Smith CM, Watson DI, Leong MP, Mayne GC, Michael MZ, Wijnhoven BP, Hussey DJ. miR-200 family expression is downregulated upon neoplastic progression of Barrett’s esophagus. World J Gastroenterol 2011; 17(8): 1036-1044 [PMID: 21448356 DOI: 10.3748/wjg.v17.i8.1036]
Corresponding Author of This Article
Dr. Damian J Hussey, Department of Surgery, Flinders University, Flinders Medical Centre, Room 3D213, Bedford Park, South Australia 5042, Australia. damian.hussey@flinders.edu.au
Article-Type of This Article
Brief Article
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Cameron M Smith, David I Watson, Mary P Leong, George C Mayne, Damian J Hussey, Department of Surgery, Flinders University, Bedford Park, South Australia 5042, Australia
Michael Z Michael, Department of Gastroenterology and Hepatology, Flinders University, Bedford Park, South Australia 5042, Australia
Bas PL Wijnhoven, Department of Surgery, Erasmus Medical Centre, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
ORCID number: $[AuthorORCIDs]
Author contributions: Hussey DJ and Smith CM conceived the experiments and analyzed the data; Smith CM, Leong MP and Mayne GC carried out the experiments; Watson DI, Wijnhoven BPL and Michael MZ contributed to study design and analyzed the data; all authors were involved in writing the paper and had final approval of the submitted version.
Supported by National Health and Medical Research Council, Australia
Correspondence to: Dr. Damian J Hussey, Department of Surgery, Flinders University, Flinders Medical Centre, Room 3D213, Bedford Park, South Australia 5042, Australia. damian.hussey@flinders.edu.au
Telephone: +8-618-82046091 Fax: +8-618-82046130
Received: July 21, 2010 Revised: September 13, 2010 Accepted: September 20, 2010 Published online: February 28, 2011
Abstract
AIM: To investigate miR-200 family expression in Barrett’s epithelium, gastric and duodenal epithelia, and esophageal adenocarcinoma.
METHODS: Real-time reverse transcriptase-polymerase chain reaction was used to measure miR-200, ZEB1 and ZEB2 expression. Ingenuity Pathway Analysis of miR-200 targets was used to predict biological outcomes.
RESULTS: Barrett’s epithelium expressed lower levels of miR-141 and miR-200c than did gastric and duodenal epithelia (P < 0.001). In silico analysis indicated roles for the miR-200 family in molecular pathways that distinguish Barrett’s epithelium from gastric and duodenal epithelia, and which control apoptosis and proliferation. All miR-200 members were downregulated in adenocarcinoma (P < 0.02), and miR-200c expression was also downregulated in non-invasive epithelium adjacent to adenocarcinoma (P < 0.02). The expression of all miR-200 members was lower in Barrett’s epithelium derived high-grade dysplastic cell lines than in a cell line derived from benign Barrett’s epithelium. We observed significant inverse correlations between miR-200 family expression and ZEB1 and ZEB2 expression in Barrett’s epithelium and esophageal adenocarcinoma (P < 0.05).
CONCLUSION: miR-200 expression might contribute to the anti-apoptotic and proliferative phenotype of Barrett’s epithelium and regulate key neoplastic processes in this epithelium.
