Acid-induced p16 hypermethylation contributes to development of esophageal adenocarcinoma via activation of NADPH oxidase NOX5-S

To activate NAD(P)H oxidase with a brief pulse of photodynamic action

Reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidases (NOX) are a major cellular source of reactive oxygen species, regulating vital physiological functions, whose dys-regulation leads to a plethora of major diseases. Much effort has been made to develop varied types of NOX inhibitors, but biotechnologies for spatially and temporally controlled NOX activation, however, are not readily available. We previously found that ultraviolet A (UVA) irradiation activates NOX2 in rodent mast cells, to elicit persistent calcium spikes. NOX2 is composed of multiple subunits, making studies of its activation rather complicated. Here we show that the single-subunit nonrodent-expressing NOX5, when expressed ectopically in CHO-K1 cells, is activated by UVA irradiation (380 nm, 0.1-12 mW/cm2, 1.5 min) inducing repetitive calcium spikes, as monitored by Fura-2 fluorescent calcium imaging. UVA-elicited calcium oscillations are inhibited by NOX inhibitor diphenyleneiodonium chloride (DPI) and blocked by singlet oxygen (1O2) quencher Trolox-C (300 μM). A brief pulse of photodynamic action (1.5 min) with photosensitizer sulfonated aluminum phthalocyanine (SALPC 2 μM, 675 nm, 85 mW/cm2) in NOX5-CHO-K1 cells, or with genetically encoded protein photosensitizer miniSOG fused to N-terminus of NOX5 (450 nm, 85 mW/cm2) in miniSOG-NOX5-CHO-K1 cells, induces persistent calcium oscillations, which are blocked by DPI. In the presence of Trolox-C, miniSOG photodynamic action no longer induces any calcium increases in miniSOG-NOX5-CHO-K1 cells. DUOX2 in human thyroid follicular cells SW579 and in DUOX2-CHO-K1 cells is similarly activated by UVA irradiation and SALPC photodynamic action. These data together suggest that NOX   is activated with a brief pulse of photodynamic action.

Loss of fragile WWOX gene leads to senescence escape and genome instability

Induction of DNA damage response (DDR) to ensure accurate duplication of genetic information is crucial for maintaining genome integrity during DNA replication. Cellular senescence is a DDR mechanism that prevents the proliferation of cells with damaged DNA to avoid mitotic anomalies and inheritance of the damage over cell generations. Human WWOX gene resides within a common fragile site FRA16D that is preferentially prone to form breaks on metaphase chromosome upon replication stress. We report here that primary Wwox knockout (Wwox-/-) mouse embryonic fibroblasts (MEFs) and WWOX-knockdown human dermal fibroblasts failed to undergo replication-induced cellular senescence after multiple passages in vitro. Strikingly, by greater than 20 passages, accelerated cell cycle progression and increased apoptosis occurred in these late-passage Wwox-/- MEFs. These cells exhibited γH2AX upregulation and microsatellite instability, indicating massive accumulation of nuclear DNA lesions. Ultraviolet radiation-induced premature senescence was also blocked by WWOX knockdown in human HEK293T cells. Mechanistically, overproduction of cytosolic reactive oxygen species caused p16Ink4a promoter hypermethylation, aberrant p53/p21Cip1/Waf1 signaling axis and accelerated p27Kip1 protein degradation, thereby leading to the failure of senescence induction in Wwox-deficient cells after serial passage in culture. We determined that significantly reduced protein stability or loss-of-function A135P/V213G mutations in the DNA-binding domain of p53 caused defective induction of p21Cip1/Waf1 in late-passage Wwox-/- MEFs. Treatment of N-acetyl-L-cysteine prevented downregulation of cyclin-dependent kinase inhibitors and induced senescence in Wwox-/- MEFs. Our findings support an important role for fragile WWOX gene in inducing cellular senescence for maintaining genome integrity during DDR through alleviating oxidative stress.

Epigenetic Alterations from Barrett's Esophagus to Esophageal Adenocarcinoma

Barrett's esophagus (BE) is a disease entity that is a sequela of chronic gastroesophageal reflux disease that may result in esophageal adenocarcinoma (EAC) due to columnar epithelial dysplasia. The histological degree of dysplasia is the sole biomarker frequently utilized by clinicians. However, the cost of endoscopy and the fact that the degree of dysplasia does not progress in many patients with BE diminish the effectiveness of histological grading as a perfect biomarker. Multiple or more quantitative biomarkers are required by clinicians since early diagnosis is crucial in esophageal adenocancers, which have a high mortality rate. The presence of epigenetic factors in the early stages of this neoplastic transformation holds promise as a predictive biomarker. In this review, current studies on DNA methylations, histone modifications, and noncoding RNAs (miRNAs) that have been discovered during the progression from BE dysplasia to EAC were collated.

Enhancement of DNA hypomethylation alterations by gastric and bile acids promotes chromosomal instability in Barrett's epithelial cell line

Gastric and bile acid reflux leads to chronic inflammation, resulting in methylation alterations in Barrett's esophagus (BE) together with chromosomal instability (CIN). We investigated DNA hypomethylation following acid exposure and confirmed its significance in BE-related carcinogenesis by inducing CIN in vitro. OACP4C, an esophageal cancer cell line, and CP-A, a non-dysplastic cell line originating from BE, were exposed to acidic conditions using deoxycholic acid. CP-A exhibited substantially increased DNA hypomethylation of alpha satellite sequences in the centromere region, as well as increased levels of alpha satellite transcripts, but no changes were observed in the long interspersed nucleotide element-1 sequences distributed throughout the entire genome. These changes were not clearly found in OACP4C. Copy number changes at specific chromosomes were identified in CP-A, along with an increased number of cells exhibiting abnormal segregations, whereas these changes were rarely observed in OACP4C. The changes were maintained after several cell divisions. These findings suggest that alpha satellites are likely targets of DNA hypomethylation induced by acid exposure. CP-A was more sensitive to acid exposure than OACP4C, indicating that acid-induced DNA hypomethylation is involved in cancer development rather than progression, which could be involved in the underlying mechanism of esophagogastric junction carcinoma development.

