Validation of a rodent model of Barrett’s esophagus using quantitative gene expression profiling

Trefoil factor 1 inhibits the development of esophageal adenocarcinoma from Barrett's epithelium

Trefoil factor family 1 (TFF1) is one of three members of the trefoil factor family that are abundantly expressed in the gastrointestinal mucosal epithelium. Recent studies have shown that TFF1 acts as a tumor suppressor in gastric, pancreatic and hepatocellular carcinogenesis; however, little is known about its function in esophageal carcinogenesis, especially in esophageal adenocarcinoma (EAC). Barrett's epithelium is the metaplastic columnar epithelium of the esophagus and a known premalignant lesion of EAC. To investigate the role of TFF1 in EAC development, a mouse model of Barrett's epithelium was employed, and human specimens of EAC were assessed by immunohistochemistry (IHC) and methylation-specific PCR. Wild-type (WT) mice underwent gastrojejunostomy on the forestomach, resulting in the development of Barrett's epithelium-like (BE-like) epithelium adjacent to the anastomotic site. BE-like epithelium in these mice expressed TFF1, indicating the association of TFF1 with esophageal adenocarcinoma. TFF1-knockout (TFF1KO) mice underwent the same procedure as well, revealing that a deficiency in TFF1 resulted in the development of adenocarcinoma in the anastomotic site, presumably from BE-like epithelium. IHC of human samples revealed strong TFF1 expression in Barrett's epithelium, which was lost in some EACs, confirming the association between TFF1 and EAC development. Aberrant DNA hypermethylation in TFF1 promoter lesions was detected in TFF1-negative human EAC samples, further confirming not only the role of TFF1 in EAC but also the underlying mechanisms of TFF1 regulation. In addition, IHC revealed the nuclear translocation of β-catenin in human and mouse EAC, suggesting that activation of the Wnt/β-catenin pathway was induced by the loss of TFF1. In conclusion, these results indicate that TFF1 functions as a tumor suppressor to inhibit the development of esophageal carcinogenesis from Barrett's epithelium.

Inhibition of the BMP pathway prevents development of Barrett's-associated adenocarcinoma in a surgical rat model

INTRODUCTION

Esophageal adenocarcinoma (EAC) is an aggressive cancer, associated with reflux esophagitis and intestinal metaplasia (IM). One underlying biological mechanism, which possibly drives the development of EAC, is the dysregulated expression of Bone Morphogenetic Proteins (BMPs).

AIM

To investigate if local delivery of Noggin, a BMP antagonist, reduced EAC.

METHODS

After obtaining proof of principal on local delivery of a Noggin/Sucralfate substance, a randomized controlled trial to test the effects of Noggin on EAC development was performed in a surgical rat model. In the model, an esophago-jejunostomy leads to development of reflux-esophagitis, IM and eventually EAC. Rats were treated by Noggin/Sucralfate or Sucralfate alone. Treatment was administered from 26 to 29 weeks after the operation.

RESULTS

Of the 112 operated rats, 52 survived beyond 26 weeks. Finally, 25 rats treated with Noggin/Sucralfate and 21 with Sucralfate, were evaluated. At the end, 39 (85%) of the animals had IM while 28 (61%) developed cancer. There were significantly more cancers in the Noggin/Sucralfate arm (50%) versus the Sucralfate group (73%) (Chi square, P < 0.05). Most cancers were mucous producing T3 adenocarcinomas. There were no significant differences in the amount of IM, size or grade of the cancers, or expression of columnar and squamous markers between the two groups.

CONCLUSION

In this study, we demonstrated that inhibition of BMPs by Noggin reduced development of EAC in a surgical esophagitis-IM-EAC rat model. In future, effective targeting of the BMP pathway with selective BMP-inhibitors could become an important asset to improve EAC patient outcome.

Serial Endoscopic Evaluation of Esophageal Disease in a Cancer Model: A Paradigm Shift for Esophageal Adenocarcinoma (EAC) Drug Discovery and Development

A rat model of surgically induced reflux recapitulates the development and progression of human esophageal adenocarcinoma (EAC). In this study, reflux was induced in rats followed by postoperative endoscopy with biopsy, to diagnose and monitor disease progression. Overall, percentage agreement between visual endoscopy and gold standard histology was 95%, with disease-specific classification accuracies of 100% and 75% for Barrett's with dysplasia and EAC, respectively. Additionally, the percentage agreement for biopsy in tumors >4 mm was 75%. Thereby, establishing endoscopic evaluation as a reliable tool to assess disease progression and provide biopsies for downstream correlates in a de novo EAC model.

