Glutathione S-transferase M1 and P1 polymorphisms and risk of breast cancer and fibrocystic breast conditions in Chinese women

Worldwide Systematic Review of GSTM1 and GSTT1 Null Genotypes by Continent, Ethnicity, and Therapeutic Area

Glutathione S-transferase Mu 1 (GSTM1) and glutathione S-transferase theta 1 (GSTT1) enzymes are glutathione-S-transferases with broad significance for susceptibility or resistance to multifactorial human diseases, as well as detoxification of environmental chemicals and drugs. Moreover, some individuals may have a complete deletion of GSTM1 and GSTT1 genes, which can contribute to patient-to-patient variability in drug safety and efficacy. GSTM1 and GSTT1 gene deletion frequencies can vary according to ethnicity and continental origin of the studied population with implications for achieving the goal of precision/personalized medicine in clinical practice. We report here a worldwide systematic review of the null genotypes in these two clinically important genes by continents, ethnicities, and therapeutic areas (TAs). Searches were performed in the PubMed database covering the period from 1992 to 2020. Out of the 1925 articles included, most studies analyzed European individuals, corroborating the literature failure for not adequately considering the non-European ethnicities. The frequency of GSTM1 and GSTT1 null genotypes was higher in patients than in healthy volunteers. Conversely, in East Asians, higher frequencies of the null genotypes were observed in healthy volunteers than patients. Oncology was the most intensively studied TA (57% of the articles) in relation to GSTM1 and GSTT1. In all, these results demonstrate that there is an important gap in the literature in terms of failure to consider a broader range of populations, as well as diseases wherein GSTM1 and GSTT1 variations have clinical and biological implications. To achieve precision/personalized medicine on a global/worldwide scale, with equity and inclusiveness, this knowledge/research gap ought to be remedied in studies of GSTM1 and GSTT1 null genotypes. To the best of our knowledge, this is the largest systematic review conducted to date addressing the GSTM1 and GSTT1 null genotypes worldwide. The analyses from the 1925 articles highlighted the current knowledge gaps in different TAs, ethnicities, and populations. Filling these gaps is of importance, given the role these genes play in relation to the metabolism of substances to which we have frequent contact with, the associations observed between their deletion and diseases such as cancer, in addition to the interethnic differences observed for the deletion frequencies of these genes.

Genetic Factors Associated With Tardive Dyskinesia: From Pre-clinical Models to Clinical Studies

Tardive dyskinesia is a severe motor adverse event of antipsychotic medication, characterized by involuntary athetoid movements of the trunk, limbs, and/or orofacial areas. It affects two to ten patients under long-term administration of antipsychotics that do not subside for years even after the drug is stopped. Dopamine, serotonin, cannabinoid receptors, oxidative stress, plasticity factors, signaling cascades, as well as CYP isoenzymes and transporters have been associated with tardive dyskinesia (TD) occurrence in terms of genetic variability and metabolic capacity. Besides the factors related to the drug and the dose and patients’ clinical characteristics, a very crucial variable of TD development is individual susceptibility and genetic predisposition. This review summarizes the studies in experimental animal models and clinical studies focusing on the impact of genetic variations on TD occurrence. We identified eight genes emerging from preclinical findings that also reached statistical significance in at least one clinical study. The results of clinical studies are often conflicting and non-conclusive enough to support implementation in clinical practice.

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.

Impact of xenobiotic-metabolizing gene polymorphisms on breast cancer risk in South Indian women

BACKGROUND

Functional variants of the xenobiotic-metabolizing genes (XMG) might modulate breast cancer (BC) risk by altering the rate of metabolism and clearance of myriad types of potent carcinogens from the breast tissue. Despite mounting evidence on the role of XMG variants on BC risk, the current knowledge regarding their influence on BC development is still fragmentary.

METHODS

The present study examined the candidate genetic variants in CYP1A1, NQO1, GST-T1, GST-M1, and GST-P1 in 1002 subjects (502 BC patients and 500 disease-free women). PCR-RFLP was employed to genotype the mono-nucleotide variation in CYP1A1, NQO1, and GST-P1, and allele-specific PCR was used to detect the deletion polymorphism in GST-T1 and GST-M1 genes.

