Heterocyclic aromatic amine [HCA] intake and prostate cancer risk: effect modification by genetic variants

Genetic variants of antioxidant and xenobiotic metabolizing enzymes and their association with prostate cancer: A meta-analysis and functional in silico analysis

The development and progression of prostate cancer (PCa) depends on complex interactions between genetic, environmental and dietary factors that modulate the carcinogenesis process. Interactions between chemical exposures and genetic polymorphisms in genes encoding xenobiotic metabolizing enzymes (XME), antioxidant enzymes and DNA repair enzymes have been reported as the main drivers of cancer. Thus, a better understanding of the causal risk factors for PCa will provide avenues to identify men at increased risk and will contribute to develop effective detection and prevention methods. We performed a meta-analysis on 17,518 cases and 42,507 controls obtained from 42 studies to determine whether seven SNPs and one CNV pertaining to oxidative stress, xenobiotic detoxification and DNA repair enzymes are associated with the risk of PCa (GPX1 (rs1050450), XRCC1 (rs25487), PON1 (rs662), SOD2 (rs4880), CAT (rs1001179), GSTP1 (rs1695) and CNV GSTM1). A significant increased risk of PCa was found for SOD2 (rs4880) ORGG+GA vs. AA 1.08; 95%CI 1.01-1.15, CAT (rs1001179) ORTT vs. TC+CC 1.39; 95%CI 1.17-1.66, PON1 (rs662) ORCT vs. CC+TT 1.17; 95%CI 1.01-1.35, GSTP1 (rs1695) ORGG vs. GA+AA 1.20; 95%CI 1.05-1.38 and GSTM1 (dual null vs. functional genotype) ORN vs. NN1+NN2 1.34; 95%CI 1.10-1.64. The meta-analysis showed that the CNV GSTM1, and the SNPs GSTP1 (rs1695) and CAT (rs1001179) are strongly associated with a greater risk of PCa and, to a lesser extent, the genetic variants SOD2 (rs4880) and PON1 (rs662). Although several antioxidant enzymes and XME play an important role in the PCa development, other risk factors such as chemical exposures should also be considered to gain insight on PCa risk. The functional in silico analysis showed that the genetic variants studied had no clinical implication regarding malignancy, except for GPX1 (rs1050450) SNP.

Association between SOD2 V16A variant and urological cancer risk

Background: The correlation between superoxide dismutase 2 (SOD2) V16A variant and urological cancer susceptibility has been widely studied, however, with divergent results.

Results: Totally, 9,910 cancer patients and 11,239 control subjects were enrolled. V16A variant is associated with an increased susceptibility to urological cancer (A-allele vs. V-allele: OR = 1.06, 95% CI = 1.00 – 1.13, P = 0.047; AA+AV vs. VV: OR = 1.09, 95% CI = 1.02 – 1.16, P = 0.008), especially for prostate cancer (PCa). Serum SOD2 level of PCa patients with VV+VA genotypes was lower than in those with AA genotypes. SOD2 expression is downregulated in both prostate and bladder cancer, as compared to the control. Furthermore, SOD2 was found to be downregulated in more advanced PCa participants, as compared to the ones in early stages. PCa subjects with low SOD2 expression displayed a shorter disease-free survival (DFS) time compared to that of the high SOD2 expression counterparts.

Conclusions: The SOD2 V16A variant may be associated with increased urological cancer susceptibility, especially for prostate cancer.

Methods: A pooled analysis utilizing odds ratios (ORs), in silico tools and ELISA was adopted to demonstrate this association. We also used immunohistochemical staining (IHS) to assess SOD2 expression.

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline Alters Autophagosome Maturation, Cellular Lipidomic Profiles, and Expression of Core Pluripotent Factors

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), one of the most abundant heterocyclic aromatic amines (HAAs) found in the human diet, is primarily produced during high-temperature meat or fish cooking. While MeIQx has been investigated as a potential carcinogen, the cytotoxicity and related molecular mechanisms remain unclear. Here, we demonstrate that autophagosome maturation is blocked by MeIQx. Mechanistically, MeIQx inhibits acidification of lysosomes rather than prevents autophagosome-lysosome fusion. Moreover, cellular lipid profiles are altered by MeIQx treatment. Notably, many phospholipids and sphingolipids are significantly upregulated after exposure to MeIQx. Furthermore, MeIQx decreases expression of pluripotency-associated proteins in mouse embryonic stem cells (ESCs). Together, MeIQx blocks autophagosome maturation through inhibiting acidification of lysosomes, alters lipid metabolism, and decreases expression of pluripotent factors. Our studies provide more cytotoxic evidence and elucidate related mechanisms on the risk of HAA exposure and are expected to promote supervision of food safety and human health.

