Downregulation of p63 upon exposure to bile salts and acid in normal and cancer esophageal cells in culture

Protein adduction causes non-mutational inhibition of p53 tumor suppressor

p53 is a key tumor suppressor that is frequently mutated in human tumors. In this study, we investigated how p53 is regulated in precancerous lesions prior to mutations in the p53 gene. Analyzing esophageal cells in conditions of genotoxic stress that promotes development of esophageal adenocarcinoma, we find that p53 protein is adducted with reactive isolevuglandins (isoLGs), products of lipid peroxidation. Modification of p53 protein with isoLGs diminishes its acetylation and binding to the promoters of p53 target genes causing modulation of p53-dependent transcription. It also leads to accumulation of adducted p53 protein in intracellular amyloid-like aggregates that can be inhibited by isoLG scavenger 2-HOBA in vitro and in vivo. Taken together, our studies reveal a posttranslational modification of p53 protein that causes molecular aggregation of p53 protein and its non-mutational inactivation in conditions of DNA damage that may play an important role in human tumorigenesis.

The Oxidative Damage and Inflammation Mechanisms in GERD-Induced Barrett's Esophagus

Barrett's esophagus is a major complication of gastro-esophageal reflux disease and an important precursor lesion for the development of Barrett's metaplasia and esophageal adenocarcinoma. However, the cellular and molecular mechanisms of Barrett's metaplasia remain unclear. Inflammation-associated oxidative DNA damage could contribute to Barrett's esophagus. It has been demonstrated that poly(ADP-ribose) polymerases (PARPs)-associated with ADP-ribosylation plays an important role in DNA damage and inflammatory response. A previous study indicated that there is inflammatory infiltration and oxidative DNA damage in the lower esophagus due to acid/bile reflux, and gastric acid could induce DNA damage in culture esophageal cells. This review will discuss the mechanisms of Barrett's metaplasia and adenocarcinoma underlying oxidative DNA damage in gastro-esophageal reflux disease patients based on recent clinical and basic findings.

Iron deficiency linked to altered bile acid metabolism promotes Helicobacter pylori-induced inflammation-driven gastric carcinogenesis

Gastric carcinogenesis is mediated by complex interactions among Helicobacter pylori, host, and environmental factors. Here, we demonstrate that H. pylori augmented gastric injury in INS-GAS mice under iron-deficient conditions. Mechanistically, these phenotypes were not driven by alterations in the gastric microbiota; however, discovery-based and targeted metabolomics revealed that bile acids were significantly altered in H. pylori-infected mice with iron deficiency, with significant upregulation of deoxycholic acid (DCA), a carcinogenic bile acid. The severity of gastric injury was further augmented when H. pylori-infected mice were treated with DCA, and, in vitro, DCA increased translocation of the H. pylori oncoprotein CagA into host cells. Conversely, bile acid sequestration attenuated H. pylori-induced injury under conditions of iron deficiency. To translate these findings to human populations, we evaluated the association between bile acid sequestrant use and gastric cancer risk in a large human cohort. Among 416,885 individuals, a significant dose-dependent reduction in risk was associated with cumulative bile acid sequestrant use. Further, expression of the bile acid receptor transmembrane G protein-coupled bile acid receptor 5 (TGR5) paralleled the severity of carcinogenic lesions in humans. These data demonstrate that increased H. pylori-induced injury within the context of iron deficiency is tightly linked to altered bile acid metabolism, which may promote gastric carcinogenesis.

P63 Deficiency and CDX2 Overexpression Lead to Barrett's-Like Metaplasia in Mouse Esophageal Epithelium

BACKGROUND

The cellular origin and molecular mechanisms of Barrett's esophagus (BE) are still controversial. Trans-differentiation is a mechanism characterized by activation of the intestinal differentiation program and inactivation of the squamous differentiation program.

AIMS

Renal capsule grafting (RCG) was used to elucidate whether CDX2 overexpression on the basis of P63 deficiency in the esophageal epithelium may generate intestinal metaplasia.

METHODS

P63^-/-;Villin-Cdx2 embryos were generated by crossing P63^+/- mice with Villin-Cdx2 mice. E18.5 esophagus was xenografted in a renal capsule grafting (RCG) model. At 1, 2, or 4 weeks after RCG, the mouse esophagus was immunostained for a proliferation marker (BrdU), squamous transcription factors (SOX2, PAX9), squamous differentiation markers (CK5, CK4, and CK1), intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6), intestinal columnar epithelial cell markers (A33, CK8), goblet cell marker (MUC2, TFF3), Paneth cell markers (LYZ and SOX9), enteroendocrine cell marker (CHA), and Tuft cell marker (DCAMKL1).

RESULTS

The P63^-/-;Villin-Cdx2 RCG esophagus was lined with proliferating PAS/AB+ cuboidal cells and formed an intestinal crypt-like structure. The goblet cell markers (TFF3 and MUC2) and intestinal transcription factors (CDX1, HNF1α, HNF4α, GATA4, and GATA6) were expressed although no typical morphology of goblet cells was observed. Other intestinal cell markers including enteroendocrine cell marker (CHA), Paneth cell markers (LYZ and Sox9), and intestinal secretory cell marker (UEA/WGA) were also expressed in the P63^-/-;Villin-Cdx2 RCG esophagus. Squamous cell markers (PAX9 and SOX2) were also expressed, suggesting a transitional phenotype.

CONCLUSION

CDX2 overexpression on the basis of P63 deficiency in esophageal epithelial cells induces Barrett's-like metaplasia in vivo. Additional factors may be needed to drive this transitional phenotype into full-blown BE.

SPT6 loss permits the transdifferentiation of keratinocytes into an intestinal fate that resembles Barrett's metaplasia

Transient depletion of the transcription elongation factor SPT6 in the keratinocyte has been recently shown to inhibit epidermal differentiation and stratification; instead, they transdifferentiate into a gut-like lineage. We show here that this phenomenon of transdifferentiation recapitulates Barrett's metaplasia, the only human pathophysiologic condition in which a stratified squamous epithelium that is injured due to chronic acid reflux is trans-committed into an intestinal fate. The evidence we present here not only lend support to the notion that the keratinocytes are potentially the cell of origin of Barrett's metaplasia but also provide mechanistic insights linking transient acid exposure, downregulation of SPT6, stalled transcription of the master regulator of epidermal fate TP63, loss of epidermal fate, and metaplastic progression. Because Barrett's metaplasia in the esophagus is a pre-neoplastic condition with no preclinical human models, these findings have a profound impact on the modeling Barrett's metaplasia-in-a-dish.

