Genetic polymorphisms in GSTM1, GSTP1, and GSTT1 and the risk for breast cancer: results from the Shanghai Breast Cancer Study and meta-analysis

Identification of target proteins for breast cancer genetic risk loci and blood risk biomarkers in a large study by integrating genomic and proteomic data

Genome-wide association studies (GWAS) have identified around 200 loci associated with breast cancer risk. However, protein targets for these loci remain largely unknown. Identifying protein targets and biomarkers can improve the understanding of cancer biology and etiology and identify high-risk individuals for cancer prevention. In this study, we investigated genetically predicted levels of 1142 circulating proteins with breast cancer risk in 133 384 cases and 113 789 controls of European ancestry included in the Breast Cancer Association Consortium (BCAC). We identified 22 blood protein biomarkers associated with the risk of overall breast cancer at a false discovery rate (FDR) <0.05, including nine proteins encoded by genes located at least 500 kb away from previously reported risk variants for breast cancer. Analyses focusing on 124 encoding genes located at GWAS-identified breast cancer risk loci found 20 proteins associated with overall breast cancer risk and one protein associated with triple-negative breast cancer risk at FDR <0.05. Adjustment for the GWAS-identified risk variants significantly attenuated the association for 13 of these proteins, suggesting that these proteins may be the targets of these GWAS-identified risk loci. The identified proteins are involved in various biological processes, including glutathione conjugation, STAT5 signaling and NF-κB signaling pathways. Our study identified novel protein targets and risk biomarkers for breast cancer risk.

Evaluation of molecular markers GSTM1 and GSTT1 and clinical factors in breast cancer: case-control study and literature review

The study was conducted to evaluate the frequency of polymorphisms in GSTM1 and GSTT1 genes in patients with breast cancer compared with individuals without history of cancer, and the association of these polymorphisms with clinical/epidemiological parameters.There were evaluated 752 women (219 patients and 533 controls). Molecular analysis was performed by the Polymerase Chain Reaction (PCR). Statistical analysis was used multiple logistic regression and descriptive statistics.Age ≥50 years (OR =3.22, 95% CI =2.30 - 4.51, p <0.001) and alcohol consumption (OR =1.60, 95% CI =1.13 - 2.27, p = 0.008) were associated to the development of breast cancer, while smoking and null genotypes GSTM1 and GSTT1 presented no association. GSTM1 and GSTT1 polymorphisms presented no relationship with the clinical and histopathological parameters or molecular subtypes of breast cancer. Ninety-two percent of tumors were invasive ductal, 66% were grade II, 65% were larger than 2 cm, the stages II (35.3%) and III (31.2%) were the most prevalent, and 47.7% were molecular subtype luminal B.Individuals aged ≥50 years and alcohol consumers have more chance to developing breast cancer. GSTM1 and GSTT1 polymorphisms are not associated to the risk of breast cancer.

Association of GSTP1 p.Ile105Val (rs1695, c.313A > G) Variant with the Risk of Breast Carcinoma among Egyptian Women

Several reports examined the association of the GSTP1 p.Ile105Val (rs1695, c.313A > G) variant with the elevated risk of multiple cancerous diseases involving breast carcinoma, but with inconclusive findings. The primary purpose of this study is to test the association of this essential variant with the risk of breast carcinoma among Egyptian females. This case-control study was conducted based on 200 participants involving 100 women diagnosed with breast carcinoma and 100 unrelated cancer-free controls from the same district. The genomic DNA for all participants was genotyped utilizing T-ARMS-PCR procedure. The frequencies of the GSTP1 p.Ile105Val (rs1695, c.313A > G) variant indicated a statistically significant with the elevated risk of breast carcinoma under various genetic models, including allelic (OR = 2.48, P-value < 0.001) and dominant (OR = 2.36, P-value = 0.003) models. In conclusion, the GSTP1 p.Ile105Val (rs1695, c.313A > G) variant was considered as an independent risk factor for breast carcinoma among Egyptian women.

Glutathione S transferase T1 gene polymorphism and its promoter methylation are associated with breast cancer susceptibility in Egyptian women

BACKGROUND

Breast cancer (BC) is one of the leading causes of cancer mortality in women. Glutathione S-transferase (GSTT1) is involved in activation of detoxification reactions and catalysis of chemicals conjugation with glutathione. GSTT1 genotype is a limiting factor for some environmental diseases. Epigenetic changes have an essential role in BC through inappropriate interaction between genomic and environmental risk factors.

AIM

This study was directed to explore the association of BC risk with GSTT1 genetic variations and its methylation status in Egyptian women.

DESIGN AND METHODS

This study included 100 healthy women as the control group and 100 patients were clinically and histologically diagnosed with breast cancer. All blood samples were used for genomic DNA extraction. GSTT1 genotyping was accomplished by multiplex PCR and methylation-specific PCR was used to analyze the GSTT1 promoter methylation status.

RESULTS

Breast cancer patients showed significant incidence of null GSTT1 in relation to controls (p = 0.004). GSTT1 gene promoter methylation status showed significant difference between hypermethylated and unmethylated patients when compared with healthy subjects (p = 0.005). GSTT1 promoter methylation status was not significantly associated with null genotype. There was no significant association between GSTT1-null genotypes and BC stage in cases with or without family history, but for promotor methylation, there was significant association with stage III and IV breast cancer disease.

CONCLUSION

GSTT1 null genetic variant and promoter hypermethylation in the GSTT region of the gene may be considered as critical risk factors for BC in Egyptian women.

Antioxidant-Rich Diet, GSTP1 rs1871042 Polymorphism, and Gastric Cancer Risk in a Hospital-Based Case-Control Study

Background

Chronic gastritis along with Helicobacter pylori (H. pylori) infection has been implicated in inflammatory response-related genes linked to the causation of gastric cancer. Glutathione S-transferase Pi (GSTP1) plays a role in regulating oxidative stress and detoxification against carcinogenesis. In this study, we aimed to determine whether an antioxidant-rich diet is associated with gastric cancer risk and identify how this association could be altered by GSTP1 genetic variants.

Methods

This study included 1,245 participants (415 cases and 830 controls) matched for age and sex. The dietary antioxidant capacity was estimated based on the oxygen radical absorbance capacity (ORAC) incorporated with a semiquantitative food frequency questionnaire. Five single nucleotide polymorphisms (SNPs) of GSTP1 (rs1695, rs749174, rs1871042, rs4891, and rs947895) were selected among the exome array genotype data.

Results

High dietary ORAC was inversely associated with gastric cancer (hydrophilic ORAC OR _{T3vs. T1}, 95% CI = 0.57, 0.39–0.82, P = 0.004; lipophilic ORAC = 0.66, 0.45–0.95, P = 0.021; total phenolics = 0.57, 0.39–0.83, P = 0.005). The polymorphism rs1871042 increased the risk of gastric cancer (OR, 95% CI = 1.55, 1.10–2.16, P = 0.01, CT+TT vs. CC). A remarkably reduced risk of gastric cancer was observed among those who had a high dietary ORAC according to rs1871042 polymorphism (hydrophilic ORAC OR _{T3vs. T1}, 95% CI = 0.36, 0.17–0.78, P for trend = 0.013; lipophilic ORAC = 0.58, 0.37–0.93, P for trend = 0.021; total phenolics = 0.38, 0.17–0.83, P for trend = 0.019).

Conclusions

Our findings indicate that dietary ORAC intake may be inversely associated with the risk of gastric cancer altered by genetic variants of GSTP1, providing new intervention strategies for gastric cancer patients.

