A functional polymorphism in the DNA methyltransferase-3A promoter modifies the susceptibility in gastric cancer but not in esophageal carcinoma

Oncogenes and tumor suppressor genes: functions and roles in cancers

Cancer, being the most formidable ailment, has had a profound impact on the human health. The disease is primarily associated with genetic mutations that impact oncogenes and tumor suppressor genes (TSGs). Recently, growing evidence have shown that X-linked TSGs have specific role in cancer progression and metastasis as well. Interestingly, our genome harbors around substantial portion of genes that function as tumor suppressors, and the X chromosome alone harbors a considerable number of TSGs. The scenario becomes even more compelling as X-linked TSGs are adaptive to key epigenetic processes such as X chromosome inactivation. Therefore, delineating the new paradigm related to X-linked TSGs, for instance, their crosstalk with autosome and involvement in cancer initiation, progression, and metastasis becomes utmost importance. Considering this, herein, we present a comprehensive discussion of X-linked TSG dysregulation in various cancers as a consequence of genetic variations and epigenetic alterations. In addition, the dynamic role of X-linked TSGs in sex chromosome-autosome crosstalk in cancer genome remodeling is being explored thoroughly. Besides, the functional roles of ncRNAs, role of X-linked TSG in immunomodulation and in gender-based cancer disparities has also been highlighted. Overall, the focal idea of the present article is to recapitulate the findings on X-linked TSG regulation in the cancer landscape and to redefine their role toward improving cancer treatment strategies.

Mast cell degranulation and bradykinin-induced angioedema - searching for the missing link

Initiation of the bradykinin generation cascade is responsible for the occurrence of attacks in some types of angioedema without wheals. Hereditary angioedema due to C1 inhibitor deficiency (HAE-C1-INH) is one such clinical entity. In this paper, we explore the existing evidence that mast cells (MCs) degranulation may contribute to the activation of the kallikrein-kinin system cascade, followed by bradykinin formation and angioedema. We present the multidirectional effects of MC-derived heparin and other polyanions on the major components of the kinin-kallikrein system, particularly on the factor XII activation. Although, bradykinin- and histamine-mediated symptoms are distinct clinical phenomena, they share some common features, such as some similar triggers and a predilection to occur at sites where mast cells reside, namely the skin and mucous membranes. In addition, recent observations indicate a high incidence of hypersensitivity reactions associated with MC degranulation in the HAE-C1-INH patient population. However, not all of these can be explained by IgE-dependent mechanisms. Mast cell-related G protein-coupled receptor-X2 (MRGPRX2), which has recently attracted scientific interest, may be involved in the activation of MCs through a different pathway. Therefore, we reviewed MRGPRX2 ligands that HAE-C1-INH patients may be exposed to in their daily lives and that may affect MCs degranulation. We also discussed the known inter- and intra-individual variability in the course of HAE-C1-INH in relation to factors responsible for possible variability in the strength of the response to MRGPRX2 receptor stimulation. The above issues raise several questions for future research. It is not known to what extent a prophylactic or therapeutic intervention targeting the pathways of one mechanism (mast cell degranulation) may affect the other (bradykinin production), or whether the number of mast cells at a specific body site and their reactivity to triggers such as pressure, allergens or MRGPRX2 agonists may influence the occurrence of HAE-C1-INH attacks at that site.

An updated meta-analysis investigating the association between DNMTs gene polymorphism andgastric cancer risk

Gastric cancer (GC) is a prominent global health issue, as it ranks as the fifth most prevalent type of cancer and the fourth most significant cause of cancer-related mortality worldwide. Although H. pylori is known to play a role in the development of GC, genetic factors also play a role in its onset and progression. Recent studies have shown that genetic polymorphisms are strongly associated with the development of GC and that certain single nucleotide polymorphisms (SNPs) can be used as biomarkers for early diagnosis and prevention. Epigenetic disturbances, such as DNA methylation, are involved in the development of GC, and mutations in the DNA methyltransferase (DNMT) gene have been found to increase the risk of GC. However, previous findings on the association between DNMTs SNPs and GC risk have been inconsistent. In this study, an updated meta-analysis of three well-studied and controversial DNMTs polymorphic loci, DNMT1 rs16999593, DNMT3A rs1550117 and DNMT3B rs1569686, was performed to provide more reliable results. It was found that DNMT1 rs16999593 was not associated with GC, DNMT3A rs1550117 may have a positive association with GC risk, and DNMT3B rs1569686 may be a protective factor for GC. These findings may provide valuable information for early diagnosis and prevention of GC, but further studies are needed to confirm these results.

DNMT3B rs2424913 as a Risk Factor for Congenital Heart Defects in Down Syndrome

Impairments of the genes that encode enzymes that are involved in one-carbon metabolism because of the presence of gene polymorphisms can affect the methylation pattern. The altered methylation profiles of the genes involved in cardiogenesis may result in congenital heart defects (CHDs). The aim of this study was to investigate the association between the MTHFR rs1801133, MTHFR rs1801131, MTRR rs1801394, DNMT1 rs2228611, DNMT3A rs1550117, DNMT3B rs1569686, and DNMT3B rs2424913 gene polymorphisms and congenital heart defects in Down syndrome (DS) individuals. The study was conducted on 350 participants, including 134 DS individuals with CHDs (DSCHD+), 124 DS individuals without CHDs (DSCHD−), and 92 individuals with non-syndromic CHD. The genotyping was performed using the PCR–RFLP method. A statistically significant higher frequency of the DNMT3B rs2424913 TT in the DSCHD+ individuals was observed. The DNMT3B rs2424913 TT genotype, as well as the T allele, had significantly higher frequencies in the individuals with DS and atrial septal defects (ASDs) in comparison with the individuals with DS and other CHDs. Furthermore, our results indicate a statistically significant effect of the DNMT3B rs1569686 TT genotype in individuals with non-syndromic CHDs. The results of the study suggest that the DNMT3B rs2424913 TT genotypes may be a possible predisposing factor for CHDs in DS individuals, and especially those with ASDs.

MDM4: What do we know about the association between its polymorphisms and cancer?

MDM4 is an important p53-negative regulator, consequently, it is involved in cell proliferation, DNA repair, and apoptosis regulation. MDM4 overexpression and amplification are described to lead to cancer formation, metastasis, and poor disease prognosis. Several MDM4 SNPs are in non-coding regions, and some affect the MDM4 regulation by disrupting the micro RNA binding site in 3'UTR (untranslated region). Here, we gathered several association studies with different MDM4 SNPs and populations to understand the relationship between its SNPs and solid tumor risk. Many studies failed to replicate their results regarding different populations, cancer types, and risk genotypes, leading to conflicting conclusions. We suggested that distinct haplotype patterns in different populations might affect the association between MDM4 SNPs and cancer risk. Thus, we propose to investigate some linkage SNPs in specific haplotypes to provide informative MDM4 markers for association studies with cancer.

Significance of the Estrogen Hormone and Single Nucleotide Polymorphisms in the Progression of Breast Cancer among Female

Breast cancer is one of the most frequent types of malignancies among women and is internationally recognized as the main reason for cancer-caused mortality. Most breast tumors are heterogeneous and genetically complicated due to the involvement of several genes. Therefore, it is clinically important to study genetic variants that increase the risk of breast cancer. It is identified that the presence of polymorphisms in genes encoding regulatory hormones is linked to a higher risk of breast cancer. Additionally, circulating estrogen levels are connected to aromatase (CYP19A1) genes, which is a recognized risk factor for breast cancer progression. In this paper, the authors present a review study on the effect of estrogen and its Single Nucleotide Polymorphisms (SNPs) in the occurrence of breast cancer. This review mainly aimed to find out the connection between CYP19A1 gene variations and the risk of breast cancer, as well as its clinical characteristics and prognosis. Due to the highly special activity of the CYP19A1 enzyme in steroid production, suppression of the targeted CYP19A1 is a focused medication for breast cancer patients, which has only minor adverse effects. Numerous clinical trials over the last decade have shown that Aromatase inhibitors (AIs) not only outperform tamoxifen in terms of effectiveness but also have a lower adverse effect profile.  The AI is now widely accepted as a routine therapy option for postmenopausal females with Estrogen receptor-positive (ER+) breast cancer. Furthermore, not only dysregulation of gene expression in different genes related to distinguished pathways, such as estrogen metabolism, is essential in the progression of breast cancer but also particular SNPs can play an essential role in particular genes, such as CYP19A1. Different studies have demonstrated that these SNPs can be located in different sites of these genes, which are collected in this review. In a nutshell, more specific clinical trials are required to demonstrate the precise meditative role of anti-estrogen drugs in the treatment of ER+ breast cancer patients. Furthermore, more genotype analyses are needed to confirm the role of SNPs in the progression of breast cancer.

