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

GSTM1 and GSTP1 Polymorphisms Affect Outcome in Colorectal Adenocarcinoma

Background and Objectives: Despite improvements in screening programs, a large number of patients with colorectal cancer (CRC) are diagnosed in an advanced disease stage. Previous investigations imply that glutathione transferases (GSTs) might be associated with the development and progression of CRC. Moreover, the detoxification mechanism of oxaliplatin, which represents the first line of treatment for advanced CRC, is mediated via certain GSTs. The aim of this study was to evaluate the significance of certain GST genetic variants on CRC prognosis and the efficacy of oxaliplatin-based treatment. Materials and Methods: This prospective study included 523 patients diagnosed with CRC in the period between 2014 and 2016, at the Digestive Surgery Clinic, University Clinical Center of Serbia, Belgrade. Patients were followed for a median of 43.47 ± 17.01 months (minimum 1-63 months). Additionally, 109 patients with advanced disease, after surgical treatment, received FOLFOX6 treatment as a first-line therapy between 2014 and 2020. The Kaplan-Meier method was used to analyze cumulative survival, and the Cox proportional hazard regression model was used to study the effects of different GST genotypes on overall survival. Results: Individuals with the GSTM1-null genotype and the GSTP1 IleVal+ValVal (variant) genotype had significantly shorter survival when compared to referent genotypes (GSTM1-active and GSTP1 IleIle) (log-rank: p = 0.001). Moreover, individuals with the GSTM1-null genotype who received 5-FU-based treatment had statistically significantly shorter survival when compared to individuals with the GSTM1-active genotype (log-rank: p = 0.05). Conclusions: Both GSTM1-null and GSTP1 IleVal+ValVal (variant) genotypes are associated with significantly shorter survival in CRC patients. What is more, the GSTM1-null genotype is associated with shorter survival in patients receiving FOLOFOX6 treatment.

The mechanism of dehydroandrographolide inhibiting metastasis in gastric cancer based on network pharmacology and bioinformatics

Gastric cancer (GC) is the most aggressive malignant tumor of the digestive tract. However, there is still a lack of effective treatment methods in clinical practice. Studies have shown that dehydroandrographolide (DA) has been shown to have anti-cancer activity in a variety of cancers, but it has not been reported in GC. Firstly, we obtained data on DA target genes, GC-related genes, and differentially expressed genes (DEGs) from the PharmMapper, GeneCards, and GEO databases, respectively. Then, the STRING database was used to construct the protein-protein interaction network of intersection genes, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of intersection genes were performed. Finally, 8 hub target genes were identified by analyzing their expression and prognostic survival, and molecular docking between the hub genes and DA was performed. In this study, 293 DA drug target genes, 11,366 GC-related genes, and 3184 DEGs were identified. Gene Ontology and KEGG analysis showed that the intersection genes of DA targets and GC-related genes were mainly related to cancer pathways involving apoptosis and cell adhesion. The intersection genes of DEGs, DA targets, and GC-related genes were also mainly related to cancer pathways involving chemical carcinogenesis, and drug metabolism. The molecular docking results showed that the 8 hub target genes had an apparent affinity for DA, which could be used as potential targets for DA treatment of GC. The results of this study show that the molecular mechanism by which DA inhibits GC metastasis involves multiple target genes. It may play an essential role in inhibiting the invasion and metastasis of GC by regulating the expression and polymorphism of hub target genes, such as MMP9, MMP12, CTSB, ESRRG, GSTA1, ADHIC, CA2, and AKR1C2.

Individual and combined effects of GSTM1 and GSTT1 polymorphisms on colorectal cancer risk: an updated meta-analysis

BACKGROUND

The presence or absence of glutathione S-transferase M1 gene (GSTM1) and glutathione S-transferase T1 gene (GSTT1) polymorphisms, and their combined effects have been suggested as a risk factor for colorectal cancer (CRC). However, the results are inconsistent.

OBJECTIVES

An updated meta-analysis was performed to solve the controversy.

METHODS

Meta-analyses of Observational Studies in Epidemiology (MOOSE) guidelines were used.

