Quantitative, tissue-specific analysis of cyclooxygenase gene expression in the pathogenesis of Barrett's adenocarcinoma

Melatonin in Prevention of the Sequence from Reflux Esophagitis to Barrett's Esophagus and Esophageal Adenocarcinoma: Experimental and Clinical Perspectives

Melatonin is a tryptophan-derived molecule with pleiotropic activities which is produced in all living organisms. This "sleep" hormone is a free radical scavenger, which activates several anti-oxidative enzymes and mechanisms. Melatonin, a highly lipophilic hormone, can reach body target cells rapidly, acting as the circadian signal to alter numerous physiological functions in the body. This indoleamine can protect the organs against a variety of damaging agents via multiple signaling. This review focused on the role played by melatonin in the mechanism of esophagoprotection, starting with its short-term protection against acute reflux esophagitis and then investigating the long-term prevention of chronic inflammation that leads to gastroesophageal reflux disease (GERD) and Barrett's esophagus. Since both of these condition are also identified as major risk factors for esophageal carcinoma, we provide some experimental and clinical evidence that supplementation therapy with melatonin could be useful in esophageal injury by protecting various animal models and patients with GERD from erosions, Barrett's esophagus and neoplasia. The physiological aspects of the synthesis and release of this indoleamine in the gut, including its release into portal circulation and liver uptake is examined. The beneficial influence of melatonin in preventing esophageal injury from acid-pepsin and acid-pepsin-bile exposure in animals as well as the usefulness of melatonin and its precursor, L-tryptophan in prophylactic and supplementary therapy against esophageal disorders in humans, are also discussed.

Barrett's oesophagus: treatment with surgery

Barrett's oesophagus develops as a consequence of gastro-oesophageal reflux disease and may progress to oesophageal adenocarcinoma. Antireflux surgery is an option for patients with reflux disease, but the efficacy and impact on the natural history of disease in patients with Barrett's oesophagus is controversial. This review addresses the existing data on these important issues.

Role of aspirin in chemoprevention of esophageal adenocarcinoma: a meta-analysis

OBJECTIVE

To identify whether regular aspirin use protects against esophageal adenocarcinoma (EA) and if so, the effect of the duration and frequency of drug exposure.

METHODS

Studies were selected from five journal/trial databases based on defined inclusion and exclusion criteria; most notably, the provision of multivariate EA odds ratios (ORs) in those taking regular aspirin. A subgroup analysis was then performed by stratifying the results according to the frequency and duration of aspirin use. The reliability of these investigations was assessed by calculating study heterogeneity and observing any elements of publication bias.

RESULTS

Nine studies were selected for the main analysis, of which five were included in the frequency analysis and three assessed the duration of aspirin use. Data pooling revealed a statistically significant EA OR of 0.671 (95% CI 0.526-0.856, P = 0.001) among all aspirin users, suggesting a protective effect. The results for duration and frequency did not reach statistical significance but nonetheless suggested possible benefits of longer, more frequent drug regimens that may be statistically confirmed by studies of larger sample sizes. Funnel plots and statistical tests demonstrated a minimal impact of publication bias on our results.

CONCLUSION

Aspirin use confers a significant protective effect against EA with a suggestion that the degree of protection may be increased by the longer duration and higher frequency of usage.

Early diagnostic biomarkers for esophageal adenocarcinoma--the current state of play

Esophageal adenocarcinoma (EAC) is one of the two most common types of esophageal cancer with alarming increase in incidence and very poor prognosis. Aiming to detect EAC early, currently high-risk patients are monitored using an endoscopic-biopsy approach. However, this approach is prone to sampling error and interobserver variability. Diagnostic tissue biomarkers related to genomic and cell-cycle abnormalities have shown promising results, although with current technology these tests are difficult to implement in the screening of high-risk patients for early neoplastic changes. Differential miRNA profiles and aberrant protein glycosylation in tissue samples have been reported to improve performance of existing tissue-based diagnostic biomarkers. In contrast to tissue biomarkers, circulating biomarkers are more amenable to population-screening strategies, due to the ease and low cost of testing. Studies have already shown altered circulating glycans and DNA methylation in BE/EAC, whereas disease-associated changes in circulating miRNA remain to be determined. Future research should focus on identification and validation of these circulating biomarkers in large-scale trials to develop in vitro diagnostic tools to screen population at risk for EAC development.