Evaluation of genetic variants in nucleosome remodeling and deacetylase (NuRD) complex subunits encoding genes and gastric cancer susceptibility

Epigenetic complex NuRD (nucleosome remodeling and deacetylase) engages in a range of basic cellular processes, including chromatin modification. Changes in the activity of NuRD complex can influence gastric cancer progression. Multivariate logistic regression analyses were used to estimate the association between single-nucleotide polymorphisms (SNPs) and gastric cancer risk. Expression quantitative trait loci (eQTL) analysis was used to analyze the relationship between the genotypes and gene expression levels using data from the genotype tissue expression project (GTEx). Gene expression was calculated using databases from The Cancer Genome Atlas (TCGA) and The Gene Expression Omnibus (GEO). Kaplan-Meier plotter was used to evaluate the association between gene expression and survival. SNP rs11064275 T allele in CHD4, rs892022 A allele and rs2033481 A allele in GATAD2A were found to contribute to the decreased risk of gastric cancer. The increase in the number of favorable alleles of these three SNPs was associated with a lower risk of gastric cancer. rs2033481 and rs892022 were substantially correlated with GATAD2A mRNA expression levels. Meanwhile, we detected that the CHD4 and GATAD2A mRNA expression was increased in gastric cancer tissues compared with the adjacent normal tissues. Furthermore, we found that patients with higher CHD4 or GATAD2A mRNA expression level had more advantageous overall survival. Our findings indicated that genetic variants in NuRD complex subunits encoding genes may be promising predictors of gastric cancer risk.

Misregulation of the expression and activity of DNA methyltransferases in cancer

In mammals, DNA methyltransferases DNMT1 and DNMT3's (A, B and L) deposit and maintain DNA methylation in dividing and nondividing cells. Although these enzymes have an unremarkable DNA sequence specificity (CpG), their regional specificity is regulated by interactions with various protein factors, chromatin modifiers, and post-translational modifications of histones. Changes in the DNMT expression or interacting partners affect DNA methylation patterns. Consequently, the acquired gene expression may increase the proliferative potential of cells, often concomitant with loss of cell identity as found in cancer. Aberrant DNA methylation, including hypermethylation and hypomethylation at various genomic regions, therefore, is a hallmark of most cancers. Additionally, somatic mutations in DNMTs that affect catalytic activity were mapped in Acute Myeloid Leukemia cancer cells. Despite being very effective in some cancers, the clinically approved DNMT inhibitors lack specificity, which could result in a wide range of deleterious effects. Elucidating distinct molecular mechanisms of DNMTs will facilitate the discovery of alternative cancer therapeutic targets. This review is focused on: (i) the structure and characteristics of DNMTs, (ii) the prevalence of mutations and abnormal expression of DNMTs in cancer, (iii) factors that mediate their abnormal expression and (iv) the effect of anomalous DNMT-complexes in cancer.

Single nucleotide polymorphisms of whole genes and atrophic gastritis susceptibility:a systematic review and meta-analysis

BACKGROUND

Atrophic gastritis (AG) is one of the important precancerous lesions of gastric cancer. Single nucleotide polymorphisms (SNPs) are closely related to AG susceptibility. However, the research conclusions on the predictive potential of SNPs are inconsistent. The study aims to retrospect the association between SNPs of whole genes and AG risk by meta-analysis.

MATERIALS AND METHODS

Up to April 29, 2020, a systematic literature search for the relationship of SNPs with AG susceptibility was performed utilizing PubMed, Web of Science and Chinese National Knowledge Infrastructure. The overall and stratified meta-analyses on extracted data were conducted by Stata11.2.

RESULTS

33 case-control studies were enrolled containing 9951 AG patients and 17,252 healthy controls, and 17 SNPs in 12 different genes were systematically reviewed. The results indicated that 12 genes could be categorized based on their functions, including immune response, cell proliferation and apoptosis, and DNA damage repair. For the SNPs in immune response-related genes, the C allele of TLR1 rs4833095 T/C increased AG risk to 1.21-fold and the recessive model of TLR4 rs11536878 in the TLR gene family decreased AG susceptibility to 0.48-fold. The variant alleles of IL-10 rs1800871 (OR = 1.21) and IL-8 rs4073 (OR = 1.22) in the IL gene family were positively associated with AG risk. PSCA rs2294008 enhanced AG risk in all genetic models. SNPs associated with AG susceptibility were mainly focused on immune response-related genes.

CONCLUSION

These SNPs related to immune response could influence on AG risk and have potential to be AG predictive biomarkers. It is worth noting that the number of studies for each SNPs were insufficient due to the limited published researches and updated meta-analysis needs to be performed based on extensive relevant studies for more reliable results.

Epigenetic Regulatory Enzymes: mutation Prevalence and Coexistence in Cancers

Epigenetic regulation is an important layer of transcriptional control with the particularity to affect the broad spectrum of genome. Over the years, largely due to the substantial number of recurrent mutations, there have been hundreds of novel driver genes characterized in various cancers. Additionally, the relative contribution of two dysregulated epigenomic entities (DNA methylation and histone modifications) that gradually drive the cancer phenotype remains in the research focus. However, a complex scenario arises when the disease phenotype does not harbor any relevant mutation or an abnormal transcription level. Although the cancer landscape involves the contribution of multiple genetic and non-genetic factors, herein, we discuss specifically the mutation spectrum of epigenetically-related enzymes in cancer. In addition, we address the coexistence of these two epigenetic entities in malignant human diseases, especially cancer. We suggest that the study of epigenetically-related somatic mutations in the early cellular differentiation stage of embryonic development might help to understand their later-staged footprints in the cancer genome. Furthermore, understanding the co-occurrence and/or inverse association of different disease types and redefining the general definition of "healthy" controls could provide insights into the genome reorganization.

Deciphering the genetic code of DNA methylation

DNA methylation plays crucial roles in many biological processes and abnormal DNA methylation patterns are often observed in diseases. Recent studies have shed light on cis-acting DNA elements that regulate locus-specific DNA methylation, which involves transcription factors, histone modification and DNA secondary structures. In addition, several recent studies have surveyed DNA motifs that regulate DNA methylation and suggest potential applications in diagnosis and prognosis. Here, we discuss the current biological foundation for the cis-acting genetic code that regulates DNA methylation. We review the computational models that predict DNA methylation with genetic features and discuss the biological insights revealed from these models. We also provide an in-depth discussion on how to leverage such knowledge in clinical applications, particularly in the context of liquid biopsy for early cancer diagnosis and treatment.

Effect of DNMT3A polymorphisms on CpG island hypermethylation in gastric mucosa

Background

CpG methylation of tumor suppressor genes occurs in the early stage of carcinogenesis. Detecting risk factors for aberrant CpG methylation is clinically important for predicting cancer development. DNA methyltransferase (DNMT) 3a is considered to play critical roles in the DNA methylation process during pathogenesis. In this study, we evaluated the association between DNMT3A polymorphisms (rs6733868 and rs13428812) and CpG methylation status in non-cancerous gastric mucosa.

Methods

We determined the DNMT3A genotype and CpG methylation status of 4 genes (p14^ARF, p16^INK4a, DAPK, and CDH1) in 510 subjects without gastric cancer. Helicobacter pylori (HP) infection status was determined by the rapid urease test, urea breath test, speculum examination, or serum antibody test. We determined the DNMT3A genotype using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). CpG methylation status was determined by methylation-specific polymerase chain reaction (MSP). When the methylated band was stronger than 10 ng/μL according to the DNA marker, we judged CpG island hypermethylation (CIHM) to be present. Associations between genotypes and susceptibilities were assessed by logistic regression analysis.

