Effects of dietary intake and genetic factors on hypermethylation of the hMLH1 gene promoter in gastric cancer

Heterogeneity and Adjuvant Therapeutic Approaches in MSI-H/dMMR Resectable Gastric Cancer: Emerging Trends in Immunotherapy

Gastric cancer (GC) remains one of the world's most common and fatal malignant tumors. With a refined understanding of molecular typing in recent years, microsatellite instability (MSI) has become a major molecular typing approach for gastric cancer. MSI is well recognized for its important role during the immunotherapy of advanced GC. However, its value remains unclear in resectable gastric cancer. The reported incidence of microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) in resectable gastric cancer varies widely, with no consensus reached on the value of postoperative adjuvant therapy in patients with MSI-H/dMMR resectable GC. It has been established that MSI-H/dMMR tumor cells can elicit an endogenous immune antitumor response and ubiquitously express immune checkpoint ligands such as PD-1 or PD-L1. On the basis of these considerations, MSI-H/dMMR resectable GCs are responsive to adjuvant immunotherapy, although limited research has hitherto been conducted. In this review, we comprehensively describe the differences in geographic distribution and pathological stages in patients with MSI-H/dMMR with resectable gastric cancer and explore the value of adjuvant chemotherapy and immunotherapy on MSI-H/dMMR to provide a foothold for the individualized treatment of this patient population.

Impact of individual factors on DNA methylation of drug metabolism genes: A systematic review

Individual differences in drug response have always existed in clinical treatment. Many non-genetic factors show non-negligible impacts on personalized medicine. Emerging studies have demonstrated epigenetic could connect non-genetic factors and individual treatment differences. We used systematic retrieval methods and reviewed studies that showed individual factors' impact on DNA methylation of drug metabolism genes. In total, 68 studies were included, and half (n = 36) were cohort studies. Six aspects of individual factors were summarized from the perspective of personalized medicine: parental exposure, environmental pollutants exposure, obesity and diet, drugs, gender and others. The most research (n = 11) focused on ABCG1 methylation. The majority of studies showed non-genetic factors could result in a significant DNA methylation alteration in drug metabolism genes, which subsequently affects the pharmacokinetic processes. However, the underlying mechanism remained unknown. Finally, some viewpoints were presented for future research.

Metabolic codependencies in the tumor microenvironment and gastric cancer: Difficulties and opportunities

Oncogenesis and the development of tumors affect metabolism throughout the body. Metabolic reprogramming (also known as metabolic remodeling) is a feature of malignant tumors that is driven by oncogenic changes in the cancer cells themselves as well as by cytokines in the tumor microenvironment. These include endothelial cells, matrix fibroblasts, immune cells, and malignant tumor cells. The heterogeneity of mutant clones is affected by the actions of other cells in the tumor and by metabolites and cytokines in the microenvironment. Metabolism can also influence immune cell phenotype and function. Metabolic reprogramming of cancer cells is the result of a convergence of both internal and external signals. The basal metabolic state is maintained by internal signaling, while external signaling fine-tunes the metabolic process based on metabolite availability and cellular needs. This paper reviews the metabolic characteristics of gastric cancer, focusing on the intrinsic and extrinsic mechanisms that drive cancer metabolism in the tumor microenvironment, and interactions between tumor cell metabolic changes and microenvironment metabolic changes. This information will be helpful for the individualized metabolic treatment of gastric cancers.

A Radiomics Nomogram Integrated With Clinic-Radiological Features for Preoperative Prediction of DNA Mismatch Repair Deficiency in Gastric Adenocarcinoma

Purpose

To develop and validate a radiomics nomogram integrated with clinic-radiological features for preoperative prediction of DNA mismatch repair deficiency (dMMR) in gastric adenocarcinoma.

Materials and Methods

From March 2014 to August 2020, 161 patients with pathologically confirmed gastric adenocarcinoma were included from two centers (center 1 as the training and internal testing sets, n = 101; center 2 as the external testing sets, n = 60). All patients underwent preoperative contrast-enhanced computerized tomography (CT) examination. Radiomics features were extracted from portal-venous phase CT images. Max-relevance and min-redundancy (mRMR) and least absolute shrinkage and selection operator (LASSO) methods were used to select features, and then radiomics signature was constructed using logistic regression analysis. A radiomics nomogram was built incorporating the radiomics signature and independent clinical predictors. The model performance was assessed using receiver operating characteristic (ROC) curve analysis, calibration curve, and decision curve analysis (DCA).

Results

The radiomics signature, which was constructed using two selected features, was significantly associated with dMMR gastric adenocarcinoma in the training and internal testing sets (P < 0.05). The radiomics signature model showed a moderate discrimination ability with an area under the ROC curve (AUC) of 0.81 in the training set, which was confirmed with an AUC of 0.78 in the internal testing set. The radiomics nomogram consisting of the radiomics signature and clinical factors (age, sex, and location) showed excellent discrimination in the training, internal testing, and external testing sets with AUCs of 0.93, 0.82, and 0.83, respectively. Further, calibration curves and DCA analysis demonstrated good fit and clinical utility of the radiomics nomogram.

Conclusions

The radiomics nomogram combining radiomics signature and clinical characteristics (age, sex, and location) may be used to individually predict dMMR of gastric adenocarcinoma.

Patterns of Nutrient Intake in Relation to Gastric Cancer: A Case Control Study

Gastric Cancer (GC) is the most common cancer among Iranian men. We conducted a case-control study to investigate the association between patterns of nutrient intake and the risk of GC in Iran. We enrolled 178 GC patients and 271 controls matched for age and sex. We collected dietary intakes using a validated diet history questionnaire. We performed factor analysis on 28 nutrients using multivariate logistic regression models on tertiles of factor scores and estimated odds ratios (OR) and 95% confidence intervals (95% CI). We identified three nutrient patterns. The first pattern included pantothenic acid, riboflavin, zinc, animal protein, and calcium. Selenium, thiamin, carbohydrate, vegetable protein, niacin and low intake of vitamin E loaded the second pattern, and the third pattern was abundant in fiber, carotene, vitamin C and A. We found no significant association between GC and any of the dietary patterns. However, in the first patterns, men in the highest tertile had significantly higher odds of GC than the lowest (OR = 2.15, 95% CI: 1.13-4.09, p trend = 0.02). A dietary pattern loaded by animal products may increase the risk of GC among Iranian men. Larger studies are required to approve these findings in overall and in different subgroups.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1931697.

