Extracellular matrix hyaluronan modulates fat cell differentiation and primary cilia dynamics

Hyaluronan is an important extracellular matrix component, with poorly documented physiological role in the context of lipid-rich adipose tissue. We have investigated the global impact of hyaluronan removal from adipose tissue environment by in vitro exposure to exogenous hyaluronidase (or heat inactivated enzyme). Gene set expression analysis from RNA sequencing revealed downregulated adipogenesis as a main response to hyaluronan removal from human adipose tissue samples, which was confirmed by hyaluronidase-mediated inhibition of adipocyte differentiation in the 3T3L1 adipose cell line. Hyaluronidase exposure starting from the time of induction with the differentiation cocktail reduced lipid accumulation in mature adipocytes, limited the expression of terminal differentiation marker genes, and impaired the early induction of co-regulated Cebpa and Pparg mRNA. Reduction of Cebpa and Pparg expression by exogenous hyaluronidase was also observed in cultured primary preadipocytes from subcutaneous, visceral or brown adipose tissue of mice. Mechanistically, inhibition of adipogenesis by hyaluronan removal was not caused by changes in osmotic pressure or cell inflammatory status, could not be mimicked by exposure to threose, a metabolite generated by hyaluronan degradation, and was not linked to alteration in endogenous Wnt ligands expression. Rather, we observed that hyaluronan removal associated with disrupted primary cilia dynamics, with elongated cilium and higher proportions of preadipocytes that remained ciliated in hyaluronidase-treated conditions. Thus, our study points to a new link between ciliogenesis and hyaluronan impacting adipose tissue development.

Tissue pleiotropic effect of biotin and prebiotic supplementation in established obesity

Combination therapies targeting multiple organs and metabolic pathways are promising therapeutic options to combat obesity progression and/or its comorbidities. The alterations in the composition of the gut microbiota initially observed in obesity have been extended recently to functional alterations. Bacterial functions involve metabolites synthesis that may contribute to both the gut microbiota and the host physiology. Among them are B vitamins, whose metabolism at the systemic, tissue or microbial level are dysfunctional in obesity. We previously reported that the combination of oral supplementation of a prebiotic (fructo-oligosaccharides, FOS) and vitamin B7/B8 (biotin) impedes fat mass accumulation and hyperglycemia in mice with established obesity. This was associated with an attenuation of dysbiosis with improved microbial vitamin metabolism. We now extend this study by characterizing whole-body energy metabolism along with adipose tissue transcriptome and histology in this mouse model. We observed that FOS resulted in increased caloric excretion in parallel with down-regulation of genes and proteins involved in jejunal lipid transport. The combined treatments also strongly inhibited the accumulation of subcutaneous fat mass, with a reduced adipocyte size and expression of lipid metabolism genes. Down-regulation of inflammatory and fibrotic genes and proteins was also observed in both visceral and brown adipose tissues and liver by combined FOS and biotin supplementation. In conclusion, oral administration of a prebiotic and biotin has a beneficial impact on the metabolism of key organs involved in the pathophysiology of obesity, which could have promising translational applications.

Eosinophils protect from metabolic alterations triggered by obesity

BACKGROUND

Eosinophils are generally related to helminth infections or allergies. Their association with metabolic alterations and adipose tissue (AT) remodeling has been demonstrated mainly in animal models of obesity. However, their physiological role in driving metabolic features has not yet been well described. Herein, we aimed to evaluate the participation of eosinophils in metabolic and adipose tissue homeostasis in mice and humans, focusing on a translational perspective.

MATERIAL AND METHODS

Male BALB/c wild-type (WT) mice and GATA-1 knockout (Δdb/GATA-1^-/-) mice were followed until 16-week-age in a regular diet or were fed with a high-refined-carbohydrate (HC) diet or high-fat (HF) diet for eight weeks. In subjects with obesity, clinical parameters and omental AT gene expression were evaluated.

