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

Understanding the malignant potential of gastric metaplasia of the oesophagus and its relevance to Barrett's oesophagus surveillance: individual-level data analysis

OBJECTIVE

Whether gastric metaplasia (GM) of the oesophagus should be considered as Barrett's oesophagus (BO) is controversial. Given concern intestinal metaplasia (IM) may be missed due to sampling, the UK guidelines include GM as a type of BO. Here, we investigated whether the risk of misdiagnosis and the malignant potential of GM warrant its place in the UK surveillance.

DESIGN

We performed a thorough pathology and endoscopy review to follow clinical outcomes in a novel UK cohort of 244 patients, covering 1854 person years of follow-up. We complemented this with a comparative genomic analysis of 160 GM and IM specimens, focused on early molecular hallmarks of BO and oesophageal adenocarcinoma (OAC).

RESULTS

We found that 58 of 77 short-segment (<3 cm) GM (SS-GM) cases (75%) continued to be observed as GM-only across a median of 4.4 years of follow-up. We observed that disease progression in GM-only cases and GM+IM cases (cases with reported GM on some occasions, IM on others) was significantly lower than in the IM-only cases (Kaplan-Meier, p=0.03). Genomic analysis revealed that the mutation burden in GM is significantly lower than in IM (p<0.01). Moreover, GM does not bear the mutational hallmarks of OAC, with an absence of associated signatures and driver gene mutations. Finally, we established that GM found adjacent to OAC is evolutionarily distant from cancer.

CONCLUSION

SS-GM is a distinct entity from SS-IM and the malignant potential of GM is lower than IM. It is questionable whether SS-GM warrants inclusion in BO surveillance.

Low-grade dysplasia in Barrett's esophagus: A problematic diagnosis

Although low-grade dysplasia (LGD) in Barrett's esophagus (BE) is a histopathological diagnosis based on different histological abnormalities, it is still problematic for different reasons. Patients without confirmed diagnosis of LGD undergo unnecessary and intensified follow-up where the risk of progression is low in the majority of cases. In contrast, the presence of confirmed LGD indicates a high risk of progression. In this article we try to address these reasons focusing on re-confirmation of LGD diagnosis, interobserver agreement, and persistent confirmed LGD. The progression risk of LGD to high-grade dysplasia and esophageal adenocarcinoma will also be reviewed.

Global variations in diagnostic guidelines for Barrett's esophagus

Endoscopic diagnosis of gastroesophageal junction and Barrett's esophagus is essential for surveillance and early detection of esophageal adenocarcinoma and esophagogastric junction cancer. Despite its small size, the gastroesophageal junction has many inherent problems, including marked differences in diagnostic methods for Barrett's esophagus in international guidelines. To define Barrett's esophagus, gastroesophageal junction location should be clarified. Although gastric folds and palisade vessels are landmarks for identifying this junction, they are sometimes difficult to observe due to air entry or reflux esophagitis. The possibility of diagnosing a malignancy associated with Barrett's esophagus <1 cm, identified using palisade vessels, should be re-examined. Nontargeted biopsies of Barrett's esophagus are commonly used to detect intestinal metaplasia, dysplasia, and cancer as described in the Seattle protocol. Barrett's esophagus with intestinal metaplasia has a high risk of becoming cancerous. Furthermore, the frequency of cancer in patients with Barrett's esophagus without intestinal metaplasia is high, and the guidelines differ on whether to include the presence of intestinal metaplasia in the diagnosis of Barrett's esophagus. Use of advanced imaging technologies, including narrow-band imaging with magnifying endoscopy and linked color imaging, is reportedly valid for diagnosing Barrett's esophagus. Furthermore, artificial intelligence has facilitated the diagnosis of Barrett's esophagus through its deep learning and image recognition capabilities. However, it is necessary to first use the endoscopic definition of the gastroesophageal junction, which is common in all countries, and then elucidate the characteristics of Barrett's esophagus in each region, for example, length differences in the risk of carcinogenesis with and without intestinal metaplasia.

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.