Epithelial cell transforming 2 is regulated by Yes-associated protein 1 and mediates pancreatic cancer progression and metastasis

Pancreatic ductal adenocarcinoma (PDAC) is highly metastatic and represents one of the deadliest forms of human cancers. Previous studies showed that activation of Yes-associated protein 1 (YAP1) plays a key role in malignant transformation in the pancreas. In this study, we found that YAP1 regulates the expression of epithelial cell transforming 2 (ECT2), a guanine nucleotide exchange factor for Rho-like GTPases. By immunohistochemistry analysis of human tissues, we show that ECT2 is highly expressed in primary PDAC and liver metastasis but not in normal pancreas. These correlations were also observed in a mouse model of PDAC, where pancreatic transformation is driven by mutants of Kras and Trp53. Notably, nuclear ECT2 is upregulated in the transition from preneoplastic lesions to PDAC. High levels of YAP1 or ECT2 expression correlates with the poor overall survival rate of patients with PDAC. We further demonstrate that ECT2 is required for pancreatic cancer cell proliferation and migration in vitro. Finally, using a syngeneic orthotopic xenograft mouse model for pancreatic cancer, we found that ablation of ECT2 expression reduces pancreatic cancer growth and dissemination to the liver. These findings highlight the critical role of ECT2 in promoting pancreatic cancer growth and metastasis and provides insights into the development of novel methods for early detection and treatment.NEW & NOTEWORTHY Pancreatic ductal adenocarcinoma is one of the deadliest forms of human cancers. In this study, we identified a novel signaling mechanism involved in PDAC progression and metastasis. Yes-associated protein 1 mediates the expression of epithelial cell transforming 2, which is elevated in PDAC and correlates with poor survival. Epithelial cell transforming 2 is required for PDAC growth and metastasis. This study provides insights into the development of novel methods for early detection and treatment of PDAC.

Human esophageal myofibroblasts increase squamous epithelial thickness via paracrine mechanisms in an in vitro model of gastroesophageal reflux disease

The pathogenesis of esophageal injury in gastroesophageal reflux disease (GERD) is incompletely understood. We modeled exposure of human esophageal myofibroblasts (HEMFs) to gastroesophageal reflux by repeated treatment with pH 4.5 and pH 4.5 bile salts and determined the effects on the epithelium in a 3D organotypic-like air-liquid interface model. Total, basal and supra-basal thickness of the epithelium were measured and immunostaining for p63, for basal (CK 14) and supra-basal (CK 4) squamous differentiation markers, and for cell proliferation (PCNA) were performed. Epithelial cell proliferation in response to HEMF conditioned media was also assessed in 2D culture. In the 3D organotypic model, total epithelial thickness increased similarly with pH 4.5 and pH 4.5 bile salt treated versus untreated and bile salt treated HEMF conditioned media. Epithelial p63 immunostaining was increased and multilayered. There was expansion of the CK14+ basal and CK4+ supra-basal layers in the epithelium established with conditioned media from pH 4.5 and pH 4.5 bile salt treated HEMFs versus untreated HEMF conditioned media. PCNA + cells per μm of tissue were unchanged in the basal layer across all treatment conditions while PCNA + cells per total DAPI + cells were decreased. In 2D culture, basal epithelial proliferation decreased with conditioned media from pH 4.5 and pH 4.5 bile salt treated HEMFs compared to conditioned media from untreated HEMF conditioned media. Secreted factors from HEMFs treated with acidic stimuli encountered in GERD increase epithelial thickness compared to secreted factors from untreated HEMFs and expand both basal and supra-basal layers. Our findings demonstrate for the first time paracrine regulation of the squamous epithelium from acid stimulated HEMFs. The effects of secreted factors from acid treated HEMFs on basal cell proliferation in this model and the mechanism mediating the increase in epithelial thickness merit further investigation.

Pathogenesis and Cells of Origin of Barrett's Esophagus

In patients with Barrett's esophagus (BE), metaplastic columnar mucosa containing epithelial cells with gastric and intestinal features replaces esophageal squamous mucosa damaged by gastroesophageal reflux disease. This condition is estimated to affect 5.6% of adults in the United States, and is a major risk factor for esophageal adenocarcinoma. Despite the prevalence and importance of BE, its pathogenesis is incompletely understood and there are disagreements over the cells of origin. We review mechanisms of BE pathogenesis, including transdifferentiation and transcommitment, and discuss potential cells of origin, including basal cells of the squamous epithelium, cells of esophageal submucosal glands and their ducts, cells of the proximal stomach, and specialized populations of cells at the esophagogastric junction (residual embryonic cells and transitional basal cells). We discuss the concept of metaplasia as a wound-healing response, and how cardiac mucosa might be the precursor of the intestinal metaplasia of BE. Finally, we discuss shortcomings in current diagnostic criteria for BE that have important clinical implications.

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.

The cyclical hit model: how paligenosis might establish the mutational landscape in Barrett's esophagus and esophageal adenocarcinoma

PURPOSE OF REVIEW

In this review, we explore a paligenosis-based model to explain Barrett's esophagus development and progression: 'the cyclical hit model.'

RECENT FINDINGS

Genomic analyses have highlighted the high mutational burden of esophageal adenocarcinoma, Barrett's esophagus, and even normal esophageal epithelium. Somatic mutations in key genes including TP53 occur early in the neoplastic progression sequence of Barrett's esophagus, whereas chromosomal amplification resulting in oncogene activation occurs as a critical late event. Paligenosis is a shared injury response mechanism characterized by activation of autophagy, expression of progenitor markers, and increased mTORC signaling-induced cell-cycle reentry. In the setting of chronic injury/inflammation, cycles of paligenosis may allow accumulation of mutations until eventually the mutational burden, in concert perhaps with mutations in key driver oncogenes, finally alters the cell's ability to redifferentiate, leading to the emergence of a potential neoplastic clone.