COX-2 mRNA is increased in oesophageal mucosal cells by a proton pump inhibitor

BACKGROUND

Barrett's oesophagus develops in some individuals with gastro-oesophageal reflux and is the precursor to oesophageal adenocarcinoma. Proton pump inhibitors (PPIs) suppress gastric acid production and are used to treat reflux. Clinical trials suggest that cyclooxygenase (COX) inhibitors might prevent oesophageal cancer, although PPIs could offset this by increasing COX-2 expression in Barrett's oesophagus. To investigate this, we evaluated the impact of a PPI on COX expression in oesophageal mucosal cells.

METHODS

The effect of the PPI esomeprazole on COX-1 and COX-2 mRNA levels in oesophageal cells was determined. Oesophageal cell lines OE33 (adenocarcinoma-derived) and HET-1A (immortalized squamous cells) and a control intestinal cell line HT29 (colon carcinoma) were treated for 24 h, with increasing concentrations of the esomeprazole.

RESULTS

COX-2, but not COX-1, mRNA levels dose-dependently increased in OE33 and HET-1A cells versus esomeprazole concentration. COX-2 mRNA levels did not increase in HT29 cells.

CONCLUSIONS

Exposure to esomeprazole increases COX-2 mRNA in oesophageal cells. This might contribute to the lack of benefit for COX inhibitors for oesophageal cancer prevention in recent clinical studies.

Cox2 and β-catenin/T-cell factor signaling intestinalize human esophageal keratinocytes when cultured under organotypic conditions

The incidence of esophageal adenocarcinoma (EAC) is rising in the United States. An important risk factor for EAC is the presence of Barrett esophagus (BE). BE is the replacement of normal squamous esophageal epithelium with a specialized columnar epithelium in response to chronic acid and bile reflux. However, the emergence of BE from squamous keratinocytes has not yet been demonstrated. Our research has focused on this. Wnt and cyclooxygenase 2 (Cox2) are two pathways whose activation has been associated with BE and progression to EAC, but their role has not been tested experimentally. To explore their contribution, we engineered a human esophageal keratinocyte cell line to express either a dominant-active Wnt effector CatCLef or a Cox2 complementary DNA. In a two-dimensional culture environment, Cox2 expression increases cell proliferation and migration, but neither transgene induces known BE markers. In contrast, when these cells were placed into three-dimensional organotypic culture conditions, we observed more profound effects. CatCLef-expressing cells were more proliferative, developed a thicker epithelium, and upregulated Notch signaling and several BE markers including NHE2. Cox2 expression also increased cell proliferation and induced a thicker epithelium. More importantly, we observed cysts form within the epithelium, filled with intestinal mucins including Muc5B and Muc17. This suggests that Cox2 expression in a three-dimensional culture environment induces a lineage of mucin-secreting cells and supports an important causal role for Cox2 in BE pathogenesis. We conclude that in vitro modeling of BE pathogenesis can be improved by enhancing Wnt signaling and Cox2 activity and using three-dimensional organotypic culture conditions.

Cyclooxygenase-2 expression in esophageal epithelium before and after photodynamic therapy for Barrett's esophagus with high-grade dysplasia or intramucosal carcinoma

Cyclooxygenase-2 expression is upregulated in Barrett's esophagus and esophageal adenocarcinoma. Photodynamic therapy using porfimer sodium can result in ablation of dysplasia and intramucosal carcinoma, eradication of Barrett's esophagus, and restitution of squamous epithelium. The aim of this study was to determine the effect of photodynamic therapy on cyclooxygenase-2 expression in esophageal epithelium. Paired pre- and post-photodynamic therapy biopsy samples from the same anatomical levels of 20 individuals who had undergone photodynamic therapy for Barrett's esophagus with high-grade dysplasia and/or intramucosal carcinoma were immunostained using a cyclooxygenase-2 monoclonal antibody. Cyclooxygenase-2 expression was graded in squamous epithelium, Barrett's esophagus, and neoplasia (if present) as follows: grade 0 (no staining), grade 1 (staining in 1-10% of cells), grade 2 (staining in 11-90% of cells), and grade 3 (staining in >90% of cells). Pre-photodynamic therapy median cyclooxygenase-2 expression was grade 2 (range 1-3) in neoplastic foci and grade 1 (range 1-3) in nondysplastic Barrett's esophagus (P=0.0009 for pairwise comparison). With the exception of a few cells staining in the basal epithelial layers, median cyclooxygenase-2 expression was graded as 0 (similar to controls) in both pre-photodynamic therapy squamous epithelium and post-photodynamic therapy neosquamous epithelium. This was significantly lower when compared to either neoplastic foci (P<0.0001) or nondysplastic Barrett's esophagus (P<0.0001) pre-photodynamic therapy. Notably, in four patients with post-photodynamic therapy recurrent neoplasia, cyclooxygenase-2 expression returned to elevated levels. Cyclooxygenase-2 expression is elevated in Barrett's esophagus with high-grade dysplasia or intramucosal carcinoma prior to photodynamic therapy. Following successful photodynamic therapy, cyclooxygenase-2 expression in neosquamous epithelium returns to a low baseline level similar to that observed in native esophageal squamous epithelium. Post-photodynamic therapy neoplastic recurrence is associated with elevated cyclooxygenase-2 expression. Prospective studies should determine whether cyclooxygenase inhibitors have a role as adjuvant therapy to prevent recurrence of Barrett's esophagus following endoscopic therapy.

