Dynamic effects of acid on Barrett's esophagus. An ex vivo proliferation and differentiation model

Barrett's Esophagus and Associated Dysplasia

Early detection of dysplasia and effective management are critical steps in halting neoplastic progression in patients with Barrett's esophagus (BE). This review provides a contemporary overview of the BE-related dysplasia, its role in guiding surveillance and management, and discusses emerging diagnostic and therapeutic approaches that might further enhance patient management. Novel, noninvasive techniques for sampling and surveillance, adjunct biomarkers for risk assessment, and their limitations are also discussed.

Revisiting Proton Pump Inhibitors as Chemoprophylaxis Against the Progression of Barrett's Esophagus

PURPOSE OF REVIEW

Barrett's esophagus (BE) is associated with chronic gastroesophageal reflux disease and is a known precursor to esophageal adenocarcinoma. While endoscopic surveillance strategies and the role for endoscopic eradication therapy have been well established, there has been much interest in identifying chemopreventive agents to disrupt or halt the metaplasia-dysplasia-carcinoma sequence in patients with BE.

RECENT FINDINGS

No pharmacological agent has held more hope in reducing the risk of neoplastic progression in BE than proton pump inhibitors (PPIs). However, data supporting PPIs for chemoprevention have largely been from observational cohort and case-control studies with mixed results. In this review, we revisit the literature and highlight the role of PPIs in patients with BE as it pertains to chemoprophylaxis against the progression of BE to dysplasia and esophageal adenocarcinoma.

The 8th Wonder of the Cancer World: Esophageal Cancer and Inflammation

Esophageal cancer is a devastating malignancy which can be detected at an early stage but is more often diagnosed as an advanced process. It affects both men and women and inflicts the young and the elderly. There are multiple underlying factors involved in the pathogenesis of this cancer including inflammation. The interplay of these factors promotes inflammation through various mechanisms including the recruitment of pro-inflammatory cells, mediators such as cytokines, reactive oxygen species, and interleukins, among others. The presentation can vary widely with one of the most notable symptoms being dysphagia. Diagnosis is based on clinical symptomatology, imaging and endoscopy with biopsy. Once the diagnosis has been established, treatment and prognosis are based on the stage of the disease. This review outlines esophageal cancer and its link to inflammation in relation to pathogenesis, along with clinical features, diagnosis and treatment.

The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity

The five plasma membrane Na⁺/H⁺ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pH_i regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na⁺ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na⁺/H⁺ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.

SPT6 loss permits the transdifferentiation of keratinocytes into an intestinal fate that resembles Barrett's metaplasia

Transient depletion of the transcription elongation factor SPT6 in the keratinocyte has been recently shown to inhibit epidermal differentiation and stratification; instead, they transdifferentiate into a gut-like lineage. We show here that this phenomenon of transdifferentiation recapitulates Barrett's metaplasia, the only human pathophysiologic condition in which a stratified squamous epithelium that is injured due to chronic acid reflux is trans-committed into an intestinal fate. The evidence we present here not only lend support to the notion that the keratinocytes are potentially the cell of origin of Barrett's metaplasia but also provide mechanistic insights linking transient acid exposure, downregulation of SPT6, stalled transcription of the master regulator of epidermal fate TP63, loss of epidermal fate, and metaplastic progression. Because Barrett's metaplasia in the esophagus is a pre-neoplastic condition with no preclinical human models, these findings have a profound impact on the modeling Barrett's metaplasia-in-a-dish.

Antireflux and Endoscopic Therapies for Barrett Esophagus and Superficial Esophageal Neoplasia

Barrett esophagus (BE), defined as intestinal metaplasia of the distal esophageal mucosa, typically results from chronic gastroesophageal reflux disease and is the only known precursor of esophageal adenocarcinoma. The standard of care for the management of early esophageal neoplasia in the setting of BE has changed drastically over the past 15 years. Further investigation into diagnostic and therapeutic adjuncts will continue to improve our ability to control or cure BE before its advancement to a life-threatening malignancy.

Low-Cost Method and Biochip for Measuring the Trans-Epithelial Electrical Resistance (TEER) of Esophageal Epithelium

Trans-epithelial electrical resistance (TEER) is a good indicator of the barrier integrity of epithelial tissues and is often employed in biomedical research as an effective tool to assess ion transport and permeability of tight junctions. The Ussing chamber is the gold standard for measuring TEER of tissue specimens, but it has major drawbacks: it is a macroscopic method that requires a careful and labor intensive sample mounting protocol, allows a very limited viability for the mounted sample, has large parasitic components and low throughput as it cannot perform multiple simultaneous measurements, and this sophisticated and delicate apparatus has a relatively high cost. This paper demonstrates a low-cost home-made “sandwich ring” method which was used to measure the TEER of tissue specimens effectively. This method inspired the subsequent design of a biochip fabricated using standard soft lithography and laser engraving technologies, with which the TEER of pig epithelial tissues was measured. Moreover, it was possible to temporarily preserve the tissue specimens for days in the biochip and monitor the TEER continuously. Tissue responses after exposure tests to media of various pH values were also successfully recorded using the biochip. All these demonstrate that this biochip could be an effective, cheaper, and easier to use Ussing chamber substitute that may have relevant applications in clinical practice.

