Genetic polymorphism of glutathione S-transferase P1 gene and lung cancer risk

Glutathione S-transferase pi 1 variant and squamous cell carcinoma susceptibility: a meta-analysis of 52 case-control studies

Background

There are several meta-analyses on the genetic relationship between the rs1695 polymorphism within the GSTP1 (glutathione S-transferase pi 1) gene and the risk of different SCC (squamous cell carcinoma) diseases, such as ESCC (oesophageal SCC), HNSCC (head and neck SCC), LSCC (lung SCC), and SSCC (skin SCC). Nevertheless, no unified conclusions have been drawn.

Methods

Herein, an updated meta-analysis was performed to evaluate the probable impact of GSTP1 rs1695 on the susceptibility to different SCC diseases under six genetic models (allele, carrier, homozygote, heterozygote, dominant, and recessive). Three online databases, namely, PubMed, WOS (Web of Science), and Embase (Excerpta Medica Database), were searched.

Results

Initially, we obtained a total of 497 articles. Based on our selection criteria, we eventually included 52 case-control studies (9763 cases/15,028 controls) from 47 eligible articles. As shown in the pooling analysis, there was no difference in the risk of overall SCC disease between cases and controls [allele, P_a (P value of association test) = 0.601; carrier, P_a = 0.587; homozygote, P_a = 0.689; heterozygote, P_a = 0.167; dominant, P_a = 0.289; dominant, P_a = 0.548]. Similar results were obtained after stratification by race (Asian/Caucasian), genotyping, control source, and disease type (ESCC/HNSCC/LSCC/SSCC) (all P_a > 0.05).

Conclusion

The rs1695 polymorphism within the GSTP1 gene is not associated with the risk of overall SCC or a specific SCC type, including ESCC, HNSCC, LSCC, and SSCC.

Association of glutathione S-transferase P1 gene polymorphism with the risk of small-cell carcinoma of lung cancer

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) gene polymorphism and the risk of small-cell carcinoma of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of small-cell carcinoma of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Ten reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and small-cell carcinoma of lung cancer. The G allele and GG genotype were not associated with the susceptibility of risk of small-cell carcinoma in overall populations, East-Asians and Turkish population. However, there was an association between GG genotype with the risk of small-cell carcinoma in Caucasians. In conclusion, GG genotype was associated with the risk of small-cell carcinoma in Caucasian patients with lung cancer. However, GSTP1 A/G gene polymorphism is not associated with the susceptibility of small-cell carcinoma in overall populations, East-Asians and Turkish population.

HapMap-based study on the association between MPO and GSTP1 gene polymorphisms and lung cancer susceptibility in Chinese Han population

AIM

Myeloperoxidase (MPO) and glutathione S-transferase pi 1 (GSTP1) are important carcinogen-metabolizing enzymes. The aim of this study was to investigate the association between the common polymorphisms of MPO and GSTP1 genes and lung cancer risk in Chinese Han population.

METHODS

A total of 266 subjects with lung cancer and 307 controls without personal history of the disease were recruited in this case control study. The tagSNPs approach was used to assess the common polymorphisms of MOP and GSTP1 genes and lung cancer risk according to the disequilibrium information from the HapMap project. The tagSNP rs7208693 was selected as the polymorphism site for MPO, while the haplotype-tagging SNPs rs1695, rs4891, rs762803 and rs749174 were selected as the polymorphism sites for GSTP1. The gene polymorphisms were confirmed using real-time PCR, cloning and sequencing.

RESULTS

The four GSTP1 haplotype-tagging SNPs rs1695, rs4891, rs762803 and rs749174, but not the MPO tagSNP rs7208693, exhibited an association with lung cancer susceptibility in smokers in the overall population and in the studied subgroups. When Phase 2 software was used to reconstruct the haplotype for GSTP1, the haplotype CACA (rs749174+rs1695 + rs762803+rs4891) exhibited an increased risk of lung cancer among smokers (adjust odds ratio 1.53; 95%CI 1.04-2.25, P=0.033). Furthermore, diplotype analyses demonstrated that the significant association between the risk haplotype and lung cancer. The risk haplotypes co-segregated with one or more biologically functional polymorphisms and corresponded to a recessive inheritance model.

CONCLUSION

The common polymorphisms of the GSTP1 gene may be the candidates for SNP markers for lung cancer susceptibility in Chinese Han population.

GSTP1 Ile105Val polymorphism is associated with lung cancer risk among Asian population and smokers: an updated meta-analysis

Many studies have examined the association between the GSTP1 Ile105Val (rs 1695) gene polymorphism and lung cancer risk in various populations, but their results have been inconsistent. To assess this relationship more precisely, a meta-analysis was performed. The PubMed and CNKI database was searched for case-control studies published up to July 2012. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ultimately, 42 studies, comprising 12,304 lung cancer cases and 15,729 controls were included. Overall, for G allele carriers (GA + GG) versus homozygote AA, the pooled OR was 1.05 (95% CI 0.99-1.10 P = 0.092 for heterogeneity), for GG versus AA the pooled OR was 1.04 (95% CI 0.96-1.12 P = 0.084 for heterogeneity). In the stratified analysis by ethnicity, gender, histological types of lung cancer and smoking status, a significant association was found in Asians and smokers, not in Caucasian or mixed population, Male, Female population, lung AC, SCC, SCLC or non-smokers. Publication bias was found by using the funnel plot and Egger's test. Overall, there is no evidence showing a significant correlation between GSTP1 Ile105Val gene polymorphism and lung cancer risk in overall population, however stratified analysis by ethnicity, histology, gender and smoking status, it correlate with increased lung cancer susceptibility among Asians and smokers.