RESULTS

Overall, the GSTM1 null genotype was associated with an increased CRC risk in Caucasians (odds ratio (OR) = 1.14, 95% confidence interval (CI): 1.05-1.23), Asians (OR = 1.19, 95% CI: 1.08-1.32), high-quality studies (OR = 1.12, 95% CI: 1.06-1.18). Moreover, the GSTM1 null genotype was also associated with an increased colon cancer risk (OR = 1.32, 95% CI: 1.16-1.51). The GSTT1 null genotype was also associated with an increased CRC risk in Asians (OR = 1.08, 95% CI: 1.02-1.15) and Caucasians (OR = 1.24, 95% CI: 1.09-1.41). Moreover, The GSTT1 null genotype was associated with an increased rectal cancer risk (OR = 1.13, 95% CI: 1.01-1.27, I2 = 8.3%) in subgroup analysis by tumor location. Last, the GSTM1 null/GSTT1 null genotype was associated with an increased CRC risk in Asians.

CONCLUSION

This meta-analysis indicates that the GSTM1 and GSTT1 null genotypes are associated with increased CRC risk in Asians and Caucasians, and the GSTM1 null/GSTT1 null genotype was associated with increased CRC risk in Asians.

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

Background and objective

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

Methods

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

Results

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

Conclusion

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

Identification, genomic organization and expression pattern of glutathione transferase in Pardosa pseudoannulata

The pond wolf spider, Pardosa pseudoannulata, is one of the dominant natural enemies in farmlands and plays important roles in controlling a range of insect pests. The spider is less sensitive to many insecticides than the target pests such as the brown planthopper, Nilaparvata lugens. The different sensitivity to a certain insecticide between species is mostly attributed to the differences in both molecular targets and detoxification enzymes. As one of the most important detoxification enzymes, glutathione transferases (GSTs) play a key role as phase II enzyme in the enzymic detoxification in organisms. Until now, there are few studies on spiders' GSTs, limiting the understanding of insecticide selectivity between insect pests and natural enemy spiders. In this study, based on the transcriptome and genome sequencing of P. pseudoannulata, thirteen full-length transcripts encoding GSTs were identified and analyzed. Interestingly, Delta family, which is thought to be specific to the Insecta, was identified in P. pseudoannulata. Further, vertebrate/mammalian-specific Mu family was also identified in P. pseudoannulata. The mRNA expression levels of cytosolic GSTs in different tissues were determined, and most GST genes were abundant in the gut and the fat body. To investigate GST candidates involving in insecticide detoxification, the mRNA levels of cytosolic GSTs were tested after spiders' exposure to either imidacloprid or deltamethrin. The results showed that PpGSTD3 and PpGSTT1 responded to at least one of these two insecticides. The present study helped understand the function of GSTs in P. pseudoannulata and enriched the genetic information of natural enemy spiders.

Deletion and Single Nucleotide Polymorphisms in Common Glutathione-S Transferases Contribute to Colorectal Cancer Development

Glutathione-S transferases (GSTs) are xenobiotic-conjugation enzymes involved in the detoxification process of heterocyclic aromatic amines and polycyclic aromatic hydrocarbons, widely recognized risk factors of colorectal cancer (CRC) development. Polymorphism in GSTs often leads to alteration or complete lack of enzyme activity, which might have an effect on CRC carcinogenesis. Aim of this study was to investigate GST gene variants as risk factors in patients with CRC. A total of 523 CRC patients administered for surgical resection and 400 matched controls were included. Deletion polymorphism of GSTs M1 and T1 was investigated by polymerase chain reaction. Single nucleotide polymorphism of GST A1 and P1 was investigated by restriction fragment length polymorphism method. The association between GST genotype and risk of CRC development was found in carriers of GSTT1-null and GSTP1-variant genotypes individually (p = 0.050 and p = 0.016, respectively). Furthermore, statistically significant association was found when combination of GSTP1-variant genotype with any of other three common GST genotypes was analyzed with respect to CRC susceptibility. Additionally, patients with combined GSTM1-null/GSTT1-null/GSTA1 low-activity/GSTP1-variant genotype showed 2.71-fold increased risk of developing CRC (p = 0.037). This study supports hypothesis that GST polymorphisms might have an important role in the process of the CRC development. Additionally, GSTM1-null/ GSTT1-null/ GSTA1 low-activity/ GSTP1-variant genotype could be combination of GST genotypes whose carriers are more prone to CRC development.

