Meta- and pooled analyses of the effects of glutathione S-transferase M1 polymorphisms and smoking on lung cancer risk

Effects of Glutathione S-Transferases (GSTM1, GSTT1 and GSTP1) gene variants in combination with smoking or drinking on cancers: A meta-analysis

BACKGROUND

This meta-analysis aimed to systematically summarize the association between cancer risks and glutathione s-transferases (GSTs) among smokers and drinkers.

METHODS

Literature was searched through PubMed, Web of Science, CNKI, and WANFANG published from 2001 to 2022. Stata was used with fixed-effect model or random-effect model to calculate pooled odds ratios (ORs) and the 95% confidence interval (95% CI). Sensitivity and heterogeneity calculations were performed, and publication bias was analyzed by Begg and Egger's test. Regression analysis was performed on the correlated variables about heterogeneity, and the false-positive report probabilities (FPRP) and the Bayesian False Discovery Probability (BFDP) were calculated to assess the confidence of a statistically significant association.

RESULTS

A total of 85 studies were eligible for GSTs and cancer with smoking status (19,604 cases and 23,710 controls), including 14 articles referring to drinking status (4409 cases and 5645 controls). GSTM1-null had significant associations with cancer risks (for smokers: OR = 1.347, 95% CI: 1.196-1.516, P < .001; for nonsmokers: OR = 1.423, 95% CI: 1.270-1.594, P < .001; for drinkers: OR = 1.748, 95% CI: 1.093-2.797, P = .02). GSTT1-null had significant associations with cancer risks (for smokers: OR = 1.356, 95% CI: 1.114-1.651, P = .002; for nonsmokers: OR = 1.103, 95% CI: 1.011-1.204, P = .028; for drinkers: OR = 1.423, 95% CI: 1.042-1.942, P = .026; for nondrinkers: OR = 1.458, 95% CI: 1.014-2.098, P = .042). Negative associations were found between GSTP1rs1695(AG + GG/AA) and cancer risks among nondrinkers (OR = 0.840, 95% CI: 0.711-0.985, P = .032).

CONCLUSIONS

GSTM1-null and GSTT1-null might be related cancers in combination with smoking or drinking, and GSTP1rs1695 might be associated with cancers among drinkers.

Association of genetic polymorphism of glutathione S-transferases with colorectal cancer susceptibility in snuff (Naswar) addicts

Abstract The current study aimed to investigate the relationship between polymorphisms in detoxifying (GSTM1, GSTT1, and GSTP1) genes and their association with colorectal cancer (CRC) in tobacco addicts of Pashtun ethnicity. Polymorphisms in the selected genes were genotyped in a case-control study consisting of 100 histologically confirmed male CRC patients and 100 birth-year and gender-matched healthy controls using the PCR−RFLP method. The GSTM1 null, and GSTT1 null genotypes were significantly contributed to the risk of CRC in the cases (OR= 3.131, 95% CI: 1.451−6.758, P = 0.004, and OR= 3.541, 95% CI: 1.716−7.306, P = 0.001, respectively), whereas the association observed for GSTP1 Val/Val (1.139, 95% CI: 0.356−3.644, P = 0.826) did not show statistical significance. The combined GSTM1 null and GSTT1 null showed a 41-fold increased risk (95% CI: 4.945−351.950, P = 0.001), while, the combined GSTM1 null and GSTP1 Ile/Val or Val/Val variant genotypes exhibited about 3-fold (95% CI: 1.196−7.414, P = 0.019) increased risk to CRC. Similarly, the combined GSTT1 null and GSTP1 Ile/Val or Val/Val variant genotypes showed about a 3-fold (95% CI: 1.285−8.101, P = 0.013) increased risk of CRC. In the combination of three GST genotypes, the GSTM1 null, GSTT1 null, and GSTP1 Ile/Val or Val/Val variant genotypes demonstrated a more than a 22-fold (95% CI: 2.441−212.106, P = 0.006) increased risk of CRC. Our findings suggest that GSTM1 and GSTT1 polymorphism and its combination with GSTP1 may be associated with CRC susceptibility in the Naswar addicted Pashtun population of Khyber Pakhtunkhwa, Pakistan.

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

Thirty-five previous meta-analyses have been reported on the individual glutathione S-transferase M1 (GSTM1) present/null, glutathione S-transferase T1 (GSTT1) present/null, and glutathione S-transferase P1 (GSTP1) IIe105Val polymorphisms with lung cancer (LC) risk. However, they did not appraise the credibility and explore the combined effects between the 3 genes and LC risk.We performed a meta-analysis and re-analysis of systematic previous meta-analyses to solve the above problems.Meta-analyses of Observational Studies in Epidemiology guidelines were used. Moreover, we employed false-positive report probability (FPRP), Bayesian false discovery probability (BFDP), and the Venice criteria to verify the credibility of current and previous meta-analyses.Significantly increased LC risk was considered as "highly credible" or "positive" for GSTM1 null genotype in Japanese (odds ratio (OR) = 1.30, 95% confidence interval (CI) = 1.17-1.44, I2 = 0.0%, statistical power = 0.997, FPRP = 0.008, BFDP = 0.037, and Venice criteria: AAB), for GSTT1 null genotype in Asians (OR = 1.23, 95% CI = 1.12-1.36, I2 = 49.1%, statistical power = 1.000, FPRP = 0.051, BFDP = 0.771, and Venice criteria: ABB), especially Chinese populations (OR = 1.31, 95% CI = 1.16-1.49, I2 = 48.9%, Statistical power = 0.980, FPRP = 0.039, BFDP = 0.673, and Venice criteria: ABB), and for GSTP1 IIe105Val polymorphism in Asians (Val vs IIe: OR = 1.28, 95% CI = 1.17-1.42, I2 = 30.3%, statistical power = 0.999, FPRP = 0.003, BFDP = 0.183, and Venice criteria: ABB). Significantly increased lung adenocarcinoma (AC) risk was also considered as "highly credible" or "positive" in Asians for the GSTM1 (OR = 1.35, 95% CI = 1.22-1.48, I2 = 25.5%, statistical power = 0.988, FPRP < 0.001, BFDP < 0.001, and Venice criteria: ABB) and GSTT1 (OR = 1.36, 95% CI = 1.17-1.58, I2 = 30.2%, statistical power = 0.900, FPRP = 0.061, BFDP = 0.727, and Venice criteria: ABB) null genotype.This study indicates that GSTM1 null genotype is associated with increased LC risk in Japanese and lung AC risk in Asians; GSTT1 null genotype is associated with increased LC risk in Chinese, and GSTP1 IIe105Val polymorphism is associated with increased LC risk in Asians.

The prognostic impact of GSTM1/GSTP1 genetic variants in bladder Cancer

Background

The glutathione S-transferases (GSTs) are a superfamily of phase II detoxifying enzymes that inactivates a wide variety of potential carcinogens through glutathione conjugation. Polymorphic changes in the GST genes have been reported to be associated with increased susceptibility to cancer development and anticancer drug resistance. In this study, we investigated the association between genetic variants in GSTM1 and GSTP1 and patients’ clinicopathological parameters. The prognostic values of such associations were evaluated among bladder cancer patients.

Methods

Genotyping of GSTM1 and GSTP1 in bladder cancer patients was assessed using polymerase chain reaction followed by DNA sequencing. Overall survival was estimated using the Kaplan-Meier method and multiple logistic regression and correlation analysis were performed.

