Expression of the intestinal marker Cdx2 in the columnar-lined esophagus with and without intestinal (Barrett's) metaplasia

Molecular Biology and Clinical Management of Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) is a highly lethal malignancy. Due to its rising incidence, EAC has become a severe health challenge in Western countries. Current treatment strategies are mainly chosen based on disease stage and clinical features, whereas the biological background is hardly considered. In this study, we performed a comprehensive review of existing studies and discussed how etiology, genetics and epigenetic characteristics, together with the tumor microenvironment, contribute to the malignant behavior and dismal prognosis of EAC. During the development of EAC, several intestinal-type proteins and signaling cascades are induced. The anti-inflammatory and immunosuppressive microenvironment is associated with poor survival. The accumulation of somatic mutations at the early phase and chromosomal structural rearrangements at relatively later time points contribute to the dynamic and heterogeneous genetic landscape of EAC. EAC is also characterized by frequent DNA methylation and dysregulation of microRNAs. We summarize the findings of dysregulations of specific cytokines, chemokines and immune cells in the tumor microenvironment and conclude that DNA methylation and microRNAs vary with each different phase of BE, LGD, HGD, early EAC and invasive EAC. Furthermore, we discuss the suitability of the currently employed therapies in the clinic and possible new therapies in the future. The development of targeted and immune therapies has been hampered by the heterogeneous genetic characteristics of EAC. In view of this, the up-to-date knowledge revealed by this work is absolutely important for future EAC studies and the discovery of new therapeutics.

Ectopic expression of HNF4α in Het1A cells induces an invasive phenotype

Barrett's oesophagus (BO) is a pathological condition in which the squamous epithelium of the distal oesophagus is replaced by an intestinal-like columnar epithelium originating from the gastric cardia. Several somatic mutations contribute to the intestinal-like metaplasia. Once these have occurred in a single cell, it will be unable to expand further unless the altered cell can colonise the surrounding squamous epithelium of the oesophagus. The mechanisms by which this happens are still unknown. Here we have established an in vitro system for examining the competitive behaviour of two epithelia. We find that when an oesophageal epithelium model (Het1A cells) is confronted by an intestinal epithelium model (Caco-2 cells), the intestinal cells expand into the oesophageal domain. In this case the boundary involves overgrowth by the Caco-2 cells and the formation of isolated colonies. Two key transcription factors, normally involved in intestinal development, HNF4α and CDX2, are both expressed in BO. We examined the competitive ability of Het1A cells stably expressing HNF4α or CDX2 and placed in confrontation with unmodified Het1A cells. The key result is that stable expression of HNF4α, but not CDX2, increased the ability of the cells to migrate and push into the unmodified Het1A domain. In this situation the boundary between the cell types is a sharp one, as is normally seen in BO. The experiments were conducted using a variety of extracellular substrates, which all tended to increase the cell migration compared to uncoated plastic. These data provide evidence that HNF4α expression could have a potential role in the competitive spread of BO into the oesophagus as HNF4α increases the ability of cells to invade into the adjacent stratified squamous epithelium, thus enabling a single mutant cell eventually to generate a macroscopic patch of metaplasia.

Lack of Association between Epidermal Growth Factor or Its Receptor and Reflux Esophagitis, Barrett’s Esophagus, and Esophageal Adenocarcinoma: A Case-Control Study

The epidermal growth factor (EGF) and its receptor (EGFR) gene-gene interactions were shown to increase the susceptibility to esophageal cancer. However, the role of the EGF/EGFR pathway in the development of gastroesophageal reflux disease (GERD) and its complications (reflux esophagitis (RE), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC)) remains unclear. This association study is aimed at investigating functional EGF and EGFR gene polymorphisms, their mRNA expression in esophageal tissues, and EGF plasma levels in relation to RE, BE, and EAC development in the Central European population. 301 patients with RE/BE/EAC (cases) as well as 98 patients with nonerosive reflux disease (NERD) and 8 healthy individuals (controls) were genotyped for +61 A>G EGF (rs4444903) and +142285 G>A EGFR (rs2227983) polymorphisms using the TaqMan quantitative polymerase chain reaction (qPCR). In random subgroups, the EGF and EGFR mRNA expressions were analyzed by reverse transcription qPCR in esophageal tissue with and without endoscopically visible pathological changes; and the EGF plasma levels were determined by enzyme-linked immunosorbent assay. None of the genotyped SNPs nor EGF-EGFR genotype interactions were associated with RE, BE, or EAC development (p > 0.05). Moreover, mRNA expression of neither EGF nor EGFR differed between samples of the esophageal tissue with and without endoscopically visible pathology (p > 0.05) nor between samples from patients with different diagnoses, i.e., RE, BE, or EAC (p > 0.05). Nevertheless, the lower EGF mRNA expression in carriers of combined genotypes AA +61 EGF (rs4444903) and GG +142285 EGFR (rs2227983; p < 0.05) suggests a possible direct/indirect effect of EGF-EGFR gene interactions on EGF gene expression. In conclusion, EGF and EGFR gene variants and their mRNA/protein expression were not associated with RE, BE or EAC development in the Central European population.

Kyoto international consensus report on anatomy, pathophysiology and clinical significance of the gastro-oesophageal junction

OBJECTIVE

An international meeting was organised to develop consensus on (1) the landmarks to define the gastro-oesophageal junction (GOJ), (2) the occurrence and pathophysiological significance of the cardiac gland, (3) the definition of the gastro-oesophageal junctional zone (GOJZ) and (4) the causes of inflammation, metaplasia and neoplasia occurring in the GOJZ.

DESIGN

Clinical questions relevant to the afore-mentioned major issues were drafted for which expert panels formulated relevant statements and textural explanations.A Delphi method using an anonymous system was employed to develop the consensus, the level of which was predefined as ≥80% of agreement. Two rounds of voting and amendments were completed before the meeting at which clinical questions and consensus were finalised.

RESULTS

Twenty eight clinical questions and statements were finalised after extensive amendments. Critical consensus was achieved: (1) definition for the GOJ, (2) definition of the GOJZ spanning 1 cm proximal and distal to the GOJ as defined by the end of palisade vessels was accepted based on the anatomical distribution of cardiac type gland, (3) chemical and bacterial (Helicobacter pylori) factors as the primary causes of inflammation, metaplasia and neoplasia occurring in the GOJZ, (4) a new definition of Barrett's oesophagus (BO).

CONCLUSIONS

This international consensus on the new definitions of BO, GOJ and the GOJZ will be instrumental in future studies aiming to resolve many issues on this important anatomic area and hopefully will lead to better classification and management of the diseases surrounding the GOJ.

Transcription factor-mediated intestinal metaplasia and the role of a shadow enhancer

Here, Singh et al. show extensive but selective recruitment of intestinal enhancers by CDX2 in gastric cells and that HNF4A-mediated ectopic CDX2 expression in the stomach occurs through a conserved shadow cis-element. These findings identify mechanisms for TF-driven intestinal metaplasia and a likely pathogenic TF hierarchy.

Barrett's esophagus (BE) and gastric intestinal metaplasia are related premalignant conditions in which areas of human stomach epithelium express mixed gastric and intestinal features. Intestinal transcription factors (TFs) are expressed in both conditions, with unclear causal roles and cis-regulatory mechanisms. Ectopic CDX2 reprogrammed isogenic mouse stomach organoid lines to a hybrid stomach–intestinal state transcriptionally similar to clinical metaplasia; squamous esophageal organoids resisted this CDX2-mediated effect. Reprogramming was associated with induced activity at thousands of previously inaccessible intestine-restricted enhancers, where CDX2 occupied DNA directly. HNF4A, a TF recently implicated in BE pathogenesis, induced weaker intestinalization by binding a novel shadow Cdx2 enhancer and hence activating Cdx2 expression. CRISPR/Cas9-mediated germline deletion of that cis-element demonstrated its requirement in Cdx2 induction and in the resulting activation of intestinal genes in stomach cells. dCas9-conjugated KRAB repression mapped this activity to the shadow enhancer's HNF4A binding site. Altogether, we show extensive but selective recruitment of intestinal enhancers by CDX2 in gastric cells and that HNF4A-mediated ectopic CDX2 expression in the stomach occurs through a conserved shadow cis-element. These findings identify mechanisms for TF-driven intestinal metaplasia and a likely pathogenic TF hierarchy.