RESULTS

Regarding CYP1A1-M1 polymorphism, the heterozygous TC and mutant CC genotype conferred 1.47-fold (95% CI 1.13-1.91, p = 0.004) and 1.84-fold (95% CI 1.17-2.91, p = 0.009) elevated risk of BC. GST-T1 null genotype was associated with increased BC risk (OR 1.47; 95% CI 1.02-2.11, p = 0.037). For the NQO1 C609T variant, the mutant T allele was associated with BC risk with an odds ratio of 1.22 (95% CI 1.02-1.48, p = 0.034). Combinatorial analysis indicated that the presence of NQO1*2 (CT), CYP1A1-M1 (CC), and GST-P1 rs1695 (AG) genotypes conferred 16.7-fold elevated risk of BC (95% CI 3.65-76.85; p < 0.001). Moreover, GST-M1 null genotype was associated with the development of larger primary breast tumors.

CONCLUSION

Xenobiotic-metabolizing gene polymorphisms may play a crucial role in mammary carcinogenesis in South Indian women.

Meta-analysis of genetic polymorphisms in xenobiotic metabolizing enzymes and their association with breast cancer risk

Studies on the association of cytochrome p450 A1 (m1, m2), catechol-O-methyltransferase (COMT) H108L, glutathione S-transferase (GST) T1 and M1 polymorphisms with breast cancer risk were inconclusive. The current study was aimed to clarify the ambiguity in genetic associations of these enzymes with breast cancer risk on a global perspective. A systematic literature search was carried out in PubMed, Google Scholar and Medline, covering all the case-control studies published until September 2017. A meta-analysis was performed based on the random-effect and fixed-effect models to calculate the overall association of each genetic variant with breast cancer risk. Of the five polymorphisms studied, GSTT1 (OR: 1.07, 95% CI: 1.02-1.12 and OR: 1.08, 95% CI: 1.01-1.15 for fixed-effect and random-effect models, respectively) and GSTM1 (OR: 1.22, 95% CI: 1.17-1.26 and OR: 1.25, 95% CI: 1.12-1.35 for fixed-effect and random-effect models, respectively) null polymorphisms exhibited an increased risk for breast cancer in both the models. Cochrane Q-test and I² statistics revealed heterogeneity in association with these polymorphisms (P< 0.0001) with no evidence of publication bias. Thus, GSTT1 and GSTM1 null polymorphisms are risk factors for breast cancer.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

Association of glutathione S-transferase T1, M1, and P1 polymorphisms in the breast cancer risk: a meta-analysis

BACKGROUND

Several case-control studies investigating the relationship between genetic polymorphisms of glutathione S-transferase (GST) M1, GSTT1, and GSTP1 (rs1695) and the risk of breast cancer have reported contradictory results. We therefore performed a meta-analysis to clarify this issue.

MATERIALS AND METHODS

An updated meta-analysis using PubMed and Web of Knowledge databases for the eligible case-control studies was performed. Random- or fixed-effects model was used.

RESULTS

A total of 10,067 cancer cases and 12,276 controls in 41 independent case-control studies from 19 articles were included in this meta-analysis. Significant increase in risk of breast cancer for Asians was found in GSTM1-null genotype (P=0.012, odds ratio [OR] =1.17, 95% confidence interval [CI] =1.04-1.32) and GSTT1-null genotype (P=0.039, OR =1.19, 95% CI =1.01-1.41). In addition, our results showed that the GSTP1 (rs1695) polymorphisms can significantly increase the risk among Caucasians (P=0.042, OR =1.16, 95% CI =1.01-1.34). Sensitivity analysis and publication bias further confirmed the dependability of the results in this meta-analysis.

CONCLUSION

Our results demonstrate that both GSTM1- and GSTT1-null polymorphisms are associated with an increased risk of breast cancer in Asians and that GSTP1 Val105Ile (rs1695) polymorphism is associated with an increased breast cancer risk in Caucasians.

Association of glutathione S-transferase T1, M1 and P1 polymorphisms in the breast cancer risk: a meta-analysis in Asian population

BACKGROUND

Published data regarding the associations between glutathione S-transferase (GST) T1, M1 and P1 polymorphisms and breast cancer risk are inconclusive. The aim of this study is to comprehensively evaluate the genetic risk of GST genes for breast cancer.

MATERIALS AND METHODS

A systematic literature search was carried out in Pubmed, Medline (Ovid), Embase, CBM, CNKI, Weipu, and Wanfang database, covering all publications (last search was performed on May 20, 2015). Statistical analysis was performed using Revman 5.2 and STATA 12.0 softwares.

