Chemoprevention for Barrett's esophagus trial. Design and outcome measures

Barrett's Metaplasia Progression towards Esophageal Adenocarcinoma: An Attempt to Select a Panel of Molecular Sensors and to Reflect Clinical Alterations by Experimental Models

The molecular processes that predispose the development of Barrett’s esophagus (BE) towards esophageal adenocarcinoma (EAC) induced by gastrointestinal reflux disease (GERD) are still under investigation. In this study, based on a scientific literature screening and an analysis of clinical datasets, we selected a panel of 20 genes covering BE- and EAC-specific molecular markers (FZD5, IFNGR1, IL1A, IL1B, IL1R1, IL1RN, KRT4, KRT8, KRT15, KRT18, NFKBIL1, PTGS1, PTGS2, SOCS3, SOX4, SOX9, SOX15, TIMP1, TMEM2, TNFRSF10B). Furthermore, we aimed to reflect these alterations within an experimental and translational in vitro model of BE to EAC progression. We performed a comparison between expression profiles in GSE clinical databases with an in vitro model of GERD involving a BE cell line (BAR-T) and EAC cell lines (OE33 and OE19). Molecular responses of cells treated with acidified bile mixture (BM) at concentration of 100 and 250 μM for 30 min per day were evaluated. We also determined a basal mRNA expression within untreated, wild type cell lines on subsequent stages of BE and EAC development. We observed that an appropriately optimized in vitro model based on the combination of BAR-T, OE33 and OE19 cell lines reflects in 65% and more the clinical molecular alterations observed during BE and EAC development. We also confirmed previous observations that exposure to BM (GERD in vitro) activated carcinogenesis in non-dysplastic cells, inducing molecular alternations in the advanced stages of BE. We conclude that it is possible to induce, to a high extent, the molecular profile observed clinically within appropriately and carefully optimized experimental models, triggering EAC development. This experimental scheme and molecular marker panel might be implemented in further research, e.g., aiming to develop and evaluate novel compounds and prodrugs targeting GERD as well as BE and EAC prevention and treatment.

COX-derived prostanoid pathways in gastrointestinal cancer development and progression: novel targets for prevention and intervention

Arachidonic acid metabolism through cyclooxygenase (COX) pathways leads to the generation of biologically active eicosanoids. Eicosanoid expression levels vary during development and progression of gastrointestinal (GI) malignancies. COX-2 is the major COX-isoform responsible for G.I. cancer development/progression. COX-2 expression increases during progression from a normal to cancerous state. Evidence from observational studies has demonstrated that chronic NSAID use reduces the risk of cancer development, while both incidence and risk of death due to G.I. cancers were significantly reduced by daily aspirin intake. A number of randomized controlled trials (APC trial, Prevention of Sporadic Adenomatous Polyps trial, APPROVe trial) have also shown a significant protective effect in patients receiving selective COX-2 inhibitors. However, chronic use of selective COX-2 inhibitors at high doses was associated with increased cardiovascular risk, while NSAIDs have also been associated with increased risk. More recently, downstream effectors of COX-signaling have been investigated in cancer development/progression. PGE(2), which binds to both EP and PPAR receptors, is the major prostanoid implicated in the carcinogenesis of G.I. cancers. The role of TXA(2) in G.I. cancers has also been examined, although further studies are required to uncover its role in carcinogenesis. Other prostanoids investigated include PGD(2) and its metabolite 15d-PGJ2, PGF(1α) and PGI(2). Targeting these prostanoids in G.I. cancers has the promise of avoiding cardiovascular toxicity associated with chronic selective COX-2 inhibition, while maintaining anti-tumor reactivity. A progressive sequence from normal to pre-malignant to a malignant state has been identified in G.I. cancers. In this review, we will discuss the role of the COX-derived prostanoids in G.I. cancer development and progression. Targeting these downstream prostanoids for chemoprevention and/or treatment of G.I. cancers will also be discussed. Finally, we will highlight the latest pre-clinical technologies as well as avenues for future investigation in this highly topical research field.

Inflammation-related carcinogenesis and prevention in esophageal adenocarcinoma using rat duodenoesophageal reflux models

Development from chronic inflammation to Barrett's adenocarcinoma is known as one of the inflammation-related carcinogenesis routes. Gastroesophageal reflux disease induces regurgitant esophagitis, and esophageal mucosa is usually regenerated by squamous epithelium, but sometimes and somewhere replaced with metaplastic columnar epithelium. Specialized columnar epithelium, so-called Barrett's epithelium (BE), is a risk factor for dysplasia and adenocarcinoma in esophagus. Several experiments using rodent model inducing duodenogastroesophageal reflux or duodenoesophageal reflux revealed that columnar epithelium, first emerging at the proliferative zone, progresses to dysplasia and finally adenocarcinoma, and exogenous carcinogen is not necessary for cancer development. It is demonstrated that duodenal juice rather than gastric juice is essential to develop esophageal adenocarcinoma in not only rodent experiments, but also clinical studies. Antireflux surgery and chemoprevention by proton pump inhibitors, nonsteroidal anti-inflammatory drugs, selective cyclooxygenase-2 inhibitors, green tea, retinoic acid and thioproline showed preventive effects on the development of Barrett's adenocarcinoma in rodent models, but it remains controversial whether antireflux surgery could regress BE and prevent esophageal cancer in clinical observation. The Chemoprevention for Barrett's Esophagus Trial (CBET), a phase IIb, multicenter, randomized, double-masked study using celecoxib in patients with Barrett's dysplasia failed to prove to prevent progression of dysplasia to cancer. The AspECT (Aspirin Esomeprazole Chemoprevention Trial), a large multicenter phase III randomized trial to evaluate the effects of esomeprazole and/or aspirin on the rate of progression to high-grade dysplasia or adenocarcinoma in patients with BE is now ongoing.