Results

The minor allele frequencies of both polymorphisms (rs6733868 and rs13428812) were lower in the CpG methylated groups of each of the 4 genes (p14^ARF, p16^INK4a, DAPK, and CDH1). Using a dominant genetic model, rs6733868 was significantly associated with the hypermethylation of each gene, whereas rs13428812 was associated with the methylation of 3 genes (all except p14^ARF). When low-CIHM was defined as 1 or 2 CpG islands methylated and high-CIHM was defined as 3 or more CpG islands methylated, carrying the minor allele of rs6733868 was associated with both decreased low- and high-CIHM, and that of rs13428812 also was associated with a decrease. Comparing low-CIHM with high-CIHM, carrying the minor alleles of rs6733868 or rs13428812 was related to decreased susceptibility to high-CIHM. In HP-infected subjects, carrying the minor alleles of rs6733868 or rs13428812 had a significantly greater association with decreased susceptibility to high-CIHM.

Conclusions

Our study indicates that polymorphisms of DNMT3A are associated with the accumulation of gene methylation in gastric mucosa. Carrying the minor alleles of rs6733868 or rs13428812 inhibits aberrant gene methylations, which are typically enhanced by HP infection.

Evaluating the Possible Association between PD-1 (Rs11568821, Rs2227981, Rs2227982) and PD-L1 (Rs4143815, Rs2890658) Polymorphisms and Susceptibility to Breast Cancer in a Sample of Southeast Iranian Women

INTRODUCTION

Programmed cell death-1 (PD-1) and its ligands (PD-L1 and PD-L2) play a critical role as a  regulator of immune-system cells, including T cell, natural killer T (NKT), monocytes, dendritic cells (DC), and B cells.

OBJECTIVE

This study aimed to find a possible association between PD-1 (rs11568821, rs2227981, rs2227982), and PD-L1 (rs4143815, rs2890658) variants and Breast Cancer (BC) risk in a sample of southeast Iranian women.

METHOD

The case-control study consisted of 520 individuals, including 260 histologically confirmed BC patients and 260 non-cancer age-matching healthy women as the control group. The Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and Tetra-Primer Amplification Refractory Mutation System-Polymerase Chain Reaction (T-ARMS-PCR) methods were used for genotyping of PD-1 (rs11568821, rs2227981, rs2227982), and PD-L1 (rs4143815, rs2890658) polymorphisms.

RESULTS AND CONCLUSION

Our findings indicated that the PD-L1 rs4143815 (G/C) variant meaningfully reduced the risk of BC. However, the PD-L1 rs2890658 variant increased the BC risk in the AC genotype as well as the A allele. Furthermore, we could not find a meaningful association between PD-1 rs11568821, PD-1 rs2227981, PD-1 rs2227982, and BC. Our team examined the possible association between variants and clinicopathological characteristics, including age, size of tumour, lymph node, histology, grade of tumour, estrogen and progesterone receptors status as well as human growth factor receptor 2 (HER2). Our findings demonstrated that PD-L1 rs4143815, PD-L1 rs2890658, PD-1 rs2227982 had a significant association with age. Additionally, we found a significant relation between PD-1 rs2227982 variant and tumour size. Statistical analyzes of PD-1 rs2227981 and PD-1 rs11568821 variants showed a meaningful relation between tumour grade and tumour stage (p=0.006), respectively.<br />.

IKBKB rs2272736 is Associated with Gastric Cancer Survival

Background

IKBKB/IKKβ, as the core catalytic subunit of IκB kinase complex, participates in mediation of the classical NF-κB pathway, which has been linked to inflammation and tumorigenesis. Previous studies have shown that single nucleotide polymorphisms in IKBKB have been related to gastric cancer, but how they associate to the clinical outcome is not yet clear. In this study, we retrospectively investigated the associations between single nucleotide polymorphisms located in IKBKB and gastric cancer survival.

Materials and Methods

IKBKB rs2272736 was genotyped in 1210 patients with primary gastric cancer in a Han Chinese population, and the relationships between rs2272736 and overall survival were evaluated. We conducted Cox proportional hazards regression, which was performed to estimate the effects of single nucleotide polymorphisms on the overall survival of patients, adjusted for potential confounding variables.

Results

We found that patients with rs2272736 A allele in IKBKB had significantly prolonged overall survival time compared to those with the G allele (HR = 0.83, 95% CI = 0.68–1.00, P = 0.050). In addition, AA genotype was demonstrated to have reduced risk of death for gastric cancer compared with that associated with the GG/GA genotypes, which was more common in patients with cardiac carcinoma, well-differentiated and moderately differentiated tumors, TNM Ⅰ/Ⅱ stages and intestinal type.

Conclusion

Our findings have shown that single nucleotide polymorphism rs2272736 in IKBKB may be a promising prognostic biomarker which should promote personalized treatment.

Epigenetic Mechanisms in Gastric Cancer: Potential New Therapeutic Opportunities

Gastric cancer (GC) is one of the deadliest malignancies worldwide. Complex disease heterogeneity, late diagnosis, and suboptimal therapies result in the poor prognosis of patients. Besides genetic alterations and environmental factors, it has been demonstrated that alterations of the epigenetic machinery guide cancer onset and progression, representing a hallmark of gastric malignancies. Moreover, epigenetic mechanisms undergo an intricate crosstalk, and distinct epigenomic profiles can be shaped under different microenvironmental contexts. In this scenario, targeting epigenetic mechanisms could be an interesting therapeutic strategy to overcome gastric cancer heterogeneity, and the efforts conducted to date are delivering promising results. In this review, we summarize the key epigenetic events involved in gastric cancer development. We conclude with a discussion of new promising epigenetic strategies for gastric cancer treatment.

The correlation of combined OGG1, CYP1A1 and GSTP1 gene variants and risk of lung cancer of male Iraqi waterpipe tobacco smokers

Genetic polymorphisms of genes whose products are responsible for activities, such as xenobiotic metabolism, mutagen detoxification and DNA-repair, have been predicted to be associated with the risk of developing lung cancer (LC). The association of LC with tobacco smoking has been extensively investigated, but no studies have focused on the Arab ethnicity. Previously, we examined the association between genetic polymorphisms among Phase I and Phase II metabolism genes and the risk of LC. Here, we extend the data by examining the correlation of OGG1 Ser326Cys combined with CYP1A1 (Ile462Val and MspI) and GSTP1 (Ile105Val and Ala103Val) polymorphisms with the risk of LC. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and gene sequencing were carried out for genotyping the OGG1 polymorphisms of 123 LC patients and 129 controls. No significant differences in the frequencies of the OGG1 mutant allele between patients and controls were found. The distributions of heterozygous Ser/Cys or Cys/Cys genotypes of OGG1 were not associated with the risk of LC either according to the histological types of LC or based on waterpipe tobacco (WP) smoking status. In contrast, the combined effect of OGG1 variants with CYP1A1 and GSTP1 variants revealed a significant correlation with the OGG1 Ser326Cys-CYP1A1 MspI variants pairing. This association was significant (p = 0.001) in individuals who carried homozygous or heterozygous variant type genotypes of both genes in a reference with carriers of both wild-type genotypes (wt/wt - wt/wt). The odds ratios were 2.99 (95% CI 1.67-5.36), 2.68 (95% CI 1.08-6.62), and 2.80 (95% CI 1.18-6.69) for those who carried (wt/wt - wt/vt + vt/vt), (wt/vt + vt/vt - wt/wt), and (wt/vt + vt/vt - wt/vt + vt/vt), respectively. The study suggests a limited correlation is present between carrying OGG1 Ser326Cys polymorphism and the risk of developing LC in Arab populations.

Polymorphisms of genes required for methionine synthesis and DNA methylation influence mitochondrial DNA methylation

Aim: Impaired methylation of the mitochondrial DNA and particularly in the regulatory displacement loop (D-loop) region, is increasingly observed in patients with neurodegenerative disorders. The present study aims to investigate if common polymorphisms of genes required for one-carbon metabolism (MTHFR, MTRR, MTR and RFC-1) and DNA methylation reactions (DNMT1, DNMT3A and DNMT3B) influence D-loop methylation levels. Materials & methods: D-loop methylation data were available from 133 late-onset Alzheimer's disease patients and 130 matched controls. Genotyping was performed with PCR-RFLP or high resolution melting techniques. Results: Both MTRR 66A > G and DNMT3A -448A > G polymorphisms were significantly associated with D-loop methylation levels. Conclusion: This exploratory study suggests that MTRR and DNMT3A polymorphisms influence mitochondrial DNA methylation; further research is required to better address this issue.

