New strategies in Barrett's esophagus: integrating clonal evolutionary theory with clinical management

BRCA mutations and gastrointestinal cancers: When to expect the unexpected?

BRCA1/2 pathogenic variants are widely known as major risk factors mainly for breast and ovarian cancer, while their role in gastrointestinal (GI) malignancies such as colorectal cancer (CRC), gastric cancer and oesophageal cancer (OeC) is still not well established. The main objective of this review is to summarise the available evidence on this matter. The studies included in the review were selected from PubMed/GoogleScholar/ScienceDirect databases to identify published articles where BRCA1/2 pathogenic variants were assessed either as a risk factor or a prognostic/predictive factor in these malignancies. Our review suggests that BRCA1/2 might have a role as a risk factor for colorectal, gastric and OeC, albeit with differences among these diseases: In particular BRCA1 seems to be much more frequently mutated in CRC whereas BRCA2 appears to be much more closely associated with gastric and OeC. Early-onset cancer seems to be also associated with BRCA1/2 mutations and a few studies suggest a positive prognostic role of these mutations. The assessment of a potentially predictive role of these mutations is hampered by the fact that most patients with these diseases have been treated with platinum compounds, where it is expected that a higher probability of response should be seen. A few clinical trials focused on poly (ADP-ribose) polymerase inhibitors use in GI cancers are currently ongoing.

European Laryngological Society position paper on laryngeal dysplasia Part I: aetiology and pathological classification

Purpose of review

To give an overview of the current knowledge regarding the aetiology, epidemiology, and classification of laryngeal dysplasia (LD) and to highlight the contributions of recent literature. As most cases of dysplasia occur at the glottic level and data on diagnosis and management are almost exclusively from this location, laryngeal dysplasia in this position paper is taken to be synonymous with dysplasia of the vocal folds.

Summary

LD has long been recognized as a precursor lesion to laryngeal squamous cell carcinoma (SCC). Tobacco and alcohol consumption are the two single most important etiological factors for the development of LD. There is currently insufficient evidence to support a role of reflux. Although varying levels of human papillomavirus have been identified in LD, its causal role is still uncertain, and there are data suggesting that it may be limited. Dysplasia has a varying presentation including leukoplakia, erythroleukoplakia, mucosal reddening or thickening with exophytic, “tumor-like” alterations. About 50% of leukoplakic lesions will contain some form of dysplasia. It has become clear that the traditionally accepted molecular pathways to cancer, involving accumulated mutations in a specific order, do not apply to LD. Although the molecular nature of the progression of LD to SCC is still unclear, it can be concluded that the risk of malignant transformation does rise with increasing grade of dysplasia, but not predictably so. Consequently, grading systems are inherently troubled by the weak correlation between the degree of the dysplasia and the risk of malignant transformation. The best data on LD grading and outcomes come from the Ljubljana group, forming the basis for the World Health Organization classification published in 2017.

Molecular Evolution of Metaplasia to Adenocarcinoma in the Esophagus

Esophageal adenocarcinoma (EAC) develops from Barrett's esophagus (BE), a condition where the normal squamous epithelia is replaced by specialized intestinal metaplasia in response to chronic gastroesophageal acid reflux. In a minority of individuals, BE can progress to low- and high-grade dysplasia and eventually to intra-mucosal and then invasive carcinoma. BE provides researchers with a unique model to characterize the process by which a carcinoma arises from its precursor lesion. Molecular studies of BE have demonstrated that it is not simply a metaplastic tissue, but rather it harbors frequent alterations that are also present in dysplastic BE and in EAC. Both BE and EAC are characterized by loss of heterozygosity, aneuploidy, specific genetic mutations, and clonal diversity. Epigenetic abnormalities, primary alterations in DNA methylation, are also frequently seen in BE and EAC. Candidate gene and array-based approaches have demonstrated that numerous tumor suppressor genes exhibit aberrant promoter methylation, and some of these altered genes are associated with the neoplastic progression of BE. It has also been shown that the BE and EAC epigenomes are characterized by hypomethylation of intragenic and non-coding regions Recent studies have also provided new insight into the evolutionary forces underlying the molecular alterations seen in BE and EAC and into the molecular pathogenesis of EAC.

