Role of retinoid X receptor mRNA expression in Barrett's esophagus

Prebiotic proanthocyanidins inhibit bile reflux-induced esophageal adenocarcinoma through reshaping the gut microbiome and esophageal metabolome

The gut and local esophageal microbiome progressively shift from healthy commensal bacteria to inflammatory-linked pathogenic bacteria in patients with gastroesophageal reflux disease, Barrett's esophagus and esophageal adenocarcinoma (EAC). However, mechanisms by which microbial communities and metabolites contribute to reflux-driven EAC remain incompletely understood and challenging to target. Herein, we utilized a rat reflux-induced EAC model to investigate targeting the gut microbiome-esophageal metabolome axis with cranberry proanthocyanidins (C-PAC) to inhibit EAC progression. Sprague Dawley rats, with or without reflux-induction received water or C-PAC ad libitum (700 µg/rat/day) for 25 or 40 weeks. C-PAC exerted prebiotic activity abrogating reflux-induced dysbiosis, and mitigating bile acid metabolism and transport, culminating in significant inhibition of EAC through TLR/NF-κB/P53 signaling cascades. At the species level, C-PAC mitigated reflux-induced pathogenic bacteria (Clostridium perfringens, Escherichia coli, and Proteus mirabilis). C-PAC specifically reversed reflux-induced bacterial, inflammatory and immune-implicated proteins and genes including Ccl4, Cd14, Crp, Cxcl1, Il6, Il1β, Lbp, Lcn2, Myd88, Nfkb1, Tlr2 and Tlr4 aligning with changes in human EAC progression, as confirmed through public databases. C-PAC is a safe promising dietary constituent that may be utilized alone or potentially as an adjuvant to current therapies to prevent EAC progression through ameliorating reflux-induced dysbiosis, inflammation and cellular damage.

Demystifying the Functional Role of Nuclear Receptors in Esophageal Cancer

Esophageal cancer (EC), an aggressive and poorly understood disease, is one of the top causes of cancer-related fatalities. GLOBOCAN 2020 reports that there are 544,076 deaths and 604,100 new cases expected worldwide. Even though there are various advancements in treatment procedures, this cancer has been reported as one of the most difficult cancers to cure, and to increase patient survival; treatment targets still need to be established. Nuclear receptors (NRs) are a type of transcription factor, which has a key role in several biological processes such as reproduction, development, cellular differentiation, stress response, immunity, metabolism, lipids, and drugs, and are essential regulators of several diseases, including cancer. Numerous studies have demonstrated the importance of NRs in tumor immunology and proved the well-known roles of multiple NRs in modulating proliferation, differentiation, and apoptosis. There are surplus of studies conducted on NRs and their implications in EC, but only a few studies have demonstrated the diagnostic and prognostic potential of NRs. Therefore, there is still a paucity of the role of NRs and different ways to target them in EC cells to stop them from spreading malignancy. This review emphasizes the significance of NRs in EC by discussing their diverse agonists as well as antagonists and their response to tumor progression. Additionally, we emphasize NRs’ potential to serve as a novel therapeutic target and their capacity to treat and prevent EC.

20(S)-Protopanaxadiol inhibits epithelial-mesenchymal transition by promoting retinoid X receptor alpha in human colorectal carcinoma cells

Colorectal carcinoma (CRC) recurrence is often accompanied by metastasis. Most metastasis undergo through epithelial‐mesenchymal transition (EMT). Studies showed that retinol X receptor alpha (RXRα) and 20(S)‐Protopanaxadiol (PPD) have anti‐tumour effects. However, the anti‐metastasis effect of 20(S)‐PPD and the effect of RXRα on EMT‐induced metastasis are few studies on. Therefore, the role of RXRα and 20(S)‐PPD in CRC cell metastasis remains to be fully elucidated. RXRα with clinicopathological characteristics and EMT‐related expression in clinical samples were examined. Then, RXRα and EMT level in SW480 and SW620 cells, overexpressed and silenced RXRα in SW620 cells and SW480 cells, respectively, were evaluated. Finally, 20(S)‐PPD effect on SW620 and SW480 cells was evaluated. The results showed that a lower RXRα expression in cancer tissues, and a moderate negative correlation between RXRα and N stage, and tended to higher level of EMT. SW480 and SW620 cells had the highest and lowest RXRα expression among four CRC cell lines. SW480 had lower EMT level than SW620. Furthermore, 20(S)‐PPD increased RXRα and inhibited EMT level in SW620 cell. Finally, 20(S)‐PPD cannot restore SW480 cells EMT level to normal when RXRα silencing. These findings suggest that 20(S)‐PPD may inhibit EMT process in CRC cells by regulating RXRα expression.