Modulation of Reactive Oxygen Species in Cancers: Recent Advances

Oxidation-reduction reactions played a significant role in the chemical evolution of life forms on oxygenated earth. Cellular respiration is dependent on such redox reactions, and any imbalance leads to the accumulation of reactive oxygen species (ROS), resulting in both chronic and acute illnesses. According to the International Agency for Research on Cancer (IARC), by 2040, the global burden of new cancer cases is expected to be around 27.5 million, with 16.3 million cancer deaths due to an increase in risk factors such as unhealthy lifestyle, environmental factors, aberrant gene mutations, and resistance to therapies. ROS play an important role in cellular signalling, but they can cause severe damage to tissues when present at higher levels. Elevated and chronic levels of ROS are pertinent in carcinogenesis, while several therapeutic strategies rely on altering cellular ROS to eliminate tumour cells as they are more susceptible to ROS-induced damage than normal cells. Given this selective targeting potential, therapies that can effectively modulate ROS levels have been the focus of intense research in recent years. The current review describes biologically relevant ROS, its origins in solid and haematological cancers, and the current status of evolving antioxidant and pro-oxidant therapies in cancers.

Epigenetic effects of graphene oxide and its derivatives: A mini-review

Graphene oxide (GO), an engineered nanomaterial, has a two-dimensional structure with carbon atoms arranged in a hexagonal array. While it has been widely used in many industries, such as biomedicine, electronics, and biosensors, there are still concerns over its safety. Recently, many studies have focused on the potential toxicity of GO. Epigenetic toxicity is an important aspect of a material's toxicological profile, since changes in gene expression have been associated with carcinogenicity and disease progression. In this review, we focus on the epigenetic alterations caused by GO, including DNA methylation, histone modification, and altered expression of non-coding RNAs. GO can affect DNA methyltransferase activity and disrupt the methylation of cytosine bases in DNA strands, leading to alteration of genome expression. Modulation of histones by GO, targeting histone deacetylase and demethylase, as well as dysregulation of miRNA and lncRNA expression have been reported. Further studies are required to determine the mechanisms of GO-induced epigenetic alterations.

Barrett's Epithelium to Esophageal Adenocarcinoma: Is There a "Point of No Return"?

Background: Esophageal adenocarcinoma (EA) arises from Barrett's epithelium (BE), and chronic gastroesophageal reflux disease is considered the strongest risk factor for disease progression. All BE patients undergo acid suppressive therapy, surveillance, and BE removal by surgery or endoscopic ablation, yet the incidence of EAC continues to increase. Despite the known side effects and mortality, the one-size-fits-all approach is the standard clinical management as there are no reliable methods for risk stratification. Methods: Paired-end Illumina NextSeq500 RNA sequencing was performed on total RNA extracted from 20-week intervals (0, 20, 40, and 60 W) of an in vitro BE carcinogenesis (BEC) model to construct time series global gene expression patterns (GEPs). The cells from two strategic time points (20 and 40 W) based on the GEPs were grown for another 20 weeks, with and without further acid and bile salt (ABS) stimulation, and the recurrent neoplastic cell phenotypes were evaluated. Results: Hierarchical clustering of 866 genes with ≥ twofold change in transcript levels across the four time points revealed maximum variation between the BEC20W and BEC40W cells. Enrichment analysis confirmed that the genes altered ≥ twofold during this window period associated with carcinogenesis and malignancy. Intriguingly, the BEC20W cells required further ABS exposure to gain neoplastic changes, but the BEC40W cells progressed to malignant transformation after 20 weeks even in the absence of additional ABS. Discussion: The transcriptomic gene expression patterns in the BEC model demonstrate evidence of a clear threshold in the progression of BE to malignancy. Catastrophic transcriptomic changes during a window period culminate in the commitment of the BE cells to a "point of no return," and removal of ABS is not effective in preventing their malignant transformation. Discerning this "point of no return" during BE surveillance by tracking the GEPs has the potential to evaluate risk of BE progression and enable personalized clinical management.

NOX2-Derived Reactive Oxygen Species in Cancer

The formation of reactive oxygen species (ROS) by the myeloid cell NADPH oxidase NOX2 is critical for the destruction of engulfed microorganisms. However, recent studies imply that ROS, formed by NOX2⁺ myeloid cells in the malignant microenvironment, exert multiple actions of relevance to the growth and spread of neoplastic cells. By generating ROS, tumor-infiltrating myeloid cells and NOX2⁺ leukemic myeloid cells may thus (i) compromise the function and viability of adjacent cytotoxic lymphocytes, including natural killer (NK) cells and T cells, (ii) oxidize DNA to trigger cancer-promoting somatic mutations, and (iii) affect the redox balance in cancer cells to control their proliferation and survival. Here, we discuss the impact of NOX2-derived ROS for tumorigenesis, tumor progression, regulation of antitumor immunity, and metastasis. We propose that NOX2 may be a targetable immune checkpoint in cancer.

Gastrointestinal pharmacology: practical tips for the esophagologist

Gastroesophageal reflux disease (GERD) is primarily a motor disorder, and its pathogenesis is multifactorial. As a consequence, treatment should be able to address the underlying pathophysiology. Proton pump inhibitors (PPIs) are the mainstay of medical therapy for GERD, but these drugs only provide the control of symptoms and lesions without curing the disease. However, continuous acid suppression with PPIs is recommended for patients with Barrett's esophagus because of their potential chemopreventive effects. In addition to the antisecretory activity, these compounds display several pharmacological properties, often overlooked in clinical practice. PPIs can indeed affect gastric motility, exert a mucosal protective effect, and an antioxidant, anti-inflammatory, and antineoplastic activity, also protecting cancer cells from developing chemo- or radiotherapeutic resistance. Even in the third millennium, current pharmacologic approaches to address GERD are limited. Reflux inhibitors represent a promise unfulfilled, effective and safe prokinetics are lacking, and antidepressants, despite being effective in selected patients, give rise to adverse events in a large proportion of them. While waiting for new drug classes (like potassium-competitive acid blockers), reassessing old drugs (namely alginate-containing formulations), and paving the new avenue of esophageal mucosal protection are, at the present time, the only reliable alternatives to acid suppression.

