Association of transforming growth factor alpha (TGFA) and its precursors with malignant change in Barrett's epithelium: biological and clinical variables

Triiodothyronine (T3) upregulates the expression of proto-oncogene TGFA independent of MAPK/ERK pathway activation in the human breast adenocarcinoma cell line, MCF7

OBJECTIVE

To verify the physiological action of triiodothyronine T3 on the expression of transforming growth factor α (TGFA) mRNA in MCF7 cells by inhibition of RNA Polymerase II and the MAPK/ERK pathway.

MATERIALS AND METHODS

The cell line was treated with T3 at a physiological dose (10-9M) for 10 minutes, 1 and 4 hour (h) in the presence or absence of the inhibitors, α-amanitin (RNA polymerase II inhibitor) and PD98059 (MAPK/ERK pathway inhibitor). TGFA mRNA expression was analyzed by RT-PCR. For data analysis, we used ANOVA, complemented with the Tukey test and Student t-test, with a minimum significance of 5%.

RESULTS

T3 increases the expression of TGFA mRNA in MCF7 cells in 4 h of treatment. Inhibition of RNA polymerase II modulates the effect of T3 treatment on the expression of TGFA in MCF7 cells. Activation of the MAPK/ERK pathway is not required for T3 to affect the expression of TGFA mRNA.

CONCLUSION

Treatment with a physiological concentration of T3 after RNA polymerase II inhibition altered the expression of TGFA. Inhibition of the MAPK/ERK pathway after T3 treatment does not interfere with the TGFA gene expression in a breast adenocarcinoma cell line.

The dichotomy in carcinogenesis of the distal esophagus and esophagogastric junction: intestinal-type vs cardiac-type mucosa-associated adenocarcinoma

Adenocarcinoma of the distal esophagus and esophagogastric junction continues to rise in incidence. An intestinal metaplasia (Barrett esophagus)-dysplasia-carcinoma sequence induced by gastroesophageal reflux disease is well established. However, a significant number of adenocarcinomas in the vicinity of the esophagogastric junction are seen in the background of gastric/cardiac-type mucosa without intestinal metaplasia. Thus, the aim of this study was to investigate the role of Barrett esophagus (intestinal-type mucosa) in the classification and prognosis of tumors of the distal esophagus and esophagogastric junction. Clinicopathological and molecular characteristics were examined in 157 consecutively resected adenocarcinomas of the distal esophagus and esophagogastric junction and were compared between tumors arising in association with intestinal-type and cardiac-type mucosa. Intestinal-type mucosa-associated adenocarcinomas were more likely to be associated with younger age (P=0.0057), reflux symptoms (P<0.0001), proximal location (P=0.0009), lower T stage (P<0.0001), fewer nodal metastases (P=0.0001), absence of lymphatic (P<0.0001), venous (P=0.0060) or perineural (P<0.0001) invasion. Histologically, intestinal-type mucosa-associated tumors were more likely to be low-grade glandular tumors (P=0.0095) of intestinal or mixed immunophenotype (P=0.015) and express nuclear β-catenin (P=0.0080), whereas tumors arising in a background of cardiac-type mucosa were more frequently associated with EGFR amplification (P=0.0051). Five-year overall survival rate was significantly higher in patients with intestinal-type mucosa-associated tumors (28 vs 9%, P=0.0015), although no survival benefit was seen after adjusting for potential confounders. Our findings support the theory that multiple distinct pathways of tumorigenesis exist in the vicinity of the esophagogastric junction, including one in which tumors arise from dysplastic intestinal metaplasia (intestinal pathway), and one potentially involving dysplasia of the cardiac-type mucosa (non-intestinal pathway). Additional studies are warranted to further clarify their pathogenesis and the molecular mechanisms involved.

