Cellular origin of Barrett's esophagus: controversy and therapeutic implications

Intestinal metaplasia in progression of Barrett's esophagus to esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has been increasing year by year. The prognosis of EAC is poor, and the 5-year survival rate is less than 20%. Barrett's esophagus (BE) is the only known precancerous lesion of EAC. BE with intestinal metaplasia (IM) has a higher risk of progressing to EAC. Exploring the mechanism of IM and finding targeted therapeutic targets for BE has become an important measure for tumor prevention. Bile acid reflux is considered an important factor in the occurrence of IM and promotes the progression of BE to EAC. However, the molecular regulatory mechanism of bile reflux induced IM and carcinogenesis remains unclear. This article reviews the environment, significance, and cell origin theory of IM, toxic effects of bile reflux, and molecular changes of IM progression to tumor, aiming to improve clinicians' understanding of IM in BE and provide evidence for early intervention of BE and prevention and treatment of EAC.

AI-assisted discovery of an ethnicity-influenced driver of cell transformation in esophageal and gastroesophageal junction adenocarcinomas

Although Barrett's metaplasia of the esophagus (BE) is the only known precursor lesion to esophageal adenocarcinomas (EACs), drivers of cellular transformation in BE remain incompletely understood. We use an artificial intelligence-guided network approach to study EAC initiation and progression. Key predictions are subsequently validated in a human organoid model, in patient-derived biopsy specimens of BE, a case-control study of genomics of BE progression, and in a cross-sectional study of 113 patients with BE and EACs. Our model classified healthy esophagus from BE and BE from EACs in several publicly available gene expression data sets (n = 932 samples). The model confirmed that all EACs must originate from BE and pinpointed a CXCL8/IL8↔neutrophil immune microenvironment as a driver of cellular transformation in EACs and gastroesophageal junction adenocarcinomas. This driver is prominent in White individuals but is notably absent in African Americans (AAs). Network-derived gene signatures, independent signatures of neutrophil processes, CXCL8/IL8 expression, and an absolute neutrophil count (ANC) are associated with risk of progression. SNPs associated with changes in ANC by ethnicity (e.g., benign ethnic neutropenia [BEN]) modify that risk. Findings define a racially influenced immunological basis for cell transformation and suggest that BEN in AAs may be a deterrent to BE→EAC progression.

The Immune Underpinnings of Barrett's-Associated Adenocarcinogenesis: a Retrial of Nefarious Immunologic Co-Conspirators

There is no doubt that chronic gastroesophageal reflux disease increases the risk of esophageal adenocarcinoma (EAC) by several fold (odds ratio, 6.4; 95% CI, 4.6-9.1), and some relationships between reflux disease-mediated inflammation and oncogenic processes have been explored; however, the precise interconnections between the immune response and genomic instabilities underlying these pathologic processes only now are emerging. Furthermore, the precise cell of origin of the precancerous stages associated with EAC development, Barrett's esophagus, be it cardia resident or embryonic remnant, may shape our interpretation of the likely immune drivers. This review integrates the current collective knowledge of the immunology underlying EAC development and outlines a framework connecting proinflammatory pathways, such as those mediated by interleukin 1β, tumor necrosis factor α, leukemia inhibitory factor, interleukin 6, signal transduction and activator of transcription 3, nuclear factor-κB, cyclooxygenase-2, and transforming growth factor β, with oncogenic pathways in the gastroesophageal reflux disease-Barrett's esophagus-EAC cancer sequence. Further defining these immune and molecular railroads may show a map of the routes taken by gastroesophageal cells on their journey toward EAC tumor phylogeny. The selective pressures applied by this immune-induced journey likely impact the phenotype and genotype of the resulting oncogenic destination and further exploration of lesser-defined immune drivers may be useful in future individualized therapies or enhanced selective application of recent immune-driven therapeutics.

Cellular Plasticity, Reprogramming, and Regeneration: Metaplasia in the Stomach and Beyond