Association between glutathione S-transferase T1 null genotype and risk of lung cancer: a meta-analysis of 55 studies

The relationship between glutathione S-transferase T1 (GSTT1) gene polymorphism and the risk of lung cancer from the published reports are still conflicting. This study was conducted to evaluate the relationship between GSTT1 polymorphism and the risk of lung cancer. A comprehensive research was conducted through the databases, and 55 studies were recruited into this meta-analysis for the association of null genotype of GSTT1 with lung cancer susceptibility, consisting of 15,140 patients with lung cancer and 16,662 controls. There was a significant association between GSTT1 null genotype and lung cancer risk in the overall populations (OR = 1.138, 95% CI = 1.032-1.255, P heterogeneity = 0.000, P = 0.009). Furthermore, GSTT1 null genotype was associated with the lung cancer risk in Asians (OR = 1.469, 95% CI = 1.228-1.757, P heterogeneity = 0.000, P = 0.000). However, GSTT1 null genotype was not associated with the risk of lung cancer in Caucasians and Africans. In conclusion, GSTT1 null genotype is associated with the lung cancer in overall populations and in Asians.

A meta-analysis of the relationship between glutathione S-transferase T1 null/presence gene polymorphism and the risk of lung cancer including 31802 subjects

The relationship between glutathione S-transferase T1 (GSTT1) null/presence gene polymorphism and the risk of lung cancer from the published reports are still conflicting. This study was conducted to evaluate the relationship between GSTT1 null/presence gene polymorphism and the risk of lung cancer using meta-analysis method. The association studies were identified from PubMed, and Cochrane Library on July 1, 2012, and eligible investigations were included and synthesized using meta-analysis method. 51 reports were recruited into this meta-analysis for the association of null genotype of GSTT1 with lung cancer susceptibility, consisting of 15,140 patients with lung cancer and 16,662 controls. There was a marked association between GSTT1 null genotype and lung cancer risk in overall populations (OR = 1.15, 95 % CI 1.04-1.27, P = 0.007). Furthermore, GSTT1 null genotype was associated with the lung cancer risk in Asians (OR = 1.47, 95 % CI 1.23-1.76, P < 0.0001). However, GSTT1 null genotype was not associated with the risk of lung cancer in Caucasians, Brazilian population and Africans. In conclusion, GSTT1 null genotype is associated with the lung cancer in overall populations and in Asians.

The GSTP1 Ile105Val polymorphism is not associated with susceptibility to colorectal cancer

The glutathione S transferase (GST) family is a major part of cellular defense mechanisms against endogenous and exogenous substances, many of which have carcinogenic potential. Alteration in the expression level or structure of the glutathione-S-transferase (GST) enzymes may lead to inadequate detoxification of potential carcinogens and consequently contribute to cancer development. A member of the glutathione-S-transferase (GST) family, GSTP1, is an attractive candidate for involvement in susceptibility to carcinogen-associated colorectal cancer. An A>G transition in exon 5 resulting in an Ile105Val amino acid substitution has been identified which alters catalytic efficiency. The present study investigated the possible impact of Ile105Val GSTP1 polymorphism on susceptibility to colorectal cancer. in Jordan We examined 90 tissue samples previously diagnosed with colorectal carcinoma, and 56 non-cancerous colon tissues. DNA was extracted from paraffin embedded tissues and the status of the GSTP1 polymorphism was determined using a polymerase chain reaction restriction fragment length polymorphism (RFLP) method. No statistically significant differences were found between colorectal cancer cases and controls for the GSTP1 Ile/Ile, Ile/Val and Val/Val genotypes. The glutathione S-transferase polymorphism was not associated with risk in colorectal cancer cases in Jordan stratified by age, sex, site, grade or tumor stage. In conclusion, the GSTP1 Ile105Val polymorphism is unlikely to affect the risk of colorectal cancer.

Association of glutathione S-transferase P1 gene polymorphism with the histological types of lung cancer: a meta-analysis

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) A/G gene polymorphism and the histological types of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and histological types of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Seventeen reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and histological types of lung cancer. The G allele and GG genotype were not associated with the susceptibility of risk of squamous cell carcinomas, adenocarcinomas, small cell carcinoma, non-small cell carcinoma or large cell carcinoma. However, in the sub-group analysis, there was an association between G allele/GG genotype with the risk of squamous cell carcinomas in East-Asians and GG genotype was associated with the risk of small cell carcinoma in Caucasians. In conclusion, GSTP1 A/G gene polymorphism is not associated with the susceptibility of squamous cell carcinomas, adenocarcinomas, small cell carcinoma, non-small cell carcinoma or large cell carcinoma.

Glutathione-S-transferase (GST) polymorphisms are associated with relapse after radical prostatectomy

BACKGROUND

Organ confined prostate cancer (PCa) can be cured by radical retropubic prostatectomy (RRP); however, some tumors will still recur. Current tools fail to identify patients at risk of recurrence. Glutathione-S-transferases (GSTs) are involved in the metabolism of carcinogens, hormones and drugs. Thus, genetic polymorphisms that modify the GST activities may modify the risk of PCa recurrence.

METHODS

We retrospectively recruited Argentine PCa patients treated with RRP to study the association between GST polymorphisms and PCa biochemical relapse after RRP. We genotyped germline DNA in 105 patients for: GSTP1 c.313A>G (p.105 Ile>Val, rs1695) by PCR-RFLP; and GSTT1 null and GSTM1 null polymorphisms by multiplex PCR. Kaplan-Meier curves and Cox proportional hazard models were used to evaluate these associations.

RESULTS

Patients with GSTP1 c.313GG genotype showed shorter biochemical relapse-free survival (BRFS) (P = 0.003) and higher risk for recurrence in unadjusted (Hazard ratio (HR) = 3.16, 95% confidence interval (95% CI) = 1.41-7.06, P = 0.005) and multivariate models (HR = 3.01, 95% CI = 1.13-8.02, P = 0.028). We did not find significant associations for GSTT1 and GSTM1 genotypes. In addition, we found shorter BRFS (P = 0.010) and increased risk for recurrence for patients having two or more risk alleles when we combined the genotypes of the three GSTs in multivariate models (HR = 3.06, 95% CI = 1.20-7.80, P = 0.019).