Results

The GSTM1 null genotype was significantly associated with poor overall survival compared with the wild-type GSTM1 genotype. There was a trend towards better overall survival in patients with wild-type GSTP1 allele (AA) compared with GSTP1 (AG/GG) genotype. Interestingly, Kaplan-meier survival curve for GSTM1 null patients adjusted for sub-cohort with amplified HER2 gene showed poor survival compared with the GSTM1 null/ non-amplified HER2 gene. Also the same population when adjusted with HER2 protein expression, data showed poor survival for patients harboring GSTM1 null/high HER2 protein expression compared with low protein expression.

Conclusion

This study focuses on the impact of GSTM1 null genotype on bladder cancer patients’ outcome. Further investigations are required to delineate the underlying mechanisms of combined GSTM^−/− and HER2 status in bladder cancer.

Genetic diversity, inbreeding and cancer

Genetic diversity is essential for adaptive capacities, providing organisms with the potential of successfully responding to intrinsic and extrinsic challenges. Although a clear reciprocal link between genetic diversity and resistance to parasites and pathogens has been established across taxa, the impact of loss of genetic diversity by inbreeding on the emergence and progression of non-communicable diseases, such as cancer, has been overlooked. Here we provide an overview of such associations and show that low genetic diversity and inbreeding associate with an increased risk of cancer in both humans and animals. Cancer being a multifaceted disease, loss of genetic diversity can directly (via accumulation of oncogenic homozygous mutations) and indirectly (via increased susceptibility to oncogenic pathogens) impact abnormal cell emergence and escape of immune surveillance. The observed link between reduced genetic diversity and cancer in wildlife may further imperil the long-term survival of numerous endangered species, highlighting the need to consider the impact of cancer in conservation biology. Finally, the somewhat incongruent data originating from human studies suggest that the association between genetic diversity and cancer development is multifactorial and may be tumour specific. Further studies are therefore crucial in order to elucidate the underpinnings of the interactions between genetic diversity, inbreeding and cancer.

Association of Glutathione-S-Transferases M1 and T1 Deletional Variants with Development of Oral Squamous Cell Carcinoma: A Study in the South-East of Iran

Background:

The role of genetic polymorphisms in genes of Glutathione-S-transferases (GST) enzymes in susceptibility to oral cavity cancers is controversial. Oral Squamous Cell Carcinoma (OSCC) is the most common oral cavity neoplasm. Aimed to evaluate the potential impacts of two well-known null variants residing in the gene encoding GSTM1 and GSTT1 enzymes of OSCC patients in the southeast of Iran.

Methods:

In a case-control design, 113 individuals (50 OSCC patients, and 63 healthy subjects) were included. DNA was extracted using paraffin-embedded tissues. GST genotyping was carried out using multiplex PCR.

Results:

In 113 participants, 41 (36.3%) and 72 (63.7%) were males and females respectively. No significant difference was recognized for distribution of GSTM1 (P=0.11) and GSTT1 (P=0.28) null genotypes between OSCC patients (58%, and 24% respectively) and healthy controls (42.9% and 15.9% respectively). Also, no significant difference was noted regarding the frequency of GSTM1 null genotype in different histological grades, however, those patients with more aggressive disease (poorly differentiated or grade III) revealed with a significantly higher ratio (66.7%) of GSTT1 null genotype (P=0.002). The highest odds ratio for OSCC was related to combined null genotypes for GSTM1 and GSTT1 (OR=2.5, 95% CI: 0.7-9.2), however, this was not statistically significant finding (P=0.15).

Conclusion:

Null genotypes polymorphisms were more common in OSCC than healthy individuals. GSTT1 null genotype may be an important genetic factor in the progression of OSCC.

GSTM1-null and GSTT1-active genotypes as risk determinants of primary open angle glaucoma among smokers

AIM

To evaluate glutathione transferase theta 1 and mu 1 (GSTT1 and GSTM1) polymorphisms as determinants of primary open angle glaucoma (POAG) risk, independently or in combination with cigarette smoking, hypertension and diabetes mellitus.

METHODS

A case-control study with 102 POAG patients and 202 age and gender-matched controls was carried out. Multiplex-polymerase chain reaction method was used for the analysis of GSTM1 and GSTT1 polymorphisms. The differences between two groups were tested by the t-test or χ² test. Logistic regression analysis was used for assessing the risk for disease development.

RESULTS

The presence of GSTM1-null genotype did not contribute independently towards the risk of POAG. However, individuals with GSTT1-active genotype were at almost two-fold increased risk to develop glaucoma (P=0.044) which increased up to 4.36 when combined with GSTM1-null carriers (P=0.024). When glutathione transferase (GST) genotypes were analyzed in association with cigarette smoking, hypertension and diabetes, only carriers of GSTT1-active genotype had significantly increased risk of POAG development in comparison with GSTT1-null genotype individuals with no history of smoking, hypertension and diabetes, respectively (OR=3.52, P=0.003; OR=10.02, P<0.001; OR=4.53, P=0.002).

CONCLUSION

The results obtained indicate that both GSTM1-null and GSTT1-active genotypes are associated with increased POAG risk among smokers, suggesting potential gene-environment interaction in glaucoma development.

The Role of Cruciferous Vegetables and Isothiocyanates for Lung Cancer Prevention: Current Status, Challenges, and Future Research Directions

Lung cancer remains a leading cause of cancer-related deaths in the United States. Although smoking and air pollution exposure are primary risk factors of lung cancer, diet has also been reported to contribute to lung cancer risk. Cruciferous vegetables contain many bioactive compounds that alter the detoxification process of air-borne carcinogenic compounds and, thereby, may decrease lung cancer risk. In the meta-analysis of 31 observational studies, cruciferous vegetable intake is inversely associated with lung cancer risk (summary odds ratio/relative risk = 0.81 and 95% confidence interval = 0.74-0.89 for comparing the highest with lowest intake categories). More observational studies need to measure urinary isothiocyanate (ITC) concentrations and investigate their association with lung cancer risk in populations with relatively high intake of cruciferous vegetables. Current evidence is limited to two phase 2 clinical trials with incomplete reporting. Hence, more short-term clinical phase 2 trials need to examine effects of various amounts and types of cruciferous vegetables on biomarkers of risk and efficacy before a large phase 3 trial can be conducted to assess effects upon lung cancer risk. This would help further elucidate whether the inverse association observed with self-reported cruciferous vegetable intake is indeed due to ITC content or other bioactive compounds.

CYP2E1 and GSTM1 gene polymorphisms, environmental factors, and the susceptibility to lung cancer

OBJECTIVE

To investigate the relationships between the CYP2E1 RsaI polymorphism, GSTM1 polymorphism, and the susceptibility to lung cancer, along with the interactions between environmental factors and these genes.

METHODS

A case-control study was carried out to explore the independent effect of gene polymorphisms on risk of lung cancer, and the combined effects of gene loci. The stratification analysis of age, sex, smoking, and drinking combined with positive loci was also analyzed, and any interaction was identified.

RESULTS

The logistic regression analysis showed that there were statistical relationships between the CYP2E1 RsaI TT genotype and lung cancer, GSTM1 (-) and lung cancer. The combined effect's analysis of these 2 loci showed that, with an increase in the number of risk alleles, the risk of lung cancer also increased (supposing 0 risk allele as the reference group). Subjects carrying 3 risk alleles had the highest risk of developing lung cancer with an adjusted OR = 10.38 (95% CI 2.10-51.35). Stratified analysis showed that, in women, nonsmoking subjects, or nondrinking subjects, the combined effects could increase the risk of lung cancer; no heterogeneity was found between these layers except sex. The interaction analysis showed that, supposing the male, GSTM1 (+) genotype as the reference, the female, GSTM1 (-) genotype had a significantly increased risk of lung cancer (OR = 2.17 [1.01-4.70]); when the non-smoking, GSTM1 (+) genotype subjects was the reference group, smoking, GSTM1 (+) genotype subjects and smoking, GSTM1 (-) genotype subjects had significantly higher risk of lung cancer (OR = 2.00 [1.01-3.96], OR = 2.89 [1.28-6.54]).

