Evaluation of SRD5A2 sequence variants in susceptibility to hereditary and sporadic prostate cancer

Epidemiology of Prostate Cancer

Prostate cancer is the second most frequent cancer diagnosis made in men and the fifth leading cause of death worldwide. Prostate cancer may be asymptomatic at the early stage and often has an indolent course that may require only active surveillance. Based on GLOBOCAN 2018 estimates, 1,276,106 new cases of prostate cancer were reported worldwide in 2018, with higher prevalence in the developed countries. Differences in the incidence rates worldwide reflect differences in the use of diagnostic testing. Prostate cancer incidence and mortality rates are strongly related to the age with the highest incidence being seen in elderly men (> 65 years of age). African-American men have the highest incidence rates and more aggressive type of prostate cancer compared to White men. There is no evidence yet on how to prevent prostate cancer; however, it is possible to lower the risk by limiting high-fat foods, increasing the intake of vegetables and fruits and performing more exercise. Screening is highly recommended at age 45 for men with familial history and African-American men. Up-to-date statistics on prostate cancer occurrence and outcomes along with a better understanding of the etiology and causative risk factors are essential for the primary prevention of this disease.

Relationship between SRD5A2 rs9282858 polymorphism and the susceptibility of prostate cancer: A meta-analysis based on 20 publications

The pathogenetic mechanism of prostate cancer (PCa) has not been understood completely, and gene polymorphisms have been demonstrated to play a critical role in the course. It has been reported that rs9282858 polymorphism of steroid 5-α-reductase type 2 (SRD5A2) may affect the susceptibility of PCa, but some researches showed different results. We therefore carried out a meta-analysis to clarify this relationship.Relevant studies were identified through PubMed and Chinese National Knowledge Infrastructure databases concerning the association between SRD5A2 rs9282858 polymorphism and PCa. Odds ratios (ORs) with their 95% confidence intervals (95% CIs) were calculated to assess the strength of the association. Additionally, stratified analyses were performed based on ethnicity and source of control. Besides, heterogeneity test, sensitivity analysis, and publication bias evaluation were conducted in current meta-analysis as well.Ultimately, 20 publications incorporating 30 case-control studies were included in this meta-analysis, involving a total of 7300 cases and 7952 controls. The overall results demonstrated that SRD5A2 rs9282858 polymorphism was remarkably associated with increased susceptibility of PCa (TT vs. AA: OR = 4.08, 95% CI = 1.94-8.58; TT + AT vs. AA: OR = 1.28, 95% CI = 1.11-1.47; TT vs. AA + AT: OR = 4.44, 95% CI = 2.12-9.27; allele T vs. allele A: OR = 1.34, 95% CI = 1.17-1.54). After subgroup analyses by ethnicity and source of control, we also observed a similar trend in Latinos, other-ethnicity, population-based, and hospital-based groups under corresponding genetic models.Our findings indicate that SRD5A2 rs9282858 polymorphism may be a susceptible factor to PCa.

Genetic variation: effect on prostate cancer

The crucial role of androgens in the development of prostate cancer is well established. The aim of this review is to examine the role of constitutional (germline) and tumor-specific (somatic) polymorphisms within important regulatory genes of prostate cancer. These include genes encoding enzymes of the androgen biosynthetic pathway, the androgen receptor gene, genes that encode proteins of the signal transduction pathways that may have a role in disease progression and survival, and genes involved in prostate cancer angiogenesis. Characterization of deregulated pathways critical to cancer cell growth have lead to the development of new treatments, including the CYP17 inhibitor abiraterone and clinical trials using novel drugs that are ongoing or recently completed [1]. The pharmacogenetics of the drugs used to treat prostate cancer will also be addressed. This review will define how germline polymorphisms are known affect a multitude of pathways, and therefore phenotypes, in prostate cancer etiology, progression, and treatment.

Multimodality therapy for patients with high-risk prostate cancer: current status and future directions

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer death in American men. Although high-risk disease accounts for less than 15% of diagnoses, high-risk prostate cancer patients have a cancer-specific mortality rate of 15% at 10 years. There is currently no consensus on the optimal management of high-risk disease because (1) there are different primary modalities available (ie, surgery, radiation), for which there are no randomized trials comparing efficacy; and (2) unstandardized timing of different therapies (ie, neoadjuvant v concurrent v adjuvant), which makes comparisons of efficacy problematic. Increased understanding into the mechanisms leading to the formation of advanced metastatic disease has spurred the development of agents to target these pathways. However, new questions regarding optimal management of disease arise with regard to the role of these therapies in combination with "conventional" primary modalities for earlier stage, high-risk prostate cancer patients. In this article, we review the transforming world of multimodality therapy in high-risk prostate cancer.