RESULTS

Eosinophils lack in mice fed a regular diet induced insulin resistance and increased adiposity. Their adipose tissue showed augmented cytokine levels, which could be attributed to increased leukocytes in the tissue, such as neutrophils and pro-inflammatory macrophages. Bone marrow transplant from WT mice to Δdb/GATA-1^-/- mice showed some improvement in glucose metabolism with lower adipose tissue mass accretion. Upon an unhealthy diet challenge, Δdb/GATA-1^-/- mice fed HC diet showed a mild degree of adiposity and glucose metabolic dysfunction severe in those mice fed HF diet. The expression of eosinophil markers in omental AT from humans with severe obesity was positively correlated to eosinophil cytokines and insulin sensitivity surrogate markers and negatively correlated to systemic insulin, HOMA-IR, and android fat mass.

CONCLUSIONS

Eosinophils seem to have a physiological role by controlling systemic and adipose tissue metabolic homeostasis by modulating glucose metabolism, inflammation, and visceral fat expansion, even in lean mice. Indeed, eosinophils also seem to modulate glucose homeostasis in human obesity.

Beta-hydroxybutyrate dampens adipose progenitors' profibrotic activation through canonical Tgfβ signaling and non-canonical ZFP36-dependent mechanisms

BACKGROUND/PURPOSE

Adipose tissue contains progenitor cells that contribute to beneficial tissue expansion when needed by de novo adipocyte formation (classical white or beige fat cells with thermogenic potential). However, in chronic obesity, they can exhibit an activated pro-fibrotic, extracellular matrix (ECM)-depositing phenotype that highly aggravates obesity-related adipose tissue dysfunction.

METHODS

Given that progenitors' fibrotic activation and fat cell browning appear to be antagonistic cell fates, we have examined the anti-fibrotic potential of pro-browning agents in an obesogenic condition.

RESULTS

In obese mice fed a high fat diet, thermoneutral housing, which induces brown fat cell dormancy, increases the expression of ECM gene programs compared to conventionally raised animals, indicating aggravation of obesity-related tissue fibrosis at thermoneutrality. In a model of primary cultured murine adipose progenitors, we found that exposure to β-hydroxybutyrate selectively reduced Tgfβ-dependent profibrotic responses of ECM genes like Ctgf, Loxl2 and Fn1. This effect is observed in both subcutaneous and visceral-derived adipose progenitors, as well as in 3T3-L1 fibroblasts. In 30 patients with obesity eligible for bariatric surgery, those with higher circulating β-hydroxybutyrate levels have lower subcutaneous adipose tissue fibrotic scores. Mechanistically, β-hydroxybutyrate limits Tgfβ-dependent collagen accumulation and reduces Smad2-3 protein expression and phosphorylation in visceral progenitors. Moreover, β-hydroxybutyrate induces the expression of the ZFP36 gene, encoding a post-transcriptional regulator that promotes the degradation of mRNA by binding to AU-rich sites within 3'UTRs. Importantly, complete ZFP36 deficiency in a mouse embryonic fibroblast line from null mice, or siRNA knock-down in primary progenitors, indicate that ZFP36 is required for β-hydroxybutyrate anti-fibrotic effects.

CONCLUSION

These data unravel the potential of β-hydroxybutyrate to limit adipose tissue matrix deposition, a finding that might exploited in an obesogenic context.

SLC6A14 Impacts Cystic Fibrosis Lung Disease Severity via mTOR and Epithelial Repair Modulation

Cystic fibrosis (CF), due to pathogenic variants in CFTR gene, is associated with chronic infection/inflammation responsible for airway epithelium alteration and lung function decline. Modifier genes induce phenotype variability between people with CF (pwCF) carrying the same CFTR variants. Among these, the gene encoding for the amino acid transporter SLC6A14 has been associated with lung disease severity and age of primary airway infection by the bacteria Pseudomonas aeruginosa. In this study, we investigated whether the single nucleotide polymorphism (SNP) rs3788766, located within SLC6A14 promoter, is associated with lung disease severity in a large French cohort of pwCF. We also studied the consequences of this SNP on SLC6A14 promoter activity using a luciferase reporter and the role of SLC6A14 in the mechanistic target of rapamycin kinase (mTOR) signaling pathway and airway epithelial repair. We confirm that SLC6A14 rs3788766 SNP is associated with lung disease severity in pwCF (p = 0.020; n = 3,257, pancreatic insufficient, aged 6–40 years old), with the minor allele G being deleterious. In bronchial epithelial cell lines deficient for CFTR, SLC6A14 promoter activity is reduced in the presence of the rs3788766 G allele. SLC6A14 inhibition with a specific pharmacological blocker reduced ³H-arginine transport, mTOR phosphorylation, and bronchial epithelial repair rates in wound healing assays. To conclude, our study highlights that SLC6A14 genotype might affect lung disease severity of people with cystic fibrosis via mTOR and epithelial repair mechanism modulation in the lung.