Effect of Proton Pump Inhibitor Therapy on NOX5, mPGES1 and iNOS expression in Barrett's Esophagus

Acid reflux may contribute to the progression from Barrett’s esophagus (BE) to esophageal adenocarcinoma (EA). However, it is not clear whether the molecular changes present in BE patients are reversible after proton pump inhibitor (PPI) treatment. In this study we examined whether PPI treatment affects NOX5, microsomal prostaglandin E synthase (mPGES)-1 and inducible nitric oxide synthase (iNOS) expression. We found that NADPH oxidase 5 (NOX5), mPGES-1 and iNOS were significantly increased in BE mucosa. One-month PPI treatment significantly decreased NOX5, mPGES1 and iNOS. In BAR-T cells, NOX5 mRNA and p16 promoter methylation increased after pulsed acid treatment in a time-dependent manner. Four or eight-week-acid induced increase in NOX5 mRNA, NOX5 protein and p16 methylation may be reversible. Twelve-week acid treatment also significantly increased NOX5, mPGES1 and iNOS mRNA expression. However, twelve-week-acid-induced changes only partially restored or did not recover at all after the cells were cultured at pH 7.2 for 8 weeks. We conclude that NOX5, mPGES1 and iNOS may be reversible after PPI treatment. Short-term acid-induced increase in NOX5 expression and p16 methylation might be reversible, whereas long-term acid-induced changes only partially recovered 8 weeks after removal of acid treatment.

Stressing the (Epi)Genome: Dealing with Reactive Oxygen Species in Cancer

SIGNIFICANCE

Growing evidence indicates cross-talk between reactive oxygen species (ROS) and several key epigenetic processes such as DNA methylation, histone modifications, and miRNAs in normal physiology and human pathologies including cancer. This review focuses on how ROS-induced oxidative stress, metabolic intermediates, and epigenetic processes influence each other in various cancers. Recent Advances: ROS alter chromatin structure and metabolism that impact the epigenetic landscape in cancer cells. Several site-specific DNA methylation changes have been identified in different cancers and are discussed in the review. We also discuss the interplay of epigenetic enzymes and miRNAs in influencing malignant transformation in an ROS-dependent manner.

CRITICAL ISSUES

Loss of ROS-mediated signaling mostly by epigenetic regulation may promote tumorigenesis. In contrast, augmented oxidative stress because of high ROS levels may precipitate epigenetic alterations to effect various phases of carcinogenesis. We address both aspects in the review.

FUTURE DIRECTIONS

Several drugs targeting ROS are under various stages of clinical development. Recent analysis of human cancers has revealed pervasive deregulation of the epigenetic machinery. Thus, a better understanding of the cross-talk between ROS and epigenetic alterations in cancer could lead to the identification of new drug targets and more effective treatment modalities.

NADPH oxidase 5 promotes proliferation and fibrosis in human hepatic stellate cells

NADPH oxidase (Nox) variants Nox1, Nox2 and Nox4 are implicated in the progression of liver fibrosis. However, the role of Nox5 is not yet known, mainly due to the lack of this enzyme in rat and mouse genomes. Here we describe the expression and functional relevance of Nox5 in the human cell line of hepatic stellate cells (HSC) LX-2. Under basal conditions, three long (Nox5-L: Nox5α, -β, and -δ) and a short (Nox5-S or Nox5ε) splice variants were detected, which were silenced with specific siRNAs for Nox5. The most abundant isoform was Nox5-S, accounting for more than 90% of Nox5 protein. Overexpression of Nox5β generated reactive oxygen species (ROS) in the presence of calcium, as judged by the production of hydrogen peroxide, L-012 luminescence and cytochrome c reduction. Nox5ε did not generated ROS under these conditions, and a reduced ROS production was observed when co-expressed with Nox5β. In contrast, dihydroethidium oxidation was increased by Nox5β or Nox5ε, suggesting that Nox5ε induced intracellular oxidative stress by an unknown mechanism. Functional studies showed that both Nox5β and Nox5ε stimulated the proliferation of LX-2 cells and the collagen type I levels, while Nox5 siRNAs inhibited these effects. Interestingly, TGF-β and angiotensin II upregulated Nox5 expression, which was reduced in cells pre-incubated with catalase. Further studies silencing Nox5 in TGF-β-treated cells resulted in a reduction of collagen levels via p38 MAPK. Collectively, these results show for the first time that Nox5 can play a relevant role in the proliferation and fibrosis on human HSC.

Silencing DNA methyltransferase 1 leads to the activation of the esophageal suppressor gene p16 in vitro and in vivo

Previous studies have demonstrated that DNA methyltransferase 1 (DNMT1) is required for the maintenance of DNA methylation and epigenetic changes that may lead to the development of esophageal squamous cell carcinoma (ESCC). In order to investigate whether the silencing of DNMT1 protects tumor suppressor genes, including p16, and is able to be used as a potential therapy for human ESCC, short hairpin RNA targeting DNMT1 (shRNA-DNMT1) was synthesized and transfected into the human ESCC lines KYSE150 and KYSE410, which were then injected into the backs of nude mice prior to harvesting. Results from the reverse transcription-quantitative polymerase chain reaction (PCR) and western blotting demonstrated that p16 mRNA expression was increased in the shRNA-DNMT1-transfected ESCC cell lines in vitro and in vivo. Consistent with the immunohistochemistry results, p16 was expressed in tumor tissue from nude mice that had been transplanted with the modified human ESCC lines. It was also observed that p16 methylation was inhibited following transfection with shRNA-DNMT1 as detected using methylation-specific PCR analysis. The results of the present study suggest that silencing DNMT1 serves a protective role through the demethylation and subsequent activation of p16 in vitro and in vivo.

Silencer-of-Death Domain Mediates Acid-Induced Decrease in Cell Apoptosis in Barrett's Associated Esophageal Adenocarcinoma Cells

We have shown that NADPH oxidase (NOX)5-S may mediate the acid-induced decrease in cell apoptosis. However, mechanisms of NOX5-S-dependent decrease in cell apoptosis are not fully understood. In this study, we found that silencer-of-death domain (SODD) was significantly increased in esophageal adenocarcinoma (EA) tissues, EA cell lines FLO and OE33, and a dysplastic cell line CP-B. Strong SODD immunostaining was significantly higher in low-grade dysplasia (66.7%), high-grade dysplasia (81.2%), and EA (71.2%) than in Barrett's mucosa (10.5%). Acid treatment significantly increased SODD protein and mRNA expression and promoter activity in FLO cells, an increase that was significantly decreased by the knockdown of NOX5-S and nuclear factor κB (NF-κB)1 p50 with their small interfering RNAs. Similarly, acid-induced increase of SODD mRNA was blocked by knockdown of NOX5-S and p50 in a BE cell line CP-A. Overexpression of NOX5-S significantly increased SODD protein expression in FLO cells. Moreover, overexpression of NOX5-S or p50 significantly increased the SODD promoter activity and decreased the caspase 9 activity or apoptosis. NOX5-S overexpression-induced increase in SODD promoter activity was significantly decreased by knockdown of p50. In addition, acid treatment significantly decreased the caspase 9 activity, a decrease that was significantly inhibited by knockdown of SODD. Furthermore, chromatin immunoprecipitation assay showed that NF-κB1 p50 bound to SODD genomic DNA containing a NF-κB-binding element GGGGACACCCT. This binding element was further confirmed by a gel mobility shift assay. We conclude that acid-induced increase in SODD expression and decrease in cell apoptosis may depend on the activation of NOX5-S and NF-κB1 p50 in FLO cells.