SUMMARY

Under conditions of chronic gastroesophageal refluxate exposure, the normal esophageal squamous epithelium might undergo multiple cycles of paligenosis, allowing initially silent mutations to accumulate until key events impart mutant clones with an oncogenic survival advantage.

IL-1β Inflammatory Cytokine-Induced TP63 Isoform ∆NP63α Signaling Cascade Contributes to Cisplatin Resistance in Human Breast Cancer Cells

The mechanisms behind the induction of malignancy and chemoresistance in breast cancer cells are still not completely understood. Inflammation is associated with the induction of malignancy in different types of cancer and is highlighted as an important factor for chemoresistance. In previous work, we demonstrated that the inflammatory cytokine interleukin 1β (IL-1β)-induced upregulation of genes was associated with chemoresistance in breast cancer cells. Here, we evaluated the participation and the expression profile of TP63 in the induction of resistance to cisplatin. By loss-of-function assays, we identified that IL-1β particularly upregulates the expression of the tumor protein 63 (TP63) isoform ΔNP63α, through the activation of the IL-1β/IL-1RI/β-catenin signaling pathway. Upregulation of ΔNP63α leads to an increase in the expression of the cell survival factors epidermal growth factor receptor (EGFR) and phosphatase 1D (Wip1), and a decrease in the DNA damage sensor, ataxia-telangiectasia mutated (ATM). The participation of these processes in the increase of resistance to cisplatin was confirmed by silencing TP63 expression or by inhibition of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) activity in the IL-1β/IL-1RI/β-catenin signaling pathway. These data reinforced the importance of an inflammatory environment in the induction of drug resistance in cancer cells and uncovered a molecular mechanism where the IL-1β signaling pathway potentiates the acquisition of cisplatin resistance in breast cancer cells.

Are Gastric and Esophageal Metaplasia Relatives? The Case for Barrett's Stemming from SPEM

Chronic injury and inflammation in the esophagus can cause a change in cellular differentiation known as metaplasia. Most commonly, the differentiation changes manifest as Barrett's esophagus (BE), characterized by the normal stratified squamous epithelium converting into a cuboidal-columnar, glandular morphology. BE cells can phenotypically resemble specific normal cell types of the stomach or intestine, or they can have overlapping phenotypes in disorganized admixtures. The stomach can also undergo metaplasia characterized by aberrant gastric or intestinal differentiation patterns. In both organs, it has been argued that metaplasia may represent a recapitulation of the embryonic or juvenile gastrointestinal tract, as cells access a developmental progenitor genetic program that can help repair damaged tissue. Here, we review the normal development of esophagus and stomach, and describe how BE represents an intermixing of cells resembling gastric pseudopyloric (SPEM) and intestinal metaplasia. We discuss a cellular process recently termed "paligenosis" that governs how mature, differentiated cells can revert to a proliferating progenitor state in metaplasia. We discuss the "Cyclical Hit" theory in which paligenosis might be involved in the increased risk of metaplasia for progression to cancer. However, somatic mutations might occur in proliferative phases and then be warehoused upon redifferentiation. Through years of chronic injury and many rounds of paligenosis and dedifferentiation, eventually a cell with a mutation that prevents dedifferentiation may arise and clonally expand fueling stable metaplasia and potentially thereafter acquiring additional mutations and progressing to dysplasia and cancer.

Rethinking the bile acid/gut microbiome axis in cancer

Dietary factors, probiotic agents, aging and antibiotics/medicines impact on gut microbiome composition leading to disturbances in localised microbial populations. The impact can be profound and underlies a plethora of human disorders, including the focus of this review; cancer. Compromised microbiome populations can alter bile acid signalling and produce distinct pathophysiological bile acid profiles. These in turn have been associated with cancer development and progression. Exposure to high levels of bile acids, combined with localised molecular/genome instability leads to the acquisition of bile mediated neoplastic alterations, generating apoptotic resistant proliferation phenotypes. However, in recent years, several studies have emerged advocating the therapeutic benefits of bile acid signalling in suppressing molecular and phenotypic hallmarks of cancer progression. These studies suggest that in some instances, bile acids may reduce cancer phenotypic effects, thereby limiting metastatic potential. In this review, we contextualise the current state of the art to propose that the bile acid/gut microbiome axis can influence cancer progression to the extent that classical in vitro cancer hallmarks of malignancy (cell invasion, cell migration, clonogenicity, and cell adhesion) are significantly reduced. We readily acknowledge the existence of a bile acid/gut microbiome axis in cancer initiation, however, in light of recent advances, we focus exclusively on the role of bile acids as potentially beneficial molecules in suppressing cancer progression. Finally, we theorise that suppressing aggressive malignant phenotypes through bile acid/gut microbiome axis modulation could uncover new and innovative disease management strategies for managing cancers in vulnerable cohorts.

Barrett's metaplasia develops from cellular reprograming of esophageal squamous epithelium due to gastroesophageal reflux

