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Ewing sarcoma (ES) is characterized by chimeric fusion proteins, which act as oncogenes. Over the last decade, patient survival has not increased, especially for high risk patients. Knowing that ion channels are studied for their implication in tumorigenesis, the aim of this work is to study the involvement of the SK1 potassium channels in ES. RNA-Seq analyses showed a high restricted expression ofKCNN1, the gene encoding SK1, only in ES patients, and its expression is inversely correlated with patient survival. EWS-FLI1 silencing demonstrated the regulation ofKCNN1by these fusion proteins, which bind at GGAA microsatellites nearKCNN1promoter. In addition,KCNN1has been shown to be involved in the regulation of ES cell proliferation, its silencing being associated with a slowing of the cell cycle. Finally,KCNN1expression modulates membrane potential and calcium flux suggesting the role of calcium inKCNN1driving cell proliferation. These results highlight thatKCNN1is a direct EWS-FLI1 and EWS-ERG target, and is involved in the regulation of ES cell proliferation, making it an interesting therapeutic target in ES.

Despite recent improvements in therapeutic management of osteosarcoma, ongoing challenges in improving the response to chemotherapy warrants new strategies still needed to improve overall patient survival. In this study, we investigated in vivo the effects of RAD001 (Everolimus), a new orally available mTOR inhibitor, on the growth of human and mouse osteosarcoma cells either alone or in combination with zoledronate (ZOL), an anti-osteoporotic drug used to treat bone metastases. RAD001 inhibited osteosarcoma cell proliferation in a dose- and time-dependent manner with no modification of cell-cycle distribution. Combination with ZOL augmented this inhibition of cell proliferation, decreasing PI3K/mTOR signaling compared with single treatments. Notably, in contrast to RAD001, ZOL downregulated isoprenylated membrane-bound Ras concomitantly with an increase of nonisoprenylated cytosolic Ras in sensitive and resistant osteosarcoma cell lines to both drugs. Moreover, ZOL and RAD001 synergized to decrease Ras isoprenylation and GTP-bound Ras levels. Further, the drug combination reduced tumor development in two murine models of osteoblastic or osteolytic osteosarcoma. We found that ZOL could reverse RAD001 resistance in osteosarcoma, limiting osteosarcoma cell growth in combination with RAD001. Our findings rationalize further study of the applications of mTOR and mevalonate pathway inhibitors that can limit protein prenylation pathways. Cancer Res; 70(24); 10329–39. ©2010 AACR.

Supplementary Data 3 from Zoledronic Acid Potentiates mTOR Inhibition and Abolishes the Resistance of Osteosarcoma Cells to RAD001 (Everolimus): Pivotal Role of the Prenylation Process

Supplementary Data 1 from Zoledronic Acid Potentiates mTOR Inhibition and Abolishes the Resistance of Osteosarcoma Cells to RAD001 (Everolimus): Pivotal Role of the Prenylation Process

Supplementary Data 2 from Zoledronic Acid Potentiates mTOR Inhibition and Abolishes the Resistance of Osteosarcoma Cells to RAD001 (Everolimus): Pivotal Role of the Prenylation Process

Despite advances in clinical management, osteosarcoma and Ewing sarcoma, the two most frequent malignant primary bone tumors at pediatric age, still have a poor prognosis for high-risk patients (i.e., relapsed or metastatic disease). Triggering a TRAIL pro-apoptotic pathway represents a promising therapeutic approach, but previous studies have described resistance mechanisms that could explain the declining interest of such an approach in clinical trials. In this study, eight relevant human cell lines were used to represent the heterogeneity of the response to the TRAIL pro-apoptotic effect in pediatric bone tumors and two cell-derived xenograft models were developed, originating from a sensitive and a resistant cell line. The DR5 agonist antibody AMG655 (Conatumumab) was selected as an example of TRAIL-based therapy. In both TRAIL-sensitive and TRAIL-resistant cell lines, two signaling pathways were activated following AMG655 treatment, the canonical extrinsic apoptotic pathway and a non-apoptotic pathway, involving the recruitment of RIPK1 on the DR5 protein complex, activating both pro-survival and pro-proliferative effectors. However, the resulting balance of these two pathways was different, leading to apoptosis only in sensitive cells. In vivo, AMG655 treatment reduced tumor development of the sensitive model but accelerated tumor growth of the resistant one. We proposed two independent strategies to overcome this issue: (1) a proof-of-concept targeting of RIPK1 by shRNA approach and (2) the use of a novel highly-potent TRAIL-receptor agonist; both shifting the balance in favor of apoptosis. These observations are paving the way to resurrect TRAIL-based therapies in pediatric bone tumors to help predict the response to treatment, and propose a relevant adjuvant strategy for future therapeutic development.

Osteosarcoma (OS) is the most common malignant bone tumor in children and teenagers. In many cases, such as poor response to treatment or the presence of metastases at diagnosis, the survival rate of patients remains very low. Although in the literature, more and more studies are emerging on the role of Ubiquitin-Specific Proteases (USPs) in the development of many cancers, few data exist regarding OS. In this context, RNA-sequencing analysis of OS cells and mesenchymal stem cells differentiated or not differentiated into osteoblasts reveals increased expression of four USPs in OS tumor cells: USP6, USP27x, USP41 and USP43. Tissue microarray analysis of patient biopsies demonstrates the nucleic and/or cytoplasmic expression of these four USPs at the protein level. Interestingly, Kaplan–Meyer analysis shows that the expression of two USPs, USP6 and USP41, is correlated with patient survival. In vivo experiments using a preclinical OS model, finally demonstrate that PR619, a USP inhibitor able to enhance protein ubiquitination in OS cell lines, reduces primary OS tumor growth and the development of lung metastases. In this context, in vitro experiments show that PR619 decreases the viability of OS cells, mainly by inducing a caspase3/7-dependent cell apoptosis. Overall, these results demonstrate the relevance of targeting USPs in OS.

Background Calcific tendonitis of the rotator cuff is due to carbonated apatite deposits in the shoulder tendons. During the evolution of the disease, an acute inflammatory episode may occur leading to the disappearance of the calcification. Although hydroxyapatite crystal-induced inflammation has been previously studied with synthetic crystals, no data are available with calcifications extracted from patients suffering from calcific tendinopathy. The objective of the study was to explore the inflammatory properties of human calcifications and the pathways involved. Methods Human calcifications and synthetic hydroxyapatite were used in vitro to stimulate human monocytes and macrophages, the human myeloid cell line THP-1, and human tenocytes. The release of IL-1β, IL-6, and IL-8 by cells was quantified by ELISA. The gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR. NF-kB activation and NLRP3 involvement were assessed in THP-1 cells using a NF-kB inhibitor and a caspase-1 inhibitor. The inflammatory properties were then assessed in vivo using a mouse air pouch model. Results Human calcifications were able to induce a significant release of IL-1β when incubated with monocytes, macrophages, and THP-1 only if they were first primed with LPS (monocytes and macrophages) or PMA (THP-1). Stimulation of THP-1 by human calcifications led to similar levels of IL-1β when compared to synthetic hydroxyapatite although these levels were significantly inferior in monocytes and macrophages. The patient’s crystals enhanced mRNA expression of pro-IL-1β, as well as IL-18, NF-kB, and TGFβ when IL-6 and TNFα expression were not. IL-1β production was reduced by the inhibition of caspase-1 indicating the role of NLRP3 inflammasome. In vivo, injection of human calcifications or synthetic hydroxyapatite in the air pouch led to a significant increase in membrane thickness although significant overexpression of IL-1β was only observed for synthetic hydroxyapatite. Conclusions As synthetic hydroxyapatite, human calcifications were able to induce an inflammatory response resulting in the production of IL-1β after NF-kB activation and through NLRP3 inflammasome. In some experiments, IL-1β induction was lower with human calcifications compared to synthetic apatite. Differences in size, shape, and protein content may explain this observation.