Association between MnSOD Val16Ala Polymorphism and Cancer Risk: Evidence from 33,098 Cases and 37,831 Controls

Manganese superoxide dismutase (MnSOD) plays a critical role in the defense against reactive oxygen species. The association between MnSOD Val16Ala polymorphism and cancer risk has been widely studied, but the results are contradictory. To obtain more precision on the association, we performed the current meta-analysis with 33,098 cases and 37,831 controls from 88 studies retrieved from PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI), and Wanfang databases. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of association. We found that the polymorphism was associated with an increased overall cancer risk (homozygous: OR = 1.09, 95% CI = 1.00-1.19; heterozygous: OR = 1.07, 95% CI = 1.02-1.12; dominant: OR = 1.08, 95% CI = 1.02-1.14; and allele comparison: OR = 1.06, 95% CI = 1.02-1.11). Stratification analysis further showed an increased risk for prostate cancer, Asians, Caucasians, population-based studies, hospital-based studies, low quality and high quality studies. However, the increased risk for MnSOD Val16Ala polymorphism among Asians needs further validation based on the false-positive report probability (FPRP) test. To summarize, this meta-analysis suggests that the MnSOD Val16Ala polymorphism is associated with significantly increased cancer risk, which needs further validation in single large studies.

Association of Glutathione S-Transferase Polymorphisms with Dietary Composition but Not Anthropometry in Obese as Well as Nonobese Individuals

OBJECTIVES

Glutathione S-transferases (GSTs) are detoxifying enzymes for a number of substrates, including some food compounds. Selected GST polymorphisms have been proven to significantly affect enzymatic activity; however, it is unclear whether this altered metabolism influences dietary composition. The objective of this study was to locate the correlation between GST polymorphisms and selected nutritional parameters, namely, fiber and vitamin C intake.

METHODS

This study was conducted on a cohort of 472 individuals (mean age 45.26 years; mean body mass index [BMI] 32.36) from the South Moravian region of the Czech Republic. Basic anthropometrical parameters were measured and no association was found for the selected polymorphisms. Polymorphisms in GSTA1, GSTM1, and GSTT1 were genotyped using a polymerase chain reaction (PCR)-based methodology. Food intake was monitored using a self-administered 7-day questionnaire that was subsequently analyzed with a special focus on vitamin C intake, fiber intake, and total energy intake.

RESULTS

For GSTA1 and GSTM1 polymorphisms, an association was observed with fiber intake. Though no association was found with vitamin C intake, mean vitamin C intake was found to be higher than recommended daily values. No association was found with either daily energy intake or anthropometric parameters.

CONCLUSION

Based on our results, GST polymorphisms seem to affect dietary composition; however, they have no effect on total energy intake or any association with obesity.

Association between manganese superoxide dismutase (MnSOD) polymorphism and prostate cancer susceptibility: a meta-analysis

BACKGROUND

Previous studies have investigated the relationship between manganese superoxide dismutase (MnSOD) Val16Ala polymorphism and prostate cancer susceptibility, but the results have remained controversial. This meta-analysis was therefore performed to clarify this association.

METHODS

The databases PubMed, Embase and Web of Science were searched for relevant available studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the strength of the association. Publication bias was estimated using Begg's funnel plots and Egger's regression test. Trial sequential analysis was used to reduce the risk of type I error and estimate whether the evidence of the results was sufficient.

RESULTS

Overall, a significant increased risk of prostate cancer was associated with MnSOD Val16Ala polymorphism for the heterozygote model (OR = 1.14; 95% CI, 1.05-1.24), homozygote model (OR = 1.18; 95% CI, 1.02-1.36), dominant model (OR = 1.24; 95% CI, 1.07-1.44) and recessive model (OR = 1.10; 95% CI, 0.96-1.24). In the subgroup analysis by genotyping method, the results were statistically significant for the TaqMan and PCR-RFLP methods. In addition, when stratified by sample size, statistically significant increased risks were found among both large samples and small samples. Furthermore, when stratified by source of control, significant results were detected in both population-based controls and hospital-based controls. By trial sequential analyses, these findings in the current study were shown to be based on sufficient evidence.

