Glutathione S-transferase M1, T1 and P1 genetic polymorphisms, cigarette smoking and gastric 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.

Genotoxicity of inhalational anesthetics and its relationship with the polymorphisms of GSTT1, GSTM1, and GSTP1 genes

Due to their wide applications, concern exists regarding possible genotoxic effects of inhalational anesthetics (IAs) among operating room personnel. This study was undertaken to examine genotoxic properties of co-exposure to nitrous oxide, sevoflurane, and isoflurane on induction of micronucleus (MN) and chromosomal aberrations (CAs) and to determine whether any associations exist between polymorphisms of GST genes and the level of genomic damage measured by MN and CAs assays. Sixty operating room personnel and 60 unexposed referent nurses were studied. The workers' exposure to the IAs was determined. DNA damage was evaluated by MN and CAs assays. Additionally, the GSTM1, GSTT1, and GSTP1 polymorphisms were detected. The mean concentrations of nitrous oxide, isoflurane, and sevoflurane were found to be 850.92 ± 919.78, 2.40 ± 0.86, and 0.18 ± 0.14 ppm, respectively. The frequency of MN and CAs in the exposed group was significantly higher than that of the non-exposed group. The frequency of MN was significantly higher in referent nurses with null GSTT1, compared to referent nurses with positive GSTT1. The frequency of MN was significantly higher in exposed individuals carrying the combined genotype of GSTT1 (-), GSTM1 (-), and GSTP1 AG as compared with subjects carrying a combination of GSTT1 (+), GSTM1 (+), and GSTP1 AA. Statistically significant associations were noted between exposure to the IAs, gender, and the combination of the three GSTs genotypes with MN frequency. These findings indicate that inhalation exposure to IAs induces genotoxic response and the polymorphisms of GSTs genes might modulate the effect of exposure to IAs on MN.

The Interaction of Smoking with Gene Polymorphisms on Four Digestive Cancers: A Systematic Review and Meta-Analysis

The main purpose of this study was to perform a meta-analysis to assess the interaction between smoking and nine genes (GSTM1, GSTT1, GSTP1, CYP1A1, NAT2, SULT1A1, hOGG1, XRCC1 and p53) on colorectal cancer, gastric cancer, liver cancer and oesophageal cancer. Published articles from the PubMed, ISI and EMBASE databases were retrieved. A total of 67 case-control studies or nested case-control studies were identified for the analysis. The pooled jodds ratio (OR) with 95% confidence interval (CI) was calculated using the random effect model. The overall study showed that the GSTM1 polymorphism was associated with the risk of the four digestive cancers among Asian population (OR 1.284, 95% CI: 1.122-1.470, p: 0). Subgroup analyses by cancer site showed that GSTM1 null genotype increased the gastric cancer risk in total population (OR 1.335, 95% CI: 1.145-1.556, p: 0). However, the association of GSTM1 null genotype with the oesophageal cancer risk was found in smokers (OR 1.382, 95% CI: 1.009-1.894, p:0.044), but not in non-smokers (OR 1.250, 95% CI: 0.826-1.891, p:0.290). Moreover, smokers with the CYP1A1 IIe462Val polymorphism were at an increased cancer risk in Asian population (OR=1.585, 95% CI 1.029-2.442, p: 0.037). None of the other gene-smoking interactions was observed in the above cancers. This meta-analysis reveals two potential gene-smoking interactions, one is between smoking and GSTM1 on oesophageal cancer, and the other is between smoking and CYP1A1 IIe462Val on the four cancers in Asian population. Future studies need to be conducted to verify the conclusions.

Smoking Status and Gastric Cancer Risk: An Updated Meta-Analysis of Case-Control Studies Published in the past Ten Years

Background

A meta-analysis of published studies was performed in order to clarify the risk of gastric cancer associated with cigarette smoking status.

Methods

Eligible studies were all the case-control studies investigating an association between smoking status and gastric cancer published from January 1, 1997, until June 30, 2006. In order to evaluate the quality of the published data, a qualitative scoring of papers was applied. The principal outcome measure was the odds ratio for the risk of gastric cancer associated with the smoking status using a random effects model. Cigarette smoking status was assessed in two ways: ever (current and ex) versus never smokers; current versus never smokers.

Results

We found a statistically significant result for the association between ever smoking status and gastric cancer risk (OR = 1.48; 95% CI, 1.28–1.71), considering 14,442 cases and 73,918 controls. Moreover, we found an odds ratio of 1.69 for current smoker status in comparison to never smokers (95% CI, 1.35–2.11). Considering only high quality studies, the odds ratio increased by 43% for gastric cancer risk in ever smokers (OR = 1.43; 95% CI, 1.24–1.66; Q = 378.60, P <0.00001; I2 = 90%) and by 57% in current smokers (OR = 1.57; 95% CI, 1.24–2.01). We also considered separately Caucasians and Asian studies, finding for ever smokers an odds ratio of 1.46 (95% CI, 1.25–1.70; Q = 125.68, P <0.00001; I2 = 82.5%) and of 1.47 (95% CI, 1.13–1.91; Q = 366.77, P <0.00001; I2 = 94%), respectively.

Conclusions

From the results of this quantitative meta-analysis, it appears that cigarette smoking has to be considered an important risk factor. The use of qualitative scoring decreases the magnitude of the relationship both for ever and current smoker exposure by 5–12%. Future studies on this topic need to clarify the biological interaction between environmental factors (such as cigarette smoking) and different polymorphisms on gastric cancer.

Prevention of Gastric Cancer: Eradication of Helicobacter Pylori and Beyond

Although its prevalence is declining, gastric cancer remains a significant public health issue. The bacterium Helicobacter pylori is known to colonize the human stomach and induce chronic atrophic gastritis, intestinal metaplasia, and gastric cancer. Results using a Mongolian gerbil model revealed that H. pylori infection increased the incidence of carcinogen-induced adenocarcinoma, whereas curative treatment of H. pylori significantly lowered cancer incidence. Furthermore, some epidemiological studies have shown that eradication of H. pylori reduces the development of metachronous cancer in humans. However, other reports have warned that human cases of atrophic metaplastic gastritis are already at risk for gastric cancer development, even after eradication of these bacteria. In this article, we discuss the effectiveness of H. pylori eradication and the morphological changes that occur in gastric dysplasia/cancer lesions. We further assess the control of gastric cancer using various chemopreventive agents.

GENOTYPE ASSOCIATION GSTM1 NULL AND GASTRIC CANCER: EVIDENCE-BASED META-ANALYSIS

BACKGROUND

Gastric cancer is the fourth most common cancer in men and the sixth among women, except for non-melanoma skin tumors, in Brazil. Epidemiological evidences reveal the multifactorial etiology of this cancer, highlighting risk factors such as: infection by the bacterium Helicobacter pylori, advanced age, smoking, chronic alcohol abuse, eating habits and genetic polymorphisms. Considering the context of genetic polymorphisms, there is the absence of the GSTM1 gene. The lack of GSTM1 function to detoxify xenobiotics and promote defense against oxidative stress leads to increased DNA damage, promoting gastric carcinogenesis. This process is multifactorial and the development of gastric cancer results from a complex interaction of these variables.

OBJECTIVE

The aim of this study was to investigate the association of GSTM1 null polymorphism in the pathogenesis of gastric cancer.