The mucosa of the body of the stomach (ie, the gastric corpus) uses 2 overlapping, depth-dependent mechanisms to respond to injury. Superficial injury heals via surface cells with histopathologic changes like foveolar hyperplasia. Deeper, usually chronic, injury/inflammation, most frequently induced by the carcinogenic bacteria Helicobacter pylori, elicits glandular histopathologic alterations, initially manifesting as pyloric (also known as pseudopyloric) metaplasia. In this pyloric metaplasia, corpus glands become antrum (pylorus)-like with loss of acid-secreting parietal cells (atrophic gastritis), expansion of foveolar cells, and reprogramming of digestive enzyme-secreting chief cells into deep antral gland-like mucous cells. After acute parietal cell loss, chief cells can reprogram through an orderly stepwise progression (paligenosis) initiated by interleukin-13-secreting innate lymphoid cells (ILC2s). First, massive lysosomal activation helps mitigate reactive oxygen species and remove damaged organelles. Second, mucus and wound-healing proteins (eg, TFF2) and other transcriptional alterations are induced, at which point the reprogrammed chief cells are recognized as mucus-secreting spasmolytic polypeptide-expressing metaplasia cells. In chronic severe injury, glands with pyloric metaplasia can harbor both actively proliferating spasmolytic polypeptide-expressing metaplasia cells and eventually intestine-like cells. Gastric glands with such lineage confusion (mixed incomplete intestinal metaplasia and proliferative spasmolytic polypeptide-expressing metaplasia) may be at particular risk for progression to dysplasia and cancer. A pyloric-like pattern of metaplasia after injury also occurs in other gastrointestinal organs including esophagus, pancreas, and intestines, and the paligenosis program itself seems broadly conserved across tissues and species. Here we discuss aspects of metaplasia in stomach, incorporating data derived from animal models and work on human cells and tissues in correlation with diagnostic and clinical implications.

Gene Expression in Barrett's Esophagus Cell Lines Resemble Esophageal Squamous Cell Carcinoma Instead of Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) is strongly associated with Barrett's esophagus (BE), a pre-malignant condition resulting from gastric reflux. Esophageal squamous cell carcinoma (ESCC), the other major subtype of esophageal cancer, shows strong association with smoking and alcohol intake and no association with gastric reflux. In this study, we constructed and validated gene expression signatures of EAC vs. ESCC tumors using publicly available datasets, and subsequently assessed the enrichment levels of these signatures in commonly used EAC and ESCC cell lines, normal esophageal tissues and normal esophageal cell lines, and primary BE tissues and BE cell lines. We found that unlike ESCC cell lines which were quite similar to primary ESCC tumors, EAC cell lines were considerably different from primary EAC tumors but still more similar to EAC tumors than ESCC tumors, as the genes up in EAC vs. ESCC (EAChi) had considerably lower expression in EAC cell lines than EAC tumors. However, more surprisingly, unlike various normal cell lines (EPC2, Het-1A) which were very similar to various tissues from normal esophagus, BE cell lines (BAR-T, CP-A) were extremely different from primary BE tissues, as BE cell lines had substantially lower levels of EAChi and substantially higher levels of ESCChi gene expression. This ESCC-like profile of the BAR-T remained unaltered even after prolonged exposure to an acidic bile mixture in vitro resulting in malignant transformation of this cell line. However, primary BE tissues had EAC-like gene expression profiles as expected. Only one EAC case from the Cancer Genome Atlas resembled BE cell lines, and while it had the clinical profile and some mutational features of EAC, it had some mutational features, the copy number alteration profile, and the gene expression profile of ESCC instead. These incomprehensible changes in gene expression patterns may result in ambiguous changes in the phenotype and warrants careful evaluation to inform selection of appropriate in vitro tools for future studies on esophageal adenocarcinoma.

SPT6 loss permits the transdifferentiation of keratinocytes into an intestinal fate that resembles Barrett's metaplasia

Transient depletion of the transcription elongation factor SPT6 in the keratinocyte has been recently shown to inhibit epidermal differentiation and stratification; instead, they transdifferentiate into a gut-like lineage. We show here that this phenomenon of transdifferentiation recapitulates Barrett's metaplasia, the only human pathophysiologic condition in which a stratified squamous epithelium that is injured due to chronic acid reflux is trans-committed into an intestinal fate. The evidence we present here not only lend support to the notion that the keratinocytes are potentially the cell of origin of Barrett's metaplasia but also provide mechanistic insights linking transient acid exposure, downregulation of SPT6, stalled transcription of the master regulator of epidermal fate TP63, loss of epidermal fate, and metaplastic progression. Because Barrett's metaplasia in the esophagus is a pre-neoplastic condition with no preclinical human models, these findings have a profound impact on the modeling Barrett's metaplasia-in-a-dish.

Epithelial cell plasticity: breaking boundaries and changing landscapes

Epithelial tissues respond to a wide variety of environmental and genotoxic stresses. As an adaptive mechanism, cells can deviate from their natural paths to acquire new identities, both within and across lineages. Under extreme conditions, epithelial tissues can utilize "shape-shifting" mechanisms whereby they alter their form and function at a tissue-wide scale. Mounting evidence suggests that in order to acquire these alternate tissue identities, cells follow a core set of "tissue logic" principles based on developmental paradigms. Here, we review the terminology and the concepts that have been put forward to describe cell plasticity. We also provide insights into various cell intrinsic and extrinsic factors, including genetic mutations, inflammation, microbiota, and therapeutic agents that contribute to cell plasticity. Additionally, we discuss recent studies that have sought to decode the "syntax" of plasticity-i.e., the cellular and molecular principles through which cells acquire new identities in both homeostatic and malignant epithelial tissues-and how these processes can be manipulated for developing novel cancer therapeutics.