Evolutionary dynamics in Barrett oesophagus: implications for surveillance, risk stratification and therapy

Cancer development is a dynamic evolutionary process characterized by marked intratumoural heterogeneity at the genetic, epigenetic and phenotypic levels. Barrett oesophagus, the pre-malignant condition to oesophageal adenocarcinoma (EAC), is an exemplary system to longitudinally study the evolution of malignancy. Evidence has emerged of Barrett oesophagus lesions pre-programmed for progression to EAC many years before clinical detection, indicating a considerable window for therapeutic intervention. In this Review, we explore the mechanisms underlying clonal expansion and contraction that establish the Barrett oesophagus clonal mosaicism over time and space and discuss intrinsic genotypic and extrinsic environmental drivers that direct the evolutionary trajectory of Barrett oesophagus towards a malignant phenotype. We propose that understanding and exploiting the evolutionary dynamics of Barrett oesophagus will identify novel therapeutic targets, improve prognostic tools and offer the opportunity for personalized surveillance programmes geared to prevent progression to EAC.

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.

MMP-12 siRNA improves the homeostasis of the small intestine and metabolic dysfunction in high-fat diet feeding-induced obese mice

The changes of small intestinal homeostasis have been recognized to contribute essentially to the obese development. However, the core small intestinal regulator which mediates over-nutrient impacts on the homeostasis of the small intestines remains elusive. Here, we identify the MMP-12 as such a responsive factor in mouse small intestines. Taking advantages of the nano delivery system, we demonstrate that small intestine-specific MMP-12 knockdown alleviates high-fat diet feeding-induced metabolic disorders and improves intestinal homeostasis in mice, including a significant decrease in lipid transportation, bile acid reabsorption, and inflammation. In parallel, the small intestinal integrity is recovered and the gut microbiota composition is reversed towards that under normal diet feeding. Mechanistically, MMP-12, differing from its traditional elastolytic function, acts as a transcriptional factor to activate Fabp4 transcription through epigenetic modification. In translational medicine, clinical applications of our nanosystem and therapeutic interventions targeting MMP-12 will benefit patients with obesity and associated diseases.

Pseudopyloric Metaplasia Is Not Associated With the Development of Gastric Cancer

INTRODUCTION

Corpus atrophic gastritis (CAG) is associated with intestinal metaplasia (IM) and pseudopyloric metaplasia (PPM). Prospective data on corpus mucosa PPM and its link to the development of gastric cancer (GC) are lacking. This study aimed to investigate the relationship between the presence of corpus mucosa PPM at baseline and the development of GC at follow-up in patients with CAG.

METHODS

A longitudinal cohort study was conducted on patients with consecutive CAG adhering to endoscopic-histological surveillance. Patients were stratified for the presence/absence of corpus PPM without concomitant corpus IM at baseline, and the occurrence of gastric neoplastic lesions at the longest available follow-up was assessed.

RESULTS

A total of 292 patients with CAG with a follow-up of 4.2 (3-17) years were included. At baseline, corpus PPM without corpus IM was diagnosed in 62 patients (21.2%). At the follow-up, GC was detected in 5 patients (1.7%) and gastric dysplasia (GD) in 4 patients (1.4%). In all these 9 patients with GC/GD at the follow-up, corpus IM was present at baseline and follow-up. Age <50 years (odds ratio [OR] 2.5), absence of pernicious anemia (OR 4.3), and absence of severe corpus atrophy (OR 2.3) were associated with corpus PPM without corpus IM.

DISCUSSION

At the 4.2-year follow-up, in patients with CAG characterized at baseline with corpus PPM without corpus IM, GC or GD was not observed because these lesions were consistently associated with corpus IM. Corpus PPM without corpus IM was associated with younger age, absence of pernicious anemia, and severe corpus atrophy, suggesting a lower stage of disease progression. Corpus PPM alone seems not to be associated with GC, whose development seems to require the presence of corpus IM as a necessary step.