CONCLUSIONS

This meta-analysis indicated that the Ala allele of the MnSOD gene polymorphism increases prostate cancer susceptibility.

Cancer Risk and Eicosanoid Production: Interaction between the Protective Effect of Long Chain Omega-3 Polyunsaturated Fatty Acid Intake and Genotype

Dietary inclusion of fish and fish supplements as a means to improve cancer prognosis and prevent tumour growth is largely controversial. Long chain omega-3 polyunsaturated fatty acids (LCn-3 PUFA), eicosapentaenoic acid and docosahexaenoic acid, may modulate the production of inflammatory eicosanoids, thereby influencing local inflammatory status, which is important in cancer development. Although in vitro studies have demonstrated inhibition of tumour cell growth and proliferation by LCn-3 PUFA, results from human studies have been mainly inconsistent. Genes involved in the desaturation of fatty acids, as well as the genes encoding enzymes responsible for eicosanoid production, are known to be implicated in tumour development. This review discusses the current evidence for an interaction between genetic polymorphisms and dietary LCn-3 PUFA in the risk for breast, prostate and colorectal cancers, in regards to inflammation and eicosanoid synthesis.

GSTT1 Null Genotype Significantly Increases the Susceptibility to Urinary System Cancer: Evidences from 63,876 Subjects

GSTT1 gene plays an important role in detoxification and clearance of reactive oxygen species(ROS). A null variant in this gene has been demonstrated to confer cancer susceptibility. Although many studies have demonstrated the association between GSTT1 null polymorphism and urinary system cancer susceptibility, several publications reported opposite conclusions. For better understanding the effects of this polymorphism on the risk of urinary system cancer, a updated meta-analysis was performed with a total of 26,666 cases and 37,210 controls extracted from 117 studies, by following the latest meta-analysis guidelines (PRISMA). The results suggested that the GSTT1 null genotype was significantly associated with an increased risk of urinary system cancer (OR=1.13, 95%CI=1.05-1.22). Furthermore, stratified analyses by the type of cancer, ethnicity, source of control and quality score presented a significantly increased risk associated with GSTT1 null genotype in bladder and prostate cancer subgroup, Caucasians and Indians subgroup, population-based(PB) subgroup, medium quality and low quality subgroup. Overall, our meta-analysis suggested that GSTT1 null genotype is a potential cancer susceptibility variant. Well-designed and large-cohort studies are needed to confirm the association between GSTT1 null genotype and urinary system cancer risk.

GSTM1 Gene Polymorphism is Implicated in Increased Susceptibility to Prostate Cancer in Caucasians and Asians

Published reports on the relationship between GSTM1 gene polymorphisms and prostate cancer risk are heterogeneous in their conclusions, and the significance of these polymorphisms is still debated. This meta-analysis was performed to attempt to combine comparable studies, thereby increasing sample size and statistical significance in order to obtain a better evaluation of the association between GSTM1 polymorphisms and prostate cancer risk. The association investigations were identified from PubMed, Cochrane Library, and China Biological Medicine Database on March 1, 2014. Forty-three reports were recruited into this meta-analysis that contained data from 6741 patients and 9053 controls. There was a marked association between the GSTM1 null genotype and prostate cancer risk in the overall population (odds ratio = 1.39, 95% confidence interval: 1.21-1.60, P <00001), caucasians (odds ratio = 1.48, 95% confidence interval: 1.23-1.79, P <0001) and Asians (odds ratio = 1.62, 95% confidence interval: 1.16-2.27, P = .005). However, the GSTM1 null genotype was not associated with prostate cancer risk in Africans (odds ratio = 0.77, 95% confidence interval: 0.53-1.13, P = 0.19) and African Americans (odds ratio = 1.00, 95% confidence interval: 0.69-1.45, P = 0.99). In conclusion, GSTM1 null genotype was a risk factor to predict the prostate cancer risk in the overall population, Caucasians, and Asians. Although compelling, limitations inherent to meta-analysis, study design of the individual studies, and most importantly, possible gene-gene and gene-environment interactions, as well as the potential involvement of glutathione S-transferases in multiple cellular processes make drawing definite conclusions difficult.

