Epidermal growth factor receptors in the oesophagus

From genetics to signaling pathways: molecular pathogenesis of esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) has one of the fastest rising incidence rates in the U.S. and many other Western countries. One of the unique risk factors for EAC is gastroesophageal reflux disease (GERD), a chronic digestive condition in which acidic contents from the stomach, frequently mixed with duodenal bile, enter the esophagus resulting in esophageal tissue injury. At the cellular level, progression to EAC is underlined by continuous DNA damage caused by reflux and chronic inflammatory factors that increase the mutation rate and promote genomic instability. Despite recent successes in cancer diagnostics and treatment, EAC remains a poorly treatable disease. Recent research has shed new light on molecular alterations underlying progression to EAC and revealed novel treatment options. This review focuses on the genetic and molecular studies of EAC. The molecular changes that occur during the transformation of normal Barrett's esophagus to esophageal adenocarcinoma are also discussed.

Role of saliva in esophageal defense: implications in patients with nonerosive reflux disease

Background:

It has been previously demonstrated that patients with reflux esophagitis exhibit a significant impairment in the secretion of salivary protective components versus controls. However, the secretion of salivary protective factors in patients with nonerosive reflux disease (NERD) is not explored. The authors therefore studied the secretion of salivary volume, pH, bicarbonate, nonbicarbonate glycoconjugate, protein, epidermal growth factor (EGF), transforming growth factor alpha (TGF-α) and prostaglandin E2 in patients with NERD and compared with the corresponding values in controls (CTRL).

Methods:

Salivary secretion was collected during basal condition, mastication and intraesophageal mechanical (tubing, balloon) and chemical (initial saline, acid, acid/pepsin, final saline) stimulations, respectively, mimicking the natural gastroesophageal reflux.

Results:

Salivary volume, protein and TGF-α outputs in patients with NERD were significantly higher than CTRL during intraesophageal mechanical (P < 0.05) and chemical stimulations (P < 0.05). Salivary bicarbonate was significantly higher in NERD than CTRL group during intraesophageal stimulation with both acid/pepsin (P < 0.05) and saline (P < 0.01). Salivary glycoconjugate secretion was significantly higher in the NERD group than the CTRL group during chewing (P < 0.05), mechanical (P < 0.05) and chemical stimulation (P < 0.01). Salivary EGF secretion was higher in patients with NERD during mechanical stimulation (P < 0.05).

Conclusions:

Patients with NERD demonstrated a significantly stronger salivary secretory response in terms of volume, bicarbonate, glycoconjugate, protein, EGF and TGF-α than asymptomatic controls. This enhanced salivary esophagoprotection is potentially mediating resistance to the development of endoscopic mucosal changes by gastroesophageal reflux.

Increase of epidermal growth factor receptor expression in progression of GERD, Barrett, and adenocarcinoma of esophagus

INTRODUCTION

Gastroesophageal reflux disease (GERD) is a pathology with a wide range of clinical and endoscopic manifestations. Epidermal growth factor receptor (EGFR), found in the epithelium of the digestive tract, plays an important role in epithelial repair and shows increased expression in different neoplasms, including esophageal tumors.

OBJECTIVES

The purpose of this study was to evaluate EGFR expression using immunohistochemistry in esophageal biopsies obtained from patients with GERD, Barrett's esophagus, and adenocarcinoma of the esophagus.

METHODS

EGFR expression was immunohistochemically determined in biopsies from 194 patients with symptoms suggestive of GERD or adenocarcinoma of the esophagus, seen at two Brazilian university hospitals between January 2003 and December 2008. Based on histopathological analysis, patients were divided into three groups: GERD, Barrett's esophagus and adenocarcinoma of the esophagus. EGFR expression was considered positive when staining was detected in the membrane.

RESULTS

Mean age was 55.25 years (range 30-90). Patients with GERD (n = 127) accounted for 65.5% of the sample, compared with 12.4% (n = 24) of patients with Barrett's esophagus and 22.2% (n = 43) of patients with esophageal adenocarcinoma. Immunohistochemical analysis was positive for EGFR in 19.1% of the patients (37/194), divided as follows: 8.7% (11/127) in the GERD group, 25% (6/24) in the Barrett's esophagus group, and 46.5% (20/43) in the esophageal adenocarcinoma group. Statistical analysis revealed significant differences between the three groups (p = 0.0001).

CONCLUSIONS

GERD patients showed lower levels of EGFR expression than patients with Barrett's esophagus or patients with adenocarcinoma of the esophagus, suggesting a direct relationship between EGFR expression and disease progression.

Functional single-nucleotide polymorphism of epidermal growth factor is associated with the development of Barrett's esophagus and esophageal adenocarcinoma

Reflux esophagitis (RO) and Barrett's esophagus (BO) can cause esophageal adenocarcinoma (OAC). The esophageal mucosa in the RO-BO-OAC cascade is chronically exposed to gastro-esophageal reflux. Epidermal growth factor (EGF) has an important role in the protection and repair of mucosal damage, and non-physiologic levels are associated with gastrointestinal tumors. The aim is to determine the functional effect of EGF gene polymorphisms on RO, BO and OAC development. A cohort of 871 unrelated Dutch Caucasians consisted of 198 healthy controls, 298 RO patients, 246 BO patients and 129 OAC patients. The frequency of the EGF-production-associated 5'UTR A+61G polymorphism was determined in these four groups. EGF immunohistochemistry was performed on BO biopsies. EGF expression was significantly lower in the G/G genotype compared with the A/G (P=0.008) and A/A (P=0.002) group. The G/G genotype was significantly more prevalent in RO (odds ratios (OR)=2.6; 95% confidence intervals (95% CI): 1.3-5.2), BO (OR=3.0; 95% CI: 1.5-6.2) and OAC (OR=4.1; 95% CI: 1.8-9.7) than in controls. The G allele is associated with reduced EGF expression and increased risk for RO, BO and OAC development. This indicates that reduced mucosal protection resulting from genetically decreased EGF expression enhances esophageal tumor development.

Comparative kinome analysis to identify putative colon tumor biomarkers

Kinase domains are the type of protein domain most commonly found in genes associated with tumorigenesis. Because of this, the human kinome (the protein kinase component of the genome) represents a promising source of cancer biomarkers and potential targets for novel anti-cancer therapies. Alterations in the human colon kinome during the progression from normal colon (NC) through adenoma (AD) to adenocarcinoma (AC) were investigated using integrated transcriptomic and proteomic datasets. Two hundred thirty kinase genes and 42 kinase proteins showed differential expression patterns (fold change ≥ 1.5) in at least one tissue pair-wise comparison (AD vs. NC, AC vs. NC, and/or AC vs. AD). Kinases that exhibited similar trends in expression at both the mRNA and protein levels were further analyzed in individual samples of NC (n = 20), AD (n = 39), and AC (n = 24) by quantitative reverse transcriptase PCR. Individual samples of NC and tumor tissue were distinguishable based on the mRNA levels of a set of 20 kinases. Altered expression of several of these kinases, including chaperone activity of bc1 complex-like (CABC1) kinase, bromodomain adjacent to zinc finger domain protein 1B (BAZ1B) kinase, calcium/calmodulin-dependent protein kinase type II subunit delta (CAMK2D), serine/threonine-protein kinase 24 (STK24), vaccinia-related kinase 3 (VRK3), and TAO kinase 3 (TAOK3), has not been previously reported in tumor tissue. These findings may have diagnostic potential and may lead to the development of novel targeted therapeutic interventions for colorectal cancer.

Risk factors for neoplastic progression in Barrett’s esophagus

Barrett’s esophagus (BE) confers a significant increased risk for development of esophageal adenocarcinoma (EAC), with the pathogenesis appearing to progress through a “metaplasia-dysplasia-carcinoma” (MDC) sequence. Many of the genetic insults driving this MDC sequence have recently been characterized, providing targets for candidate biomarkers with potential clinical utility to stratify risk in individual patients. Many clinical risk factors have been investigated, and associations with a variety of genetic, specific gastrointestinal and other modifiable factors have been proposed in the literature. This review summarizes the current understanding of the mechanisms involved in neoplastic progression of BE to EAC and critically appraises the relative roles and contributions of these putative risk factors from the published evidence currently available.