Although some studies suggested that disruption of the Hippo signaling pathway is associated with osteosarcoma progression, the molecular mechanisms by which YAP regulates primary tumor growth is not fully clarified. In addition, the validation of YAP as a therapeutic target through the use of inhibitors in a preclinical model must be demonstrated. RNA-seq analysis and Kaplan&ndash, Meier assays identified a YAP signature in osteosarcoma patients and a correlation with patients&rsquo, outcomes. Molecular and cellular analysis (RNAseq, PLA, immunoprecipitation, promoter/specific gene, proliferation, cell cycle assays) using overexpression of mutated forms of YAP able or unable to interact with TEAD, indicate that TEAD is crucial for YAP-driven cell proliferation and in vivo tumor growth. In addition, in vivo experiments using an orthotopic mice model of osteosarcoma show that two YAP/TEAD inhibitors, verteporfin and CA3, reduce primary tumor growth. In this context, in vitro experiments demonstrate that these inhibitors decrease YAP expression, YAP/TEAD transcriptional activity and cell viability mainly by their ability to induce cell apoptosis. We thus demonstrate that the YAP/TEAD signaling axis is a central actor in mediating primary tumor growth of osteosarcoma, and that the use of YAP inhibitors may be a promising therapeutic strategy against osteosarcoma tumor growth.

BackgroundOsteosarcoma is the first primary bone tumor in children and adolescents. Despite progress in the understanding of the biology of these tumors, survival rates have progressed very little in recent decades. In this context, although some studies suggested that disruption of the Hippo signaling pathway is associated with osteosarcoma progression, the molecular mechanisms by which YAP regulates primary tumor growth is not fully clarified. In addition, the validation of YAP as a therapeutic target through the use of inhibitors in a preclinical model must be demonstrated.MethodsThe identification of a YAP signature was carried out by RNAseq analysis from a cohort of patients. Survival rates were assessed by Kaplan-Meier assays. The role of TEAD in the control of osteosarcoma cell proliferation by YAP has been realized by various molecular and cellular biology approaches (RNAseq, PLA, immunoprecipitation, promoter/specific gene, proliferation, cell cycle assays) using overexpression of mutated forms of YAP able or unable to interact with TEAD. The role of TEAD in YAP regulation of primary tumor growth, and the effects of YAP inhibitors in vivo were realized using an orthotopic model of osteosarcoma. ResultsRNA-seq analysis and Kaplan-Meier assays identified a YAP signature in osteosarcoma patients and a correlation with patients outcome. Molecular and cellular analysis using overexpression of mutated forms of YAP able or unable to interact with TEAD, indicate that TEAD is crucial for YAP-driven cell proliferation and in vivo tumor growth. In addition, in vivo experiments show that two YAP/TEAD inhibitors, verteporfin and CA3, reduce primary tumor growth. In this context, in vitro experiments demonstrate that these inhibitors decrease YAP expression, YAP/TEAD transcriptional activity and cell viability mainly by their ability to induce cell apoptosis.ConclusionWe thus demonstrate that the YAP/TEAD signaling axis is a central actor in mediating primary tumor growth of osteosarcoma, and that the use of YAP inhibitors may be a promising therapeutic strategy against osteosarcoma tumor growth.

Osteosarcoma (OS) and Ewing&rsquo, s sarcoma (ES) are the most common malignant bone tumors in children and adolescents. In many cases, the prognosis remains very poor. The Sonic hedgehog (SHH) signaling pathway, strongly involved in the development of many cancers, regulate transcription via the transcriptional factors Gli1-3. In this context, RNAseq analysis of OS and ES cell lines reveals an increase of some major compounds of the SHH signaling cascade in ES cells, such as the transcriptional factor Gli1. This increase leads to an augmentation of the transcriptional response of Gli1 in ES cell lines, demonstrating a dysregulation of Gli1 signaling in ES cells and thus the rationale for targeting Gli1 in ES. The use of a preclinical model of ES demonstrates that GANT61, an inhibitor of the transcriptional factor Gli1, reduces ES primary tumor growth. In vitro experiments show that GANT61 decreases the viability of ES cell, mainly through its ability to induce caspase-3/7-dependent cell apoptosis. Taken together, these results demonstrates that GANT61 may be a promising therapeutic strategy for inhibiting the progression of primary ES tumors.

International audience; Macrophages are specialized cells that control tissue homeostasis. They include non-resident and tissue-resident macrophage populations which are characterized by the expression of particular cell surface markers and the secretion of molecules with a wide range of biological functions. The differentiation and polarization of macrophages relies on specific growth factors and their receptors. Macrophage-colony stimulating factor (CSF-1) and interleukine-34 (IL-34), also known as "twin" cytokines, are part of this regluatory landscape. CSF-1 and IL-34 share a common receptor, the macrophage-colony stimulating factor receptor (CSF-1R), which is activated in a similar way by both factors and turns on identical signaling pathways. However, there is some discrete differential activation leading to specific activities. In this review, we disscuss recent progress in understanding of the role of the twin cytokines in macrophage differentiation, from their interaction with CSF-1R and the activation of signaling pathways, to their implication in macrophage polarization of non-resident and tissue-resident macrophages. A special focus on IL-34, its involvement in pathophsyiological contexts, and its potential as a theranostic target for macrophage therapy will be proposed.

International audience; OBJECTIVES:Interleukin (IL)-38 is a newly characterised cytokine that belongs to the IL-1 family. This cytokine is expressed in the rheumatoid arthritis (RA) synovial tissue and IL-38 deficient mice have exacerbated arthritis. Here, we analysed the effect of IL-38 overexpression in the joints of arthritic mice, in human macrophages and synovial fibroblasts in vitro.METHODS:Articular injections of an adeno-associated virus (AAV) 2/8 encoding IL-38 were performed in collagen-induced arthritis (CIA), K/BxN serum transfer-induced arthritis (STIA) and antigen-induced arthritis (AIA) in mice. The effect of IL-38 overexpression was evaluated through clinical scores, immunohistochemistry, microCT, Luminex and RT-qPCR analysis. THP-1 macrophages were transduced with a lentiviral vector to overexpress IL-38.RESULTS:Clinical inflammatory scores were significantly decreased after AAV IL-38 injection in joints of mice with CIA and STIA, but not AIA. This decrease was accompanied by reduced macrophage infiltration and a decreased expression of Th17 cytokines (IL-17, IL-23, IL-22) and TNFα. However, IL-38 overexpression had no effect on cartilage or bone destruction. In vitro, the THP-1 monocytic cell line expressed less IL-6, TNFα and IL-23 after IL-38 overexpression. Conditioned media from these cells, containing released IL-38, also exert an anti-inflammatory effect on human primary macrophages and synovial fibroblasts from patients with RA.CONCLUSIONS:This study shows for the first time that IL-38 overexpression attenuates the severity of experimental arthritis. IL-38 may exert its anti-inflammatory effects by decreasing the production of proinflammatory cytokines by macrophages and synovial fibroblasts. This effect can lead to the development of novel treatment strategies in arthritis.