CONCLUSION

CYP2E1 RsaI TT genotype was a protective factor against the development of lung cancer, while GSTM1 (-) genotype was a risk factor for lung cancer. Increases in the number of the risk alleles also increased lung cancer risk. GSTM1 (-) genotype, sex, and smoking status might interact in the incidence of lung cancer.

Effects of low-to-moderate alcohol supplementation on urinary estrogen metabolites in postmenopausal women in a controlled feeding study

Heavy alcohol drinking is associated with increased breast cancer risk, but associations with low‐to‐moderate alcohol consumption are less clear and the biological mechanisms are not well defined. The objective of this study was to evaluate the effects of 8 weeks of low (15 g/d) and moderate (30 g/d) alcohol ingestion on concentrations of 15 urinary estrogen metabolites (EMs) in postmenopausal women (n = 51) in a controlled feeding study with a randomized crossover design. Compared to no alcohol, 15 g/day for 8 weeks had no effect on urinary EMs. However, compared to no alcohol, 30 g/day for 8 weeks decreased urinary 2‐hydroestrone (2‐OHE1) by 3.3% (P = 0.055) and increased 16‐epiestriol (16‐EpiE3) by 26.6% (P = 0.037). Trends for reduced urinary 2‐OHE1 (P = 0.045), reduced ratio of 2‐OH:16OH pathways (P = 0.008), and increased 16‐EpiE3 (P = 0.035) were observed as alcohol ingestion increased from 0 g to 15 g to 30 g/d. Moderate alcohol consumption for 8 weeks had modest effects on urinary concentrations of 2‐OHE1 and 16‐EpiE3 among postmenopausal women in a carefully controlled feeding study.

Pathway-based discovery of genetic interactions in breast cancer

Breast cancer is the second largest cause of cancer death among U.S. women and the leading cause of cancer death among women worldwide. Genome-wide association studies (GWAS) have identified several genetic variants associated with susceptibility to breast cancer, but these still explain less than half of the estimated genetic contribution to the disease. Combinations of variants (i.e. genetic interactions) may play an important role in breast cancer susceptibility. However, due to a lack of statistical power, the current tests for genetic interactions from GWAS data mainly leverage prior knowledge to focus on small sets of genes or SNPs that are known to have an association with breast cancer. Thus, many genetic interactions, particularly among novel variants, remain understudied. Reverse-genetic interaction screens in model organisms have shown that genetic interactions frequently cluster into highly structured motifs, where members of the same pathway share similar patterns of genetic interactions. Based on this key observation, we recently developed a method called BridGE to search for such structured motifs in genetic networks derived from GWAS studies and identify pathway-level genetic interactions in human populations. We applied BridGE to six independent breast cancer cohorts and identified significant pathway-level interactions in five cohorts. Joint analysis across all five cohorts revealed a high confidence consensus set of genetic interactions with support in multiple cohorts. The discovered interactions implicated the glutathione conjugation, vitamin D receptor, purine metabolism, mitotic prometaphase, and steroid hormone biosynthesis pathways as major modifiers of breast cancer risk. Notably, while many of the pathways identified by BridGE show clear relevance to breast cancer, variants in these pathways had not been previously discovered by traditional single variant association tests, or single pathway enrichment analysis that does not consider SNP-SNP interactions.

Polymorphisms of GSTM1, GSTT1, GSTP1 genes and chromosomal aberrations in lung cancer patients

PURPOSE

To study the potential links between genetic polymorphisms in the GSTT1, GSTM1, GSTP1 genes and the frequency of chromosomal aberrations (CAs) in lung cancer patients and healthy residents in Russian Federation.

METHODS

200 cells in well-spread metaphase with 46 chromosomes were examined for 353 newly diagnosed lung cancer patients (males) who received medical treatment in the Kemerovo Regional Oncology Center (Kemerovo, Russian Federation), and 300 healthy males from Kemerovo, Russian Federation. The polymorphisms of the GSTM1 del and GSTT1 del genes were analysed by multiplex PCR. Genotyping of the polymorphic variants in the GSTP1 (A313G, T341C) gene was performed using Real-time PCR with competing TaqMan probes complementary to the polymorphic DNA sites. The data analysis was performed using software STATISTICA 8.0 (StatSoft Inc., USA).

RESULTS

We discovered that a GSTM1 del polymorphism increases the frequency of chromosomal damage in smoking patients with lung cancer, a general group of lung cancer patients, donors with non-small cell lung cancer and patients in the latest stages of the malignant process. The synergetic effects of occupational exposure and the malignant process can induce some modifications in the cytogenetic status in lung cancer patients harbouring the GSTM1 del polymorphism.

CONCLUSIONS

CAs in peripheral blood lymphocytes can be used as biomarkers of the early biological effects of exposure to genotoxic carcinogens and may predict future cancer incidence in several epidemiologic studies. Genetic changes in genes encoding phase II detoxification enzymes are linked to decreases in the metabolic detoxification of environmentally derived genotoxic carcinogens.

Will Genetic Testing for Complex Diseases Increase Motivation to Quit Smoking? Anticipated Reactions in a Survey of Smokers

The aim of this study was to improve understanding of smokers’ potential reactions to genetic testing for smoking-related diseases. One thousand twenty-four respondents completed a postal survey; 186were smokers. Questions addressed anticipated psychological and behavioral reactions to genetic test results using hypothetical scenarios. Of smokers, 65% anticipated being motivated to quit smoking upon receiving a positive genetic test result; 39% anticipated being demotivated by a negative result. More smokers anticipated being depressed in response to receiving a positive result for cancer than for heart disease (40% vs. 24%). Anticipated motivation was associated with higher desire to quit and lower nicotine addiction, anticipated depression with poorer understanding of genetic testing, and anticipated demotivation with lower education. Smokers who have a high desire to quit may use genetic testing as a motivational tool. Understanding of genetics may be important in determining how individuals respond to genetic tests for complex diseases.

Association of CYP1A1, GSTM1 and GSTT1 gene polymorphisms with risk of non-small cell lung cancer in Andhra Pradesh region of South India

BACKGROUND

Lung cancer is one of the most preventable causes of death globally both in developed and developing countries. Although it is well established that smokers develop lung cancer, there are some smokers who are free from the disease risk. The predisposition to lung cancer is attributed to genetic polymorphisms in xenobiotic metabolizing genes. Reports on assessment of xenobiotic metabolizing genes like Cytochrome P 450 1A1 (CYP1A1), Glutathione -S -transferase M1 (GSTM1) and T1 (GSTT1) polymorphisms from India are meagre, and reports from Andhra Pradesh are lacking.

METHODS AND RESULTS

Assessment of polymorphisms in CYP1A1, GSTM1 and GSTT1 in NSCLC patients and healthy individuals specific to population of Andhra Pradesh, a South Indian state was attempted by multiplex PCR and RFLP, and this is the first study which tried to correlate oxidative stress with the polymorphisms in xenobiotic metabolizing genes. Results showed that CYP1A1 m1 'CC' genotype was significantly associated with lung cancer susceptibility with a 2.3-fold risk, CYP1A1 m2 'AG' gene polymorphisms with 8.8-fold risk and GSTT1 (-/-) genotype demonstrated a twofold risk of disease susceptibility.

