Clonal ordering of 17p and 5q allelic losses in Barrett dysplasia and adenocarcinoma

Multi-omic cross-sectional cohort study of pre-malignant Barrett's esophagus reveals early structural variation and retrotransposon activity

Barrett's esophagus is a pre-malignant lesion that can progress to esophageal adenocarcinoma. We perform a multi-omic analysis of pre-cancer samples from 146 patients with a range of outcomes, comprising 642 person years of follow-up. Whole genome sequencing reveals complex structural variants and LINE-1 retrotransposons, as well as known copy number changes, occurring even prior to dysplasia. The structural variant burden captures the most variance across the cohort and genomic profiles do not always match consensus clinical pathology dysplasia grades. Increasing structural variant burden is associated with: high levels of chromothripsis and breakage-fusion-bridge events; increased expression of genes related to cell cycle checkpoint, DNA repair and chromosomal instability; and epigenetic silencing of Wnt signalling and cell cycle genes. Timing analysis reveals molecular events triggering genomic instability with more clonal expansion in dysplastic samples. Overall genomic complexity occurs early in the Barrett's natural history and may inform the potential for cancer beyond the clinically discernible phenotype.

Risk Factors for Progression of Barrett's Esophagus to High Grade Dysplasia and Esophageal Adenocarcinoma

Barrett’s esophagus (BE) is the only known precursor to esophageal adenocarcinoma (EAC). Methods of identifying BE patients at high risk for progression to high-grade dysplasia (HGD) or EAC are needed to improve outcomes and identify who will benefit most from intensive surveillance or ablative therapy. Clinical predictors of BE progression to HGD or EAC are poorly understood, with multiple contradictory studies. We performed a retrospective study which included 460 patients at Johns Hopkins Hospital who underwent at least 2 upper endoscopies 6 months apart showing biopsy-documented BE between 1992 and 2013. Patients with EAC or HGD at the initial endoscopy were excluded. Demographic, clinicopathological, and endoscopic data were collected. Univariate and multivariate Cox proportional hazards analyses with time to progression to HGD and EAC were performed. Among 460 patients included in the study, 132 BE patients developed HGD and 62 developed EAC. Significant EAC risk factors included age, abdominal obesity, caffeine intake, and the presence of HGD. Risk factors for HGD or EAC included age, caffeine intake, and low-grade dysplasia while colonic adenomas trended towards significance. Notably, a history of statin or SSRI usage reduced the risk of EAC or HGD by 49% or 61%, respectively. Our study validated several known and identified several novel risk factors, including a history of colonic adenomas or caffeine usage. Low-grade dysplasia was a risk factor for progression but various endoscopic characteristics were not, suggesting that screening strategies should focus on histology instead. We identified SSRIs as a new potentially chemoprotective medication.

Modeling Wnt signaling by CRISPR-Cas9 genome editing recapitulates neoplasia in human Barrett epithelial organoids

Primary organoid cultures generated from patient biopsies comprise a novel improved platform for disease modeling, being genetically stable and closely recapitulating in vivo scenarios. Barrett esophagus (BE) is the major risk factor for esophageal adenocarcinoma. There has been a dearth of long-term in vitro expansion models of BE neoplastic transformation. We generated a long-term virus-free organoid expansion model of BE neoplasia from patient biopsies. Both wild-type and paired APC-knockout (APCKO) BE organoids genome-edited by CRISPR-Cas9 showed characteristic goblet cell differentiation. Autonomous Wnt activation was confirmed in APCKO organoids by overexpression of Wnt target genes and nuclear-translocated β-catenin expression after withdrawal of Wnt-3A and R-spondin-1. Wnt-activated organoids demonstrated histologic atypia, higher proliferative and replicative activity, reduced apoptosis, and prolonged culturability. Wnt-activated organoids also showed sustained protrusive migration ability accompanied by disrupted basement membrane reorganization and integrity. This CRISPR-Cas9 editing human-derived organoid model recapitulates the critical role of aberrant Wnt/β-catenin signaling activation in BE neoplastic transformation. This system can be used to study other 'driver' pathway alterations in BE-associated neoplasia, avoiding signaling noise present in immortalized or cancer-derived cell lines.

Modeling Wnt signaling by CRISPR-Cas9 genome editing recapitulates neoplasia in human Barrett epithelial organoids

Primary organoid cultures generated from patient biopsies comprise a novel improved platform for disease modeling, being genetically stable and closely recapitulating in vivo scenarios. Barrett esophagus (BE) is the major risk factor for esophageal adenocarcinoma. There has been a dearth of long-term in vitro expansion models of BE neoplastic transformation. We generated a long-term virus-free organoid expansion model of BE neoplasia from patient biopsies. Both wild-type and paired APC-knockout (APC^KO) BE organoids genome-edited by CRISPR-Cas9 showed characteristic goblet cell differentiation. Autonomous Wnt activation was confirmed in APC^KO organoids by overexpression of Wnt target genes and nuclear-translocated β-catenin expression after withdrawal of Wnt-3A and R-spondin-1. Wnt-activated organoids demonstrated histologic atypia, higher proliferative and replicative activity, reduced apoptosis, and prolonged culturability. Wnt-activated organoids also showed sustained protrusive migration ability accompanied by disrupted basement membrane reorganization and integrity. This CRISPR-Cas9 editing human-derived organoid model recapitulates the critical role of aberrant Wnt/β-catenin signaling activation in BE neoplastic transformation. This system can be used to study other 'driver' pathway alterations in BE-associated neoplasia, avoiding signaling noise present in immortalized or cancer-derived cell lines.

Review: Experimental models for Barrett's esophagus and esophageal adenocarcinoma

Several different cell culture systems and laboratory animal models have been used over the years to study Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). Most of the existing models have key differences with the human esophagus and complex pathogenesis of disease. None of the models offers an ideal system for the complex study of environmental exposure, genetic risk, and prevention strategies. In fact, different model systems may be required to answer different specific research questions about the pathogenesis of BE and EAC. Given the high mortality associated with EAC and the fact that current screening strategies miss most cases of EAC, advances in basic and translational science related to esophageal injury, repair, and carcinogenesis are clearly needed. This review describes several of the existing and potential model systems for BE and EAC with their benefits and disadvantages.

Malignant transformation of non-neoplastic Barrett's epithelial cells through well-defined genetic manipulations

Background

Human Barrett's cancer cell lines have numerous, poorly-characterized genetic abnormalities and, consequently, those lines have limited utility as models for studying the early molecular events in carcinogenesis. Cell lines with well-defined genetic lesions that recapitulate various stages of neoplastic progression in Barrett's esophagus would be most useful for such studies.

Methodology/Principal Findings

To develop such model cell lines, we started with telomerase-immortalized, non-neoplastic Barrett's epithelial (BAR-T) cells, which are spontaneously deficient in p16, and proceeded to knock down p53 using RNAi, to activate Ras by introducing oncogenic H-Ras^G12V, or both. BAR-T cells infected with either p53 RNAi or oncogenic H-Ras^G12V alone maintained cell-to-cell contact inhibition and did not exhibit anchorage-independent growth in soft agar. In contrast, the combination of p53 RNAi knockdown with expression of oncogenic H-Ras^G12V transformed the p16-deficient BAR-T cells, as evidenced by their loss of contact inhibition, by their formation of colonies in soft agar, and by their generation of tumors in immunodeficient mice.

Conclusions/Significance

Through these experiments, we have generated a number of transformed and non-transformed cell lines with well-characterized genetic abnormalities recapitulating various stages of carcinogenesis in Barrett's esophagus. These lines should be useful models for the study of carcinogenesis in Barrett's esophagus, and for testing the efficacy of chemopreventive and chemotherapeutic agents.

