The Barrett's Gland in Phenotype Space

Advances in diagnosis and management of cancer of the esophagus

Esophageal cancer is the seventh most common malignancy worldwide, with over 470 000 new cases diagnosed each year. Two distinct histological subtypes predominate, and should be considered biologically separate disease entities.1 These subtypes are esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC). Outcomes remain poor regardless of subtype, with most patients presenting with late stage disease.2 Novel strategies to improve early detection of the respective precursor lesions, squamous dysplasia, and Barrett's esophagus offer the potential to improve outcomes. The introduction of a limited number of biologic agents, as well as immune checkpoint inhibitors, is resulting in improvements in the systemic treatment of locally advanced and metastatic esophageal cancer. These developments, coupled with improvements in minimally invasive surgical and endoscopic treatment approaches, as well as adaptive and precision radiotherapy technologies, offer the potential to improve outcomes still further. This review summarizes the latest advances in the diagnosis and management of esophageal cancer, and the developments in understanding of the biology of this disease.

Concerted epithelial and stromal changes during progression of Barrett's Esophagus to invasive adenocarcinoma exposed by multi-scale, multi-omics analysis

Esophageal adenocarcinoma arises from Barrett's esophagus, a precancerous metaplastic replacement of squamous by columnar epithelium in response to chronic inflammation. Multi-omics profiling, integrating single-cell transcriptomics, extracellular matrix proteomics, tissue-mechanics and spatial proteomics of 64 samples from 12 patients' paths of progression from squamous epithelium through metaplasia, dysplasia to adenocarcinoma, revealed shared and patient-specific progression characteristics. The classic metaplastic replacement of epithelial cells was paralleled by metaplastic changes in stromal cells, ECM and tissue stiffness. Strikingly, this change in tissue state at metaplasia was already accompanied by appearance of fibroblasts with characteristics of carcinoma-associated fibroblasts and of an NK cell-associated immunosuppressive microenvironment. Thus, Barrett's esophagus progresses as a coordinated multi-component system, supporting treatment paradigms that go beyond targeting cancerous cells to incorporating stromal reprogramming.

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.

Clonal Transitions and Phenotypic Evolution in Barrett's Esophagus

BACKGROUND & AIMS

Barrett's esophagus (BE) is a risk factor for esophageal adenocarcinoma but our understanding of how it evolves is poorly understood. We investigated BE gland phenotype distribution, the clonal nature of phenotypic change, and how phenotypic diversity plays a role in progression.

METHODS

Using immunohistochemistry and histology, we analyzed the distribution and the diversity of gland phenotype between and within biopsy specimens from patients with nondysplastic BE and those who had progressed to dysplasia or had developed postesophagectomy BE. Clonal relationships were determined by the presence of shared mutations between distinct gland types using laser capture microdissection sequencing of the mitochondrial genome.

RESULTS

We identified 5 different gland phenotypes in a cohort of 51 nondysplastic patients where biopsy specimens were taken at the same anatomic site (1.0-2.0 cm superior to the gastroesophageal junction. Here, we observed the same number of glands with 1 and 2 phenotypes, but 3 phenotypes were rare. We showed a common ancestor between parietal cell-containing, mature gastric (oxyntocardiac) and goblet cell-containing, intestinal (specialized) gland phenotypes. Similarly, we have shown a clonal relationship between cardiac-type glands and specialized and mature intestinal glands. Using the Shannon diversity index as a marker of gland diversity, we observed significantly increased phenotypic diversity in patients with BE adjacent to dysplasia and predysplasia compared to nondysplastic BE and postesophagectomy BE, suggesting that diversity develops over time.

CONCLUSIONS

We showed that the range of BE phenotypes represents an evolutionary process and that changes in gland diversity may play a role in progression. Furthermore, we showed a common ancestry between gastric and intestinal-type glands in BE.

Barrett's esophagus: The pathomorphological and molecular genetic keystones of neoplastic progression

Barrett's esophagus is a widespread chronically progressing disease of heterogeneous nature. A life threatening complication of this condition is neoplastic transformation, which is often overlooked due to lack of standardized approaches in diagnosis, preventative measures and treatment. In this essay, we aim to stratify existing data to show specific associations between neoplastic transformation and the underlying processes which predate cancerous transition. We discuss pathomorphological, genetic, epigenetic, molecular and immunohistochemical methods related to neoplasia detection on the basis of Barrett's esophagus. Our review sheds light on pathways of such neoplastic progression in the distal esophagus, providing valuable insight into progression assessment, preventative targets and treatment modalities. Our results suggest that molecular, genetic and epigenetic alterations in the esophagus arise earlier than cancerous transformation, meaning the discussed targets can help form preventative strategies in at-risk patient groups.