Interaction of epidermal growth factor with COX-2 products and peroxisome proliferator-activated receptor-γ system in experimental rat Barrett's esophagus

Mixed acidic-alkaline refluxate is a major pathogenic factor in chronic esophagitis progressing to Barrett's esophagus (BE). We hypothesized that epidermal growth factor (EGF) can interact with COX-2 and peroxisome proliferator-activated receptor-γ (PPARγ) in rats surgically prepared with esophagogastroduodenal anastomosis (EGDA) with healthy or removed salivary glands to deplete salivary EGF. EGDA rats were treated with 1) vehicle, 2) EGF or PPARγ agonist pioglitazone with or without EGFR kinase inhibitor tyrphostin A46, EGF or PPARγ antagonist GW9662 respectively, 3) ranitidine or pantoprazole, and 4) the selective COX-2 inhibitor celecoxib combined with pioglitazone. At 3 mo, the esophageal damage and the esophageal blood flow (EBF) were determined, the mucosal expression of EGF, EGFR, COX-2, TNFα, and PPARγ mRNA and phospho-EGFR/EGFR protein was analyzed. All EGDA rats developed chronic esophagitis, esophageal ulcerations, and intestinal metaplasia followed by a fall in the EBF, an increase in the plasma of IL-1β, TNFα, and mucosal PGE₂ content, the overexpression of COX-2-, and EGF-EGFR mRNAs, and proteins, and these effects were aggravated by EGF and attenuated by pioglitazone. The rise in EGF and COX-2 mRNA was inhibited by pioglitazone but reversed by pioglitazone cotreated with GW9662. We conclude that 1) EGF can interact with PG/COX-2 and the PPARγ system in the mechanism of chronic esophagitis; 2) the deleterious effect of EGF involves an impairment of EBF and the overexpression of COX-2 and EGFR, and 3) agonists of PPARγ and inhibitors of EGFR may be useful in the treatment of chronic esophagitis progressing to BE.NEW & NOTEWORTHY Rats with EGDA exhibited chronic esophagitis accompanied by a fall in EBF and an increase in mucosal expression of mRNAs for EGF, COX-2, and TNFα, and these effects were exacerbated by exogenous EGF and reduced by removal of a major source of endogenous EGF with salivectomy or concurrent treatment with tyrphostin A46 or pioglitazone combined with EGF. Beneficial effects of salivectomy in an experimental model of BE were counteracted by PPARγ antagonist, whereas selective COX-2 inhibitor celecoxib synergistically with pioglitazone reduced severity of esophageal damage and protected esophageal mucosa from reflux. We propose the cross talk among EGF/EGFR, PG/COX-2, and proinflammatory cytokines with PPARγ pathway in the mechanism of pathogenesis of chronic esophagitis progressing to BE and EAC.

Oesophageal adenocarcinoma following gastric band surgery in two patients

Oesophageal adenocarcinoma following gastric band surgery has only been reported three times previously. The incidence is higher in morbidly obese patients, and its pathogenesis is correlated to reflux-induced microenvironmental changes. Bariatric surgery is transformative and its potential benefit for a substantial population is huge. Although no causal relationship with bariatric procedures has been evidenced to date, symptoms of adenocarcinoma—particularly anorexia, weight loss and dysphagia—can easily be overshadowed by alterations in eating patterns associated with weight-loss procedures. We report two cases of oesophageal adenocarcinoma in patients who had undergone a gastric banding procedure, and invite readers to consider the role that pre- and post-operative acid reflux dynamics may have precipitating neoplastic disease, and how endoscopic surveillance may play a role in prevention.

Gastroesophageal Reflux Disease Might Induce Certain-Supposedly Adaptive-Changes in the Esophagus: A Hypothesis

BACKGROUND

The increasing prevalence of GERD has become a major concern due to its major health and economic impacts. Beyond the typical unpleasant symptoms, reflux can also be the source of severe, potentially life-threatening complications, such as aspiration.

AIM

Our aim was to support our hypothesis that the human body may in some cases develop various protective mechanisms to prevent these conditions.

METHODS

Based on our experiences and review of the literature, we investigated the potential adaptive nature of seven reflux complications (hypertensive lower esophageal sphincter, achalasia, hypertensive upper esophageal sphincter, Zenker's diverticulum, Schatzki's ring, esophageal web, and Barrett's esophagus).

RESULTS

Patients with progressive GERD may develop diverse structural and functional esophageal changes that narrow the lumen of the esophagus and therefore reduce the risk of regurgitation and protect the upper aerodigestive tract from aspiration. The functional changes (hypertensive lower esophageal sphincter, achalasia, hypertensive upper esophageal sphincter) seem to be adaptive reactions aimed at easing the unpleasant symptoms and reducing acid regurgitation. The structural changes (Schatzki's ring, esophageal web) result in very similar outcomes, but we consider these are rather secondary consequences and not real adaptive mechanisms. Barrett's esophagus is a special form of adaptive protection. In these cases, patients report significant relief of their previous heartburn as Barrett's esophagus develops because of the replacement of the normal squamous epithelium of the esophagus by acid-resistant metaplastic epithelium.

CONCLUSION

We believe that GERD may induce different self-protective reactions in the esophagus that result in reduced acid regurgitation or decreased reflux symptoms.

Gastrin stimulates a cholecystokinin-2-receptor-expressing cardia progenitor cell and promotes progression of Barrett's-like esophagus

Objective

The incidence of esophageal adenocarcinoma (EAC) is increasing, but factors contributing to malignant progression of its precursor lesion, Barrett's esophagus (BE), have not been defined. Hypergastrinemia caused by long-term use of proton pump inhibitors (PPIs), has been suggested as one possible risk factor. The gastrin receptor, CCK2R, is expressed in the cardia and upregulated in BE, suggesting the involvement of the gastrin-CCK2R pathway in progression. In the L2-IL-1β mouse model, Barrett's-like esophagus arises from the gastric cardia. Therefore, we aimed to analyze the effect of hypergastrinemia on CCK2R+ progenitor cells in L2-IL-1β mice.

Design

L2-IL-1β mice were mated with hypergastrinemic (INS-GAS) mice or treated with PPIs to examine the effect of hypergastrinemia in BE progression. CCK2R-CreERT crossed with L2-IL-1β mice were used to analyze the lineage progenitor potential of CCK2R+ cells. Cardia glands were cultured in vitro, and the effect of gastrin treatment analyzed. L2-IL-1β mice were treated with a CCK2R antagonist YF476 as a potential chemopreventive drug.