Esophageal adenocarcinoma arising in Barrett esophagus

The major risk factors for esophageal adenocarcinoma are gastroesophageal reflux disease (GERD) and Barrett esophagus, a squamous-to-columnar cell metaplasia that predisposes to malignancy. Adenocarcinomas in Barrett esophagus are thought to arise through a sequence of growth-promoting, genetic alterations that accumulate until the cells have acquired the physiologic hallmarks of cancer proposed by Hanahan and Weinberg. Moreover, GERD and Barrett esophagus are associated with chronic esophagitis, and inflammation is a well known risk factor for cancer formation. The cell that gives rise to Barrett metaplasia is not known. It has been proposed that the metaplasia may arise from a change in the differentiation pattern of stem cells that either reside in the esophagus or are recruited to the esophagus from the bone marrow. Alternatively, it is possible that Barrett metaplasia develops through the conversion of one differentiated cell type into another. Regardless of the cell of origin, Barrett metaplasia ultimately must be sustained by stem cells, which might be identified by intestinal stem cell markers. An emerging concept in tumor biology is that cancer stem cells are responsible for sustaining tumor growth. If Barrett cancers develop from Barrett stem cells, then a therapy targeted at those stem cells might prevent esophageal adenocarcinoma. This report reviews the risk factors for Barrett esophagus and esophageal adenocarcinoma, the mechanisms by which genetic alterations might contribute to carcinogenesis in Barrett esophagus, and the role of stem cells in the development of Barrett metaplasia and adenocarcinoma.

REG Ialpha protein expression in Barrett's esophagus

BACKGROUND AND AIM

Accelerated cellular proliferation in Barrett's esophagus has been implicated in Barrett's elongation and malignant transformation. Therefore, growth factors may play important roles in the pathophysiology of Barrett's esophagus. Regenerating gene (REG), an epithelial growth factor, has been reported to link mucosal inflammation and subsequent carcinogenesis in the gastrointestinal tract. The aim of this study was to investigate whether REG is expressed in Barrett's esophagus and to elucidate the relationship between REG protein expression and clinicopathological factors of Barrett's esophagus.

METHODS

Between July 2003 and June 2004, 266 patients with endoscopically and histologically proven Barrett's esophagus were enrolled in this study. Before endoscopic examination, all participants were requested to answer structured questionnaires on gastroesophageal reflux symptoms and drugs usage. Mucin phenotype, cyclooxygenase-2 expression, cellular proliferation, apoptosis and REG Ialpha protein expression were investigated in the biopsy samples taken from Barrett's esophagus. Clinicopathological factors that correlated with REG Ialpha protein expression in patients with Barrett's esophagus were evaluated using multivariate logistic regression analysis.

RESULTS

REG Ialpha protein expression was observed in 48 (18.0%) of 266 patients with Barrett's esophagus by immunohistochemistry. Newly developed squamous re-epithelialization of Barrett's esophagus at biopsy sites, presence of hiatal hernia and aging were shown to correlate with REG Ialpha protein expression.

CONCLUSIONS

The present study is the first to show REG expression in Barrett's esophagus. Expression of REG Ialpha was more frequently observed in patients who showed squamous re-epithelialization of Barrett's esophagus at biopsy sites.

Leptin synergistically enhances the anti-apoptotic and growth-promoting effects of acid in OE33 oesophageal adenocarcinoma cells in culture

Obesity and gastro-oesophageal reflux are the main predisposing factors for oesophageal adenocarcinoma. We have examined the effects of transient acid exposure and leptin on OE33 oesophageal adenocarcinoma cells. Leptin and acid individually stimulated proliferation and inhibited apoptosis and the combination was synergistic. Leptin receptor protein levels were unchanged by acid exposure. The COX-2 inhibitor NS 398 blocked the effects of acid and leptin but while both acid and leptin individually significantly increased PGE2 production and COX-2 mRNA levels, the combination was not more effective than either stimulant alone. Leptin synergistically enhanced acid-stimulated EGFR and ERK phosphorylation but did not further increase JNK or p38 MAP kinase phosphorylation. Specific EGFR and ERK inhibitors reduced the effects of leptin and acid alone and in combination. The combination of increased circulating leptin levels in obesity and transient reflux of gastric acid may promote oesophageal carcinogenesis by increasing proliferation and inhibiting apoptosis.