Background:Calcific tendonitis of the rotator cuff is due to carbonated apatite deposits in the shoulder tendons. During the evolution of the disease, an acute inflammatory episode may occur leading to the disappearance of the calcification. Although hydroxyapatite crystals-induced inflammation has been previously studied with synthetic crystals, no data are available with calcifications extracted from patients suffering from calcific tendinopathy. The objective of the study was to explore the inflammatory properties of human calcifications and the pathways involved.Objectives:The objective of the study was to explore the inflammatory properties of human calcifications and the pathways involved.Methods:Human calcifications were obtained from patients treated for their shoulder pain related to a calcific tendinopathy of the rotator cuff. Calcifications were extracted by ultrasound-guided lavage and aspiration as previously described [1]. Human calcifications and synthetic hydroxyapatite (sHA) were used in vitro to stimulate human monocytes and macrophages, the human myeloid cell line THP-1 and human tenocytes. The release of IL-1β, IL-6 and IL-8 by cells was quantified by ELISA. Gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR. NF-kB activation and NLRP3 involvement was assessed in THP-1 cells using a NF-kB inhibitor and a Caspase 1 inhibitor. The inflammatory properties were then assessed in vivo using a mouse air pouch model. The membrane thickness and infiltrate were assessed 6 and 24 hours after the injection of human calcifications or synthetic hydroxyapatite using hematoxylin and eosin staining. Macrophages, neutrophils and lymphocytes infiltrates were assessed by immunohistochemistry. Total RNA was extracted from the membranes and expression of IL-1β, IL-6 and TNFβ was quantified by PCR.Results:Human calcifications were able to induce a significant release of IL-1β when incubated with monocytes, macrophages and THP-1 only if they were first primed with LPS (lipopolysaccharide) for monocytes and macrophages or PMA (Phorbol 12-myristate 13-acetate) for THP-1. No IL-1β was detected in tenocytes’ supernatants. Stimulation of THP-1 by human calcifications led to similar levels of IL-1β when compared to synthetic hydroxyapatite although these levels were significantly inferior in monocytes and macrophages. IL-6 and IL-8 levels were not increased in the supernatants after crystal stimulation. Patient’s crystals enhanced mRNA expression of pro-IL-1β, as well as IL-18, NF-kB and TGFβ when IL-6 and TNFα expression were not. IL-1β production was reduced by the inhibition NF-kB as well as Caspase 1 indicating the role of NLRP3 inflammasome. In vivo, injection of human calcifications or synthetic hydroxyapatite in air pouch led to significant increase in membrane thickness with an infiltrate mainly composed of macrophages. Significant overexpression of IL-1β was only observed in the synthetic hydroxyapatite group.Conclusion:As synthetic hydroxyapatite, human calcifications were able to induce an inflammatory response resulting in the production of IL-1β after NF-kB activation and through NLRP3 inflammasome. In some experiments, IL-1β induction was lower with human calcifications compared to synthetic apatite. Differences in size, shape and protein content may explain this observation.References:[1]Darrieutort-Laffite C, Arnolfo P, Garraud T, Adrait A, Couté Y, Louarn G, et al. Rotator Cuff Tenocytes Differentiate into Hypertrophic Chondrocyte-Like Cells to Produce Calcium Deposits in an Alkaline Phosphatase-Dependent Manner. J Clin Med. 2019 Sep 26;8(10):1544. doi: 10.3390/jcm8101544.Acknowledgements:Fondation Arthritis, Recherche et Rhumatismes and French Society for Rheumatology for their financial supportDisclosure of Interests:None declared

Osteosarcoma (OS) is the main malignant primary bone tumor in children and adolescents for whom the prognosis remains poor, especially when metastases are present at diagnosis. Because Hippo/YAP cascade plays a crucial role in cancer progression, we investigated its implication in OS development. Using proximity ligation assay and immunoprecipitation approaches, and promoter/reporter assays, we demonstrated a functional interaction between YAP and the transcriptional factor TEAD-1 in OS cell lines. To understand the specific role of this YAP/TEAD-1 interaction to regulate OS tumor growth, we generated OS cells that overexpressed a YAP protein able (YAP127A) or not able (YAP94A) to interact with TEAD-1. Using in vitro experiments and a preclinical model of OS, we demonstrated that YAP overexpression stimulates respectively OS cell proliferation and tumor growth only when YAP is able to interact with TEAD-1. Furthermore, the overexpression of YAPS94A reduces specific TEAD-1 transcriptional response and in vivo tumor growth. In contrast, the ability of YAP to stimulate OS cell migration does not depend on its ability to interact with TEAD-1. In addition, the effect of YAP overexpression (YAPS94A and YAPS127A) on OS cell migration is associated with cytoskeleton reorganization. Since we previously demonstrated the crucial role of the TGF-β/Smad3 signaling pathway in OS migration and metastatic development, we study the interaction between YAP and Smad3 in OS cells. Using proximity ligation assay and immunoprecipitation approaches, and promoter/reporter assays, we demonstrated a functional interaction between YAP and the transcriptional factor Smad3 in OS cell lines regardless of YAP’s ability to interact with TEAD-1. Finally, we investigated the effect of verteporfin, identified as an inhibitor of the Hippo signaling pathway, on OS progression. In vitro and in vivo experiments showed that verteporfin inhibits YAP/TEAD-1 cascade, OS cell proliferation, and reduces primary tumor growth. In addition, verteporfin reduces in vivo lung metastases development. In this context, in vitro experiments demonstrated that verteprofin inhibits the TGF-β/Smad3 cascade and the response of TGF-β key targets involved in the metastasis dissemination process. Together these results demonstrate that YAP/TEAD-1 interactions are crucial in OS tumor growth and suggest that YAP/SMAD3 interactions are involved in OS lung metastasis dissemination. Furthermore, we show that verteporfin may be a promising therapeutic strategy against tumor progression of OS, specifically against lung metastasis dissemination. Citation Format: Sarah Morice, Mathilde Mullard, Sarah Renault, Jérôme Amiaud, Régis Brion, Isabelle Corre, Anne Gomez-Brouchet, Françoise Redini, Franck Verrecchia. Role of YAP/TEAD and YAP/Smad signaling pathways in osteosarcoma tumor growth and lung metastasis dissemination [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr A07.