Bile acid alone, or in combination with acid, induces CDX2 expression through activation of the epidermal growth factor receptor (EGFR)

OBJECTIVES

Bile acids and acid are implicated in the development of Barrett's esophagus. Evidence suggests that Barrett's esophagus intestinal metaplasia may occur via induction of caudal homeobox gene 2 (CDX2). We hypothesized that induction of CDX2 by bile acids may be due to ligand-dependent transactivation of epidermal growth factor receptor (EGFR).

METHODS

Human mucosal epithelial cells (SEG-1) were treated for 0 to 24 h with up to 300 microM deoxycholic acid (DCA) at pH 7 or 5 with or without (w/wo) antibodies against EGFR ligand-binding site (Mab528, 3-5 mug/ml). Treatment with 100 ng/ml EGF served as control. CDX2 mRNA expression was determined by real-time polymerase chain reaction. EGFR activation was analyzed by Westerns of phosphorylated EGFR tyrosines.

RESULTS

Acid (pH 5) increased the induction of CDX2 mRNA expression caused by DCA. CDX2 mRNA induction was markedly reduced by EGFR blockade with Mab528. Each treatment (pH 5, DCA or pH 5 plus DCA) activated the EGFR on all tyrosines tested but in different time courses. Phosphorylation by DCA was inhibited by Mab528. Activation of EGFR by DCA at pH 5 resulted in EGFR degradation, while that by DCA alone did not.

CONCLUSION

Thus, CDX2 induction by DCA w/wo acid occurs through ligand-dependent transactivation of the EGFR. The variations in EGFR degradation pattern with DCA or DCA at pH 5 indicate differential transactivation pathways. The molecular pathogenesis of Barrett's esophagus may occur via bile-stimulated cell signaling through the EGFR.

Pilot study of gefitinib, oxaliplatin, and radiotherapy for esophageal adenocarcinoma: tissue effect predicts clinical response

PURPOSE

Overexpression of epidermal growth factor receptor (EGFR) in esophageal cancer is associated with poor prognosis. Preclinical studies indicate synergism between the EGFR inhibitor gefitinib and oxaliplatin or radiotherapy (RT). We report here early results of a planned phase I/II study of gefitinib, oxaliplatin, and RT for locally advanced, unresectable esophageal cancer.

METHODS AND MATERIALS

The protocol consisted of oral gefitinib 250 mg daily for 1 year plus intravenous oxaliplatin 85 or 100 mg/m(2) on days 1, 15, and 29, and RT (50.4 Gy in 28 1.8-Gy fractions). Four-quadrant biopsies were obtained at 1-cm intervals along the length of the tumor before and after treatment and the specimens were immunostained for EGFR, Erk, Akt, and their phosphorylated (activated) forms.

RESULTS

Enrollment was halted at 6 evaluable cases [all male; median age, 72.5 years (range, 51-75); and all with Eastern Cooperative Oncology Group performance status of 1]. All 6 tumors were adenocarcinomas; 5 were stage III and 1 stage IVA. Oxaliplatin was given at 85 mg/m(2) in 3 cases and at 100 mg/m(2) in 3 cases. Gefitinib therapy lasted a median 24 weeks; the median number of oxaliplatin doses was 6.5. Best responses were mucosal complete response (n = 1), partial response (n = 1), stable disease (n = 1), and progressive disease (n = 3). EGFR was expressed by tumor in 5 cases and Erk and Akt in 6 cases before treatment; no changes were noted after treatment. EGFR expression did not correlate with survival or response. No grade 4 toxicities were noted; grade 3 toxicities were diarrhea (n = 1), vomiting (n = 1), fatigue (n = 1), and constipation (n = 2). Median overall and disease-free survival times were 10.8 months and 8.4 months.

CONCLUSIONS

Gefitinib in combination with oxaliplatin and RT was tolerable, but had limited clinical activity and did not down-regulate total or activated EGFR, Akt, or Erk in esophageal tumor samples.

Epidermal growth factor receptor-directed therapy in esophageal cancer

Esophageal adenocarcinoma (EAC) is one of the fastest growing malignancies in the US. The long-term survival of patients with this cancer remains poor; only 25% of patients undergoing surgical excision are alive after 5 years. Multimodal programs that incorporate radiotherapy, chemotherapy and surgery for localized tumors may result in a modest survival advantage. However, significant strides in this disease can result from the inclusion of targeted therapies. The epidermal growth factor receptor (EGFR) family represents one such target and is receiving increasing attention due to the advent of specific inhibitors. Studies conducted by us and others have shown that the overexpression of EGFR family signaling intermediates is common in Barrett's esophagus and EAC. In the latter case, EGFR expression may have prognostic significance. EGFR inhibitors, including oral tyrosine kinase inhibitors and monoclonal antibodies, result in a synergistic antitumor effect with chemotherapeutic agents or with radiotherapy. Therefore, several ongoing studies include EGFR-directed therapy either alone or in combination with chemoradiotherapy for this disease. Our study of gefitinib, oxaliplatin and radiotherapy suggested that gefitinib can be safely incorporated into an oxaliplatin-based chemoradiation program for esophageal cancer, although the clinical activity of this combination is modest. Herein, we review the current literature on this subject.

Systematic review: the application of molecular pathogenesis to prevention and treatment of oesophageal adenocarcinoma

BACKGROUND

Oesophageal adenocarcinoma is an increasingly common cancer with a poor prognosis. It develops in a stepwise progression from Barrett's metaplasia to dysplasia, and then adenocarcinoma followed by metastasis.

AIM

To outline the key molecular changes in oesophageal adenocarcinoma and to summarize the chemopreventative and therapeutic strategies proposed.

METHODS

A literature search was performed to identify appropriate research papers in the field. Search terms included: Barrett's (o)esophagus, intestinal metaplasia, (o)esophageal adenocarcinoma, molecular changes, genetic changes, pathogenesis, chemoprevention, therapeutic strategies and treatment. The search was restricted to English language articles.

RESULTS

A large number of molecular changes have been identified in the progression from Barrett's oesophagus to oesophageal adenocarcinoma although there does not appear to be an obligate order of events. Potential chemoprevention strategies include acid suppression, anti-inflammatory agents and antioxidants. In established adenocarcinoma, targeted treatments under evaluation include receptor tyrosine kinase inhibitors of EGFR and cyclin-dependent kinase inhibitors, which may benefit a subgroup of patients.

CONCLUSIONS

Advances in molecular methodology have led to a greater understanding of the oesophageal adenocarcinoma pathways, which provides opportunities for chemoprevention and therapeutic strategies with a mechanistic basis. More work is required to assess both the safety and efficacy of these new treatments.

Comparison of Kinome Profiles of Barrett's Esophagus with Normal Squamous Esophagus and Normal Gastric Cardia

The precursor metaplastic mucosal lesion that predisposes for esophageal adenocarcinoma is Barrett's esophagus. Because the signal transduction events that occur in Barrett's esophagus are poorly understood, this study aimed at generating a comprehensive description of cellular kinase activity in Barrett's esophagus, normal squamous esophagus, and gastric cardia to gain more insight into the pathogenesis of Barrett's esophagus. Peptide arrays, exhibiting 1,176 specific consensus sequences for protein kinases, were used to produce a global analysis of cellular kinase activity in biopsies of Barrett's esophagus, and results were compared with the neighboring cardia and squamous epithelia. Several differences in kinase activity using immunoblot analysis and enzyme activity assays were validated in biopsies of 27 Barrett's esophagus patients. Three unique kinome profiles are described and compared. We identified cascades of activated kinases showing that mitogen-activated protein kinase and epidermal growth factor receptor activity are both significantly altered in Barrett's esophagus compared with squamous and gastric cardia epithelia. Another novel finding is that the glycolysis pathway is significantly up-regulated in Barrett's esophagus, which is illustrated by an up-regulated pyruvate kinase activity. Here, the unique kinome profile of Barrett's esophagus is made available as a comprehensive database. Several signaling pathways are revealed as specifically expressed in Barrett's esophagus when compared with the adjacent normal epithelia. These unique findings provide novel insight in the pathogenesis of Barrett's esophagus that will ultimately help to resolve the increasing problem of Barrett's esophagus and prevention of esophageal adenocarcinoma.