Downregulation of Glutathione S-transferase A1 suppressed tumor growth and induced cell apoptosis in A549 cell line

Glutathione S-transferase A1 (GSTA1) is a phase II detoxification enzyme and serves a crucial role in anti-cancer drug resistance. In our previous study, GSTA1 was identified to be highly expressed in various subtypes of non-small-cell lung cancer cell lines compared with human embryonic lung fibroblast cell line MRC-5. The aim of the present study was to investigate the effect of GSTA1 expression on the proliferation and apoptosis of A549 cells. GSTA1 expression was knocked down or with overexpressed using lentivirus particles. Western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to assess the protein, and mRNA levels of GSTA1 in A549 cells, respectively. The effect of GSTA1 manipulation on cell proliferation and apoptosis were investigated in vitro using MTT assays, Hoechst 33258 staining and flow cytometry, and in vivo using A549 cell line xenografts in nude mice. The results of the western blot analysis and RT-qPCR revealed that stable cell models of GSTA1 knockdown, and overexpression were established. The data of the MTT assay indicated that the downregulation of GSTA1 significantly inhibited cell proliferation compared with si-control-transfected cells. These si-GSTA1 A549 cells exhibited typical morphological changes of apoptosis, including chromatin condensation and shrunken nuclei compared with the si-control counterparts. An AnnexinV-fluorescein isothiocyanate assay verified that the downregulation of GSTA1 significantly induced cell apoptosis in vitro. In addition, overexpression of GSTA1 significantly promoted tumor growth in vivo. Accordingly, downregulation of GSTA1 suppressed tumor growth. In conclusion, GSTA1 plays an important role in regulation of cell proliferation and cell apoptosis in A549 cell line.

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.

AHR2 morpholino knockdown reduces the toxicity of total particulate matter to zebrafish embryos

The zebrafish embryo has been proposed as a 'bridge model' to study the effects of cigarette smoke on early development. Previous studies showed that exposure to total particulate matter (TPM) led to adverse effects in developing zebrafish, and suggested that the antioxidant and aryl hydrocarbon receptor (AHR) pathways play important roles. This study investigated the roles of these two pathways in mediating TPM toxicity. The study consisted of four experiments. In experiment I, zebrafish embryos were exposed from 6h post fertilization (hpf) until 96hpf to TPM0.5 and TPM1.0 (corresponding to 0.5 and 1.0μg/mL equi-nicotine units) in the presence or absence of an antioxidant (N-acetyl cysteine/NAC) or a pro-oxidant (buthionine sulfoximine/BSO). In experiment II, TPM exposures were performed in embryos that were microinjected with nuclear factor erythroid 2-related factor 2 (Nrf2), AHR2, cytochrome P450 1A (CYP1A), or CYP1B1 morpholinos, and deformities were assessed. In experiment III, embryos were exposed to TPM, and embryos/larvae were collected at 24, 48, 72, and 96hpf to assess several genes associated with the antioxidant and AHR pathways. Lastly, experiment IV assessed the activity and protein levels of CYP1A and CYP1B1 after exposure to TPM. We demonstrate that the incidence of TPM-induced deformities was generally not affected by NAC/BSO treatments or Nrf2 knockdown. In contrast, AHR2 knockdown reduced, while CYP1A or CYP1B1 knockdowns elevated the incidence of some deformities. Moreover, as shown by gene expression the AHR pathway, but not the antioxidant pathway, was induced in response to TPM exposure, providing further evidence for its importance in mediating TPM toxicity.

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.

A systemic review of glutathione S-transferase P1 Ile105Val polymorphism and colorectal cancer risk

OBJECTIVES

To investigate the correlation between glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism and colorectal cancer (CRC) risk.

METHODS

Studies were identified to investigate the association between GSTP1 Ile105Val polymorphism and CRC risk. Systematic computerized searches of the PubMed, Chinese National Knowledge Infrastructure, WANFANG and SinoMed were performed. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were used to measure GSTP1 Ile105Val polymorphisms and CRC risk.

