Expression of cyclooxygenase 2, microsomal prostaglandin E synthase 1, and EP receptors is increased in rat oesophageal squamous cell dysplasia and Barrett's metaplasia induced by duodenal contents reflux

Current Status of Chemoprevention in Barrett's Esophagus

Candidates for chemoprevention in Barrett's esophagus have long been suggested and there has been observational data to support many drugs, including statins, hormone replacement therapy, metformin, proton pump inhibitor therapy, and aspirin. Proton pump inhibitor therapy and aspirin are the most promising agents. Data suggest that aspirin and proton pump inhibitor therapy can decrease the risk of neoplastic progression in Barrett's esophagus. Further, the combination of aspirin and proton pump inhibitor therapy decrease all-cause mortality by approximately 33%. Future guideline groups need to evaluate the evidence rigorously, but the combination of proton pump inhibitor therapy and aspirin is promising.

Prostaglandin E2 as a therapeutic target in bladder cancer: From basic science to clinical trials

Bladder cancer (BCa) is a common solid tumor marked by high rates of recurrence, especially in non-muscle invasive disease. Prostaglandin E₂ (PGE₂) is a ubiquitously present lipid mediator responsible for numerous physiological actions. Inhibition of cyclooxygenase (COX) enzymes by the non-steroidal anti-inflammatory (NSAID) class of drugs results in reduced PGE₂ levels. NSAID usage has been associated with reductions in cancers such as BCa. Clinical trials using NSAIDs to prevent recurrence have had mixed results, but largely converge on issues with cardiotoxicity. The purpose of this review is to understand the basic science behind how and why inhibitors of PGE₂ may be effective against BCa, and to explore alternate therapeutic modalities for addressing the role of PGE₂ without the associated cardiotoxicity. We will address the role of PGE₂ in a diverse array of cancer-related functions including stemness, immunosuppression, proliferation, cellular signaling and more.

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

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

Targeting the COX1/2-Driven thromboxane A2 pathway suppresses Barrett's esophagus and esophageal adenocarcinoma development

Background

Barrett's esophagus (BE), a complication of gastroesophageal reflux disease (GERD), predisposes patients to esophageal adenocarcinoma (EAC). Reliable biomarkers for early detection and discovery of potential drug targets are urgently needed for improved BE and EAC patient outcomes.

Methods

Patient biopsy samples were evaluated for COX1/2, and thromboxane A2 synthase (TBXAS) expression. Circulating prostaglandins biosynthesis was determined using enzyme immunoassay kits. Anchorage-independent cell growth assay, crystal violet staining assay, and xenograft experiments were conducted to assess BE and EAC cell growth. A surgical mouse model of reflux (i.e., esophagoduodenostomy) was established and samples were analyzed using an enzyme immunoassay kit, immunohistochemistry, immunoblotting, or RT-PCR. Esophageal biopsy samples (pre- and post-intervention) were obtained from a randomized clinical trial in which participants were administered esomeprazole (40 mg) twice daily in combination with an acetylsalicylic acid (ASA) placebo or 81 or 325 mg ASA for 28 days. Esophageal biopsy specimens before and after the intervention period were analyzed.

Findings

COX2 and TBXAS are highly expressed in BE and EAC patients accompanied by a pronounced elevation of circulating TXA2 levels. ASA suppressed BE and EAC growth by targeting the TXA2 pathway. Additionally, biopsies from 49 patients (with similar baseline characteristics) showed that ASA substantially decreased serum TXA2 levels, resulting in reduced inflammation.

Interpretation

This study establishes the importance of the COX1/2-driven TXA2 pathway in BE and EAC pathophysiology and lays the groundwork for introducing a TXA2-targeting strategy for EAC prevention and early detection.

Funding

Hormel Foundation, Exact Sciences, Pentax Medical, Intromedic and National Cancer.

Animal Models of Barrett's Esophagus and Esophageal Adenocarcinoma-Past, Present, and Future

Esophageal adenocarcinoma is the fastest rising cancer in the United States. It develops from long-standing gastroesophageal reflux disease which affects >20% of the general population. It carries a very poor prognosis with 5-year survival <20%. The disease is known to sequentially progress from reflux esophagitis to a metaplastic precursor, Barrett's esophagus and then onto dysplasia and esophageal adenocarcinoma. However, only few patients with reflux develop Barrett's esophagus and only a minority of these turn malignant. The reason for this heterogeneity in clinical progression is unknown. To improve patient management, molecular changes which facilitate disease progression must be identified. Animal models can provide a comprehensive functional and anatomic platform for such a study. Rats and mice have been the most widely studied but disease homology with humans has been questioned. No animal model naturally simulates the inflammation to adenocarcinoma progression as in humans, with all models requiring surgical bypass or destruction of existing antireflux mechanisms. Valuable properties of individual models could be utilized to holistically evaluate disease progression. In this review paper, we critically examined the current animal models of Barrett's esophagus, their differences and homologies with human disease and how they have shaped our current understanding of Barrett's carcinogenesis.

Loss of EP2 receptor subtype in colonic cells compromise epithelial barrier integrity by altering claudin-4

Prostaglandin E₂ (PGE₂) is a bioactive lipid mediator that exerts its biological function through interaction with four different subtypes of E-Prostanoid receptor namely EP1, EP2, EP3 and EP4. It has been known that EP2 receptor is differentially over-expressed in the epithelia of inflamed human colonic mucosa. However, the significance of the differential expression in altering epithelial barrier function is not known. In this study, we used Caco-2 cells expressing EP2 receptor, either high (EP2S) or low (EP2A), as a model epithelia and determined the barrier function of these cell monolayers by measuring the trans epithelial resistance (TER). Basal TER of EP2A (but not EP2S) monolayer was significantly lower suggesting a loss of colonic epithelial barrier integrity. In comparison, the TER of wild type Caco-2 was decreased in response to an EP2 receptor specific antagonist (AH-6809) indicating an important role for EP2 receptor in the maintenance of epithelial barrier function. The decrease TER in EP2A monolayer corresponded with a significant loss of the tight junction (TJ) protein claudin-4 without affecting other major TJ proteins. Similarly, EP2 receptor antagonism/siRNA based silencing significantly decreased claudin-4 expression in EP2S cells. Surprisingly, alteration in claudin-4 was not transcriptionally regulated in EP2A cells but rather undergoes increased proteosomal degradation. Moreover, among the TER compromising cytokines examined (IL-8, IL-1β, TNF-α, IFN-γ) only IFN-γ was significantly up regulated in EP2A cells. However, IFN-γ did not significantly decreased claudin-4 expression in Caco-2 cells indicating no role for IFN-γ in degrading claudin-4. We conclude that differential down-regulation of EP2 receptor play a major role in compromising colonic epithelial barrier function by selectively increasing proteosomal degradation of claudin-4.

Functional role of CD44v-xCT system in the development of spasmolytic polypeptide-expressing metaplasia

Cancer development is often preceded by the appearance of preneoplastic lesions. In gastric carcinogenesis, chronic inflammation and histopathologic progression of the stomach epithelium lead to the development of metaplasia and eventually adenocarcinoma. The cell surface protein CD44, especially its variant isoforms (CD44v), has been implicated in metaplasia-carcinoma sequence progression in the stomach. We recently found that CD44v interacts with and stabilizes xCT, a subunit of the cystine transporter system xc(-), in cancer cells and thereby increases cystine uptake and confers resistance to various types of cellular stress in vivo. The functional relevance of CD44v and xCT in the development of preneoplastic lesions, however, has remained unknown. We have now examined the role of the CD44v-xCT system in the development of spasmolytic polypeptide-expressing metaplasia (SPEM) in mouse models of gastric carcinogenesis. CD44v was found to be expressed de novo in SPEM, and CD44v(+) metaplastic cells manifested upregulation of xCT expression compared with CD44v(-) cells. Genetic ablation of CD44 or treatment with sulfasalazine, an inhibitor of xCT-dependent cystine transport, suppressed the development of SPEM and subsequent gastric tumor growth. Therapy targeted to CD44v-xCT could thus prove effective for prevention or attenuation of the CD44v-dependent development of preneoplastic lesions and cancer.