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.

Hybrid Stomach-Intestinal Chromatin States Underlie Human Barrett's Metaplasia

BACKGROUND & AIMS

Tissue metaplasia is uncommon in adults because established cis-element programs resist rewiring. In Barrett's esophagus, the distal esophageal mucosa acquires a predominantly intestinal character, with notable gastric features, and is predisposed to developing invasive cancers. We sought to understand the chromatin underpinnings of Barrett's metaplasia and why it commonly displays simultaneous gastric and intestinal properties.

METHODS

We profiled cis-regulatory elements with active histone modifications in primary human biopsy materials using chromatin immunoprecipitation followed by DNA sequencing. Mutations in Barrett's esophagus were examined in relation to tissue-specific enhancer landscapes using a random forest machine-learning algorithm. We also profiled open chromatin at single-cell resolution in primary Barrett's biopsy specimens using the assay for transposase-accessible chromatin. We used 1- and 2-color immunohistochemistry to examine protein expression of tissue-restricted genes.

RESULTS

Barrett's esophagus bears epigenome fingerprints of human stomach and intestinal columnar, but not esophageal squamous, epithelia. Mutational patterns were best explained as arising on the epigenome background of active gastric cis-elements, supporting the view that adjoining stomach epithelium is a likely tissue source. Individual cells in Barrett's metaplasia coexpress gastric and intestinal genes, reflecting concomitant chromatin access at enhancers ordinarily restricted to one or the other epithelium. Protein expression of stomach-specific mucins; CLDN18; and a novel gastric marker, ANXA10, showed extensive tissue and subclonal heterogeneity of dual stomach-intestinal cell states.

CONCLUSIONS

These findings reveal mixed and dynamic tissue-restricted chromatin states and phenotypic heterogeneity in Barrett's esophagus. Pervasive intragland variation argues against stem-cell governance of this phenotype.

Molecular phenotyping reveals the identity of Barrett's esophagus and its malignant transition

The origin of human metaplastic states and their propensity for cancer is poorly understood. Barrett's esophagus is a common metaplastic condition that increases the risk for esophageal adenocarcinoma, and its cellular origin is enigmatic. To address this, we harvested tissues spanning the gastroesophageal junction from healthy and diseased donors, including isolation of esophageal submucosal glands. A combination of single-cell transcriptomic profiling, in silico lineage tracing from methylation, open chromatin and somatic mutation analyses, and functional studies in organoid models showed that Barrett's esophagus originates from gastric cardia through c-MYC and HNF4A-driven transcriptional programs. Furthermore, our data indicate that esophageal adenocarcinoma likely arises from undifferentiated Barrett's esophagus cell types even in the absence of a pathologically identifiable metaplastic precursor, illuminating early detection strategies.

GATA4 blocks squamous epithelial cell gene expression in human esophageal squamous cells

GATA4 promotes columnar epithelial cell fate during gastric development. When ectopically expressed in the developing mouse forestomach, the tissue emerges as columnar-like rather than stratified squamous with gene expression changes that parallel those observed in the pre-malignant squamous to columnar metaplasia known as Barrett's esophagus (BE). GATA4 mRNA up-regulation and gene amplification occur in BE and its associated cancer, esophageal adenocarcinoma (EAC), and GATA4 gene amplification correlates with poor patient outcomes. Here, we explored the effect of ectopic expression of GATA4 in mature human esophageal squamous epithelial cells. We found that GATA4 expression in esophageal squamous epithelial cells compromised squamous cell marker gene expression and up-regulated expression of the canonical columnar cell cytokeratin KRT8. We observed GATA4 occupancy in the p63, KRT5, and KRT15 promoters, suggesting that GATA4 directly represses expression of squamous epithelial cell marker genes. Finally, we verified GATA4 protein expression in BE and EAC and found that exposure of esophageal squamous epithelial cells to acid and bile, known BE risk factors, induced GATA4 mRNA expression. We conclude that GATA4 suppresses expression of genes marking the stratified squamous epithelial cell lineage and that this repressive action by GATA4 may have implications in BE and EAC.

