Null genotype of GSTT1 contributes to esophageal cancer risk in Asian populations: evidence from a meta-analysis

Constitutively Higher Level of GSTT2 in Esophageal Tissues From African Americans Protects Cells Against DNA Damage

BACKGROUND & AIMS

African American and European American individuals have a similar prevalence of gastroesophageal reflux disease (GERD), yet esophageal adenocarcinoma (EAC) disproportionately affects European American individuals. We investigated whether the esophageal squamous mucosa of African American individuals has features that protect against GERD-induced damage, compared with European American individuals.

METHODS

We performed transcriptional profile analysis of esophageal squamous mucosa tissues from 20 African American and 20 European American individuals (24 with no disease and 16 with Barrett's esophagus and/or EAC). We confirmed our findings in a cohort of 56 patients and analyzed DNA samples from patients to identify associated variants. Observations were validated using matched genomic sequence and expression data from lymphoblasts from the 1000 Genomes Project. A panel of esophageal samples from African American and European American subjects was used to confirm allele-related differences in protein levels. The esophageal squamous-derived cell line Het-1A and a rat esophagogastroduodenal anastomosis model for reflux-generated esophageal damage were used to investigate the effects of the DNA-damaging agent cumene-hydroperoxide (cum-OOH) and a chemopreventive cranberry proanthocyanidin (C-PAC) extract, respectively, on levels of protein and messenger RNA (mRNA).

RESULTS

We found significantly higher levels of glutathione S-transferase theta 2 (GSTT2) mRNA in squamous mucosa from African American compared with European American individuals and associated these with variants within the GSTT2 locus in African American individuals. We confirmed that 2 previously identified genomic variants at the GSTT2 locus, a 37-kb deletion and a 17-bp promoter duplication, reduce expression of GSTT2 in tissues from European American individuals. The nonduplicated 17-bp promoter was more common in tissue samples from populations of African descendant. GSTT2 protected Het-1A esophageal squamous cells from cum-OOH-induced DNA damage. Addition of C-PAC increased GSTT2 expression in Het-1A cells incubated with cum-OOH and in rats with reflux-induced esophageal damage. C-PAC also reduced levels of DNA damage in reflux-exposed rat esophagi, as observed by reduced levels of phospho-H2A histone family member X.

CONCLUSIONS

We found GSTT2 to protect esophageal squamous cells against DNA damage from genotoxic stress and that GSTT2 expression can be induced by C-PAC. Increased levels of GSTT2 in esophageal tissues of African American individuals might protect them from GERD-induced damage and contribute to the low incidence of EAC in this population.

Cumulative evidence for association between genetic polymorphisms and esophageal cancer susceptibility: A review with evidence from meta-analysis and genome-wide association studies

An increasing number of publications had reported the association between single‐nucleotide polymorphisms (SNPs) and esophageal cancer (EC) risk in the past decades. Results from these publications were controversial. We used PubMed, Medline, and Web of Science to identify meta‐analysis articles published before 30 July 2018, that summarize a comprehensive investigation for cumulative evidence of genetic polymorphisms of EC and its subtype risk. Two methods, Venice criteria and false‐positive report probability (FPRP) tests, were used to assess cumulative evidence of significant associations. At last, 107 meta‐analyses were considered to be in conformity with the inclusion criteria, yielding 51 variants associated with EC or esophageal squamous cell carcinoma (ESCC). Thirty‐eight variants were considered to be nominally significant associated with risk of EC or ESCC, whereas the rest showed non‐association. In additional, five variants on five genes were rated as strong cumulative epidemiological evidence for a nominally significant association with EC and ESCC risk, including CYP1A1 rs1048943, EGF rs444903, HOTAIR rs920778, MMP2 rs243865, and PLCE1 rs2274223, 10 variants were rated as moderate, and 18 variants were rated as weak. Additionally, 17 SNPs were verified noteworthy in six genomewide association studies (GWAS) using FPRP methods. Collectively, this review offered a comprehensively referenced information with cumulative evidence of associations between genetic polymorphisms and EC and ESCC risk.

Association between the Glutathione-S-transferase T1 null genotype and esophageal cancer susceptibility: a meta-analysis involving 11,163 subjects

Background

Glutathione-S-Transferase T1 (GSTT1) null genotype has been shown to be associated with the risk of esophageal cancer. However, the results remain inconsistent. Thus a comprehensive meta-analysis was conducted to assess the strength of association between GSTT1 null genotype and the risk of esophageal cancer.

Materials and Methods

A literature search of PubMed, Embase, China National Knowledge Infrastructure (CNKI) and Wanfang databases up to March 31, 2017 was conducted and 30 eligible articles with 4482 cases and 6681 controls were finally recruited. The strength of correlation between GSTT1 polymorphism and the susceptibility of esophageal cancer was assessed by the crude odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analyses and sensitivity analyses were performed to further identify the association.