Genetic diversity during the development of Barrett's oesophagus-associated adenocarcinoma: how, when and why?

Recent investigations into Barrett's oesophagus at the level of individual crypts have found significant genetic heterogeneity within a single lesion. Furthermore, this genetic diversity has been shown to predict cancer development. In the present article, we review the genetic alterations implicated in disease progression in Barrett's oesophagus and discuss how genetic diversity could arise during tumorigenesis. Three arguments are discussed: a high mutation rate coupled with strong selection, clonal interaction driving progression, and a hitherto unidentified alteration that disrupts epithelial cell homoeostasis. Suggestions are made for future research to distinguish which of these theories is the predominant mechanism in Barrett's oesophagus-associated tumorigenesis.

Transformation of benign Barrett's epithelium by repeated acid and bile exposure over 65 weeks: a novel in vitro model

The mechanism by which gastroesophageal reflux promotes metaplasia→dysplasia→carcinoma is unknown. The aim of the study is to determine if repeated exposure to acid and bile confers a tumorigenic phenotype in a telomerase (hTERT)-immortalized benign Barrett's cell line (BAR-T). BAR-T cells were exposed to acid (pH 4) (A) and bile salt (200 μM glycochenodeoxycholic acid) (B) daily for 5 min up to 65+ weeks. The control cells were grown in parallel without any A or B treatment. Cell morphology, proliferation, transformation, and molecular changes in the gene expression for COX-2, TC22, p53 and p53 target genes were analyzed at 8-12 weeks intervals. At 46 weeks BAR-T cells exposed to (A+B) showed distinct phenotypic changes: forming clusters and acini, and at 65 weeks displayed foci in monolayer, and formed distinct colonies in soft agar. Untreated cells did not show any such changes. In A+B-treated BAR-T cells, COX-2 mRNA increased 10- to 20-fold, TC22 mRNA increased by 2- to 3-fold at 22-65 weeks, p53, MDM2, PERP, and p21mRNA increased 2.5-, 6.4-, 4-, and 2.6-fold respectively when compared to untreated cells at 34 weeks. However, at 58 weeks onward, there was a sharp decline of p53 and its target genes to the baseline level. At 65 weeks A+B-treated BAR-T cells formed tumor in nude mice whereas untreated cells did not. We demonstrate a novel in vitro model of transformation of a benign Barrett's cell line following repeated exposure to A+B over the course of 65 weeks.

Lgr5, an intestinal stem cell marker, is abnormally expressed in Barrett's esophagus and esophageal adenocarcinoma

Lgr5 (leucine-rich-repeat-containing G-protein-coupled receptor 5), a recently discovered intestinal stem cell marker, is expressed in premalignant lesions including Barrett's esophagus (BE) and cancers including colon cancer, ovarian cancer, and hepatocellular carcinoma. It was also recently found to be expressed in tumor spheres prepared from colon cancer, suggesting that it will likely serve as a cancer stem cell marker. We sought to examine Lgr5 as a biomarker in BE-associated neoplasia. Using standard immunohistochemistry, we performed immunostaining on 81 esophageal specimens (53 biopsy specimens and 28 surgical resections) representing BE, BE-associated dysplasia, and esophageal adenocarcinoma (EAC). Each immunostain was scored based on intensity of immunostaining and percentage of positive cells. For 24 EAC cases, survival analysis was performed with expression scores and other clinicopathological variables. We found that Lgr5 expression was detected in 70% of BE cases and between 90 and 100% of advanced dysplastic lesions and EAC. The intensity of expression was significantly higher in high-grade dysplasia and EAC than BE. In EAC, high Lgr5 expression scores (> or = 5) were associated with worse survival, independent of stage, age, and neoadjuvant/adjuvant therapy (P = 0.03). Our findings suggest that Lgr5 has potential utility as a biomarker for BE-associated dysplasia and EAC.

In benign Barrett's epithelial cells, acid exposure generates reactive oxygen species that cause DNA double-strand breaks

Cells that sustain double-strand breaks (DSB) can develop genomic instability, which contributes to carcinogenesis, and agents that cause DSBs are considered potential carcinogens. We looked for evidence of acid-induced DNA damage, including DSBs, in benign Barrett's epithelial (BAR-T) cell lines in vitro and in patients with Barrett's esophagus in vivo. In BAR-T cells, we also explored the mechanisms underlying acid-induced DNA damage. We exposed BAR-T cells to acid in the presence of a fluorescent probe for reactive oxygen species (ROS) and in the presence or absence of disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (which prevents intracellular acidification) and N-acety-l-cysteine (a scavenger of ROS). DSBs were detected by Western blotting and immunofluorescence for histone H2AX phosphorylation and by CometAssay. During endoscopy in patients with Barrett's esophagus, we took biopsy specimens from the metaplastic mucosa before and after esophageal perfusion with 0.1 N HCl for 3 min and sought DSBs by Western blotting for histone H2AX phosphorylation. In BAR-T cells, acid exposure resulted in ROS production and caused a time-dependent increase in levels of phospho-H2AX that continued for at least 48 h. Pretreatment with disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate or N-acety-l-cysteine prevented the acid-induced increase in phospho-H2AX levels. DSBs also were detected in biopsy specimens of Barrett's metaplasia following esophageal acid perfusion in all of 6 patients with Barrett's esophagus. Acid exposure causes DSBs in Barrett's epithelial cells through ROS produced as a consequence of intracellular acidification. These findings suggest that acid can be considered a carcinogen in Barrett's esophagus.

Chromosomal abnormalities and novel disease-related regions in progression from Barrett's esophagus to esophageal adenocarcinoma

Barrett's esophagus (BE) is a metaplastic condition caused by chronic gastroesophageal reflux which represents an early step in the development of esophageal adenocarcinoma (EAC). Single-nucleotide polymorphism microarray (SNP-chip) analysis is a novel, precise, high-throughput approach to examine genomic alterations in neoplasia. Using 250K SNP-chips, we examined the neoplastic progression of BE to EAC, studying 11 matched sample sets: 6 sets of normal esophagus (NE), BE and EAC, 4 of NE and BE and 1 of NE and EAC. Six (60%) of 10 total BE samples and 4 (57%) of 7 total EAC samples exhibited 1 or more genomic abnormalities comprising deletions, duplications, amplifications and copy-number-neutral loss of heterozygosity (CNN-LOH). Several shared abnormalities were identified, including chromosome 9p CNN-LOH [2 BE samples (20%)], deletion of CDKN2A [4 BE samples (40%)] and amplification of 17q12-21.2 involving the ERBB2, RARA and TOP2A genes [3.1 Mb, 2 EAC (29%)]. Interestingly, 1 BE sample contained a homozygous deletion spanning 9p22.3-p22.2 (1.2 Mb): this region harbors only 1 known gene, basonuclin 2 (BNC2). Real-time PCR analysis confirmed the deletion of this gene and decreased the expression of BNC2 mRNA in the BE sample. Furthermore, transfection and stable expression of BNC2 caused growth arrest of OE33 EAC cells, suggesting that BNC2 functions as a tumor suppressor gene in the esophagus and that deletion of this gene occurs during the development of EAC. Thus, this SNP-chip analysis has identified several early cytogenetic events and novel candidate cancer-related genes that are potentially involved in the evolution of BE to EAC.

Loss of heterozygosities in Barrett esophagus, dysplasia, and adenocarcinoma detected by esophageal brushing cytology and gastroesophageal biopsy

BACKGROUND

Esophageal brushing cytology (EBC) and gastroesophageal biopsy (GEB) are complementary procedures for the evaluation of gastroesophageal lesions that help guide surveillance and treatment.

