Association between serum sex hormone levels and prostate cancer: effect of prostate cancer on serum testosterone levels

Dietary Glycemic Index and Glycemic Load and the Risk of Prostate Cancer: An Updated Systematic Review and Dose-Response Meta-Analysis

A meta-analysis in 2015 revealed no significant association between glycemic index (GI), glycemic load (GL), and prostate cancer. Moreover, until now, no study has examined the dose-response association of GI, GL, and prostate cancer yet. The online databases were searched by two independent researchers for relevant publications up to Jan. 2019, using relevant keywords. Nine studies including five prospective and four case-control studies were included in the current systematic review and meta-analysis. These studies have included 290,911 individuals. We found a significant positive dose-response association between dietary GI and prostate cancer (P_nonlinearity = 0.03). Comparing individuals in the highest category of GI with those in the lowest category, no significant association was found between GI and prostate cancer (combined effect size: 1.08, 95% CI: 0.97-1.19, P = 0.17). Furthermore, no significant association was seen between dietary GL and prostate cancer in both dose-response analysis and when comparing the highest versus lowest categories of GL (combined effect size: 1.03, 95% CI: 0.91-1.16, P = 0.65). In conclusion, we found a significant positive dose-response association between dietary GI and prostate cancer. However, significant association was not seen for dietary GL.

The in vitro and in vivo anti-cancer activities of a standardized quassinoids composition from Eurycoma longifolia on LNCaP human prostate cancer cells

Quassinoids are a group of diterpenoids found in plants from the Simaroubaceae family. They are also the major bioactive compounds found in Eurycoma longifolia which is commonly used as traditional medicine in South East Asia to treat various ailments including sexual dysfunction and infertility. These uses are attributed to its ability to improve testosterone level in men. Chronic consumption of E. longifolia extracts has been reported to increase testosterone level in men and animal model but its effect on prostate growth remains unknown. Therefore, the present study investigates the effects of a standardized total quassinoids composition (SQ40) containing 40% of the total quassinoids found in E. longifolia on LNCaP human prostate cancer cell line. SQ40 inhibited LNCaP cell growth at IC₅₀ value of 5.97 μg/mL while the IC₅₀ on RWPE-1 human prostate normal cells was 59.26 μg/mL. SQ40 also inhibited 5α-dihydrotestosterone-stimulated growth in LNCaP cells dose-dependently. The inhibitory effect of SQ40 in anchorage-independent growth of LNCaP cells was also demonstrated using soft agar assay. SQ40 suppressed LNCaP cell growth via G₀/G₁ phase arrest which was accompanied by the down-regulation of CDK4, CDK2, Cyclin D1 and Cyclin D3 and up-regulation of p21^Waf1/Cip1 protein levels. SQ40 at higher concentrations or longer treatment duration can cause G₂M growth arrest leading to apoptotic cell death as demonstrated by the detection of poly(ADP-ribose) polymerase cleavage in LNCaP cells. Moreover, SQ40 also inhibited androgen receptor translocation to nucleus which is important for the transactivation of its target gene, prostate-specific antigen (PSA) and resulted in a significant reduction of PSA secretion after the treatment. In addition, intraperitoneal injection of 5 and 10 mg/kg of SQ40 also significantly suppressed the LNCaP tumor growth on mouse xenograft model. Results from the present study suggest that the standardized total quassinoids composition from E. longifolia promotes anti-prostate cancer activities in LNCaP human prostate cancer cells.