P63 Deficiency and CDX2 Overexpression Lead to Barrett's-Like Metaplasia in Mouse Esophageal Epithelium

BACKGROUND

The cellular origin and molecular mechanisms of Barrett's esophagus (BE) are still controversial. Trans-differentiation is a mechanism characterized by activation of the intestinal differentiation program and inactivation of the squamous differentiation program.

AIMS

Renal capsule grafting (RCG) was used to elucidate whether CDX2 overexpression on the basis of P63 deficiency in the esophageal epithelium may generate intestinal metaplasia.

METHODS

P63^-/-;Villin-Cdx2 embryos were generated by crossing P63^+/- mice with Villin-Cdx2 mice. E18.5 esophagus was xenografted in a renal capsule grafting (RCG) model. At 1, 2, or 4 weeks after RCG, the mouse esophagus was immunostained for a proliferation marker (BrdU), squamous transcription factors (SOX2, PAX9), squamous differentiation markers (CK5, CK4, and CK1), intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6), intestinal columnar epithelial cell markers (A33, CK8), goblet cell marker (MUC2, TFF3), Paneth cell markers (LYZ and SOX9), enteroendocrine cell marker (CHA), and Tuft cell marker (DCAMKL1).

RESULTS

The P63^-/-;Villin-Cdx2 RCG esophagus was lined with proliferating PAS/AB+ cuboidal cells and formed an intestinal crypt-like structure. The goblet cell markers (TFF3 and MUC2) and intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6) were expressed although no typical morphology of goblet cells was observed. Other intestinal cell markers including enteroendocrine cell marker (CHA), Paneth cell markers (LYZ and Sox9), and intestinal secretory cell marker (UEA/WGA) were also expressed in the P63^-/-;Villin-Cdx2 RCG esophagus. Squamous cell markers (PAX9 and SOX2) were also expressed, suggesting a transitional phenotype.

CONCLUSION

CDX2 overexpression on the basis of P63 deficiency in esophageal epithelial cells induces Barrett's-like metaplasia in vivo. Additional factors may be needed to drive this transitional phenotype into full-blown BE.

Gastro-esophageal reflux disease and Barrett's esophagus: an overview with an histologic diagnostic approach

The first part of this overview on non-neoplastic esophagus is focused on gastro-esophageal reflux disease (GERD) and Barrett’s esophagus. In the last 20 years much has changed in histological approach to biopsies of patients with gastro-esophageal reflux disease. In particular, elementary histologic lesions have been well defined and modality of evaluation and grade are detailed, their sensitivity and specificity has been evaluated and their use has been validated by several authors. Also if there is not a clinical indication to perform biopsies in patient with GERD, the diagnosis of microscopic esophagitis, when biopsies are provided, can be performed by following simple rules for evaluation which allow pathologists to make the diagnosis with confidence. On the other hand, biopsies are required for the diagnosis of Barrett’s esophagus. This diagnosis is the synthesis of endoscopic picture (which has to be provided with the proper description on extent and with adequate biopsies number) and histologic pattern. The current guidelines and expert opinions for the correct management of these diagnosis are detailed.

Barrett's Esophagus and Intestinal Metaplasia

Intestinal metaplasia refers to the replacement of the differentiated and mature normal mucosal epithelium outside the intestinal tract by the intestinal epithelium. This paper briefly describes the etiology and clinical significance of intestinal metaplasia in Barrett’s esophagus. This article summarizes the impact of intestinal metaplasia on the diagnosis, monitoring, and treatment of Barrett’s esophagus according to different guidelines. We also briefly explore the basis for the endoscopic diagnosis of intestinal metaplasia in Barrett’s esophagus. The identification techniques of goblet cells in Barrett’s esophagus are also elucidated by some scholars. Additionally, we further elaborate on the current treatment methods related to Barrett’s esophagus.

CDX-2 Expression in Esophageal Biopsies Without Goblet Cell Intestinal Metaplasia May Be Predictive of Barrett's Esophagus

BACKGROUND

CDX-2 is a nuclear homeobox transcription factor not normally expressed in esophageal and gastric epithelia, reported to highlight intestinal metaplasia (IM) in the esophagus. Pathological absence of goblet cells at initial screening via hematoxylin and eosin (HE) and alcian blue (AB) staining results in patient exclusion from surveillance programs.

AIMS

This study aimed to determine whether non-goblet cell IM, as defined by CDX-2 positivity, can be considered to be a precursor to Barrett's esophagus (BE).

METHODS

This study received IRB approval (17,284). Patients with gastroesophageal reflux disease (n = 181) who underwent upper-gastrointestinal endoscopy with biopsies of the distal esophagus to rule out BE using HE/AB staining and CDX-2 immunostaining were followed for 3 years. Initial and follow-up staining results were evaluated for age/sex.

RESULTS

Differences between development of goblet cell IM in CDX-2-negative and CDX-2-positive groups were evaluated. A Kaplan-Meier curve showed that, out of the 134 patients initially positive for CDX-2, 25 (18.7%) had developed goblet cell IM after 2 years and 106 (79.1%) after 3 years. Conversely, of the 47 patients initially negative for CDX-2, 8 (17.9%) developed goblet cell IM after 24 months and only 11 (23.8%) after 40 to 45 months (P = .049; age-adjusted Cox proportional hazard regression model).

CONCLUSION

In cases that are initially AB negative and CDX-2 positive, CDX-2 was demonstrated to have a potential prognostic utility for early detection of progression to BE. CDX-2 expression is significantly predictive for risk of goblet cell IM development 40 to 45 months after initial biopsy.

Cdx2 Animal Models Reveal Developmental Origins of Cancers

The Cdx2 homeobox gene is important in assigning positional identity during the finely orchestrated process of embryogenesis. In adults, regenerative responses to tissues damage can require a replay of these same developmental pathways. Errors in reassigning positional identity during regeneration can cause metaplasias-normal tissue arising in an abnormal location-and this in turn, is a well-recognized cancer risk factor. In animal models, a gain of Cdx2 function can elicit a posterior shift in tissue identity, modeling intestinal-type metaplasias of the esophagus (Barrett's esophagus) and stomach. Conversely, loss of Cdx2 function can elicit an anterior shift in tissue identity, inducing serrated-type lesions expressing gastric markers in the colon. These metaplasias are major risk factors for the later development of esophageal, stomach and colon cancer. Leukemia, another cancer in which Cdx2 is ectopically expressed, may have mechanistic parallels with epithelial cancers in terms of stress-induced reprogramming. This review will address how animal models have refined our understanding of the role of Cdx2 in these common human cancers.

From genetics to signaling pathways: molecular pathogenesis of esophageal adenocarcinoma

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

Barretts's carcinogenesis

Barrett's esophagus is considered a precancerous lesion of esophageal adenocarcinoma (EAC). Long‐segment Barrett's esophagus, which is generally associated with intestinal metaplasia, has a higher rate of carcinogenesis than short‐segment Barrett's esophagus, which is mainly composed of cardiac‐type mucosa. However, a large number of cases reportedly develop EAC from the cardiac‐type mucosa which has the potential to involve intestinal phenotypes. There is no consensus regarding whether the definition of Barrett's epithelium should include intestinal metaplasia. Basic researches using rodent models have provided information regarding the origins of Barrett's epithelium. Nevertheless, it remains unclear whether differentiated gastric columnar epithelium or stratified esophageal squamous epithelium undergo transdifferentiation into the intestinal‐type columnar epithelium, transcommittment into the columnar epithelium, or whether the other pathways exist. Reflux of duodenal fluid including bile acids into the stomach may occur when an individual lies down after eating, which could cause the digestive juices to collect in the fornix of the stomach. N‐nitroso‐bile acids are produced with nitrites that are secreted from the salivary glands, and bile acids can drive expression of pro‐inflammatory cytokines via EGFR or the NF‐κB pathway. These steps may contribute significantly to carcinogenesis.