Osteosarcoma (OS) is the main malignant primary bone tumor in children and adolescents for whom the prognosis remains poor, especially when metastases are present at diagnosis. Because a) gene set enrichment analysis (GSEA) of expression data from a cohort of OS patients reveals a Hippo conserved signature in OS and b) proximity ligation (PLA) and immunoprecipitation (IP) assays have shown an interaction between YAP and TEAD, the main effector of Hippo signaling pathway, in OS cell lines, we investigated its implication in OS development. To elucidate the role of TEAD in YAP-driven OS development, we probed the consequences of YAP activation using overexpression of YAPS127A (constitutively active YAP) and YAPS94A (TEAD-binding deficient YAP protein). Firstly, in vivo and in vitro experiments demonstrate a) the crucial role of TEAD in YAP-driven cell proliferation and in vivo tumor growth and b) a correlation between the expression of TEAD1 and the survival outcomes of OS patients. In this context RNAseq analysis and GSEA identified more than 300 genes related to cell proliferation that are significantly overexpressed in YAPS127A cells compared to control cells and YAPS94A cells. Secondly, we study the effects of YAP/TEAD interactions on the main biologic functions’ links to metastasis dissemination. We show an increase of cell migration using KHOS-S94A and KHOS-S127A, suggesting that YAP/TEAD interaction is not necessary to increase migration in OS. GSEA identifies genes related to epithelial-mesenchymal-transition (EMT), cell migration and TGF-β that are significantly overexpressed in YAPS127A and YAPS94A cells, strongly suggesting that TEAD is not required in YAP-driven expression of genes related to EMT, cell migration, and TGF-β signaling. Thirdly, using PLA and IP, we show an interaction of YAP/SMAD3 in OS cell line independently of YAP/TEAD interaction. In this context, using Tβ²R1 inhibitor, SD-208, we demonstrate the role of TGF-β/smad signaling in YAP-driven cell migration and metastatic process in OS. Finally, we investigated the effect of verteporfin, identified as an inhibitor of the Hippo signaling pathway, on OS progression. In vivo experiments showed that verteporfin reduces primary tumor growth and lung metastases development. In vitro experiments demonstrated that verteporfin decreases cell viability and inhibits the TGF-β/Smad3 cascade and the response of TGF-β key targets involved in the metastasis dissemination process. Together, these results defined the specific role of TEAD and SMAD3 in YAP-driven OS tumor and lung metastatic process. In addition, we demonstrated that YAP could be considered as a therapeutic target in OS. Citation Format: Sarah Morice, Geoffroy Danieau, Mathilde Mullard, Jérôme Amiaud, Régis Brion, Sarah Renault, Robel Tesfaye, Maryne Dupuy, Julie Talbot, Benjamin Ory, Bénédicte Brounais-Le Royer, Isabelle Corre, Anne Brouchet-Gomez, Françoise Rédini, Franck Verrecchia. Respective role of TEAD and Smad signaling in YAP-mediated osteosarcoma tumor growth and lung metastatic development [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr A29.

Osteosarcoma is the most common malignant bone tumor in the pediatric population, representing around 4 cases per million people per year in the world. Patient survival is closely related to the response of tumor cells to chemotherapy, reaching 70% at 5 years for patients with localized disease, but only 25% for high-risk patients with relapsed or metastatic disease. In 20% of cases, patients have detectable metastases at diagnosis, preferentially in the lungs, which is a sign of poor prognosis. However, it is estimated that around 80% of patients have pulmonary micrometastases, sometimes undetectable at diagnosis by imaging techniques. This makes metastatic dissemination a significant issue in the management of osteosarcoma. In addition, the survival rate has not evolved since the past decades and there is no current efficient therapy for these patients. Therefore, it is necessary to develop new therapeutic strategies. In this context, a dysregulation of the canonical Wnt signaling pathway (Wnt/β-catenin) has been reported in many osteosarcoma cases, but its implication in the development of primary and metastatic osteosarcoma is still controversial. An increase in β-catenin expression has been described in human osteosarcoma tissues compared to normal bones. Thus, we evaluated the antitumor potential of ICG-001, a small molecule that specifically binds to the transcriptional co-activator CREB-Binding Protein (CBP), disrupting its interaction with β-catenin and thus suppressing the Wnt/β-catenin target gene expression. First, we demonstrated that ICG-001 inhibits β-catenin/CBP-dependent transcription as evaluated by TCF-LEF reporter assay and RT-qPCR on β-catenin target genes in three human osteosarcoma cell lines, KHOS, MG63, and SJSA1. Moreover, ICG-001 decreases proliferation of osteosarcoma cells in a dose- and time-dependent manner, associated with a cell cycle blockade in G0/G1 phase after 24h of treatment, but without any effect on cell death. However, surprisingly, ICG-001 promotes KHOS, MG63, and SJSA1 cell migration in vitro and the development of pulmonary metastases in a murine xenograft model of osteosarcoma induced by injection of KHOS cells in a paratibial site. This study therefore raises new questions about the role of the Wnt/β-catenin pathway in the metastatic development of osteosarcoma. Thus, it is necessary to identify the different signatures of the signaling pathways potentially activated after disruption of the β-catenin and CBP interaction in osteosarcoma cells and responsible for the prometastatic effect of this drug. Citation Format: Geoffroy Danieau, Sarah Morice, Sarah Renault, Kevin Biteau, Régis Brion, Jérôme Amiaud, Frédéric Lezot, Franck Verrecchia, Françoise Rédini, Bénédicte Brounais-Le Royer. Prometastatic effect of ICG-001, a β-catenin/CBP dependent transcription inhibitor, in osteosarcoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B26.

Background: Osteosarcoma is the most frequent form of malignant pediatric bone tumor. Despite the current therapeutic arsenal, patient life-expectancy remains low if metastases are detected at the time of diagnosis, justifying research into better knowledge at all stages of osteosarcoma ontogenesis and identification of new therapeutic targets. Receptor Activator of Nuclear factor &kappa, B (RANK)expression has been reported in osteosarcoma cells, raising the question of Receptor Activator of Nuclear factor &kappa, B Ligand (RANKL)/RANK signaling implications in these tumor cells (intrinsic), in addition to previously reported implications through osteoclast activation in the tumor microenvironment (extrinsic). Methods: Based on in vitro and in vivo experimentations using human and mouse osteosarcoma cell lines, the consequences on the main cellular processes of RANK expression in osteosarcoma cells were analyzed. Results: The results revealed that RANK expression had no impact on cell proliferation and tumor growth, but stimulated cellular differentiation and, in an immune-compromised environment, increased the number of lung metastases. The analysis of RANKL, RANK and osteoprotegerin (OPG) expressions in biopsies of a cohort of patients revealed that while RANK expression in osteosarcoma cells was not significantly different between patients with or without metastases at the time of diagnosis, the OPG/RANK ratio decreased significantly. Conclusion: Altogether, these results are in favor of RANKL-RANK signaling inhibition as an adjuvant for the treatment of osteosarcoma.