Neutrophil to lymphocyte ratio and risk of neoplastic progression in patients with Barrett's esophagus

BACKGROUND

Patient's with Barrett's esophagus (BE) are at risk of progression to esophageal adenocarcinoma (EAC). Neutrophil to lymphocyte ratio (NLR) was found to be a predictor of poor prognosis in patients with EAC; however, its performance in premalignant esophageal lesions is vague. We aimed to evaluate the utility of NLR as a predictor of histologic progression in patients with BE. METHODS : A prospective cohort of patients with proven BE in a tertiary referral center was retrospectively analyzed. All biopsies were reviewed by an expert gastrointestinal pathologist. The discriminatory capacity of NLR was evaluated by area under the receiver operating characteristic (AUC) curve analysis and Cox regression analysis.

RESULTS

324 patients (mean age 62.3 years, 241 [74.4 %] males) were included in the final analysis. Overall, 13 patients demonstrated histologic progression to neoplasia over a mean follow-up of 3.7 years (progression risk 1.0 % per year). The AUC of NLR for progression to high grade dysplasia (HGD) or EAC was 0.88 (95 % confidence interval [CI] 0.83 - 0.96), and baseline NLR was associated with a 3-fold increase of progression to HGD and EAC during follow-up (hazard ratio [HR] 3.2, 95 %CI 1.5 - 5.8; P < 0.001). Notably, in a subgroup analysis of patients with nondysplastic BE (NDBE) at presentation, NLR was also a risk factor for histologic progression (HR 2.4, 95 %CI 1.7 - 3.4; P < 0.001).

CONCLUSION

NLR predicted histologic progression in patients with BE. Patients with NDBE and NLR above 2.4 can be considered for specific surveillance programs with shorter intervals between sessions.

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.

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.

Columnar metaplasia and Barrett’s esophagus: morphological heterogeneity and immunohistochemical phenotype

Barrett’s esophagus (BE) is a pathologically confirmed intestinal metaplasia (CM) of the distal esophagus. BE is recognized as a potential complication of gastroesophageal reflux disease (GERD) and a premalignant condition with a high risk of neoplastic progression. The aim of this study was to compare the morphology of biopsied BE segments and CM segments extending < 1 cm and > 1 cm above the gastroesophageal junction (GEJ), as well as to perform the immunohistochemical analysis of biopsies with BE and CM > 1 cm above GEJ with or without dysplasia. The study recruited 92 patients with GERD: 42 patients with BE, 24 patients with CM > 1 cm above GEJ (С0М1.5–С13M14) and 26 patients with CM < 1 cm above GEJ (С0М0.3–0.8). Comparative analysis of tissue morphology revealed an association between the reactive changes in the epithelium and the severity of esophagitis in all groups. Reactive changes were detected significantly more often in BE segments than in CM segments > 1 cm (Mann-Whitney U, p < 0.05). Eight patients with BE (19.05%) were found to have low-grade dysplasia. One patient with CM > 1 cm above GEJ (4.2%) had high-grade dysplasia with cardiac-type metaplasia and immunohistochemical features of submorphological enteralization. Immunohistochemical testing for the intestinal and gastric markers of cell differentiation revealed the signs of submorphological enteralisation in all esophageal specimens with cardiac and fundic type metaplasia and in the specimens with BE in the areas lacking goblet cells.

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.

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.

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.

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.

Detection of Mutations in Barrett's Esophagus Before Progression to High-Grade Dysplasia or Adenocarcinoma

BACKGROUND & AIMS

Barrett's esophagus (BE) is the greatest risk factor for esophageal adenocarcinoma (EAC), but only a small proportion of patients with BE develop cancer. Biomarkers might be able to identify patients at highest risk of progression. We investigated genomic differences in surveillance biopsies collected from patients whose BE subsequently progressed compared to patients whose disease did not progress.

METHODS

We performed a retrospective case-control study of 24 patients with BE that progressed to high-grade dysplasia (HGD, n = 14) or EAC (n = 10). The control group (n = 73, called non-progressors) comprised patients with BE and at least 5 years of total endoscopic biopsy surveillance without progression to HGD or EAC. From each patient, we selected a single tissue sample obtained more than 1 year before progression (cases) or more than 2 years before the end of follow-up (controls). Pathogenic mutations, gene copy numbers, and ploidy were compared between samples from progressors and non-progressors.