Overview of major molecular alterations during progression from Barrett's esophagus to esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) develops in the sequential transformation of normal epithelium into metaplastic epithelium, called Barrett's esophagus (BE), then to dysplasia, and finally cancer. BE is a common condition in which normal stratified squamous epithelium of the esophagus is replaced with an intestine-like columnar epithelium, and it is the most prominent risk factor for EAC. This review aims to impartially systemize the knowledge from a large number of publications that describe the molecular and biochemical alterations occurring over this progression sequence. In order to provide an unbiased extraction of the knowledge from the literature, a text-mining methodology was used to select genes that are involved in the BE progression, with the top candidate genes found to be TP53, CDKN2A, CTNNB1, CDH1, GPX3, and NOX5. In addition, sample frequencies across analyzed patient cohorts at each stage of disease progression are summarized. All six genes are altered in the majority of EAC patients, and accumulation of alterations correlates well with the sequential progression of BE to cancer, indicating that the text-mining method is a valid approach for gene prioritization. This review discusses how, besides being cancer drivers, these genes are functionally interconnected and might collectively be considered a central hub of BE progression.

Evaluation of p16 hypermethylation in oral submucous fibrosis: A quantitative and comparative analysis in buccal cells and saliva using real-time methylation-specific polymerase chain reaction

Aims:

The aim of this study was to quantitatively investigate the hypermethylation of p16 gene in buccal cells and saliva of oral submucous fibrosis (OSMF) patients using real-time quantitative methylation-specific polymerase chain reaction (PCR) and to compare the values of two methods.

Subjects and Methods:

A total of 120 samples were taken from 60 subjects selected for this study, of which 30 were controls and 30 patients were clinically and histopathologically diagnosed with OSMF. In both groups, two sets of samples were collected, one directly from the buccal cells through cytobrush technique and the other through salivary rinse. We analyzed the samples for the presence of p16 hypermethylation using quantitative real-time PCR.

Results:

In OSMF, the hypermethylation status of p16 in buccal cells was very high (93.3%) and in salivary samples, it was partially methylated (50%). However, no hypermethylation was found in controls suggesting that significant quantity of p16 hypermethylation was present in buccal cells and saliva in OSMF.

Conclusions:

This study indicates that buccal cell sampling may be a better method for evaluation than the salivary samples. It signifies that hypermethylation of p16 is an important factor to be considered in epigenetic alterations of normal cells to oral precancer, i.e. OSMF.

Rho Kinase ROCK2 Mediates Acid-Induced NADPH Oxidase NOX5-S Expression in Human Esophageal Adenocarcinoma Cells

Mechanisms of the progression from Barrett’s esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. We have shown that NOX5-S may be involved in this progression. However, how acid upregulates NOX5-S is not well known. We found that acid-induced increase in NOX5-S expression was significantly decreased by the Rho kinase (ROCK) inhibitor Y27632 in BE mucosal biopsies and FLO-1 EA cells. In addition, acid treatment significantly increased the Rho kinase activity in FLO-1 cells. The acid-induced increase in NOX5-S expression and H₂O₂ production was significantly decreased by knockdown of Rho kinase ROCK2, but not by knockdown of ROCK1. Conversely, the overexpression of the constitutively active ROCK2, but not the constitutively active ROCK1, significantly enhanced the NOX5-S expression and H₂O₂ production. Moreover, the acid-induced increase in Rho kinase activity and in NOX5-S mRNA expression was blocked by the removal of calcium in both FLO-1 and OE33 cells. The calcium ionophore A23187 significantly increased the Rho kinase activity and NOX5-S mRNA expression. We conclude that acid-induced increase in NOX5-S expression and H₂O₂ production may depend on the activation of ROCK2, but not ROCK1, in EA cells. The acid-induced activation of Rho kinase may be mediated by the intracellular calcium increase. It is possible that persistent acid reflux present in BE patients may increase the intracellular calcium, activate ROCK2 and thereby upregulate NOX5-S. High levels of reactive oxygen species derived from NOX5-S may cause DNA damage and thereby contribute to the progression from BE to EA.

ROS signaling by NADPH oxidase 5 modulates the proliferation and survival of prostate carcinoma cells

Prostate cancer (PCa) is the most commonly diagnosed cancer and second leading cause of male cancer death in Western nations. Thus, new treatment modalities are urgently needed. Elevated production of reactive oxygen species (ROS) by NADPH oxidase (Nox) enzymes is implicated in tumorigenesis of the prostate and other tissues. However, the identity of the Nox enzyme(s) involved in prostate carcinogenesis remains largely unknown. Analysis of radical prostatectomy tissue samples and benign and malignant prostate epithelial cell lines identified Nox5 as an abundantly expressed Nox isoform. Consistently, immunohistochemical staining of a human PCa tissue microarray revealed distinct Nox5 expression in epithelial cells of benign and malignant prostatic glands. shRNA-mediated knockdown of Nox5 impaired proliferation of Nox5-expressing (PC-3, LNCaP) but not Nox5-negative (DU145) PCa cell lines. Similar effects were observed upon ROS ablation via the antioxidant N-acetylcysteine confirming ROS as the mediators. In addition, Nox5 silencing increased apoptosis of PC-3 cells. Concomitantly, protein kinase C zeta (PKCζ) protein levels and c-Jun N-terminal kinase (JNK) phosphorylation were reduced. Moreover, the effect of Nox5 knockdown on PC-3 cell proliferation could be mimicked by pharmacological inhibition of JNK. Collectively, these data indicate that Nox5 is expressed at functionally relevant levels in the human prostate and clinical PCa. Moreover, findings herein suggest that Nox5-derived ROS and subsequent depletion of PKCζ and JNK inactivation play a critical role in modulating intracellular signaling cascades involved in the proliferation and survival of PCa cells. © 2014 The Authors. Molecular Carcinogenesis published by Wiley Periodicals, Inc.

