Bile acids in combination with low pH induce oxidative stress and oxidative DNA damage: relevance to the pathogenesis of Barrett's oesophagus

Clinical course of gastroesophageal reflux disease and impact of treatment in symptomatic young patients

In symptomatic young patients with gastroesophageal reflux symptoms, early identification of progressive gastroesophageal reflux disease (GERD) is critical to prevent long-term complications associated with hiatal hernia, increased esophageal acid and nonacid exposure, release of proinflammatory cytokines, and development of intestinal metaplasia, endoscopically visible Barrett's esophagus, and dysplasia leading to esophageal adenocarcinoma. Progression of GERD may occur in asymptomatic patients and in those under continuous acid-suppressive medication. The long-term side effects of proton-pump inhibitors, chemopreventive agents, and radiofrequency ablation are contentious. In patients with early-stage disease, when the lower esophageal sphincter function is still preserved and before endoscopically visible Barrett's esophagus develops, novel laparoscopic procedures, such as magnetic and electric sphincter augmentation, may have a greater role than conventional surgical therapy. A multidisciplinary approach to GERD by a dedicated team of gastroenterologists and surgeons might impact the patients' lifestyle, the therapeutic choices, and the course of the disease. Biological markers are needed to precisely assess the risk of disease progression and to tailor surveillance, ablation, and management.

Acid/bile exposure triggers TRAIL-mediated apoptosis in esophageal cancer cells by suppressing the decoy receptors and c-FLIPR

Esophageal adenocarcinoma essentially develops from esophageal inflammation caused by chronic GERD. During GERD episodes, the lower esophageal epithelium is repeatedly exposed to stomach acid, which often contains duodenal bile salts that prompt malignant transformation. TRAIL is one of the cytokines produced in response to such insults and targets the transformed cells exclusively. In this study, we simulated GERD episodes in vitro by exposing the cancer cells to acid or acid/bile combination and found that the cancer cells lived through acid attacks by expression of the decoy receptors and c-FLIP_R but died of TRAIL-mediated apoptosis when bile salts were present. Further investigation revealed that acid/bile exposure downregulated the decoy receptors and thereby facilitated TRAIL signaling; meantime, it inhibited protein kinase C activity and thus expedited c-FLIP_R degradation, allowing apoptosis to take place.

Bacterial biofilm in colorectal cancer: What is the real mechanism of action?

Human colorectal cancer is the third most common cancer around the world. Colorectal cancer has various risk factors, but current works have bolded a significant activity for the microbiota of the human colon in the development of this disease. Bacterial biofilm has been mediated to non-malignant pathologies like inflammatory bowel disease but has not been fully documented in the setting of colorectal cancer. The investigation has currently found that bacterial biofilm is mediated to colon cancer in the human and linked to the location of human cancer, with almost all right-sided adenomas of colon cancers possessing bacterial biofilm, whilst left-sided cancer is rarely biofilm positive. The profound comprehension of the changes in colorectal cancer can provide interesting novel concepts for anticancer treatments. In this review, we will summarize and examine the new knowledge about the links between colorectal cancer and bacterial biofilm.

5-Fluorouracil treatment induces characteristic T>G mutations in human cancer

5-Fluorouracil (5-FU) is a chemotherapeutic drug commonly used for the treatment of solid cancers. It is proposed that 5-FU interferes with nucleotide synthesis and incorporates into DNA, which may have a mutational impact on both surviving tumor and healthy cells. Here, we treat intestinal organoids with 5-FU and find a highly characteristic mutational pattern that is dominated by T>G substitutions in a CTT context. Tumor whole genome sequencing data confirms that this signature is also identified in vivo in colorectal and breast cancer patients who have received 5-FU treatment. Taken together, our results demonstrate that 5-FU is mutagenic and may drive tumor evolution and increase the risk of secondary malignancies. Furthermore, the identified signature shows a strong resemblance to COSMIC signature 17, the hallmark signature of treatment-naive esophageal and gastric tumors, which indicates that distinct endogenous and exogenous triggers can converge onto highly similar mutational signatures.

Differential Expression Profiles of Oxidative Stress Levels, 8-oxo-dG and 4-HNE, in Barrett's Esophagus Compared to Esophageal Adenocarcinoma

Barrett’s esophagus (BE), a chronic inflammatory condition, is the leading risk factor for esophageal adenocarcinoma (EAC). In inflammation to cancer pathways, oxidative stress profiles have been linked to cancer progression. However, the relevance of oxidative stress profiles along the BE-disease sequence remains to be elucidated. In this study, markers of oxidative stress; DNA adducts (8-oxo-dG) and lipoperoxidation (4-HNE), and markers of proliferation (Ki67) were measured in patient biopsies representing the BE-disease sequence. Differences in expression of these markers in Barrett’s patients with cancer-progression and non-progression were examined. Proliferation was reduced in Barrett’s specialized intestinal metaplasia (SIM) compared with EAC (p < 0.035). Correcting for cell proliferation levels, a confounding factor, linked to oxidative stress profiles, SIM demonstrated increased levels of 8-oxo-dG and 4-HNE (p < 0.05) compared with EAC. Longitudinal analysis of Barrett’s patients demonstrated decreased levels of 8-oxo-dG in SIM cancer progression (p < 0.05). BE is an environment of increased oxidative stress and inflammation. Patients with progressive disease demonstrated reduced oxidative stress levels in 8-oxo-dG. Perhaps these alterations facilitate Barrett’s progression, whereas in non-progressive disease, cells follow the rules of increased oxidative stress ultimately triggers cell apoptosis, thereby preventing propagation and survival.

Activin A-mediated epithelial de-differentiation contributes to injury repair in an in vitro gastrointestinal reflux model

Reflux esophagitis is a result of esophageal exposure to acid and bile during episodes of gastroesophageal reflux. Aside from chemical injury to the esophageal epithelium, it has been shown that acid and bile induce cytokine-mediated injury by stimulating the release of pro-inflammatory cytokines. During the repair and healing process following reflux injury, the squamous esophageal cells are replaced with a columnar epithelium causing Barrett's metaplasia, which predisposes patients to esophageal adenocarcinoma. We identified a novel player in gastroesophageal reflux injury, the TGFβ family member Activin A (ActA), which is a known regulator of inflammation and tissue repair. In this study, we show that in response to bile salt and acidified media (pH 4) exposure, emulating the milieu to which the distal esophagus is exposed during gastroesophageal reflux, long-term treated, tolerant esophageal keratinocytes exhibit increased ActA secretion and a pro-inflammatory cytokine signature. Furthermore, we noted increased motility and expression of the stem cell markers SOX9, LGR5 and DCLK1 supporting the notion that repair mechanisms were activated in the bile salt/acid-tolerant keratinocytes. Additionally, these experiments demonstrated that de-differentiation as characterized by the induction of YAP1, FOXO3 and KRT17 was altered by ActA/TGFβ signaling. Collectively, our results suggest a pivotal role for ActA in the inflammatory GERD environment by modulating esophageal tissue repair and de-differentiation.