Alcohol consumption and risk of stomach cancer: A meta-analysis

Stomach cancer is one of the most common cancers in the world. The relationship between alcohol consumption and the risk of stomach cancer remains unclear. Epidemiology studies investigating this relationship have shown inconsistent findings. A meta-analysis was performed to explore the association between alcohol consumption and increased stomach cancer risk. Eighty-one epidemiology studies, including 68 case-control studies and 13 cohort studies, were included in this study. A significant association was found between alcohol consumption and increased risk of stomach cancer (OR = 1.20, 95% CI 1.12-1.27). To explore the source of the significant heterogeneity (p < 0.05, I² = 86%), analysis was stratified by study type (case-control study and cohort study), control type (hospital-based control and population-based control), gender (male, female, and mix), race (White and Asian), region (United States, Sweden, China, Japan), subsite of stomach cancer, and type of alcohol. The stratified analyses found that region and cancer subsite are major sources of the high heterogeneity. The inconsistent results in different regions and different subsites might be related to smoking rates, Helicobacter pylori infection, obesity, and potential genetic susceptibility. The positive association between drinking and increased risk of stomach cancer is consistent in stratified analyses. The dose-response analysis showed a clear trend that a higher daily intake of alcohol is associated with a higher risk of stomach cancer.

How Dietary Factors Affect DNA Methylation: Lesson from Epidemiological Studies

Over the past decades, DNA methylation has been proposed as a molecular mechanism underlying the positive or negative effects of diet on human health. Despite the number of studies on this topic is rapidly increasing, the relationship between dietary factors, changes in DNA methylation and health outcomes remains unclear. In this review, we summarize the literature from observational studies (cross-sectional, retrospective, or prospective) which examined the association of dietary factors (nutrients, foods, and dietary patterns) with DNA methylation markers among diseased or healthy people during the lifetime. Next, we discuss the methodological pitfalls by examining strengths and limitations of published studies. Finally, we close with a discussion on future challenges of this field of research, raising the need for large-size prospective studies evaluating the association between diet and DNA methylation in health and diseases for appropriate public health strategies.

Effect of Helicobacter pylori Infection on GATA-5 and TFF1 Regulation, Comparison Between Pediatric and Adult Patients

BACKGROUND

GATA factors, which constitute a family of transcription regulatory proteins, participate in gastrointestinal development. Trefoil factor 1 (TFF1) plays a crucial role in mucosal defense and healing, and evidence suggests that GATA-5 mediated its regulation. Gastric cancer is a multiple-step process triggered by Helicobacter pylori and is characterized by accumulation of molecular and epigenetic alteration. The aim of this study was to evaluate the effect of H. pylori infection on the regulation of GATA-5 and TFF1 in vitro and in vivo.

RESULTS

Infected cells exhibited upregulation of GATA-5 and TFF1 after 48 h. An increase in GATA-5 and TFF1 mRNA levels was also found in mice samples after 6 and 12 months of infection, respectively. In human samples, we found an association between H. pylori infection and GATA-5 upregulation. In fact, among H. pylori-infected patients, hypermethylation was observed in 45.5% of pediatric samples, in 62.6% of chronic gastritis samples, and in 63% of gastric cancer samples. Regarding TFF1, the expression levels were similar in pediatrics and adults patients, and were independent of H. pylori infection, and the expression of these factors was downregulated in gastric cancer samples. GATA-5 promoter methylation was associated with a decrease in TFF1 mRNA levels.

CONCLUSIONS

Our results suggest that the upregulation of GATA-5 and TFF1 observed in vitro and in vivo may be correlated with a protective effect of the mucosa in response to infection. The epigenetic inactivation of GATA-5 observed in human biopsies from infected patients may suggest that this alteration is an early event occurring in association with H. pylori infection.

Association Between hMLH1 Promoter Methylation and Risk of Gastric Cancer: A Meta-Analysis

Background: Human mutL homolog 1 (hMLH1) is located on chromosome 3q21-23. As a classic tumor suppressor gene, many researchers have studied the association between hMLH1 promoter methylation and gastric cancer, but their conclusions were not always consistent. Therefore, we performed a meta-analysis to make a more integrated and precise estimate of the associations.

Method: PubMed, EMBASE, and Cochrane Library were retrieved without language restrictions. Data were analyzed by Review Manager 5.2 and Stata 12.0 software. Odds ratio (OR) with 95% confidence interval (95%CI) was used to assess the statistical associations.

Result: A total of 39 studies published before January 20, 2018 were included in this study. The results indicated that the frequency of hMLH1 promoter methylation in gastric cancers was substantially higher than that in non-cancer controls (OR = 7.94, 95%CI = 4.32–14.58, P < 0.001). Furthermore, hMLH1 promoter methylation had considerable associations with lymph node metastasis, microsatellite instability (MSI), and low expression of hMLH1 protein (OR = 1.53, 95%CI = 1.04–2.26, P = 0.03; OR = 15.33, 95%CI = 9.26–25.36, P < 0.001; OR = 37.86, 95%CI = 18.03–79.50, P < 0.001, respectively). No association was found between hMLH1 promoter methylation and Lauren classification or Helicobacter pylori (HP) infection status.

Conclusion: The present study provides evidence that promoter methylation of hMLH1 is a major causative event in the occurrence and development of human gastric cancer.

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

Background

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

Methods

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

Results

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

Conclusions

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

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.

Association between CYP2E1 polymorphisms and risk of gastric cancer: An updated meta-analysis of 32 case-control studies

Previous studies suggested that RsaI/PstI and DraI polymorphisms on cytochrome P450 2E1 (CYP2E1) may be associated with susceptibility to gastric cancer (GC). However, this association remains ambiguous. A meta-analysis of previously published studies was performed in an attempt to elucidate this association. The odds ratio and 95% confidence interval were used to assess the strength of the association. In the overall analyses of RsaI/PstI and DraI, no association was identified. In the subgroup analyses, RsaI/PstI was identified to increase the risk of GC in the smoking population. In addition, in the previous studies of interactions with other genes, RsaI/PstI was revealed to be associated with increased GC risks when glutathione S-transferase-µ-1 or glutathione S-transferase θ-1 was null or DraI was homozygous wild-type. However, these stratified analyses were lacking credibility due to the limitation of correlational study numbers. In conclusion, CYP2E1 polymorphisms revealed no association with the risk of GC.

Meta-analysis of association studies of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese

BACKGROUND

A great number of studies have shown that cytochrome P450 1A1 (CYP1A1) genetic polymorphisms, CYP1A1 Msp I and CYP1A1 Ile/Val, might be risk factors for digestive tract cancers, including esophageal cancer (EC), gastric cancer (GC), hepatic carcinoma (HC), as well as colorectal cancer (CC), but the results are controversial. In this study, a meta-analysis of this literature aimed to clarify associations of CYP1A1 genetic polymorphisms with digestive tract cancer susceptibility in Chinese populations.

MATERIALS AND METHODS

Eligible case-control studies published until December 2013 were retrieved by systematic literature searches from PubMed, Embase, CBM, CNKI and other Chinese databases by two investigators independently. The associated literature was acquired through deliberate search and selection based on established inclusion criteria. Fixed- effects or random-effects models were used to estimate odds ratios (ORs and 95%CIs). The meta-analysis was conducted using Review Manager 5.2 and Stata 12.0 softwares with stability evaluated by both stratified and sensitivity analyses. Moreover, sensitivity analysis and publication bias diagnostics confirmed the reliability and stability.