METHODS

A meta-analysis was conducted from 70 articles collected in SciELO and PubMed databases, between September 2015 and July 2016. In order to evaluate a possible association, we used the odds ratio (OR) and confidence interval of 95% (CI 95%). To assess the heterogeneity of the studies was used the chi-square test. Statistical analysis was performed using the BioEstat® 5.3.

RESULTS

This study included 70 studies of case-control, including 28,549 individuals, which were assessed for the null polymorphism of the GSTM1 gene, and of which 11,208 (39.26%) were cases and 17,341 (60.74%) were controls. The final analysis showed that the presence of the GSTM1 gene acts as a protective factor against the development of gastric cancer (OR=0.788; 95%CI 0.725-0.857; P<0.0001). Positive statistical association was found in Asia (OR=0.736; 95%CI 0.670-0.809; P<0.0001) and Eurasia (OR=0.671; 95%CI 0.456-0.988; P=0.05). However, statistically significant data was not obtained in Europe (OR=1.033; 95%CI 0.873-1.222; P=0.705) and America (OR=0.866; 95%CI 0.549-1.364; P=0.534). Therefore, the results can not be deduced around the world.

CONCLUSION

This meta-analysis concluded that the presence of the GSTM1 gene is a protector for the emergence of gastric cancer, especially in Asian countries, but this result was not found in Europe and America.

Copy number variation analysis by ligation-dependent PCR based on magnetic nanoparticles and chemiluminescence

A novel system for copy number variation (CNV) analysis was developed in the present study using a combination of magnetic separation and chemiluminescence (CL) detection technique. The amino-modified probes were firstly immobilized onto carboxylated magnetic nanoparticles (MNPs) and then hybridized with biotin-dUTP products, followed by amplification with ligation-dependent polymerase chain reaction (PCR). After streptavidin-modified alkaline phosphatase (STV-AP) bonding and magnetic separation, the CL signals were then detected. Results showed that the quantification of PCR products could be reflected by CL signal values. Under optimum conditions, the CL system was characterized for quantitative analysis and the CL intensity exhibited a linear correlation with logarithm of the target concentration. To validate the methodology, copy numbers of six genes from the human genome were detected. To compare the detection accuracy, multiplex ligation-dependent probe amplification (MLPA) and MNPs-CL detection were performed. Overall, there were two discrepancies by MLPA analysis, while only one by MNPs-CL detection. This research demonstrated that the novel MNPs-CL system is a useful analytical tool which shows simple, sensitive, and specific characters which are suitable for CNV analysis. Moreover, this system should be improved further and its application in the genome variation detection of various diseases is currently under further investigation.

Glutathione S-transferase gene GSTM1, gene-gene interaction, and gastric cancer susceptibility: evidence from an updated meta-analysis

Background

The null genotype of GSTM1 have been implicated in gastric cancer risk, but numerous individual studies showed mixed, or even conflicting results. Thus, a meta-analysis was performed.

Results

We identified 54 individual studies involving 9,322 cases and 15,118 controls through computer-based searches of PubMed, Embase, and Cochrane Library. It was found that the null genotype of GSTM1 was associated with an increased gastric cancer risk (OR = 1.207, 95% CI: 1.106-1.317, P < 0.001), under the random-effects model (I² : 49.9%, P_Q <0.001). From stratification analyses for ethnicity, alcohol drinking, Helicobacter pylori infection, an effect modification of gastric cancer risk was found in the subgroups of ethnicity, smoking status, Helicobacter pylori infection, whereas null result was found in the subgroups of alcohol drinking. We also undertook gene-gene interaction analysis between GSTM1 and GSTT1 genes for gastric cancer risk, and the results indicated that the dual null genotypes of GSTM1 and GSTT1 might elevate the risk of gastric cancer (OR = 1.505, 95% CI: 1.165-1.944, P = 002).

Conclusions

This meta-analysis suggests that the null genotype of GSTM1 may be a important genetic risk factor for gastric cancer development.

Glutathione S-transferase M1 null genotype meta-analysis on gastric cancer risk

Background

Glutathione S-transferases (GSTs) have proved to be involved in the detoxifying several carcinogens and may play an important role in carcinogenesis of cancer. Previous studies on the association between Glutathione S-transferase M1 (GSTM1) polymorphism and gastric cancer (GC) risk reported inconclusive results. To get a precise result, we conducted this present meta-analysis through pooling all eligible studies.

Methods

A comprehensive databases of Pubmed, Embase, Web of Science, and the Chinese Biomedical Database (CBM) were searched for case–control studies investigating the association between GSTM1 null genotype and GC risk. Odds ratios (OR) and 95% confidence intervals (95% CI) were used to assess this possible association. A χ2-based Q-test was used to examine the heterogeneity assumption. Begg’s and Egger’s test were used to examine the potential publication bias. The leave-one-out sensitivity analysis was conducted to determine whether our assumptions or decisions have a major effect on the results of present work. Statistical analyses were performed with the software program STATA 12.0.

Results

A total of 47 eligible case–control studies were identified, including 6,678 cases and 12,912 controls. Our analyses suggested that GSTM1 null genotype was significantly associated with increased risk of GC (OR = 1.186, 95% CI = 1.057-1.329, P_{heterogenetiy} = 0.000, P = 0.004). Significant association was also found in Asians (OR = 1.269, 95% CI = 1.106-1.455, P_{heterogenetiy} = 0.002, P = 0.001). However, GSTM1 null genotype was not contributed to GC risk in Caucasians (OR = 1.115, 95% CI = 0.937-1.326, P_{heterogenetiy} = 0.000, P = 0.222). In the subgroup analysis stratified by sources of controls, significant association was detected in hospital-based studies (OR = 1.355, 95% CI = 1.179-1.557, P_{heterogenetiy} = 0.001, P = 0.000), while there was no significant association detected in population-based studies (OR = 1.017, 95% CI = 0.862-1.200, P_{heterogenetiy} = 0.000, P = 0.840).

Conclusion

This meta-analysis showed the evidence that GSTM1 null genotype contributed to the development of GC.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1644180505119533.

Cytochrome P450 1A1, 2E1 and GSTM1 gene polymorphisms and susceptibility to colorectal cancer in the Saudi population

BACKGROUND

The Saudi population has experienced a sharp increase in colorectal and gastric cancer incidences within the last few years. The relationship between gene polymorphisms of xenobiotic metabolizing enzymes and colorectal cancer (CRC) incidence has not previously investigated among the Saudi population. The aim of the present study was to investigate contributions of CYP1A1, CYP2E1, and GSTM1 gene polymorphisms.

MATERIALS AND METHODS

Blood samples were collected from CRC patients and healthy controls and genotypes were determined by polymerase chain reaction restriction fragment length polymorphism and sequencing.

RESULTS AND CONCLUSIONS

CYP2E1*6 was not significantly associated with CRC development (odd ratio=1.29; confidence interval 0.68-2.45). A remarkable and statistically significant association was observed among patients with CYP1Awt/*2A (odd ratio=3.65; 95% confidence interval 1.39-9.57). The GSTM1*0/*0 genotype was found in 2% of CRC patients under investigation. The levels of CYP1A1, CYP2E1 and GSTM1 mRNA gene expression were found to be 4, 4.2 and 4.8 fold, respectively, by quantitative real time PCR. The results of the present case-control study show that the studied Saudi population resembles Caucasians with respect to the considered polymorphisms. Investigation of genetic risk factors and susceptibility gene polymorphisms in our Saudi population should be helpful for better understanding of CRC etiology.