Functional oesophageal epithelial defense against acid

Functional oesophageal epithelial defense, including cell proliferation, restitution, buffers and ion transporters, plays a significant role in maintaining mucosal integrity and enabling rapid repair after injury. Growth factors such as epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) are associated with oesophageal epithelial proliferation or restitution. Na+/H+ exchanger-1, an ion transporter, regulates intracellular pH and cell volume, and may have roles in cell proliferation, migration and survival. Cytokine, adhesion molecules, cyclooxygenase-2 and free radicals are associated with oesophageal inflammation and breach of the functional epithelial defense. Although the oesophagus does not have strong functional epithelial defense against acid, this defensive mechanisms may be involved in the pathogenesis of non-erosive gastro-oesophageal reflux disease. Medical therapy may be developed in future to enhance functional oesophageal epithelial defense.

Dynamic change of epidermal growth factor in neonatal rat with intestine injury

AIM: To determine whether diminished levels of epidermal growth factor (EGF) were present in neo-natal rats with intestinal injury and related with the degree of intestinal injury, so we modeled a model in neo-natal rats of intestinal injury and to examine the dynamic levels of EGF on injury of intestine.

METHODS: One-day-old Wistar rat pups received an intraperitoneally injection with 4 mg/kg lipopolysaccharide (LPS), followed by collection of ileum tissue at 1, 3, 6, 12, and 24 h following LPS administration. The ileum was for histological evaluation of NEC and for measurements of EGF using ABC-ELISA. The correlation between the degree of intestinal injury and levels of EGF was determined.

RESULTS: The LPS-injected pups also showed a significant increase in injury scores at 1, 3, 6, 12, and 24 h [respectively, (1.08±0.61), (1.63±0.84), (1.95±0.72), (2.42±0.43) and (2.21±0.53)] vs the control (0.12±0.17) (P<0.01). EGF levels at 1, 3, 6, 12 h [respectively, (245.6±49.0), (221.4±39.0), (223.4±48.1), (246.0±46.6)] pg/mg were significantly loss than the control (275.6±50.4) pg/mg (P<0.05). There was a significant negative correlation between the EGF levels and the grade of intestinal injury within 24 h (P<0.05).

CONCLUSION: Neo-natal rats with intestinal injury have significantly lower levels of ileum EGF. Reduced levels of this growth factor might be related to the pathogenesis of NEC.

Molecular alterations during development of esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma has risen significantly over the last decades. During esophageal carcinogenesis many molecular alterations occur that disrupt essential cellular processes, directing the cell to a rapidly proliferating, immortal state. The chronic inflammation that is present in Barrett's esophagus creates an environment in which such molecular alterations are both induced and tolerated. Here, the novel insights in the molecular mechanisms that underlie the development of esophageal adenocarcinoma are reviewed, focusing on the role of inflammation, angiogenesis, apoptosis inhibition, loss of cell cycle control, and loss of cell-cell adhesion. These novel developments will open new perspectives for diagnosis, treatment, and prevention of esophageal adenocarcinoma.

Epidermal growth factor receptor expression correlates with histologic grade in resected esophageal adenocarcinoma

Activation of the epidermal growth factor receptor (EGFR) has a role in oncogenesis and may correlate with prognosis. The aim of this study was to examine EGFR expression in esophageal adenocarcinoma and correlate EGFR status with pathologic and clinical prognostic features. An exploratory retrospective review of 38 patients with surgically resected esophageal adenocarcinoma was performed. All patients underwent an esophagogastrectomy with regional lymphadenectomy; 24 patients underwent primary resection and 14 patients had surgery after preoperative chemoradiation therapy. Immunohistochemical analysis was performed on paraffin-embedded tissue samples using an EGFR monoclonal antibody. Low- and moderate-grade tumors were positive for EGFR expression in 2 of 15 patients; poorly differentiated tumors were positive for EGFR expression in 13 of 23 patients (p=0.02). The median survival was 35 months (confidence interval [CI]: 29-40) for EGFR negative patients (n=23) and 16 months (CI: 10-22) for EGFR positive patients (n=13) (p=0.10). Disease recurred in 3 of 21 EGFR negative patients and 6 of 13 EGFR positive patients (p=0.06). Poorly differentiated adenocarcinomas of the esophagus demonstrated higher EGFR expression compared to low-grade tumors based upon immunohistochemical analysis. A trend toward improved disease-free and overall survival was seen in EGFR negative patients.

Increased expression of transforming growth factor-alpha and epidermal growth factor receptors in rat chronic reflux esophagitis

BACKGROUND AND AIM

Transforming growth factor-alpha (TGF-alpha), which binds to epidermal growth factor receptors (EGF-R), stimulates esophageal epithelial cell proliferation, enabling rapid repair after mucosal injury. The aim of the present study was to examine epithelial proliferation and dynamics of TGF-alpha and EGF-R gene and protein expression in rat chronic acid reflux esophagitis.

METHODS

Gastric acid reflux esophagitis was induced in Wistar rats by ligating the transitional region between the forestomach and the glandular portion, and by covering the duodenum near the pyloric ring with a small piece of an 18Fr Nélaton catheter. Epithelial cell proliferation was assessed by bromodeoxyuridine (BrdU) uptake. Expression of TGF-alpha and EGF-R mRNA and protein was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS

Esophageal lesions were observed in the lower and middle esophagus. Histologically, a significant increase in mucosal thickening with elongation of lamina propria papillae and basal cell hyperplasia was observed. The BrdU labeling index was significantly increased from 2.7 +/- 1.0 in normal mucosa and 2.8 +/- 1.2 in background mucosa adjacent to the esophageal lesion, to 60.3 +/- 32.7 in the lesions of chronic esophagitis. Expression of TGF-alpha and EGF-R mRNA in the esophageal lesion significantly increased compared to those in the control and background tissue, whereas treatment with rabeprazole significantly inhibited increases in TGF-alpha and EGF-R mRNA expression. According to immunohistochemical study, TGF-alpha and EGF-R revealed strong expression in esophageal lesions compared with control and background mucosa. The superficial layer of the esophagus was strongly positive for TGF-alpha and most cells in regions of basal hyperplasia had a positive reaction for EGF-R in the esophagitis lesion.

CONCLUSION

Epithelial proliferation and expression of TGF-alpha and EGF-R were significantly increased in rat chronic reflux esophagitis. Activation of TGF-alpha and EGF-R genes in response to acid reflux may facilitate rapid mucosal healing by stimulating epithelial proliferation. These results suggest that TGF-alpha and EGF-R play crucial roles in rat chronic reflux esophagitis.

Dilated intercellular spaces and shunt permeability in nonerosive acid-damaged esophageal epithelium

OBJECTIVES

It has recently been established that patients with nonerosive reflux disease have on biopsy within esophageal epithelium a lesion known as dilated intercellular spaces (DIS).

METHODS

To further explore the nature and implications of this lesion, in vitro models of nonerosive acid and acid-pepsin damage were created in Ussing chamber-mounted rabbit esophageal epithelium. Using these models circuit analysis and permeability studies were carried out, the latter using dextran of varying size and human epidermal growth factor (EGF).

RESULTS

Luminal HCl, pH 1.1, or HCl, pH 2.0 + pepsin, 1 mg/ml, for 30 min significantly reduced transepithelial electrical resistance (RT) but produced no gross erosions or histologic evidence of cell necrosis. Transmission electron microscopy, however, documented the presence of DIS. Circuit analysis on healthy esophageal epithelium showed that shunt resistance (RS) was much lower than apical membrane, basolateral membrane and transcellular resistances (Ra, Rb, and Rcell, respectively) and approached that of RT. Further, circuit analysis on acid and acid-pepsin damaged tissues showed that the declines in RT resulted from declines in RS. Moreover, the declines in RT (and so RS) were associated with a linear increase in permeability to 4 kD dextrans as well as an increase in permeability to 6 kD EGF and dextrans as large as 20 kD.