Clear: Composition of Likelihoods for Evolve and Resequence Experiments

The advent of next generation sequencing technologies has made whole-genome and whole-population sampling possible, even for eukaryotes with large genomes. With this development, experimental evolution studies can be designed to observe molecular evolution "in action" via evolve-and-resequence (E&R) experiments. Among other applications, E&R studies can be used to locate the genes and variants responsible for genetic adaptation. Most existing literature on time-series data analysis often assumes large population size, accurate allele frequency estimates, or wide time spans. These assumptions do not hold in many E&R studies. In this article, we propose a method-composition of likelihoods for evolve-and-resequence experiments (Clear)-to identify signatures of selection in small population E&R experiments. Clear takes whole-genome sequences of pools of individuals as input, and properly addresses heterogeneous ascertainment bias resulting from uneven coverage. Clear also provides unbiased estimates of model parameters, including population size, selection strength, and dominance, while being computationally efficient. Extensive simulations show that Clear achieves higher power in detecting and localizing selection over a wide range of parameters, and is robust to variation of coverage. We applied the Clear statistic to multiple E&R experiments, including data from a study of adaptation of Drosophila melanogaster to alternating temperatures and a study of outcrossing yeast populations, and identified multiple regions under selection with genome-wide significance.

Genomics, Endoscopy, and Control of Gastroesophageal Cancers: A Perspective

In The Cancer Genome Atlas the goals were to define how to treat advanced cancers with targeted therapy. However, the challenges facing cancer interception for early detection and prevention include length bias in which current screening and surveillance approaches frequently miss rapidly progressing cancers that then present at advanced stages in the clinic with symptoms (underdiagnosis). In contrast, many early detection strategies detect benign conditions that may never progress to cancer during a lifetime, and the patient dies of unrelated causes (overdiagnosis). This challenge to cancer interception is believed to be due to the speed at which the neoplasm evolves, called length bias sampling; rapidly progressing cancers are missed by current early detection strategies. In contrast, slowly or non-progressing cancers or their precursors are selectively detected. This has led to the concept of cancer interception, which can be defined as active interception of a biological process that drives cancer development before the patient presents in the clinic with an advanced, symptomatic cancer. The solutions needed to advance strategies for cancer interception require assessing the rate at which the cancer evolves over time and space. This is an essential challenge that needs to be addressed by robust study designs including normal and non-progressing controls when known to be appropriate.

Bulk Genotyping of Biopsies Can Create Spurious Evidence for Hetereogeneity in Mutation Content

When multiple samples are taken from the neoplastic tissues of a single patient, it is natural to compare their mutation content. This is often done by bulk genotyping of whole biopsies, but the chance that a mutation will be detected in bulk genotyping depends on its local frequency in the sample. When the underlying mutation count per cell is equal, homogenous biopsies will have more high-frequency mutations, and thus more detectable mutations, than heterogeneous ones. Using simulations, we show that bulk genotyping of data simulated under a neutral model of somatic evolution generates strong spurious evidence for non-neutrality, because the pattern of tissue growth systematically generates differences in biopsy heterogeneity. Any experiment which compares mutation content across bulk-genotyped biopsies may therefore suggest mutation rate or selection intensity variation even when these forces are absent. We discuss computational and experimental approaches for resolving this problem.

Researchers who take multiple samples from a cancer or pre-cancer tissue and find that some samples show far more mutations than others are likely to conclude that the high-mutation samples reflect cells with an abnormal mutation or growth rate. We considered the common practice of testing a bulk sample for mutations, which finds only mutations that are common within the sample. Our computer simulations show that even when all cells have identical mutation and growth rates, testing bulk samples frequently leads to spurious detection of rate differences. This can lead to false conclusions about the causes and progress of cancer. We discuss possible solutions involving either genetic testing of single cells or the use of computer algorithms to detect rare mutations within a sample.