METHODS

The authors investigated loss of heterozygosity (LOH) of 17 microsatellite repeat markers near tumor suppressor genes in gastroesophageal lesions on 34 concomitant EBCs and GEBs.

RESULTS

The results indicated that there was progressive accumulation of LOHs toward malignant transformation. EBC samples a greater area than GEB, and more LOHs are detected by EBC than GEB. The combination of cytomorphology and detection of LOHs can improve diagnostic accuracy and is a more useful methodology with which to evaluate gastroesophageal lesions than either EBC or GEB alone. The authors also found that LOHs at 1p36, 9p21, and 17p13 may play an important role in Barrett esophagus (BE), LOHs at 10q23, 17p13, and 17q12 in low-grade dysplasia (LGD), LOHs at 5q23 and 17q21 in high-grade dysplasia (HGD), and LOHs at 5q23 and 21q22 in adenocarcinoma.

CONCLUSIONS

Detection of LOHs targeting tumor suppressor genes can be useful in evaluating gastroesophageal lesions, studying oncogenesis of gastroesophageal adenocarcinoma, and, in combination with EBC and GEB, determining surveillance for BE and LGD and/or treatment for HGD and adenocarcinoma.

Genome-wide analysis of genetic alterations in Barrett's adenocarcinoma using single nucleotide polymorphism arrays

We performed genome-wide analysis of copy-number changes and loss of heterozygosity (LOH) in Barrett's esophageal adenocarcinoma by single nucleotide polymorphism (SNP) microarrays to identify associated genomic alterations. DNA from 27 esophageal adenocarcinomas and 14 matching normal tissues was subjected to SNP microarrays. The data were analyzed using dChipSNP software. Copy-number changes occurring in at least 25% of the cases and LOH occurring in at least 19% were regarded as relevant changes. As a validation, fluorescence in situ hybridization (FISH) of 8q24.21 (CMYC) and 8p23.1 (SOX7) was performed. Previously described genomic alterations in esophageal adenocarcinomas could be confirmed by SNP microarrays, such as amplification on 8q (CMYC, confirmed by FISH) and 20q13 or deletion/LOH on 3p (FHIT) and 9p (CDKN2A). Moreover, frequent gains were detected on 2p23.3, 7q11.22, 13q31.1, 14q32.31, 17q23.2 and 20q13.2 harboring several novel candidate genes. The highest copy numbers were seen on 8p23.1, the location of SOX7, which could be demonstrated to be involved in amplification by FISH. A nuclear overexpression of the transcription factor SOX7 could be detected by immunohistochemistry in two amplified tumors. Copy-number losses were seen on 18q21.32 and 20p11.21, harboring interesting candidate genes, such as CDH20 and CST4. Finally, a novel LOH region could be identified on 6p in at least 19% of the cases. In conclusion, SNP microarrays are a valuable tool to detect DNA copy-number changes and LOH at a high resolution. Using this technique, we identified several novel genes and DNA regions associated with esophageal adenocarcinoma.

p16 mutation spectrum in the premalignant condition Barrett's esophagus

Background

Mutation, promoter hypermethylation and loss of heterozygosity involving the tumor suppressor gene p16 (CDKN2a/INK4a) have been detected in a wide variety of human cancers, but much less is known concerning the frequency and spectrum of p16 mutations in premalignant conditions.

Methods and Findings

We have determined the p16 mutation spectrum for a cohort of 304 patients with Barrett's esophagus, a premalignant condition that predisposes to the development of esophageal adenocarcinoma. Forty seven mutations were detected by sequencing of p16 exon 2 in 44 BE patients (14.5%) with a mutation spectrum consistent with that caused by oxidative damage and chronic inflammation. The percentage of patients with p16 mutations increased with increasing histologic grade. In addition, samples from 3 out of 19 patients (15.8%) who underwent esophagectomy were found to have mutations.

Conclusions

The results of this study suggest the environment of the esophagus in BE patients can both generate and select for clones with p16 mutations.

Epithelial metaplasia and the development of cancer

Metaplasia means the conversion, in postnatal life, of one cell type to another. Understanding the steps leading to metaplasia is important for two reasons. Firstly, it tells us something about the normal developmental biology of the tissues that interconvert. Secondly, metaplasia predisposes to certain forms of neoplasia. So understanding the molecular and cellular mechanisms underlying metaplasia will provide insights into clinical diagnosis and potential therapies. One of the best-described examples of metaplasia is Barrett's metaplasia or the appearance of intestinal-like columnar tissue in the oesophagus. Barrett's metaplasia develops as a result of gastro-oesophageal reflux and is considered the precursor lesion for oesophageal adenocarcinoma. While we know quite a bit about the molecular events associated with the development of oesophageal adenocarcinoma, our understanding of the initial events leading to Barrett's metaplasia is lacking. In the present review we will focus on examples of metaplasia that lead to neoplasia and discuss some of the underlying molecular and cellular mechanisms.

Beyond Field Effect: Analysis of Shrunken Centroids in Normal Esophageal Epithelia Detects Concomitant Esophageal Adenocarcinoma

BACKGROUND AND AIMS: Because of the extremely low neoplastic progression rate in Barrett's esophagus, it is difficult to diagnose patients with concomitant adenocarcinoma early in their disease course. If biomarkers existed in normal squamous esophageal epithelium to identify patients with concomitant esophageal adenocarcinoma, potential applications would be far-reaching. The aim of the current study was to identify global gene expression patterns in normal esophageal epithelium capable of revealing simultaneous esophageal adenocarcinoma, even located remotely in the esophagus. METHODS: Tissues comprised normal esophageal epithelia from 9 patients with esophageal adenocarcinoma, 8 patients lacking esophageal adenocarcinoma or Barrett's, and 6 patients with Barrett's esophagus alone. cDNA microarrays were performed, and pattern recognition in each of these subgroups was achieved using shrunken nearest centroid predictors. RESULTS: Our method accurately discriminated normal esophageal epithelia of 8/8 patients without esophageal adenocarcinoma or Barrett's esophagus and of 6/6 patients with Barrett's esophagus alone from normal esophageal epithelia of 9/9 patients with Barrett's esophagus and concomitant esophageal adenocarcinoma. Moreover, we identified genes differentially expressed between the above subgroups. Thus, based on their corresponding normal esophageal epithelia alone, our method accurately diagnosed patients who had concomitant esophageal adenocarcinoma. CONCLUSIONS: These global gene expression patterns, along with individual genes culled from them, represent potential biomarkers for the early diagnosis of esophageal adenocarcinoma from normal esophageal epithelia. Genes discovered in normal esophagus that are differentially expressed in patients with vs. without esophageal adenocarcinoma merit further pursuit in molecular genetic, functional, and therapeutic interventional studies.

Mutagen Sensitivity and Neoplastic Progression in Patients with Barrett's Esophagus: A Prospective Analysis

BACKGROUND

Defects in DNA damage recognition and repair have been associated with a wide variety of cancers. We conducted a prospective study to determine whether mutagen sensitivity, as determined by an in vitro assay, was associated with the future development of cancer in patients with Barrett's esophagus, which is associated with increased risk of progression to esophageal adenocarcinoma.

METHODS

We measured sensitivity to bleomycin in peripheral blood lymphocytes in a cohort of 220 patients with Barrett's esophagus. We followed these patients for 1,230 person-years (range, 3 months to 10.1 years; median, 6.4 years), using development of cancer and aneuploidy as end points. A subset of these patients was evaluated for inactivation of tumor-suppressor genes CDKN2A/p16 and TP53 [by mutation and loss of heterozygosity (LOH)] in their Barrett's segments at the time of, or before, the bleomycin test, and the patients were stratified by CDKN2A/p16 and TP53 status in an analysis of mutagen sensitivity and progression.

