Measurement of Intracellular Ca2+ for Studying GPCR-Mediated Lipid Signaling.

Intracellular Ca2+ can be conveniently monitored by sensitive Ca2+ fluorescent dyes in live cells. The Gαq involved lipid signaling pathways and, thus, can be studied by intracellular Ca2+ imaging. Here we describe the protocols to measure intracellular Ca2+ for studying PEG2-EP1 activity in esophageal smooth muscle cells. The ratiometric Fura-2 imaging provides quantitative data, and the Fluo-4 confocal microscopic imaging has high-spatial resolution.

Mucosa-penetrating liposomes for esophageal local drug delivery.

Local drug delivery to the esophagus is hampered by rapid transit time and poor permeability of the mucosa. If some strategies aimed to improve the residence time have been proposed, non-invasive approaches to increase the drug penetration in the mucosa have not been described so far. Herein, we designed mucosa-penetrating liposomes to favor the penetration and retention of curcumin (CURC) in the esophagus. A novel mucosa penetrating peptide (MPP), SLENKGP, was selected by Phage Display and conjugated to pegylated liposomes at different PEG and MPP's surface densities. Pegylation assured a long residence time of liposomes (at least 30 min) in the esophagus in vivo, but it did not favor the penetration of CURC in the mucosa. MPP-decorated liposomes instead delivered a significant higher amount of CURC in the mucosa compared to naked pegylated liposomes. Confocal microscopy studies showed that naked pegylated liposomes remain confined in the superficial layers of the mucosa whereas MPP-decorated liposomes penetrate the whole epithelium. In vitro, MPP reduced the interaction of PEG with mucin, meanwhile favoring the paracellular penetration of liposomes across epithelial cell multilayers. In conclusion, pegylated liposomes represent a valid approach to target the esophagus and the surface functionalization with MPP enhances their penetration in the mucosa.

Lysophosphatidic acid promotes ESCC progression by increasing the level of CCL2 secreted by esophageal epithelial cells.

BACKGROUND: Lysophosphatidic acid (LPA) is a small bioactive lipid which acts as a potent regulator in various tumor progressions through six G-protein-coupled receptors (LPA1-LPA6). Our previous study demonstrated that the LPA-producing enzyme, autotaxin (ATX), was upregulated in esophageal squamous cell carcinoma (ESCC) and ATX high expression levels indicated a poor prognosis. Esophageal squamous cell carcinoma is a type of malignant tumor which originates from epithelial cells. Its progression can be affected by the interaction between cancer cells and normal cells. However, the impact of LPA on the interaction between esophageal epithelial cells and cancer cells in the development of ESCC remains uncertain. METHODS: MTS and Edu assays were performed to determine ESCC cell proliferation in culture medium (CM) derived from LPA-stimulated esophageal epithelial cells (Het-1a). A wound healing assay, transwell migration and an invasion assay were performed to assess the metastatic ability of ESCC cells. Cytokine array analysis was conducted to detect the differentially secreted cytokines in CM. The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were utilized to uncover the pathways and cytokines that are influenced by LPA in ESCC. Immunohistochemical staining was employed to measure the expression of ATX and CCL2 in early-stage ESCC. Quantitative real-time PCR, western blot, enzyme-linked immunosorbent assay and an antibody neutralization assay were employed to measure the mechanism of LPA-mediated communication between epithelial cells and cancer cells. RESULTS: Functional experiments showed that exposing ESCC cancer cells to CM from LPA-treated Het-1a results in promoting proliferation, migration, invasion and epithelial-mesenchymal transition processes. Using cytokine array analysis, we discovered that LPA triggers the release of multiple cytokines from epithelial cells. After screening of the TCGA and GEO databases, CCL2 was identified and found to be correlated with ATX expression in ESCC. Furthermore, CCL2 levels in both mRNA expression and secretion were observed to be upregulated in epithelial cells upon stimulation with LPA. Blocking CCL2 effectively reduced the pro-migration influence of CM derived from LPA-treated Het-1a. Mechanism studies have demonstrated that LPA activated the NF-κB signaling pathway through LPA1/3, ultimately causing an increase in CCL2 expression and secretion in Het-1a. CONCLUSIONS: Our findings, taken together, demonstrate that CM from LPA-treated esophageal epithelial cells plays a significant role in promoting the progression of ESCC, with CCL2 acting as the primary regulator.

Red2Flpe-SCON: a versatile, multicolor strategy for generating mosaic conditional knockout mice.