Computer-assisted brush-biopsy analysis for the detection of dysplasia in a high-risk Barrett's esophagus surveillance population

BACKGROUND

Barrett's epithelial dysplasia, the direct precursor to esophageal adenocarcinoma, is often unapparent and frequently missed during surveillance of Barrett's esophagus with four-quadrant forceps biopsy protocol.

AIM

To determine whether the detection of dysplasia is improved by adding computer-assisted brush biopsy (EndoCDx©) to four-quadrant biopsy protocol.

METHODS

Patients with a history of Barrett's esophagus with dysplasia scheduled for endoscopic surveillance were recruited from four academic medical centers. Patients underwent brush biopsy followed by four-quadrant biopsy every 1-2 cm. The results from brush and forceps biopsy were reviewed independently by pathologists blinded to the other's results.

RESULTS

Among 151 patients enrolled (124 men, 27 women; mean age: 65), 117 (77.5%) had forceps and brush-biopsy specimens adequate for interpretation. The mean number of forceps biopsies was 11.9 (median 10, range 2-40) and brush biopsies was 2.0 (median 2, range 1-4). The overall yield of forceps alone was 25.2% (n = 38). Brush biopsy added an additional 16 positive cases increasing the yield of dysplasia detection by 42% (95% CI: 20.7-72.7). The number needed to test (NNT) to detect one additional case of dysplasia was 9.4 (95% CI: 6.4-17.7). There were no significant differences in results among different centers, between standard versus jumbo forceps, or between forceps biopsies taken every 1 cm versus every 2 cm.

CONCLUSIONS

These data suggest that computer-assisted brush biopsy is a useful adjunct to standard endoscopic surveillance regimens for the identification of dysplasia in Barrett's esophagus.

Acid reflux and oesophageal cancer

Barrett's metaplasia is one of the commonest premalignant lesions in the western world following colorectal adenomas. One in 50 of the adult population develops Barrett's as a consequence of chronic gastro-oesophageal reflux. The mucosal inflammation seen within patients with gastro-oesophageal reflux seems likely to drive the growth of the metaplastic mucosa and also help direct further oncological change, yet the molecular events that characterize the pathway from inflammation to metaplasia to dysplasia and adenocarcinoma are poorly understood. There is hope that understanding the role of oesophageal inflammation will provide important insight into the development of Barrett's metaplasia and oesophageal cancer. This chapter will discuss the inflammation seen within context of Barrett's oesophagus and also clinical trials which hope to address this common premalignant disease. There are several ongoing clinical trials which are aiming to provide data using anti-inflammatory therapies to tackle this important premalignant condition. There is new data presented which suggests that data from the aspirin esomeprazole chemoprevention trial (AspECT) may hold the clue to disease treatment and that the cytokine TNF-α seems to be a key signalling molecule in the metaplasia-dysplasia-carcinoma sequence. Specifically it appears that both epigenetic and inherited genetics cooperate to modulate the prognosis.

Use of image transformation to track the natural history of diseases

The inability to precisely measure the area of a lesion can impair the study of its natural history and response to therapy. This is especially true in case of gastrointestinal lesions, where a standard imaging technique is endoscopy and an unaided visual interpretation of the size of the lesion is difficult. This study presents a novel technique that provides precise measurement of 2-dimensional lesions in cylinder-like organs.

Treatment for Barrett's oesophagus

BACKGROUND

Treatments for Barrett's oesophagus, the precursor lesion of adenocarcinoma, are available but whether these therapies effectively prevent the development of adenocarcinoma, and in some cases eradicate the Barrett's oesophagus segment, remains unclear.

OBJECTIVES

To summarise, quantify and compare the efficacy of pharmacological, surgical and endoscopic treatments for the eradication of dysplastic and non-dysplastic Barrett's oesophagus and prevention of these states from progression to adenocarcinoma.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library 2004, issue 4), MEDLINE (1966 to June 2008) and EMBASE (1980 to June 2008).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing medical, endoscopic or non-resectional surgical treatments for Barrett's oesophagus. The primary outcome measures were complete eradication of Barrett's and dysplasia at 12 months, and reduction in the number of patients progressing to cancer at five years or latest time point.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and assessed the quality of the trials included in the analysis.

MAIN RESULTS

Sixteen studies, including 1074 patients, were included. The mean number of participants in the studies was small (n = 49; range 8 to 208). Most studies did not report on the primary outcomes. Medical and surgical interventions to reduce symptoms and sequelae of gastro-oesophageal reflux disease (GORD) did not induce significant eradication of Barrett's oesophagus or dysplasia. Endoscopic therapies (photodynamic therapy (PDT with aminolevulinic acid or porfimer sodium), argon plasma coagulation (APC) and radiofrequency ablation (RFA)) all induced regression of Barrett's oesophagus and dysplasia. The data for photodynamic therapy were heterogeneous with a mean eradication rate of 51% for Barrett's oesophagus and between 56% and 100% for dysplasia, depending on the treatment regimens. The variation in photodynamic therapy eradication rates for dysplasia was dependent on the drug, source and dose of light. Radiofrequency ablation resulted in eradication rates of 82% and 94% for Barrett's oesophagus and dysplasia respectively, compared to a sham treatment. Endoscopic treatments were generally well tolerated, however all were associated with some buried glands, particularly following argon plasma coagulation and photodynamic therapy, as well as photosensitivity and strictures induced by porfimer sodium based photodynamic therapy in particular.