Meta-analysis of the association of glutathione S-transferase T1 null/presence gene polymorphism with the risk of gastric carcinoma

A possible association of glutathione S-transferase T1 (GSTT1) null/presence gene polymorphism and an increased risk of developing gastric carcinoma is still unclear and hotly debated. This investigation was performed to assess the association of the GSTT1 null/presence gene polymorphism with the risk of gastric carcinoma via a meta-analysis to increase sample size and statistical significance. PubMed, Cochrane Library and CBM-disc (China Biological Medicine Database) were searched on March 1, 2013, association reports were identified, and eligible studies were recruited and synthesized. Fifty-two reports were found to be suitable for this meta-analysis for the association of the GSTT1 null genotype with gastric carcinoma risk. The results showed that there was a significantly increased gastric carcinoma risk when the GSTT1 null genotype was present in the overall population (OR 1.21, 95 % CI 1.11-1.32, P < 0.0001), Caucasians (OR 1.25, 95 % CI 1.05-1.48, P = 0.01), East-Asians (OR 1.18, 95 % CI 1.06-1.31, P = 0.003), and Chinese (OR 1.24, 95 % CI 1.07-1.44, P = 0.005). However, no statistically relevant association could be established for the Indian ethnic group (OR 1.33, 95 % CI 0.94-1.90, P = 0.11). In conclusion, the GSTT1 null genotype is associated with an increased gastric carcinoma risk in the overall population, Caucasians, East-Asians, and Chinese.

GSTM1 null genotype is associated with increased risk of gastric cancer in both ever-smokers and non-smokers: a meta-analysis of case-control studies

Previous studies have suggested that the glutathione S-transferases M1 (GSTM1) null genotype is associated with the risk of gastric cancer. However, the interaction between GSTM1 null genotype and smoking for the risk of gastric cancer is still elusive. Therefore, we performed a meta-analysis to ascertain this issue. Databases of PubMed, EMBASE, and China National Knowledge Infrastructure were searched to retrieve relevant studies. Smokers were categorized as "ever-smokers" and "non-smokers." Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to estimate the association strength. Subgroup analyses according to ethnicity, source of control, and sample size were also conducted. A total of 15 eligible studies, including 4,687 gastric cancer cases and 7,002 controls, were identified. We found that the GSTM1 null genotype was associated with increased risk of gastric cancer among ever-smokers (OR = 1.460, 95% CI 1.064-2.003, heterogeneity: P = 0.019). The null genotype also significantly increased the risk of gastric cancer among non-smokers (OR = 1.777, 95% CI 1.301-2.426, heterogeneity: P < 0.01). Stratified analysis according to ethnicity showed that the GSTM1 null genotype was associated with increased risk of gastric cancer among Asians both in ever-smokers (OR = 1.841, 95% CI 1.184-2.861) and non-smokers (OR = 1.773, 95% CI 1.382-2.275). In conclusion, the GSMT1 null genotype significantly increased the risk of gastric cancer both in ever-smokers and non-smokers.

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.

Meta-analysis: glutathione S-transferase T1 null allele is associated with gastric cancer risk

Allelic variant within genes encoding glutathione S-transferase T1 (GSTT1) has been suggested to be a possible risk factor of gastric cancer, but previous studies provide controversial results. This study aimed to assess the effects of GSTT1 polymorphism on gastric cancer by means of meta-analysis. We included published studies on the relationship between GSTT1 null allele and gastric cancer risk after searching electronic databases. A meta-analysis was conducted by calculating the pooled odds ratios (OR) and the 95% confidence intervals (95% CI). Forty-two studies with a total of 8,203 gastric cancer cases and 13,866 controls were included into this meta-analysis. When all 42 studies were pooled into this meta-analysis, there was a significant association between the GSTT1 null allele and gastric cancer risk (OR = 1.24, 95% CI 1.14-1.36, P < 0.00001). Sensitivity analysis by excluding individual studies showed that there was no effect on the pooled OR with 95% CI. After excluding studies with low quality, there was still a significant association between the GSTT1 null allele and gastric cancer risk (OR = 1.24, 95% CI 1.13-1.36, P < 0.00001). In the subgroup analysis, there was a significant association between the GSTT1 null allele and gastric cancer risk in both Europeans and Asians. There was no risk of publication bias in this meta-analysis. Our results suggest that GSTT1 null allele is associated with increased risk of gastric cancer.

Quantitative assessment of the influence of glutathione S-transferase T1 null variant on gastric cancer risk

Glutathione S-transferase T1 (GSTT1) catalyzes reactions between glutathione and lipophilic compounds with electrophilic centers, leading to neutralization of toxic compounds, xenobiotics, and products of oxidative stress. In the past decade, a number of case-control studies have been carried out to investigate the relationship between the GSTT1 null polymorphism and gastric cancer (GC), but the results have been inconclusive. To investigate this inconsistency, we performed a meta-analysis of 46 studies involving a total of 9012 GC cases and 14,215 controls for null variant of the GSTT1 gene to evaluate the effect of GSTT1 on genetic susceptibility for GC. Potential sources of heterogeneity including ethnicity, source of control, and sample size were also assessed. Overall, significantly increased GC risk was associated with GSTT1 null polymorphism with OR of 1.20 (95% CI, 1.10-1.32; P < 0.05). In the subgroup analysis by ethnicity, significantly increased risks were found in East Asians and Indians, while no significant associations were found among Caucasian, and Middle Eastern and African populations. By pooling data from 19 studies that considered combinations of GSTT1 and GSTM1 genotypes, a statistically significant increased risk for GC (OR = 2.04, 95% CI, 1.49-2.64; P < 0.05) was detected for individuals with dual deletion in both genes compared with positive genotypes. In addition, we found that cigarette smoking and alcohol drinking may modified the association of GSTT1 null genotypes with the risk of GC. In conclusion, this meta-analysis suggests that GSTT1 null polymorphism is associated with elevated GC risk, but these associations vary in different ethnic populations.

Glulathione-S-transferases gene polymorphism in prediction of gastric cancer risk by smoking and Helicobacter pylori infection status

AIM

To evaluate the association of glutathione S-transferases gene polymorphisms with the risk of gastric cancer, with reference to smoking and Helicobacter pylori infection.

METHODS

We conducted a 1:1 matched case-control study with 410 gastric cancer cases and 410 cancer-free controls. Polymorphisms of GSTM1, GSTT1 and GSTP1 were determined using PCR-CTPP.

RESULTS

The GSTM1 and GSTT1 null genotypes were significantly associated with the risk of gastric cancer after adjusting for potential confounding factors (OR=1.68, 95% CI=1.32-2.23 for null GSTM1, OR=1.73; 95% CI=1.24-2.13 for null GSTT1). The combination of null GSTM1 and null GSTT1 conferred an elevated risk (OR=2.54, 95% CI=1.55-3.39). However, no association was found for GSTP1 polymorphism The smoking modified the association of GSTM1 and GSTT1 null genotypes with the risk of gastric cancer.