Gastroesophageal reflux disease (GERD) clinically predisposes to columnar Barrett's metaplasia (BM) in the distal esophagus. We demonstrate evidence supporting the cellular origin of BM from reprograming or transcommitment of resident normal esophageal squamous (NES) epithelial cells in response to acid and bile (A + B) exposure using an in vitro cell culture model. The hTERT-immortalized NES cell line NES-B10T was exposed 5 min/day to an A + B mixture for 30 wk. Morphological changes, mRNA, and protein expression levels for the inflammatory marker cyclooxygenase-2; the lineage-determining transcription factors TAp63 (squamous), CDX2, and SOX9 (both columnar); and the columnar lineage markers Villin, Muc-2, CK8, and mAb Das-1 (incomplete phenotype of intestinal metaplasia) were assessed every 10 wk. Markers of columnar lineage and inflammation increased progressively, while squamous lineage-determining transcriptional factors were significantly decreased both at the mRNA and/or protein level in the NES-B10T cells at/after A + B treatment for 30 wk. Distinct modifications in morphological features were only observed at/after 30 wk of A + B exposure. These changes acquired by the NES-B10T 30-wk cells were retained even after cessation of A + B exposure for at least 3 wk. This study provides evidence that chronic exposure to the physiological components of gastric refluxate leads to repression of the discernable squamous transcriptional factors and activation of latent columnar transcriptional factors. This reflects the alteration in lineage commitment of the precursor-like biphenotypic, NES-B10T cells in response to A + B exposure as the possible origin of BM from the resident NES cells.NEW & NOTEWORTHY This study provides evidence of the origins of Barrett's metaplasia from lineage transcommitment of resident esophageal cells after chronic exposure to gastroesophageal refluxate. The preterminal progenitor-like squamous cells alter their differentiation and develop biphenotypic characteristics, expressing markers of incomplete-type columnar metaplasia. Development of these biphenotypic precursors in vitro is a unique model to study pathogenesis of Barrett's metaplasia and esophageal adenocarcinoma.

Prevention of DNA damage in Barrett's esophageal cells exposed to acidic bile salts

Esophageal adenocarcinoma (EA) is one of the fastest rising tumors in the USA. The major risk factor for EA is gastroesophageal reflux disease (GERD). During GERD, esophageal cells are exposed to refluxate which contains gastric acid frequently mixed with duodenal bile. This may lead to mucosal injury and Barrett's metaplasia (BE) that are important factors contributing to development of EA. In this study, we investigated DNA damage in BE cells exposed to acidic bile salts and explored for potential protective strategies. Exposure of BE cells to acidic bile salts led to significant DNA damage, which in turn, was due to generation of reactive oxygen species (ROS). We found that acidic bile salts induce a rapid increase in superoxide radicals and hydrogen peroxide, which were determined using electron paramagnetic resonance spectroscopy and Amplex Red assay. Analyzing a panel of natural antioxidants, we identified apocynin to be the most effective in protecting esophageal cells from DNA damage induced by acidic bile salts. Mechanistic analyses showed that apocynin inhibited ROS generation and increases the DNA repair capacity of BE cells. We identified BRCA1 and p73 proteins as apocynin targets. Downregulation of p73 inhibited the protective effect of apocynin. Taken together, our results suggest potential application of natural compounds such as apocynin for prevention of reflux-induced DNA damage and GERD-associated tumorigenesis.

Characterization of oncocytes in deep esophageal glands

Deep esophageal glands play a vital role in the protection and regeneration of the esophageal mucosa. Conditions such as gastroesophageal reflux disease and Barrett's esophagus have been associated with a change in the usual glands by oncocytic metaplasia. However, little is known regarding the function of oncocytes or the relevance of this metaplastic change in the human esophagus. We hypothesized that oncocytes of deep esophageal glands also express markers characteristic of a ductal epithelial phenotype because similar oncocytes have been described as part of large ductal epithelial cells in salivary glands. We used immunohistochemical stains to define structural, functional, proliferative, and potential stem/progenitor characteristics of oncocytes. Oncocytes did not express mucins or lysozyme C, two molecules found in mucous cells and used for antimicrobial defense. Oncocytes did not express CK5, a cytokeratin found in myoepithelial cells and basal epithelial cells, but expressed CK7, a cytokeratin found in intralobular ductal epithelial cells and luminal epithelial cells of the main duct. Oncocytes expressed cystic fibrosis transmembrane conductance regulator and sodium/potassium ATPase, ion channels that play a role in bicarbonate secretion. Membrane-bound beta-catenin was detected in oncocytes, but these cells did not express the proliferative marker Ki67. Approximately, a third of oncocytes expressed SOX9 and p63, transcription factors expressed in epithelial progenitor cells in multiple organs. Moreover, oncocytes expressed CD44, a transmembrane Glycoprotein expressed in cancer stem cells. Taken together, our data show that oncocytes express markers of intralobular ductal epithelial cells and luminal epithelial cells of the main duct. Additionally, our observations suggest that oncocytes act as epithelial progenitor cells and play a role in bicarbonate secretion. Since oncocytic metaplasia is associated with conditions of chronic acid injury, it is possible that oncocytes replace the mucous cells in deep esophageal glands (dEG) as an adaptive change to counteract injury from acid reflux. The marker characterization suggests that oncocytes may originate from transdifferentiation of myoepithelial and mucous cells. This transdifferentiation might lead to an overall decrease of mucins production and secretion by the dEG and a subsequent reduction of the protection conferred by the viscoelastic mucous layer.

Bile acids destabilise HIF-1α and promote anti-tumour phenotypes in cancer cell models

Background

The role of the microbiome has become synonymous with human health and disease. Bile acids, as essential components of the microbiome, have gained sustained credibility as potential modulators of cancer progression in several disease models. At physiological concentrations, bile acids appear to influence cancer phenotypes, although conflicting data surrounds their precise physiological mechanism of action. Previously, we demonstrated bile acids destabilised the HIF-1α subunit of the Hypoxic-Inducible Factor-1 (HIF-1) transcription factor. HIF-1 overexpression is an early biomarker of tumour metastasis and is associated with tumour resistance to conventional therapies, and poor prognosis in a range of different cancers.

Methods

Here we investigated the effects of bile acids on the cancer growth and migratory potential of cell lines where HIF-1α is known to be active under hypoxic conditions. HIF-1α status was investigated in A-549 lung, DU-145 prostate and MCF-7 breast cancer cell lines exposed to bile acids (CDCA and DCA). Cell adhesion, invasion, migration was assessed in DU-145 cells while clonogenic growth was assessed in all cell lines.

Results

Intracellular HIF-1α was destabilised in the presence of bile acids in all cell lines tested. Bile acids were not cytotoxic but exhibited greatly reduced clonogenic potential in two out of three cell lines. In the migratory prostate cancer cell line DU-145, bile acids impaired cell adhesion, migration and invasion. CDCA and DCA destabilised HIF-1α in all cells and significantly suppressed key cancer progression associated phenotypes; clonogenic growth, invasion and migration in DU-145 cells.