RESULTS

Bleomycin-sensitive patients were found to be at significantly greater risk of developing aneuploidy (adjusted hazard ratio, 3.71; 95% confidence interval, 1.44-9.53) and nonsignificantly greater risk of cancer (adjusted hazard ratio, 1.63; 95% confidence interval, 0.71-3.75). Among patients with detectable LOH at the TP53 locus (on chromosome 17p), increasing bleomycin sensitivity was associated with increased risk of developing cancer (P(trend) < 0.001) and aneuploidy (P(trend) = 0.005).

CONCLUSIONS

This study supports the hypothesis that sensitivity to mutagens increases the risk of neoplastic progression in persons with Barrett's esophagus, particularly those with 17p LOH including TP53.

Multistage carcinogenesis in Barrett's esophagus

The multistage carcinogenesis of esophageal adenocarcinoma is a process of clonal evolution within Barrett's esophagus neoplasms. The initiating event for Barrett's esophagus is unknown, but is associated with chronic gastric reflux which probably also promotes progression. Inactivation of both alleles of CDKN2A appear to be early events causing clonal expansion. Clones with TP53 inactivated expand if they have already inactivated CDKN2A. After TP53 has been inactivated, tetraploid and aneuploid clones tend to develop. The final events that lead to invasion and metastasis are unknown. Evolutionary biology provides important tools to understand clonal evolution in progression and cancer prevention.

Genomic amplification of MET with boundaries within fragile site FRA7G and upregulation of MET pathways in esophageal adenocarcinoma

Esophageal adenocarcinoma (EA) is characterized by a poor prognosis making the identification of clinically targetable proteins essential for improving patient outcome. We report the involvement of multiple alterations of the MET pathway in EA development and progression. Microarray analysis of Barrett's metaplasia, dysplasia, and EA revealed overexpression of the MET oncogene in EAs but only those with MET gene amplification. STS-amplification mapping revealed that the boundary of the MET amplicon in these EAs is defined by fragile site FRA7G. We also identified an amplicon at 11p13 that resulted in amplification and overexpression of CD44, a gene involved in MET autophosphorylation upon HGF stimulation. Tissue microarrays with phospho-MET-specific antibodies demonstrated a uniformly high abundance of MET activation in primary EA and cells metastatic to lymph nodes but to a lesser extent in a subset of metaplastic and dysplastic Barrett's samples. Increased expression of multiple genes in the MET pathway associated with invasive growth, for example, many MMPs and osteopontin, also was found in EAs. Treatment of EA-derived cell lines with geldanamycin, an inhibitor for tyrosine kinases including MET receptor kinase, reduced cell migration and induced EA cell apoptosis. The data indicate that upregulation of the MET pathway may contribute to the poor outcome of EA patients and that therapeutic agents targeting this pathway may help improve patient survival.

Genomic analysis of Barrett's esophagus after ablative therapy: persistence of genetic alterations at tumor suppressor loci

Barrett's esophagus (BE) is a major predisposing factor for the development of esophageal adenocarcinoma. Current strategies for treatment of BE, both dysplastic and nondysplastic, include photodynamic therapy (PDT) and argon plasma coagulation (APC). However, the effect of ablative therapy at the genetic level is unclear. We performed loss of heterozygosity (LOH) analysis of BE in baseline and follow-up biopsy specimens from 21 patients with BE (17 male, 4 female) treated with PDT and/or APC. At baseline, 14 patients had intestinal metaplasia without dysplasia (MET), 4 low-grade dysplasia (LGD) and 3 high-grade dysplasia (HGD). LOH was assessed using a panel of 9 polymorphic markers for evaluation of the P53 gene on 17p, P16 on 9p, DCC and SMAD4 on 18q and the APC gene on 5q. The tissue specimens obtained at baseline (t = 0) were analysed, as well as the first (t = 1; mean interval: 4 months) and last (t = 2; mean interval: 8 months) available biopsy with residual or recurrent BE after ablation. At t = 0, allelic loss was detected of 5q in 27%, 9p in 56%, 17p in 31% and 18q in 6% of informative cases. At t = 1 (18 patients with persistent MET and 3 with LGD) and at t = 2 (8 MET, 2 LGD), the LOH patterns were not statistically different from t = 0. Further, multiple genetic lineages before and after therapy were detected in 15 cases illustrating the multiclonal nature of BE. We conclude that recurrent and/or persistent BE after ablative therapy still contains genetic alterations associated with malignant progression to cancer. Therefore, the goal of treatment should be the complete elimination of Barrett's mucosa.

Gastroesophageal reflux and cancer

The causal relationship between GERD and esophageal adenocarcinoma, although unclear just a few decades ago, now is established fairly well. The physiologic changes and the biocellular alterations of the damaged esophageal mucosa are documented better. Despite this knowledge, the dramatic increase in the incidence of esophageal cancer cannot be explained. The absolute risk of esophageal adenocarcinoma arising from GERD is low, and, at present, does not justify population-screening programs. Still, with the notion that adenocarcinoma of the esophagus is an aggressive cancer once documented, important questions still are in need of answers for patients suffering from reflux symptoms. Patients who have reflux disease are not necessarily symptomatic. It remains unclear if patients experiencing reflux symptoms should undergo mandatory endoscopy with biopsies at the esophagogastric junction. Furthermore, metaplasia of the lower esophagus often is not readily recognizable at endoscopy, and only biopsies can document abnormal histology. A severe and prolonged history of reflux always should orient to the possibility of a reflux-related columnar-lined esophagus. Once documented, Barrett's esophagus needs to be seen as a premalignant condition not necessarily leading to adenocarcinoma formation; despite their increased risk of tumor formation, most patients who have Barrett's esophagus die of other causes. During regular endoscopic follow-up, multilevel circumferential biopsies should document the evolution of the histologic changes in the lower esophagus and at the gastroesophageal junction of these patients. It is the only method available to document the appearance of dysplasia. It still is unclear if medicine or surgery provides the best quality of life and the best protection against the development of dysplasia and the possible progression toward adenocarcinoma formation when intestinal metaplasia is present in the esophagus.

The molecular biology of esophageal adenocarcinoma

BACKGROUND

Barrett's esophagus is an acquired metaplastic change that occurs in the distal esophagus secondary to chronic gastroesophageal reflux. This premalignant condition forms the most important risk factor for developing esophageal adenocarcinoma, which is an extremely aggressive tumor with a 5-year survival rate of less than 25%. Carcinomas that arise in the setting of Barrett's esophagus are thought to develop as part of the metaplasia-dysplasia-carcinoma sequence.

OBJECTIVE

To review the current knowledge on the genomic alterations involved in the development of Barrett's esophagus and its progression to dysplasia and/or cancer.

RESULTS

Several changes in gene structure, gene expression, and protein structure are associated with the progression of Barrett's esophagus to adenocarcinoma. Accumulation of these changes seems to be essential, rather than the exact sequence of these changes. Multiple molecular pathways are involved and interact with each other. Alterations in tumor suppressor genes, amongst which p53 and p16, are early events in the metaplasia-dysplasia-adenocarcinoma sequence, followed by loss of cell cycle checkpoints. Ongoing genomic instability leads to cumulative genetic errors and thereby the generation of multiple clones of transformed cells.