Leptin stimulates proliferation and inhibits apoptosis in Barrett's esophageal adenocarcinoma cells by cyclooxygenase-2-dependent, prostaglandin-E2-mediated transactivation of the epidermal growth factor receptor and c-Jun NH2-terminal kinase activation

Obesity is an important risk factor for esophageal adenocarcinoma (EAC), and elevated serum leptin is characteristic of obesity. We hypothesized that leptin may have biological effects in promoting esophageal adenocarcinoma and examined the effects of leptin on the OE33 Barrett's-derived EAC line. Proliferation was assessed by dimethylthiazoldiphenyltetra-zoliumbromide and 5-bromo-2'-deoxyuridine incorporation assays and apoptosis by ELISA of intracellular nucleosomes. Intracellular signaling was examined using specific pharmacological inhibitors and direct detection of phosphorylated active kinases. Expression of the long and short leptin receptors by OE33 cells was confirmed by RT-PCR, Western blotting and immunocytochemistry. Leptin stimulated OE33 cell proliferation in a dose-dependent manner and inhibited apoptosis. These effects were dependent on cyclooxygenase (COX)-2 and replicated by adding prostaglandin E2 (PGE2). The effects of PGE2 and leptin were abolished by the EP-4 antagonist AH23848. ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and Janus tyrosine kinase (JAK)-2 were activated upstream of COX-2 induction, whereas the epidermal growth factor receptor and c-Jun NH2-terminal kinase (JNK) were downstream of COX-2. The activation of ERK and Akt but not p38 MAPK was JAK2 dependent. PGE2 stimulated phosphorylation of JNK in an EGF receptor-dependent manner, and activation of the epidermal growth factor receptor required protein kinase C, src, and matrix metalloproteinase activities. We conclude that leptin stimulates cell proliferation and inhibits apoptosis in OAC cells via ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and JAK2-dependent activation of COX-2 and PGE2 production. Subsequent PGE2-mediated transactivation of the epidermal growth factor receptor and JNK activation are essential to the leptin effects. These effects may contribute to the greatly increased risk of esophageal adenocarcinoma in obesity.

Multistage carcinogenesis in Barrett's esophagus

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

Gain of allelic gene expression for IGF-II occurs frequently in Barrett's esophagus

The IGF-II gene normally exhibits genomic imprinting, a DNA modification that allows the expression of only one of the two inherited alleles. With loss of imprinting, there is a gain of allelic gene expression (GOAGE) due to IGF-II being expressed by both alleles. GOAGE for IGF-II has been demonstrated in a number of malignancies and in normal epithelia surrounding malignancies, but not in epithelia without associated neoplasia. We hypothesized that nonneoplastic Barrett's epithelium might have GOAGE for IGF-II that could facilitate its progression to neoplasia. Endoscopic biopsies were obtained from metaplastic esophageal, normal gastric, and normal duodenal epithelia from 43 patients with Barrett's esophagus. Genomic DNA were analyzed using PCR followed by ApaI restriction enzyme digestion or allele-specific PCR to identify an ApaI polymorphism of IGF-II. cDNA from patients with the ApaI polymorphism were analyzed for IGF-II GOAGE using exon connection PCR, followed by a secondary nested PCR and ApaI restriction enzyme digestion. We found that 13 (30%) of 43 samples of Barrett's metaplasia contained the ApaI polymorphism and were thus informative for IGF-II, and sufficient material was available for GOAGE analysis in 9 of those 13 cases. GOAGE for IGF-II was demonstrated in five (56%) of those nine cases. All patients with GOAGE in Barrett's metaplasia also demonstrated GOAGE in the gastric and duodenal epithelia. In contrast, patients without GOAGE in Barrett's metaplasia also had no GOAGE in their gastric and duodenal epithelia. We conclude that in patients with Barrett's esophagus, GOAGE for IGF-II is found frequently in the metaplastic esophageal epithelium as well as in normal gastric and duodenal epithelia.

Mechanisms of disease: Carcinogenesis in Barrett's esophagus

The pathogenesis of cancer in Barrett's esophagus is multifactorial. Gastroesophageal reflux seems to be important in the initiation of Barrett's esophagus, but its role in promoting carcinogenesis has yet to be established. Diet, lifestyle and carcinogens, especially the nitrates, may be important in the development of carcinogenesis, and require further investigation. Inhibition of reflux-stimulated inflammatory changes, for example by inhibiting cyclooxygenase, holds promise for decreasing cancer progression. Similarly, dietary and lifestyle modification used in the management of reflux may also help to prevent the development of esophageal cancer. The molecular changes that are associated with the development of cancer in Barrett's esophagus offer several potential areas of intervention to prevent and manage esophageal cancer. Limiting cell growth, increasing apoptosis of damaged cells, limiting cell invasion and angiogenesis factors could be useful to accomplish this goal. Having a greater understanding of the pathogenesis of this condition can only help to develop more management options in the future.