RESULTS

A total of 12,035 cases and 13,911 controls in 34 case-control studies were included in this meta-analysis. The results suggested that the GSTM1 and GSTP1 polymorphisms can obviously increase the risk of breast cancer in Asian population (odds ratio (OR) = 1.18, 95% confidence interval (CI) = 1.04-1.33, P = 0.008 and OR = 1.23, 95% CI = 1.07-1.41, P = 0.003, respectively), especially in East Asian (OR = 1.14, 95% CI = 1.01-1.27, P = 0.03 and OR = 1.15, 95% CI = 1.03-1.28, P = 0.01, respectively) and hospital-based case-control study (HCC) group (OR = 1.32, 95% CI = 1.11-1.56, P = 0.001 and OR = 1.38, 95% CI = 1.03-1.84, P = 0.03, respectively), while the association between GSTT1 null genotype and breast cancer risk is not significant (OR = 1.08, 95% CI = 0.93-1.25, P = 0.3).

CONCLUSIONS

This meta-analysis indicated that the GSTM1 and GSTP1 polymorphisms might significantly contribute to breast cancer susceptibility in Asian population, especially in East Asian, while the GSTT1 polymorphism might not be associated with breast cancer.

Toxicogenetic profile and cancer risk in Lebanese

An increasing number of genetic polymorphisms in drug-metabolizing enzymes (DME) were identified among different ethnic groups. Some of these polymorphisms are associated with an increased cancer risk, while others remain equivocal. However, there is sufficient evidence that these associations become significant in populations overexposed to environmental carcinogens. Hence, genetic differences in expression activity of both Phase I and Phase II enzymes may affect cancer risk in exposed populations. In Lebanon, there has been a marked rise in reported cancer incidence since the 1990s. There are also indicators of exposure to unusually high levels of environmental pollutants and carcinogens in the country. This review considers this high cancer incidence by exploring a potential gene-environment model based on available DME polymorphism prevalence, and their impact on bladder, colorectal, prostate, breast, and lung cancer in the Lebanese population. The examined DME include glutathione S-transferases (GST), N-acetyltransferases (NAT), and cytochromes P-450 (CYP). Data suggest that these DME influence bladder cancer risk in the Lebanese population. Evidence indicates that identification of a gene-environment interaction model may help in defining future research priorities and preventive cancer control strategies in this country, particularly for breast and lung 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.

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.

Selected estrogen receptor 1 and androgen receptor gene polymorphisms in relation to risk of breast cancer and fibrocystic breast conditions among Chinese women

BACKGROUND

Polymorphisms in sex hormone receptor-encoding genes may alter the activity of sex hormone receptors and thereby affect susceptibility to breast cancer and related outcomes.

METHODS

In a case-control study of women from Shanghai, China, we examined the risk of breast cancer and fibrocystic breast conditions associated with the ESR1 PvuII (rs2234693) and XbaI (rs9340799) and AR CAG repeat ((CAG)(n)) and GGC repeat ((GGC)(n)) polymorphisms among 614 women with breast cancer, 467 women with fibrocystic conditions, and 879 women without breast disease. We also evaluated whether risk differed by the presence/absence of proliferative changes (in the extratumoral epithelium or fibrocystic lesion), menopausal status, or body mass index (BMI). Age-adjusted odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated using logistic regression.

RESULTS

Only associations with AR (CAG)(n) and (GGC)(n) genotypes were detected. Allocating AR (CAG)(n) genotypes into six categories, with the (CAG)(22-24)/(CAG)(22-24) genotype category designated as the reference group, the (CAG)(>24)/(CAG)(>24) genotype category was associated with an increased risk of fibrocystic breast conditions (OR, 1.8; 95% CI, 1.1-3.0). Relative to the AR (GGC)(17)/(GGC)(17) genotype, the (GGC)(17)/(GGC)(14) genotype was associated with elevated risks of incident breast cancer (OR, 2.6; 95% CI, 1.3-5.4) and fibrocystic conditions (OR, 2.3; 95% CI, 1.1-4.5). Results did not differ according to proliferation status, menopausal status, or BMI.

CONCLUSION

Although these data lend support for a link between AR variation and breast disease development, given the low frequency of the putative risk-conferring genotypes and other constraints, further confirmation of our results is needed.

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.

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.

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.