Modulation of NRF2 signaling pathway by nuclear receptors: implications for cancer

Nuclear factor-erythroid 2 p45-related factor 2 (NRF2, also known as Nfe2l2) plays a critical role in regulating cellular defense against electrophilic and oxidative stress by activating the expression of an array of antioxidant response element-dependent genes. On one hand, NRF2 activators have been used in clinical trials for cancer prevention and the treatment of diseases associated with oxidative stress; on the other hand, constitutive activation of NRF2 in many types of tumors contributes to the survival and growth of cancer cells, as well as resistance to anticancer therapy. In this review, we provide an overview of the NRF2 signaling pathway and discuss its role in carcinogenesis. We also introduce the inhibition of NRF2 by nuclear receptors. Further, we address the biological significance of regulation of the NRF2 signaling pathway by nuclear receptors in health and disease. Finally, we discuss the possible impact of NRF2 inhibition by nuclear receptors on cancer therapy.

Embryological signaling pathways in Barrett's metaplasia development and malignant transformation; mechanisms and therapeutic opportunities

Barrett's metaplasia of the esophagus (BE) is the precursor lesion of esophageal adenocarcinoma (EAC), a deadly disease with a 5-year overall survival of less than 20%. The molecular mechanisms of BE development and its transformation to EAC are poorly understood and current surveillance and treatment strategies are of limited efficacy. Increasing evidence suggests that aberrant signaling through pathways active in the embryological development of the esophagus contributes to BE development and progression to EAC. We discuss the role that the Bone morphogenetic protein, Hedgehog, Wingless-Type MMTV Integration Site Family (WNT) and Retinoic acid signaling pathways play during embryological development of the esophagus and their contribution to BE development and malignant transformation. Modulation of these pathways provides new therapeutic opportunities. By integrating findings in developmental biology with those from translational research and clinical trials, this review provides a platform for future studies aimed at improving current management of BE and EAC.

RXRα inhibits the NRF2-ARE signaling pathway through a direct interaction with the Neh7 domain of NRF2

The transcription factor NRF2 (NFE2L2) is a pivotal activator of genes encoding cytoprotective and detoxifying enzymes that limit the action of cytotoxic therapies in cancer. NRF2 acts by binding antioxidant response elements (ARE) in its target genes, but there is relatively limited knowledge about how it is negatively controlled. Here, we report that retinoic X receptor alpha (RXRα) is a hitherto unrecognized repressor of NRF2. RNAi-mediated knockdown of RXRα increased basal ARE-driven gene expression and induction of ARE-driven genes by the NRF2 activator tert-butylhydroquinone (tBHQ). Conversely, overexpression of RXRα decreased ARE-driven gene expression. Biochemical investigations showed that RXRα interacts physically with NRF2 in cancer cells and in murine small intestine and liver tissues. Furthermore, RXRα bound to ARE sequences in the promoters of NRF2-regulated genes. RXRα loading onto AREs was concomitant with the presence of NRF2, supporting the hypothesis that a direct interaction between the two proteins on gene promoters accounts for the antagonism of ARE-driven gene expression. Mutation analyses revealed that interaction between the two transcription factors involves the DNA-binding domain of RXRα and a region comprising amino acids 209-316 in human NRF2 that had not been defined functionally, but that we now designate as the NRF2-ECH homology (Neh) 7 domain. In non-small cell lung cancer cells where NRF2 levels are elevated, RXRα expression downregulated NRF2 and sensitized cells to the cytotoxic effects of therapeutic drugs. In summary, our findings show that RXRα diminishes cytoprotection by NRF2 by binding directly to the newly defined Neh7 domain in NRF2.

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.

MicroRNAs, development of Barrett’s esophagus, and progression to esophageal adenocarcinoma

Barrett’s esophagus is a premalignant condition caused by gastroesophageal reflux. Once developed, it can progress through varying grades of dysplasia to esophageal adenocarcinoma. Whilst it is well accepted that Barrett’s esophagus is caused by gastroesophageal reflux, the molecular mechanisms of its pathogenesis and progression to cancer remain unclear. MicroRNAs (miRNAs) are short segments of RNA that have been shown to control the expression of many human genes. They have been implicated in most cellular processes, and the role of miRNAs in disease development is becoming increasingly evident. Understanding altered miRNA expression is likely to help unravel the molecular mechanisms that underpin the development of Barrett’s esophagus and its progression to cancer.

Quantitative analysis of survivin RNA expression in blood as a non-invasive predictor of response to neoadjuvant radiochemotherapy in esophageal cancer

BACKGROUND AND OBJECTIVES

Analysis of survivin RNA expression in peripheral blood as a non-invasive molecular predictor of response to neoadjuvant radiochemotherapy in patients with locally advanced cancer of the esophagus.