AUTHORS' CONCLUSIONS

Despite their failure to eradicate Barrett's oesophagus, the role of medical and surgical interventions to reduce the troubling symptoms and sequelae of GORD is not questioned. Whether therapies for GORD reduce the cancer risk is not yet known. Ablative therapies have an increasing role in the management of dysplasia within Barrett's and current data would favour the use of radiofrequency ablation compared with photodynamic therapy. Radiofrequency ablation has been shown to yield significantly fewer complications than photodynamic therapy and is very efficacious at eradicating both dysplasia and Barrett's itself. However, long-term follow-up data are still needed before radiofrequency ablation can be used in routine clinical care without the need for very careful post-treatment surveillance. More clinical trial data and in particular randomised controlled trials are required to assess whether or not the cancer risk is reduced in routine clinical practice.

In vivo cancer biomarkers of esophageal neoplasia

The emergence of in vivo cancer biomarkers is promising tool for early detection, risk stratification, and therapeutic intervention in the esophagus, where adenocarcinoma is increasing at a rate that is faster than any other in industrialized nations. Exciting advances in target identification, probe development, and optical instrumentation are creating tremendous new opportunities for advancing techniques of molecular imaging. Progress in these areas is being made with small animal models of esophageal cancer using surgical approaches to induce reflux of acid and bile, and these findings are beginning to be evaluated in the clinic. Further identification of relevant targets, characterization of specific probes, and development of endoscopic imaging technologies are needed to further this direction in the field of molecular medicine. In the future, new methods that use in vivo cancer biomarkers for the early detection of neoplastic changes in the setting of Barrett's esophagus will become available.

Cyclooxygenase-2 (COX-2) in carcinogenesis and selective COX-2 inhibitors for chemoprevention in gastrointestinal cancers

INTRODUCTION

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to have a property to inhibit tumor development in some cancers while it shows various side effects such as gastrointestinal bleeding and renal disorder. Selective cyclooxygenase (COX)-2 inhibitors (coxibs) were originally developed as one of anti-inflammatory drugs to avoid side effect of NSAIDs. Fortunately, the coxibs was also proved to have an inhibiting effect on tumorigenesis by many experimental studies using cell lines and animal models like NSAIDs.

DISCUSSION

Since a randomized study for polyp chemoprevention by celecoxib in familial adenomatous polyposis (FAP) patients demonstrated a significant reduction in the number of colorectal polyps, the clinical use of celecoxib was approved for FAP patients. Three large trials using celecoxib (the Adenoma Prevention with Celebrex and the Prevention of Spontaneous Adenomatopus Polyps) or refecoxib (the Adenomatous Polyp Prevention on Vioxx) for the recurrence of colorectal polyps in patients with a history of colorectal adenoma polypectomized confirmed chemopreventive effects on colorectal adenoma but two of three trails alerted us a hazard of cardiovascular (CV) events. Thereafter, some coxibs were withdrawn from the market because they showed to increase risk of serious CV events including heart attacks and strokes. But recent reports concluded that a merit of the reduction in gastrointestinal events by coxibs exceeded a demerit of the increase in serious CV events. In this review, a role of COX-2 in carcinogenesis of gastrointestinal tract and a future of coxibs for chemoprevention are discussed.

Modeling using baseline characteristics in a small multicenter clinical trial for Barrett's esophagus

OBJECTIVE

Utilizing data obtained during a multicenter investigation, this paper illustrates how the use of covariates and careful modeling techniques can be useful in assessing whether a negative outcome from a small multicenter clinical trial could be due to imbalance in baseline characteristics. The Chemoprevention for Barrett's Esophagus Trial (CBET) was a phase IIb, multicenter, randomized, placebo-controlled trial of celecoxib in patients with Barrett's esophagus. The primary outcomes for the original study were the proportion of biopsy samples exhibiting dysplasia in the celecoxib and placebo groups. The secondary and tertiary outcomes included histologic change and measurements of biologically relevant markers, including COX-1 and -2 mRNA, prostanoid levels, and methylation of tumor suppressor genes p16, APC, and E-cadherin. The original study reported no significant differences in primary, secondary or tertiary outcomes. In this paper, we focus on the results of one of the secondary measures, quantitative endoscopy (QE).

DESIGN

The study utilizes data from 56 patients in the CBET for whom baseline (BL) QE and one-year follow-up QE (F04) studies were performed. Of these, 29 were treated with celecoxib (200 mg twice daily for a minimum of 48 weeks) and 27 received the placebo. These patients are segmented as to the presence or absence of circumferential, tongues or islands of Barrett's.

MEASUREMENTS

The response of interest is total affected area at one year (Total F04); affected area at baseline (Total BL) is used as a covariate.

RESULTS

Controlling for complexity and clinic, there is a significant treatment effect. In addition, there is significant evidence that the area of Barrett's involvement decreased for patients in the treatment group.

CONCLUSIONS

That there was a decrease for the celecoxib over the placebo group adds to the body of evidence that relates COX-2 specific inhibitors and cancer incidence.

Effect of n-3 polyunsaturated fatty acids on Barrett's epithelium in the human lower esophagus

BACKGROUND

Epidemiologic studies suggest a reduced risk of esophageal adenocarcinoma in populations with a high consumption of fish, and n-3 fatty acids inhibit experimental carcinogenesis. One possible explanation is the suppression of eicosanoid production through inhibition of cyclooxygenase 2 (COX-2).

OBJECTIVE

The objective was to determine the effects of dietary supplementation with the n-3 fatty acid eicosapentaenoic acid (EPA) on a number of biological endpoints in Barrett's esophagus.