RESULTS

A total of 23 retrospective studies were included in the meta-analysis. During all studies including 6,981 cases and 8,977 controls, sample sizes ranged from 146 to 2,144. Overall, the pooled results revealed that Ile105Val polymorphism was not associated with CRC risk and confused results were found in subgroup analyses. Further meta-analyses were conducted after excluding low-quality studies. GSTP1 Ile105Val is associated with increased risk of CRC limited in studies with matched control. There was no significant heterogeneity in all genetic comparisons, but heterogeneity existed in subgroup analyses of heterozygous and dominant comparisons. The meta-regression analyses indicated that matched controls were the significant factor influencing between-study heterogeneity in all possible influential factors including published year, ethnicity, source of control, sample size, Hardy-Weinberg equilibrium (HWE) in control and matched controls. Sensitivity analysis revealed the pooled ORs were not changed before and after removal of each single study in all genetic comparisons, indicating the robustness of the results.

CONCLUSIONS

GSTP1 Ile105Val might be associated with increased risk of CRC. However, more high-quality case-control studies should be performed to confirm the authenticity of our conclusion.

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.

Toxicogenetic profile and cancer risk in Lebanese

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

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.

Glutathione S-transferase T1 gene polymorphism and colorectal cancer risk: an updated analysis

BACKGROUND AND OBJECTIVE

The association between glutathione S-transferase T1 (GSTT1) gene polymorphisms and colorectal cancer (CRC) susceptibility is still controversial. In order to clarify the effect of GSTT1 genotype on the CRC risk, we carried out an updated meta-analysis of published case-control studies to provide more precise evidence.

METHODS

Two investigators independently searched the databases of Pubmed, EMBASE and China National Knowledge Infrastructure (CNKI) up to October 15, 2012. Crude odds ratios (OR) and 95% confidence intervals (CI) were calculated to investigate the strength of the association in a fixed- or random-effects model depending on statistical heterogeneity.

RESULTS

Forty-six case-control studies with 15,373 colorectal cancer cases and 21,238 controls were included. Overall, the pooled results indicated that GSTT1 null genotype was significantly associated with increased CRC risk (OR=1.21, 95% CI=1.10-1.33). When stratifying for ethnicity and control sources, we also observed positive association between GSTT1 null genotype and increased risk of CRC. When stratifying by the location, we found there was a statistically significant association in the rectal cancer (OR=1.28, 95% CI=1.01-1.64), but not in colon cancer (OR=1.27, 95% CI=0.94-1.73). Subgroup analyses for Dukes stage, histological differentiation of CRC and smoking habit did not reveal any significant differences in genotype distribution. In addition, we observed a strong correlation between increased CRC risk and the combined GSTM1 and GSTT1 null genotype.

CONCLUSIONS

This meta-analysis suggests that the GSTT1 null genotype may contribute to increased risk of colorectal cancer. More well-designed studies based on larger population are needed to confirm our results.

Exploring the proteomic landscape of a gastric cancer biopsy with the shotgun imaging analyzer

Accessing localized proteomic profiles has emerged as a fundamental strategy to understand the biology of diseases, as recently demonstrated, for example, in the context of determining cancer resection margins with improved precision. Here, we analyze a gastric cancer biopsy sectioned into 10 parts, each one subjected to MudPIT analysis. We introduce a software tool, named Shotgun Imaging Analyzer and inspired in MALDI imaging, to enable the overlaying of a protein's expression heat map on a tissue picture. The software is tightly integrated with the NeXtProt database, so it enables the browsing of identified proteins according to chromosomes, quickly listing human proteins never identified by mass spectrometry (i.e., the so-called missing proteins), and the automatic search for proteins that are more expressed over a specific region of interest on the biopsy, all of which constitute goals that are clearly well-aligned with those of the C-HPP. Our software has been able to highlight an intense expression of proteins previously known to be correlated with cancers (e.g., glutathione S-transferase Mu 3), and in particular, we draw attention to Gastrokine-2, a "missing protein" identified in this work of which we were able to clearly delineate the tumoral region from the "healthy" with our approach. Data are available via ProteomeXchange with identifier PXD000584.

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.

CYP1A1, GSTM1, GSTT1 and NQO1 polymorphisms and colorectal adenomas in Japanese men

AIM: To investigate the role of functional genetic polymorphisms of metabolic enzymes of tobacco carcinogens in the development of colorectal adenomas.