Elevated exposure to polycyclic aromatic hydrocarbons (PAHs) may trigger cancers in Pakistan: an environmental, occupational, and genetic perspective

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds which are emitted through incomplete combustion of organic materials, fossil fuels, consumption of processed meat, smoked food, and from various industrial activities. High molecular mass and mobility make PAHs widespread and lethal for human health. A cellular system in human detoxifies these toxicants through specialized enzymatic machinery called xenobiotic-metabolizing (CYP450) and phase-II (GSTs) enzymes (XMEs). These metabolizing enzymes include cytochromes P450 family (CYP1, CYP2), glutathione s-transferases, and ALDHs. Gene polymorphisms in XMEs encoding genes can compromise their metabolizing capacity to detoxify ingested carcinogens (PAHs etc.) that may lead to prolong and elevated exposure to ingested toxicants and may consequently lead to cancer. Moreover, PAHs can induce cancer through reprograming XMEs' gene functions by altering their epigenetic markers. This review article discusses possible interplay between individual's gene polymorphism in XMEs' genes, their altered epigenetic markers, and exposure to PAHs in cancer susceptibility in Pakistan.

Frequency and Association Of GSTM1 and GSTT1 Gene Polymorphisms with Survival in Breast Cancer Patients

Objective:

Glutathione S-transferase M1 and T1 (GSTM1 and GSTT1) are the key detoxification enzymes of xenobiotics, including chemotherapeutic drugs. The deletion polymorphisms of GSTM1 and GSTT1 genes are associated with reduced enzyme activity that influenced clinical outcomes of chemotherapeutic agents in breast cancer. However, there is limited information among Thai patients. This research aims to explore the frequency and role of GSTM1 and GSTT1 polymorphisms on survival among Thai patients with breast cancer.

Methods:

The retrospective cohort study was performed. Demographic data and clinicopathology characteristics were collected from hospital base registry data and medical records. A multiplex qualitative real-time PCR method was used to detect the presence or absence of the GSTM1 and GSTT1 gene in the genomic DNA samples of the participants.

Results:

The frequencies of the GSTM1 and GSTT1 null genotypes in 198 breast cancer patients were 65.70% and 33.30%, respectively. The overall survival at 1, 3 and 5 years were 95.00%, 83.00%, 71.00% respectively. The log rank test and Cox proportional hazards revealed a significant different in the 5-years overall survival according to lymph node metastasis and tumor stage (P = 0.014 and P < 0.001). No associations between overall survival and GSTM1 or GSTT1 genotype were found in single or combined genotypes analyses (P = 0.76 and P= 0.15).

Conclusion:

The results of our study provided the epidemiological information for prognostic of survival in breast cancer patients treated with chemotherapy.

Individual and combined effects of GSTM1, GSTT1, and GSTP1 polymorphisms on breast cancer risk: A meta-analysis and re-analysis of systematic meta-analyses

Background

Fourteen previous meta-analyses have been published to analyze the polymorphisms of individual GSTM1 present/null, GSTT1 present/null, and GSTP1 IIe105Val on breast cancer (BC) risk. However, their meta-analyses did not explore the combined effects of the three genetic polymorphisms on BC risk. In addition, they did not evaluate the credibility of statistically significant associations. Furthermore, a multitude of new articles have been published on these themes, and therefore a meta-analysis and re-analysis of systematic previous meta-analyses were performed to further explore these issues.

Objectives

To determine the association between the individual and combined effects of GSTM1, GSTT1, and GSTP1 polymorphisms on breast cancer risk.

Methods

Crude odds ratios (ORs) and their 95% confidence intervals (CIs) were applied to estimate the association between individual and combined effects of GSTM1, GSTT1, and GSTP1 polymorphisms on BC risk. To evaluate the credibility of statistically significant associations in the current and previous meta-analyses, we applied the the false-positive report probabilities (FPRP) test and the Venice criteria.

Results

101 publications were selected to evaluate the individual and combined effects of GSTM1, GSTT1 and GSTP1 polymorphisms on BC risk. Overall, statistically significant elevated BC risk was found in any individual and combined effects of GSTM1 present/null, GSTT1 present/null, and GSTP1 IIe105Val polymorphisms. However, when we restricted studies only involving with high-quality, matching, HWE, and genotyping examination performed blindly or with quality control, significantly increased BC risk was only found in overall population for GSTM1 null genotype, among all populations, Caucasians, and postmenopausal women for the combined effects of GSTM1 and GSTT1 polymorphisms, and in overall analysis for the combined effects of GSTM1, GSTT1, and GSTP1 IIe105Val polymorphisms. Further, less-credible positive results were identified when we evaluated the credibility of positive results of the current and previous meta-analyses.

Conclusions

This meta-analysis indicates that the individual and combined effects of GSTM1, GSTT1 and GSTP1 polymorphisms may be not associated with increased BC risk.

Glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) variants and breast cancer risk in Burkina Faso

Background and objective

Breast cancer remains the most common cause of cancer mortality in women. The aim of this study was to investigate associations between genetic variability in GSTM1 and GSTT1 and susceptibility to breast cancer.

Methods

Genomic DNA was extracted from blood samples for 80 cases of histologically diagnosed breast cancer and 100 control subjects. Genotyping analyses were performed by PCR-based methods. Associations between specific genotypes and the development of breast cancer were examined using logistic regression to calculate odds ratios [1] and 95% confidence intervals (95%CI).

Results

No correlation was found between GSTM1-null and breast cancer (OR = 1.83; 95%CI 0.90-3.71; p = 0.10), while GSTT1-null (OR = 2.42; 95%CI 1.17-5.02; p= 0.01) was associated with increased breast cancer risk. The GSTM1/GSTT1 double null was not associated with an increased risk of developing breast cancer (OR = 2.52; 95%CI 0.75-8.45; p = 0.20). Furthermore, analysis found no association between GSTM1-null (OR =1.12; 95%CI 0.08-15.50; p = 1.00) or GSTT1-null (OR = 1.71; 95%CI 0.13-22.51; p = 1.00) and the disease stage of familial breast cancer patients or sporadic breast cancer patients (GSTM1 (OR = 0.40; 95%CI 0.12-1.32; p = 0.20) and GSTT1 (OR = 1.41; 95%CI 0.39-5.12; p = 0.75)). Also, body mass index (BMI) was not associated with increased or decreased breast cancer risk in either GSTM1-null (OR = 0.60; 95%CI 0.21-1.68; p = 0.44) or GSTT1-null (OR = 0.60; 95%CI 0.21-1.68; p =0.45).

Conclusion

Our results suggest that only GSTT1-null is associated with increased susceptibility to breast cancer development.

Combined effects of GSTM1 and GSTT1 polymorphisms on breast cancer risk: A MOOSE-compliant meta-analysis and false-positive report probabilities test

Many molecular epidemiology studies have reported an association between the combined effects of glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) polymorphisms on breast cancer risk. However, the results have been controversial.A meta-analysis was performed to clarify this issue.Meta-analysis of observational studies in epidemiology guidelines was used. Pooled the crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random-effects model or fixed-effects model. Several subgroup analyses were conducted by ethnicity, source of control, matching, and menopausal status. In addition, we also performed sensitivity analysis and publication bias. Moreover, a false-positive report probability (FPRP) test was applied to assess positive results.A significantly increased breast cancer risk was observed in overall population (GSTM1 null/GSTT1 present [- +] vs GSTM1 present/GSTT1 present [+ +]: OR = 1.19, 95% CI: 1.03-1.36, GSTM1 null/GSTT1 null [- -] vs + +: OR = 1.63, 95% CI: 1.29-2.06, (- +) + GSTM1 present/GSTT1 null (+ -) vs + +: OR = 1.17, 95% CI: 1.05-1.31, (- +) + (+ -) + (- -) vs + +: OR = 1.27, 95% CI: 1.12-1.44, and - - vs (- +) + (+ -) + (+ +): OR = 1.39, 95% CI: 1.17-1.66) and several subgroup analyses, such as Caucasians, Indians, postmenopausal women, and so on. However, positive results were only considered noteworthy in overall population (- - vs + +: FPRP = 0.150 and (- +) + (+ -) + (- -) vs + +: FPRP = 0.162). Moreover, no significant association was observed when we used the trim and fill method to adjust the pooled data from all populations. Further, none of positive results of sensitivity analysis were considered noteworthy (FPRP >0.2).These positive findings should be interpreted with caution and indicate that an increased breast cancer risk may most likely result from false-positive results, rather than from true associations or biological factors on the combined effects of GSTM1 and GSTT1. Future studies should be based on sample sizes well-powered and attention needs to be paid to study design to further identify this issue.