The indications for biopsy in routine upper gastrointestinal endoscopy

This review describes the indications and contraindications for endoscopic biopsy, in routine practice, of the upper gastrointestinal (GI) tract. We accept that this review provides grounds for controversy, as our stance in certain situations is counter to some national guidelines. Nevertheless, we provide evidence to support our viewpoints, especially on efficiency and economic grounds. We describe the particular controversies concerning the biopsy assessment of Barrett's oesophagus, chronic gastritis and the duodenum in the investigation of coeliac disease. We accept that there are indications for more extensive upper GI biopsy protocols in children than in adults; the latter constitute our main focus in this article. We would encourage detailed discussion between pathologists and their endoscopy colleagues about the indications, or lack of them, for routine upper GI endoscopic biopsy, as studies have shown that adherence to agreed guidelines has resulted in a very considerable diminution in the biopsy workload without compromising patient management. Furthermore, where biopsy is indicated, we emphasise the importance of accompanying clinical information provided to the pathologist, in particular regarding biopsy site(s), and regular feedback to endoscopists to improve and maintain the quality of such information. Finally, local dialogue is also advised, when necessary, to indicate to endoscopists the need to appropriately segregate biopsies into separate, individually labelled specimens, to maximise the information that can be derived by pathological evaluation and thereby improve the quality of the final pathology report.

Current concepts in tumour-derived organoids

Cancer comprises a collection of highly proliferative and heterogeneous cells growing within an adaptive and evolving tumour microenvironment. Cancer survival rates have significantly improved following decades of cancer research. However, many experimental and preclinical studies do not translate to the bedside, reflecting the challenges of modelling the complexities and multicellular basis of human disease. Organoids are novel, complex, three-dimensional ex vivo tissue cultures that are derived from embryonic stem cells, induced pluripotent stem cells or tissue-resident progenitor cells, and represent a near-physiological model for studying cancer. Organoids develop by self-organisation, and can accurately represent the diverse genetic, cellular and pathophysiological hallmarks of cancer. In addition, co-culture methods and the ability to genetically manipulate these organoids have widened their utility in cancer research. Organoids thus offer a new and exciting platform for studying cancer and directing personalised therapies. This review aims to highlight how organoids are shaping the future of cancer research.

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.

Crypt fusion as a homeostatic mechanism in the human colon

OBJECTIVE

The crypt population in the human intestine is dynamic: crypts can divide to produce two new daughter crypts through a process termed crypt fission, but whether this is balanced by a second process to remove crypts, as recently shown in mouse models, is uncertain. We examined whether crypt fusion (the process of two neighbouring crypts fusing into a single daughter crypt) occurs in the human colon.

DESIGN

We used somatic alterations in the gene cytochrome c oxidase (CCO) as lineage tracing markers to assess the clonality of bifurcating colon crypts (n=309 bifurcating crypts from 13 patients). Mathematical modelling was used to determine whether the existence of crypt fusion can explain the experimental data, and how the process of fusion influences the rate of crypt fission.

RESULTS

In 55% (21/38) of bifurcating crypts in which clonality could be assessed, we observed perfect segregation of clonal lineages to the respective crypt arms. Mathematical modelling showed that this frequency of perfect segregation could not be explained by fission alone (p<10-20). With the rates of fission and fusion taken to be approximately equal, we then used the distribution of CCO-deficient patch size to estimate the rate of crypt fission, finding a value of around 0.011 divisions/crypt/year.

CONCLUSIONS

We have provided the evidence that human colonic crypts undergo fusion, a potential homeostatic process to regulate total crypt number. The existence of crypt fusion in the human colon adds a new facet to our understanding of the highly dynamic and plastic phenotype of the colonic epithelium.

Glyco-conjugated bile acids drive the initial metaplastic gland formation from multi-layered glands through crypt-fission in a murine model

Bile acid reflux is known to be associated with the development of Barrett’s esophagus and esophageal adenocarcinoma (EAC), yet the role of specific bile acids and the mechanism behind the metaplastic changes is unclear. Here, we demonstrate that multi-layered glandular structures at the squamo-columnar junction in mice contain multiple cell lineages, which resemble the human esophageal submucosal gland ducts. Exposing mice to patient’s refluxates induced expansion of multi-layered glandular structures and development of columnar metaplasia at the squamo-columnar junction. The glycine conjugated bile acids induced an intestinal type of metaplasia more typical for Barrett’s esophagus. Through lineage tracing, we excluded the involvement of K5⁺, DCLK1⁺, and LGR5⁺ progenitor cells as the primary source in the development of the glandular metaplastic epithelium. We show that the mechanism behind development of metaplasia involves crypt fission and may be independent of stem cell proliferation. Our findings support the hypothesis that in humans, BE arises from non-squamous cells residing in submucosal gland ducts and that induction of intestinal type of metaplasia is most effectively induced by glycine-conjugated bile acids. These novel insights may lead to more effective strategies to prevent development of Barrett’s esophagus and esophageal adenocarcinoma.