LGR5 in Barrett's Esophagus and its Utility in Predicting Patients at Increased Risk of Advanced Neoplasia

The expression of LGR5, a known stem cell marker, is poorly understood in Barrett's esophagus (BE) and related neoplasia. The aim of this study was to evaluate LGR5 in BE and related neoplasia and to evaluate its utility as a potential biomarker of progression to advanced neoplasia.

The Cellular Origin of Barrett's Esophagus and Its Stem Cells

The incidence of esophageal adenocarcinoma is rapidly increasing in Western countries. This is despite the introduction of sophisticated endoscopic techniques and our ability to readily monitor the presumed precursor lesion known as Barrett's esophagus. Preemptive approaches, including radiofrequency ablation (RFA), and photodynamic therapy (PDT) for Barrett's esophagus and dysplasia are achieving dramatic initial results. Although the long-term efficacy of these nonspecific ablative therapies is awaiting longitudinal studies, reports of recurrences are increasing. More targeted therapies, particularly directed at the stem cells of Barrett's esophagus, demand knowing the origin of this intestinal metaplasia (IM). The prevailing concept holds that Barrett's esophagus arises from the "transcommitment" of esophageal stem cells to produce an intestine-like epithelium. An alternative explanation derives from the discovery of a discrete population of residual embryonic cells (RECs) existing at the gastroesophageal junction in normal individuals that expands and colonizes regions of the esophagus denuded by chronic reflux. These RECs form IM within days of esophageal injury, suggesting a novel mechanism of tumorigenesis.A corollary of this work is that the Barrett's stem cell is distinct from that of the squamous epithelium and, once identified, will form the basis of new preemptive strategies for addressing Barrett's and its related neoplasia.

Origins of Metaplasia in Barrett's Esophagus: Is this an Esophageal Stem or Progenitor Cell Disease?

The incidence of esophageal adenocarcinoma has been increasing in Western countries over the past several decades. Though Barrett's esophagus, in which the normal esophageal squamous epithelium is replaced with metaplastic intestinalized columnar cells due to chronic damage from gastroesophageal reflux, is accepted as the requisite precursor lesion for esophageal adenocarcinoma, the Barrett's esophagus cell of origin and the molecular mechanism underlying esophageal epithelial metaplasia remain controversial. Much effort has been dedicated towards identifying the Barrett's esophagus cell of origin since this could lead to more effective prevention and treatment strategies for both Barrett's esophagus and esophageal adenocarcinoma. Previously, it was hypothesized that terminally differentiated esophageal squamous cells might undergo direct conversion into specialized intestinal columnar cells via the process of transdifferentiation. However, there is increasing evidence that stem and/or progenitor cells are molecularly reprogrammed through the process of transcommitment to differentiate into the columnar cell lineages that characterize Barrett's esophagus. Given that Barrett's esophagus originates at the gastroesophageal junction, the boundary between the distal esophagus and gastric cardia, potential sources of these stem and/or progenitor cells include columnar cells from the squamocolumnar junction or neighboring gastric cardia, native esophageal squamous cells, native esophageal cuboidal or columnar cells from submucosal glands or ducts, or circulating bone marrow-derived cells. In this review, we focus on native esophageal specific stem and/or progenitor cells and detail molecular mediators of transcommitment based on recent insights gained from novel mouse models and clinical observations from patients.

Origins of Metaplasia in the Esophagus: Is This a GE Junction Stem Cell Disease?

The incidence of esophageal adenocarcinoma (EAC) and its precursor lesion Barrett's esophagus (BE) has been increasing steadily in the western world in recent decades. Understanding the cellular origins of BE and the conditions responsible for their malignant transformation would greatly facilitate risk assessment and identification of patients at risk of progression, but this topic remains a source of debate. Here, we review recent findings that have provided support for the gastroesophageal junction (GEJ) as the main source of stem cells that give rise to BE and EAC. These include both gastric cardia cells and transitional basal cells. Furthermore, we discuss the role of chronic injury and inflammation in a tumor microenvironment as a major factor in promoting stem cell expansion and proliferation as well as transformation of the GEJ-derived stem cells and progression to EAC. We conclude that there exists a large amount of empirical support for the GEJ as the likely source of BE stem cells. While BE seems to resemble a successful adaptation to esophageal damage, carcinogenesis appears as a consequence of natural selection at the level of GEJ stem cells, and later glands, that expand into the esophagus wherein the local ecology creates the selective landscape for cancer progression.