CONCLUSION

GSTM1 and GSTT1 null genotypes are associated with increased risk of gastric cancer, and smoking modifies the association.

Association between the GSTP1 codon 105 polymorphism and gastric cancer risk: an updated meta-analysis

OBJECTIVE

The current meta-analysis was performed to address a more accurate estimation of the association between glutathione S-transferase P1 (GSTP1) codon 105 polymorphism and risk of gastric cancer (GC), which has been widely reported with conflicting results.

METHODS

A comprehensive literature search was conducted to identify all the relevant studies. Fixed or random effect models were selected based on the heterogeneity test. Publication bias was estimated using Begg's funnel plots and Egger's regression test.

RESULTS

A total of 20 studies containing 2,821 GC cases and 6,240 controls were finally included in the analyses. Overall, no significant association between GSTP1 polymorphism and GC risk was observed in worldwide populations. However, subgroup analysis stratified by ethnicity showed that GSTP1 polymorphism was significantly associated with increased risk of GC in Asians (G vs. A, OR = 1.273, 95%CI=1.011-1.605; GG vs. AA, OR=2.103, 95%CI=1.197- 3.387; GG vs. AA+AG, OR =2.103, 95%CI=1.186-3.414). In contrast, no significant association was found in Caucasians in any genetic models, except for with AG vs. AA (OR=0.791, 95%CI=0.669-0.936). Furthermore, the GSTP1 polymorphism was found to be significantly associated with GC in patients with H. pylori infection and in those with a cardiac GC. Subgroup analysis stratified by Lauren's classification and smoking status showed no significant association with any genetic model. No studies were found to significantly influence the pooled effects in each genetic mode, and no potential publication bias was detected.

CONCLUSIONS

This meta-analysis suggested that the GSTP1 polymorphism might be associated with increased risk of GC in Asians, while GSTP1 heterozygote genotype seemed to be associated with reduced risk of GC. Since potential confounders could not be ruled out completely, further studies are needed to confirm these results.

Association between glutathione S-transferase T1 null genotype and gastric cancer risk: a meta-analysis of 48 studies

BACKGROUND

Glutathione S-transferases (GSTs) have proved to be involved in the detoxifying several carcinogens and may play an important role in carcinogenesis of cancer. Previous studies on the association between Glutathione S-transferase T1 (GSTT1) polymorphism and gastric cancer risk reported inconclusive results. To clarify the possible association, we conducted a meta-analysis of eligible studies.

METHODS

We searched in the Pubmed, Embase, and Wangfang Medicine databases for studies assessing the association between GSTT1 null genotype and gastric cancer risk. The pooled odds ratio (OR) and its 95% confidence interval (95%CI) was calculated to assess the strength of the association. A total of 48 studies with a total of 24,440 individuals were ultimately eligible for meta-analysis.

RESULTS

Overall, GSTT1 null genotype was significantly associated with increased risk of gastric cancer (Random-effect OR = 1.23, 95%CI 1.13-1.35, P OR <0.001, I(2) = 45.5%). Significant association was also found in Caucasians, East Asians, and Indians (P Caucasians = 0.010; P East Asians = 0.003; P Indians = 0.017). After adjusting for other confounding variables, GSTT1 null genotype was also significantly associated with increased risk of gastric cancer (Random-effect OR = 1.43, 95%CI 1.20-1.71, P OR <0.001, I(2) = 48.1%).

CONCLUSION

The meta-analysis provides strong evidence for the significant association between GSTT1 null genotype and increased risk of gastric cancer.

Combined effects of GSTO1 and SULT1A1 polymorphisms and cigarette smoking on urothelial carcinoma risk in a Taiwanese population

BACKGROUND/PURPOSE

Cigarette smoking is the main risk factor for urothelial carcinoma of the bladder (UCB). Glutathione S-transferase omega 1 (GSTO1) and sulfotransferase 1A1 (SULT1A1) have been reported to be associated with the metabolism of polycyclic aromatic hydrocarbons (PAHs) and aromatic amines. The aim of the present study was to investigate the combined effects of polymorphisms in GSTO1 and SULT1A1 genes and cigarette smoking on UCB risk in a Taiwanese population.

METHODS

A total of 300 patients with histopathologically confirmed UCB and 233 cancer-free controls were recruited from the Department of Urology of Tung's Taichung Metro Harbor Hospital and Taipei Medical University Hospital. A comprehensive interview was conducted to collect personal information, including demographic characteristics and cigarette smoking status. A multivariate-adjusted logistic regression was performed to estimate the risk of UCB.

RESULTS

A significantly increased risk of UCB was observed in ever smokers [odds ratio (OR) = 2.3]. The Ala/Ala genotype of the GSTO1 gene and the Arg/Arg genotype of the SULT1A1 gene were associated with a significantly increased risk of UCB, with ORs of 1.8 [95% confidence interval (CI) = 1.2-2.6] and 2.1 (95% CI = 1.6-4.5), respectively. Significantly increased UCB risks were found in heavy smokers with the Ala/Ala genotype of the GSTO1 gene (OR = 4.2) and the Arg/Arg genotype of the SULT1A1 gene (OR = 6.8). Furthermore, a significant synergistic effect in an additive model (OR = 3.5) between the GSTO1 Ala/Ala genotype and the SULT1A1 Arg/Arg genotype on UCB risk was observed.

CONCLUSION

The present study provided epidemiological evidence for a significantly increased risk of UCB in ever smokers with the Ala/Ala genotype of the GSTO1 gene and the Arg/Arg genotype of the SULT1A1 gene.

Relevance of GSTM1, GSTT1, and GSTP1 gene polymorphisms to gastric cancer susceptibility and phenotype

Human glutathione S-transferases (GSTs) are phase II metabolizing enzymes that play a key role in protecting against cancer by detoxifying numerous potentially cytotoxic/genotoxic compounds. The genes encoding the human GST isoenzymes GSTM(mu)1, GSTT(theta)1 and GSTP(pi)1 harbour polymorphisms, which have been considered important modifiers of the individual risk for environmentally induced cancers such as gastric cancer (GC). However, results are inconsistent among studies from different geographic areas and ethnic groups. Our goal was to perform a nationwide, case-control study in Spain to evaluate the relevance of several functional GST gene polymorphisms and environmental factors to GC risk and phenotype. DNA from 557 GC patients and 557 sex- and age-matched healthy controls (HC) was typed for two deletions in the GSTM1 and GSTT1 genes and two SNPs in the GSTP1 gene (rs1695 and rs1138272) using polymerase chain reaction-restriction fragment length polymorphism methods. Logistic regression analysis identified Helicobacter pylori infection with CagA strains [odds ratio (OR): 2.36; 95% confidence interval (CI): 1.78-3.15], smoking habit (OR: 2.10; 95% CI: 1.48-2.97) and family history of GC (OR: 3.2; 95% CI: 2.02-5.16) as independent risk factors for GC. No differences in the frequencies of GSTM1 or GSTT1 null genotypes were observed between cases and controls (GSTM1: 50.8% vs. 48%; GSTT1: 21.5% vs. 21%). Moreover, simultaneous carriage of both, the GSTM1 and the GSTT1 null genotypes, was almost identical in both groups (10.7% in GC vs. 10.6% in HC). In addition, no significant differences in GSTP1 Ile105Val (rs1695) and GSTP1 Val114Ala (rs1138272) genotype distribution were observed between GC patients and controls. Subgroup analysis for age, gender, Helicobacter pylori status, smoking habits, family history of GC, anatomic location and histological subtype revealed no significant association between GST variants and GC risk. Our results show that the GST polymorphisms evaluated in this study are not relevant when determining the individual susceptibility to GC or phenotype in a South-European population.