Results

Hypergastrinemia resulted in increased proliferation and expansion of Barrett's-like esophagus. Lineage tracing experiments revealed that CCK2R+ cells are long-lived progenitors that can give rise to such lesions under chronic inflammation. Gastrin stimulated organoid growth in cardia culture, while CCK2R inhibition prevented Barrett's-like esophagus and dysplasia.

Conclusions

Our data suggest a progression model for BE to EAC in which CCK2R+ progenitor cells, stimulated by hypergastrinemia, proliferate to give rise to metaplasia and dysplasia. Hypergastrinemia can result from PPI use, and the effects of hypergastrinemia in human BE should be studied further.

Esophageal 3D Culture Systems as Modeling Tools in Esophageal Epithelial Pathobiology and Personalized Medicine

The stratified squamous epithelium of the esophagus shows a proliferative basal layer of keratinocytes that undergo terminal differentiation in overlying suprabasal layers. Esophageal pathologies, including eosinophilic esophagitis, gastroesophageal reflux disease, Barrett's esophagus, squamous cell carcinoma, and adenocarcinoma, cause perturbations in the esophageal epithelial proliferation-differentiation gradient. Three-dimensional (3D) culture platforms mimicking in vivo esophageal epithelial tissue architecture ex vivo have emerged as powerful experimental tools for the investigation of esophageal biology in the context of homeostasis and pathology. Herein, we describe types of 3D culture that are used to model the esophagus, including organotypic, organoid, and spheroid culture systems. We discuss the development and optimization of various esophageal 3D culture models; highlight the applications, strengths, and limitations of each method; and summarize how these models have been used to evaluate the esophagus under homeostatic conditions as well as under the duress of inflammation and precancerous/cancerous conditions. Finally, we present future perspectives regarding the use of esophageal 3D models in basic science research as well as translational studies with the potential for personalized medicine.

Past, present and future of Barrett's oesophagus

Barrett's oesophagus is a condition which predisposes towards development of oesophageal adenocarcinoma, a highly lethal tumour which has been increasing in incidence in the Western world over the past three decades. There have been tremendous advances in the field of Barrett's oesophagus, not only in diagnostic modalities, but also in therapeutic strategies available to treat this premalignant disease. In this review, we discuss the past, present and future of Barrett's oesophagus. We describe the historical and new evolving diagnostic criteria of Barrett's oesophagus, while also comparing and contrasting the British Society of Gastroenterology guidelines, American College of Gastroenterology guidelines and International Benign Barrett's and CAncer Taskforce (BOBCAT) for Barrett's oesophagus. Advances in endoscopic modalities such as confocal and volumetric laser endomicroscopy, and a non-endoscopic sampling device, the Cytosponge, are described which could aid in identification of Barrett's oesophagus. With regards to therapy we review the evidence for the utility of endoscopic mucosal resection and radiofrequency ablation when coupled with better characterization of dysplasia. These endoscopic advances have transformed the management of Barrett's oesophagus from a primarily surgical disease into an endoscopically managed condition.

Lack of incremental effect of histamine receptor antagonists over proton pump inhibitors on the risk of neoplastic progression in patients with Barrett's esophagus: a cohort study

OBJECTIVE

Long-term acid suppression reduces the risk of progression to esophageal adenocarcinoma (EAC) in patients with Barrett's esophagus (BE). Given recent reports about the harmful effects of using chronic proton pump inhibitors (PPI) there is renewed interest in alternative methods of acid suppression. Hence, we studied the effect of H2 receptor antagonists (H₂ RA) on the risk of progression to neoplasia in our BE cohort.

METHODS

This is a retrospective analysis of prospectively collected data of patients in our BE registry from 2002 to 2015. Patients' characteristics, endoscopic findings, such as the length of BE, hiatal hernia size and histological findings and patients' use of medications such as PPI, aspirin, H₂ RA, metformin and antihyperlipidemic agents were studied.

RESULTS

The cohort consisted of 1466 patients with a mean age of 61 ± 13 years. The patients had a predominance of male sex (76.7% [1118/1457]) and Caucasian race (96.6% [1209/1252]). After excluding prevalent high-grade dysplasia (HGD) or EAC, 1025 patients had a median follow up of 43.6 months during which 57 patients progressed to HGD or EAC. PPI use (56% in progressors vs 69% in non-progressors; P = 0.007) but not H₂ RA use (12% progressors vs 19% in non-progressors P = 0.162) was associated with lower risk of neoplastic progression. On multivariate analysis, there was no synergistic effect of addition of H₂ RA to PPI on risk of neoplastic progression to HGD or EAC (relative risk 0.33; confidence intervals 0.05-2.29, P = 0.262).

CONCLUSION

H₂ RA do not seem to have a chemopreventive role in patients with BE.

Proton pump inhibitors on pancreatic cancer risk and survival

BACKGROUND

Hypergastrinemia may promote the development and progression of pancreatic cancer. Proton pump inhibitor (PPI) therapy is known to cause hypergastrinemia. We sought to determine the association between PPI therapy and the risk of developing pancreatic cancer as well as survival following pancreatic cancer diagnosis.

METHODS

We conducted a nested case-control study and a retrospective cohort study in The Health Improvement Network (THIN), a medical records database representative of the UK population. In the case-control study, each patient with incident pancreatic cancer was matched with up to four controls based on age, sex, practice site and both duration and calendar time of follow-up using incidence density sampling. The odds ratios (ORs) and 95% confidence intervals (CIs) for pancreatic cancer risk associated with PPI use were estimated using multivariable conditional logistic regression. The retrospective cohort study compared the survival of pancreatic cancer patients according to their PPI exposure at the time of diagnosis. The effect of PPI use on pancreatic cancer survival was assessed using a multivariable Cox regression analysis.

RESULTS

The case-control study included 4113 cases and 16,072 matched controls. PPI use was more prevalent in cases than controls (53% vs. 26% active users). Adjusting for diabetes, smoking, alcohol use and BMI, PPI users including both former users and active users with longer cumulative PPI use had a higher risk of pancreatic cancer compared to non-users. When assessing survival following pancreatic cancer diagnosis, only short-term, active users had a modest decrease in survival.