Steroid 5-alpha-reductase type 2 (SRD5A2) V89L and A49T polymorphisms and sporadic prostate cancer risk: a meta-analysis

Steroid 5-α-reductase type 2 (SRD5A2) V89L and A49T polymorphisms are thought to play a crucial role in the androgen synthesis and metabolic pathway, but their associations with prostate cancer risk remain controversial. To provide a more precise estimation of the associations between V89L and A49T polymorphisms and prostate cancer risk, we performed a meta-analysis using all published case-control studies of prostate cancer since January 1995. We used odds ratio (OR) and its 95% confidence interval (CI) to assess the strength of the association under various genetic models in both overall and stratified analyses. We also calculated the false-positive report probability, the power of the current study, and the observed P value for significant findings. This analysis included 45 eligible studies of a total of 15,562 cases and 15,385 controls, in which no significant associations were found for the V89L polymorphisms under all genetic models. However, small excess prostate cancer risk was associated with the 49T allele in mixed populations compared with the 49A allele (OR = 1.24, 95% CI = 1.02-1.50), and similar results were observed in Caucasians (OR = 1.24, 95% CI = 1.01-1.53). The sensitivity analysis further strengthened the validity of these findings without publication bias. Although there was no overall association between V89L and prostate cancer risk, A49T might play a role in the etiology of prostate cancer among Caucasians. Additional large and well-designed studies are warranted to validate these findings.

Prostate cancer genomics, biology, and risk assessment through genome-wide association studies

Prostate cancer (PC) is the most common malignancy observed in men. It is evident that genetic factors play some important roles in PC etiology. Recently, genome-wide association studies in diverse ethnic groups have identified more than 40 germline variants of various genes or chromosomal loci that are significantly associated with PC susceptibility, including multiple 8q24 loci, prostate-specific genes, metabolic and hormone-related genes, and many regions where no coding gene is annotated. However, there are only a few variants or genes for which biological significance or functions have been elucidated so far. The greatest challenge related to genome-wide association studies loci in prostate genomics is to understand the functional consequences of these PC-associated loci and their involvement in PC biology and carcinogenesis. There have been attempts to determine PC risk estimations by combining multiple PC-associated variants for clinical tests, and these can identify a very minor population with high risk of PC. However, they cannot distinguish risk of aggressive PC from that of non-aggressive PC. Further identification of PC-susceptibility loci in larger genome-wide association studies cohorts and biological insights gained from such functional analyses have the potential to translate into clinical benefits, including the development of reliable biomarkers, risk estimation, and effective strategies for screening and prevention of PC.

Mechanisms of prostate cancer initiation and progression

Prostate cancer is a major health problem as it continues to be the most frequently diagnosed cancer in men in the Western world. While improved early detection significantly decreased mortality, prostate cancer still remains the second leading cause of cancer-related death in Western men. Understanding the mechanisms of prostate cancer initiation and progression should have a significant impact on development of novel therapeutic approaches that can help to combat this disease. The recent explosion of novel high-throughput genetic technologies together with studies in animal models and human tissues allowed a comprehensive analysis and functional validation of the molecular changes. This chapter will summarize and discuss recently identified critical genetic and epigenetic changes that drive prostate cancer initiation and progression. These discoveries should help concentrate the efforts of drug development on key pathways and molecules, and finally translate the knowledge that is gained from mechanistic studies into effective treatments.

Meta-analysis of three polymorphisms in the steroid-5-alpha-reductase, alpha polypeptide 2 gene (SRD5A2) and risk of prostate cancer

The steroid-5-alpha-reductase, alpha polypeptide 2 (SRD5A2) gene plays a crucial role in androgen metabolism pathway in human prostate. It encodes SRD5A2 enzyme, which catalyses testosterone to dihydrotestosterone (DHT). DHT is the main active structure binding with androgen receptor (AR). After the activation of AR, it further regulates a series of target genes in androgen metabolism pathway. However, no clear consensus has been reached on the association between the SRD5A2 V89L, A49T and TA repeat polymorphisms and prostate cancer (PCa) risk. Thus, we performed a meta-analysis of 31 association studies with 14,726 PCa cases and 15,802 controls. We found no association between PCa and 89L compared with 89V allele [odds ratio (OR) = 1.02, 95% confidence interval (CI) 0.98-1.06, P(heterogeneity) = 0.44]. The 49T allele showed a significantly elevated effect on the high stage (Stages III-IV) of PCa risk both under the dominant genetic model (OR = 2.13, 95% CI 1.44-3.15, P(heterogeneity) = 0.65) and in the contrast T versus A allele (OR = 2.06, 95% CI 1.41-3.02, P(heterogeneity) = 0.69). There was a significantly decreased association between PCa and long TA repeat as compared versus short TA repeat (OR = 0.86, 95% CI 0.74-1.00, P(heterogeneity) = 0.79). No significant between-study heterogeneity was found in all subjects under four genetic models (dominant model, recessive model, allele comparison and homozygosity comparison) for these three polymorphisms, respectively, so the fixed effects model was used to pool the result. Our result indicated that carriers of 49T might improve the risk of PCa in higher stages (Stages III-IV), carriers of long TA repeat might decrease the risk of PCa and 89L may not be an important risk factor for PCa. However, due to the limited sample sizes, this meta-analysis did not achieve sufficiently conclusive results. Still more well-designed studies should be performed to clarify the role of these three polymorphisms in the development of PCa.