MATERIAL AND METHODS

Blood samples were drawn from 29 patients with esophageal cancer prior to neoadjuvant radiochemotherapy. After extraction of cellular tumor-RNA from blood samples, quantitative expression analysis of survivin was done by quantitative real-time RT-PCR.

RESULTS

Twenty of 29 (69%) of patients showed a minor histopathological response and 9 of 29 (31%) showed a major-response to neadjuvant radiochemotherapy. RNA expression in blood of patients was detectable for survivin in 27.6%, and in 100% for beta-actin. The mean survivin expression was not significantly different between minor- and major-responders. No significant associations were detected between survivin expression levels and patients clinical variables. A high expression level for survivin was significantly associated with a minor-response to neoadjuvant treatment (P = 0.042). Relative survivin expression levels above 0.15 were not associated with major histopathological response (sensitivity: 35%; specificity: 100%).

CONCLUSION

Minor-response to the applied therapy was significantly associated with a high survivin RNA expression level in patient's blood. Survivin appears to be a specific non-invasive predictor of response to neoadjuvant therapy in esophageal cancer.

Effect of Fas, FasL and Caspase-3 on apoptosis of retinoic acid-induced gastric carcinoma cells

AIM: To explore the effect on apoptosis of retinoic acid (RA)-induced BGC-803 gastric carcinoma cells and its relationship with the expression of Fas, FasL and Caspase-3.

METHODS: BGC-803 cells were treated with different concentrations of RA (0.001, 0.01, 0.1, 1, 10, 20 μmol/L) for 72 h. Then methyl-tetrazolium (MTT) assay was performed to determine the growth inhibition of BGC-803 cells; cell apoptosis rate was determined using flow cytometry; the feature of cell apoptosis was observed by Hoechst33342/PI staining; the mRNA expression of Fas, FasL and Caspase-3 were estimated using reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: After BGC-803 cells were treated with RA (0.1-20 μmol/L) for 72 h, RA inhibited the growth of cells significantly compared with that in the control group (32.61%, 44.42%, 48.14%, 51.15% vs 0.657%; all P < 0.01). Cells in G₂/M were significantly increased after the cells were treated with 20 μmol/L RA for 12 h, 24 h and 48 h. G₁ peak specific to apoptosis was observed and also observed were chromatic agglutination and rupture of caryon membrane. Expressions of Fas, FasL and Caspase-3 mRNA were up-regulated significantly by RA for 48 h compared with that in the control group.

CONCLUSION: Fas, FasL and Caspase-3 are involved in gastric carcinoma cell apoptosis induced by RA.

Columnar lined (Barrett's) esophagus: future perspectives

Columnar lined esophagus (CLE) or Barrett's esophagus is the precursor for esophageal adenocarcinoma. Future advances in understanding and management of this condition as well as improving the quality of care of CLE patients depends on answering essential questions. It is important to standardize the criteria for CLE definition. The rapid increase in incidence of CLE and adenocarcinoma raises serious concerns that the current management of gastroesophageal reflux disease (GERD) needs reassessment. The risk factors that determine who will and will not develop CLE are as yet undetermined. There is a need to develop a clinical risk stratification tool, which will help in determining who should be screened. The impact of elimination of GERD on the natural history of CLE is one important area for future research. The benefit of surveillance strategies remains unproven and the ideal endoscopic frequency, protocols and markers of cancer risk are unknown. Dysplasia may not provide the gold standard marker of cancer risk because of some inherited problems. A better technique than the current endoscopic pinch biopsy protocol is needed. To overcome the limitations of histological markers, many other markers of cancer risk needs to be developed and validated. The key question as to whether cancer risk is actually reduced by the new ablation modalities remains unanswered. The natural history of dysplasia and its management needs to be clarified. Although many questions have to be answered, it seems, however, that at least some answers exist, and these and proposals for answering some of these questions are underlined throughout this review.

IGFBP-3 and IGFBP-10 (CYR61) up-regulation during the development of Barrett's oesophagus and associated oesophageal adenocarcinoma: potential biomarkers of disease risk