Barrett oesophagus

Barrett oesophagus (BE), the only known histological precursor of oesophageal adenocarcinoma (EAC), is a condition in which the squamous epithelium of the oesophagus is replaced by columnar epithelium as an adaptive response to gastro-oesophageal reflux. EAC has one of the fastest rising incidences of cancers in Western countries and has a dismal prognosis. BE is usually detected during endoscopic examination, and diagnosis is confirmed by the histological presence of intestinal metaplasia. Advances in genomics and transcriptomics have improved our understanding of the pathogenesis and malignant progression of intestinal metaplasia. As the majority of EAC cases are diagnosed in individuals without a known history of BE, screening for BE could potentially decrease disease-related mortality. Owing to the pre-malignant nature of BE, endoscopic surveillance of patients with BE is imperative for early detection and treatment of dysplasia to prevent further progression to invasive EAC. Developments in endoscopic therapy have resulted in a major shift in the treatment of patients with BE who have dysplasia or early EAC, from surgical resection to endoscopic resection and ablation. In addition to symptom control by optimization of lifestyle and pharmacological therapy with proton pump inhibitors, chemopreventive strategies based on NSAIDs and statins are currently being investigated for BE management.

Are Gastric and Esophageal Metaplasia Relatives? The Case for Barrett's Stemming from SPEM

Chronic injury and inflammation in the esophagus can cause a change in cellular differentiation known as metaplasia. Most commonly, the differentiation changes manifest as Barrett's esophagus (BE), characterized by the normal stratified squamous epithelium converting into a cuboidal-columnar, glandular morphology. BE cells can phenotypically resemble specific normal cell types of the stomach or intestine, or they can have overlapping phenotypes in disorganized admixtures. The stomach can also undergo metaplasia characterized by aberrant gastric or intestinal differentiation patterns. In both organs, it has been argued that metaplasia may represent a recapitulation of the embryonic or juvenile gastrointestinal tract, as cells access a developmental progenitor genetic program that can help repair damaged tissue. Here, we review the normal development of esophagus and stomach, and describe how BE represents an intermixing of cells resembling gastric pseudopyloric (SPEM) and intestinal metaplasia. We discuss a cellular process recently termed "paligenosis" that governs how mature, differentiated cells can revert to a proliferating progenitor state in metaplasia. We discuss the "Cyclical Hit" theory in which paligenosis might be involved in the increased risk of metaplasia for progression to cancer. However, somatic mutations might occur in proliferative phases and then be warehoused upon redifferentiation. Through years of chronic injury and many rounds of paligenosis and dedifferentiation, eventually a cell with a mutation that prevents dedifferentiation may arise and clonally expand fueling stable metaplasia and potentially thereafter acquiring additional mutations and progressing to dysplasia and cancer.

Histology of Barrett's Metaplasia: Do Goblet Cells Matter?

This review has provided a summary of the biology of goblet cell metaplasia in CLE as it pertains to BE. Goblet cells are terminally differentiated nonproliferative cells that have many overlapping histochemical characteristics with mucinous columnar cells and pseudogoblet cells. There is an abundance of evidence that suggests that use of goblet cells as a biomarker of BE, and its progression to malignancy, is problematic. Some of these limitations include the fact that the background non-goblet epithelium in most patients with CLE is biologically intestinalized and contains molecular abnormalities similar to goblet cell CLE, goblet cells fluctuate with time and decrease in number with progression of neoplasia, and pathologists have problems with interpretation, and distinction, of goblet cells from other types of cells in the esophagus. Sampling error results in sensitivity and specificity issues that limit its positive predictive value. Goblet cells are fewest in number in the same population of patients with CLE that are hardest to detect endoscopically (i.e., those with short or ultrashort CLE). Nevertheless, the risk of cancer in patients with short-segment BE, a condition difficult to distinguish from the stomach, is very low regardless of the presence or absence of goblet cells so it is unclear what the role of goblet cells is in these patients as a biomarker. Nevertheless, if the answer to the following question, "Would you as a gastroenterologist recommend surveillance for a patient with clear endoscopic evidence of CLE, particularly if it is ≥ 3 cm in length, but in which goblet cells were not reported to be present by the pathologist," is yes, then the US requirement for goblet cells as part of the criteria for "BE" is superfluous.

Aspirin prevents NF-κB activation and CDX2 expression stimulated by acid and bile salts in oesophageal squamous cells of patients with Barrett's oesophagus

OBJECTIVE

In previous studies using oesophageal squamous cells from patients with Barrett's oesophagus (normal oesophageal squamous (NES)-B cells) and from patients without Barrett's oesophagus (NES-G cells), we showed that acid and bile salts induced caudal-related homeobox transcription factor 2 (CDX2) expression only in NES-B cells. CDX2, a transcription factor required to form intestinal epithelium, is a target of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signalling, which can be inhibited by aspirin. We explored mechanisms underlying differences between NES-B and NES-G cells in CDX2 expression and effects of aspirin on that CDX2 expression.

DESIGN

We exposed NES-B and NES-G cells to acid and bile salts, with and without aspirin, and evaluated effects on IκB-NF-κB-PKAc complex activation, p65 NF-κB subunit function, and CDX2 expression.

RESULTS

In both NES-B and NES-G cells, acid and bile salts activated nicotinamide adenine dinucleotide phosphate oxidase to generate H₂O₂, which activated the IκB-NF-κB-PKAc complex. NES-B cells exhibited higher levels of phosphorylated IκB and p65 and greater NF-κB transcriptional activity than NES-G cells, indicating greater IκB-NF-κB-PKAc complex activation by acid and bile salts in NES-B cells, and p65 siRNA prevented their increased expression of CDX2. Aspirin blocked IκB phosphorylation, p65 nuclear translocation, CDX2 promoter activation and CDX2 expression induced by acid and bile salts in NES-B cells.

CONCLUSIONS

Differences between NES-B and NES-G cells in NF-κB activation by acid and bile salts can account for their differences in CDX2 expression, and their CDX2 expression can be blocked by aspirin. These findings might explain why some patients with GORD develop Barrett's oesophagus while others do not, and why aspirin might protect against development of Barrett's oesophagus.

Reflux esophagitis and its role in the pathogenesis of Barrett's metaplasia

Reflux esophagitis damages the squamous epithelium that normally lines the esophagus, and promotes replacement of the damaged squamous lining by the intestinal metaplasia of Barrett's esophagus, the precursor of esophageal adenocarcinoma. Therefore, to prevent the development of Barrett's metaplasia and esophageal adenocarcinoma, the pathogenesis of reflux esophagitis must be understood. We have reported that reflux esophagitis, both in a rat model and in humans, develops as a cytokine-mediated inflammatory injury (i.e., cytokine sizzle), not as a caustic chemical injury (i.e., acid burn), as traditionally has been assumed. Moreover, reflux induces activation of hypoxia inducible factor (HIF)-2α, which enhances the transcriptional activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) causing increases in pro-inflammatory cytokines and in migration of T lymphocytes, an underlying molecular mechanism for this cytokine-mediated injury. In some individuals, reflux esophagitis heals with Barrett's metaplasia. A number of possibilities exist for the origin of the progenitor cells that give rise to this intestinal metaplasia including those of the esophagus, the proximal stomach, or the bone marrow. However, intestinal cells are not normally found in the esophagus, the stomach, or the bone marrow. Thus, the development of Barrett's intestinal metaplasia must involve some molecular reprogramming of key developmental transcription factors within the progenitor cell, a process termed transcommitment, which may be initiated by the noxious components of the gastric refluxate. This review will highlight recent studies on the pathogenesis of reflux esophagitis and on reflux-related molecular reprogramming of esophageal squamous epithelial cells in the pathogenesis of Barrett's metaplasia.