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.

Biomarkers in exploring the frontiers of diagnosis, prognosis, and therapy of Barrett's esophagus

Barrett's esophagus (BE) is the principal risk factor for esophageal adenocarcinoma. BE patients currently undergo periodic endoscopic surveillance with tissue sampling and histopathologic assessment for dysplasia. They frequently are prescribed proton pump inhibitors to pharmacologically suppress gastric acid that is the cause of BE. These standard endoscopic and pharmacologic approaches for managing BE are crude at best. Identification of novel tissue biomarkers within BE may allow for more accurate endoscopic risk stratification and provide potential targets for chemoprevention.

MicroRNA-196a & microRNA-101 expression in Barrett's oesophagus in patients with medically and surgically treated gastro-oesophageal reflux

BACKGROUND

Proton pump inhibitor (PPI) medication and surgical fundoplication are used for the control of gastro-oesophageal reflux in patients with Barrett's oesophagus, but differ in their effectiveness for both acid and bile reflux. This might impact on the inflammatory processes that are associated with progression of Barrett's oesophagus to cancer, and this may be evident in the gene expression profile and microRNA expression pattern in Barrett's oesophagus mucosa. We hypothesised that two miRNAs with inflammatory and oncogenic roles, miR-101 and miR-196a, are differentially expressed in Barrett's oesophagus epithelium in patients with reflux treated medically vs. surgically.

FINDINGS

Mucosal tissue was obtained at endoscopy from patients with Barrett's oesophagus whose reflux was controlled by proton pump inhibitor (PPI) therapy (n = 20) or by fundoplication (n = 19). RNA was extracted and the expression of miR-101 and miR-196a was measured using real-time reverse transcription - polymerase chain reaction. There were no significant differences in miR-101 and miR-196a expression in Barrett's oesophagus epithelium in patients treated by PPI vs. fundoplication (p = 0.768 and 0.211 respectively). Secondary analysis showed a correlation between miR-196a expression and Barrett's oesophagus segment length (p = 0.014).

CONCLUSION

The method of reflux treatment did not influence the expression of miR-101 and miR-196a in Barrett's oesophagus. This data does not provide support to the hypothesis that surgical treatment of reflux better prevents cancer development in Barrett's oesophagus. The association between miR-196a expression and Barrett's oesophagus length is consistent with a tumour promoting role for miR-196a in Barrett's oesophagus.

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.

Immunohistochemical analysis of selected molecular markers in esophagus precancerous, adenocarcinoma and squamous cell carcinoma in Iranian subjects

BACKGROUND

The molecular and cellular mechanisms linking chronic inflammation and gastrointestinal malignancy are not known with certainty.

AIM

To investigate changes in potential causative factors during progression of esophagus cancer in a population living in high-risk area in Iran.

SUBJECTS

Formalin-fixed, paraffin-embedded esophageal specimens (n=87) from patients with gastroesophageal reflux disease (GERD), Barrett's metaplasia, adenocarcinoma (ADC) and squamous cells carcinoma (SCC) were collected based on their pathological diagnosis.

METHODS

Immunohistochemical (IHC) technique was used to study tissue accumulation of P53, P21, cyclooxygenase-2 (COX-2), glutathione S-transferase-P (GST-Pi) and nitrotyrosine (NT) in patients and controls.

