Bile acids and Barrett's oesophagus: a sine qua non or coincidence?

Barrett's Metaplasia Progression towards Esophageal Adenocarcinoma: An Attempt to Select a Panel of Molecular Sensors and to Reflect Clinical Alterations by Experimental Models

The molecular processes that predispose the development of Barrett’s esophagus (BE) towards esophageal adenocarcinoma (EAC) induced by gastrointestinal reflux disease (GERD) are still under investigation. In this study, based on a scientific literature screening and an analysis of clinical datasets, we selected a panel of 20 genes covering BE- and EAC-specific molecular markers (FZD5, IFNGR1, IL1A, IL1B, IL1R1, IL1RN, KRT4, KRT8, KRT15, KRT18, NFKBIL1, PTGS1, PTGS2, SOCS3, SOX4, SOX9, SOX15, TIMP1, TMEM2, TNFRSF10B). Furthermore, we aimed to reflect these alterations within an experimental and translational in vitro model of BE to EAC progression. We performed a comparison between expression profiles in GSE clinical databases with an in vitro model of GERD involving a BE cell line (BAR-T) and EAC cell lines (OE33 and OE19). Molecular responses of cells treated with acidified bile mixture (BM) at concentration of 100 and 250 μM for 30 min per day were evaluated. We also determined a basal mRNA expression within untreated, wild type cell lines on subsequent stages of BE and EAC development. We observed that an appropriately optimized in vitro model based on the combination of BAR-T, OE33 and OE19 cell lines reflects in 65% and more the clinical molecular alterations observed during BE and EAC development. We also confirmed previous observations that exposure to BM (GERD in vitro) activated carcinogenesis in non-dysplastic cells, inducing molecular alternations in the advanced stages of BE. We conclude that it is possible to induce, to a high extent, the molecular profile observed clinically within appropriately and carefully optimized experimental models, triggering EAC development. This experimental scheme and molecular marker panel might be implemented in further research, e.g., aiming to develop and evaluate novel compounds and prodrugs targeting GERD as well as BE and EAC prevention and treatment.

APE1 Upregulates MMP-14 via Redox-Sensitive ARF6-Mediated Recycling to Promote Cell Invasion of Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) is an aggressive malignancy with poor clinical outcome. The incidence of EAC has been rising rapidly in the past three decades. Here, we showed that apurinic/apyrimidinic endonuclease (APE1) is overexpressed in EAC cell lines, and patients' samples of dysplasia and EAC. Downregulation of APE1 or inhibition of its redox function significantly repressed invasion. Overexpression of a redox-defective mutant, C65A, abrogated the proinvasive phenotype of APE1. APE1 regulated invasion via upregulation of matrix metalloproteinase 14 (MMP-14), which subsequently activated MMP-2, leading to degradation of the extracellular matrix in a redox-dependent manner. Downregulation of APE1 or inhibition of its redox function decreased the rate of endocytosis and recycling of MMP-14 protein. APE1 interacted with ARF6, a key regulator of MMP-14 recycling, which maintained ARF6 activity in an APE1-redox-dependent manner, promoting its ability to regulate MMP-14 recycling to the cell surface. In summary, these findings identify a novel redox-sensitive APE1-ARF6-MMP-14 signaling axis that mediates cellular invasion in esophageal carcinogenesis. SIGNIFICANCE: This study demonstrates the association between oxidative stress and the development and metastatic behavior of esophageal adenocarcinoma.

Exposure of Barrett's and esophageal adenocarcinoma cells to bile acids activates EGFR-STAT3 signaling axis via induction of APE1

