DNA damage levels are raised in Barrett's oesophageal mucosa relative to the squamous epithelium of the oesophagus

From genetics to signaling pathways: molecular pathogenesis of esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) has one of the fastest rising incidence rates in the U.S. and many other Western countries. One of the unique risk factors for EAC is gastroesophageal reflux disease (GERD), a chronic digestive condition in which acidic contents from the stomach, frequently mixed with duodenal bile, enter the esophagus resulting in esophageal tissue injury. At the cellular level, progression to EAC is underlined by continuous DNA damage caused by reflux and chronic inflammatory factors that increase the mutation rate and promote genomic instability. Despite recent successes in cancer diagnostics and treatment, EAC remains a poorly treatable disease. Recent research has shed new light on molecular alterations underlying progression to EAC and revealed novel treatment options. This review focuses on the genetic and molecular studies of EAC. The molecular changes that occur during the transformation of normal Barrett's esophagus to esophageal adenocarcinoma are also discussed.

Modeling Esophagitis Using Human Three-Dimensional Organotypic Culture System

Esophagitis, whether caused by acid reflux, allergic responses, graft-versus-host disease, drugs, or infections, is a common condition of the gastrointestinal tract affecting nearly 20% of the US population. The instigating agent typically triggers an inflammatory response. The resulting inflammation is a risk factor for the development of esophageal strictures, Barrett esophagus, and esophageal adenocarcinoma. Research into the pathophysiology of these conditions has been limited by the availability of animal and human model systems. Three-dimensional organotypic tissue culture (OTC) is an innovative three-dimensional multicellular in vitro platform that recapitulates normal esophageal epithelial stratification and differentiation. We hypothesized that this platform can be used to model esophagitis to better understand the interactions between immune cells and the esophageal epithelium. We found that human immune cells remain viable and respond to cytokines when cultured under OTC conditions. The acute inflammatory environment induced in the OTC significantly affected the overlying epithelium, inducing a regenerative response marked by increased cell proliferation and epithelial hyperplasia. Moreover, oxidative stress from the acute inflammation induced DNA damage and strand breaks in epithelial cells, which could be reversed by antioxidant treatment. These findings support the importance of immune cell-mediated esophageal injury in esophagitis and confirms the utility of the OTC platform to characterize the underlying molecular events in esophagitis.

Acetic Acid Enhanced Narrow Band Imaging for the Diagnosis of Gastric Intestinal Metaplasia

Gastric intestinal metaplasia (GIM) is a precancerous lesion of the stomach. The detection of GIM using conventional white-light endoscopy (WLE) is difficult. In this study, we determined whether acetic acid-enhanced narrow band imaging (AA-NBI) improves the detection of GIM. A consecutive cohort of 132 individuals aged 40 years or older was subjected to upper gastrointestinal endoscopy using WLE, NBI and AA-NBI. The ability of the three methods to diagnose GIM in patients was compared. Histological assessment (per-patient and per-biopsy) was used for the accuracy assessment. Sixty-six (50.0%) out of the 132 individuals examined were found to have GIM, of which 44 (66.7%) were diagnosed correctly by NBI (sensitivity 66.7% and specificity 68.2%) and 58 (87.9%) were correctly identified by AA–NBI (sensitivity 87.9% and specificity 68.2%), as compared to only 22 (33.3%) by WLE (sensitivity 33.3% and specificity 28.8%). Therefore, the sensitivity of AA–NBI in the diagnosis of GIM was significantly higher than NBI (p<0.05) and WLE (p < 0.001). Our study indicates that AA-NBI can improve the accuracy of endoscopy-targeted biopsies for GIM.

Molecular mechanisms of constitutive and inducible NF-kappaB activation in oesophageal adenocarcinoma

BACKGROUND

Nuclear factor-kappaB (NF-κB) regulates the expression of a large number of genes involved in the immune and inflammatory response. NF-κB is constitutively activated in oesophageal tumour tissues and induced in oesophageal cells by bile and acid. The aim of the present study was to define the mechanisms underlying NF-κB activation in oesophageal adenocarcinoma.

PATIENTS AND METHODS

Fresh biopsy specimens were obtained from 20 patients with oesophageal adenocarcinoma. The activation of NF-κB in oesophageal tumour specimens and oesophageal SKGT-4 cells was assessed by gel mobility shift and Western blotting. Phosphorylation of protein kinase B (AKT/PKB), Ikappa kinase-alpha/beta (IKK-α/β) and extracellular signal-regulated kinase 1/2 (ERK1/2) was examined by Western blotting. High content analysis was used to quantify NF-κB translocation in oesophageal cells.

RESULTS

Oesophageal tumour tissues had higher levels of NF-κB. Increased levels of phosphorylated AKT and IKK-α/β and ERK1/2 were detected in tumour tissues compared with normal oesophageal mucosa. Exposure of SKGT-4 cells to deoxycholic acid (DCA) or acid resulted in NF-κB activation and phosphorylation of AKT, IKK-α/β and ERK1/2. Specific inhibitors for phosphoinositide 3-kinase; PI3K (LY294002 and worhmannin) and ERK1/2 inhibitors (PD98059 and U0126) suppressed DCA- and acid-induced NF-κB activation. The proteasome inhibitor MG-132 and the antioxidants vitamin C and pyrrolidine dithiocarbamate (PDTC) also inhibited NF-κB activation.

CONCLUSIONS

Our data demonstrate a major role for PI3K/AKT-IKK-α/β-ERK1/2 signalling pathway in NF-κB activation in oesophageal adenocarcinoma. These results suggest that NF-κB may be a prognostic marker for oesophageal adenocarcinoma, and modulating of NF-κB may uncover new therapeutic strategies.