Citation: Smith CM, Watson DI, Leong MP, Mayne GC, Michael MZ, Wijnhoven BP, Hussey DJ. miR-200 family expression is downregulated upon neoplastic progression of Barrett’s esophagus. World J Gastroenterol 2011; 17(8): 1036-1044
Barrett’s esophagus is characterized by the replacement of the normal stratified squamous esophageal epithelium with metaplastic columnar epithelium. Metaplasia to Barrett’s esophagus is probably an adaptive response to the insult from reflux of gastric acid and duodenal bile salts into the esophagus, which occurs in chronic gastroesophageal reflux[1]. Barrett’s esophagus epithelium possesses secretory and absorptive cell types, and these closely resemble those found in normal gastric and intestinal epithelia[2,3]. mRNA expression profiling studies confirm its similarity to gastric and duodenal epithelia[4-6]. However, Barrett’s esophagus epithelium also expresses a specific cluster of genes, including those associated with alterations in cell cycle/proliferation, apoptosis, stress response, and cellular migration pathways, and these distinguish it from all related gastrointestinal mucosae[4]. Other studies have confirmed unique phenotypic characteristics of Barrett’s epithelium that correspond with this specific gene expression cluster. For example, unlike gastric and duodenal epithelia, cellular proliferation in Barrett’s esophagus continues along the upper crypt and at the luminal surface, possibly due to abnormal cell cycle entry or exit[7]. Furthermore, Barrett’s esophagus epithelium expresses unusually high levels of anti-apoptotic proteins[8] and can mount a unique anti-apoptotic and proliferative response to reflux[9-12].
Barrett’s esophagus is clinically important because it is the only visibly identifiable precursor to esophageal adenocarcinoma[13]. Progression to dysplastic stages involves increased abnormalities in the cell cycle and overall proliferation[13]. Neoplastic progression commonly occurs without obvious symptoms, and at the time of diagnosis, most patients with esophageal adenocarcinoma have local invasion or metastases[14]. Several lines of evidence suggest that epithelial to mesenchymal transition is required for local invasion and metastasis[15]. Epithelial to mesenchymal transition involves inhibition of E-cadherin expression and transition from epithelial to fibroblastic cell type, with associated alterations in cellular adhesion and migration[15]. Other studies have presented immunohistochemical, gene expression and cell line data that suggest a role for epithelial to mesenchymal transition in esophageal adenocarcinoma[16,17].
miRNAs downregulate target gene expression at the post-transcriptional level through the binding of their “seed” sequences with complementary sites in the 3’-untranslated region of target mRNAs[18]. The miR-200 family of miRNAs (miR-141, 200a, 200b, 200c and 429) are key regulators/inhibitors of epithelial to mesenchymal transition, and act to maintain the epithelial phenotype by targeting the expression of the E-cadherin transcriptional repressors ZEB1 and ZEB2[19-21]. Accordingly, the number of studies reporting downregulation of miR-200 family expression in cancer is increasing[19-25]. In addition, members of the miR-200 family have recently been shown to affect other cell behaviors including proliferation, cell cycle and apoptosis[26-28].
Given the unique gene expression profile and cellular behavior in Barrett’s esophagus epithelium, the phenotypic features that characterize its neoplastic progression, and the potential relevance of epithelial to mesenchymal transition to esophageal adenocarcinoma, we sought to determine the expression of miR-200 family members in gastric, duodenal and Barrett’s esophagus epithelium, and to assess their expression with neoplastic progression of Barrett’s esophagus. We hypothesized that Barrett’s esophagus epithelium may possess a miR-200 expression profile different to gastric and duodenal epithelia, and that downregulation of miR-200 family expression may occur upon progression to esophageal adenocarcinoma.
MATERIALS AND METHODS
Tissue collection and processing
Tissues from patients diagnosed with either Barrett’s esophagus (n = 17) or esophageal adenocarcinoma (n = 20) were collected at endoscopy or after surgical resection. The clinical research ethics committees of Flinders University and Erasmus Medical Centre approved the protocol for this study. Details of the collection process, information about the clinical characteristics of the patients, and RNA isolation from tissues have been published in full elsewhere[29]. In brief, endoscopic biopsy samples were obtained from the second part of the duodenum, proximal stomach, and distal esophagus. All biopsies were immediately stored in RNAlater (Ambion, Austin, TX, USA) and frozen at -20°C until required. All biopsy samples used in this study were collected from the most distal level of endoscopically visualized Barrett’s esophagus epithelium, which was confirmed by concurrent histopathology to be from columnar mucosa with intestinal metaplasia. In individuals with esophageal adenocarcinoma, a similar biopsy collection protocol was used for endoscopic biopsy. Samples were obtained from the second part of the duodenum, proximal stomach and the adenocarcinoma. Samples from surgical resection specimens were obtained from the normal upper stomach, and the tumor site, and immediately stored in RNAlater (Ambion) and frozen at -20°C until required. If any Barrett’s esophagus epithelium was present proximal to an esophageal adenocarcinoma, this was also sampled using the same protocols. Samples from patients with adenocarcinoma of the esophagus were always obtained before any neoadjuvant chemotherapy or radiotherapy was commenced, if clinically indicated.