The development of Barret’s esophagus (BE) and its progression to esophageal adenocarcinoma (EAC) is highly linked to exposure to acidic bile salts due to chronic gastroesophageal reflux disease (GERD). In this study, we investigated the role of Apurinic/apyrimidinic endonuclease 1 /redox effector factor-1 (APE-1/REF-1) in STAT3 activation in response to EAC. Our results indicate that APE1 is constitutively overexpressed in EAC whereas its expression is transiently induced in response to acidic bile salts in non-neoplastic BE. Using overexpression or shRNA knockdown of APE1, we found that APE1 is required for phosphorylation, nuclear localization, and transcription activation of STAT3. By using an APE1 redox-specific mutant (C65A) and APE1 redox inhibitor (E3330), we demonstrate that APE1 activates STAT3 in a redox-dependent manner. By using pharmacologic inhibitors and genetic knockdown systems, we found that EGFR is a required link between APE1 and STAT3. EGFR phosphorylation (Y1068) was directly associated with APE1 levels and redox function. Co-immunoprecipitation and proximity ligation assays indicated that APE-1 coexists and interacts with the EGFR-STAT3 protein complex. Consistent with these findings, we demonstrated a significant induction in mRNA expression levels of STAT3 target genes (IL-6, IL-17A, BCL-xL, Survivin and c-Myc) in BE and EAC cells, following acidic bile salts treatment. ChIP assays indicated that acidic bile salts treatment enhances binding of STAT3 to the promoter of its target genes, Survivin and BCL-xL. Inhibition of APE1/REF-1 redox activity using E3330 abrogated STAT3 DNA binding and transcriptional activity. The induction of APE-1 - STAT3 axis in acidic bile salts conditions provided a survival advantage and promoted cellular proliferation. In summary, our study provides multiple pieces of evidence supporting a critical role for APE1 induction in activating the EGFR-STAT3 signaling axis in response to acidic bile salts, the main risk factors for Barrett’s carcinogenesis.

Lack of correlation between gastroesophageal reflux disease symptoms and esophageal lesions after sleeve gastrectomy

BACKGROUND

The postoperative development or worsening of gastroesophageal reflux disease (GERD) represents the major drawback of laparoscopic sleeve gastrectomy (SG). A GERD diagnosis is often based only on symptoms and proton pump inhibitors (PPI) intake, while objective tests like esophagogastroduodenoscopy and pH measurements are performed less frequently.

OBJECTIVES

To evaluate the association between reflux symptoms and GERD-related esophageal lesions.

SETTINGS

University hospital, Rome, Italy.

METHODS

A comprehensive clinical control entailing GERD symptoms, PPI intake, and esophagogastroduodenoscopy was proposed to all patients who underwent SG between June 2007 and February 2011, irrespective of the presence of GERD symptoms. One hundred forty-four of 219 patients agreed to take part in the study (follow-up rate: 65.8%).

RESULTS

After a mean follow-up of 66 months, GERD symptoms and PPI intake were recorded in 70.2% and 63.9% of patients, respectively. Mean visual analogue scale score was 2.9 ± 3.3. The overall frequency of erosive esophagitis was 59.8%, while nondysplastic Barrett's esophagus was detected in 13.1%. The frequency of esophageal biliary reflux was 68%. GERD symptoms and visual analogue scale score were not significantly associated with the development of erosive esophagitis and Barrett's esophagus and the severity of the esophageal lesions. Moreover, the frequency of erosive esophagitis and Barrett's esophagus in patients consuming PPI were similar to that of patients without PPI.

CONCLUSION

Symptoms investigation alone is not a reliable tool to diagnose GERD after SG. The use of objective diagnostic tests, such as esophagogastroduodenoscopy, should be carefully considered in the postoperative follow-up schedule of SG patients.

APE1-mediated DNA damage repair provides survival advantage for esophageal adenocarcinoma cells in response to acidic bile salts

Chronic Gastroesophageal Reflux Disease (GERD) is the main risk factor for the development of Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (EAC). Accordingly, EAC cells are subjected to high levels of oxidative stress and subsequent DNA damage. In this study, we investigated the expression and role of Apurinic/apyrimidinic endonuclease 1 (APE1) protein in promoting cancer cell survival by counteracting the lethal effects of acidic bile salts (ABS)-induced DNA damage. Immunohistochemistry analysis of human tissue samples demonstrated overexpression of APE1 in more than half of EACs (70 of 130), as compared to normal esophagus and non-dysplastic BE samples (P < 0.01). To mimic in vivo conditions, we treated in vitro cell models with a cocktail of ABS. The knockdown of endogenous APE1 in EAC FLO-1 cells significantly increased oxidative DNA damage (P < 0.01) and DNA single- and double-strand breaks (P < 0.01), whereas overexpression of APE1 in EAC OE33 cells reversed these effects. Annexin V/PI staining indicated that the APE1 expression in OE33 cells protects against ABS-induced apoptosis. In contrast, knockdown of endogenous APE1 in FLO-1 cells increased apoptosis under the same conditions. Mechanistic investigations indicated that the pro-survival function of APE1 was associated with the regulation of stress response c-Jun N-terminal protein kinase (JNK) and p38 kinases. Pharmacological inhibition of APE1 base excision repair (BER) function decreased cell survival and enhanced activation of JNK and p38 kinases by ABS. Our findings suggest that constitutive overexpression of APE1 in EAC may be an adaptive pro-survival mechanism that protects against the genotoxic lethal effects of bile reflux episodes.