Dynamics of SOX2 and CDX2 Expression in Barrett's Mucosa

Barrett's esophagus (BE) is the replacement of the normal esophageal squamous epithelium by a columnar lining epithelium. It is a premalignant condition for the development of adenocarcinoma of the esophagus and esophagogastric junction. BE is associated with gastroesophageal reflux which might change the expression profile of key transcription factors involved in the establishment of tissue differentiation, namely, SOX2 (associated with esophageal and gastric differentiation) and CDX2 (associated with intestinal differentiation). Here, we sought to characterize the expression profile of SOX2 and CDX2 in the sequential alterations of the esophageal mucosa towards adenocarcinoma and compare it with the well-established gastric and intestinal mucin profiles (MUC5AC, MUC6, and MUC2). We observed that SOX2 and CDX2 expression correlates with gastric and intestinal differentiation in BE, defined by morphological parameters and mucin expression. We show the presence of a complete intestinal profile in BE, without gastric mucins and without SOX2, and we observed an evolutionary modulation of the metaplastic phenotype by SOX2 and CDX2. We observed that adenocarcinomas harbor more frequently a mixed gastric and intestinal phenotype. In conclusion, our study establishes a role for transcription factors SOX2 and CDX2 in the progression from gastric to gastrointestinal differentiation in Barrett's metaplasia.

Evolution of oesophageal adenocarcinoma from metaplastic columnar epithelium without goblet cells in Barrett's oesophagus

OBJECTIVE

Barrett's oesophagus commonly presents as a patchwork of columnar metaplasia with and without goblet cells in the distal oesophagus. The presence of metaplastic columnar epithelium with goblet cells on oesophageal biopsy is a marker of cancer progression risk, but it is unclear whether clonal expansion and progression in Barrett's oesophagus is exclusive to columnar epithelium with goblet cells.

DESIGN

We developed a novel method to trace the clonal ancestry of an oesophageal adenocarcinoma across an entire Barrett's segment. Clonal expansions in Barrett's mucosa were identified using cytochrome c oxidase enzyme histochemistry. Somatic mutations were identified through mitochondrial DNA sequencing and single gland whole exome sequencing.

RESULTS

By tracing the clonal origin of an oesophageal adenocarcinoma across an entire Barrett's segment through a combination of histopathological spatial mapping and clonal ordering, we find that this cancer developed from a premalignant clonal expansion in non-dysplastic ('cardia-type') columnar metaplasia without goblet cells.

CONCLUSION

Our data demonstrate the premalignant potential of metaplastic columnar epithelium without goblet cells in the context of Barrett's oesophagus.

Transcommitment: Paving the Way to Barrett's Metaplasia

Barrett's esophagus is the condition in which metaplastic columnar epithelium that predisposes to cancer development replaces stratified squamous epithelium in the distal esophagus. Potential sources for the cell or tissue of origin for metaplastic Barrett's epithelium are reviewed including native esophageal differentiated squamous cells, progenitor cells native to the esophagus located within the squamous epithelium or in the submucosal glands or ducts, circulating bone marrow-derived stem cells, and columnar progenitor cells from the squamocolumnar junction or the gastric cardia that proximally shift into the esophagus to fill voids left by damaged squamous epithelium. Wherever its source the original cell must undergo molecular reprogramming (i.e., either transdifferentiation or transcommitment) to give rise to specialized intestinal metaplasia. Transcription factors that specify squamous, columnar, intestinal, and mucus-secreting epithelial differentiation are discussed. An improved understanding of how esophageal columnar metaplasia forms could lead to development of effective treatment or prevention strategies for Barrett's esophagus. It could also more broadly inform upon normal tissue development and differentiation, wound healing, and stem cell biology.

The changing role of the pathologist in the management of Barrett's oesophagus

Pathological specimens from columnar-lined oesophagus (CLO) comprise a considerable proportion of the workload of gastrointestinal pathologists in Western countries. There remain controversies concerning the diagnostic role of pathology. More recently, in the UK at least, the diagnosis has been regarded as primarily an endoscopic endeavour, with pathology being corroborative and only diagnostic when endoscopic features are equivocal or when there are additional features that make the endoscopic diagnosis unclear. There is also recognition that demonstration of intestinalisation or 'goblet cells' is not paramount, and should not be required for the diagnosis. There have been notable changes in the management of CLO neoplasia: pathologists are centrally involved in its management. Pathological assessment of endoscopic mucosal resection (EMR) specimens provides the most useful means of determining the management of early neoplasia and of determining indications for surgery. This represents an extraordinarily rapid change in management, in that, <10 years ago, laborious Seattle-type biopsy protocols were recommended, and high grade dysplasia was an indication for resectional surgery. Now, individual patient management is paramount: multi-professional meetings determine management after biopsy and EMR assessment. One significant change is that major resections are undertaken less often, in Western countries, for CLO neoplasia.

CDX2 protein expression compared to alcian blue staining in the evaluation of esophageal intestinal metaplasia

AIM: To compare the sensitivity and specificity of CDX2 and alcian blue (AB) pH 2.5 staining in identifying esophageal intestinal metaplasia.

METHODS: One hundred and ninty-nine biopsies from 186 patients were retrospectively reviewed and categorized as Barrett’s esophagus (BE) (n = 108); non-Barrett’s esophagus (NBE) (n = 48); columnar blue cells (CB) and esophageal glands (EG) (n = 43). The biopsies were stained with AB and immunostained for CDX2 using a mouse monoclonal antibody from Biogenex (clone CDX2-88) and the Ventana Discovery X automated immunostainer. The positive and negative predictive value of each group was used to determine the predictive power of CDX2 and AB in diagnosing intestinal metaplasia.

RESULTS: All of the 108 BE biopsies (100%) were positive for AB and 102 of them (94.4%) were positive for CDX2. The six BE patients (5.6%) who failed to stain with CDX2 were found to have lost the focus of intestinal metaplasia upon deeper sectioning for immunostaining. Both AB and CDX2 were negative in 43 out of 48 (89.6%) NBE cases. Five NBE patients (10.4%) were falsely positive for AB due to the presence of EG and CB in these biopsies. These cases were all CDX2 negative. In addition, 5 AB negative NBE were found to be CDX2 positive. Based on these results the CDX2 immunostain had similar sensitivity but higher specificity (100% vs about 91%) than AB in detecting intestinal type metaplasia in these samples. Our data shows that CDX2 has a better PPV in detecting intestinal metaplasia as compared to AB (95.6% vs 71.5%, respectively).

CONCLUSION: CDX2 has a better positive predictive value than AB in detecting intestinal metaplasia. CDX2 may be useful when challenged by gastro-esophageal biopsies containing mimikers of BE.

Barrett's oesophagus diagnostic criteria: endoscopy and histology

This review summarizes the endoscopic and histologic features of Barrett's oesophagus(BO) as well as some of the recent advancements and controversies. BO represents metaplastic conversion of normal squamous epithelium of tubular oesophagus to columnar epithelium. The diagnosis of BO requires a combination of endoscopic and histopathologic findings. There is worldwide controversy regarding the exact definition of BO, particularly with regard to the requirement to histologically identify goblet cells in biopsies. The presence and detectability of goblet cells might vary depending on a variety of factors and is subject to sampling error. Therefore, a systematic biopsy sampling with sufficient number of biopsies is currently recommended to limit the likelihood of a false negative result for detection of goblet cells. There are both endoscopic and pathologic challenges in evaluating gastro-oesophageal junction biopsies in patients with irregular Z lines to determine the exact location of the sample (i.e., oesophagus versus stomach). Recently, several novel endoscopic techniques have been developed to improve BO detection. However, none have been validated yet in clinical practice. The surveillance of patients with BO relies on histologic evaluation of dysplasia. However, there are significant pathologic limitations and diagnostic variability in evaluating the presence and grading of BO dysplasia, particularly with regard to the more recently recognized non-intestinal types of dysplasia. All BO dysplasia samples should be reviewed by an expert gastrointestinal pathologist to confirm the diagnosis. Finally, it is important to emphasize that close interaction between gastroenterologists and pathologists is essential to ensure proper evaluation of endoscopic biopsies in order to optimize the surveillance and clinical management of patients with BO.