Gastroesophageal reflux and cancer

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

Molecular targets for treatment of Barrett's esophagus

SUMMARY. Esophageal cancer is one of the most deadly forms of gastrointestinal cancer with a mortality rate exceeding 90%. The major risk factors for esophageal adenocarcinoma are gastroesophageal reflux disease (GERD) and its sequela, Barrett's esophagus. GERD commonly leads to esophagitis. In a minority of patients however, ongoing GERD leads to replacement of esophageal squamous mucosa with metaplastic, intestinal-type Barrett's mucosa. In the setting of continued peptic injury, Barrett's mucosa can give rise to esophageal adenocarcinoma. Despite the widespread use of potent acid suppressive therapies for patients with GERD, the incidence of esophageal adenocarcinoma, among white men in the USA, the UK and Europe has continued to rise. Cancers in Barrett's esophagus arise through a sequence of genetic events that endow the cells with six essential physiologic hallmarks of cancer as described by Hanahan and Weinberg in 2000. These cancer hallmarks include the ability to proliferate without exogenous stimulation, to resist growth-inhibitory signals, to avoid triggering the programmed death mechanism (apoptosis), to resist cell senescence, to develop new vascular supplies (angiogenesis), and to invade and metastasize. While the acquisition of these essential attributes is not specific to the neoplastic progression of Barrett's esophagus, this review will focus on the genetic alterations that occur in Barrett's cells that contribute to the acquisition of each of the hallmarks. Moreover, potential diagnostic and therapeutic strategies for Barrett's patients aimed at each of these cancer hallmarks will be reviewed.

Proton pump inhibitors are associated with reduced incidence of dysplasia in Barrett's esophagus

BACKGROUND AND AIMS

Esophageal acid exposure is important in the pathogenesis of Barrett's esophagus (BE), and possibly in the progression of BE to dysplasia and carcinoma. The aim of this study is to compare the development of dysplasia in BE patients treated with or without proton pump inhibitor (PPI) or histamine 2-receptor antagonist (H2RA).

METHODS

We analyzed prospectively collected data by a single endoscopist on patients with BE in a VA (Veterans Affairs) setting over a 20-yr time period (1981-2000). A pathologist used standard criteria to diagnose BE/dysplasia. Pharmacy information after 1994 was retrieved from a computerized database, and from research files for the period before that. The receipt and the duration of H2RA and/or PPI use was compared between those with and without dysplasia. The incidence of dysplasia was examined in a Kaplan-Meier survival analysis stratified by PPI treatment status, and the risk of dysplasia was examined in a Cox multiple regression analysis controlling for demographic features, length of BE, and the year of BE diagnosis.

RESULTS

We analyzed data for 236 unique veteran patients with a mean age at BE diagnosis of 61.5 yr, 86% Caucasian, and 98% male. During 1,170 patient-yr of follow-up, 56 patients developed dysplasia giving an annual incidence rate of 4.7%. Of those, 14 had high-grade dysplasia. The cumulative incidence of dysplasia was significantly lower among patients who received PPI after BE diagnosis than in those who received no therapy or H2RA; log rank test (p < 0.001). Furthermore, among those on PPIs, a longer duration of use was associated with less frequent occurrence of dysplasia. In multivariate analysis, the use of PPI after BE diagnosis was independently associated with reduced risk of dysplasia, hazards ratio: 0.25 (95% CI 0.13-0.47), p < 0.0001. Longer segments of BE and Caucasian race were other independent risk factors for developing dysplasia. In general, similar findings were observed when only cases with high-grade dysplasia were analyzed.

CONCLUSIONS

These results indicate that PPI therapy is associated with a significant reduction in the risk of developing dysplasia in patients with BE. However, more studies are required to confirm this finding.

The pathogenesis of Barrett's esophagus

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

The role of receptor tyrosine kinase inhibition in treating gastrointestinal malignancy

Tyrosine kinase receptors are proteins that transduce the signal from many growth factor and cytokine ligands to produce intracellular responses. As such they can activate multiple signalling cascade pathways and influence cell division, migration and survival. Many show upregulation in certain malignancies, including those of the gastrointestinal tract, and are thought to play key roles in carcinogenesis. This makes them attractive targets for drug therapy and in recent years many inhibitors have been developed. This review discusses the current situation regarding the development of inhibitors with particular reference to the erbB family, the insulin-like growth factor receptor, the Met receptor, the receptor for vascular endothelial growth factor and the Kit receptor. The evidence will be related back to cancers of the gut lumen. Clinical effectiveness in this area seems to lie in using a combinatorial approach that inhibits multiple key signalling points, and the reasons for this will be discussed.