NRF2 antioxidant response protects against acidic bile salts-induced oxidative stress and DNA damage in esophageal cells

Gastroesophageal reflux disease (GERD) is the main risk factor for Barrett's tumorigenesis. In this study, we investigated the role of NRF2 in response to exposure to acidic bile salts (ABS), in conditions that mimic GERD, using Barrett's esophagus cell models. We detected an increase in NRF2 protein levels, following exposure to ABS. We found oxidization of cysteines (cysteines with oxidized thiol groups) in KEAP1 protein with a weaker interaction between NRF2 and KEAP1, following ABS exposure. Treatment with bile salts increased nuclear NRF2 levels, enhancing its transcription activity, as measured by an ARE (antioxidant response element) luciferase reporter assay. The mRNA expression levels of NRF2 target genes, HO-1 and GR, were increased in response to ABS exposure. Using genetic overexpression and knockdown of NRF2, we found that NRF2 has a critical role in suppressing ABS-induced ROS levels, oxidative DNA damage, DNA double strand breaks, and apoptosis. Collectively, our results suggest that transient induction of NRF2 in response to ABS plays a pivotal role in protecting esophageal cells by maintaining the levels of oxidative stress and DNA damage below lethal levels under GERD conditions.

Evaluating the structural complexity of isomeric bile acids with ion mobility spectrometry

Bile acids (BAs) play an integral role in digestion through the absorption of nutrients, emulsification of fats and fat-soluble vitamins, and maintenance of cholesterol levels. Metabolic disruption, diabetes, colorectal cancer, and numerous other diseases have been linked with BA disruption, making improved BA analyses essential. To date, most BA measurements are performed using liquid chromatography separations in conjunction with mass spectrometry measurements (LC-MS). However, 10-40 min LC gradients are often used for BA analyses and these may not even be sufficient for distinguishing all the important isomers present in the human body. Ion mobility spectrometry (IMS) is a promising tool for BA evaluations due to its ability to quickly separate isomeric molecules with subtle structural differences. In this study, we utilized drift tube IMS (DTIMS) coupled with MS to characterize 56 different unlabeled BA standards and 16 deuterated versions. In the DTIMS-MS analyses of 12 isomer groups, BAs with smaller m/z values were easily separated in either their deprotonated or sodiated forms (or both). However, as the BAs grew in m/z value, they became more difficult to separate with two isomer groups being inseparable. Metal ions such as copper and zinc were then added to the overlapping BAs, and due to different binding sites, the resulting complexes were separable. Thus, the rapid structural measurements possible with DTIMS-MS show great potential for BAs measurements with and without prior LC separations.

Genome-wide analysis of genomic alterations induced by oxidative DNA damage in yeast

Oxidative DNA damage is a threat to genome stability. Using a genetic system in yeast that allows detection of mitotic recombination, we found that the frequency of crossovers is greatly elevated when cells are treated with hydrogen peroxide (H2O2). Using a combination of microarray analysis and genomic sequencing, we mapped the breakpoints of mitotic recombination events and other chromosome rearrangements at a resolution of about 1 kb. Gene conversions and crossovers were the two most common types of events, but we also observed deletions, duplications, and chromosome aneuploidy. In addition, H2O2-treated cells had elevated rates of point mutations (particularly A to T/T to A and C to G/G to C transversions) and small insertions/deletions (in/dels). In cells that underwent multiple rounds of H2O2 treatments, we identified a genetic alteration that resulted in improved H2O2 tolerance by amplification of the CTT1 gene that encodes cytosolic catalase T. Lastly, we showed that cells grown in the absence of oxygen have reduced levels of recombination. This study provided multiple novel insights into how oxidative stress affects genomic instability and phenotypic evolution in aerobic cells.

Matrix association region/scaffold attachment region: the crucial player in defining the positions of chromosome breaks mediated by bile acid-induced apoptosis in nasopharyngeal epithelial cells

Background

It has been found that chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC). CRS can be caused by gastro-oesophageal reflux (GOR) that may reach nasopharynx. The major component of refluxate, bile acid (BA) has been found to be carcinogenic and genotoxic. BA-induced apoptosis has been associated with various cancers. We have previously demonstrated that BA induced apoptosis and gene cleavages in nasopharyngeal epithelial cells. Chromosomal cleavage occurs at the early stage of both apoptosis and chromosome rearrangement. It was suggested that chromosome breaks tend to cluster in the region containing matrix association region/scaffold attachment region (MAR/SAR). This study hypothesised that BA may cause chromosome breaks at MAR/SAR leading to chromosome aberrations in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is a deletion hotspot in NPC.

Methods

Potential MAR/SAR sites were predicted in the AF9 gene by using MAR/SAR prediction tools. Normal nasopharyngeal epithelial cells (NP69) and NPC cells (TWO4) were treated with BA at neutral and acidic pH. Inverse-PCR (IPCR) was used to identify chromosome breaks in SAR region (contains MAR/SAR) and non-SAR region (does not contain MAR/SAR). To map the chromosomal breakpoints within the AF9 SAR and non-SAR regions, DNA sequencing was performed.

Results

In the AF9 SAR region, the gene cleavage frequencies of BA-treated NP69 and TWO4 cells were significantly higher than those of untreated control. As for the AF9 non-SAR region, no significant difference in cleavage frequency was detected between untreated and BA-treated cells. A few breakpoints detected in the SAR region were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukaemia (MLL) gene in an acute lymphoblastic leukaemia (ALL) patient.

Conclusions

Our findings suggest that MAR/SAR may be involved in defining the positions of chromosomal breakages induced by BA. Our report here, for the first time, unravelled the relation of these BA-induced chromosomal breakages to the AF9 chromatin structure.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0465-4) contains supplementary material, which is available to authorized users.

Activation of EGFR-DNA-PKcs pathway by IGFBP2 protects esophageal adenocarcinoma cells from acidic bile salts-induced DNA damage

Background

The incidence of esophageal adenocarcinoma (EAC) is rising rapidly in the US and Western countries. The development of Barrett’s esophagus (BE) and its progression to EAC have been linked to chronic gastroesophageal reflux disease (GERD). Exposure of BE and EAC cells to acidic bile salts (ABS) in GERD conditions induces high levels of oxidative stress and DNA damage. In this study, we investigated the role of insulin-like growth factor binding protein 2 (IGFBP2) in regulating ABS-induced DNA double-strand breaks.

Methods

Real-time RT-PCR, western blot, immunohistochemistry, immunofluorescence, co-immunoprecipitation, flow cytometry, and cycloheximide (CHX) chase assays were used in this study. To mimic GERD conditions, a cocktail of acidic bile salts (pH 4) was used in 2D and 3D organotypic culture models. Overexpression and knockdown of IGFBP2 in EAC cells were established to examine the functional and mechanistic roles of IGFBP2 in ABS-induced DNA damage.

Results

Our results demonstrated high levels of IGFBP2 mRNA and protein in EAC cell lines as compared to precancerous Barrett’s cell lines, and IGFBP2 is frequently overexpressed in EACs (31/57). Treatment of EAC cells with ABS, to mimic GERD conditions, induced high levels of IGFBP2 expression. Knocking down endogenous IGFBP2 in FLO1 cells (with constitutive high levels of IGFBP2) led to a significant increase in DNA double-strand breaks and apoptosis, following transient exposure to ABS. On the other hand, overexpression of exogenous IGFBP2 in OE33 cells (with low endogenous levels of IGFBP2) had a protective effect against ABS-induced double-strand breaks and apoptosis. We found that IGFBP2 is required for ABS-induced nuclear accumulation and phosphorylation of EGFR and DNA-PKcs, which are necessary for DNA damage repair activity. Using co-immunoprecipitation assay, we detected co-localization of IGFBP2 with EGFR and DNA-PKcs, following acidic bile salts treatment. We further demonstrated, using cycloheximide chase assay, that IGFBP2 promotes EGFR protein stability in response to ABS exposure.

Conclusions

IGFBP2 protects EAC cells against ABS-induced DNA damage and apoptosis through stabilization and activation of EGFR - DNA-PKcs signaling axis.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-1021-y) contains supplementary material, which is available to authorized users.