CONCLUSIONS

A combined role of genetic polymorphisms and smoking status can be attributed for the cause of lung cancer. Further, the association between oxidative stress and genetic polymorphisms showed a correlation between GSTT1 and super oxide dismutase activity; CYP1A1 m1, m2 and GSTT1 with glutathione peroxidase activity; CYP1A1 m1 and GSTM1 with melondialdehyde levels; and CYP1A1 m1 and GSTT1 with 8-oxo-7,8-dihydro-2'-deoxyguanosine. A higher risk of lung cancer seems to be associated with combined gene polymorphisms of phase I and phase II enzymes than that ascribed to single gene polymorphism.

GSTM1 polymorphism contribute to colorectal cancer in Asian populations: a prospective meta-analysis

Glutathione S-transferases (GSTs) are enzymes which expressed in many tissues and play important roles in neutralization of toxic compounds, and protecting hosts against cancer. Among several GSTs, Glutathione S-transferases mu (GSTM) has been drawn attention upon the association with the genetic risk for many types of cancers. But whether the GSTM1 polymorphisms confer the susceptibility to colorectal cancer in Asians has not been well established. We searched the PubMed database with GSTM1, polymorphism and colorectal cancer, attempting to identify the eligible studies. In total, 33 case-control studies in Asian populations with 8502 colorectal cancer patients and 13699 controls were included in the current meta-analysis. The association between the polymorphism and susceptibility to colorectal cancer was evaluated by the odds ratio (OR) and 95% confidence intervals (CI). The pooled meta-analysis suggested that GSTM1 null variant was correlated to the colorectal cancer risk in Asians. There was a marginal heterogeneity among these eligible studies. Nevertheless, cumulative meta-analysis observed a trend of an obvious association between the GSTM1 null genotype and colorectal cancer risk in Asians. In summary, the meta-analysis suggested that GSTM1 null polymorphism confer the susceptibility to colorectal cancer in Asians, especially in Chinese populations.

Systematic Review and Meta-Analysis of the Relationship between EPHX1 Polymorphisms and the Risk of Head and Neck Cancer

Aim

To evaluate the association between the EPHX1 Tyr113His and His139Arg polymorphisms in the EPHX1 gene and the risk of head and neck cancer.

Materials and Methods

Studies on the association of EPHX1 Tyr113His and His139Arg polymorphisms with HNC performed up until June 1st, 2014, were identified using a predefined search strategy. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of these associations.

Results

In this meta-analysis, 10 case-control studies, which included 9 studies of Tyr113His (1890 cases and 1894 controls) and 10 studies of His139Arg polymorphisms (1982 cases and 2024 controls), were considered eligible for inclusion. Overall, the pooled results indicated that the EPHX1 Tyr113His polymorphism was significantly associated with increased HNC risk (Tyr/His vs. Tyr/Tyr, OR = 1.26, 95%1.02–1.57;His/His+ Tyr/His vs. Tyr/Tyr, OR = 1.29, 95% I = 1.03–1.61). However, no significant association was found between the His139Arg polymorphism and HNC risk. In the subgroup analysis, a statistically significant association between the EPHX1 Tyr113His polymorphism and HNC was observed in population-based case-control studies (PCC), which involved less than 500 participants and genotype frequencies in HWE. This association showed minimal heterogeneity after excluding studies that were determined to contribute to heterogeneity. After categorizing the studies by publication time, a sensitivity analysis and cumulative meta-analysis of the two associations were conducted, and the results of the two analyses were consistent.

Conclusion

Our meta-analysis suggests that EPHX1 Tyr113His polymorphism may be a risk factor for HNC, while the EPHX1 His139Arg polymorphism has no association with HNC risk.

Vitamin D receptor BsmI polymorphism and colorectal cancer risk: an updated analysis

BACKGROUND

Previous studies have investigated the association between the vitamin D receptor (VDR) BsmI polymorphism and colorectal cancer (CRC) susceptibility, but the results were conflicting. The aim of this study is to quantitatively summarize the relationship between this polymorphism and CRC risk.

MATERIALS AND METHODS

Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure (CNKI) and Chinese Biomedicine databases for studies published before November 2013. Summary odds ratios (ORs) and 95% confidence intervals (95%CIs) for VDR BsmI polymorphism and CRC were calculated in a fixed- effects model (the Mantel-Haenszel method) and a random-effects model (the DerSimonian and Laird method) when appropriate.

RESULTS

This meta-analysis included 14 case-control studies, which included 10,822 CRC cases and 11,779 controls. Overall, the variant genotype (BB) of the BsmI was associated with a lower CRC risk when compared with the wild-type bb homozygote (OR=0.66, 95%CI: 0.49-0.88). Similarly, a decreased CRC risk was also found in the dominant and recessive models. When stratifying for ethnicity, source of controls, and study sample size, associations were observed among Caucasians, population-based studies and studies with large study sample size (>1000 subjects). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. No publication bias was found in the present study.

CONCLUSIONS

This updated meta-analysis suggests that the VDR BsmI polymorphism may be associated with a moderate protective effect against CRC.

Contemplating genetic feedback regarding lung cancer susceptibility

BACKGROUND AND PURPOSE

We examined three theoretical models (self-enhancement theory, consistency theory, and a combined model) for understanding how expectations and test result favorability influence smokers' desire for a retest following hypothetical genetic test results.

METHOD

College smokers (N = 128) read a brochure describing a biomarker for lung cancer (the GSTM1 gene) then reported whether they thought they had the gene (indicating lower lung cancer risk) or were missing the gene (indicating higher lung cancer risk). Participants then reported whether they would get retested if they received favorable GSTM1 results versus unfavorable GSTM1 results.

RESULTS

Participants were most likely to want a retest, suggesting rejection of the results, if they expected favorable news yet received unfavorable news.

CONCLUSION

The findings supported the combined model such that smokers expressed greatest interest in a retest when they imagined genetic risk feedback that challenges both enhancement and consistency motives.

The clinical relevance of the miR-197/CKS1B/STAT3-mediated PD-L1 network in chemoresistant non-small-cell lung cancer

Programmed cell death ligand-1 (PD-L1) has recently gained considerable attention for its role in tumor immune escape. Here, we identify a miR-197/CKS1B/STAT3-mediated PD-L1 network in chemoresistant non-small-cell lung cancer (NSCLC), independent of immunoinhibitory signals. miR-197 is downregulated in platinum-resistant NSCLC specimens, resulting in the promotion of chemoresistance, tumorigenicity, and pulmonary metastasis in vitro and in vivo. Mechanistic investigations reveal that a miR-197-mediated CKS1B/STAT3 axis exerts tumor progression regulated by various oncogenic genes (Bcl-2, c-Myc, and cyclin D1), and PD-L1 is a putative biomarker of this axis. Furthermore, we demonstrate that a miR-197 mimic sensitizes PD-L1^high drug-resistant cells to chemotherapy. These results indicate that the biological interaction between PD-L1 and chemoresistance occurs through the microRNA regulatory cascade. More importantly, expression levels of miR-197 are inversely correlated with PD-L1 expression (n = 177; P = 0.026) and are associated with worse overall survival (P = 0.015). Our discoveries suggest that the miR-197/CKS1B/STAT3-mediated network can drive tumor PD-L1 expression as a biomarker of this cascade, and miR-197 replacement therapy may be a potential treatment strategy for chemoresistant NSCLC.