CONCLUSIONS

Long-term PPI therapy may be associated with pancreatic cancer risk. While PPI users recently started on treatment had a slightly worse survival, this result likely is from reverse causation.

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.

Interplay Between Inflammation and Epigenetic Changes in Cancer

Immune responses can suppress tumorigenesis, but also contribute to cancer initiation and progression suggesting a complex interaction between the immune system and cancer. Epigenetic alterations, which are heritable changes in gene expression without changes to the DNA sequence, also play a role in carcinogenesis through silencing expression of tumor suppressor genes and activating oncogenic signaling. Interestingly, epithelial cells at sites of chronic inflammation undergo DNA methylation alterations that are similar to those present in cancer cells, suggesting that inflammation may initiate cancer-specific epigenetic changes in epithelial cells. Furthermore, epigenetic changes occur during immune cell differentiation and participate in regulating the immune response, including the regulation of inflammatory cytokines. Cancer cells utilize epigenetic silencing of immune-related genes to evade the immune response. This chapter will detail the interactions between inflammation and epigenetics in tumor initiation, promotion, and immune evasion and how these connections are being leveraged in cancer prevention and treatment.

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.

Combining simple patient-oriented tests with state-of-the-art molecular diagnostics for early diagnosis of cancer

Early diagnosis is an important strategy to improve outcomes from cancer. Oesophageal adenocarcinoma is an example of a cancer that presents late, with very poor outcomes, and for which the presence of the precursor lesion Barrett's oesophagus provides the opportunity to intervene at an early stage. In this review, I describe the challenges in the field and the work that we have done to devise a conceptually novel approach to early diagnosis, using a cell collection device (Cytosponge), coupled with molecular assays. This is a personal perspective in which I also describe the career pathway that led me into academic gastroenterology, and the rewards and challenges of translational research in molecular diagnostics. There are fantastic opportunities for clinicians wishing to pursue academic medicine, because it is a time when massive strides are being made in a whole number of areas; for example: imaging, sequencing technology and targeted therapies. Clinicians who can straddle the laboratory and the clinic are essential, to maximise the progress that can be made for the benefit of patients.

The Effect of Proton Pump Inhibitors on Barrett's Esophagus

Proton pump inhibitors (PPIs) may protect against carcinogenesis in Barrett's esophagus because they eliminate the chronic esophageal inflammation of reflux esophagitis, and because they decrease esophageal exposure to acid, which can cause cancer-promoting DNA damage and increase proliferation in Barrett's metaplasia. Most clinical studies of PPIs and cancer development in Barrett's esophagus have found a cancer-protective effect for these drugs, although there are some contradictory data. Chemoprevention of dysplasia and cancer in Barrett's esophagus with PPIs appears to be cost-effective, and the indirect evidence supporting a cancer-protective role for PPIs is strong enough to warrant PPI treatment of virtually all patients with Barrett's esophagus.

Acid suppression and surgical therapy for Barrett's oesophagus

Gastro-oesophageal reflux disease is a common medical problem in developed countries, and is a risk factor for the development of Barrett's oesophagus and oesophageal adenocarcinoma. Both proton pump inhibitor therapy and antireflux surgery are effective at controlling endoscopic signs and symptoms of gastro-oesophageal reflux in patients with Barrett's oesophagus, but often fail to eliminate pathological oesophageal acid exposure. The current available studies strongly suggest that acid suppressive therapy, both pharmacological as well as surgical acid suppression, can reduce the risk the development and progression in patients with Barrett's oesophagus, but are not capable of complete prevention. No significant differences have been found between pharmacological and surgical therapy. For clinical practice, patients should be prescribed a proton pump inhibitor once daily as maintenance therapy, with the dose guided by symptoms. Antireflux surgery can be a good alternative to proton pump inhibitor therapy, but should be primarily offered to patients with symptomatic reflux, and not to asymptomatic patients with the rationale to protect against cancer.

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.

Role of proton pump inhibitor on esophageal carcinogenesis and pancreatic acinar cell metaplasia development: an experimental in vivo study

Chronic gastro-duodenal reflux in the esophagus is a major risk for intestinal metaplasia and Barrett’s adenocarcinoma. A role for chronic use of proton pump inhibitor (PPI) in the increased incidence of esophageal adenocarcinoma in Western countries has been previously suggested. The aim of this work was to study the effect of chronic administration of omeprazole (a proton pump inhibitor) per os in a model of reflux induced esophageal carcinogenesis. One week after esophago-gastro-jejunostomy, 115 Sprague-Dawley rats were randomized to receive 10 mg/Kg per day of omeprazole or placebo, 5 days per week. The esophago-gastric specimens were collected 28±2 weeks after randomization and analyzed in a blinded fashion. Mortality and esophageal metaplasia rates did not differ between the two groups (p = 0.99 for mortality, p = 0.36 for intestinal metaplasia and p = 0.66 for multi-layered epithelium). Gastric pancreatic acinar cell metaplasia (PACM) was more frequently observed in PPI-treated rats (p = 0.003). Severe ulcer lesions significantly prevailed in the placebo group (p = 0.03). Locally invasive esophageal epithelial neoplasia were observed in 23/39 PPI-treated versus 14/42 placebo-animals (p = 0.03). In conclusion, chronic omeprazole treatment improved the healing of esophageal ulcerative lesions. Locally invasive neoplastic lesions and PACM prevailed among PPI-treated animals. However, neither an effect on the overall mortality nor on the incidence of pre-neoplastic lesions was observed in this work.