Genomic landscape of oxidative DNA damage and repair reveals regioselective protection from mutagenesis

BACKGROUND

DNA is subject to constant chemical modification and damage, which eventually results in variable mutation rates throughout the genome. Although detailed molecular mechanisms of DNA damage and repair are well understood, damage impact and execution of repair across a genome remain poorly defined.

RESULTS

To bridge the gap between our understanding of DNA repair and mutation distributions, we developed a novel method, AP-seq, capable of mapping apurinic sites and 8-oxo-7,8-dihydroguanine bases at approximately 250-bp resolution on a genome-wide scale. We directly demonstrate that the accumulation rate of apurinic sites varies widely across the genome, with hot spots acquiring many times more damage than cold spots. Unlike single nucleotide variants (SNVs) in cancers, damage burden correlates with marks for open chromatin notably H3K9ac and H3K4me2. Apurinic sites and oxidative damage are also highly enriched in transposable elements and other repetitive sequences. In contrast, we observe a reduction at chromatin loop anchors with increased damage load towards inactive compartments. Less damage is found at promoters, exons, and termination sites, but not introns, in a seemingly transcription-independent but GC content-dependent manner. Leveraging cancer genomic data, we also find locally reduced SNV rates in promoters, coding sequence, and other functional elements.

CONCLUSIONS

Our study reveals that oxidative DNA damage accumulation and repair differ strongly across the genome, but culminate in a previously unappreciated mechanism that safeguards the regulatory and coding regions of genes from mutations.

High-Efficiency, Matrix Interference-Free, General Applicable Probes for Bile Acids Extraction and Detection

Although bile acids (BAs) have been suggested as important biomarkers for endocrine diseases, the identification and quantification of different BAs are still challenges due to their enormous species and wide range concentrations. Herein, a copolymer probe based on β-cyclodextrin (β-CD) is fabricated through a simple in-mold photopolymerization for the selective extraction of BAs. Through the unique stereochemical affinity between BAs and the cavity of β-CD, the custom probe shows superior enriching capacities to series BAs. Moreover, the outstanding extraction ability is proved to be consistent in various interfering conditions, including pH changing and the addition of complex matrix. Further comparison shows that the stereostructure of the nucleus of BAs plays a vital role during the formation of the β-CD/BA complex, indicating the potential for efficient extraction of other BAs, including their structural analogues or some unknown ones. The developed probe is used for solid phase microextraction, and the limits of detection are lower than 0.075 ng mL-1 by coupling to high performance liquid chromatography-tandem mass analysis. The results in this study highlight the potential for effective improvement of immediate detection and profiling of BAs in real samples, which will make a tremendous impact in the analytical field or clinical diagnosis.

A phase I pilot study evaluating the beneficial effects of black raspberries in patients with Barrett's esophagus

Black raspberries inhibit a broad range of cancers in preclinical models which has led to clinical evaluations targeting premalignant lesions of the colon, oral cavity and esophagus. A phase I pilot study was conducted in twenty Barrett's esophagus (BE) patients to investigate the effect of lyophilized black raspberries (LBR) on urinary metabolites and markers of lipid peroxidation, DNA damage and tissue markers of cellular proliferation, detoxification, and inflammation. Surveys, biopsies, blood and urine samples were collected before and after 6 months of LBR treatment (32 or 45 g). LBR significantly reduced urinary excretion of 8-epi-prostaglandin F2α, a marker of lipid peroxidation linked to oxidative stress and free radical damage. Urinary levels of the ellagitannin metabolites, urolithin A-glucuronide, urolithin A-sulfate and dimethylellagic acid glucuronide were significantly increased following 12 and 26 weeks of LBR consumption and may prove useful as indicators of compliance in future clinical studies. Immunohistochemical staining of BE biopsies following LBR treatment showed significant increases in mean GST-pi levels, with 55.6% of subjects responding favorably. In summary, LBR significantly decreased urinary lipid peroxidation levels and significantly increased GST-pi, a marker of detoxification, in BE epithelium. Still, LBR may need to be formulated differently, administered at higher concentrations or multiple times a day to increase efficacy.

Mutational signature distribution varies with DNA replication timing and strand asymmetry

BACKGROUND

DNA replication plays an important role in mutagenesis, yet little is known about how it interacts with other mutagenic processes. Here, we use somatic mutation signatures-each representing a mutagenic process-derived from 3056 patients spanning 19 cancer types to quantify the strand asymmetry of mutational signatures around replication origins and between early and late replicating regions.

RESULTS

We observe that most of the detected mutational signatures are significantly correlated with the timing or direction of DNA replication. The properties of these associations are distinct for different signatures and shed new light on several mutagenic processes. For example, our results suggest that oxidative damage to the nucleotide pool substantially contributes to the mutational landscape of esophageal adenocarcinoma.

CONCLUSIONS

Together, our results indicate an interaction between DNA replication, the associated damage repair, and most mutagenic processes.

Exposure of Barrett's and esophageal adenocarcinoma cells to bile acids activates EGFR-STAT3 signaling axis via induction of APE1

The development of Barret’s esophagus (BE) and its progression to esophageal adenocarcinoma (EAC) is highly linked to exposure to acidic bile salts due to chronic gastroesophageal reflux disease (GERD). In this study, we investigated the role of Apurinic/apyrimidinic endonuclease 1 /redox effector factor-1 (APE-1/REF-1) in STAT3 activation in response to EAC. Our results indicate that APE1 is constitutively overexpressed in EAC whereas its expression is transiently induced in response to acidic bile salts in non-neoplastic BE. Using overexpression or shRNA knockdown of APE1, we found that APE1 is required for phosphorylation, nuclear localization, and transcription activation of STAT3. By using an APE1 redox-specific mutant (C65A) and APE1 redox inhibitor (E3330), we demonstrate that APE1 activates STAT3 in a redox-dependent manner. By using pharmacologic inhibitors and genetic knockdown systems, we found that EGFR is a required link between APE1 and STAT3. EGFR phosphorylation (Y1068) was directly associated with APE1 levels and redox function. Co-immunoprecipitation and proximity ligation assays indicated that APE-1 coexists and interacts with the EGFR-STAT3 protein complex. Consistent with these findings, we demonstrated a significant induction in mRNA expression levels of STAT3 target genes (IL-6, IL-17A, BCL-xL, Survivin and c-Myc) in BE and EAC cells, following acidic bile salts treatment. ChIP assays indicated that acidic bile salts treatment enhances binding of STAT3 to the promoter of its target genes, Survivin and BCL-xL. Inhibition of APE1/REF-1 redox activity using E3330 abrogated STAT3 DNA binding and transcriptional activity. The induction of APE-1 - STAT3 axis in acidic bile salts conditions provided a survival advantage and promoted cellular proliferation. In summary, our study provides multiple pieces of evidence supporting a critical role for APE1 induction in activating the EGFR-STAT3 signaling axis in response to acidic bile salts, the main risk factors for Barrett’s carcinogenesis.

Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells: implications in chromosome rearrangement

BACKGROUND

Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, caspase-activated deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC.

METHODS

We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced.

RESULTS

BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient.

CONCLUSIONS

These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells.