Current issues in Barrett's esophagus and Barrett's-related dysplasia

Surgical pathologists frequently encounter biopsies in patients with Barrett's esophagus (BE), defined as replacement of the normal stratified squamous epithelium of the distal esophagus by metaplastic columnar epithelium containing goblet cells. Thus, one of the primary roles of the pathologist is to definitively identify goblet cells, best done on routine stained sections. It has recently been questioned as to whether goblet cells should be absolutely necessary to render a diagnosis of BE, given immunohistochemical and flow cytometric similarities between columnar-lined esophagus with and without goblet cells. Once a diagnosis of BE is rendered, the pathologist must state, using a simple classification, whether the biopsy is negative for dysplasia or shows dysplasia (low-grade dysplasia or high-grade dysplasia). However, there are a number of known pitfalls in distinguishing dysplasia from reactive epithelium, and it can be similarly difficult to distinguish low-grade dysplasia from high-grade dysplasia. In addition, there are some cases in which the distinction of high-grade dysplasia from intramucosal adenocarcinoma can be challenging. All of these issues are summarized in this paper.

The Barrett's Gland in Phenotype Space

Barrett's esophagus is characterized by the erosive replacement of esophageal squamous epithelium by a range of metaplastic glandular phenotypes. These glandular phenotypes likely change over time, and their distribution varies along the Barrett's segment. Although much recent work has addressed Barrett's esophagus from the genomic viewpoint-its genotype space-the fact that the phenotype of Barrett's esophagus is nonstatic points to conversion between phenotypes and suggests that Barrett's esophagus also exists in phenotype space. Here we explore this latter concept, investigating the scope of glandular phenotypes in Barrett's esophagus and how they exist in physical and temporal space as well as their evolution and their life history. We conclude that individual Barrett's glands are clonal units; because of this important fact, we propose that it is the Barrett's gland that is the unit of selection in phenotypic and indeed neoplastic progression. Transition between metaplastic phenotypes may be governed by neutral drift akin to niche turnover in normal and dysplastic niches. In consequence, the phenotype of Barrett's glands assumes considerable importance, and we make a strong plea for the integration of the Barrett's gland in both genotype and phenotype space in future work.

Intestinal metaplasia in Barrett's oesophagus may be an epiphenomenon rather than a preneoplastic condition, and CDX2-positive cardiac-type epithelium is associated with minute Barrett's tumour

AIMS

Although intestinal-type epithelium in Barrett's oesophagus has been traditionally recognized as having a distinct malignant potential, whether this also holds true for cardiac-type epithelium remains controversial. The aim of this study was to identify a type of epithelium that is highly associated with Barrett's tumour.

METHODS AND RESULTS

We analysed tumours and the corresponding background mucosa with special regard to tumour size in 40 cases of superficial Barrett's tumour by using immunohistochemical staining for CDX2, CD10, MUC2, MUC5AC, and MUC6. Intestinal metaplasia in tumour-adjacent mucosa was not associated with tumour size, but was significantly correlated with the extent of Barrett's oesophagus (P < 0.001). The majority (69.2%, 9/13) of small tumours (≤10 mm) had no intestinal metaplasia in adjacent non-neoplastic mucosae. Minute (≤5 mm) tumours were significantly associated with a gastric immunophenotype (P < 0.001). Purely gastric-immunophenotype tumour cells expressed CDX2, and cardiac-type epithelium adjacent to small tumours also showed low-level CDX2 expression.

CONCLUSIONS

Our data suggest that intestinal metaplasia in Barrett's oesophagus is an epiphenomenon rather than a preneoplastic condition, and that CDX2-positive cardiac-type epithelium is highly associated with minute Barrett's tumour. Further prospective studies are needed to evaluate the risk of malignancy of cardiac-type epithelium with regard to sub-morphological intestinalization.

Modeling human gastrointestinal inflammatory diseases using microphysiological culture systems

Gastrointestinal illnesses are a significant health burden for the US population, with 40 million office visits each year for gastrointestinal complaints and nearly 250,000 deaths. Acute and chronic inflammations are a common element of many gastrointestinal diseases. Inflammatory processes may be initiated by a chemical injury (acid reflux in the esophagus), an infectious agent (Helicobacter pylori infection in the stomach), autoimmune processes (graft versus host disease after bone marrow transplantation), or idiopathic (as in the case of inflammatory bowel diseases). Inflammation in these settings can contribute to acute complaints (pain, bleeding, obstruction, and diarrhea) as well as chronic sequelae including strictures and cancer. Research into the pathophysiology of these conditions has been limited by the availability of primary human tissues or appropriate animal models that attempt to physiologically model the human disease. With the many recent advances in tissue engineering and primary human cell culture systems, it is conceivable that these approaches can be adapted to develop novel human ex vivo systems that incorporate many human cell types to recapitulate in vivo growth and differentiation in inflammatory microphysiological environments. Such an advance in technology would improve our understanding of human disease progression and enhance our ability to test for disease prevention strategies and novel therapeutics. We will review current models for the inflammatory and immunological aspects of Barrett's esophagus, acute graft versus host disease, and inflammatory bowel disease and explore recent advances in culture methodologies that make these novel microphysiological research systems possible.

Single nucleotide polymorphisms of caudal type homeobox 1 and 2 are associated with Barrett's esophagus

BACKGROUND

Barrett's esophagus (BE), the premalignant lesion of esophageal adenocarcinoma, is believed to develop as a result of chronic gastroesophageal reflux disease (GERD). Approximately 10 % of subjects with GERD progress to BE. Genetic, epigenetic and other risk factors may contribute to this inter-individual variability. Caudal type homeobox 1 (Cdx1) and Caudal type homeobox 2 (Cdx2) play important regulatory roles in the development of human BE.

AIMS

To determine associations between Cdx1 and Cdx2 single nucleotide polymorphisms (SNPs) and BE.

METHODS

Genomic DNA was extracted from blood samples collected from BE (n = 109) and GERD (n = 223) patients for genotyping of 5 SNPs each of Cdx1 and Cdx2 using TaqMan allelic discrimination assays. Odds ratios and 95 % confidence intervals of SNPs and haplotypes were calculated with a logistic regression model adjusted for factors including age, sex and hiatal hernia. Interactions between genetic variants and these three risk factors were also analyzed.

RESULTS

Older age (≥50 years), male sex and hiatal hernia were significantly associated with BE (P < 0.001). Five variants of Cdx1 SNPs (rs3776082, rs717746 and rs3776083), one Cdx1 haplotype, and three variants of Cdx2 SNPs (rs4769585 and rs3812863) were associated with BE (P < 0.05). Statistically significant interactions were detected between most of these SNPs and the three risk factors (P < 0.05).

CONCLUSION

Certain SNPs of Cdx1 and Cdx2 and their interactions with other risk factors are associated with BE, and may contribute to human susceptibility to BE.