Identification of the GST-T1 and GST-M1 null genotypes using high resolution melting analysis

Glutathione S-transferases, including GST-T1 and GST-M1, are known to be involved in the phase II detoxification pathways for xenobiotics as well as in the metabolism of endogenous compounds. Polymorphisms in these genes have been linked to an increased susceptibility to carcinogenesis and associated with risk factors that predispose to certain inflammatory diseases. In addition, GST-T1 and GST-M1 null genotypes have been shown to be responsible for interindividual variations in the metabolism of arsenic, a known human carcinogen. To assess the specific GST genotypes in the Mexican population chronically exposed to arsenic, we have developed a multiplex High Resolution Melting PCR (HRM-PCR) analysis using a LightCycler480 instrument. This method is based on analysis of the PCR product melting curve that discriminates PCR products according to their lengths and base sequences. Three pairs of primers that specifically recognize GST-T1, GST-M1, and β-globin, an internal control, to produce amplicons of different length were designed and combined with LightCycler480 High Resolution Melting Master Mix containing ResoLight, a completely saturating DNA dye. Data collected from melting curve analysis were evaluated using LightCycler480 software to determine specific melting temperatures of individual melting curves representing target genes. Using this newly developed multiplex HRM-PCR analysis, we evaluated GST-T1 and GST-M1 genotypes in 504 DNA samples isolated from the blood of individuals residing in Zimapan, Lagunera, and Chihuahua regions in Mexico. We found that the Zimapan and Lagunera populations have similar GST-T1 and GST-M1 genotype frequencies which differ from those of the Chihuahua population. In addition, 14 individuals have been identified as carriers of the double null genotype, i.e., null genotypes in both GST-T1 and GST-M1 genes. Although this procedure does not distinguish between biallelic (+/+) and monoallelic (+/-) genotypes, it can be used in an automated workflow as a simple, sensitive, and time and money saving procedure for rapid identification of the GST-T1 and GST-M1 positive or null genotypes.

Association between gastric mucosal glutathione-S-transferase activity, glutathione-S-transferase gene polymorphisms and Helicobacter pylori infection in gastric cancer

AIM

Helicobacter pylori infection, though common, leads to gastric cancer (GC) in less than 1% individuals, suggesting the role of host factors. We previously reported the role of glutathione-S-transferase (GST) polymorphisms, the gene encoding a carcinogen-detoxifying enzyme, in GC. This study was aimed to evaluate GST enzyme activity, GST polymorphism, glutathione (GSH) levels and H. pylori in patients with GC.

METHODS

GST and GSH levels were estimated in gastric biopsies of 52 patients with GC, 37 functional dyspepsia (FD) and 39 peptic ulcer (PU), and correlated with H. pylori (ELISA) infection and GST polymorphisms. GST polymorphisms were separately analyzed in relationship to H. pylori in 82 GC, 72 FD, 53 PU and 89 healthy controls (HC).

RESULTS

GST activity was lower in patients with GC in comparison to PU (p = 0.03), but GSH levels were comparable. GSTT1 null genotype (GSTT1*0) and simultaneous deletion of both GSTT1 and GSTM1 genes was associated with lower enzyme activity (p = 0.02 and 0.01, respectively). GST and GSH levels in H. pylori positive and negative patients with GC, FD and PU were comparable. Presence of H. pylori infection along with GSTT1*0 (p = 0.006) and GSTM1*0 (p = 0.05) was associated with lower enzyme activity. GSTT1*0 was associated with higher odds ratio (OR) of GC in presence of H. pylori (GC vs. HC: p = 0.02, OR 2.6 [95% CI = 1-6] vs. p = 0.7, 1.3 [0.4-5.0]; GC vs. PU: p = 0.04, OR 3 [95% CI = 1-9] vs. not applicable (OR could not be computed as frequency of GSTT1*0 in H. pylori negative patients with PU was zero)].

CONCLUSIONS

GC is associated with reduced GST activity. Odds ratio of GC associated with GSTT1*0 is enhanced in presence of H. pylori probably due to combined effect of both on enzyme activity.

CYP1A1, CYP2E1, and GSTM1 gene polymorphisms and susceptibility to colorectal and gastric cancer among Lebanese

Mutations in the genes encoding enzymes involved in the metabolism of chemical carcinogens can significantly affect the risk of cell transformation and cancer development. The resident Lebanese population has experienced a sharp increase in cancer incidence within the last few years. The relationship between gene polymorphisms of metabolic enzymes and gastrointestinal (GI) cancer incidence was not previously investigated. The aim of this study was to investigate the relationship between CYP1A1, CYP2E1, and GSTM1 gene polymorphisms and GI cancer incidence among Lebanese. Blood and/or paraffin-embedded biopsy samples were collected from patients and healthy controls. The genotypes were determined by polymerase chain reaction and polymerase chain reaction-restriction fragment length polymorphism. The results of the present case-control study show that the studied Lebanese population generally resembles Caucasian populations with respect to the considered polymorphisms. Further, the GSTM1*0/*0 genotype is a significant risk factor for gastric (odds ratio = 4.1; 95% confidence interval: 1.2-14.5) and colorectal cancers (odds ratio = 3.8; 95% confidence interval: 1.7-8.5); on the other hand, CYP1A1*2A and CYP2E1*6 alone are not significantly associated with GI cancer development, although CYP1A1*2A was more frequent among patients. A remarkable and statistically significant 36.5-fold increase in the risk of gastric cancer was observed among patients with CYP1A1*2A/*2A combined with GSTM1*0/*0. The investigation of genetic risk factors and susceptibility gene polymorphisms in Lebanese is helpful for better understanding of GI cancer etiology.

The association between GSTM1 polymorphism and gastric cancer risk: a meta-analysis

Relationship of gastric cancer with the GSTM1 polymorphism was reported with inconsistent results. The objective of this study was to quantitatively evaluate the association between GSTM1 polymorphism and gastric cancer susceptibility. Relevant studies were identified from PubMed and references of retrieved articles. A meta-analysis was performed, which included 38 studies with 6,605 gastric cancer cases and 11,311 controls. The combined result based on all studies showed there was a significant link between GSTM1 null genotype and gastric cancer (OR=1.20, 95%CI: 1.08-1.34). When stratifying for the race, the phenomenon was found that gastric cancer case had a significantly higher frequency of GSTM1 null genotype than control in Asians (OR=1.27, 95%CI: 1.10-1.47). However, there was not enough evidence to show there was a significant difference in GSTM1 null genotype distribution between gastric cancer case and control in Caucasians (OR=1.13, 95%CI: 0.96-1.32). This meta-analysis indicated that GSTM1 null genotype might be associated with increased gastric cancer risk in Asians. However, this meta-analysis did not provide an evidence of confirming association between GSTM1 polymorphism and gastric cancer in Caucasians.