RESULTS

P53 expression was not detected in esophageal tissues from normal and GERD samples, whereas it was found positive in Barrett's, ADC, and SCC samples. P21 positive sample was relatively higher in ADC patients as compared to that in SCC (ADC: 52.6%; SCC: 25%). GST-Pi expression was equally accumulated in all the samples. NT was predominantly expressed in ADC (72.7%). COX-2 expression was significantly higher in Barrett's (60.0%) and ADC (66.6%) as compared to that in GERD, SCC and normal. These data were further confirmed by detecting the scores of immunostainings in all the positive samples.

CONCLUSION

The pathological changes in ADC and SCC samples which were associated with increasing frequency of NT and COX-2 provides further evidence for involvement of these inflammatory factors in progression of esophagus cancer.

Loss of heterozygosity at thymidylate synthase locus in Barrett's metaplasia, dysplasia, and carcinoma sequences

Background

Thymidylate synthase (TS) is known to have a unique 28 bp tandemly repeated sequence in the promoter region, and the majorities of subjects have a heterozygous double repeat/triple repeat genotype in their non-cancerous tissue. Loss of heterozygosity (LOH) at the TS locus is known to occur in cancer patients, but there is no evidence that it is present in precancerous tissue. The aim of this study was to analyze the frequency and timing of LOH at the TS locus in Barrett-associated adenocarcinoma (BA) and its precursory lesions, such as intestinal metaplasia (IM) and dysplasia.

Methods

One hundred twenty-three samples (including 37 with gastroesophageal reflux disease (GERD), 29 with IM, 13 with dysplasia, and 44 with BA) were obtained from 100 patients. Biopsies were obtained from the lower esophageal mucosa/IM/dysplasia/BA, when available. Normal squamous tissue from the upper esophagus was taken as a control. All tissues were analyzed for the TS genotype and TS mRNA expression using the real-time reverse-transcription polymerase chain reaction (RT-PCR) method after laser-capture microdissection.

Results

Among the patients with informative heterozygous genotype in their control samples, no sample with LOH at the TS locus was observed in the lower esophageal mucosa in GERD patients (0/22 samples). However, 6 out of 21 samples (28.6%) had LOH in IM, 2 of 7 (28.6%) in dysplasia, and 10 of 25 (40.0%) in BA. No significant difference in TS mRNA expression levels was observed between TS genotypes.

Conclusion

Our results demonstrate that LOH is a relatively frequent and early event in the IM-BA sequence.

Intramucosal distribution of WNT signaling components in human esophagus

BACKGROUND

The molecular mechanisms governing the biology and pathobiology of esophageal squamous mucosa in health and disease are not completely understood. Earlier genome-wide expression study of normal-looking esophageal squamous mucosa has shown differential expression of the Wingless-type MMTV integration site family (Wnt) modulators Dickkopf (Dkk) homologs among healthy individuals and patients with reflux esophagitis and Barrett metaplasia suggesting that the Wnt pathway may be involved in esophageal mucosal biology.

STUDY

Seven full-thickness human donor esophagi were cryosectioned for immunohistochemical analysis, and lamina propria (LP), basal (BC), intermediate (IC), and superficial (SC) cells were also dissected by laser-capture microdissection for real-time polymerase chain reaction.

RESULTS

Wnt1, 2b, and 3a were expressed primarily in BC, Wnt3, and 5b in LP, and Wnt5a in IC. Frizzled 1, low-density lipoprotein receptor-related protein 6, secreted frizzled-related protein 1, T-cell-specific transcription factor 3, and dishevelled 3 were expressed highest in LP decreasing precipitously medially toward SC. Dkk1 predominantly expressed in SC was more than 100-folds greater than other layers (P<0.001). Dkk4 was expressed primarily in SC but Dkk3 was opposite with greatest expression in LP. Immunohistochemical analysis showed Wnt1 and 3a in BC, Wnt5a in IC and SC, Dkk1 predominantly in SC, Dkk4 in SC and IC, and Dkk3 and SFRP1 in LP and BC

7beta-Hydroxy-epiandrosterone-mediated regulation of the prostaglandin synthesis pathway in human peripheral blood monocytes