DESIGN

Fifty-two participants with known Barrett's esophagus underwent endoscopy. Biopsy samples were obtained from a recorded level within the area of Barrett's esophagus, and then 27 patients were randomly assigned to consume EPA capsules (1.5 g/d) for 6 mo or no supplement (controls). At the end of this period, patients again underwent endoscopy, and biopsy samples were collected at the same level. Tissue samples were analyzed for mucosal lipid, prostaglandin E2, leukotriene B4, COX-2 protein, and RNA concentrations. Cellular proliferation was also measured, by Ki-67 immunohistochemistry.

RESULTS

The EPA content of esophageal mucosa increased over the study period in the n-3-supplemented subjects and was significantly different from the content in the controls (P < 0.01). There was also a significant decline in COX-2 protein concentrations (measured by immunoblotting) in the n-3 group, and the difference was significant from that in the controls (P < 0.05); no difference in COX-2 RNA concentrations was observed between groups. This change in COX-2 protein was inversely related to the change in EPA content (P < 0.05). There was no significant difference in the change in prostaglandin E2, leukotriene B4, or cellular proliferation between the 2 groups.

CONCLUSION

Supplementation with EPA significantly changed n-3 fatty acid concentrations and reduced COX-2 concentrations in Barrett's tissue.

Quantitative endoscopy in the chemoprevention of Barrett's Esophagus Trial

The Chemoprevention for Barrett's Esophagus Trial (CBET) was a phase IIb, multicenter, randomized, placebo-controlled trial of celecoxib in patients with Barrett's esophagus. The overall outcome of the study was that there were no significant differences in primary, secondary, or tertiary outcomes. The purpose of the current study is to focus on results related to the method of measuring lesion size called quantitative endoscopy (QE). The design includes a review of a total number of studies and then restricts analyses to the four clinics that enrolled more than four patients each for whom a baseline and 1-year QE study was performed, comparing intra- and inter-patient and clinic differences in Barrett's esophagus. Measurements include the number of total QEs and adverse events, changes in areas from baseline to 1 year and other intervals, classification of Barrett's lesion type with respect to patients, clinics, and treatment. A total of 309 QE studies were completed with no adverse events. Differences in surface area measurements over time for a particular patient are smaller than the differences for randomly selected patients. The complexity mix (as defined by the mix of circumferential, tongues, and islands) of the Barrett's lesions varied with different clinics. In conclusion, QE is an efficient, safe, and accurate way to measure the area of Barrett's lesions variation between different clinical sites may be attributable to a subtle type of selection bias at the individual clinics rather than to regional differences.

Secondary chemoprevention of Barrett's esophagus with celecoxib: results of a randomized trial

BACKGROUND

Barrett's esophagus is a premalignant condition that is a risk factor for the development of esophageal adenocarcinoma, a disease whose incidence is rapidly increasing. Because aspirin and other nonsteroidal anti-inflammatory drugs, such as celecoxib, may decrease the risk of developing esophageal cancer, we investigated the effect of long-term administration of celecoxib in patients with Barrett's esophagus with dysplasia.

METHODS

Chemoprevention for Barrett's Esophagus Trial (CBET) is a phase IIb multicenter randomized placebo-controlled trial of celecoxib in patients with Barrett's esophagus and low- or high-grade dysplasia. Patients were randomly assigned to treatment with 200 mg of celecoxib or placebo, both administered orally twice daily, and then stratified by grade of dysplasia. The primary outcome was the change from baseline to 48 weeks of treatment in the proportion of biopsy samples with dysplasia between the celecoxib and placebo arms. Secondary and tertiary outcomes included evaluation of changes in histology and expression levels of relevant biomarkers. All statistical tests were two-sided.

RESULTS

From April 1, 2000, through June 30, 2003, 222 patients were registered into CBET, and 100 of them with low- or high-grade Barrett's dysplasia were randomly assigned to treatment (49 to celecoxib and 51 to placebo). After 48 weeks of treatment, no difference was observed in the median change in the proportion of biopsy samples with dysplasia or cancer between treatment groups in either the low-grade (median change with celecoxib = -0.09, interquartile range [IQR] = -0.32 to 0.14 and with placebo = -0.07, IQR = -0.26 to 0.12; P = .64) or high-grade (median change with celecoxib = 0.12, IQR = -0.31 to 0.55, and with placebo = 0.02, IQR = -0.24 to 0.28; P = .88) stratum. No statistically significant differences in total surface area of the Barrett's esophagus; in prostaglandin levels; in cyclooxygenase-1/2 mRNA levels; or in methylation of tumor suppressor genes p16, adenomatous polyposis coli, and E-cadherin were found with celecoxib compared with placebo.

CONCLUSIONS

Administration of 200 mg of celecoxib twice daily for 48 weeks of treatment does not appear to prevent progression of Barrett's dysplasia to cancer.

Secondary chemoprevention of Barrett's esophagus with celecoxib: results of a randomized trial

BACKGROUND

Barrett's esophagus is a premalignant condition that is a risk factor for the development of esophageal adenocarcinoma, a disease whose incidence is rapidly increasing. Because aspirin and other nonsteroidal anti-inflammatory drugs, such as celecoxib, may decrease the risk of developing esophageal cancer, we investigated the effect of long-term administration of celecoxib in patients with Barrett's esophagus with dysplasia.

METHODS

Chemoprevention for Barrett's Esophagus Trial (CBET) is a phase IIb multicenter randomized placebo-controlled trial of celecoxib in patients with Barrett's esophagus and low- or high-grade dysplasia. Patients were randomly assigned to treatment with 200 mg of celecoxib or placebo, both administered orally twice daily, and then stratified by grade of dysplasia. The primary outcome was the change from baseline to 48 weeks of treatment in the proportion of biopsy samples with dysplasia between the celecoxib and placebo arms. Secondary and tertiary outcomes included evaluation of changes in histology and expression levels of relevant biomarkers. All statistical tests were two-sided.