Cold-Atmospheric Plasma Induces Tumor Cell Death in Preclinical In Vivo and In Vitro Models of Human Cholangiocarcinoma

Through the last decade, cold atmospheric plasma (CAP) has emerged as an innovative therapeutic option for cancer treatment. Recently, we have set up a potentially safe atmospheric pressure plasma jet device that displays antitumoral properties in a preclinical model of cholangiocarcinoma (CCA), a rare and very aggressive cancer emerging from the biliary tree with few efficient treatments. In the present study, we aimed at deciphering the molecular mechanisms underlying the antitumor effects of CAP towards CCA in both an in vivo and in vitro context. In vivo, using subcutaneous xenografts into immunocompromised mice, CAP treatment of CCA induced DNA lesions and tumor cell apoptosis, as evaluated by 8-oxoguanine and cleaved caspase-3 immunohistochemistry, respectively. The analysis of the tumor microenvironment showed changes in markers related to macrophage polarization. In vitro, the incubation of CCA cells with CAP-treated culture media (i.e., plasma-activated media, PAM) led to a dose response decrease in cell survival. At molecular level, CAP treatment induced double-strand DNA breaks, followed by an increased phosphorylation and activation of the cell cycle master regulators CHK1 and p53, leading to cell cycle arrest and cell death by apoptosis. In conclusion, CAP is a novel therapeutic option to consider for CCA in the future.

[68Ga]RGD Versus [18F]FDG PET Imaging in Monitoring Treatment Response of a Mouse Model of Human Glioblastoma Tumor with Bevacizumab and/or Temozolomide

PURPOSE

The aim of this study was to evaluate positron emission tomography (PET) imaging with [⁶⁸Ga]NODAGA-c(RGDfK) ([⁶⁸Ga]RGD), in comparison with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG), for early monitoring of the efficacy of an antiangiogenic agent associated or not with chemotherapy, in a mouse model of glioblastoma (GB).

PROCEDURES

Mice bearing U87MG human GB cells line were parted into five groups of five mice each. One group was imaged at baseline before the treatment phase; another group was treated with bevacizumab (BVZ), another group with temozolomide (TMZ), another group with both agents, and the last one was the control group. Tumors growth and biological properties were evaluated by caliper measurements and PET imaging at three time points (baseline, during treatment t1 = 4-6 days and t2 = 10-12 days). At the end of the study, tumors were counted and analyzed by immunohistochemistry (CD31 to evaluate microvessel density).

RESULTS

The tumor volume assessed by caliper measurements was significantly greater at t1 in the control group than in the TMZ + BVZ-treated group or in the BVZ-treated group. At t2, tumor volume of all treated groups was significantly smaller than that of the control group. [¹⁸F]FDG PET failed to reflect this efficacy of treatment. In contrast, at t1, the [⁶⁸Ga]RGD tumor uptake was concordant with tumor growth in controls and in treated groups. At t2, a significant increase in tumor uptake of [⁶⁸Ga]RGD vs. t1 was only observed in the TMZ-treated group, reflecting a lack of angiogenesis inhibition, whereas TMZ + BVZ resulted in a dramatic tumor arrest, reduction in microvessel density and stable tumor [⁶⁸Ga]RGD uptake.

CONCLUSIONS

[⁶⁸Ga]RGD is a useful PET agent for in vivo angiogenesis imaging and can be useful for monitoring antiangiogenic treatment associated or not with chemotherapy.