CONCLUSIONS

Our results give support to the implementation of GSTs genotyping for personalized therapies as a novel alternative for PCa management for patients who undergo RRP. To the best of our knowledge, this is the first study that examined GST polymorphisms in PCa progression in Argentine men. Replication of our findings in larger cohort is warranted.

Association of glutathione S-transferase P1 gene polymorphism with the susceptibility of lung cancer

The conclusions of the published reports on the relationship between glutathione S-transferase P1 (GSTP1) gene polymorphism and the risk of lung cancer are still debated. GSTP1 is one of the important mutant sites reported at present. This meta-analysis was performed to evaluate the association between GSTP1 and the risk of lung cancer. The association investigations were identified from PubMed and Cochrane Library, and eligible studies were included and synthesized using meta-analysis method. Forty-four reports were included into this meta-analysis for the association of GSTP1 A/G gene polymorphism and lung cancer susceptibility, consisting of 12,363 patients with lung cancer and 13,948 controls. The association between GSTPI G allele and lung cancer risk was found in this meta-analysis (OR 1.08, 95 % CI 1.02-1.15, P = 0.01). However, the GG genotype and AA genotype were not associated with the susceptibility of lung cancer. Furthermore, there was no association between GSTP1 A/G gene polymorphism and the risk of lung cancer in Caucasians, and East-Asians. In conclusion, GSTP1 G allele is associated with the lung cancer susceptibility. However, more studies on the relationship between GSTP1 A/G gene polymorphism and the risk of lung cancer should be performed in the future.

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.

Assessment of cumulative evidence for the association between glutathione S-transferase polymorphisms and lung cancer: application of the Venice interim guidelines

OBJECTIVE

There is an overwhelming abundance of genetic association studies available in the literature, which can often be collectively difficult to interpret. To address this issue, the Venice interim guidelines were established for determining the credibility of the cumulative evidence. The objective of this report is to evaluate the literature on the association of common glutathione S-transferase (GST) variants (GSTM1 null, GSTT1 null and GSTP1 Ile105Val polymorphism) and lung cancer, and to assess the credibility of the associations using the newly proposed cumulative evidence guidelines.

METHODS

Information from the literature was enriched with an updated meta-analysis and a pooled analysis using data from the Genetic Susceptibility to Environmental Carcinogens database.

RESULTS

There was a significant association between GSTM1 null and lung cancer for the meta-analysis (meta odds ratio=1.17, 95% confidence interval: 1.10-1.25) and pooled analysis (adjusted odds ratio=1.10, 95% confidence interval: 1.04-1.16), although substantial heterogeneity was present. No overall association between lung cancer and GSTT1 null or GSTP1 Ile105Val was found. When the Venice criteria was applied, cumulative evidence for all associations were considered 'weak', with the exception of East Asian carriers of the G allele of GSTP1 Ile105Val, which was graded as 'moderate' evidence.

CONCLUSION

Despite the large amounts of studies, and several statistically significant summary estimates produced by meta-analyses, the application of the Venice criteria suggests extensive heterogeneity and susceptibility to bias for the studies on association of common genetic polymorphisms, such as with GST variants and lung cancer.

Meta- and pooled analysis of GSTP1 polymorphism and lung cancer: a HuGE-GSEC review

Lung cancer is the most common cancer worldwide. Polymorphisms in genes associated with carcinogen metabolism may modulate risk of disease. Glutathione S-transferase pi (GSTP1) detoxifies polycyclic aromatic hydrocarbons found in cigarette smoke and is the most highly expressed glutathione S-transferase in lung tissue. A polymorphism in the GSTP1 gene, an A-to-G transition in exon 5 (Ile105Val, 313A --> 313G), results in lower activity among individuals who carry the valine allele. The authors present a meta- and a pooled analysis of case-control studies that examined the association between this polymorphism in GSTP1 and lung cancer risk (27 studies, 8,322 cases and 8,844 controls and 15 studies, 4,282 cases and 5,032 controls, respectively). Overall, the meta-analysis found no significant association between lung cancer risk and the GSTP1 exon 5 polymorphism. In the pooled analysis, there was an overall association (odds ratio = 1.11, 95% confidence interval: 1.03, 1.21) between lung cancer and carriage of the GSTP1 Val/Val or Ile/Val genotype compared with those carrying the Ile/Ile genotype. Increased risk varied by histologic type in Asians. There appears to be evidence for interaction between amount of smoking, the GSTP1 exon 5 polymorphism, and risk of lung cancer in whites.

Haplotype-tagging single nucleotide polymorphisms in the GSTP1 gene promoter and susceptibility to lung cancer

BACKGROUND

Glutathione S-transferase (GST) P1 is a major phase II xenobiotic-metabolizing enzyme in the human lung. Our laboratory had previously identified nine single nucleotide polymorphisms (SNPs) in the GSTP1 gene promoter, which were then grouped into three main haplotypes (Hap1, Hap2, and Hap3) based on statistical inference. Hap3 was found to display a high expression phenotype. The main objective of the current study was to test the association between GSTP1 promoter haplotypes with the risk of lung cancer after determining the promoter haplotypes experimentally through cloning and sequencing.

METHODS

We conducted a case-control analysis of 150 subjects with lung cancer and 329 controls with no personal history of the disease. The three statistically inferred GSTP1 promoter haplotypes were confirmed experimentally through cloning and sequencing. Haplotype-tagging SNPs were selected and GSTP1 haplotypes were tested for genetic association to lung cancer using unconditional logistic regression after adjusting for confounders. Statistical interaction between GSTP1 promoter haplotypes with either cigarette smoking or dietary fruit and vegetable intake were tested using the likelihood ratio test.

RESULTS

We did not find protective effects of Hap3 against lung cancer, despite an adequately powered design for this main effect. Homozygous variants of tagSNPs -1738 T>A and -354 G>T, which tag Hap2, showed an increased (but statistically non-significant) risk of lung cancer among all subjects as well as among individuals with low fruit and vegetable intake, compared to homozygous wildtypes for these SNPs. We did not find significant interactions between Hap2 and dietary intake of fruits and vegetables.

