The glutathione S-transferase P1 341C>T polymorphism and cancer risk: a meta-analysis of 28 case-control studies

Molecular Genetics of Abnormal Redox Homeostasis in Type 2 Diabetes Mellitus

Numerous studies have shown that oxidative stress resulting from an imbalance between the production of free radicals and their neutralization by antioxidant enzymes is one of the major pathological disorders underlying the development and progression of type 2 diabetes (T2D). The present review summarizes the current state of the art advances in understanding the role of abnormal redox homeostasis in the molecular mechanisms of T2D and provides comprehensive information on the characteristics and biological functions of antioxidant and oxidative enzymes, as well as discusses genetic studies conducted so far in order to investigate the contribution of polymorphisms in genes encoding redox state-regulating enzymes to the disease pathogenesis.

TLR4 Polymorphisms and Expression in Solid Cancers

Toll-like receptors (TLRs) are a type of pattern-recognition receptor (PRR) that are part of the innate immune system known to recognize pathogen-associated molecular patterns and thereby play a crucial role in host immune response. Among the various known TLRs, TLR4 is one of the most extensively studied PRRs expressed by immune, certain nonimmune, and tumor cells. When TLR4 binds with the bacterial lipopolysaccharide, it induces production of proinflammatory cytokines, chemokines, and effector molecules as part of the immune response. Continuous exposure to pathogens and TLR4 signaling results in chronic inflammation that may further lead to malignant transformation. TLR4 is a highly polymorphic gene, and genetic variations are known to influence host immune response, leading to dysregulation of signaling pathway, which may affect an individual's susceptibility to various diseases, including cancer. Furthermore, TLR4 expression in different tumor types may also serve as a marker for tumor proliferation, differentiation, metastasis, prognosis, and patient survival. This review aims to summarize various reports related to TLR4 polymorphisms and expression patterns and their influences on different cancer types with a special focus on solid tumors.

Comprehensive Analysis of the Association Between the rs1138272 Polymorphism of the GSTP1 Gene and Cancer Susceptibility

Background: We obtained conflicting results regarding the relationship between the genetic role of the rs1138272 C/T polymorphism of the GSTP1 (Glutathione S-Transferase pi) gene and the risk of various cancers.

Methods: Using the presently available data, a meta-analysis was conducted to comprehensively evaluate the genetic relationship between the GSTP1 rs1138272 polymorphism and cancer susceptibility.

Results: A total of 43 studies including 15,688 cases and 17,143 controls were recruited into our quantitative synthesis. In the overall population, we observed an increased risk of overall cancer cases, compared with unrelated controls, in the genetic models of allele T vs. allele C (P-association = 0.007, OR = 1.17), carrier T vs. carrier C (P-association = 0.035, OR = 1.11), TT vs. CC (P-association = 0.002, OR = 1.45), TT vs. CC+CT (P-association = 0.009, OR = 1.42), and CT+TT vs. CC (P-association = 0.027, OR = 1.13). We detected similar positive results within the Asian population. Additionally, there was a significant increase in the incidence of cancer for Africans under all genetic models (all P-association < 0.05, OR > 1). When targeting the Caucasian population, we detected a positive association with the TT vs. CC and TT vs. CC+CT models in the “Colorectal cancer” (P-association < 0.05, OR < 1) and “Head and neck cancer” (P-association < 0.05, OR > 1) subgroups. For the “Lung cancer” subgroup, we observed a slightly increased risk in Caucasians under the models of allele T vs. allele C, carrier T vs. carrier C, CT vs. CC, and CT+TT vs. CC (P-association < 0.05, OR > 1).

Conclusion: The TT genotype of the GSTP1 rs1138272 polymorphism is likely related to the susceptibility to overall cancer in the Asian and African populations and, specifically, “Colorectal” and “Head and neck” cancers in the Caucasian population. In addition, the CT genotype of the GSTP1 rs1138272 polymorphism may be linked to the risk of lung cancer in Caucasians. Additional evidence is required to confirm this conclusion.

Genetic Variation in GSTP1, Lung Function, Risk of Lung Cancer, and Mortality

INTRODUCTION

Glutathione S-transferase pi 1 metabolizes carcinogens from tobacco smoke in the lung. We tested whether genetically altered glutathione S-transferase pi 1 activity affects lung function and risk for tobacco-related cancer and mortality in the general population.

METHODS

We genotyped 66,069 individuals from the white general population for two common functional variants in the glutathione S-transferase pi 1 gene (GSTP1)-amino acid isoleucine 105 changed to a valine (Ile105Val) and amino acid alanine 114 changed to a valine (Ala114Val)-and recorded lung function, lung cancer, tobacco-related cancer, and death as outcomes.