Hallmarks of cancer progression in Barrett's oesophagus

CONTEXT

Hanahan and Weinberg proposed in 200 that carcinogenesis involves DNA changes that enable cells to:provide their own growth signals, ignore growth-inhibitory signals, avoid apoptosis, replicate without limit, sustain angiogenesis, and invade and proliferate in unnatural locations. The metaplastic cells of Barrett's oesophagus are predisposed to develop these cancer hallmarks.

STARTING POINT

The genetic changes that have been described in Barrett's oesophagus can be categorised according to the predominant cancer hallmark affected. For example, M Auvinen and colleagues recently observed abnormalities in the expression of vascular endothelial growth factors (VEGFs) in Barrett's oesophagus (J Clin Oncol 2002; 20: 2971-79). These abnormalities can be categorised as those that affect angiogenesis, a process that is essential for the development and progression of tumours. WHERE NEXT? The cancer hallmarks of Barrett's oesophagus provide a framework to categorise the genetic abnormalities described and to further understanding of the genetic events that underlie oesophageal carcinogenesis.

Genetic pathways involved in the progression of Barrett's metaplasia to adenocarcinoma

BACKGROUND

The prediction of which patients with Barrett's metaplasia will develop cancer is difficult. Better genetic characterization of the condition may aid clinicians in devising more effective management and follow-up strategies.

METHODS

A review was undertaken of the accumulated genetic data relating to the progression of squamous epithelium to adenocarcinoma. The normal functions of a number of cancer-related genes are described and an explanation is given of how alterations in these genes interfere with normal cell processes and lead to cancer.

RESULTS AND CONCLUSION

The main genetic alterations accompanying the progression through dysplasia to adenocarcinoma were collated from 135 papers. The principal genetic changes implicated are the loss of p16 gene expression (by deletion or hypermethylation), the loss of p53 expression (by mutation and deletion), the increase in cyclin D1 expression, the induction of aneuploidy and the losses of the Rb, DCC and APC chromosomal loci.

Cellular and molecular mechanisms responsible for progression of Barrett's metaplasia to esophageal carcinoma

Barrett's metaplasia is found in approximately 12% to 18% of patients undergoing upper endoscopy for symptoms of reflux. Barrett's metaplasia is a premalignant condition and remains the number one risk factor for developing esophageal adenocarcinoma. There has been an increase in the incidence of esophageal adenocarcinoma in the past two decades, making it the most rapidly rising cancer in the United States and Western Europe. This article describes the progression from Barrett's metaplasia to esophageal adenocarcinoma and predictors for the development of adenocarcinoma in Barrett's metaplasia. Barrett's metaplasia represents a histological mosaic, with dysplastic tissue adjacent to non-dysplastic tissue. The histologic changes leading to adenocarcinoma are accompanied by alterations at the molecular level, including the accumulation of gene mutations and changes in gene expression. The determination of the molecular events that occur in the transition from normal esophageal squamous mucosa to dysplasia and to esophageal adenocarcinoma have lead to a better understanding of the process of the transformation to adenocarcinoma. This knowledge will lead to better biomarkers to diagnose and assess cancer risk.

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

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

Cdx2 ectopic expression induces gastric intestinal metaplasia in transgenic mice

BACKGROUND & AIMS

Intestinal-type gastric cancer is often preceded by intestinal metaplasia in humans. The genetic events responsible for the transdifferentiation that occurs in intestinal metaplasia are not well understood. Cdx2, a transcription factor whose expression is normally limited to the intestine, has been detected in gastric intestinal metaplasia. Cdx2 induces differentiation of intestinal epithelial cells in vitro; therefore, we sought to establish whether a causal relationship exists between Cdx2 activation and intestinal metaplasia.

METHODS

Cdx2 expression was directed to the gastric mucosa in transgenic mice using cis-regulatory elements of Foxa3 (Hnf3gamma). Transgenic mice were analyzed for histologic and gene expression changes.