Preclinical models for the study of Barrett's carcinogenesis

Barrett's esophagus (BE) is clinically significant, as it is the only known precursor lesion for esophageal adenocarcinoma. To develop improved therapies for the treatment of BE, a greater understanding of the disease process at the molecular genetic level is needed. However, achieving a greater understanding will require improved preclinical models so that the disease process can be more closely studied and novel therapies can be tested. Our concise review highlights progress in the development of preclinical models for the study of BE and identifies the most suitable model in which to test novel therapies.

PI3K/mTOR Dual Inhibitor, LY3023414, Demonstrates Potent Antitumor Efficacy Against Esophageal Adenocarcinoma in a Rat Model

OBJECTIVE

The purpose of the current study is to determine the efficacy of a PI3K/mTOR dual inhibitor, LY3023414, on established EAC in an in vivo model.

BACKGROUND

Esophageal adenocarcinoma (EAC) is a highly lethal cancer with limited treatment options. The PI3K/mTOR pathway is upregulated in EAC and may be a target for novel therapies.

METHODS

Esophagojejunostomy was performed on Sprague-Dawley rats to induce carcinogenesis, and LY3023414 was cyclically administered intraperitoneally between 32 and 40 weeks postsurgery to treatment animals. Magnetic resonance imaging (MRI) and histology were used to determine clinical response. Immunohistochemistry, immunofluorescence, and Western blot were used to validate apoptosis by cleaved caspase-3, proliferation by Ki67, and pathway inhibition, respectively.

RESULTS

Mean MRI tumor volume increased by 109.2% in controls (n = 32) and decreased by 56.8% in treatment animals (n=17) (P < 0.01). Treatment with LY3023414 demonstrated tumor volume increase in 0% (control = 46.4%) (P < 0.01), decrease in 58.8% (control = 7.1%) (P < 0.01), and stable volume in 41.2% (control = 46.4%) (P = 0.77). EAC prevalence in controls increased by 25%; whereas, prevalence in treatment animals decreased by 29.4% (P < 0.01). Approximately, 75% of treatment animals presenting with residual masses on MRI had a histological response >50%. Increased apoptosis by cleaved caspase-3 (P = 0.03) and decreased proliferation by Ki67 (P < 0.01) were demonstrated in the treatment arm, when compared with the control arm. On Western blot analysis of pathway checkpoints, p-mTOR (p=0.03) and PI3K-α (P = 0.04) were downregulated in treatment responsive residual tumors, when compared with controls.

CONCLUSIONS

LY3023414 demonstrates efficacy against EAC in a preclinical model, establishing the rationale for clinical testing.

Columnar Metaplasia in Three Types of Surgical Mouse Models of Esophageal Reflux

BACKGROUND AND AIMS

Esophageal adenocarcinoma develops in the setting of gastroesophageal reflux and columnar metaplasia in distal esophagus. Columnar metaplasia arising in gastroesophageal reflux models has developed in rat; however, gastroesophageal reflux models in mice have not been well-characterized.

METHODS

One hundred thirty-five C57Bl/6J mice aged 8 weeks old were divided into the following operations: esophagogastrojejunostomy (side-to-side) (EGJ), esophageal separation and esophagojejunostomy (end-to-side) (EJ), and EJ and gastrectomy (end-to-side) (EJ/TG). The animals were euthanized after 40 weeks and the histology of the junction was examined. Immunohistochemistry for p53, PDX-1, and CDX-2 was performed.

RESULTS

Metaplasia developed in 15/33 (45.5%) of EGJ, 0/38 (0%) of EJ, and 6/39 (15.4%) of EJ/TG (P < .05) and dysplasia developed 7/33 (21.2%) of EGJ, 0% of EJ, and 1/39 (2.6%) of EJ/TG. p53 was positive in all of the dysplastic regions, 12/15 (80%) metaplasias in the EGJ model, and 1/6 (16.7%) metaplasia in the EJ/TG model. CDX-2 was positive in all cases of metaplasias, but decreased in some cases of dysplasia. PDX-1 was positive in 7/8 (88%) cases of dysplasia and in 15/21 (71%) cases of metaplasia (P < .05).