RESULTS

From April 1, 2000, through June 30, 2003, 222 patients were registered into CBET, and 100 of them with low- or high-grade Barrett's dysplasia were randomly assigned to treatment (49 to celecoxib and 51 to placebo). After 48 weeks of treatment, no difference was observed in the median change in the proportion of biopsy samples with dysplasia or cancer between treatment groups in either the low-grade (median change with celecoxib = -0.09, interquartile range [IQR] = -0.32 to 0.14 and with placebo = -0.07, IQR = -0.26 to 0.12; P = .64) or high-grade (median change with celecoxib = 0.12, IQR = -0.31 to 0.55, and with placebo = 0.02, IQR = -0.24 to 0.28; P = .88) stratum. No statistically significant differences in total surface area of the Barrett's esophagus; in prostaglandin levels; in cyclooxygenase-1/2 mRNA levels; or in methylation of tumor suppressor genes p16, adenomatous polyposis coli, and E-cadherin were found with celecoxib compared with placebo.

CONCLUSIONS

Administration of 200 mg of celecoxib twice daily for 48 weeks of treatment does not appear to prevent progression of Barrett's dysplasia to cancer.

Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward

This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.

Antireflux surgery normalizes cyclooxygenase-2 expression in squamous epithelium of the distal esophagus

BACKGROUND

In some patients GERD presents with heartburn and regurgitation symptoms but a relative paucity of endoscopic and clinical findings, while in others symptoms may be minor or absent yet there is significant mucosal damage on endoscopy including the presence of Barrett's esophagus. The initial injury of gastroesophageal reflux is to the squamous esophageal mucosa, but while substantial research has been devoted to determining which genes are involved in the progression of Barrett's to dysplasia and cancer, little is known about the gene expression alterations in the squamous mucosa of patients with reflux. We hypothesized that the expression of cyclooxygenase-2 (Cox-2) might be increased in the squamous esophageal mucosal of patients with reflux, and might be a molecular indicator of reflux injury. Further, we hypothesized that Cox-2 expression in the squamous mucosa would be reduced following the elimination of reflux with an antireflux operation.

METHODS

Biopsies of the distal esophageal squamous mucosa were taken 3 cm above the squamocolumnar junction (SCJ) in 28 GERD patients before and after Nissen fundoplication. Following microdissection and RNA isolation, quantitative real-time PCR was used to measure Cox-2 gene expression in paraffin-embedded (N = 16) and fresh frozen (N = 12) tissue. Biopsies from patients (paraffin N = 15, frozen N = 14) with normal acid exposure and no evidence of mucosal injury were analyzed as controls.

RESULTS

Median Cox-2 expression in the squamous epithelium from paraffin embedded biopsies in patients with reflux disease was significantly increased compared to controls (p = 0.04). The presence of esophagitis or Barrett's esophagus did not significantly alter the expression of Cox-2 compared to patients with nonerosive reflux disease (NERD). After antireflux surgery median Cox-2 expression values were significantly reduced (p = 0.0003) and were normalized to levels similar to controls without reflux (p = 0.74). Similar results were observed in the prospectively obtained fresh frozen tissue.

CONCLUSIONS

Cox-2 gene expression is increased in the distal esophageal squamous mucosa of most patients with GERD, and the elevation was similar whether there was mucosal injury in the form of esophagitis or Barrett's or no visible mucosal injury. This suggests that increased Cox-2 expression may serve as a molecular marker of reflux disease. The increased Cox-2 expression in patients with reflux was usually normalized following antireflux surgery. These findings demonstrate for the first time that gene expression can be altered by surgical correction of reflux. Thus, in addition to symptom control and improvement in the quality of life, perhaps future studies assessing the efficacy of antireflux therapy should also focus on the impact of the therapy on gene expression in the esophageal squamous mucosa.

Multistage carcinogenesis in Barrett's esophagus

The multistage carcinogenesis of esophageal adenocarcinoma is a process of clonal evolution within Barrett's esophagus neoplasms. The initiating event for Barrett's esophagus is unknown, but is associated with chronic gastric reflux which probably also promotes progression. Inactivation of both alleles of CDKN2A appear to be early events causing clonal expansion. Clones with TP53 inactivated expand if they have already inactivated CDKN2A. After TP53 has been inactivated, tetraploid and aneuploid clones tend to develop. The final events that lead to invasion and metastasis are unknown. Evolutionary biology provides important tools to understand clonal evolution in progression and cancer prevention.

Role of cyclooxygenase-2 in the carcinogenesis of gastrointestinal tract cancers: A review and report of personal experience

Selective cyclooxygenase (COX)-2 inhibitors (coxibs) were developed as one of the anti-inflammatory drugs to avoid the various side effects of non-steroidal anti-inflammatory drugs (NSAIDs). However, coxibs also have an ability to inhibit tumor development of various kinds the same way that NSAIDs do. Many experimental studies using cell lines and animal models demonstrated an ability to prevent tumor proliferation of COX-2 inhibitors. After performing a randomized study for polyp chemoprevention study in patients with familial adenomatous polyposis (FAP), which showed that the treatment with celecoxib, one of the coxibs, significantly reduced the number of colorectal polyps in 2000, the U.S. Food and Drug Administration (FDA) immediately approved the clinical use of celecoxib for FAP patients. However, some coxibs were recently reported to increase the risk of serious cardiovascular events including heart attack and stroke. In this article we review a role of COX-2 in carcinogenesis of gastrointestinal tract, such as the esophagus, stomach and colorectum, and also analyze the prospect of coxibs for chemoprevention of gastrointestinal tract tumors.