An investigation into the association between DNA damage and dietary fatty acid in men with prostate cancer

Prostate cancer is a growing problem in New Zealand and worldwide, as populations adopt a Western style dietary pattern. In particular, dietary fat is believed to be associated with oxidative stress, which in turn may be associated with cancer risk and development. In addition, DNA damage is associated with the risk of various cancers, and is regarded as an ideal biomarker for the assessment of the influence of foods on cancer. In the study presented here, 20 men with prostate cancer adhered to a modified Mediterranean style diet for three months. Dietary records, blood fatty acid levels, prostate specific antigen, C-reactive protein and DNA damage were assessed pre- and post-intervention. DNA damage was inversely correlated with dietary adherence (p = 0.013) and whole blood monounsaturated fatty acids (p = 0.009) and oleic acid (p = 0.020). DNA damage was positively correlated with the intake of dairy products (p = 0.043), red meat (p = 0.007) and whole blood omega-6 polyunsaturated fatty acids (p = 0.015). Both the source and type of dietary fat changed significantly over the course of the dietary intervention. Levels of DNA damage were correlated with various dietary fat sources and types of dietary fat.

GSTT1 polymorphism and the risk of developing prostate cancer

A possible association between glutathione S-transferase theta 1 gene (GSTT1) polymorphism and the risk of developing prostate cancer is currently hotly debated, but evidence from various epidemiologic studies remains unclear. This investigation was performed to assess whether an association between GSTT1 polymorphism and prostate cancer risk exists by using meta-analysis to combine comparable studies, thereby increasing sample size and statistical significance, as well as to identify patterns in various studies. The association reports were identified from the PubMed database and the Cochrane Library on March 1, 2013, and data from eligible studies (from 1999-2012) were synthesized. Thirty-eight reports were included in this meta-analysis on the association of the null genotype of GSTT1 with prostate cancer risk. No solid association between the GSTT1 null genotype and prostate cancer risk could be established for the overall population (odds ratio = 1.11, 95% confidence interval: 0.97, 1.27; P = 0.13). However, the GSTT1 null genotype was distinctly associated with prostate cancer risk in Caucasians (odds ratio = 1.24, 95% confidence interval: 1.03, 1.48, P = 0.02). In conclusion, the GSTT1 null genotype is associated with prostate cancer risk in Caucasians, but not in the overall population.

Prostate cancer and the influence of dietary factors and supplements: a systematic review

Background

Prostate cancer is the second most common cause of cancer worldwide after lung cancer. There is increasing evidence that diet and lifestyle plays a crucial role in prostate cancer biology and tumourigenesis. Prostate cancer itself represents a good model of cancer in which to look for chemopreventive agents due to the high disease prevalence, slowly progressive nature, and long latency period. Dietary agents have gained considerable attention, often receiving much publicity in the media.

Aim

To review the key evidence available for potential chemopreventive nutrients.

Methods

The methodology for this review involved a PubMed search from 1990 to 2013 using the key-words “diet and prostate cancer”, “nutrition and prostate cancer”, “dietary factors and prostate cancer”, “prostate cancer epidemiology”, “prostate cancer prevention”, “prostate cancer progression”.

Results

Red meat, dietary fat and milk intake should be minimised as they appear to increase the risk of prostate cancer. Fruit and vegetables and polyphenols may be preventive in prostate cancer, but further studies are needed to draw more solid conclusions and to clarify their role in patients with an established diagnosis of prostate cancer. Selenium and vitamin supplements cannot be advocated for the prevention of prostate cancer and indeed higher doses may be associated with a worse prognosis. There is no specific evidence regarding benefits of probiotics or prebiotics in prostate cancer.

Conclusions

From the wealth of evidence available, many recommendations can be made although more randomised control trials are required. These need to be carefully designed due to the many confounding factors and heterogeneity of the population.

Polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) in ovarian cancer risk

Glutathione S-transferases (GSTs) are ubiquitous, multifunctional phase II metabolic enzymes responsible for the detoxification of estrogen involved in the development of ovarian cancer. Data from epidemiological studies show conflicting results that remain to be further clarified. We estimated in this study the genetic effects of GSTM1 and GSTT1 polymorphisms on ovarian cancer risk. Eligible studies of the two polymorphisms and ovarian cancer risk were identified from China National Knowledge Infrastructure (CNKI), PubMed, Embase, and Web of Science. We summarized all data and performed a meta-analysis. Odds ratio (OR) and 95 % CI was calculated by using the fixed effects model to estimate the associations. Eight eligible studies were finally identified providing 2,397 cases and 2,910 controls for GSTM1 polymorphism and 2,049 cases and 2,668 controls for GSTT1 polymorphism. The overall data showed that carries of the GSTM1 null genotype did not have significantly increased ovarian cancer risk compared with those who carried the GSTM1 present genotype (null vs. present-OR, 1.01; 95 % CI, 0.91-1.11; heterogeneity, P=0.672). Similarly, for GSTT1 polymorphism, we observed no association under the investigated model in the overall analysis (null vs. present-OR, 1.02; 95 % CI, 0.89-1.17; heterogeneity, P=0.372), and in the subgroup of Caucasian subjects (null vs. present-OR, 0.99; 95 % CI, 0.86-1.14; heterogeneity, P=0.959). The meta-analysis does not provide a strong evidence for causal associations between GSTM1 and GSTT1 polymorphisms and risk of ovarian cancer in Caucasians.