Can we classify ampullary tumours better? Clinical, pathological and molecular features. Results of an AGEO study

Background

Ampullary adenocarcinoma (AA) originates from either intestinal (INT) or pancreaticobiliary (PB) epithelium. Different prognostic factors of recurrence have been identified in previous studies.

Methods

In 91 AA patients of the AGEO retrospective multicentre cohort, we evaluated the centrally reviewed morphological classification, panel markers of Ang et al. including CK7, CK20, MUC1, MUC2 and CDX2, the 50-gene panel mutational analysis, and the clinicopathological AGEO prognostic score.

Results

Forty-three (47%) of the 91 tumours were Ang-INT, 29 (32%) were Ang-PB, 18 (20%) were ambiguous (Ang-AMB) and one could not be classified. Among these 90 tumours, 68.7% of INT tumours were Ang-INT and 78.2% of PB tumours were Ang-PB. MUC5AC expression was detected in 32.5% of the 86 evaluable cases. Among 71 tumours, KRAS, TP53, APC and PIK3CA were the most frequently mutated genes. The KRAS mutation was significantly more frequent in the PB subtype. In multivariate analysis, only AGEO prognostic score and tumour subtype were associated with relapse-free survival. Only AGEO prognostic score was associated with overall survival.

Conclusions

Mutational analysis and MUC5AC expression provide no additional value in the prognostic evaluation of AA patients. Ang et al. classification and the AGEO prognostic score were confirmed as a strong prognosticator for disease recurrence.

Insulin receptor isoform A favors tumor progression in human hepatocellular carcinoma by increasing stem/progenitor cell features

Hepatocellular carcinoma (HCC) is one of the most common and deadly neoplasms. Insulin receptor (IR) exists in two isoforms, IR-A and IR-B, the latter being predominantly expressed in normal adult hepatocytes while IR-A is overexpressed in HCC to the detriment of IR-B. This study evaluated the biological functions associated with IR-A overexpression in HCC in relation to expression of its ligand IGF-II. The value of INSRA:INSRB ratio which was increased in _˜70% of 85 HCC was associated with stem/progenitor cell features such as cytokeratin-19 and α-fetoprotein and correlated with shorter patient survival. IGF2 mRNA upregulation was observed in 9.4% of HCC and was not associated with higher INSRA:INSRB ratios. Ectopic overexpression of IR-A in two HCC cell lines presenting a strong autocrine IGF-II secretion loop or not stimulated cell migration and invasion. In cells cultured as spheroids, IR-A overexpression promoted gene programs related to stemness, inflammation and cell movement. IR-A also increased cell line tumorigenicity in vivo after injection to immunosuppressed mice and the sphere-forming cells made a significant contribution to this effect. Altogether, these results demonstrate that IR-A is a novel player in HCC progression.

Diet-Induced Dysbiosis and Genetic Background Synergize With Cystic Fibrosis Transmembrane Conductance Regulator Deficiency to Promote Cholangiopathy in Mice

The most typical expression of cystic fibrosis (CF)-related liver disease is a cholangiopathy that can progress to cirrhosis. We aimed to determine the potential impact of environmental and genetic factors on the development of CF-related cholangiopathy in mice. Cystic fibrosis transmembrane conductance regulator (Cftr)^-/- mice and Cftr ^+/+ littermates in a congenic C57BL/6J background were fed a high medium-chain triglyceride (MCT) diet. Liver histopathology, fecal microbiota, intestinal inflammation and barrier function, bile acid homeostasis, and liver transcriptome were analyzed in 3-month-old males. Subsequently, MCT diet was changed for chow with polyethylene glycol (PEG) and the genetic background for a mixed C57BL/6J;129/Ola background (resulting from three backcrosses), to test their effect on phenotype. C57BL/6J Cftr ^-/- mice on an MCT diet developed cholangiopathy features that were associated with dysbiosis, primarily Escherichia coli enrichment, and low-grade intestinal inflammation. Compared with Cftr ^+/+ littermates, they displayed increased intestinal permeability and a lack of secondary bile acids together with a low expression of ileal bile acid transporters. Dietary-induced (chow with PEG) changes in gut microbiota composition largely prevented the development of cholangiopathy in Cftr ^-/- mice. Regardless of Cftr status, mice in a mixed C57BL/6J;129/Ola background developed fatty liver under an MCT diet. The Cftr ^-/- mice in the mixed background showed no cholangiopathy, which was not explained by a difference in gut microbiota or intestinal permeability, compared with congenic mice. Transcriptomic analysis of the liver revealed differential expression, notably of immune-related genes, in mice of the congenic versus mixed background. In conclusion, our findings suggest that CFTR deficiency causes abnormal intestinal permeability, which, combined with diet-induced dysbiosis and immune-related genetic susceptibility, promotes CF-related cholangiopathy.