RESULTS

TP53 mutations were detected in 46% of samples from progressors and 5% of non-progressors. In this case-control sample set, TP53 mutations in BE tissues increased the adjusted risk of progression 13.8-fold (95% confidence interval, 3.2-61.0) (P < .001). We did not observe significant differences in ploidy or copy-number profile between groups. We identified 147 pathogenic mutations in 57 distinct genes-the average number of pathogenic mutations was higher in samples from progressors (n = 2.5) than non-progressors (n = 1.2) (P < .001). TP53 and other somatic mutations were recurrently detected in samples with limited copy-number changes (aneuploidy).

CONCLUSIONS

In genomic analyses of BE tissues from patients with or without later progression to HGD or EAC, we found significantly higher numbers of TP53 mutations in BE from patients with subsequent progression. These mutations were frequently detected before the onset of dysplasia or substantial changes in copy number.

The evolving role of endoscopy in the diagnosis of premalignant gastric lesions

Gastric adenocarcinoma is a disease that is often detected late, at a stage when curative treatment is unachievable. This must be addressed through changes in our approach to the identification of patients at increased risk by improving the detection and risk assessment of premalignant changes in the stomach, including chronic atrophic gastritis and intestinal metaplasia. Current guidelines recommend utilising random biopsies in a pathology-led approach in order to stage the extent and severity of gastritis and intestinal metaplasia. This random method is poorly reproducible and prone to sampling error and fails to acknowledge recent advances in our understanding of the progression to gastric cancer as a non-linear, branching evolutionary model. Data suggest that recent advances in endoscopic imaging modalities, such as narrow band imaging, can achieve a high degree of accuracy in the stomach for the diagnosis of these premalignant changes. In this review, we outline recent data to support a paradigm shift towards an endoscopy-led approach to diagnosis and staging of premalignant changes in the stomach. High-quality endoscopic interrogation of the chronically inflamed stomach mucosa, supported by targeted biopsies, will lead to more accurate risk assessment, with reduced rates of under or missed diagnoses.

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.

Clonality analysis of synchronous gastro-oesophageal junction carcinoma and distal gastric cancer by whole-exome sequencing

Gastro-oesophageal junction (GEJ) carcinoma and distal gastric cancer (GC) have distinct epidemiology and clinical features and their relationship is uncertain. Synchronous multiple gastric cancers located mostly at proximal and distal sites provide rare specimens for investigating the comprehensive genomic relationships among these cancers in the context of identical genetic circumstances. Formalin-fixed, paraffin-embedded (FFPE) samples from 12 patients with synchronous GEJ carcinoma and distal GC were collected in this study. Whole-exome sequencing (WES) was performed using normal tissues as a control. Mutational profiling, clonality analysis, a detailed clinico-pathological review, determination of MSI status, EBER in situ hybridization (ISH), and programmed cell death 1 (PD-1)/programmed death-ligand 1 (PD-L1) immunohistochemical staining were performed. Twenty-three of the 24 samples were microsatellite-stable (MSS). Subclonal analysis revealed that nine pairs of GEJ and distal GC tumours in neoadjuvant chemotherapy naïve patients developed independently from different origins. Two patients who received neoadjuvant chemotherapy shared clonal origins with highly similar somatic alterations. The remaining one patient who shared a rare mutation died within 6.2 months at the N3 stage. However, the enriched pathway identified from the overall mutation spectra in distal GC and GEJ carcinoma showed the close relationship of these cancers. Thus, although these cancers may have similar characteristics, histopathological and genetic profiling from single tumour specimens may still underestimate the mutational burden and somatic heterogeneity of multiple GCs. In addition, this series of cases also showed a PD-L1 expression rate of 58.3% and 66.7% in distal GC and GEJ carcinoma, respectively, with all the cases expressing PD-1. This result suggests the potential benefit of immunotherapeutic treatments. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.