Transgenic overexpression of cdx1b induces metaplastic changes of gene expression in zebrafish esophageal squamous epithelium

Cdx2 has been suggested to play an important role in Barrett's esophagus or intestinal metaplasia (IM) in the esophagus. To investigate whether transgenic overexpression of cdx1b, the functional equivalent of mammalian Cdx2 in zebrafish, may lead to IM of zebrafish esophageal squamous epithelium, a transgenic zebrafish system was developed by expressing cdx1b gene under the control of zebrafish keratin 5 promoter (krt5p). Gene expression in the esophageal squamous epithelium of wild-type and transgenic zebrafish was analyzed by Affymetrix microarray and confirmed by in situ hybridization. Morphology, mucin expression, cell proliferation, and apoptosis were analyzed by hematoxylin & eosin (HE) staining, Periodic acid Schiff (PAS) Alcian blue staining, proliferating cell nuclear antigen (PCNA) immunohistochemical staining, and TUNEL assay as well. cdx1b was found to be overexpressed in the nuclei of esophageal squamous epithelial cells of the transgenic zebrafish. Ectopic expression of cdx1b disturbed the development of this epithelium in larval zebrafish and induced metaplastic changes in gene expression in the esophageal squamous epithelial cells of adult zebrafish, that is, up-regulation of intestinal differentiation markers and down-regulation of squamous differentiation markers. However, cdx1b failed to induce histological IM, or to modulate cell proliferation and apoptosis in the squamous epithelium of adult transgenic zebrafish.

Predictable Marker for Regression of Barrett's Esophagus by Proton Pump Inhibitor Treatment in Korea

Background/Aims

There has been no report regarding the regression of Barrett's esophagus (BE) by continuous treatment of proton pump inhibitor (PPI). The aim of this study was to determine the regression rate of BE by PPI and predictable markers related to regression.

Methods

Thirty-five patients diagnosed as BE were consecutively enrolled and most of them took continuous PPI. The 25 patients underwent endoscopic surveillance and received biopsy. If the specialized intestinal metaplasia (SIM) was lost at any point of surveillance and did not recur, the case was regarded as the regression group. The proportion of SIM was graded and the mucin phenotype was decided using immunohistochemistry for MUC2, MUC5AC and MUC6. To assess the cell proliferation indexes and the degree of intestinal maturation, immunohistochemistry for Ki67 and CDX2 were performed.

Results

The regression of BE occurred in the 11 (44%) patients. The clinical and demographic factors showed no difference between the regression (n = 11) and persistence group (n = 14). The lower grade of SIM (P < 0.001) and gastric predominant mucin phenotype (P = 0.018) were more frequent, and the number of Ki67 positive cell per gland (P = 0.008) and the mean extent of CDX2 (P = 0.022) were lower in the regression group than in the persistence group.

Conclusions

The regression of BE by PPI treatment was frequent in Korea. The immunohistochemical detection of mucin phenotype, grade of SIM, Ki67 and CDX2 expression in Barrett's mucosa could be useful as a predictable marker for regression of SIM in BE.

Sox9 drives columnar differentiation of esophageal squamous epithelium: a possible role in the pathogenesis of Barrett's esophagus

The molecular mechanism underlying the development of Barrett's esophagus (BE), the precursor to esophageal adenocarcinoma, remains unknown. Our previous work implicated sonic hedgehog (Shh) signaling as a possible driver of BE and suggested that bone morphogenetic protein 4 (Bmp4) and Sox9 were downstream mediators. We have utilized a novel in vivo tissue reconstitution model to investigate the relative roles of Bmp4 and Sox9 in driving metaplasia. Epithelia reconstituted from squamous epithelial cells or empty vector-transduced cells had a stratified squamous phenotype, reminiscent of normal esophagus. Expression of Bmp4 in the stromal compartment activated signaling in the epithelium but did not alter the squamous phenotype. In contrast, expression of Sox9 in squamous epithelial cells induced formation of columnar-like epithelium with expression of the columnar differentiation marker cytokeratin 8 and the intestinal-specific glycoprotein A33. In patient tissue, A33 protein was expressed specifically in BE, but not in normal esophagus. Expression of Cdx2, another putative driver of BE, alone had no effect on reconstitution of a squamous epithelium. Furthermore, epithelium coexpressing Cdx2 and Sox9 had a phenotype similar to epithelium expressing Sox9 alone. Our results demonstrate that Sox9 is sufficient to drive columnar differentiation of squamous epithelium and expression of an intestinal differentiation marker, reminiscent of BE. These data suggest that Shh-mediated expression of Sox9 may be an important early event in the development of BE and that the potential for inhibitors of the hedgehog pathway to be used in the treatment of BE and/or esophageal adenocarcinoma could be tested in the near future.

Molecular biomarkers and ablative therapies for Barrett's esophagus

Barrett's esophagus is the major risk factor for esophageal adenocarcinoma. Endoscopic interventions that ablate Barrett's esophagus mucosa lead to replacement with a new squamous (neosquamous) mucosa, but it can be difficult to achieve complete ablation. Knowing whether cancer is less likely to develop in neosquamous mucosa or residual Barrett's esophagus after ablation is critical for determining the efficacy of treatment. This issue can be informed by assessing biomarkers that are associated with an increased risk of progression to adenocarcinoma. Although there are few postablation biomarker studies, evidence suggests that neosquamous mucosa may have a reduced risk of adenocarcinoma in patients who have been treated for dysplasia or cancer, but some patients who do not have complete eradication of nondysplastic Barrett's esophagus may still be at risk. Biomarkers could be used to optimize endoscopic surveillance strategies following ablation, but this needs to be assessed by clinical studies and economic modeling.

Molecular basis of esophageal cancer development and progression

This article discusses the molecular basis of esophageal cancer development and subsequent progression of disease. Differing epidemiologic factors are associated with esophageal adenocarcinoma and squamous cell carcinoma. These 2 different histologic types have differing putative underlying mechanisms of transdifferentiation from normal esophageal mucosa to malignant histologies via gene dysregulation, biochemical modifications, and altered cell signaling pathways. Our developing understanding of the molecular events underlying esophageal cancer is leading to the establishment of identifiable biomarkers and the clinical use of molecularly targeted treatment agents. The identification of driving genetic mutations and altered signaling pathways has also had favorable outcomes.

Activation of the BMP4 pathway and early expression of CDX2 characterize non-specialized columnar metaplasia in a human model of Barrett's esophagus

BACKGROUND

A human model of gastroesophageal reflux disease was used to examine the contribution of a non-specialized columnar type of metaplasia (NSCM) and key molecular events (BMP4 and CDX2) in the development of Barrett's esophagus.

METHODS

Biopsies of the remnant esophagus from 18 patients undergoing esophagectomy with gastric preservation were taken at 6-36-month intervals postoperatively and examined for activation of the BMP pathway (BMP4/P-Smad 1/5/8) and CDX2 and CDX1 expression by imunohistochemistry, quantitative real-time PCR, Western blot, and in situ hybridization.

RESULTS

A short segment (mean 15.6 mm) of NSCM was detected in 10 (56%) patients, with an increasing prevalence from 17% at 6 months to 62% at 36 months. Nuclear expression of P-Smad 1/5/8 in the squamous epithelium close to the anastomosis with strong expression in all epithelial cells of NSCM areas was found. Forty-eight (63%) biopsies with NSCM showed scattered nuclear expression of CDX2. Two cases showed isolated glands at 18, 24, and 36 months that fully expressed CDX2 and co-expressed CDX1. BMP4 mRNA and CDX2 mRNA levels were significantly greater in NSCM than in squamous epithelium.

CONCLUSIONS

BMP4 activation in NSCM and early expression of CDX2 are involved in the columnar epithelial differentiation of Barrett's esophagus.

Long-term follow-up of Barrett's epithelium: medical versus antireflux surgical therapy

BACKGROUND

Barrett's esophagus (BE) is the most serious complication of GERD. In BE patients, this observational study compares the effects of antireflux surgery versus antisecretory medical therapy.

METHODS

Overall, 89 BE patients (long BE = 45; short BE = 44) were considered: 45 patients underwent antireflux surgery and 44 underwent medical therapy. At both initial and follow-up endoscopy, symptoms were assessed using a detailed questionnaire; BE phenotypic changes [intestinal metaplasia (IM) presence/type, Cdx2 expression] were assessed by histology (H&E), histochemistry (HID), and immunohistochemistry. Surgical failures were defined as follows: (1) abnormal 24-h pH monitoring results after surgery, (2) endoscopically evident recurrent esophagitis, and (3) recurrent hiatal hernia or slipped fundoplication on endoscopy or barium swallow.