The Role of Gastroesophageal Reflux and Other Factors during Progression to Esophageal Adenocarcinoma

BACKGROUND

U.S. esophageal adenocarcinoma (EAC) incidence increased over 5-fold between 1975 and 2009. Symptomatic gastroesophageal reflux disease (sGERD) elevates the risk for EAC. However, a simple calculation suggests that changes in sGERD prevalence can explain at most approximately 16% of this trend. Importantly, a mechanistic understanding of the influence of sGERD and other factors (OF) on EAC is lacking.

METHODS

A multiscale model was developed to estimate temporal trends for sGERD and OF, and their mechanistic role during carcinogenesis. Model calibration was to Surveillance, Epidemiology, and End Results (SEER) incidence and age-dependent sGERD data using maximum likelihood and Markov chain Monte Carlo (MCMC) methods.

RESULTS

Among men, 77.8% [95% credibility interval (CI), 64.9%-85.6%] of the incidence trend is attributable to OF, 13.4% (95% CI, 11.4%-17.3%) to sGERD, and 8.8% (95% CI, 4.2%-13.7%) to sGERD-OF interactions. Among women, 32.6% (95% CI, 27.0%-39.9%) of the trend is attributable to OF, 13.6% (95% CI, 12.5%-15.9%) to sGERD, and 47.4% (95% CI, 30.7%-64.6%) to interactions. The predicted trends were compared with historical trends for obesity, smoking, and proton pump inhibitor use. Interestingly, predicted OF cohort trends correlated most highly with median body mass index (BMI) at age 50 (r = 0.988 for men; r = 0.998 for women).

CONCLUSIONS

sGERD and OF mechanistically increase premalignant cell promotion, which increases EAC risk exponentially with exposure duration.

IMPACT

Surveillance should target individuals with long-duration sGERD and OF exposures.

Activity of mitogen-activated protein kinases in the esophageal epithelium of patients with Barrett's esophagus

Barrett's esophagus (BE), a complication of gastroesophageal reflux disease, is associated with an increased risk of esophageal cancer. Mitogen-activated protein kinases may play an important role in the pathogenesis of this process. We aimed to evaluate mitogen-activated protein kinases activity in esophageal mucosa of patients with BE and find possible relationship between reflux type and BE. Twenty-four patients (mean age: 59 years) with gastroesophageal reflux disease symptoms and endoscopically suspected esophageal metaplasia (ESEM) were prospectively enrolled for testing by a multichannel intraluminal impedance monitoring along with a Bilitec 2000. Endoscopic biopsies were taken from methylene blue-positive pit patterns (sites suggesting specialized intestinal metaplasia [SIM]), from 2 cm above the Z-line and from cardial parts of the stomach. The biopsies were analyzed for extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 activity by Western blot. Seventeen ESEMs had histologically proven metaplasia: eight patients had SIM and nine had gastric-type epithelia (GE). Biliary reflux was more evident in SIM (P = 0.019) but not in GE (P = 0.019); non-biliary reflux was typical for GE (P = 0.005) but not for SIM (P = 0.04). Strong activations of ERK and p38 were found predominantly in SIM, but not in normal esophageal mucosa (NE) (P = 0.01 and P < 0.001 respectively). Strong signals for active JNK and p38 were detected in GE, but not in NE (P = 0.006 and P = 0.02 respectively). ERK activity was significantly higher than p38 activity in ESEM patients only with GE (P = 0.02). The strong activation of ERK, but not JNK is indicative of SIM. The presence of bile in gastroesophageal refluxate is predisposing to SIM, but not to GE in esophageal mucosa.