CONCLUSIONS

Within the multistep process of esophageal adenocarcinogenesis, to date no single molecular marker came forward able to predict who will and who will not develop cancer in the setting of Barrett's esophagus. Instead, panels of markers need to be developed in the future allowing to indicate disease progression. Identification of crucial molecular pathways involved in esophageal adenocarcinogenesis would ultimately improve therapy and facilitate development of new treatment strategies.

Selectively advantageous mutations and hitchhikers in neoplasms: p16 lesions are selected in Barrett's esophagus

Neoplastic progression is an evolutionary process characterized by genomic instability and waves of clonal expansions carrying genetic and epigenetic lesions to fixation (100% of the cell population). However, an evolutionarily neutral lesion may also reach fixation if it spreads as a hitchhiker on a selective sweep. We sought to distinguish advantageous lesions from hitchhikers in the premalignant condition Barrett's esophagus. Patients (211) had biopsies taken at 2-cm intervals in their Barrett's segments. Purified epithelial cells were assayed for loss of heterozygosity and microsatellite shifts on chromosomes 9 and 17, sequence mutations in CDKN2A/MTS1/INK4a (p16) and TP53 (p53), and methylation of the p16 promoter. We measured the expanse of a lesion in a Barrett's segment as the proportion of proliferating cells that carried a lesion in that locus. We then selected the lesion having expanses >90% in the greatest number of patients as our first putative advantageous lesion. We filtered out hitchhikers by removing all expanses of other lesions that did not occur independent of the advantageous lesion. The entire process was repeated on the remaining expanses to identify additional advantageous lesions. p16 loss of heterozygosity, promoter methylation, and sequence mutations have strong, independent, advantageous effects on Barrett's cells early in progression. Second lesions in p16 and p53 are associated with later selective sweeps. Virtually all of the other lesion expansions, including microsatellite shifts, could be explained as hitchhikers on p16 lesion clonal expansions. These techniques can be applied to any neoplasm.

Biomarkers of esophageal adenocarcinoma and Barrett's esophagus

The rising incidence and poor prognosis of esophageal adenocarcinoma in the Western world have intensified research efforts into earlier methods of detection of this disease and its relationship to Barrett's esophagus. The progression of Barrett's esophagus to adenocarcinoma has been the focus of particular scrutiny, and a number of potential tissue and serum-based disease biomarkers have emerged. The epidemiology and pathogenesis of esophageal adenocarcinoma are outlined. Tissue biomarkers allowing risk stratification of Barrett's are reviewed as well as strategies currently being used to discover novel biomarkers that will facilitate the early detection of esophageal adenocarcinoma. Finally, the uses of biomarkers as predictive tests for targeted treatments and as surrogate endpoints in chemoprevention trials are considered.

The role of protein kinase C-alpha (PKC-alpha) in malignancies of the gastrointestinal tract

Drugs specifically designed to block cellular signalling proteins are currently evaluated as a new way to treat gastrointestinal tumours. One such "new targeted agent" is aprinocarsen, an antisense oligonucleotide that specifically blocks the mRNA of protein kinase C-alpha (PKC-alpha). Blocking PKC-alpha, an important cellular signalling molecule associated with tumour growth, is anticipated to result in tumour cell arrest and achieve clinical benefits. However, it is not known which patients may benefit most from a specific inhibition of PKC-alpha. Past experience with other novel targeted agents suggests that expression of the target molecule is an important factor for the success of such a specific therapy. Therefore, reviewing the specific role of PKC-alpha in various gastrointestinal tumours may contribute to focus the clinical development of selective or specific PKC-alpha inhibitors, such as aprinocarsen, on those patients with a distinctive PKC-alpha expression pattern.

Flow cytometric enrichment for respiratory epithelial cells in sputum

BACKGROUND

Induced sputum, in contrast to bronchoscopic biopsies and lavages, is an easily obtained source of biological specimens. However, obtaining abnormal exfoliated cells for detailed molecular studies is limited because respiratory epithelial cells comprise only about 1% of sputum cell populations.

METHODS

We developed a multiparameter flow sorting strategy to purify epithelial cells from nonepithelial sputum cells, using anti-cytokeratin antibody AE1/AE3 to recognize human epithelial cells and DAPI to stain DNA. We excluded cells with a high degree of side-scatter, which were composed predominantly of squamous cells and contaminating macrophages. The remaining cytokeratin-positive respiratory epithelial cells were then sorted based on anti-cytokeratin (PE) vs DNA (DAPI) parameters.

RESULTS

In this proof of principle study, the AE1AE3 cytokeratin/DNA flow sorting strategy enriched rare diploid respiratory epithelial cells from an average of 1.1% of cells in unsorted induced sputum samples to average purities of 42%. Thus, AE1AE3 flow-sorting results in a 38-fold enrichment of these cells.

CONCLUSIONS

We report a multiparameter flow cytometric assay to detect and enrich rare respiratory epithelial cells from induced sputum samples to average purities of 42%. With further development, this methodology may be useful as part of a molecular screening approach of populations at high risk for lung cancer.

Barrett's esophagus: environmental influences in the progression of dysplasia

Barrett's esophagus (BE) is composed of multiple lineages including Paneth cells and endocrine cells in addition to gastric and intestinal cells. Although the origin of the BE stem cell is a matter of conjecture, the stem cells are clearly multipotent, and therefore the phenotype is restricted by genomic imprinting (termed restricted potency). Recent evidence suggests that the microenvironment may select various lineages. In this regard the proportion of gastric and specialized intestinal metaplastic cells has been attributed to the composition of the refluxate, acid or bile, respectively. Experimental evidence also implicates specific xenobiotics in this process, including bile acids. In particular we discuss the potential biologic roles of bile acids in epithelial adaptation from in vivo and in vitro models.

Barrett's esophagus: model of neoplastic progression

Human cancer progression is characterized by clonal expansion of cells with accumulated genetic errors. Invasive carcinomas contain all the genetic errors that were acquired during neoplastic progression and then continue to accumulate further abnormalities, leading to tumor heterogeneity. Many investigations of human cancer have given valuable insights in genetic abnormalities important for tumor biology. Early events responsible for neoplastic progression, however, are often impossible to investigate in invasive cancers because the premalignant tissue in which the tumors develop are often overgrown and the premalignant conditions cannot be studied in vivo because they are either not detected owing to lack of symptoms or are removed before cancer develops. Unlike many other premalignant conditions Barrett's esophagus is often associated with symptoms leading to diagnosis at an early stage before cancer develops, and the premalignant epithelium is seldom removed at an early stage of cancer progression. Furthermore, in patients who present with invasive carcinoma the tumor is often surrounded by premalignant epithelium, which is available for further investigations. Therefore Barrett's esophagus is an excellent model in which to study the early events of neoplastic progression. It may not only contribute to a better understanding of the neoplastic process but also provide a base for safer assessment of cancer risk during surveillance for early detection of esophageal adenocarcinoma.

Losses of heterozygosity on chromosomes 9p and 17p are frequent events in Barrett's metaplasia not associated with dysplasia or adenocarcinoma

OBJECTIVE

Losses of heterozygosity (LOH) on chromosomes 9p and 17p frequently accompany malignant transformation of Barrett's esophagus (BE). They have been reported in adenocarcinoma, dysplasia, and adjacent metaplasia of patients with long-segment BE (LSBE). This study aimed to evaluate and compare the frequency of LOH on 9p and 17p in patients with long- and short-segment BE (SSBE) without dysplasia or adenocarcinoma.

METHODS

Matched metaplasia and blood DNA were evaluated for LOH on chromosomes 9p and 17p in patients with a previous diagnosis of BE and no dysplasia or cancer.