A Computational Modeling Approach for Deriving Biomarkers to Predict Cancer Risk in Premalignant Disease

The lack of effective biomarkers for predicting cancer risk in premalignant disease is a major clinical problem. There is a near-limitless list of candidate biomarkers, and it remains unclear how best to sample the tissue in space and time. Practical constraints mean that only a few of these candidate biomarker strategies can be evaluated empirically, and there is no framework to determine which of the plethora of possibilities is the most promising. Here, we have sought to solve this problem by developing a theoretical platform for in silico biomarker development. We construct a simple computational model of carcinogenesis in premalignant disease and use the model to evaluate an extensive list of tissue sampling strategies and different molecular measures of these samples. Our model predicts that (i) taking more biopsies improves prognostication, but with diminishing returns for each additional biopsy; (ii) longitudinally collected biopsies provide slightly more prognostic information than a single biopsy collected at the latest possible time point; (iii) measurements of clonal diversity are more prognostic than measurements of the presence or absence of a particular abnormality and are particularly robust to confounding by tissue sampling; and (iv) the spatial pattern of clonal expansions is a particularly prognostic measure. This study demonstrates how the use of a mechanistic framework provided by computational modeling can diminish empirical constraints on biomarker development.

Mutational spectrum of Barrett's stem cells suggests paths to initiation of a precancerous lesion

The precancerous lesion known as Barrett's oesophagus can evolve to oesophageal adenocarcinoma in decades-long processes of regenerative growth. Here we report the isolation and propagation of distinct, patient-matched stem cells of Barrett's, gastric and oesophageal epithelia that yield divergent tumour types following in vitro transformation and xenografting. Genomic analyses reveal a broad mutational spectrum unique to Barrett's stem cells that likely reflects their risk for oncogenesis. Remarkably, 25% of cases show no cancer-related genomic changes, suggesting that Barrett's initiates without driver mutations. Most cases, however, sustain patterns of deletions almost identical to adenocarcinoma though tumour-associated gene amplifications were absent. Notably, those suspected of low-grade dysplasia have p53 mutations or undergo amplifications of proto-oncogenes and receptor tyrosine kinases, implicating these events in lethal transitions. Our findings suggest paths for the initiation and progression of Barrett's and define a discrete stem cell underlying its regenerative growth whose eradication could prevent oesophageal adenocarcinoma.

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.

Genetic Insights in Barrett's Esophagus and Esophageal Adenocarcinoma

Beginning in the 1980s, an alarming rise in the incidence of esophageal adenocarcinoma (EA) led to screening of patients with reflux to detect Barrett's esophagus (BE) and surveillance of BE to detect early EA. This strategy, based on linear progression disease models, resulted in selective detection of BE that does not progress to EA over a lifetime (overdiagnosis) and missed BE that rapidly progresses to EA (underdiagnosis). Here we review the historical thought processes that resulted in this undesired outcome and the transformation in our understanding of genetic and evolutionary principles governing neoplastic progression that has come from application of modern genomic technologies to cancers and their precursors. This new synthesis provides improved strategies for prevention and early detection of EA by addressing the environmental and mutational processes that can determine "windows of opportunity" in time to detect rapidly progressing BE and distinguish it from slowly or nonprogressing BE.

High Goblet Cell Count Is Inversely Associated with Ploidy Abnormalities and Risk of Adenocarcinoma in Barrett's Esophagus

Purpose

Goblet cells may represent a potentially successful adaptive response to acid and bile by producing a thick mucous barrier that protects against cancer development in Barrett's esophagus (BE). The aim of this study was to determine the relationship between goblet cells (GC) and risk of progression to adenocarcinoma, and DNA content flow cytometric abnormalities, in BE patients.

Experimental Design

Baseline mucosal biopsies (N=2988) from 213 patients, 32 of whom developed cancer during the follow up period, enrolled in a prospective dynamic cohort of BE patients were scored in a blinded fashion, for the total number (#) of GC, mean # of GC/crypt (GC density), # of crypts with ≥ 1 GC, and the proportion of crypts with ≥1 GC, in both dysplastic and non-dysplastic epithelium separately. The relationship between these four GC parameters and DNA content flow cytometric abnormalities and adenocarcinoma outcome was compared, after adjustment for age, gender, and BE segment length.