The role of inflammation in cancer of the esophagus

Esophageal adenocarcinoma is the eighth most common malignancy worldwide. The overall prognosis is poor, with 5-year survival ranges of approximately 15-25%, and 30-50% for patients who can be treated with curative intent. There has been a marked increase in incidence of esophageal adenocarcinoma over the last 30 years, with chronic and severe reflux, diet and obesity identified as principal factors fuelling this rise in the West. Esophageal adenocarcinoma is an exemplar model of an inflammation-associated cancer. The key molecular pathways driving tumor development and influencing tumor biology are the subject of considerable research efforts, and is the principal focus of this review. In addition, the diverse range of changes occurring in the local immune response, tissue microenvironment, metabolic profile, intracellular signaling mechanisms and microRNA signatures are discussed, as well as novel targeted therapies.

Progression of Barrett oesophagus: role of endoscopic and histological predictors

Barrett oesophagus is an important precursor lesion for the development of oesophageal adenocarcinoma (OAC). Upper gastrointestinal endoscopy is the modality most widely used to visualize and biopsy the oesophagus to establish a diagnosis. Additional clues are available at the time of endoscopy that can identify high-risk features known to increase the risk of progression to OAC, such as the length of the Barrett oesophagus segment, length of hiatal hernia and the presence of nodularity or visible endoscopic lesions in this segment. Until molecular biomarkers are identified and validated as adjunctive tools for risk stratification, knowledge of endoscopic features could complement dysplasia grading for risk stratification of patients with Barrett oesophagus and identify subgroups at risk of progression to OAC. This approach would, in turn, facilitate more rational tailoring of endoscopic surveillance. This Review summarizes the current role of endoscopic and histological factors involved in neoplastic progression of Barrett oesophagus to OAC, and provides an overview of the risk-prediction models that have utilized endoscopic and histological factors for risk stratification in patients with Barrett oesophagus.

Incidence and predictors of adenocarcinoma following endoscopic ablation of Barrett's esophagus

BACKGROUND

The rate and risk factors of recurrent or metachronous adenocarcinoma following endoscopic ablation therapy in patients with Barrett's esophagus (BE) have not been specifically reported.

AIM

The aim of this study was to determine the incidence and predictors of adenocarcinoma after ablation therapy for BE high-grade dysplasia (HGD) or intramucosal carcinoma (IMC).

METHODS

This is a single center, retrospective review of prospectively collected data on consecutive cases of endoscopic ablation for BE. A total of 223 patients with BE (HGD or IMC) were treated by ablation between 1996 and 2011. Primary outcome measures were recurrence and new development of adenocarcinoma after ablation. Recurrence was defined as the presence of adenocarcinoma following the absence of adenocarcinoma in biopsy samples from two consecutive surveillance endoscopies. Logistic regression analysis was performed to assess predictors of adenocarcinoma after ablation.

RESULTS

One hundred and eighty-three patients were included in the final analysis, and 40 patients were excluded: 22 for palliative ablation, eight lost to follow-up, five for residual carcinoma and five for postoperative state. Median follow-up was 39 months. Recurrence or new development of adenocarcinoma was found in 20 patients (11 %) and the median time to recurrence/development of adenocarcinoma was 11.5 months. Independent predictors of recurrent or metachronous adenocarcinoma were hiatal hernia size ≥ 4 cm (odds ratio 3.649, P = 0.0233) and histology (HGD/adenocarcinoma) after first ablation (odds ratio 4.141, P = 0.0065).

CONCLUSIONS

Adenocarcinoma after endoscopic therapy for HGD or IMC in BE is associated with large hiatal hernia and histology status after initial ablation therapy.

Cost-effectiveness of chemoprevention with proton pump inhibitors in Barrett's esophagus

BACKGROUND

Proton pump inhibitors (PPIs) may reduce the risk of esophageal adenocarcinoma (EAC) in patients with Barrett's esophagus. PPIs are prescribed for virtually all patients with Barrett's esophagus, irrespective of the presence of reflux symptoms, and represent a de facto chemopreventive agent in this population. However, long-term PPI use has been associated with several adverse effects, and the cost-effectiveness of chemoprevention with PPIs has not been evaluated.

AIM

The purpose of this study was to assess the cost-effectiveness of PPIs for the prevention of EAC in Barrett's esophagus without reflux.

METHODS

We designed a state-transition Markov microsimulation model of a hypothetical cohort of 50-year-old white men with Barrett's esophagus. We modeled chemoprevention with PPIs or no chemoprevention, with endoscopic surveillance for all treatment arms. Outcome measures were life-years, quality-adjusted life years (QALYs), incident EAC cases and deaths, costs, and incremental cost-effectiveness ratios.

RESULTS

Assuming 50% reduction in EAC, chemoprevention with PPIs was a cost-effective strategy compared to no chemoprevention. In our model, administration of PPIs cost $23,000 per patient and resulted in a gain of 0.32 QALYs for an incremental cost-effectiveness ratio of $12,000/QALY. In sensitivity analyses, PPIs would be cost-effective at $50,000/QALY if they reduce EAC risk by at least 19%.

CONCLUSIONS

Chemoprevention with PPIs in patients with Barrett's esophagus without reflux is cost-effective if PPIs reduce EAC by a minimum of 19%. The identification of subgroups of Barrett's esophagus patients at increased risk for progression would lead to more cost-effective strategies for the prevention of esophageal adenocarcinoma.

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.

Does Barrett's esophagus regress after surgery (or proton pump inhibitors)?