RESULTS

Reversion of IM was observed in 12/44 SSBE and 0/45 LSBE patients (p < 0.01). Reversion was more frequently observed after effective antireflux surgery than after medical treatment (p = 0.04). In patients with no further evidence of IM after therapy, Cdx2 expression was also absent (p = 0.02). The extent of IM was reduced, and the IM phenotype improved in SSBE patients after surgery.

CONCLUSIONS

Patients with short BE (but not those with long BE) may benefit from surgically reducing the esophagus' exposure to GE reflux; among these patients, successful surgery carries a higher IM reversion rate than medical treatment.

Molecular mechanisms of Barrett's esophagus

Barrett's esophagus (BE) is defined as the metaplastic conversion of esophageal squamous epithelium to intestinalized columnar epithelium. As a premalignant lesion of esophageal adenocarcinoma (EAC), BE develops as a result of chronic gastroesophageal reflux disease (GERD). Many studies have been conducted to understand the molecular mechanisms of this disease. This review summarizes recent results involving squamous and intestinal transcription factors, signaling pathways, stromal factors, microRNAs, and other factors in the development of BE. A conceptual framework is proposed to guide future studies. We expect elucidation of the molecular mechanisms of BE to help in the development of improved management of GERD, BE, and EAC.

CDX2 as a marker for intestinal differentiation: Its utility and limitations

CDX2 is a nuclear homeobox transcription factor that belongs to the caudal-related family of CDX homeobox genes. The gene encoding CDX2 is a nonclustered hexapeptide located on chromosome 13q12-13. Homeobox genes play an essential role in the control of normal embryonic development. CDX2 is crucial for axial patterning of the alimentary tract during embryonic development and is involved in the processes of intestinal cell proliferation, differentiation, adhesion, and apoptosis. It is considered specific for enterocytes and has been used for the diagnosis of primary and metastatic colorectal adenocarcinoma. CDX2 expression has been reported to be organ specific and is normally expressed throughout embryonic and postnatal life within the nuclei of epithelial cells of the alimentary tract from the proximal duodenum to the distal rectum. In this review, the authors elaborate on the diagnostic utility of CDX2 in gastrointestinal tumors and other neoplasms with intestinal differentiation. Limitations with its use as the sole predictor of a gastrointestinal origin of metastatic carcinomas are also discussed.

Molecular mechanisms of Barrett's esophagus and adenocarcinoma

The following on molecular mechanisms of Barrett's esophagus and adenocarcinoma contains commentaries on the mechanism of bile and gastric acid induced damage; the roles of BMP-4 and CDX-2 in the development of intestinal metaplasia; the transcription factors driving intestinalization in Barrett's esophagus; the contribution of bone marrow to metaplasia and adenocarcinoma; activation and inactivation of transcription factors; and a novel study design targeting molecular pathways in Barrett's esophagus.

Ectopic Cdx2 expression in murine esophagus models an intermediate stage in the emergence of Barrett's esophagus

Barrett's esophagus (BE) is an intestinal metaplasia that occurs in the setting of chronic acid and bile reflux and is associated with a risk for adenocarcinoma. Expression of intestine-specific transcription factors in the esophagus likely contributes to metaplasia development. Our objective was to explore the effects of an intestine-specific transcription factor when expressed in the mouse esophageal epithelium. Transgenic mice were derived in which the transcription factor Cdx2 is expressed in squamous epithelium using the murine Keratin-14 gene promoter. Effects of the transgene upon cell proliferation and differentiation, gene expression, and barrier integrity were explored. K14-Cdx2 mice express the Cdx2 transgene in esophageal squamous tissues. Cdx2 expression was associated with reduced basal epithelial cell proliferation and altered cell morphology. Ultrastructurally two changes were noted. Cdx2 expression was associated with dilated space between the basal cells and diminished cell-cell adhesion caused by reduced Desmocollin-3 mRNA and protein expression. This compromised epithelial barrier function, as the measured trans-epithelial electrical resistance (TEER) of the K14-Cdx2 epithelium was significantly reduced compared to controls (1189 Ohm*cm(2) ±343.5 to 508 Ohm*cm(2)±92.48, p = 0.0532). Secondly, basal cells with features of a transitional cell type, intermediate between keratinocytes and columnar Barrett's epithelial cells, were observed. These cells had reduced keratin bundles and increased endoplasmic reticulum levels, suggesting the adoption of secretory-cell features. Moreover, at the ultrastructural level they resembled "Distinctive" cells associated with multilayered epithelium. Treatment of the K14-Cdx2 mice with 5'-Azacytidine elicited expression of BE-associated genes including Cdx1, Krt18, and Slc26a3/Dra, suggesting the phenotype could be advanced under certain conditions. We conclude that ectopic Cdx2 expression in keratinocytes alters cell proliferation, barrier function, and differentiation. These altered cells represent a transitional cell type between normal squamous and columnar BE cells. The K14-Cdx2 mice represent a useful model to study progression from squamous epithelium to BE.

Biology of Barrett's esophagus and esophageal adenocarcinoma

The past few years have brought new advances in our understanding of the molecular mechanisms underlying the development of Barrett's esophagus and esophageal adenocarcinoma. Although knowledge of the genetic basis for these conditions has not yet translated into clinically useful biomarkers, the current pace of biomedical discovery holds endless possibilities for molecular medicine to improve the diagnosis and management of patients with these conditions. This article provides a useful conceptual basis for understanding the molecular events involved in the making of Barrett metaplasia and in its neoplastic progression, and provides a rationale for evaluating studies on the application of molecular medicine to the diagnosis and management of patients with Barrett's esophagus and esophageal adenocarcinoma.

Esophageal adenocarcinoma: treatment modalities in the era of targeted therapy

Esophageal adenocarcinoma is an aggressive malignancy with a poor outcome, and its incidence continues to rise at an alarming rate. Current treatment strategies combining chemotherapy, radiation, and surgery are plagued with high rates of recurrence and metastasis. Multiple molecular pathways including the epidermal growth factor receptor, vascular endothelial growth factor, v-erb-b2 erythroblastic leukemia viral oncogene homolog (ERBB2), and Aurora kinase pathways are activated in many esophageal adenocarcinomas. In many cases, these pathways have critical roles in tumor progression. Research on the mechanisms by which these pathways contribute to disease progression has resulted in numerous biologic agents and small molecules with the potential to improve outcome. The promise of targeted therapy and personalized medicine in improving the clinical outcome is now closer than it has ever been.

Diagnostic challenges in the pathologic evaluation of Barrett esophagus

CONTEXT

Barrett esophagus represents an unstable epithelium resulting from chronic gastroesophageal reflux disease. Patients with Barrett esophagus routinely undergo endoscopic examination to detect dysplasia and early carcinoma. Although appropriate classification of Barrett esophagus and neoplasia is usually straightforward, persistent esophageal inflammation may induce epithelial changes that mimic, or mask, dysplasia. Recent data also indicate that specific molecular changes occur in nondysplastic Barrett mucosa and herald the development of dysplasia and/or carcinoma.

OBJECTIVE

To describe problematic aspects of biopsy interpretation in tissue samples of the gastroesophageal junction and distal esophagus, including the diagnostic criteria for Barrett esophagus, the importance of the gastric cardia, and pitfalls to the diagnosis of dysplasia. Ancillary studies that have recently emerged as potential adjuncts to the evaluation of patients with Barrett esophagus will be briefly discussed.

DATA SOURCES

A comprehensive review of the relevant literature indexed in PubMed (National Library of Medicine) was performed.