Computer-Aided Analysis of Gland-Like Subsurface Hyposcattering Structures in Barrett’s Esophagus Using Optical Coherence Tomography

(1) Background: Barrett’s esophagus (BE) is a complication of chronic gastroesophageal reflux disease and is a precursor to esophageal adenocarcinoma. The clinical implication of subsurface glandular structures of Barrett’s esophagus is not well understood. Optical coherence tomography (OCT), also known as volumetric laser endomicroscopy (VLE), can assess subsurface glandular structures, which appear as subsurface hyposcattering structures (SHSs). The aim of this study is to develop a computer-aided algorithm and apply it to investigate the characteristics of SHSs in BE using clinical VLE data; (2) Methods: SHSs were identified with an initial detection followed by machine learning. Comprehensive SHS characteristics including the number, volume, depth, size and shape were quantified. Clinical VLE datasets collected from 35 patients with a history of dysplasia undergoing BE surveillance were analyzed to study the general SHS distribution and characteristics in BE. A subset of radiofrequency ablation (RFA) patient data were further analyzed to investigate the pre-RFA SHS characteristics and post-RFA treatment response; (3) Results: SHSs in the BE region were significantly shallower, more vertical, less eccentric, and more regular, as compared with squamous SHSs. SHSs in the BE region which became neosquamous epithelium after RFA were shallower than those in the regions that remained BE. Pre-ablation squamous SHSs with higher eccentricity correlated strongly with larger reduction of post-ablation BE length for less elderly patients; (4) Conclusions: The computer algorithm is potentially a valuable tool for studying the roles of SHSs in BE.

Is Barrett's-Associated Esophageal Adenocarcinoma a Clonal Disease?

In this study, we argue that the basic clonal unit that makes up the Barrett's segment is at the level of the gland. There is expansion of this clonal unit, the gland, by fission, and there is evidence that the Barrett's segment is itself a clonal proliferation. Barrett's esophagus arises from both goblet cell-containing metaplasia and non-goblet cell-containing metaplasia and may arise from a stable clone, but the genomic changes occurring are subject to selection, usually with little or no evolution, appearing indolent from the evolutionary perspective. Genomic changes leading to dysplastic phenotypes are selected, but without any single clone predominating within the segment.

The metaplastic mosaic of Barrett's oesophagus

Barrett's oesophagus surveillance biopsies represent a significant share of the daily workload for a busy histopathology department. Given the emphasis on endoscopic detection and dysplasia grading, it is easy to forget that the benefits of these screening programs remain unproven. The majority of patients are at low risk of progression to oesophageal adenocarcinoma, and periodic surveillance of these patients is burdensome and costly. Here, we investigate the parallels in the development of Barrett's oesophagus and other scenarios of wound healing in the intestine. There is now increased recognition of the full range of glandular phenotypes that can be found in patients' surveillance biopsies, and emerging evidence suggests parallel pathways to oesophageal adenocarcinoma. Greater understanding of the conditions that favour progression to cancer in the distal oesophagus will allow us to focus resources on patients at increased risk.

Insights Into the Pathophysiology of Esophageal Adenocarcinoma

Although researchers have identified genetic alterations that contribute to development of esophageal adenocarcinoma, we know little about features of patients or environmental factors that mediate progression of chronic acid biliary reflux to Barrett's esophagus and cancer. Increasing our understanding of the mechanisms by which normal squamous epithelium progresses to early-stage invasive cancer will help formulate rational surveillance guidelines and allow us to divest resources away from patients at low risk of malignancy. We review the cellular and genetic alterations that occur during progression of Barrett's esophagus, based on findings from clinical studies and mouse models of disease. We review the features of the luminal and mucosal microenvironment of Barrett's esophagus that promote, in a small proportion of patients, development of esophageal adenocarcinoma. Markers of clonal evolution can be used to determine patient risk for cancer and set surveillance intervals.