Role of MUC1 rs4072037 polymorphism in gastric cancer: a meta-analysis

Background and objective: To further determine the association between mucin 1 (MUC1) rs4072037 polymorphism and gastric cancer risk on the basis of previously published studies. Methodology: PubMed and Embase were used to search all the available publications. The relative risk of the correlation was shown as odds ratio (OR) with 95% confidence interval (95% CI) under all the genetic comparisons. Subgroup analyses based on ethnicity, study design and HWE were also executed to detect effects of specific factors on the risk of gastric cancer. Results: MUC1 rs4072037 polymorphism was observed to reduce the risk of gastric cancer under the five genetic comparisons [(GG versus AA: OR (95% CI)=0.72 (0.61, 0.84); GG + GA versus AA: OR (95% CI)=0.82 (0.76, 0.88); GG versus AA + GA: OR (95% CI)=0.83 (0.71, 0.96); G versus A: OR (95% CI)=0.78 (0.72, 0.84); GA versus AA: OR (95% CI)=0.80 (0.74, 0.87)]. This decreased risk of gastric cancer was also detected in subgroup analyses based on ancestry (Asian and Caucasian), study design (population-based and hospital-based) and HWE (P _HWE>0.05). Conclusions: MUC1 rs4072037 polymorphism may have an important role in gastric cancer, and this protective effect may vary among different ethnic populations and control subjects.

DNMT3B rs1569686 and rs2424913 gene polymorphisms are associated with positive family history of preterm birth and smoking status

AIM

To evaluate the association between spontaneous preterm birth (SPTB) and DNA methyltransferase (DNMT)1, 3A, 3B, and 3L gene polymorphisms, and their contribution to the clinical characteristics of women with SPTB and their newborns.

METHODS

This case-control study, conducted in 2018, enrolled 162 women with SPTB and 162 women with term delivery. DNMT1 rs2228611, DNMT3A rs1550117, DNMT3B rs1569686, DNMT3B rs2424913, and DNMT3L rs2070565 single nucleotide polymorphisms were genotyped using polymerase chain reaction and restriction fragment length polymorphism methods. The clinical characteristics included in the analysis were family history of preterm birth, maternal smoking, maternal age, gestational week at delivery, and fetal birth weight.

RESULTS

DNMT gene polymorphisms were not significantly associated with SPTB. DNMT3B rs1569686 and rs2424913 minor alleles (T) were significantly more frequent in women with familial PTB than in women with non-familial PTB, increasing the odds for familial PTB 3.30 and 3.54 times under dominant genetic models. They were also significantly more frequent in women with SPTB who smoked before pregnancy, reaching the most significant association under additive genetic models (odds ratio 6.86, 95% confidence interval 2.25-20.86, P<0.001; odds ratio 3.77, 95% confidence interval 1.36-10.52, P=0.011, respectively).

CONCLUSIONS

DNMT3B rs1569686 and rs2424913 gene polymorphisms might be associated with positive family history of PTB and smoking status.

Association of genetic polymorphisms in DNMT3A with the progression of gastric mucosal atrophy and susceptibility to gastric cancer in Japan

The aim of the present study was to investigate whether single nucleotide polymorphisms in the DNMT3A gene are associated with susceptibility to gastric cancer in the Japanese population. The present case-control study examined the associations between single nucleotide polymorphisms (rs6733868 and rs13428812) in DNMT3A and cancer susceptibility in 343 patients with gastric cancer and 708 subjects without gastric malignancies on upper gastro-duodenal endoscopy. Of 708 controls, 409 were classified into two groups histologically: 99 cases with and 310 cases without gastric mucosal atrophy. Overall, homozygosity for the DNMT3A rs6733868 minor allele was significantly associated with a reduced risk of gastric cancer (odds ratio [OR], 0.621; 95% confidence interval [CI], 0.402-0.958; P=0.031), especially of the intestinal type (OR, 0.494; 95% CI, 0.274-0.890; P=0.019). In subjects >60 years, rs6733868 minor allele homozygosity was significantly associated with gastric cancer susceptibility. Carriers of the rs6733868 minor allele had a reduced risk of severe gastric mucosal atrophy (OR, 0.495; 95% CI, 0.299-0.826; P=0.0069). In addition, the number of minor alleles of both rs6733868 and rs13428812 was significantly correlated with the risk of Helicobacter pylori (HP) infection (P=0.0070 and P=0.0050, respectively). However, rs13428812 was not associated with severe gastric mucosal atrophy or gastric carcinogenesis. The present results suggest that DNMT3A polymorphisms serve roles in the progression from HP infection to gastric mucosal atrophy and gastric carcinogenesis in terms of degree and manner.

DNA methyltransferases and gastric cancer: insight into targeted therapy

Gastric cancer is a major health problem worldwide occupying most frequent causes of cancer-related mortality. In addition to genetic modifications, epigenetic alterations catalyzed by DNA methyltransferases (DNMTs) are a well-characterized epigenetic hallmark in gastric cancer. The reversible nature of epigenetic alterations and central role of DNA methylation in diverse biological processes provides an opportunity for using DNMT inhibitors to enhance the efficacy of chemotherapeutics. In this review, we discussed key factors or mechanisms such as SNPs, infections and genetic modifications that trigger DNMTs level modification in gastric cancer, and their potential roles in cancer progression. Finally, we focused on how inhibitors of the DNMTs can most effectively be used for the treatment of gastric cancer with multidrug resistance.

Association of five genetic variations in DNMT1 and DNMT3A with gastric cancer in a Chinese population

AIM

To determine whether genetic variations in DNMT1 and DNMT3A could be associated with gastric cancer risk.

MATERIALS & METHODS

A total of 466 patients and 452 healthy controls were enrolled in this study. Genotypes were examined by using the Sequenom MassARRAY platform.

RESULTS

No significant differences in the distribution frequencies were observed between the groups. However, subgroup analysis revealed that, in the group aged ≤60 years, DNMT3A rs13420827 was associated with reduced gastric cancer risk, and that carrier of GC/GG genotype was associated with reduced risk of gastric cancer with low differentiation or at the T3-T4 stage.

CONCLUSION

This study suggests that five genetic variations of interest in DNMT1 and DNMT3A are not associated with the presence of gastric cancer, but that rs13420827 may contribute to the gastric cancer risk for those younger individuals, the risk of which may be influenced by the characteristics of tumor.

DNA methyltransferase 3A isoform b contributes to repressing E-cadherin through cooperation of DNA methylation and H3K27/H3K9 methylation in EMT-related metastasis of gastric cancer

DNA methyltransferase 3A (DNMT3A) has been recognised as a key element of epigenetic regulation in normal development, and the aberrant regulation of DNMT3A is implicated in multiple types of cancers, especially haematological malignancies. However, its clinical significance and detailed functional role in solid tumours remain unknown, although abnormal expression has gained widespread attention in these cancers. Here, we show that DNMT3A isoform b (DNMT3Ab), a member of the DNMT3A isoform family, is critical for directing epithelial-mesenchymal transition (EMT)-associated metastasis in gastric cancer (GC). DNMT3Ab is positively linked to tumour-node-metastasis (TNM) stage, lymph node metastasis and poor prognosis in GC patients. Overexpression of DNMT3Ab promotes GC cell migration and invasion as well as EMT through repression of E-cadherin. Meanwhile, DNMT3Ab promotes lung metastasis of GC in vivo. Mechanistic studies indicate that DNMT3Ab mediates the epigenetic inaction of the E-cadherin gene via DNA hypermethylation and histone modifications of H3K9me2 and H3K27me3. Depletion of DNMT3Ab effectively restores the expression of E-cadherin and reverses TGF-β-induced EMT by reducing DNA methylation, H3K9me2 and H3K27me3 levels at the E-cadherin promoter. Importantly, DNMT3Ab cooperated with H3K9me2 and H3K27me3 contributes to the transcriptional regulation of E-cadherin in a Snail-dependent manner. Further, gene expression profiling analysis indicates that multiple metastasis-associated genes and oncogenic signalling pathways are regulated in response to DNMT3Ab overexpression. These results identify DNMT3Ab as a crucial regulator of metastasis-related genes in GC. Targeting the DNMT3Ab/Snail/E-cadherin axis may provide a promising therapeutic strategy in the treatment of metastatic GC with high DNMT3Ab expression.