Image-based lineage tracing enables tissue turnover kinetics and lineage potentials of different adult cell populations to be investigated. Previously, we reported a genetic mouse model system, Red2Onco, which ectopically expressed mutated oncogenes together with red fluorescent proteins (RFP). This system enabled the expansion kinetics and neighboring effects of oncogenic clones to be dissected. We now report Red2Flpe-SCON: a mosaic knockout system that uses multicolor reporters to label both mutant and wild-type cells. We develop the Red2Flpe mouse line for red clone-specific Flpe expression, as well as the FRT-based SCON (Short Conditional IntrON) method to facilitate tunable conditional mosaic knockouts in mice. We use the Red2Flpe-SCON method to study Sox2 mutant clonal analysis in the esophageal epithelium of adult mice which reveal that the stem cell gene, Sox2, is less essential for adult stem cell maintenance itself, but rather for stem cell proliferation and differentiation.

YAP1 regulates esophageal stem cells' self-renewal and differentiation.

Esophageal epithelium is one of the most proliferative and regenerative epithelia in our body, indicating robust stem cell activity. However, the underlying mechanisms regulating the self-renewal and differentiation of esophageal stem cells need to be more elucidated. Here, we identify the role of YAP1 in esophageal stem cells. YAP1 is differentially expressed in the nuclei of esophageal basal cells. Furthermore, the treatment of verteporfin, a YAP1 inhibitor, interfered with esophageal organoid formation. Consistently, YAP1 deletion decreased esophageal organoid formation and the expression of basal genes while increasing the expression of suprabasal genes. Finally, global transcriptomic analysis revealed that YAP1 inhibition induced a significant enrichment of gene sets related to keratinization and cornification, while depleting gene sets related to DNA repair and chromosome maintenance. Our data uncover a novel regulatory mechanism for esophageal stem cells, which could provide a potential strategy for esophageal regenerative medicine.

Jag1/2 maintain esophageal homeostasis and suppress foregut tumorigenesis by restricting the basal progenitor cell pool.

Basal progenitor cells are crucial for maintaining foregut (the esophagus and forestomach) homeostasis. When their function is dysregulated, it can promote inflammation and tumorigenesis. However, the mechanisms underlying these processes remain largely unclear. Here, we employ genetic mouse models to reveal that Jag1/2 regulate esophageal homeostasis and foregut tumorigenesis by modulating the function of basal progenitor cells. Deletion of Jag1/2 in mice disrupts esophageal and forestomach epithelial homeostasis. Mechanistically, Jag1/2 deficiency impairs activation of Notch signaling, leading to reduced squamous epithelial differentiation and expansion of basal progenitor cells. Moreover, Jag1/2 deficiency exacerbates the deoxycholic acid (DCA)-induced squamous epithelial injury and accelerates the initiation of squamous cell carcinoma (SCC) in the forestomach. Importantly, expression levels of JAG1/2 are lower in the early stages of human esophageal squamous cell carcinoma (ESCC) carcinogenesis. Collectively, our study demonstrates that Jag1/2 are important for maintaining esophageal and forestomach homeostasis and the onset of foregut SCC.

Defining the contribution of Troy-positive progenitor cells to the mouse esophageal epithelium.

Progenitor cells adapt their behavior in response to tissue demands. However, the molecular mechanisms controlling esophageal progenitor decisions remain largely unknown. Here, we demonstrate the presence of a Troy (Tnfrsf19)-expressing progenitor subpopulation localized to defined regions along the mouse esophageal axis. Lineage tracing and mathematical modeling demonstrate that Troy-positive progenitor cells are prone to undergoing symmetrical fate choices and contribute to esophageal tissue homeostasis long term. Functionally, TROY inhibits progenitor proliferation and enables commitment to differentiation without affecting fate symmetry. Whereas Troy expression is stable during esophageal homeostasis, progenitor cells downregulate Troy in response to tissue stress, enabling proliferative expansion of basal cells refractory to differentiation and reestablishment of tissue homeostasis. Our results demonstrate functional, spatially restricted progenitor heterogeneity in the esophageal epithelium and identify how dynamic regulation of Troy coordinates tissue generation.

Localization of sensory nerve terminals containing calcitonin gene-related peptide (CGRP) on striated muscle fibers in the rat esophagus: Evidence for triple innervation via motor endplates.

