Glutathione S-transferase P1 ILE105Val polymorphism in occupationally exposed bladder cancer cases

Promoter methylation and Ile105val polymorphism of GSTP1 gene in the modulation of colorectal cancer risk in ethnic Kashmiri population

BACKGROUND

Glutathione-S-transferases (GSTs) are the most important phase II enzymes of the xenobiotic pathway responsible for the detoxification of carcinogens. GSTP1 gene polymorphisms are mostly associated with a lack or an alteration of enzymatic activity toward several substrates thus resulting in increased cancer susceptibility. GSTP1 promoter methylation is also frequently associated with tumor development or poor prognosis in a wide range of tumors.

AIM

In this study, we examined the role of genetic polymorphism and promoter methylation of GSTP1 gene in the context of modulation of risk of colorectal cancer (CRC) in Kashmiri population.

METHODS

This study used tissue tumor samples (114) and blood samples from (160) patients with CRC and 200 blood samples from healthy donors. GSTP1 polymorphism was studied using polymerase chain reaction (PCR)-restriction fragment length polymorphism and methylation using methylation-specific PCR.

RESULTS

There was no significant association between GSTP1 I105V genotypes and the CRC (P>0.05). However, we found a significant association of the Val/Val variant genotype with the dwelling and smoking status (P-value < 0.05). Overall, the homozygous variant Val/Val genotype was associated with a modestly elevated risk for CRC (OR = 1.57; 95% CI = 0.67-3.57). Methyl-specific-PCR analysis revealed 25.4% methylation of the GSTP1 promoter in CRC cases and was not found to be statistically significantly associated with clinicopathological parameters of the CRC cases (P>0.05). Also, no significant associations of any of the three genotypes with promoter hypermethylation were observed.

CONCLUSION

We conclude that promoter hypermethylation in homozygous GSTP1 mutants did not elevate the risk of CRC in Kashmiri population.

Polymorphisms of xenobiotic metabolizing enzymes in bladder cancer patients of the Semmelweis University Budapest, Hungary

Polymorphic xenobiotic metabolizing enzymes such as N-acetyltransferase 2 (NAT2) or glutathione S-transferase M1 (GSTM1) are known to modulate bladder cancer risk. As no apparent data were available from Hungary, a former member of the eastern European economic organization, a study was performed in Budapest. In total, 182 bladder cancer cases and 78 cancer-free controls were investigated by questionnaire. Genotypes of NAT2, GSTM1, GSTT1, rs1058396 and rs17674580 were determined by standard methods. Current smokers' crude odds ratio (OR) (3.43) and former smokers crude OR (2.36) displayed a significantly increased bladder cancer risk. The risk rose by a factor of 1.56 per 10 pack years. Exposure to fumes was associated with an elevated bladder cancer risk (23% cases, 13% controls). Sixty-four % of the cases and 59% of controls were slow NAT2 acetylators. It was not possible to establish a particular impact of NAT2*6A and *7B genotypes (15 cases, 8%, 5 controls, 7%). GSTT1 exerted no marked influence on bladder cancer (negative 21% cases vs. 22% controls). The portion of GSTM1 negative bladder cancer patients was increased (63% cases vs. 54% controls). The SLC14A1 SNPs rs1058396[AG/GG] and the nearby rs17674580[CT/TT] occurred more frequently in cases (79% and 68%) than controls (77% and 55%). The portion of GSTM1 negative bladder cancer patients is comparable with portions reported from other industrialized areas like Lutherstadt Wittenberg/Germany (58%), Dortmund/Germany (70%), Brescia/Italy (66%) or an occupational case-control series in Germany (56%). Data indicate that GSTM1 is a susceptibility factor for environmentally triggered bladder cancer rather than for smoking-mediated bladder cancer.

Urinary bladder cancer risk factors in an area of former coal, iron, and steel industries in Germany

This study was performed to investigate the frequency of bladder cancer in patients with an occupational history such as underground hard coal mining and/or painting after the structural change in the local industry. A total of 206 patients with bladder cancer and 207 controls were enlisted regarding occupational and nonoccupational bladder cancer risk factors by questionnaire. The phase II enzymes N-acetyltransferase 2 (NAT2), glutathione S-transferases M1 (GSTM1), and T1 (GSTT1) and the single nucleotide polymorphism (SNP) rs11892031[A/C] reported to be associated with bladder cancer in genome-wide association studies were genotyped. The bladder cancer risk in varnishers and underground hard coal miners was increased as previously shown in a study in this area performed in the 1980s. The occupation of a car mechanic was associated with a significantly elevated bladder cancer risk and higher in the case of underground hard coal miners even though the mine was closed in 1987. The frequency of GSTM1 negative genotype was comparable in cases and controls (53% versus 54%). In the case of NAT2, the slow NAT2 genotype was more frequent (62% versus 58%) and ultra-slow NAT2 genotype (NAT2*6A and/or *7B alleles only) was 23% versus 15%. An occupational history of a varnisher or an underground hard coal miner remains a risk factor for bladder cancer occurrence. Data indicate that in the case of bladder cancer, GSTM1 is a susceptibility factor related to environmental and/or occupational exposure.