Results

High GC parameters were inversely associated with DNA content flow cytometric abnormalities, such as aneuploidy, ploidy >2.7N, and an elevated 4N fraction > 6%, and with risk of adenocarcinoma. However, a Kaplan-Meier analysis showed that the total # of GC and the total # crypts with ≥1 GC were the only significant GC parameters (p<0.001 and 0.003, respectively).

Conclusions

The results of this study show, for the first time, an inverse relationship between high GC counts and flow cytometric abnormalities and risk of adenocarcinoma in BE. Further studies are needed to determine if GC depleted foci within esophageal columnar mucosa are more prone to neoplastic progression or whether loss of GC occurs secondary to underlying genetic abnormalities.

Assessment of mutational load in biopsy tissue provides additional information about genomic instability to histological classifications of Barrett's esophagus

PURPOSE

Progression of Barrett's esophagus (BE) to esophageal adenocarcinoma (EAC) is associated with accumulated genomic instability. Current risk stratification of BE for EAC relies on histological classification and grade of dysplasia. However, histology alone cannot assess the risk of patients with inconsistent or non-dysplastic BE histology. We, therefore, examined the presence and extent of genomic instability in advanced and less advanced BE histology using mutational load (ML).

METHODS

ML summarized the presence and clonality of loss of heterozygosity (LOH) mutations and the emergence of new alleles, manifested as microsatellite instability (MSI) mutations, in ten genomic loci around tumor suppressor genes associated with EAC. The ML of 877 microdissected targets from BE biopsies was correlated to their histology. Histological targets were categorized into three levels: no ML, low ML, and high ML.

RESULTS

Increasing ML correlated with increasingly severe histology. By contrast, proportions of targets that lacked mutations decreased with increasingly severe histology. A portion of targets with non-dysplastic and low-grade histology shared a similar ML as those with higher risk and EAC disease. The addition of MSI characterization to ML helped to differentiate the ML between advanced and less advanced histology.

CONCLUSIONS

Given that EAC is associated with accumulated genomic instability, high ML in less severe histology may identify BE disease at greater risk of progression to EAC. ML may help to better manage BE in early histological stages and when histology alone provides insufficient information.

The Barrett's Gland in Phenotype Space

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

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.

Molecular epidemiology of and genetic susceptibility to esophageal cancer

The following, from the 12th OESO World Conference: Cancers of the Esophagus, includes commentaries on clonal evolution in Barrett's carcinogenesis; biomarkers for early detection of esophageal cancer; the role of the methylguanine methyl transferase biomarker in the management of adenocarcinoma; and the discovery of high-risk genes in families.

Hereditary Factors in Esophageal Adenocarcinoma

BACKGROUND

The vast majority of Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC) cases are sporadic and caused by somatic mutations. However, over the last decades several families have been identified with clustering of EAC. Here, we review data from the published literature in order to address the current knowledge on familial EAC.

SUMMARY

Although familial EAC comprises a relatively small group of patients, it is a clinically relevant category due to the poor prognosis of this type of cancer. Efforts should be made to identify specific genetic risk factors for familial EAC to enable identification of relatives at risk, since endoscopic surveillance can diagnose preneoplastic or early neoplastic lesions leading to early treatment, with improved outcome.

KEY MESSAGE

Although familial EAC comprises a relatively small group of patients, this is a clinically relevant category due to the poor prognosis. Efforts should be made to identify specific genetic risk factors for familial EAC in order to facilitate the identification of other family members with a predisposition for this type of cancer.

PRACTICAL IMPLICATIONS

Approximately 7% of BE and EAC cases are considered familial. Age at diagnosis is generally lower for patients with familial EAC as compared to sporadic cases, while other known risk factors for EAC, such as male gender and Caucasian ethnicity, do not differ between the two groups. In several described families with clustering of EAC the pattern of inheritance seems to be consistent with a rare autosomal dominant genetic trait. However, some association has been found with (attenuated) familial adenomatous polyposis, mismatch repair deficiency and recently with the genes MSR1, ASCC1 and CTHRC1. Nevertheless, no specific genetic predisposition has yet been identified.