International audience; In vitro and in vivo discrepancy in inducing apoptosis by mesenchymal stromal cells delivering membrane-bound tumor necrosis factorÀrelated apoptosis inducing ligand in osteosarcoma pre-clinical models Abstract Background: Osteosarcoma (OS) is the most frequent pediatric malignant bone tumor. OS patients have not seen any major therapeutic progress in the last 30 years, in particular in the case of metastatic disease, which requires new therapeutic strategies. The pro-apoptotic cytokine Tumor necrosis factor (TNF)ÀRelated Apoptosis Inducing Ligand (TRAIL) can selectively kill tumor cells while sparing normal cells, making it a promising therapeutic tool in several types of cancer. However, many OS cell lines appear resistant to recombinant human (rh)TRAIL-induced apoptosis. We, therefore, hypothesized that TRAIL presentation at the membrane level of carrier cells might overcome this resistance and trigger apoptosis. Methods: To address this, human adipose mesenchymal stromal cells (MSCs) transfected in a stable manner to express membrane-bound full-length human TRAIL (mbTRAIL) were co-cultured with several human OS cell lines. Results: This induced apoptosis by cell-to-cell contact even in cell lines initially resistant to rhTRAIL. In contrast, mbTRAIL delivered by MSCs was not able to counteract tumor progression in this OS orthotopic model. Discussion: This was partly due to the fact that MSCs showed a potential to support tumor development. Moreover, the expression of mbTRAIL did not show caspase activation in adjacent tumor cells.

International audience; Although it has been demonstrated that human bone marrow stromal cells (hBMSCs) express the ubiquitous connexin43 (Cx43) and form functional gap junctions, their role in the early differentiation of hBMSCs into osteoblasts remains poorly documented. Using in vitro assays, we show that Cx43 expression and gap junctional intercellular communication (GJIC) are increased during the differentiation of hBMSCs into osteoblasts, both at the protein and mRNA levels. Two independent procedures to reduce GJIC, a pharmacological approach with GJIC inhibitors (18α-glycyrrhetinic acid and Gap27 peptide) and a molecular approach using small interfering RNA against Cx43, demonstrated that the presence of Cx43 and functional junctional channels are essential to the ability of hBMSCs to differentiate into osteoblasts in vitro. In addition, a reduced GJIC decreases the expression of Runx2, the major transcription factor implicated in the control of osteoblast commitment and early differentiation of hBMSCs into osteoblasts, suggesting that GJIC mediated by Cx43 is implicated in this process. Together our results demonstrate that GJIC mediated by the Cx43 channels plays a central role throughout the differentiation of hBMSC into osteoblasts, from the early stages to the process of mineralization. K E Y W O R D S cell differentiation, connexin43, gap junction, human bone marrow stromal cells, intercellular communication, osteoblast

International audience; Humans are chronically exposed to multiple environmental pollutants such as pesticides with no significant evidence about the safety of such poly-exposures. We exposed mesenchymal stem cells (MSC) to very low doses of mixture of seven pesticides frequently detected in food samples for 21 days in vitro. We observed a permanent phenotype modification with a specific induction of an oxidative stress-related senescence. Pesticide mixture also induced a shift in MSC differentiation towards adipogenesis but did not initiate a tumorigenic transformation. In modified MSC in which a premalignant phenotype was induced, the exposure to pesticide mixture promoted tumorigenic phenotype both in vitro and in vivo after cell implantation, in all nude mice. Our results suggest that a common combination of pesticides can induce a premature ageing of adult MSC, and as such could accelerate age-related diseases. Exposure to pesticide mixture may also promote the tumorigenic transformation in a predisposed stromal environment. STEM CELLS 2017;35:800-811 SIGNIFICANCE STATEMENT The environmental exposure to pesticides is recognized as a potential threat to human health. However, little is known on the effect of pesticides on stem cells. Here we show that a pesticide mixture, at doses commonly found in western diet, promotes stress-related senescence in normal MSC and tumorigenesis in premalignant MSC. Our results provide a new insight in the effect of pesticides on the acceleration of stem cell ageing and possibly on cancer.

Cutibacterium acnes (formerly Propionibacterium acnes) is recognized as a pathogen in foreign-body infections (arthroplasty or spinal instrumentation). To date, the direct impact of C. acnes on bone cells has never been explored. The clade of 11 C. acnes clinical isolates was determined by MLST. Human osteoblasts and osteoclasts were infected by live C. acnes. The whole genome sequence of six isolates of this collection was analyzed. CC36 C. acnes strains were significantly less internalized by osteoblasts and osteoclasts than CC18 and CC28 C. acnes strains (p ≤ 0.05). The CC18 C. acnes ATCC6919 isolate could survive intracellularly for at least 96 hours. C. acnes significantly decreased the resorption ability of osteoclasts with a major impact by the CC36 strain (p ≤ 0.05). Genome analysis revealed 27 genes possibly linked to these phenotypic behaviors. We showed a direct impact of C. acnes on bone cells, providing new explanations about the development of C. acnes foreign-body infections.

Background. Macrophages and synovial fibroblasts (SF) are two major cells implicated in the pathogenesis of rheumatoid arthritis (RA). SF could be a source of cytokines and growth factors driving macrophages survival and activation. Here, we studied the effect of SF on monocyte viability and phenotype.Methods. SF were isolated from synovial tissue of RA patients and CD14+ cells were isolated from peripheral blood of healthy donors. SF conditioned media were collected after 24 hours of culture with or without stimulation with TNFαor IL-1β. Macrophages polarisation was studied by flow cytometry.Results. Conditioned medium from SF significantly increased monocytes viability by 60% compared to CD14+ cells cultured in medium alone(P<0.001). This effect was enhanced using conditioned media from IL-1βand TNFαstimulated SF. GM-CSF but not M-CSF nor IL34 blocking antibodies was able to significantly decrease monocyte viability by 30% when added to the conditioned media from IL-1βand TNFαstimulated SF(P<0.001). Finally, monocyte cultured in presence of SF conditioned media did not exhibit a specific M1 or M2 phenotype.Conclusion. Overall, rheumatoid arthritis synovial fibroblasts stimulated with proinflammatory cytokines (IL-1βand TNFα) promote monocyte viability via GM-CSF but do not induce a specific macrophage polarization.

Ewing's sarcoma (ES) is a primary bone tumor characterized by a chromosomic translocation between the EWS gene and a member of the ETS gene family, mainly FLI1, which leads to an aberrant transcription factor EWS–FLI1 that promotes tumorigenicity. Gap junctions are intercellular channels composed of transmembrane proteins (connexin: Cx), that allow direct intercellular communication between adjacent cells. Numerous studies have shown that tumorigenesis may be associated with a loss of gap junctional intercellular communication (GJIC). Loss of Cx43 expression was observed at the protein and mRNA levels in ES cell lines compared to those measured in human mesenchymal stem cells. A673 ES cells stably transfected with an shRNA targeting EWS–FLI1 showed an increase in Cx43 expression (at the mRNA, protein and transcriptional levels) and GJIC. In an osteolytic murine model of ES, the overexpression of Cx43 in ES cells dramatically reduced tumor growth, leading to a significant increase in animal survival. In vitro assays showed that Cx43 overexpression increases the p27 level with an associated marked decrease of Rb phosphorylation, consistent with the observed blockade of the cell cycle in G0/G1 phase. In addition, the bone microarchitectural parameters, assessed by micro-CT analysis, showed an increased bone volume when Cx43 expression was enhanced. Histological analysis demonstrated that the overexpression of Cx43 in ES tumor cells inhibits osteoclast activity and therefore bone resorption. Our study demonstrated that the loss of Cx43 expression in ES cells plays a crucial role in the development of the primary tumor and the associated bone osteolysis.