CONCLUSIONS

In nonerosive acid-damaged esophageal epithelium DIS develop in association with and as a marker of reduced transepithelial resistance and increased shunt permeability. This change in shunt permeability upon acid or acid-pepsin exposure is substantial, permitting dextran molecules as large as 20 kD (33 A) to diffuse across the epithelium. Also, this shunt leak enables luminal EGF at 6 kD to diffuse across the acid-damaged epithelium and by so doing enables it to access its receptors on epithelial basal cells. We hypothesize that the shunt leak of EGF may in part account for the development of a reparative phenomenon on esophageal biopsy in patients with nonerosive reflux disease known as basal cell hyperplasia.

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.

[Epidermal growth factor: a probable oral and digestive health protector]

The integrity of oral and digestive mucosa depend on many salivary components like the Epidermal Growth Factor (EGF). Sometimes indicative, sometimes stimulated or modulated factor of oral and digestive health, EGF appears as a clinical marker in neoplastic and inflammatory diseases. As cellular growth factor, it protects the digestive mucosa with stimulation of mucus production and with inhibition of gastric secretion. Equally implicated in healing process, it enhances this one, and determines, in patients, more or less sensibility to inflammatory damages. Its strategic place in various pathologies, as stomach ulcer and tumoral process, open research prospects with a real potential of repair and pronostic.

Increased expression of epidermal growth factor receptors in basal cell hyperplasia of the oesophagus after acid reflux oesophagitis in rats

BACKGROUND

Epidermal growth factor (EGF), which binds to EGF receptors (EGF-R), stimulates oesophageal epithelial cell proliferation, enabling rapid repair after mucosal injury. In the normal human oesophageal epithelium, EGF-R expression is present and confined to the basal layer.

AIM

To examine histological changes in and dynamics of EGF-R expression during healing after acid reflux oesophagitis in a rat model.

METHODS

Gastric acid reflux oesophagitis was induced in Wistar rats by ligation of the pylorus and the transitional region between the forestomach and the grandular portion for 5 h, followed by release of both ligations. Rats were killed 7 and 14 days after production of oesophagitis to examine macroscopic and histological changes as well as dynamics of EGF-R expression. Epithelial cell proliferation was assessed by bromodeoxyuridine (BrdU) uptake, and expression of EGF-R mRNA and protein by RT-PCR and Western blotting or immunohistochemistry.

RESULTS

Gastric acid reflux induced erosive and ulcerative mucosal lesions in the lower and middle part of the oesophagus. These lesions were healed by 14 days and histologically showed thickening of the oesophageal epithelium from 41.11 +/- 3.09 microm in controls to 142.73 +/- 11.59 microm (P < 0.001) in ligated rats, as well as elongation of papillae and basal cell hyperplasia. The number of BrdU-positive cells among basal cells on day 14 was significantly increased from 7.1 +/- 0.8/field in controls to 30.9 +/- 3.0/field in ligated rats. Expression of EGF-R mRNA and protein was significantly increased on day 14 and most basal cells were immunohistochemically positive in both BrdU and EGF-R staining.

CONCLUSION

Acid reflux-induced oesophageal injury caused basal cell hyperplasia with an increase in cell proliferation and EGF-R expression. Activation of EGF-R gene and protein in response to acid reflux-induced injury may facilitate mucosal healing. These results suggest that epidermal growth factor receptors play a crucial role in healing after acid reflux oesophagitis in rats.

Distribution of epidermal growth factor receptor (EGFr) in normal and acute peptic-injured equine gastric squamous epithelium

Growth factors are important in healing and restoration of injured gastrointestinal tissues and, therefore, we characterised temporally the distribution and density of epidermal growth factor receptor (EGFr) in normal and peptic-injured gastric squamous epithelium of horses. Lesions were induced in the equine gastric squamous epithelium using a feed deprivation protocol that results in prolonged increased gastric acidity. Fifteen mature horses, 9 geldings and 6 mares, age 3 to 20 years, were used and divided into 3 groups: Group 1 (n = 5) were subjected to euthanasia for problems unrelated to the gastrointestinal tract and had normal-appearing gastric squamous mucosal epithelium; Groups 2 (n = 5) and 3 (n = 5) had lesions induced in the gastric squamous epithelium by alternating 24 h periods of feed deprivation and ad libitum access to hay, for a total of 48 h and 96 h, respectively. Following lethal injection of a barbiturate, stomachs were removed and fixed by filling with 4- 6 l 10% buffered formalin. Sections were made from normal stomachs and lesions in the gastric squamous epithelium adjacent to the margo plicatus along the right side of the stomach/greater curvature and the lesser curvature. A modified avidin-biotin immunoperoxidase technique was used to stain the formalin-fixed tissue specimens for EGFr. A computerised image analysis system was used to measure area occupied by EGFr (EGFr area) and mean EGFr density in 4 zones within the epithelium extending from the basal cell layers toward the lumen. Measurements were made of epithelium in an erosion bed, at the margin of an ulcer or erosion, and 10-15 mm distant from the lesion margin. Additionally, EGFr area and density were measured in epithelial cells adjacent to capillaries in the epithelium. Intermittent feed deprivation resulted in erosion and ulceration of the gastric squamous epithelium of each horse. Mean EGFr area and density were greatest (P<0.05) in the basal layer of epithelia from all horses, and EGFr staining diminished progressively toward the lumen. Tissues from Group 3 had significantly greater EGFr area in the lesion margin than epithelia from Group 2. EGFr density was less in the epithelia of erosion beds from Groups 2 and 3 compared to normal epithelium, and EGFr area in Group 2 erosion bed epithelia was significantly less than in normal epithelium and epithelia of Group 3. EGFr area in cells adjacent to epithelial capillaries of Group 3 was significantly greater than that of Group 1. Mitotic cell activity was significantly greater in epithelia associated with ulcers and erosions in Groups 2 and 3 compared to normal tissues from Group 1 horses. Staining for EGFr in the glandular mucosa adjacent to squamous epithelium at the margo plicatus was inconsistent and typically faint when present. EGFr distribution in equine gastric squamous epithelium was greatest in regions of greatest cell proliferation, and these areas were in the basal layers of epithelium and immediately adjacent to capillaries. There was evidence that EGFr is induced in peptic-injured equine gastric squamous epithelium. A receptor ligand, EGF or transforming growth factoralpha, may be a factor in healing of gastric squamous mucosal ulcers in horses. Further research should be directed at identifying this ligand and determining its origin in equine gastric mucosa.

Immunoreactive epidermal growth factor receptors are present in gastrointestinal epithelial cells of preterm infants with necrotising enterocolitis

INTRODUCTION

Epidermal growth factor (EGF) affects epithelial cell proliferation, differentiation and migration in the gastrointestinal tract of experimental animals, and increases proliferation when given intravenously to children with congenital microvillous atrophy or necrotising enteritis. The aim of the present study is to determine whether EGF receptors (EGFR) are present in the gut epithelium of preterm infants, and to discover whether neonatal necrotising enterocolitis (NEC) is associated with the absence of EGFR from mucosal cells.

METHODS

Tissues were taken from involved colon and small intestine of four preterm infants with NEC, and control tissues were taken from four other neonates who had laparatomies for congenital malformations. Sections of the tissues were examined histopathologically after treatment with a monoclonal antibody against the external domain of the EGFR (Zymed Laboratories, San Francisco, CA, USA).

RESULTS

Histopathological examination confirmed diagnosis of NEC in the involved bowel and controls showed appearance within normal limit. Immunoreactive EGFR were present on the epithelial cells of both the colon and small intestine, localised on the basolateral membrane of the cells of both subject and the controls. There was no apparent reduction in expression compared with controls.