CONCLUSIONS

Our results do not support significant main and modifying effects for GSTP1 promoter haplotypes on susceptibility to lung cancer in this population, but reinforce the protective effects of dietary intake of fruits and vegetables.

Genetic Polymorphism in Glutathione Transferases (GST): Population distribution of GSTM1, T1, and P1 conjugating activity

Glutathione transferases (GST) catalyze the conjugation of glutathione (GSH) with electrophiles, many of which may otherwise interact with protein or DNA. In select cases such as halogenated solvents, GST-mediated conjugation may lead to a more toxic or mutagenic metabolite. Polymorphisms that exert substantial effects on GST function were noted in human populations for several isozymes. This analysis focuses on three well-characterized isozymes, GSTM1, T1, and P1, in which polymorphisms were extensively studied with respect to DNA adducts and cancer in molecular epidemiologic studies. The current review and analysis focused upon how polymorphisms in these GST contributed to population variability in GST function. The first step in developing this review was to characterize the influence of genotype on phenotype (enzyme function) and the frequency of the polymorphisms across major population groups for all three GST. This information was then incorporated into Monte Carlo simulations to develop population distributions of enzyme function. These simulations were run separately for GSTM1, T1, and P1, and also for the combination of these isozymes, to assess the possibility of overlapping substrate specificity. Monte Carlo simulations indicated large interindividual variability for GSTM1 and T1 due to the presence of the null (zero activity) genotype, which is common in all populations studied. Even for GSTM1 or T1 non-null individuals, there was considerable interindividual variability with a bimodal distribution of enzyme activity evident. GSTP1 polymorphisms are associated with somewhat less variability due to the absence of null genotypes. However, in all cases simulated, the estimated variability is sufficiently large to warrant consideration of GST function distributions in assessments involving GST-mediated activation or detoxification of xenobiotics. Ideally, such assessments would involve physiologically based toxicokinetic (PBTK) modeling to assess population variability in internal dose.

Influence of glutathione S-transferase polymorphisms on cognitive functioning effects induced by p,p'-DDT among preschoolers

BACKGROUND

Early-life exposure to p,p'-DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane] is associated with a decrease in cognitive skills among preschoolers at 4 years of age. We hypothesized that genetic variability in glutathione S-transferase (GST) genes (GSTP1, GSTM1, and GSTT1) could influence the effects of prenatal exposure to p,p'-DDT.

METHODS

We used data from 326 children assessed in a prospective population-based birth cohort at the age of 4 years. In that study, the McCarthy Scales of Children's Abilities were administrated by psychologists, organochlorine compounds were measured in cord serum, and genotyping was conducted for the coding variant Ile105Val from GSTP1 and for null alleles from GSTM1 and GSTT1. We used linear regression models to measure the association between organochlorines and neurodevelopmental scores by GST polymorphisms.

RESULTS

p,p'-DDT cord serum concentration was inversely associated with general cognitive, memory, quantitative, and verbal skills, as well as executive function and working memory, in children who had any GSTP1 Val-105 allele. GSTP1 polymorphisms and prenatal p,p'-DDT exposure showed a statistically significant interaction for general cognitive skills (p = 0.05), quantitative skills (p = 0.02), executive function (p = 0.01), and working memory (p = 0.02). There were no significant associations between p,p'-DDT and cognitive functioning at 4 years of age according to GSTM1 and GSTT1 polymorphisms.

CONCLUSIONS

Results indicate that children with GSTP1 Val-105 allele were at higher risk of the adverse cognitive functioning effects of prenatal p,p'-DDT exposure.

Glutathione S-transferase M1 (GSTM1) polymorphisms and lung cancer: a literature-based systematic HuGE review and meta-analysis

Multiple genes have been studied for potential associations with lung cancer. The gene most frequently associated with increased risk has been glutathione S-transferase M1 (GSTM1). The glutathione S-transferase enzyme family is known to catalyze detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins, and products of oxidative stress. In this review, the authors summarize the available evidence associating lung cancer with the GSTM1 gene. They describe results from an updated meta-analysis of 98 published genetic association studies investigating the relation between the GSTM1 null variant and lung cancer risk including 19,638 lung cancer cases and 25,266 controls (counting cases and controls in each study only once). All studies considered, the GSTM1 null variant was associated with an increased risk of lung cancer (odds ratio (OR) = 1.22, 95% confidence interval (CI): 1.14, 1.30), but no increase in risk was seen (OR = 1.01, 95% CI: 0.91, 1.12) when only the five largest studies (>500 cases each) were considered. Furthermore, while GSTM1 null status conferred a significantly increased risk of lung cancer to East Asians (OR = 1.38, 95% CI: 1.24, 1.55), such a genotype did not confer increased risk to Caucasians. More data regarding the predictive value of GSTM1 genetic testing are needed before population-based testing may be reasonably considered.

Five glutathione s-transferase gene variants in 23,452 cases of lung cancer and 30,397 controls: meta-analysis of 130 studies

BACKGROUND

Glutathione S-transferases (GSTs) are known to abolish or reduce the activities of intracellular enzymes that help detoxify environmental carcinogens, such as those found in tobacco smoke. It has been suggested that polymorphisms in the GST genes are risk factors for lung cancer, but a large number of studies have reported apparently conflicting results.

METHODS AND FINDINGS

Literature-based meta-analysis was supplemented by tabular data from investigators of all relevant studies of five GST polymorphisms (GSTM1 null, GSTT1 null, I105V, and A114V polymorphisms in the GSTP1 genes, and GSTM3 intron 6 polymorphism) available before August, 2005, with investigation of potential sources of heterogeneity. Included in the present meta-analysis were 130 studies, involving a total of 23,452 lung cancer cases and 30,397 controls. In a combined analysis, the relative risks for lung cancer of the GSTM1 null and GSTT1 null polymorphisms were 1.18 (95% confidence interval [CI]: 1.14-1.23) and 1.09 (95% CI: 1.02-1.16), respectively, but in the larger studies they were only 1.04 (95% CI: 0.95-1.14) and 0.99 (95% CI: 0.86-1.11), respectively. In addition to size of study, ethnic background was a significant source of heterogeneity among studies of the GSTM1 null genotype, with possibly weaker associations in studies of individuals of European continental ancestry. Combined analyses of studies of the 105V, 114V, and GSTM3*B variants showed no significant overall associations with lung cancer, yielding per-allele relative risks of 1.04 (95% CI: 0.99-1.09), 1.15 (95% CI: 0.95-1.39), and 1.05 (95% CI: 0.89-1.23), respectively.