RESULTS

Histologic examination of the gastric mucosa of the Foxa3/Cdx2 mice revealed the presence of alcian blue-positive intestinal-type goblet cells, a hallmark of intestinal metaplasia. In addition, Cdx2 induced the expression of intestine-specific genes.

CONCLUSIONS

Gastric expression of Cdx2 alone was sufficient to induce intestinal metaplasia in mice. These mice represent a powerful tool to investigate the molecular mechanisms that promote intestinal metaplasia. Moreover, as gastric cancer in humans is often preceded by intestinal metaplasia, the phenotype described here strongly suggests involvement of Cdx2 in the initiation of the process leading to intestinal neoplasia of the gastric mucosa.

Dysplasia in barrett's esophagus. New techniques and markers

In this article, the authors describe the histologic features and classification of dysplasia in Barrett's esophagus. The histologic problems in the diagnosis and grading of dysplasia are discussed. Techniques that can serve as aids to the histologic diagnosis of dysplasia, such as flow cytometry and molecular markers, are reviewed.

The treatment, management and prevention of oesophageal cancer

The combination of a rising incidence and a poor survival rate makes oesophageal cancer a major health issue. Adenocarcinoma of the oesophagus is associated with one of the commonest pre-malignant lesions recognised, Barrett's metaplasia. This provides a focus for early detection and intervention. The subjects of acid suppression, bile reflux, COX-2 inhibition and ablation therapy will be discussed herewith. Established carcinoma is now rarely treated by surgery alone and this review discusses the benefits of multimodality therapy combined with more accurate staging techniques. Finally an emerging understanding of the molecular events that characterise the transition to carcinoma may provide novel targets in cancer therapy such as epidermal growth factor receptor (EGFR) and TNF-alpha. This review will focus on some of the future developments in the treatment of oesophageal cancer.

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

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

Biomarkers in Barrett esophagus

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

Biomarkers in Barrett esophagus

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

Barrett's esophagus: an overview of the molecular biology

The significance of specialized intestinal metaplasia in the esophagus is its associated risk with esophageal adenocarcinoma. This tumor has increased in incidence by over 70% in 20 years. Specialized intestinal metaplasia is the most important risk factor for adenocarcinoma of the esophagus and has been reported in 9-32% of unselected patients in general endoscopy units. The annual risk of esophageal adenocarcinoma for patients with specialized intestinal metaplasia is thought to be approximately 1%, at least 30 times that of the general population. Those with long segments of specialized intestinal metaplasia are thought to be at the greatest risk. Both environmental and molecular changes have been identified in the transition from squamous epithelium through specialized intestinal metaplasia to esophageal adenocarcinoma. The most important molecular changes include impaired regulation of the cell cycle, altered function of known oncogenes and tumor-suppressor genes, changes in cell adhesion molecules, and aneuploidy. This has given rise to a metaplasia/dysplasia/carcinoma model for the evolution of esophageal carcinoma.

Molecular evolution of the metaplasia-dysplasia-adenocarcinoma sequence in the esophagus

The incidence of adenocarcinoma of the esophagus has been increasing in developing countries over the last three decades and probably reflects a genuine increase in the incidence of its recognized precursor lesion, Barrett's metaplasia. Despite advances in multimodality therapy, the prognosis for invasive esophageal adenocarcinoma is poor. An improved understanding of the molecular biology of this disease may allow improved diagnosis, therapy, and prognosis. We focus on recent developments in the molecular and cell biology of Barrett's metaplasia, a heterogeneous lesion affecting the transitional zone of the gastro-esophageal junction whose associated molecular alterations may vary both in nature and temporally. Early premalignant clones produce biological and genetic heterogeneity as seen by multiple p53 mutations, p16 mutations, aneuploidy, and abnormal methylation resulting in stepwise changes in differentiation, proliferation, and apoptosis, allowing disease progression under selective pressure. Abnormalities in expression of growth factors of the epidermal growth factor family and cell adhesion molecules, especially cadherin/catenin complexes, may occur early in invasion. Exploitation of these molecular events may lead to a more appropriate diagnosis and understanding of these lesions in the future.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

The histopathology and biologic prognostic factors of Barrett's esophagus: a review