BACKGROUND: Many esophageal striated muscles of mammals are dually innervated by the vagal and enteric nerves. Recently, substance P (SP)-sensory nerve terminals with calcitonin gene-related peptide (CGRP) were found on a few striated muscle fibers in the rat esophagus, implying that these muscle fibers are triply innervated. In this study, we examined the localization and origin of CGRP-nerve endings in striated muscles to consider their possible roles in the esophagus regarding triple innervation. METHODS: Wholemounts of the rat esophagus were immunolabeled to detect CGRP-nerve endings in striated muscles. Also, retrograde tracing was performed by injecting Fast Blue (FB) into the esophagus, and cryostat sections of the medulla oblongata, nodose ganglion (NG), and the tenth thoracic (T10) dorsal root ganglion (DRG) were immunostained to identify the origin of the CGRP-nerve endings. RESULTS: CGRP-fine, varicose nerve endings were localized in motor endplates on a few esophageal striated muscle fibers (4 %), most of which received nitric oxide (NO) synthase nerve terminals, and most of the CGRP nerve endings were SP- and transient receptor potential vanilloid member 1 (TRPV1)-positive. Retrograde tracing showed many FB-labeled CGRP-neurons positive for SP and TRPV1 in the NG and T10 DGR. CONCLUSIONS: This study suggests that the CGRP-varicose nerve endings containing SP and TRPV1 in motor endplates are sensory, and a few esophageal striated muscle fibers are triply innervated. The nerve endings may detect acetylcholine-derived acetic acid from the vagal motor nerve endings and NO from esophageal intrinsic nerve terminals in the motor endplates to regulate esophageal motility.

Automated Capillary Electrophoresis Immunoblot for the Detection of Alpha-Synuclein in Mouse Tissue.

Background: Alpha-synuclein (aSyn) is a key player in neurodegenerative diseases such as Parkinson's disease (PD), dementia with Lewy bodies, or multiple system atrophy. aSyn is expressed throughout the brain, and can also be detected in various peripheral tissues. In fact, initial symptoms of PD are non-motoric and include autonomic dysfunction, suggesting that the periphery might play an important role in early development of the disease. aSyn is expressed at relatively low levels in non-central tissues, which brings challenges for its detection and quantification in different tissues. Objective: Our goal was to assess the sensitivity of aSyn detection in central and peripheral mouse tissues through capillary electrophoresis (CE) immunoblot, considering the traditional SDS-PAGE immunoblot as the current standard. Methods: Tissues from central and non-central origin from wild type mice were extracted, and included midbrain, inner ear, and esophagus/stomach. aSyn detection was assessed through immunoblotting using Simple Western size-based CE and SDS-PAGE. Results: CE immunoblots show a consistent detection of aSyn in central and peripheral tissues. Through SDS-PAGE, immunoblots revealed a reliable signal corresponding to aSyn, particularly following membrane fixation. Conclusion: Our results suggest a reliable detection of aSyn in central and peripheral tissues using the CE Simple Western immunoblot system. These observations can serve as preliminary datasets when aiming to formally compare CE with SDS-PAGE, as well as for further characterization of aSyn using this technique.

Differentially expressed genes of esophageal tissue in male acute and chronic sleep deprivation mice.

Gastroesophageal reflux disease (GERD) is associated with sleep disturbances. However, mechanisms underlying these interactions remain unclear. Male acute and chronic sleep deprivation (SD) mice were used for this study. Mice in the chronic SD group exhibited anxiety- and depression-like behaviors. We further performed high-throughput genome sequencing and bioinformatics analysis to screen for featured differentially expressed genes (DEGs) in the esophageal tissue. The acute SD group, comprised 25 DEGs including 14 downregulated and 11 upregulated genes. Compared with the acute SD group, more DEGs were present in the chronic SD group, with a total of 169 DEGs, including 88 downregulated and 81 upregulated genes. Some DEGs that were closely related to GERD and associated esophageal diseases were significantly different in the chronic SD group. Quantitative real-time polymerase chain reaction verified the downregulation of Krt4, Krt13, Krt15 and Calml3 and upregulation of Baxl1 and Per3. Notably, these DEGs are involved in biological processes, which might be the pathways of the neuroregulatory mechanisms of DEGs expression.

Expression of CD25, mast cell markers and T-cell markers in eosinophilic esophagitis.