METHODS: The study subjects were 455 patients with colorectal adenomas and 1052 controls with no polyps who underwent total colonoscopy in a preretirement health examination at two Self Defense Forces hospitals. The genetic polymorphisms studied were CYP1A1*2A (rs 4646903), CYP1A1*2C (rs 1048943), GSTM1 (null or non-null genotype), GSTT1 (null or non-null genotype) and NQO1 C609T (rs 1800566). Genotypes were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism or PCR method using genomic DNA extracted from the buffy coat. Cigarette smoking and other lifestyle factors were ascertained by a self-administered questionnaire. The associations of the polymorphisms with colorectal adenomas were examined by means of OR and 95%CI, which were derived from logistic regression analysis. Statistical adjustment was made for smoking, alcohol use, body mass index and other factors. The gene-gene interaction and effect modification of smoking were evaluated by the likelihood ratio test.

RESULTS: None of the five polymorphisms showed a significant association with colorectal adenomas, nor was the combination of GSTM1 and GSTT1. A borderline significant interaction was observed for the combination of CYP1A1*2C and NQO1 (P = 0.051). The OR associated with CYP1A1*2C was significantly lower than unity among individuals with the NQO1 609CC genotype. The adjusted OR for the combination of the CYP1A1*2C allele and NQO1 609CC genotype was 0.61 (95%CI: 0.42-0.91). Although the interaction was not statistically significant (P = 0.24), the OR for individuals carrying the CYP1A1*2C allele and GSTT1 null genotype decreased significantly compared with those who had neither CYP1A1*2C allele nor GSTT1 null genotype (adjusted OR: 0.69, 95%CI: 0.49-0.97). Smoking did not modify the associations of the individual polymorphisms with colorectal adenomas. There was no measurable effect modification of smoking even regarding the combination of the genetic polymorphisms of the phase I and phase II enzymes.

CONCLUSION: Combination of the CYP1A1*2C and NQO1 609CC genotypes was associated with a decreased risk of colorectal adenomas regardless of smoking status.

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.

Role of pharmacogenetics in busulfan/cyclophosphamide conditioning therapy prior to hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is a curative treatment for several malignant and nonmalignant disorders. Busulfan (Bu) and cyclophosphamide (Cy) are the most commonly used alkylators in high-dose pretransplant conditioning for HSCT; a treatment that is correlated with drug-related toxicity and relapse. Pharmacogenetic investigations have shown that CYP450, as well as aldehyde dehydrogenase, are clearly involved with Cy metabolism and are associated with altered treatment response, Cy metabolism and the unique stem-cell sparing capacity. Moreover, glutathione-S-transferase isoenzymes have been associated with cellular outward transport of various alkylating agents, including Cy metabolites, melphalan, Bu and chlorambucil. A shift from genetic-based studies to whole-genome-based investigations of Cy- and Bu-associated markers may contribute to personalizing the conditioning therapy and enhancing the clinical outcome of HSCT.

Proteomic analysis of gastric cancer and immunoblot validation of potential biomarkers

AIM: To search for and validate differentially expressed proteins in patients with gastric adenocarcinoma.

METHODS: We used two-dimensional gel electrophoresis and mass spectrometry to search for differentially expressed proteins in patients with gastric adenocarcinoma. A set of proteins was validated with immunoblotting.

RESULTS: We identified 30 different proteins involved in various biological processes: metabolism, development, death, response to stress, cell cycle, cell communication, transport, and cell motility. Eight proteins were chosen for further validation by immunoblotting. Our results show that gastrokine-1, 39S ribosomal protein L12 (mitochondrial precursor), plasma cell-induced resident endoplasmic reticulum protein, and glutathione S-transferase mu 3 were significantly underexpressed in gastric adenocarcinoma relative to adjacent non-tumor tissue samples. On the other hand, septin-2, ubiquitin-conjugating enzyme E2 N, and transaldolase were significantly overexpressed. Translationally controlled tumor protein was shown to be differentially expressed only in patients with cancer of the gastric cardia/esophageal border.

CONCLUSION: This work presents a set of possible diagnostic biomarkers, validated for the first time. It might contribute to the efforts of understanding gastric cancer carcinogenesis.

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.