CONCLUSION

NEC in preterm infants is not associated with absence of EGFR. The presence of EGFR in gut epithelial cells raises the possibility of using EGF for prophylaxis or treatment of NEC.

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.

The potential role of the esophageal pre-epithelial barrier components in the maintenance of integrity of the esophageal mucosa in patients with endoscopically negative gastroesophageal reflux disease

OBJECTIVE

Patients with gastroesophageal reflux disease (GERD) accompanied by erosive reflux esophagitis (RE) exhibit an impairment within the esophageal pre-epithelial barrier protective components that may facilitate the development and/or progression of the mucosal injury. Little is known, however, whether such impairment is a general phenomenon affecting all patients with GERD or whether this is a characteristic feature only of patients with erosive RE. We therefore studied the rate of secretion of esophageal inorganic and organic protective factors in patients with endoscopically negative [E (-)] GERD and compared these results with the corresponding values in asymptomatic volunteers (CTRL).

METHODS

The study was conducted on 33 white asymptomatic volunteers and 10 white patients with a long history of GERD confirmed by 24-h pH monitoring and a grossly negative upper endoscopy. Esophageal secretion was collected during mucosal exposure to NaCl, HCl, HC/pepsin and NaCl using the esophageal perfusion catheter. In collected samples all investigated parameters were measured.

RESULTS

The pH of esophageal secretion and its content of bicarbonate, EGF, and PGE2 in patients with E (-) GERD and asymptomatic volunteers were similar. Unexpectedly, the rate of esophageal glycoconjugate (predominantly mucin) secretion was significantly higher in patients with E (-) GERD than in controls during perfusion with HCl (p < 0.05). Furthermore, secretion of protein in patients with E (-) GERD was significantly higher than in the control group during the mucosal exposure to HCl/Pepsin (p < 0.05). The nonbicarbonate buffer secretion during perfusion with HCl and HCl/Pepsin as well as the rate of esophageal TGFalpha output during infusion of final saline in patients with E (-) GERD were significantly lower than in CTRL group (p < 0.05).

CONCLUSIONS

Our data indicate that patients with E (-) GERD have an esophageal secretory potential, in terms of glycoconjugate and protein, higher than that in asymptomatic controls. This phenomenon in patients with E (-) GERD may, by enhancing the quantity of the esophageal pre-epithelial barrier, help to prevent the development of erosive esophagitis. A significantly lower esophageal secretory response in patients with E (-) GERD in terms of nonbicarbonate buffers and TGFalpha may facilitate the development of GERD symptoms and histological changes of GERD, respectively.

Salivary and gastric epidermal growth factor in patients with Zollinger-Ellison syndrome: its protective potential

OBJECTIVE

Evidence is accumulating that epidermal growth factor (EGF) is a major molecule contributing to the maintenance of the integrity of the upper alimentary tract mucosa before and after injury by acid and pepsin. Patients with Zollinger-Ellison Syndrome (ZES) typically have hypersecretion of acid and pepsin; however, the concentration and rate of secretion of salivary and gastric EGF that could counteract these potentially aggressive factors are unknown. Accordingly, this study was conducted to determine whether EGF affords mucosal protection in ZES patients.

METHODS

The concentration and output of salivary (sEGF) and gastric epidermal growth factor (gEGF) were measured in eight patients with ZES and the results compared to those in 17 patients with nonulcer dyspepsia (NUD), serving as a control group. All patients had normal esophageal and gastric mucosa as determined by endoscopy. Total saliva was collected during 1-h parafilm- and 1-h pentagastrin/parafilm-stimulated conditions, as well as basal and pentagastrin-stimulated gastric juice. The concentration and output of EGF were determined by radioimmunoassay.

RESULTS

The concentration of EGF in saliva collected from ZES patients after parafilm chewing was significantly higher compared to that in NUD patients (4.61 +/- 0.59 vs 2.75 +/- 0.50 ng/ml, p < 0.05). The concentration of EGF in saliva collected after pentagastrin stimulation in ZES patients was also significantly higher than in NUD patients (4.37 +/- 0.73 vs 2.22 +/- 0.37 ng/ml, p < 0.05). Salivary EGF output during parafilm chewing in ZES and NUD were similar (68 +/- 6.4 vs 109 +/- 25.2 ng/h). Salivary EGF output after administration of pentagastrin in ZES and NUD was also similar (66 +/- 6.1 vs 132 +/- 45.4 ng/h). Basal EGF output in the gastric juice of patients with ZES was 3-fold higher than in patients with NUD (801 +/- 73 vs 271 +/- 32 ng/h, p < 0.01). Pentagastrin-stimulated EGF output was similar in both groups (705 +/- 92 vs 675 +/- 168 ng/h).

CONCLUSIONS

Patients with ZES have a significantly higher EGF concentration in saliva and EGF output in basal gastric juice. This elevated content of salivary and gastric EGF in ZES patients may play a protective role in preventing the development of reflux esophagitis and gastric ulcer under the impact of gastric acid and pepsin hypersecretion.

Esophageal submucosal glands: structure and function

A three-tiered defense system exists in the esophagus, which serves a dual purpose of both limiting the degree of gastroesophageal reflux and minimizing the risk of acid-induced mucosal injury. The antireflux barrier, composed of both the lower esophageal sphincter and the diaphragmatic pinchcock, is the first line of defense and serves to limit the frequency and volume of refluxed gastric contents. When the antireflux barrier fails, the second line of defense, esophageal clearance, comes into play and serves to limit the duration of contact between gastric contents and the esophageal epithelium. Mechanisms involved in esophageal clearance include gravity and esophageal peristalsis, which remove volume, and secretions from swallowed saliva and esophageal submucosal glands, which neutralize acid. The third line of defense, tissue resistance, is necessary when acid contact time is prolonged such as when esophageal clearance is either ineffective or not operative (e.g., during sleep). Most studies that have examined esophageal clearance mechanisms have focused on the roles of esophageal peristalsis and salivary secretion, but the role of submucosal gland secretions is less well understood. This article reviews the structure and function of esophageal submucosal glands and discusses the potential role of their secretory products in esophageal clearance and tissue resistance.

Gastro-oesophageal reflux disease and Helicobacter pylori: an intricate relation

Heartburn is a common symptom affecting 21-44% of the adult population on a monthly basis. Oesophagitis is less common, affecting 2% of individuals. Epidemiological studies have shown that patients with gastro-oesophageal reflux disease (GORD) have similar incidence rates of Helicobacter pylori infection as do controls. Some groups have reported that there is a lower incidence, deducing that infection does not cause, and in some way confers protection against GORD. Additional supportive evidence is available from reports of GORD development following successful H pylori eradication. The mechanisms involved are complicated. Individuals with H pylori induced pangastritis and subsequent hypochlorhydria may be protected whereas those with an antral predominant gastritis, as in duodenal ulcer disease, with an increased acid output may be prone to development of GORD. Recent evidence has linked H pylori infection with the development of inflammation of the gastric cardia---carditis. Reports are available which show that carditis is a frequent finding in patients with GORD. The incidence of both cardia and oesophageal carcinoma is increasing. The relation between GORD, carditis, intestinal metaplasia, and cardia carcinoma is unclear. Intestinal metaplasia may result from multifocal atrophic gastritis, linked to H pylori infection or from GORD and the development of Barrett's oesophagus. Long term follow up studies will be required to assess the malignant potential of these histological entities and whether or not H pylori infection has an aetiological role.

Saliva and esophageal protection

There has been much interest in recent years in the potential protective role of saliva in the esophagus. Variables such as salivary volume and neutralizing capacity have been studied both during basal conditions and in response to esophageal acid exposure, in healthy subjects and in patients with esophagitis. In addition to its known neutralizing capacity, saliva also contains growth factors. These polypeptides (of which epidermal growth factor has been studied most) have cytoprotective and healing properties in various segments of the gastrointestinal tract. Therefore, a deficiency in one or more of these growth factors might be a contributing factor in the development of gastroesophageal reflux disease (GERD) or its complication, such as Barrett's metaplasia. However, human studies have produced contradictory results regarding salivary growth factor deficiency in such patients. Current methods of investigation make it difficult to assess the importance of saliva in GERD. This may be due in part to the multifactorial nature of the disease and the difficulty in long-term, selective manipulation of salivary function in humans. Given the present data in the literature, it is therefore unknown if saliva plays an important role in esophageal protection.