Occupational exposures and genetic susceptibility to urinary tract cancers: a systematic review and meta-analysis

This study aims to summarize the current knowledge on the relationship between genetic polymorphisms, occupational exposures, and urinary tract cancers. We searched MEDLINE, ISI Web of science, and SCOPUS online databases for all articles published in English language up to September 2016. A meta-analysis was performed to provide summary estimates for the association between a certain genetic polymorphism, occupational exposure and bladder cancer (BC) or kidney cancer (KC), when appropriate. Fifteen studies on BC and six on KC were deemed eligible for the review. With regard to BC, an overall odds ratio (OR) of 2.07 [95% confidence interval (CI): 1.38-3.09] for those with GSTM1 and an OR of 2.07 (95% CI: 1.38-3.09) for those with GSTT1 null genotype were reported when exposed to polycyclic aromatic hydrocarbons (PAHs). NAT2 slow genotype carriers had an OR of 3.59 (95% CI: 2.62-4.93) for BC when exposed to aromatic amines and an OR of 2.07 (95% CI: 1.36-3.15) when exposed to PAHs. With regard to KC and pesticide exposure, the meta-analysis reported an OR of 4.38 (95% CI: 2.28-8.41) for GSTM1 present genotype, an OR of 2.59 (95% CI: 1.62-4.15) for GSTT1-present genotype and an OR of 6.51 (95% CI: 2.85-14.89) for combined effects of GSTM1 and GSTT1 active genotypes. This meta-analysis indicates a possible association between the variant genotypes of GSTM1, GSTT1, NAT2 and SULT1A1, occupational exposure to aromatic amines or PAHs, and development of BC. Our results suggest that polymorphisms in GSTM1 and GSTT1 genes could influence the risk for developing KC in individuals occupationally exposed to pesticides.

The relationship between GSTA1, GSTM1, GSTP1, and GSTT1 genetic polymorphisms and bladder cancer susceptibility: A meta-analysis

BACKGROUND

Previous studies have investigated the relationship between GSTA1, GSTM1, GSTP1, and GSTT1 polymorphisms and bladder cancer (BCa) susceptibility, respectively, but the results remain inconsistent. So, we conducted this meta-analysis including 79 case-control studies to explore such relationships.

METHODS

We searched PubMed, EMBASE, Cochrane library, Web of Science, and CNKI for relevant available studies. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were implemented to evaluate the intensity of associations. Publication bias was estimated using Begg funnel plots and Egger regression test. To assess the stability of the results, we used sensitivity analysis with the method of calculating the results again by omitting 1 single study each time. Between-study heterogeneity was tested using the I statistic.

RESULTS

No significant association between GSTA1 polymorphism and BCa susceptibility (OR = 1.05, 95% CI 0.83-1.33) was noted. Besides, meaningful association between individuals who carried the GSTM1 null genotype and increased BCa risk was detected (OR = 1.39, 95%CI 1.28-1.51). When stratified by ethnicity, significant difference was found in both Caucasian (OR = 1.39, 95% CI 1.23-1.58) and Asian populations (OR = 1.45, 95% CI 1.31-1.61). Moreover, in the subgroup analysis by source of controls (SOC), the results were significant in both hospital-based control groups (OR = 1.49, 95% CI 1.35-1.64) and population-based control groups (OR = 1.21, 95% CI = 1.07-1.37). Additionally, the analysis revealed no significant association between GSTP1 polymorphism and BCa risk (OR = 1.07, 95% CI 0.96-1.20). What is more, significant associations between GSTT1 polymorphism and BCa susceptibility were discovered (OR = 1.11, 95% CI 1.00-1.22). In the subgroup analysis by ethnicity, significant associations between GSTT1 null genotype and BCa risk were observed only in Caucasians (OR = 1.25, 95% CI 1.09-1.44). Furthermore, when stratified by SOC, no obvious relationship was found between the GSTT1 null genotype polymorphism with hospital-based population (OR = 1.11, 95% CI 0.97-1.28) or population-based population (OR = 1.10, 95% CI 0.96-1.27).

