Genomic analysis of Barrett's esophagus after ablative therapy: persistence of genetic alterations at tumor suppressor loci

Barrett's esophagus (BE) is a major predisposing factor for the development of esophageal adenocarcinoma. Current strategies for treatment of BE, both dysplastic and nondysplastic, include photodynamic therapy (PDT) and argon plasma coagulation (APC). However, the effect of ablative therapy at the genetic level is unclear. We performed loss of heterozygosity (LOH) analysis of BE in baseline and follow-up biopsy specimens from 21 patients with BE (17 male, 4 female) treated with PDT and/or APC. At baseline, 14 patients had intestinal metaplasia without dysplasia (MET), 4 low-grade dysplasia (LGD) and 3 high-grade dysplasia (HGD). LOH was assessed using a panel of 9 polymorphic markers for evaluation of the P53 gene on 17p, P16 on 9p, DCC and SMAD4 on 18q and the APC gene on 5q. The tissue specimens obtained at baseline (t = 0) were analysed, as well as the first (t = 1; mean interval: 4 months) and last (t = 2; mean interval: 8 months) available biopsy with residual or recurrent BE after ablation. At t = 0, allelic loss was detected of 5q in 27%, 9p in 56%, 17p in 31% and 18q in 6% of informative cases. At t = 1 (18 patients with persistent MET and 3 with LGD) and at t = 2 (8 MET, 2 LGD), the LOH patterns were not statistically different from t = 0. Further, multiple genetic lineages before and after therapy were detected in 15 cases illustrating the multiclonal nature of BE. We conclude that recurrent and/or persistent BE after ablative therapy still contains genetic alterations associated with malignant progression to cancer. Therefore, the goal of treatment should be the complete elimination of Barrett's mucosa.     

Adenocarcinoma in Barrett's esophagus

Adenocarcinoma arising in association with the columnar-lined esophagus is now recognized with increasing frequency. The incidence of malignant degeneration in Barrett's esophagus, its etiology, and pathogenesis are all issues of ongoing debate. The role of gastroesophageal reflux in driving the malignant change remains unproven. Surgical resection is the treatment of choice; however, prognosis is generally poor. Surveillance of patients with non-malignant Barrett's esophagus permits detection of early lesions where resection results in excellent long-term survival.     

Oxidative stress has a role in malignant transformation in Barrett's oesophagus

Mechanisms underlying the development of oesophageal adenocarcinoma are poorly understood. To discover the role of oxidative stress and radical scavenger capacity in the malignant transformation of Barrett's oesophagus, we measured myeloperoxidase activity, superoxide dismutase activity, glutathione content and total aromatic DNA adducts. Mucosal specimens came from 52 patients in 6 groups: symptomatic gastro-oesophageal reflux disease (GORD) without and with endoscopic oesophagitis, Barrett's epithelium without and with dysplasia, adenocarcinoma in the oesophagus and controls. In the GORD-oesophagitis-metaplasia-dysplasia-adenocarcinoma sequence, glutathione content was progressively lower and myeloperoxidase activity higher than in controls, plateauing at Barrett's epithelium without dysplasia. Only in Barrett's epithelium with dysplasia was SOD activity significantly increased. In all patient groups, DNA adduct levels were significantly higher than the control level. Though these levels between patient groups did not differ significantly, the level was highest in Barrett's epithelium without dysplasia and progressively lower in Barrett's with dysplasia and adenocarcinoma. Pooled data showed a negative correlation between glutathione content and DNA adducts (-0.28, p = 0.05). Simultaneous formation of DNA adducts, increased myeloperoxidase-related oxidative stress, decreased antioxidant capacity (glutathione content) and the negative correlation between glutathione content and DNA adducts in the GORD-oesophagitis-metaplasia-dysplasia-adenocarcinoma sequence of Barrett's oesophagus indicate a role in the pathogenesis and malignant transformation related to oxidative stress.     

Management of Barrett's esophagus

Barrett's esophagus represents replacement of normal distal esophageal squamous epithelium with specialized columnar epithelium containing goblet cells. Typically arising in the setting of chronic gastroesophageal reflux disease, the presence of Barrett's esophagus carries a 50- to 100-fold increased risk of developing esophageal cancer. Risk factors include male sex, smoking history, obesity, Caucasian ethnicity, age > 50 and > 5-year history of reflux symptoms. Aggressive medical or surgical antireflux therapy may ameliorate symptoms, but have not yet been proven to affect the risk of developing esophageal adenocarcinoma in randomized trials. Although dysplasia is an imperfect biomarker for the development of subsequent malignancy, random sampling of esophageal tissue for dysplasia remains the clinical standard. There have been no studies to establish that endoscopic screening/surveillance programs decrease the rates of death from cancer. Fit patients with Barrett's esophagus and high-grade dysplasia should undergo esophagectomy to prevent the risk of developing esophageal adenocarcinoma. For non-operative candidates, endoscopic ablative approaches may represent a reasonable therapeutic alternative.     

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.     