7alpha-Hydroxy-DHEA, 7beta-hydroxy-DHEA and 7beta-hydroxy-EpiA are native metabolites of dehydroepiandrosterone (DHEA) and epiandrosterone (EpiA). Since numerous steroids are reported to interfere with inflammatory and immune processes, our objective was to test the effects of these hydroxysteroids on prostaglandin (PG) production and related enzyme gene expression. Human peripheral blood monocytes were cultured for 4 and 24 h in the presence of each of the steroids (1-100 nM), with and without addition of TNF-alpha (10 ng/mL). Levels of PGE(2), PGD(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) were measured in the incubation medium, and cell content of cyclooxygenase (COX-2), and PGE and PGD synthases (m-PGES1, H-PGDS, L-PGDS), and peroxisome proliferator activated receptor (PPAR-gamma) was assessed by quantitative RT-PCR and Western blots. Addition of TNF-alpha resulted in elevated PG production and increased COX-2 and m-PGES1 levels. Among the three steroids tested, only 7beta-hydroxy-EpiA decreased COX-2, m-PGES1 and PPAR-gamma expression while markedly decreasing PGE(2) and increasing 15d-PGJ(2) production. These results suggest that 7beta-hydroxy-EpiA is a native trigger of cellular protection through simultaneous activation of 15d-PGJ(2) and depression of PGE(2) synthesis, and that these effects may be mediated by activation of a putative receptor, specific for 7beta-hydroxy-EpiA.

Expression of prostaglandin E synthase in Barrett's cancer

Expression of prostaglandin E synthase (PGES) - an enzyme of the prostaglandin biosynthetic pathway with suspected impact on carcinogenesis--was studied in Barrett's cancer to determine its pathogenetic role and prognostic impact in this entity. Expression analysis of PGES was performed on mRNA level (quantitative reverse transcription polymerase chain rection [RT-PCR]) in a large surgical series of 123 primary resected adenocarcinomas of the distal esophagus (Barrett's cancer). Gene expression results were correlated with clinical parameters, overall survival and expression levels of previously analyzed target genes of the cyclooxygenase (COX) pathway (COX-1, COX-2) and mediators of angiogenesis (vascular endothelial growth factor [VEGF]-A) and lymphangiogenesis [VEGF-C]. Expression of PGES was demonstrated in all 123 tumors (100%) on mRNA level (quantitative RT-PCR). Relative mRNA expression levels were highly variable between different cases. Gene expression showed a strong positive correlation with both COX isoforms (COX-1: r = 0.502, P < 0.001; COX-2: r = 0.679, P < 0.001), with the angiogenetic VEGF-A (r = 0.583, P < 0.001) and with the lymphangiogentic VEGF-C (r = 0.465, P < 0.001). PGES mRNA expression showed no significant correlation with clinicopathologic parameters (i.e. pTNM categories, UICC stage, survival). Variable overexpression of PGES seems to be potentially implicated in Barrett's carcinogenesis. Gene expression of PGES is strongly correlated with other mediators of the prostaglandin biosynthetic pathway, that is both COX isoforms (COX-1 and COX-2). However, no impact on patients' outcome in relation to PGES expression was found.

Large intra- and inter-individual variability of genes expression levels limits potential predictive value of molecular diagnosis of dysplasia in Barrett's esophagus

Barrett's esophagus represents a well-defined precursor lesion of esophageal adenocarcinoma, although only a subset of patients with these lesions advances to invasive cancer. Currently, reliable markers predicting neoplastic progression in Barrett's esophagus are lacking. The only clinically useful risk factor is the presence of dysplasia in Barrett's epithelium, but its use as a prognostic marker of disease progression has several significant limitations. Thus, identification of biomarkers of potential prognostic value in dysplasia development in Barrett's esophagus is highly important. The aim of the study was to determine if expression levels of selected genes support histologic diagnosis of dysplastic changes in Barrett's esophagus. Upon rigorous sampling and independent histopathologic examination of endoscopic specimens by two experienced gastrointestinal pathologists, 56 patients with Barrett's esophagus (16 negative for dysplasia, 15 with indefinite, 21 with low-grade, and 4 with high-grade dysplasia) were selected for molecular analysis. The relative mRNA levels of ten selected genes were estimated by quantitative real-time polymerase chain reaction (PCR) analysis. Although expression of nine genes showed trends toward down- or upregulation during progression from Barrett's esophagus without dysplasia to Barrett's esophagus with high-grade dysplasia, only a decrease in S100A2 mRNA levels was statistically significant (P<0.05). However, there was considerable variation among individuals and significant overlapping of ranges. Furthermore, detailed, comparative analysis of serial samples from Barrett's mucosa and normal squamous epithelium shows large intra-individual variability of gene expression levels. In conclusion, expression of this set of ten genes cannot be used as a molecular marker aiding histological examination of dysplasia in Barrett's esophagus. Significant inter- and intra-patient variations of gene expression levels makes use of the selected genes impractical.