Global changes in gene expression of Barrett's esophagus compared to normal squamous esophagus and gastric cardia tissues

BACKGROUND

Barrett's esophagus (BE) is a metaplastic precursor lesion of esophageal adenocarcinoma (EA), the most rapidly increasing cancer in western societies. While the prevalence of BE is increasing, the vast majority of EA occurs in patients with undiagnosed BE. Thus, we sought to identify genes that are altered in BE compared to the normal mucosa of the esophagus, and which may be potential biomarkers for the development or diagnosis of BE.

DESIGN

We performed gene expression analysis using HG-U133A Affymetrix chips on fresh frozen tissue samples of Barrett's metaplasia and matched normal mucosa from squamous esophagus (NE) and gastric cardia (NC) in 40 BE patients.

RESULTS

Using a cut off of 2-fold and P<1.12E-06 (0.05 with Bonferroni correction), we identified 1324 differentially-expressed genes comparing BE vs NE and 649 differentially-expressed genes comparing BE vs NC. Except for individual genes such as the SOXs and PROM1 that were dysregulated only in BE vs NE, we found a subset of genes (n = 205) whose expression was significantly altered in both BE vs NE and BE vs NC. These genes were overrepresented in different pathways, including TGF-β and Notch.

CONCLUSION

Our findings provide additional data on the global transcriptome in BE tissues compared to matched NE and NC tissues which should promote further understanding of the functions and regulatory mechanisms of genes involved in BE development, as well as insight into novel genes that may be useful as potential biomarkers for the diagnosis of BE in the future.

Identifying signatures of selection in genetic time series

Both genetic drift and natural selection cause the frequencies of alleles in a population to vary over time. Discriminating between these two evolutionary forces, based on a time series of samples from a population, remains an outstanding problem with increasing relevance to modern data sets. Even in the idealized situation when the sampled locus is independent of all other loci, this problem is difficult to solve, especially when the size of the population from which the samples are drawn is unknown. A standard χ(2)-based likelihood-ratio test was previously proposed to address this problem. Here we show that the χ(2)-test of selection substantially underestimates the probability of type I error, leading to more false positives than indicated by its P-value, especially at stringent P-values. We introduce two methods to correct this bias. The empirical likelihood-ratio test (ELRT) rejects neutrality when the likelihood-ratio statistic falls in the tail of the empirical distribution obtained under the most likely neutral population size. The frequency increment test (FIT) rejects neutrality if the distribution of normalized allele-frequency increments exhibits a mean that deviates significantly from zero. We characterize the statistical power of these two tests for selection, and we apply them to three experimental data sets. We demonstrate that both ELRT and FIT have power to detect selection in practical parameter regimes, such as those encountered in microbial evolution experiments. Our analysis applies to a single diallelic locus, assumed independent of all other loci, which is most relevant to full-genome selection scans in sexual organisms, and also to evolution experiments in asexual organisms as long as clonal interference is weak. Different techniques will be required to detect selection in time series of cosegregating linked loci.

Single-cell analysis reveals early manifestation of cancerous phenotype in pre-malignant esophageal cells

Cellular heterogeneity plays a pivotal role in a variety of functional processes in vivo including carcinogenesis. However, our knowledge about cell-to-cell diversity and how differences in individual cells manifest in alterations at the population level remains very limited mainly due to the lack of appropriate tools enabling studies at the single-cell level. We present a study on changes in cellular heterogeneity in the context of pre-malignant progression in response to hypoxic stress. Utilizing pre-malignant progression of Barrett's esophagus (BE) as a disease model system we studied molecular mechanisms underlying the progression from metaplastic to dysplastic (pre-cancerous) stage. We used newly developed methods enabling measurements of cell-to-cell differences in copy numbers of mitochondrial DNA, expression levels of a set of mitochondrial and nuclear genes involved in hypoxia response pathways, and mitochondrial membrane potential. In contrast to bulk cell studies reported earlier, our study shows significant differences between metaplastic and dysplastic BE cells in both average values and single-cell parameter distributions of mtDNA copy numbers, mitochondrial function, and mRNA expression levels of studied genes. Based on single-cell data analysis, we propose that mitochondria may be one of the key factors in pre-malignant progression in BE.