RESULTS

Eighteen case control studies with 1, 747 cases and 2, 923 controls were selected for CYP1A1 MspI polymorphisms, and twenty case-control studies with 3, 790 cases and 4, 907 controls for the CYP1A1 Ile/ Val polymorphisms. Correlation associations between CYP1A1 Ile/Val polymorphisms and digestive tract cancers susceptibility were observed in four genetic models in the meta-analysis (GG vs AA:OR= 2.03, 95%CI =1.52- 2.72; AG vs AA: OR=1.26, 95%CI =1.07-1.48; [ GG+AG vs AA] :OR =1.42, 95%CI=1.20-1.68, [GG vs AA+AG ]:OR=1.80, 95%CI =1.40-2.31). There was no association between CYP1A1 Msp I polymorphisms and digestive tract cancer risk. Subgroup analysis for tumor type showed a significant association of CYP1A1 Ile/Val genetic polymorphisms with EC in China. However, available data collected by the study failed to reveal remarkable associations of GC or HC with CYP1A1 Ile/Val genetic polymorphisms and EC, GC or CC with CYP1A1 MspI genetic polymorphisms.

CONCLUSIONS

Our results indicated that CYP1A1 Ile/Val genetic polymorphisms, but not CYP1A1 Msp I polymorphisms, are associated with an increased digestive tract cancer risk in Chinese population. Additional well-designed studies, with larger sample size, focusing on different ethnicities and cancer types are now warranted to validate this finding.

Long non-coding RNAs in gastric cancer: versatile mechanisms and potential for clinical translation

Gastric cancer (GC) remains a serious threat to many people, representing the second leading cause of cancer-related death worldwide. The lack of early diagnostic biomarkers, effective prognostic indicators and therapeutic targets all account for the poor prognosis of GC. Therefore, the identification of novel molecular biomarkers for early diagnosis, therapeutic response, and prognosis are urgently needed. High-throughput sequencing has identified a large number of transcribed long non-coding RNAs (lncRNAs) throughout the human genome. Accumulating evidence demonstrates that these lncRNAs play multiple roles in regulating gene expression at the transcriptional, post-transcriptional, and epigenetic levels. Aberrant expression of lncRNAs occurs in various pathological processes, including GC. Many dysregulated lncRNAs in GC have been significantly associated with a larger tumor size, higher degree of tumor invasion, lymph node and distant metastasis, and poorer survival outcome. In this review, we will provide an overview of the pathogenesis of GC, the characteristics and regulatory functions of lncRNAs, and the versatile mechanisms of lncRNAs in GC development, as well as evaluate the translational potential of lncRNAs as novel diagnostic and prognostic biomarkers and therapeutic targets in GC.

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.

The effect of CYP1A1 and CYP1A2 polymorphisms on gastric cancer risk among different ethnicities: a systematic review and meta-analysis

Potential Cytochrome P450s (CYPs) 1A1 MspI, 1A1 Ile462Val, 1A2*1 F, and/or 1A2*1C polymorphisms have been implicated in gastric cancer risk among different ethnicities. We aimed to explore the effect of CYP 1A1 MspI, 1A1 Ile462Val, 1A2*1 F, and/or 1A2*1C polymorphisms on the susceptibility to gastric cancer among different ethnicities through a systematic review and meta-analysis. Each initially included article was scored for quality appraisal. Desirable data were extracted and registered into databases. A number of 11 studies were ultimately eligible for the meta-analysis of CYP1A1 MspI polymorphism, eight studies for the meta-analysis of 1A1 Ile462Val polymorphism, and two studies for the meta-analysis of 1A2*1 F polymorphism. None of genetic model was evidently suggested, and thus all the genetic models were presented. Potential sources of heterogeneity were sought out via subgroup and sensitivity analyses, and publication biases were estimated. In our meta-analysis, significant results could be found in mutational heterozygous CT genotype, compared with wild TT genotype, among large sample size subgroup for CYP1A1 MspI polymorphism. Regarding CYP1A1 Ile462Val polymorphism, no statistically significant results could be found. For CYP1A2*1 F polymorphism, mutational heterozygous AC genotype, compared with wild-type AA, has deleterious effects, whereas mutational homozygous CC genotype, compared with mutational heterozygous type AC, has protective effects but lacks statistically significant difference despite its a proximity to 0.05. Combined mutational homozygous CC genotype and wild-type homozygous AA, compared with mutational heterozygous AC genotype, has protective effects. Our meta-analysis suggests no associations between CYP1A1 Ile462Val polymorphism and gastric cancer, but possible associations between CYP1A1 MspI and CYP1A2*1 F polymorphisms and gastric cancer, which needs to be further reinforced or refuted among different ethnicities in well-designed large-scale high-quality studies.

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.

Early environmental factors, alteration of epigenetic marks and metabolic disease susceptibility

The environmental conditions that are experienced in early life can profoundly influence human biology and long-term health. Early-life nutrition and stress are among the best documented examples of such conditions because they influence the adult risk of developing metabolic diseases, such as type 2 diabetes mellitus (T2D) and cardiovascular diseases. It is now becoming increasingly accepted that environmental compounds including nutrients can produce changes in the genome activity that in spite of not altering DNA sequence can produce important, stable and transgenerational alterations in the phenotype. Epigenetic changes, in particular DNA methylation and histone acetylation/methylation, provide a 'memory' of developmental plastic responses to early environment and are central to the generation of phenotypes and their stability throughout the life course. Their effects may only become manifest later in life, e.g. in terms of altered responses to environmental challenges.

Promoter hypermethylation of CDKN2A, MGMT, MLH1, and DAPK genes in laryngeal squamous cell carcinoma and their associations with clinical profiles of the patients

BACKGROUND

Laryngeal squamous cell carcinoma (laryngeal SCC) is a frequently occurring cancer of the head and neck area. Epigenetic changes of tumor-related genes contribute to its genesis and progression.

METHODS

We assessed promoter methylation status of the selected genes (CDKN2A, MGMT, MLH1, and DAPK) using methylation-sensitive high resolution melting (MS-HRM) in 100 patients with laryngeal SCC and studied the correlations with clinical characteristics.

RESULTS

The prevalence of promoter methylation in MGMT, CDKN2A, MLH1, and DAPK was 59 of 97 (60.8%), 46 of 97 (47.4%), 45 of 97 (46.4%), and 41 of 97 patients (42.3%), respectively. Significantly increased methylation of CDKN2A was observed in heavy smokers. Epigenetic inactivation of CDKN2A and MLH1 were found to be associated with lymph node involvement. An inverse correlation was present between MLH1 methylation and alcohol consumption.

CONCLUSION

Our results strongly suggest that deregulation of p16-associated, and MLH1-associated pathways, because of promoter hypermethylation, is associated with increased cancer cell migration, tumor invasiveness, and, thus, aggressive phenotype.