CONCLUSIONS

The risk of lung cancer is not strongly associated with the I105V and A114V polymorphisms in the GSTP1 gene or with GSTM3 intron 6 polymorphism. Given the non-significant associations in the larger studies, the relevance of the weakly positive overall associations with the GSTM1 null and the GSTT1 null polymorphisms is uncertain. As lung cancer has important environmental causes, understanding any genetic contribution to it in general populations will require the conduct of particularly large and comprehensive studies.

Association between glutathione S-transferase pi polymorphisms and survival in patients with advanced nonsmall cell lung carcinoma

BACKGROUND

Glutathione S-transferase (GST) pi (GSTP1) is a detoxification enzyme with substrate specificity for both exogenous carcinogens and chemotherapy agents. Genetic polymorphisms of GSTP1 exon 5 (Ile105Val) and exon 6 (Ala114Val) appear to reduce this enzyme's activity. Previously, the authors reported that the exon 6 variant was associated with an increased risk of lung carcinoma, particularly among men, younger patients, and ever smokers. In this study, the authors hypothesized that variant GSTP1 genotype would result in reduced inactivation of chemotherapy agents and improved survival in patients with advanced-stage nonsmall cell lung carcinoma (NSCLC), a population that is likely to receive platinum-based chemotherapy.

METHODS

Patients with Stage III and IV NSCLC who were enrolled in a molecular epidemiology study were identified, and a polymerase chain reaction-restriction fragment length polymorphism assay was used to genotype GSTP1 exons 5 and 6 in 424 patients and 425 patients, respectively.

RESULTS

Patients who had the exon 6 variant genotype (Ala/Val or Val/Val) had significantly better survival compared with patients who had the wild type genotype (Ala/Ala; P = 0.037), with median survival of 16.1 months and 11.4 months, respectively. Multivariate analysis revealed a reduced adjusted hazard ratio (HR) of death associated with the exon 6 variant genotype of 0.75 (95% confidence interval [95% CI], 0.54-1.05). This protective association was observed in younger patients (younger than age 62 yrs; HR, 0.59; 95% CI, 0.57-0.97) and in males (HR, 0.64; 95% CI, 0.41-0.99). GSTP1 exon 5 genotype was not associated with survival.

CONCLUSIONS

GSTP1 exon 6 variant genotypes may be associated with improved survival among patients with Stage III and IV NSCLC.

An association between glutathione S-transferase P1 gene polymorphism and younger age at onset of lung carcinoma

BACKGROUND

Among the genes that encode the glutathione S-transferase (GST) superfamily of Phase 2 metabolizing enzymes, GSTP1 has the highest expression in the lung. The polymorphic GSTP1 gene encodes glutathione S-transferase pi, which is an enzyme that detoxifies cigarette carcinogens, such as benzo-[a]-pyrene. The variant GSTP1 GG genotype is associated with lower enzymatic activity and higher DNA adduct levels in human lymphocytes compared with the AA genotype.

METHODS

The authors evaluated the association of GSTP1 genotypes with lung cancer in 1921 cases and 1343 controls of Caucasian descent by using polymerase chain reaction-restriction fragment length polymorphism techniques. The results were analyzed with multiple logistic regression adjusting for age, gender, smoking status, and pack-years. To investigate specifically the subset of younger lung cancer patients and controls, the effect of age (either as a dichotomous or continuous variable in separate models) was analyzed as a modifying factor of the association between the GSTP1 polymorphism and lung cancer.

RESULTS

The GSTP1 GG genotype was not associated with an overall increased risk of lung cancer (adjusted odds ratio, 1.02; 95% confidence interval [95% CI], 0.78-1.34) compared with the GSTP1 AA genotype. In both models that evaluated the gene-age interaction, an overall statistically significant interaction (P < .01) was observed between age and the GG genotype. However, for the model that included age as a dichotomous variable, the odds ratio of lung cancer risk with the GG genotype compared with the AA among individuals age </=50 years was 2.67 (95% CI, 1.36-5.22); in older individuals, the risk was 0.87 (95% CI, 0.65-1.2).

CONCLUSIONS

The GSTP1 GG genotype was associated with increased lung cancer susceptibility among younger study participants.

ADVANCES IN CANCER EPIDEMIOLOGY: Understanding Causal Mechanisms and the Evidence for Implementing Interventions

In a worldwide population of 6 billion, in the year 2000, approximately 10 million cancers were diagnosed, and there were an estimated 6.2 million cancer deaths. Whereas the universality of cancer incidence and mortality is established, the burden of cancer by type or organ site is distributed unequally between developing and industrialized nations. Populations in developing countries are disproportionately affected by cancers in which infectious agents are causal. Our review of advances in cancer epidemiology underscores the complexity of pathogenic mechanisms mediated by chronic inflammation, obesity, and gene-environment interactions as in tobacco and alcohol carcinogenesis. Ultimately, the implementation of effective cancer control interventions that will serve to alleviate the cancer burden must integrate basic and applied research in the behavioral, social, biomedical, and population sciences.