Pyloric metaplasia, pseudopyloric metaplasia, ulcer-associated cell lineage and spasmolytic polypeptide-expressing metaplasia: reparative lineages in the gastrointestinal mucosa

The gastrointestinal mucosae provide a critical barrier between the external and internal milieu. Thus, damage to the mucosa requires an immediate response to provide appropriate wound closure and healing. Metaplastic lineages with phenotypes similar to the mucous glands of the distal stomach or Brunner's glands have been associated with various injurious scenarios in the stomach, small bowel, and colon. These lineages have been assigned various names including pyloric metaplasia, pseudopyloric metaplasia, ulcer-associated cell lineage (UACL), and spasmolytic polypeptide-expressing metaplasia (SPEM). A re-examination of the literature on these various forms of mucous cell metaplasia suggests that pyloric-type mucosal gland lineages may provide a ubiquitous response to mucosal injury throughout the gastrointestinal tract as well as in the pancreas, esophagus, and other mucosal surfaces. While the cellular origin of these putative reparative lineages likely varies in different regions of the gut, their final phenotypes may converge on a pyloric-type gland dedicated to mucous secretion. In addition to their healing properties in the setting of acute injury, these pyloric-type lineages may also represent precursors to neoplastic transitions in the face of chronic inflammatory influences. Further investigations are needed to determine how discrete molecular profiles relate to the origin and function of pyloric-type metaplasias previously described by histological characteristics in multiple epithelial mucosal systems in the setting of acute and chronic damage. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Barrett's metaplasia develops from cellular reprograming of esophageal squamous epithelium due to gastroesophageal reflux

Gastroesophageal reflux disease (GERD) clinically predisposes to columnar Barrett's metaplasia (BM) in the distal esophagus. We demonstrate evidence supporting the cellular origin of BM from reprograming or transcommitment of resident normal esophageal squamous (NES) epithelial cells in response to acid and bile (A + B) exposure using an in vitro cell culture model. The hTERT-immortalized NES cell line NES-B10T was exposed 5 min/day to an A + B mixture for 30 wk. Morphological changes, mRNA, and protein expression levels for the inflammatory marker cyclooxygenase-2; the lineage-determining transcription factors TAp63 (squamous), CDX2, and SOX9 (both columnar); and the columnar lineage markers Villin, Muc-2, CK8, and mAb Das-1 (incomplete phenotype of intestinal metaplasia) were assessed every 10 wk. Markers of columnar lineage and inflammation increased progressively, while squamous lineage-determining transcriptional factors were significantly decreased both at the mRNA and/or protein level in the NES-B10T cells at/after A + B treatment for 30 wk. Distinct modifications in morphological features were only observed at/after 30 wk of A + B exposure. These changes acquired by the NES-B10T 30-wk cells were retained even after cessation of A + B exposure for at least 3 wk. This study provides evidence that chronic exposure to the physiological components of gastric refluxate leads to repression of the discernable squamous transcriptional factors and activation of latent columnar transcriptional factors. This reflects the alteration in lineage commitment of the precursor-like biphenotypic, NES-B10T cells in response to A + B exposure as the possible origin of BM from the resident NES cells.NEW & NOTEWORTHY This study provides evidence of the origins of Barrett's metaplasia from lineage transcommitment of resident esophageal cells after chronic exposure to gastroesophageal refluxate. The preterminal progenitor-like squamous cells alter their differentiation and develop biphenotypic characteristics, expressing markers of incomplete-type columnar metaplasia. Development of these biphenotypic precursors in vitro is a unique model to study pathogenesis of Barrett's metaplasia and esophageal adenocarcinoma.

Constrained Score Statistics Identify Genetic Variants Interacting with Multiple Risk Factors in Barrett's Esophagus

Few gene-environment interactions (G × E) have been discovered in cancer epidemiology thus far, in part due to the large number of possible G × E to be investigated and inherent low statistical power of traditional analytic methods for discovering G × E. We consider simultaneously testing for interactions between several related exposures and a genetic variant in a genome-wide study. To improve power, constrained testing strategies are proposed for multivariate gene-environment interactions at two levels: interactions that have the same direction (one-sided or bidirectional hypotheses) or are proportional to respective exposure main effects (a variant of Tukey's one-degree test). Score statistics were developed to expedite the genome-wide computation. We conducted extensive simulations to evaluate validity and power performance of the proposed statistics, applied them to the genetic and environmental exposure data for esophageal adenocarcinoma and Barrett's esophagus from the Barretts Esophagus and Esophageal Adenocarcinoma Consortium (BEACON), and discovered three loci simultaneously interacting with gastresophageal reflux, obesity, and tobacco smoking with genome-wide significance. These findings deepen understanding of the genetic and environmental architecture of Barrett's esophagus and esophageal adenocarcinoma.