In Vivo Short-Term Topical Application of BAY 11-7082 Prevents the Acidic Bile-Induced mRNA and miRNA Oncogenic Phenotypes in Exposed Murine Hypopharyngeal Mucosa

PURPOSE: Bile-containing gastroesophageal reflux may promote cancer at extraesophageal sites. Acidic bile can accelerate NF-κB activation and molecular events, linked to premalignant changes in murine hypopharyngeal mucosa (HM). We hypothesize that short-term in vivo topical application of NF-κB inhibitor BAY 11-7082 can prevent acidic bile–induced early preneoplastic molecular events, suggesting its potential role in disease prevention. EXPERIMENTAL DESIGN: We topically exposed HM (C57Bl/6j wild-type) to a mixture of bile acids at pH 3.0 with and without BAY 11-7082 3 times/day for 7 days. We used immunofluorescence, Western blotting, immunohistochemistry, quantitative polymerase chain reaction, and polymerase chain reaction microarrays to identify NF-κB activation and its associated oncogenic mRNA and miRNA phenotypes, in murine hypopharyngeal cells in vitro and in murine HM in vivo. RESULTS: Short-term exposure of HM to acidic bile is a potent stimulus accelerating the expression of NF-κB signaling (70 out of 84 genes) and oncogenic molecules. Topical application of BAY 11-7082 sufficiently blocks the effect of acidic bile. BAY 11-7082 eliminates NF-κB activation in regenerating basal cells of acidic bile–treated HM and prevents overexpression of molecules central to head and neck cancer, including bcl-2, STAT3, EGFR, TNF-α, and WNT5A. NF-κB inhibitor reverses the upregulated “oncomirs” miR-155 and miR-192 and the downregulated “tumor suppressors” miR-451a and miR-375 phenotypes in HM affected by acidic bile. CONCLUSION: There is novel evidence that acidic bile–induced NF-κB–related oncogenic mRNA and miRNA phenotypes are generated after short-term 7-day mucosal exposure and that topical mucosal application of BAY 11-7082 can prevent the acidic bile–induced molecular alterations associated with unregulated cell growth and proliferation of hypopharyngeal cells.

NSAID use and somatic exomic mutations in Barrett's esophagus

Background

Use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to protect against tetraploidy, aneuploidy, and chromosomal alterations in the metaplastic condition Barrett’s esophagus (BE) and to lower the incidence and mortality of esophageal adenocarcinoma (EA). The esophagus is exposed to both intrinsic and extrinsic mutagens resulting from gastric reflux, chronic inflammation, and exposure to environmental carcinogens such as those found in cigarettes. Here we test the hypothesis that NSAID use inhibits accumulation of point mutations/indels during somatic genomic evolution in BE.

Methods

Whole exome sequences were generated from 82 purified epithelial biopsies and paired blood samples from a cross-sectional study of 41 NSAID users and 41 non-users matched by sex, age, smoking, and continuous time using or not using NSAIDs.

Results

NSAID use reduced overall frequency of point mutations across the spectrum of mutation types, lowered the frequency of mutations even when adjusted for both TP53 mutation and smoking status, and decreased the prevalence of clones with high variant allele frequency. Never smokers who consistently used NSAIDs had fewer point mutations in signature 17, which is commonly found in EA. NSAID users had, on average, a 50% reduction in functional gene mutations in nine cancer-associated pathways and also had less diversity in pathway mutational burden compared to non-users.

Conclusions

These results indicate NSAID use functions to limit overall mutations on which selection can act and supports a model in which specific mutant cell populations survive or expand better in the absence of NSAIDs.

Electronic supplementary material

The online version of this article (10.1186/s13073-018-0520-y) contains supplementary material, which is available to authorized users.

Inhibition of NF-κB prevents the acidic bile-induced oncogenic mRNA phenotype, in human hypopharyngeal cells

Bile-containing gastro-duodenal reflux has been clinically considered an independent risk factor in hypopharyngeal carcinogenesis. We recently showed that the chronic effect of acidic bile, at pH 4.0, selectively induces NF-κB activation and accelerates the transcriptional levels of genes, linked to head and neck cancer, in normal hypopharyngeal epithelial cells. Here, we hypothesize that NF-κB inhibition is capable of preventing the acidic bile-induced and cancer-related mRNA phenotype, in treated normal human hypopharyngeal cells. In this setting we used BAY 11-7082, a specific and well documented pharmacologic inhibitor of NF-κB, and we observed that BAY 11-7082 effectively inhibits the acidic bile-induced gene expression profiling of the NF-κB signaling pathway (down-regulation of 72 out of 84 analyzed genes). NF-κB inhibition significantly prevents the acidic bile-induced transcriptional activation of NF-κB transcriptional factors, RELA (p65) and c-REL, as well as genes related to and commonly found in established HNSCC cell lines. These include anti-apoptotic bcl-2, oncogenic STAT3, EGFR, ∆Np63, TNF-α and WNT5A, as well as cytokines IL-1β and IL-6. Our findings are consistent with our hypothesis demonstrating that NF-κB inhibition effectively prevents the acidic bile-induced cancer-related mRNA phenotype in normal human hypopharyngeal epithelial cells supporting an understanding that NF-κB may be a critical link between acidic bile and early preneoplastic events in this setting.

APE1-mediated DNA damage repair provides survival advantage for esophageal adenocarcinoma cells in response to acidic bile salts

Chronic Gastroesophageal Reflux Disease (GERD) is the main risk factor for the development of Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (EAC). Accordingly, EAC cells are subjected to high levels of oxidative stress and subsequent DNA damage. In this study, we investigated the expression and role of Apurinic/apyrimidinic endonuclease 1 (APE1) protein in promoting cancer cell survival by counteracting the lethal effects of acidic bile salts (ABS)-induced DNA damage. Immunohistochemistry analysis of human tissue samples demonstrated overexpression of APE1 in more than half of EACs (70 of 130), as compared to normal esophagus and non-dysplastic BE samples (P < 0.01). To mimic in vivo conditions, we treated in vitro cell models with a cocktail of ABS. The knockdown of endogenous APE1 in EAC FLO-1 cells significantly increased oxidative DNA damage (P < 0.01) and DNA single- and double-strand breaks (P < 0.01), whereas overexpression of APE1 in EAC OE33 cells reversed these effects. Annexin V/PI staining indicated that the APE1 expression in OE33 cells protects against ABS-induced apoptosis. In contrast, knockdown of endogenous APE1 in FLO-1 cells increased apoptosis under the same conditions. Mechanistic investigations indicated that the pro-survival function of APE1 was associated with the regulation of stress response c-Jun N-terminal protein kinase (JNK) and p38 kinases. Pharmacological inhibition of APE1 base excision repair (BER) function decreased cell survival and enhanced activation of JNK and p38 kinases by ABS. Our findings suggest that constitutive overexpression of APE1 in EAC may be an adaptive pro-survival mechanism that protects against the genotoxic lethal effects of bile reflux episodes.

Influence of Bile Acids on Colorectal Cancer Risk: Potential Mechanisms Mediated by Diet - Gut Microbiota Interactions

Purpose of review

To review the evidence for the tumorigenic effects of food-stimulated bile acids on the colon and interaction with the gut microbiota.

Recent Findings

High-fat diets promote the hepatic synthesis of bile acids and increase their delivery to the colonic lumen. Here, they stimulate the growth and activity of 7α-dehydroxylating bacteria, which convert primary into secondary bile acids that show tumorigenic activity, especially deoxycholic acid (DCA). Fecal levels of secondary bile acids correlate with mucosal and metabolic markers of colorectal cancer (CRC) risk in high and low risk adult individuals and can be modified within a few weeks by dietary change. While gut bacteria regulate the bile acid pool via complex microbial biotransformation, bile acids alter the gut microbiota composition due to their antimicrobial properties. This mutual reaction induces altered bile acid pools and dysbiotic compositions of the gut microbiota that may show tumor-promoting activity of bile acids beyond their conversion to DCA.