Reflux induces DNA strand breaks and expression changes of MMP1+9+14 in a human miniorgan culture model

Gastroesophageal reflux disease has been implicated in the pathogenesis of adenocarcinoma of the oesophagus. The same applies to laryngopharyngeal reflux (LPR) and squamous cell cancer of the head and neck, but so far, this link has not been proven. The impact of low pH and bile acids has not been studied extensively in cells other than oesophageal cancer cell lines and tissue. The aims of this study were to investigate the pathogenic potential of reflux and its single components on the mucosa of the upper respiratory tract. We measured DNA stability in human miniorgan cultures (MOCs) and primary epithelial cell cultures (EpCs) in response to reflux by the alkaline comet assay. As matrix metalloproteinases (MMPs) are involved in extracellular matrix remodelling processes and may contribute to cancer progression, we studied the expression of MMP1, -9, and -14 in MOCs, EpC, UM-SCC-22B, and FADUDD. DNA strand breaks (DNA-SBs) increased significantly at low pH and after incubation with human or artificial gastric juice. Single incubation with glycochenodeoxycholic acid also showed a significant increase in DNA-SBs. In epithelial cell cultures, human gastric juice increased the number of DNA-SBs at pH 4.5 and 5.5. Artificial gastric juice significantly up regulated the gene expression of MMP9. Western blot analysis confirmed the results of gene expression analysis, but the up regulation of MMP1, -9, and -14 was donor-specific. Reflux has the ability to promote genomic instability and may contribute to micro environmental changes suitable for the initiation of malignancy. Further functional gene analysis may elucidate the role of laryngopharyngeal reflux in the development of head neck squamous cell carcinoma (HNSCC).

Marginal turbid band and light blue crest, signs observed in magnifying narrow-band imaging endoscopy, are indicative of gastric intestinal metaplasia

Background

Gastric intestinal metaplasia (IM) usually appears in flat mucosa and shows few morphologic changes, making diagnosis using conventional endoscopy unreliable. Magnifying narrow-band imaging (NBI) endoscopy enables evaluation of detailed morphological features that correspond with the underlying histology. The aim of this study was to investigate and clarify the diagnostic efficacy of magnifying NBI endoscopic findings for the prediction and diagnosis of IM.

Methods

Forty-seven patients were prospectively enrolled, and magnifying NBI examinations were performed in the lesser curvature of the midbody and the greater curvature of the upper body. The marginal turbid band (MTB) was defined as an enclosing white turbid band on the epithelial surface/gyri; light blue crest (LBC), as a fine, blue-white line on the crest of the epithelial surface/gyri. Immediately after observation under magnifying endoscopy, biopsy specimens were obtained from the evaluated areas.

Results

The degree of IM significantly increased with increasing MTB/LBC positivity (MTB^-/LBC^-, 0.00 ± 0.00; MTB⁺/LBC^-, 0.44 ± 0.51; MTB⁺/LBC⁺, 0.94 ± 0.24; p < 0.001). Moderate-to-severe IM was more common in MTB⁺/LBC⁺ areas than in MTB⁺/LBC^- areas (p < 0.001). For the diagnosis of IM, MTB had a sensitivity, specificity, and accuracy of 100%, 66.0%, and 81.7%, respectively, and the corresponding values for LBC were 72.1%, 96.0%, and 84.9%.

Conclusion

MTB and LBC observed in the gastric mucosa with magnifying NBI endoscopy are highly accurate indicators of the presence of IM. MTB likely represents a sign of early gastric IM, while LBC appears with progression to severe IM.

Proton pump inhibitors suppress iNOS-dependent DNA damage in Barrett's esophagus by increasing Mn-SOD expression

Barrett's esophagus (BE), an inflammatory disease, is a risk factor for Barrett's esophageal adenocarcinoma (BEA). Treatment of BE patients with proton pump inhibitors (PPIs) is expected to reduce the risk of BEA. We performed an immunohistochemical study to examine the formation of nitrative and oxidative DNA lesions, 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxygaunosine (8-oxodG), in normal esophageal, BE with pre- and post-treatment by PPIs and BEA tissues. We also observed the expression of an oxidant-generating enzyme (iNOS) and its transcription factor NF-κB, an antioxidant enzyme (Mn-SOD), its transcription factor (Nrf2) and an Nrf2 inhibitor (Keap1). The immunoreactivity of DNA lesions was significantly higher in the order of BEA>BE>normal tissues. iNOS expression was significantly higher in the order of BEA>BE>normal tissues, while Mn-SOD expression was significantly lower in the order of BEA<BE<normal tissues. Interestingly, Mn-SOD expression and the nuclear localization of Nrf2 were significantly increased, and the formation of DNA lesions was significantly decreased in BE tissues after PPIs treatment for 3-6months. Keap1 and iNOS expression was not significantly changed by the PPIs treatment in BE tissues. These results indicate that 8-nitroguanine and 8-oxodG play a role in BE-derived BEA. Additionally, PPIs treatment may trigger the activation and nuclear translocation of Nrf2 resulting in the expression of antioxidant genes, leading to DNA damage suppression. These DNA lesions can be useful biomarkers to predict both the risk of BEA and the efficacy of PPIs treatment to prevent BEA in BE patients.

DNA repair and mutagen sensitivity of epithelial cells and lymphocytes in oropharyngeal cancer

Tobacco-associated nitrosamines are known carcinogens causing DNA damage in epithelial cells of the head and neck. A matched case-control study was performed to evaluate the sensitivity of patients with squamous cell cancer (SCC) of the oropharynx, and controls to tobacco-associated nitrosamines. Quantitative DNA repair was evaluated following a period of 15 and 30 min. Fresh biopsies from 100 male donors of macroscopically healthy oropharyngeal cells and lymphocytes (50 SCC patients and 50 controls) were incubated with N-nitrosodiethylamine (NDEA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or N-nitrosonornicotine (NNN). DNA damage in epithelial cells and lymphocytes was assessed using the comet assay. Following incubation with NDEA, cells underwent a period of DNA repair. All of the nitrosamines caused equivalent genotoxic damage in mucosal cells and lymphocytes of the two groups. Lymphocyte DNA repair capacity in the control group (26.8 and 37.1% after 15 and 30 min) was comparable to the tumor group (23.6 and 40.6%). However, epithelial cell DNA repair capacity of carcinoma patients was significantly reduced to 17.1% (15 min) and 23% (30 min) compared to the DNA repair of the control group (36.2%, 15 min and 46.0%, 30 min). Mutagen sensitivity was comparable in patients and controls. Thus, reduced epithelial cell DNA repair capacity of tumor patients is a possible endogenous risk factor for the development of head and neck squamous cell cancer.