CONCLUSIONS

The EGJ model, which causes reflux of gastric acid and duodenal content, developed metaplasia and dysplasia most frequently. No metaplasia developed in the EJ model in which gastric juice and duodenal content mixed before reflux. Thus, duodenal contents alone can induce columnar metaplasia and dysplasia; however, the combination of gastric acid with duodenal content reflux can cause metaplasia and dysplasia more efficiently.

The association between sleeve gastrectomy and histopathologic changes consistent with esophagitis in a rodent model

BACKGROUND

As the association between sleeve gastrectomy (SG) and gastroesophageal reflux disease remains unclear, the aim of this study was to evaluate whether performance of SG impacts the development and severity of esophagitis in a rodent model.

SETTING

University Hospital.

METHODS

Wistar rats (Charles River Institute, Wilmington, MA) were fed a high fat diet (HFD) for 4 months and then were divided into 3 cohorts of nearly equal mean weight: HFD only (n = 25), sham operation+HFD (n = 29), and SG+HFD (n = 19). Animals were euthanized at 12 weeks. The esophagus was harvested en-bloc and processed for histologic assessment by a board certified pathologist, blinded to the animal treatment group. Reflux was graded by severity and defined as the presence of inflammation in the esophageal squamous mucosa.

RESULTS

Rats who underwent SG had significantly increased reflux severity, compared with sham and HFD alone (21.1% versus 0% versus 4.5%, P = .02), respectively. No difference was demonstrated in negative, mild, or moderate esophagitis between the control, sham, and sleeve groups. Using nonparametric ANOVA, the mean severity score for severe esophagitis was significantly increased in the SG group versus sham or HFD group (1.5 versus .81 versus 1.36, P = .0202) respectively. Following multinomial logistic regression to assess for confounding variables to the severity scores, final weight, and change in weight, had no effect on severity of esophagitis between the 3 groups (P > .373).

CONCLUSIONS

SG is independently associated with histopathologic changes consistent with severe esophagitis in an animal model, likely secondary to gastroesophageal reflux.

Detection of fluorescent organic nanoparticles by confocal laser endomicroscopy in a rat model of Barrett's esophageal adenocarcinoma

For many years, novel strategies for cancer detection and treatment using nanoparticles (NPs) have been developed. Esophageal adenocarcinoma is the sixth leading cause of cancer-related deaths in Western countries, and despite recent advances in early detection and treatment, its prognosis is still very poor. This study investigated the use of fluorescent organic NPs as potential diagnostic tool in an experimental in vivo model of Barrett’s esophageal adenocarcinoma. NPs were made of modified polysaccharides loaded with [4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran] (DCM), a well-known fluorescent dye. The NP periphery might or might not be decorated with ASYNYDA peptide that has an affinity for esophageal cancer cells. Non-operated and operated rats in which gastroesophageal reflux was surgically induced received both types of NPs (NP-DCM and NP-DCM-ASYNYDA) by intravenous route. Localization of mucosal NPs was assessed in vivo by confocal laser endomicroscopy, a technique which enables a “real time” and in situ visualization of the tissue at a cellular level. After injection of NP-DCM and NP-DCM-ASYNYDA, fluorescence was observed in rats affected by esophageal cancer, whereas no signal was observed in control non-operated rats, or in rats with simple esophagitis or Barrett’s esophagus mucosa. Fluorescence was observable in vivo 30 minutes after the administration of NPs. Interestingly, NP-DCM-ASYNYDA induced strong fluorescence intensity 24 hours after administration. These observations suggested that NPs could reach the tumor cells, likely by enhanced permeability and retention effect, and the peptide ASYNYDA gave them high specificity for esophageal cancer cells. Thus, the combination of NP platform and confocal laser endomicroscopy could play an important role for highlighting esophageal cancer conditions. This result supports the potential of this strategy as a targeted carrier for photoactive and bioactive molecules in esophageal cancer diagnosis and treatment.