Oesophageal adenocarcinoma and gastric cancer: should we mind the gap?

Over recent decades we have witnessed a shift in the anatomical distribution of gastric cancer (GC), which increasingly originates from the proximal stomach near the junction with the oesophagus. In parallel, there has been a dramatic rise in the incidence of oesophageal adenocarcinoma (OAC) in the lower oesophagus, which is associated with antecedent Barrett oesophagus (BO). In this context, there has been uncertainty regarding the characterization of adenocarcinomas spanning the area from the lower oesophagus to the distal stomach. Most relevant to this discussion is the distinction, if any, between OAC and intestinal-type GC of the proximal stomach. It is therefore timely to review our current understanding of OAC and intestinal-type GC, integrating advances from cell-of-origin studies and comprehensive genomic alteration analyses, ultimately enabling better insight into the relationship between these two cancers.

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.

Mechanisms of esophageal adenocarcinoma formation and approaches to chemopreventive intervention

The incidence of esophageal adenocarcinoma (EAC), a debilitating and highly lethal malignancy, has risen dramatically over the past 40 years in the United States and other Western countries. To reverse this trend, EAC prevention and early detection efforts by clinicians, academic researchers and endoscope manufacturers have targeted Barrett's esophagus (BE), the widely accepted EAC precursor lesion. Data from surgical, endoscopic and pre-clinical investigations strongly support the malignant potential of BE. For patients with BE, the risk of developing EAC has been estimated at 11- to 125-fold greater than that of the individual at average risk. Nevertheless, screening for BE in symptomatic patients (ie, with symptoms of reflux) and surveillance in patients diagnosed with BE have not had a substantial impact on the incidence, morbidity or mortality of EAC; the overwhelming majority of EAC patients are diagnosed without a pre-operative diagnosis of BE. This article will discuss the current state of the science of esophageal adenocarcinoma prevention, including ideas about carcinogenesis and its underlying genomic and molecular level mechanisms, and suggest strategies for a systems approach to targeted preventive management.

Microanatomy of the cervical and anorectal squamocolumnar junctions: a proposed model for anatomical differences in HPV-related cancer risk

Human papilloma virus (HPV) infection causes cancers and their precursors (high-grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junction cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high-grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n=37) and topography and immunophenotype of anal squamous neoplasms (n=97) were studied. A discrete anal transition zone was composed of multilayered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with-and identical in appearance to-the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, which harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and the cervix: (1) the anal transition zone does not harbor a single monolayer of residual undifferentiated embryonic cells and (2) the dominant tumor immunophenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that, at birth, the embryonic cells in the anal transition zone have already begun to differentiate, presenting a metaplasia that-similar to vaginal and vulvar epithelium-is less prone to HPV-directed carcinogenesis. This in turn underscores the link between cancer risk and a very small and discrete population of vulnerable squamocolumnar junction cells in the cervix.

The Role of Gastroesophageal Reflux and Other Factors during Progression to Esophageal Adenocarcinoma

BACKGROUND

U.S. esophageal adenocarcinoma (EAC) incidence increased over 5-fold between 1975 and 2009. Symptomatic gastroesophageal reflux disease (sGERD) elevates the risk for EAC. However, a simple calculation suggests that changes in sGERD prevalence can explain at most approximately 16% of this trend. Importantly, a mechanistic understanding of the influence of sGERD and other factors (OF) on EAC is lacking.

METHODS

A multiscale model was developed to estimate temporal trends for sGERD and OF, and their mechanistic role during carcinogenesis. Model calibration was to Surveillance, Epidemiology, and End Results (SEER) incidence and age-dependent sGERD data using maximum likelihood and Markov chain Monte Carlo (MCMC) methods.

RESULTS

Among men, 77.8% [95% credibility interval (CI), 64.9%-85.6%] of the incidence trend is attributable to OF, 13.4% (95% CI, 11.4%-17.3%) to sGERD, and 8.8% (95% CI, 4.2%-13.7%) to sGERD-OF interactions. Among women, 32.6% (95% CI, 27.0%-39.9%) of the trend is attributable to OF, 13.6% (95% CI, 12.5%-15.9%) to sGERD, and 47.4% (95% CI, 30.7%-64.6%) to interactions. The predicted trends were compared with historical trends for obesity, smoking, and proton pump inhibitor use. Interestingly, predicted OF cohort trends correlated most highly with median body mass index (BMI) at age 50 (r = 0.988 for men; r = 0.998 for women).