Influence of Progenitor-Derived Regeneration Markers on Hepatitis C Virus-Related Cirrhosis Outcome (ANRS CO12 CirVir Cohort)

Progenitor-derived regeneration gives rise to the aberrant expression of biliary markers such as cytokeratin 7 (K7) and epithelial cell adhesion molecule (EpCAM) in hepatocytes. We aimed to describe the expression of these molecules in patients with compensated hepatitis C virus (HCV)-related cirrhosis and to investigate its potential influence on cirrhosis complications. Among patients with Child-Pugh A uncomplicated HCV-related cirrhosis enrolled in the prospective ANRS CO12 CirVir cohort, we selected individuals with a liver biopsy collected within 2 years before inclusion in the study. K7 and EpCAM immunostaining identified intermediate hepatobiliary cells. The influence of biliary marker expres-sion in hepatocytes on decompensation events and the occurrence of hepatocellular carcinoma (HCC) was studied using a multivariate Cox proportional hazards regression model. Among the 337 patients eligible for the study (men, 67%; median age, 52 years), 198 (58.8%) had biopsies with K7-positive hepatocytes including extensive staining in 40 (11.9%) and 203 had EpCAM-positive hepatocytes (60.6%). During follow-up (median, 54.2 months), 47 patients (14%) experienced a decompensation event, and HCC was diagnosed in 37 patients (11%). Extensive K7 staining was independently associated with the occurrence of a decompensation event (hazard ratio [HR], 3.00; 95% confidence interval [CI], 1.30-6.89; P = 0.010). EpCAM expression was independently associated with HCC occurrence (HR, 2.37; 95% CI, 1.07-5.23; P =0.033) along with age and a low prothrombin ratio.

CONCLUSION

Progenitor-derived regeneration depicted by K7 and EpCAM immunostaining of hepatocytes in liver biopsies of patients with compensated HCV-related cirrhosis marks a cirrhosis stage more prone to develop complications. (HEPATOLOGY 2018; 68:1534-1548).

Identification of Positively and Negatively Selected Driver Gene Mutations Associated With Colorectal Cancer With Microsatellite Instability

BACKGROUND & AIMS

Recent studies have shown that cancers arise as a result of the positive selection of driver somatic events in tumor DNA, with negative selection playing only a minor role, if any. However, these investigations were concerned with alterations at nonrepetitive sequences and did not take into account mutations in repetitive sequences that have very high pathophysiological relevance in the tumors showing microsatellite instability (MSI) resulting from mismatch repair deficiency investigated in the present study.

METHODS

We performed whole-exome sequencing of 47 MSI colorectal cancers (CRCs) and confirmed results in an independent cohort of 53 MSI CRCs. We used a probabilistic model of mutational events within microsatellites, while adapting pre-existing models to analyze nonrepetitive DNA sequences. Negatively selected coding alterations in MSI CRCs were investigated for their functional and clinical impact in CRC cell lines and in a third cohort of 164 MSI CRC patients.