Genetic diversity during the development of Barrett's oesophagus-associated adenocarcinoma: how, when and why?

Recent investigations into Barrett's oesophagus at the level of individual crypts have found significant genetic heterogeneity within a single lesion. Furthermore, this genetic diversity has been shown to predict cancer development. In the present article, we review the genetic alterations implicated in disease progression in Barrett's oesophagus and discuss how genetic diversity could arise during tumorigenesis. Three arguments are discussed: a high mutation rate coupled with strong selection, clonal interaction driving progression, and a hitherto unidentified alteration that disrupts epithelial cell homoeostasis. Suggestions are made for future research to distinguish which of these theories is the predominant mechanism in Barrett's oesophagus-associated tumorigenesis.

Prevalence and predictors of recurrent neoplasia after ablation of Barrett's esophagus

BACKGROUND

The incidence and risk factors for recurrence of dysplasia after ablation of Barrett's esophagus (BE) have not been well defined.

OBJECTIVE

To determine the rate and predictors of dysplasia/neoplasia recurrence after photodynamic therapy (PDT) in BE.

SETTING

Retrospective analysis of a prospective cohort of BE patients seen at a specialized BE unit.

METHODS

Patients underwent a standard protocol assessment with esophagogastroduodenoscopy and 4-quadrant biopsies every centimeter at 3-month intervals after ablation. Recurrence was defined as the appearance of any grade of dysplasia or neoplasia after 2 consecutive endoscopies without dysplasia. Entry histology, demographics, length of BE, presence and length of diaphragmatic hernia, EMR, stricture formation, nonsteroidal anti-inflammatory drug use, smoking, and the presence of nondysplastic BE or squamous epithelium were assessed for univariate associations. Time-to-recurrence analysis was done by using Cox proportional hazards regression. A multivariate model was constructed to establish independent associations with recurrence.

RESULTS

A total of 363 patients underwent PDT with or without EMR. Of these, 261 patients were included in the final analysis (44 lost to follow-up, 46 had residual dysplasia, and 12 had no dysplasia at baseline). Indication for ablation was low-grade dysplasia (53 patients, 20%), high-grade dysplasia (152 patients, 58%), and intramucosal cancer (56 patients, 21%). Median follow-up was 36 months (interquartile range 18-79 months). Recurrence occurred in 45 patients. Median time to recurrence was 17 months (interquartile range 8-45 months). Significant predictors of recurrence on the multivariate model were older age (hazard ratio [HR] 1.04, P=.029), presence of residual nondysplastic BE (HR 2.88, P=.012), and a history of smoking (HR 2.68, P=.048).

LIMITATIONS

Possibility of missing prevalent dysplasia despite aggressive surveillance.

CONCLUSION

Recurrence of dysplasia/neoplasia after PDT ablation is associated with advanced age, smoking, and residual BE.

Transformation of benign Barrett's epithelium by repeated acid and bile exposure over 65 weeks: a novel in vitro model

The mechanism by which gastroesophageal reflux promotes metaplasia→dysplasia→carcinoma is unknown. The aim of the study is to determine if repeated exposure to acid and bile confers a tumorigenic phenotype in a telomerase (hTERT)-immortalized benign Barrett's cell line (BAR-T). BAR-T cells were exposed to acid (pH 4) (A) and bile salt (200 μM glycochenodeoxycholic acid) (B) daily for 5 min up to 65+ weeks. The control cells were grown in parallel without any A or B treatment. Cell morphology, proliferation, transformation, and molecular changes in the gene expression for COX-2, TC22, p53 and p53 target genes were analyzed at 8-12 weeks intervals. At 46 weeks BAR-T cells exposed to (A+B) showed distinct phenotypic changes: forming clusters and acini, and at 65 weeks displayed foci in monolayer, and formed distinct colonies in soft agar. Untreated cells did not show any such changes. In A+B-treated BAR-T cells, COX-2 mRNA increased 10- to 20-fold, TC22 mRNA increased by 2- to 3-fold at 22-65 weeks, p53, MDM2, PERP, and p21mRNA increased 2.5-, 6.4-, 4-, and 2.6-fold respectively when compared to untreated cells at 34 weeks. However, at 58 weeks onward, there was a sharp decline of p53 and its target genes to the baseline level. At 65 weeks A+B-treated BAR-T cells formed tumor in nude mice whereas untreated cells did not. We demonstrate a novel in vitro model of transformation of a benign Barrett's cell line following repeated exposure to A+B over the course of 65 weeks.