RESULTS

Lung function was increased stepwise with the Ile105Val genotype overall (p < 0.01) and among smokers separately (p < 0.01). Adjusted hazard ratios for lung cancer, tobacco-related cancer, and death were reduced stepwise with the Ile105Val genotype (p < 0.02): Ile105Val homozygotes and heterozygotes versus noncarriers had hazard ratios for lung cancer of 0.64 (0.47-0.89) and 0.93 (0.78-1.11), for tobacco-related cancer of 0.74 (0.60-0.92) and 0.92 (0.81-1.04), and hazard ratios for death of 0.87 (0.80-0.95) and 0.94 (0.89-0.99), respectively. Population prevented fractions of lung cancer, tobacco-related cancer, and death due to Ile105Val homozygosity were 4%, 3% and 2%, respectively. The Ala114Val genotype was associated with reduced mortality (p < 0.01) but not with lung function, lung cancer, or tobacco-related cancer.

CONCLUSION

GSTP1 Ile105Val was associated with increased lung function, reduced risk for lung cancer and tobacco-related cancer, and reduced all-cause mortality in the general population.

ARLTS1 polymorphism is associated with an increased risk of familial cancer: evidence from a meta-analysis

Adenosine diphosphate (ADP)-ribosylation factor-like tumour suppressor gene 1(ARLTS1) might be associated with an increased risk of several types of familial cancers. However, previous studies have shown that cancer susceptibility is not completely consistent with ARLTS1 polymorphisms, and the precise mechanism remains unknown. Therefore, we conducted a meta-analysis of case-control studies by searching the PubMed, Embase, OVID, Science Direct and Chinese National Knowledge Infrastructure (CNKI) databases. In total, 12 studies met the inclusion criteria and were included in this meta-analysis. Statistical analyses were performed using STATA 11.0 software. Overall, the Cys148Arg T > C variant significantly increased cancer risk (CC vs. TT: OR = 1.27, 95% CI = 1.15–1.41, P < 0.05). The stratification indicated that the Cys148Arg variant is significantly associated with sporadic cancer (CC vs. TT: OR = 1.36, 95% CI = 1.18–1.55) and familial cancer (CC vs. TT: OR = 1.26, 95% CI = 1.12–1.43). Trp149Stop, Pro131Leu, Ser99Ser and Leu132Leu were not correlated with cancer susceptibility. Based on these results, we demonstrated that the ARLTS1 Cys148Arg polymorphism is associated with an increased risk of sporadic cancer and familial cancer, and there were no associations between the other four SNPs (i.e., Trp149Stop, Pro131Leu, Ser99Ser and Leu132Leu) and cancer risk.

Genetic Polymorphisms of Cytochrome P4501A1 (CYP1A1) and Glutathione S-Transferase P1 (GSTP1) and Risk of Hepatocellular Carcinoma Among Chronic Hepatitis C Patients in Egypt

Cytochrome P450 1A1 (CYP1A1) and Glutathione S-transferase P1 (GSTP1) genes are involved in the metabolism of many carcinogens. Polymorphisms in these genes with altered enzyme activity have been reported. The present study evaluated the synergistic effect between CYP1A1 and GSTP1 gene polymorphisms and smoking on development of HCV-related liver disease and hepatocellular carcinoma (HCC). The patients group comprised 40 patients with HCC and 40 patients with liver cirrhosis. The control group comprised 40 healthy subjects having no history of malignancy. The genetic polymorphisms were studied using polymerase chain reaction restriction fragment length polymorphism (PCR RFLP) technique on blood samples. The number of current or former smoker among HCC and cirrhotic patients as well as the median Pack/year of cigarette smoked were significantly higher in HCC and liver cirrhotic patients than in control group. Subjects with CYP1A1 gene variants (m1 and m3) had no significant risk to develop cirrhosis or HCC compared to control group. Individuals carrying the Ile/Val genotype of GSTP1 had a significant increased risk of HCC (OR of 2.2, 95 % CI 1.143-4.261) and had larger tumor size. No significant risk was observed on combining both genes variants or on combining smoking with variants of both genes. In conclusion, the GSTP1 Ile/Val genotype and Val allele are associated with an increased risk of HCC. CYP1A1 and GSTP1 genes variants interaction did not increase the risk of HCC.

Differences in Redox Regulatory Systems in Human Lung and Liver Tumors Suggest Different Avenues for Therapy

A common characteristic of many cancer cells is that they suffer from oxidative stress. They, therefore, require effective redox regulatory systems to combat the higher levels of reactive oxygen species that accompany accelerated growth compared to the normal cells of origin. An elevated dependence on these systems in cancers suggests that targeting these systems may provide an avenue for retarding the malignancy process. Herein, we examined the redox regulatory systems in human liver and lung cancers by comparing human lung adenocarcinoma and liver carcinoma to their respective surrounding normal tissues. Significant differences were found in the two major redox systems, the thioredoxin and glutathione systems. Thioredoxin reductase 1 levels were elevated in both malignancies, but thioredoxin was highly upregulated in lung tumor and only slightly upregulated in liver tumor, while peroxiredoxin 1 was highly elevated in lung tumor, but downregulated in liver tumor. There were also major differences within the glutathione system between the malignancies and their normal tissues. The data suggest a greater dependence of liver on either the thioredoxin or glutathione system to drive the malignancy, while lung cancer appeared to depend primarily on the thioredoxin system.