Elevated expression of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in primary sclerosing cholangitis: ιmplications for cholangiocarcinogenesis

Cholangiocarcinoma (CCA) occurs frequently in primary sclerosing cholangitis (PSC). Cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) induced by inflammation are believed to mediate prostaglandin E2 (PGE2) production thereby promoting carcinogenesis. Their expression in PSC-associated CCA tissues and non-neoplastic bile duct epithelial cells (BDECs) in PSC was investigated. COX-2 and mPGES-1 levels in 15 PSC patients (7 with CCA) were scored using immunohistochemical staining. The results were compared with those obtained in CCA tissues and non-neoplastic BDECs (controls) of 15 sporadic CCA patients. Non-neoplastic BDECs from large and small bile ducts were investigated separately. The mRNA expression levels of COX-2 and mPGES-1 in CCA tissues were analyzed by quantitative polymerase chain reaction. Ki-67 immunostaining was performed to evaluate cell proliferation. COX-2 was strongly expressed in PSC-associated CCA tissues and non-neoplastic BDECs in PSC. This expression was significantly upregulated in both compared with sporadic CCA tissues and non-neoplastic BDECs in sporadic CCA (both P<0.01). mPGES-1 was expressed at moderate to strong levels in PSC. Compared with controls, the expression was significantly higher in non-neoplastic small BDECs (P<0.01). COX-2 mRNA levels were significantly higher in PSC-associated tissues than in sporadic CCA tissues (P<0.01). Conversely, no differences were observed in mPGES-1 mRNA levels. Ki-67 labeling indices were higher in PSC-associated CCA tissues and non-neoplastic BDECs in PSC than in controls. In conclusion, COX-2 and mPGES-1 were highly expressed in PSC-associated CCA tissues and non-neoplastic BDECs in PSC, suggesting the involvement of COX-2 and mPGES-1 in cholangiocarcinogenesis.

NADPH oxidase NOX5-S and nuclear factor κB1 mediate acid-induced microsomal prostaglandin E synthase-1 expression in Barrett's esophageal adenocarcinoma cells

The mechanisms of progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA) are not known. Cycloxygenase-2 (COX-2)-derived prostaglandin E₂ (PGE₂) has been shown to be important in esophageal tumorigenesis. We have shown that COX-2 mediates acid-induced PGE₂ production. The prostaglandin E synthase (PGES) responsible for acid-induced PGE2 production in BE, however, is not known. We found that microsomal PGES1 (mPGES1), mPGES2, and cytosolic PGES (cPGES) were present in FLO EA cells. Pulsed acid treatment significantly increased mPGES1 mRNA and protein levels but had little or no effect on mPGES2 or cPGES mRNA. Knockdown of mPGES1 by mPGES1 small interfering RNA (siRNA) blocked acid-induced increase in PGE2 production and thymidine incorporation. Knockdown of NADPH oxidase, NOX5-S, a variant lacking calcium-binding domains, by NOX5 siRNA significantly inhibited acid-induced increase in mPGES1 expression, thymidine incorporation, and PGE2 production. Overexpression of NOX5-S significantly increased the luciferase activity in FLO cells transfected with a nuclear factor κB (NF-κB) in vivo activation reporter plasmid pNF-κB-Luc. Knockdown of NF-κB1 p50 by p50 siRNA significantly decreased acid-induced increase in mPGES1 expression, thymidine incorporation, and PGE₂ production. Two novel NF-κB binding elements, GGAGTCTCCC and CGGGACACCC, were identified in the mPGES1 gene promoter. We conclude that mPGES1 mediates acid-induced increase in PGE₂ production and cell proliferation. Acid-induced mPGES1 expression depends on activation of NOX5-S and NF-κB1 p50. Microsomal PGES1 may be a potential target to prevent or treat EA.

Can the rat be used as a valid model of human esophageal adenocarcinoma?

Animal models of Barrett's metaplasia and esophageal adenocarcinoma are important to further characterize the disease and test potential therapies. This paper reviews the development of the surgical model of esophageal adenocarcinoma in the rat and considers whether this model provides a biologically accurate representation of Barrett's esophagus and esophageal adenocarcinoma in humans.

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.

Molecular basis for maize as a risk factor for esophageal cancer in a South African population via a prostaglandin E2 positive feedback mechanism

The incidence of squamous cancer of the esophagus varies up to a hundredfold in different regions of the world. In Transkei, South Africa, a particularly high incidence of the disease is observed. We have previously proposed an association between a maize-rich diet and elevated levels of intragastric prostaglandin E2 production (PGE(2)). Here we investigate the molecular mechanisms by which a high-maize diet could lead to increased incidence of squamous cancer of the esophagus. We confirm that levels of PGE(2) are high (606.8 pg/ml) in the gastric fluid of individuals from Transkei. We also show that treatment of esophageal cells with linoleic acid, which is found at high levels in maize and is a precursor to PGE(2), leads to increased cell proliferation. Similarly, treatment of cells with PGE(2) or with gastric fluid from Transkeians also leads to increased proliferation. Our data suggest that the high levels of PGE(2) associated with a maize-rich diet stimulate cell division and induce the enzyme COX 2, resulting in a positive feedback mechanism that predisposes the esophagus to carcinoma.

Fibroblast-derived HB-EGF promotes Cdx2 expression in esophageal squamous cells

The molecular basis of attaining columnar phenotype in Barrett's esophagus is poorly understood. One hypothesis states that factors locally produced by cells of mesenchymal origin in chronic reflux esophagitis induce metaplastic transformation. This study was performed to elucidate the factors secreted from fibroblasts that cause columnar phenotype in adjacent squamous epithelium. Human fibroblast cells were exposed to acidified medium for 20 min, followed by medium neutralization for 2 h, and then total RNA was hybridized to Sentrix Human-6 Expression BeadChips. Furthermore, esophageal mucosal biopsy specimens from reflux esophagitis patients were examined for HB-EGF expression using immunohistochemistry. In addition, cells from the human esophageal squamous epithelial cell line HET1A were treated with recombinant HB-EGF, and changes in expressions of Cdx2 and columnar markers were analyzed. The gene expression profile revealed significant upregulation of a variety of growth factors and inflammatory chemokines in response to acid exposure. Among them, HB-EGF was upregulated more than 10-fold. Biopsy specimens from reflux esophagitis patients showed a strong expression of HB-EGF in fibroblast cells underlying the damaged epithelium. Furthermore, in vitro stimulation of HET1A cells with HB-EGF increased Cdx2 in dose-dependent manners. Functional analysis of human Cdx2 promoter also revealed its upregulation by HB-EGF stimulation, showing the role of potential responsive elements (AP-1 and NF-kappaB) for its transcriptional activation. Moreover, the columnar markers cytokeratin 7 and villin were also upregulated by HB-EGF stimulation. HB-EGF induces several genes characteristics of columnar phenotypes of esophageal squamous epithelium in a paracrine manner.