Three measurable and modifiable enteric microbial biotransformations relevant to cancer prevention and treatment

Interdisciplinary scientific evaluation of the human microbiota has identified three enteric microbial biotransformations of particular relevance for human health and well-being, especially cancer. Two biotransformations are counterproductive; one is productive. First, selective bacteria can reverse beneficial hepatic hydroxylation to produce toxic secondary bile acids, especially deoxycholic acid. Second, numerous bacterial species can reverse hepatic detoxification-in a sense, retoxify hormones and xeonobiotics-by deglucuronidation. Third, numerous enteric bacteria can effect a very positive biotransformation through the production of butyrate, a small chain fatty acid with anti-cancer activity. Each biotransformation is addressed in sequence for its relevance in representative gastrointestinal and extra-intestinal cancers. This is not a complete review of their connection with every type of cancer. The intent is to introduce the reader to clinically relevant microbial biochemistry plus the emerging evidence that links these to both carcinogenesis and treatment. Included is the evidence base to guide counseling for potentially helpful dietary adjustments.

Optical detection of preneoplastic lesions of the central airways

Current routine diagnosis of premalignant lesions of the central airways is hampered due to a limited sensitivity (white light bronchoscopy) and resolution (computer tomography (CT), positron emission tomography (PET)) of currently used techniques. To improve the detection of these subtle mucosal abnormalities, novel optical imaging bronchoscopic techniques have been developed over the past decade. In this review we highlight the technological developments in the field of endoscopic imaging, and describe their advantages and disadvantages in clinical use.

Expression, localization and polymorphisms of the nuclear receptor PXR in Barrett's esophagus and esophageal adenocarcinoma

BACKGROUND

The continuous exposure of esophageal epithelium to refluxate may induce ectopic expression of bile-responsive genes and contribute to the development of Barrett's esophagus (BE) and esophageal adenocarcinoma. In normal physiology of the gut and liver, the nuclear receptor Pregnane × Receptor (PXR) is an important factor in the detoxification of xenobiotics and bile acid homeostasis. This study aimed to investigate the expression and genetic variation of PXR in reflux esophagitis (RE), Barrett's esophagus (BE) and esophageal adenocarcinoma.

METHODS

PXR mRNA levels and protein expression were determined in biopsies from patients with adenocarcinoma, BE, or RE, and healthy controls. Esophageal cell lines were stimulated with lithocholic acid and rifampicin. PXR polymorphisms 25385C/T, 7635A/G, and 8055C/T were genotyped in 249 BE patients, 233 RE patients, and 201 controls matched for age and gender.

RESULTS

PXR mRNA levels were significantly higher in adenocarcinoma tissue and columnar Barrett's epithelium, compared to squamous epithelium of these BE patients (P<0.001), and RE patients (P=0.003). Immunohistochemical staining of PXR showed predominantly cytoplasmic expression in BE tissue, whereas nuclear expression was found in adenocarcinoma tissue. In cell lines, stimulation with lithocholic acid did not increase PXR mRNA levels, but did induce nuclear translocation of PXR protein. Genotyping of the PXR 7635A/G polymorphism revealed that the G allele was significantly more prevalent in BE than in RE or controls (P=0.037).

CONCLUSIONS

PXR expresses in BE and adenocarcinoma tissue, and showed nuclear localization in adenocarcinoma tissue. Upon stimulation with lithocholic acid, PXR translocates to the nuclei of OE19 adenocarcinoma cells. Together with the observed association of a PXR polymorphism and BE, this data implies that PXR may have a function in prediction and treatment of esophageal disease.

Deoxycholic acid causes DNA damage while inducing apoptotic resistance through NF-κB activation in benign Barrett's epithelial cells

Gastroesophageal reflux is associated with adenocarcinoma in Barrett's esophagus, but the incidence of this tumor is rising, despite widespread use of acid-suppressing medications. This suggests that refluxed material other than acid might contribute to carcinogenesis. We looked for potentially carcinogenetic effects of two bile acids, deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA), on Barrett's epithelial cells in vitro and in vivo. We exposed Barrett's (BAR-T) cells to DCA or UDCA and studied the generation of reactive oxygen/nitrogen species (ROS/RNS); expression of phosphorylated H2AX (a marker of DNA damage), phosphorylated IkBα, and phosphorylated p65 (activated NF-κB pathway proteins); and apoptosis. During endoscopy in patients, we took biopsy specimens of Barrett's mucosa before and after esophageal perfusion with DCA or UDCA and assessed DNA damage and NF-κB activation. Exposure to DCA, but not UDCA, resulted in ROS/RNS production, DNA damage, and NF-κB activation but did not increase the rate of apoptosis in BAR-T cells. Pretreatment with N-acetyl-l-cysteine (a ROS scavenger) prevented DNA damage after DCA exposure, and DCA did induce apoptosis in cells treated with NF-κB inhibitors (BAY 11-7085 or AdIκB superrepressor). DNA damage and NF-κB activation were detected in biopsy specimens of Barrett's mucosa taken after esophageal perfusion with DCA, but not UDCA. These data show that, in Barrett's epithelial cells, DCA induces ROS/RNS production, which causes genotoxic injury, and simultaneously induces activation of the NF-κB pathway, which enables cells with DNA damage to resist apoptosis. We have demonstrated molecular mechanisms whereby bile reflux might contribute to carcinogenesis in Barrett's esophagus.