Methylation pattern of THBS1, GATA-4, and HIC1 in pediatric and adult patients infected with Helicobacter pylori

BACKGROUND

Helicobacter pylori infection is usually acquired in childhood and persists into adulthood if untreated. The bacterium induces a chronic inflammatory response, which is associated with epigenetic alterations in oncogenes, tumor-suppressor genes, cell-cycle regulators, and cell-adhesion molecules.

AIM

The aim of this study was to analyze the effect of H. pylori infection on the methylation status of Thrombospondin-1 (THBS1), Hypermethylated in cancer 1 (HIC1) and Gata binding protein-4 (GATA-4) in gastric biopsy samples from children and adults infected or uninfected with the bacterium and in samples obtained from gastric cancer patients.

METHODS

The methylation pattern was analyzed with methylation-specific PCR.

RESULTS

Our results showed that H. pylori infection was associated with methylation of the promoter regions of the THBS1 and GATA-4 genes in pediatric and adult samples (p < 0.01). HIC1 showed the lowest level of methylation, which was not an early event during gastric carcinogenesis.

CONCLUSIONS

The results from this study indicate that methylation of THBS1 and GATA-4 occurs in the early stages of chronic gastritis and gastric cancer in association with H. pylori infection; however, in gastric cancer samples, other mechanisms cooperate with the down-regulation of these genes. Methylation of HIC1 may not be the principal mechanism implicated in its down-regulation in gastric cancer samples.

Interleukin polymorphisms and differential methylation status in gastric cancer: an association with Helicobacter pylori infection

AIM

Interleukin polymorphisms and Helicobacter pylori infection are believed to play critical roles in DNA methylation, a process frequently associated with carcinogenesis. The aim of this study was to determine the associations between interleukin polymorphisms and methylation status of three genes related to gastric cancer. Furthermore, the influence of the H. pylori strains was evaluated.

MATERIALS & METHODS

75 gastric tumor samples had the DNA extracted for interleukin polymorphisms genotyping by PCR-RFLP, promoter methylation by MS-PCR and detection and subtyping of H. pylori by PCR.

RESULTS

In the cardia tumors, methylation in the COX-2 promoter was associated with IL1RN*2 (p = 0.015), and the associated genotypes IL1B511T + IL1RN*2 seem to be important in the methylation of COX-2 (p = 0.013), especially in the presence of cagA(+) (p = 0.026) and vacAs1 (p = 0.025) H. pylori strains. The associated genotypes IL6 CC+TNF GG seem to be involved in the unmethylation of CDKN2A (p = 0.046), along with H. pylori cagA(+) infection.

CONCLUSION

DNA methylation in gastric cancer seems to be influenced by the presence of interleukin polymorphisms and by the H. pylori cagA/vacAs1m1 strains.

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.

Intake of soy products and other foods and gastric cancer risk: a prospective study

Background

Gastric cancer, the most common cancer in the world, is affected by some foods or food groups. We examined the relationship between dietary intake and stomach cancer risk in the Korean Multi-Center Cancer Cohort (KMCC).

Methods

The KMCC included 19 688 Korean men and women who were enrolled from 1993 to 2004. Of those subjects, 9724 completed a brief 14-food frequency questionnaire at baseline. Through record linkage with the Korean Central Cancer Registry and National Death Certificate databases, we documented 166 gastric cancer cases as of December 31, 2008. Cox proportional hazard models were used to estimate relative risks (RRs) and 95% CIs.

Results

Frequent intake of soybean/tofu was significantly associated with reduced risk of gastric cancer, after adjustment for age, sex, cigarette smoking, body mass index, alcohol consumption, and area of residence (P for trend = 0.036). We found a significant inverse association between soybean/tofu intake and gastric cancer risk among women (RR = 0.41, 95% CI: 0.22–0.78). Men with a high soybean/tofu intake had a lower risk of gastric cancer, but the reduction was not statistically significant (RR = 0.77, 95% CI: 0.52–1.13). There was no interaction between soybean/tofu intake and cigarette smoking in relation to gastric cancer risk (P for interaction = 0.268).

Conclusions

Frequent soybean/tofu intake was associated with lower risk of gastric cancer.

Towards incorporating epigenetic mechanisms into carcinogen identification and evaluation

Remarkable progress in the field of epigenetics has turned academic, medical and public attention to the potential applications of these new advances in medicine and various fields of biomedical research. The result is a broader appreciation of epigenetic phenomena in the a etiology of common human diseases, most notably cancer. These advances also represent an exciting opportunity to incorporate epigenetics and epigenomics into carcinogen identification and safety assessment. Current epigenetic studies, including major international sequencing projects, are expected to generate information for establishing the 'normal' epigenome of tissues and cell types as well as the physiological variability of the epigenome against which carcinogen exposure can be assessed. Recently, epigenetic events have emerged as key mechanisms in cancer development, and while our search of the Monograph Volume 100 revealed that epigenetics have played a modest role in evaluating human carcinogens by the International Agency for Research on Cancer (IARC) Monographs so far, epigenetic data might play a pivotal role in the future. Here, we review (i) the current status of incorporation of epigenetics in carcinogen evaluation in the IARC Monographs Programme, (ii) potential modes of action for epigenetic carcinogens, (iii) current in vivo and in vitro technologies to detect epigenetic carcinogens, (iv) genomic regions and epigenetic modifications and their biological consequences and (v) critical technological and biological issues in assessment of epigenetic carcinogens. We also discuss the issues related to opportunities and challenges in the application of epigenetic testing in carcinogen identification and evaluation. Although the application of epigenetic assays in carcinogen evaluation is still in its infancy, important data are being generated and valuable scientific resources are being established that should catalyse future applications of epigenetic testing.

CYP2E1 RsaI/PstI polymorphism and gastric cancer susceptibility: meta-analyses based on 24 case-control studies

Background

Previous reports implicate CYP2E1 RsaI/PstI polymorphism as a possible risk factor for several cancers. Published studies on the relationship of CYP2E1 RsaI/PstI polymorphisms with the susceptibility to gastric cancer are controversial. This study aimed to determine this relationship accurately.

Methods

Meta-analyses that assessed the association of CYP2E1 RsaI/PstI variations with gastric cancer were conducted. Subgroup analyses on ethnicity, smoking status, alcohol consumption, and source of controls were also performed. Eligible studies up to Mar 2012 were identified.

Results

After rigorous searching and screening, 24 case-control studies comprising 3022 cases and 4635 controls were selected for analysis. The overall data failed to indicate the significant associations of CYP2E1 RsaI/PstI polymorphisms with the gastric cancer risk [c2 vs. c1: odds ratio (OR) = 1.06; 95% confidence interval (CI) = 0.88–1.28; c2c2 vs. c1c1: OR = 1.23; 95% CI = 0.78–1.92; c2c2+c1c2 vs. c1c1: OR = 0.93; 95% CI = 0.79–1.10]. Similar results were observed in the subgroup analyses on ethnicity, drinking status, and source of controls. However, in the subgroup analysis on smoking status, a borderline increase in cancer risk was found among long-term smokers (c2c2+c1c2 vs. c1c1: OR = 1.39; 95% CI = 1.00–1.92).