Combined effects of CYP1A1 MspI and GSTM1 genetic polymorphisms on risk of lung cancer: an updated meta-analysis

Genetic polymorphisms of cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) genes might contribute to the variability in individual susceptibility to lung cancer, but the reported results from individual studies are not always consistent. We therefore conducted a meta-analysis to systematically estimate the associations between polymorphisms of these two genes and risk of lung cancer. Twenty-one studies with 8,926 subjects were finally enrolled into this study. Meta-analysis was performed by RevMan 5.2. Odds ratio (OR) and its 95 % confidence interval (CI) were calculated to evaluate the susceptibility to lung cancer. Compared with the wild-type homozygous genotype, significantly elevated risk of lung cancer were associated with variant CYP1A1 MspI (m1/m2 + m2/m2 vs. m1/m1: OR = 1.27, 95 % CI = 1.12-1.43, P < 0.001) and deletion of GSTM1 (null vs. present: OR = 1.26, 95 % CI = 1.13-1.40, P < 0.001). Both the two genetic polymorphisms were independently associated with the risk of lung cancer. The pooled OR of lung cancer for population with both CYP1A1 MspI and GSTM1 mutations (MspI m1/m2 or m2/m2 and GSTM1 null) was 1.62 (95 % CI 1.27-2.07, P < 0.001) when compared with those without any of the above mutations, which is higher than single genetic polymorphism. In the stratified analysis, significantly higher risks of lung cancer associated with above genetic polymorphisms were found only in Asian population. This meta-analysis suggests that the CYP1A1 MspI and GSTM1 polymorphisms correlate with increased lung cancer susceptibility independently, and that there is an interaction between the two genes. However, the associations vary in different ethnic populations.

Meta-analysis reveals a lack of association between UGT2B17 deletion polymorphism and tumor susceptibility

Purpose

UGT2B17 is a vital member of the UGT2 family and functions as a detoxification enzyme which catalyzes the glucuronidation of lipophilic compounds. Accumulating evidences implicates that it may contribute to the susceptibility of tumor risk. Identification of a UGT2B17 deletion polymorphism has attracted studies to evaluate the association between the UGT2B17 deletion polymorphism and tumor risk in diverse populations. However, the available results are conflicting.

Methods

A meta-analysis based on 14 studies from 10 publications including 5,732 cases and 5,112 controls was performed. Published literature from PubMed, EMBASE and Web of Science was pooled and the crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the associations.

Results

Conclusively, our results indicate that individuals with a UGT2B17 deletion polymorphism were associated with tumor risks (OR = 1.29, 95% CI = 1.03–1.63, P<0.001) in a recessive model. However, after excluding two studies for their heterogeneity, the result then demonstrated that the UGT2B17 deletion polymorphism was not associated with tumor risks (OR = 1.118, 95%CI = 0.938–1.332, P>0.1). A subgroup analysis based on tumor type, sex or race did not show significant results.

Conclusion

These results suggest that the UGT2B17 deletion polymorphism is not associated with tumor risks.

Risk effects of GST gene polymorphisms in patients with acute myeloid leukemia: a prospective study

Glutathione S-transferase (GST) enzyme levels are associated with risk of many cancers, including hematologic tumours. We here aimed to investigate the relationships between GSTM1, GSTT1 and GSTP1 polymorphisms and the risk of AML. Genotyping of GSTs was based upon duplex polymerase-chain-reactions with the confronting- two-pair primer (PCR-CTPP) method in 163 cases and 204 controls. Individuals carrying null GSTT1 genotype had a 1.64 fold risk of acute leukemia relative to a non-null genotype (P<0.05). A heavy risk was observed in those carrying combination of null genotypes of GSTM1 and GSTT1 and GSTP1 Val allele genotypes when compared with those carrying wild genotypes, with an OR (95% CI) of 3.39 (1.26-9.26) (P<0.05). These findings indicate that genetic variants of GST and especially the GSTT1 gene have a critical function in the development of AML. Our study offers important insights into the molecular etiology of AML.

Nutritional countermeasures targeting reactive oxygen species in cancer: from mechanisms to biomarkers and clinical evidence

Reactive oxygen species (ROS) exert various biological effects and contribute to signaling events during physiological and pathological processes. Enhanced levels of ROS are highly associated with different tumors, a Western lifestyle, and a nutritional regime. The supplementation of food with traditional antioxidants was shown to be protective against cancer in a number of studies both in vitro and in vivo. However, recent large-scale human trials in well-nourished populations did not confirm the beneficial role of antioxidants in cancer, whereas there is a well-established connection between longevity of several human populations and increased amount of antioxidants in their diets. Although our knowledge about ROS generators, ROS scavengers, and ROS signaling has improved, the knowledge about the direct link between nutrition, ROS levels, and cancer is limited. These limitations are partly due to lack of standardized reliable ROS measurement methods, easily usable biomarkers, knowledge of ROS action in cellular compartments, and individual genetic predispositions. The current review summarizes ROS formation due to nutrition with respect to macronutrients and antioxidant micronutrients in the context of cancer and discusses signaling mechanisms, used biomarkers, and its limitations along with large-scale human trials.

The GSTM1 null genotype increased risk of gastric cancer: a meta-analysis based on 46 studies

Background

Glutathione S-transferases M1 (GSTM1) is an important phase II metabolizing enzyme. The null genotype of GSTM1 causes total loss of GSTM1 enzyme activity and numerous studies have investigated the association between GSTM1 null genotype and gastric cancer risk.

Methods

This meta-analysis was designed to investigate the relationship between GSTM1 null genotype and susceptibility to gastric cancer and assess the influence of Helicobacter pylori infection, smoking, Lauren’s classification, and other factors. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the association strength.

Results

A total of 46 eligible studies were indentified and analyzed in this meta-analysis, including 8138 cases of gastric cancer and 13867 controls. Pooled results showed that the GSTM1 null genotype was associated with a significantly increased risk of gastric cancer (OR=1.217, 95% CI: 1.113-1.331, P_{heterogeneity}<0.001). Sub-group analysis suggested that the significant association was only observed in Asians (OR=1.273, 95%: 1.137-1.426, P_{heterogeneity} = 0.002), but not in Caucasians. The increased risk was found among H. pylori positive population (OR=1.928, 95% CI: 1.028-3.615, P_{heterogeneity}=0.065), while no association was found among H. pylori negative population (OR=0.969, 95% CI: 0.618-1.521, P_{heterogeneity}=0.168). For smoking status, the GSTM1 null genotype increased risk of gastric cancer in both ever-smokers and non-smokers. Source of control, sample size, location of tumor and Lauren’s classification did not modify the association.

Conclusions

In this meta-analysis based on 46 epidemiological studies, we show that the GSTM1 null genotype is associated with an increased risk of gastric cancer among Asians but not among Caucasians. H. pylori infection but not smoking status could modify the association.