Conclusions

These findings suggest previously unobserved roles for bile acids as physiologically relevant molecules targeting hypoxic tumour progression.

Transcommitment: Paving the Way to Barrett's Metaplasia

Barrett's esophagus is the condition in which metaplastic columnar epithelium that predisposes to cancer development replaces stratified squamous epithelium in the distal esophagus. Potential sources for the cell or tissue of origin for metaplastic Barrett's epithelium are reviewed including native esophageal differentiated squamous cells, progenitor cells native to the esophagus located within the squamous epithelium or in the submucosal glands or ducts, circulating bone marrow-derived stem cells, and columnar progenitor cells from the squamocolumnar junction or the gastric cardia that proximally shift into the esophagus to fill voids left by damaged squamous epithelium. Wherever its source the original cell must undergo molecular reprogramming (i.e., either transdifferentiation or transcommitment) to give rise to specialized intestinal metaplasia. Transcription factors that specify squamous, columnar, intestinal, and mucus-secreting epithelial differentiation are discussed. An improved understanding of how esophageal columnar metaplasia forms could lead to development of effective treatment or prevention strategies for Barrett's esophagus. It could also more broadly inform upon normal tissue development and differentiation, wound healing, and stem cell biology.

Golgi phosphoprotein 2 (GOLPH2) is a novel bile acid-responsive modulator of oesophageal cell migration and invasion

BACKGROUND

The aetiology of Barrett's oesophagus (BO) and oesophageal cancer is poorly understood. We previously demonstrated that Golgi structure and function is altered in oesophageal cancer cells. A Golgi-associated protein, GOLPH2, was previously established as a tissue biomarker for BO. Cellular functions for GOLPH2 are currently unknown, therefore in this study we sought to investigate functional roles for this Golgi-associated protein in oesophageal disease.

METHODS

Expression, intracellular localisation and secretion of GOLPH2 were identified by immunofluorescence, immunohistochemistry and western blot. GOLPH2 expression constructs and siRNA were used to identify cellular functions for GOLPH2.

RESULTS

We demonstrate that the structure of the Golgi is fragmented and the intracellular localisation of GOLPH2 is altered in BO and oesophageal adenocarcinoma tissue. GOLPH2 is secreted by oesophageal cancer cells and GOLPH2 expression, cleavage and secretion facilitate cell migration and invasion. Furthermore, exposure of cells to DCA, a bile acid component of gastric refluxate and known tumour promoter for oesophageal cancer, causes disassembly of the Golgi structure into ministacks, resulting in cleavage and secretion of GOLPH2.

CONCLUSIONS

This study demonstrates that GOLPH2 may be a useful tissue biomarker for oesophageal disease. We provide a novel mechanistic insight into the aetiology of oesophageal cancer and reveal novel functions for GOLPH2 in regulating tumour cell migration and invasion, important functions for the metastatic process in oesophageal cancer.

Mechanisms of Barrett's oesophagus: intestinal differentiation, stem cells, and tissue models

Barrett's oesophagus (BE) is defined as any metaplastic columnar epithelium in the distal oesophagus which replaces normal squamous epithelium and which predisposes to cancer development. It is this second requirement, the predisposition to cancer, which makes this condition both clinically highly relevant and an important area for ongoing research. While BE has been defined pathologically since the 1950's (Allison and Johnstone, Thorax 1955), and identified as a risk factor for esophageal adenocarcinoma since the 1970's (Naef A.P., et al J Thorac Cardiovasc Surg. 1975), our understanding of the molecular events giving rise to this condition remains limited. Herein we will examine what is known about the intestinal features of BE and how well it recapitulates the intestinal epithelium, including stem identity and function. Finally, we will explore laboratory models of this condition presently in use and under development, to identify new insights they may provide into this important clinical condition.

Bile acid induces MUC2 expression and inhibits tumor invasion in gastric carcinomas

PURPOSE

Bile acids might induce mucin expression and regulate tumor behavior in esophageal and colon cancers. However, little is known about the effect of bile acids on tumor invasiveness of gastric carcinoma (GC). The aim of the current study was to elucidate the mechanisms by which bile acids regulate tumor invasion in GC.

METHODS

We investigated bile acid-induced MUC2 expression and cell invasion and migration in the cultured GC cell lines, SNU-216, and MKN45. In addition, immunohistochemical analysis of MUC2 and Snail was performed on 389 archival paraffin-embedded tissues of GC to evaluate the correlation of their expression with prognosis.

RESULTS

Deoxycholic acid (DCA), a secondary bile acid, had no effect on the viability of SNU-216 and MKN45 GC cells at low concentrations (0-100 μM), but decreased viability at a higher concentration (200 μM). MKN45 cells showed higher MUC2 expression than SNU-216 cells under basal conditions. DCA treatment upregulated MUC2 mRNA expression in both SNU-216 and MKN45 cells. Expression of Snail and MMP9 was markedly decreased by DCA treatment, and E-cadherin expression was subsequently increased. DCA significantly inhibited invasion and migration of SNU-216 and MKN45 cells. In human GC, MUC2 expression showed a negative correlation with Snail expression (P = 0.021) and a significantly positive correlation with better prognosis (P = 0.023).

CONCLUSIONS

Taken together, our data suggest that DCA induced MUC2 expression in GC cells and inhibited tumor invasion and migration. Additionally, MUC2-expressing GCs showed low rates of Snail expression and were associated with a favorable prognosis.

Hacking cell differentiation: transcriptional rerouting in reprogramming, lineage infidelity and metaplasia

Initiating neoplastic cell transformation events are of paramount importance for the comprehension of regeneration and vanguard oncogenic processes but are difficult to characterize and frequently clinically overlooked. In epithelia, pre-neoplastic transformation stages are often distinguished by the appearance of phenotypic features of another differentiated tissue, termed metaplasia. In haemato/lymphopoietic malignancies, cell lineage ambiguity is increasingly recorded. Both, metaplasia and biphenotypic leukaemia/lymphoma represent examples of dysregulated cell differentiation that reflect a history of trans-differentiation and/or epigenetic reprogramming. Here we compare the similarity between molecular events of experimental cell trans-differentiation as an emerging therapeutic concept, with lineage confusion, as in metaplasia and dysplasia forecasting tumour development.