Barrett's esophagus, the condition in which metaplastic columnar epithelium that predisposes to cancer development replaces the squamous epithelium that normally lines the distal esophagus, is a complication of gastroesophageal reflux disease (GERD). Metaplasia is a potentially reversible condition, and partial regression of Barrett's metaplasia has been documented with effective medical or surgical therapy for GERD. The important issue for patient management is not whether antireflux treatment causes Barrett's esophagus to regress, but rather whether antireflux therapy prevents cancer in Barrett's esophagus. Proton pump inhibitors (PPIs) would be expected to prevent this cancer because they heal reflux esophagitis, reduce exposure to a potential carcinogen (acid), and might prevent acid-induced proliferation and cancer-promoting cytokine secretion by esophageal epithelial cells. Furthermore, observational studies have shown that PPI use is associated with a decreased incidence of neoplasia in Barrett's esophagus. In theory, successful antireflux surgery, which eliminates the reflux of both acid and bile, should be better for cancer prevention than medical therapy, which only decreases the reflux of acid. However, high-quality studies show no significant difference in cancer incidence between medically and surgically treated patients with GERD and Barrett's esophagus. Furthermore, for individual patients with nondysplastic Barrett's metaplasia, the cancer risk is so small and the number needed to treat for cancer prevention with surgery so large, that it does not matter whether or not surgery provides a tiny margin of extra protection against cancer beyond that provided by medical therapy. The cost and risks of the operation overwhelm any small, additional cancer protective benefit. Antireflux surgery is very effective at controlling the endoscopic signs and symptoms of GERD, but the operation should not be recommended to patients solely with the rationale that it protects against cancer better than medical therapy.

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).

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.

Risk factors for esophageal adenocarcinoma after antireflux surgery

OBJECTIVES

Gastroesophageal reflux is the main risk factor for esophageal adenocarcinoma, but there is no strong support for any cancer-protective effect after antireflux surgery. We hypothesized that recurrent reflux or high exposure to other established risk factors, that is, obesity and tobacco smoking, are overrepresented among patients who despite antireflux surgery develop esophageal adenocarcinoma.

DESIGN

A population-based case-control study was nested within an antireflux surgery cohort from the Swedish Patient Register between 1965 and 2006. Cases were patients who developed esophageal adenocarcinoma more than 5 years after antireflux surgery, whereas randomly selected controls were matched to the cases regarding age, sex, and calendar year of the antireflux surgery. Study exposures among cases and controls were collected through review of medical records. Data on cancer were assessed through the Swedish Cancer Register. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using multivariable conditional logistic regression, adjusted for recurrent reflux, body mass index (BMI), tobacco smoking, and type of antireflux surgery.

RESULTS

From 14,102 patients in the total antireflux surgery cohort, 55 cases and 240 controls were included. Patients who developed esophageal adenocarcinoma were 3 times more likely to have recurrent reflux after their antireflux surgery, compared with those who had not (OR: 3.1, 95% CI: 1.5-6.3). There were no statistically significant differences in risk when comparing BMI of 30 kg/m or more with BMI of less than 25 kg/m (OR: 1.6, CI: 0.8-3.5), ever smokers with never smokers (OR: 1.4, 95% CI: 0.7-2.8), or total fundoplication with partial fundoplication (OR: 0.6, 95% CI: 0.3-1.3).

CONCLUSIONS

Recurrence of reflux might explain the lack of protective effect of antireflux surgery regarding risk of developing esophageal adenocarcinoma.

The effect of rabeprazole on LES tone in experimental rat model

INTRODUCTION

Despite adequate treatment with proton pump inhibitors (PPIs), symptoms of gastroesophageal reflux disease (GERD) may remain persistent as well as Barrett's esophagus may emerge. It may be proposed that the relaxant effect of PPIs on the smooth muscles may lead to resistance of symptoms. The aim of this study is to investigate effects of rabeprazole on the lower esophageal sphincter (LES) pressure with a rat model.

MATERIALS AND METHODS

Sixteen rats were grouped as control and treatment groups. After obtaining LES tissues followed by a 60 min equilibration period for stabilization, contractile response to carbachol was obtained by application of single dose of carbachol to have a final concentration of 10(-6) M in the organ bath. After the contractions reached a plateau, concentration-response relationships for rabeprazole were obtained in a cumulative manner in the treatment group.

RESULTS

In the carbachol contracted LES preparations; 1.5 × 10(-6) and 1.5×10(-5) M of rabeprazole caused 6.08% and 11.34% relaxations respectively which were not statistically significant. However, mean integral relaxation value for 4.5 × 10(-5) M of rabeprazole was 17.34% and this relaxation was significant compared with controls.

CONCLUSIONS

In the present study, rabeprazole caused no direct significant change in LES tone in the therapeutic dose range applied to the organ bath. However, rabeprazole at the high dose caused a significant decrease in the LES tone.

Evidence for a functional role of epigenetically regulated midcluster HOXB genes in the development of Barrett esophagus

Barrett esophagus (BE) is a human metaplastic condition that is the only known precursor to esophageal adenocarcinoma. BE is characterized by a posterior intestinal-like phenotype in an anterior organ and therefore it is reminiscent of homeotic transformations, which can occur in transgenic animal models during embryonic development as a consequence of mutations in HOX genes. In humans, acquired deregulation of HOX genes during adulthood has been linked to carcinogenesis; however, little is known about their role in the pathogenesis of premalignant conditions. We hypothesized that HOX genes may be implicated in the development of BE. We demonstrated that three midcluster HOXB genes (HOXB5, HOXB6, and HOXB7) are overexpressed in BE, compared with the anatomically adjacent normal esophagus and gastric cardia. The midcluster HOXB gene signature in BE is identical to that seen in normal colonic epithelium. Ectopic expression of these three genes in normal squamous esophageal cells in vitro induces markers of intestinal differentiation, such as KRT20, MUC2, and VILLIN. In BE-associated adenocarcinoma, the activation midcluster HOXB gene is associated with loss of H3K27me3 and gain of AcH3, compared with normal esophagus. These changes in histone posttranslational modifications correlate with specific chromatin decompaction at the HOXB locus. We suggest that epigenetically regulated alterations of HOX gene expression can trigger changes in the transcriptional program of adult esophageal cells, with implications for the early stages of carcinogenesis.