Summary

Bile acids act as tumor promoters in the colon. Diet and the gut microbiota are most likely the key drivers that mediate and confer bile acid-associated tumorigenic activity. Bacterial conversion of bile acids in the colon has a significant impact on their tumorigenic activity, substantiating the hypothesis that diet affects CRC risk through its effects on colonic microbial metabolism.

Activation of NADPH oxidases leads to DNA damage in esophageal cells

Gastroesophageal reflux disease (GERD) is the strongest known risk factor for esophageal adenocarcinoma. In the center of tumorigenic events caused by GERD is repeated damage of esophageal tissues by the refluxate. In this study, we focused on a genotoxic aspect of exposure of esophageal cells to acidic bile reflux (BA/A). Analyzing cells generated from patients with Barrett's esophagus and human esophageal specimens, we found that BA/A cause significant DNA damage that is mediated by reactive-oxygen species. ROS originate from mitochondria and NADPH oxidases. We specifically identified NOX1 and NOX2 enzymes to be responsible for ROS generation. Inhibition of NOX2 and NOX1 with siRNA or chemical inhibitors significantly suppresses ROS production and DNA damage induced by BA/A. Mechanistically, our data showed that exposure of esophageal cells to acidic bile salts induces phosphorylation of the p47^phox subunit of NOX2 and its translocation to the cellular membrane. This process is mediated by protein kinase C, which is activated by BA/A. Taken together, our studies suggest that inhibition of ROS induced by reflux can be a useful strategy for preventing DNA damage and decreasing the risk of tumorigenic transformation caused by GERD.

Total Oxidant/Antioxidant Status in Sera of Patients with Esophageal Cancer

BACKGROUND Oxidative stress parameters such as total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) have been studied in breast, thyroid, and simple esophageal cancers (EC). We evaluated these parameters in patients with EC and analyzed their correlations with treatment outcomes. MATERIAL AND METHODS Serum TOS, TAS, and OSI in 92 patients with EC at different clinical stages and in 64 healthy people (controls) were measured. RESULTS Serum TOS, TAS, and OSI were significantly different between patients with EC and healthy controls (all p<0.001); however, there were no significant differences across different clinical stages (all p>0.05). These factors are not correlated with smoking or drinking history (all p>0.05). Patients with EC with higher TOS and OSI and lower TAS had better responses to chemotherapy and/or radiotherapy, but there was no significant correlation with different responses (all p>0.05). In a receiver operating characteristic curve analysis comparing patients with EC with healthy controls, the Youden indices were 0.391, 0.886, and 1, respectively. CONCLUSIONS Serum TOS, TAS, and OSI were significantly different between patients with EC and healthy controls. In patients with EC, these factors were not correlated with smoking or drinking history or with clinical stage. Patients with EC with higher TOS and OSI and lower TAS had a trend towards better outcomes but it did not reach significance. Serum TOS and OSI are potential diagnostic biomarkers that can be used to identify cases of EC.

The Benefits of Combination Therapy with Esomeprazole and Rebamipide in Symptom Improvement in Reflux Esophagitis: An International Multicenter Study

Background/Aims

To investigate the effects of esomeprazole and rebamipide combination therapy on symptomatic improvement in patients with reflux esophagitis.

Methods

A total of 501 patients with reflux esophagitis were randomized into one of the following two treatment regimens: 40 mg esomeprazole plus 300 mg rebamipide daily (combination therapy group) or 40 mg esomeprazole daily (monotherapy group). We used a symptom questionnaire that evaluated heartburn, acid regurgitation, and four upper gastrointestinal symptoms. The primary efficacy end point was the mean decrease in the total symptom score.

Results

The mean decreases in the total symptom score at 4 weeks were estimated to be -18.1±13.8 in the combination therapy group and -15.1±11.9 in the monotherapy group (p=0.011). Changes in reflux symptoms from baseline after 4 weeks of treatment were -8.4±6.6 in the combination therapy group and -6.8±5.9 in the monotherapy group (p=0.009).

Conclusions

Over a 4-week treatment course, esomeprazole and rebamipide combination therapy was more effective in decreasing the symptoms of reflux esophagitis than esomeprazole monotherapy.

Clustered Mutation Signatures Reveal that Error-Prone DNA Repair Targets Mutations to Active Genes

Many processes can cause the same nucleotide change in a genome, making the identification of the mechanisms causing mutations a difficult challenge. Here, we show that clustered mutations provide a more precise fingerprint of mutagenic processes. Of nine clustered mutation signatures identified from >1,000 tumor genomes, three relate to variable APOBEC activity and three are associated with tobacco smoking. An additional signature matches the spectrum of translesion DNA polymerase eta (POLH). In lymphoid cells, these mutations target promoters, consistent with AID-initiated somatic hypermutation. In solid tumors, however, they are associated with UV exposure and alcohol consumption and target the H3K36me3 chromatin of active genes in a mismatch repair (MMR)-dependent manner. These regions normally have a low mutation rate because error-free MMR also targets H3K36me3 chromatin. Carcinogens and error-prone repair therefore redistribute mutations to the more important regions of the genome, contributing a substantial mutation load in many tumors, including driver mutations.

Past, present and future of Barrett's oesophagus

Barrett's oesophagus is a condition which predisposes towards development of oesophageal adenocarcinoma, a highly lethal tumour which has been increasing in incidence in the Western world over the past three decades. There have been tremendous advances in the field of Barrett's oesophagus, not only in diagnostic modalities, but also in therapeutic strategies available to treat this premalignant disease. In this review, we discuss the past, present and future of Barrett's oesophagus. We describe the historical and new evolving diagnostic criteria of Barrett's oesophagus, while also comparing and contrasting the British Society of Gastroenterology guidelines, American College of Gastroenterology guidelines and International Benign Barrett's and CAncer Taskforce (BOBCAT) for Barrett's oesophagus. Advances in endoscopic modalities such as confocal and volumetric laser endomicroscopy, and a non-endoscopic sampling device, the Cytosponge, are described which could aid in identification of Barrett's oesophagus. With regards to therapy we review the evidence for the utility of endoscopic mucosal resection and radiofrequency ablation when coupled with better characterization of dysplasia. These endoscopic advances have transformed the management of Barrett's oesophagus from a primarily surgical disease into an endoscopically managed condition.

Modeling Esophagitis Using Human Three-Dimensional Organotypic Culture System

Esophagitis, whether caused by acid reflux, allergic responses, graft-versus-host disease, drugs, or infections, is a common condition of the gastrointestinal tract affecting nearly 20% of the US population. The instigating agent typically triggers an inflammatory response. The resulting inflammation is a risk factor for the development of esophageal strictures, Barrett esophagus, and esophageal adenocarcinoma. Research into the pathophysiology of these conditions has been limited by the availability of animal and human model systems. Three-dimensional organotypic tissue culture (OTC) is an innovative three-dimensional multicellular in vitro platform that recapitulates normal esophageal epithelial stratification and differentiation. We hypothesized that this platform can be used to model esophagitis to better understand the interactions between immune cells and the esophageal epithelium. We found that human immune cells remain viable and respond to cytokines when cultured under OTC conditions. The acute inflammatory environment induced in the OTC significantly affected the overlying epithelium, inducing a regenerative response marked by increased cell proliferation and epithelial hyperplasia. Moreover, oxidative stress from the acute inflammation induced DNA damage and strand breaks in epithelial cells, which could be reversed by antioxidant treatment. These findings support the importance of immune cell-mediated esophageal injury in esophagitis and confirms the utility of the OTC platform to characterize the underlying molecular events in esophagitis.