The role of oxidative DNA damage, DNA repair, GSTM1, SOD2 and OGG1 polymorphisms in individual susceptibility to Barrett’s esophagus

Determination of the genetic alterations, which play a role in the etiology of Barrett’s esophagus (BE), could help identify high-risk individuals for esophageal adenocarcinoma (EA). The aim of the present study was to investigate the role of oxidative DNA damage, glutathione (GSH) concentration as oxidative stress parameters and DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms as individual susceptibility parameters in the etiology of BE. The study groups comprised BE patients who were clinically diagnosed (n = 40) and a healthy control group (n = 40). Basal DNA damage, pyrimidine and purine base damage after H2O2 induction, H 2O2 sensitivity, DNA repair capacity, oxidized pyrimidine and purine base damage repair were evaluated in peripheral blood lymphocytes with a modified comet assay using specific endonucleases (Endo III and Fpg). Polymerase chain reaction—restriction length polymorphism (PCR-RFLP)-based assays were used for genotyping. The patient group showed elevated levels of basal DNA damage, pyrimidine base damage and H2O2 sensitivity as compared to controls (p < .05). DNA repair capacity, oxidized pyrimidine and purine base damage repair capacity, were not statistically different between patients and controls. GSH concentration was found to be significantly lower in smoking patients than in the controls (p < .05). None of the genetic variations changed the risk of having BE disease. However, patients carrying the variant OGG1 Cys allele showed elevated levels of pyrimidine base damage as compared to patients carrying the wild-type OGG1 Ser (p < .05). The results of this study point to a role of oxidative DNA damage in BE. However, DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms appeared to play no role in the individual susceptibility to this disease.

In benign Barrett's epithelial cells, acid exposure generates reactive oxygen species that cause DNA double-strand breaks

Cells that sustain double-strand breaks (DSB) can develop genomic instability, which contributes to carcinogenesis, and agents that cause DSBs are considered potential carcinogens. We looked for evidence of acid-induced DNA damage, including DSBs, in benign Barrett's epithelial (BAR-T) cell lines in vitro and in patients with Barrett's esophagus in vivo. In BAR-T cells, we also explored the mechanisms underlying acid-induced DNA damage. We exposed BAR-T cells to acid in the presence of a fluorescent probe for reactive oxygen species (ROS) and in the presence or absence of disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (which prevents intracellular acidification) and N-acety-l-cysteine (a scavenger of ROS). DSBs were detected by Western blotting and immunofluorescence for histone H2AX phosphorylation and by CometAssay. During endoscopy in patients with Barrett's esophagus, we took biopsy specimens from the metaplastic mucosa before and after esophageal perfusion with 0.1 N HCl for 3 min and sought DSBs by Western blotting for histone H2AX phosphorylation. In BAR-T cells, acid exposure resulted in ROS production and caused a time-dependent increase in levels of phospho-H2AX that continued for at least 48 h. Pretreatment with disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate or N-acety-l-cysteine prevented the acid-induced increase in phospho-H2AX levels. DSBs also were detected in biopsy specimens of Barrett's metaplasia following esophageal acid perfusion in all of 6 patients with Barrett's esophagus. Acid exposure causes DSBs in Barrett's epithelial cells through ROS produced as a consequence of intracellular acidification. These findings suggest that acid can be considered a carcinogen in Barrett's esophagus.

Cdx genes, inflammation and the pathogenesis of Barrett's metaplasia

Metaplasia is the conversion of one cell or tissue type to another and can predispose patients to neoplasia. Perhaps one of the best-known examples of metaplasia is Barrett's metaplasia (BM), a pathological condition in which the distal oesophageal epithelium switches from stratified squamous to intestinal-type columnar epithelium. BM predisposes to oesophageal adenocarcinoma and is the consequence of long-term acid bile reflux. The incidence of BM and oesophageal adenocarcinoma has risen dramatically in recent years. A key event in the pathogenesis of BM is the induction of oesophageal CDX2 expression. Importantly, recent data reveal the molecular mechanisms that link inflammation in the development of Barrett's metaplasia, CDX2 and the progression to cancer. This review highlights the relationship between inflammation, metaplasia and carcinogenesis.

Different redox states in malignant and nonmalignant esophageal epithelial cells and differential cytotoxic responses to bile acid and honokiol

Esophageal adenocarcinoma (EAC) is a highly lethal cancer in western countries. EAC cells are believed to develop from esophageal epithelial cells through complex transformation processes involving inflammation and oxidative stress. The purpose of this study was to compare the redox status of malignant and nonmalignant esophageal epithelial cells and to test their responses to bile acid-induced oxidative stress and to treatment with honokiol (HNK), a natural product with anticancer activity. We demonstrated that esophageal adenocarcinoma cells express significantly higher levels of antioxidant molecules and were resistant to reactive oxygen species (ROS) stress induced by bile acid, but were sensitive to the cytotoxic action of HNK. Mechanistic study showed that HNK caused cancer cell death by disruption of mitochondrial transmembrane potential and was correlated with cyclophilin D (CypD) expression. Inhibition of CypD by cyclosporin A or abrogation of its expression by siRNA significantly suppressed the cytotoxicity of HNK, suggesting that CypD may be a key molecule that mediates the cytotoxicity. Our study suggests that the high antioxidant capacity in EAC cells confers on them the ability to survive the oxidative microenvironment in the reflux esophagus, and that HNK is a promising compound to kill the transformed cells preferentially.

Barrett's esophagus

Barrett's esophagus is an important step in the pathway to esophageal adenocarcinoma. Since most patients with Barrett's esophagus are undiagnosed and patients present with advanced adenocarcinoma de novo, prognosis for this disease remains poor. To identify those people with Barrett's esophagus who are at particular risk many new technologies are being developed. In association with these advances in risk stratification, progress is being made in the endoscopic treatment of Barrett's. Chemoprevention is also an area of interest and trials are underway.