IL-34 is a proinflammatory cytokine implicated in rheumatoid arthritis (RA). The current study aimed to assess the IL-34 expression in response to two members of the transforming growth factor (TGF)-β family, TGF-β1 and bone morphogenetic protein (BMP)-2, in synovial fibroblasts from RA patients. IL-34, TGF-β1, and BMP-2 productions were measured in patient synovial fluids by enzyme-linked immunosorbent assay. IL-34 mRNA levels were quantified by real-time quantitative PCR in human synovial fibroblasts and murine mesenchymal stem cells. Pharmacologic inhibitions were used to determine the involvement of activin receptor-like kinase 1 (ALK1) and ALK5 downstream TGF-β1 and BMP-2. IL-34, TGF-β1, and BMP-2 were expressed in synovial fluids from RA patients. We found a significant correlation between IL-34 and TGF-β1 expressions. Levels of both IL-34 and TGF-β1 were thus correlated with the total leukocyte counts in the synovial fluids. TGF-β1 and BMP-2 decreased IL-34 expression in the synovial fibroblasts or in murine mesenchymal stem cells in a dose- and time-dependent manner through ALK5 and ALK1 pathways, respectively. In addition, TGF-β1 and BMP-2 antagonized tumor necrosis factor α–induced IL-34 gene expression. This work identifies TGF-β1 and BMP-2 as potent inhibitors of IL-34 expression in RA synovial fibroblasts. These cytokines, as upstream inhibitors of IL-34, may thus contribute to antagonize inflammation and bone erosions in RA.

Bone resorption by osteoclasts and bone formation by osteoblasts are tightly coupled processes implicating factors in TNF, bone morphogenetic protein, and Wnt families. In osteoimmunology, macrophages were described as another critical cell population regulating bone formation by osteoblasts but the coupling factors were not identified. Using a high-throughput approach, we identified here Oncostatin M (OSM), a cytokine of the IL-6 family, as a major coupling factor produced by activated circulating CD14+ or bone marrow CD11b+ monocytes/macrophages that induce osteoblast differentiation and matrix mineralization from human mesenchymal stem cells while inhibiting adipogenesis. Upon activation of toll-like receptors (TLRs) by lipopolysaccharide or endogenous ligands, OSM was produced in classically activated inflammatory M1 and not M2 macrophages, through a cyclooxygenase-2 and prostaglandin-E2 regulatory loop. Stimulation of osteogenesis by activated monocytes/macrophages was prevented using neutralizing antibodies or siRNA to OSM, OSM receptor subunits gp130 and OSMR, or to the downstream transcription factor STAT3. The induced osteoblast differentiation program culminated with enhanced expression of CCAAT-enhancer-binding protein δ, Cbfa1, and alkaline phosphatase. Overexpression of OSM in the tibia of mice has led to new bone apposition with no sign of bone resorption. Two other cytokines have also a potent role in bone formation induced by monocytes/macrophages and activation of TLRs: IL-6 and leukemia inhibitory factor. We propose that during bone inflammation, infection, or injury, the IL-6 family signaling network activated by macrophages and TLR ligands stimulates bone formation that is largely uncoupled from bone resorption and is thus an important target for anabolic bone therapies. Disclosure of potential conflicts of interest is found at the end of this article.

International audience; Interleukin-34 (IL-34) is a newly-discovered homodimeric cytokine that regulates, like Macrophage Colony-Stimulating Factor (M-CSF), the differentiation of the myeloid lineage through M-CSF receptor (M-CSFR) signaling pathways. To date, both cytokines have been considered as competitive cytokines with regard to the M-CSFR. The aim of the present work was to study the functional relationships of these cytokines on cells expressing the M-CSFR. We demonstrate that simultaneous addition of M-CSF and IL-34 led to a specific activation pattern on the M-CSFR, with higher phosphorylation of the tyrosine residues at low concentrations. Similarly, both cytokines showed an additive effect on cellular proliferation or viability. In addition, BIAcore experiments demonstrated that M-CSF binds to IL-34, and molecular docking studies predicted the formation of a heteromeric M-CSF/IL-34 cytokine. A proximity ligation assay confirmed this interaction between the cytokines. Finally, co-expression of the M-CSFR and its ligands differentially regulated M-CSFR trafficking into the cell. This study establishes a new foundation for the understanding of the functional relationship between IL-34 and M-CSF, and gives a new vision for the development of therapeutic approaches targeting the IL-34/M-CSF/M-CSFR axis.

The development of osteosarcoma, the most common malignant primary bone tumor is characterized by a vicious cycle established between tumor proliferation and paratumor osteolysis. This osteolysis is mainly regulated by the receptor activator of nuclear factor κB ligand (RANKL). Preclinical studies have demonstrated that Rankl blockade by soluble receptors is an effective strategy to prevent osteolytic lesions leading to osteosarcoma inhibition. A new therapeutic option could be to directly inhibit Rankl expression by small interfering RNAs (Rkl-siRNAs) and combine these molecules with chemotherapy to counteract the osteosarcoma development more efficiently. An efficient siRNA sequence directed against both mouse and rat mRNAs coding Rankl was first validated in vitro and tested in two models of osteosarcoma: a syngenic osteolytic POS-1 model induced in immunocompetent mice and a xenograft osteocondensant model of rat OSRGA in athymic mice. Intratumor injections of Rankl-directed siRNAs in combination with the cationic liposome RPR209120/DOPE reduced the local and systemic Rankl production and protected bone from paratumor osteolysis. Although Rkl-siRNAs alone had no effect on tumor development in both osteosarcoma models, it significantly blocked tumor progression when combined with ifosfamide compared with chemotherapy alone. Our results indicate that siRNAs could be delivered using cationic liposomes and thereby could inhibit Rankl production in a specific manner in osteosarcoma models. Moreover, the Rankl inhibition mediated by RNA interference strategy improves the therapeutic response of primary osteosarcoma to chemotherapy.