Animal Models of Barrett's Esophagus and Esophageal Adenocarcinoma-Past, Present, and Future

Esophageal adenocarcinoma is the fastest rising cancer in the United States. It develops from long-standing gastroesophageal reflux disease which affects >20% of the general population. It carries a very poor prognosis with 5-year survival <20%. The disease is known to sequentially progress from reflux esophagitis to a metaplastic precursor, Barrett's esophagus and then onto dysplasia and esophageal adenocarcinoma. However, only few patients with reflux develop Barrett's esophagus and only a minority of these turn malignant. The reason for this heterogeneity in clinical progression is unknown. To improve patient management, molecular changes which facilitate disease progression must be identified. Animal models can provide a comprehensive functional and anatomic platform for such a study. Rats and mice have been the most widely studied but disease homology with humans has been questioned. No animal model naturally simulates the inflammation to adenocarcinoma progression as in humans, with all models requiring surgical bypass or destruction of existing antireflux mechanisms. Valuable properties of individual models could be utilized to holistically evaluate disease progression. In this review paper, we critically examined the current animal models of Barrett's esophagus, their differences and homologies with human disease and how they have shaped our current understanding of Barrett's carcinogenesis.

In vivo molecular imaging of HER2 expression in a rat model of Barrett's esophagus adenocarcinoma

Human epidermal growth factor receptor 2 (HER2) is involved in the malignant progression of several human cancers, including esophageal adenocarcinoma (EAC). The purpose of this study was to evaluate HER2 overexpression and to explore the feasibility of confocal laser endomicroscopy for in vivo molecular imaging of HER2 status in an animal model of Barrett's-related EAC. Rats underwent esophagojejunostomy with gastric preservation. At 30 weeks post-surgery, the esophagus of 46 rats was studied; endoscopic and histological findings were correlated with HER2 immunofluorescence on excised biopsies and gross specimens. At this age, 23/46 rats developed Barrett's esophagus (BE), and 6/46 had cancer (four EAC and two squamous cell carcinomas). A significant overexpression of HER2 was observed in esophageal adenocarcinoma compared with normal squamous esophagus (9.4-fold) and BE (6.0-fold). AKT and its phosphorylated form were also overexpressed in cancer areas. Molecular imaging was performed at 80 weeks post-surgery in four rats after tail injection of fluorescent-labeled anti-HER2 antibody. At this age, 3/4 rats developed advance adenocarcinoma and showed in vivo overexpression of HER2 by molecular confocal laser endomicroscopy with heterogeneous distribution within cancer; no HER2 signal was observed in normal or Barrett's tissues. Therefore, HER2 overexpression is a typical feature of the surgical induced model of EAC that can be easily quantified in vivo using an innovative mini-invasive approach including confocal endomicroscopy; this approach may avoid limits of histological evaluation of HER2 status on 'blinded' biopsies.

Establishing magnetic resonance imaging as an accurate and reliable tool to diagnose and monitor esophageal cancer in a rat model

OBJECTIVE

To assess the reliability of magnetic resonance imaging (MRI) for detection of esophageal cancer in the Levrat model of end-to-side esophagojejunostomy.

BACKGROUND

The Levrat model has proven utility in terms of its ability to replicate Barrett's carcinogenesis by inducing gastroduodenoesophageal reflux (GDER). Due to lack of data on the utility of non-invasive methods for detection of esophageal cancer, treatment efficacy studies have been limited, as adenocarcinoma histology has only been validated post-mortem. It would therefore be of great value if the validity and reliability of MRI could be established in this setting.

METHODS

Chronic GDER reflux was induced in 19 male Sprague-Dawley rats using the modified Levrat model. At 40 weeks post-surgery, all animals underwent endoscopy, MRI scanning, and post-mortem histological analysis of the esophagus and anastomosis. With post-mortem histology serving as the gold standard, assessment of presence of esophageal cancer was made by five esophageal specialists and five radiologists on endoscopy and MRI, respectively.

RESULTS

The accuracy of MRI and endoscopic analysis to correctly identify cancer vs. no cancer was 85.3% and 50.5%, respectively. ROC curves demonstrated that MRI rating had an AUC of 0.966 (p<0.001) and endoscopy rating had an AUC of 0.534 (p = 0.804). The sensitivity and specificity of MRI for identifying cancer vs. no-cancer was 89.1% and 80% respectively, as compared to 45.5% and 57.5% for endoscopy. False positive rates of MRI and endoscopy were 20% and 42.5%, respectively.

CONCLUSIONS

MRI is a more reliable diagnostic method than endoscopy in the Levrat model. The non-invasiveness of the tool and its potential to volumetrically quantify the size and number of tumors likely makes it even more useful in evaluating novel agents and their efficacy in treatment studies of esophageal cancer.