Proinflammatory cytokines and bile acids upregulate ΔNp73 protein, an inhibitor of p53 and p73 tumor suppressors

Gastroesophageal reflux disease (GERD) is the main etiological factor behind the recent rapid increase in the incidence of esophageal adenocarcinoma. During reflux, esophageal cells are exposed to bile at low pH resulting in cellular damage and inflammation, which are known to facilitate cancer development. In this study, we investigated the regulation of p73 isoform, ΔNp73α, in the reflux condition. Previous studies have reported that ΔNp73 exhibits anti-apoptotic and oncogenic properties through inhibition of p53 and p73 proteins. We found that direct exposure of esophageal cells to bile acids in an acidic environment alters the phosphorylation of ΔNp73, its subcellular localization and increases ΔNp73 protein levels. Upregulation of ΔNp73 was also observed in esophageal tissues collected from patients with GERD and Barrett’s metaplasia, a precancerous lesion in the esophagus associated with gastric reflux. c-Abl, p38 MAPK, and IKK protein kinases were identified to interact in the regulation of ΔNp73. Their inhibition with chemotherapeutic agents and siRNA suppresses ΔNp73. We also found that pro-inflammatory cytokines, IL-1β and TNFα, are potent inducers of ΔNp73α, which further enhance the bile acids/acid effect. Combined, our studies provide evidence that gastroesophageal reflux alters the regulation of oncogenic ΔNp73 isoform that may facilitate tumorigenic transformation of esophageal metaplastic epithelium.

The p63 protein isoform ΔNp63α inhibits epithelial-mesenchymal transition in human bladder cancer cells: role of MIR-205

Epithelial-mesenchymal transition (EMT) is a physiological process that plays important roles in tumor metastasis, "stemness," and drug resistance. EMT is typically characterized by the loss of the epithelial marker E-cadherin and increased expression of EMT-associated transcriptional repressors, including ZEB1 and ZEB2. The miR-200 family and miR-205 prevent EMT through suppression of ZEB1/2. p53 has been implicated in the regulation of miR-200c, but the mechanisms controlling miR-205 expression remain elusive. Here we report that the p53 family member and p63 isoform, ΔNp63α, promotes miR-205 transcription and controls EMT in human bladder cancer cells. ΔNp63α, E-cadherin and miR-205 were coexpressed in a panel of bladder cancer cell lines (n = 28) and a cohort of primary bladder tumors (n = 98). Stable knockdown of ΔNp63α in the "epithelial" bladder cancer cell line UM-UC6 decreased the expression of miR-205 and induced the expression of ZEB1/2, effects that were reversed by expression of exogenous miR-205. Conversely, overexpression of ΔNp63α in the "mesenchymal" bladder cancer cell line UM-UC3 induced miR-205 and suppressed ZEB1/2. ΔNp63α knockdown reduced the expression of the primary and mature forms of miR-205 and the miR-205 "host" gene (miR-205HG) and decreased binding of RNA Pol II to the miR-205HG promoter, inhibiting miR-205HG transcription. Finally, high miR-205 expression was associated with adverse clinical outcomes in bladder cancer patients. Together, our data demonstrate that ΔNp63α-mediated expression of miR-205 contributes to the regulation of EMT in bladder cancer cells and identify miR-205 as a molecular marker of the lethal subset of human bladder cancers.

A surprise cell of origin for Barrett's esophagus

Barrett's esophagus is a metaplasia of the distal esophagus that is the only recognized precursor of esophageal adenocarcinoma. Despite a characteristic histology, the pathogenesis of Barrett's has remained obscure. A recent paper from the laboratories of Wa Xian and Frank McKeon presents evidence for a novel cell of origin of Barrett's. Their work is based on studies of mice engineered to lack the squamous epithelial stem cell survival factor p63. These mice develop a metaplasia of the proximal stomach and esophagus that harbors substantial histological and molecular features of Barrett's. The metaplasia appears to form from embryonic progenitor cells that normally persists post-natally only at the squamo-columnar junction. Moreover, in their model, the metaplasia is initiated not by mutation but by reduced competition between these cells and squamous epithelial cells.

Molecular mechanisms of Barrett's esophagus

Barrett's esophagus (BE) is defined as the metaplastic conversion of esophageal squamous epithelium to intestinalized columnar epithelium. As a premalignant lesion of esophageal adenocarcinoma (EAC), BE develops as a result of chronic gastroesophageal reflux disease (GERD). Many studies have been conducted to understand the molecular mechanisms of this disease. This review summarizes recent results involving squamous and intestinal transcription factors, signaling pathways, stromal factors, microRNAs, and other factors in the development of BE. A conceptual framework is proposed to guide future studies. We expect elucidation of the molecular mechanisms of BE to help in the development of improved management of GERD, BE, and EAC.

p73 protein regulates DNA damage repair

Although the p53 tumor suppressor is relatively well characterized, much less is known about the functions of other members of the p53 family, p73 and p63. Here, we present evidence that in specific pathological conditions caused by exposure of normal cells to bile acids in acidic conditions, p73 protein plays the predominant role in the DNA damage response. These pathological conditions frequently occur during gastric reflux in the human esophagus and are associated with progression to esophageal adenocarcinoma. We found that despite strong DNA damage induced by bile acid exposure, only p73 (but not p53 and p63) is selectively activated in a c-Abl kinase-dependent manner. The activated p73 protein induces DNA damage repair. Using a human DNA repair PCR array, we identified multiple DNA repair genes affected by p73. Two glycosylases involved in base excision repair, SMUG1 and MUTYH, were characterized and found to be transcriptionally regulated by p73 in DNA damage conditions. Using a surgical procedure in mice, which recapitulates bile acid exposure, we found that p73 deficiency is associated with increased DNA damage. These findings were further investigated with organotypic and traditional cell cultures. Collectively our studies demonstrate that p73 plays an important role in the regulation of DNA damage repair.