Interleukin-34 (IL-34) is a newly discovered regulator of myeloid lineage differentiation, proliferation, and survival, acting via the macrophage-colony stimulating factor receptor (M-CSF receptor, c-fms). M-CSF, the main ligand for c-fms, is required for osteoclastogenesis and has been already identified as a critical contributor of the pathogenesis of giant cell tumours of bone (GCTs), tumours rich in osteoclasts. According to the key role of M-CSF in osteoclastogenesis and GCTs, the expression of IL-34 in human GCTs was first assessed. Quantitative analysis of IL-34 mRNA expression in 14 human GCTs revealed expression of this cytokine in GCTs as well as M-CSF and c-fms. Immunohistochemistry demonstrated that osteoclast-like cells exhibited a huge immunostaining for IL-34 and that mononuclear stromal cells were slightly positive for this protein. In contrast to osteoblasts, bone-resorbing osteoclasts showed very strong staining for IL-34, suggesting its potential role in the pathogenesis of GCTs by facilitating osteoclast formation. The role of IL-34 in osteoclastogenesis was then studied in murine and human models. IL-34 was able to support RANKL-induced osteoclastogenesis in the absence of M-CSF in all models. Multinucleated cells generated in the presence of IL-34 and RANKL expressed specific osteoclastic markers and resorbed dentine. IL-34 induced phosphorylation of ERK 1/2 and Akt through the activation of c-fms, as revealed by the inhibition of signalling by a specific c-fms tyrosine kinase inhibitor. Furthermore, IL-34 stimulated RANKL-induced osteoclastogenesis by promoting the adhesion and proliferation of osteoclast progenitors, and had no effect on osteoclast survival. Overall, these data reveal that IL-34 can be entirely substituted for M-CSF in RANKL-induced osteoclastogenesis, thus identifying a new biological activity for this cytokine and a contribution to the pathogenesis of GCTs.

Heme oxygenase-1 (HO-1) exerts its functions via the catabolism of heme into carbon monoxide (CO), Fe2+, and biliverdin, as well as by depletion of free heme. We have recently described that overexpression of HO-1 is associated with the tolerogenic capacity to dendritic cells (DCs) stimulated by LPS. In this study, we demonstrate that treatment of human monocyte-derived DCs with CO blocks TLR3 and 4-induced phenotypic maturation, secretion of proinflammatory cytokines, and alloreactive T cell proliferation, while preserving IL-10 production. Treatment of DCs with biliverdin, bilirubin, and deferoxamine or replenishing intracellular heme stores had no effect on DC maturation. HO-1 and CO inhibited LPS-induced activation of the IFN regulatory factor 3 pathway and their effects were independent of p38, ERK, and JNK MAPK. HO-1 and CO treatment also inhibited mouse DC maturation in vitro and mouse DC immunogenic properties in vivo, as shown by adoptive cell transfer in a transgenic model of induced diabetes. Thus, for the first time, our data show that CO treatment inhibits DC immunogenicity induced by TLR ligands and that blockade of IFN regulatory factor 3 is associated with this effect.

We have previously shown that human monocyte-derived dendritic cells (DC) express indoleamine 2,3-dioxygenase (IDO), as well as several other enzymes of the kynurenine pathway at the mRNA level upon maturation. The tolerogenic mechanisms of this pathway remain unclear. Here we show that LPS-treated DC metabolize tryptophan as far as quinolinate. We found that IDO contributes to LPS and TNF-alpha + poly(I:C)-induced DC maturation since IDO inhibition using two different inhibitors impairs DC maturation. IDO knock-down using short-hairpin RNA also led to diminished LPS-induced maturation. In line with these results, the tryptophan-derived catabolites 3-hydroxyanthranilic acid and 3-hydroxykynurenine increased maturation of LPS-treated DC. Concerning the molecular mechanisms of this effect, IDO acts as an intermediate pathway in LPS-induced production of reactive oxygen species and NF-kappaB activation, two processes that lead to DC maturation. Finally, we show that mature DC expand CD4(+)CD25(high) regulatory T cells in an IDO-dependent manner. In conclusion, we show that IDO constitutes an intermediate pathway in DC maturation leading to expansion of CD4(+)CD25(high) regulatory T cells.

International audience; One sentence summary: This study describes the interaction of Escherichia coli clinical strains with an osteoblastic cell line, showing no internalization unlike Staphylococcus aureus, but a strong cytotoxicity of the Hly-A producing strains. Editor: Patrik M. Bavoil ABSTRACT Escherichia coli is one of the first causes of Gram-negative orthopedic implant infections (OII), but little is known about the pathogenicity of this species in such infections that are increasing due to the ageing of the population. We report how this pathogen interacts with human osteoblastic MG-63 cells in vitro, by comparing 20 OII E. coli strains to two Staphylococcus aureus and two Pseudomonas aeruginosa strains. LDH release assay revealed that 6/20 (30%) OII E. coli induced MG-63 cell lysis whereas none of the four control strains was cytotoxic after 4 h of coculture. This high cytotoxicity was associated with hemolytic properties and linked to hlyA gene expression. We further showed by gentamicin protection assay and confocal microscopy that the non-cytotoxic E. coli were not able to invade MG-63 cells unlike S. aureus strains (internalization rate

Primary cancer cell dissemination is a key event during the metastatic cascade, but context-specific determinants of this process remain largely undefined. Multiple reports have suggested that the p53 (TP53) family member p63 (TP63) plays an antimetastatic role through its minor epithelial isoform containing the N-terminal transactivation domain (TAp63). However, the role and contribution of the major p63 isoform lacking this domain, ΔNp63α, remain largely undefined. Here, we report a distinct and TAp63-independent mechanism by which ΔNp63α-expressing cells within a TGFβ-rich microenvironment become positively selected for metastatic dissemination. Orthotopic transplantation of ΔNp63α-expressing human osteosarcoma cells into athymic mice resulted in larger and more frequent lung metastases than transplantation of control cells. Mechanistic investigations revealed that ΔNp63α repressed miR-527 and miR-665, leading to the upregulation of two TGFβ effectors, SMAD4 and TβRII (TGFBR2). Furthermore, we provide evidence that this mechanism reflects a fundamental role for ΔNp63α in the normal wound-healing response. We show that ΔNp63α-mediated repression of miR-527/665 controls a TGFβ-dependent signaling node that switches off antimigratory miR-198 by suppressing the expression of the regulatory factor, KSRP (KHSRP). Collectively, these findings reveal that a novel miRNA network involved in the regulation of physiologic wound-healing responses is hijacked and suppressed by tumor cells to promote metastatic dissemination. Cancer Res; 76(11); 3236–51. ©2016 AACR.

International audience; Interleukin-34 (IL-34) was recently characterized as the M-CSF "twin" cytokine, regulating the proliferation/differentiation/survival of myeloid cells. The implication of M-CSF in oncology was initially suspected by the reduced metastatic dissemination in knock-out mice, due to angiogenesis impairment. Based on this observation, our work studied the involvement of IL-34 in the pathogenesis of osteosarcoma. The in vivo effects of IL-34 were assessed on tissue vasculature and macrophage infiltration in a murine preclinical model based on a paratibial inoculation of human osteosarcoma cells overexpressing or not IL-34 or M-CSF. In vitro investigations using endothelial cell precursors and mature HUVEC cells were performed to analyse the involvement of IL-34 in angiogenesis and myeloid cell adhesion. The data revealed that IL-34 overexpression was associated with the progression of osteosarcoma (tumor growth, lung metastases) and an increase of neo-angiogenesis. In vitro analyses demonstrated that IL-34 stimulated endothelial cell proliferation and vascular cord formation. Pre-treatment of endothelial cells by chondroitinases/heparinases reduced the formation of vascular tubes and abolished the associated cell signalling. In addition, IL-34 increased the in vivo recruitment of M2 tumor-associated macrophages into the tumor tissue. IL-34 increased in vitro monocyte/CD34(+) cell adhesion to activated HUVEC monolayers under physiological shear stress conditions. This work also demonstrates that IL-34 is expressed by osteosarcoma cells, is regulated by TNF-α, IL-1β, and contributes to osteosarcoma growth by increasing the neo-angiogenesis and the recruitment of M2 macrophages. By promoting new vessel formation and extravasation of immune cells, IL-34 may play a key role in tumor development and inflammatory diseases.