Genetic variation in CYP19A1 and risk of breast cancer and fibrocystic breast conditions among women in Shanghai, China

CYP19A1 encodes for aromatase, which irreversibly converts androgens to estrogens; variation in this gene may affect individual susceptibility to breast cancer and other sex hormone-dependent outcomes. In a case-control study nested within a breast self-examination trial conducted in China, we examined whether CYP19A1 polymorphisms (rs1870049, rs1004982, rs28566535, rs936306, rs11636639, rs767199, rs4775936, rs11575899, rs10046, and rs4646) were associated with risk of breast cancer and fibrocystic breast conditions. Cases were diagnosed with breast cancer (n = 614) or fibrocystic breast conditions (n = 465) during 1989 to 2000. Controls were free of breast disease during the same period (n = 879). Presence of proliferative changes within the extratumoral tissue of women with breast cancer and the lesions of women with fibrocystic conditions only was assessed. None of the polymorphisms were associated with overall risk of breast cancer or fibrocystic breast conditions. Differences in breast cancer risk, however, were observed by proliferation status. The risk of breast cancer with (but not without) proliferative fibrocystic conditions was increased among women homozygous for the minor allele of rs1004982 (C), rs28566535 (C), rs936306 (T), and rs4775936 (C) relative to those homozygous for the major allele [age-adjusted odds ratios (95% confidence intervals), 2.19 (1.24-3.85), 2.20 (1.27-3.82), 1.94 (1.13-3.30), and 1.95 (1.07-3.58), respectively]. Also, haplotypes inferred using all polymorphisms were not associated with overall risk of either outcome, although some block-specific haplotypes were associated with an increased risk of breast cancer with concurrent proliferative fibrocystic conditions. Our findings suggest that CYP19A1 variation may enhance breast cancer development in some women, but further confirmation is warranted.

Polymorphisms in steroid hormone biosynthesis genes and risk of breast cancer and fibrocystic breast conditions in Chinese women

Common variants in genes encoding for key enzymes involved in steroidogenesis may alter sex steroid hormone levels, thereby influencing susceptibility to breast carcinoma and related conditions. In a case-control study of Chinese women, we examined genotypes of the CYP11A1 pentanucleotide [(TAAAA)n] repeat (D15S520), CYP17A1 rs743572, and HSD17B1 rs605059 polymorphisms in relation to the risk of breast cancer and fibrocystic breast conditions, comparing 615 women with breast cancer and 467 women with fibrocystic breast conditions separately with 879 women without clinical breast disease. We also evaluated whether these relationships differed by the presence of proliferation in the extratumoral epithelium or fibrocystic lesions, menopausal status, or body mass index. Only CYP11A1 genotype was related to breast cancer risk, with women homozygous for the 4-repeat allele, relative to those homozygous for the 6-repeat allele, at reduced risk (age-adjusted odds ratio, 0.58; 95% confidence interval, 0.37-0.91). There was some suggestion of a stronger inverse association for breast cancer with evidence of proliferation in the extratumoral epithelium than for breast cancer without extratumoral proliferation. Breast cancer risk associated with CYP11A1 genotype did not differ by menopausal status or body mass index level. No associations between CYP11A1, CYP17A1, and HSD17B1 genotypes and risk of fibrocystic breast conditions were observed. Our findings support the possibility that common allelic variation at the CYP11A1 D15S520 locus alters breast cancer risk in Chinese women.

hPMC2 is required for recruiting an ERbeta coactivator complex to mediate transcriptional upregulation of NQO1 and protection against oxidative DNA damage by tamoxifen

In the presence of ERbeta, trans-hydroxytamoxifen (TOT) protects cells against 17beta-estradiol (E(2))-induced oxidative DNA damage (ODD) and this correlates with increased expression of the antioxidative enzyme quinone reductase (QR). Here, we investigate the molecular mechanism responsible for ERbeta-mediated protection against ODD. We observe constitutive interaction between ERbeta and the novel protein hPMC2. Using a combination of breast epithelial cell lines that are either positive or negative for ERalpha, we demonstrate TOT-dependent recruitment of both ERbeta and hPMC2 to the EpRE (electrophile response element)-regulated antioxidative enzyme QR. We further demonstrate TOT-dependent corecruitment of the coactivators Nrf2, PARP-1 (poly (ADP-ribose) polymerase 1) and topoisomerase IIbeta, both in the presence and absence of ERalpha. However, absence of either ERbeta or hPMC2 results in nonrecruitment of PARP-1 and topoisomerase IIbeta, loss of antioxidative enzyme induction and attenuated protection against ODD by TOT even in the presence of Nrf2 and ERalpha. These findings indicate minor role for Nrf2 and ERalpha in TOT-dependent antioxidative gene regulation. However, downregulation of PARP-1 attenuates TOT-dependent antioxidative gene induction. We conclude that ERbeta and hPMC2 are required for TOT-dependent recruitment of coactivators such as PARP-1 to the EpRE resulting in the induction of antioxidative enzymes and subsequent protection against ODD.