Effects of refluxate pH values on duodenogastroesophageal reflux-induced esophageal adenocarcinoma

AIM: To determine the effects of duodenogastric juice pH on the development of esophageal adenocarcinoma (EAC).

METHODS: An animal model of duodenogastroesophageal reflux was established using Sprague-Dawley (SD) rats undergoing esophagoduodenostomy (ED). The development of EAC was investigated in rats exposed to duodenogastric juice of different pH. The rats were divided into three groups: low-pH group (group A), high-pH group (group B) and a sham-operated group as a control (group C) (n = 30 rats in each group). The incidence of esophagitis, Barrett’s esophagus (BE), intestinal metaplasia with dysplasia and EAC was observed 40 wk after the treatment.

RESULTS: The incidence rate of esophagitis, BE, intestinal metaplasia with dysplasia and EAC was higher in groups A and B compared with the control group after 40 wk (P < 0.01), being 96% and 100% (P > 0.05), 88% and 82.4% (P > 0.05), 20% and 52.1% (P < 0.05), and 8% and 39% (P < 0.05), respectively.

CONCLUSION: Non-acidic refluxate increases the occurrence of intestinal metaplasia with dysplasia and EAC while the low-pH gastric juice exerts a protective effect in the presence of duodenal juice. The non-acid reflux is particularly important in the progression from BE to cancer. Therefore, control of duodenal reflux may be an important prophylaxis for EAC.

Systematic review: the role of bile acids in the pathogenesis of gastro-oesophageal reflux disease and related neoplasia

BACKGROUND

Factors other than acid may play a role in gastro-oesophageal reflux disease (GERD) and its complications.

AIM

To assessed the role of bile acids in the pathogenesis of GERD, Barrett's oesophagus and Barrett's-related neoplasia.

METHODS

We conducted a systematic review of computerised bibliographic databases for original articles involving humans or human oesophageal tissue or cells that assessed exposure to or manipulation of bile acids. Outcomes assessed included GERD symptoms; gross oesophageal injury; Barrett's oesophagus and related neoplasia; and intermediate markers of inflammation, proliferation or neoplasia.

RESULTS

Eighty-three original articles were included. In in vivo studies, bile acids concentrations were higher in the oesophageal aspirates of patients with GERD than controls, and bile acids infusions triggered GERD symptoms, especially in high concentrations or in combination with acid. In ex vivo/in vitro studies, bile acids stimulated squamous oesophageal cells and Barrett's epithelial cells to produce inflammatory mediators (e.g., IL-8 and COX-2) and caused oxidative stress, DNA damage and apoptosis. They also induced squamous cells to change their gene expression pattern to resemble intestinal-type cells and caused Barrett's cells to increase expression of intestinal-type genes.

CONCLUSIONS

In aggregate, these studies suggest that bile acids may contribute to the pathogenesis of symptoms, oesophagitis and Barrett's metaplasia with related carcinogenesis in patients with GERD. However, all study results are not uniform and substantial differences in study parameters may explain at least some of this variation.

The pathogenesis of Barrett's metaplasia and the progression to esophageal adenocarcinoma

The most important risk factor for the development of Barrett's esophagus is the reflux of both gastric and duodenal contents into the esophagus. The reason why Barrett's metaplasia develops only in a minority of patients suffering from gastroesophageal reflux disease remains unknown.The exact mechanism behind the transition of normal squamous epithelium into specialized columnar epithelium is also unclear. It is likely that stem cells are involved in this metaplastic change, as they are the only permanent residents of the epithelium. Several tumorigenic steps that lead to the underlying genetic instability, which is indispensable in the progression from columnar metaplasia to esophageal adenocarcinoma have been described. This review outlines the process of pathogenesis of Barrett's metaplasia and its progression to esophageal adenocarcinoma.