GSTP1 Ala114Val polymorphism and colorectal cancer risk: a meta-analysis

Studies investigating the association between cytochrome glutathione S-transferase P1 (GSTP1) Ala114Val polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure, and Chinese Biomedicine databases. Summary odds ratios (ORs) and 95 % confidence intervals (95 % CIs) for GSTP1 polymorphism and CRC were calculated in a fixed effects model (the Mantel-Haenszel method) and a random effects model (the DerSimonian and Laird method) when appropriate. The pooled ORs were performed for co-dominant model (ValVal vs. AlaAla, AlaVal vs. AlaAla), dominant model (ValVal + AlaVal vs. AlaAla), and recessive model (ValVal vs. AlaVal + AlaAla). This meta-analysis included seven case-control studies, which included 3,173 CRC cases and 3,323 controls. Overall, the variant genotypes (ValVal and AlaVal) of the Ala114Val were not associated with CRC risk when compared with the wild-type AlaAla homozygote. Similarly, no associations were found in the dominant and recessive models. When stratifying for ethnicity, Hardy-Weinberg equilibrium in controls, study sample size, and source of controls, a significantly increased risk was observed among Asians (AlaVal vs. AlaAla, OR=1.67, 95 % CI=1.08-2.59; dominant model, OR=1.74, 95 % CI=1.14-2.67). No heterogeneity or publication bias was found in the present study. This meta-analysis suggests that the GSTP1 Ala114Val polymorphism may not be associated with CRC risk, while the observed increase in risk of CRC may be due to small-study bias.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

An association between XPC Lys939Gln polymorphism and the risk of bladder cancer: a meta-analysis

The polymorphism Lys939Gln in xeroderma pigmentosum complementation group C (XPC) gene has been reported to be associated with bladder cancer in some studies, though the results remain inconclusive. To explore this relationship between XPC Lys939Gln polymorphism and the susceptibility for bladder cancer and the impact of smoking exposures, a cumulative meta-analysis was performed in this study. PubMed and EMBASE databases have been systematically searched to identify relevant studies. Data were abstracted independently by two reviewers. A meta-analysis was performed to examine the association between XPC Lys939Gln polymorphism and susceptibility to bladder cancer (BC). Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated. Thirteen studies were chosen in this meta-analysis, involving 4,927 BC cases (1,119 Asian, 2,670 Caucasian, and 1,138 mixed) and 5,185 controls (1,399 Asian, 2,629 Caucasian, and 1,157 mixed). The XPC 939Gln allele was significantly associated with increased risk of BC based on allelic contrast (OR = 1.11, 95 % CI = 1.02-1.21), homozygote comparison (OR = 1.35, 95 % CI = 1.08-1.68), and a recessive genetic model (OR = 1.36, 95 % CI = 1.09-1.68). The results from the present meta-analysis indicated that the 939Gln polymorphism in XPC is a risk factor for bladder carcinogenesis. Further large and well-designed studies are needed to confirm this conclusion.

Association of GSTM1 null allele with prostate cancer risk: evidence from 36 case-control studies

BACKGROUND

Glutathione S-transferase M1 (GSTM1) is thought to be involved in detoxifying several carcinogens and may play a vital role in tumorigenesis. Numerous studies have evaluated the association between GSTM1 null/present polymorphism and risk of prostate cancer (PCa). However, the results remain inconsistent. To derive a more precise estimation, we performed a meta-analysis.

METHODOLOGY/PRINCIPAL FINDINGS

A comprehensive search was conducted to identify all eligible case-control studies. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. The overall association was significant (OR = 1.28, 95% CI: 1.11-1.48, P = 0.001). Moreover, subgroup analyses showed GSTM1 null genotype significantly associated with PCa risk among Asians (OR = 1.35, 95% CI: 1.03-1.78, P = 0.03) but not among Caucasians (OR = 1.12, 95% CI: 0.96-1.31, P = 0.16). In addition, we did not find that smoking modified the genotype effect on the risk of PCa.

CONCLUSIONS/SIGNIFICANCE

The present meta-analysis suggested that GSTM1 null allele was a low-penetrant risk factor for PCa among Asians.

Polymorphisms of DNA repair gene XRCC1 and hepatocellular carcinoma risk among East Asians: a meta-analysis

Association studies on the X-ray repair cross-complementing group 1 (XRCC1) polymorphisms (Arg194Trp, Arg280His, and Arg399Gln) in hepatocellular carcinoma (HCC) have shown conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Published literatures from PubMed, Embase, CNKI, and Chinese Biomedicine Database were retrieved. Pooled odds ratio (OR) with 95 % confidence interval (CI) was calculated using fixed- or random-effects model. Thirteen studies including 3,011 HCC cases and 3,619 controls were included in the meta-analysis of the association between XRCC1 Arg399Gln polymorphism and HCC risk. The results indicated that Arg399Gln polymorphism was significantly associated with risk of HCC in a codominant model (Gln/Gln vs. Arg/Arg, OR = 1.32, 95 % CI = 1.08-1.61; Arg/Gln vs. Arg/Arg, OR = 1.41, 95 % CI = 1.12-1.80) and a dominant model (Gln/Gln + Arg/Gln vs. Arg/Arg, OR = 1.39, 95 % CI = 1.15-1.69), but not in a recessive model (Gln/Gln vs. Arg/Gln + Arg/Arg, OR = 1.13, 95 % CI = 0.95-1.35). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. When stratifying for region and source of controls, persistent results were observed in any subgroup. No evidence of association of Arg194Trp (980 HCC cases and 966 controls) and Arg280His (1,200 HCC cases and 1,236 controls) with HCC risk was found. No publication bias was found in the present study. The results from the present meta-analysis indicated that the Arg399Gln polymorphisms of XRCC1 may be a genetic susceptibility for HCC in the East Asian population. Further, large and well-designed studies are needed to confirm this conclusion.

GSTM1 and GSTT1 copy numbers and mRNA expression in lung cancer

Large fractions of the human population do not express GSTM1 and GSTT1 (GSTM1/T1) enzymes because of deletions in these genes. These variations affect xenobiotic metabolism and have been evaluated in relation to lung cancer risk, mostly based on null/present gene models. We measured GSTM1/T1 heterozygous deletions, not tested in genome-wide association studies, in 2,120 controls and 2,100 cases from the Environment And Genetics in Lung cancer Etiology (EAGLE) study. We evaluated their effect on mRNA expression on lung tissue and peripheral blood samples and their association with lung cancer risk overall and by histology types. We tested the null/present, dominant, and additive models using logistic regression. Cigarette smoking and gender were studied as possible modifiers. Gene expression from blood and lung tissue cells was strongly down regulated in subjects carrying GSTM1/T1 deletions by both trend and dominant models (P < 0.001). In contrast to the null/present model, analyses distinguishing subjects with 0, 1, or 2 GSTM1/T1 deletions revealed several associations. There was a decreased lung cancer risk in never-smokers (OR = 0.44; 95%CI = 0.23-0.82; P = 0.01) and women (OR = 0.50; 95%CI = 0.28-0.90; P = 0.02) carrying 1 or 2 GSTM1 deletions. Analogously, male smokers had an increased risk (OR = 1.13; 95%CI = 1.0-1.28; P = 0.05) and women a decreased risk (OR = 0.78; 95%CI = 0.63-0.97; P = 0.02) for increasing GSTT1 deletions. The corresponding gene smoking and gene-gender interactions were significant (P < 0.05). Our results suggest that decreased activity of GSTM1/T1 enzymes elevates lung cancer risk in male smokers, likely due to impaired carcinogens' detoxification. A protective effect of the same mutations may be operative in never-smokers and women, possibly because of reduced activity of other genotoxic chemicals.

Genetic polymorphisms in CYP1A1, GSTM1, GSTP1 and GSTT1 metabolic genes and risk of lung cancer in Asturias

BACKGROUND

Metabolic genes have been associated with the function of metabolizing and detoxifying environmental carcinogens. Polymorphisms present in these genes could lead to changes in their metabolizing and detoxifying ability and thus may contribute to individual susceptibility to different types of cancer. We investigated if the individual and/or combined modifying effects of the CYP1A1 MspI T6235C, GSTM1 present/null, GSTT1 present/null and GSTP1 Ile105Val polymorphisms are related to the risk of developing lung cancer in relation to tobacco consumption and occupation in Asturias, Northern Spain.