GSTM1 null allele is a risk factor for gastric cancer development in Asians

Glutathione S-transferase M1 (GSTM1), which plays an important role in detoxification pathways to protect against damage caused by reactive metabolites of chemicals, has been considered as potential gastric cancer susceptibility genes. However, the published data on the association between GSTM1 present/null polymorphism and gastric cancer risk are still inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Totally, 44 studies including 5440 cases and 11607 controls were involved in the analysis. When all studies were pooled into the meta-analysis, obviously increased gastric cancer risk was found in null genotype carriers (OR=1.19, 95% CI: 1.08-1.33). When stratified by ethnicity, obviously evaluated risk was found in Asians (OR=1.31, 95% CI: 1.11-1.54) but not reached to statistically significance in Caucasians (OR=1.11, 95% CI: 0.96-1.28). In the subgroup analysis by hospital-based studies or population-based studies, statistically significantly elevated risk was found in hospital-based studies (OR=1.34, 95% CI: 1.07-1.67) but not reached to statistically significance in population-based studies (OR=1.11, 95% CI: 0.99-1.25). In summary, this meta-analysis result indicates that the GSTM1 null genotype is a low-penetrant risk factor for gastric cancer development in Asians.

Glutathione S-transferase T1 (GSTT1) gene polymorphism and gastric cancer susceptibility: a meta-analysis of epidemiologic studies

PURPOSE

Studies investigating the association between genetic polymorphism of glutathione S-transferase T1 (GSTT1) and gastric cancer risk have reported conflicting results. Therefore, we conducted this meta-analysis to provide more precise evidence.

METHODS

We searched the databases Medline, PubMed, Embase, and China National Knowledge Infrastructure up to July 30, 2009. Thirty-six studies with 4,357 gastric cancer cases and 9,796 controls were selected. Odds ratio (OR) and 95% confidence intervals (CI) were calculated based on fixed- and random-effects models.

RESULTS

The combined results based on all studies showed there was a significant link between GSTT1 null genotype and gastric cancer risk (OR = 1.14, 95%CI = 1.01-1.28). In subgroup analysis stratified on the basis of ethnic group, we also observed positive association between GSTT1 polymorphism and gastric cancer risk among Caucasians (non-Europeans + non-Americans), but not among East Asians. When stratifying by control source, the overall ORs for population- and hospital-based studies were 1.09 (95%CI = 0.94-1.28) and 1.17 (95%CI = 1.03-1.34), respectively. Subjects with both GSTM1 and GSTT1 negative genotypes had increased gastric cancer risk compared with those who had nonnull genotypes of both GST genes. Subgroup analyses for Helicobacter pylori infection and smoking habit did not reveal any significant association between GSTT1 polymorphism and gastric cancer development.

CONCLUSIONS

This meta-analysis suggests that GSTT1 gene polymorphism may be not associated with increased gastric cancer risk among Europeans, Americans, and East Asians. More large-scale studies based on the same racial group are needed.

Glutathione S-transferase M1 null genotype associated with gastric cancer among Asians

PURPOSE

The Glutathione S-transferases (GSTs) play multiple roles in the pathogenesis and treatment of cancer. Studies investigating the association between Glutathione S-transferase M1 (GSTM1) null genotype and gastric cancer risk report conflicting results. The purpose of this study was to quantitatively summarize the evidence for such a relationship.

RESULTS

This meta-analysis included 35 studies, which included 4,505 gastric cancer cases and 9,062 controls. The combined results based on all studies showed that the GSTM1 null genotype was associated with an increased risk of gastric cancer (OR = 1.15, 95% confidence interval [CI] = 1.02, 1.29). When stratifying for race, results were similar among Asians (OR = 1.24, 95% CI = 1.07, 1.44) except Caucasians (OR = 1.04, 95% CI = 0.88, 1.24). When stratifying by the location, stage, Lauren's classification, histological differentiation, lymph node metastasis, smoking, and Helicobacter pylori infection of gastric cancer, we observed that patients with diffuse classification had a significantly higher frequency null genotype (OR = 4.80, 95% CI = 1.65,13.94) than those with intestinal classification among Caucasians.

CONCLUSIONS

This meta-analysis suggests that the GSTM1 null genotype may be associated with gastric cancer among Asians.

Glutathione S-transferases: an overview in cancer research

IMPORTANCE OF THE FIELD

The Glutathione S-transferases (GSTs) have advanced beyond the classic view of their role in metabolism and are encouraging scientists to assess new approaches to cancer risk characterization and chemotherapy resistance and are opening up exciting possibilities in drug discovery.

AREAS COVERED IN THIS REVIEW

In this review, the most recent knowledge about the impact of GST genetic polymorphisms in human's cancer susceptibility, ethnic differences in the effects of risk factors and the rise of the GSTs as important targets for drug development are presented. In this context, the ethnic distribution of GST alleles in different populations, which is an important concept that is being incorporated in epidemiologic studies of cancer risk and environmental exposure, was also evaluated. We present up-to-date information about the new generation of GST-activated cytotoxic prodrugs based on GST overexpression in tumor-acquired drug resistance and the newest results of clinical trials.

WHAT THE READER WILL GAIN

A critical approach of the major advances in research of GST, underlining the new advances of GST genes polymorphisms in cancer susceptibility and target for therapeutic intervention.

TAKE HOME MESSAGE

Although polygenic factors are involved in increased risk of cancer, the interindividual GST variability plays a central role in reduce cells exposure to carcinogens.

Functional alterations in the glutathione S-transferase family associated with enhanced occurrence of esophageal carcinoma in China

Glutathione S-transferases (GST) belong to a superfamily of phase II enzymes believed to be associated with enhanced frequency of esophageal carcinoma. This study was performed to evaluate whether the GST family was associated with susceptibility to esophageal carcinoma in China. Ninety-seven patients with newly diagnosed, untreated esophageal squamous-cell carcinoma (ESCC) and 97 healthy controls matched in age, gender, and residence were recruited in this community-based case-control study. Null genotypes of GSTM1 and GSTT1 were determined by multiplex polymerase chain reaction (PCR) technique. Ile105Val polymorphism in the fifth exon, mRNA level, CpG island hypermethylation of promoter, and protein levels of GSTP1 gene were measured with peripheral blood mononuclear cell (PBMC) by PCR-restriction fragment length polymorphism (PCR-RFLP) techniques, quantitative real-time reverse transcription PCR, methylation-specific PCR (MSP), and Western blotting, respectively. The results showed that GSTM1 null genotype and GSTT1 null genotype were significantly associated with increased risk for esophageal cancer in Chinese population. Compared with the control, the relative expression levels of mRNA were significantly reduced in ESCC patients. The conditional logistic regression analysis demonstrated that increased risk for esophageal cancer was associated with CpG island hypermethylation of promoter of GSTP1 gene. GSTP1 protein levels also showed significant decrease in ESCC when adjusted for age, gender, smoking status, and alcohol use. An individual with GSTM1 or GSTT1 null genotype may thus be more susceptible to esophageal cancer development. Reduced expression in mRNA and protein levels were the main manifestations noted in aberrant function of GSTP1 gene. Data thus suggest that the CpG island hypermethylation of promoter gene may serve as a useful biomarker for early diagnosis of esophageal carcinoma development.