Molecular markers for Barrett's esophagus and its progression to cancer

PURPOSE OF REVIEW

There is a clinical need for biomarkers that can improve diagnostic accuracy and risk stratification of esophageal lesions. Here we review the current literature and highlight the most important, recent advancements in biomarkers as a supplement to histopathology for management of patients with Barrett's esophagus.

RECENT FINDINGS

A prospective cohort study in Northern Ireland shows that a small panel of biomarkers (low-grade dysplasia, abnormal DNA ploidy and Aspergillus oryzae lectin) can identify patients at high risk for developing high-grade dysplasia or cancer. Recent research in molecular imaging shows promise for molecular probes in endoscopy, using fluorescently labeled peptides or lectins to identify dysplastic areas of Barrett's epithelium. Based on the current literature, p53 immunostaining is starting to be adopted by some centers as an adjunct to histopathology diagnosis for dysplasia.

SUMMARY

The evidence base for the use of biomarkers is increasing and it appears that panels may have superior diagnostic and predictive power over single, candidate biomarkers. Prior to clinical implementation, biomarkers must overcome significant barriers including the need for large-scale prospective validation trials, and the limited ability of clinical laboratories to process and analyze complex biomarker assays.

NSAIDs modulate clonal evolution in Barrett's esophagus

Cancer is considered an outcome of decades-long clonal evolution fueled by acquisition of somatic genomic abnormalities (SGAs). Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce cancer risk, including risk of progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA). However, the cancer chemopreventive mechanisms of NSAIDs are not fully understood. We hypothesized that NSAIDs modulate clonal evolution by reducing SGA acquisition rate. We evaluated thirteen individuals with BE. Eleven had not used NSAIDs for 6.2±3.5 (mean±standard deviation) years and then began using NSAIDs for 5.6±2.7 years, whereas two had used NSAIDs for 3.3±1.4 years and then discontinued use for 7.9±0.7 years. 161 BE biopsies, collected at 5–8 time points over 6.4–19 years, were analyzed using 1Million-SNP arrays to detect SGAs. Even in the earliest biopsies there were many SGAs (284±246 in 10/13 and 1442±560 in 3/13 individuals) and in most individuals the number of SGAs changed little over time, with both increases and decreases in SGAs detected. The estimated SGA rate was 7.8 per genome per year (95% support interval [SI], 7.1–8.6) off-NSAIDs and 0.6 (95% SI 0.3–1.5) on-NSAIDs. Twelve individuals did not progress to EA. In ten we detected 279±86 SGAs affecting 53±30 Mb of the genome per biopsy per time point and in two we detected 1,463±375 SGAs affecting 180±100 Mb. In one individual who progressed to EA we detected a clone having 2,291±78 SGAs affecting 588±18 Mb of the genome at three time points in the last three of 11.4 years of follow-up. NSAIDs were associated with reduced rate of acquisition of SGAs in eleven of thirteen individuals. Barrett's cells maintained relative equilibrium level of SGAs over time with occasional punctuations by expansion of clones having massive amount of SGAs.

Cancer is a disease that develops over decades as result of accumulation of abnormalities in the genomes of otherwise normal cells. Cells in tumors compete for space and resources. Those cells able to survive the Darwinian struggle for existence within tissues progressively evolve uncontrolled growth and in some cases this results in cancer. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) reduce death rate from multiple types of cancer by about 20%. However, the mechanisms by which NSAIDs act to prevent cancer are not fully understood. By examining thirteen individuals with Barrett's esophagus over time, we showed that the rate of accumulation of genomic abnormalities decreased when most individuals started taking NSAIDs. We also observed that, surprisingly, the number of abnormalities in the Barrett's tissues did not increase much over decades. However, in one individual who progressed to esophageal cancer, we observed massive genomic abnormalities affecting 19% of the genome. These findings suggest that NSAIDs may prevent cancer by reducing the accumulation of genomic abnormalities over time and that detection of stable versus unstable genomes may be used in the clinic to help manage treatment options in Barrett's esophagus.