Results

GSTT1 null genotype significantly increased the risk of esophageal cancer (OR = 1.20; 95% CI 1.04-1.40; P < 0.05). In a subgroup analysis by ethnicity, GSTT1 null genotype was correlated with a significantly increased risk of esophageal cancer among Asians (OR = 1.33; 95% CI 1.12-1.58; P < 0.05), instead of Caucasians or Africans (OR = 0.91; 95% CI 0.65-1.26; P > 0.05 for Caucasians and OR = 1.32; 95% CI 0.98-1.77; P > 0.05 for Africans). In the analysis by histological type, GSTT1 null genotype was correlated with a significantly increased risk of esophageal squamous cell carcinoma (OR = 1.34; 95% CI 1.12-1.61; P < 0.05), particularly among Asians (OR = 1.54; 95% CI 1.30-1.82; P < 0.05), but not among Caucasians or Africans (OR = 0.87; 95% CI 0.48-1.57; P > 0.05 for Caucasians and OR = 1.32; 95% CI 0.98-1.77; P > 0.05 for Africans). In addition, there is no significant correlation between GSTT1 null genotype and the risk of esophageal adenocarcinoma (OR = 0.98; 95% CI 0.71-1.35; P > 0.05).

Conclusions

Our findings demonstrate that GSTT1 null genotype significantly increases esophageal cancer risk, particularly in Asians.

Genetic susceptibility to esophageal cancer due to CYP1A1 gene variant rs4646903 in tobacco addicted patients of Pashtun ethnicity: a case control study in Khyber Pakhtunkhwa province of Pakistan

The purpose of this study was to evaluate associations of the CYP1A1 gene variant rs4646903 polymorphism with the risk of developing esophageal cancer (EC). A case-control study was carried out in Pashtun population of Khyber Pakhtunkhwa province of Pakistan in which 140 hospital based EC cases and 196 population based healthy controls exposed to similar environmental conditions were included. A specific method based on the real time polymerase chain reaction (RT-PCR) was used to detect genotypes in case and control groups and results were then analyzed with SPSS version 20. In our population, individuals with CC and TC genotypes of the CYP1A1 rs4646903 polymorphism had significantly higher risk of EC (adjusted odds (OR): 15.709, 95%CI: 6.065-40.686, OR: 3.256 95%CI: 1.902-5.574 respectively). The 'C' allele was strongly associated with the disease (p< 0.0001). Adjusted OR was higher (1.5 times in C/C) in case of variant alleles that show the contribution of environmental and nutritional factors towards the development of EC. Our findings suggest that presence of the 'C' allele of rs4646903 (T>C) may be one of the risk alleles for EC susceptibility in Pashtun population.

Association between GSTM1 and GSTT1 polymorphisms and esophageal squamous cell carcinoma: results from a case-control study in Kashmir, India

Polymorphisms in glutathione-S-transferases (GSTs), the phase II xenobiotic detoxifying enzymes, have been associated with increased cancer risk. In this study, we assessed the association of functional polymorphisms in GSTM1 and GSTT1 with esophageal cancer in Kashmir, India, an area with a high incidence of esophageal squamous cell carcinoma (ESCC). We analyzed genotypes of GSTM1 and GSTT1 using a multiplex PCR in 492 pairs of ESCC cases and individually matched controls. The associations between polymorphisms in these genes and ESCC risk were examined by conditional logistic regression models adjusted for multiple potential confounders. In addition, the interaction between these genes and several environmental exposures with regard to ESCC risk was assessed. Our results showed an association between the GSTT1 null genotype and ESCC risk (odds ratio (OR) = 1.58; 95% confidence interval (CI) 1.04-2.39). Although GSTM1 alone was not associated with ESCC risk, individuals with the GSTM1 (-)/GSTT1 (+) genotype showed an inverse relation with ESCC risk (OR = 0.55; 95% CI 0.32-0.93), compared to GSTM1 (+)/GSTT1 (+) individuals. We found a significant interaction between the GSTT1 and GSTM1 genotypes with regard to ESCC risk (P = 0.001); however, there were no interactions between environmental factors and GSTT1 and GSTM1 genotypes. This study indicates that GSTT1 null genotype is associated with ESCC risk in Kashmiri population. The association between GSTM1 and ESCC risk needs further investigations. Interactions of these genotypes with environmental exposures should be examined in multicentric studies with bigger sample sizes.

GSTT1 is deregulated in left colon tumors

Our aim was to determine GSTT1 expression levels in left colon tumors and paired normal tissue in order to identify specific alterations in GSTT1 mRNA levels. Alterations in GSTT1 expression in twenty-four left- sided colon tumors and paired cancer free tissue were determined by qRT-PCR. Significant fold changes were determined with t-test. When compared with cancer free tissue, left colon cancers showed a significant decrease in GSTT1 expression. However, GSTT1 mRNA levels among different grades increased gradually in correlation with tumor grade. Our results suggest that downregulation of GSTT1 in left-sided colon cancers is an early event and is reversed with cancer progression, probably due to cellular defense mechanisms as a response to changes in the microenvironment.