COX-2 mRNA expression is significantly increased in acid-exposed compared to nonexposed squamous epithelium in gastroesophageal reflux disease

BACKGROUND

Little is known about the role of cyclooxygenase (COX)-2 in gastroesophageal reflux disease (GERD) and the development of Barrett's metaplasia. The objectives of this study were to further analyze COX-2 mRNA expression in patients with GERD compared to Barrett's esophagus (BE) and Barrett's cancer (BC).

METHODS

Tissue samples from 110 patients with GERD (n = 43), BE (n = 20), and BC (n = 47) were obtained in routine upper GI endoscopy. Expression levels of COX-2 were measured by quantitative real-time reverse trancriptase polymerase chain reaction (RT-PCR). Also, 24-h pH monitoring was performed in all patients of the GERD study group and the DeMeester composite score was used to match COX-2 mRNA expression with the severity of acid exposure in the lower esophagus.

RESULTS

COX-2 mRNA is progressively upregulated within the metaplasia-dysplasia-adenocarcinoma (MDA) sequence (p = 0.001). COX-2 levels of the squamous epithelium in the distal esophagus from patients with GERD and a pathologic mean DeMeester score (>14.72) were significantly higher than in patients with normal DeMeester scores (p = 0.01).

CONCLUSION

In summary our findings suggest that alterations in COX-2 mRNA expression occur independently of endoscopic or histologic signs of GERD in the acid-exposed squamous epithelium of the distal esophagus. However, this early COX-2 increase in GERD is further upregulated within the MDA sequence for yet unknown reasons.

Towards the molecular characterization of disease: comparison of molecular and histological analysis of esophageal epithelia

Reliable quantification of gene expression offers the possibility of more accurate and prognostically relevant characterization of tissues than potentially subjective interpretations of histopathologists. We measured the expression of 18 selected genes and compared them to histological features in a spectrum of esophageal disease to evaluate the feasibility of molecular characterization of normal and pathologic esophageal epithelia. Esophageal tissue biopsies from 82 patients with foregut symptoms were laser capture microdissected, and the expression levels of 18 selected genes were measured by quantitative real-time polymerase chain reaction. Linear discriminant analysis, which uses combinations of genes to distinguish between histological groups, was performed to compare gene expression and the following five histological groups: (1) normal squamous epithelium (n = 35), (2) reflux esophagitis (n = 13), (3) non-dysplastic Barrett's (n = 33), (4) dysplastic Barrett's (n = 16), (5) adenocarcinoma (n = 31). A panel of seven genes had 90-94% predictive power to distinguish non-dysplastic and dysplastic Barrett's esophagus. Clustering analysis revealed structure in gene expression values even in the absence of histology. Expression levels in 17 genes differed significantly across histological groups. Classification based on gene expression agreed with histopathological assessment in the following percentage of cases: normal squamous epithelium = 53%, reflux esophagitis = 31%, non-dysplastic Barrett's = 76%, dysplastic Barrett's = 40%, and adenocarcinoma = 59%. Interestingly, predictive power improved markedly when inflammatory and dysplastic tissues were removed (77-94%). Gene expression classification agrees well with histopathological examination. When differences occur, it is unclear whether this effect is due to intraobserver variability in pathological diagnosis or to a genuine difference between gene expression and histopathology.

Cyclooxygenase-2 inhibitors demonstrate anti-proliferative effects in oesophageal cancer cells by prostaglandin E(2)-independent mechanisms

The incidence of oesophageal cancer (OC) has risen in recent decades, with survival rates remaining poor despite surgical treatment and adjuvant chemotherapy. Studies have reported cyclooxygenase-2 (COX-2) overexpression in OC and current evidence suggests NSAIDs have major potential for chemoprevention through COX-2 inhibition. However, several reports have questioned the specificity of these inhibitors, suggesting they may act through mechanisms other than COX-2. We evaluated the effects of specific COX-2 inhibitors, NS-398 and nimesulide, on cell lines of both histological types of OC. COX-2 protein expression varied in the cell lines and corresponded with levels of prostaglandin E(2) (PGE(2)) production. Following treatment with low concentrations of NS-398 (0.1 microM), PGE(2) production was reduced dramatically, indicating inhibition of COX-2 activity. Examination of cellular morphology, caspase-3 activity and mitochondrial membrane integrity found no major induction of apoptotic cell death at concentrations below 100 microM. Tumour cell proliferation was significantly reduced at high concentrations (50-100 microM) of both inhibitors over 6 days. Cellular responses were more evident in NS-398-treated adenocarcinoma cells. However, concentrations required to inhibit proliferation were up to 1000-fold higher than those needed to inhibit enzyme activity. Addition of exogenous PGE(2) to NS-398-treated adenocarcinoma cells failed to reverse the inhibitory effects, indicating PG and COX-2 independence. It remains possible that in vivo COX-2 is the primary target, as enzyme inhibition can be achieved at low concentrations, however, inhibition of proliferation is not the primary mechanism of their anti-tumour activity.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Systematic review: Cyclo-oxygenase-2 in human oesophageal adenocarcinogenesis