Polymorphism of the SRD5A2 gene and the risk of prostate cancer

Androgens are actively involved in the development of the prostate gland and appear to be essential for prostate carcinogenesis. The product of the SRD5A2 gene, membrane‑bound steroid 5‑α‑reductase, type II enzyme, is key in testosterone metabolism. The present study explored the association between the SRD5A2 V89L gene polymorphism and the risk of developing prostate cancer. The study cohort consisted of 456 male Slovak patients, including 260 cases with histologically confirmed prostate cancer and 196 age‑matched controls without any clinically suspected infections of the prostate. Polymerase chain reaction-restriction fragment length polymorphism analysis was used to detect the SRD5A2 polymorphism on codon 89. Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) for different allele variants were calculated in order to determine the association between the SRD5A2 V89L gene polymorphism and prostate cancer. The distribution of V89L variants in the control group was consistent with the Hardy‑Weinberg equilibrium (χ2 test, P=0.266) with a significant deviation in the case group (χ2 test, P=0.04). However, no association between the SRD5A2 polymorphism and an increased risk of developing prostate cancer was identified. When the wild type VV variant was used as a reference, the ORs for different allele variants ranged from 1.11 (95% CI 0.66‑1.87, P=0.70) for the LL genotype to 0.99 (95% CI 0.68‑1.46, P=0.99) for the LL + VL genotypes. No particular allele variant was identified to exhibit an increased capacity to promote the development of highly aggressive prostate cancer (Gleason ≥7) or induce carcinogenesis at an earlier onset (<65 years of age). It was confirmed that in the population studied, the SRD5A2 V89L polymorphism was not associated with the risk of prostate cancer and SRD5A2 was not shown to be a key gene involved in prostate cancer development. Published data indicate that a combination of multiple genetic changes are required for prostate cancer development, rather than a single gene change. Therefore, it was hypothesized that high-throughput genotyping may be more effective than single nucleotide polymorphism detection.

Bisphenol A exposure during adulthood alters expression of aromatase and 5α-reductase isozymes in rat prostate

The high incidence of prostate cancer (PCa) and benign prostatic hypertrophy (BPH) in elderly men is a cause of increasing public health concern. In recent years, various environmental endocrine disruptors, such as bisphenol A (BPA), have been shown to disrupt sexual organs, including the prostate gland. However, the mechanisms underlying these effects remain unclear. Because androgens and estrogens are important factors in prostate physiopathology, our objective was to examine in rat ventral prostate the effects of adult exposure to BPA on 5α-Reductase isozymes (5α-R types 1, 2, and 3) and aromatase, key enzymes in the biosynthesis of dihydrotestosterone and estradiol, respectively. Adult rats were subcutaneously injected for four days with BPA (25, 50, 300, or 600 µg/Kg/d) dissolved in vehicle. Quantitative RT-PCR, western blot and immunohistochemical analyses showed lower mRNA and protein levels of 5α-R1 and 5α-R2 in BPA-treated groups versus controls but higher mRNA levels of 5α-R3, recently proposed as a biomarker of malignancy. However, BPA treatment augmented mRNA and protein levels of aromatase, whose increase has been described in prostate diseases. BPA-treated rats also evidenced a higher plasma estradiol/testosterone ratio, which is associated with prostate disease. Our results may offer new insights into the role of BPA in the development of prostate disease and may be of great value for studying the prostate disease risk associated with exposure to BPA in adulthood.

Murine double minute 2 promoter SNP309 polymorphism and prostate cancer risk: a meta-analysis

OBJECTIVE

The murine double minute 2 gene encodes a negative regulator of the tumor protein p53. A single nucleotide polymorphism in murine double minute 2 promoter, SNP309 T>G, has been reported to alter murine double minute 2 protein expression and to accelerate tumor formation in humans. We carried out a meta-analysis to explore the association between this polymorphism and prostate cancer risk.

METHODS

All eligible studies were searched in PubMed. Crude odds ratios, with 95% confidence intervals, were assessed for the association using fixed- and random-effects models.

RESULTS

Overall, five case-control studies (872 cases, 1005 controls) were included in the meta-analysis. A significant association between murine double minute 2 SNP309 and prostate cancer risk was observed for homozygote genetic model GG versus TT (odds ratio 0.72, 95% confidence interval 0.55-0.95, P < 0.05, P = 0.130 for heterogeneity), and for dominant model TG + GG versus TT (odds ratio 0.79, 95% confidence interval 0.65-0.96, P < 0.05, P = 0.119 for heterogeneity). The stratified analysis based on ethnicity showed a significant effect of the polymorphism on prostate cancer risk in Caucasians for GG versus TT.

CONCLUSIONS

Findings of the present meta-analysis suggest that the murine double minute 2 309 G allele might be associated with a reduced risk of prostate cancer. The effect of murine double minute 2 309 G allele on tumorigenesis might be influenced by sex and hormonal status.