Evolution of Premalignant Disease

Where does cancer come from? Although the cell-of-origin is difficult to pinpoint, cancer clones harbor information about their clonal ancestries. In an effort to find cells before they evolve into a life-threatening cancer, physicians currently diagnose premalignant diseases at frequencies that substantially exceed those of clinical cancers. Cancer risk prediction relies on our ability to distinguish between which premalignant features will lead to cancer mortality and which are characteristic of inconsequential disease. Here, we review the evolution of cancer from premalignant disease, and discuss the concept that even phenotypically normal cell progenies inherently gain more malignant potential with age. We describe the hurdles of prognosticating cancer risk in premalignant disease by making reference to the underlying continuous and multivariate natures of genotypes and phenotypes and the particular challenge inherent in defining a cell lineage as "cancerized."

Metaplasia: tissue injury adaptation and a precursor to the dysplasia-cancer sequence

Metaplasia is the replacement of one differentiated somatic cell type with another differentiated somatic cell type in the same tissue. Typically, metaplasia is triggered by environmental stimuli, which may act in concert with the deleterious effects of microorganisms and inflammation. The cell of origin for intestinal metaplasia in the oesophagus and stomach and for pancreatic acinar-ductal metaplasia has been posited through genetic mouse models and lineage tracing but has not been identified in other types of metaplasia, such as squamous metaplasia. A hallmark of metaplasia is a change in cellular identity, and this process can be regulated by transcription factors that initiate and/or maintain cellular identity, perhaps in concert with epigenetic reprogramming. Universally, metaplasia is a precursor to low-grade dysplasia, which can culminate in high-grade dysplasia and carcinoma. Improved clinical screening for and surveillance of metaplasia might lead to better prevention or early detection of dysplasia and cancer.

Porcine Esophageal Submucosal Gland Culture Model Shows Capacity for Proliferation and Differentiation

BACKGROUND & AIMS

Although cells comprising esophageal submucosal glands (ESMGs) represent a potential progenitor cell niche, new models are needed to understand their capacity to proliferate and differentiate. By histologic appearance, ESMGs have been associated with both overlying normal squamous epithelium and columnar epithelium. Our aim was to assess ESMG proliferation and differentiation in a 3-dimensional culture model.

METHODS

We evaluated proliferation in human ESMGs from normal and diseased tissue by proliferating cell nuclear antigen immunohistochemistry. Next, we compared 5-ethynyl-2'-deoxyuridine labeling in porcine ESMGs in vivo before and after esophageal injury with a novel in vitro porcine organoid ESMG model. Microarray analysis of ESMGs in culture was compared with squamous epithelium and fresh ESMGs.

RESULTS

Marked proliferation was observed in human ESMGs of diseased tissue. This activated ESMG state was recapitulated after esophageal injury in an in vivo porcine model, ESMGs assumed a ductal appearance with increased proliferation compared with control. Isolated and cultured porcine ESMGs produced buds with actively cycling cells and passaged to form epidermal growth factor-dependent spheroids. These spheroids were highly proliferative and were passaged multiple times. Two phenotypes of spheroids were identified: solid squamous (P63+) and hollow/ductal (cytokeratin 7+). Microarray analysis showed spheroids to be distinct from parent ESMGs and enriched for columnar transcripts.

CONCLUSIONS

Our results suggest that the activated ESMG state, seen in both human disease and our porcine model, may provide a source of cells to repopulate damaged epithelium in a normal manner (squamous) or abnormally (columnar epithelium). This culture model will allow the evaluation of factors that drive ESMGs in the regeneration of injured epithelium. The raw microarray data have been uploaded to the National Center for Biotechnology Information Gene Expression Omnibus (accession number: GSE100543).

Barrett's Esophagus: A Comprehensive and Contemporary Review for Pathologists

This review provides a summary of our current understanding of, and the controversies surrounding, the diagnosis, pathogenesis, histopathology, and molecular biology of Barrett's esophagus (BE) and associated neoplasia. BE is defined as columnar metaplasia of the esophagus. There is worldwide controversy regarding the diagnostic criteria of BE, mainly with regard to the requirement to histologically identify goblet cells in biopsies. Patients with BE are at increased risk for adenocarcinoma, which develops in a metaplasia-dysplasia-carcinoma sequence. Surveillance of patients with BE relies heavily on the presence and grade of dysplasia. However, there are significant pathologic limitations and diagnostic variability in evaluating dysplasia, particularly with regard to the more recently recognized unconventional variants. Identification of non-morphology-based biomarkers may help risk stratification of BE patients, and this is a subject of ongoing research. Because of recent achievements in endoscopic therapy, there has been a major shift in the treatment of BE patients with dysplasia or intramucosal cancer away from esophagectomy and toward endoscopic mucosal resection and ablation. The pathologic issues related to treatment and its complications are also discussed in this review article.