RESULTS

Both positive and negative selection of somatic mutations in DNA repeats was observed, leading us to identify the expected true driver genes associated with the MSI-driven tumorigenic process. Several coding negatively selected MSI-related mutational events (n = 5) were shown to have deleterious effects on tumor cells. In the tumors in which deleterious MSI mutations were observed despite the negative selection, they were associated with worse survival in MSI CRC patients (hazard ratio, 3; 95% CI, 1.1-7.9; P = .03), suggesting their anticancer impact should be offset by other as yet unknown oncogenic processes that contribute to a poor prognosis.

CONCLUSIONS

The present results identify the positive and negative driver somatic mutations acting in MSI-driven tumorigenesis, suggesting that genomic instability in MSI CRC plays a dual role in achieving tumor cell transformation. Exome sequencing data have been deposited in the European genome-phenome archive (accession: EGAS00001002477).

Low Levels of Microsatellite Instability at Simple Repeated Sequences Commonly Occur in Human Hepatocellular Carcinoma

BACKGROUND/AIM

The aim of this study was to assess the incidence of MSI in a large series of human hepatocellular carcinomas (HCC) with various etiologies.

MATERIALS AND METHODS

The MSI status was determined by polymerase chain reaction (PCR) using 5 mononucleotide and 13 CAn dinucleotide repeats.

RESULTS

None of the 122 HCC samples displayed an MSI-High phenotype, as defined by the presence of alterations at more than 30% of the microsatellite markers analyzed. Yet, limited microsatellite instability consisting in the insertion or deletion of a few repeat motifs was detected in 32 tumor samples (26.2%), regardless of the etiology of the underlying liver disease. MSI tended to be higher in patients with cirrhosis (p=0.051), possibly reflecting an impact of the inflammatory context in this process.

CONCLUSION

Based on a large series of HCC with various etiologies, our study allowed us to definitely conclude that MSI is not a hallmark of HCC.

CARD9 impacts colitis by altering gut microbiota metabolism of tryptophan into aryl hydrocarbon receptor ligands

Complex interactions between the host and the gut microbiota govern intestinal homeostasis but remain poorly understood. Here we reveal a relationship between gut microbiota and caspase recruitment domain family member 9 (CARD9), a susceptibility gene for inflammatory bowel disease (IBD) that functions in the immune response against microorganisms. CARD9 promotes recovery from colitis by promoting interleukin (IL)-22 production, and Card9(-/-) mice are more susceptible to colitis. The microbiota is altered in Card9(-/-) mice, and transfer of the microbiota from Card9(-/-) to wild-type, germ-free recipients increases their susceptibility to colitis. The microbiota from Card9(-/-) mice fails to metabolize tryptophan into metabolites that act as aryl hydrocarbon receptor (AHR) ligands. Intestinal inflammation is attenuated after inoculation of mice with three Lactobacillus strains capable of metabolizing tryptophan or by treatment with an AHR agonist. Reduced production of AHR ligands is also observed in the microbiota from individuals with IBD, particularly in those with CARD9 risk alleles associated with IBD. Our findings reveal that host genes affect the composition and function of the gut microbiota, altering the production of microbial metabolites and intestinal inflammation.

Mitogen-activated protein kinase-activated protein kinase 2 mediates resistance to hydrogen peroxide-induced oxidative stress in human hepatobiliary cancer cells

The development and progression of liver cancer are characterized by increased levels of reactive oxygen species (ROS). ROS-induced oxidative stress impairs cell proliferation and ultimately leads to cell death. Although liver cancer cells are especially resistant to oxidative stress, mechanisms of such resistance remain understudied. We identified the MAPK-activated protein kinase 2 (MK2)/heat shock protein 27 (Hsp27) signaling pathway mediating defenses against oxidative stress. In addition to MK2 and Hsp27 overexpression in primary liver tumors compared to adjacent nontumorous tissues, the MK2/Hsp27 pathway is activated by hydrogen peroxide-induced oxidative stress in hepatobiliary cancer cells. MK2 inactivation or inhibition of MK2 or Hsp27 expression increases caspase-3 and PARP cleavage and DNA breaks and therefore cell death. Interestingly, MK2/Hsp27 inhibition decreases antioxidant defenses such as heme oxygenase 1 through downregulation of the transcription factor nuclear factor erythroid-derived 2-like 2. Moreover, MK2/Hsp27 inhibition decreases both phosphorylation of epidermal growth factor receptor (EGFR) and expression of its ligand, heparin-binding EGF-like growth factor. A new identified partner of MK2, the scaffold PDZ protein EBP50, could facilitate these effects through MK2/Hsp27 pathway regulation. These findings demonstrate that the MK2/Hsp27 pathway actively participates in resistance to oxidative stress and may contribute to liver cancer progression.