A 6-bp Deletion Variant in a Novel Canine Glutathione-S-Transferase Gene (GSTT5) Leads to Loss of Enzyme Function

OBJECTIVES

Glutathione-S-transferases (GSTs) detoxify reactive xenobiotics, and defective GST gene polymorphisms increase cancer risk in humans. A low activity GST-theta variant was previously found in research beagles. The purpose of our study was to determine the molecular basis for this phenotype and its allele frequency in pet dogs.

METHODS

Banked livers from 45 dogs of various breeds were screened for low GST-theta activity by the substrate 1,2-dichloro-4-nitrobenzene (DCNB), and were genotyped for variants in a novel canine GST gene, GSTT5. Whole-genome sequences from 266 dogs were genotyped at one discovered variant GSTT5 locus.

RESULTS

Canine livers ranged 190-fold in GST-theta activities, and a GSTT5 exon coding variant 385_390delGACCAG (Asp129_Gln130del) was significantly associated with low activity (P < 0.0001) and a marked decrease in hepatic protein expression (P = 0.0026). Recombinant expression of variant GSTT5 led to a 92% decrease in Vmax for DCNB (P = 0.0095). The minor allele frequency (MAF) for 385_390delGACCAG was 0.144 in 45 dog livers, but was significantly higher in beagles (0.444) versus nonbeagles (0.007; P = 0.0004). The homozygous genotype was significantly over-represented in Pembroke Welsh corgis (P < 0.0001) based on available whole-genome sequence data.

CONCLUSIONS

An Asp129_Gln130del variant in canine GSTT5 is responsible for marked loss of GST-theta enzyme activity. This variant is significantly over-represented in purpose-bred laboratory beagles and in Pembroke Welsh corgis. Additional work will determine the prevalence of this variant among other purebred dogs, and will establish the substrate range of this polymorphic canine enzyme with respect to common environmental carcinogens.

Association of GSTO1 A140D and GSTO2 N142D Gene Variations with Breast Cancer Risk

Background:

Polymorphisms in glutathione S-transferase (GST) genes may contribute to breast cancer risk. The aim of this study was to investigate any association of two common GSTO1 A140D and GSTO2 N142D gene polymorphisms with breast cancer risk in an Iranian population followed by a protein structure analysis.

Materials and Methods:

In the case-control study, 303 subjects comprising 153 women with breast cancer and 150 healthy controls were included. Genotypes of GSTO1 A140D and GSTO2 N142D polymorphisms were assessed by PCR-RFLP. Bioinformatics tools were employed to evaluate the damaging effects of A140D and N142D on the structures of GSTO1 and GSTO2 proteins.

Results:

Our genetic association study revealed that the GSTO1 A140D polymorphism was associated with breast cancer in a dominant model (OR= 1.75, 95%CI= 1.07-2.86, p= 0.026). Also, the A allele was significantly associated with breast cancer risk (OR= 1.69, 95%CI= 1.09-2.60, p= 0.018). With regard to the N142D polymorphism, there were significant associations between the GG genotype (OR= 2.20, 95%CI= 1.14-4.27, p= 0.019) and the G allele (OR= 1.47, 95%CI= 1.06-2.05, p= 0.021) and risk of breast cancer. Structural analysis revealed that A140D and N142D polymorphisms cause changes in both primary and secondary structures of GSTO1 and GSTO2, respectively.

Conclusion:

Based on our results, GSTO1 A140D and GSTO2 N142D polymorphisms could be genetic risk factors for breast cancer, but further studies with larger sample sizes focusing on different ethnicities are needed to obtain more comprehensive results.

Non-coding single nucleotide variants affecting estrogen receptor binding and activity

Background

Estrogen receptor (ER) activity is critical for the development and progression of the majority of breast cancers. It is known that ER is differentially bound to DNA leading to transcriptomic and phenotypic changes in different breast cancer models. We investigated whether single nucleotide variants (SNVs) in ER binding sites (regSNVs) contribute to ER action through changes in the ER cistrome, thereby affecting disease progression. Here we developed a computational pipeline to identify SNVs in ER binding sites using chromatin immunoprecipitation sequencing (ChIP-seq) data from ER+ breast cancer models.

Methods

ER ChIP-seq data were downloaded from the Gene Expression Omnibus (GEO). GATK pipeline was used to identify SNVs and the MACS algorithm was employed to call DNA-binding sites. Determination of the potential effect of a given SNV in a binding site was inferred using reimplementation of the is-rSNP algorithm. The Cancer Genome Atlas (TCGA) data were integrated to correlate the regSNVs and gene expression in breast tumors. ChIP and luciferase assays were used to assess the allele-specific binding.

Results

Analysis of ER ChIP-seq data from MCF7 cells identified an intronic SNV in the IGF1R gene, rs62022087, predicted to increase ER binding. Functional studies confirmed that ER binds preferentially to rs62022087 versus the wild-type allele. By integrating 43 ER ChIP-seq datasets, multi-omics, and clinical data, we identified 17 regSNVs associated with altered expression of adjacent genes in ER+ disease. Of these, the top candidate was in the promoter of the GSTM1 gene and was associated with higher expression of GSTM1 in breast tumors. Survival analysis of patients with ER+ tumors revealed that higher expression of GSTM1, responsible for detoxifying carcinogens, was correlated with better outcome.

Conclusions

In conclusion, we have developed a computational approach that is capable of identifying putative regSNVs in ER ChIP-binding sites. These non-coding variants could potentially regulate target genes and may contribute to clinical prognosis in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0382-0) contains supplementary material, which is available to authorized users.

POLYMORPHISMS OF DRUG-METABOLIZING ENZYMES CYP1A2, CYP2D6, GST, NAT2 AND TRANSPORTER MDR1 IN POPULATION OF BELARUS: COMPARISON WITH SELECTED EUROPEAN AND ASIAN POPULATIONS

Drug therapeutic efficiency and development of unfavorable pharmacologic responses as well as the disease predisposition are caused first of all by patient’s genetic features. Genetic variations in genes encoding drug-metabolizing enzymes and transporter proteins are essential to understand the ethnic differences in disease occurrence, development, prognosis, therapeutic response and toxicity of drugs. For that reason, it is necessary to establish the normative frequency distribution of genotypes and alleles of these genes in a particular population. Data on frequency of pharmacogenetic polymorphisms in the of Belarus population are limited. The goal of our investigation was to analyze the frequency distribution of genotypes and alleles of genes encoding drug-metabolizing enzymes (CYP1А2, CYP2D6 – I phase; GSTs, NAT2 – II phase) and transporter protein MDR1 in the population of Belarus and comparisons with other ethnic populations. Our results indicate that clinically important genes are genetically highly variable and differ considerably between populations. Differences in allele frequencies across continents should be considered when designing clinical trials of new drugs continents should be considered when designing clinical trials of new drugs.