Bile salts differentially sensitize esophageal squamous cells to CD95 (Fas/Apo-1 receptor) mediated apoptosis

BACKGROUND

The role of nonacidic reflux contents on the pathophysiology of Barrett's esophagus remains poorly understood. We hypothesized that esophageal squamous epithelium differs from Barrett's columnar epithelium in response to bile salts with respect to subsequent changes in the cell surface expression of CD95 (Fas/Apo-1) and sensitivity to CD95-mediated apoptosis.

METHODS

Immortalized esophageal squamous cells (HET-1A) and Barrett's esophagus cells (BAR-T), and esophageal adenocarcinoma cells (Flo-1) were treated with toxic and nontoxic bile salts at concentrations observed in gastroesophageal refluxate. CD95 cell-surface expression and apoptotic response to activating anti-CD95 antibody treatment was determined by FACScan analysis.

RESULTS

Bile salt exposure resulted in a dose-dependent increase in CD95 cell-surface expression in HET-1A cells, but not BAR-T or Flo-1 cells. This response occurred rapidly, within a time-frame inconsistent with de novo protein synthesis and was blocked by protein kinase C (PKC) inhibition. Surprisingly, PKC inhibition in Flo-1 cells resulted in an increase in CD95 cell surface expression. Following bile salt exposure, a corresponding increase in the induction of CD95-mediated apoptosis was observed in HET-1A cells; PKC inhibition sensitized Flo-1 cells to apoptosis.

CONCLUSIONS

Our findings suggest that esophageal squamous cells are sensitized to CD95-mediated apoptosis following bile salt exposure. This differential response, compared with columnar epithelial cells, could exert a selection pressure that contributes to the pathophysiology of Barrett's esophagus.

[Gastro-esophageal reflux through gastric antisecretory drugs]

During the 20th century, gastro-esophageal reflux moved from the status of a rare and severe disease to that of a frequent disease occurring mostly, in the absence of any significant lesions. Proton pump inhibitors (PPIs) are the mainstay of its therapy and are prescribed mainly in an empirical way. Extradigestive manifestations require more accurate diagnostic tests and therapeutic management. The modalities of prescription of the PPIs quickly progressed toward the on-demand therapy and over-the-counter PPIs should become widespread. The relative failures of PPIs led to a profusion of new antisecretory agents but clinical improvements are presently disappointing and the rationale of this escalation is questionable. The concept of non acid gastro-esophageal reflux opens more innovative diagnostic and therapeutic perspectives which, however, must be validated. In this respect, endoscopic treatment needs more reliable techniques and more rigorous trials. Gastro-esophageal reflux refractory to PPIs corresponds mainly to functional esophageal disorders that need diagnostic and therapeutic improvements. Barrett's esophagus constitutes a major challenge for the next few years. Its screening and its prevention seem, for the moment, inaccessible. Its survey and the prevention of its complications should benefit from progress of diagnostic and interventional endoscopy.

Expression of CDX1/2 in patients with Barrett's esophagus and the effects of bile acids on CDX2 expression

AIM: To investigate CDX1 and CDX2 expressions in biopsies obtained from patients with reflux esophagitis and Barrett's esophagus and to study the effects of various bile acids on CDX2 mRNA expression in human esophageal cell line (Eca-109).

METHODS: Endoscopic biopsies were obtained at the distal esophagus in patients and classified according to histology: normal squamous mucosa (n = 5), esophagitis mucosa (n = 7), and Barrett's metaplasia (n = 8). Gene expression of CDX1 and CDX2 were measured using reverse transcription polymerase chain reaction (RT-PCR) or quantitative real-time RT-PCR. CDX2 protein expression was assessed immunohistochemically. Human esophageal cell line (Eca-109) was exposed to cell culture for 1-24 h to 100, 400, 1000 μmol/L deoxycholic acid (DCA), cholicacid (CA), and glycocholicacids (GC). CDX2 mRNA expression was determined by quantitative RT-PCR.