While eosinophilic esophagitis (EOE) is defined by histologic presence of eosinophils, a few studies have established the presence of mast cells in EOE and even shown their correlation with symptom persistence despite resolution of eosinophils. Expression of aberrant mast cell markers CD25 and CD2 have not been studied in EOE. This study quantifies the number of hotspot cells per high power field expressing CKIT/CD117, tryptase, CD25, CD2 and CD3 by immunohistochemical stains in endoscopic esophageal biopsies of the following three cohorts: (1) established and histologically confirmed EOE, (2) suspected EOE with biopsies negative for eosinophils, and (3) no history of or suspicion for EOE with histologically unremarkable biopsies. In this study, mast cells were highlighted by CKIT and tryptase in EOE, and not seen in other clinically mimicking cases. There were also significantly higher densities of CD25 and pan-T-cell marker staining in EOE cases. These findings suggest an inflammatory cellular milieu in EOE, beyond just eosinophils, that can be demonstrated by immunohistochemistry, and that invite further study into the role that these cells may play in EOE.

Drinking Large Volume of Hot Water May Cause Increased 18 F-FDG Uptake in Esophagus.

ABSTRACT: We present 2 cases of diffuse FDG accumulation in the esophagus due to drinking hot water before an 18 F-FDG PET/CT scan. Drinking large volume of hot water immediately before the FDG PET/CT study may lead to challenges in the interpretation of the hypermetabolic esophagus.

Exploring the clinical relevance of "Angico Gum": an effective biopolymer for topical protection of oesophageal mucosa in gastroesophageal reflux disease patients.

OBJECTIVES: Angico gum (AG) (Anadenanthera colubrina var. Cebil [Griseb.] Altschul) is utilized by some Brazilian communities to alleviate symptoms from gastroesophageal reflux disease. Here, we aimed to investigate the "in vitro" topical protective capacity of AG on human esophageal mucosa. METHODS: Biopsies of the distal esophageal mucosa were collected from 35 patients with heartburn (24 non-erosive and 11 with erosive oesophagitis (EE)) and mounted in Üssing chambers. AG was applied topically, followed by exposure with acid solution (pH 2.0 or pH 1.0), where transepithelial electrical resistance (TER) and The transepithelial permeability for fluorescein was assessed. The incubation of the AG labeled with FITC in the esophageal mucosa was localized by fluorescence microscopy. KEY FINDINGS: Pretreatment with AG prevented the drop in TER induced by acid solution, as well as significantly decreases the fluorescein permeability in non-erosive patients. The protective effect of AG was sustained for up to 120 min both in biopsies of non-erosive and erosive esophagitis. Confocal microscope images showed mucosal luminal adherence of FITC-labeled AG. CONCLUSION: AG had a prolonged topical protective effect against acid solution in mucosal biopsies of patients with non-erosive and erosive esophagitis.

Saliva Production and Esophageal Motility Influence Esophageal Acid Clearance Related to Post-reflux Swallow-Induced Peristaltic Wave.

BACKGROUND: The post-reflux swallow-induced peristaltic wave (PSPW) brings salivary bicarbonate to neutralize residual distal esophageal mucosal acidification. AIMS: To determine if reduced saliva production and esophageal body hypomotility would compromise PSPW-induced pH recovery in the distal esophagus. METHODS: In this multicenter retrospective cross-sectional study, patients with confirmed Sjogren's syndrome and scleroderma/mixed connective tissue disease (MCTD) who underwent high resolution manometry (HRM) and ambulatory pH-impedance monitoring off antisecretory therapy were retrospectively identified. Patients without these disorders undergoing HRM and pH-impedance monitoring for GERD symptoms were identified from the same time-period. Acid exposure time, numbers of reflux episodes and PSPW, pH recovery with PSPW, and HRM metrics were extracted. Univariate comparisons and multivariable analysis were performed to determine predictors of pH recovery with PSPW. RESULTS: Among Sjogren's syndrome (n = 34), scleroderma/MCTD (n = 14), and comparison patients with reflux symptoms (n = 96), the scleroderma/MCTD group had significantly higher AET, higher prevalence of hypomotility, lower detected reflux episodes, and very low numbers of PSPW (p ≤ 0.004 compared to other groups). There was no difference in pH-impedance metrics between Sjogren's syndrome, and comparison patients (p ≥ 0.481). Proportions with complete pH recovery with PSPW was lower in Sjogren's patients compared to comparison reflux patients (p = 0.009), predominantly in subsets with hypomotility (p < 0.001). On multivariable analysis, diagnosis of Sjogren's syndrome, scleroderma/MCTD or neither (p = 0.014) and esophageal hypomotility (p = 0.024) independently predicted lack of complete pH recovery with PSPW, while higher total reflux episodes trended (p = 0.051). CONCLUSIONS: Saliva production and motor function are both important in PSPW related pH recovery.