The stored endoscopic biopsies and resection tissues were thawed in RNAlater as required. Thirty percent of each endoscopic biopsy sample, or a small portion of the resection samples, was dissected from the thawed tissue sample, fixed in formalin, embedded in paraffin, and processed for conventional histopathology. This was done to confirm that the biopsy contained only the appropriate tissue type. The remaining tissue had any remaining RNAlater removed, and was then processed in Trizol (Invitrogen, Carlsbad, CA, USA) for RNA extraction. RNA was also extracted from cell lines derived from benign Barrett’s esophagus (Qh) and high grade dysplastic (Ch and Gi) epithelium[30].
Quantitative reverse transcriptase-polymerase chain reaction analysis of miR-200 family, ZEB1 and ZEB2 expression
miR-200 expression was determined using commercially available TaqMan® miRNA assays specific for each member of the miR-200 family (Applied Biosystems, Foster City, CA, USA). ZEB1 and ZEB2 mRNA expression was assessed using the Quantiscript® RT kit for reverse transcription and the Quantitect® SYBRGreen mastermix for polymerase chain reaction (PCR). Primer details are available upon request. miRNA expression was normalized using RNU44, and mRNA expression was normalized using 18S rRNA. Data were analyzed quantitatively using Q-Gene software[31]. Apparent differences in gene expression between the tissues were assessed for statistical significance using the Kruskal-Wallis test (significance cut-off P < 0.05). If significance was reached for this analysis, then the post hoc Holm-Bonferroni test was used for pairwise comparisons. Statistical testing was performed using Microsoft Excel. Spearman rank order correlation tests between miRNA and mRNA expression were conducted on-line (http://www.wessa.net/rankcorr.wasp). In addition to miR-200 expression, we also tested miR-215 because we have previously demonstrated downregulation of this miRNA in esophageal adenocarcinoma[29], and it was recently shown to target ZEB2 directly[32].
miRNA target prediction and pathway analysis
Target prediction using miRecords (http://mirecords.biolead.org/)[33] and a core analysis using Ingenuity Pathway Analysis (http://www.ingenuity.com) were combined to elucidate possible implications of reduced miRNA expression. Predicted targets used in this analysis were required to be predicted by at least five databases in the miRecords search engine. Ingenuity Pathway Analysis parameters were set to assess a knowledge base derived from direct and indirect associations between genes in human experiments, and also in epithelial cell lines. In the Ingenuity Pathway Analysis, genes are grouped according to function and are allocated to top associated networks and cellular functions. Ingenuity Pathway Analysis uses a right-tailed Fisher’s exact test to assign P values to each grouping, testing each result against a result from random groups of input predicted genes. Networks and cellular functions are ranked according to their score with the highest scoring networks representing the greatest statistical significance.
RESULTS
miR-200 family expression analysis in Barrett’s esophagus, gastric and duodenal epithelia
Taqman Quantitative reverse transcriptase-PCR (qRT-PCR) revealed that expression levels of miR-141 and 200c were significantly lower in Barrett’s esophagus epithelium compared with gastric and duodenal epithelia (Table 1). miR-200a and miR-200b expression was significantly lower in Barrett’s esophagus epithelium than in gastric epithelium, but did not differ in expression between Barrett’s esophagus and duodenal epithelia. The expression level of miR-429 was not significantly different across these three epithelial types.
Table 1 Relative miRNA expression in Barrett’s esophagus, gastric and duodenal mucosal tissues.