RESULTS: CDX2 mRNA expression was significantly higher in Barrett's epithelium (9.6411 ± 6.6823) and reflux esophagitis (3.9156 ± 3.6700), compared with normal esophagus (P = 0.006, 0.025 respectively). There was no significant difference between Barrett's mucosa and reflux esophagits (P = 0.133). CDX1 mRNA was not detected in all esophageal mucosa. There was no CDX2 protein expression in normal squamous esophagus, and nuclear immunoreactivity was seen in Barrett's epithelium. Perinuclear immunoreactivity for CDX2 was detected in reflux esophagitis. CDX2 mRNA expression was absent before bile acid exposure in all cell lines and increased in a dose- and time-dependent pattern with deoxycholic acid (DCA), cholicacid (CA), and glycocholicacids (GC).

CONCLUSION: CDX2 expression is up-regulated in esphagitis and Barrett's esophagus, suggesting a possible onset role for CDX2 in esophagitis-Barrett's metaplasia sequence. Bile acids can evoke high expression of CDX2 in vitro. Bile acids may play an important role in Barrett's metaplasia by influencing the expression of CDX2.

Gene expression profile comparison of Barrett's esophagus epithelial cell cultures and biopsies

Barrett's esophagus (BE) is a metaplastic process in which the normal squamous epithelium of the distal esophagus is replaced by columnar lined epithelium. The aim was to gain more insight in the process of metaplasia and to identify which genes are specifically expressed by the epithelial cells and the surrounding tissues in BE. Hereto, the gene expression profile of a BE epithelial primary cell culture was compared to that of a BE biopsy. To specifically obtain the epithelial cell layer, epithelial cells from biopsies of BE were cultured using a Barrett specific culturing medium. Serial analysis of gene expression was applied to obtain a transcription library of the primary epithelial cell culture. The transcriptome was analyzed and compared to a previously described transcriptome of a BE biopsy. Validation of results by reverse transcriptase-polymerase chain reaction was performed using tissues of 16 BE patients and 16 primary cell cultures. Over 43,000 tags were sequenced. Genes specifically expressed by the Barrett epithelial cells were for instance Lipocalin 2 and Cyclin D1, whereas annexin A10, trefoil factor (TFF)1 and TFF2 were specifically expressed in the BE biopsies. The comparison of the gene expression profiles of BE primary cultured epithelial cells with BE biopsy defines a subset of genes that are specifically expressed by the epithelial cells and another subset that most likely is expressed by the underlying stromal tissues in the BE biopsy specimens.

Activation of MUC1 mucin expression by bile acids in human esophageal adenocarcinomatous cells and tissues is mediated by the phosphatidylinositol 3-kinase

BACKGROUND

In esophageal adenocarcinoma, MUC1 mucin expression increases in early stages of the carcinogenetic sequence, during which bile reflux has been identified as a major carcinogen. However, no link between MUC1 overexpression and the presence of bile acids in the reflux has been established so far, and molecular mechanisms regulating MUC1 expression during esophageal carcinogenetic sequence are unknown. Our aim was to identify (1) the bile acids able to upregulate MUC1 expression in esophageal cancer cells and mucosal samples, (2) the regulatory regions in MUC1 promoter responsive to bile acids, and (3) the signaling pathway(s) involved in this regulation.

METHODS

MUC1 mRNA and mucin expression were studied by the means of real-time reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry, both in the human esophageal OE33 adenocarcinoma cell line and in an ex vivo explant model. MUC1 promoter was cloned and transcription regulation was studied by transient cell transfection to identify the bile acid-responsive regions. Signaling pathways involved were identified using specific pharmacologic inhibitors and siRNA approach.

RESULTS

Taurocholic, taurodeoxycholic, taurochenodeoxycholic, glycocholic, sodium glycocholate, and deoxycholic bile acids upregulated MUC1 mRNA and protein expression. The highest induction was obtained with deoxycholic and taurocholic acids in both cellular and explant models. The bile acid-mediated upregulation of MUC1 transcription occurs at the promoter level, with responsive elements located in the -1472/-234 region of the promoter, and involves the phosphatidylinositol 3-kinase signaling pathway.

CONCLUSIONS

Bile acids induce MUC1 mucin overexpression in human esophageal adenocarcinoma cells and tissues by activating its transcription through a process involving phosphatidylinositol 3-kinase.