Conclusion

CYP2E1 RsaI/PstI polymorphisms may modify the susceptibility to gastric cancer among individuals who have a smoking history. Large and well-designed studies are needed to confirm this conclusion.

Association between p16, hMLH1 and E-cadherin promoter hypermethylation and intake of local hot salted tea and sun-dried foods in Kashmiris with gastric tumors

The aim of this study was to evaluate the methylation status of three important cancer related genes viz. p16, E-cadherin and hMLH1 promoters and to associate the findings with specific dietary habits in Kashmiris, a culturally distinct population in India, with gastric cancer. The study subjects were divided into three age groups viz. 0-30 yrs (1st), 31-60 yrs (2nd) and 61-90 yrs (3rd). A highly significant association between the intake of local hot salted tea in 2nd (p=0.001) and 3rd (p=0.009) age groups was observed with the promoter hypermethylation of E cadherin. Again a highly significant association between the aberrant methylation of hMLH1 (p=0.000) and p16 (p=0.000) promoters and the intake of local hot salted tea was observed in the 2nd age group of gastric cancer patients. The intake of sun-dried food was also significantly associated with the promoter hypermethylation of E cadherin (p=0.003) and p16 (p=0.015) genes in 3rd age group. The results of the present study suggest a close association between the aberrant methylation of p16, E-cadherin and hMLH1 promoters and the intake of local hot salted tea and sun-dried foods in Kashmiri population.

Environmental epigenetics: prospects for studying epigenetic mediation of exposure-response relationships

Changes in epigenetic marks such as DNA methylation and histone acetylation are associated with a broad range of disease traits, including cancer, asthma, metabolic disorders, and various reproductive conditions. It seems plausible that changes in epigenetic state may be induced by environmental exposures such as malnutrition, tobacco smoke, air pollutants, metals, organic chemicals, other sources of oxidative stress, and the microbiome, particularly if the exposure occurs during key periods of development. Thus, epigenetic changes could represent an important pathway by which environmental factors influence disease risks, both within individuals and across generations. We discuss some of the challenges in studying epigenetic mediation of pathogenesis and describe some unique opportunities for exploring these phenomena.

Meta-analysis of the association of CYP1A1 polymorphisms with gastric cancer susceptibility and interaction with tobacco smoking

The association of two cytochrome P4501A1 (CYP1A1) polymorphisms, m1 (T6235C transition) and m2 (A4889G transition), with gastric cancer risk is inconclusive. We conducted a meta-analysis of all available studies to evaluate the potential role of the polymorphisms and their interactions with tobacco smoking in gastric cancer susceptibility. Published literature from PubMed was retrieved by two investigators independently. Fourteen case-control studies with 2,032 gastric cancer cases and 5,099 controls were selected. A fixed effects model or a random-effects model was used to estimate the odds ratio (OR) for the CYP1A1 polymorphisms and the occurrence of gastric cancer. Significant associations between CYP1A1 m1 and m2 polymorphisms and gastric cancer susceptibility were not observed in all genetic models in the overall analyses. Subgroup analyses by ethnicity and source of controls did not reveal significant associations with gastric cancer risk. Stratification analysis by smoking status found that carriers of the heterozygous and homozygous m1 genotypes decreased the susceptibility of gastric cancer among ever-smokers (pooled OR = 0.56, 95 % CI 0.36-0.89, fixed effects). In contrast, the m2 genotypes (G/G and A/G) did not show any relevance to gastric cancer risk among the smoking population (pooled OR = 1.30, 95 % CI 0.84-2.00, fixed effects). Overall, we found that the CYP1A1 polymorphism itself, either m1 or m2, did not represent an independent genetic risk factor influencing gastric cancer. However, subgroup analyses suggest that carriers of the heterozygous and homozygous m1 genotype who are exposed to tobacco smoke have a significantly lower risk of developing gastric cancer. To explain the observed reduction of gastric cancer risk, we proposed a novel hypothesis of "observation bias". This hypothesis is also applicable to explain the combined effects of other genetic polymorphisms and environmental factors on the risk of developing cancers, and the rationality of the hypothesis needs to be further investigated.

Environmentally induced epigenetic transgenerational inheritance of phenotype and disease

Environmental epigenetics has an important role in regulating phenotype formation or disease etiology. The ability of environmental factors and exposures early in life to alter somatic cell epigenomes and subsequent development is a critical factor in how environment affects biology. Environmental epigenetics provides a molecular mechanism to explain long term effects of environment on the development of altered phenotypes and "emergent" properties, which the "genetic determinism" paradigm cannot. When environmental factors permanently alter the germ line epigenome, then epigenetic transgenerational inheritance of these environmentally altered phenotypes and diseases can occur. This environmental epigenetic transgenerational inheritance of phenotype and disease is reviewed with a systems biology perspective.

Environmentally induced epigenetic transgenerational inheritance of ovarian disease

The actions of environmental toxicants and relevant mixtures in promoting the epigenetic transgenerational inheritance of ovarian disease was investigated with the use of a fungicide, a pesticide mixture, a plastic mixture, dioxin and a hydrocarbon mixture. After transient exposure of an F0 gestating female rat during embryonic gonadal sex determination, the F1 and F3 generation progeny adult onset ovarian disease was assessed. Transgenerational disease phenotypes observed included an increase in cysts resembling human polycystic ovarian disease (PCO) and a decrease in the ovarian primordial follicle pool size resembling primary ovarian insufficiency (POI). The F3 generation granulosa cells were isolated and found to have a transgenerational effect on the transcriptome and epigenome (differential DNA methylation). Epigenetic biomarkers for environmental exposure and associated gene networks were identified. Epigenetic transgenerational inheritance of ovarian disease states was induced by all the different classes of environmental compounds, suggesting a role of environmental epigenetics in ovarian disease etiology.

Implication of microsatellite instability in human gastric cancers

Microsatellite instability, one of the phenomena implicated in gastric cancer, is mainly associated with the expansion or contraction of microsatellite sequences due to replication errors caused most frequently by mutations in the mismatch repair (MMR) and tumour suppressor genes. Tumours exhibiting microsatellite instability are proven to have truncated products resulting from frequent mutations in mononucleotide or dinucleotide runs in coding and non-coding regions of the targeted genes. Epigenetic changes like hypermethylation of the promoter region of MMR genes as well as gene silencing are also responsible for the microsatellite instability phenotypes. Assessing microsatellite instability in tumours has proved to be an efficient tool for the prognosis of various cancers including colorectal and gastric cancers. Such tumours are characterized by distinct clinicopathological profiles. Biotic agents like Epstein Barr Virus and H. pylori along with other factors like family history, diet and geographical location also play an important role in the onset of gastric carcinogenesis. Instability of mitochondrial DNA has also been investigated and claimed to be involved in the occurrence of gastric cancers in humans. Development of simplified but robust and reproducible microsatellite instability based molecular tools promises efficient prognostic assessment of gastric tumours.