Molecular portrait of breast cancer in China reveals comprehensive transcriptomic likeness to Caucasian breast cancer and low prevalence of luminal A subtype

The recent dramatic increase in breast cancer incidence across China with progressive urbanization and economic development has signaled the urgent need for molecular and clinical detailing of breast cancer in the Chinese population. Our analyses of a unique transethnic collection of breast cancer frozen specimens from Shanghai Fudan Cancer Center (Chinese Han) profiled simultaneously with an analogous Caucasian Italian series revealed consistent transcriptomic data lacking in batch effects. The prevalence of Luminal A subtype was significantly lower in Chinese series, impacting the overall prevalence of estrogen receptor (ER)-positive disease in a large cohort of Chinese/Caucasian patients. Unsupervised and supervised comparison of gene and microRNA (miRNA) profiles of Chinese and Caucasian samples revealed extensive similarity in the comprehensive taxonomy of transcriptional elements regulating breast cancer biology. Partition of gene expression data using gene lists relevant to breast cancer as "intrinsic" and "extracellular matrix" genes identified Chinese and Caucasian subgroups with equivalent global gene and miRNA profiles. These findings indicate that in the Chinese and Caucasian groups, breast neoplasia and the surrounding stromal characteristics undergo the same differentiation and molecular processes. Transcriptional similarity across transethnic cohorts may simplify translational medicine approaches and clinical management of breast cancer patients worldwide.

Association between GSTP1 genotypes and hormone receptor phenotype in invasive ductal carcinomas of breast

Eighty six cases of invasive ductal breast carcinomas were utilized to investigate GSTP1 polymorphisms in certain immunohistochemistry (IHC) subtypes of breast cancer with respect to ER, PR and HER2 expression. The frequency of wild allele homozygote, heterozygote and variant allele homozygote genotypes were 46.5%, 52.3% and 1.16% respectively; Whereas 54.3% of the control subjects were GSTP1 wild type allele homozygous, 40.0% were heterozygous and 5.71% mutant allele homozygous. There was dramatic inverted relation between positive IHC ER staining and increasing grade of tumors in general (100%, 88.6%, 40.4%) and especially among tumors with heterozygote genotype of GSTP1 (70%, 35.4%, 22.7). There was increase in positive IHC HER2 staining consistent with higher grades in general (20%, 29.6%, 50.0%), especially among tumors with GSTP1 wild allele homozygote genotype (5.0%, 9.1%, 31.8%). A remarkable reverse relation was also observed between the fraction of IHC hormone receptor phenotype ER+/PR+/ HER2- and increased grade of tumors (60.0%, 45.5%, and 27.3%) especially among tumors with GSTP1 heterozygote genotype, and a similar link was noted regarding ER+/PR-/ HER2- and tumor grade. There was increase in frequency of ER-/PR-/ HER2- (0.0%, 6.8%, and 18.2%) and ER-/PR-/ HER2+ (0.0%, 4.54%, and 40.9%) consistent with the higher grades of tumors in general and especially GSTP1 heterozygote genotype tumors. As a conclusion, there is no correlation between GSTP1 polymorphism and increased risk of breast cancer i.e. the mutant allele is randomly distributed in cancer and control cases. However, there is a link between GSTP1 genotypes and hormone receptor expression status and certain phenotypes of breast cancer, which may have clinical importance.

Folate metabolism gene polymorphisms MTHFR C677T and A1298C and risk for preeclampsia: a meta-analysis

OBJECTIVES

MTHFR C677T and A1298C have been associated with the risk of preeclampsia (PE), but with conflicting results. We performed this meta-analysis to derive a more precise estimation of the association between MTHFR polymorphisms and PE.

STUDY DESIGN

An electronic search of PubMed and Chinese Biomedicine database was conducted to select studies for meta-analysis. 54 case controlled studies containing MTHFR C677T and A1298C gene polymorphisms were chosen, and odds ratio (OR) with confidence interval (CI) was used to assess the strength of this association.

RESULT

These studies evaluated 7398 cases and 11230 controls for MTHFR C677T. The overall results suggested that MTHFR C677T was associated with the risk of PE. (T vs. C: OR = 1.157, 95% CI: 1.057-1.266, p = 0.002; TT + CT vs. CC: OR = 1.165, 95% CI : 1.049-1.293, P = 0.004; TT vs. CT + CC: OR = 1.371, 95% CI: 1.153-1.63, p < 0.001). We also evaluated 1103 cases and 988 controls for MTHFR A1298C but could not demonstrate an increased risk of PE for this polymorphism (p = 0.667). A symmetric funnel plot, the Egger's test (p = 0.819) suggested a lack of publication bias.

CONCLUSION

This meta-analysis supports the idea that MTHFR C677T genotype is associated with increased risk for PE, especially in the case of Asians and Caucasians.

Gene-diet interactions in gastric cancer risk: A systematic review

AIM: To conduct a systematic review of the published epidemiological studies investigating the association of the interactions between gene variants and dietary intake with gastric cancer risk.

METHODS: A literature search was conducted in PubMed, EMBASE, and MEDLINE for articles published between January 2000 and July 2013, and 38 studies were identified. Previous studies included various dietary factors (e.g., fruits and vegetables, soybean products, salt, meat, and alcohol) and genetic variants that are involved in various metabolic pathways.

RESULTS: Studies suggest that individuals who carry high-risk genetic variants and demonstrate particular dietary habits may have an increased risk of gastric cancer compared with those who do not carry high-risk genetic variants. Distinctive dietary patterns and variations in the frequency of genetic variants may explain the higher incidence of gastric cancer in a particular region. However, most previous studies have limitations, such as a small sample size and a retrospective case-control design. In addition, past studies have been unable to elucidate the specific mechanism in gene-diet interaction associated with gastric carcinogenesis.

CONCLUSION: Additional large prospective epidemiological and experimental studies are required to identify the gene-diet metabolic pathways related to gastric cancer susceptibility.

The GSTP1 105Val allele increases breast cancer risk and aggressiveness but enhances response to cyclophosphamide chemotherapy in North China

The glutathione-S-transferase (GST) family contributes to the inactivation of various toxic compounds formed as secondary metabolites during oxidative stress. GSTP1 accounts for the majority of the GST family enzymatic activity, and the activity of GSTP1 enzyme can be altered by the presence of the Ile105Val polymorphism. In this study, we examined the polymorphic frequency of GSTP1 Ile105Val genotype in 920 breast cancer patients and 783 healthy controls in women of North China. Results showed that GSTP1 105Val allele (Ile/Val and Val/Val) was associated with a higher breast cancer risk (OR = 1.38, 95% CI: 1.14–1.69; P = 0.001) and more aggressive tumors with histological grade III (OR = 1.15, 95% CI: 1.05–1.26; P = 0.001), lymph node metastases (OR = 2.35, 95% CI: 1.72–3.21; P < 0.001), as well as ER negative (OR = 1.77, 95% CI: 1.31–2.39; P < 0.001) than those carrying the Ile/Ile allele. However, the patients with the GSTP1 105Val genotype had a better disease free survival after cyclophosphamide (CTX)-based chemotherapy than those with Ile/Ile (HR = 0.77, 95% CI: 0.45–0.91; P < 0.001). Furthermore, in vitro cellular experiments demonstrated that breast cancer cells with the GSTP1 105Val allele were significantly more sensitive to CTX-induced proliferation inhibition. Thus, we conclude that the GSTP1 105Val allele increases breast cancer risk and aggressiveness and enhance response to CTX-based chemotherapy in women of North China. Detection of the GSTP1 Ile105Val genotype may help screen for high-risk populations and direct individualized therapy.