Adenocarcinoma arising in Barrett's esophagus

A review of nine adenocarcinomas of the esophagus arising in Barrett's epithelium was undertaken. We found the disease among white males disproportionately. Risk factors and incidence rate remain to be clarified. Only one patient was in a surveillance program and only he had carcinoma discovered "early." He still survives while only one of the eight whose diagnosis followed investigation of symptoms remains alive.     

p16 expression in Barrett's esophagus and esophageal adenocarcinoma: association with genetic and epigenetic alterations

Our previous work has shown that a number of genes locating on 1q21 were down-regulated in esophageal squamous cell carcinomas (ESCC) and they may involve in carcinogenesis. To determine whether chromosome 1q LOH occurs in ESCC, we analyzed LOH in 61 ESCCs using 18 microsatellite markers on chromosome 1q. Forty-six of 61 (75.4%) tumors presented LOH at one or more loci. A significant association was found between chromosome 1q LOH and histopathological grade. LOH on D1S3466 had a negative correlation with family history, whereas LOH on D1S2777 positively correlated with smoking. These results suggest this region harbor putative tumor suppressor gene(s) contributing to tumorigenesis and differentiation in ESCC.     

食管腺癌和Barrett食管

原发于食管的腺癌约占食管癌的5%～10%,食管腺癌患者中约86%起源于Bsrrett食管,少数来自异位胃粘膜或食管粘液腺体.Barrett食管是食管腺癌最重要的危险因素,而食管特殊型肠上皮化生是食管腺癌的癌前病变.对诊断为Barrett食管的患者应纳入内镜监测计划,定期追踪和监视观察,使肿瘤在早期阶段检出.     

A multigene expression panel for the molecular diagnosis of Barrett's esophagus and Barrett's adenocarcinoma of the esophagus

In order to identify genes or combination of genes that have the power to discriminate between premalignant Barrett's esophagus and Barrett's associated adenocarcinoma, we analysed a panel of 23 genes using quantitative real-time RT-PCR (qRT-PCR, Taqman and bioinformatic tools. The genes chosen were either known to be associated with Barrett's carcinogenesis or were filtered from a previous cDNA microarray study on Barrett's adenocarcinoma. A total of 98 tissues, obtained from 19 patients with Barrett's esophagus (BE group) and 20 patients with Barrett's associated esophageal adenocarcinoma (EA group), were studied. Triplicate analysis for the full 23 gene of interest panel, and analysis of an internal control gene, was performed for all samples, for a total of more than 9016 single PCR reactions. We found distinct classes of gene expression patterns in the different types of tissues. The most informative genes clustered in six different classes and had significantly different expression levels in Barrett's esophagus tissues compared to adenocarcinoma tissues. Linear discriminant analysis (LDA) distinguished four genetically different groups. The normal squamous esophagus tissues from patients with BE or EA were not distinguishable from one another, but Barrett's esophagus tissues could be distinguished from adenocarcinoma tissues. Using the most informative genes, obtained from a logistic regression analysis, we were able to completely distinguish between benign Barrett's and Barrett's adenocarcinomas. This study provides the first non-array parallel mRNA quantitation analysis of a panel of genes in the Barrett's esophagus model of multistage carcinogenesis. Our results suggest that mRNA expression quantitation of a panel of genes can discriminate between premalignant and malignant Barrett's disease. Logistic regression and LDAs can be used to further identify, from the complete panel, gene subsets with the power to make these diagnostic distinctions. Expression analysis of a limited number of highly selected genes may have clinical usefulness for the treatment of patients with this disease.     

Natural selection in neoplastic progression of Barrett's esophagus

Neoplasms progress to cancer through a process of natural selection. The rate of evolution, and thus progression is determined by three parameters: mutation rate, population size of the evolving neoplastic cells, and intensity of selection or rate of clonal expansion. All three parameters are reviewed in the context of Barrett's esophagus, a pre-malignant neoplasm. Although Barrett's esophagus is an ideal model for the study of neoplastic clonal evolution, similar studies may be carried out in a wide variety of human neoplasms. Evolutionary analyses provide insights for clinical management, including rates of progression to cancer and emergence of resistance to interventions.     

Barrett's esophagus: ablative endoscopic techniques

Barrett's esophagus consists of a precancerous condition in which the progression from dysplasia to adenocarcinoma is now well documented. The management of patients affected by Barrett's esophagus is still debatable, in particular for the risk of surgical treatment in the presence of small precancerous lesions or early adenocarcinoma. Furthermore, quality of life after surgical resection is often poor. Endoscopy is the main diagnostic and follow-up procedure in Barrett's esophagus: it allows the detection and treatment of severe dysplasia and invasive esophageal adenocarcinoma. Endoscopic treatment also produces reduction or disappearance of intestinal metaplasia. In these cases, the aim of the treatment is to prevent dysplastic changes. Moreover, the ideal endoscopic treatment should be safe, easy to perform and cost effective. Thermal (electrocoagulation, laser, argon-plasma coagulation), photochemical (photodynamic therapy) or ablative (endoscopic mucosal resection) procedures have been proposed alone or in combination, with the aim to completely eradicate dysplastic lesions or early adenocarcinoma as an alternative to surgical treatment. Endoscopic removal of the lesions is followed by restoration of normal epithelium. Some questions about patient selection, prevention of recurrence and best endoscopic treatment still remain unanswered.     