RESULTS

We included 18 patients (12 long-segment BE and six short-segment BE). The overall prevalence of LOH was 61% (10 of 18), with no significant difference between LSBE (58%) and SSBE (50%). The frequencies of LOH on 9p and 17p were similar (35% and 39%, respectively), with 18% of the patients showing losses at both chromosomes.

CONCLUSIONS

LOH on 9p and 17p are highly frequent events in BE, even in the absence of dysplasia and adenocarcinoma. The presence of these abnormalities in non-neoplastic epithelium suggests they might be useful markers for risk stratification within endoscopic surveillance programs.

The pathogenesis of Barrett's esophagus

Significant progress has been made in clinicians' understanding of the molecular pathogenesis of BE, and the laboratory findings are beginning to lead to hypothesis-driven clinical studies; however, the following questions remain unanswered: (1) how can clinicians identify the persons most at risk for the development of esophageal adenocarcinoma, (2) what are the environmental gene interactions in esophageal carcinogenesis, and (3) can clinicians prevent the development of esophageal adenocarcinoma in the population at risk? As esophageal adenocarcinoma starts to reach epidemic proportions, further research in these areas is urgently required. With the advent of the genomic era and an explosion in studies in BE, significant progress can be made.

Pathology of Barrett's esophagus by proton magnetic resonance spectroscopy and a statistical classification strategy

BACKGROUND

Barrett's esophagus is thought to be a precursor of adenocarcinoma. The incidence of adenocarcinoma of the lower esophagus in the Western world is rising and accounts for more than 40% of esophageal carcinomas in males. It is not possible to identify which Barrett's patients are at high risk of developing malignancy. Here we applied a statistical classification strategy to the analysis of magnetic resonance spectroscopy and histopathological data from esophageal biopsies to ascertain whether this risk could be identified in Barrett's patients.

METHODS

Tissue specimens from 72 patients (29 noncancer-bearing and 43 cancer-bearing) were analyzed by one-dimensional proton magnetic resonance spectroscopy at 8.5 Tesla. Diagnostic correlation was performed between the magnetic resonance spectra and histopathology. The magnetic resonance magnitude spectra were preprocessed, followed by identification of optimal spectral regions, and were then classified by cross-validated linear discriminant analysis of rank orders of the first derivative of magnetic resonance spectra.

RESULTS

Magnetic resonance spectroscopy combined with a statistical classification strategy analysis distinguished normal esophagus from adenocarcinoma and Barrett's epithelium with an accuracy of 100%. Barrett's epithelium and adenocarcinoma were distinguished with an accuracy of 98.6% but only when 4 of the Barrett's specimens and 7 of the carcinoma specimens, determined to be "fuzzy" (ie, unable to be accurately assigned to either class) were withdrawn. The 7 cancer and 4 Barrett's specimens, determined to be "fuzzy" using the Barrett's versus cancer (B versus C) classifier, were submitted to the other two classifiers (Barrett's versus normal [B versus N] and normal versus cancer [N versus C], respectively). The 4 Barrett's specimens were assigned to Barrett's by the N versus B classifier and to normal (n = 2) or cancer (n = 2) classes by the N versus C classifier. The 7 cancer specimens were crisply assigned to the cancer class (N versus C), or for the B versus N classifier, to the Barrett's class (ie, more similar to Barrett's than to normal tissue). Visual inspection of the spectra from histologically identified Barrett's epithelium showed a gradation from normal to carcinoma.

CONCLUSIONS

Proton magnetic resonance spectroscopy of esophageal biopsies combined with a statistical classification strategy data analysis provides a robust diagnosis with a high degree of accuracy for discriminating normal epithelium from esophageal adenocarcinoma and Barrett's esophagus. Different spectral categories of Barrett's epithelium were identified both by visual inspection and by statistical classification strategy, possibly reflecting the risk of future malignant transformation.

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Molecular and biologic basis of upper gastrointestinal malignancy--esophageal carcinoma

Esophageal cancer is one of the most deadly forms of gastrointestinal cancer. Even though the incidence of esophageal adenocarcinoma has been rising in Western populations over the past two decades, esophageal squamous cell carcinoma remains the predominant type of esophageal malignancy in the remainder of the world. With the recent advances in molecular biology, high-output genome wide screening has provided comprehensive profiles of molecular alterations in human esophageal carcinomas. The elucidation of the basic mechanisms of esophageal carcinogenesis brings with it the promise of developing treatment and preventive strategies that are based on the molecular biology of these tumors. The genetic alterations discussed in this article are not unique to the formation of esophageal carcinomas and represent only a fraction of the molecular changes found in these tumors. The goal of this article is to provide the clinician with a useful conceptual basis for evaluating studies on the molecular mechanisms underlying the development of esophageal carcinomas.

Beta-catenin expression and its association with prognostic factors in adenocarcinoma developed in Barrett esophagus

The majority of the adenocarcinomas arising in Barrett esophagus manifest clinically at an advanced stage and have a poor prognosis. As a result of this poor prognosis, much attention has been directed toward the exploration of markers for neoplastic progression in Barrett esophagus. The objective of the present study was to determine the expression of beta-catenin by immunohistochemical analysis in 70 adenocarcinomas developed in Barrett esophagus and to examine its relationship to various prognostic factors currently in use. Abnormal beta-catenin expression, consisting of the loss of membranous staining and the appearance of the nuclear staining, was found in 43 cases (61%). Of patients with the 43 tumors showing abnormal beta-catenin expression, 25 (58%) survived more than 1 year. In contrast, only 7 (26%) of 27 patients with tumors showing normal beta-catenin expression survived longer than 1 year. Most of the superficial (Tis-T1) tumors (83% [10/12]) exhibited abnormal beta-catenin expression compared with only 53% (31/58) in the T2-T3 group. These results suggest a possible correlation among beta-catenin expression, tumor stage, and length of survival as prognostic factors in patients with adenocarcinoma in Barrett esophagus.

Analysis of Ki-ras gene mutations associated with DNA diploid, aneuploid, and multiploid colorectal carcinomas using a crypt isolation technique

BACKGROUND AND AIM

Current evidence suggests a possible relationship between DNA ploidy status and Ki-ras gene mutations in human cancers. However, the conventional method does not enable accurate determination of DNA ploidy status of a tumor cell. The present study attempts to clarify whether Ki-ras gene mutations are associated with DNA ploidy status in sporadic colorectal carcinomas using a crypt isolation technique coupled with DNA cytometric sorting.

METHODS

Polymerase chain reaction and single-strand conformation polymorphism and direct sequencing were used to analyze Ki-ras gene mutations in 82 sporadic colorectal carcinomas: 21 diploid, 12 aneuploid, and 49 multiploid. In addition, microsatellite instability (MSI) was assessed using seven microsatellite markers to study the relationship to Ki-ras mutations.

RESULTS

Ki-ras mutations were found in 12 of 21 diploid carcinomas and in 8 of 12 aneuploid carcinomas. In contrast, Ki-ras gene mutations were detected infrequently in the 34 multiploid carcinomas examined, 8 of which were seen in diploid populations and 10 in aneuploid populations. On the other hand, Ki-ras gene mutations were inversely correlated with MSI, which was found in diploid carcinomas only.

CONCLUSIONS

The low frequency of Ki-ras gene mutations that we observed in multiclonal colorectal carcinomas suggests that development of multiclonal colorectal carcinoma may involve a mechanism different from that involved in the development of diploid or aneuploid colorectal carcinomas.