Single nucleotide polymorphisms and cancer susceptibility

A large number of genes associated with various cancer types contain single nucleotide polymorphisms (SNPs). SNPs are located in gene promoters, exons, introns as well as 5'- and 3'- untranslated regions (UTRs) and affect gene expression by different mechanisms. These mechanisms depend on the role of the genetic elements in which the individual SNPs are located. Moreover, alterations in epigenetic regulation due to gene polymorphisms add to the complexity underlying cancer susceptibility related to SNPs. In this systematic review, we discuss the various genetic and epigenetic mechanisms involved in determining cancer susceptibility related to various SNPs located in different genetic elements. We also discuss the diagnostic potential of these SNPs and the focus for future studies.

The rs1550117 A>G variant in DNMT3A gene promoter significantly increases non-small cell lung cancer susceptibility in a Han Chinese population

In this study, we conducted a case-control study to explore the association between rs1550117 A>G variant of DNMT3A gene promoter and non-small cell lung cancer (NSCLC) susceptibility in a Han Chinese population. The genotyping of rs1550117 A>G variant was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by sequencing. Allele G of rs1550117 was associated with an increased risk of NSCLC. Moreover, individuals carrying the GG genotypes had a higher risk to develop NSCLC than the AA and GA genotype carriers. Further stratified analysis showed that rs1550117 A>G was significantly related to age (> 60 years), male, smoking and drinking. In vivo detection of DNMT3A mRNA levels in NSCLC tissues and in vitro luciferase assays consistently showed that the allele G significantly decreased DNMT3A transcription. Additional functional analysis revealed that the increased binding affinity of transcription repressor SP1, which was associated with allele G of rs1550117, led to the significant decreased expression of DNMT3A. Collectively, our results propose a suppression role of DNMT3A in NSCLC development and emphasize the dual roles of DNMT3A in tumorigenesis.

HBx represses RIZ1 expression by DNA methyltransferase 1 involvement in decreased miR-152 in hepatocellular carcinoma

Hepatitis B virus (HBV) is mainly suspected to promote hepatocellular carcinoma (HCC) development by epigenetic alteration. The HBV X protein (HBx) plays a key role in the molecular pathogenesis of HBV-related HCC. However, the mechanism of HBx-mediated hepatocarcinogenesis remains to be elucidated. RIZ1 gene, a candidate HCC suppressor gene, is frequently found to be hypermethylated and downregulated in HCC. In the present study, we show that the expression of RIZ1 was downregulated in 65% HCC tissues. Decreased expression of RIZ1 was restored by 5'-Aza in MHCC-97H HCC cell lines. HBx recombinant transfection increased DNMT1 expression level and suppressed RIZ1 expression. Moreover, knockdown of DNMT1 by siRNA restored RIZ1 expression in HCC cell SMMC-7721 and reduced methylated CpG sites of RIZ1. ChIP results showed that DNMT1 protein could bind to RIZ1 promoter, and this interaction was further enhanced with the transfected HBX recombinant. Moreover, miR-152 was decreased and involved in upregulation of DNMT1 in HBx transfected cells, at least partly, contributed to the epigenetic inactivation of RIZ1. Taken together, our data found that HBx repressed RIZ1 expression via DNMT1, which offered a new mechanism of RIZ1 inactivation in HCC, except for the widely known DNA methylation. These results enriched the epigenetic mechanism by which HBx contributes to pathogenesis of HBV-HCC.

DNA methyltransferase 3A promoter polymorphism is associated with the risk of human spontaneous abortion after assisted reproduction techniques and natural conception

PURPOSE

The aim of this study was to explore the association of the DNA-methyltransferase (DNMT)-3A and DNMT3B promoter polymorphisms with the risk of human spontaneous abortion after assisted reproduction techniques (ARTs) and natural conception.

METHODS

We collected tissues from women who underwent abortion procedures: (a) chorionic villus samples (CVS) and muscle samples (MS) from spontaneous abortions conceived by ART and natural cycle (study group), n = 152; and (b) CVS and MS from normal early pregnancy and second trimester (control group), n = 155. The single-nucleotide polymorphism (SNP) -448A > G in the DNMT3A promoter region and -149C/T polymorphism of DNMT3B were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by sequencing.

RESULTS

The allele frequency of -448A among pregnancy loss group and control group was 34.2 % vs. 16.5 %, respectively. Compared with GG carriers, the DNMT3A -448AA homozygotes had an about 16-fold increased risk of spontaneous abortion [odds ratio (OR) = 16.130, 95 % confidence interval (CI), 3.665-70.984], and AG heterozygotes had an OR of 2.027 (95 % CI, 1.247-3.293). However, the distribution of -448A > G in individuals derived from ART pregnancies was not statistically significantly compared with those derived from spontaneous pregnancies (P = 0.661). For DNMT3B, we observed genotype frequencies of 100 % (TT) in the study group and the control group.

CONCLUSIONS

The DNMT3A -448A > G polymorphism may be a novel functional SNP and contribute to its genetic susceptibility to spontaneous abortion in Chinese women, and ART may not affect the distribution of -448A > G in pregnancy loss and normal pregnancy. The observed TT genotype of DMNT3B suggests that this is the predominant genotype of this population. The findings provide new insights into the etiology of human spontaneous abortion.

Genetic polymorphism in DNMTs and gastric cancer: A systematic review and meta-analysis

Highlights

Single nucleotide polymorphisms (SNPs) in DNA methyltransferases (DNMTs) modulate protein expression and affect DNA methylation.Aberrant DNA methylation, have been associated with gastric carcinogenesis.DNMT2 rs11254413 is associated with protection for GC development.DNMT3A rs7560488, DNMT3A rs36012910 and, specially, DNMT1 rs16999593 are associated with increased susceptibility for GC development.

Abstract

Epigenetics alterations, including aberrant DNA methylation, have been associated with gastric carcinogenesis. Single nucleotide polymorphisms (SNPs) in DNA methyltransferases (DNMTs) may influence protein expression and therefore affect DNA regulation and susceptibility for Gastric Cancer (GC).We have performed a systematic review and meta-analysis involving 11 studies and a total of 24 SNPs in DNMTs were analyzed. According to literature, only 4 SNPs, DNMT1 rs16999593, DNMT2 rs11254413 and DNMT3A rs7560488 and DNMT3A rs36012910, were associated with GC. DNMT1 rs16999593 and DNMT3A rs7560488C allele and DNMT3A rs36012910 G allele showed an increased risk for GC. On the other hand, DNMT2 rs11254413 G allele presented a protective effect for GC. Additionally, the meta-analysis evaluated the SNPs analyzed in more than one study (n = 6). Results revealed that only DNMT1 rs16999593 had a statistically significant association with GC development (OR = 1.31; 95% CI = 1.08-1.60; p = 0.006 for TC + CC genotypes).Our study suggests that DNMT2 rs11254413, DNMT3A rs7560488, DNMT3A rs36012910 and, specially, DNMT1 rs16999593 may have an association with GC development. Nevertheless, further studies are need using different populations to clarify this association with GC risk.

DNMT1, DNMT3A and DNMT3B Polymorphisms Associated With Gastric Cancer Risk: A Systematic Review and Meta-analysis

BACKGROUND

Increasing studies showed that abnormal changes in single nucleotide polymorphisms (SNPs) of DNMTs (DNMT1, DNMT3A and DNMT3B) were associated with occurrence or decrease of various tumors. However, the associations between DNMTs variations and gastric cancer (GC) risk were still conflicting. We aimed to assess the effect of DNMTs polymorphisms on the susceptibility to GC.