Genetic susceptibility to tobacco-related cancer

Although cigarette smoking is the dominant risk factor for several epithelial cancers, only a small fraction of individuals with tobacco exposure develop cancer. The underlying hypothesis is that genetic factors may render certain smokers more susceptible to cancer than others. Genetic alterations in critical regulatory pathways may predispose cells to carcinogenesis. These pathways include regulation of xenobiotic metabolism; control of genomic stability, including DNA repair mechanisms, cell-cycle checkpoints, apoptosis and telomere length; and control of microenvironmental factors, such as matrix metalloproteinases, inflammation and growth factors. In addition, epigenetic events, such as promoter hypermethylation and loss of imprinting, are also involved in carcinogenesis. In this review, we will summarize recent advances in genetic susceptibility to tobacco-related cancer. Emphasizing on risk assessment, we will describe how genetic variations in the above-mentioned genetic pathways modify the tobacco-related cancer risk. In addition, we will discuss how genetic variations may assist in predicting clinical outcome, such as the natural history of cancer and treatment response. The measurements of genetic susceptibility by both genotypic and phenotypic assays are covered in the text. Finally, we present a number of current concerns that need to be addressed as the exciting field of molecular cancer epidemiology advances rapidly.

Combined effects of glutathione S-transferase polymorphisms and thyroid cancer risk

Since exposure to ionizing radiation, a risk factor for thyroid cancer, may produce genotoxins potentially eliminated by glutathione-S-transferases, we conducted a case control study to evaluate the role of the GSTM1- and GSTT1-null genotypes and GSTP1 polymorphisms in thyroid cancer. The frequency of GSTP1 Ile/Ile, GSTM1-, and GSTT1-null genotypes was increased in cancer patients when compared with control population. Considering the genotypes over-represented in thyroid cancer patients as potential risk genotypes, we carried out an odds ratio (OR) analysis considering the presence of none, one, two, or three risk genotypes. The results obtained showed that the presence of three potentially risk alleles (GSTM1 null, GSTT1 null, and GSTP1 Ile/Ile) lead to a significant OR increase for all the cases, irrespective of the type of tumor (OR=2.91), for papillary (OR=3.64) but not for follicular tumors. The presence of GSTP1 Ile/Ile leads to a significant later age of tumor onset when compared with GSTP1 Ile/Val and Val/Val (P<0.05), suggesting a possible association between GSTP1 Ile/Ile and the age of disease manifestation. These results suggest that combined GST polymorphisms lead to a moderate increased risk for thyroid cancer, especially for the papillary type, and GSTP1 polymorphisms might modulate the age of onset of the disease.

GST genetic polymorphisms and lung adenocarcinoma susceptibility in a Chinese population

Lung adenocarcinoma (AC) has been increasing over the last several decades in many countries, including China. Some of the glutathione S-transferases (GSTs) demonstrate polymorphisms which may play a role in lung AC susceptibility. Our previous study of a Chinese population found the GSTM1 null genotype to be associated with an increased risk of lung AC, and the combination of GSTM1 null genotype and CYP2E1 wild type conferred a significantly elevated risk. Here, we extended the study to investigate the potential role of GSTT1 and GSTP1 polymorphisms in likelihood of development of lung AC, either separately or in combination. This case-control study encompassed 112 cases with lung ACs and 119 age- and gender-matched cancer-free controls from Beijing. The frequencies for the GSTM1 null genotype were 61.6 and 50.4% among cases and controls, and for the GSTT1 null genotype 47.3 and 45.4%, respectively. The distribution of the GSTP1 Ile/Ile, Ile/Val and Val/Val genotypes was 59.8, 39.3 and 0.9% in cases, and 70.6, 28.6 and 0.8% in controls, respectively. No relationship between lung AC and the GSTT1 genotype was observed in the present study, either separately or in combination with the GSTM1 or GSTP1 genotypes. Although separate GSTM1 and GSTP1 polymorphisms were not statistically related to lung AC, the combination of GSTM1 null and GSTP1 Val was significantly associated with an elevated lung AC risk (OR=2.4, 95% CI 1.1-5.1).

Smoking and the Risk of Lung Cancer

BACKGROUND

GSTP1 is a gene that helps detoxify foreign substances in the body. Functional polymorphisms of GSTP1 have been studied as risk factors for lung cancer. Past studies have compared the effect of the "at risk" polymorphism in two strata of smoking pack-years (usually defined by the median among controls). We examined the interaction between GSTP1 polymorphisms and cumulative exposure to smoking and their association with lung cancer risk.

METHODS

Data are from a large hospital-based case-control study of persons treated for primary lung cancer at the Massachusetts General Hospital since 1992. Controls were drawn from friends and nonrelated family members. We genotyped 1,042 cases and 1,161 controls for GSTP1 using polymerase chain reaction-restriction fragment length polymorphism techniques.

FINDINGS

The GSTP1 GG genotype approximately doubled the lung cancer risk associated with pack-years. This interaction was stronger among current smokers. At 26 pack-years (median among controls with a smoking history), the adjusted odds ratio for the association between pack-years and lung cancer risk was 13 (95% confidence interval = 6.5-25) among current smokers with the GSTP1 GG genotype compared with 6.1 (95% confidence interval = 4.9-7.5) among those with the GSTP1 AA genotype.

CONCLUSIONS

GSTP1 GG increases the lung cancer risk associated with pack-years of smoking.

A population-based study of glutathione S-transferase M1, T1 and P1 genotypes and risk for lung cancer

A deletion polymorphism for glutathione S-transferase M1 (GSTM1) has been related to risk for lung cancer among smokers in some studies but not in others. We examined GSTM1, a GSTT1 deletion polymorphism and a common GSTP1 gene variant (iso-->val), as risk factors for lung cancer in a population-based case-control study of men. Cases (N=274) were males identified from 1993 to 1996 through the Fred Hutchinson Cancer Research Center Cancer Surveillance System registry for western Washington State. Male age-matched controls (N=501) were selected by random-digit dialing. Subjects participated in a telephone interview and blood draw. GSTM1 and GSTT1 were genotyped with a multiplex PCR assay using beta-globin as a positive control, and GSTP1 single nucleotide variant determined with PCR-based oligonucleotide ligation assays. GSTM1 absence was associated with a modest elevation in risk among all cases (odds ratio=1.27, 95% CI 0.91-1.77) and among non-small cell cancers (adenocarcinoma OR=1.58, 95% CI 0.99-2.52; squamous cell OR=1.40, 95% CI 0.83-2.34). Risk associated with GSTM1 null was increased two to sixfold among heavy smokers. GSTT1 was not associated with lung cancer risk and GSTP1 val was non-significantly associated with a modest reduction in risk, particularly among heavy smokers. No specific combination of GST genotypes was particularly associated with risk. These results support previous reports that the GSTM1 null genotype is associated with a modest increase in risk for lung cancer, particularly among heavy smokers, suggest no role for GSTT1 and the need for further study of GSTP1.