Quantitative assessment of the associations between CYP1A1 polymorphisms and gastric cancer risk

A great number of studies regarding the association between MspI and Ile462Val polymorphisms in the CYP1A1 gene and gastric cancer have been published. However, the results have been inconsistent. In this study, a meta-analysis was performed to investigate the associations. Published literature from PubMed, ISI Web of Science and other Chinese databases were searched for eligible publications. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random or fixed effect model. Nine studies (860 cases/2183 controls) for CYP1A1 MspI polymorphism and nine studies (1161 cases/3273 controls) for CYP1A1 Ile462Val polymorphism were included in this meta-analysis. MspI polymorphism was not associated with gastric cancer risk (dominant model, OR = 0.95, 95%CI 0.80-1.14; recessive model, OR = 1.01, 95%CI 0.76-1.35; CC vs. TT, OR = 1.03, 95%CI 0.76-1.41; TC vs. TT, OR = 0.95, 95%CI 0.78-1.15). Similarly, there was no association between Ile462Val polymorphism and gastric cancer risk (dominant model, OR = 0.93, 95%CI 0.79-1.10; recessive model, OR = 1.34, 95%CI 0.90-2.00; GG vs. AA, OR = 1.27, 95%CI 0.84-1.90; AG vs. AA, OR = 0.87, 95%CI 0.71-1.07). In the subgroup analysis, no significant association was found in ever smokers, never smokers, Asians and Caucasians. This meta-analysis suggested that there were no associations between CYP1A1 polymorphisms and gastric cancer.

Promoter methylation of MGMT, MLH1 and RASSF1A tumor suppressor genes in head and neck squamous cell carcinoma: pharmacological genome demethylation reduces proliferation of head and neck squamous carcinoma cells

Promoter hypermethylation of tumor suppressor genes (TSGs) is a common feature of primary cancer cells. However, to date the somatic epigenetic events that occur in head and neck squamous cell carcinoma (HNSCC) tumorigenesis have not been well-defined. In the present study, we analyzed the promoter methylation status of the genes mutL homolog 1 (MLH1), Ras-association domain family member 1 (RASSF1A) and O-6-methylguanine-DNA methyltransferase (MGMT) in 23 HNSCC samples, three control tissues and one HNSCC cell line (UM-SCC 33) using methylation-specific PCR (MSP). The expression of the three proteins was quantified by semi-quantitative immunohistochemical analysis. The cell line was treated with the demethylating agent 5-azacytidine (5-Aza) and the methylation status after 5-Aza treatment was analyzed by MSP and DNA sequencing. Proliferation was determined by Alamar blue staining. We found that the MGMT promoter in 57% of the analyzed primary tumor samples and in the cell line was hypermethylated. The MLH promoter was found to be methylated in one out of 23 (4%) tumor samples while in the examined cell line the MLH promoter was unmethylated. The RASSF1A promoter showed methylation in 13% of the tumor samples and in the cell line. MGMT expression in the group of tumor samples with a hypermethylated promoter was statistically significantly lower compared to the group of tumors with no measured hypermethylation of the MGMT promoter. After treatment of the cell line with the demethylating agent 5-Aza no demethylation of the methylated MGMT and RASSF1A genes were determined by MSP. DNA sequencing verified the MSP results, however, increased numbers of unmethylated CpG islands in the promoter region of MGMT and RASSF1A were observed. Proliferation was significantly (p<0.05) reduced after treatment with 5-Aza. In summary, we have shown promoter hypermethylation of the tumor suppressor genes MGMT and RASSF1A in HNSCC, suggesting that this epigenetic inactivation of TSGs may play a role in the development of HNSCC. 5-Aza application resulted in partial demethylation of the MGMT and RASSF1A TSGs and reduced proliferation of the tumor cells suggesting further evaluation of 5-Aza for HNSCC treatment.

Functional PstI/RsaI polymorphism in CYP2E1 is associated with the development, progression and poor outcome of gastric cancer

BACKGROUND

Cytochrome P450 2E1 (CYP2E1), an ethanol-inducible enzyme, has been shown to metabolically activate various carcinogens, which is critical for the development and progression of cancers. It has demonstrated that CYP2E1 polymorphisms alter the transcriptional activity of the gene. However, studies on the association between CYP2E1 polymorphisms (PstI/RsaI or DraI) and gastric cancer have reported conflicting results. Thus, the aim of the present study was to investigate whether CYP2E1 polymorphisms is associated with the development and progression of gastric cancer and its prognosis in Chinese patients.

METHODS

A case-control study was conducted in which CYP2E1 PstI/RsaI and DraI polymorphisms were analyzed in 510 Chinese patients with gastric cancer and 510 age- and sex- matched healthy controls by PCR-RFLP. Odds ratios were estimated by multivariate logistic regression, and the lifetime was calculated by Kaplan-Meier survival curves. In addition, a meta-analysis was also conducted to verify the findings.

RESULTS

For CYP2E1 PstI/RsaI polymorphism, C2C2 homozygotes (OR = 2.15; CI: 1.18-3.94) and C2 carriers (OR = 1.48; CI: 1.13-1.96) were associated with an increased risk of gastric cancer when compared with C1C1 homozygotes. Both C1C2 and C2C2 genotypes were associated with advanced stage, but not the grade of gastric cancer. Moreover, C2C2 genotype was identified as an independent marker of poor overall survival for gastric cancer. However, there was not any significant association between CYP2E1 DraI polymorphism and the risk of gastric cancer. In the meta-analysis, pooled data from 13 studies confirmed that the CYP2E1 PstI/RsaI polymorphism was associated with a significantly increased risk of gastric cancer.

CONCLUSION

CYP2E1 PstI/RsaI polymorphism is associated with increased risk of development, progression and poor prognosis of gastric cancer in Chinese patients. Pooled data from 13 studies, mainly in Asian countries, are in agreement with our findings.

Blood leukocyte Alu and LINE-1 methylation and gastric cancer risk in the Shanghai Women's Health Study

Background:

Recent data suggest a link between blood leukocyte DNA methylation, and cancer risk. However, reports on DNA methylation from a prospective study are unavailable for gastric cancer.

Methods:

We explored the association between methylation in pre-diagnostic blood leukocyte DNA and gastric cancer risk in a case–control study nested in the prospective Shanghai Women's Health Study cohort. Incident gastric cancer cases (n=192) and matched controls (n=384) were included in the study. Methylation of Alu and long interspersed nucleotide elements (LINE)-1 were evaluated using bisulphite pyrosequencing. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated from logistic regression adjusting for potential confounders.

Results:

Alu methylation was inversely associated with gastric cancer risk, mainly among cases diagnosed one or more years after blood collection. After excluding cases diagnosed during the first year of follow-up, the ORs for the third, second, and first quartiles of Alu methylation compared with the highest quartile were 2.43 (1.43–4.13), 1.47(0.85–2.57), and 2.22 (1.28–3.84), respectively. This association appeared to be modified by dietary intake, particularly isoflavone. In contrast, LINE-1 methylation levels were not associated with gastric cancer risk.