Interactions among smoking, obesity, and symptoms of acid reflux in Barrett's esophagus

BACKGROUND

Barrett's esophagus, a metaplastic precursor to esophageal adenocarcinoma, is becoming increasingly prevalent in many populations. Clinical studies suggest acid reflux causes Barrett's esophagus; however, no population-based estimates of risk have been reported, and the role of other health factors in modifying risk is unclear.

METHODS

We conducted a population-based case-control study in Brisbane, Australia. Cases were 167 patients with histologically confirmed Barrett's esophagus diagnosed between February and December 2003. Age-matched and sex-matched controls (n = 261) were randomly selected from a population register. Data on exposure to self-reported symptoms of acid reflux, smoking, obesity, and other factors were collected through self-completed questionnaires followed by telephone interview. Risks of Barrett's esophagus and Barrett's esophagus with dysplasia associated with these exposures were estimated by the odds ratio (OR) and 95% confidence interval (95% CI), both crude and adjusted for other factors.

RESULTS

Self-reported weekly episodes of acid reflux were associated with greatly increased risks of Barrett's esophagus (adjusted OR, 29.7; 95% CI, 12.2-72.6) and Barrett's esophagus with dysplasia (OR, 59.7; 95% CI, 18.5-193). Smoking was also associated with risk of Barrett's esophagus. We found evidence of interactions between symptoms of acid reflux and smoking and obesity. Obese people with self-reported symptoms of acid reflux had markedly higher risks of Barrett's esophagus (OR, 34.4; 95% CI, 6.3-188) than people with reflux alone (OR, 9.3; 95% CI, 1.4-62.2) or obesity alone (OR, 0.7; 95% CI, 0.2-2.4). Similarly, those reporting both acid reflux symptoms and smoking were at substantially higher risks of Barrett's esophagus (OR, 51.4; 95% CI, 14.1-188) than those reporting acid reflux or smoking alone.

CONCLUSIONS

Although history of symptoms of acid reflux is the principle factor associated with Barrett's esophagus, risks are substantially increased by obesity and smoking.

Identifying and defusing weapons of mass inflammation in carcinogenesis

The continued cancer risks associated with chronic inflammation necessitate the identification of inflammatory molecules and the cancer pathways they affect. Evidence indicates that there are multiple mechanisms linking inflammation to cancer and that there are multiple targets for chemoprevention. Here, we review some of the key factors and the cancer pathways they disturb as a necessary prerequisite to the identification of targets for chemoprevention.

COX2 expression, angiogenesis, proliferation and survival in Barrett's cancer

OBJECTIVES

To examine COX2 expression and its relation to angiogenesis, Ki67 and Bcl2 expression in Barrett's cancer.

METHODS

Specimens from 48 R0-resected Barrett's adenocarcinoma were immunostained for cyclooxygenase 2 (COX2), CD 31 and alpha-sm actin to discriminate between mature and immature vessels, Mib-1 and Bcl2. COX2 staining, angiogenesis, Ki67 expression and Bcl2 expression were also measured.

RESULTS

COX2 expression was increased in 25 of 48 cases. There was no significant correlation between COX2 expression and age, sex and tumor differentiation. A significant association was found between lymph node positive cases and elevated COX2 expression (p=0.008). The percentage of Ki67 positive cancer cells was 43.8% (range 15.4-67.5%) in the low COX2 group and 57.8% (range 12.0-84.6%) in the high COX2 group. The difference was statistically significant (p=0.046). The median neovascularisation coefficient in the low COX2 group was 11.68 (range 8.22-43.64) and 25.47 (range 8-38.3) in the high COX2 group. The difference was statistically significant (p=0.012). A significant difference in survival was observed between patients in the COX2 low category when compared with the COX2 high category (log-rank test p=0.013).

CONCLUSIONS

Elevated COX2 expression is associated with lymph-node metastases and reduced survival in Barrett's cancer. This appears to be related to the induction of angiogenesis and proliferation.

Inactivation of p16, RUNX3, and HPP1 occurs early in Barrett's-associated neoplastic progression and predicts progression risk

Patients with Barrett's esophagus (BE) are at increased risk of developing esophageal adenocarcinoma (EAC). Clinical neoplastic progression risk factors, such as age and the length of the esophageal BE segment, have been identified. However, improved molecular biomarkers predicting increased progression risk are needed for improved risk assessment and stratification. Using real-time quantitative methylation-specific PCR, we screened 10 genes (HPP1, RUNX3, RIZ1, CRBP1, 3-OST-2, APC, TIMP3, p16, MGMT, p14) for promoter hypermethylation in 77 EAC, 93 BE, and 64 normal esophagus (NE) specimens. A subset of genes manifesting significant differences in methylation frequencies between BE and EAC was then analysed in 20 dysplastic specimens. All 10 genes except p14 were frequently methylated in EACs, with RUNX3, HPP1, CRBP1, RIZ1, and OST-2 representing novel methylation targets in EAC and/or BE. p16, RUNX3, and HPP1 displayed increasing methylation frequencies in BE vs EAC. Furthermore, these increases in methylation occurred early, at the interface between BE and low-grade dysplasia (LGD). To demonstrate the silencing effect of hypermethylation, we selected the EAC cells BIC1, in which the HPP1 promoter is natively methylated, and subjected them to 5-aza-2'-deoxycytidine (Aza-C) treatment. Real-time RT-PCR indicated increased HPP1 mRNA levels after 3 days of Aza-C treatment, as well as decreased levels of methylated HPP1 DNA. Hypermethylation of a subset of six genes (APC, TIMP3, CRBP1, p16, RUNX3, and HPP1) was then tested in a retrospective longitudinal study of 99 BE and nine LGD specimens obtained from 53 BE patients undergoing surveillance endoscopy. Only high-grade dysplasia (HGD) or EAC were defined as progression end points. Two patient groups were compared: eight progressors (P) and 45 nonprogressors (NP), using Cox proportional hazards models to determine the relative progression risks of age, BE segment length, and methylation events. Multivariate analyses revealed that only hypermethylation of p16 (odds ratio (OR) 1.74, 95% confidence interval (CI) 1.33-2.20), RUNX3 (OR 1.80, 95% CI 1.08-2.81), and HPP1 (OR 1.77, 95% CI 1.06-2.81) were independently associated with an increased risk of progression, whereas age, BE segment length, and hypermethylation of TIMP3, APC, or CRBP1 were not independent risk factors. In combined analyses, risk was detectable up to, but not earlier than, 2 years preceding neoplastic progression. Hypermethylation of p16, RUNX3, and HPP1 in BE or LGD may represent independent risk factors for the progression of BE to HGD or EAC. These findings have implications regarding risk stratification, early EAC detection, and the appropriate endoscopic surveillance interval for patients with BE.