CONCLUSIONS

sGERD and OF mechanistically increase premalignant cell promotion, which increases EAC risk exponentially with exposure duration.

IMPACT

Surveillance should target individuals with long-duration sGERD and OF exposures.

Barrett oesophagus: lessons on its origins from the lesion itself

Barrett oesophagus develops when the lower oesophageal squamous epithelium is replaced with columnar epithelium, which shows both intestinal and gastric differentiation. No consensus has been reached on the origin of Barrett oesophagus. Theories include a direct origin from the oesophageal-stratified squamous epithelium, or by proximal migration of the gastric cardiac epithelium with subsequent intestinalization. Variations of this theory suggest the origin is a distinctive cell at the squamocolumnar junction, the oesophageal gland ducts, or circulating bone-marrow-derived cells. Much of the supporting evidence comes from experimental models and not from studies of Barrett mucosa. In this Perspectives article, we look at the Barrett lesion itself: at its phenotype, its complexity, its clonal architecture and its stem cell organization. We conclude that Barrett glands are unique structures, but share many similarities with gastric glands undergoing the process of intestinal metaplasia. We conclude that current evidence most strongly supports an origin from stem cells in the cardia.

Concise review: dedifferentiation meets cancer development: proof of concept for epigenetic cancer

The technology for generation of induced pluripotent stem cells (iPSCs) has made significant contributions to various scientific fields, and the field of cancer biology is no exception. Although cancer is generally believed to develop through accumulation of multiple genetic mutations, there is increasing evidence that cancer cells also acquire epigenetic abnormalities during development, maintenance, and progression. Because the epigenetic status of somatic cells changes dynamically through reprogramming, iPSC technology can be utilized to actively and globally alter the epigenetic status of differentiated cells. Using this technology, a recent study has revealed that some types of cancer can develop mainly through disruption of the epigenetic status triggered by dedifferentiation. In this paper, we outline the reprograming process and the epigenetic mechanism associated with the maintenance or conversion of cell identity. We then describe several observations suggesting that dedifferentiation can play an important role in cancer development. Finally, we introduce the system responsible for in vivo reprogramming to demonstrate the involvement of dedifferentiation-driven epigenetic disruption in cancer development, and propose that particular types of cancer can develop predominantly through epigenetic alterations.

IL-4 induces columnar-like differentiation of esophageal squamous epithelium through JAK/PI3K pathway: possible role in pathogenesis of Barrett's esophagus

Barrett's esophagus is characterized by a distinct Th2-predominant cytokine profile (IL-4) from in vivo or ex vivo evidence. The detailed role of cytokines in Barrett's esophagus, particularly whether Th2 cytokines are causative factors driving metaplastic processes, remains unknown. In this study, air-liquid interface-cultured human esophageal epithelial cells were stimulated by a Th2 cytokine, IL-4, and Th1 cytokines, TNF-α and IL-1β, continuously for 10 days. Barrier function was determined by transepithelial electrical resistance. Morphological changes were investigated by hematoxylin and eosin staining. Keratin profile (keratin 7, 8, 13, and 14) and squamous differentiation markers (involucrin) were investigated by RT-quantitative PCR, Western blotting, and immunohistochemical staining. Pharmacological inhibitors were used to identify the underlying cellular signaling. We report that IL-4, TNF-α, and IL-1β decrease barrier function, but only IL-4 significantly increases cell layers and changes cell morphology. IL-4 time dependently downregulates the expression levels of the squamous cell markers involucrin and keratin 13 and upregulates the expression levels of the columnar cell markers keratin 7 and 8. Neither TNF-α nor IL-1β shows any effect on these indexes. JAK inhibitor I and PI3K inhibitors significantly block the IL-4-induced changes in the levels of keratin 8 and 13. In conclusion, IL-4 inhibits squamous differentiation program of esophageal epithelial cells and induces differentiation toward columnar cells through the JAK/PI3K pathway. Thus IL-4 may be involved in the early stages of Barrett's esophagus development.