Gene-environment interactions in esophageal cancer

Esophageal cancer (EC) is one of the most common malignancies in low- and medium-income countries and represents a disease of public health importance because of its poor prognosis and high mortality rate in these regions. The striking variation in the prevalence of EC among different ethnic groups suggests a significant contribution of population-specific environmental and dietary factors to susceptibility to the disease. Although individuals within a demarcated geographical area are exposed to the same environment and share similar dietary habits, not all of them will develop the disease; thus genetic susceptibility to environmental risk factors may play a key role in the development of EC. A wide range of xenobiotic-metabolizing enzymes are responsible for the metabolism of carcinogens introduced via the diet or inhaled from the environment. Such dietary or environmental carcinogens can bind to DNA, resulting in mutations that may lead to carcinogenesis. Genes involved in the biosynthesis of these enzymes are all subject to genetic polymorphisms that can lead to altered expression or activity of the encoded proteins. Genetic polymorphisms may, therefore, act as molecular biomarkers that can provide important predictive information about carcinogenesis. The aim of this review is to discuss our current knowledge on the genetic risk factors associated with the development of EC in different populations; it addresses mainly the topics of genetic polymorphisms, gene-environment interactions, and carcinogenesis. We have reviewed the published data on genetic polymorphisms of enzymes involved in the metabolism of xenobiotics and discuss some of the potential gene-environment interactions underlying esophageal carcinogenesis. The main enzymes discussed in this review are the glutathione S-transferases (GSTs), N-acetyltransferases (NATs), cytochrome P450s (CYPs), sulfotransferases (SULTs), UDP-glucuronosyltransferases (UGTs), and epoxide hydrolases (EHs), all of which have key roles in the detoxification of environmental and dietary carcinogens. Finally, we discuss recent advances in the study of genetic polymorphisms associated with EC risk, specifically with regard to genome-wide association studies, and examine possible challenges of case-control studies that need to be addressed to better understand the interaction between genetic and environmental factors in esophageal carcinogenesis.

XPD Lys751Gln and Asp312Asn polymorphisms and hepatocellular carcinoma susceptibility: A meta-analysis of 11 case-control studies in an Asian population

This meta-analysis was performed to evaluate the association between xeroderma pigmentosum complementary group D (XPD) Lys751Gln and Asp312Asn polymorphisms and susceptibility to hepatocellular carcinoma (HCC). PubMed, Embase, Google Scholar and the Chinese National Knowledge Infrastructure and the Chinese Biomedicine databases were systematically searched to identify relevant studies published up to June 1, 2014. Statistical analyses were performed using Stata version 12.0 software. A total of 11 case-control studies, comprising 2,852 cases and 2,936 controls, were included. The results of the meta-analysis revealed that a significant association between the risk of HCC and variant genotypes of the XPD Lys751Gln and Asp312Asn polymorphisms was evident in the homozygote comparison [Gln/Gln versus Lys/Lys: Odds ratio (OR), 1.831; 95% confidence interval (CI), 1.001-3.349], heterozygote comparison (Lys/Gln versus Lys/Lys: OR, 1.486; 95% CI, 1.044-2.114), dominant model (Gln/Gln + Lys/Gln versus Lys/Lys: OR, 1.540; 95% CI, 1.054-2.249) and allelic contrast (Gln-allele versus Lys-allele: OR, 1.453; 95% CI, 1.032-2.046) for the Lys751Gln polymorphism and the homozygote comparison for the Asp312Asn polymorphism (Asn/Asn versus Asp/Asp: OR, 1.352; 95% CI, 1.010-1.808). By contrast, no significant association was observed in the recessive model for the Lys751Gln polymorphism (Gln/Gln versus Lys/Gln + Lys/Lys: OR, 1.603; 95% CI, 0.924-2.779), or for the heterozygote comparison (Asn/Asp versus Asp/Asp: OR, 1.229; 95% CI, 0.857-1.762), dominant model (Asn/Asn + Asp/Asn versus Asp/Asp: OR, 1.249; 95% CI, 0.910-1.715), recessive model (Asn/Asn versus Asp/Asn + Asp/Asp: OR, 1.250; 95% CI, 0.940-1.663) or allelic contrast (Asn-allele versus Asp-allele: OR, 1.226; 95% CI, 0.965-1.557) for the Asp312Asn polymorphism. The present meta-analysis has indicated that the XPD Lys751Gln polymorphism could be a potential biomarker of HCC susceptibility and that the XPD Lys751Gln and Asp312Asn polymorphisms could be risk factors for HCC susceptibility in an Asian population; however, further large-scale and well-designed studies are required to reach a more precise and comprehensive conclusion.