Abdominal obesity and gastroesophageal cancer risk: systematic review and meta-analysis of prospective studies

To systematically and quantitatively review the relation of abdominal obesity, as measured by waist circumference (WC) and waist to hip ratio (WHR), to total gastroesophageal cancer, gastric cancer (GC), and esophageal cancer. PubMed and Web of Science databases were searched for studies assessing the association between abdominal obesity and gastroesophageal cancer (GC and/or esophageal cancer) up to August 2016. A random-effect model was used to calculate the summary relative risks (RRs) and 95% confidence intervals (CIs). Seven prospective cohort studies – one publication included two separate cohorts – from six publications were included in the final analysis. A total of 2130 gastroesophageal cancer cases diagnosed amongst 913182 participants. Higher WC and WHR were significantly associated with increased risk of total gastroesophageal cancer (WC: RR 1.68, 95% CI: 1.38, 2.04; WHR: RR 1.49, 95% CI: 1.19, 1.88), GC (WC: RR 1.48, 95% CI: 1.24, 1.78; WHR: 1.33, 95% CI: 1.04, 1.70), and esophageal cancer (WC: RR 2.06, 95% CI: 1.30, 3.24; WHR: RR 1.99, 95% CI: 1.05, 3.75).Findings from our subgroup analyses showed non-significant positive associations between gastric non-cardia adenocarcinoma (GNCA) and both measures of abdominal adiposity, while gastric cardia adenocarcinoma (GCA) was positively associated with WC but not with WHR. On analysis restricted to studies that adjusted for body mass index (BMI), WC was positively associated with GC and esophageal cancer, whereas WHR was positively associated with risk of GC only. Although limited, the findings from our meta-analysis suggest the potential role of abdominal obesity in the etiology of gastric and esophageal cancers.

Diets link metabolic syndrome and colorectal cancer development (Review)

Diets have been believed to be an important factor in the development of metabolic syndrome and colorectal cancer (CRC). In recent years, many studies have shown an intimate relationship between mucosal immunity, metabolism and diets, which has led to a greater understanding of the pathophysiology of metabolic syndrome and CRC development. Although the precise effects of diets on oncogenesis have not been compl-etely elucidated, microbiota changes and inflammation are believed to be important factors that influence the development of CRC. Moreover, increased release of pro-inflammatory cytokines and alteration of adipokine levels have been observed in patients with colorectal adenoma and/or CRC, and these all have been considered as the important mechanisms that link diets to the development of metabolic syndrome and CRC. Importantly, a high-fat, low-fiber diet is associated with dysbiosis, and as the gut signature becomes more important in metabolic syndrome and CRC, an increased understanding of diets on bacterial activity in the pathogenesis of metabolic syndrome and CRC will lead to new preventive and therapeutic strategies.

Therapeutic implications of tumor interstitial acidification

Interstitial acidification is a hallmark of solid tumor tissues resulting from the combination of different factors, including cellular buffering systems, defective tissue perfusion and high rates of cellular metabolism. Besides contributing to tumor pathogenesis and promoting tumor progression, tumor acidosis constitutes an important intrinsic and extrinsic mechanism modulating therapy sensitivity and drug resistance. In fact, pharmacological properties of anticancer drugs can be affected not only by tissue structure and organization but also by the distribution of the interstitial tumor pH. The acidic tumor environment is believed to create a chemical barrier that limits the effects and activity of many anticancer drugs. In this review article we will discuss the general protumorigenic effects of acidosis, the role of tumor acidosis in the modulation of therapeutic efficacy and potential strategies to overcome pH-dependent therapy-resistance.

Translating genomic profiling to gastrointestinal cancer treatment

Next-generation sequencing enables faster, cheaper and more accurate whole-genome sequencing, allowing genome profiling and discovery of molecular features. As molecular targeted drugs are developed, treatment can be tailored according to molecular subtype. Gastric and colorectal cancers have each been divided into four subtypes according to molecular features. Profiling of the esophageal cancer genome is underway and its classification is anticipated. To date, identification of HER2 expression in gastric adenocarcinoma and KRAS, NRAS and BRAF mutations in colon cancer have proved essential for treatment decisions. However, to overcome therapy resistance and improve prognosis, further individualized therapy is required. Here, we summarize the treatment options for gastrointestinal cancer according to genomic profiling and discuss future directions.

Gastroesophageal Mucosal Injury after Cholecystectomy: An Indication for Surveillance?

BACKGROUND

Cholecystectomy alters bile release dynamics from pulsatile meal-stimulated to continuous, and results in retrograde duodeno-gastric bile reflux (DGR). Bile is implicated in mucosal injury after gastric surgery, but whether cholecystectomy causes esophagogastric mucosal inflammation, therefore increasing the risk of metaplasia, is unclear.

STUDY DESIGN

This study examined whether cholecystectomy-induced DGR promotes chronic inflammatory mucosal changes of the stomach and/or the esophagogastric junction (EGJ). Four groups of patients were studied and compared with controls. A group of patients was studied before and 1 year after cholecystectomy; 2 further groups were studied long-term post-cholecystectomy (LTPC) at 5 to 10 years and 10 to 20 years. All underwent abdominal ultrasound and upper gastrointestinal endoscopy with gastric antral and EGJ biopsies, noting the presence of gastric bile pooling. Biopsy specimens were stained for Ki67 and p53 overexpression, and the bile reflux index (BRI) was calculated.

RESULTS

At endoscopy, bile pooling was observed in 9 of 26 (34.6%) controls, in 8 of 25 (32%) patients pre-cholecystectomy, in 15 of 25 (60%) 1 year post-cholecystectomy patients (p = 0.047), and 23 of 29 (79.3%) LTPC patients (p = 0.001). Bile reflux index positivity at the EGJ increased from 19% of controls through 41% of LTPC patients (p = 0.032). Ki67 was overexpressed at the EGJ in 19% of controls, but in 62% of LTPC patients (p = 0.044); p53 was overexpressed at the EGJ in 19% of controls compared with 66% of LTPC patients (p = 0.001).

CONCLUSIONS

Duodeno-gastric bile reflux was more common in patients with gallstones than in controls, and its incidence doubled after cholecystectomy. This was associated with inflammatory changes in the gastric antrum and the EGJ, evident in most LTPC patients. Ki67 and p53 overexpression at the EGJ suggests cellular damage attributable to chronic bile exposure post-cholecystectomy, increasing the likelihood of dysplasia. Further studies are required to determine whether DGR-mediated esophageal mucosal injury is reversible or avoidable, and whether surveillance endoscopy is indicated after cholecystectomy.

Bacterial Biofilms in Colorectal Cancer Initiation and Progression

Intestinal microbiota have emerged as an important factor in colorectal cancer (CRC) initiation and progression. The currently prominent view on bacterial tumorigenesis is that CRC initiation is triggered by local mucosal colonization with specific pathogens (drivers), and that subsequent changes in the peritumoral environment allow colonization by opportunistic (passenger) microbes, further facilitating disease progression. Screening for CRC 'driver-passenger' microorganisms might thus allow early CRC diagnosis or preventive intervention. Such efforts are now being revolutionized by the notion that CRC initiation and progression require organization of bacterial communities into higher-order structures termed biofilms. We explore here the concept that a polymicrobial biofilm promotes pro-carcinogenic activities that may partially underlie progression along the adenoma-CRC axis.