BACKGROUND

Published in vitro and animal in vivo studies have demonstrated that cyclo-oxygenase-2 plays an important role during oesophageal adenocarcinogenesis. However, the extent to which these studies are directly relevant to events in the human lower oesophagus is questionable.

AIM

To perform a systematic review of all available human studies that have evaluated levels of cyclo-oxygenase-2 expression during the progression from Barrett's metaplasia to oesophageal adenocarcinoma.

METHODS

A literature search was performed to identify all studies which qualitatively or quantitatively assessed cyclo-oxygenase-2 protein or gene expression in either Barrett's, dysplastic or adenocarcinoma tissue in humans.

RESULTS

A total of 27 studies met the inclusion criteria. There was general agreement that cyclo-oxygenase-2 was either absent or very weakly expressed in normal oesophageal squamous mucosa, but considerable disagreement regarding the presence of cyclo-oxygenase-2 in Barrett's and low-grade dysplasia. All studies agreed that high-grade dysplasia and adenocarcinoma expressed cyclo-oxygenase-2 to some extent although levels varied considerably between tissue samples.

CONCLUSIONS

There is conflicting evidence in the literature for cyclo-oxygenase-2 playing an important role in early oesophageal adenocarcinogenesis. Other non-cyclo-oxygenase-2 targets may account for the epidemiological data supporting the use of non-steroidal anti-inflammatory drugs in the chemoprevention of oesophageal adenocarcinoma.

Increasing cyclooxygenase-2 (cox-2) gene expression in the progression of Barrett's esophagus to adenocarcinoma correlates with that of Bcl-2

Previous studies from our laboratory and others have suggested that increased expression of cox-2 is important in the genesis of esophageal adenocarcinoma. In vitro studies suggest that cox-2 regulates expression of the anti-apoptotic protein bcl-2, thus possibly accounting for reduced apoptosis in carcinogenesis. The aim of this study was to investigate the relationship of these 2 genes in the development of Barrett's-associated adenocarcinoma. Histologic sections from endoscopic biopsies or esophagectomy specimens were classified as non-dysplastic Barrett's (n = 30), intraepithelial neoplasia (n = 12) and adenocarcinoma (n = 48). The desired tissue was isolated by laser capture microdissection and expression levels of cox-2 and bcl-2 were measured by quantitative real-time PCR (Taqman). Gene expression levels were compared to samples of the distal esophageal squamous epithelium (n = 55) and reflux-esophagitis (n = 25), without Barrett's or cancer. Expression of both bcl-2 and cox-2 were increased in non-dysplastic Barrett's (p = 0.0077, p = 0.0037), intraepithelial neoplasia (p = 0.0053, p = 0.0220) and adenocarcinoma (p < 0.0001, p < 0.0001) compared to squamous epithelium or reflux-esophagitis. Furthermore, there is a significant correlation between these two genes, especially in carcinoma (p < 0.0001).

Nonsteroidal anti-inflammatory drugs and the esophageal inflammation-metaplasia-adenocarcinoma sequence