Flavopiridol reduces malignant transformation of the esophageal mucosa in p27 knockout mice

The cyclin-dependent kinase (cdk) inhibitor p27 preferentially inactivates cdk complexes required for progression through the G1/S transition. Loss of p27 is associated with aggressive behavior in a variety of tumors, including Barrett's associated adenocarcinoma (BAA). We have previously shown that gastroduodenal-esophageal reflux (GDER) together with N-methyl-N-benzylnitrosamine (MBN) induces Barrett's esophagus (BE) and malignant transformation of the esophageal mucosa in mice. This process is enhanced in a p27 null background. Here, we show that chronic flavopiridol administration sharply reduced the prevalence of BE in GDER/MBN-treated p27 knockout mice when compared to animals treated with diluent only (7 vs 26%, P=0.0079). Similarly, flavopiridol reduced the prevalence of BAA (11 vs 32%, P=0.0098) and overall cancer prevalence (15 vs 60%, P<0.0001). In addition, appropriate molecular targeting by flavopiridol in tumor cells was confirmed by downregulation of cyclin D1, a known target of this pan-cdk inhibitor. The results of this study represent the experimental basis for chemoprevention with cdk inhibitors in human BE and BAA.

Robotic Laparoscopic Fundoplication

Gastroesophageal reflux disease is a very common disorder, and both medical and surgical treatments have shown outstanding results. Whereas proton pump inhibitors are the mainstay of treatment, laparoscopic fundoplication has become a very attractive alternative due to its efficacy and low morbidity. There are defined patient categories that may benefit more from laparoscopy than medical therapy, but a conclusive comparison between the two is lacking. Robotic laparoscopic fundoplication can be performed safely without increased morbidity. Potential advantages include enhanced precision, improved dexterity, and remote telesurgical applications. Disadvantages include increased cost and prolonged operative times. Further studies and more long-term outcome data are needed to fully evaluate the procedure. Robotic surgery is currently in its infancy and not cost effective but has a very promising future. With further development of automatization and miniaturization features, robotic surgery may prove more efficient than conventional laparoscopy.

Genetics and prevention of oesophageal adenocarcinoma

Gastric cancer has been declining for more than half a century, whereas the incidence of oesophageal cancer is increasing rapidly. The histopathological subtype is also changing with a predominance of oesophageal adenocarcinoma compared with squamous carcinoma. The reasons for these epidemiological changes are not clear, although population-based data have implicated gastro-oesophageal reflux disease as a risk factor. In susceptible individuals reflux of duodeno-gastric contents can lead to the development of a columnar-lined oesophagus, commonly called Barrett's oesophagus. This can then progress to adenocarcinoma via a metaplasia-dysplasia-carcinoma sequence. At the current time, the mortality from oesophageal adenocarcinoma exceeds 80% at 5 years. Therefore, endoscopic surveillance programmes have been generally recommended for patients with Barrett's oesophagus in an attempt to detect early, curable lesions. Unfortunately these programmes are cumbersome and costly and have not yet been proved to reduce population mortality. In order to improve patient outcomes we need to be able to identify patients at high risk and to understand the triggers for disease progression. There is mounting evidence that there is an underlying genetic susceptibility to Barrett's oesophagus and oesophageal adenocarcinoma. However, this is likely to be as a result of multiple low penetrance susceptibility genes which have yet to be identified. Once patients are identified as having Barrett's oesophagus their chance for developing adenocarcinoma is in the order of 0.5%-1% per year. The histological assessment of dysplasia as a predictor of cancer development is highly subjective. Therefore multiple, specific somatic mutations in the tissue have been investigated as potential biomarkers. The most promising markers to date are the presence of aneuploidy, loss of heterozygosity of p53 and cyclin D1 overexpression. However, a study of evolutionary relationships suggest that mutations occur in no obligate order. Combinatorial approaches are therefore being advocated which include genomic profiling or the use of a panel of molecular markers in order to define the common molecular signatures that can then be used to predict malignant progression. An alternative approach would be to use markers for the final common pathway following genetic instability, which is the loss of proliferative control. We have demonstrated an increase in the expression of a novel proliferation marker, Mcm2, which occurs during the malignant progression of Barrett's oesophagus. These Mcm2-expressing cells are detectable on the surface, and hence a cytological approach may be applicable. In view of the role of reflux components in the pathogenesis of Barrett's oesophagus the effect of acid and bile on the cell phenotype have been studied. These studies have demonstrated that pulsatile acid and bile exposure induce cell proliferation. The mechanism for the hyperproliferative response appears to involve p38 mitogen activated protein kinase (MAPK) pathways as well as protein kinase C (PKC) and cyclo-oxygenases. A clinical implication of the laboratory studies is that suppression of acid and bile may need to be profound in order to suppress cell proliferation and, by inference, ultimately prevent the development of dysplasia. There is some support for this concept from short-term clinical studies, and a large randomised chemoprevention trial is being instigated which will evaluate the effect of proton pump inhibitors with or without aspirin. Given the epidemic increase in oesophageal adenocarcinoma and the dismal 5-year mortality rate, a radical approach is necessary to prevent cancer development in individuals with pre-malignant lesions.