Contribution of alcohol and tobacco use in gastrointestinal cancer development

Tobacco smoke and alcohol are major risk factors for a variety of cancer sites, including those of the gastrointestinal tract. Tobacco smoke contains a great number of mutagenic and carcinogenic compounds, including polycyclic carbohydrates, nitrosamines, and nicotine, while ethanol per se has only weak carcinogenic potential, but its first metabolite, acetaldehyde, is a mutagen and carcinogen, since it forms stable adducts with DNA. The possibility of proto-oncogene mutation in gastrointestinal mucosa cells may be associated with tobacco smoking-induced cancers through the formation of unfavorable DNA adducts. Individuals with defective DNA repair mechanisms and unfavorable genetic make-up for carcinogen metabolism may be at increased risk for gastrointestinal cancers. Individuals with a high production rate of acetaldehyde from ethanol also have an increased cancer risk when they drink chronically. These include individuals with a genetically determined increased acetaldehyde production due to alcohol dehydrogenase polymorphism and those with a decreased detoxification of acetaldehyde due to acetaldehyde dehydrogenase mutation. In addition, oral bacterial overgrowth due to poor oral hygiene also increases salivary acetaldehyde. Dietary deficiencies such as a lack of folate, riboflavine, and zinc may also contribute to the increase cancer risk in the alcoholic patient. It is of considerable importance that smoking and drinking act synergistically. Smoking increases the acetaldehyde burden following alcohol consumption and drinking enhances the activation of various procarcinogens present in tobacco smoke due to increased metabolic activation by an induced cytochrome P450-2E1-dependent microsomal biotransformation system in the mucosa of the upper digestive tract and the liver.

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.

Gastric carcinogenesis: Possible role of polymorphisms of GSTM1, GSTT1, and GSTP1 genes

OBJECTIVE

Although Helicobacter pylori infection is associated with gastric cancer (GC), only 1% of patients develop a malignancy, which suggests a role of host genetic factors. The aim of this study was to investigate the role of polymorphisms of GSTM1, GSTT1, and GSTP1 genes, which encode for carcinogen-detoxifying enzymes, in gastric mutagenesis.

MATERIAL AND METHODS

Genotyping of GSTT1 and GSTM1 was done using PCR, while PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) was used for genotyping of GSTP1 in 76 patients with gastric neoplasm (GN), 67 with non-ulcer dyspepsia (NUD), 44 with peptic ulcer (PU), and 100 healthy controls (HC).

RESULTS

The study population included: GN (intestinal 40 (53%), diffuse 26 (34%), primary gastric lymphoma 8 (11%) and unclassified 2 (2%)), PU (duodenal ulcer (DU) 33 (75%), gastric ulcer (GU) 10 (23%), both PU and DU 1 (2%)). GSTT1 null genotype (GSTT1*0) was more common in patients with GN (30/76 (40%)) than in those with PU (5/44 (11%); p=0.001, odds ratio (OR) 5; 95% CI=1-4) and HC (23/100 (23%); p=0.02, OR 2; 95% CI=1-4). GSTT1*0 conferred a higher cancer risk for patients with DU (2/33 (6%), OR 10; 95% CI=2-45; p=0.00). GSTM1*0 and GSTP1 variant genotypes (ile/val and val/val) not alone but in combination with GSTT1*0 conferred a higher risk in PU patients (21 (28%) versus 5 (11%); OR 3; 95% CI=1-9; p=0.04). Both GSTM1*0 (16/26 (61%) versus 10/40 (25%); p=0.003, OR 5; 95% CI=2-14) and GSTT1*0 (12/26 (46%) versus 13/40 (33%); p=0.2, OR 2; 95% CI=0.6-5) were associated with a higher risk of diffuse tumor than of intestinal tumor.

CONCLUSIONS

GSTT1*0 alone and in combination with GSTM1*0 and GSTP1 variant genotypes is a risk factor for GN in the Indian population. Low GSTT1*0 in DU patients may play a protective role against GN. GSTM1*0 and GSTT1*0 are risk factors for diffuse GC.

Association of CDH1 single nucleotide polymorphisms with susceptibility to esophageal squamous cell carcinomas and gastric cardia carcinomas

E-cadherin (CDH1) is a tumor suppressor involved in epithelial cell-cell interactions. Single nucleotide polymorphisms (SNP) in the CDH1 gene, -160C/A and -347G/GA in the 5'-promoter region and +54C/T in the 3'-untranslated region (UTR) have been shown to be associated with tumor development and progression via modifying transcriptional activity, mRNA stability or protein expression. To investigate the influence of CDH1 SNP on susceptibility to esophageal squamous cell carcinomas (ESCC) and gastric cardia adenocarcinomas (GCA), a case-control study was conducted among 333 ESCC patients, 239 GCA patients and 343 controls from a northern Chinese population. CDH1 polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis. The results showed that; (i) genotypes with the +54C allele (C/C or C/T) significantly increased the risk of developing both ESCC and GCA compared to the +54T/T genotype (age and gender adjusted odds ratio [OR] = 1.45 and 2.28, 95% confidence interval [CI] = 1.06-1.99 and 1.58-3.30, respectively), and this association was significant only among non-smokers (OR = 1.68 and 2.64, 95% CI = 1.01-2.80 and 1.43-4.87 for ESCC and GCA, respectively), and individuals without a family history of upper gastrointestinal cancer (OR = 2.63 and 2.97, 95% CI = 1.36-5.10 and 95% CI = 1.32-6.68 for ESCC and GCA, respectively); (ii) compared with the -347G/G genotype, the -347GA and GA/GA genotypes significantly increased the risk of developing GCA (OR = 1.45, 95 % CI = 1.03-2.04); (iii) there was a significant association of CDH1-160C/-347G/+54C and -160C/-347GA/+54C haplotypes with the development of GCA, compared with the -160C/-347G/+54T haplotype (OR = 1.80 and 2.21, 95% CI = 1.33-2.44 and 1.43-3.42, respectively); and (iv) the influence of CDH1 SNP on the depth of tumor invasion and lymphatic metastasis in ESCC and GCA patients was not observed in this study. The present study indicates that CDH1 polymorphisms might modify susceptibility to ESCC and/or GCA.

Glutathione S-transferase mu, omega, pi, and theta class variants and smoking in Parkinson's disease

GSTs are a family of inducible phase II enzymes that may play a neuroprotective role in Parkinson's disease (PD). GSTs may also modify PD risk by metabolizing compounds in cigarettes, as cigarette smoking is generally found to be associated with a decrease in PD risk. Using a population-based case-control study design, we examined polymorphisms of the mu, omega, pi, and theta classes of GST to elucidate the main effects and smoking-GST interactions on PD risk. From three rural California counties, we recruited 289 incident idiopathic PD cases, clinically confirmed by our study neurologist, and 270 population controls, marginally matched by age, gender, and race. We assessed main gene polymorphism associations and evaluated interactions between smoking and GST polymorphisms as departures from a multiplicative scale adjusting for age, gender, and race. We also restricted analyses to Caucasian subjects to address the potential for population stratification (n=235 cases, 220 controls). Among Caucasians, we observed a risk reduction in subjects carrying at least one variant allele for GSTO1 (OR=0.68, 95% CI: 0.47-0.98) and also GSTO2 (OR=0.64, 95% CI: 0.44-0.93); both genes were in strong linkage disequilibrium. No main gene effects were observed for the remaining polymorphisms. We noted a multiplicative interaction between ever having smoked regularly and GSTO1 (OR(interaction)=0.55, 95% CI: 0.33-0.92) and GSTO2 (OR(interaction)=0.54, 95% CI: 0.32-0.90). Results were similar when combining all races. These findings and the paucity of similar studies suggest a need for further inquiry into the association between GSTs, smoking, and PD risk.