Development and characterization of an organotypic model of Barrett's esophagus

Understanding the molecular and cellular processes underlying the development, maintenance, and progression of Barrett's esophagus (BE) presents an empirical challenge because there are no simple animal models and standard 2D cell culture can distort cellular processes. Here we describe a three-dimensional (3D) cell culture system to study BE. BE cell lines (CP-A, CP-B, CP-C, and CP-D) and esophageal squamous keratinocytes (EPC2) were cultured on a matrix consisting of esophageal fibroblasts and collagen. Comparison of growth and cytokeratin expression in the presence of all-trans retinoic acid or hydrochloric acid was made by immunohistochemistry and Alcian Blue staining to determine which treatments produced a BE phenotype of columnar cytokeratin expression in 3D culture. All-trans retinoic acid differentially affected the growth of BE cell lines in 3D culture. Notably, the non-dyplastic metaplasia-derived cell line (CP-A) expressed reduced squamous cytokeratins and enhanced columnar cytokeratins upon ATRA treatment. ATRA altered the EPC2 squamous cytokeratin profile towards a more columnar expression pattern. Cell lines derived from patients with high-grade dysplasia already expressed columnar cytokeratins and therefore did not show a systematic shift toward a more columnar phenotype with ATRA treatment. ATRA treatment, however, did reduce the squamoid-like multilayer stratification observed in all cell lines. As the first study to demonstrate long-term 3D growth of BE cell lines, we have determined that BE cells can be cultured for at least 3 weeks on a fibroblast/collagen matrix and that the use of ATRA causes a general reduction in squamous-like multilayered growth and an increase in columnar phenotype with the specific effects cell-line dependent.

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.

Role of acid suppression in the development and progression of dysplasia in patients with Barrett's esophagus

Barrett's esophagus (BE) usually develops in patients with gastroesophageal reflux disease and therefore it has been suggested that esophageal acid exposure plays an import role in the initiation of BE and its progression towards esophageal adenocarcinoma (EAC). The mechanisms whereby acid exposure causes BE are not completely revealed and the potential role of esophageal acid exposure in carcinogenesis is unclear as well. Since acid exposure is thought to play an important role in the progression of BE, therapies aimed at preventing the development of EAC have primarily focused on pharmacological and surgical acid suppression. In clinical practice, acid suppression is effective in relieving reflux symptoms and decreases esophageal acid exposure in most patients. However, in some individuals, pathological acid exposure persists and these patients continue to be at risk for developing dysplasia or EAC. To date, published trials suggest that acid suppression is able to prevent the development and progression of dysplasia in patients with BE, but definite and compelling proof is still lacking. This article reviews the mechanisms of acid-induced carcinogenesis in BE and the role of acid suppression in the prevention of neoplastic progression.

Barrett's esophagus: endoscopic treatments II

The following on endoscopic treatments of Barrett's esophagus includes commentaries on animal experiments on cryotherapy; indications for cryotherapy, choice of dosimetry, number of sessions, and role in Barrett's esophagus and adenocarcinoma; recent technical developments of RFA technology and long-term effects; the comparative effects of diverse ablation procedures and the rate of recurrence following treatment; and the indications for treatment of dysplasia and the role of radiofrequency ablation.

Chemoprevention in Barrett's oesophagus

Barrett's oesophagus normally affects the distal oesophagus when metaplastic columnar lined epithelium replaces stratified squamous epithelium which predisposes to cancer development. This develops as a consequence of chronic gastroesophageal reflux (GORD). Those with Barrett's have a 40 fold increased risk of oesophageal adenocarcinoma [1]. There are is still a lack of understanding of the natural history of the cell of origin. This does hamper research into this area. We accept that there is a limitation in testing of the pathogenesis of Barrett's oesophagus due to a lack of a universally accepted animal model. The major questions surrounding Barrett's oesophagus include validity of surveillance strategies, the optimal treatment and more importantly an agent that can prevent progression to cancer without unacceptable side effects. The main chemopreventative agents that show promise are aspirin and proton pump inhibitors (PPIs). There are other agents such as green tea, berries and antioxidants and diet that have been suggested; we discuss the evidence available for these strategies. We hope for continued improvement in the clinical trial infrastructure to facilitate testing of new pharmacological and endoscopic interventions for Barrett's oesophagus.

Chemoprevention of esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) is rising rapidly in Western countries, and effective chemoprevention for this malignancy is lacking. Endoscopic surveillance of patients with Barrett's esophagus is currently employed to diagnose EAC at earlier stages, but this strategy has several limitations. Non-steroidal anti-inflammatory drugs and proton pump inhibitors are the most promising agents for prevention of EAC, and a randomized controlled trial of aspirin and esomeprazole is ongoing. Other agents under investigation include green tea, berries, and antioxidants. Cost-effectiveness analyses have shown that chemopreventive agents need to be highly effective at preventing EAC in order to have benefit beyond endoscopic surveillance.

Curcumin promotes apoptosis, increases chemosensitivity, and inhibits nuclear factor kappaB in esophageal adenocarcinoma

The transcription factor, nuclear factor kappaB (NF-kappaB), plays a central role as a key mediator of cell survival and proliferation, and its activation may confer increased tumor chemoresistance. Curcumin, an orally available naturally occurring compound, has been shown to inhibit NF-kappaB and has a potential role in cancer chemoprevention. We investigated the effects of curcumin on NF-kappaB activity, on cell viability, and as a chemosensitizing agent with 5-fluorouracil (5-FU) or cisplatin (CDDP) in esophageal adenocarcinoma (EAC). Oligonucleotide microarray analysis of 46 cases, consisting of Barrett metaplasia, low-grade dysplasia, high-grade dysplasia and EAC, showed increased expression of NF-kappaB and IkappaB kinase subunits and decreased effector caspase expression in EAC compared with Barrett metaplasia. Stromal expression of both IkappaB and phospho-IkappaB was detected in several EAC samples by tissue microarray analysis. Curcumin alone inhibited NF-kappaB activity and induced apoptosis in both Flo-1 and OE33 EAC cell lines as determined by Western blot analysis, NF-kappaB reporter assays, and Caspase-Glo 3/7 assays. It also increased 5-FU- and CDDP-induced apoptosis in both cell lines. These data suggest that activation of NF-kappaB and inhibition of apoptosis may play a role in the progression from Barrett metaplasia to EAC. In addition, curcumin, a well-known inhibitor of NF-kappaB activity, was shown to increase apoptosis and enhance both 5-FU- and CDDP-mediated chemosensitivity, suggesting that it may have potential application in the therapy of patients with EAC.