Impact of oxidative stress during pregnancy on fetal epigenetic patterns and early origin of vascular diseases

Epidemiological studies have led scientists to postulate the developmental origins of health and disease hypothesis for noncommunicable diseases such as diabetes, cardiovascular diseases, hypertension, and obesity. However, the cellular and molecular mechanisms involved in the development of these diseases are not well understood. In various animal models, it has been observed that oxidative stress during pregnancy is associated with the early development of endothelial dysfunction in offspring. This phenomenon suggests that endothelial dysfunction may initiate in the uterus and could lead to increased risk of cardiovascular disease later in life. Currently, it is known that many of the fetal adaptive responses to environmental factors are mediated by epigenetic changes in the genome, especially by the degree of methylation in cytosines in the promoter regions of genes. These findings suggest that the establishment of a particular epigenetic pattern in the genome may be generated by oxidative stress.

Redox regulation of genome stability by effects on gene expression, epigenetic pathways and DNA damage/repair

Reactive oxygen and nitrogen species (e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. In addition, classical regulation of gene expression or activity, including gene transcription to RNA followed by translation to the protein level, by transcription factors (e.g. NF-κB, HIF-1α) and mRNA binding proteins (e.g. GAPDH, HuR) is subject to redox regulation. This review will give an update of recent discoveries in this field, and specifically highlight the impact of reactive oxygen and nitrogen species on DNA repair systems that contribute to genomic stability. Emphasis will be placed on the emerging role of redox mechanisms regulating epigenetic pathways (e.g. miRNA, DNA methylation and histone modifications). By providing clinical correlations we discuss how oxidative stress can impact on gene regulation/activity and vise versa, how epigenetic processes, other gene regulatory mechanisms and DNA repair can influence the cellular redox state and contribute or prevent development or progression of disease.

Mechanisms of superoxide signaling in epigenetic processes: relation to aging and cancer

Superoxide is a precursor of many free radicals and reactive oxygen species (ROS) in biological systems. It has been shown that superoxide regulates major epigenetic processes of DNA methylation, histone methylation, and histone acetylation. We suggested that superoxide, being a radical anion and a strong nucleophile, could participate in DNA methylation and histone methylation and acetylation through mechanism of nucleophilic substitution and free radical abstraction. In nucleophilic reactions superoxide is able to neutralize positive charges of methyl donors S-adenosyl-L-methionine (SAM) and acetyl-coenzyme A (AcCoA) enhancing their nucleophilic capacity or to deprotonate cytosine. In the reversed free radical reactions of demethylation and deacetylation superoxide is formed catalytically by the (Tet) family of dioxygenates and converted into the iron form of hydroxyl radical with subsequent oxidation and final eradication of methyl substituents. Double role of superoxide in these epigenetic processes might be of importance for understanding of ROS effects under physiological and pathological conditions including cancer and aging.

Mediator subunit 23 overexpression as a novel target for suppressing proliferation and tumorigenesis in hepatocellular carcinoma

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is the fifth most frequent cancer in the world. However, the molecular mechanisms involved in HCC are still poorly understood. Here, we study the role of mediator subunit 23 (MED23), a component of the Mediator complex, in hepatocarcinogenesis.

METHODS

We detected MED23 expression in HCC samples by real-time polymerase chain reaction (PCR) and immunohistochemistry analysis. We also knocked down and overexpressed MED23 to explore its functional role in hepatoma cell growth. The cell cycle was examined by flow cytometry analysis, and protein expression was examined by Western blot. A xenograft mouse model was used to determine whether MED23 is involved in tumorigenesis.

RESULTS

MED23 was frequently upregulated in human HCC tissues compared with paired adjacent non-tumorous liver tissues. The hepatoma cells also showed increased MED23 expression. MED23 knockdown inhibited hepatoma cell growth, whereas overexpression of MED23 promoted cell growth. Knockdown of MED23 induced a G1 to S phase arrest. Moreover, MED23 regulated the expression of p16(INK) (4a) (p16) and the phosphorylation of retinoblastoma protein (Rb). p16 was transcriptionally upregulated, and its promoter was demethylated. The G1 to S phase arrest induced by MED23 knockdown was aborted after p16 was silenced. Furthermore, MED23 knockdown suppressed tumorigenesis and regulated p16/Rb signaling in vivo.

CONCLUSIONS

Taken together, our study suggests that MED23 plays an important role in hepatocarcinogenesis, and it may be a novel target for HCC therapy.

Role of intracellular calcium and NADPH oxidase NOX5-S in acid-induced DNA damage in Barrett's cells and Barrett's esophageal adenocarcinoma cells

Mechanisms whereby acid reflux may accelerate the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. Acid and reactive oxygen species (ROS) have been reported to cause DNA damage in Barrett's cells. We have previously shown that NADPH oxidase NOX5-S is responsible for acid-induced H2O2 production in Barrett's cells and in EA cells. In this study we examined the role of intracellular calcium and NADPH oxidase NOX5-S in acid-induced DNA damage in a Barrett's EA cell line FLO and a Barrett's cell line CP-A. We found that pulsed acid treatment significantly increased tail moment in FLO and CP-A cells and histone H2AX phosphorylation in FLO cells. In addition, acid treatment significantly increased intracellular Ca(2+) in FLO cells, an increase that is blocked by Ca(2+)-free medium with EGTA and thapsigargin. Acid-induced increase in tail moment was significantly decreased by NADPH oxidase inhibitor diphenylene iodonium in FLO cells, and by blockade of intracellular Ca(2+) increase or knockdown of NOX5-S with NOX5 small-interfering RNA (siRNA) in FLO and CP-A cells. Acid-induced increase in histone H2AX phosphorylation was significantly decreased by NOX5 siRNA in FLO cells. Conversely, overexpression of NOX5-S significantly increased tail moment and histone H2AX phosphorylation in FLO cells. We conclude that pulsed acid treatment causes DNA damage via increase of intracellular calcium and activation of NOX5-S. It is possible that in BE acid reflux increases intracellular calcium, activates NOX5-S, and increases ROS production, which causes DNA damage, thereby contributing to the progression from BE to EA.