SRD5A2 V89L polymorphism and prostate cancer risk: a meta-analysis

BACKGROUND

Increasing studies investigating the association between steroid 5-alpha reductase type II gene polymorphism at codon 89 (SRD5A2 V89L) and susceptibility to prostate cancer (PCa) confer inconsistent results. To precisely estimate the relationship with more statistical power, a meta-analysis was performed.

METHODS

A comprehensive search was conducted to identify all case-control studies investigating such an association. Odds ratio (OR) and its 95% confidence interval (CI) were used to evaluate the size effect.

RESULTS

Twenty-five eligible reports were identified including 8,615 cases/9,089 controls in 33 comparisons. In overall analysis, no significant associations were found in all genetic models. Subgroup analyses by ethnicity revealed that small excess PCa risks were observed in dominant model (OR, 1.11; 95% CI, 1.03-1.19 for (LL + VL) vs. VV; P < 0.01; P(heterogeneity) = 0.49) and L allele frequency comparison (OR, 1.09; 1.03-1.15 for L allele frequency; P < 0.01; P(heterogeneity) = 0.07) in Europeans. Meanwhile, SRD5A2 V89L polymorphism was significantly associated with an increased PCa risk in men aged < or =65 under the co-dominant (OR, 1.70; 95% CI, 1.09-2.66 for LL vs. VV; P = 0.02; P(heterogeneity) = 0.31) and recessive (OR, 1.75; 95% CI, 1.14-2.68 for LL vs. (VV + VL); P = 0.01; P(heterogeneity) = 0.12) models. However, no significant associations were found in Asians and Africans.

CONCLUSIONS

Our study suggests SRD5A2 V89L polymorphism could play a low-penetrant role in PCa risk among Europeans and individuals younger than 65 years. Additional well-designed studies are warranted to validate these findings.

Steroid 5-{alpha}-reductase Type 2 (SRD5a2) gene polymorphisms and risk of prostate cancer: a HuGE review

Steroid 5-alpha-reductase type 2 (SRD5a2) is a critical enzyme in androgen metabolism. Two polymorphisms in the SRD5a2 gene, V89L (rs523349) and A49T (rs9282858), have been studied for associations with prostate cancer risk, with conflicting results. The authors conducted a systematic review and meta-analysis (1997-2007) to examine these associations and compared the results with findings from genome-wide association studies of prostate cancer. The meta-analysis included 24 case-control studies (10,088 cases and 10,120 controls for V89L and 4,998 cases and 5,451 controls for A49T). The authors found that prostate cancer was not associated with V89L (L allele vs. V allele: odds ratio = 0.99, 95% confidence interval: 0.94, 1.05) and was probably not associated with A49T (T allele vs. A allele: odds ratio = 1.10, 95% confidence interval: 0.86, 1.40). These results could have been distorted by spectrum-of-disease bias, convenience sampling of cases and controls, genotype misclassification, and/or confounding. Neither V89L nor A49T was included in microarray chips used for published genome-wide association studies. Analysis of well-designed population-based studies with pathway-based arrays containing common genetic variants could be useful for identifying genetic factors in prostate cancer.

The SRD5A2 V89L polymorphism is associated with severity of disease in men with early onset prostate cancer

BACKGROUND

Emerging evidence indicates that testosterone (T), and not dihydrotestosterone (DHT), is the most relevant androgen that promotes carcinogenesis in the prostate. Steroid 5-alpha reductase type II (SRD5A2) catalyzes the irreversible conversion of T to DHT in male reproductive organs. Because the SRD5A2 gene is highly polymorphic at codon 89, two SRD5A2 isoforms are expressed that differ in K(m) and V(max) values. The more common and rapid catalytic isoform contains a valine residue at position 89; the slower-catalytic variant contains leucine at this position.

METHODS

Thirty-three men with early onset prostate cancer (PCa) were genotyped for the SRD5A2 V89L substitution and other polymorphisms in genes encoding receptors or enzymes that play important roles in pathways of steroid metabolism to ascertain if they were associated with standard clinical measures of disease progression at the time of diagnosis.