Polymorphisms in metabolic genes related to tobacco smoke and the risk of gastric cancer in the European prospective investigation into cancer and nutrition

Metabolizing enzymes, which often display genetic polymorphisms, are involved in the activation of compounds present in tobacco smoke that may be relevant to gastric carcinogenesis. We report the results of a study looking at the association between risk of gastric adenocarcinoma and polymorphisms in genes CYP1A1, CYP1A2, EPHX1, and GSTT1. A nested case-control study was carried out within the European Prospective Investigation into Cancer and Nutrition, developed in 10 European countries. The study includes 243 newly diagnosed cases of histologically confirmed gastric adenocarcinoma and 946 controls matched by center, age, sex, and date of blood collection. Genotypes were determined in nuclear DNA from WBCs. We found an increased risk of gastric cancer for homozygotes for C (histidine) variant in Y113H of EPHX1 (odds ratio, 1.91; 95% confidence interval, 1.19-3.07) compared with subjects with TC/TT. There was also a significant increased risk for smokers carrying at least one variant allele A in Ex7+129C>A (m4) of CYP1A1 and never smokers with null GSTT1 and allele A in the locus -3859G>A of CYP1A2. Most of these genes are involved in the activation and detoxification of polycyclic aromatic hydrocarbons, suggesting a potential role of these compounds in gastric carcinogenesis.

Glutathione S-transferases mu 1, theta 1, pi 1, alpha 1 and mu 3 genetic polymorphisms and the risk of colorectal and gastric cancers in humans

INTRODUCTION

Glutathione S-transferases (GSTs) are considered to be cancer susceptibility genes as they play a role in the detoxification of carcinogenic species. This study aimed to elucidate the influence of several GST polymorphisms on colorectal and gastric cancer risk.

PATIENTS AND METHODS

GST mu1 (GSTM1), theta1 (GSTT1), pi1 (GSTP1), alpha1 (GSTA1) and mu3 (GSTM3) genotypes were determined in 144 colorectal cancer patients, 98 gastric cancer patients and 329 healthy control individuals.

RESULTS

Colorectal cancer: the risk is greater for carriers of the GSTM1 null genotype (odds ratio [OR] = 1.91, 95% confidence interval [CI] = 1.25-2.91), for carriers of the GSTT1 null genotype (OR = 3.62, 95% CI = 2.34-5.62), and for simultaneous carriers of both GSTM1 and GSTT1 null genotypes (OR = 4.98, 95% CI = 2.77-9.00). Carriers of the GSTP1 104 Val/Val genotype are at a lower risk (OR = 0.31, 95% CI = 0.09-0.88). Among carriers of the GSTP1 Ile/Ile genotype, smoking increases the risk compared with nonsmoking (OR = 2.35, 95% CI = 1.11-4.99). Gastric cancer: the risk is greater for carriers of the GSTT1 null genotype (OR = 2.58, 95% CI = 1.53-4.36) and for simultaneous carriers of both GSTM1 and GSTT1 null genotypes (OR = 3.32, 95% CI = 1.62-6.77). Carriers of the GSTP1 104 Val/Val genotype are at a lower risk (OR = 0.20, 95% CI = 0.02-0.86).

DISCUSSION

The GSTT1 null genotype, particularly if it is associated with the GSTM1 null genotype, greatly increases the risk for colorectal and gastric cancers. The GSTP1 104 Val/Val genotype may protect from both malignant tumors.

CONCLUSION

This study indicates that GST polymorphisms, in particular the GSTM1/GSTT1 double-null haplotype, can be considered low-penetrance genes for gastrointestinal cancer.

Genetic polymorphisms of glutathione S-transferase T1 (GSTT1) and susceptibility to gastric cancer: a meta-analysis

The association between glutathione S-transferase T1 (GSTT1) polymorphism and gastric cancer risk has been both confirmed and refuted in a number of published studies. Most of these studies were based on small sample sizes. We carried out a meta-analysis of the research published up to August 2005 to obtain more precise estimates of gastric cancer risk associated with GSTT1 polymorphism. In the present study, 16 case-control studies (with a total of 6717 subjects) were eligible for meta-analysis. There was no evidence of heterogeneity between the studies. The GSTT1 null genotype conferred a 1.06-fold increased risk of gastric cancer, which was not significant (95% confidence interval [CI]: 0.94-1.19). However, in the analysis of ethnic groups, we observed distinct differences associated with GSTT1 status. Restricting analyses to ethnic groups, the pooled odd ratios for the GSTT1 genotype were 1.27 in Caucasians (95% CI: 1.03-1.57) and 0.98 in Asians (95% CI: 0.86-1.13). Glutathione S-transferase M1 (GSTM1) and GSTT1 are involved in detoxification of a variety of compounds, some that overlap between enzymes and some that are highly specific. To investigate whether the profile of glutathione S-transferase genotypes was associated with risk of gastric cancer, further analyses combining the GSTT1 and GSTM1 genotypes were also carried out. There was a significant trend in risk associated with zero, one and two putative high-risk genotypes (chi2 = 9.326, d.f. = 1, P = 0.0023). Those who had null genotypes of GSTM1 and GSTT1 had an increased gastric cancer risk compared with those who had both active genes (odds ratio = 2.08, 95% CI: 1.42-3.10).

Interaction models of CYP1A1, GSTM1 polymorphisms and tobacco smoking in intestinal gastric cancer

AIM: To explore the interaction models of the cytochrome P-450 (CYP) 1A1 Val variant and glutathione S-transferase (GST) M1 null polymorphisms with tobacco smoking in the occurrence of intestinal gastric cancer.

METHODS: A community-based case-control study was conducted in Yangzhong. Subjects included 114 intestinal types of gastric cancer with endoscopic and pathological diagnosis during January 1997 and December 1998, and 693 controls selected from their spouse, siblings or siblings-in-law who had no history of digestive system cancer. Logistic regression was used to estimate the interaction models.

RESULTS: The frequency of the CYP1A1 Val variant allele in cases did not differ from that in controls. The OR of GSTM1 null genotype was 2.0 (95% confidence interval [95%CI]: 1.2-3.1, P<0.01). It showed a significant type 2 form of interaction model when both CYP1A1 Valvariant allele and former tobacco smoking existed (i.e., among the multiplicative effects, the disease risk is increased by the tobacco exposure alone but not by the CYP1A1 variant alone). The interaction index g was 2.8, and OR_eg(95%CI) was 5.0 (1.9-13.4). GSTM1 null genotype and former tobacco smoking were significant in a type 4 interaction model (i.e., the disease risk is increased by GSTM1 null genotype or tobacco exposure alone among the multiplicative effects). The interaction index g and OR_eg (95%CI) were 3.4 and 8.4 (3.4-20.9), respectively.

CONCLUSION: Different interaction models of CYP1A1 Val variant allele and GSTM1 null genotype with tobacco smoking will contribute to understanding carcinogenic mechanism, but there is a need to further investigate in larger scale studies.