Caudal -related homeobox 2 ( Cdx2 ) has been suggested as an early marker of Barrett's esophagus (BE), which is the premalignant lesion of esophageal adenocarcinoma (EAC). However, the mechanism of ectopic Cdx2 expression in the esophageal epithelial cells and its role in the development of BE remained unclear. RT–PCR, pyrosequencing and methylation-specific PCR were used to determine expression and promoter methylation of Cdx2 in human esophageal epithelial cells (HET1A and SEG1) after treatment with 5-aza-2′-deoxycytidine (DAC), acid, bile acids and their combination. HET1A cells with stable transfection of Cdx2 were characterized for morphology and gene expression profiles with Affymetrix array. We found Cdx2 was expressed in most human EAC cell lines, but not in squamous epithelial cell lines. DAC-induced demethylation and expression of Cdx2 in HET1A and SEG1 cells, and treatment with a DNA methylating agent counteracted the effect of DAC. Treatment of HET1A and SEG1 cells with acid, bile acids or both also resulted in promoter demethylation and expression of Cdx2 . HET1A cells with stable transfection of human Cdx2 formed crypt-like structures in vitro . Microarray analysis and quantitative real-time PCR showed that stable transfection of Cdx2 up-regulated differentiation markers of intestinal columnar epithelial cells and goblet cells in HET1A cells. This may be partially due to modulation of Notch signaling pathway, as western blotting confirmed down-regulation of Hes1 and up-regulation of Atoh1 and Muc2. Our data suggest that exposure to acid and/or bile acids may activate Cdx2 expression in human esophageal epithelial cells through promoter demethylation, and ectopic Cdx2 expression in esophageal squamous epithelial cells may contribute to intestinal metaplasia of the esophagus.

In rats, esophagogastroduodenal anastomosis (EGDA) without concomitant chemical carcinogen treatment leads to gastroesophageal reflux disease, multilayered epithelium (MLE, a presumed precursor in intestinal metaplasia), columnar-lined esophagus, dysplasia, and esophageal adenocarcinoma. Previously we have shown that columnar-lined esophagus in EGDA rats resembled human Barrett's esophagus (BE) in its morphology, mucin features and expression of differentiation markers (Lab. Invest. 2004;84:753–765). The purpose of this study was to compare the phenotype of rat MLE with human MLE, in order to gain insight into the nature of MLE and its potential role in the development of BE.

Objective: As a major cellular defence mechanism, the Nrf2/Keap1 pathway regulates expression of genes involved in detoxification and stress response. Here we hypothesise that Nrf2 is involved in oesophageal barrier function and plays a protective role against gastro-oesophageal reflux disease (GERD). Design: Human oesophageal biopsy samples, mouse surgical models and Nrf2 ^−/− mice were used to assess the role of the Nrf2/Keap1 pathway in oesophageal barrier function. Trans-epithelial electrical resistance (TEER) was measured with mini-Ussing chambers. HE staining and transmission electron microscopy were used to examine tissue morphology, while gene microarray, immunohistochemistry, western blotting and chromatin immunoprecipitation (ChIP) analysis were used to assess gene expression. Results: Nrf2 was expressed in normal oesophageal epithelium and activated in GERD of both humans and mice. Nrf2 deficiency and gastro-oesophageal reflux in mice, alone or in combination, reduced TEER and increased intercellular space in oesophageal epithelium. Nrf2 target genes and gene sets associated with oxidoreductase activity, mitochondrial biogenesis and energy production were downregulated in the oesophageal epithelium of Nrf2 ^−/− mice. Consistent with the antioxidative function of Nrf2, a DNA oxidative damage marker (8OHdG) dramatically increased in oesophageal epithelial cells of Nrf2 ^−/− mice compared with those of wild-type mice. Interestingly, ATP biogenesis, Cox IV (a mitochondrial protein) and Claudin 4 (Cldn4) expression were downregulated in the oesophageal epithelium of Nrf2 ^−/− mice, suggesting that energy-dependent tight junction integrity was subject to Nrf2 regulation. ChIP analysis confirmed the binding of Nrf2 to Cldn4 promoter. Conclusions: Nrf2 deficiency impairs oesophageal barrier function through disrupting energy-dependent tight junction.

Esophageal squamous cell carcinoma continues to heavily burden clinicians worldwide. Researchers have discovered the genomic landscape of esophageal squamous cell carcinoma, which holds promise for an era of personalized oncology care. One of the most pressing problems facing this issue is to improve the understanding of the newly available genomic data, and identify the driver-gene mutations, pathways, and networks. The emergence of a legion of novel targeted agents has generated much hope and hype regarding more potent treatment regimens, but the accuracy of drug selection is still arguable. Other problems, such as cancer heterogeneity, drug resistance, exceptional responders, and side effects, have to be surmounted. Evolving topics in personalized oncology, such as interpretation of genomics data, issues in targeted therapy, research approaches for targeted therapy, and future perspectives, will be discussed in this editorial.

Mutations in the genes encoding nuclear factor (erythroid-derived 2)-like 2 (NRF2), Kelch-like ECH-associated protein 1 (KEAP1), and cullin 3 (CUL3) are commonly observed in human esophageal squamous cell carcinoma (ESCC) and result in activation of the NRF2 signaling pathway. Moreover, hyperactivity of the transcription factor Nrf2 has been found to cause esophageal hyperproliferation and hyperkeratosis in mice. However, the underlying mechanism is unclear. In this study, we aimed to understand the molecular mechanisms of esophageal hyperproliferation in mice due to hyperactive Nrf2. Esophageal tissues were obtained from genetically modified mice that differed in the status of the Nrf2 gene and genes in the same pathway (Nrf2^-/-, Keap1^-/-, K5Cre;Pkm2^fl/fl;Keap1^-/-, and wild-type) and analyzed for metabolomic profiles, Nrf2 ChIP-Seq, and gene expression. We found that hyperactive Nrf2 causes metabolic reprogramming and up-regulation of metabolic genes in the mouse esophagus. One of the glycolysis genes encoding pyruvate kinase M2 (Pkm2) was not only differentially up-regulated, but also glycosylated and oligomerized, resulting in increased ATP biosynthesis. However, constitutive knockout of Pkm2 failed to inhibit this esophageal phenotype in vivo, and this failure may have been due to compensation by Pkm1 up-regulation. Transient inhibition of NRF2 or glycolysis inhibited the growth of human ESCC cells in which NRF2 is hyperactive in vitro. In summary, hyperactive Nrf2 causes metabolic reprogramming in the mouse esophagus through its transcriptional regulation of metabolic genes. Blocking glycolysis transiently inhibits cell proliferation and may therefore have therapeutically beneficial effects on NRF2^high ESCC in humans.