CONCLUSIONS

Barrett esophagus is currently defined as the presence of intestinal metaplasia in samples obtained from an endoscopically evident abnormality in the distal esophagus. Diagnosis and grading of dysplasia in mucosal biopsies remain the most reliable method to assess risk for neoplastic progression, but its classification may be hindered by superimposed inflammatory changes and suffers from considerable interobserver variability. Therefore, immunohistochemical studies and molecular assessment for TP53, CDKN2A , and DNA content abnormalities have emerged as potential adjuncts to the detection of dysplasia.

Acid and bile salt-induced CDX2 expression differs in esophageal squamous cells from patients with and without Barrett's esophagus

BACKGROUND & AIMS

It is not clear why only a minority of patients with gastroesophageal reflux disease (GERD) develop Barrett's esophagus. We hypothesized that differences among individuals in molecular pathways activated when esophageal squamous epithelium is exposed to reflux underlie the development of Barrett's metaplasia.

METHODS

We used esophageal squamous cell lines from patients who had GERD with Barrett's esophagus (normal esophageal squamous [NES]-B3T and NES-B10T) and without Barrett's esophagus (NES-G2T and NES-G4T) to study effects of acid and bile salts on expression of the CDX2 gene. Bay 11-705, Ad5 inhibitor kappaB(IkappaB)alpha-SR, and site-directed mutagenesis were used to explore effects of nuclear factor-kappaB (NF-kappaB) inhibition on CDX2 promoter activity; DNA binding of the NF-kappaB subunits p50 and p65 was assessed by chromatin immune-precipitation.

RESULTS

Acid and bile salts increased CDX2 messenger RNA (mRNA), protein, and promoter activity in NES-B3T and NES-B10T cells, but not in NES-G2T or NES-G4T cells. Inhibition of NF-kappaB abolished the increase in CDX2 promoter activity. Increased CDX2 promoter activity was associated with nuclear translocation of p50, which bound to the promoter. We found CDX2 mRNA in 7 of 10 esophageal squamous biopsy specimens from patients with Barrett's esophagus, but in only 1 of 10 such specimens from patients who had GERD without Barrett's esophagus.

CONCLUSIONS

Acid and bile salts induce CDX2 mRNA and protein expression in esophageal squamous cells from patients with Barrett's esophagus, but not from GERD patients without Barrett's esophagus. We speculate that these differences in acid- and bile salt-induced activation of molecular pathways may underlie the development of Barrett's metaplasia.

Foveolar type dysplasia in Barrett esophagus

Adenocarcinoma of the lower esophagus and esophagogastric junction is increasing in incidence in Western countries. A metaplasia (Barrett esophagus)-dysplasia-carcinoma sequence induced by gastroesophageal reflux disease is established. Two patterns of Barrett dysplasias have been described-adenomatous (type 1) and non-adenomatous (type 2 or foveolar/hyperplastic type). Interestingly, little is known about non-adenomatous dysplasia. Esophagogastrectomy cases from 41 patients with glandular dysplasia with and without associated invasive adenocarcinoma of the lower esophagus were evaluated for expression of MUC2, MUC5AC, CDX2, villin, Ki67 and p53. Results were correlated with sub-classification of the dysplasia into morphologic patterns of adenomatous vs foveolar vs hybrid type. In addition, clinicopathological parameters including the presence and extent of background intestinal metaplasia were also evaluated. Foveolar type dysplasia was present in 46% of the cases and thus, was more common than adenomatous type or hybrid type (both approximately 27%) dysplasia. Immunohistochemistry confirmed the histological stratification in all cases. Foveolar type dysplasia commonly expressed MUC5AC (P<0.12) but was consistently negative for markers of intestinal differentiation, MUC2, CDX2 and villin (all P<0.01). By contrast, adenomatous type dysplasia frequently displayed intestinal differentiation markers (all P<0.0001) Hybrid-type dysplasia was similar to adenomatous type dysplasia in showing expression of intestinal differentiation markers (P<0.01) and therefore could not be sustained as a separate category. In conclusion, our study provides evidence for a non intestinal pathway to neoplastic development in Barrett esophagus, that is, gastric metaplasia-foveolar dysplasia-adenocarcinoma.

Intestinal differentiation in metaplastic, nongoblet columnar epithelium in the esophagus

Barrett esophagus (BE) is defined by the presence of metaplastic esophageal columnar epithelium with goblet cells within endoscopically recognizable areas of the esophagus. However, some carcinomas in BE, or from the gastroesophageal junction region, develop within mucosa devoid of goblet cells. However, the biologic properties, pathogenesis, and risk of malignancy of metaplastic, esophageal nongoblet columnar epithelium, is, essentially, unknown. In this study, 89 patients with metaplastic esophageal columnar epithelium were evaluated immunohistochemically for markers of intestinal differentiation, such as MUC2, DAS-1, Villin, and CDX2, a marker of gastric differentiation (MUC5AC), and Ki67, a marker of cell proliferation. Of the 89 patients, 59 had columnar metaplasia with goblet cells (BE), which were further separated into low-density goblet cell and high-density goblet cell groups based on the percentage of crypts with goblet cells, and 30 patients had columnar metaplasia of the esophagus without goblet cells. As controls, gastric biopsies from 19 age and sex matched patients without esophageal or gastric pathology were used. The rate of positivity of the markers and the location of Ki67 staining was evaluated only in non-goblet columnar epithelium from all patient groups. Patients with metaplastic esophageal columnar epithelium without goblet cells showed positivity for MUC5AC, MUC2, DAS-1, Villin, and CDX2 in 100%, 0%, 30%, 17%, and 43% of cases, respectively. 17% of cases showed aberrant surface Ki67 positivity. These values were significantly higher than gastric controls, which showed absence of staining for all markers except MUC5AC (100%). In patients with metaplastic esophageal columnar epithelium with goblet cells (BE) a significant increased rate of staining was observed for all markers, except MUC5AC. In addition, both MUC2 and surface Ki67 staining were significantly increased in BE patients with high-density goblet cells versus those with low-density goblet cells. In a separate analysis in which metaplastic esophageal nongoblet epithelium was evaluated in areas of mucosa devoid of goblet cells compared with areas of mucosa with goblet cells, from patients who had goblet cells elsewhere in the mucosa (N=59), no significant differences were observed with regard to the percentage of cases that stained with any of the markers in the nongoblet epithelium in areas devoid of goblet cells, similar to the patient group with metaplastic esophageal epithelium without goblet cells (N=30). Similar to above, in all cases, expression of intestinal markers increased in areas of mucosa adjacent to goblet cells. This study provides evidence that metaplastic esophageal columnar epithelium without goblet cells shows phenotypic evidence of intestinal differentiation and supports the theory that squamous epithelium converts initially to nongoblet columnar epithelium before goblet cell metaplasia. Further prospective studies are needed to evaluate the pathogenetic sequence, natural history, and risk of malignancy of metaplastic esophageal nongoblet epithelium.

The molecular pathogenesis of Barrett's esophagus: common signaling pathways in embryogenesis metaplasia and neoplasia

Although Barrett's esophagus has been recognized for over 50 years, the cellular and molecular mechanisms leading to the replacement of squamous esophageal epithelium with a columnar type are largely unknown. Barrett's is known to be an acquired process secondary to chronic gastroesophageal reflux disease and occurs in the presence of severe disruption of the gastroesophageal barrier and reflux of a mixture of gastric and duodenal content. Current hypothesis suggest that epithelial change occurs due to stimulation of esophageal stem cells present in the basal layers of the epithelium or submucosal glands, toward a columnar epithelial differentiation pathway. The transcription factor CDX2 seems to play a key role in promoting the cellular biology necessary for columnar differentiation, and can be induced by bile salt and acid stimulation. Several cellular signaling pathways responsible for modulation of intestinal differentiation have also been identified and include WNT, Notch, BMP, Sonic HH and TGFB. These also have been shown to respond to stimulation by bile acids, acid or both and may influence CDX2 expression. Their relative activity within the stem cell population is almost certainly responsible for the development of the esophageal columnar epithelial phenotype we know as Barrett's esophagus.