Barrett's Esophagus: New insights in the genetic patchwork of transdifferentiation and malignant transformation

De behandeling en vooruitzichten voor patiënten met een slokdarm carcinoom zijn weinig hoopgevend. Vroegtijdige detectie en preventie zijn noodzakelijk, en daarom richt veel onderzoek zich op de premaligne Barrett slokdarm, waarin gezond slokdarm epitheel vervangen is door darmachtig epitheel. De precieze ontstaanswijze en progressie van een Barrett slokdarm is onduidelijk. Daarom heeft dit proefschrift zich gericht op genen die van belang kunnen zijn hierin. Allereerst vonden wij dat de nucleaire receptor Pregnane X Receptor (PXR) niet aanwezig is in gezond slokdarm epitheel, maar wel in het darmachtige epitheel van Barrett slokdarm en adenocarcinomen. In adenocarcinomen werd PXR na blootstelling aan galzuren, in de celkernen gevonden waar het actief andere genen reguleert. Wij concluderen dat PXR mogelijk een voorspeller is van progressie in Barrett slokdarm. In een histologische studie hebben wij deze hypothese verder onderzocht en hierin aangetoond dat de combinatie van de eerder bestudeerde galzuur receptor Farnesoid X Receptor (FXR) en PXR, klinische waarde hebben voor de diagnostiek van dysplasie. Verder vonden wij dat bepaalde DNA mutaties in het regulerende deel van het Vitamine D receptor (VDR) gen geassocieerd zijn met een verminderd expressie van het VDR gen in Barrett slokdarm middels de binding van transcriptie factor GATA1. Het haplotype dat deze mutaties omvat is bovendien geassocieerd met een twee maal lager risico op het manifesteren van een Barrett slokdarm (OR 0.44; 95%CI 0.23-0.85) of adenocarcinoom in de slokdarm (OR 0.50; 95%CI 0.27-0.96). Het identificeren van dragers van dit haplotype is een eerste stap in het ontwikkelen van persoonspecifieke behandelingen voor slokdarmkanker. Ten slotte zochten we genen die verantwoordelijk kunnen zijn voor Barrett’s slokdarm. Een proces vergelijkbaar met Barrett’s metaplasie vindt plaats tijdens de embryonale ontwikkeling van het maag-darmkanaal, waarin Homeobox (HOX) genen een cruciale rol spelen. Wij toonden het belang van HOXA genen aan voor het epitheel van het volwassen maag-darmkanaal en identificeerden HOXA7 en A11 als belangrijke galgereguleerde spelers in Barrett metaplasie. Aanvullende studies zijn nodig om de regulerende rol van HOX genen te bestuderen in het ontstaan van Barrett slokdarm

Composition of the mucosa-associated microbiota along the entire gastrointestinal tract of human individuals

Background: Homeostasis of the gastrointestinal tract depends on a healthy bacterial microbiota, with alterations in microbiota composition suggested to contribute to diseases. To unravel bacterial contribution to disease pathology, a thorough understanding of the microbiota of the complete gastrointestinal tract is essential. To date, most microbial analyses have either focused on faecal samples, or on the microbial constitution of one gastrointestinal location instead of different locations within one individual. Objective: We aimed to analyse the mucosal microbiome along the entire gastrointestinal tract within the same individuals. Methods: Mucosal biopsies were taken from nine different sites in 14 individuals undergoing antegrade and subsequent retrograde double-balloon enteroscopy. The bacterial composition was characterised using 16 S rRNA sequencing with Illumina Miseq. Results: At double-balloon enteroscopy, one individual had a caecal adenocarcinoma and one individual had Peutz-Jeghers polyps. The composition of the microbiota distinctively changed along the gastrointestinal tract with larger bacterial load, diversity and abundance of Firmicutes and Bacteroidetes in the lower gastrointestinal tract than the upper gastrointestinal tract, which was predominated by Proteobacteria and Firmicutes. Conclusions: We show that gastrointestinal location is a larger determinant of mucosal microbial diversity than inter-person differences. These data provide a baseline for further studies investigating gastrointestinal microbiota-related disease

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

Background: The continuous exposure of esophageal epithelium to refluxate may induce ectopic expression of bile-responsive genes and contribute to the development of Barrett's esophagus (BE) and esophageal adenocarcinoma. In normal physiology of the gut and liver, the nuclear receptor Pregnane × Receptor (PXR) is an important factor in the detoxification of xenobiotics and bile acid homeostasis. This study aimed to investigate the expression and genetic variation of PXR in reflux esophagitis (RE), Barrett's esophagus (BE) and esophageal adenocarcinoma.Methods: PXR mRNA levels and protein expression were determined in biopsies from patients with adenocarcinoma, BE, or RE, and healthy controls. Esophageal cell lines were stimulated with lithocholic acid and rifampicin. PXR polymorphisms 25385C/T, 7635A/G, and 8055C/T were genotyped in 249 BE patients, 233 RE patients, and 201 controls matched for age and gender.Results: PXR mRNA levels were significantly higher in adenocarcinoma tissue and columnar Barrett's epithelium, compared to squamous epithelium of these BE patients (P < 0.001), and RE patients (P = 0.003). Immunohistochemical staining of PXR showed predominantly cytoplasmic expression in BE tissue, whereas nuclear expression was found in adenocarcinoma tissue. In cell lines, stimulation with lithocholic acid did not increase PXR mRNA levels, but did induce nuclear translocation of PXR protein. Genotyping of the PXR 7635A/G polymorphism revealed that the G allele was significantly more prevalent in BE than in RE or controls (P = 0.037).Conclusions: PXR expresses in BE and adenocarcinoma tissue, and showed nuclear localization in adenocarcinoma tissue. Upon stimulation with lithocholic acid, PXR translocates to the nuclei of OE19 adenocarcinoma cells. Together with the observed association of a PXR polymorphism and BE, this data implies that PXR may have a function in prediction and treatment of esophageal disease