Histopathologic characteristics of early adenocarcinoma in Barrett's esophagus

To elucidate the early events of cancer development in the columnar cell-lined lower esophagus, 13 esophagectomy specimens with early adenocarcinoma (T1) were histopathologically studied and the morphometry of the lesion was performed on a histologic map. Eleven (84.6%) of the 13 early Barrett's carcinomas were contiguous to both the distinctive specialized-type Barrett's mucosa and squamous epithelium. Furthermore, ten (76.9%) of the 13 tumors had residual squamous islands on the surface. These data suggest that carcinomas in Barrett's esophagus mostly develop at a place very close to the squamocolumnar epithelial border. The distance from the tumor center to the nearest squamous epithelium, including squamous islands, was 2 cm or less in all cases but one. Therefore, the authors conclude that the primary site of cancer development in Barrett's esophagus is the metaplastic columnar-lined area, particularly of specialized type, within 2 cm from the squamocolumnar epithelial border.     

Genomic alterations in preneoplastic lesions

The genomic alterations in preneoplastic lesions are summarized in this review. 3p and 9p in the lung, 9p in the bladder, 8p in the prostata, 19q and 1p in oligodendroglioma, and 22q in meningioma were reported to be deleted. Somatic mutation of p53 was found in preneoplastic lesions of the esophagus, stomach, colon, thyroid, and astrocytoma. Adenoma-carcinoma sequence (Apc, ras, p53 gene alterations) in colon, LKB1 gene in Peutz-Jeghers syndrome, Smad4 in juvenile polyposis, hMSH2, hMLH1, PMS1, PMS2 genes in HNPCC, VHL gene in kidney, WT1 in Wilms tumor, RB gene in retinoblastoma, and ret gene in MEN were reportedly altered in preneoplastic lesions involved in hereditary tumors. Cervical dysplasia and papilloma of the head and neck infected by human papilloma virus and liver infected by B-type hepatitis virus are also precancerous. Genomic instability, APC gene alteration, point mutation of K-ras in preneoplastic lesions of stomach and K-ras and p16 alterations in metaplasia of pancreas were also found. Advances in research on genomic alterations in preneoplastic lesions will contribute to prevention and early detection of cancer.     

Biomarkers of esophageal adenocarcinoma and Barrett's esophagus

The rising incidence and poor prognosis of esophageal adenocarcinoma in the Western world have intensified research efforts into earlier methods of detection of this disease and its relationship to Barrett's esophagus. The progression of Barrett's esophagus to adenocarcinoma has been the focus of particular scrutiny, and a number of potential tissue and serum-based disease biomarkers have emerged. The epidemiology and pathogenesis of esophageal adenocarcinoma are outlined. Tissue biomarkers allowing risk stratification of Barrett's are reviewed as well as strategies currently being used to discover novel biomarkers that will facilitate the early detection of esophageal adenocarcinoma. Finally, the uses of biomarkers as predictive tests for targeted treatments and as surrogate endpoints in chemoprevention trials are considered.     

Barrett's esophagus in three children after antileukemia chemotherapy

Barrett's esophagus, a columnar metaplasia of the lower esophagus that is usually associated with gastroesophageal reflux (GER), was found in three children on long-term antileukemia chemotherapy. Two of the children had been on a standard acute lymphoblastic leukemia (ALL) maintenance protocol with 2 to 3 years of methotrexate and 6-mercaptopurine administration. The third child received daunorubicin, cytosine arabinoside, and 6-thioguanine for treatment of acute myelogenous leukemia (AML). None of the patients had clinical or pathologic evidence of GER disease. We propose that the Barrett's esophagus in these patients did not result from the usual peptic esophagitis, but rather from chemotherapy-induced esophageal mucosal injury.     

Clinical use of p53 in Barrett's esophagus.

Barrett's esophagus is an established precursor to esophageal adenocarcinoma. Whereas most patients with Barrett's esophagus do not progress to adenocarcinoma, patients with progression have a poor prognosis. Current management strategies use frequent endoscopic surveillance and multiple nontargeted biopsies. This approach, however, may miss dysplastic areas. Furthermore, given the relatively high prevalence of Barrett's esophagus but low incidence of progression, this invasive and expensive approach has not been shown to be cost-effective. Thus, there is intense interest in using biomarkers to identify patients at increased risk of progressing to adenocarcinoma. This has included examination of mutations in the tumor suppressor gene, p53. In this report, we discuss the biology of p53 and the incidence of p53 mutations in Barrett's esophagus and review relevant studies regarding the ability of p53 to predict neoplastic progression. Additionally, we report our results of the expression of p53 by immunohistochemistry in a group of 18 patients that have undergone endoscopic esophageal mucosal resection for dysplasia. Although the presence of a p53 mutation increases the risk of neoplastic progression, the absence of this mutation does not abrogate the risk. Continuing efforts, therefore, are needed to define and prospectively validate a panel of biomarkers to risk-stratify patients with Barrett's esophagus. Determination of p53 mutational status may ultimately be a component of such a panel.