Predicted implications of reduced miR-200 family expression in Barrett’s esophagus
Core Ingenuity Pathway Analysis on predicted targets of miR-141 and miR-200c were performed to determine the probable biological effects of their reduced expression. The collection of target predictions from multiple algorithms, presented in miRecords, listed 272 gene targets for miR-141 and 429 targets for miR-200c. The top associated biological networks for these targets are illustrated in Figure 1, and the biological functions associated with these targets are listed in Table 2.
Figure 1 Top associated network functions for miR-141 and miR-200c.
A: Ingenuity Pathway Analysis predicted that the top associated network functions for miR-141 were gene expression, cell death and cell cycle (P = 1 × 10-35). B: The top associated network functions for miR-200c were cell morphology, cellular assembly and organization, cellular function and maintenance (P = 1 × 10-38). Predicted targets of miR-141 or miR-200c are highlighted in grey. Uncolored entries represent molecules that are associated with the pathway but are not predicted miR-141 or miR-200c targets. The P values were derived from a right-tailed Fisher’s exact test to calculate the probability that each predicted miRNA target matches the ascribed network function due to chance alone.
Table 2 Top molecular and cellular functions of miR-200 gene targets.
miRNA
Molecular and cellular functions
Molecules involved
P value
Cell cycle
41
1.90E-07-2.82E-02
Gene expression
53
4.94E-07-2.82E-02
miR-141
Cellular movement
39
2.45E-05-2.82E-02
Cellular assembly and organization
61
2.88E-04-2.82E-02
Cellular growth and proliferation
68
2.88E-04-2.28E-02
Gene expression
84
1.37E-09-2.32E-02
Cellular growth and proliferation
108
5.65E-05-2.32E-02
miR-200c
Cell cycle
53
9.17E-05-2.32E-02
Cell death
95
9.62E-05-2.32E-02
Cellular assembly and organization
55
1.19E-04-2.32E-02
miR-200, ZEB1 and ZEB2 expression in Barrett’s esophagus and esophageal adenocarcinoma
Expression of all members of the miR-200 family was significantly lower in esophageal adenocarcinoma compared with Barrett’s esophagus epithelium (Table 3). The median expression of all miR-200 family members was lower in Barrett’s esophagus epithelium proximal to esophageal adenocarcinoma than in Barrett’s epithelium from patients without cancer or dysplasia. However, after post hoc analysis, only the difference in miR-200c expression was statistically significant. To determine whether this could indicate downregulation of miR-200 expression in dysplasia, prior to the development of adenocarcinoma, miR-200 family expression was further assessed in a non-dysplastic Barrett’s esophagus derived cell line (Qh), and two cell lines derived from Barrett’s esophagus with high-grade dysplasia (Ch, Gi). Figure 2 shows that the expression of all miR-200 members was markedly reduced in both dysplastic cell lines compared to expression in the benign cell line.
Figure 2 miR-200 family expression in benign Barrett’s and dysplastic cell lines.
Relative expression of all miR-141, miR-200a, miR-200b and miR-429, normalized to U44 expression is shown on the left hand y axis. Relative expression of miR-200c is shown on the right hand y axis. The pattern of relative expression of miR-200 members in the Qh (benign Barrett’s) cell line closely resembled that in benign Barrett’s esophagus mucosa (see relative expression values in Table 1).
Table 3 miRNA expression in Barrett’s esophagus and esophageal adenocarcinoma.
To determine whether the miRNA switch for epithelial to mesenchymal transition might be active in esophageal adenocarcinoma development, we also assessed the mRNA expression of miR-200 targets ZEB1 and ZEB2. ZEB1 and ZEB2 expression was significantly higher in esophageal adenocarcinoma compared to Barrett’s esophagus epithelium from patients without cancer or dysplasia (Table 4). There were significant inverse correlations between the expression of ZEB1/ZEB2 and the expression of some miR-200 members. miR-215 and ZEB2 expression were inversely correlated (Table 4).
Table 4 ZEB1 and ZEB2 expression in Barrettt’s epithelium and esophageal adenocarcinoma.