Dys-regulation of the insulin-like growth factor (IGF) system increases the risk of a number of malignancies. The aim of this study was to investigate the role of members of the IGF binding protein (IGFBP) superfamily in the development of oesophageal adenocarcinoma (EAC) and their possible use as markers of disease risk. Expression of IGFBP-2, IGFBP-3, IGFBP-4, and IGFBP-10/CYR61 was assessed using Real-Time-polymerase chain reaction (PCR) and immunohistochemistry in oesophageal tissues from Barrett's oesophagus (BE) patients with and without associated EAC, and in control subjects. IGFBP-3, IGFBP-4, and IGFBP-10/CYR61 mRNA levels were up-regulated in Barrett's (n=17) and tumour tissue of EAC patients (n=18) compared with normal tissue of control subjects without BE or EAC (n=18) (p<0.001). Over-expression of IGFBP-3 and IGFBP-10/CYR61 proteins was observed in Barrett's, dysplastic and tumour tissue of EAC cases (n=47 for IGFBP-10; n=39 for IGFBP-3) compared with adjacent normal epithelium (p<0.050). Notably, IGFBP-3, IGFBP-4, and IGFBP-10/CYR61 expression in Barrett's tissue of EAC cases (n=17) was significantly (p<0.001) higher than in Barrett's tissue of BE patients with no sign of progression to cancer (n=15). Overall, the results suggest that members of the IGFBP superfamily are up-regulated during oesophageal carcinogenesis and merit further investigation as markers of EAC risk.

The molecular signature of normal squamous esophageal epithelium identifies the presence of a field effect and can discriminate between patients with Barrett's esophagus and patients with Barrett's-associated adenocarcinoma

BACKGROUND AND AIM

Genetic alterations in the normal tissues surrounding various cancers have been described, but a comprehensive analysis of this carcinogenic field effect in Barrett's-associated adenocarcinoma of the esophagus disease has not been reported. The aim of this study was to analyze the gene expression profile of a panel of highly selected genes in the normal squamous esophagus epihelium of patients with Barrett's esophagus, patients with Barrett's-associated adenocarcinoma, and a healthy control group to define the existence of a carcinogenic field effect, and to investigate the clinical importance of such a field effect in the management of Barrett's disease.

METHODS

Forty-nine histologic normal squamous esophageal epithelia collected from 19 patients with Barrett's esophagus, 20 patients with Barrett's-associated esophageal adenocarcinoma, and a healthy control group of 10 patients were studied. A quantitative real-time reverse transcription-PCR method (TaqMan) was used to measure the expression of a panel of genes with known associations with gastrointestinal carcinogenesis.

RESULTS

A widespread carcinogenic field effect was detected for more than 50% of the genes analyzed including Bax, BFT, CDX2, COX2, DAPK, DNMT1, GSTP1, RARalpha, RARgamma, RXRalpha, RXRbeta, SPARC, TSPAN, and VEGF. Based on the expression signature of the normal appearing squamous esophagus, a linear discriminant analysis was able to distinguish between the three groups of patients with an error rate of 0%.

CONCLUSION

This study provides the first comprehensive investigation of a carcinogenic field effect in Barrett's esophagus disease. Based on the gene expression signature of the normal esophagus, patients could be correctly characterized according to their pathologic classification by applying a linear discriminant analysis. Our results provide evidence that a molecular classification might have clinical importance for the diagnosis and treatment of patients with Barrett's esophagus disease.

Role of retinoic acid receptors in squamous-cell carcinoma in human esophagus

Background

Worldwide, cancer in the esophagus ranks among the 10 most common cancers. Alterations of retinoic acid receptors (e.g. RARα, β, γ, and RXRα, β, γ) expression is considered to play an important role in development of squamous-cell carcinoma (SCC), which is the most common esophageal cancer. Alcohol consumption and smoking, which can alter retinoic acid receptor levels, have been identified as key risk factors in the development of carcinoma in the aero-digestive tract. Therefore, the aim of the present study was to evaluate protein levels of retinoic acid receptors (i.e. RARα, β, γ, and RXRβ) in esophageal SCC and surrounding normal tissue of patients with untreated SCC and controls.

Methods

All study participants completed a questionnaire concerning smoking and alcohol drinking habits as well as anthropometrical parameters. Protein levels of RARα, β, γ, and RXRβ were determined by Western Blot in normal esophageal tissue and tissue obtained from SCC of 21 patients with newly diagnosed esophageal SCC and normal esophageal tissue of 10 controls.

Results

Protein levels of RARγ were significantly lower by ~68% in SCC compared to normal surrounding tissue in patients with SCC that smoked and/or consumed elevated amounts of alcohol. Furthermore, RARα protein levels were significantly lower (~- 45%) in SCC in comparison to normal esophageal mucosa in patients with elevated alcohol intake. When comparing protein levels of retinoic acid receptors between normal tissue of patients with SCC and controls, RARγ protein levels were found to be significantly higher (~2.7-fold) in normal esophageal tissue of SCC patients than in esophageal tissue obtained from controls. No differences were found for RARα, β, and RXRβ protein levels between normal esophageal tissue of patients and that of controls.

Conclusion

In conclusion, results of the present study suggest that alterations of retinoic acid receptors protein may contribute in the development of SCC in esophagus and that in some patients life style (e.g. smoking and alcohol consumption) may be a critical component in the alteration of retinoic acid receptor levels in esophagus.