Genetic polymorphisms of CYP2E1, GST, and NAT2 enzymes are not associated with risk of breast cancer in a sample of Lebanese women

Changes in the activity of drug metabolizing enzymes (DMEs) are potentially associated with cancer risk. This relationship is attributed to their involvement in the bioactivation of multiple procarcinogens or the metabolism of multiple substrates including an array of xenobiotics and environmental carcinogens. 326 Lebanese women of whom 99 were cancer free (controls) and 227 were diagnosed with breast cancer (cases) were included. Blood for DNA was collected and medical charts were reviewed. Three genotyping methods were employed including: (1) restriction fragment length polymorphism (RFLP) for CYP2E1*5B, CYP2E1*6, NAT2*5 and NAT2*6; (2) gel electrophoresis for GSTM1 and GSTT1; and (3) real-time PCR for GSTP1 Ile/Val polymorphism. We analyzed the relationship between genetic susceptibilities in selected xenobiotic metabolizing genes and breast cancer risk. Allele frequencies were fairly similar to previously reported values from neighboring populations with relevant migration routes. There were no statistically significant differences in the distribution of variant carcinogen metabolizing genes between cases and controls even after adjusting for age at diagnosis, menopausal status, smoking, and alcohol intake. Despite its limitations, this is the first study that assesses the role of genetic polymorphisms in DMEs with breast cancer in a sample of Lebanese women. Further studies are needed to determine the genetic predisposition and gene-environment interactions of breast cancer in this population.

Effects of glutathione-S-transferase polymorphisms on the risk of breast cancer: a population-based case-control study in Pakistan

Cancer is widely accepted as one of the major health issues. Diet composition and exposure to environmental genotoxic and carcinogenic agents such as polycyclic aromatic hydrocarbons (PAHs) are among the causative factors for various types of cancers, including breast cancer. Low penetrance genes including glutathione S transferases (GST) in association with environmental factors can contribute greatly in the development of breast cancer. We were interested to investigate the association of the polymorphisms of GSTM1, GSTT1, GSTP1 and GSTO2 with the risk of breast cancer in the Pakistani population. One hundred women visiting the Department of Radiology and Oncology, Nishter Hospital, Multan with pathologically confirmed breast cancer, and 100 healthy volunteers from central Pakistan were enrolled in the present study. The strength of the association of various factors with breast cancer was measured by calculating odd ratios (ORs) which were determined by logistic regression. All P values cited are two-sided; differences resulting in a P value of less or equal to 0.05 were declared statistically significant. The Hardy Weinberg equilibrium was tested for the genotype proportions in the control group, as a measure of quality control. Those aged 36-45, in menopause or with a history of cancer in the family had a significantly higher prevalence of breast cancer compared with controls. The frequency of GSTM1 and GSTT1 was similar in both control and patients suggesting no association with the risk of cancer development, however GSTM1 and GSTT1 were significantly linked with the risk of breast cancer in smokers and in women with a history of breast cancer in the family respectively. Similarly women homozygous for GSTP1 or GSTO2 and with a history of breast cancer, or in menopause, were at greater risk of breast cancer than wild type or heterozygotes. Our data suggest that genetic differences in some GST genes may be linked with an increased susceptibility to breast cancer. Furthermore it also gives an insight into the interaction between the GST polymorphisms and pre-menopausal diagnosis of breast cancer.

A meta-analysis of the association of glutathione S-transferase P1 gene polymorphism with the susceptibility of breast cancer

Glutathione S-transferase P1 (GSTP1) is one of the important mutant sites for the cancer risk at present. The conclusions of the published reports on the relationship between GSTP1 A/G gene polymorphism and the risk of breast cancer are still debated. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of breast cancer. The association reports were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. 35 investigations were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and breast cancer susceptibility, consisting of 40,347 subjects (18,665 patients with breast cancer and 21,682 controls). The association between GSTP1 A/G gene polymorphism and breast cancer risk was not found for overall population, Caucasians and Africans. Interestingly, the GSTP1 A/G gene polymorphism was associated with the susceptibility of breast cancer in Asians (G allele: OR = 1.10, 95 % CI: 1.04-1.17, P = 0.001; GG genotype: OR = 1.36, 95 % CI: 1.14-1.62, P = 0.0008; AA genotype: OR = 0.92, 95 % CI: 0.85-0.98, P = 0.02). Furthermore, the GSTP1 A/G gene polymorphism was associated with the susceptibility of breast cancer for the analysis of the controls from hospital. In conclusion, GSTP1 A/G gene polymorphism is associated with the breast cancer susceptibility in Asians. However, more studies on the relationship between GSTP1 A/G gene polymorphism and the risk of breast cancer should be performed in further.

Polymorphisms of catechol estrogens metabolism pathway genes and breast cancer risk in Mexican women

Breast cancer is associated to estrogen exposure. Allelic variants involved in estrogen metabolism might change the risk of developing this neoplasia. We examined the potential association of breast cancer risk in Mexican women with the polymorphisms CYP1A1 rs1048943, CYP1B1 rs1056836, COMT rs4680, GSTP1 rs1695, GSTT1 null and GSTM1 null which are involved in estrogen metabolism pathway. This study included 150 cases and 150 controls. A significant association was observed between, CYP1A1 rs1048943 (OR = 1.95, C.I. 1.13-3.36) and GSTP1 rs1695 (OR = 2.39, C.I. 1.24-4.24) polymorphisms with the risk of breast cancer. This risk was increased when the women were stratified according to their menopausal status. The results show that breast cancer risk significantly increases in women with 3-6 risk polymorphisms (OR = 3.75, C.I. 1.44-9.74).

GSTM1, GSTT1, and GSTP1 polymorphisms, breast cancer risk factors and mammographic density in women submitted to breast cancer screening

Genetic polymorphisms in genes related to the metabolism of xenobiotics, such as genes of the glutathione S-transferases (GSTM1, GSTT1, and GSTP1) superfamily have been associated with an increased risk for breast cancer (BC). Considering the high incidence of BC in the city of Porto Alegre in southern Brazil, the purpose of this study was to characterize genotypic and allelic frequencies of polymorphisms in GSTM1, GSTT1, and GSTP1, and correlate these molecular findings with established risk factors for breast cancer including mammographic density, in a sample of 750 asymptomatic women undergoing mammographic screening. Molecular tests were performed using the multiplex polymerase chain reaction (PCR) for GSTM1 and GSTT1, and quantitative PCR for GSTP1 polymorphisms. Overall, the frequencies of GSTM1 and GSTT1 null genotypes were 45% and 21%, respectively. For GSTP1 polymorphism, genotypic frequencies were 44% for the Ile/Ile genotype, 44% for the Ile/Val genotype, and 12% for Val/Val genotype, with an allelic frequency of 66% for the wild type allele in this population, similar to results of previous international publications. There was a statistically significant association between the combined GSTM1 and GSTT1 null genotypes (M-/T-) and mammographic density in post menopausal women (p = 0.031). When the GSTT1 null (T-) genotype was analyzed isolated, the association with mammographic density in post menopausal women and in the overall sample was also statistically significant (p = 0.023 and p = 0.027, respectively). These findings suggest an association of GSTM1 and GSTT1 null genotypes with mammographic density.