METHODS

Firstly, we did a meta-analysis for 7 SNPs (rs16999593, rs2228611, rs8101866 in DNMT1, rs1550117, rs13420827 in DNMT3A, rs1569686, rs2424913 in DNMT3B). Four genetic models (homozygote, heterozygote, dominant and recessive model) were used. Moreover, a meta-sensitivity and subgroup analysis was performed to clarify heterogeneity source. Lastly, 17 SNPs that couldn't be meta-analyzed were presented in a systematic review.

FINDINGS

20 studies were included, 13 studies could be meta-analyzed and 7 ones could not. Firstly, a meta-analysis on 13 studies (3959 GC cases and 5992 controls) for 7 SNPs showed that GC risk increased in rs16999593 (heterozygote model: OR 1.36, 95%CI 1.14-1.61; dominant model: OR 1.36, 95%CI 1.15-1.60) and rs1550117 (homozygote model: OR 2.03, 95%CI 1.38-3.00; dominant model: OR 1.20, 95%CI 1.01-1.42; recessive model: OR 1.96, 95%CI 1.33-2.89) but decreased in rs1569686 (dominant model: OR 0.74, 95%CI 0.61-0.90). The remaining SNPs were not found associated with GC risk. Furthermore, the subgroup analysis indicated that for rs1550117 and rs1569686, the significant associations were particularly found in people from Chinese Jiangsu province (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.48, 95%CI 0.36-0.64) and that PCR-RFLP was a sensitive method to discover significant associations (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.49, 95%CI 0.37-0.65). Lastly, a systematic review on 7 studies for 17 SNPs suggested that rs36012910, rs7560488 and rs6087990 might have a potential effect on GC initiation.

CONCLUSION

This meta-analysis demonstrated that rs16999593 and rs1550117 could contribute to GC risk and that rs1569686 might be a protective factor against gastric carcinogenesis. By using these SNPs as biomarkers, it is feasible to estimate the risk of acquiring GC and thus formulate timely preventive strategy.

Association of DNA methyltransferase polymorphisms with susceptibility to primary gouty arthritis

Gouty arthritis is the most common type of inflammatory and immune disease, and the prevalence and incidence of gout increases annually. Genetic variations in the DNA methyltransferases (DNMTs) gene have not, to the best of our knowledge, been reported to influence gene expression and to participate in the pathogenesis of gout. The aim of the present study was to investigate whether the DNMT1, DNMT3A and DNMT3B polymorphisms contribute to gout susceptibility. These polymorphisms were screened for in 336 gout patients and 306 healthy control subjects (from a South China population) for association with gout. The distribution frequencies of DNMT1 rs2228611 AA genotype (P=0.007) and A allele (P=0.002; odds ratio=1.508, 95% confidence interval=1.158-1.964) were found to be significantly increased in the gout patients when compared with those in the healthy control subjects. The rs1550117 in DNMT3A and rs2424913 in DNMT3B exhibited no significant associations with gout susceptibility between the patients and control subjects. These results demonstrated that the DNMT1 rs2228611 polymorphism may be involved in the pathogenesis of gout, while DNMT3A rs1550117 and DNMT3B rs2424913 did not show any obvious significance in the current study; thus, may not be used as risk factors to predict the susceptibility to gout. However, further studies are required to investigate the functions and regulatory mechanism of the polymorphisms of DNMTs in gout.

Evaluation of DNMT3A genetic polymorphisms as outcome predictors in AML patients

DNMT3A mutation is known as a recurrent event in acute myelogenous leukemia (AML) patients. However, association between DNMT3A genetic polymorphisms and AML patients' outcomes is unknown. DNMT3A 11 SNPs (rs11695471, rs2289195, rs734693, rs2276598, rs1465825, rs7590760, rs13401241, rs7581217, rs749131, rs41284843 and rs7560488) were genotyped in 344 diagnostic non-FAB-M3 AML patients from southern China. Patients underwent combined chemotherapy with cytarabine and anthracyclines. DNMT3A mRNA expression was analyzed in PBMCs from randomly selected AML patients. Multivariate analysis and combined genotype analysis showed that rs2276598 was associated with increased while rs11695471 and rs734693 were associated with decreased chemosensitivity (P<0.05), while rs11695471 (worse for OS), rs2289195 (favorable for OS and DFS) and rs2276598 (favorable for DFS) were significantly associated with disease prognosis (P<0.05). In conclusion, DNMT3A polymorphisms may be potential predictive markers for AML patients' outcomes, which might improve prognostic stratification of AML.

Gene-gene and gene-sex epistatic interactions of DNMT1, DNMT3A and DNMT3B in autoimmune thyroid disease

The aim of this study was to investigate the associations of DNA methyltransferases (DNMTs) polymorphisms with susceptibility to autoimmune thyroid diseases (AITDs) and to test gene-gene/gene-sex epistasis interactions. Eight single-nucleotide polymorphisms (SNPs) in DNMT1, DNMT3A and DNMT3B were selected and genotyped by multiplex polymerase chain reaction combined with ligase detection reaction method (PCR-LDR). A total of 685 Graves' disease (GD) patients, 353 Hashimoto's thyroiditis (HT) patients and 909 healthy controls were included in the final analysis. Epistasis was tested by additive model, multiplicative model and general multifactor dimensionality reduction (general MDR). Rs2424913 (DNMT3B) and rs2228611 (DNMT1) were associated with susceptibility to AITD and GD in the dominant and overdominant model, respectively (rs2424913: P=0.009 for AITD, P=0.0041 for GD; rs2228611: P=0.035 for AITD, P=0.043 for GD). Multiplicative and multiple high dimensional gene-gene or gene-sex interactions were also observed in this study. We have found evidence for a potential role of rs2424913 (DNMT3B) and rs2228611 (DNMT1) in AITD susceptibility and identified novel gene-gene/gene-sex interactions in AITD. Our study may highlight sex and genes of DNMTs family as contributors to the pathogenesis of AITD.

Interaction between Helicobacter pylori and host genetic variants in gastric carcinogenesis

Helicobacter pylori (H. pylori) is the definite carcinogen of gastric cancer. H. pylori infection induces chronic inflammation, causes DNA damage and aberrant methylation of genes and these pathways are involved in H. pylori-related gastric carcinogenesis. Polymorphisms of the genes involved in these pathways could alter susceptibility to gastric cancer. In this mini review, we focused on the role of polymorphisms in these genes on the susceptibility to gastric cancer, with a particular emphasis on their possible interactions with H. pylori infection. We found that many studies on this theme did not simultaneously report H. pylori infection and the interactions remained inconclusive.

DNMT3A rs1550117 Polymorphism is Associated With Late-Onset Alzheimer's Disease in a Chinese Population

Alzheimer's disease (AD) is classified as a neurodegenerative disease, impacting on brain integrity and functioning, resulting in a progressive deterioration of cognitive capabilities. Epigenetic changes can be acquired over the life span and mediate environmental effects on gene expression. DNA-methyltransferase 3A (DNMT3A) plays an important role in the development of embryogenesis and the generation of aberrant methylation late-onset AD (LOAD). In this study, the rs1550117 polymorphism of DNMT3A was determined by polymerase chain reaction/restriction fragment length polymorphism and confirmed by sequencing. The results showed that AA genotype carriers had a 2.08-fold risk of developing LOAD in comparison with GG genotype carriers (odds ratio [OR] = 2.08, 95% confidence interval [CI]: 1.03-4.21,P= .038) and had a 2.05-fold risk for LOAD compared with GG+GA genotype carriers (OR = 2.05, 95% CI: 1.03-4.11,P= .038), indicating that the DNMT3A polymorphism supports a major role in the pathogenesis of LOAD and can be used as a stratification marker to predict an individual's susceptibility to LOAD.