An animal model to evaluate the function and regulation of the adaptively evolving stress protein SEP53 in oesophageal bile damage responses

Squamous epithelium in mammals has evolved an atypical stress response involving down-regulation of the classic HSP70 protein and induction of sets of proteins including one named SEP53. This atypical stress response might be due to the unusual environmental pressures placed on squamous tissue. In fact, SEP53 plays a role as an anti-apoptotic factor in response to DNA damage induced by deoxycholic acid stresses implicated in oesophageal reflux disease. SEP53 also has a genetic signature characteristic of an adaptively and rapidly evolving gene, and this observation has been used to imply a role for SEP53 in immunity. Physiological models of squamous tissue are required to further define the regulation and function of SEP53. We examined whether porcine squamous epithelium would be a good model to study SEP53, since this animal suffers from a bile-reflux disease in squamous oesophageal tissue. We have (1) cloned and sequenced the porcine SEP53 locus from porcine bacterial artificial chromosome genomic DNA, (2) confirmed the strikingly divergent nature of the C-terminal portion of the SEP53 gene amongst mammals, (3) discovered that a function of the conserved N-terminal domain of the gene is to maintain cytoplasmic localisation, and (4) examined SEP53 expression in normal and diseased porcine pars oesophagea. SEP53 expression in porcine tissue was relatively confined to gastric squamous epithelium, consistent with its expression in normal human squamous epithelium. Immunohistochemical staining for SEP53 protein in normal and damaged pars oesophagea demonstrated significant stabilisation of SEP53 protein in the injured tissue. These results suggest that porcine squamous epithelium would be a robust physiological model to examine the evolution and function of the SEP53 stress pathway in modulating stress-induced responses in squamous tissue.

The expression of 8-hydroxydeoxyguanosine in oesophageal tissues and tumours

PURPOSE

The most common marker of oxidative DNA damage is 8-hydroxydeoxyguanosine (8-OHdG), which is linked with several malignancies. In the present study we investigated whether DNA damage linked to oxidative stress (as 8-OHdG) is present in Barrett's mucosa with or without associated adenocarcinoma or high-grade dysplasia and in normal controls' squamous mucosa.

EXPERIMENTAL DESIGN

We measured 8-OHdG in 51 patients (13 Barrett's metaplasia, six Barrett's oesophagus with high-grade dysplasia, 18 adenocarcinoma of the distal oesophagus/oesophagogastric junction and 14 normal controls). The amount of DNA damage was determined by high-performance liquid chromatography in oesophagus samples obtained either from endoscopy or as samples from surgery. The median 8-OHdG concentration was expressed as the ratio of 8-OHdG per 10(5) deoxyguanosine.

RESULTS

Analysis revealed that 8-OHdG was present in both Barrett's metaplasia with and without dysplasia as well as in adenocarcinoma of the oesophagus/oesophagogastric junction. Although the study group was small the amount of 8-OHdG was significantly increased in the distal oesophagus both in Barrett's epithelium 1.26 (0.08-29.47) and in high-grade dysplasia 1.35 (1.04-1.65) as well as in adenocarcinoma of oesophagus/oesophagogastric junction 1.08 (0.59-1.94) compared to controls 0.06 (0-4.08) (p=0.002, p=0.012, p=0.001, respectively). Barrett's patients had no significant difference in 8-OHdG levels between their distal and proximal oesophageal samples.

CONCLUSIONS

Our results show the presence of oxidative DNA damage in the distal oesophagus of patients with Barrett's oesophagus and adenocarcinoma of the oesophagus/oesophagogastric junction. This may have a connection to carcinogenesis in Barrett's oesophagus.

In non-neoplastic Barrett's epithelial cells, acid exerts early antiproliferative effects through activation of the Chk2 pathway

Acid exerts pro-proliferative effects in Barrett's-associated esophageal adenocarcinoma cells. In non-neoplastic Barrett's epithelial (BAR-T) cells, in contrast, we have shown that acid exposure has antiproliferative effects. To explore our hypothesis that the acid-induced, antiproliferative effects are mediated by alterations in the proteins that regulate the G(1)-S cell cycle checkpoint, we exposed non-neoplastic Barrett's cells to acidic media (pH 4.0) and analyzed G(1)-S checkpoint proteins' expression, phosphorylation, and activity levels by Western blot. We studied acid effects on growth (by cell counts), proliferation (by flow cytometry and bromodeoxyuridine incorporation), cell viability (by trypan blue staining), and apoptosis (by annexin V staining), and we used caffeine and small interfering RNA to assess the effects of checkpoint kinase 2 (Chk2) inhibition on G(1)-S progression. Acid exposure significantly decreased cell numbers without affecting cell viability and with only a slight increase in apoptosis. Within 2 h of acid exposure, there was a delay in progression through the G(1)-S checkpoint that was associated with increased phosphorylation of Chk2, decreased levels of Cdc25A, and decreased activity of cyclin E-cyclin-dependent kinase 2; by 4 h, a continued delay at G(1)-S was associated with increased expression of p53 and p21. Caffeine and Chk2 siRNA abolished the acid-induced G(1)-S delay at 2 but not at 4 h. We conclude that acid exposure in non-neoplastic BAR-T cells causes early antiproliferative effects that are mediated by the activation of Chk2. Thus, we have elucidated a mechanism whereby acid can exert disparate effects on proliferation in neoplastic and non-neoplastic BAR-T cells.

Nitric oxide and acid induce double-strand DNA breaks in Barrett's esophagus carcinogenesis via distinct mechanisms

BACKGROUND & AIMS

The luminal microenvironment including acid and nitric oxide (NO) has been implicated in Barrett's esophagus carcinogenesis. We investigated the ability of acid and NO to induce DNA damage in esophageal cells.

METHODS

Transformed and primary Barrett's esophagus and adenocarcinoma cells were exposed to either acid, (pH 3.5), +/- antioxidant or NO from a donor or generated by acidification of nitrite in the presence of ascorbate +/- NO scavenger. Phosphorylation of histone H2AX and the neutral comet assay were used to detect DNA double-strand breaks (DSBs). Intracellular levels of reactive oxygen species and NO were detected with fluorescent dyes. Mitochondrial viability was measured with a rhodamine dye. Long-term survival was assessed by clonogenic assay.

RESULTS

Exposure to acid (pH 3.5) for > or =15 minutes induced DSBs in all cell lines (P < .05). There was a concomitant increase in intracellular reactive oxygen species in the absence of mitochondrial damage, and pretreatment with antioxidants inhibited DNA damage. Exposure to physiologic concentrations of NO produced from the NO donor or acidification of salivary nitrite induced DSBs in a dose- (>25 micromol/L) and cell-dependent manner (adenocarcinoma >Barrett's esophagus, P < .05). This occurred preferentially in S-phase cells consistent with stalled replication forks and was blocked with a NO scavenger. NO also induced DSBs in primary Barrett's esophagus cells treated ex vivo. Cells were able to survive when exposed to acid and NO.