Different management for Helicobacter pylori positive and negative patients with gastro-oesophageal reflux disease?

Available evidence would suggest that Helicobacter pylori infection does not contribute to the pathogenesis of gastro-oesophageal reflux disease. The prevalence of H pylori infection in patients with reflux disease is no greater than that in control populations. There are some data suggesting that the organism has a protective role: patients with duodenal ulcers develop reflux disease after H pylori eradication, whereas in patients with oesophageal reflux those with H pylori infection have less severe reflux changes. There is also evidence indicating that the presence of H pylori augments the anti-secretory properties of both the H2 receptor antagonists and proton pump inhibitors (PPIs), suggesting that eradication therapy may not be beneficial. However, the considerable recent interest in the association between H pylori and reflux disease has largely been generated by studies outlining the interactions between H pylori infection and acid suppression in the long term. In H pylori positive patients, therapy with PPIs is associated with a proximal extension of the infection and its associated gastritis. In addition long term PPI therapy is reported to be associated with an accelerated development of atrophic gastritis, suggesting that H pylori should be diagnosed and treated. Although these latter findings in particular need confirmation, H pylori eradication therapy should be considered in this patient group, at least until there is evidence to the contrary.

Impact of smoking cessation on salivary function in healthy volunteers

BACKGROUND

Salivary bicarbonate and epidermal growth factor (EGF) have an important protective role in the oesophagus. The effect of smoking cessation on these aspects of salivary function is unknown.

METHODS

Salivary bicarbonate secretion and EGF output were measured before and after attempted smoking cessation in 28 healthy volunteers. Urinary cotinine excretion was used to assess compliance.

RESULTS

Negative correlations were found between salivary flow rate and age (rho = -0.34) and between cigarette consumption and salivary flow (rho = -0.27) and salivary bicarbonate concentrations (rho = -0.32). Smoking cessation was associated with a significant increase in salivary bicarbonate secretion (day 0, 1.7 (0.14-6.2); day 7, 3.6 (0.52-6.4); day 21, 3.3 (0.44-6.6) micromol min(-1); P < 0.01) but left salivary EGF output unchanged.

CONCLUSION

Smoking cessation is associated with significant improvements in salivary bicarbonate secretion. This would benefit patients with reflux disease who stop smoking.

Trends in the management of gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease is common, with up to 10% of the general population experiencing heartburn on a daily basis. It is a chronic condition and follow-up studies indicate the presence of symptoms at least 20 years after initial diagnosis. In addition to lifestyle modifications, management usually involves the use of an acid suppressant from the H2-receptor antagonist or proton pump inhibitor groups or a prokinetic agent at some stage. In terms of initial symptom resolution and mucosal healing the proton pump inhibitors are consistently superior to the other available agents. However, while it is possible to keep the majority of patients in remission while taking medications, almost all patients have a recurrence of symptoms within six months of stopping medications. The introduction of laparoscopic fundoplication has produced promising initial results but the long-term benefits of this procedure remain to be established. The role of Helicobacter pylori eradication in the management of gastro-oesophageal reflux disease needs further evaluation.

Role of epidermal growth factor (EGF) in oesophageal mucosal integrity

Oesophageal mucosa has well established protective mechanisms, which operate within pre-epithelial, epithelial and post-epithelial compartments. Since refluxed acid and pepsin always act from the luminal side of the mucosa, protective factors like EGF, operating as a part of pre-epithelial defence, are thought to be pivotal in the maintenance of the integrity of the oesophageal mucosa. The significant contribution of salivary EGF to the quality of the oesophageal mucosal barrier has been demonstrated in an experimental setting and in a clinical scenario. Patients with low salivary EGF levels are predisposed to severe oesophageal damage if they develop gastro-oesophageal reflux and are a high-risk group for development of Barrett's oesophagus. Not only the salivary glands but also the human oesophagus has a profound ability to elaborate and release EGF. Some changes in luminal release of EGF during oesophageal mucosal exposure to intraluminal damaging factors imply its role in the oesophageal protective mechanisms. To exert biological effects within the oesophageal mucosal compartment, EGF requires binding to the ligand-binding domain of its receptor. This process results in receptor dimerisation, autophosphorylation and activation of intracellular signal transduction pathways. EGF receptors are localised on the basolateral and luminal aspect of the mucosal cells playing an important role in fast regeneration of oesophageal epithelium through the high mitotic activity of its proliferative zone. An increase in the rate of salivary EGF secretion during masticatory stimulation suggests its potential therapeutic benefit in the treatment of patients with damaged oesophageal mucosa.

Expression of epidermal growth factor, transforming growth factor-alpha and their receptor in the human oesophagus

Increasing evidence indicates that epidermal growth factor and transforming growth factor-alpha are involved in the maintenance of oesophageal mucosal integrity. However, their cellular origin and the exact localization of their receptor in the oesophagus are still unclear. Therefore, we examined the expression of the two growth factors and their shared receptor in the normal human oesophagus at both mRNA and protein level, by immunohistochemistry, in situ hybridization and reverse transcription-polymerase chain reaction. In addition to being expressed in the proliferative compartment of the oesophageal epithelium, the receptor was found in a variety of cells, including smooth muscle cells, submucosal gland cells and the epithelium lining their ducts. Immunohistochemically, the pattern of distribution of epidermal growth factor paralleled that of its receptor. In situ hybridization demonstrated epidermal growth factor mRNA expression in the oesophageal epithelium and submucosal glands. Additionally, amplified transcripts of predicted size were detected by reverse transcription-polymerase chain reaction, thus confirming that authentic transcripts of the growth factor exist in the normal human oesophagus. Transforming growth factor-alpha mRNA and protein expression, while similar to that of epidermal growth factor, predominated in the more differentiated cell layers of the stratified squamous epithelium. These results demonstrate that the normal oesophagus can synthesize both growth factors. Moreover, the peculiar distribution of these peptides and the concomitant expression of their receptor in multiple cell types suggest that the two growth factors may exert diverse physiological functions in the oesophagus and participate in defence and reparative events following mucosal injury.

Disorders of the oesophagus and stomach in infants

Pathological processes and disease entities in the upper gastrointestinal (GI) tract, specifically those of the oesophagus and the stomach in infancy, have received a disproportionately small amount of attention until recently when appreciation of their pathophysiology and concordant importance in terms of symptomatology has been highlighted. This is probably a phenomenon secondary to improved diagnostic yield from the recent technical advances in areas such as infant endoscopy and a shift in opinion regarding the pathophysiological origin of ubiquitous symptoms of infancy such as feeding disorders, colic and irritability. In addition, the apparently complex interactions of various aetiological factors such as pH-independent gastro-oesophageal reflux (GOR), cow's milk protein intolerance (CMPI), Helicobacter pylori gastritis and upper GI motor disorders have in the past 1-2 years become underlined in terms of aetiopathogenesis and have radically changed thinking regarding diagnosis and therapy of infants with apparent upper-GI-associated symptoms. The contribution to comprehension of infant upper GI disorders of inflammatory paradigms and ontogeny of the upper GI tract is also a recent area worthy of mention. The recent advances in all of these areas and their contribution to the understanding, and subsequent diagnosis and therapy, of upper GI symptoms and their explanation by way of aetiopathogenesis will be explored in this chapter.

Short segment Barrett's oesophagus: prevalence, diagnosis and associations

BACKGROUND

Prevalence of short segment Barrett's (SSB) oesophagus, defined as the absence of macroscopic Barrett's but histologically identifiable intestinal metaplasia, has been reported to be 18% based on haematoxylin and eosin (H&E) staining.