Operatively induced chronic reflux in rats: a suitable model for studying esophageal carcinogenesis?

BACKGROUND

The mechanisms of esophageal reflux leading to esophageal adenocarcinoma (EA) remain poorly understood. This study appraises critically an operatively induced chronic reflux rat model.

METHODS

We randomized 108 Sprague-Dawley rats into 2 experimental groups; one was performing esophagoduodenal (ED) anastomosis with or without gastrectomy to induce duodeno-esophageal reflux (DER group; n = 63), and the other involved duodeno-gastro-esophageal reflux (DGER group; n = 45). Control groups included (i) Roux-en-Y esophagojejunal anastomosis, (ii) laparotomy alone, (iii) subtotal gastrectomy to induce duodenogastric reflux (DGR group), and (iv) the same procedure as in the DGER group plus proton pump inhibition (PPI group). The esophagus underwent histologic and molecular analyses.

RESULTS

The prevalence of Barrett's esophagus (BE), dysplasia, and EA in the experimental groups was 41%, 7%, and 11%, respectively. Histologic and molecular analyses in groups DER, DGER, and DGR suggested that BE occurred through de novo intestinal metaplasia and proximal migration of duodenal cells. No distant metastases were identified. The molecular characteristics of both BE and EA were similar to humans. BE was more common, and dysplasia and EA less frequent in the DER group when compared with the DGER group (44% vs 24% [P = .038] and 7% vs 25% [P = .012], respectively). Compared with the DGER group, carcinogenic sequence occurred less frequently in the PPI-treated group (P = .019).

CONCLUSION

Despite pathophysiologic differences with humans, the rat model of esophagoduodenostomy reproduces accurately histologic and molecular lesions in the carcinogenetic sequence of BE and allowed us to identify novel, tumor-associated proteins that may be potential biomarkers and new therapeutic targets in EA.

Prevention of Barrett esophagus and esophageal adenocarcinoma by smoothened inhibitor in a rat model of gastroesophageal reflux disease

BACKGROUND

Activated hedgehog (Hh) pathway is associated with development of both Barrett esophagus (BE) and esophageal adenocarcinoma (EAC). We hypothesize that blockade of the Hh pathway with smoothened (Smo) inhibitor can prevent the development of BE/EAC in the Levrat model, in which induced gastroduodenoesophageal reflux (GDER) leads to esophageal carcinogenesis.

METHODS

GDER was induced in 6- to 8-week-old male Sprague-Dawley rats. The Smo inhibitor (10 mg/kg/d) was given orally on postoperative weeks 10 to 16, 18 to 22, and 24 to 28, and rats were killed on week 28. The primary outcome measure was the incidence of BE and EAC. To examine potential therapeutic effects of Smo inhibition on tumor tissue, semiquantitative immunohistochemistry for Ki-67 and caspase 3 was performed. In treated animals that developed cancer, gene expression was analyzed.

RESULTS

Thirty-eight of 48 controls and 32 of 46 treated animals survived to 28 weeks. messenger ribonucleic acid (mRNA) expression of Indian Hh, a ligand of transmembrane receptor patched 1, was 184× higher in BE and 99× higher in EAC compared with normal esophageal tissue (P = 0.0239 and P = 0.0004, respectively). Compared with controls, the incidence of BE and EAC was decreased in treated animals by 35.7% (relative risk reduction, 36%; P = 0.0015) and 36% (relative risk reduction, 62%; P = 0.0033), respectively. Compared with untreated EAC, Ki-67 was downregulated (P = 0.04) and cleaved caspase 3 was no different in treated EAC (P = 0.398). Of the 84 well-known genes involved in cancer drug resistance, 50 were dysregulated in treated EAC (P < 0.05 for each gene).

CONCLUSIONS

Smo inhibitor prevents the development of BE and EAC in an in vivo model of GDER.

Can the rat be used as a valid model of human esophageal adenocarcinoma?

Animal models of Barrett's metaplasia and esophageal adenocarcinoma are important to further characterize the disease and test potential therapies. This paper reviews the development of the surgical model of esophageal adenocarcinoma in the rat and considers whether this model provides a biologically accurate representation of Barrett's esophagus and esophageal adenocarcinoma in humans.