Fold↑
miR-141
miR-200a
miR-200b
miR-200c
miR-429
miR-215
ZEB1
2.9
R = -0.2
R = -0.4
R = -0.5
R = -0.5
R = -0.3
R = -0.3
P < 0.0001
P = 0.341
P = 0.046
P = 0.009
P = 0.006
P = 0.159
P = 0.152
ZEB2
1.5
R = -0.3
R = -0.3
R = -0.5
R = -0.5
R = -0.4
R = -0.4
P = 0.029
P = 0.101
P = 0.085
P = 0.008
P = 0.015
P = 0.067
P = 0.044
DISCUSSION
We found that miR-141 and miR-200c were expressed at lower levels in Barrett’s esophagus epithelium, compared to normal gastric and duodenal epithelia. Bioinformatics analysis indicated that this might contribute to the cell cycle, stress response (proliferation, apoptosis), and cellular migration behavior, which are known to make Barrett’s esophagus epithelium different to gastric and duodenal epithelia[4,7-12,34]. The reduced miR-200 levels that we observed in Barrett’s esophagus epithelium adjacent to adenocarcinoma, and Barrett’s esophagus with high-grade dysplasia derived cell lines suggested an association between down-regulation of miR-200 expression and neoplastic progression in Barrett’s esophagus. The increased expressions of ZEB1 and ZEB2 in esophageal adenocarcinoma, and their inverse correlations with miR-200 expression, are consistent with induction of epithelial to mesenchymal transition mediated by loss of miR-200 expression. Taken together with the known biological functions of the miR-200 family[26-28], our study provides evidence for their influence in patterning the known unique gene expression[4] and phenotypic characteristics[4,7-12,34] of benign Barrett’s esophagus epithelium, as well as features that characterize its neoplastic progression[13]. Furthermore, our data indicate that the miRNA switch for turning on epithelial to mesenchymal transition[20] might be activated during the development of esophageal adenocarcinoma.
Although the miR-200 family has some redundancy in seed sequence, and therefore the genes they target, they act co-operatively to control the expression of their targets, and a change in expression of just one member is sufficient to alter target transcript levels[20]. miR-141 and miR-200c are known to modulate apoptosis, cell cycle and proliferation, and cellular migration through regulation of their target genes[26-28]. Several in vivo and in vitro studies have elucidated the molecules/complexes that are upregulated/activated in Barrett’s epithelium and are responsible for its unique anti-apoptotic and proliferative responses to reflux-induced stress. These include three mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase, p38 and C-Jun N-terminal kinase[35]; protein kinase C[11]; phosphatidylinositol 3-kinases (PI3K) and downstream Akt[36]; and transcription factors nuclear factor (NF)-κB[37] and activator protein-1[36]. Our combined target prediction and Ingenuity Pathway Analysis predicted indirect (or direct in the case of Akt) targeting of all of the aforementioned molecules/complexes in the top associated network functions of miR-141 and/or miR-200c. Overall, this suggests that reduced miR-141 and miR-200c expression in Barrett’s esophagus epithelium (vs gastric and duodenal epithelia) might activate molecular pathways that are known to promote the specific response of Barrett’s esophagus epithelium to the insult of gastroesophageal reflux.
Our analysis predicted direct targeting and downregulation of fibronectin by miR-200c, and this was evident in the top associated network. A recent study has shown that fibronectin expression is reduced in cell lines in direct response to miR-200c expression[38]. Therefore, it is reasonable to expect that fibronectin expression should be higher in Barrett’s esophagus epithelium than in gastric and duodenal epithelia; due at least partly to reduced miR-200c expression in Barrett’s esophagus. In agreement with this, fibronectin is in the gene expression cluster that separates Barrett’s esophagus epithelium from gastric and duodenal epithelium[4]. Fibronectin has key roles in cellular adhesion and migration[39]. In the development of Barrett’s esophagus, its expression is proposed to help facilitate expansion of epithelial cell populations in order to replace areas of denuded squamous epithelium with metaplastic cells[4]. Furthermore, fibronectin expression contributes to increased proliferative and anti-apoptotic behavior through NF-κB and PI3K signaling[40]. Taken together, these observations lend support to the biological validity of our bioinformatics-based approach, and further promote a likely role for reduced miR-200c expression in Barrett’s esophagus.