AIMS

To define the prevalence of SSB oesophagus using H&E and alcian blue staining and to determine whether SSB oesophagus is associated with inflammation at the gastro-oesophageal junction (GOJ).

SUBJECTS

Consecutive patients (n = 158) presenting for endoscopy completed a structured interview.

METHODS

Two biopsy specimens taken from the GOJ were stained with H&E, alcian blue and Giemsa. A third specimen was obtained from the distal oesophagus. Intestinal metaplasia was diagnosed if goblet cells were definitely identified by two independent observers.

RESULTS

SSB oesophagus was present in 46 (prevalence 36%, 95% confidence interval (CI) 28.5-43.5) using alcian blue staining. If H&E had been the sole staining method used, 50% cases of intestinal metaplasia would have been overlooked. There were no cases of intestinal metaplasia identified by H&E but missed by alcian blue staining. Logistic regression analysis identified age (odds ratio (OR) per decade 1.03, 95% CI 1.01-1.06), histological oesophagitis (OR 3.2, 95% CI 1.4-7.2) and inflammation at the gastrooesophageal junction (OR 5.9, 95% CI 2.2-15.6) as independent risk factors for SSB oesophagus.

CONCLUSION

Unrecognised SSB oesophagus is highly prevalent in patients presenting for diagnostic upper endoscopy if alcian blue staining is applied.

Adaptation of esophageal mucosa to acid- and pepsin-induced damage: role of nitric oxide and epidermal growth factor

To study whether the esophageal mucosa was able to elicit mucosal adaptation, we induced esophageal damage by perfusing acidified pepsin in rabbits. Mucosal adaptation was induced by preexposing the esophageal mucosa to a mild irritant (acidified saline) for 60 min prior to acidified pepsin (strong irritant). Macroscopic and microscopic esophageal injury, cell proliferation, and mucosal barrier function (H+, K+, hemoglobin flux rates) were studied. Preexposure of the esophageal mucosa to acidified saline significantly decreased both the mucosal damage and the mucosal barrier dysfunction induced by acidified pepsin. The development of this phenomenon was nondependent on cell proliferation. Concomitant treatment with either the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine, or the perfusion of immunospecific EGF-receptor antibodies or tyrphostin-25, an inhibitor of the tyrosine kinase activities ligated to the intracytoplasmatic domain of the EGF receptor, during the preexposure period completely reversed the protection induced by acid. We conclude that the rabbit esophageal mucosa shows mucosal adaptation to acid and pepsin. The development of this phenomenon is fast, not dependent on cell proliferation, and dependent, at least in part, on nitric oxide and EGF-receptor-mediated mechanisms.

Detrimental impact of acid and pepsin on the rate of luminal release of transforming growth factor alpha. Its potential pathogenetic role in the development of reflux esophagitis

The impact of intraluminal acid and pepsin on the rate of esophageal luminal release of transforming growth factor alpha (TGF alpha), measured by RIA, in 21 asymptomatic volunteers and 26 patients with reflux esophagitis (RE) was investigated. Esophageal secretion was collected, using an esophageal perfusion catheter, during mucosal exposure to NaCl, HCl or HCl/Pepsin and final saline. The basal rate of luminal TGF alpha release in controls was steady throughout the entire four perfusion periods with saline. This rate declined by 71% during mucosal exposure to HCl (p = 0.002) and by 74% during esophageal perfusion with HCl/pepsin (p = 0.011). The basal rate of luminal TGF alpha release in patients with RE was 27% higher than the corresponding value in controls (1.076 +/- 0.140 vs. 0.850 +/- 0.180 ng/min, p = 0.050). Mucosal exposure to acid and acid/pepsin solutions in RE patients also resulted in a significant decline in the luminal release of TGF alpha by 43% (p < 0.001) and by 42% (p < 0.001) respectively. Despite this decline, TGF alpha in patients with RE was significantly higher (p < 0.001) than in controls. The decline in esophageal TGF alpha release during HCl and HCl/pepsin exposure may facilitate the development of mucosal damage. The increase in esophageal TGF alpha release in patients with RE may represent a compensatory mechanism developed by the mucosal inflammatory changes.

Duodenogastric reflux causes growth stimulation of foregut mucosa potentiated by gastric acid blockade

We investigated whether duodenogastric reflux (DGR) together with gastroesophageal reflux causes growth stimulation of the foregut mucosa and if additional gastric acid suppression enhances the effect of DGR. DGR was induced in rats using a split gastroenterostomy. A cardiomyotomy was performed across the gastroeophageal junction in order to enhance reflux into the esophagus. DGR rats were divided into six subgroups: DGR, DGR + truncal vagotomy, DGR + omeprazole, DGR + gastrin receptor blockade, DGR + omeprazole + gastrin receptor blockade, and DGR + gastrin. Two sham groups, one with and one without omeprazole treatment, served as controls. DGR significantly increased the weight and DNA content of the esophageal and gastric mucosa, which was further enhanced by vagotomy or omeprazole. Histology revealed foveolar hyperplasia in the stomach and esophageal mucosal hyperplasia in these groups. In addition, severe esophagitis was found in the DGR group receiving omeprazole. Omeprazole without DGR had no growth-stimulating effect on the foregut mucosa. DGR-induced growth stimulation was accompanied by hypergastrinemia. Increased growth in the stomach but not the esophagus was inhibited by gastrin receptor blockade. Gastrin administration did not result in enhancement of DGR-induced growth stimulation of the foregut mucosa. It is concluded that DGR, often present in severe reflux esophagitis, causes mucosal growth of the foregut of rats. This trophic response may explain why severe reflux esophagitis is associated with an increased risk of esophageal adenocarcinoma. DGR-induced growth stimulation of the foregut is potentiated by gastric acid suppression, suggesting that chronic antisecretory medication in gastroesophageal reflux may not always be advisable. Omeprazole + DGR caused severe esophageal damage, which may explain why antisecretory medication may fail to heal severe reflux esophagitis.

The epidermal growth factor receptor (EGF-R) is present on the basolateral, but not the apical, surface of enterocytes in the human gastrointestinal tract

BACKGROUND

While it is clear that luminal epidermal growth factor (EGF) stimulates repair of the damaged bowel, its significance in maintaining normal gut growth remains uncertain. If EGF is important in maintaining normal gut growth, the EGF receptor (EGF-R) should be present on the apical (luminal) surface in addition to the basolateral surface. AIMS/SUBJECTS/METHODS: This study examined the distribution of the EGF-R in the epithelium throughout the human gastro-intestinal tract using immunohistochemistry, electron microscopy, and western blotting of brush border preparations.

RESULTS

Immunostaining of the oesophagus showed circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R negative. In the normal stomach, small intestine, and colon, immunostaining localised the receptor to the basolateral surface with the apical membranes being consistently negative. EGF-R positivity within the small intestine appeared to be almost entirely restricted to the proliferative (crypt) region. Western blotting demonstrated a 170 kDa protein in whole tissue homogenates but not in the brush border vesicle preparations.

CONCLUSIONS

As the EGF-R is located only on the basolateral surfaces in the normal adult gastrointestinal tract, the major role of luminal EGF is probably to stimulate repair rather than to maintain normal gut growth.

Role of salivary and seric epidermal growth factor in pathogenesis of reflux esophagitis in chronic alcoholics and nondrinkers

Our objective was to investigate the putative role of epidermal growth factor (EGF) in esophagitis pathogenesis in both nondrinkers and chronic alcoholics. We studied the EGF serum level, the EGF salivary concentration, and the esophageal EGF receptor expression in different groups of patients with esophagitis: nondrinkers with typical symptoms of gastroesophageal reflux (N = 12) and chronic alcoholics (N = 12), and in controls: chronic alcoholics without esophagitis (N = 16) and healthy nondrinkers (N = 12). All patients had an endoscopy with esophageal biopsies, 24-hr esophageal pH-metry, and esophageal manometry. EGF serum levels and EGF salivary concentrations were determined by radioimmunoassay. EGF receptor expression was determined by immunohistochemistry. Both the EGF serum level and the EGF salivary concentration remained constant, 328 +/- 21 pg/ml and 305 +/- 48 pg/ml, respectively, regardless of alcohol intake and the presence or absence of esophagitis. In addition, the presence of esophagitis did not affect the EGF receptor expression. These results suggest that seric and salivary EGF is not involved in the pathogenesis of reflux esophagitis in nondrinkers and in chronic alcoholics.