The Origins of Gastric Cancer From Gastric Stem Cells: Lessons From Mouse Models

The cellular origin of digestive cancers has been a long-standing question in the cancer field. Mouse models have identified long-lived stem cells in most organ systems, including the luminal gastrointestinal tract, and numerous studies have pointed to tissue resident stem cells as the main cellular origin of cancer. During gastric carcinogenesis, chronic inflammation induces genetic and epigenetic alterations in long-lived stem cells, along with expansion of stem cell niches, eventually leading to invasive cancer. The gastric corpus and antrum have distinct stem cells and stem cell niches, suggesting differential regulation of cancer initiation at the 2 sites. In this short review, we discuss recent experimental models and human studies, which provide important insights into the pathogenesis of gastric cancer.

Goblet Cell Ratio in Combination with Differentiation and Stem Cell Markers in Barrett Esophagus Allow Distinction of Patients with and without Esophageal Adenocarcinoma

The increasing incidence of esophageal adenocarcinoma (EAC) is mirrored by the increasing prevalence of Barrett esophagus, a precursor lesion resulting in a large number of individuals "at risk" for this lethal malignancy. Among patients with Barrett esophagus, only about 0.3% annually will develop EAC. Because large numbers of patients are followed in endoscopic surveillance, there is a need for risk prediction among a growing population of patients with Barrett esophagus. We identified four potential biomarkers from an inflammation (IL1β)-dependent mouse model of Barrett esophagus and tested them in 189 patients with Barrett esophagus with and without high-grade dysplasia (HGD)/early cancer (T1). The primary goal was to distinguish patients with Barrett esophagus with no evidence of dysplasia from those with dysplasia. Increasing stem cell marker LGR5 and niche cell marker DCLK1 and decreasing differentiation marker (secretory mucus cells, TFF2⁺ cells) correlated with elevated tumor score in the mouse. Having outlined the origin of those markers in the Barrett esophagus mouse model, we showed the applicability for human Barrett esophagus. We compared 94 patients with nondysplastic Barrett esophagus tissue with 95 patients with Barrett esophagus and HGD or early cancer. Low levels of TFF2 (AUC 87.2%) provided the best discrimination between nondysplastic Barrett esophagus and Barrett esophagus with cancer, followed by high levels of DCLK1 (AUC 83.4%), low goblet cell ratio (AUC 79.4%), and high LGR5 (AUC 71.4%). The goblet cell ratio, rather than the presence of goblet cells per se, was found to be an important discriminator. These findings may be useful in developing future risk prediction models for patients with Barrett esophagus and ultimately to improve EAC surveillance. Cancer Prev Res; 10(1); 55-66. ©2016 AACR.

New paradigms in clonal evolution: punctuated equilibrium in cancer

Evolutionary theories are themselves subject to evolution. Clonal evolution - the model that describes the initiation and progression of cancer - is entering a period of profound change, brought about largely by technological developments in genome analysis. A flurry of recent publications, using modern mathematical and bioinformatics techniques, have revealed both punctuated and neutral evolution phenomena that are poorly explained by the conventional graduated perspectives. In this review, we propose that a hybrid model, inspired by the evolutionary model of punctuated equilibrium, could better explain these recent observations. We also discuss the conceptual changes and clinical implications of variable evolutionary tempos. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.

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.

The Complex, Clonal, and Controversial Nature of Barrett's Esophagus

Barrett's esophagus (BO) is a preneoplastic condition described as the replacement of the stratified squamous epithelium of the distal esophagus with one that histologically presents as a diverse mixture of metaplastic glands resembling gastric or intestinal-type columnar epithelium. The clonal origins of BO are still unclear. More recently, we have begun to investigate the relationship between the various metaplastic gland phenotypes observed in BO, how they evolve, and the cancer risk they bestow. Studies have revealed that glands along the BO segment are clonal units containing a single stem cell clone that can give rise to all the differentiated epithelial cell types in glands. Clonal lineage tracing analysis has revealed that Barrett's glands are capable of bifurcation and this facilitates clonal expansion and competition. In fact, BO in some patients appears to consist of multiple, independently initiated clones that compete with each other for space and possibly resources. This chapter discusses the concepts of clonal competition and expansion in BO and sets out to query what we know about the role of gland diversity and phenotypic evolution within this complex columnar metaplasia.