Association between glutathione S-transferase p1 polymorphisms and lung cancer risk in Caucasians: a case-control study

Glutathione transferases (GSTs), a multiple gene family of phase II enzymes, catalyze detoxifying endogenous reactions with glutathione and protect cellular macromolecules from damage caused by cytotoxic and carcinogenic agents. Glutathione S-transferase p1 (GSTP1), the most abundant GST isoform in the lung, metabolizes numerous carcinogenic compounds including benzo[a]pyrene, a tobacco carcinogen. Previous studies suggest that genetic polymorphisms of GSTP1 exon 5 (Ile105Val) and exon 6 (Ala114Val) have functional effects on the GST gene product resulting in reduced enzyme activity. Individuals with reduced GST enzymatic activity may be at a greater risk for cancer due to decreased detoxification of carcinogenic and mutagenic compounds. Utilizing a hospital-based case-control study, we investigated the association between GSTP1 polymorphisms at exons 5 and 6 with lung cancer risk. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was used to successfully genotype the GSTP1 exons 5 and 6 polymorphism in 582 Caucasian lung cancer cases and 600 frequency matched Caucasian controls. There was no association between the exon 5 variant genotypes (A/G+G/G) and overall lung cancer risk (OR=1.09; 95% CI 0.82-1.45) nor when stratified by age, gender, and smoking status. However, the exon 6 variant genotypes (C/T+T/T) were associated with a statistically significant elevated lung cancer risk (OR=1.40; 95% CI 1.06-1.92). Additionally, there was an increase in lung cancer risk for the exon 6 variant genotypes in younger individuals (<62 years) (OR=1.63; 95% C.I. 1.07-2.49) but no effect in older individuals (OR=1.14; 95% CI 0.72-1.81). A statistically significant increased risk of lung cancer was also observed for the exon 6 variant genotypes among men (OR=2.17; 95% CI 1.41-3.33), but not among women (OR=0.80; 95% CI 0.51-1.28). Among ever smokers, the exon 6 variant genotypes were associated with an elevated lung cancer risk (OR=1.58; 95% CI 1.14-2.19), which was not evident for never smokers (OR=0.53; 95% CI 0.21-1.33). These data demonstrate that the GSTP1 exon 6 polymorphism, but not the exon 5 polymorphism, is associated with lung cancer risk that is especially evident in men, younger individuals, and ever smokers.

Microsomal epoxide hydrolase and glutathione S-transferase polymorphisms in relation to laryngeal carcinoma risk

Two polymorphic sites of the microsomal epoxide hydrolase gene (EPHX1, 113Tyr-->113His, 139His-->139Arg) and four glutathione S-transferase genes (GSTM1, GSTM3, GSTP1, GSTT1) were genotyped in a group of patients with larynx cancer (N=204) and in a group of healthy controls (N=203), all Spanish caucasians. After adjusting for gender, age, and tobacco smoking, none of the polymorphisms alone were found to be associated with larynx cancer risk. The analysis of EPHX1/GST combinations, however, showed a significant over-representation of patients with a combination of 113Tyr/113Tyr EPHX1 and 105Ile/105Ile GSTP1 (adjusted odds ratio (OR): 1.95; 95% confidence interval (CI): 1.02-3.78). The calculation of the predicted epoxide hydrolase (EH) activity also showed an increased risk for the individuals with both predicted high activity EH and 105Ile/105Ile GSTP1 (OR: 2.90; 95% CI: 1.10-7.67). These results on larynx cancer tend to confirm a former study on lung cancer (Cancer Lett. 173 (2001) 155) suggesting the existence of an interaction between variants of EH and GSTpi, both enzymes being involved in the metabolism of aromatic hydrocarbons, that may increase susceptibility to tobacco-related cancers.

Genetic polymorphism of enzymes involved in xenobiotic metabolism and the risk of lung cancer

Chronic inhalation of cigarette smoke is a major risk factor for the development of lung cancer. It has been suggested that genetic susceptibility may contribute to the risk, because only a small portion of smokers develops the disease. Several polymorphisms that involve the metabolic activation or detoxification of carcinogens derived from cigarette smoke have been found to be associated with lung cancer risk. Many studies have focused on the relation between the distribution of polymorphic variants of different forms of the metabolic enzymes and lung cancer susceptibility. In this respect two groups of genetic polymorphisms of enzymes involved in xenobiotic metabolism, cytochrome P450 (CYP) and glutathione S-transferases (GSTs), have been discussed.CYP multigene superfamily consists of 10 subfamilies (CYP1-CYP10). A positive association between development of lung cancer and the mutant homozygous genotype ofCYP1A1 gene has been reported in several Japanese populations but such an association has not been observed in either Caucasians or African-Americans. The relation betweenCYP2D6 and lung cancer remains conflicting and inconclusive. Several polymorphisms have been identified at theCYP2E1 locus. No definitive link between the polymorphisms ofCYP2E1 and the risk of lung cancer has, however, been identified. The role of otherCYP2 isoforms in lung carcinogenesis has not been sufficiently investigated.GSTs form a superfamily of genes consisting of five distinct families, namedGSTA, GSTM, GSTP, GSTT andGSTS. The role ofGSTM, GSTT1 orGSTP1 polymorphism in modifying the lung cancer risk may be more limited than has been so far anticipated.Although some genetic polymorphisms discussed here have not shown significant increases/decreases in risk, individuals with differing genotypes may have different susceptibilities to lung cancer. Hopefully, in future studies it will be possible to screen for lung cancer using specific biomarkers.