Autophagy levels are elevated in barrett's esophagus and promote cell survival from acid and oxidative stress

Autophagy is a highly conserved mechanism that is activated during cellular stress. We hypothesized that autophagy may be induced by acid reflux, which causes injury, and inflammation, and therefore, contributes to the pathogenesis of Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). Currently, the role of autophagy in BE and EAC is poorly studied. We quantitatively define autophagy levels in human BE cell lines, a transgenic mouse model of BE, and human BE, and EAC biopsies. Human non-dysplastic BE had the highest basal number of autophagic vesicles (AVs), while AVs were reduced in normal squamous cells and dysplastic BE cells, and nearly absent in EAC. To demonstrate a functional role for autophagy in BE pathogenesis, normal squamous (STR), non-dysplastic BE (CPA), dysplastic BE (CPD), and EAC (OE19) cell lines were exposed to an acid pulse (pH 3.5) followed by incubation in the presence or absence of chloroquine, an autophagy inhibitor. Acid exposure increased reactive oxygen species (ROS) levels in STR and CPA cells. Chloroquine alone had a small impact on intracellular ROS or cell survival. However, combination of chloroquine with the acid pulse resulted in a significant increase in ROS levels at 6 h in STR and CPA cells, and increased cell death in all cell lines. These findings establish increased numbers of AVs in human BE compared to normal squamous or EAC, and suggest that autophagy functions to improve cell survival after acid reflux injury. Autophagy may thus play a critical role in BE pathogenesis and progression. © 2015 Wiley Periodicals, Inc.

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.

Increased Oxidative Stress in the Proximal Stomach of Patients with Barrett's Esophagus and Adenocarcinoma of the Esophagus and Esophagogastric Junction

OBJECTIVES: Oxidative stress (OS) is an essential element in the pathogenesis of Barrett’s esophagus (BE) and its transformation to adenocarcinoma (EAC). The state of OS in the proximal stomach of patients with BE and EAC is unknown. Isoprostanes are a specific marker of OS not previously used to determine OS from BE/EAC tissue samples. PATIENTS AND METHODS: OS was measured in 42 patients with BE (n = 9), EAC (n = 9), or both (n = 24) and 15 control patients. A STAT-8-Isoprostane EIA Kit served to identify 8-Isoprostanes (8-IP), and a Glutathione Assay Kit was used to measure glutathione reduced form (GSH) and glutathione oxidized form. An OxiSelect Oxidative DNA Damage ELISA Kit (8-OHdG) served to measure 8-OH-deoxyguanosine. RESULTS: The 8-IP (P = .039) and 8-OHdG (P = .008) levels were higher, and the GSH level lower (P = .031), in the proximal stomach of the study group than in that of the controls. Helicobacter pylori infection was present in 8% of the study patients. CONCLUSIONS: In the proximal stomach of BE and EAC patients, OS was elevated and antioxidative capacity was reduced. This finding suggests that the gastroesophageal reflux causing BE also induces oxidative stress in the proximal stomach and may contribute to the development of cancer in the proximal stomach and gastric cardia.

Clinical Study of Ursodeoxycholic Acid in Barrett's Esophagus Patients

Prior research strongly implicates gastric acid and bile acids, two major components of the gastroesophageal refluxate, in the development of Barrett's esophagus and its pathogenesis. Ursodeoxycholic acid (UDCA), a hydrophilic bile acid, has been shown to protect esophageal cells against oxidative stress induced by cytotoxic bile acids. We conducted a pilot clinical study to evaluate the clinical activity of UDCA in patients with Barrett's esophagus. Twenty-nine patients with Barrett's esophagus received UDCA treatment at a daily dose of 13 to 15 mg/kg/day for 6 months. The clinical activity of UDCA was assessed by evaluating changes in gastric bile acid composition and markers of oxidative DNA damage (8-hydroxydeoxyguanosine), cell proliferation (Ki67), and apoptosis (cleaved caspase-3) in Barrett's esophagus epithelium. The bile acid concentrations in gastric fluid were measured by liquid chromatography/mass spectrometry. At baseline, UDCA (sum of unchanged and glycine/taurine conjugates) accounted for 18.2% of total gastric bile acids. After UDCA intervention, UDCA increased significantly to account for 93.4% of total gastric bile acids (P < 0.0001). The expression of markers of oxidative DNA damage, cell proliferation, and apoptosis was assessed in the Barrett's esophagus biopsies by IHC. The selected tissue biomarkers were unchanged after 6 months of UDCA intervention. We conclude that high-dose UDCA supplementation for 6 months resulted in favorable changes in gastric bile acid composition but did not modulate selected markers of oxidative DNA damage, cell proliferation, and apoptosis in the Barrett's esophagus epithelium. Cancer Prev Res; 9(7); 528-33. ©2016 AACRSee related article by Brian J. Reid, p. 512.

Risk factors for Barrett's esophagus

Barrett's esophagus (BE) is a well-recognized precursor of esophageal adenocarcinoma (EAC) and is defined as ≥1 cm segment of salmon-colored mucosa extending above the gastroesophageal junction into the tubular esophagus with biopsy confirmation of metaplastic replacement of the normal squamous epithelium by intestinal-type columnar epithelium. The incidence of both BE and EAC has been increasing over the past few decades. As a result, preventing the development of BE by identifying and understanding its modifiable and non-modifiable risk factors may help reduce the incidence of EAC. Over the recent past, a tremendous amount of progress has been made towards improving our knowledge of risk factors and pathogenesis of BE. This article reviews the evidence for the various risk factors for developing BE.

Protective effect of agaro-oligosaccharides on gut dysbiosis and colon tumorigenesis in high-fat diet-fed mice

High-fat diet (HFD)-induced alteration in the gut microbial composition, known as dysbiosis, is increasingly recognized as a major risk factor for various diseases, including colon cancer. This report describes a comprehensive investigation of the effect of agaro-oligosaccharides (AGO) on HFD-induced gut dysbiosis, including alterations in short-chain fatty acid contents and bile acid metabolism in mice. C57BL/6N mice were fed a control diet or HFD, with or without AGO. Terminal restriction fragment-length polymorphism (T-RFLP) analysis produced their fecal microbiota profiles. Profiles of cecal organic acids and serum bile acids were determined, respectively, using HPLC and liquid chromatography-tandem mass spectrometry systems. T-RFLP analyses showed that an HFD changed the gut microbiota significantly. Changes in the microbiota composition induced by an HFD were characterized by a decrease in the order Lactobacillales and by an increase in the Clostridium subcluster XIVa. These changes of the microbiota community generated by HFD treatment were suppressed by AGO supplementation. As supported by the data of the proportion of Lactobacillales order, the concentration of lactic acid increased in the HFD + AGO group. Data from the serum bile acid profile showed that the level of deoxycholic acid, a carcinogenic secondary bile acid produced by gut bacteria, was increased in HFD-receiving mice. The upregulation tended to be suppressed by AGO supplementation. Finally, results show that AGO supplementation suppressed the azoxymethane-induced generation of aberrant crypt foci in the colon derived from HFD-treated mice. Our results suggest that oral intake of AGO prevents HFD-induced gut dysbiosis, thereby inhibiting colon carcinogenesis.