Evaluation of the heme oxygenase-1 expression in esophagitis and esophageal cancer induced by different reflux experimental models and diethylnitrosamine

PURPOSE: To study the expression of heme-oxygenase-1 (HO-1), an enzyme induced by oxidative stress, in specimens obtained from an experimental model in rats that evaluated the role of gastric and duodenal reflux in esophageal carcinogenesis. METHODS: Esophageal specimens embedded in paraffin obtained from different experimental groups of rats were used for immunohistochemistry analysis of HO-1 expression. The rats had been divided into the following groups and were killed after 22 weeks: (1) cardioplasty to induce acid reflux; (2) esophagoduodenal anastomosis to induce duodenal reflux; (3) no treatment; (4) cardioplasty + diethylnitrosamine (DEN); (5) esophagoduodenal anastomosis + DEN; and (6) DEN. The study sample comprised 3 specimens from each group with the most severe histopathological lesions found on each study branch. RESULTS: The expression of HO-1 was seen only in rat specimens submitted to esophagoduodenal anastomosis (Groups 2 and 5), and the analysis of mean fluorescence intensity revealed a significant increase of HO-1 expression (4.8 and 4.6 fold, respectively) when compared with the control group (Group 3) (p<0.05). The main target for HO-1 induction was the inflammatory cells inside the tumor or in subepithelial areas. Rats exposed to gastric reflux had no HO-1 expression. CONCLUSION: Reflux esophagitis induced by reflux of duodenal contents, which provoked considerable oxidative stress, may play an important role in esophageal carcinogenesis. Acid reflux did not induce oxidative stress in this experimental model.

Microsomal prostaglandin E synthase-1 inhibition blocks proliferation and enhances apoptosis in oesophageal adenocarcinoma cells without affecting endothelial prostacyclin production

Prostaglandins are important in the progression of various gastrointestinal cancers including oesophageal adenocarcinoma (OAC). Cyclo-oxygenase (COX)-2 inhibitors reduce OAC prostaglandin production but also have potentially detrimental effects on vascular endothelial function by reducing prostacyclin production and increasing the risk of cardiovascular events. We have examined the effects of inhibiting microsomal prostaglandin synthase-1 (mPGES-1), the enzyme downstream of COX-2 in the prostaglandin synthetic cascade. In OAC cells, reduction of mPGES-1 with RNA interference blocked PGE2 production, inhibited serum-induced proliferation and enhanced apoptosis in the COX-2 expressing cell lines (OE33 and FLO) but had no effect in COX-2 deficient BIC-1 cells. Three different methods of inhibiting mPGES-1 (RNA interference, a novel small molecule inhibitor and the endogenous inhibitor 15-deoxy-Delta(12,14)-PGJ(2)) also blocked leptin induced mPGES-1 expression and PGE2 production and abolished the leptin-induced proliferative and anti-apoptotic effects in OE33 cells, without affecting COX-2 expression. The anti-proliferative effects were equivalent to those produced by COX-2 inhibitory concentrations of celecoxib and NS-398. However, unlike the two COX-2 inhibitors, mPGES-1 inhibition did not reduce endothelial prostacyclin production. In contrast to the effects of the COX-2 inhibitor celecoxib, mPGES-1 inhibition had no effects on Akt kinase activity in OAC cells. We conclude that inhibition of mPGES-1 has potentially beneficial effects in OAC without the potentially detrimental effects on vascular endothelial prostacyclin synthesis. We have also confirmed that celecoxib has anticancer actions separate from the inhibition of COX-2. Inhibition of mPGES-1 may be therapeutically useful in the treatment and prevention of OAC.

Acid and bile salt up-regulate BMP4 expression in human esophageal epithelium cells

OBJECTIVE

Barrett's esophagus (BE) with an intestinal-type epithelium is thought to be a precancerous lesion of adenocarcinoma of the esophagus. The pathophysiology of Barrett's metaplasia is poorly understood. Previous studies suggest that differentiation of multipotent cells to columnar epithelium may be one of the possible mechanisms. Bone morphogenetic protein 4 (BMP4), a factor determining the fate of cells, is up-regulated in BE and esophagitis mucosa when compared with normal squamous or non-goblet cell-containing cardiac epithelium. The aim of this study was to demonstrate that BMP4 is a molecular mediator that links etiological agents of BE to the phenotypic changes in human esophagus epithelium cells (HEECs).

MATERIAL AND METHODS

Primary cultured HEECs were used to investigate the effect of acid and bile salt on BMP4 expression and to examine the biological effects of BMP4 on HEECs.

RESULTS

Acid and bile salt increased the expression of BMP4. In addition, recombinant human BMP4 induced villin expression in HEECs, as did chronic acid exposure, which can be effectively inhibited by Noggin, a specific antagonist of BMP4. Results from a Western blot assay suggest that BMP4 induces activation of smad1 and promotes protein expression of ID2 and CDX2.

CONCLUSION

BMP4 may play an important role in the development of BE.

Prostaglandin EP2 receptor expression is increased in Barrett's oesophagus and oesophageal adenocarcinoma

BACKGROUND

Accumulating evidence suggests that cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) is involved in oesophageal adenocarcinogenesis. PGE2 exerts its biological action by binding to specific receptors (EP1, EP2, EP3 and EP4).

AIM

To investigate which PGE2 receptor subtypes regulate PGE2 signals in the oesophageal adenocarcinoma sequence.

METHODS

Expression was determined in oesophageal biopsies from 85 patients with oesophagitis, Barrett's metaplasia, intraepithelial neoplasia, oesophageal adenocarcinoma and normal oesophagus. Levels of mRNA and protein expression were determined by quantitative PCR, immunohistochemistry and western-blot. Expression of EP receptors was also determined in response to acid and bile exposure in the Barrett's adenocarcinoma cell line OE33.

RESULTS

All four EP receptors subtypes were expressed in human oesophageal tissues. COX-2 and, especially, EP2 were increased in the Barrett's metaplasia-intraepithelial neoplasia-adenocarcinoma sequence. Expression of the EP4 receptor protein was increased in oesophageal adenocarcinoma. In contrast, expression levels of COX-1 and EP3 receptor were decreased along the sequence. No differences in EP1 expression were found. Treatment with the bile acid deoxycholate increased COX-2, EP1, EP2 and EP4 expression in OE33 cells.

CONCLUSIONS

Our data suggest that in addition to COX-2, EP2 and EP4 receptors could be a selective target in the prevention and/or treatment of the Barrett's-associated adenocarcinoma.

Hypoxia activates the cyclooxygenase-2-prostaglandin E synthase axis

Hypoxia-inducible factors (HIFs), in particular HIF-1alpha, have been implicated in tumor biology. However, HIF target genes in the esophageal tumor microenvironment remain elusive. Gene expression profiling was performed upon hypoxia-exposed non-transformed immortalized human esophageal epithelial cells, EPC2-hTERT, and comparing with a gene signature of esophageal squamous cell carcinoma (ESCC). In addition to known HIF-1alpha target genes such as carbonic anhydrase 9, insulin-like growth factor binding protein-3 (IGFBP3) and cyclooxygenase (COX)-2, prostaglandin E synthase (PTGES) was identified as a novel target gene among the commonly upregulated genes in ESCC as well as the cells exposed to hypoxia. The PTGES induction was augmented upon stabilization of HIF-1alpha by hypoxia or cobalt chloride under normoxic conditions and suppressed by dominant-negative HIF-1alpha. Whereas PTGES messenger RNA (mRNA) was negatively regulated by normoxia, PTGES protein remained stable upon reoxygenation. Prostaglandin E(2) (PGE(2)) biosynthesis was documented in transformed human esophageal cells by ectopic expression of PTGES as well as RNA interference directed against PTGES. Moreover, hypoxia stimulated PGE(2) production in a HIF-1alpha-dependent manner. In ESCC, PTGES was overexpressed frequently at the mRNA and protein levels. Finally, COX-2 and PTGES were colocalized in primary tumors along with HIF-1alpha and IGFBP3. Activation of the COX-2-PTGES axis in primary tumors was further corroborated by concomitant upregulation of interleukin-1beta and downregulation of hydroxylprostaglandin dehydrogenase. Thus, PTGES is a novel HIF-1alpha target gene, involved in prostaglandin E biosynthesis in the esophageal tumor hypoxic microenvironment, and this has implications in diverse tumors types, especially of squamous origin.