CONCLUSIONS

Both acid and NO have the potential to generate DSBs in the esophagus and via distinct mechanisms.

The NAD(P)H:quinone oxidoreductase I C609T polymorphism modifies the risk of Barrett esophagus and esophageal adenocarcinoma

PURPOSE

The role of genetic susceptibility to esophageal adenocarcinoma and its precursor lesion Barrett esophagus has not been fully elucidated. This study investigated the effect of polymorphisms in the manganese superoxide dismutase (MnSOD) and NAD(P)H:quinone oxidoreductase 1 (NQO1) genes in modulating the risk of developing Barrett esophagus or esophageal adenocarcinoma.

METHODS

A total of 584 patients (146 esophagitis, 200 Barrett esophagus, 144 esophageal adenocarcinoma, and 94 controls) were genotyped for the MnSOD C14T and NQO1 C609T polymorphisms using polymerase chain reaction and restriction fragment length polymorphism analysis.

RESULTS

The NQO1 TT genotype was less common in Barrett esophagus (2.0%) and esophageal adenocarcinoma (1.4%) patients, compared with both esophagitis patients (7.6%) and controls (5.4%). After adjustment for sex, age, body mass index, reflux symptoms, and smoking status, patients with the homozygous TT genotype had a 4.5-fold decreased risk of developing Barrett esophagus (odds ratio = 0.22, 95% confidence interval = 0.07-0.76, P = 0.01) and a 6.2-fold decreased risk of esophageal adenocarcinoma (odds ratio = 0.16, 95% confidence intervals = 0.03-0.94, P = 0.04) compared with individuals with the TC and CC genotypes. No significant differences between groups were observed for the MnSOD polymorphism (P = 0.289).

CONCLUSIONS

Overall, the results of this study suggest that the NQO1 TT genotype may offer protection from reflux complications such as Barrett esophagus and esophageal adenocarcinoma.

GERD is associated with shortened telomeres in the squamous epithelium of the distal esophagus

Telomeres are repetitive DNA sequences located at the ends of chromosomes. Telomeres are shortened by repeated cell divisions and by oxidative DNA damage, and cells with critically shortened telomeres cannot divide. We hypothesized that chronic gastroesophageal reflux disease (GERD)-induced injury of the esophageal squamous epithelium results in progressive telomeric shortening that eventually might interfere with mucosal healing. To address our hypothesis, we compared telomere length and telomerase activity in biopsy specimens of esophageal squamous epithelium from GERD patients and control patients. Endoscopic biopsies were taken from the esophageal squamous epithelium of 38 patients with GERD [10 long-segment Barrett's esophagus (LSBE), 15 short-segment (SSBE), 13 GERD without Barrett's esophagus] and 16 control patients without GERD. Telomere length was assessed using the terminal restriction fragment assay, and telomerase activity was studied by the PCR-based telomeric repeat amplification protocol assay. Patients with GERD had significantly shorter telomeres in the distal esophagus than controls [8.3 +/- 0.5 vs. 10.9 +/- 1.5 (SE) Kbp, P = 0.043]. Among the patients with GERD, telomere length in the distal esophagus did not differ significantly in those with and without Barrett's esophagus (LSBE 7.9 +/- 0.8, SSBE 8.6 +/- 0.9, GERD without BE 8.7 +/- 1.0 Kbp). No significant differences in telomerase activity in the distal esophagus were noted between patients with GERD and controls (4.0 +/- 0.39 vs. 5.2 +/- 0.53 RIUs). Telomeres in the squamous epithelium of the distal esophagus of patients who have GERD, with and without Barrett's esophagus, are significantly shorter than those of patients without GERD despite similar levels of telomerase activity.

Systematic review: the application of molecular pathogenesis to prevention and treatment of oesophageal adenocarcinoma

BACKGROUND

Oesophageal adenocarcinoma is an increasingly common cancer with a poor prognosis. It develops in a stepwise progression from Barrett's metaplasia to dysplasia, and then adenocarcinoma followed by metastasis.

AIM

To outline the key molecular changes in oesophageal adenocarcinoma and to summarize the chemopreventative and therapeutic strategies proposed.

METHODS

A literature search was performed to identify appropriate research papers in the field. Search terms included: Barrett's (o)esophagus, intestinal metaplasia, (o)esophageal adenocarcinoma, molecular changes, genetic changes, pathogenesis, chemoprevention, therapeutic strategies and treatment. The search was restricted to English language articles.

RESULTS

A large number of molecular changes have been identified in the progression from Barrett's oesophagus to oesophageal adenocarcinoma although there does not appear to be an obligate order of events. Potential chemoprevention strategies include acid suppression, anti-inflammatory agents and antioxidants. In established adenocarcinoma, targeted treatments under evaluation include receptor tyrosine kinase inhibitors of EGFR and cyclin-dependent kinase inhibitors, which may benefit a subgroup of patients.

CONCLUSIONS

Advances in molecular methodology have led to a greater understanding of the oesophageal adenocarcinoma pathways, which provides opportunities for chemoprevention and therapeutic strategies with a mechanistic basis. More work is required to assess both the safety and efficacy of these new treatments.

Risk factors for Barrett’s oesophagus and oesophageal adenocarcinoma: Results from the FINBAR study

AIM: To investigate risk factors associated with Barrett’s oesophagus and oesophageal adenocarcinoma.

METHODS: This all-Ireland population-based case-control study recruited 224 Barrett’s oesophagus patients, 227 oesophageal adenocarcinoma patients and 260 controls. All participants underwent a structured interview with information obtained about potential lifestyle and environmental risk factors.