Biomarkers and molecular imaging in gastrointestinal cancers

The best means to improve gastrointestinal cancer survival is screening and treatment of early lesions. In esophageal adenocarcinoma, it is believed that low-grade dysplasia and perhaps even high-risk Barrett's esophagus represent the most attractive targets for achieving a cure. An issue with Barrett's esophagus is that endoscopy alone cannot distinguish Barrett's esophagus from columnar-lined epithelium or from areas of low-grade dysplasia. Much effort, therefore, has been devoted to discover molecular biomarkers of high-risk states and to develop imaging tools for detecting these biomarkers in a manner that could assist real-time in vivo targeting of sites for biopsy. The strategy we have used is to generate stem cell clones from Barrett's esophagus biopsy specimens and to compare their gene expression profiles with patient-matched stem cell clones of the esophageal squamous epithelia and gastric cardia. It is anticipated that by mining the expression data sets of these Barrett's stem cell clones, we will be able to identify unique cell surface markers of the Barrett's stem cells against which cytotoxic antibodies or aptamers can be developed and used to aid the endoscopist in identifying regions of atypia for biopsy, perform a real-time diagnosis, stratify patients during the examination, and, ultimately, direct therapy in a preemptive manner.

Through the glass darkly: intraepithelial neoplasia, top-down differentiation, and the road to ovarian cancer

It is currently hoped that deaths from extra-uterine high-grade serous cancer (HGSC) will be reduced via opportunistic salpingectomy in healthy women. Accumulated data implicate the fimbria as a site of origin and descriptive molecular pathology and experimental evidence strongly support a serous carcinogenic sequence in the Fallopian tube. Both direct and indirect ('surrogate') precursors suggest that the benign tube undergoes important biological changes after menopause, acquiring abnormalities in gene expression that are often shared with malignancy, including PAX2, ALDH1, LEF1, RCN1, RUNX2, beta-catenin, EZH2, and others. However, the tube can be linked to only some HGSCs, recharging arguments that nearby peritoneum/ovarian surface epithelium (POSE) also hosts progenitors to this malignancy. A major sticking point is the difference in immunophenotype between POSE and Müllerian epithelium, essentially requiring mesothelial to Müllerian differentiation prior to or during malignant transformation to HGSC. However, emerging evidence implicates an embryonic or progenitor phenotype in the adult female genital tract with the capacity to differentiate, normally or during neoplastic transformation. Recently, a putative cell of origin for cervical cancer has been identified in the squamo-columnar (SC) junction, projecting a model whereby Krt7+ embryonic progenitors give rise to immunophenotypically distinct progeny under stromal influences via 'top down' differentiation. Similar differentiation can be seen in the endometrium with a parallel in juxtaposed mesothelial and Müllerian differentiation in the ovary. Abrupt mesothelial-Müllerian transitions remain to be proven, but would explain the rapid evolution, short asymptomatic interval, and absence of a defined epithelial starting point in many HGSCs. Resolving this question will require accurately distinguishing progenitor from progeny tumour cells in HGSC and pinpointing where initial transformation and trans-differentiation occur, whether in the tube or POSE. Both will be critical to expectations from prophylactic salpingectomy and future approaches to pelvic serous cancer prevention.

Subsquamous intestinal metaplasia after ablation of Barrett's esophagus: frequency and importance

PURPOSE OF REVIEW

This article reviews reports on the prevalence of subsquamous intestinal metaplasia (SSIM) in patients with Barrett's esophagus, and the implications of SSIM in the neoplastic progression of Barrett's esophagus to esophageal adenocarcinoma.

RECENT FINDINGS

Endoscopic eradication therapy for dysplastic Barrett's esophagus has become an encouraging alternative to esophagectomy or continued endoscopic surveillance. However, the presence of SSIM before and after ablation is concerning because this tissue may have potential for malignant progression, is not visible by conventional endoscopy, and may evade detection by random esophageal biopsy sampling methods. Advances in endoscopic high-resolution three-dimensional optical coherence tomography recently have revealed SSIM in a majority of patients both before and after complete eradication of Barrett's esophagus by radiofrequency ablation. Studies suggest that although cells of Barrett's glands are highly proliferative, the cells of these buried glands are more dormant. Nevertheless, the malignant potential of SSIM cells remains undetermined.

SUMMARY

Novel endoscopic imaging demonstrates that SSIM is present in the majority of patients with Barrett's esophagus, both before and after ablative therapy. Although these subsquamous cells exhibit less proliferative activity than those of typical surface Barrett's glands, the malignant potential of the buried glands, especially when challenged by injurious factors, remains largely unknown. Future methods to detect subsurface dysplasia will be needed.