CONCLUSION

This study suggested that GSTM1 null genotype and GSTT1 null genotype might be related to higher BCa risk, respectively. However, no associations were observed between GSTA1 or GSTP1 polymorphisms and BCa susceptibility.

Glutathione S-transferase P1 gene polymorphism and bladder cancer susceptibility: an updated analysis

Studies investigating the association between glutathione S-transferase P1 (GSTP1) gene polymorphism and bladder cancer (BC) risk have reported conflicting results. In order to clarify the effect of GSTP1 polymorphism on the BC susceptibility, we conducted an updated system review of published epidemiology studies to provide more precise evidence. We performed a systematic search of PubMed, EMBASE, and China National Knowledge Infrastructure (CNKI). 20 studies with 4,428 BC cases and 5,457 controls were identified. The combined analyses based on all studies showed that there was a significant difference in the genotype distribution in GSTP1(A313G) polymorphism between BC cases and controls not only in Asians (GG vs. AA + AG, OR = 1.59, 95 % CI = 1.01-2.51) but also in Caucasians (GG vs. AA + AG, OR = 1.51, 95 % CI = 1.11-2.06). Upon stratification for smoking status, we observed no statistically significant difference in genotype distribution of GSTP1 in ever-smokers. Combination of the high-risk genotypes (GSTM1 null + GSTT1 null + GSTP1 313 A/G or G/G) demonstrated further increase in the BC risk (OR = 6.64, 95 %CI = 3.63-12.16). This meta-analysis suggests that GSTP1 313 G/G polymorphism is a strong predisposing risk factor for BC.

GSTP1 methylation and polymorphism increase the risk of breast cancer and the effects of diet and lifestyle in breast cancer patients

Glutathione S-transferases (GSTs) are an important group of isoenzymes that play an essential role in the detoxification of carcinogens. Polymorphism at exon 5 of the GST π family decreases the catalytic activity and affects the detoxification ability of the enzyme, GSTP1. GSTP1 promoter hypermethylation and loss of expression are frequently observed in various types of carcinoma. We hypothesized that somatic epigenetic modification in homozygous mutants increases the degree to which breast cancer risk is affected by lifestyle factors and dietary habits. The present study used tumor biopsies and blood samples from 215 breast cancer patients and 215 blood samples from healthy donors. GSTP1 polymorphism was studied using PCR-restriction fragment length polymorphism, methylation using methylation-specific PCR and loss of expression using immunohistochemistry and western blotting. No significant increase was observed in the breast cancer risk of individuals with the mutant (Val) allele [odds ratio (OR), 1.48; 95% confidence interval (CI), 0.97–2.26 for heterozygotes; OR, 1.42; 95% CI, 0.86–2.42 homozygous mutants]. GSTP1 promoter hypermethylation was detected in one-third of tumor biopsies (74/215) and was found to be associated with a loss of expression. Genotype and tumor methylation associations were not observed. Estrogen (ER) and progesterone (PR) receptor-positive tumors had a higher methylation frequency. GSTP1 polymorphism was not associated with increased promoter hypermethylation. The results suggest that GSTP1 methylation is a major event in breast carcinogenesis and may act as a tumor-specific biomarker.

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.

Environmental factors promoting bladder cancer

PURPOSE OF REVIEW

To understand the molecular mechanisms of bladder carcinogenesis in relation to environmental carcinogens in order to provide a given population with a preventive value of bladder cancer.

RECENT FINDINGS

Cigarette smoking, aromatic amines contained in dyes, chronic inflammation due to infection such as schistosomiasis, anticancer drugs, drug abuse of analgesic, and radiation are considered as well known risk factors of bladder cancer. Several environmental factors are supposed to be involved in carcinogenesis, cancer progression, and patient's prognosis in bladder cancer. On the basis of the results of recent genetic studies in relation to bladder carcinogenesis, several genetic polymorphisms of detoxification or DNA repair such as N-acetyltransferase 2, glutathione S-transferases, and human 8-oxoguanine DNA glycosylase 1 give us important information in relation to environmental risk factors and ethnic differences for predicting the prognosis of patients with bladder cancer.

SUMMARY

Prevention of environmental carcinogens is important from the viewpoint of the social and clinical problems since elucidation of the correlation between epidemiologic and genetic phenomenon enable us to improve the life expectancy and quality of life of bladder cancer patients.

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.