RESULTS: Gastro-oesophageal reflux was associated with Barrett’s [OR 12.0 (95% CI 7.64-18.7)] and oesophageal adenocarcinoma [OR 3.48 (95% CI 2.25-5.41)]. Oesophageal adenocarcinoma patients were more likely than controls to be ex- or current smokers [OR 1.72 (95% CI 1.06-2.81) and OR 4.84 (95% CI 2.72-8.61) respectively] and to have a high body mass index [OR 2.69 (95% CI 1.62-4.46)]. No significant associations were observed between these risk factors and Barrett's oesophagus. Fruit but not vegetables were negatively associated with oesophageal adenocarcinoma [OR 0.50 (95% CI 0.30-0.86)].

CONCLUSION: A high body mass index, a diet low in fruit and cigarette smoking may be involved in the progression from Barrett’s oesophagus to oesophageal adenocarcinoma.

Transitioning from preclinical to clinical chemopreventive assessments of lyophilized black raspberries: interim results show berries modulate markers of oxidative stress in Barrett's esophagus patients

Increased fruit and vegetable consumption is associated with decreased risk of a number of cancers of epithelial origin, including esophageal cancer. Dietary administration of lyophilized black raspberries (LBRs) has significantly inhibited chemically induced oral, esophageal, and colon carcinogenesis in animal models. Likewise, berry extracts added to cell cultures significantly inhibited cancer-associated processes. Positive results in preclinical studies have supported further investigation of berries and berry extracts in high-risk human cohorts, including patients with existing premalignancy or patients at risk for cancer recurrence. We are currently conducting a 6-mo chemopreventive pilot study administering 32 or 45 g (female and male, respectively) of LBRs to patients with Barrett's esophagus (BE), a premalignant esophageal condition in which the normal stratified squamous epithelium changes to a metaplastic columnar-lined epithelium. BE's importance lies in the fact that it confers a 30- to 40-fold increased risk for the development of esophageal adenocarcinoma, a rapidly increasing and extremely deadly malignancy. This is a report on interim findings from 10 patients. To date, the results support that daily consumption of LBRs promotes reductions in the urinary excretion of two markers of oxidative stress, 8-epi-prostaglandin F2alpha (8-Iso-PGF2) and, to a lesser more-variable extent, 8-hydroxy-2'-deoxyguanosine (8-OHdG), among patients with BE.

Mutagen Sensitivity and Neoplastic Progression in Patients with Barrett's Esophagus: A Prospective Analysis

BACKGROUND

Defects in DNA damage recognition and repair have been associated with a wide variety of cancers. We conducted a prospective study to determine whether mutagen sensitivity, as determined by an in vitro assay, was associated with the future development of cancer in patients with Barrett's esophagus, which is associated with increased risk of progression to esophageal adenocarcinoma.

METHODS

We measured sensitivity to bleomycin in peripheral blood lymphocytes in a cohort of 220 patients with Barrett's esophagus. We followed these patients for 1,230 person-years (range, 3 months to 10.1 years; median, 6.4 years), using development of cancer and aneuploidy as end points. A subset of these patients was evaluated for inactivation of tumor-suppressor genes CDKN2A/p16 and TP53 [by mutation and loss of heterozygosity (LOH)] in their Barrett's segments at the time of, or before, the bleomycin test, and the patients were stratified by CDKN2A/p16 and TP53 status in an analysis of mutagen sensitivity and progression.

RESULTS

Bleomycin-sensitive patients were found to be at significantly greater risk of developing aneuploidy (adjusted hazard ratio, 3.71; 95% confidence interval, 1.44-9.53) and nonsignificantly greater risk of cancer (adjusted hazard ratio, 1.63; 95% confidence interval, 0.71-3.75). Among patients with detectable LOH at the TP53 locus (on chromosome 17p), increasing bleomycin sensitivity was associated with increased risk of developing cancer (P(trend) < 0.001) and aneuploidy (P(trend) = 0.005).

CONCLUSIONS

This study supports the hypothesis that sensitivity to mutagens increases the risk of neoplastic progression in persons with Barrett's esophagus, particularly those with 17p LOH including TP53.

Evaluation of systemic oxidative status and mononuclear leukocytes DNA damage in children with caustic esophageal stricture

Esophageal stricture (ES) due to accidentally caustic digestions is a common problem in children. Mucosal damage and repeated dilatations lead to chronic inflammation and finally ES. We investigated the oxidative status and DNA damage of children with ES. Five children with ES were compared with the same age- and sex-matched healthy subjects. Oxidative status of plasma was evaluated by measuring myeloperoxidase (MPO) activity, and total peroxide (TP) level. Anti-oxidative status of the plasma was evaluated by measuring catalase (CAT) activity, and total antioxidant response (TAR). We used the Single Cell Gel Electrophoresis (also called Comet Assay) to measure DNA strand break in peripheral blood mononuclear leukocytes. Mean MPO activity and TP levels in the ES group were significantly higher than the control group (0.83 +/- 0.35, 0.09 +/- 0.03 and 0.98 +/- 0.38, 0.34 +/- 0.20, P = 0.009 and P = 0.047 respectively). There was no significant difference in CAT activity and TAR levels between the two groups (P = 0.347). DNA damage in patients with ES was increased compared to control subjects (108.8 +/- 51.2 and 57.6 +/- 31.2 arbitrary units, respectively), but this difference was not significant statistically (P= 0.09). This study shows that systemic oxidative stress and alteration at the nuclear level occur in patients with ES, as a result of multiple dilatations and tissue injury. On the other hand, these results support that patients with ES may benefit from antioxidant treatment.

Health practices and leukocyte DNA damage in Japanese hard-metal workers

OBJECTIVES

To investigate associations between total lifestyles and levels of leukocyte DNA damage in healthy Japanese workers.