Effect of CYP17 and PSA gene polymorphisms on prostate cancer risk and circulating PSA levels in the Slovak population

Cytochrome P-450c17α (CYP17) and prostate-specific antigen (PSA) genes, which are involved in the androgen metabolism cascade, have been studied as possible candidates for genetic influences on prostate cancer development. Contradictory results prompted us to evaluate the frequencies of polymorphisms in the CYP17 and PSA genes as well as the association between these genetic variants and serum PSA levels in prostate cancer patients and men routinely screened for prostate cancer with PSA in the Slovak male population. The CYP17 and PSA polymorphisms were determined by the PCR-RFLP analysis in 197 Caucasian prostate cancer patients and 256 Caucasian controls. We did not find any association between the CYP17 and PSA genotypes and prostate cancer risk overall, or by grade. Also the total serum PSA levels in the cases with the AG or AA genotype were not significantly higher than in the men with the GG genotype (P > 0.05). Our study did not provide support for the hypothesized relationship between CYP17 and PSA gene polymorphisms and prostate cancer in the Slovak male population.

The impact of common genetic variations in genes of the sex hormone metabolic pathways on steroid hormone levels and prostate cancer aggressiveness

Our previous work suggested that there was no significant association between plasma steroid hormone levels and prostate cancer tumor grade at diagnosis. In this study, we systematically tested the hypothesis that inherited variations in the androgen and estrogen metabolic pathways may be associated with plasma levels of steroid hormones, or prostate cancer aggressiveness at diagnosis. Plasma hormone levels including total testosterone, total estradiol, and sex hormone-binding globulin were measured in a cohort of 508 patients identified with localized prostate cancer. D'Amico risk classification at diagnosis was also determined. A total of 143 single-nucleotide polymorphisms (SNPs) from 30 genes that are involved in androgen and estrogen metabolism were selected for analysis. The global association of genotypes with plasma hormone levels and prostate cancer aggressiveness (D'Amico risk classification) was statistically analyzed. Q values were estimated to account for multiple testing. We observed significant associations between plasma testosterone level and SNPs in HSD17B2 (rs1424151), HSD17B3 (rs9409407), and HSD17B1 (rs12602084), with P values of 0.002, 0.006, and 0.006, respectively. We also observed borderline significant associations between prostate aggressiveness at diagnosis and SNPs in AKR1C1 (rs11252845; P = 0.005), UGT2B15 (rs2045100; P = 0.007), and HSD17B12 (rs7932905; P = 0.008). No individual SNP was associated with both clinical variables. Genetic variants of genes in hormone metabolic pathways may influence plasma androgen levels or prostate cancer aggressiveness. However, it seems that the inherited variations affecting plasma hormone levels differ from those affecting disease aggressiveness.

ELAC2 polymorphisms and prostate cancer risk: a meta-analysis based on 18 case-control studies

Polymorphisms in the elaC homolog-2 (ELAC2)/HPC2 gene have been hypothesized to alter the risk of prostate cancer. However, the results of the related published studies remained conflicting. We performed a meta-analysis of 18 studies evaluating the association between ELAC2 Ser217Leu and Ala541Thr polymorphisms and prostate cancer risk. Overall, ELAC2 Leu217 allele was associated with increased prostate cancer risk as compared with the Ser217 allele (odds ratio (OR)=1.13, 95% confidence interval (CI): 1.03–1.24, P=0.019 for heterogeneity), as well as in the heterozygote comparison (OR=1.21, 95% CI: 1.07–1.36, P=0.034 for heterogeneity) and the dominant genetic model (OR=1.20, 95% CI: 1.07–1.35, P=0.025 for heterogeneity). Furthermore, the ELAC2 Thr541 allele was associated with increased prostate cancer risk as compared with the Ala541 allele (OR=1.22, 95% CI: 1.00–0.48, P=0.131 for heterogeneity). In the stratified analyses for Ser217Leu polymorphism, there was significantly increased prostate cancer risk in Asian and Caucasian populations, and studies using sporadic and familial prostate cancer cases. Similar result was found in the Asian population in the stratified analyses for Ala541Thr polymorphism. This meta-analysis showed evidence that ELAC2 Ser217Leu and Ala541Thr polymorphisms were associated with prostate cancer risk, and might be low-penetrance susceptibility markers of prostate cancer.