Assessment of nonsteroidal anti-inflammatory drug-induced hepatotoxicity

INTRODUCTION

Liver toxicity related to NSAIDs is of outstanding importance because of the wide use of these drugs. NSAIDs are responsible for roughly 10% of the total of cases of drug-induced hepatotoxicity. The assessment of NSAID-induced hepatotoxicity, presently based on clinical and analytical biomarkers, is critical for early diagnosis and immediate withdrawal of the causing drug.

AREAS COVERED

The review presents an overview of current knowledge of the assessments of NSAID-induced hepatotoxicity with emphasis on the causative drugs, the NSAID-specific mechanisms involved, and a summary of genetic and non-genetic risk factors. Additionally, the authors discuss genetic factors which show NSAID-specific risk, namely CYP2C, UGT2B7, GSTM1 and GSTT1, as well as HLA alleles. The paper includes a list of the NSAID 'usual suspects' that cause hepatotoxicity based on the integrated information of drug-induced hepatotoxicity databases.

EXPERT OPINION

The ultimate goal of this research is pre-prescription testing. Unfortunately, genetic testing, alone, is not sufficient to predict NSAID-induced hepatotoxicity. The development of genetic biomarkers capable of identifying at-risk individuals will not be complete until we develop the ability to fully characterize patients' phenomes and the phenome-genome interaction in patients with NSAID-induced hepatotoxicity. Additionally, a characterization of the metabolic profile of the causative drug in patients with NSAID-induced hepatotoxicity would add crucial information which is presently disregarded in most studies. The full development of robust biomarkers will require the combination of several disciplines including causal statistics, phenomics, genomics, transcriptomics and metabonomics.

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.

CYP2W1 variant alleles in Caucasians and association of the CYP2W1 G541A (Ala181Thr) polymorphism with increased colorectal cancer risk

AIMS

To detect differences in the frequency of the known nonsynonymous CYP2W1 polymorphisms between colorectal cancer patients and healthy subjects.

MATERIALS & METHODS

The study group consisted of 150 colorectal patients and 263 controls. The presence of five nonsynonymous CYP2W1 polymorphisms was analyzed by novel amplification-restriction methods.

RESULTS

Two nonsynonymous SNPs causing the amino acid substitutions Val432Ile and Gln482His were monomorphic in the population study. Two nonsynonymous SNPs previously unknown in Caucasians, 1463T (rs3808348) and 173C (no rs number assigned), were detected in the population study, although these were not associated with colorectal cancer risk. Regarding the 541G/A polymorphism (rs3735684), the 541G allele (odds ratio: 2.2; 95% CI: 1.2-4.1) and the 541GG genotype (odds ratio: 2.06; 95% CI: 1.1-3.9) were associated with increased colorectal cancer risk in the population studied. Conversely, the 173C-541A-1463C haplotype (odds ratio: 0.46; 95% CI: 0.2-0.9) showed a protective odds ratio value.

CONCLUSION

CYP2W1 variant alleles are common among Caucasian individuals and, of these, the CYP2W1 G541A (Ala181Thr) polymorphism is associated with increased colorectal cancer risk.

Association of xenobiotic metabolizing enzymes genetic polymorphisms with esophageal cancer in Kashmir Valley and influence of environmental factors

The Kashmir Valley has an elevated incidence rate of esophageal cancer (EC). Several environmental and genetic factors have been suspected for development of EC. A case-control study was performed in 135 EC patients and 195 healthy controls to analyze association of polymorphisms in glutathione S-transferase (GST) mu (GSTM1), GST theta (GSTT1), GST pi (GSTP1), GSTM3, Cytochrome P450 (CYP)1A1, and CYP2E1 genes with susceptibility to EC as well as their interaction with environmental factors such as smoking and high consumption of salted tea in Kashmir valley. All subjects were genotyped through polymerase chain reaction restriction fragment length polymorphism. Data was statistically analyzed using the chi-square test and logistic regression model. Results showed that GSTP1313 val/val and CYP2E1c1c2 genotypes imparted risk for esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma [EADC; odds ratio (OR) = 3.24, 95% confidence interval (CI) = 1.30-8.05; OR = 4.20, 95% CI = 1.65-10.70], respectively. GSTM3AB genotype/B allele was found to be associated with low risk for EC. Tobacco smoking through hukka (water pipe) and consumption of salted tea itself were high risk factors for developing EC (OR = 21.44, 95% CI = 11.63-39.54; OR = 14.86, 95% CI = 8.41-26.24), and the risks were modulated through the interaction of GSTM3AB, GSTP1val/val genotypes. In conclusion, GSTP1val/val and CYP2E1c1c2 genotypes/c2 allele increased the risk of ESCC and EADC, respectively, in the Kashmiri population; whereas GSTM3AB genotype imparted lower risk for both ESCC and EADC.