Association study between the DNMT3A -448A>G polymorphism and risk of Alzheimer's disease in Caucasians of Italian origin

Increasing evidence points to an epigenetic contribution in Alzheimer's disease (AD) pathogenesis. In this regard, variants and polymorphisms of DNA methyltransferase genes (DNMTs) are being investigated for their contribution to cognitive decline and dementia, but results are still scarce or controversial. In the present study we genotyped 710 Caucasian subjects of Italian descent, including 320 late-onset AD (LOAD) patients, 70 individuals with amnestic Mild Cognitive Impairment (MCI), and 320 matched healthy controls, for the presence of a functional DNMT3A -448A>G (rs1550117) polymorphism, searching for association with disease risk. In addition, we searched for correlation between the studied polymorphism and circulating levels of folate, homocysteine (hcy) and vitamin B12, all involved in DNA methylation reactions and available from 189 LOAD patients and 186 matched controls. Both allele and genotype frequencies of rs1550117 were closely similar between MCI, LOAD and control subjects, and no association with dementia or pre-dementia conditions was observed. Plasma hcy levels were significantly higher (p = 0.04) and serum folate levels significantly lower (p = 0.01) in LOAD than in controls, but no difference in circulating folate, hcy or vitamin B12 levels was seen between carriers and non-carriers of the minor DNMT3A -448A allele. Collectively, present results confirmed previous associations of increased hcy and decreased folate with LOAD risk, but do not support an association between the DNMT3A -448A>G polymorphism and AD in our population.

hsa-miR-29c and hsa-miR-135b differential expression as potential biomarker of gastric carcinogenesis

AIM

To investigate the expression profiles of hsa-miR-29c and hsa-miR-135b in gastric mucosal samples and their values as gastric carcinogenesis biomarkers.

METHODS

The expression levels of hsa-miR-29c and hsa-miR-135b in normal gastric mucosa, non-atrophic chronic gastritis, intestinal metaplasia and intestinal-type gastric adenocarcinoma were analysed using quantitative real-time PCR. The difference between hsa-miR-29c and hsa-miR-135b expression profiles in the grouped samples was evaluated by ANOVA and Student's t-test tests. The results were adjusted for multiple testing by using Bonferroni's correction. P values ≤ 0.05 were considered statistically significant. To evaluate hsa-miR-29c and hsa-miR-135b expressions as potential biomarkers of gastric carcinogenesis, we performed a receiver operating characteristic curve analysis and the derived area under the curve, and a Categorical Principal Components Analysis. In silico identification of the genetic targets of hsa-miR-29c and hsa-miR-135b was performed using different prediction tools, in order to identify possible genes involved in gastric carcinogenesis.

RESULTS

The expression levels of hsa-miR-29c were higher in normal gastric mucosal samples, and decreased progressively in non-atrophic chronic gastritis samples, intestinal metaplasia samples and intestinal-type gastric adenocarcinoma samples. The expression of hsa-miR-29c in the gastric lesions showed that non-atrophic gastritis have an intermediate profile to gastric normal mucosa and intestinal-type gastric adenocarcinoma, and that intestinal metaplasia samples presented an expression pattern similar to that in intestinal-type gastric adenocarcinoma. This microRNA (miRNA) has a good discriminatory accuracy between normal gastric samples and (1) intestinal-type gastric adenocarcinoma; and (2) intestinal metaplasia, and regulates the DMNT3A oncogene. hsa-miR-135b is up-regulated in non-atrophic chronic gastritis and intestinal metaplasia samples and down-regulated in normal gastric mucosa and intestinal-type gastric adenocarcinoma samples. Non-atrophic chronic gastritis and intestinal metaplasia are significantly different from normal gastric mucosa samples. hsa-miR-135b expression presented a greater discriminatory accuracy between normal samples and gastric lesions. This miRNA was associated with Helicobacter pylori presence in non-atrophic chronic gastritis samples and regulates the APC and KLF4 tumour suppressor genes.

CONCLUSION

Our results provide evidence of epigenetic alterations in non-atrophic chronic gastritis and intestinal metaplasia and suggest that hsa-miR-29c and hsa-miR-135b are promising biomarkers of gastric carcinogenesis.

DNA methyltransferase 3a rs1550117 genetic polymorphism predicts poor survival in gastric cancer patients

DNA methyltransferase 3a (DNMT3a) have been suggested to play a crucial role in human cancer prognosis. Single nucleotide polymorphisms (SNPs) in DNMT3a genes may have an impact on the prognosis of cancers. This study aimed to investigate the association between SNPs of DNMT3a gene and prognosis of gastric cancer (GC). Two sites of DNMT3a SNPs, rs1550117 and rs13420827 were selected and genotyped using TaqMan assay in 447 GC patients who received gastrectomy. Effects of genotypes on clinical outcomes of GC were calculated by Kaplan-Meier survival analysis and Cox regression model. We found that the AG or AA genotype of rs1550117 was associated with significantly poorer survival and increased death risk of GC compared with GG genotype (dominant model: HR=1.35, 95% CI=1.01-1.80, P=0.043). Further multivariate Cox regression analysis revealed that in addition to the known factors including male, larger tumor sizes and high clinical stage, rs1550117 variant was an independently predictive factor for survival in GC patients. No significant association was found between rs13420827 genetic variants and GC prognosis. Our findings first demonstrated that DNMT3a rs1550117 polymorphism may be a potential biomarker in predicting overall survival of GC patients.

Genetic susceptibility to arsenic-induced skin lesions and health effects: a review

Arsenic toxicity in humans manifests several outcomes in humans, which include arsenic-induced genomic instability, DNA damage, impaired DNA repair, carcinogenesis, dermatological lesions and other health related problems. Of the 137 million individuals affected, nearly 26 million individuals are in the state of West Bengal, India. Studies have identified dermatological lesions like keratosis, basal cell carcinoma, Bowen’s diseases, squamous cell carcinoma, etc., as key indicators of aggressive arsenic toxicity in humans. Although a large number of individuals are exposed to arsenic but only about 15 to 20 % individuals showed arsenic induced skin lesions. This clearly indicates that genetic susceptibility plays an important role in arsenic susceptibility. Analyses of genetic susceptibility have been carried out to study the prevalence of single nucleotide polymorphisms (SNPs) in number of genes as they might be involved arsenic metabolism and detoxification. It has been observed that a number SNPs in these genes were significantly associated with arsenic induced skin lesions and other health effects. In the present review we try to coalesce the different observations and associations of SNPs with arsenic-induced toxicity, with special emphasis on the study population from West Bengal. We have adopted certain candidate gene approaches to evaluate the association of arsenic-induced toxic outcomes like skin lesions, conjunctival irritations, DNA damage, epimutagenesis, cancer, etc. This review shall be helpful in understanding the importance of genetic make-up of an individual towards evaluating the xenotoxic outcomes, like those in case of arsenic exposure.

Common genetic variants in epigenetic machinery genes and risk of upper gastrointestinal cancers

BACKGROUND

Populations in north central China are at high risk for oesophageal squamous cell carcinoma (ESCC) and gastric cancer (GC), and genetic variation in epigenetic machinery genes and pathways may contribute to this risk.

METHODS

We used the adaptive multilocus joint test to analyse 192 epigenetic genes involved in chromatin remodelling, DNA methylation and microRNA biosynthesis in 1942 ESCC and 1758 GC cases [1126 cardia (GCA) and 632 non-cardia adenocarcinoma (GNCA)] and 2111 controls with Chinese ancestry. We examined potential function of risk alleles using in silico and expression quantitative trait loci (eQTLs) analyses.

RESULTS

Suggestive pathway-based associations were observed for the overall epigenetic (P-value(PATH) = 0.034) and chromatin remodelling (P-value(PATH) = 0.039) pathways with risk of GCA, but not GC, GNCA or ESCC. Overall, 37 different epigenetic machinery genes were associated with risk of one or more upper gastrointestinal (UGI) cancer sites (P-value(GENE )< 0.05), including 14 chromatin remodelling genes whose products are involved in the regulation of HOX genes. We identified a gastric eQTL (rs12724079; rho = 0.37; P = 0.0006) which regulates mRNA expression of ASH1L. Several suggestive eQTLs were also found in oesophageal (rs10898459 in EED), gastric cardia (rs7157322 in DICER1; rs8179271 in ASH1L), and gastric non-cardia (rs1790733 in PPP1CA) tissues.

CONCLUSIONS

Results of our analyses provide limited but suggestive evidence for a role of epigenetic gene variation in the aetiology of UGI cancer.