Conclusion:

Evidence from this prospective study is consistent with the hypothesis that DNA hypomethylation in blood leukocytes may be related to cancer risk, including risk of gastric cancer.

On the role of autophagy in human diseases: a gender perspective

Cytopathological features of cells from males and females, i.e. XX and XY isolated cells, have been demonstrated to represent a key variable in the mechanism underlying gender disparity in human diseases. Major insights came from the studies of gender differences in cell fate, e.g. in apoptotic susceptibility. We report here some novel insights recently emerged from literature that are referred as to a cytoprotection mechanism by which cells recycle cytoplasm and dispose of excess or defective organelles, i.e. autophagy. Autophagy and related genes have first been identified in yeast. Orthologue genes have subsequently been found in other organisms, including human beings. This stimulated the research in the field and, thanks to the use of molecular genetics and cell biology in different model systems, autophagy gained the attention of several research groups operating to analyse the pathogenetic mechanisms of human diseases. It remains unclear, however, whether autophagy can exert a protective effect or instead contribute to the pathogenesis of important human diseases. On the basis of the growing importance of sex/gender as key determinant of human pathology and of the known differences between males and females in the onset, progression, drug susceptibility and outcome of a plethora of diseases, the idea that autophagy could represent key and critical factor should be taken into account. In the review, we summarize our current knowledge about the role of autophagy in some paradigmatic human diseases (cancer, neurodegenerative, autoimmune, cardiovascular) and the role of ‘cell sex’ differences in this context.

Inactivation of the putative suppressor gene DOK1 by promoter hypermethylation in primary human cancers

The DOK1 gene is a putative tumour suppressor gene located on the human chromosome 2p13 which is frequently rearranged in leukaemia and other human tumours. We previously reported that the DOK1 gene can be mutated and its expression down-regulated in human malignancies. However, the mechanism underlying DOK1 silencing remains largely unknown. We show here that unscheduled silencing of DOK1 expression through aberrant hypermethylation is a frequent event in a variety of human malignancies. DOK1 was found to be silenced in nine head and neck cancer (HNC) cell lines studied and DOK1 CpG hypermethylation correlated with loss of gene expression in these cells. DOK1 expression could be restored via demethylating treatment using 5-aza-2'deoxycytidine. In addition, transduction of cancer cell lines with DOK1 impaired their proliferation, consistent with the critical role of epigenetic silencing of DOK1 in the development and maintenance of malignant cells. We further observed that DOK1 hypermethylation occurs frequently in a variety of primary human neoplasm including solid tumours (93% in HNC, 81% in lung cancer) and haematopoietic malignancy (64% in Burkitt's lymphoma). Control blood samples and exfoliated mouth epithelial cells from healthy individuals showed a low level of DOK1 methylation, suggesting that DOK1 hypermethylation is a tumour specific event. Finally, an inverse correlation was observed between the level of DOK1 gene methylation and its expression in tumour and adjacent non tumour tissues. Thus, hypermethylation of DOK1 is a potentially critical event in human carcinogenesis, and may be a potential cancer biomarker and an attractive target for epigenetic-based therapy.

Aberrant CpG island hypermethylation in pediatric gastric mucosa in association with Helicobacter pylori infection

CONTEXT

Helicobacter pylori infection is primarily acquired during childhood and persists throughout life in the absence of eradication with antibiotics. Helicobacter pylori infection induces methylation in the promoter CpG island loci in gastric epithelial cells. Thus, aberrant CpG island hypermethylation in gastric epithelial cells likely occurs early in life, although there are no existing data supporting this notion.

OBJECTIVES

To identify whether aberrant CpG island hypermethylation occurs in pediatric stomach mucosa in association with H pylori infection and to compare methylation profiles of samples from pediatric and adult stomach tissues.

DESIGN

We analyzed pediatric (n = 47) and adult (n = 38) gastric mucosa samples for their methylation status in 12 promoter CpG island loci using the MethyLight assay and compared the number of methylated genes and the methylation levels in individual genes between H pylori -positive and H pylori -negative sample results and between pediatric and adult samples.

RESULTS

The average number of methylated genes was significantly higher in H pylori -infected pediatric samples than in H pylori -negative pediatric samples (3.4 versus 0.3, P < .001) and in H pylori -infected adult samples than in H pylori -negative adult samples (7.6 versus 0.9, P < .001). Seven genes showed significantly higher methylation levels in H pylori -infected pediatric samples than in H pylori -negative pediatric samples (all values were P < .05).

CONCLUSIONS

These results indicate that CpG island hypermethylation occurs in pediatric gastric mucosa in association with H pylori infection and that the genes affected by H pylori -associated hypermethylation were similar in pediatric and adult samples.

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.

Hypermethylation of carcinogen metabolism genes, CYP1A1, CYP2A13 and GSTM1 genes in head and neck cancer

OBJECTIVES

To investigate the role of aberrant hypermethylation of carcinogen metabolism pathway genes, CYP1A1, CYP2A13 and GSTM1 in head and neck cancer independently as well as its relation to tobacco and alcohol consumption and CYP1A1 and CYP2A13 polymorphisms in Indian population.

METHODS

  Seventy-three histologically confirmed head and neck cancer patients undergoing treatment in Postgraduate Institute of Medical Education and Research, Chandigarh, India were recruited. Non-cancerous tissues were obtained from 19 trauma subjects undergoing maxillofacial surgery. Methylation-specific PCR was performed to determine the methylation status of selected genes.

RESULTS

The aberrant hypermethylation of CYP1A1, CYP2A13 and GSTM1 genes was found in cancer tissues with frequency of about 39.7%, 27.4%, and 58.1%, respectively, and in normal healthy tissues with a frequency of about 10.5%, 15.8%, and 20.0%, respectively. Hypermethylation of CYP1A1 (P 0.027) and GSTM1 (P 0.010) showed significant association with head and neck cancer. We also observed significant interaction between smoking and methylation status of CYP1A1 (P 0.029) and CYP2A13 (P -0.034) in head and neck cancer. No association was observed between methylation status and alcohol consumption, clinical features and genetic polymorphisms of CYP1A1 and CYP2A13.

CONCLUSIONS

  Hypermethylation of carcinogen metabolism pathway genes independently and in interaction with smoking is associated with increased risk of head and neck cancer.

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.

DNA methylation of cancer genome

DNA methylation plays an important role in regulating normal development and carcinogenesis. Current understanding of the biological roles of DNA methylation is limited to its role in the regulation of gene transcription, genomic imprinting, genomic stability, and X chromosome inactivation. In the past 2 decades, a large number of changes have been identified in cancer epigenomes when compared with normals. These alterations fall into two main categories, namely, hypermethylation of tumor suppressor genes and hypomethylation of oncogenes or heterochromatin, respectively. Aberrant methylation of genes controlling the cell cycle, proliferation, apoptosis, metastasis, drug resistance, and intracellular signaling has been identified in multiple cancer types. Recent advancements in whole-genome analysis of methylome have yielded numerous differentially methylated regions, the functions of which are largely unknown. With the development of high resolution tiling microarrays and high throughput DNA sequencing, more cancer methylomes will be profiled, facilitating the identification of new candidate genes or ncRNAs that are related to oncogenesis, new prognostic markers, and the discovery of new target genes for cancer therapy.