Barrett metaplasia: reassessment of treatment and follow-up

PURPOSE OF REVIEW

The incidence of esophageal adenocarcinoma continues to rise in the Western world, with a mean 5-year survival of less than 20%. There has therefore been increasing interest in the precursor lesion, Barrett's esophagus. However, adenocarcinoma will not develop in most patients with Barrett's esophagus. This review summarizes the data on the management of Barrett's esophagus that have been published since January 2003.

RECENT FINDINGS

The control of reflux symptoms significantly improves quality of life, and surgical antireflux therapy may gradually cause regression of the Barrett segment compared with proton pump inhibitor therapy. The data substantiate the claim that the cancer risk in Barrett esophagus is lower than had hitherto been suggested. The risk factors for progression include increasing age and length of segment, macroscopic inflammatory changes, loss of heterozygosity over several genetic loci, and increased proliferation status. The extent of high-grade dysplasia may not accurately predict cancer development, and continued surveillance, rather than intervention, for such patients may decrease the chances of curative treatment. Long-term follow-up data are beginning to accumulate for nonsurgical treatment strategies. Chemoprevention trials are under way to evaluate the role of acid suppression and nonsteroidal anti-inflammatory drugs and their derivatives.

SUMMARY

At this time, endoscopic surveillance and surgical management remain the mainstay, but continued research efforts should enable risk stratification and cancer prevention in the future.

Overexpression of 5-Lipoxygenase in Rat and Human Esophageal Adenocarcinoma and Inhibitory Effects of Zileuton and Celecoxib on Carcinogenesis

PURPOSE

Aberrant arachidonic acid (AA) metabolism, especially through the cyclooxygenase (Cox) and 5-lipoxygenase (5-Lox) pathways, has been suggested to play an important role in the development of esophageal adenocarcinoma (EAC). The purpose of this study was to investigate the expression of 5-Lox in EAC of a rat model and in human samples as well as the chemopreventive effects of zileuton (a specific 5-Lox inhibitor) and celecoxib (a specific Cox2 inhibitor) in the rat EAC model.

EXPERIMENTAL DESIGN

5-Lox expression in EAC of a rat esophagogastroduodenal anastomosis model and of humans was examined with immunohistochemistry. A chemoprevention study was designed to test whether zileuton and celecoxib could suppress aberrant AA metabolism and esophageal adenocarcinogenesis.

RESULTS

With immunohistochemistry, we found that 5-Lox was overexpressed during esophageal adenocarcinogenesis in our rat model and in humans. In the chemoprevention study, EAC incidence was reduced in a dose-dependent manner from 68.8% (11 of 16) to 44.4% (8 of 18; P > 0.05) and 31.3% (5 of 16; P < 0.05) by 500 and 1,000 ppm zileuton, respectively, and to 33.3% (7 of 21; P < 0.05) and 20% (3 of 15; P < 0.05) by 500 and 1,000 ppm celecoxib, respectively. With isobolographic analysis, zileuton and celecoxib, both at a dose of 500 ppm, had an additive effect by reducing the tumor incidence to 16.7% (3 of 18, P < 0.01). Leukotriene B4 and prostaglandin E2 levels in the esophageal tissues were also significantly reduced by zileuton and celecoxib.

CONCLUSIONS

This study clearly demonstrated that 5-Lox and Cox2 play important roles in the development of EAC. Both zileuton and celecoxib had inhibitory effects on esophageal adenocarcinogenesis through inhibition on their respective enzymes of AA metabolism.

p27 and Barrett's esophagus: a review*

The rising prevalence of Barrett's esophagus and Barrett's associated adenocarcinoma in the Western world has stimulated increasing interest in this disease. This has resulted in a plethora of articles concerning its molecular biology, but the tumor suppressor gene, p27, has received little attention. In this article, we review the literature concerning the role of p27 in Barrett's esophagus and its malignant transformation, and we evaluate its possible role as an important clinical biomarker, as well as potential chemopreventive clinical agents aimed at substituting its antitumoral activity.

Cyclooxygenase-2 and Gastrointestinal Cancer

The cyclooxygenase (COX) enzymes (COX-1 and COX-2) are key enzymes of prostaglandin (PG) biosynthesis. Nonselective non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the enzymatic activity of both COX-1 and COX-2. Selective COX-2 inhibitors have been developed that appear to have 50% less gastrointestinal toxicity than traditional nonselective NSAIDs. Experimental evidence suggests that the COX pathway is involved in tumor promotion. Evidence to support this comes from both clinical and laboratory findings suggesting that chronic NSAID use reduces the relative risk for developing colorectal cancer (CRC). Although the precise mechanism or mechanisms by which these drugs affect tumor progression is not completely understood, it is likely that part of their anti-tumor effect is due to inhibition of the COX- 2 enzyme. COX-2 levels are increased in CRC as well as in several other solid malignancies. COX-2-derived bioactive lipid products promote tumor-associated n eovascularization, inhibit cell death, and stimulate cell proliferation and motility. Additionally, treatment with COX-2-selective inhibitors reduces polyp burden in animal models of intestinal neoplasia and in humans with familial adenomatous polyposis (FAP). Ongoing human clinical trails are under way to test the efficacy of COX-2-selective inhibitors in a number of human cancers.