DNA methylation as an adjunct to histopathology to detect prevalent, inconspicuous dysplasia and early-stage neoplasia in Barrett's esophagus

PURPOSE

Endoscopic surveillance of Barrett's esophagus is problematic because dysplasia/early-stage neoplasia is frequently invisible and likely to be missed because of sampling bias. Molecular abnormalities may be more diffuse than dysplasia. The aim was therefore to test whether DNA methylation, especially on imprinted and X-chromosome genes, is able to detect dysplasia/early-stage neoplasia.

EXPERIMENTAL DESIGN

27K methylation arrays were used to find genes best able to differentiate between 22 Barrett's esophagus and 24 esophageal adenocarcinoma (EAC) samples. These were validated using pyrosequencing on a retrospective cohort (60 Barrett's esophagus, 36 dysplastic, and 90 EAC) and then in a prospective multicenter study (98 Barrett's esophagus patients, including 28 dysplastic and 9 early EAC) designed to utilize biomarkers to stratify patients according to their prevalent dysplasia/EAC status.

RESULTS

Genes (23%) on the array, including 7% of X-linked and 69% of imprinted genes, have shown statistically significant changes in methylation in EAC versus Barrett's esophagus (Wilcoxon P < 0.05). 6/7 selected candidate genes were successfully internally (Pearson's P < 0.01) and externally validated (ANOVA P < 0.001). Four genes (SLC22A18, PIGR, GJA12, and RIN2) showed the greatest area under curve (0.988) to distinguish between Barrett's esophagus and dysplasia/EAC in the retrospective cohort. This methylation panel was able to stratify patients from the prospective cohort into three risk groups based on the number of genes methylated (low risk: <2 genes, intermediate: 2, and high: >2).

CONCLUSION

Widespread DNA methylation changes were observed in Barrett's carcinogenesis including ≈70% of known imprinted genes. A four-gene methylation panel stratified patients with Barrett's esophagus into three risk groups with potential clinical utility.

Correlation of the presence and extent of loss of heterozygosity mutations with histological classifications of Barrett's esophagus

Background

Recent advances in the management of Barrett’s Esophagus (BE) have placed greater emphasis on accurate diagnosis of BE as well as better prediction of risk for progression to esophageal adenocarcinoma (EAC). Histological evaluation of BE is particularly challenging with significant inter-observer variability. We explored the presence and extent of genomic instability in BE biopsy specimens as a means to add supplementary information to the histological classification and clinical decision-making related to early disease.

Methods

We reviewed histology slides from 271 patients known to have BE. Using histological features as a guide, we microdissected target cell populations with various histological classifications of BE (intestinal metaplasia, “indefinite for dysplasia”, low grade dysplasia, or high grade dysplasia). DNA was extracted from microdissected targets and analyzed for loss of heterozygosity (LOH) using a panel of 16 LOH mutational markers associated with tumor suppressor genes at chromosomal loci 1p, 3p, 5q, 9p, 10q, 17p, 17q, 18q, 21q, 22q. The presence or absence of mutations and the clonality of each mutation were determined for each marker.

Results

The presence and clonal expansion of LOH mutations was formulated into mutational load (ML) for each microdissected target analyzed. ML correlated with the histological classification of microdissected targets, with increasingly severe histology having higher ML. Three levels of mutation load (no ML, low ML, and high ML) were defined based on the population of microdissected targets histologically classified as intestinal metaplasia. All microdissected targets with dysplasia had mutations, with a high ML consistently present in high grade dysplasia targets. Microdissected targets histologically classified as intestinal metaplasia or “indefinite for dysplasia” spanned a range of no, low, and high ML.

Conclusions

The results of this study reinforce the association of genomic instability with disease progression in BE. The presence and extent (clonality) of genomic instability, as assessed by mutational load, may assist histology in defining early stages of BE that are potentially at greater risk for disease progression. Assessment of mutational load using our panel of LOH mutational markers may be a useful adjunct to microscopic inspection of biopsy specimens, and thereby, improve patient management.