Prostaglandin E(2) synthase inhibition as a therapeutic target

BACKGROUND

Most NSAIDs function by inhibiting biosynthesis of PGE(2) by inhibition of COX-1 and/or COX-2. Since COX-1 has a protective function in the gastro-intestinal tract (GIT), non-selective inhibition of both cycloxy genases leads to moderate to severe gastro-intestinal intolerance. Attempts to identify selective inhibitors of COX-2, led to the identification of celecoxib and rofecoxib. However, long-term use of these drugs has serious adverse effects of sudden myocardial infarction and thrombosis. Drug-mediated imbalance in the levels of prostaglandin I(2) (PGI(2)) and thromboxane A(2) (TXA(2)) with a bias towards TXA(2) may be the primary reason for these events. This resulted in the drugs being withdrawn from the market, leaving a need for an effective and safe anti-inflammatory drug.

METHODS

Recently, the focus of research has shifted to enzymes downstream of COX in the prosta glandin biosynthetic pathway such as prostaglandin E(2) synthases. Microsomal prostaglandin E(2) synthase-1 (mPGES-1) specifically isomerizes PGH(2) to PGE(2), under inflammatory conditions. In this review, we examine the biology of mPGES-1 and its role in disease. Progress in designing molecules that can selectively inhibit mPGES-1 is reviewed.

CONCLUSION

mPGES-1 has the potential to be a target for anti-inflammatory therapy, devoid of adverse GIT and cardiac effects and warrants further investigation.

Epithelial metaplasia: adult stem cell reprogramming and (pre)neoplastic transformation mediated by inflammation?

Throughout adult life, new developmental commitment of adult stem cells causes metaplastic conversions to occur frequently in some organs. These reversible epithelial replacements are almost always observed in association with chronic inflammation and persistent irritation. Although metaplasia is not synonymous with dysplasia, clinical surveillance has demonstrated that these adaptive processes have an increased susceptibility to evolve into cancer. We propose that cytokines and other soluble factors released by both epithelial and inflammatory cells might alter the transcription-factor expression profile of stem cells and lead to the development of metaplasia. Furthermore, inflammatory mediators might also promote the malignant transformation of epithelial metaplasia by inducing genetic and epigenetic changes and by preventing the immune system from mounting an efficient anti-tumour immune response. A better understanding of the molecular mechanisms leading to metaplasia might help in the design of new therapies for neoplastic and degenerative diseases.

A selective cyclooxygenase-2 inhibitor prevents inflammation-related squamous cell carcinogenesis of the forestomach via duodenogastric reflux in rats

BACKGROUND

Duodenal reflux causes inflammation-related squamous cell carcinogenesis in the forestomach of rats without any carcinogens. The aim of this study was to investigate the efficacy of a selective cyclooxygenase (COX)-2 inhibitor, meloxicam, in preventing this carcinogenesis.

METHODS

A series of 188 rats underwent a surgical duodenogastric reflux procedure and were divided into 2 groups. One group was given commercial chow (control group), and the other was given experimental chow containing meloxicam (0.3 mg/kg body weight/day) (meloxicam group). The animals were sequentially sacrificed at Weeks 20, 30, 40, 50, and 60 after surgery. The forestomach was examined for the presence of carcinoma, the incidence of reflux-related morphological changes, COX-2 expression, and its activity.

RESULTS

At Week 60, squamous cell carcinoma developed in 8 of 21 animals (38%) in the control group, but none of 20 (0%) in the meloxicam group (P<.05). In addition, basal cell dysplasia developed in 19 of 21 (90%) animals in the control group, but only 4 of 20 (20%) in the meloxicam group (P<.01). COX-2 immunoreactivity was predominantly detected in macrophages in the epithelial stroma. Compared with nonsurgical rats, RNA expression of COX-2 in the epithelium was up-regulated, reaching peak at an early stage of Week 20 in both groups (P<.005). The expression of microsomal prostaglandin E synthase-1 was lower in the meloxicam group than in the control group. PGE2 production was significantly suppressed throughout the experiment in the meloxicam group compared with the control group (P<.005).

CONCLUSIONS

Meloxicam was effective in preventing reflux-induced squamous cell carcinogenesis via an inflamed squamous epithelium.

E series of prostaglandin receptor 2-mediated activation of extracellular signal-regulated kinase/activator protein-1 signaling is required for the mitogenic action of prostaglandin E2 in esophageal squamous-cell carcinoma

The use of nonsteroidal anti-inflammatory drugs is associated with a lower risk for esophageal squamous cell carcinoma, in which overexpression of cyclooxygenase-2 (COX-2) is frequently reported. Prostaglandin E(2) (PGE(2)), a COX-2-derived eicosanoid, is implicated in the promotion of cancer growth. However, the precise role of PGE(2) in the disease development of esophageal squamous cell carcinoma remains elusive. In this study, we investigated the effect of PGE(2) on the proliferation of cultured esophageal squamous cell carcinoma cells (HKESC-1). Results showed that HKESC-1 cells expressed all four series of prostaglandin (EP) receptors, namely, EP1 to EP4 receptors. In this regard, PGE(2) and the EP2 receptor agonist (+/-)-15-deoxy-16S-hydroxy-17-cyclobutyl PGE(1) methyl ester (butaprost) markedly increased HKESC-1 cell proliferation. Moreover, the mitogenic effect of PGE(2) was significantly attenuated by RNA interference-mediated knockdown of the EP2 receptor, indicating that this receptor mediated the mitogenic effect of PGE(2). In this connection, PGE(2) and butaprost induced phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2), whose down-regulation by RNA interference significantly attenuated PGE(2)-induced cell proliferation. In addition, PGE(2) and butaprost increased c-Fos expression and activator protein 1 (AP-1) transcriptional activity, which were abolished by the mitogen-activated protein kinase/Erk kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)-butadiene ethanolate (U0126). AP-1-binding inhibitor curcumin also partially reversed the mitogenic effect of PGE(2). Taken together, these data demonstrate for the first time that the EP2 receptor mediates the mitogenic effect of PGE(2) in esophageal squamous cell carcinoma via activation of the Erk/AP-1 pathway. This study supports the growth-promoting action of PGE(2) in esophageal squamous cell carcinoma and the potential application of EP2 receptor antagonists in the treatment of this disease.

Esophageal adenocarcinoma in "mice and men": back to basics!

Adenocarcinoma related to Barrett's esophagus (BE) is increasing in the West faster than any other cancer. There are many potential chemopreventive agents as well as predictive biomarkers of cancer progression, but what is required is a robust high-throughput model in which to test hypotheses preclinically. The pathophysiology of metaplasia and cancer has been studied in 10 animal species. Though they have considerable genetic divergence, anatomical dissimilarity, and experimental flaws, they have provided some data to test in the clinic, especially relating to activation of common genetic pathways, role of hypergastrinemia, and duodenogastric reflux in cancer progression. In this regard, the human postesophagectomy model, which has a 30% recurrence of BE within 3 yr and a 5% recurrence of adenocarcinoma over 10 yr, is now being utilized to understand how human metaplasia occurs. Furthermore, improved clinical trial designs mean that more sophisticated questions can be addressed in man.

Carcinogenesis in reflux disease--in search for bile-specific effects

Bile reflux may play a key role for esophageal carcinogenesis in reflux disease. In search for bile-specific effects, the animal model of esophageal cancer was applied in a mutagenesis assay. Big Blue transgenic mice were operated with microsurgical techniques. Seven had total gastrectomy with esophagojejunostomy creating esophageal reflux of bile and five had a sham operation. After 24 weeks, the mutation frequency (MF) was measured through standard Big Blue mutagenesis assay in the esophageal mucosa and the duodenum as control. Esophageal reflux resulted in esophagitis in the distal esophagus. The MF in esophageal mucosa was 1.6 times higher in animals with reflux than in sham-operated animals; it was identical in the duodenum. In conclusion, the mutagenic potential of bile reflux has been confirmed. However, mechanisms of carcinogenesis in the esophageal cancer model other than chronic inflammation could not be identified because of the only moderately increased MF.