Regulation of NADPH oxidase 5 by protein kinase C isoforms

NADPH oxidase5 (Nox5) is a novel Nox isoform which has recently been recognized as having important roles in the pathogenesis of coronary artery disease, acute myocardial infarction, fetal ventricular septal defect and cancer. The activity of Nox5 and production of reactive oxygen species is regulated by intracellular calcium levels and phosphorylation. However, the kinases that phosphorylate Nox5 remain poorly understood. Previous studies have shown that the phosphorylation of Nox5 is PKC dependent, but this contention was based on the use of pharmacological inhibitors and the isoforms of PKC involved remain unknown. Thus, the major goals of this study were to determine whether PKC can directly regulate Nox5 phosphorylation and activity, to identify which isoforms are involved in the process, and to understand the functional significance of this pathway in disease. We found that a relatively specific PKCα inhibitor, Ro-32-0432, dose-dependently inhibited PMA-induced superoxide production from Nox5. PMA-stimulated Nox5 activity was significantly reduced in cells with genetic silencing of PKCα and PKCε, enhanced by loss of PKCδ and the silencing of PKCθ expression was without effect. A constitutively active form of PKCα robustly increased basal and PMA-stimulated Nox5 activity and promoted the phosphorylation of Nox5 on Ser490, Thr494, and Ser498. In contrast, constitutively active PKCε potently inhibited both basal and PMA-dependent Nox5 activity. Co-IP and in vitro kinase assay experiments demonstrated that PKCα directly binds to Nox5 and modifies Nox5 phosphorylation and activity. Exposure of endothelial cells to high glucose significantly increased PKCα activation, and enhanced Nox5 derived superoxide in a manner that was in prevented by a PKCα inhibitor, Go 6976. In summary, our study reveals that PKCα is the primary isoform mediating the activation of Nox5 and this maybe of significance in our understanding of the vascular complications of diabetes and other diseases with increased ROS production.

New nucleophilic mechanisms of ros-dependent epigenetic modifications: comparison of aging and cancer

It has been shown that ROS (reactive oxygen species, superoxide and hydrogen peroxide) regulate major epigenetic processes, DNA methylation and histone acetylation, although the mechanism of ROS action (ROS signaling) is still unknown. Both DNA methylation and histone acetylation are nucleophilic processes and therefore ROS signaling through typical free radical processes, for example hydrogen atom abstraction is impossible. However, being "super-nucleophile" superoxide can participate in these reactions. Now we propose new nucleophilic mechanisms of DNA methylation and histone modification. During DNA methylation superoxide can deprotonate the cytosine molecule at C-5 position and by this accelerate the reaction of DNA with the positive-charged intermediate S-adenosyl-L-methionine (SAM). Superoxide can also deprotonate histone N-terminal tail lysines and accelerate the formation of their complexes with acetyl-coenzyme A (AcCoA), the supplier of acetyl groups. In cancer cells ROS enhance DNA methylation causing the silencing of tumor suppressor and antioxidant genes and enhancing the proliferation of cancer cells under condition of oxidative stress. ROS signaling in senescent cells probably causes DNA hypomethylation although there are insufficient data for such proposal.

Role of NADPH oxidase NOX5-S, NF-κB, and DNMT1 in acid-induced p16 hypermethylation in Barrett's cells

Inactivation of tumor suppressor genes via promoter hypermethylation may play an important role in the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA). We have previously shown that acid-induced p16 gene promoter hypermethylation may depend on activation of NADPH oxidase NOX5-S in BAR-T cells and OE33 EA cells. DNA methyltransferase 1 (DNMT1) is known to participate in maintaining established patterns of DNA methylation in dividing cells and may play an important role in the development of cancer. Therefore, we examined whether DNMT1 is involved in acid-induced p16 gene promoter hypermethylation in BAR-T cells. We found that the acid significantly increased p16 gene promoter methylation, decreased p16 mRNA, and increased cell proliferation, effects that may depend on activation of DNMT1 in BAR-T cells. DNMT1 is overexpressed in EA cells FLO and OE33 and EA tissues. Acid treatment upregulated DNMT1 mRNA expression and increased DNMT1 promoter activity. Acid-induced increases in DNMT1 mRNA expression and promoter activity were significantly decreased by knockdown of NOX5-S and NF-κB1 p50. Conversely, overexpression of NOX5-S, p50, or p65 significantly increased DNMT1 promoter activity. Knockdown of NOX5-S significantly decreased the acid-induced increase in luciferase activity in cells transfected with pNFκB-Luc. An NF-κB binding element GGGGTATCCC was identified in the DNMT1 gene promoter. We conclude that the acid-induced increase in p16 gene promoter methylation, downregulation of p16 mRNA, and increase in cell proliferation may depend on activation of DNMT1 in BAR-T cells. Acid-induced DNMT1 expression may depend on sequential activation of NOX5-S and NF-κB1 p50.

The esophagitis to adenocarcinoma sequence; the role of inflammation

Esophageal adenocarcinoma (EAC) is the eighth most common cancer worldwide, and approximately 15% of patients survive 5years. Reflux disease (GERD) and Barrett's esophagus (BE) are major risk factors for the development of EAC, and epidemiologic studies highlight a strong association with obesity. The immune, inflammatory and intracellular signaling changes resulting from chronic inflammation of the esophageal squamous epithelium are increasingly well characterized. In GERD and Barrett's, an essential role for T-cells in the initiation of inflammation in the esophagus has been identified, and a balance between T-cell responses and phenotype may play an important role in disease progression. Obesity is a chronic low-grade inflammatory state, fueled by adipose tissue derived- inflammatory mediators such as IL-6, TNF-α and leptin, representing a novel area for targeted research. Additionally, reactive oxygen species (ROS) and receptor tyrosine kinase (RTK) activation may drive progression from esophagitis to EAC, and downstream signaling pathways employed by these molecules may be important. This review will explain the diverse range of mechanisms potentially driving and maintaining inflammation within the esophagus and explore both existing and future therapeutic strategies targeting the process.

Balancing reactive oxygen species in the epigenome: NADPH oxidases as target and perpetrator

SIGNIFICANCE

NADPH oxidases are important sources for regulated generation of reactive oxygen species (ROS). The main ROS produced are superoxide and hydrogen peroxide, both of which are redox signaling molecules in the context of various cellular functions. Redox imbalance due to excessive or insufficient ROS is a hallmark of pathophysiological aspects, including cancer development and progression.