Genome-based prediction of breast cancer risk in the general population: a modeling study based on meta-analyses of genetic associations

BACKGROUND

Genome-wide association studies identified novel breast cancer susceptibility variants that could be used to predict breast cancer in asymptomatic women. This review and modeling study aimed to investigate the current and potential predictive performance of genetic risk models.

METHODS

Genotypes and disease status were simulated for a population of 10,000 women. Genetic risk models were constructed from polymorphisms from meta-analysis including, in separate scenarios, all polymorphisms or statistically significant polymorphisms only. We additionally investigated the magnitude of the odds ratios (OR) for 1 to 100 hypothetical polymorphisms that would be needed to achieve similar discriminative accuracy as available prediction models [modeled range of area under the receiver operating characteristic curve (AUC) 0.70-0.80].

RESULTS

Of the 96 polymorphisms that had been investigated in meta-analyses, 41 showed significant associations. AUC was 0.68 for the genetic risk model based on all 96 polymorphisms and 0.67 for the 41 significant polymorphisms. Addition of 50 additional variants, each with risk allele frequencies of 0.30, requires per-allele ORs of 1.2 to increase this AUC to 0.70, 1.3 to increase AUC to 0.75, and 1.5 to increase AUC to 0.80. To achieve AUC of 0.80, even 100 additional variants would need per-allele ORs of 1.3 to 1.7, depending on risk allele frequencies.

CONCLUSION

The predictive ability of genetic risk models in breast cancer has the potential to become comparable to that of current breast cancer risk models.

IMPACT

Risk prediction based on low susceptibility variants becomes a realistic tool in prevention of nonfamilial breast cancer.

Null genotypes of GSTM1 and GSTT1 contribute to risk of cervical neoplasia: an evidence-based meta-analysis

Background and Objectives

Glutathione S-transferases (GSTs) are multifunctional enzymes that play a key role in the detoxification of varieties of both endogenous products of oxidative stress and exogenous carcinogens.

Methods

In this meta-analysis, twenty-five studies were identified by searching PubMed, EMBASE, ISI Web of Science and CBM databases: 23 evaluated GSTM1 and 19 evaluated GSTT1. Crude odds ratios with corresponding 95% confidence intervals were used to estimate the association between GSTM1 and GSTT1 polymorphisms and risk of cervical neoplasia. Subgroup analyses were conducted by pathological history, ethnicity, source of DNA for genotyping, quality score, and matching variable.

Results

The null genotypes of GSTM1 and GSTT1 polymorphisms were associated with a significantly increased risk of cervical neoplasia (for GSTM1: OR = 1.40; 95%CI, 1.19–1.65; for GSTT1: OR = 1.30; 95%CI, 1.05–1.62, respectively). Subgroup analyses showed that the null genotype of GSTM1 increased the risk of cervical neoplasia in Asians, studies with DNA isolation from white blood cells and tissue samples, both high and low quality studies, and matched studies. In GSTM1-GSTT1 interaction analysis, individuals with dual null genotype were associated with a significantly increased risk of cervical neoplasia (OR = 1.72; 95%CI, 1.18–2.51).

Conclusion

These findings indicate that GSTM1 and GSTT1 polymorphisms, particularly GSTM1-GSTT1 interaction, may play critical roles in the development of cervical neoplasia. A conservative manner should be adopted to interpret these results because of obvious heterogeneity between-study, unadjusted data, and relatively small sample size in this meta-analysis. Well designed studies with larger sample size are of great value to confirm these results.

Evaluation of functional genetic variants for breast cancer risk: results from the Shanghai breast cancer study

In previous studies among 1,144 cases and 1,256 controls recruited in stage 1 of the Shanghai Breast Cancer Study (SBCS I; 1996-1998), 18 known or potentially functional single nucleotide polymorphisms (SNPs) in 16 genes were found to be associated with breast cancer risk. The authors evaluated these associations among 1,918 cases and 1,819 controls recruited in stage 2 of the SBCS (SBCS II; 2002-2005) using genetic effect models and subgroup analyses predetermined from SBCS I results. Five SNPs (AHR rs2066853, ATM rs1003623, ESR1 rs2234693, GSTP1 rs1695, and SHBG rs6259) showed generally consistent results in SBCS I and SBCS II and statistically significant associations with breast cancer risk in combined analyses, mostly in subgroups defined by age or menopausal status. Further, the relation between breast cancer risk and SHBG rs6259 was found to vary by body mass index (weight (kg)/height (m)(2)) (P for interaction = 0.003). The strongest reduction in risk associated with SHBG rs6259 was found for lean (body mass index <23) postmenopausal minor allele carriers (odds ratio = 0.6, 95% confidence interval: 0.5, 0.8; P = 4.6 × 10(-4)). This biologically plausible and highly significant finding provides strong evidence for a true association among Asian women. This study also highlights the value of gene-environment interaction analyses in evaluating genetic factors for complex diseases.

Urinary polyphenols, glutathione S-transferases copy number variation, and breast cancer risk: results from the Shanghai women's health study

In vitro studies have found that flavanol epigallocatechin (EGC) and flavonols, but not flavanol epicatechin (EC), activate glutathione S-transferases (GSTs), a family of phase II enzymes that detoxify reactive oxygen species, such as catechol estrogen metabolites. This study was designed to investigate prospectively whether urinary excretion of tea polyphenols interacts with GST polymorphisms to influence breast cancer risk. We conducted a study of 352 incident breast cancer cases and 701 individually matched controls nested within the Shanghai Women's Health Study cohort of women aged 40-70 yr at baseline. Liquid chromatography tandem mass spectrometry was used to measure urinary excretion of flavanols and flavonols. Real-time multiplex PCR was used to quantify the copy number variation in the GSTM1 and GSTT1 genes. Urinary excretion of flavonols and flavanols, particularly EGC (P = 0.02), was significantly higher among women null for GSTM1 than those positive for GSTM1. Flavonols and flavanols (EGC in particular) were associated with a reduced risk of breast cancer among those null for GSTM1 and GSTT1, with a P-value of 0.04 for the interaction between EGC and GSTM1 polymorphism. In contrast, among women possessing both GSTM1 and GSTT1, breast cancer risk increased with levels of flavonols, particularly kaempferol. The differential associations between polyphenols and breast cancer risk by GST polymorphisms, if confirmed, may provide a new avenue for the personalized prevention of breast cancer.

Glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms, smoking, and their interaction in oral cancer: a HuGE review and meta-analysis

The association between glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms and oral cancer is not consistent across studies, and data on their interaction with smoking in oral cancer are lacking. The authors systematically searched PubMed and SciVerse Scopus for case-control studies examining the association between null genotypes of the GSTM1 and GSTT1 genes and oral cancer. Twenty-eight case-control studies published in English were identified. Summary odds ratios were derived via random-effects models. The summary odds ratio for the GSTM1 null genotype was 1.43 in Asians (95% confidence interval (CI): 1.14, 1.78; P < 0.01, I (2) = 73%) and 0.98 in Caucasians (95% CI: 0.76, 1.28; P = 0.91, I (2) = 0%). Case-only analysis of 6 studies (552 cases) showed an inverse multiplicative interaction between GSTM1 null polymorphisms and smoking (ever/high levels of smoking vs. never/low levels) (odds ratio (OR) = 0.51, 95% CI: 0.32, 0.82; P = 0.01, I (2) = 34%). The GSTT1 null genotype was not significantly associated with oral cancer in Asians (OR = 1.07, 95% CI: 0.82, 1.38; P = 0.63, I (2) = 65%) or Caucasians (OR = 1.04, 95% CI: 0.41, 2.65; P = 0.93, I (2) = 55%). In conclusion, the GSTM1 null genotype may be associated with a higher risk of oral cancer in Asians but not in Caucasians, and this effect may be modified by smoking status. The GSTT1 null genotype may not be associated with oral cancer.