METHODS

A hospital-based case-control study (CAPUA Study) was designed including 789 lung cancer patients and 789 control subjects matched in ethnicity, age, sex, and hospital. Genotypes were determined by PCR or PCR-RFLP. Individual and combination effects were analysed using an unconditional logistic regression adjusting for age, pack-years, family history of any cancer and occupation.

RESULTS

No statistically significant main effects were observed for the carcinogen metabolism genes in relation to lung cancer risk. In addition, the analysis did not reveal any significant gene-gene, gene-tobacco smoking or gene-occupational exposure interactions relative to lung cancer susceptibility. Lastly, no significant gene-gene combination effects were observed.

CONCLUSIONS

These results suggest that genetic polymorphisms in the CYP1A1, GSTM1, GSTT1 and GSTP1 metabolic genes were not significantly associated with lung cancer risk in the current study. The results of the analysis of gene-gene interactions of CYP1A1 MspI T6235C, GSTM1 present/null, GSTT1 present/null and GSTP1 Ile105Val polymorphisms in lung cancer risk indicate that these genes do not interact in lung cancer development.

Genetic polymorphisms involved in carcinogen metabolism and DNA repair and lung cancer risk in a Japanese population

BACKGROUND

Several components of overall lung carcinogenesis, carcinogen metabolic and DNA repair pathways may be involved in individual genetic susceptibility to lung cancer.

METHODS

We evaluated the role of cytochrome P450 (CYP) 1A1 rs4646903 and rs104894, glutathione S-transferase (GST) M1 and GSTT1 deletion polymorphisms, GSTP1 rs1695, x-ray repair, excision repair cross-complementing group 2 (ERCC2) rs13181, complementing defective in Chinese hamster 1 rs25487, and XRCC3 rs861539 in a case-control study comprising 462 lung cancer cases and 379 controls in a Japanese population. Unconditional logistic regression was used to assess the adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

CYP1A1 rs4646903 (OR = 1.72, 95% CI = 1.25-2.38), rs1048943 (OR = 1.40, 95% CI = 1.02-1.92), the GSTM1 deletion polymorphism (OR = 1.38, 95% CI = 1.01-1.89), GSTP1 rs1695 (OR =1.48, 95% CI = 1.04-2.11), ERCC2 rs13181 (OR = 1.89, 95% CI = 1.28-2.78), and Chinese hamster 1 rs25487 (OR = 1.54, 95% CI = 1.12-2.13) were associated with lung cancer risk whereas the GSTT1 deletion polymorphism and XRCC3 rs861539 were not. A pertinent combination of multiple "at-risk" genotypes of CYP1A1 rs4646903, the GSTM1 deletion polymorphism and ERCC2 rs13181 was at a 5.94-fold (95% CI = 2.77-12.7) increased risk of lung cancer.

CONCLUSIONS

A pertinent combination of multiple at-risk genotypes may detect a high-risk group. Further studies are warranted to verify our findings.

CYP1B1 Asn453Ser polymorphism and colorectal cancer risk: a meta-analysis

Studies investigating the association between cytochrome P450 1B1 (CYP1B1) Asn453Ser (453 A/G, rs1800440) polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline and Embase Databases. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) for CYP1B1 polymorphism and CRC were calculated in a fixed-effects model (the Mantel-Haenszel method) and a random-effects model (the DerSimonian and Laird method) when appropriate. The pooled ORs were performed for co-dominant model (GG vs AA, GA vs AA), dominant model (GG+GA vs AA), and recessive model (GG vs GA+AA). This meta-analysis included 7 case-control studies, which included 6375 CRC cases and 7003 controls. Overall, the variant genotypes (GG and GA) of the 453 A/G were not associated with CRC risk when compared with the wild-type AA homozygote (GG vs AA, OR=0.94, 95% CI=0.77-1.14; GA vs AA, OR=0.99, 95% CI=0.87-1.12). Similarly, no associations were found in the dominant and recessive models (dominant model, OR=0.98, 95% CI=0.87-1.09; recessive model, OR=0.94, 95% CI=0.77-1.14). When stratifying for country, study sample size, matched control and source of controls, no evidence of significant association was observed in any subgroup, except among those studies from "Canada". No publication bias was found in the present study. No association was found between the CYP1B1 Asn453Ser polymorphism and risk of CRC among Caucasians.

Systematic review and meta-analysis of the relationship between EPHX1 polymorphisms and colorectal cancer risk

BACKGROUND

Microsomal epoxide hydrolase (EPHX1) plays an important role in both the activation and detoxification of PAHs, which are carcinogens found in cooked meat and tobacco smoking. Polymorphisms at exons 3 and 4 of the EPHX1 gene have been reported to be associated with variations in EPHX1 activity. The aim of this study is to quantitatively summarize the relationship between EPHX1 polymorphisms and colorectal cancer (CRC) risk.

METHODS

Two investigators independently searched the Medline, Embase, CNKI, and Chinese Biomedicine Databases for studies published before June 2012. Summary odds ratios (ORs) and 95% confidence intervals (CIs) for EPHX1 Tyr113His (rs1051740) and His139Arg (rs2234922) polymorphisms and CRC were calculated in a fixed-effects model and a random-effects model when appropriate.

RESULTS

This meta-analysis yielded 14 case-control studies, which included 13 studies for Tyr113His (6395 cases and 7893 controls) and 13 studies for His139Arg polymorphisms (5375 cases and 6962 controls). Overall, the pooled results indicated that EPHX1 Tyr113His polymorphism was not associated with CRC risk; while the His139Arg polymorphism was significantly associated with decreased CRC risk (Arg/His vs. His/His, OR = 0.90, 95%CI = 0.83-0.98; dominant model, OR = 0.92, 95%CI = 0.85-0.99). The statistically significant association between EPHX1 His139Arg polymorphism and CRC was observed among Caucasians and population-based case-control studies. This association showed little heterogeneity and remained consistently strong when analyses were limited to studies in which genotype frequencies were in Hardy-Weinberg equilibrium, or limited to studies with matched controls. When cumulative meta-analyses of the two associations were conducted by studies' publication time, the results were persistent and robust.

CONCLUSION

This meta-analysis suggests that EPHX1 Tyr113His polymorphism may be not associated with CRC development; while the EPHX1 His139Arg polymorphism may have a potential protective effect on CRC.

Testing different communication formats on responses to imagined risk of having versus missing the GSTM1 gene

Genetic markers of lung cancer susceptibility, such as the common variant of the glutathione S-transferase Mu 1 gene (GSTM1-null), confer small probabilities of disease risk. The authors explored the influence of different approaches to communicating the small variations in risk associated with this biomarker. College smokers (N = 128) imagined that they had the GSTM1 wild-type variant versus the GSTM1 null-type variant. The authors presented lung cancer risk in 6 ways that varied the risk format (absolute risk vs. incremental risk) and the presentation style of the information (no graphics vs. graphic display of foreground only vs. graphic display of foreground + background). Presentation style had minor effects. However, absolute risk information increased negative emotions more than did incremental risk information. Perceptions of risk and negative emotions were most profoundly affected by the difference between having the GSTM1 wild-type variant versus the GSTM1 null-type variant. The authors discuss implications for conveying small probabilities related to genetic risk.