In Barrett's esophagus, stratified squamous mucosa of the lower third of the esophagus is replaced by columnar mucosa, as a complication of chronic gastroesophageal reflux. The presence of Barrett's esophagus appears to be a major factor in the progression to adenocarcinoma of the lower third of the esophagus. Therefore it is crucial to identify the subset of patients at risk for the development of adenocarcinoma. Dysplasia is an important histologic feature to evaluate because it identifies those patients who require follow-up. The diagnosis of biopsies with lesser degrees of abnormalities, however, makes microscopic evaluation less helpful in identifying patients who need more frequent endoscopic biopsy surveillance. DNA ploidy and the use of monoclonal antibodies, such as suppressor gene product p53, oncogene cerbB-2, and Ki-67, have added dramatically to our understanding of the biology of Barrett's metaplasia and have given us objective indicators to predict the presence of an increased risk of developing cancer.

The molecular basis for carcinogenesis in metaplastic columnar-lined esophagus

A wide variety of biologic events and mechanisms appear to have roles in the development and progression of Barrett's esophagus-associated neoplastic lesions. Figure 5 is a schematic depiction of these events. This is known as an infernogram (named after Dante's Inferno) (S. Kern, unpublished presentations, 1996). Events at the bottom rings of the inferno are high-frequency mutations; nearer to the top of the inferno are the less common events. The next several years promise many further discoveries of not only high-frequency and low-frequency events, but also their application. Some of the molecular alterations already studied show promise as markers for early cancer detection or prognostication. Eventually, applications of these discoveries should yield new and more effective means of preventing and treating the deadly complications of this troublesome premalignant condition.

Biomarkers for malignancy in the columnar-lined esophagus

The biological mechanisms underlying the progression from normal esophageal squamous mucosa to Barrett's epithelium associated with dysplasia and finally to esophageal adenocarcinoma is becoming increasingly well understood. Histologic determination of Barrett's-associated dysplasia remains of paramount importance; however, genetic and biochemical biomarkers of Barrett's metaplasia and dysplasia will facilitate clinical diagnosis, endoscopic surveillance, and monitoring of new therapeutic interventions as they evolve. This article covers conventional and novel biomarkers in Barrett's esophagus.

Expression of c-Myc, TGF-alpha and EGF-receptor in sporadic medullary thyroid carcinoma

In 20 patients with sporadic medullary thyroid carcinoma (MTC), immuno-histochemistry was used to localize the expression of the c-Myc oncoprotein, transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) and these three markers were analysed regarding their relation to histopathological and histochemical variables of the tumours. The detection rates of c-Myc, TGF-alpha and EGFR were 90%, 90% and 95% respectively. Concomitant demonstration of the markers was reflected in significant associations (correlation factor between TGF-alpha and EGFR was 0.93, p < 0.001). The markers were almost invariably located within the cytoplasm, which might suggest their crucial role in growth regulation and cell differentiation; this seems especially true of TGF-alpha and EGFR. The different markers showed no relation to either histopathological or histochemical variables (tumour behaviour, tumour size, tumour cell type). The prominent co-expression of c-Myc, TGF-alpha and EGFR proteins indicates that in MTC these factors might be of importance for tumour cell proliferation via autocrine growth stimulation.

Growth factors: potential for the management of solid epithelial tumours

At present we are on the threshold of an enormous change in clinical practice. The application of molecular medicine has already started and the area of growth factor biology is particularly relevant to this endeavor (Figure 6) (Jankowski and Polak 1996). Perhaps the major limitation to this process is the rate at which the clinician can comprehend and then undertake carefully designed molecular studies in gastroenterology. In time monographs that specifically address the issue of molecular medicine in clinical gene analysis and manipulation may perhaps replace standard text books (see Jankowski and Polak, 1996).

Morphological analysis of gastro-esophageal diseases by molecular cell techniques

The molecular cell sciences have had a great impact in the analysis of the genetic and epigenetic events of esophageal and gastric tumorigenesis. In other regions of the alimentary tract such as the colon, the serial identification of the molecular events in the corresponding morphological lesions is perhaps most advanced. This is, in part, due to the relative ease of the histological characterisation of the premalignant lesions. In this regard the analysis of morphological and molecular adaptation in the alimentary tract is inextricable. This review aims, therefore, to judiciously assess the relative applications of contemporary techniques in investigative histopathology.