Predictors of progression in Barrett's esophagus II: baseline 17p (p53) loss of heterozygosity identifies a patient subset at increased risk for neoplastic progression

OBJECTIVES

Most patients with Barrett's esophagus do not progress to cancer, but those who do seem to have markedly increased survival when cancers are detected at an early stage. Most surveillance programs are based on histological assessment of dysplasia, but dysplasia is subject to observer variation and transient diagnoses of dysplasia increase the cost of medical care. We have previously validated flow cytometric increased 4N fractions and aneuploidy as predictors of progression to cancer in Barrett's esophagus. However, multiple somatic genetic lesions develop during neoplastic progression in Barrett's esophagus, and it is likely that a panel of objective biomarkers will be required to manage the cancer risk optimally.

METHODS

We prospectively evaluated endoscopic biopsies from 325 patients with Barrett's esophagus, 269 of whom had one or more follow-up endoscopies, by a robust platform for loss of heterozygosity (LOH) analysis, using baseline 17p (p53) LOH as a predictor and increased 4N, aneuploidy, high-grade dysplasia, and esophageal adenocarcinoma as outcomes.

RESULTS

The prevalence of 17p (p53) LOH at baseline increased from 6% in negative for dysplasia to 57% in high-grade dysplasia (p < 0.001). Patients with 17p (p53) LOH had increased rates of progression to cancer (relative risk [RR] = 16, p < 0.001), high-grade dysplasia (RR = 3.6, p = 0.02), increased 4N (RR = 6.1, p < 0.001), and aneuploidy (RR = 7.5, p < 0.001).

CONCLUSIONS

Patients with 17p (p53) LOH are at increased risk for progression to esophageal adenocarcinoma as well as high-grade dysplasia, increased 4N, and aneuploidy. 17p (p53) LOH is a predictor of progression in Barrett's esophagus that can be combined with a panel of other validated biomarkers for risk assessment as well as intermediate endpoints in prevention trials.

Review article: a conceptual approach to understanding the molecular mechanisms of cancer development in Barrett's oesophagus

Oesophageal adenocarcinoma is one of the most deadly human malignancies. Gastro-oesophageal reflux disease (GERD) has been established as a strong risk factor for oesophageal adenocarcinoma, and more than 40% of adult Americans experience regular GERD symptoms. GERD can be complicated by oesophagitis, and by replacement of oesophageal squamous mucosa with metaplastic, intestinal-type epithelium (Barrett's oesophagus) that is predisposed to malignancy. Cancers in Barrett's oesophagus arise through a sequence of genetic alterations which endow unlimited proliferative capacity upon the cells by affecting components of the cell cycle clock apparatus-the pivotal molecular machinery in the cell nucleus that controls whether a cell will proliferate, differentiate, become quiescent or die. This report describes how the genetic abnormalities that have been recognized in Barrett's oesophagus might promote carcinogenesis through effects on the cell cycle clock machinery. The goal of this review is to provide the clinician with a useful conceptual basis for evaluating studies on the molecular mechanisms underlying the progression from metaplasia to carcinoma in Barrett's oesophagus.

Molecular cytogenetic evaluation of gastric cardia adenocarcinoma and precursor lesions

Analyses of cancer incidence data in the United States and Western Europe revealed steadily rising rates over the past decades of adenocarcinomas of the esophagus and gastric cardia. Genetic information on gastric cardia adenocarcinoma and its preneoplasias is sparse. We have used comparative genomic hybridization to obtain a genome-wide overview of 20 archival gastric cardia adenocarcinomas and 10 adjacent preneoplastic lesions (4 metaplasias, 1 low-grade dysplasia, 5 high-grade dysplasias). Multiple genetic alterations were discriminated in all adenocarcinomas. Frequent loss (> or =25% of all tumors) was detected, in decreasing order of frequency, on 5q, 18q, 4q, 3p, 9p, 2q, 11q, 14q, 21q, 4p, 9q, 16q, 1p, and 8p. Frequent gain (> or =25% of all tumors) was disclosed, in decreasing order of frequency, on 20q, 7p, 8q, 1q, 7q, 20p, 17q, 13q, Xp, 6q, 8p, 19q, 5p, 6p, and Xq. Loss of the Y chromosome was found in 60% of male cases. High level amplification was frequently (>10% of all tumors) detected on 7q21, 8p22, 12p11.2, 17q12-q21, and 19q13.1-q13.2. The precursor lesions showed multiple aberrations in all high-grade dysplasias, whereas few genetic changes were discerned in LGD and metaplasias. High level amplifications were also found in high-grade dysplasias, ie, on 7q21, 8p22, and 17q12-q21. Moreover, the percentage of aberrations was not significantly different for invasive carcinomas or high-grade dysplasias. Approximately 70% of the precursor aberrations were also present in the adjacent carcinoma. Minimal overlapping regions in the preneoplasias included loss on 18q12-q21 and gains on 8q23 and 17q12-q21, suggesting involvement of genes residing in these regions. In conclusion, we have (i) created a map of genetic alterations in gastric cardia adenocarcinomas and (ii) provided evidence for the presence of a metaplasia-dysplasia-carcinoma sequence in this poorly understood type of cancer.

Biomarkers in Barrett esophagus

Barrett esophagus is a premalignant condition that may progress to adenocarcinoma. The risk of developing cancer has been estimated to be approximately 1 in 250 patient-years of observation; however, there appear to be subsets of patients at much higher risk. Risk stratification has previously been determined by histological identification of dysplasia. Several new biomarkers are being tested to help clinicians better determine the risk of cancer development. Although none of these biomarkers has been proven in a prospective study to predict the onset of cancer, they have been correlated with cancer development. Most of these are factors that have been associated with cancer development in other organs. These include assessment of cell proliferation, expression of cyclooxygenase 2, growth factors and oncogenes, secretory factors, cell cycle proteins, adhesion molecules, and aneuploidy and other genetic abnormalities. In addition to their role as potential cancer biomarkers, these factors have increasingly been reported as surrogate markers to monitor the effectiveness of conservative treatments for Barrett esophagus. In this article, biological markers are reviewed for their relevance in Barrett esophagus. Although most biological markers need to be evaluated further and, for most, prospective follow-up studies are lacking, at present abnormal ploidy status, P16 and P53 gene abnormalities, or allelic losses are the most extensively documented.

Dysplasia as a predictive marker for invasive carcinoma in Barrett esophagus: a follow-up study based on 138 cases from a diagnostic variability study