Neither Antioxidants nor COX-2 Inhibition Protect Against Esophageal Inflammation in an Experimental Model of Severe Reflux

BACKGROUND

Reflux-induced injury and oxidative stress result in esophageal inflammation and the potential for progression to intestinal metaplasia and adenocarcinoma. Proton-pump inhibitors represent the standard medical approach, but anti-inflammatories and antioxidants offer novel therapeutic possibilities.

MATERIALS AND METHODS

Six weeks after an esophagojejunostomy reflux procedure, female Wistar rats (n = 100) were randomized to receive either an antioxidant (vitamin C, 8 mg or 28 mg/day), a cyclooxygenase-2 (COX-2) inhibitor (rofecoxib, 1 mg/day), or no therapy. After sacrifice 16 weeks later, esophageal injury was scored using pathologic and image analysis scoring.

RESULTS

Esophagitis was present in all 63 animals completing the study and was severe in 27 (43%). No animal developed metaplasia or tumor. The extent of inflammation and esophageal ulceration were not significantly different between experimental groups.

CONCLUSIONS

In this model of reflux injury, antioxidants and COX-2 inhibitors failed to ameliorate the severe inflammation induced. Further experimental designs should evaluate these novel approaches in less severe experimental models.

Sulindac prevents esophageal adenocarcinomas induced by gastroduodenal reflux in rats

PURPOSE

It is known that cyclooxygenase (COX)-2 expression is increased in Barrett's esophagus and esophageal adenocarcinomas. We studied COX-2 expression and the effect sulindac has on the genesis of Barrett's esophagus and adenocarcinoma in rats undergoing esophagogastroduodenal anastomosis (EGDA).

MATERIALS AND METHODS

Fifty-one rats were divided into a control group (n=27), a 500 ppm sulindac-treated group (n=15) and 1000 ppm sulindac-treated group (n=9). Randomly selected rats were killed by diethyl ether inhalation at 20 and 40 weeks after surgery.

RESULTS

At 40 weeks, rats treated with 1000 ppm sulindac showed narrower esophageal diameter and milder inflammation than the control rats. At 40 weeks, the incidence of Barrett's esophagus was similar between control and sulindac-treated groups, but the incidence of adenocarcinoma was significantly lower in the 1000 ppm sulindac-treated group than either the control or 500 ppm sulindac-treated groups. COX-2 was significantly increased in the lower esophagus of control rats killed at 40 weeks. Cyclin D1 expression was negligible in the sulindac- treated group compared with the control group.

CONCLUSION

We suggest that the chemopreventive effect of sulindac is related to decreased COX-2 and cyclin D1 expression, which may be influenced by reduced inflammation.

COX-2 induction by unconjugated bile acids involves reactive oxygen species-mediated signalling pathways in Barrett's oesophagus and oesophageal adenocarcinoma

OBJECTIVES

Bile reflux contributes to oesophageal injury and neoplasia. COX-2 is involved in both inflammation and carcinogenesis; however, the precise mechanisms by which bile acids promote COX-2 expression in the oesophagus are largely unknown. We analysed the molecular mechanisms that govern bile acid-mediated expression of COX-2 in Barrett's oesophagus and oesophageal adenocarcinoma (OA).

DESIGN

The effects of bile acids on COX-2 expression were analysed in immortalised Barrett's oesophagus and OA cells using immunoblotting and transient transfections. Pharmacological inhibitors, phospho-specific antibodies, dominant-negative mutants and siRNA techniques were used to identify relevant signalling pathways. Flow cytometry and reactive oxygen species (ROS) scavengers were used to examine ROS involvement. Immunohistochemistry was performed on oesophageal mucosa obtained from an established rat model of bile reflux.

RESULTS

Unconjugated bile acids potently stimulated COX-2 expression and induced AKT and ERK1/2 phosphorylation in concert with COX-2 induction. These findings were mimicked in the in vivo rat model. Dominant-negative (DN) AKT and LY294002 (PI3K inhibitor) or U0126 (MEK-1/2 inhibitor) blocked chenodeoxycholic acid (CD) and deoxycholic acid (DC) mediated COX-2 induction. CD and DC also induced CREB phosphorylation and AP-1 activity. CREB-specific siRNA and DN AP-1 blocked CD and DC-induced COX-2 induction. Finally, CD and DC increased intracellular ROS, while ROS scavengers blocked COX-2 induction and the signalling pathways involved.

CONCLUSIONS

Unconjugated bile acids induce CREB and AP-1-dependent COX-2 expression in Barrett's oesophagus and OA through ROS-mediated activation of PI3K/AKT and ERK1/2. This study enhances our understanding of the molecular mechanisms by which bile acids promote the development of oesophageal adenocarcinoma.

Membrane prostaglandin E synthase-1: a novel therapeutic target

Prostaglandin E(2) (PGE(2)) is the most abundant prostaglandin in the human body. It has a large number of biological actions that it exerts via four types of receptors, EP1-4. PGE(2) is formed from arachidonic acid by cyclooxygenase (COX-1 and COX-2)-catalyzed formation of prostaglandin H(2) (PGH(2)) and further transformation by PGE synthases. The isomerization of the endoperoxide PGH(2) to PGE(2) is catalyzed by three different PGE synthases, viz. cytosolic PGE synthase (cPGES) and two membrane-bound PGE synthases, mPGES-1 and mPGES-2. Of these isomerases, cPGES and mPGES-2 are constitutive enzymes, whereas mPGES-1 is mainly an induced isomerase. cPGES uses PGH(2) produced by COX-1 whereas mPGES-1 uses COX-2-derived endoperoxide. mPGES-2 can use both sources of PGH(2). mPGES-1 is a member of the membrane associated proteins involved in eicosanoid and glutathione metabolism (MAPEG) superfamily. It requires glutathione as an essential cofactor for its activity. mPGES-1 is up-regulated in response to various proinflammatory stimuli with a concomitant increased expression of COX-2. The coordinate increased expression of COX-2 and mPGES-1 is reversed by glucocorticoids. Differences in the kinetics of the expression of the two enzymes suggest distinct regulatory mechanisms for their expression. Studies, mainly from disruption of the mPGES-1 gene in mice, indicate key roles of mPGES-1-generated PGE(2) in female reproduction and in pathological conditions such as inflammation, pain, fever, anorexia, atherosclerosis, stroke, and tumorigenesis. These findings indicate that mPGES-1 is a potential target for the development of therapeutic agents for treatment of several diseases.

Neither Antioxidants nor COX-2 Inhibition Protect Against Esophageal Inflammation in an Experimental Model of Severe Reflux

BACKGROUND

Reflux-induced injury and oxidative stress result in esophageal inflammation and the potential for progression to intestinal metaplasia and adenocarcinoma. Proton-pump inhibitors represent the standard medical approach, but anti-inflammatories and antioxidants offer novel therapeutic possibilities.

MATERIALS AND METHODS

Six weeks after an esophagojejunostomy reflux procedure, female Wistar rats (n = 100) were randomized to receive either an antioxidant (vitamin C, 8 mg or 28 mg/day), a cyclooxygenase-2 (COX-2) inhibitor (rofecoxib, 1 mg/day), or no therapy. After sacrifice 16 weeks later, esophageal injury was scored using pathologic and image analysis scoring.

RESULTS

Esophagitis was present in all 63 animals completing the study and severe in 27 (43%). No animal developed metaplasia or tumor. The extent of inflammation and esophageal ulceration were not significantly different between experimental groups.

CONCLUSIONS

In this model of reflux injury, antioxidants and COX-2 inhibitors failed to ameliorate the severe inflammation induced. Further experimental designs should evaluate these novel approaches in less severe experimental models.