RECENT ADVANCES

Epigenetic silencing of NADPH oxidases by hypermethylation of their promoter region or of the genes required for their assembly and activity occurs in diseases, such as lung cancer, and may represent an early stage of neoplastic transformation.

CRITICAL ISSUES

Loss of ROS-mediated signaling by epigenetic silencing may promote tumorigenesis. Conversely, increased oxidative stress caused by oncogene-induced overexpression of NADPH oxidases may also drive epigenetic instability. Thus, the cellular redox balance is likely vital in carcinogenesis.

FUTURE DIRECTIONS

NADPH oxidases may serve as prognostic tumor biomarker, especially when their individual expression is confined to accessible tissues, such as mucosal epithelia or blood. Further validation of NADPH oxidase/dual oxidase enzymes as candidate markers will require well controlled, large-scale clinical data sets. This review is focused on NADPH oxidases as targets of epigenetic changes in cancer and on the emerging role of ROS as inducers of epigenetic changes.

NADPH Oxidases NOXs and DUOXs as putative targets for cancer therapy

Reactive oxygen species (ROS) form a class of molecules with both positive and negative impacts on cellular health. Negatively, ROS may react with cellular constituents including proteins, lipids, and DNA to generate an array of oxidative lesions. These lesions may compromise genome stability which is critical for long-term cellular homeostasis and healthy progeny. Paradoxically, ROS also function as strong signalling molecules that mediate various growth-related responses, so their presence is also essential for cellular metabolism. While ROS are generated in an unregulated manner by physical stresses such as exposure to ionizing radiation and biochemical malfunctions such as mitochondrial leakage, cells also contain the NADPH oxidases NOXs and DUOXs, which specifically generate ROS in a wide variety of tissues. While the NOXs/DUOXs may be involved in maintaining optimal cellular redox levels, there is also accumulating evidence that NADPH oxidases-derived ROS may elevate the risk for genomic instability and cancer. Cancer cells may produce high levels of ROS, and in some cases, the source of these ROS has been linked to NOX/DUOX deregulation as reported for prostate cancer (NOX1 and NOX5), melanoma and glioblastoma (NOX4) among others. In addition, recent studies reveal that targeting NADPH oxidases with NOXs inhibitors may impair tumor growth in vivo; indicating that these proteins may be useful targets in future clinical strategies to fight cancer. This review provides an overview of the current knowledge concerning these enzymes, their roles in cancer, and their potential as targets in future cancer therapies.

The roles of beta-adrenergic receptors in tumorigenesis and the possible use of beta-adrenergic blockers for cancer treatment: possible genetic and cell-signaling mechanisms

Cancer is the leading cause of death in the USA, and the incidence of cancer increases dramatically with age. Beta-adrenergic blockers appear to have a beneficial clinical effect in cancer patients. In this paper, we review the evidence of an association between β-adrenergic blockade and cancer. Genetic studies have provided the opportunity to determine which proteins link β-adrenergic blockade to cancer pathology. In particular, this link involves the major histocompatibility complex class II molecules, the renin-angiotensin system, transcription factor nuclear factor-kappa-light-chain-enhancer of activated B cells, poly(ADP-ribose) polymerase-1, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate oxidase. Beta-adrenergic blockers also exert anticancer effects through non-genomic factors, including matrix metalloproteinase, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, oxidative stress, and nitric oxide synthase. In conclusion, β-adrenergic blockade may play a beneficial role in cancer treatment. Additional investigations that examine β-adrenergic blockers as cancer therapeutics are required to further elucidate this role.

Molecular basis of esophageal cancer development and progression

This article discusses the molecular basis of esophageal cancer development and subsequent progression of disease. Differing epidemiologic factors are associated with esophageal adenocarcinoma and squamous cell carcinoma. These 2 different histologic types have differing putative underlying mechanisms of transdifferentiation from normal esophageal mucosa to malignant histologies via gene dysregulation, biochemical modifications, and altered cell signaling pathways. Our developing understanding of the molecular events underlying esophageal cancer is leading to the establishment of identifiable biomarkers and the clinical use of molecularly targeted treatment agents. The identification of driving genetic mutations and altered signaling pathways has also had favorable outcomes.

Review of the molecular profile and modern prognostic markers for gastric lymphoma: how do they affect clinical practice?

Primary gastric lymphoma is a rare cancer of the stomach with an indeterminate prognosis. Recently, a series of molecular prognostic markers has been introduced to better describe this clinical entity. This review describes the clinical importance of several oncogenes, apoptotic genes and chromosomal mutations in the initiation and progress of primary non-Hodgkin gastric lymphoma and their effect on patient survival. We also outline the prognostic clinical importance of certain cellular adhesion molecules, such as ICAM and PECAM-1, in patients with gastric lymphoma, and we analyze the correlation of these molecules with apoptosis, angiogenesis, tumour growth and metastatic potential. We also focus on the host-immune response and the impact of Helicobacter pylori infection on gastric lymphoma development and progression. Finally, we explore the therapeutic methods currently available for gastric lymphoma, comparing the traditional invasive approach with more recent conservative options, and we stress the importance of the application of novel molecular markers in clinical practice.

NOX5: from basic biology to signaling and disease

In mammals, the NADPH oxidase family of enzymes comprises seven members: NOXs 1-5, DUOX1, and DUOX2. All of these enzymes function to move an electron across cellular membranes, transferring it to oxygen to generate the superoxide anion. This generation of reactive oxygen species has important physiological and pathophysiological roles. NOX5 is perhaps the least well understood of these NOX isoforms, in part because the gene is not present in mice or rats. In recent years, however, there has been a rapid increase in our understanding of the NOX5 gene, the structural and biochemical aspects of the NOX5 enzyme, the role NOX5 plays in health and disease, and the development of novel NOX inhibitors. This review takes a look back at some historical aspects of the discovery of NOX5 and summarizes our current understanding of the enzyme.

Barrett's esophagus: progression to adenocarcinoma and markers

The following on progression to adenocarcinoma and markers of Barrett's esophagus includes commentariess on the expression of claudin 4 in Barrett's adenocarcinoma; the role of acid and bile salts; the role of insulin-like growth factor; the value of reactive oxygen species; the importance of abnormal methylation; genetic alterations in stromal cells and genomic changes in the epithelial cells; the value of confocal laser endomicroscopy for the subsurface analysis of the mucosa; indications for statins as adjuvant chemotherapeutic agent; the sequence of molecular events in malignant progression in Barrett's mucosa; and the value of the macroscopic markers and of p53 mutations.