Chemosensitivity and survival in gastric cancer patients with microsatellite instability

INTRODUCTION

Conflicting data exist regarding the relevance of high-frequency microsatellite instability (MSI-H) for predicting the prognosis and benefits of 5-fluorouracil (5-FU)-based chemotherapy. This study investigated the usefulness of MSI as either a prognostic indicator or predictor of distinct clinical attributes regarding the use of adjuvant chemotherapy with 5-FU and its analogues in gastric cancer.

MATERIALS AND METHODS

Data and tumor specimens were collected from 240 gastric cancer patients from 1993 to 2002. Five microsatellite loci were analyzed using a high-intensity microsatellite analysis reported previously. A Cox proportional hazard model was used to compare the clinical data and survival as well as any associations between MSI and 5-FU treatment status of patients with MSI or microsatellite stability (MSS) gastric cancers. A 3-(4,5-dimethyl-2-thiazolyl) -2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was conducted in 168 cases to investigate chemosensitivity to 5-FU.

RESULTS

This analysis identified 22 MSI-H (9.4%), 25 MSI-L (10.7%), and 193 MSS (79.9%) tumors. Gastric cancer with MSI-H tended to have increased likelihood to show higher age, antral location of the tumor, and lymph vessel involvement (P < 0.05). Univariate analyses failed to show any difference between the MSI-H and MSS/MSI-L groups with respect to overall survival. Furthermore, survival after the administration of 5-FU did not correlate with MSI status, and MSI was not associated with 5-FU sensitivity by MTT assay.

CONCLUSION

The results of this study indicate that MSI status has no clear influence on overall survival or response to 5-FU in gastric cancer.

Cell proliferation-related genetic polymorphisms and gastric cancer risk: systematic review and meta-analysis

Apart from Helicobacter pylori infection and lifestyle factors, host genetic susceptibility has been suggested to contribute to individual variation in gastric cancer risk as well. Aiming to evaluate the associations between host cell proliferation-related genetic polymorphisms and gastric cancer susceptibility, we reviewed the related studies published until 15 September 2008 and quantitatively summarized the associations of the most widely studied polymorphisms (TP53 Arg72Pro, L-myc EcoRI) using meta-analysis. Fifty-five eligible studies were included in this review. Twenty-three polymorphisms significantly related to gastric cancer risk in at least one study were identified. Polymorphisms determining higher levels of growth factors, which are important for tissue repair, were recently observed to be associated with reduced risk of gastric cancer. In the meta-analysis, TP53 72Pro was associated with increased risk of diffuse gastric cancer among Asians (OR, 1.44; 95% CI, 1.04-1.99), but decreased risk of intestinal gastric cancer among Caucasians (OR, 0.56; 95% CI, 0.36-0.89). This review suggests that cell proliferation-related genetic polymorphisms could be candidate biomarkers of gastric cancer risk, but current evidence for the use for risk stratification is still very limited. Modestly significant associations in meta-analyses stratified by population or type of gastric cancer may be observed by chance because of the limited number of studies and small sample size. Larger studies are warranted to clarify the effect of cell proliferation-related genetic polymorphisms on gastric carcinogenesis.

Molecular epidemiology of genetic susceptibility to gastric cancer: focus on single nucleotide polymorphisms in gastric carcinogenesis

Gastric cancer is a disease of gene-environment interactions, as suggested by the varying geographic patterns of its incidence. Even in areas with high rates of Helicobacter pylori infection, only a small proportion of infected individuals develop gastric cancer. Genetic susceptibility to gastric cancer can be investigated by common genetic variants, such as single nucleotide polymorphisms (SNPs), in various genes that regulate multiple biological pathways. The susceptibility to gastric carcinogenesis has a substantial influence on the population attributable risk by modulating the effects of environmental risk factors. Despite recent progress in the field of the molecular epidemiology of cancer, a re-evaluation of gastric cancer susceptibility and potentially functional SNPs in candidate genes is necessary, given the inconsistency of previous reported studies. This review focuses on genetic variants that contribute to the etiology of gastric cancer, particularly those SNPs involved in inflammatory response, metabolism of chemical carcinogens, DNA repair, and tumor suppression. In the future, well-designed large multicenter population-based studies will be needed to validate current findings and provide the rationale for identifying at-risk subpopulations for primary prevention of gastric cancer.

Aberrant methylation of p16 predicts candidates for 5-fluorouracil-based adjuvant therapy in gastric cancer patients

BACKGROUND

Aberrant methylation of some cancer-related genes has been reported to correlate with sensitivity to chemotherapeutic agents. The present study was designed to determine whether DNA methylation in six cancer-related genes affects recurrence of gastric cancer in patients who received 5-fluorouracil-based adjuvant chemotherapy.

METHODS

The methylation status of six genes, MGMT, CHFR, hMLH1, p16INK4a, E-cadherin, and Runx3, was analyzed in 56 surgically resected gastric cancer tissue specimens by methylation-specific polymerase chain reaction. Of the 56 patients who underwent surgical resection, 38 received 5-fluorouracil (5-FU)-based adjuvant chemotherapy postoperatively (adjuvant group), whereas the other 18 (32%) did not (surgery group).

RESULTS

There were no significant differences between the two groups with respect to sex, cancer differentiation, depth of tumor invasion, lymph node metastasis, lymphatic invasion, vascular invasion and tumor stage. Among the genes, methylation of p16INK4a showed a significant correlation with longer survival in the 38 patients of the adjuvant group, but not in the 18 patients of the surgery group. A multivariate analysis identified p16INK4a methylation to be an independent factor predicting a longer recurrence-free period under 5-FU-based adjuvant chemotherapy.

CONCLUSIONS

The present study demonstrated for the first time that gastric cancer patients with p16INK4a methylation specifically benefit from 5-FU-based adjuvant chemotherapy.

Relationship between Helicobacter pylori and DNA mismatch repair system

Helicobacter pylori infection causes the defect of mismatch repair (MMR) in eucaryotes, and microsatellite instability (MSI) in gastric epithelial cells, which increases the spontaneous mutation of relative genes, and finally results in the susceptibility to tumors in human bodies. DNA MMR can prevent the excessive proliferation of mutant cells and development of tumors by correcting mismatched bases, which occur in the process of duplication and recombination, and inducing apoptosis of the cells in which DNA had been seriously impaired. The majority of the mutation in mismatch repair gene is the gene mutation in which substitution exceeds the absence or insertion of the single basic group. In MMR, hMLH1 and hMSH2 gene are the main controlling genes. Current research showed that H pylori infection might lead to functional defect of MMR, which had played an important role in the development of gastric carcinomas. In this article, we reviewed the correlations between H pylori infection and DNA mismatch repair system.