International audience; OBJECTIVE/BACKGROUND:Arterial calcification, a process that mimics bone formation, is an independent risk factor of cardiovascular morbidity and mortality, and has a significant impact on surgical and endovascular procedures and outcomes. Research efforts have focused mainly on the coronary arteries, while data regarding the femoral territory remain scarce.METHODS:Femoral endarterectomy specimens, clinical data, and plasma from a cohort of patients were collected prospectively. Histological analysis was performed to characterize the cellular populations present in the atherosclerotic lesions, and that were potentially involved in the formation of bone like arterial calcification known as osteoid metaplasia (OM). Enzyme linked immunosorbent assays and cell culture assays were conducted in order to understand the cellular and molecular mechanisms underlying the formation of OM in the lesions.RESULTS:Twenty-eight of the 43 femoral plaques (65%) displayed OM. OM included osteoblast and osteoclast like cells, but very few of the latter exhibited the functional ability to resorb mineral tissue. As in bone, osteoprotegerin (OPG) was significantly associated with the presence of OM (p = .04). Likewise, a high plasma OPG/receptor activator for the nuclear factor kappa B ligand (RANKL) ratio was significantly associated with the presence of OM (p = .03). At the cellular level, there was a greater presence of pericytes in OM+ compared with OM- lesions (5.59 ± 1.09 vs. 2.42 ± 0.58, percentage of area staining [region of interest]; p = .04); in vitro, pericytes were able to inhibit the osteoblastic differentiation of human mesenchymal stem cells, suggesting that they are involved in regulating arterial calcification.CONCLUSION:These results suggest that bone like arterial calcification (OM) is highly prevalent at femoral level. Pericyte cells and the OPG/RANK/RANKL triad seem to be critical to the formation of this ectopic osteoid tissue and represent interesting potential therapeutic targets to reduce the clinical impact of arterial calcification.

International audience; Receptor activator of nuclear factor kappa-B (RANK) and RANK-ligand are relevant targets for the treatment of polyethylene particle-induced osteolysis. This study assessed the local administration of siRNA, targeting both human RANK and mouse Rank transcripts in a mouse model. Four groups of mice were implanted with polyethylene (PE) particles in the calvaria and treated locally with 2.5, 5 and 10 mg of RANK siRNA or a control siRNA delivered by the cationic liposome DMAPAP/DOPE. The tissues were harvested at day 9 after surgery and evaluated by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) immunohistochemistry for macrophages and osteoblasts, and gene relative expression of inflammatory and osteolytic markers. 10 mu g of RANK siRNA exerted a protective effect against PE particle-induced osteolysis, decreasing the bone loss and the osteoclastogenesis, demonstrated by the significant increase in the bone volume (P < 0.001) and by the reduction in both the number of TRAP cells and osteoclast activity (P < 0.01). A bone anabolic effect demonstrated by the formation of new trabecular bone was confirmed by the increased immunopositive staining for osteoblast-specific proteins. In addition, 5 and 10 mu g of RANK siRNA downregulated the expression of pro-inflammatory cytokines (P < 0.01) without depletion of macrophages. Our findings show that RANK siRNA delivered locally by a synthetic vector may be an effective approach for reducing osteolysis and may even stimulate bone formation in aseptic loosening of prosthetic implants. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Heme oxygenase-1 (HO-1) is an intracellular enzyme that degrades heme and inhibits immune responses and inflammation in vivo. In most cell types, HO-1 is inducible by inflammatory stimuli and oxidative stress. Here we demonstrate that human monocyte-derived immature dendritic cells (iDCs) and several but not all freshly isolated rat splenic DC subsets and rat bone marrow-derived iDCs, spontaneously express HO-1. HO-1 expression drastically decreases during human and rat DC maturation induced in vitro. In human tissues, iDCs also express HO-1, whereas mature DCs do not. Induction of HO-1 expression with cobalt protoporphyrin (CoPP) in human and rat DCs inhibits lipopolysaccharide (LPS)-induced phenotypic maturation and secretion of proinflammatory cytokines, resulting in the inhibition of alloreactive T-cell proliferation. CoPP-treated DCs, however, retain the ability to produce the anti-inflammatory cytokine interleukin 10 (IL-10). Reactive oxygen species induced by LPS in DCs were inhibited by induction of HO-1. In conclusion, we identify, for the first time, the capacity of HO-1 to block maturation of DCs and to inhibit proinflammatory and allogeneic immune responses while preserving IL-10 production. This novel immune function for HO-1 may be of interest for the inhibition of immune responses in autoimmune diseases, transplantation, and other conditions involving activation of the immune system. (Blood. 2005;106:1694-1702)

Interleukin-34 (IL-34) was recently characterized as the M-CSF "twin" cytokine, regulating the proliferation/differentiation/survival of myeloid cells. The implication of M-CSF in oncology was initially suspected by the reduced metastatic dissemination in knock-out mice, due to angiogenesis impairment. Based on this observation, our work studied the involvement of IL-34 in the pathogenesis of osteosarcoma. The in vivo effects of IL-34 were assessed on tissue vasculature and macrophage infiltration in a murine preclinical model based on a paratibial inoculation of human osteosarcoma cells overexpressing or not IL-34 or M-CSF. In vitro investigations using endothelial cell precursors and mature HUVEC cells were performed to analyse the involvement of IL-34 in angiogenesis and myeloid cell adhesion. The data revealed that IL-34 overexpression was associated with the progression of osteosarcoma (tumor growth, lung metastases) and an increase of neo-angiogenesis. In vitro analyses demonstrated that IL-34 stimulated endothelial cell proliferation and vascular cord formation. Pre-treatment of endothelial cells by chondroitinases/heparinases reduced the formation of vascular tubes and abolished the associated cell signalling. In addition, IL-34 increased the in vivo recruitment of M2 tumor-associated macrophages into the tumor tissue. IL-34 increased in vitro monocyte/CD34(+) cell adhesion to activated HUVEC monolayers under physiological shear stress conditions. This work also demonstrates that IL-34 is expressed by osteosarcoma cells, is regulated by TNF-α, IL-1β, and contributes to osteosarcoma growth by increasing the neo-angiogenesis and the recruitment of M2 macrophages. By promoting new vessel formation and extravasation of immune cells, IL-34 may play a key role in tumor development and inflammatory diseases.