Observational studies suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of esophageal adenocarcinoma, but it is not known at what stage they may act in the esophageal inflammation-metaplasia-adenocarcinoma sequence. In an all-Ireland case-control study, we investigated the relationship between the use of NSAIDs and risk of reflux esophagitis, Barrett's esophagus, and esophageal adenocarcinoma. Patients with esophageal adenocarcinoma, long-segment Barrett's esophagus and population controls were recruited from throughout Ireland. Esophagitis patients were recruited from Northern Ireland only. Data were collected on known and potential risk factors for esophageal adenocarcinoma and on the use of NSAIDs, including aspirin, at least 1 year before interview. Associations between use of NSAIDs and the stages of the esophageal inflammation-metaplasia-adenocarcinoma sequence were estimated by multiple logistic regression. In total, 230 reflux esophagitis, 224 Barrett's esophagus, and 227 esophageal adenocarcinoma and 260 population controls were recruited. Use of aspirin and NSAIDs was associated with a reduced risk of Barrett's esophagus [odds ratio [OR; 95% confidence interval (95% CI)], 0.53 (0.31-0.90) and 0.40 (0.19-0.81), respectively] and esophageal adenocarcinoma [OR (95% CI), 0.57 (0.36-0.93) and 0.58 (0.31-1.08), respectively]. Barrett's esophagus and esophageal adenocarcinoma patients were less likely than controls to have used NSAIDs. Selection or recall bias may explain these results and the results of previous observational studies indicating a protective effect of NSAIDs against esophageal adenocarcinoma. If NSAIDs have a true protective effect on the esophageal inflammation-metaplasia-adenocarcinoma sequence, they may act early in the sequence.

Dickkopf homologs in squamous mucosa of esophagitis patients are overexpressed compared with Barrett's patients and healthy controls

OBJECTIVES

Esophageal mucosal response to acid exposure varies from minimal changes to erosions/ulcerations and Barrett's metaplasia. While differences in acid contact time have been suggested, the reason for these different responses is not completely understood. The aim of this study was to identify and compare gene expression differences between normal distal and proximal squamous esophageal mucosa (SM) in esophagitis patients with that of healthy controls and Barrett's patients.

METHODS

Gene microarray was performed on laser-capture microdissected epithelial cells isolated from biopsy specimens followed by real-time PCR. The effect of acidic pH (pH 4.5) on Dickkopf Homolog 1 (Dkk-1) expression in the human esophageal epithelial cell line (Het-1A) was determined.

RESULTS

Gene microarray analysis demonstrated that the upregulation of five genes in the distal compared with the proximal SM in esophagitis patients was greater than the healthy controls and Barrett's patients. Overexpression of Dkk-1 and Dkk-4 was further confirmed by real-time PCR. Dkk-1 and Dkk-4 mRNA levels in the distal SM of the esophagitis patients were 7.0- and 3.1-fold higher, respectively, than in the distal SM of the Barrett's patients and 4.1- and 4.1-fold higher than in healthy controls, respectively. Dkk-1 protein expression in the distal esophagitis SM was also higher than the Barrett's patients and healthy controls. Acidic pH exposure of Het-1A cells resulted in Dkk-1 upregulation at the level of both mRNA and protein.

CONCLUSIONS

Dkk-1 and Dkk-4 may potentially be involved in the development of different injuries in response to pathological gastroesophageal acid reflux.

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.

Low pH induces co-ordinate regulation of gene expression in oesophageal cells

The development of gastro-oesophageal reflux disease (GORD) is known to be a causative risk factor in the evolution of adenocarcinoma of the oesophagus. The major component of this reflux is gastric acid. However, the impact of low pH on gene expression has not been extensively studied in oesophageal cells. This study utilizes a transcriptomic and bioinformatic approach to assess regulation of gene expression in response to low pH. In more detail, oesophageal adenocarcinoma cell lines were exposed to a range of pH environments. Affymetrix microarrays were used for gene-expression analysis and results were validated using cycle limitation and real-time RT-PCR analysis, as well as northern and western blotting. Comparative promoter transcription factor binding site (TFBS) analysis (MatInspector) of hierarchically clustered gene-expression data was employed to identify the elements which may co-ordinately regulate individual gene clusters. Initial experiments demonstrated maximal induction of EGR1 gene expression at pH 6.5. Subsequent array experimentation revealed significant induction of gene expression from such functional categories as DNA damage response (EGR1-4, ATF3) and cell-cycle control (GADD34, GADD45, p57). Changes in expression of EGR1, EGR3, ATF3, MKP-1, FOSB, CTGF and CYR61 were verified in separate experiments and in a variety of oesophageal cell lines. TFBS analysis of promoters identified transcription factors that may co-ordinately regulate gene-expression clusters, Cluster 1: Oct-1, AP4R; Cluster 2: NF-kB, EGRF; Cluster 3: IKRS, AP-1F. Low pH has the ability to induce genes and pathways which can provide an environment suitable for the progression of malignancy. Further functional analysis of the genes and clusters identified in this low pH study is likely to lead to new insights into the pathogenesis and therapeutics of GORD and oesophageal cancer.