Polymorphisms of glutathione-S-transferase genes and the risk of aerodigestive tract cancers in the Northeast Indian population

BACKGROUND

Widespread use of tobacco and betel quid consumption and a high incidence of tobacco-associated aerodigestive tract cancers have been reported in different ethnic groups from several regions of Northeast (NE) India. This study was done to explore the possibility of phase II metabolic enzymes being responsible for the high prevalence of cancers in this region of India.

METHODS

Samples from 370 cases with oral, gastric, and lung cancers and 270 controls were analyzed for polymorphism of glutathione-S-transferase (GST) genes using polymerase chain reaction-restriction fragment length polymorphism-based methods.

RESULTS AND CONCLUSIONS

Tobacco smoking and betel quid chewing were found to be high risk factors for oral and lung cancers but not for gastric cancer, whereas tobacco chewing was found to be a risk factor for oral cancer but not for gastric or lung cancer. The variant genotypes of GSTP1 were not associated with any of the aerodigestive tract cancers. GSTT1 and GSTM1 null genotypes appeared to play a protective role for lung cancer (odds ratio [OR] = 0.47, 95% confidence interval [95% CI]: 0.24-0.93, p = 0.03) and (OR = 0.52, 95% CI: 0.28-0.96, p = 0.04), but they were not associated with oral and gastric cancers. However, when data was analyzed in different geographic regions the GSTT1 null genotype was found to be a significant risk factor for oral (OR = 2.58, 95% CI 1.01-6.61, p = 0.05) as well as gastric cancer (OR = 3.08, 95% CI 1.32-7.19, p = 0.009) in samples obtained from the Assam region of NE India. This is the first study on the association of GST polymorphisms and aerodigestive tract cancers in the high-risk region of NE India.

Two common nonsynonymous paraoxonase 1 (PON1) gene polymorphisms and brain astrocytoma and meningioma

BACKGROUND

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.

METHODS

Seventy one consecutive patients with brain tumors (43 with astrocytoma grade II/III and 28 with meningioma) with ages ranging 21 to 76 years, and 220 healthy controls subjects were analyzed for the frequency of the nonsynonymous PON1 genotypes L55M rs854560 and Q192R rs662. All participants were adult Caucasian individuals recruited in the central area of Spain.

RESULTS

The frequencies of the PON1 genotypes and allelic variants of the polymorphisms PON1 L55M and PON1 Q192R did not differ significantly between patients with astrocytoma and meningioma and controls. The minor allele frequencies were as follows: PON1 55L, 0.398, 0.328 and 0.286 for patients with astrocytoma, meningioma and control individuals, respectively; PON1 192R, 0.341, 0.362 and 0.302 for patients with astrocytoma, meningioma and control individuals, respectively. Correction for age, gender, or education, made no difference in odds ratios and the p values remained non-significant. Haplotype association analyses did not identify any significant association with the risk of developing astrocytoma or meningioma.

CONCLUSIONS

Common nonsynonymous PON1 polymorphisms are not related with the risk of developing astrocytoma and meningioma.

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.

Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

Background

It is uncertain whether smoking is related to colorectal cancer risk. Cytochrome P-450 CYP1A1, glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are important enzymes in the metabolism of tobacco carcinogens, and functional genetic polymorphisms are known for these enzymes. We investigated the relation of cigarette smoking and related genetic polymorphisms to colorectal cancer risk, with special reference to the interaction between smoking and genetic polymorphism.

Methods

We used data from the Fukuoka Colorectal Cancer Study, a population-based case-control study, including 685 cases and 778 controls who gave informed consent to genetic analysis. Interview was conducted to assess lifestyle factors, and DNA was extracted from buffy coat.