Systematic review: the role of bile acids in the pathogenesis of gastro-oesophageal reflux disease and related neoplasia

BACKGROUND

Factors other than acid may play a role in gastro-oesophageal reflux disease (GERD) and its complications.

AIM

To assessed the role of bile acids in the pathogenesis of GERD, Barrett's oesophagus and Barrett's-related neoplasia.

METHODS

We conducted a systematic review of computerised bibliographic databases for original articles involving humans or human oesophageal tissue or cells that assessed exposure to or manipulation of bile acids. Outcomes assessed included GERD symptoms; gross oesophageal injury; Barrett's oesophagus and related neoplasia; and intermediate markers of inflammation, proliferation or neoplasia.

RESULTS

Eighty-three original articles were included. In in vivo studies, bile acids concentrations were higher in the oesophageal aspirates of patients with GERD than controls, and bile acids infusions triggered GERD symptoms, especially in high concentrations or in combination with acid. In ex vivo/in vitro studies, bile acids stimulated squamous oesophageal cells and Barrett's epithelial cells to produce inflammatory mediators (e.g., IL-8 and COX-2) and caused oxidative stress, DNA damage and apoptosis. They also induced squamous cells to change their gene expression pattern to resemble intestinal-type cells and caused Barrett's cells to increase expression of intestinal-type genes.

CONCLUSIONS

In aggregate, these studies suggest that bile acids may contribute to the pathogenesis of symptoms, oesophagitis and Barrett's metaplasia with related carcinogenesis in patients with GERD. However, all study results are not uniform and substantial differences in study parameters may explain at least some of this variation.

CHRNA5 as negative regulator of nicotine signaling in normal and cancer bronchial cells: effects on motility, migration and p63 expression

Genome-wide association studies have linked lung cancer risk with a region of chromosome 15q25.1 containing CHRNA3, CHRNA5 and CHRNB4 encoding α3, α5 and β4 subunits of nicotinic acetylcholine receptors (nAChR), respectively. One of the strongest associations was observed for a non-silent single-nucleotide polymorphism at codon 398 in CHRNA5. Here, we have used pharmacological (antagonists) or genetic (RNA interference) interventions to modulate the activity of CHRNA5 in non-transformed bronchial cells and in lung cancer cell lines. In both cell types, silencing CHRNA5 or inhibiting receptors containing nAChR α5 with α-conotoxin MII exerted a nicotine-like effect, with increased motility and invasiveness in vitro and increasing calcium influx. The effects on motility were enhanced by addition of nicotine but blocked by inhibiting CHRNA7, which encodes the homopentameric receptor α7 subunit. Silencing CHRNA5 also decreased the expression of cell adhesion molecules P120 and ZO-1 in lung cancer cells as well as the expression of DeltaNp63α in squamous cell carcinoma cell lines. These results demonstrate a role for CHRNA5 in modulating adhesion and motility in bronchial cells, as well as in regulating p63, a potential oncogene in squamous cell carcinoma.

A comparison of primary oesophageal squamous epithelial cells with HET-1A in organotypic culture

BACKGROUND INFORMATION

Carcinoma of the oesophagus is the sixth leading cause of cancer death in the western world and is associated with a 5-year survival of less than 15%. Recent evidence suggests that stromal-epithelial interactions are fundamental in carcinogenesis. The advent of co-culture techniques permits the investigation of cross-talk between the stroma and epithelium in a physiological setting. We have characterized a histologically representative oesophageal organotypic model and have used it to compare the most commonly used squamous oesophageal cell line, HET-1A, with primary oesophageal squamous cells for use in studies of the oesophageal epithelium in vitro.

RESULTS

When grown in an organotypic culture with normal fibroblasts, the oesophageal carcinoma cell lines OE21 (squamous) and OE19 (adenocarcinoma) morphologically resembled the tumour of origin with evidence of stromal invasion and mucus production, respectively. However, HET-1A cells, which were derived from normal squamous oesophageal cells, appeared dysplastic and failed to display evidence of squamous differentiation. By comparison with primary oesophageal epithelial cells, the HET-1A cells were highly proliferative and did not express the epithelial markers E-cadherin or CK5/6 (casein kinase 5/6), or the stratified epithelial marker ΔNp63, but did express the mesenchymal markers vimentin and N-cadherin.

CONCLUSION

Studies of epithelial carcinogenesis will benefit from culture systems which allow manipulation of the stromal and epithelial layers independently. We have developed an organotypic culture using primary oesophageal squamous cells and fibroblasts in which a stratified epithelium with a proliferative basal layer that stains strongly for ΔNp63 develops. This model will be suitable for the study of the molecular events in the development of Barrett's oesophagus. The most commonly used normal oesophageal squamous cell line, HET-1A, does not have the characteristics of normal oesophageal squamous cells and should not be used in models of the normal oesophageal epithelium. Until more representative cell lines are available, future studies in oesophageal cancer will be reliant on the availability and manipulation of primary tissue.

Intraepithelial p63-dependent expression of distinct components of cell adhesion complexes in normal esophageal mucosa and squamous cell carcinoma

TP63 gene is a member of TP53 tumor suppressor gene family that encodes several protein isoforms involved in the process of epithelial stratification and in epithelial-mesenchyme interactions. TP63 is amplified in a significant proportion of squamous cell carcinoma of the esophagus (ESCC), resulting in the hyper-expression of DeltaNp63 as the major p63 isoform. To better understand the contribution of this high expression to tumorigenesis, we have analyzed the impact of intraepithelial p63 expression on the expression of cell adhesion complexes in normal esophagus and in ESCC cell lines. Cells expressing p63 showed an adhesion pattern characterized by lack of tight junctions and presence of adherens junctions. Cell differentiation was accompanied by a decrease in p63 and by a shift to adhesion patterns involving tight junctions. Silencing of p63 mRNA in ESCC cell lines resulted in a similar shift, characterized by increased expression of component of tight junctions, decreased cell-to-cell communication and downregulation of cell proliferation. These results indicate that DeltaNp63 may contribute to esophageal squamous carcinogenesis by maintaining cell adhesion patterns compatible with cell proliferation.