Correlating of GSTM1, GSTT1, and GSTP1 genetic polymorphisms with the risk and expressions in children with isolated Hirschsprung disease

PURPOSE

The present study aimed to examine an association between the glutathione S-transferases (GSTs) polymorphisms (GSTM1, GSTT1, and GSTP1) genetic polymorphisms with the risk and expression in children with isolated Hirschsprung disease (HD).

METHODS

GSTM1, GSTT1, and GSTP1 genetic polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism analysis in 80 HD and 180 normal children (controls). The genic expressions were detected by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). The protein expressions were detected by Western blot.

RESULTS

The GSTM1 null genotype especially is associated with a greater risk of HD (X(2) = 1.129, P = 0.288, OR = 0.851, 95% CI = 0.632-1.146). The GSTT1 null genotype especially is associated with a greater risk of HD (X(2) = 6.165, P = 0.013, OR = 1.472, 95% CI = 1.084-1.999). The GSTP1 null genotype especially is associated with a greater risk of HD (X(2) = 4.748, P = 0.029, OR = 0.701, 95% CI = 0.509-0.964). GSTP1 and GSTP1 expressions were higher than GSTM1 in HD patients. Positive expressive rate of the GSTT1 and GSTP1 were 40.56% and 56.67% in HD. The mRNA and protein expressions level of GSTT1 and GSTP1 genes were significantly higher in HD than controls (P < 0.05). Positive expressive rate of the GSTM1 was 10.56% in HD. The GSTM1 was low expressed between in HD and controls (P > 0.05).

CONCLUSIONS

The GSTP1 genetic polymorphisms correlate to HD. We postulate that inherited gene deletion of GSTT1 and GSTP1 may produce increased genotoxic susceptibility for HD respectively, following exposure to xenobiotics that are substrates for these enzymes.

Evaluation of the influence of polymorphic variants CYP1A1 2B, CYP1B1 2, CYP3A4 1B, GSTM1 0, and GSTT1 0 in prostate cancer

BACKGROUND/OBJECTIVE

Genetic polymorphisms in cytochrome P-450 (CYPs) and glutathione S-transferase (GSTs) genes can influence the appearance of tumors by the formation of new enzymes with altered activities. In the present study, 5 polymorphic variants were examined in 154 patients with prostate carcinoma and in 154 controls.

MATERIALS AND METHODS

DNA analysis was carried out through PCR-based methods. The statistical methods used were odds ratio and confidence interval (95% CI), χ(2), Fisher, and Mann-Whitney.

RESULTS

The study showed absence of association for CYP1A1 2B, CYP1B1 2, GSTM1 0, and GSTT1 0. The statistical analysis implied a positive association of variant CYP3A4 1B for prostate cancer. The combined analysis of CYP1A1 2B, CYP1B1 2, and CYP3A4 1B genotypes showed positive association. The analysis of histopathologic parameters detected statistically significant differences for Gleason score and biochemistry recurrence risk. The presence of the GSTT1 0 genotype in red meat consumers increased the risk for this disease.

CONCLUSION

Some polymorphic variants analyzed can influence the development and the progression of prostate cancer.

Genetic Polymorphisms of CYP2E1, GSTP1, NQO1 and MPO and the Risk of Nasopharyngeal Carcinoma in a Han Chinese Population of Southern China

BACKGROUND

Southern China is a major area for endemic nasopharyngeal carcinoma (NPC). Genetic factors as well as environmental factors play a role in development of NPC. To investigate the roles of previously described carcinogen metabolism gene variants for NPC susceptibility in a Han Chinese population, we conducted a case-control study in two independent study population groups afflicted with NPC in Guangdong and Guangxi Provinces of southern China.

METHODS

Five single nucleotide polymorphisms (SNPs) of CYP2E1-rs2031920, CYP2E1-rs6413432, GSTP1-rs947894, MPO-rs2333227 and NQO1-rs1800566 were genotyped by PCR-based RFLP, sequencing and TaqMan assay in 358 NPC cases and 629 controls (phase I cohort). Logistic regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (CI). To confirm our results, sixteen tag SNPs for GSTP1, MPO, NQO1 (which 100% covered these genes), and 4 functional SNPs of CYP2E1 were genotyped in another cohort of 213 NPC cases and 230 controls (phase II cohort).

RESULTS

No significant associations in NPC risk were observed for the five polymorphisms tested in the phase I cohort. In an additional stratified analysis for phase I, there was no significant association between cases and controls in NPC high risk population (EBV/IgA/VCA positive population). Analysis of 14 tagging SNPs within the same genes in an independent phase II cohort were in agreement with no SNPs significantly associated with NPC.

CONCLUSIONS

Our results suggest that polymorphism of CYP2E1, GSTP1, MPO and NQO1 genes does not contribute to overall NPC risk in a Han Chinese in southern China.

Glutathione S-transferase P1 Ile105Val polymorphism and breast cancer risk: a meta-analysis involving 34,658 subjects

Glutathione S-transferase P1 (GSTP1) is involved in a wide range of detoxifying reactions. Any alteration in the structure, function, or expression of GSTP1 gene may alter the ability of a cell to inactivate carcinogens or mutagens, and thus modify an individual's risk to cancer. Previous epidemiological studies on the potential association between GSTP1 Ile105Val polymorphism and breast cancer risk have produced inconsistent results. In order to drive a more precise estimation of this association, we performed a meta-analysis of 30 published case-control studies including 15,901 cases and 18,757 controls. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. The results of this meta-analysis showed that GSTP1 Ile105Val polymorphism was not associated with breast cancer susceptibility in overall population. However, in subgroup analysis by ethnicity, we found a significant association among Asian population (for Val/Val vs. Ile/Ile: OR 1.27, 95% CI 1.02-1.83; for the recessive model Val/Val vs. Ile/Ile + Ile/Val: OR 1.42, 95% CI 1.20-1.69). When stratified by study design, significantly elevated susceptibility to breast cancer was found among hospital-based studies (for Val/Val vs. Ile/Ile: OR 1.38, 95% CI 1.16-1.63; for recessive model Val/Val vs. Ile/Val + Ile/Ile: OR 1.31, 95% CI 1.12-1.55; for dominant model: Val/Val + Ile/Val vs. Ile/Ile: OR 1.10, 95% CI 1.02-1.19). In conclusion, our meta-analysis suggests that GSTP1 Ile105Val polymorphism may increase susceptibility to breast cancer in Asian population.

Preliminary examination of polymorphisms of GSTM1, GSTT1, and GSTZ1 in relation to semen quality

BACKGROUND

Environmental, lifestyle, and occupational exposures on semen quality have been investigated in epidemiological studies with inconsistent results. Genetic factors involved in toxicant activation and detoxification have been examined in relation to the risk of outcomes such as cancer, cardiovascular, and neurologic disorders. However, the effect of common genetic variants in the metabolism of toxicants on semen quality parameters has rarely been evaluated. In this analysis, we evaluated functional SNPs of three genes of the glutathione-S-transferase (GSTM1, GSTT1, GSTZ1) enzyme family.

METHODS

Participants were 228 presumed fertile men recruited as part of a community-based study. Semen outcome data from this study included total sperm count and concentration, sperm morphology, and sperm DNA integrity and chromatin maturity. DNA was obtained from 162 men from a mouth-rinse sample and genotyped for the presence of GSTT1-1 and GSTM1-1 null genotypes and the GSTZ1 SNPs at positions 94 (rs3177427) and 124 (rs3177429). We used multivariable linear regression to assess the relationship between each genotype and sperm outcomes.