Results

In comparison with lifelong nonsmokers, the odds ratios (OR) of colorectal cancer for <400, 400-799 and ≥800 cigarette-years were 0.65 (95% confidence interval [CI], 0.45-0.89), 1.16 (0.83-1.62) and 1.14 (0.73-1.77), respectively. A decreased risk associated with light smoking was observed only for colon cancer, and rectal cancer showed an increased risk among those with ≥400 cigarette-years (OR 1.60, 95% CI 1.04-2.45). None of the polymorphisms under study was singly associated with colorectal cancer risk. Of the gene-gene interactions studied, the composite genotype of CYP1A1*2A or CYP1A1*2C and GSTT1 polymorphisms was associated with a decreased risk of colorectal cancer, showing a nearly statistically significant (P_interaction = 0.06) or significant interaction (P_interaction = 0.02). The composite genotypes of these two polymorphisms, however, showed no measurable interaction with cigarette smoking in relation to colorectal cancer risk.

Conclusions

Cigarette smoking may be associated with increased risk of rectal cancer, but not of colon cancer. The observed interactions between CYP1A1 and GSTT1 polymorphisms warrant further confirmation.

Glutathione S-transferase M1 polymorphism and sporadic colorectal cancer risk: An updating meta-analysis and HuGE review of 36 case-control studies

PURPOSE

Sporadic colorectal cancer (CRC) is considered to be a multifactorial disease, in which multiple exposures to endogenous factors interact with individual genetic background in a complex manner, resulting in modulation of the risk. The glutathione S-transferase M1 gene (GSTM1) is a particularly attractive candidate for CRC susceptibility because it codes an enzyme involved in the metabolism of environmental carcinogens. However, the epidemiological findings have been inconsistent.

METHODS

To evaluate this association, we performed an extensive meta-analysis of 36 case-control studies (including 10,009 cases and 15,070 controls).

RESULTS

Overall, the combined data showed that GSTM1 deficiency is associated with a marginal effect on CRC risk (odds ratio [OR] = 1.13; 95% confidence interval [CI]: 1.03-1.23; P for heterogeneity <0.001). When stratified by race and tumor site, significant results were only observed in Caucasians (OR = 1.14, 95% CI: 1.01-1.27; P for heterogeneity <0.001), whereas no increased risk was detected in other subgroups.

CONCLUSIONS

The findings of our study support the suggestion that GSTM1 polymorphism is associated with an increased risk of CRC, especially in the Caucasian population. Further investigation into the association between GSTM1 polymorphism and the risk of CRC is warranted and should include larger sample sizes and other genetic polymorphisms in metabolism of environmental carcinogens.

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.

GSTM1, GSTT1, GSTP1, GSTA1 and colorectal cancer risk: a comprehensive meta-analysis

Glutathione S-transferases (GSTs) catalyse reactions between glutathione and lipophilic compounds with electrophilic centres, leading to neutralisation of toxic compounds, xenobiotics and products of oxidative stress. Controversy exists about whether GST polymorphisms (GSTM1 null/present genotype, GSTT1 null/present genotype, GSTP1 Ile105Val and GSTA1 *A/*B) represent risk factors for colorectal cancer. This meta-analysis aims to examine the associations between the above-mentioned polymorphisms and colorectal cancer risk. Forty-four studies were eligible for GSTM1 (11,998 colorectal cancer cases, 17,552 controls), 34 studies for GSTT1 (8596 cases, 13,589 controls), 19 studies for GSTP1 (5421 cases, 7671 controls) and four studies for GSTA1 polymorphism (1648 cases, 2039 controls). Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. Separate analyses were conducted on Caucasian and Chinese populations. Where appropriate, sensitivity analysis concerning the deviation of genotype frequencies in controls from the Hardy-Weinberg equilibrium was performed. GSTM1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.150, 95% confidence interval (CI): 1.060-1.248, random effects); no significant association was detected for Chinese subjects (pooled OR=1.025, 95% CI: 0.903-1.163, fixed effects). Similarly, GSTT1 null allele carriers exhibited increased colorectal cancer risk in Caucasian populations (pooled OR=1.312, 95% CI: 1.119-1.538, random effects); the association in Chinese subjects was not significant (pooled OR=1.068, 95% CI: 0.788-1.449, random effects). Concerning GSTP1 Ile105Val no significant associations were demonstrated in either race. GSTA1 *A/*B polymorphism was not associated with colorectal cancer risk. GSTM1 and GSTT1 null genotypes confer additional risk for colorectal cancer in Caucasian populations.