of prostatism: impact of urinary symptoms on quality of life in 2115 randomly selected community men. Urology. 1994;44:825–831.
- Girman CJ, Jacobsen SJ, Guess HA, et al. Natural history of prostatism: relationship among symptoms, prostate volume and peak urinary flow rate. J Urol. 1995;153:1510–1515.
- Girman CJ, Jacobsen SJ, Rhodes T, et al. Association of health-related quality of life and benign prostatic enlargement. Eur Urol. 1999;35:277–284.
- Mochtar CA, Laan W, Van Houwelingen KP, et al. Polymorphisms in the alpha1A-adrenoceptor gene do not modify the short- and long-term efficacy of alpha1-adrenoceptor antagonists in the treatment of benign prostatic hyperplasia. BJU Int. 2006;97:852–855.
- McVary KT, Razzaq A, Lee C, et al. Growth of the rat prostate gland is facilitated by the autonomic nervous system. Biol Reprod. 1994;51:99–107.
- Boesch ST, Corvin S, Zhang J, et al. Modulation of the differentiation status of cultured prostatic smooth muscle cells by an α1-adrenergic receptor antagonist. Prostate. 1999;39:226–233.
- Qian X, Yu G, Qian Y, et al. Efficacy of 5α-reductase inhibitors for patients with large benign prostatic hyperplasia (>80 mL) after transurethral resection of the prostate. Aging Male. 2015;18:238–243.
- Price D. Potential mechanisms of action of superselective α(1)-adrenoceptor antagonists. Eur Urol. 2001;40:5–11.
- Civantos Calzada B, Aleixandre de Artinano A. α-adrenoceptor subtypes. Pharmacol Res. 2001;44:195–208.
- Nasu K, Moriyama N, Kawabe K, et al. Quantification and distribution of α1-adrenoceptor subtype mRNAs in human prostate: comparison of benign hypertrophied tissue and non-hypertrophied tissue. Br J Pharmacol. 1996;119:797–803.
- Malloy BJ, Price DT, Price RR, et al. α1-adrenergic receptor subtypes in human detrusor. J Urol. 1998;160:937–943.
- Ko WJ, Han HH, Ham WS, et al. Daily use of sildenafil 50mg at night effectively ameliorates nocturia in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia: an exploratory multicenter, double-blind, randomized, placebo-controlled study. Aging Male. 2017;20:81–88.
- Pajovic B, Radojevic N, Dimitrovski A, et al. The therapeutic potential of royal jelly in benign prostatic hyperplasia. Comparison with contemporary literature. Aging Male. 2016;19:192–196.
- Meuleman EJ, Legros JJ, Bouloux PM, et al. Effects of long-term oral testosterone undecanoate therapy on urinary symptoms: data from a 1-year, placebo-controlled, dose-ranging trial in aging men with symptomatic hypogonadism. Aging Male. 2015;18:157–163.
- Favilla V, Russo GI, Privitera S, et al. Impact of combination therapy 5-alpha reductase inhibitors (5-ARI) plus alpha-blockers (AB) on erectile dysfunction and decrease of libido in patients with LUTS/BPH: a systematic review with meta-analysis. Aging Male. 2016;19:175–181.
- Purcell S, Neale B, Todd-Brown K, et al. PLINK: a tool set for whole-genome association and population-based linkage analyses. Am J Hum Genet. 2007;81:559–575.
- Barry MJ, Fowler FJ, Bin L, et al. The natural history of patients with benign prostatic hyperplasia as diagnosed by North American urologists. J Urol. 1997;157:10–14; discussion 14–15.
- Stroup SP, Palazzi-Churas K, Kopp RP, et al. Trends in adverse events of benign prostatic hyperplasia (BPH) in the USA, 1998 to 2008. BJU Int. 2012;109:84–87.
- McConnell JD, Roehrborn CG, Bautista OM, et al. The long-term effect of doxazosin, finasteride, and combination therapy on the clinical progression of benign prostatic hyperplasia. N Engl J Med. 2003;349:2387–2398.
- Kaplan SA, Lee JY, Meehan AG, et al. Long-term treatment with finasteride improves clinical progression of benign prostatic hyperplasia in men with an enlarged versus a smaller prostate: data from the MTOPS trial. J Urol. 2011;185:1369–1373.
- Berges R, Gsur A, Feik E, et al. Association of polymorphisms in CYP19A1 and CYP3A4 genes with lower urinary tract symptoms, prostate volume, uroflow and PSA in a population-based sample. World J Urol. 2011;29:143–148.
- Dai F, Lin X, Chang C, et al. Nuclear export of Smad2 and Smad3 by RanBP3 facilitates termination of TGF-β signaling. Dev Cell. 2009;16:345–357.
- Bontemps Y, Vuillermoz B, Antonicelli F, et al. Specific protein-1 is a universal regulator of UDP-glucose dehydrogenase expression: its positive involvement in transforming growth factor-β signaling and inhibition in hypoxia. J Biol Chem. 2003;278:21566–21575.
- Foglar R, Shibata K, Horie K, et al. Use of recombinant α 1-adrenoceptors to characterize subtype selectivity of drugs for the treatment of prostatic hypertrophy. Eur J Pharmacol. 1995;288:201–207.
- Wilt TJ, MacDonald R, Nelson D. Tamsulosin for treating lower urinary tract symptoms compatible with benign prostatic obstruction: a systematic review of efficacy and adverse effects. J Urol. 2002;167:177–183.
- Kim J, Yanagihara Y, Kikugawa T, et al. A signaling network in phenylephrine-induced benign prostatic hyperplasia. Endocrinology. 2009;150:3576–3583.
- Mononen N, Schleutker J. Polymorphisms in genes involved in androgen pathways as risk factors for prostate cancer. J Urol. 2009;181:1541–1549.
- Wojnowski L. Genetics of the variable expression of CYP3A in humans. Ther Drug Monit. 2004;26:192–199.
- Gsur A, Feik E, Madersbacher S. Genetic polymorphisms and prostate cancer risk. World J Urol. 2004;21:414–423.
- Tayeb MT, Clark C, Sharp L, et al. CYP3A4 promoter variant is associated with prostate cancer risk in men with benign prostate hyperplasia. Oncol Rep. 2002;9:653–655.
- Alcaraz A, Hammerer P, Tubaro A, et al. Is there evidence of a relationship between benign prostatic hyperplasia and prostate cancer? Findings of a literature review. Eur Urol. 2009;55:864–873.
- Sciarra A, Di Silverio F, Salciccia S, et al. Inflammation and chronic prostatic diseases: evidence for a link? Eur Urol. 2007;52:964–972.
- De Nunzio C, Kramer G, Marberger M, et al. The controversial relationship between benign prostatic hyperplasia and prostate cancer: the role of inflammation. Eur Urol. 2011;60:106–117.
- Arivazhagan J, Nandeesha H, Dorairajan LN, et al. Association of elevated interleukin-17 and angiopoietin-2 with prostate size in benign prostatic hyperplasia. Aging Male. 2017;20:115–118.
- Fwu CW, Eggers PW, Kaplan SA, et al. Long-term effects of doxazosin, finasteride and combination therapy on quality of life in men with benign prostatic hyperplasia. J Urol. 2013;190:187–193.
- Parsons JK, Kashefi C. Physical activity, benign prostatic hyperplasia, and lower urinary tract symptoms. Eur Urol. 2008;53:1228–1235.