Barrett's Esophagus and esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has risen dramatically over the past three decades in western countries. The importance of Barrett's esophagus (BE) derives from its potential to transform to adenocarcinoma. BE is characterized by endoscopically recognized displacement of the squamocolumnar junction proximal to the gastroesophageal junction, with replacement of squamous mucosa with columnar lined mucosa. Adenocarcinomas of the esophagus appear to arise from Barrett's mucosa through progressive degrees of dysplasia, but the pathogenesis and natural history of this process are still unclear. Much of our knowledge regarding BE and the risk of EAC is based on observational and cross-sectional analyses, and recommendations regarding management have traditionally represented "expert opinion." The past few years have seen an explosion in new information and the initiation of longitudinal studies to define the risk of adenocarcinoma in BE, the identification of predictive and prognostic markers of cancer risk, sensitive and cost-effective methods of surveillance, and methods of management of dysplasia and early neoplasia including disease prevention.

Epithelial metaplasia: adult stem cell reprogramming and (pre)neoplastic transformation mediated by inflammation?

Throughout adult life, new developmental commitment of adult stem cells causes metaplastic conversions to occur frequently in some organs. These reversible epithelial replacements are almost always observed in association with chronic inflammation and persistent irritation. Although metaplasia is not synonymous with dysplasia, clinical surveillance has demonstrated that these adaptive processes have an increased susceptibility to evolve into cancer. We propose that cytokines and other soluble factors released by both epithelial and inflammatory cells might alter the transcription-factor expression profile of stem cells and lead to the development of metaplasia. Furthermore, inflammatory mediators might also promote the malignant transformation of epithelial metaplasia by inducing genetic and epigenetic changes and by preventing the immune system from mounting an efficient anti-tumour immune response. A better understanding of the molecular mechanisms leading to metaplasia might help in the design of new therapies for neoplastic and degenerative diseases.

Deoxycholic acid induces the overexpression of intestinal mucin, MUC2, via NF-kB signaling pathway in human esophageal adenocarcinoma cells

Background

Mucin alterations are a common feature of esophageal neoplasia, and alterations in MUC2 mucin have been associated with tumor progression in the esophagus. Bile acids have been linked to esophageal adenocarcinoma and mucin secretion, but their effects on mucin gene expression in human esophageal adenocarcinoma cells is unknown.

Methods

Human esophageal adenocarcinoma cells were treated 18 hours with 50–300 μM deoxycholic acid, chenodeoxycholic acid, or taurocholic acid. MUC2 transcription was assayed using a MUC2 promoter reporter luciferase construct and MUC2 protein was assayed by Western blot analysis. Transcription Nuclear factor-κB activity was measured using a Nuclear factor-κB reporter construct and confirmed by Western blot analysis for Nuclear factor-κB p65.

Results

MUC2 transcription and MUC2 protein expression were increased four to five fold by bile acids in a time and dose-dependent manner with no effect on cell viability. Nuclear factor-κB activity was also increased. Treatment with the putative chemopreventive agent aspirin, which decreased Nuclear factor-κB activity, also decreased MUC2 transcription. Nuclear factor-κB p65 siRNA decreased MUC2 transcription, confirming the significance of Nuclear factor-κB in MUC2 induction by deoxycholic acid. Calphostin C, a specific inhibitor of protein kinase C (PKC), greatly decreased bile acid induced MUC2 transcription and Nuclear factor-κB activity, whereas inhibitors of MAP kinase had no effect.

Conclusion

Deoxycholic acid induced MUC2 overexpression in human esophageal adenocarcinoma cells by activation of Nuclear factor-κB transcription through a process involving PKC-dependent but not PKA, independent of activation of MAP kinase.

Recent advances in p53 research: an interdisciplinary perspective

The TP53 gene is one of the most studied genes in human cancer. In recent years, considerable interest was focused on mutant p53, the abnormal protein product of TP53 somatic or germline alleles with missense mutations that often accumulate in cancer cells. There is now compelling experimental evidence that many mutations can exert mutant-specific, gain-of-function effects by perturbing the regulation of expression of multiple genes. This notion is supported by the observation that targeted mutant p53 expression enhances the formation of specific cancers in the mouse even in the absence of wild-type p53 expression. In addition, clinical studies are producing a wealth of functional pathway data demonstrating correlations between specific TP53 mutations and gene expression patterns identified by transcriptome studies. These correlations imply that alteration of p53 function is critical in shaping gene expression patterns in cancer. Finally, progress is being made in the development of new therapeutic approaches targeting p53 alterations. Key advances regarding the structural, biochemical and functional properties of normal and mutant p53 proteins, their abnormal regulation and distribution in human cancers, and their associations with clinical and pathological cancer characteristics are reviewed. New opportunities for translational research for improving cancer detection, prognosis, prevention and therapy based upon the integration of this knowledge are described.

Multilayered epithelium in a rat model and human Barrett's esophagus: similar expression patterns of transcription factors and differentiation markers

Background

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.

Methods

Serial sectioning was performed on tissue samples from 32 EGDA rats and 13 patients with established BE. Tissue sections were immunohistochemically stained for a variety of transcription factors and differentiation markers of esophageal squamous epithelium and intestinal columnar epithelium.

Results

We detected MLE in 56.3% (18/32) of EGDA rats, and in all human samples. As expected, both rat and human squamous epithelium, but not intestinal metaplasia, expressed squamous transcription factors and differentiation markers (p63, Sox2, CK14 and CK4) in all cases. Both rat and human intestinal metaplasia, but not squamous epithelium, expressed intestinal transcription factors and differentiation markers (Cdx2, GATA4, HNF1α, villin and Muc2) in all cases. Rat MLE shared expression patterns of Sox2, CK4, Cdx2, GATA4, villin and Muc2 with human MLE. However, p63 and CK14 were expressed in a higher proportion of rat MLE compared to humans.

Conclusion

These data indicate that rat MLE shares similar properties to human MLE in its expression pattern of these markers, not withstanding small differences, and support the concept that MLE may be a transitional stage in the metaplastic conversion of squamous to columnar epithelium in BE.