The expression pattern of prostaglandin E synthase and EP receptor isoforms in normal mouse skin and preinvasive skin neoplasms

Prostaglandin (PG) E(2), the predominant PG in skin, accumulates in experimentally produced mouse skin tumors. PGE(2) induces proliferation of mouse keratinocytes in vitro, epidermal hyperplasia and dysplasia, a promoted epidermis phenotype, and angiogenesis in keratin 5 promoter (K5) cyclooxygenase (COX)-2-transgenic NMRI mouse skin in vivo. PGE(2) is synthesized by COX-catalysed oxygenation of arachidonic acid to PGH(2) and its conversion to PGE(2) by prostaglandin E synthase (PGES) isoforms. PGE(2) signals via PGE(2) receptor isoforms EP1-EP4. Here, we investigated the expression profiles of PGES and EP receptors in wild type NMRI mouse skin constitutively expressing COX-1 when compared with the hyperplastic/dysplastic skin of homozygous K5 COX-2-transgenic mice and papillomas of both genotypes, which, in addition to COX-1, overexpress COX-2. The three PGES are constitutively expressed in normal and transgenic skin independent of the COX expression status. In papillomas, the increased PGE(2) levels correlate with an increased expression of mPGES-1 and cPGES. All four EP receptors were expressed in normal and transgenic skin. Only EP3 was slightly increased in transgenic skin. In papillomas of both genotypes, the expression levels of EP1 and EP4 were low when compared with those in wild type back skin. EP2 was the predominant receptor in papillomas of wild type and transgenic mice. In papillomas of wild type mice EP3 levels were slightly elevated when compared with transgenic tumors. EP1 and EP2 were localized in basal keratinocytes, sebaceous glands and CD31-positive vessels. Thus, normal and preinvasive mouse skin express the complete protein repertoire for PGE(2) biosynthesis and signalling.

Do acid and bile reflux into the esophagus simultaneously? Temporal relationship between duodenogastro-esophageal reflux and esophageal pH

BACKGROUND

Duodenogastro-esophageal reflux (DGER) is an important factor in the pathogenesis of reflux esophagitis. Animal studies have demonstrated that the injurious effect of duodenal juice components depends on pH. The purpose of the present study was to investigate the temporal relationship between DGER and esophageal pH.

METHODS

Seventy-six children with symptoms of gastro-esophageal reflux disease (27 without, 31 with mild, 18 with severe esophagitis) underwent 24 h simultaneous esophageal pH and bilirubin monitoring with Bilitec 2000. The recordings were analyzed for (i) pH at the beginning of DGER episodes; (ii) relative duration of DGER in eight defined pH intervals of 1 pH unit; and (iii) differences in relative duration of DGER between the three groups of children.

RESULTS

DGER episodes most frequently began at pH between 6 and 7. DGER was present in the esophagus across the spectrum of esophageal pH, with the biggest relative duration between pH 3 and 5. However, in children without esophagitis relative duration of DGER was longest between pH 5 and 6, in children with mild esophagitis between pH 4 and 5, while in those with severe esophagitis it was between pH 2 and 4 (P < 0.001).

CONCLUSIONS

DGER appears across the whole esophageal pH spectrum. The more severe the esophagitis, the lower the pH at which DGER occurs, resulting in simultaneous damaging effects of acid and duodenal juice components.

Prostaglandin E2 receptor distribution and function in the gastrointestinal tract

Prostaglandin E2 (PGE2) is one of the most important biologically active prostanoids found throughout the gastrointestinal tract. Despite the fact that PGE2 regulates many physiological functions of the gut including mucosal protection, gastrointestinal secretion and motility, it is implicated in the pathophysiology of inflammatory bowel diseases (IBD) and colorectal neoplasia. The varied biological functions exerted by PGE2 are through the pharmacologically distinct, G-protein coupled plasma membrane receptors termed EP receptors. Disruptions of various prostanoid receptor genes have helped in unravelling the physiological functions of these receptors. To date, all four subtypes of EP receptors have been individually knocked out in mice and various phenotypes have been reported for each subtype. Similarly, in vitro and in vivo studies using EP receptor agonists and antagonists have helped in uncoupling the diverse functions of PGE2 signalling involving distinct EP receptors in the gut. In this review, we will summarize and conceptualize the salient features of EP receptor subtypes, their regional functions in the gut and how expressions of EP receptors are altered during disease states.

Effects of selective PGE2 receptor antagonists in esophageal adenocarcinoma cells derived from Barrett's esophagus

Accumulating evidence suggests that COX-2-derived prostaglandin E(2) (PGE(2)) plays an important role in esophageal adenocarcinogenesis. Recently, PGE(2) receptors (EP) have been shown to be involved in colon cancer development. Since it is not known which receptors regulate PGE(2) signals in esophageal adenocarcinoma, we investigated the role of EP receptors using a human Barrett's-derived esophageal adenocarcinoma cell line (OE33). OE33 cells expressed COX-1, COX-2, EP(1), EP(2) and EP(4) but not EP(3) receptors as determined by real time RT-PCR and Western-blot. Treatment with 5-aza-dC restored expression, suggesting that hypermethylation is involved in EP(3) downregulation. Endogenous PGE(2) production was mainly due to COX-2, since this was significantly suppressed with COX-2 inhibitors (NS-398 and SC-58125), but not COX-1 inhibitors (SC-560). Cell proliferation ((3)H-thymidine uptake) was significantly inhibited by NS-398 and SC-58125, the EP(1) antagonist SC-51322, AH6809 (EP(1)/EP(2) antagonist), and the EP(4) antagonist AH23848B, but was not affected by exogenous PGE(2). However, treatment with the selective EP(2) agonist Butaprost or 16,16-dimethylPGE(2) significantly inhibited butyrate-induced apoptosis and stimulated OE33 cell migration. The effect of exogenous PGE(2) on migration was attenuated when cells were first treated with EP(1) and EP(4) antagonists. These findings suggest a potential role for EP selective antagonists in the treatment of esophageal adenocarcinoma.

Leptin stimulates proliferation and inhibits apoptosis in Barrett's esophageal adenocarcinoma cells by cyclooxygenase-2-dependent, prostaglandin-E2-mediated transactivation of the epidermal growth factor receptor and c-Jun NH2-terminal kinase activation

Obesity is an important risk factor for esophageal adenocarcinoma (EAC), and elevated serum leptin is characteristic of obesity. We hypothesized that leptin may have biological effects in promoting esophageal adenocarcinoma and examined the effects of leptin on the OE33 Barrett's-derived EAC line. Proliferation was assessed by dimethylthiazoldiphenyltetra-zoliumbromide and 5-bromo-2'-deoxyuridine incorporation assays and apoptosis by ELISA of intracellular nucleosomes. Intracellular signaling was examined using specific pharmacological inhibitors and direct detection of phosphorylated active kinases. Expression of the long and short leptin receptors by OE33 cells was confirmed by RT-PCR, Western blotting and immunocytochemistry. Leptin stimulated OE33 cell proliferation in a dose-dependent manner and inhibited apoptosis. These effects were dependent on cyclooxygenase (COX)-2 and replicated by adding prostaglandin E2 (PGE2). The effects of PGE2 and leptin were abolished by the EP-4 antagonist AH23848. ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and Janus tyrosine kinase (JAK)-2 were activated upstream of COX-2 induction, whereas the epidermal growth factor receptor and c-Jun NH2-terminal kinase (JNK) were downstream of COX-2. The activation of ERK and Akt but not p38 MAPK was JAK2 dependent. PGE2 stimulated phosphorylation of JNK in an EGF receptor-dependent manner, and activation of the epidermal growth factor receptor required protein kinase C, src, and matrix metalloproteinase activities. We conclude that leptin stimulates cell proliferation and inhibits apoptosis in OAC cells via ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and JAK2-dependent activation of COX-2 and PGE2 production. Subsequent PGE2-mediated transactivation of the epidermal growth factor receptor and JNK activation are essential to the leptin effects. These effects may contribute to the greatly increased risk of esophageal adenocarcinoma in obesity.

Biliary laryngopharyngeal reflux: a new pathological entity

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent understanding of the harmful effects of gastric and duodenal agents on mucosa of the upper aerodigestive tract in patients with duodeno-gastro-esophageal reflux.