Genetic Variations and Gastric Cancer

<b><i>Background:</i></b> Gastric cancer (GC) has an apparent hereditary component. However, in a large fraction of gastric cases, no known genetic syndrome or family history can be identified, suggesting the presence of ‘missing heritability' in GC etiology. Genome-wide association studies (GWAS) and traditional candidate gene studies have both led to the identification of multiple replicable common genetic variants associated with GC risk. <b><i>Summary:</i></b> We summarize the genetic variants associated with GC risk identified up to date. Achievements derived from translational cancer research including the following aspects: (a) contribution to the our understanding of gastric tumorigenesis, (b) guidance to individualized treatment and (c) prediction of patient prognosis. We also prospect future research direction such as post-GWAS analyses and rare variants studies. <b><i>Key Message:</i></b> Many genetic variants were found through GWAS or candidate gene studies, and interpreting their underlying mechanisms will help us translate risk profiles generated from these variations into use in the clinical setting for targeted screening and treatment. <b><i>Practical Implications:</i></b> Investigation of the potential use of genetic variations as prognostic and predictive markers is a developing field. Many people could benefit from a better understanding of genetic polymorphisms to potentially identify a priori individuals who might have the best chance of survival and therefore derive most clinical benefit from treatment. Outcomes of particular scientific interest for molecular epidemiologic studies should include overall survival, recurrence- and progression-free survival, response to treatment, and early and late toxicities stemming from chemotherapy and radiation.

Cancer type-specific epigenetic changes: gastric cancer

Gastric cancer (GC) remains a major cause of mortality despite declining rate in the world. Epigenetic alterations contribute significantly to the development and progression of gastric tumors. Epigenetic refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA, and these changes lead to transcriptional activation or silencing of the gene. Over the years, the study of epigenetic processes has increased, and novel therapeutic approaches have emerged. This chapter summarizes the main epigenomic mechanisms described recently involved in gastric carcinogenesis, focusing on the roles that aberrant DNA methylation, histone modifications (histone acetylation and methylation), and miRNAs (oncogenic and tumor suppressor function of miRNA) play in the onset and progression of gastric tumors. Clinical implications of these epigenetic alterations in GC are also discussed.

Association of DNA methyltransferases 3A and 3B polymorphisms, and plasma folate levels with the risk of urothelial carcinoma

BACKGROUND

Interindividual genetic variations of human DNA methyltransferases (DNMTs), which involve the methyl donor from the folate-related one-carbon metabolism pathway, are hypothesized as a risk factor for urothelial carcinoma (UC). Therefore, we evaluated the role of gene-environment interaction in UC carcinogenesis.

METHODS

A hospital-based case-control study was conducted by recruiting 192 patients with UC and 381 controls. Their plasma folate levels were measured using a competitive immunoassay kit. In addition, DNMT3A -448A>G and DNMT3B -579G>T genotyping was evaluated using a polymerase chain reaction-restriction fragment length polymorphism technique. Multivariate logistic regression and 95% confidence intervals (CIs) were applied to estimate the UC risk.

RESULTS

We observed that patients with UC exhibited a higher prevalence rate of folate insufficiency (folate levels ≤6 ng/mL) compared with the controls (35.94% and 18.37%, respectively). Furthermore, folate levels were higher in the prevalent UC patients than in the incident UC patients. However, folate insufficiency was similarly associated with a nearly two-fold increase in the risk of UC regardless of the UC patient group. In addition, the frequencies of the variant alleles for DNMT3A and DNMT3B were 0.80 and 0.92, respectively, and no association was observed with UC risk. However, participants with a variant homozygous genotype of DNMT3B -579G>T and folate insufficiency or with high cumulative cigarette smoking exhibited an increased risk of UC.

CONCLUSION

Overall, environmental factors may contribute more significantly to UC carcinogenesis compared with genetic susceptibility. Future studies should investigate other polymorphisms of DNMT3A and DNMT3B to determine genetic susceptibility.

MTHFR C677T polymorphism contributes to the risk for gastric cancer

Methylenetetrahydrofolate reductase (MTHFR) has been demonstrated to be involved in carcinogenesis. Increasing individual studies have investigated the role of MTHFR C677T polymorphism in gastric cancer pathogenesis, but with inconsistent findings. The aim of this study was to clarify the potential association of the MTHFR C677T polymorphism with gastric cancer risk by pooling all available data from published case-control studies. We searched the PubMed, Embase, Web of Science, and Wanfang databases for all relevant publications to date. The pooled odds ratio (OR) with corresponding 95 % confidence interval (95% CI) was calculated. Stratified analysis and sensitivity analysis were also carried out to estimate the strength of this association. A total of 25 case-control studies with 6,572 cases and 9,584 controls were retrieved. Overall, the ORs under five contrast models indicated that the MTHFR C677T variant was positively associated with gastric cancer risk (ORT vs. C = 1.21, 95% CI 1.10–1.34, P(OR) < 0.001; OR(TT vs. CC) = 1.47, 95% CI 1.22–1.76, P(OR) < 0.001; OR(TC vs. CC) = 1.20, 95% CI 1.03-1.40, P(OR) = 0.022; OR(TT + TC vs. CC) = 1.27, 95% CI 1.10-1.47, P(OR) = 0.001; OR(TT vs. CC + TC) = 1.29, 95% CI 1.15-1.46, P(OR) < 0.001). Stratified analyses according to ethnicity and source of controls further confirmed the significant correlations. The current meta-analysis provides strong evidence that the MTHFR C677T polymorphism may be a risk factor for gastric cancer among Asians and Caucasians.

Genetic variants of DNMT3A and systemic lupus erythematosus susceptibility

OBJECTIVES

A significant increase in DNA methyltransferase 3A (DNMT3A) transcript levels has recently been demonstrated in peripheral blood mononuclear cells from systemic lupus erythematosus (SLE) patients as compared to healthy individuals.

METHODS

Employing high resolution melting curve analysis (HRM) and PCR-restriction fragment length polymorphism analysis, we assessed the frequency of five single nucleotide polymorphisms (SNPs) of this gene: rs2289195, rs7590760, rs13401241, rs749131 and rs1550117, situated in different linkage disequilibrium blocks of the DNMT3A gene in two hundred and fifty seven women with SLE and six hundred and twenty five controls.

RESULTS

The lowest p values of the trend test were observed for the DNMT3A -448A> G (rs1550117) SNP (ptrend = 0.0111). We also found that, in a dominant inheritance model, the DNMT3A -448A> G SNP may protect from SLE development [odds ratio (OR) = 0.494 (0.294-0.830), p = 0.0068, pcorr = 0.034]. Furthermore, we observed that the DNMT3A -448A > G SNP in dominant inheritance models may protect from immunologic manifestations of SLE [OR = 0.1753 (95% CI = 0.04976-0.6176, p = 0.0026, pcorr = 0.0468).

CONCLUSIONS

Our study demonstrates that the DNMT3A -448A> G SNP might protect from SLE and its immunologic manifestations in a sample from the Polish population.

A novel functional TagSNP Rs7560488 in the DNMT3A1 promoter is associated with susceptibility to gastric cancer by modulating promoter activity

DNA-methyltransferase (DNMT)-3A which contains DNMT3A1 and DNMT3A2 isoforms have been suggested to play a crucial role in carcinogenesis and showed aberrant expression in most cancers. Accumulated evidences also indicated that single nucleotide polymorphisms (SNP) in DNMT genes were associated with susceptibility to different tumors. We hypothesized that genetic variants in DNMT3A1 promoter region are associated with gastric cancer risk. We selected the tagSNPs from the HapMap database for the Chinese and genotyped in a case-control study to evaluate the association with gastric cancer (GC) in a Chinese population. We identified that the functional tagSNP rs7560488 T>C associated with a significantly increased risk of GC. In vitro functional analysis by luciferase reporter assay and EMSA indicated that the tagSNP rs7560488 T>C substantially altered transcriptional activity of DNMT3A1 gene via influencing the binding of some transcriptional factors, although a definite transcriptional factor remains to be established. Compared with TT homozygotes, subjects who were TC heterozygotes and CC homozygotes exhibited a reduced expression of DNMT3A1. Furthermore, stratified analysis showed that individuals who harbor TC or CC genotypes less than 60 years old were more susceptible to GC. Our results suggest that the genetic variations in the DNMT3A1 promoter contribute to the susceptibility to GC and also provide an insight that tagSNP rs7560488 T>C may be a promising biomarker for predicting GC genetic susceptibility and a valuable information in GC pathogenesis.