Iron and thiols as two major players in carcinogenesis: friends or foes?

Iron is the most abundant metal in the human body and mainly works as a cofactor for proteins such as hemoglobin and various enzymes. No independent life forms on earth can survive without iron. However, excess iron is intimately associated with carcinogenesis by increasing oxidative stress via its catalytic activity to generate hydroxyl radicals. Biomolecules with redox-active sulfhydryl function(s) (thiol compounds) are necessary for the maintenance of mildly reductive cellular environments to counteract oxidative stress, and for the execution of redox reactions for metabolism and detoxification. Involvement of glutathione S-transferase and thioredoxin has long attracted the attention of cancer researchers. Here, I update recent findings on the involvement of iron and thiol compounds during carcinogenesis and in cancer cells. It is now recognized that the cystine/glutamate transporter (antiporter) is intimately associated with ferroptosis, an iron-dependent, non-apoptotic form of cell death, observed in cancer cells, and also with cancer stem cells; the former with transporter blockage but the latter with its stabilization. Excess iron in the presence of oxygen appears the most common known mutagen. Ironically, the persistent activation of antioxidant systems via genetic alterations in Nrf2 and Keap1 also contributes to carcinogenesis. Therefore, it is difficult to conclude the role of iron and thiol compounds as friends or foes, which depends on the quantity/distribution and induction/flexibility, respectively. Avoiding further mutation would be the most helpful strategy for cancer prevention, and myriad of efforts are being made to sort out the weaknesses of cancer cells.

Association between TNF-α gene 308G>A polymorphism and lung cancer risk: a meta-analysis

Many studies have investigated the association between tumor necrosis factor alpha (TNF-α) gene 308G/A polymorphism and lung cancer risk, but the results were inconsistent. We thus comprehensively searched the PubMed, EMBASE, and BIOSIS Previews databases and extracted data from all eligible articles to estimate the association between TNF-α gene 308G/A polymorphism and lung cancer risk. The pooled odds ratio (OR) with 95 % confidence intervals (CIs) were calculated. Twelve case-control studies in 11 articles involving 2,436 cases and 2,573 controls were included in the meta-analysis to assess the association between TNF-α gene 308G>A polymorphism and susceptibility to lung cancer. Overall, TNF-α gene 308G>A polymorphism was significantly associated with an increased risk of lung cancer for A vs. G (OR = 1.13, 95 % CI 1.00 ~ 1.27, P = 0.04). Subgroup analysis by ethnicity showed that there was a significant association between TNF-α gene 308G>A polymorphism and increased risk of lung cancer in Asians, but not in Caucasians. In subgroup analysis by tumor type, there were significant associations between TNF-α gene 308G>A polymorphism and increased risk of lung cancer in small cell lung cancer (SCLC) for AA+AG vs. GG, in non-small cell lung cancer (NSCLC) for A vs. G, AA vs. GG, and AA+AG vs. GG. No association between the genotypes and different stages of lung cancer was detected. The meta-analysis suggests that TNF-α gene 308G>A polymorphism is associated with an increased risk of lung cancer, particularly among Asians, both for SCLC and NSCLC, considering tumor type.

Association between SOD2 C47T polymorphism and lung cancer susceptibility: a meta-analysis

Lung cancer is one of the most common cancers worldwide, but its etiology is still unclear. Superoxide dismutase 2 (SOD2) plays an essential role in oxidative stress and may be involved in the development of lung cancer. The association between SOD2 C47T polymorphism and lung cancer risk has been widely investigated, but the results of previous studies are contradictory. We conducted a meta-analysis to comprehensively assess the association between SOD2 C47T polymorphism and lung cancer. The association was estimated by odds ratio (OR) with 95 % confidence interval (95 % CI). A total of 10 studies with 5,146 cases and 6,173 controls were identified. The results showed that SOD2 C47T polymorphism was significantly associated with lung cancer (T versus C: OR = 0.88, 95 % CI = 0.83-0.93, P < 0.001; TT versus CC: OR = 0.74, 95 % CI = 0.66-0.83, P < 0.001; TT versus

CC/CT

OR = 0.81, 95 % CI = 0.73-0.89, P < 0.001). Subgroup analysis by ethnicity suggested that SOD2 C47T polymorphism was significantly associated with lung cancer in both East Asians and Caucasians. Conclusively, this meta-analysis strongly suggests that SOD2 C47T polymorphism is significantly associated with lung cancer.