RECENT FINDINGS

The damaging action of duodeno-gastro-esophageal reflux on the gastro-esophageal mucosa and its potential etiological role in the development of many inflammatory and neoplastic patterns have been well documented in the literature. Recently, there has been increasing evidence that duodeno-gastro-esophageal reflux may also be related to several laryngeal disorders and clinical studies confirm that reflux after gastric resection may enhance the development of laryngeal malignancies. Finally, there have been experimental attempts to confirm that duodenal contents may contribute to inflammation and carcinogenesis in the pharynx or larynx, as it is known to do in the esophagus.

SUMMARY

The association between duodeno-gastro-esophageal reflux and laryngeal lesions is of great interest to otolaryngologists because it focuses attention on a new pathological entity that could be classified as biliary laryngopharyngeal reflux. This condition, as an acid one, seems to represent an important dangerous, endogenous risk factor involved in the pathogenesis of inflammatory, precancerous and neoplastic laryngeal lesions. For these reasons, particular attention is required in the future regarding the understanding of the local environment, individual susceptibility and clinical treatment. Finally, new antireflux therapy should be considered to control not only the acid gastric component of the refluxate but also the duodenal component.

Treatment of oesophageal bile reflux in children: the results of a prospective study with omeprazole

OBJECTIVES

Reflux of duodenal juice into the oesophagus has a role in the pathogenesis of both oesophageal and laryngopharyngeal inflammatory and neoplastic lesions. As little is known about effective therapy, we studied the effect of proton pump inhibitor therapy on oesophageal bile reflux in children.

METHODS

Twenty-nine children with moderate to severe erosive oesophagitis and abnormal oesophageal bile reflux were studied before and after treatment with omeprazole 1 mg/kg per day. Outcomes included a clinical symptom score, oesophageal acid and bile reflux (simultaneous 24-hour pH and Bilitec 2000 monitoring), and mucosal healing.

RESULTS

After 8 weeks of therapy, 17 (59%) of the patients were symptom-free, and 5 (17%) had minimal symptoms. Mucosal healing or reduction to low-grade oesophagitis was achieved in 25 children (86%; P < 0.0005). Mean percentages of total, upright, and supine time with oesophageal pH less than 4 were reduced from 17.0%, 16.8%, and 19.2% before treatment, to 2.83%, 3.17%, and 2.07%, respectively, after treatment (all P < 0.00001). Similarly, mean percentages of total, upright, and supine time with bile reflux were reduced from 16.96%, 12.67%, and 22.0%, to 2.27%, 1.91%, and 2.23%, respectively (P < 0.000001, P < 0.0001, and P < 0.000001, respectively).

CONCLUSIONS

Omeprazole 1 mg/kg per day is an effective therapy for the majority of children with severe erosive oesophagitis due to abnormal isolated bile reflux or combined acid and bile reflux. It remains unclear how patients with treatment-resistant bile reflux should be managed.

Roles of cyclooxygenase 2 and microsomal prostaglandin E synthase 1 in rat acid reflux oesophagitis

BACKGROUND

Although prostaglandin E2 (PGE2), cyclooxygenase 2 (COX-2), and microsomal prostaglandin E synthase 1 (mPGES-1) are known to play a role in various inflammatory events, their roles in the pathogenesis of gastro-oesophageal reflux disease are not known.

AIMS

We examined the dynamics of COX-1, COX-2, mPGES-1, mPGES-2, cytosolic PGES (cPGES), and PGE2 synthetic activity in rat acid reflux oesophagitis and the effects of COX-2 inhibitors on the severity of oesophagitis.

METHODS

Acid reflux oesophagitis was induced by ligating the transitional region between the forestomach and the glandular portion and wrapping the duodenum near the pylorus. Rats were killed on day 3 (acute phase) or day 21 (chronic phase) after induction of oesophagitis.

RESULTS

Expression of COX-2 and mPGES-1 was markedly increased in oesophagitis while modest changes in COX-1, cPGES, and mPGES-2 expression were observed. COX-2 and mPGES-1 were colocalised in epithelial cells of the basal layer, as well as inflammatory and mesenchymal cells in the lamina propria and submucosa. COX-2 inhibitors significantly reduced the severity of chronic oesophagitis but did not affect acute oesophageal lesions. COX-2 inhibitors significantly inhibited the increase in PGE2 synthesis in oesophageal lesions on both days 3 and 21. Epithelial proliferation was significantly increased in the basal layer on day 21. Inflammatory cells and epithelial cells of the basal layer exhibited reactions for EP4 in oesophagitis.

CONCLUSION

PGE2 derived from COX-2 and mPGES-1 plays a significant role in the pathogenesis of chronic acid reflux oesophagitis, and possibly in basal hyperplasia and persistent inflammatory cell infiltration.

A novel external esophageal perfusion model for reflux esophageal injury

The current animal models of esophagitis and Barrett's esophagus consist of surgeries that divert the gastroduodenal contents to the esophagus. The limitations of these models are the inability to control the amount and concentration of the refluxate and the causing of significant postoperative stress and morbidity. Eighteen adult rats were cannulated at the upper esophagus and connected to a subcutaneous osmotic micropump to perfuse the esophageal lumen with bile and acid. Animals were sacrificed after 7 days of perfusion. Histological changes were determined. Cell proliferation, apoptosis, lipid peroxidation, and glutathione were measured. Histopathological changes in the bile- or acid-perfused esophagus were consistent with the findings associated with reflux esophagitis. Enhanced proliferation and apoptosis were seen, along with increased oxidative stress. The external esophageal perfusion model enabled precise control of the injurious agent. It induced the histologic and cellular injury of reflux esophagitis after 7 days.

Bile acids directly augment caudal related homeobox gene Cdx2 expression in oesophageal keratinocytes in Barrett's epithelium

BACKGROUND AND AIMS

The mechanism of transformation to intestinal metaplasia in Barrett's oesophagus has not been clarified. We investigated the effects of various bile acids on expression of the caudal related homeobox gene Cdx2 in cultured oesophageal squamous epithelial cells. In addition, morphological and histochemical changes in squamous cells to intestinal epithelial cells were studied in response to bile acid induced expression of Cdx2.

METHODS

A rat model of Barrett's oesophagus was created by anastomosing the oesophagus and jejunum, and Cdx2 expression was investigated by immunohistochemistry. Also, the response of various bile acids on Cdx2 gene expression was studied in the human colon epithelial cell lines Caco-2 and HT-29, as well as in cultured rat oesophageal squamous epithelial cells using a Cdx2 promoter luciferase assay. In addition, primary cultured oesophageal squamous epithelial cells were transfected with Cdx2 expression vectors and their possible transformation to intestinal-type epithelial cells was investigated.

RESULTS

Oesophagojejunal anastomoses formed intestinal goblet cell metaplasia in rat oesophagus specimens and metaplastic epithelia strongly expressed Cdx2. When the effects of 11 types of bile acids on Cdx2 gene expression were examined, only cholic acid (CA) and dehydrocholic acid dose dependently increased Cdx2 promoter activity and Cdx2 protein production in Caco-2 and HT-29 cells, and cultured rat oesophageal keratinocytes. Results from mutation analysis of Cdx2 promoter suggested that two nuclear factor kappaB (NFkappaB) binding sites were responsible for the bile acid induced activation of the Cdx2 promoter. When bile acids were measured in oesophageal refluxate of rats with experimental Barrett's oesophagus, the concentration of CA was found to be consistent with the experimental dose that augmented Cdx2 expression in vitro. Furthermore, transfection of the Cdx2 expression vector in cultured rat oesophageal keratinocytes induced production of intestinal-type mucin, MUC2, in cells that expressed Cdx2.

CONCLUSIONS

We found that CA activates Cdx2 promoter via NFkappaB and stimulates production of Cdx2 protein in oesophageal keratinocytes with production of intestinal-type mucin. This may be one of the mechanisms of metaplasia in Barrett's oesophagus.