METHODS

Eight health practices were investigated in 118 Japanese hard-metal workers by questionnaire in Osaka, Japan, in July 2004. Peripheral leukocyte DNA damage levels, as expressed by comet parameters, were determined using an alkaline comet assay.

RESULTS

After crediting one point to each of the health practices and accumulating them into a health practice index (HPI: 0-8 points), subjects with poor health practices (HPI = 0-3 points) showed a significantly higher tail moment than those with moderate (HPI = 4, 5 points) or good health practices (HPI = 6-8 points) (P < 0.01). Risk estimates for tail moment above the 75th percentile showed that, compared to those with good health practices, subjects with moderate health practices had an odds ratio of 1.76 (95% CI: 0.52, 5.91), and those with poor health practices had an odds ratio of 6.75 (95% CI: 1.80, 25.27) (P(trend) < 0.01). Multiple regression analysis showed that HPI was a significant predictor of the decreased tail moment (P < 0.01).

CONCLUSION

Poor lifestyles demonstrate a cumulative association with leukocyte DNA damage in these Japanese hard-metal workers.

Predictors of esophageal cancer risk: assessment of susceptibility to DNA damage using comet assay

Individuals' susceptibility to DNA damage could be identified by mutagen-challenged assays. We tested the hypothesis that susceptibility to DNA damage, measured by comet assay, may be associated with increased esophageal cancer (EC) risk. We recruited 102 subjects with previously untreated EC and 112 healthy controls. Baseline (untreated), benzo[a]pyrene diol epoxide (BPDE)-induced, and gamma-radiation-induced DNA damage were quantified by the Olive tail moment parameter. The mean tail moment was significantly higher in cases than in controls at baseline (case vs. control: 2.6 vs. 1.9, P < 0.01), after BPDE induction (case vs. control: 3.8 vs. 2.7, P < 0.01), and after gamma-radiation-induction (case vs. control: 5.0 vs. 3.8, P < 0.01). When data were dichotomized with the median values in the controls, a significantly increased risk for EC was observed for high baseline tail moment [odds ratio (OR) = 5.7, 95% confidence interval (CI) = 2.9-11.4], high BPDE-induced tail moment (OR = 5.8, 95% CI = 2.9-11.8), and high gamma-radiation-induced tail moment (OR = 4.6, 95% CI = 2.4-8.8). Further, the association between DNA damage and EC was stronger in never smokers than in ever smokers. Compared with subjects not sensitive to both mutagens, individuals sensitive to only one mutagen showed a 3.4-fold risk for EC and those sensitive to both mutagens showed an 8.7-fold risk for EC. Thus, we conclude that susceptibility to DNA damage as assessed by comet assay might help identify individuals with high EC risk.

Expression profile of malignant and nonmalignant lesions of esophagus and stomach: differential activity of functional modules related to inflammation and lipid metabolism

Adenocarcinomas of stomach and esophagus are frequently associated with preceding inflammatory alterations of the normal mucosa. Whereas intestinal metaplasia of the gastric mucosa is associated with higher risk of malignization, Barrett's disease is a risk factor for adenocarcinoma of the esophagus. Barrett's disease is characterized by the substitution of the squamous mucosa of the esophagus by a columnar tissue classified histopathologically as intestinal metaplasia. Using cDNA microarrays, we determined the expression profile of normal gastric and esophageal mucosa as well as intestinal metaplasia and adenocarcinomas from both organs. Data were explored to define functional alterations related to the transformation from squamous to columnar epithelium and the malignant transformation from intestinal metaplasia to adenocarcinomas. Based on their expression profile, adenocarcinomas of the esophagus showed stronger correlation with intestinal metaplasia of the stomach than with Barrett's mucosa. Second, we identified two functional modules, lipid metabolism and cytokine, as being altered with higher statistical significance. Whereas the lipid metabolism module is active in samples representing intestinal metaplasia and inactive in adenocarcinomas, the cytokine module is inactive in samples representing normal esophagus and esophagitis. Using the concept of relevance networks, we determined the changes in linear correlation of genes pertaining to these two functional modules. Exploitation of the data presented herein will help in the precise molecular characterization of adenocarcinoma from the distal esophagus, avoiding the topographical and descriptive classification that is currently adopted, and help with the proper management of patients with Barrett's disease.

Risk factors, DNA damage, and disease progression in Barrett's esophagus

Esophageal adenocarcinoma develops on a background of Barrett's esophagus. A number of risk factors have been linked to both conditions, including gastroesophageal reflux and smoking. However, the molecular mechanisms by which these factors influence disease progression remain unclear. One possibility is that risk factors generate promutagenic DNA damage in the esophagus. The comet assay was used to measure DNA damage in esophageal (Barrett's and squamous) and gastric mucosa of Barrett's patients with (n = 24) or without (n = 50) associated adenocarcinoma or high-grade dysplasia in comparison with control patients (squamous mucosa) without Barrett's esophagus (n = 64). Patients completed a questionnaire detailing exposure to some of the known risk factors for Barrett's esophagus and adenocarcinoma. In Barrett's esophagus patients, DNA damage was higher in Barrett's mucosa compared with normal esophageal and gastric mucosa (P < 0.001). In addition, the highest quartile of DNA damage in Barrett's mucosa was associated with an increased risk (odds ratio, 9.4; 95% confidence interval, 1.1-83.4; P = 0.044) of developing adenocarcinoma or high-grade dysplasia compared with DNA damage levels in the lowest quartile. Smoking was associated with higher DNA damage in squamous epithelium in all patient groups (P < 0.01) and in Barrett's mucosa (P < 0.05) in Barrett's esophagus patients only. In controls only, current reflux was associated with higher DNA damage, whereas anti-inflammatory drug use resulted in lower levels. Collectively, these data imply a genotoxic insult to the premalignant Barrett's mucosa that may explain the genetic instability in this tissue and the progression to adenocarcinoma. There is an indication for a role for smoking in inducing DNA damage in esophageal mucosa but an understanding of the role of reflux requires further investigation.