Is genomic evaluation feasible in endoscopic studies of Barrett's esophagus? A pilot study

Barrett's Esophagus: Emerging Knowledge and Management Strategies

The incidence of esophageal adenocarcinoma (EAC) has increased exponentially in the last 3 decades. Barrett's esophagus (BE) is the only known precursor of EAC. Patients with BE have a greater than 40 folds higher risk of EAC compared with the general population. Recent years have witnessed a revolution in the clinical and molecular research related to BE. However, several aspects of this condition remain controversial. Data regarding the true prevalence of BE have varied widely. Recent studies have suggested a lower incidence of EAC in nondysplastic BE (NDBE) than previously reported. There is paucity of prospective data showing a survival benefit of screening or surveillance for BE. Furthermore, the ever-increasing emphasis on healthcare cost containment has called for reexamination of the screening and surveillance strategies for BE. There is a need for identification of reliable clinical predictors or molecular biomarkers to risk-stratify patients who might benefit the most from screening or surveillance for BE. Finally, new therapies have emerged for the management of dysplastic BE. In this paper, we highlight the key areas of controversy and uncertainty surrounding BE. The paper discusses, in detail, the current literature about the molecular pathogenesis, biomarkers, histopathological diagnosis, and management strategies for BE.

Gene expression in Barrett's esophagus: laser capture versus whole tissue

OBJECTIVE

Diagnosis of Barrett's esophagus (BE) is typically done through morphologic analysis of esophageal tissue biopsy. Such samples contain several cell types. Laser capture microdissection (LCM) allows the isolation of specific cells from heterogeneous cell populations. The purpose of this study was to determine the degree of overlap of the two sample types and to define a set of genes that might serve as biochemical markers for BE.

MATERIAL AND METHODS

Biopsies were obtained from regions of the glandular tissue of BE and normal esophagus from 9 subjects with BE. Samples from 5 subjects were examined as whole tissue (BE [whole]; E [whole]), and in 4 subjects the glandular epithelium of BE was isolated using LCM (BE [LCM]) and compared with the averaged values (E [LCM]) for both basal cell (B [LCM]) and squamous cell (S [LCM]) epithelium.

RESULTS

Gene expression revealed 1797 probe sets between BE [whole] and E [whole] (fold change > 2.0; p<0.001). Most of these genes (74%) were also differentially expressed between BE [LCM] and E [LCM], showing that there was high concordance between the two sampling methods. LCM provided a great deal of additional information (2113 genes) about the alterations in gene expression that may represent the BE phenotype.

CONCLUSIONS

There are differences in gene expression profiles depending on whether specimens are whole tissue biopsies or LCM dissected. Whole tissue biopsies should prove satisfactory for diagnostic purposes. Because the data from LCM samples delineated many more Barrett's-specific genes, this procedure might provide more information regarding pathogenesis than would whole tissue material.

Cdx1 and c-Myc foster the initiation of transdifferentiation of the normal esophageal squamous epithelium toward Barrett's esophagus

Background

Barrett's esophagus is a premalignant condition whereby the normal stratified squamous esophageal epithelium undergoes a transdifferentiation program resulting in a simple columnar epithelium reminiscent of the small intestine. These changes are typically associated with the stratified squamous epithelium chronically exposed to acid and bile salts as a result of gastroesophageal reflux disease (GERD). Despite this well-defined epidemiologic association between acid reflux and Barrett's esophagus, the genetic changes that induce this transdifferentiation process in esophageal keratinocytes have remained undefined.

Methodology/Principal Findings

To begin to identify the genetic changes responsible for transdifferentiaiton in Barrett's esophagus, we performed a microarray analysis of normal esophageal, Barrett's esophagus and small intestinal biopsy specimens to identify candidate signaling pathways and transcription factors that may be involved. Through this screen we identified the Cdx1 homeodomain transcription factor and the c-myc pathway as possible candidates. Cdx1 and c-myc were then tested for their ability to induce transdifferentiation in immortalized human esophageal keratinocytes using organotypic culturing methods. Analyses of these cultures reveal that c-myc and cdx1 cooperate to induce mucin production and changes in keratin expression that are observed in the epithelium of Barrett's esophagus.