The development of high-grade dysplasia significantly increases the risk of progression to esophageal adenocarcinoma[41,42]. Features of dysplastic epithelium that make it distinct from benign Barrett’s esophagus epithelium include increased proliferative and anti-apoptotic behavior[13]. We found that miR-200c expression is downregulated in Barrett’s esophagus sampled from patients with a concurrent esophageal cancer, and the entire miR-200 family was downregulated in cell lines derived from patients with high-grade dysplasia. Our pathway analysis indicates that this could result in the molecular events known to contribute to the features of dysplastic Barrett’s esophagus, including increased signaling through MAPK pathways[43], increased activation and expression of NF-κB[44,45], and increased activation of Akt[43,46]. Activation of Akt is stimulated by interaction of the obesity-related hormone leptin and its receptor, and this results in increased proliferation and resistance to apoptosis in Barrett’s esophagus derived cancer cell lines[46]. The leptin receptor is downregulated in vitro in response to miR-200c expression[38], and our miRecords searches predicted direct targeting of the leptin receptor by miR-200c. We speculate that reduced miR-200 family expression in dysplasia could be an important mechanism for leptin receptor mediated activation of Akt, and this could contribute to the established link between obesity and an increased risk of esophageal adenocarcinoma development[47]. In further support of the direct relevance of decreased miR-200 expression to the molecular features of neoplastic progression of Barrett’s esophagus, we found that three gene transcripts (EGR3, HS3ST1 and RPS6KB1), listed in miRecords to be targets of miR-200c, were present in a panel of 18 transcripts that are upregulated in Barrett’s epithelium, from which cancer has arisen versus benign Barrett’s esophagus epithelium[48].
Downregulation of E-cadherin expression via transcriptional repression is a central mechanism for epithelial to mesenchymal transition[15]. ZEB1 and ZEB2 are amongst a group of transcription factors that repress transcription of E-cadherin[15]. ZEB1 and ZEB2 are targets of the miR-200 family, and an increase in ZEB1 and ZEB2 activity caused by downregulation of miR-200 expression is sufficient to induce epithelial to mesenchymal transition[20]. Epithelial to mesenchymal transition that is promoted by downregulation of the miR-200 family has now been implicated as an important mechanism for invasion and metastasis in several cancers[20,22-25]. Previous epithelial and mesenchymal cell marker studies have provided evidence for the involvement of epithelial mesenchymal transition in the development of esophageal adenocarcinoma[16,17], but to the best of our knowledge, no studies have investigated loss of miR-200 mediated control of ZEB1 and ZEB2 expression as a possible mechanism for epithelial to mesenchymal transition in this disease. We found downregulation of the entire miR-200 family and upregulation of ZEB1 and ZEB2 transcription levels upon progression of Barrett’s esophagus to adenocarcinoma. We observed significant inverse correlations between expression of miR-200 members and ZEB1/ZEB2 transcripts. miR-215 expression, which we have previously reported as downregulated in neoplastic progression of Barrett’s esophagus[29], was also inversely correlated with ZEB2 expression. miR-215 has recently been shown to target ZEB2 expression directly in kidney cells[32], and our results suggest the same in Barrett’s esophagus. Together, these results suggest that the miR-200 family contributes to control of ZEB1 and ZEB2 expression in Barrett’s esophagus, and this might be important for maintaining the epithelial phenotype. They add to the current evidence for the involvement of epithelial to mesenchymal transition in esophageal adenocarcinoma, and indicate downregulation of miR-200 expression as a potential mechanism for this.