EGF/EGFR axis contributes to the progression of cholangiocarcinoma through the induction of an epithelial-mesenchymal transition

BACKGROUND & AIMS

Epithelial-mesenchymal transition (EMT) is a cellular process involved in cancer progression. The first step of EMT consists in the disruption of E-cadherin-mediated adherens junctions. Cholangiocarcinoma (CCA), a cancer with a poor prognosis due to local invasion and metastasis, displays EMT features. EGFR, a receptor tyrosine kinase, plays a major role in CCA progression. The aim of the study was to determine if EMT is induced by EGFR in CCA cells.

METHODS

In vivo, the expression of E-cadherin was analysed in CCA tumours of 100 patients and correlated with pathological features and EGFR expression, and in a xenograft model in mice treated with gefitinib, an inhibitor of EGFR. In vitro, the regulation of EMT by EGFR was investigated in CCA cell lines.

RESULTS

In human CCA, a cytoplasmic localization of E-cadherin occurred in 50% of the tumours was associated with the peripheral type of CCA, tumour size, the presence of satellite nodules and EGFR overexpression. In xenografted tumours, E-cadherin displayed a cytoplasmic pattern whereas the treatment of mice with gefitinib restored the membranous expression of E-cadherin. In vitro, EGF induced scattering of CCA cells that resulted from the disruption of adherens junctions. Internalization and decreased expression of E-cadherin, as well as nuclear translocation of β-catenin, were observed in EGF-treated CCA cells. In these cells, EMT-transcription factors (i.e., Slug and Zeb-1) and mesenchymal markers (i.e., N-cadherin and α-SMA) were induced, favoring cell invasiveness through cytoskeleton remodeling. All these effects were inhibited by gefitinib.

CONCLUSIONS

The EGF/EGFR axis triggers EMT in CCA cells highlighting the key role of this pathway in CCA progression.

Hepatic myofibroblasts promote the progression of human cholangiocarcinoma through activation of epidermal growth factor receptor

Intrahepatic cholangiocarcinoma (CCA) is characterized by an abundant desmoplastic environment. Poor prognosis of CCA has been associated with the presence of alpha-smooth muscle actin (α-SMA)-positive myofibroblasts (MFs) in the stroma and with the sustained activation of the epidermal growth factor receptor (EGFR) in tumor cells. Among EGFR ligands, heparin-binding epidermal growth factor (HB-EGF) has emerged as a paracrine factor that contributes to intercellular communications between MFs and tumor cells in several cancers. This study was designed to test whether hepatic MFs contributed to CCA progression through EGFR signaling. The interplay between CCA cells and hepatic MFs was examined first in vivo, using subcutaneous xenografts into immunocompromised mice. In these experiments, cotransplantation of CCA cells with human liver myofibroblasts (HLMFs) increased tumor incidence, size, and metastatic dissemination of tumors. These effects were abolished by gefitinib, an EGFR tyrosine kinase inhibitor. Immunohistochemical analyses of human CCA tissues showed that stromal MFs expressed HB-EGF, whereas EGFR was detected in cancer cells. In vitro, HLMFs produced HB-EGF and their conditioned media induced EGFR activation and promoted disruption of adherens junctions, migratory and invasive properties in CCA cells. These effects were abolished in the presence of gefitinib or HB-EGF-neutralizing antibody. We also showed that CCA cells produced transforming growth factor beta 1, which, in turn, induced HB-EGF expression in HLMFs.

CONCLUSION

A reciprocal cross-talk between CCA cells and myofibroblasts through the HB-EGF/EGFR axis contributes to CCA progression.