Identification of lineage-uncommitted, long-lived, label-retaining cells in healthy human esophagus and stomach, and in metaplastic esophagus

BACKGROUND & AIMS

The existence of slowly cycling, adult stem cells has been challenged by the identification of actively cycling cells. We investigated the existence of uncommitted, slowly cycling cells by tracking 5-iodo-2'-deoxyuridine (IdU) label-retaining cells (LRCs) in normal esophagus, Barrett's esophagus (BE), esophageal dysplasia, adenocarcinoma, and healthy stomach tissues from patients.

METHODS

Four patients (3 undergoing esophagectomy, 1 undergoing esophageal endoscopic mucosal resection for dysplasia and an esophagectomy for esophageal adenocarcinoma) received intravenous infusion of IdU (200 mg/m(2) body surface area; maximum dose, 400 mg) over a 30-minute period; the IdU had a circulation half-life of 8 hours. Tissues were collected at 7, 11, 29, and 67 days after infusion, from regions of healthy esophagus, BE, dysplasia, adenocarcinoma, and healthy stomach; they were analyzed by in situ hybridization, flow cytometry, and immunohistochemical analyses.

RESULTS

No LRCs were found in dysplasias or adenocarcinomas, but there were significant numbers of LRCs in the base of glands from BE tissue, in the papillae of the basal layer of the esophageal squamous epithelium, and in the neck/isthmus region of healthy stomach. These cells cycled slowly because IdU was retained for at least 67 days and co-labeling with Ki-67 was infrequent. In glands from BE tissues, most cells did not express defensin-5, Muc-2, or chromogranin A, indicating that they were not lineage committed. Some cells labeled for endocrine markers and IdU at 67 days; these cells represented a small population (<0.1%) of epithelial cells at this time point. The epithelial turnover time of the healthy esophageal mucosa was approximately 11 days (twice that of the intestine).

CONCLUSIONS

LRCs of human esophagus and stomach have many features of stem cells (long lived, slow cycling, uncommitted, and multipotent), and can be found in a recognized stem cell niche. Further analyses of these cells, in healthy and metaplastic epithelia, is required.

Barrett esophagus: what a mouse model can teach us about human disease

The incidence of esophageal adenocarcinoma (EAC) is rapidly rising in the western world and accounts for 2% of all cancer-related deaths. The precursor lesion for EAC is Barrett esophagus (BE), which is strongly associated with gastresophageal reflux disease. A major limitation to the study of EAC has been the absence of tractable and genetically modifiable preclinical models of BE. A mouse model of BE and EAC that resembles human disease could provide novel insights into the origins and molecular pathogenesis of BE. In addition, validated animal models could help stratify BE patients given the limited predictive power of current standard endoscopic measures and clinical assessment. Here, we review the findings from recently developed mouse models of BE and EAC and their impact on clinical decision making, surveillance programs and therapeutic options. The data, taken together, suggest potential origins of BE from the gastric cardia, a role of bile acid and hypergatrinemia for carcinogenesis, a growing importance for columnar-like epithelium and a critical role for Notch signaling.

Structural alterations of the mucosa stroma in the Barrett's esophagus metaplasia-dysplasia-adenocarcinoma sequence

BACKGROUND AND AIM

Accumulating evidence suggests that the extracellular matrix play important roles in intercellular communications and contribute to the development of a number of diseases, including diseases of the gastrointestinal tract. The present study examined the structural characteristics and alterations of the extracellular matrix of the mucosa stroma in the Barrett's esophagus metaplasia-dysplasia-adenocarcinoma sequence.

METHODS

A total of 41 esophageal tissue specimens (15 esophageal adenocarcinoma, 10 Barrett's esophagus intestinal metaplasia, seven dysplasia and nine normal esophagus) were studied. The present study used transmission electron microscopy and computerized quantitative electron-microscopic analysis in order to investigate the characteristics of the extracellular matrix of the mucosa.

RESULTS

The study revealed that marked structural alterations of the mucosa stroma, relating to changes in the distribution and appearance of collagen fibers as well as to changes in numbers of matrix microvesicles, occur in Barrett's esophagus and esophageal adenocarcinoma. It was found that there were 3.1 times more microvesicles in the stroma in Barrett's esophagus than in the stroma of the normal esophagus (P<0.0001) and that there were 5.8 times more microvesicles in esophageal adenocarcinoma than in the normal esophagus (P<0.0001). There were 1.9 times more microvesicles in esophageal adenocarcinoma than in Barrett's esophagus (P=0.0043).

CONCLUSIONS

The study demonstrates distinctive alterations of the mucosa stroma extracellular matrix in the metaplasia-dysplasia-adenocarcinoma sequence. The findings suggest that the redistribution of collagen fibers and increases in numbers of matrix microvesicles may play roles in the formation of specialized intestinal metaplasia and the development of adenocarcinoma.