RESULTS

The expression of at least one SRD5A2 leucine allele in young men with PCa was associated with more significant disease at the time of presentation, as was defined by pretreatment PSA level, clinical staging and Gleason score when compared with affected subjects harboring the more common SRD5A2 valine variant. A dosage effect of a single leucine allele was evident in heterozygotes, as values of their clinical and pathological variables were consistently situated between the extremes of the homozygous V or L phenotypes.

CONCLUSION

The SRD5A2 leucine isoform appears to be acting in a dose-dependent manner as a significant disease-modifying factor in young men diagnosed with PCa.

No association between the SRD5A2 gene A49T missense variant and prostate cancer risk: lessons learned

The steroid 5-alpha reductase type II gene (SRD5A2) encodes the enzyme which converts testosterone (T) to the more active androgen dihydrotestosterone. A non-synonymous single-nucleotide polymorphism, A49T (rs9282858), in SRD5A2 has been implicated in prostate cancer risk; however, results have been inconsistent. In 1999, we reported a strong association between the A49T variant and prostate cancer risk among African-Americans and Latinos in the Hawaii-Los Angeles Multiethnic Cohort (MEC). We report here an updated analysis of MEC data including the five major ethnic groups of the MEC, an increased sample size, improved genotyping technology and a comprehensive meta-analysis of the published literature. We found a non-statistically significant positive association between prostate cancer risk and carrying either the AT or TT genotype [odds ratio (OR) = 1.16, 95% confidence interval (CI) 0.79-1.69] in the MEC. This finding is in contrast to our previous results of ORs of 3.28 and 2.50 for the association between prostate cancer risk and the variant in African-American and Latino men, respectively; this can be accounted for by genotyping error in our earlier study. Meta-analysis of the published literature, including the current MEC data, shows a summary OR of 1.13 (95% CI 0.95-1.34) for the A49T variant with prostate cancer risk among sporadic, unselected cases. After evaluating more than 6000 cases and 6000 controls, there is little evidence of a role for the SRD5A2 A49T variant in prostate cancer risk. Overall, this report highlights the importance of rigorous genotyping quality control measures and replication efforts in genetic association studies.

The epidemiology of sex steroid hormones and their signaling and metabolic pathways in the etiology of prostate cancer

The purpose of this review is to discuss the epidemiologic literature on the association of sex steroid hormones and components of their signaling and metabolic pathways with prostate cancer and to describe data evaluating racial variation in sex steroid hormone pathways as a possible explanation for the notably higher risk of prostate cancer in African-American men compared to white or Asian men. Although sex steroid hormones likely contribute to the growth and progression of prostate cancer, associations between hormones and prostate cancer risk across the range of normal levels have been difficult to reliably demonstrate epidemiologically. Methodologic issues no doubt have made the detection of these associations difficult. Of particular importance are (1) the inadequacy of measuring circulating hormones in middle age as a surrogate for the exposure in the target cells in the prostate at the relevant time in life and (2) the current inability to integrate across components of the sex steroid hormone signaling pathway to fully capture target cell androgenic and estrogenic stimulation. Although the approach of evaluating polymorphisms in genes involved in sex steroid hormone signaling or metabolism as a way to minimize some of the issues in the direct measurement of hormones is logical, the findings among these studies are somewhat difficult to reconcile as well. The problems of the changing case mix due to screening for elevated PSA, small sample sizes increasing the likelihood of false negative and false positive results, the controls and their allele frequencies not being representative of the population at risk, and lack of knowledge of the functional consequence of a polymorphism in relation to other polymorphisms in that gene or without consideration of other genes involved in the same pathway may be contributory. The primary result of the Prostate Cancer Prevention Trial confirms that intraprostatic dihydrotestosterone levels in the normal range indeed do contribute to the growth of prostate adenocarcinoma. However, the secondary result of higher-grade disease in cases in the finasteride arm coupled with clinical studies showing higher grade disease in non-metastatic cases with lower serum androgens, if not a pathological artifact or detection bias in the finasteride arm, possibly suggests a complex relationship between androgens and the growth versus differentiation of a prostate tumor. Finally, racial variation in components of the sex steroid hormone pathway do appear to exist, but whether the extent of the variation is adequately great such that it accounts for some of the substantial differences in prostate cancer incidence among blacks, whites, and Asians is unclear.

Genetic alterations in prostate cancer

Prostate cancer is the number one malignancy among men. The search for causative factors has proven to be difficult and, accordingly, treatment options for advanced prostate cancer remain limited. However, technologic breakthroughs in the fields of genetics and molecular biology have advanced our understanding of the mechanisms involved in prostate carcinogenesis. The aim of this article is to review the most recent evidence for the role of various genetic insults at specific steps in tumor formation and to suggest potential therapeutic targets.