Epidermal growth factor in saliva and gastric juice: response to histamine

Epidermal growth factor (EGF) was measured in saliva and in gastric juice under basal conditions and after histamine stimulation (0.04 mg kg-1h-1). Sixty subjects studied comprised 20 normal volunteers, 20 patients with duodenal ulcer (DU), and 20 patients with non-ulcer dyspepsia (NUD). There was no difference in basal salivary EGF concentrations between control and DU or control and NUD subjects, but the EGF concentration in DU patients exceeded that in NUD patients (p < 0.05). Basal gastric juice concentrations of EGF were similar in all three groups. There was no difference between basal salivary and gastric EGF concentrations (p > > 0.05). After histamine stimulation, salivary and gastric EGF concentrations increased in all three groups: the increase was greater in gastric juice than saliva (p < 0.0001). There were no significant differences in the salivary EGF concentrations of controls and NUD patients, or controls and DU patients, but values were significantly higher when DU and NUD patients were compared (p = < 0.05). In the gastric juice, EGF increased more in DU patients than in controls or NUD patients (p < 0.05). This effect was not linked to the greater acid secretion in DU than in the other groups. There was no influence of gender or smoking on the EGF concentration. This evidence suggests that the stomach itself may be able to secrete large amounts of EGF and that histamine is a potent stimulus. It is more likely that the gastric EGF is responding to the presence of a duodenal ulcer than that lack of EGF is responsible for persistence of the ulcer.

Epidermal growth factor attenuates the sclerotherapy-induced biomechanical properties of the oesophagus. An experimental study in minipigs

BACKGROUND

The effect of epidermal growth factor (EGF) on the biomechanical properties of the oesophagus subjected to sclerotherapy was studied in Goettingen minipigs by means of impedance planimetry.

METHODS

Seventeen animals underwent three sessions of weekly endoscopic sclerotherapy. During these 3 weeks and for the subsequent 2 weeks they were treated with either EGF or placebo. After another 3 weeks an impedance planimetric study was done. Ten healthy non-sclerosed pigs were studied as controls. Impedance planimetry was performed by stepwise pressure-induced balloon inflation for analysis of oesophageal cross-sectional area 5 and 10 cm above the gastro-oesophageal junction (GEJ).

RESULTS

Systemic treatment with EGF (total daily dose of 30 micrograms/kg/day, administered subcutaneously) for 3 to 7 days per week combined with a weekly paravenous injection of 20-40 micrograms/kg attenuated the oesophageal damage caused by sclerotherapy, implying less pronounced narrowing 5 cm above and less dilation 10 cm above the GEJ.

CONCLUSION

These observations suggest a potential therapeutic role for EGF in attenuating sclerotherapy-induced oesophageal injury.

Review article: factors protecting the oesophagus against acid-mediated injury

Reflux of gastric acid and pepsins into the lower oesophagus causes symptoms such as heartburn and nausea, and tissue injury leading to erosive oesophagitis and stricture formation. This article reviews the mechanisms involved in protecting the oesophagus against acid-mediated injury, including the role of the lower oesophageal sphincter, secondary oesophageal peristalsis and swallowed saliva. The oesophageal mucosa has inherent abilities to resist acid damage, and recent data from three laboratories suggest a secretory function with local production of bicarbonate and mucus responsive to local acidification. The evidence for these putative oesophageal defence mechanisms is discussed.

Effect of alcohol on gastrointestinal cell regeneration as a possible mechanism in alcohol-associated carcinogenesis

Chronic ethanol consumption is a major risk factor for oropharyngeal, esophageal, and rectal cancer. Because hyperregenerative gastrointestinal mucosa has an increased susceptibility towards chemical carcinogens and thus influences carcinogenesis, various studies have been performed to evaluate the effect of chronic ethanol consumption on mucosal cell turnover. In the rat, morphometric analysis showed that in chronically ethanol-fed rats the size of the basal cell nuclei of the oral mucosa from the floor of the mouth, the edge of the tongue, and the base of the tongue were significantly enlarged. The size of the basal cell layer was increased and the stratification of the cells was altered. The percentage of cells in S-phase of the cell cycle was significantly higher in ethanol-fed rats compared to controls. In addition, mucosal atrophy was found. Similar to the oropharynx, in the esophagus chronic ethanol consumption increased cell proliferation depending on salivary gland function, because only in the presence of the salivary glands was this stimulative effect of alcohol on cell turnover found. Subsequently, chronic ethanol ingestion significantly stimulated crypt cell production rate in the rectum, in an age-dependent manner. This hyperregeneration, which was only observed in the rectum but not in the remaining colon, was associated with an expansion of the proliferative compartment of the crypt. Such an expansion is correlated with increased risk for rectal cancer. In addition, crypt cell production rates in the rectal crypts can be correlated with mucosal acetaldehyde concentrations, underlining a toxic effect of acetaldehyde on the rectal mucosa that is answered by compansatory hyperregeneration. These data from the rat model could be confirmed in humans. In conclusion, chronic ethanol consumption leads to mucosal hyperregeneration in gastrointestinal mucosa associated with a high risk for cancer and may therefore be at least one mechanism by which alcohol exerts its cocarcinogenic effect.

Developmental expression of transforming growth factor-alpha and epidermal growth factor receptor proteins in the human pancreas and digestive tract

This study was designed to localize transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) expression in the developing human gastrointestinal tract and pancreas. Immunohistochemical techniques using specific antibodies against human TGF-alpha and EGFR were performed on digestive tissues of fetuses from 9 to 10 to 24 weeks of gestation, children and adults. In fetuses, TGF-alpha and EGFR proteins were expressed in all epithelial tissues studied with a good correlation and from an age as early as 9 to 10 weeks of gestation, except for TGF-alpha in the esophagus. The strongest TGF-alpha immunostaining was noted in the stomach and the proximal colon. Unexpectedly, immunoreactive gut endocrine cells were observed with the two antibodies used. Relatively numerous in fetuses, they decreased in number with age and were rare in adults particularly along the colon. Enteroglucagonsecreting cells were shown to express TGF-alpha, while some gastrin, somatostatin and pancreatic glucagon cells were immunostained with EGFR antibodies. The presence of TGF-alpha and its receptor in digestive tract epithelium and pancreatic tissues early in fetal life suggests a functional role for TGF-alpha during the developmental process of the digestive system. We demonstrate that TGF-alpha is also produced by endocrine cells and might have an additional mode of action other than paracrine, at least during fetal life.

Systemic treatment with recombinant human epidermal growth factor accelerates healing of sclerotherapy-induced esophageal ulcers and prevents esophageal stricture formations in pigs

Human epidermal growth factor (EGF), a small polypeptide (6 kDa) with mitogenic properties, has been implicated in the protection of gastrointestinal mucosal integrity. The efficacy of EGF in the prevention and healing of sclerotherapy-induced esophageal lesions was investigated in 24 minipigs with surgically induced portal hypertension. In addition, the effect of EGF on intragastric acidity and pharmacokinetics was investigated as possible means to explain its protective mechanism of action. The animals underwent three weekly sessions of sclerotherapy with polidocanol 2% and were concomitantly and for an additional three weeks treated with either placebo or EGF administered paravenously in the esophagus and/or subcutaneously. The subcutaneous treatment with EGF significantly (P < 0.05) reduced esophageal stricture and scar formations associated with sclerotherapy. Gastric pH values were significantly (P < 0.01) elevated only in animals receiving subcutaneous injections of EGF. Furthermore, the subcutaneous administration of EGF was associated with unexpected prolonged plasma concentration of the peptide. These results suggest a possible clinical value of EGF as an adjunctive treatment with the sclerotherapy.