Autophagy Contributes to Homeostasis in Esophageal Epithelium Where High Autophagic Vesicle Level Marks Basal Cells With Limited Proliferation and Enhanced Self-Renewal Potential.

BACKGROUND & AIMS: Autophagy plays roles in esophageal pathologies both benign and malignant. Here, we aim to define the role of autophagy in esophageal epithelial homeostasis. METHODS: We generated tamoxifen-inducible, squamous epithelial-specific Atg7 (autophagy related 7) conditional knockout mice to evaluate effects on esophageal homeostasis and response to the carcinogen 4-nitroquinoline 1-oxide (4NQO) using histologic and biochemical analyses. We fluorescence-activated cell sorted esophageal basal cells based on fluorescence of the autophagic vesicle (AV)-identifying dye Cyto-ID and then subjected these cells to transmission electron microscopy, image flow cytometry, three-dimensional organoid assays, RNA sequencing, and cell cycle analysis. Three-dimensional organoids were subjected to passaging, single-cell RNA sequencing, cell cycle analysis, and immunostaining. RESULTS: Genetic autophagy inhibition in squamous epithelium resulted in increased proliferation of esophageal basal cells under homeostatic conditions and also was associated with significant weight loss in mice treated with 4NQO that further displayed perturbed epithelial tissue architecture. Esophageal basal cells with high AV level (Cyto-IDHigh) displayed limited organoid formation capability on initial plating but passaged more efficiently than their counterparts with low AV level (Cyto-IDLow). RNA sequencing suggested increased autophagy in Cyto-IDHigh esophageal basal cells along with decreased cell cycle progression, the latter of which was confirmed by cell cycle analysis. Single-cell RNA sequencing of three-dimensional organoids generated by Cyto-IDLow and Cyto-IDHigh cells identified expansion of 3 cell populations and enrichment of G2/M-associated genes in the Cyto-IDHigh group. Ki67 expression was also increased in organoids generated by Cyto-IDHigh cells, including in basal cells localized beyond the outermost cell layer. CONCLUSIONS: Autophagy contributes to maintenance of the esophageal proliferation-differentiation gradient. Esophageal basal cells with high AV level exhibit limited proliferation and generate three-dimensional organoids with enhanced self-renewal capacity.

TGF-ß1 inhibitor P144 protects against benign restenosis after esophageal stenting through TGF-ß1/Smads signaling pathway inhibition.

BACKGROUND AND STUDY AIMS: Esophageal restenosis is a serious complication after esophageal stent placement, which influences the clinical prognosis of stent implantation and the patient's quality of life. TGF-ß1/Smads signaling pathway plays an important role in the development of the eosinophilic esophagitis and scar repair after skin trauma. However, the role of TGF-ß1/Smads in the development of esophageal restenosis after esophageal stent placement remains unknown. Our study aimed to investigate whether TGF-ß1/Smads plays an important role in the development of esophageal restenosis after esophageal stent, and whether the exogenous TGF-ß1 inhibitor supplement could ameliorate the esophageal restenosis after esophageal stent. MATERIAL AND METHODS: We established the model of esophageal restenosis after esophageal stenting in rats, and determined the expression levels of TGF-ß1/Smads signaling pathway and the relevant markers of fibroblast activation by immunochemistry (IHC), Western Blot and real time qPCR. Those all the indicators were also determined in esophageal fibroblast when exposed to rhTGF-ß1 with or without TGF-ß1 inhibitor P144. RESULTS: The serum level of IL-1ß and TNFα were significantly increased in stent implantation group compared to blank control group, and obviously ameliorated when treated with P144. The TGF-ß1/Smads signaling pathway and the relevant markers of fibroblast activation were significantly increased in stent implantation group compared to blank control group, and obviously ameliorated when treated with P144. Those all the indicators were significantly increased when exposed to rhTGF-ß1, and obviously decreased when treated with P144. CONCLUSIONS: TGF-ß1 Inhibitor P144 could protect against benign restenosis after esophageal stenting by down-regulating the expression levels of relevant markers of fibroblast activation through TGF-ß1/Smads signaling pathway inhibition, and may be used as a novel therapy for benign restenosis after esophageal stenting.

[Standardized and quality-assured predictive PD-L1 testing in the upper gastrointestinal tract. German version]. / Standardisierte und qualitätsgesicherte prädiktive PD-L1-Testung im oberen Gastrointestinaltrakt.