The tumor microenvironment in esophageal cancer

Esophageal cancer is a deadly disease, ranking sixth among all cancers in mortality. Despite incremental advances in diagnostics and therapeutics, esophageal cancer still carries a poor prognosis, and thus there remains a need to elucidate the molecular mechanisms underlying this disease. There is accumulating evidence that a comprehensive understanding of the molecular composition of esophageal cancer requires attention to not only tumor cells but also the tumor microenvironment, which contains diverse cell populations, signaling factors, and structural molecules that interact with tumor cells and support all stages of tumorigenesis. In esophageal cancer, environmental exposures can trigger chronic inflammation, which leads to constitutive activation of pro-inflammatory signaling pathways that promote survival and proliferation. Anti-tumor immunity is attenuated by cell populations such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), as well as immune checkpoints like programmed death-1 (PD-1). Other immune cells such as tumor-associated macrophages can have other pro-tumorigenic functions, including the induction of angiogenesis and tumor cell invasion. Cancer-associated fibroblasts secrete growth factors and alter the extracellular matrix (ECM) to create a tumor niche and enhance tumor cell migration and metastasis. Further study of how these TME components relate to the different stages of tumor progression in each esophageal cancer subtype will lead to development of novel and specific TME-targeting therapeutic strategies, which offer considerable potential especially in the setting of combination therapy.

Role of nitric oxide in the pathogenesis of Barrett’s-associated carcinogenesis

Barrett’s esophagus (BE), a premalignant condition to Barrett’s adenocarcinoma (BAC), is closely associated with chronic inflammation due to gastro-esophageal reflux. Caudal type homeobox 2 (CDX2), a representative marker of BE, is increased during the metaplastic and neoplastic transformation of BE. Nitric oxide (NO) has been proposed to be a crucial mediator of Barrett’s carcinogenesis. We previously demonstrated that CDX2 might be induced directly under stimulation of large amounts of NO generated around the gastro-esophageal junction (GEJ) by activating epithelial growth factor receptor in a ligand-independent manner. Thus, we reviewed recent developments on the role of NO in Barrett’s carcinogenesis. Notably, recent studies have reported that microbial communities in the distal esophagus are significantly different among groups with a normal esophagus, reflux esophagitis, BE or BAC, despite there being no difference in the bacterial quantity. Considering that microorganism components can be one of the major sources of large amounts of NO, these studies suggest that the bacterial composition in the distal esophagus might play an important role in regulating NO production during the carcinogenic process. Controlling an inflammatory reaction due to gastro-esophageal reflux or bacterial composition around the GEJ might help prevent the progression of Barrett’s carcinogenesis by inhibiting NO production.

Gut microbiota imbalance and colorectal cancer

The gut microbiota acts as a real organ. The symbiotic interactions between resident micro-organisms and the digestive tract highly contribute to maintain the gut homeostasis. However, alterations to the microbiome caused by environmental changes (e.g., infection, diet and/or lifestyle) can disturb this symbiotic relationship and promote disease, such as inflammatory bowel diseases and cancer. Colorectal cancer is a complex association of tumoral cells, non-neoplastic cells and a large amount of micro-organisms, and the involvement of the microbiota in colorectal carcinogenesis is becoming increasingly clear. Indeed, many changes in the bacterial composition of the gut microbiota have been reported in colorectal cancer, suggesting a major role of dysbiosis in colorectal carcinogenesis. Some bacterial species have been identified and suspected to play a role in colorectal carcinogenesis, such as Streptococcus bovis, Helicobacter pylori, Bacteroides fragilis, Enterococcus faecalis, Clostridium septicum, Fusobacterium spp. and Escherichia coli. The potential pro-carcinogenic effects of these bacteria are now better understood. In this review, we discuss the possible links between the bacterial microbiota and colorectal carcinogenesis, focusing on dysbiosis and the potential pro-carcinogenic properties of bacteria, such as genotoxicity and other virulence factors, inflammation, host defenses modulation, bacterial-derived metabolism, oxidative stress and anti-oxidative defenses modulation. We lastly describe how bacterial microbiota modifications could represent novel prognosis markers and/or targets for innovative therapeutic strategies.

The implications of oxidative stress and antioxidant therapies in Inflammatory Bowel Disease: Clinical aspects and animal models

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory disorder characterized by alternating phases of clinical relapse and remission. The etiology of IBD remains largely unknown, although a combination of patient's immune response, genetics, microbiome, and environment plays an important role in disturbing intestinal homeostasis, leading to development and perpetuation of the inflammatory cascade in IBD. As chronic intestinal inflammation is associated with the formation of reactive oxygen and reactive nitrogen species (ROS and RNS), oxidative and nitrosative stress has been proposed as one of the major contributing factor in the IBD development. Substantial evidence suggests that IBD is associated with an imbalance between increased ROS and decreased antioxidant activity, which may explain, at least in part, many of the clinical pathophysiological features of both CD and UC patients. Hereby, we review the presently known oxidant and antioxidant mechanisms involved in IBD-specific events, the animal models used to determine these specific features, and also the antioxidant therapies proposed in IBD patients.

Mechanisms of esophageal adenocarcinoma formation and approaches to chemopreventive intervention

The incidence of esophageal adenocarcinoma (EAC), a debilitating and highly lethal malignancy, has risen dramatically over the past 40 years in the United States and other Western countries. To reverse this trend, EAC prevention and early detection efforts by clinicians, academic researchers and endoscope manufacturers have targeted Barrett's esophagus (BE), the widely accepted EAC precursor lesion. Data from surgical, endoscopic and pre-clinical investigations strongly support the malignant potential of BE. For patients with BE, the risk of developing EAC has been estimated at 11- to 125-fold greater than that of the individual at average risk. Nevertheless, screening for BE in symptomatic patients (ie, with symptoms of reflux) and surveillance in patients diagnosed with BE have not had a substantial impact on the incidence, morbidity or mortality of EAC; the overwhelming majority of EAC patients are diagnosed without a pre-operative diagnosis of BE. This article will discuss the current state of the science of esophageal adenocarcinoma prevention, including ideas about carcinogenesis and its underlying genomic and molecular level mechanisms, and suggest strategies for a systems approach to targeted preventive management.

Esophageal Cancer: Insights From Mouse Models

Esophageal cancer is the eighth leading cause of cancer and the sixth most common cause of cancer-related death worldwide. Despite recent advances in the development of surgical techniques in combination with the use of radiotherapy and chemotherapy, the prognosis for esophageal cancer remains poor. The cellular and molecular mechanisms that drive the pathogenesis of esophageal cancer are still poorly understood. Hence, understanding these mechanisms is crucial to improving outcomes for patients with esophageal cancer. Mouse models constitute valuable tools for modeling human cancers and for the preclinical testing of therapeutic strategies in a manner not possible in human subjects. Mice are excellent models for studying human cancers because they are similar to humans at the physiological and molecular levels and because they have a shorter gestation time and life cycle. Moreover, a wide range of well-developed technologies for introducing genetic modifications into mice are currently available. In this review, we describe how different mouse models are used to study esophageal cancer.

Barrett's esophagus: recent insights into pathogenesis and cellular ontogeny

Esophageal adenocarcinoma (EAC) has increased 6-fold in its incidence in the last 2 decades. Evidence supports the hypothesis of stepwise progression from normal squamous epithelium → reflux esophagitis → metaplasia (Barrett's esophagus, BE) → dysplasia → adenocarcinoma. The precursor, BE, stands as the bridge connecting the widespread but naive reflux disease and the rare but fatal EAC. The step of metaplasia from squamous to intestine-like columnar phenotype is perhaps pivotal in promoting dysplastic vulnerability. It is widely accepted that chronic inflammation because of gastroesophageal reflux disease leads to the development of metaplasia, however the precise molecular mechanism is yet to be discovered. Additionally, how this seemingly adaptive change in the cellular phenotype promotes dysplasia remains a mystery. This conceptual void is deterring further translational research and clouding clinical decision making. This article critically reviews theories on the pathogenesis of Barrett's esophagus and the various controversies surrounding its diagnosis. We further discuss unanswered questions and future directions, which are vital in formulating effective preventive and therapeutic guidelines for Barrett's esophagus.