With regard to the potential clinical relevance of our findings, we hypothesize that the miR-200 family might be useful biomarkers for identifying patients with Barrett’s esophagus who are at increased risk of adenocarcinoma. They may also be helpful for assessing the potential antineoplastic effects of medical and surgical treatment of Barrett’s esophagus. Further studies are required to evaluate this hypothesis. Recent advances in delivery of small RNAs in a clinical setting[49], and the demonstrated in vitro antineoplastic effects of endogenous miR-200 expression[38,50], suggest a possible future role for the therapeutic use of this family of miRNAs in treating early cancer in Barrett’s epithelium.
Our study had some limitations. First, we used Barrett’s esophagus epithelium proximal to cancer, and cell lines derived from dysplastic epithelium, to determine evidence for reduced miR-200 expression in dysplasia. We did not demonstrate miR-200 downregulation in dysplastic epithelium from patients who did not have invasive cancer, and this is an important area for investigation in future studies. Second, although our study provides evidence for effects of miR-200 expression on known gene-expression and phenotypic features of benign and dysplastic Barrett’s esophagus, we did not expand this evidence using functional studies.
In summary, we showed that the miR-200 expression profile in Barrett’s esophagus distinguished it from gastric and duodenal epithelia, and that downregulation of miR-200 expression was associated with dysplasia and adenocarcinoma. Further investigation is warranted to evaluate whether changes in the expression of these miRNAs can be used to identify patients with Barrett’s esophagus who are at risk of progression to esophageal adenocarcinoma.
COMMENTS
Background
Barrett’s esophagus is a precursor to esophageal adenocarcinoma and develops in response to chronic gastroesophageal reflux. Barrett’s esophagus epithelium closely resembles that of the stomach and small intestine. However, some genes are expressed uniquely in Barrett’s esophagus, and this is associated with pronounced anti-apoptotic and proliferative behavior in response to reflux. Esophageal adenocarcinoma development may involve an epithelial to mesenchymal transition-mediated acquisition of invasive phenotype. The miR-200 family of miRNAs can regulate cell death and proliferation, and control epithelial to mesenchymal transition through targeting ofZEB1andZEB2gene expression.
Research frontiers
miRNAs have been implicated in almost every cellular process investigated. Recent evidence highlights a role for the miR-200 family members in numerous cellular processes including cell proliferation, cell death and epithelial to mesenchymal transition. All of these processes have been implicated in Barrett’s esophagus and esophageal adenocarcinoma. We identified aberrant expression of the miR-200 family in Barrett’s esophagus and esophageal adenocarcinoma and hypothesize that this differential expression contributes to aspects of neoplastic progression.
Innovations and breakthroughs
This study is the first to identify differential expression of the miR-200 family in Barrett’s esophagus and esophageal adenocarcinoma. The miR-200 family expression data in Barrett’s esophagus paired with functional studies in other cell types provides evidence that aberrant miR-200 family member expression may contribute to the increased proliferation and decreased cell death associated with Barrett’s esophagus. The complete downregulation of the miR-200 family and subsequent upregulation of mRNA targets ZEB1 and ZEB2 in esophageal adenocarcinoma mimics what is seen in epithelial to mesenchymal transition and other invasive solid tumors, which suggests that the miR-200 family is involved in invasive esophageal adenocarcinoma development.
Applications
We hypothesize that the miR-200 family might be useful biomarkers for identifying patients with Barrett’s esophagus who are at increased risk of adenocarcinoma. They may also be helpful for assessing the potential antineoplastic effects of medical and surgical treatment of Barrett’s esophagus.
Terminology
Barrett’s esophagus is a precursor to esophageal adenocarcinoma and develops in response to chronic gastroesophageal reflux. The miR-200 family of miRNAs can regulate cell death and proliferation, and control epithelial to mesenchymal transition through targeting ofZEB1andZEB2gene expression.
Peer review
This is a well-written manuscript that describes miRNAs in Barrett’s epithelium. The authors’ conclusions are supported by the data.
Footnotes
Peer reviewer: Joseph J Cullen, MD, Professor, Department of Surgery, University of Iowa Carver College of Medicine, 4605 JCP, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, United States
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