As a result of the high approval dynamics and the growing number of immuno-oncological therapy concepts, the complexity of therapy decisions and control in the area of carcinomas of the esophagus, gastroesophageal junction and stomach is constantly increasing. Since the treatment indication for PD­1 inhibitors that are currently approved in the European Union is often linked to the expression of PD-L1 (programmed cell death-ligand 1), the evaluation of tissue-based predictive markers by the pathologist is of crucial importance for treatment stratification. Even though the immunohistochemical analysis of the PD-L1 expression status is one of the best studied, therapy-relevant biomarkers for an immuno-oncological treatment, due to the high heterogeneity of carcinomas of the upper gastrointestinal tract, there are challenges in daily clinical diagnostic work with regard to implementation, standardization and interpretation of testing. An interdisciplinary group of experts from Germany has taken a position on relevant questions from daily pathological and clinical practice, which concern the starting material, quality-assured testing and the interpretation of pathological findings, and has developed recommendations for structured reporting.

Alterations in gene expression and microbiome composition upon calcium-sensing receptor deletion in the mouse esophagus.

The calcium-sensing receptor (CaSR), a G protein-coupled receptor, regulates Ca2+ concentration in plasma by regulating parathyroid hormone secretion. In other tissues, it is reported to play roles in cellular differentiation and migration and in secretion and absorption. We reported previously that CaSR can be conditionally deleted in the mouse esophagus. This conditional knockout (KO) (EsoCaSR-/-) model showed a significant reduction in the levels of adherens and tight junction proteins and had a marked buildup of bacteria on the luminal esophageal surface. To further examine the role of CaSR, we used RNA sequencing to determine gene expression profiles in esophageal epithelia of control and EsoCaSR-/-mice RNA Seq data indicated upregulation of gene sets involved in DNA replication and cell cycle in EsoCaSR-/-. This is accompanied by the downregulation of gene sets involved in the innate immune response and protein homeostasis including peptide elongation and protein trafficking. Ingenuity pathway analysis (IPA) demonstrated that these genes are mapped to important biological networks including calcium and Ras homologus A (RhoA) signaling pathways. To further explore the bacterial buildup in EsoCaSR-/- esophageal tissue, 16S sequencing of the mucosal-associated bacterial microbiome was performed. Three bacterial species, g_Rodentibacter, s_Rodentibacter_unclassified, and s_Lactobacillus_hilgardi were significantly increased in EsoCaSR-/-. Furthermore, metagenomic analysis of 16S sequences indicated that pathways related to oxidative phosphorylation and metabolism were downregulated in EsoCaSR-/- tissues. These data demonstrate that CaSR impacts major pathways of cell proliferation, differentiation, cell cycle, and innate immune response in esophageal epithelium. The disruption of these pathways causes inflammation and significant modifications of the microbiome.NEW & NOTEWORTHY Calcium-sensing receptor (CaSR) plays a significant role in maintaining the barrier function of esophageal epithelium. Using RNA sequencing, we show that conditional deletion of CaSR from mouse esophagus causes upregulation of genes involved in DNA replication and cell cycle and downregulation of genes involved in the innate immune response, protein translation, and cellular protein synthesis. Pathway analysis shows disruption of signaling pathways of calcium and actin cytoskeleton. These changes caused inflammation and esophageal dysbiosis.

The p53 DNA damage response and Fanconi anemia DNA repair pathway protect against acetaldehyde-induced replication stress in esophageal keratinocytes.

Alcohol contributes to cellular accumulation of acetaldehyde, a primary metabolite of alcohol and a major human carcinogen. Acetaldehyde can form DNA adducts and induce interstrand crosslinks (ICLs) that are repaired by the Fanconi anemia DNA repair pathway (FA pathway). Individuals with deficiency in acetaldehyde detoxification or in the FA pathway have an increased risk of squamous-cell carcinomas (SCCs) including those of the esophagus. In a recent report, we described the molecular basis of acetaldehyde-induced DNA damage in esophageal keratinocytes [1]. We demonstrated that, at physiologically relevant concentrations, acetaldehyde induces DNA damage at the DNA replication fork. This resulted in replication stress, leading to activation of the ATR-Chk1-dependent cell cycle checkpoints. We also reported that the p53 DNA damage response is elevated in response to acetaldehyde and that the FA pathway limits acetaldehyde-induced genomic instability. Here, we highlight these findings and present additional results to discuss the role of the FA pathway and p53 DNA damage response in the protection against genomic instability and esophageal carcinogenesis.