Conclusions/Significance

These data demonstrate the ability of Cdx1 and c-myc to initiate the earliest stages of transdifferentiation of esophageal keratinocytes toward a cell fate characteristic of Barrett's esophagus.

Advances in gene chip technique in Barrett's metaplasia and adenocarcinoma

Gene chip methods are applied to the study of gene expression. The differentially expressed genes in different specimens may be detected with parallel analysis by gene chip, which has greatly improved the traditional experiments in that only a single or several gene expressions need to be observed for each test, thereby speeding up the identification of differentially expressed genes and the construction of differential expression profiles. Many studies have applied this technology for Barrett's metaplasia and adenocarcinoma, and identified a number of candidate genes useful as biomarkers in cancer staging, prediction of recurrence, prognosis and treatment selection. This review described the gene expression profile and molecular changes related to Barrett's metaplasia and adenocarcinoma of the esophagus, with emphasis on its prognostic value and possibilities for targeted therapy in a clinical setting.

Surveillance history of endoscopically treated patients with early Barrett's neoplasia: nonadherence to the Seattle biopsy protocol leads to sampling error

The study's aim was to retrospectively evaluate the surveillance history of Barrett's esophagus (BE) patients with endoscopically treated early neoplasia. All BE patients endoscopically treated for early cancer (EC) or high-grade intraepithelial neoplasia (HGIN) in a lesion or mass between 1998 and 2005 were included. Endoscopy and histology records were reviewed. Ninety-four patients (78 males, mean age 67 years, 24 HGIN, 70 EC) were included. In 36 (38%) patients, HGIN/EC was diagnosed at (or within 6 months after) initial endoscopy. The remaining 58 (62%) patients had a surveillance history (median duration 7 years, mean 6.7 endoscopies). Seventy-nine percent of these had low-grade intraepithelial neoplasia (LGIN) diagnosed at least once during their surveillance period with a median of seven endoscopies and a median number of biopsies that was 50% of what should have been taken according to the Seattle protocol. Patients without any dysplasia during earlier surveillance (n = 12, 21%) had undergone significantly less endoscopies (median four endoscopies, P = 0.02) and had a median biopsy percentage that was 23% of the Seattle protocol (P < 0.001 versus 50% in LGIN). In this selected cohort of patients with early Barrett's neoplasia, 38% of patients were diagnosed at initial endoscopy. Of the patients with a surveillance history, 79% had shown LGIN prior to HGIN/EC diagnosis. Only 21% of patients had a surveillance history without any dysplasia, which in general encompassed endoscopies with an insufficient number of biopsies, suggesting sampling error. This underlines the importance of obtaining an adequate number of biopsies during surveillance endoscopies.

Molecular defense mechanisms of Barrett's metaplasia estimated by an integrative genomics

Barrett's esophagus is characterized by the replacement of squamous epithelium with specialized intestinal metaplastic mucosa. The exact mechanisms of initiation and development of Barrett's metaplasia remain unknown, but a hypothesis of "successful adaptation" against noxious reflux components has been proposed. To search for the repertoire of adaptation mechanisms of Barrett's metaplasia, we employed high-throughput functional genomic and proteomic methods that defined the molecular background of metaplastic mucosa resistance to reflux. Transcriptional profiling was established for 23 pairs of esophageal squamous epithelium and Barrett's metaplasia tissue samples using Affymetrix U133A 2.0 GeneChips and validated by quantitative real-time polymerase chain reaction. Differences in protein composition were assessed by electrophoretic and mass-spectrometry-based methods. Among 2,822 genes differentially expressed between Barrett's metaplasia and squamous epithelium, we observed significantly overexpressed metaplastic mucosa genes that encode cytokines and growth factors, constituents of extracellular matrix, basement membrane and tight junctions, and proteins involved in prostaglandin and phosphoinositol metabolism, nitric oxide production, and bioenergetics. Their expression likely reflects defense and repair responses of metaplastic mucosa, whereas overexpression of genes encoding heat shock proteins and several protein kinases in squamous epithelium may reflect lower resistance of normal esophageal epithelium than Barrett's metaplasia to reflux components. Despite the methodological and interpretative difficulties in data analyses discussed in this paper, our studies confirm that Barrett's metaplasia may be regarded as a specific microevolution allowing for accumulation of mucosal morphological and physiological changes that better protect against reflux injury.