Systematic review: the chemoprevention of oesophageal adenocarcinoma

The incidence of oesophageal adenocarcinoma is increasing in the UK faster than any other malignancy. Despite its relatively poor prognosis and the limited success of existing treatments, there is enthusiasm that chemopreventive agents might be able to stem the transition from normal squamous epithelium to adenocarcinoma. We discuss gastro-oesophageal reflux as the main risk factor for the development of Barrett's metaplasia, the only known precursor of oesophageal adenocarcinoma. Treatment options for reflux disease are considered with regard to their effects on cancer risk. Recent advances in the molecular and cell biology of Barrett's are outlined, and potential targets for chemoprevention examined. Available treatments for reflux disease have not convincingly altered the likelihood of cancer development. Epidemiological and animal studies support the use of non-steroidal anti-inflammatory drugs as potential chemopreventive agents. Dietary agents, however, have a more favourable side-effect profile and may prove to be an attractive alternative, although more work is needed to fully explore this prospect.

Expression of COX-2 in Barrett's esophagus and esophageal adenocarcinoma and its significance

AIM: To explore the significance of cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) level in human Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC).

METHODS: The expression of COX-2 mRNA, the distribution of COX-2 protein, and the content of PGE2 were detected in the endoscopic biopsies of from BE (n = 16), EAC (n = 17), and normal controls (n = 20) by reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and radioimmunoassay (RIA), respectively.

RESULTS: The positive rate of COX-2 mRNA was 87.50% (14/16) and 88.24% (15/17) in BE and EAC patients, respectively, which were significantly higher than that in the normal controls (25%, P < 0.01). Furthermore, COX-2 protein was expressed in the epithelial cytoplasm of BE patients (81.25%, 13/16) and the plasm of cancer cells in EAC patients (76.47%, 13/17), which were significantly higher than that in the normal controls (20.00%, 4/20). The contents of PGE2 (pg/mg) in BE (541.41 ± 34.30) and EAC patients (559.22 ± 37.77) were also significantly higher than those in the normal controls (357.10 ± 37.58) (P < 0.05). No significant difference was found between BE and EAC patients in COX-2 mRNA, protein expression and PGE2 content (P>0.05).

CONCLUSION: COX-2 mRNA and its protein are overexpressed, and the level of PGE2 is increased in BE and EAC group. COX-2 and PGE2 may be involved in the development of Barrett's esophagus and esophageal adenocarcinoma.

Cyclooxygenase-2 expression and cell proliferation are increased in MUC2-positive area of columnar-lined esophagus

Columnar-lined esophagus is composed of intestinal type and gastric type epithelium. Only the specialized or intestinal type columnar epithelium is susceptible to the development of esophageal adenocarcinoma. The aim of the present paper was to evaluate the expression of cyclooxygenase (COX) and microsomal prostaglandin E synthase (mPGES) in gastric-type and intestinal-type metaplasia in columnar-lined esophagus and compare these with cell proliferation. Biopsy specimens of 30 columnar-lined esophagus patients were collected, and immunohistochemistry was performed for secretory mucins (MUC2, MUC5AC), COX, mPGES and cell proliferation (Ki-67). The MUC2-positive area had higher COX-2 expression and cell proliferation than the MUC5AC-positive area. There was a close correlation between COX-2 expression and cell proliferation. In contrast, the expression of COX-1, mPGES-1 and -2 was similar between intestinal metaplasia and gastric metaplasia. In conclusion, intestinal-type columnar-lined esophagus possesses COX-2 expression and a higher proliferation potential, suggesting that esophageal adenocarcinoma may arise from specialized columnar-lined esophagus.

Expression of inducible nitric oxide synthase is increased in rat Barrett's esophagus induced by duodenal contents reflux

Barrett's esophagus is a premalignant condition of esophageal adenocarcinoma. Inducible nitric oxide synthase (iNOS) is induced by cytokines and can generate locally high concentrations of nitric oxide (NO), whose metabolites can mediate genotoxicity and influence multistage carcinogenesis by causing DNA damage. Therefore, we evaluated the immunolocalization and expression of iNOS in surgically induced rat Barrett's esophagus. Esophagoduodenal anastomosis was performed in rats for inducing reflux of duodenal contents. Rats were killed at postoperative 10, 20, 30 and 40 weeks. We examined histologic changes and iNOS expression in esophagus by immunohistochemistry and reverse transcription-polymerase chain reaction. Eighty six percent of experimental rats showed Barrett's esophagus above esophagoduodenal junction. iNOS immunoreactivity was clearly observed in the epithelial cells of Barrett's esophagus, predominantly at the apical surface of epithelial cells. Cytoplasmic staining was also seen only in atypical Barrett's esophagus. iNOS mRNA was detected only in the lower esophagus of experimental group. In conclusion, this study suggests that iNOS has some roles on Barrett's esophagus formation.

Barrett's oesophagus with predominant intestinal metaplasia correlates with superficial cyclo-oxygenase-2 expression, increased proliferation and reduced apoptosis: changes that are partially reversed by non-steroidal anti-inflammatory drugs usage

BACKGROUND

Cyclo-oxygenase-2 expression has been reported to play an important role in the metaplasia-dysplasia-carcinoma sequence in Barrett's oesophagus. However, the existence of cyclo-oxygenase-2 expressing cells in Barrett's epithelium is still uncertain.

AIM

To identify the cells that express cyclo-oxygenase-2 protein and to investigate the relationship between cyclo-oxygenase-2 expression and mucin-phenotype of Barrett's epithelium.

METHODS

Sections from 466 biopsy samples of Barrett's epithelium from 358 non-medicated patients were immunohistochemically examined for the cyclo-oxygenase-2 expression, mucin-phenotype, cell proliferation and apoptosis.

RESULTS

Cyclo-oxygenase-2 expression was detected in 71.0% of Barrett's epithelium biopsy samples. In Barrett's epithelium with the gastric predominant mucin-phenotype, cyclo-oxygenase-2 expression was mainly found in stromal and deep epithelial cells, whereas in intestinal predominant mucin-phenotype, it was mostly in superficial epithelial cell. A significant elevation of proliferating cell nuclear antigen index and suppression of apoptotic index was observed in Barrett's epithelium with superficial epithelial cyclo-oxygenase-2 expression. Neither such elevation of proliferating cell nuclear antigen index nor the suppression of apoptotic index could be found in chronic non-steroidal anti-inflammatory drugs users.

CONCLUSIONS

Barrett's epithelium with intestinal mucin and superficial epithelial cyclo-oxygenase-2 expression possess a higher proliferation potential, but this risk may be thwarted by non-steroidal anti-inflammatory drugs administration.

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Expression of proteins related to prostaglandin E2 biosynthesis is increased in human gastric cancer and during gastric carcinogenesis

Prostaglandin E2 (PGE2) is related to carcinogenesis. Cyclooxygenase (COX) and prostaglandin E synthase (PGES) are involved in PGE2 synthesis. However, overall situation of COX and microsomal PGES (mPGES) expression in gastric cancer has not been studied in detail. The expression of COX and mPGES was evaluated in 45 cases of gastric cancer (22 intestinal type and 23 diffuse type), 13 gastric dysplasia, 15 intestinal metaplasia, 18 Helicobacter pylori associated gastritis, and 10 normal gastric tissues by performing immunohistochemistry and Western blot analysis. COX-1 expression was higher in intestinal type cancers than diffuse ones. COX-2 and mPGES-1 were expressed more in cancers than in paired nonneoplastic adjacent tissues, and intestinal type cancers showed higher expression of COX-2 than diffuse ones. The expression of COX and mPGES was gradually increased with progression of gastric lesions and the highest in dysplasia. mPGES-1 was expressed not only in epithelial cells but also in stromal cells, whose phenotype was myofibroblast, endothelial cells and others. In conclusion, proteins related to PGE2 biosynthesis affect both histogenesis and the carcinogenesis of human gastric cancer.