Significant association of Glutathione S-transferase T1 null genotype with prostate cancer risk: a meta-analysis of 26,393 subjects

Background

Recent studies on the association between Glutathione S-transferase T1 (GSTT1) polymorphism and risk of prostate cancer showed inconclusive results. To clarify this possible association, we conducted a meta-analysis of published studies.

Methods

Data were collected from the following electronic databases: Pubmed, Embase, and Chinese Biomedical Database (CBM). The odds ratio (OR) and its 95% confidence interval (95%CI) was used to assess the strength of the association. We summarized the data on the association between GSTT1 null genotype and risk of prostate cancer in the overall population, and performed subgroup analyses by ethnicity, adjusted ORs, and types of controls.

Results

Ultimately, a total of 43 studies with a total of 26,393 subjects (9,934 cases and 16,459 controls) were eligible for meta-analysis. Overall, there was a significant association between GSTT1 null genotype and increased risk of prostate cancer (OR = 1.14, 95%CI 1.01–1.29, P = 0.034). Meta-analysis of adjusted ORs also showed a significant association between GSTT1 null genotype and increased risk of prostate cancer (OR = 1.34, 95%CI 1.09–1.64, P = 0.006). Similar results were found in the subgroup analyses by ethnicity and types of controls.

Conclusion

This meta-analysis demonstrates that GSTT1 null genotype is associated with prostate cancer susceptibility, and GSTT1 null genotype contributes to increased risk of prostate cancer.

Genetic polymorphisms of GSTM1, GSTT1, and GSTP1 with prostate cancer risk: a meta-analysis of 57 studies

Background and Objectives

The GSTM1, GSTT1 and GSTP1 polymorphisms might be involved in inactivation of procarcinogens that contribute to the genesis and progression of cancers. However, studies investigating the association between GSTM1, GSTT1 or GSTP1 polymorphisms and prostate cancer (PCa) risk report conflicting results, therefore, we conducted a meta-analysis to re-examine the controversy.

Methods

Published literature from PubMed, Embase, Google Scholar and China National Knowledge Infrastructure (CNKI) were searched (updated to June 2, 2012). According to our inclusion criteria, studies that observed the association between GSTM1, GSTT1 or GSTP1 polymorphisms and PCa risk were included. The principal outcome measure was the odds ratio (OR) with 95% confidence interval (CI) for the risk of PCa associated with GSTM1, GSTT1 and GSTP1 polymorphisms.

Results

Fifty-seven studies involving 11313 cases and 12934 controls were recruited. The overall OR, which was 1.2854 (95% CI = 1.1405–1.4487), revealed a significant risk of PCa and GSTM1 null genotype, and the similar results were observed when stratified by ethnicity and control source. Further, the more important is that the present study first reported the high risks of PCa for people who with dual null genotype of GSTM1 and GSTT1 (OR = 1.4353, 95% CI = 1.0345–1.9913), or who with GSTT1 null genotype and GSTP1 A131G polymorphism (OR = 1.7335, 95% CI = 1.1067–2.7152). But no association was determined between GSTT1 null genotype (OR = 1.102, 95% CI = 0.9596–1.2655) or GSTP1 A131G polymorphism (OR = 1.0845, 95% CI = 0.96–1.2251) and the PCa risk.

Conclusions

Our meta-analysis suggested that the people with GSTM1 null genotype, with dual null genotype of GSTM1 and GSTT1, or with GSTT1 null genotype and GSTP1 A131G polymorphism are associated with high risks of PCa, but no association was found between GSTT1 null genotype or GSTP1 A131G polymorphism and the risk of PCa. Further rigorous analytical studies are highly expected to confirm our conclusions and assess gene-environment interactions with PCa risk.