The objective of endoscopic surveillance in Barrett esophagus (BE) is to assess the risk of subsequent development of invasive carcinoma. Criteria for morphologic evaluation of dysplasia, the presumed precursor lesion, have been established, although there are surprisingly few data in the literature correlating biopsy diagnosis of dysplasia with outcome. We collected follow-up information on 138 patients with BE whose initial endoscopic biopsy specimens had been selected for submission in an interobserver variability study performed by 12 pathologists with special interest in gastrointestinal pathology and reviewed blindly twice each by all the participants. Cases were scored as BE with no dysplasia, atypia indefinite for dysplasia (IND), low-grade dysplasia (LGD), high-grade dysplasia (HGD), intramucosal carcinoma, and frankly invasive carcinoma, thus generating 24 scores on each biopsy specimen. Clinical follow-up was obtained and correlated with both the submitting diagnoses and majority diagnoses. Kaplan-Meier statistics were used to compare both the submitting and majority diagnoses with outcome using detection or documentation of invasive carcinoma as the endpoint. Using the submitting diagnoses, no invasive carcinomas were detected in 44 cases diagnosed as BE (median follow-up, 38.5 months). Carcinomas were detected in 4 of 22 (18%) cases submitted as IND (median progression-free survival of 62 months), in 4 of 25 (15%) cases of LGD (median progression-free survival of 60 months), in 20 of 33 cases of HGD (median progression-free survival, 8 months), and all 13 (100%) cases submitted as adenocarcinoma. Grade on initial biopsy correlated significantly with progression to invasive carcinoma (log-rank P =.0001). Majority diagnosis was achieved in 99 of the cases. Using the majority diagnoses, no invasive carcinomas were found in 50 cases of BE (median follow-up, 48 months), and carcinomas were detected in 1 of 7 (14%) IND cases (80% progression-free survival at 2 months), 3 of 15 (20%) LGD (median progression-free survival, 60 months), 9 of 15 (60%) HGD (median progression-free survival, 7 months), and all 12 (100%) carcinoma. Initial grading again correlated significantly with progression to invasive carcinoma (log-rank P =.0001). However, there were 39 cases without a majority diagnosis. Among these, no carcinomas developed in 8 cases with an average score between BE and IND. Carcinomas were detected in 9 of 21 (43%) cases with an average score between IND and LGD, and 7 of 10 (70%) cases with an average score between LGD and HGD. There were ulcers in 8 of 39 cases (20%) of the "no-majority" group and in 13 of 99 (13%) of the majority cases. Of 21 total ulcerated cases, cancer was demonstrated in 15 (71%) of these on follow-up. These data support combining the IND and LGD categories for surveillance purposes. Cases without dysplasia may be followed up conservatively. The data obtained from submitted diagnoses as opposed to those from blind review suggest that knowledge of the clinical findings aids in diagnosis. The data also support the assertion that HGD is strongly associated with invasive carcinoma. Rebiopsy of ulcerated areas should be considered because they may harbor malignancy. Histologic grading of dysplasia using established criteria is a powerful prognosticator in BE. HUM PATHOL 32:379-388.

Biomarkers in Barrett esophagus

Barrett esophagus is a premalignant condition that may progress to adenocarcinoma. The risk of developing cancer has been estimated to be approximately 1 in 250 patient-years of observation; however, there appear to be subsets of patients at much higher risk. Risk stratification has previously been determined by histological identification of dysplasia. Several new biomarkers are being tested to help clinicians better determine the risk of cancer development. Although none of these biomarkers has been proven in a prospective study to predict the onset of cancer, they have been correlated with cancer development. Most of these are factors that have been associated with cancer development in other organs. These include assessment of cell proliferation, expression of cyclooxygenase 2, growth factors and oncogenes, secretory factors, cell cycle proteins, adhesion molecules, and aneuploidy and other genetic abnormalities. In addition to their role as potential cancer biomarkers, these factors have increasingly been reported as surrogate markers to monitor the effectiveness of conservative treatments for Barrett esophagus. In this article, biological markers are reviewed for their relevance in Barrett esophagus. Although most biological markers need to be evaluated further and, for most, prospective follow-up studies are lacking, at present abnormal ploidy status, P16 and P53 gene abnormalities, or allelic losses are the most extensively documented.

Molecular biology of Barrett's adenocarcinoma

OBJECTIVE

To review the current knowledge on the genetic alterations involved in the development and progression of Barrett's esophagus-associated neoplastic lesions.

SUMMARY BACKGROUND DATA

Barrett's esophagus (BE) is a premalignant condition in which the normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. BE predisposes patients to the development of esophageal adenocarcinoma. Endoscopic surveillance can detect esophageal adenocarcinomas when they are early and curable, but most of the adenocarcinomas are detected at an advanced stage. Despite advances in multimodal therapy, the prognosis for invasive esophageal adenocarcinoma is poor. A better understanding of the molecular evolution of the Barrett's metaplasia to dysplasia to adenocarcinoma sequence may allow improved diagnosis, therapy, and prognosis.

METHODS

The authors reviewed data from the published literature to address what is known about the molecular changes thought to be important in the pathogenesis of BE-associated neoplastic lesions.

RESULTS

The progression of Barrett's metaplasia to adenocarcinoma is associated with several changes in gene structure, gene expression, and protein structure. Some of the molecular alterations already showed promise as markers for early cancer detection or prognostication. Among these, alterations in the p53 and p16 genes and cell cycle abnormalities or aneuploidy appear to be the most important and well-characterized molecular changes. However, the exact sequence of events is not known, and probably multiple molecular pathways interact and are involved in the progression of BE to adenocarcinoma.

CONCLUSIONS

Further research into the molecular biology of BE-associated adenocarcinoma will enhance our understanding of the genetic events critical for the initiation and progression of Barrett's adenocarcinoma, leading to more effective surveillance and treatment.

Molecular alterations of Barrett's esophagus on microdissected endoscopic biopsies

Alterations in proto-oncogenes and tumor suppressor genes play a role in the sequence from Barrett's metaplasia to esophageal adenocarcinoma. The present study aims to ascertain whether molecular abnormalities take place in Barrett's metaplasia and low-grade dysplasia and to correlate them with the histological features of the esophageal mucosa. Forty-one formalin-fixed, paraffin-embedded endoscopic esophageal biopsies were classified according to the type of metaplastic changes (noncolumnar fundic and cardial metaplasia; columnar metaplasia, with and without intestinal features). After microdissection samples were examined for loss of heterozygosity (LOH) using polymorphic markers on 5q (D5S82), corresponding to APC (adenomatous polyposis coli) gene, 13q (CA repeat in intron 2 position 14815 to 14998 of the retinoblastoma gene), 17p (D17S513) corresponding to p53 locus, and for p53 mutations. Molecular alterations including LOH, allelic imbalance, and microsatellite instability could be detected in all types of metaplastic changes and sporadically in the squamous epithelium adjacent to the metaplastic tissue. Molecular alterations involving microsatellites D5S82 and the CA repeat inside the retinoblastoma gene were more frequent in nonintestinal metaplasia whereas those involving the p53 locus took place in columnar intestinal metaplasia and in low-grade dysplasia. Clonal changes were demonstrated in different metaplastic areas in three patients. Genetic alterations comprising LOH and microsatellite instability characterize Barrett's mucosa and appear related to the type of metaplastic change. Some of them precede the development of intestinal metaplasia, suggesting that genetic alterations take place earlier than previously thought.

Genetic alterations in DNA diploid, aneuploid and multiploid colorectal carcinomas identified by the crypt isolation technique

Loss of heterozygosity (LOH) and microsatellite instability (MSI) commonly occur in colorectal carcinomas. However, the role of these genetic alterations in determining DNA ploidy status of tumors (diploid, aneuploid and multiploid) remains unclear. In the present study, we attempted to clarify the relationship between genetic alterations and DNA ploidy status. Crypt isolation coupled with DNA cytometric sorting and polymerase chain reaction assay (17 microsatellite markers) were used to study allelic losses and MSI in 59 colorectal carcinomas (diploid, 15; aneuploid, 10 and multiploid, 34). Of the 15 diploid carcinomas, 6 exhibited MSI in which allelic losses were rarely found. The other 9 diploid tumors mostly exhibited allelic losses, but none displayed MSI status. Whereas allelic losses frequently occurred in the aneuploid carcinomas and the aneuploid populations of multiploid carcinomas, they were rarely detected in the diploid populations of multiploid carcinomas. MSI status was not observed in aneuploid carcinomas nor in either population of multiploid carcinomas. Although multiploid carcinomas genetically resemble aneuploid carcinomas in the expression of the severe LOH phenotype, the genetic alterations seen in the diploid populations of multiploid carcinomas may differ from those of diploid carcinomas. Furthermore, all diploid, aneuploid and both the diploid and aneuploid fractions of the multiploid tumors that were non-MSI exhibited a high rate of LOH, suggesting that LOH is independent of the tumor's ploidy status.