Vitamin D receptor polymorphisms are associated with reduced esophageal vitamin D receptor expression and reduced esophageal adenocarcinoma risk

Epidemiological studies indicate that vitamin D exerts a protective effect on the development of various solid cancers. However, concerns have been raised regarding the potential deleterious role of high vitamin D levels in the development of esophageal adenocarcinoma (EAC). This study investigated genetic variation in the vitamin D receptor (VDR) in relation to its expression and risk of Barrett esophagus (BE) and EAC. VDR gene regulation was investigated by immunohistochemistry, reverse transcriptase–polymerase chain reaction (RT-PCR) and gel shift assays. Fifteen haplotype tagging single-nucleotide polymorphisms (SNPs) of the VDR gene were analyzed in 858 patients with reflux esophagitis (RE), BE or EAC and 202 healthy controls. VDR mRNA expression was higher in BE compared with squamous epithelium. VDR protein was located in the nucleus in BE. An rs1989969T/rs2238135G haplotype was identified in the 5’ regulatory region of the VDR gene. It was associated with an approximately two-fold reduced risk of RE, BE and EAC. Analysis of a replication cohort was done for BE that confirmed this. The rs1989969T allele causes a GATA-1 transcription factor binding site to appear. The signaling of GATA-1, which is regarded as a negative transcriptional regulator, could explain the findings for rs1989969. The rs2238135G allele was associated with a significantly reduced VDR expression in BE; for the rs1989969T allele, a trend in reduced VDR expression was observed. We identified a VDR haplotype associated with reduced esophageal VDR expression and a reduced incidence of RE, BE and EAC. This VDR haplotype could be useful in identifying individuals who benefit most from vitamin D chemoprevention

HOXA13 in etiology and oncogenic potential of Barrett’s esophagus

Barrett’s esophagus is a pro-oncogenic lesion in the proximal gastrointestinal tract, but with a distal colon-like morphology. Here the authors report that the distal HOX gene HOXA13 is expressed in Barrett’s esophagus and in single cells of the physiological esophagus, and may underlie the phenotypic aspects of metaplasia and increase proliferation

Common variants at the MHC locus and at chromosome 16q24.1 predispose to Barrett's esophagus

Barrett's esophagus is an increasingly common disease that is strongly associated with reflux of stomach acid and usually a hiatus hernia, and it strongly predisposes to esophageal adenocarcinoma (EAC), a tumor with a very poor prognosis. We report the first genome-wide association study on Barrett's esophagus, comprising 1,852 UK cases and 5,172 UK controls in the discovery stage and 5,986 cases and 12,825 controls in the replication stage. Variants at two loci were associated with disease risk: chromosome 6p21, rs9257809 (P-combined = 4.09 x 10(-9); odds ratio (OR) = 1.21, 95% confidence interval (CI) = 1.13-1.28), within the major histocompatibility complex locus, and chromosome 16q24, rs9936833 (P-combined = 2.74 x 10(-10); OR = 1.14, 95% CI = 1.10-1.19), for which the closest protein-coding gene is FOXF1, which is implicated in esophageal development and structure. We found evidence that many common variants of small effect contribute to genetic susceptibility to Barrett's esophagus and that SNP alleles predisposing to obesity also increase risk for Barrett's esophagus

Common variants at the MHC locus and at chromosome 16q24.1 predispose to Barrett's esophagus

Barrett's esophagus is an increasingly common disease that is strongly associated with reflux of stomach acid and usually a hiatus hernia, and it strongly predisposes to esophageal adenocarcinoma (EAC), a tumor with a very poor prognosis. We report the first genome-wide association study on Barrett's esophagus, comprising 1,852 UK cases and 5,172 UK controls in the discovery stage and 5,986 cases and 12,825 controls in the replication stage. Variants at two loci were associated with disease risk: chromosome 6p21, rs9257809 (P combined = 4.09 × 10-9; odds ratio (OR) = 1.21, 95% confidence interval (CI) =1.13-1.28), within the major histocompatibility complex locus, and chromosome 16q24, rs9936833 (P combined = 2.74 × 10-10; OR = 1.14, 95% CI = 1.10-1.19), for which the closest protein-coding gene is FOXF1, which is implicated in esophageal development and structure. We found evidence that many common variants of small effect contribute to genetic susceptibility to Barrett's esophagus and that SNP alleles predisposing to obesity also increase risk for Barrett's esophagus. © 2012 Nature America, Inc. All rights reserved

Common variants at the MHC locus and at chromosome 16q24.1 predispose to Barrett's esophagus

Barrett's esophagus is an increasingly common disease that is strongly associated with reflux of stomach acid and usually a hiatus hernia, and it strongly predisposes to esophageal adenocarcinoma (EAC), a tumor with a very poor prognosis. We report the first genome-wide association study on Barrett's esophagus, comprising 1,852 UK cases and 5,172 UK controls in the discovery stage and 5,986 cases and 12,825 controls in the replication stage. Variants at two loci were associated with disease risk: chromosome 6p21, rs9257809 (Pcombined = 4.09 × 10−9; odds ratio (OR) = 1.21, 95% confidence interval (CI) =1.13–1.28), within the major histocompatibility complex locus, and chromosome 16q24, rs9936833 (Pcombined = 2.74 × 10−10; OR = 1.14, 95% CI = 1.10–1.19), for which the closest protein-coding gene is FOXF1, which is implicated in esophageal development and structure. We found evidence that many common variants of small effect contribute to genetic susceptibility to Barrett's esophagus and that SNP alleles predisposing to obesity also increase risk for Barrett's esophagus