RESULTS

Overall, our results did not reveal a consistent pattern between GSTM1 and GSTZ genotypes and increased occurrence of adverse sperm outcomes. However, the GSTT1 non-null genotype yielded the coefficients with the largest magnitude for sperm count and sperm concentration (beta=-0.528, 95% CI -1.238 to 0.199 and beta=-0.353, 95% CI -0.708 to 0.001, respectively), suggesting that it might be adverse.

CONCLUSIONS

These results indicate that common polymorphisms in GST genes do not negatively impact sperm parameters in healthy men with good semen quality. Contrary to expectations, the GSTT1 non-null genotype was associated with reduced sperm concentration and count in semen. Further study with a larger study size and inclusion of gene-exposure interactions is warranted.

Glutathione S-transferase M1 polymorphism and breast cancer susceptibility: a meta-analysis involving 46,281 subjects

Published data on the association between present/null polymorphism of glutathione S-transferase M1 (GSTM1) and breast cancer risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Medline, PubMed, Embase, and Web of Science were searched. Crude ORs with 95% CIs were used to assess the strength of association between the GSTM1 present/null polymorphism and breast cancer risk. The pooled ORs were performed for null versus present genotype. A total of 59 studies including 20,993 cases and 25,288 controls were involved in this meta-analysis. Overall, significantly elevated breast cancer risk was associated with null genotype when all studies were pooled into the meta-analysis (OR = 1.10, 95% CI = 1.04-1.16). In the subgroup analysis by ethnicity, significantly increased risks were found for Caucasians (OR = 1.05, 95% CI = 1.00-1.10) and Asians (OR = 1.21, 95% CI = 1.08-1.35). When stratified by population-based studies or hospital-based studies, statistically significantly elevated risks were found among population-based studies (OR = 1.11, 95% CI = 1.03-1.20). In the subgroup analysis by menopausal status, statistically significantly increased risks were found among postmenopausal women (OR = 1.15, 95% CI = 1.04-1.28). In conclusion, this meta-analysis suggests that the GSTM1 null genotype is a low-penetrant risk factor for developing breast cancer.

No evidence for glutathione S-transferases GSTA2, GSTM2, GSTO1, GSTO2, and GSTZ1 in breast cancer risk

Breast cancer is a complex disease and in recent years a number of breast cancer susceptibility genes have been identified, but the role of low penetrance susceptibility genes has not been completely resolved. Glutathione S-transferases (GSTs) are phase II xenobiotic metabolizing enzymes involved in the detoxification of chemical carcinogens and environmental pollutants and play an important role in cell defense mechanisms against oxidative stress. They have been in the spot light for the investigation of a potential association with breast cancer risk but so far, sparse or even no data for a potential contribution of GSTA2, GSTM2, GSTO, and GSTZ to breast cancer risk are available. We genotyped GSTA2_448_C > G (rs2180314), GSTA2_742_A > C (rs6577), GSTM2_-832_T > C (rs638820), GSTO1_-1242_G > A (rs2164624), GSTO1_419_A > C (rs4925), GSTO2_-183_A > G (rs2297235), GSTO2_342_A > G (rs156697), GSTZ1_-4378_A > G (rs1046428), and GSTZ1_94_G > A (rs3177427) by MALDI-TOF MS in the German GENICA breast cancer case-control collection of 1021 cases and 1015 controls and performed breast cancer risk association in general and with respect to the stratifications: menopausal status, family history of breast or ovarian cancer, use of oral contraceptives, use of hormone therapy, body mass index, and smoking as well as histopathological tumor characteristics including hormone receptor status, grade, histology, and node status. We did not observe any breast cancer risk associations and conclude that it is unlikely that glutathione S-transferases GSTA2, GSTM2, GSTO1, GSTO2, and GSTZ1 participate in breast cancer susceptibility.

Genetic variants in GSTM3 gene within GSTM4-GSTM2-GSTM1-GSTM5-GSTM3 cluster influence breast cancer susceptibility depending on GSTM1

Mu class of Glutathione-S-transferase (GSTM) genes arrange in a tandem on chromosome 1p13.3. The relationship between genetic variants in the GSTM1-5 gene cluster and breast cancer is still ambiguous. In the present study, 17 tagging single-nucleotide polymorphisms (SNPs) covering the GSTMs cluster were originally selected and 11 validated SNPs were used for genotyping 921 cases and 711 controls. The association analyses were performed according to the absence or presence of GSTM1. In the GSTM1-/- group, the allele frequency of one SNP in GSTM3 was significantly different between cases and controls (P = 2.0 x 10(-4), corrected P = 0.001), with odds ratio of 1.75 (95% confidence interval, 1.26-2.44). The observed association in the GSTM1-/- group was successfully replicated in an independent population set (familial/early-onset breast cancer cases, n = 267; community-based controls, n = 667). The combined P values were robust (10(-6)) and the false positive report probability (FPRP) values were low. In contrast, no susceptibility allele/haplotype was identified when the GSTM1 gene was present. Based on epidemiological observations, we further identified two genetic variants in the GSTM3 locus accounting for differential expression of GSTM3 in normal breast tissues by such means as altering binding of RNA-pol-II. Protective genotypes were correlated with higher GSTM3 expression levels. In conclusion, SNPs/haplotypes in the GSTM3 gene within the GSTMs gene cluster are likely to contribute to breast cancer risk when the GSTM1 is absent. We infer that GSTM3 catalyzing ability in normal breast tissue might protect against breast carcinogenesis.

GSTT1 and GSTP1 polymorphisms and breast cancer risk: a meta-analysis

Cytosolic glutathione S-transferase comprises multiple isoenzymes; studies have principally examined mu-1 (GSTM1: null/present), theta-1 (GSTT1: null/present) and pi-1 (GSTP1 Ile105Val) gene polymorphisms concerning breast cancer risk. Regarding GSTT1 and GSTP1 polymorphisms, studies remain controversial and no recent meta-analysis has appeared. This meta-analysis aims to examine whether GSTT1 and GSTP1 polymorphisms are associated with breast cancer risk. Separate analyses were performed on Chinese and non-Chinese populations, in an attempt to investigate race-specific effects. Eligible articles were identified by a search of MEDLINE bibliographic database for the period up to August 2009. Regarding GSTT1 null/present genotype, 41 case-control studies were eligible (16,589 breast cancer cases and 19,995 controls); 30 case-control studies were eligible for GSTP1 Ile105Val (16,908 cases and 20,016 controls). Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. At the overall analysis, the null GSTT1 genotype was associated with elevated breast cancer risk (pooled OR = 1.114, 95% CI: 1.035-1.199, random effects). However, the association seemed confined to non-Chinese populations (33 studies, pooled OR = 1.128, 95% CI: 1.042-1.221, random effects), given that the association was not significant in the subset of Chinese studies (eight studies, pooled OR = 1.061, 95% CI: 0.875-1.286, random effects). Regarding GSTP1 Ile105Val, no statistically significant associations were detected in non-Chinese populations (25 studies). On the other hand, the GG genotype was associated with increased breast cancer risk in Chinese populations (five studies, pooled OR = 1.297, 95% CI: 1.023-1.645, fixed effects); accordingly, the recessive model yielded statistically significant results (pooled OR = 1.273, 95% CI: 1.006-1.610, fixed effects). In conclusion, polymorphisms of both GSTT1 and GSTP1 genes seem associated with elevated breast cancer risk in a race-specific manner. Given the small number of Chinese studies, the finding on GSTP1 Ile105Val merits further investigation.