Impact of interactions of cigarette smoking with NAT2 polymorphisms on rheumatoid arthritis risk in African Americans

OBJECTIVE

To examine whether polymorphisms in genes coding for drug-metabolizing enzymes (DMEs) have an impact on rheumatoid arthritis (RA) risk due to cigarette smoking in African Americans.

METHODS

Smoking status was evaluated in African American patients with RA compared with non-RA controls, with smoking exposure categorized as heavy smoker (≥10 pack-years) versus never smoker/<10 pack-years. Individuals were genotyped for a homozygous deletion polymorphism in the M1 gene loci of glutathione S-transferase (GSTM1-null) in addition to tagging single-nucleotide polymorphisms (SNPs) in N-acetyltransferase 1 (NAT1), NAT2, and epoxide hydrolase 1 (EPXH1). Associations of these genotypes with RA risk were examined using logistic regression, and gene-smoking interactions were assessed.

RESULTS

There were no significant associations of any DME genotype with RA. After adjustment for multiple comparisons, there were significant additive interactions between heavy smoking and the NAT2 SNPs rs9987109 (P(additive) = 0.000003) and rs1208 (P(additive) = 0.00001); the attributable proportion due to interaction ranged from 0.61 to 0.67. None of the multiplicative gene-smoking interactions examined remained significant with regard to overall disease risk, after adjustment for multiple testing. There was no evidence of significant gene-smoking interactions in analyses of GSTM1-null, NAT1, or EPXH1. DME gene-smoking interactions were similar when cases were limited to those patients who were positive for anti-citrullinated protein antibodies.

CONCLUSION

Among African Americans, RA risk imposed by heavy smoking appears to be mediated in part by genetic variation in NAT2. While further studies are needed to elucidate the mechanisms underpinning these interactions, these SNPs appear to identify African American smokers at a much higher risk for RA, in whom the relative risk is at least 2-fold higher when compared to nonsmokers lacking these risk alleles.

Motivations for genetic testing for lung cancer risk among young smokers

OBJECTIVE

To examine why young people might want to undergo genetic susceptibility testing for lung cancer despite knowing that tested gene variants are associated with small increases in disease risk.

METHODS

The authors used a mixed-method approach to evaluate motives for and against genetic testing and the association between these motivations and testing intentions in 128 college students who smoke.

RESULTS

Exploratory factor analysis yielded four reliable factors: Test Scepticism, Test Optimism, Knowledge Enhancement and Smoking Optimism. Test Optimism and Knowledge Enhancement correlated positively with intentions to test in bivariate and multivariate analyses (ps<0.001). Test Scepticism correlated negatively with testing intentions in multivariate analyses (p<0.05). Open-ended questions assessing testing motivations generally replicated themes of the quantitative survey.

CONCLUSION

In addition to learning about health risks, young people may be motivated to seek genetic testing for reasons, such as gaining knowledge about new genetic technologies more broadly.

Correlation of CYP1A1, GSTP1 and GSTM1 gene polymorphisms and lung cancer risk among smokers

Lung cancer is the leading cause of cancer mortality worldwide and tobacco smoking has been established as its biggest risk factor. Cigarette smoke contains several carcinogens. Most of them need to be activated by phase I enzymes, such as cytochrome P450 (CYP), while phase II enzymes, such as glutathione S-transferases are responsible for the detoxification of activated forms. The present study aimed to determine the role of CYP1A1, GSTP1 and GSTM1 gene polymorphisms in smoking-related lung cancer risk. It also aimed to investigate the association of the above polymorphisms with clinicopathological parameters, as well as their effect on survival. One hundred newly diagnosed lung cancer patients with advanced disease and 125 healthy controls with a smoking history participated in the study. The participants were screened for the presence of the following polymorphisms: MspI (CYP1A1), Ile105Val (GSTP1) and GSTM1 deletion. The above polymorphisms were also examined with regards to gender, age, histological type and survival. GSTP1 Ile/Val and GSTM1-null genotypes were associated with increased lung cancer risk and the presence of the combination of the three non-wild-type genotypes increases susceptibility to lung cancer (OR 3.328, 95% CI=1.681-6.587, p=0.001). In the non-small cell lung cancer group, the GSTP1 homozygous variant was significantly associated with increased lung cancer risk (p=0.008) and shorter survival. The results of this study suggest that the GSTP1 Ile/Val genotype and GSTM1 deletion contribute to increased lung cancer susceptibility. Moreover, GSTP1 Val/Val genotype is associated with increased lung cancer risk and shorter survival in non-small cell lung cancer patients.

Genetic variability in molecular responses to chemical exposure

Individuals differ in their response to environmental exposures. In the following, we describe examples and paradigms of studying heritable differences in response to exposure-commonly known as "gene-environment interaction" or "ecogenetics"-and their relation to disease etiology and susceptibility. Our discussion is framed in three parts. In the first, we describe replicated examples of studies that have typified the field, single genetic variant, and exposure associations to disease. Second, we describe how studies have scaled up search for interaction using genome-wide measurement modalities, bioinformatics, and model organisms. Finally, we discuss a more comprehensive representation of chemical exposures as the "envirome" and how we may use the envirome to examine interplay between genetics and the environment.

Association between GSTM1, GSTT1, and GSTP1 polymorphisms and lung cancer risk in a Turkish population

Several studies focused on investigating genetic polymorphisms in order to estimate genetic contribution to lung cancer often showed conflicting results. In this study, we investigated the role of GSTM1, GSTT1, GSTP1 exon 5 and exon 6 polymorphisms on developing lung cancer and histological subtypes in 213 lung cancer patients and 231 controls. GSTM1 null, GSTT1 null, and GSTP1 exon 5 variant genotypes did not show a significant risk for developing lung cancer overall. Significant association was noted between GSTP1 exon 6 variant genotypes and overall lung cancer risk (OR 2.17, 95% CI 1.25-3.78; P = 0.006). These results show that GSTP1 exon 6 polymorphism might be an important factor in determining lung cancer susceptibility in a Turkish population.

CYP1B1 Leu432Val polymorphism and colorectal cancer risk among Caucasians: a meta-analysis

Studies investigating the association between cytochrome P450 1B1 (CYP1B1) Leu432Val (432 C/G, rs1056836) polymorphism and colorectal cancer (CRC) risk report conflicting results. The aim of this study was to quantitatively summarize the evidence for such a relationship. Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure, and Chinese Biomedicine Databases. Summary odds ratios (ORs) and 95% confidence intervals (95% CIs) for CYP1B1 polymorphism and CRC were calculated in a fixed-effects model and a random-effects model when appropriate. The pooled ORs were performed for co-dominant model (GG vs. CC, GC vs. CC), dominant model (GG + GC vs. CC), and recessive model (GG vs. GC + CC). This meta-analysis included ten case-control studies, which included 8,466 CRC cases and 9,301 controls. Overall, the variant genotypes (GG and GC) of the 432 C/G were not associated with CRC risk when compared with the wild-type CC homozygote (GG vs. CC, OR = 1.01, 95% CI = 0.93-1.10; GC vs. CC, OR = 0.97, 95% CI = 0.90-1.04), without any between-study heterogeneity. Similarly, no associations were found in the dominant and recessive models (dominant model, OR = 0.98, 95% CI = 0.92-1.05; recessive model, OR = 1.03, 95% CI = 0.96-1.11). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. When stratifying for country, matched control and source of controls, no evidence of significant association was observed in any subgroup. No publication bias was found in the present study. No association is found between the CYP1B1 Leu432Val polymorphism and risk of CRC among Caucasians.