Lung cancer susceptibility in relation to combined polymorphisms of microsomal epoxide hydrolase and glutathione S-transferase P1

Human microsomal epoxide hydrolase (mEH) catalyzes a key step in the biotransformation of benzo[a]pyrene that yields the highly mutagenic (+)-anti-7,8-diol-9,10 epoxide (BPDE). Two polymorphisms have been described in the coding region of the mEH gene (EPHX1) that produce two protein variants: 113Tyr-->113His (exon 3) and 139His-->139Arg (exon 4). We performed a case-control study among Northwestern Mediterranean Caucasians to investigate a possible association between these EPHX1 variants and lung cancer risk. Both EPHX1 polymorphisms were analyzed in a group of lung cancer patients (n=176) and in a control group of healthy smokers (n=187). The results showed a significantly decreased risk for the rare homozygous 113His/113His (adjusted odds ratio (OR): 0.44, 95% confidence interval (CI): 0.27-0.71) and 139Arg/139Arg (adjusted OR: 0.55, 95% CI: 0.33-0.91) compared with the major wild-types 113Tyr/113Tyr and 139His/139His, respectively, as the references. Thereafter, we analyzed the EPHX1 variants in combination with three glutathione S-transferase polymorphic genes (GSTM1, GSTT1, and GSTP1) and we found a significant overepresentation of cancer patients with a combination of exon 3 113Tyr/113Tyr EPHX1 and exon 5 105Ile/105Ile GSTP1 (adjusted OR: 2.34, 95% CI: 1.21-4.52). The polymorphic site within the exon 5 of GSTP1 results in a Ile-->Val substitution, and the isoleucine GSTpi isoform has been found in vitro to be less active than the valine isoform towards the conjugation of BPDE. The 113 Tyr/Tyr EPHX1 encodes for a high-activity mEH. Our results agree with these observations in vitro and suggest that a genetically determined combination of a high-activity mEH and a low-activity GSTpi may increase lung cancer risk among smokers.

Genetic polymorphisms of biotransformation enzymes: allele frequencies in the population of the Czech Republic

Polymerase chain reaction-restriction fragment length polymorphism based genotyping assays were used to determine the frequency of polymorphisms in CYP1A1 (3'-flanking region), CYP2E1 (5'-flanking region and intron 6), EPHX (exon 3 and exon 4), GSTM1 (deletion), GSTP1 (exon 5) and GSTT1 (deletion) in a group of 416 Czech individuals. A comprehensive overview of the methodology is also presented. We have found the following frequencies of mutated alleles: CYP1A1-m2, 0.097; CYP2E1-C, 0.077; CYP2E1-c2, 0.023; EPHX(exon 3)-His, 0.381; EPHX(exon 4)-Arg, 0.198; GSTM1-null, 0.51; GSTP1-Val, 0.3; GSTT1-null, 0.164. These values are similar to those presented in the majority of studies on European Caucasians, although a few cases of significant differences in the distribution of genotypes were found. These differences were most probably caused by methodological variations or statistical bias in the analyses of low numbers of samples in the control groups of some authors. Based on the results of EPHX genotyping, the activity of its protein product was deduced and the Czech population was divided into three subgroups with low, medium and high EPHX activity. We found that 43% of the Czech population would fall into the low, 44% into the medium and 13% into the high EPHX activity group. The data obtained may prove to be very useful for epidemiological studies on the influence of genetic polymorphisms of biotransformation enzymes on carcinogenesis or other environment-related diseases.

Mammalian class theta GST and differential susceptibility to carcinogens: a review

Glutathione S-transferases (GSTs) are an important part of the cellular detoxification system and, perhaps, evolved to protect cells against reactive oxygen metabolites. Theta is considered the most ancient among the GSTs and theta-like GSTs are found in mammals, fish, insects, plants, unicellular algae, and bacteria. It is thought that an ancestral theta-gene underwent an early duplication before the divergence of fungi and animals and further duplications generated the variety of the other classes of GSTs (alpha, mu, phi, etc.). The comparison of the aminoacidic homologies among mammals suggests that a duplication of an ancient GST theta occurred before the speciation of mammals and resulted in the subunits GSTT1 and GSTT2. The ancestral GST theta has a dehalogenase activity towards several halogenated compounds, such as the dichloromethane. In fact, some aerobic and anaerobic methylotrophic bacteria can use these molecules as the sole carbon and energy source. The mammalian GST theta cannot sustain the growth of bacteria but still retains the dehalogenating activity. Therefore, although mammalian GST theta behaves as a scavenger towards electrophiles, such as epoxides, it acts also as metabolic activator for halogenated compounds, producing a variety of intermediates potentially dangerous for DNA and cells. For example, mice exposed to dichloromethane show a dose-dependent incidence of cancer via the GSTT1-1 pathway. Because GSTT1-1 is polymorphic in humans, with about 20% of Caucasians and 80% of Asians lacking the enzyme, the relationship between the phenotype and the incidence of cancer has been investigated extensively in order to detect GSTT1-1-associated differential susceptibility towards endogenous or exogenous carcinogens. The lack of the enzyme is related to a slightly increased risk of cancer of the bladder, gastro-intestinal tract, and for tobacco-related tumors (lung or oral cavity). More pronounced risks were found in males with the GSTT1-null genotype for brain diseases and skin basal cell carcinomas not related to sunlight exposures. Moreover, there was an increased risk of kidney and liver tumors in humans with the GSTT1-1 positive genotype following exposures to halogenated solvents. Interestingly, the liver and kidney are two organs that express the highest level of GST theta in the human body. Thus, the GSTT1-1 genotype is suspected to confer decreased or increased risk of cancer in relation to the source of exposure; in vitro studies, mostly conducted on metabolites of butadiene, confirm the protective action of GSTT1-1, whereas, thus far, experimental studies prove that the increasing risk is limited.