Esophageal disease: updated information on inflammation

The following on esophageal disease provides updated information the mucosal defense against acid and acid-pepsin injury; the roles of platelet activating factor, mast cells, proinflammatory cytokines, and chemokines in inflammation; differences and similarities in erosive and nonerosive esophagitis; acid and vanilloid receptors in esophageal mucosa; and bile acid receptors in esophageal epithelium.

Barrett's esophagus: genetic and cell changes

The following includes commentaries on how genetic code of Barrett's esophagus (BE) patients, the mechanisms for GERD-induced esophageal expression of caudal homeobox, and the development of Barrett's metaplasia are increasingly better known, including the role of stromal genes in oncogenesis. Additional lessons have been learned in vitro models in nonneoplastic cell lines, yet there are limitations to what can be expected from BE-derived cell lines. Other topics discussed include clonal diversity in Barrett's esophagus; the application of peptide arrays to clinical samples of metaplastic mucosa; proliferation and apoptosis of Barrett's cell lines; tissue biomarkers for neoplasia; and transcription factors associated with BE.

Signaling in H2O2-induced increase in cell proliferation in Barrett's esophageal adenocarcinoma cells

Mechanisms whereby acid reflux may accelerate the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. We have previously shown that NADPH oxidase NOX5-S generates reactive oxygen species (ROS) when Barrett's metaplastic cells are exposed to acid. Besides metaplastic cells, other H(2)O(2)-producing cells (e.g., inflammatory cells) present in BE mucosa may produce additional ROS, which may also affect metaplastic cells contributing to esophageal tumorigenesis. In this study, we investigate whether exogenous H(2)O(2) stimulates cell proliferation by increasing NOX5-S expression. Low dose (10(-13) M) of H(2)O(2) significantly increased thymidine incorporation, NOX5-S mRNA, and protein expression in a Barrett's EA cell line FLO. H(2)O(2)-induced increase in NOX5-S expression was significantly inhibited by knockdown of nuclear factor (NF)-κB1 p50 with p50 small interfering RNA (siRNA) in EA cell lines FLO and OE33. H(2)O(2) significantly increased p65 phosphorylation and the luciferase activity in FLO cells transfected with a NF-κB activation reporter plasmid pNF-κB-Luc. H(2)O(2)-induced increase in luciferase activity in FLO cells was significantly decreased by knockdown of extracellular signal-regulated kinase 2 (ERK2) mitogen-activated protein kinase (MAPK). Overexpression of p50 and p65 remarkably increased the luciferase activity in FLO cells transfected with a NOX5-S reporter plasmid NOX5-LP. In addition, H(2)O(2)-induced thymidine incorporation in FLO cells was significantly decreased by the MAPK kinase 1/2 inhibitor 2'-amino-3'methoxyflavone (PD98059) and ERK2 siRNA but not by ERK1 siRNA. Likewise, H(2)O(2)-induced increase in NOX5-S expression was significantly decreased by ERK2 siRNA in FLO and OE33 cells. We conclude that a low dose of H(2)O(2) increases cell proliferation. H(2)O(2)-induced increase in cell proliferation may depend on sequential activation of ERK2 MAPK, NF-κB1 p50, and NOX5-S.

Role of Rac1 in regulation of NOX5-S function in Barrett's esophageal adenocarcinoma cells

We have shown that a novel NADPH oxidase isoform, NOX5-S, is the major isoform of NADPH oxidases in an esophageal adenocarcinoma (EA) cell line, FLO, and is overexpressed in Barrett's mucosa with high-grade dysplasia. NOX5-S is responsible for acid-induced reactive oxygen species production. In this study, we found that mRNA levels of NOX5-S were significantly higher in FLO EA cells than in the normal human esophageal squamous cell line HET-1A or in a Barrett cell line, BAR-T. The mRNA levels of NOX5-S were also significantly increased in EA tissues. The data suggest that NOX5-S may be important in the development of EA. Mechanisms of functional regulation of NOX5-S are not fully understood. We show that small G protein Rac1 was present in HET-1A cells, BAR-T cells, and EA cell lines FLO and OE33. Rac1 protein levels were significantly higher in FLO and OE33 cells than in HET-1A or BAR-T cells. Knockdown of Rac1 with Rac1 small interfering RNA significantly decreased acid-induced increase in H(2)O(2) production in FLO EA cells. Overexpression of constitutively active Rac1 significantly increased H(2)O(2) production, an increase that was blocked by knockdown of NOX5-S. By immunofluorescence staining and immunoprecipitation, we found that NOX5-S was present in the cytosol of FLO EA cells and colocalized with Rac1 and SERCA1/2 Ca(2+)-ATPase which is located in the endoplasmic reticulum membrane. We conclude that Rac1 may be important in activation of NOX5-S in FLO EA cells.

Diet folate, DNA methylation and genetic polymorphisms of MTHFR C677T in association with the prognosis of esophageal squamous cell carcinoma

Background

Folic acid may affect the development of human cancers. However, few studies have evaluated the consumption of diet folate in the prognosis of patients with esophageal squamous cell carcinoma (ESCC).

Methods

One hundred and twenty five ESCC patients underwent esophagectomy between January 2005 and March 2006 in the Yangzhong People's Hospital were recruited and followed up. The effects of diet folate, aberrant DNA methylation of selected genes and methylenetetrahydrofolate reductase (MTHFR) C677T genetic polymorphisms on the prognosis of ESCC were evaluated by using Cox proportional hazard regression models.

Results

Our analysis showed an inverse association between diet folate intake and the risk of death after esophagectomy. The median survival time was 3.06 years for low or moderate folate consumption and over 4.59 years for high folate consumption. After adjusting for potential confounders, the hazard ratios (95% confidence interval) [HRs (95% CI)] were 0.72 (0.36-1.46) for moderate and 0.39 (0.20-0.78) for high folate intake, respectively (P for trend = 0.007). This preventive effect was more evident in patients carrying MTHFR 677CC genotype. No significant relation was observed between aberrant DNA methylation of P16, MGMT and hMLH1 gene, as well as MTHFR C677T genetic polymorphisms and the prognosis of ESCC.

Conclusions

Our research indicated that diet folate intake may have benefits on the prognosis of ESCC after esophagectomy. From a practical viewpoint, the findings of our study help to establish practical intervention and surveillance strategies for managements of ESCC patients and can finally decrease the disease burden.