In vitro and ex vivo models of extended reflux exposure demonstrate that weakly acidic mixed reflux heightens NF-kB-mediated gene expression

The development of Barrett's esophagus and its progression to adenocarcinoma are clearly linked to reflux of acid and bile. Our objective in this study was to develop an optimized ex vivo biopsy culture technique to study the molecular signaling events induced after insult with individual refluxate constituents. We illustrate the utility of this method by showing results for NF-kB centered cell signaling, and compare the results with those obtained from esophageal cell lines. We show that upregulation of the two NF-kB target genes show differences in pH preference, with IL-8 being preferentially upregulated by DCA at neutral pH, and IkB being upregulated by neutral DCA, acidic DCA, and acid alone. This was found to be true in both cell lines and biopsy cultures. The maximum responses were noted in both models when mixed reflux (DCA at pH 6) was utilized, perhaps reflecting the pH preference of DCA (pKa 6.2). Both the optimized ex vivo models, and the in vitro cell lines show that bile and acid are capable of inducing NF-kB dependent gene expression, with some interesting differences in preferred transcriptional target. In conclusion, in both cells and cultured biopsies, similar reflux driven gene expression changes were noted, with maximum effects noted with DCA exposures at pH 6.

Esophageal adenocarcinoma arising after antireflux surgery: a population-based analysis

OBJECTIVE

Fundoplication is widely used to treat gastroesophageal reflux disease (GERD). Whether it diminishes the development of esophageal adenocarcinoma (EAC) is, however, controversial. Our aim was to define, at the national level in Finland, frequency and predisposing factors for post-fundoplication EAC.

METHODS

For this population-based study from 1980 to 2006, Finland's administrative databases provided preliminary data. Analyses of EAC patient records (N = 1035) led us to include those with preceding antireflux surgery. Conservatively treated patients were not analyzed. The EAC incidence in patients with antireflux surgery was compared with that in the general population (1987-2006) by means of standardized incidence ratio (SIR).

RESULTS

A total of 53 (5.1%) EAC patients had undergone antireflux surgery. Of these patients with male predominance (74%), preoperatively 41 (77%) had developed endoscopic esophagitis, 40 (75%) hiatal hernia, 24 (45%) Barrett's esophagus (BE), nine (17%) ulcer in the esophagus or gastroesophageal junction, and three (6%) stricture. Postoperatively, histologically confirmed BE was present in 42 (79%). Antireflux surgery had preceded EAC at a mean interval of 10.1 years (range 0.5-25.6 years). This interval was significantly (p=0.02) shorter in patients with long-term functioning fundoplication (n = 15; 30%) at EAC diagnosis (6.4 years, range 0.5-15.2 years) than in those (n = 22, 44%) with failure (11.2 years, range 4.0-24.3 years). Overall, the SIR for EAC after antireflux surgery (1987-2006) was 9.21.

CONCLUSIONS

Intention-to-treat GERD with antireflux surgery does not prevent EAC. It often develops more than 5 years postoperatively, also in the patients with a good antireflux barrier. Only one-third of the patients had, however, a functioning fundoplication. Preoperative BE and endoscopic esophagitis may be risk factors. Prospective, long-term, randomized studies in experienced centers may reveal the definite effect of antireflux surgery on EAC development.

Randomised clinical trial: twice daily esomeprazole 40 mg vs. pantoprazole 40 mg in Barrett's oesophagus for 1 year

BACKGROUND

Barrett's oesophagus is regarded as the most important risk factor for development of oesophageal adenocarcinoma. According to current guidelines, treatment should be limited to symptomatic Barrett's oesophagus.

AIM

To evaluate the expression of Ki67, cyclooxygenase-2 (COX-2) and apoptosis in Barrett's oesophagus after 12 months of double-dose proton pump inhibitor therapy. The effectiveness of esomeprazole and pantoprazole was also compared.

METHODS

Seventy-seven nondysplastic Barrett's oesophagus patients underwent baseline upper endoscopy. Patients were then randomised into two groups: one group was allocated to receive esomeprazole 40 mg b.d. and the other group pantoprazole 40 mg b.d. for 12 months. A follow-up endoscopy was performed at the end of treatment. Sixty-five of 77 patients agreed to undergo oesophageal manometry and 24-h pH-metry. Barrett's oesophagus biopsies, obtained at baseline and after treatment, were analysed using immunohistochemistry to assess Ki67 and COX-2 expression; apoptosis was evaluated using TUNEL.

RESULTS

In the esomeprazole group, a significant decrease in Ki67 and COX-2 expression, as well as an increase in apoptosis, were observed (P < 0.05). By contrast, in the pantoprazole group Ki67, COX-2 and apoptosis did not vary significantly from baseline. By 24-h oesophageal pH-monitoring, a normal acid exposure time was recorded in patients treated with esomeprazole, while those allocated to pantoprazole displayed abnormal acid exposure (P < 0.05).

CONCLUSIONS

Treatment of Barrett's oesophagus patients with high-dose esomeprazole, but not pantoprazole, promoted a decrease in proliferative markers, concomitantly with a decrease in apoptotic cell death. Moreover, esomeprazole allowed a better oesophageal acid control than pantoprazole.

Barrett's esophagus

Barrett's esophagus is an acquired metaplastic abnormality in which the normal stratified squamous epithelium lining of the esophagus is replaced by an intestinal-like columnar epithelium. While in itself a benign and asymptomatic disorder, the clinical importance of this relatively common condition relates to its role as a precursor lesion to esophageal adenocarcinoma, the incidence of which has dramatically increased in Western populations in recent years. Although known to arise as a consequence of chronic gastroesophageal reflux, the cellular and molecular mechanisms underlying development Barrett's esophagus and its progression to cancer remain unclear.