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Abstract
Siglecs (sialic acid-binding immunoglobulin-like lectins) are a family of vertebrate glycan-binding cell-surface proteins. The majority mediate cellular inhibitory activity once engaged by specific ligands or ligand-mimicking molecules. As a result, Siglec engagement is now of interest as a strategy to therapeutically dampen unwanted cellular responses. When considering allergic inflammation, human eosinophils and mast cells express overlapping but distinct patterns of Siglecs. For example, Siglec-6 is selectively and prominently expressed on mast cells while Siglec-8 is highly specific for both eosinophils and mast cells. This review will focus on a subset of Siglecs and their various endogenous or synthetic sialoside ligands that regulate eosinophil and mast cell function and survival. It will also summarize how certain Siglecs have become the focus of novel therapies for allergic and other eosinophil- and mast cell-related diseases.
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Affiliation(s)
- Jeremy A O'Sullivan
- Division of Allergy and Immunology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | | | - Robert P Schleimer
- Division of Allergy and Immunology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Bruce S Bochner
- Division of Allergy and Immunology, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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Smiljkovic D, Herrmann H, Sadovnik I, Gamperl S, Berger D, Stefanzl G, Eisenwort G, Hoermann G, Kopanja S, Dorofeeva Y, Focke-Tejkl M, Jaksch P, Hoetzenecker K, Szepfalusi Z, Valenta R, Arock M, Valent P. Expression and regulation of Siglec-6 (CD327) on human mast cells and basophils. J Allergy Clin Immunol 2023; 151:202-211. [PMID: 35953001 DOI: 10.1016/j.jaci.2022.07.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 07/22/2022] [Accepted: 07/29/2022] [Indexed: 02/04/2023]
Abstract
BACKGROUND Mast cells (MC) and basophils are effector cells of allergic reactions and display a number of activation-linked cell surface antigens. Of these antigens, however, only a few are functionally relevant and specifically expressed in these cells. OBJECTIVE We sought to identify MC- and basophil-specific surface molecules and to study their cellular distribution and regulation during cytokine-induced and IgE-dependent activation. METHODS Multicolor flow cytometry was performed to recognize surface antigens and to determine changes in antigen expression upon activation. RESULTS We identified Siglec-6 (CD327) as a differentially regulated surface antigen on human MC and basophils. In the bone marrow, Siglec-6 was expressed abundantly on MC in patients with mastocytosis and in reactive states, but it was not detected on other myeloid cells, with the exception of basophils and monocytes. In healthy individuals, allergic patients, and patients with chronic myeloid leukemia (CML), Siglec-6 was identified on CD203c+ blood basophils, a subset of CD19+ B lymphocytes, and few CD14+ monocytes, but not on other blood leukocytes. CML basophils expressed higher levels of Siglec-6 than normal basophils. IL-3 promoted Siglec-6 expression on normal and CML basophils, and stem cell factor increased the expression of Siglec-6 on tissue MC. Unexpectedly, IgE-dependent activation resulted in downregulation of Siglec-6 in IL-3-primed basophils, whereas in MC, IgE-dependent activation augmented stem cell factor-induced upregulation of Siglec-6. CONCLUSIONS Siglec-6 is a dynamically regulated marker of MC and basophils. Activated MC and basophils exhibit unique Siglec-6 responses, including cytokine-dependent upregulation and unique, cell-specific, responses to IgE-receptor cross-linking.
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Affiliation(s)
- Dubravka Smiljkovic
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria; Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria
| | - Harald Herrmann
- Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria; Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Irina Sadovnik
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria; Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria
| | - Susanne Gamperl
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria
| | - Daniela Berger
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria
| | - Gabriele Stefanzl
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria
| | - Gregor Eisenwort
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria; Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria
| | - Gregor Hoermann
- Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria; MLL Munich Leukemia Laboratory, Munich, Germany
| | - Sonja Kopanja
- Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, Vienna, Austria
| | - Yulia Dorofeeva
- Department of Pathophysiology, Division of Immunopathology, Center for Pathophysiology, Immunology, and Infectiology, Medical University of Vienna, Vienna, Austria
| | - Margarete Focke-Tejkl
- Department of Pathophysiology, Division of Immunopathology, Center for Pathophysiology, Immunology, and Infectiology, Medical University of Vienna, Vienna, Austria; Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Peter Jaksch
- Department of Thoracic Surgery, Medical University of Vienna, Vienna, Austria
| | - Konrad Hoetzenecker
- Department of Thoracic Surgery, Medical University of Vienna, Vienna, Austria
| | - Zsolt Szepfalusi
- Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, Vienna, Austria
| | - Rudolf Valenta
- Department of Pathophysiology, Division of Immunopathology, Center for Pathophysiology, Immunology, and Infectiology, Medical University of Vienna, Vienna, Austria; Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Michel Arock
- Laboratory of Hematology, Pitié-Salpêtrière Hospital, Paris, France
| | - Peter Valent
- Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria; Ludwig Boltzmann Institute for Hematology and Oncology, Medical University of Vienna, Vienna, Austria.
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Stefanski AL, Renecle MD, Kramer A, Sehgal S, Narasimhan P, Rumer KK, Winn VD. Siglec-6 Signaling Uses Src Kinase Tyrosine Phosphorylation and SHP-2 Recruitment. Cells 2022; 11. [PMID: 36359823 DOI: 10.3390/cells11213427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 10/23/2022] [Accepted: 10/25/2022] [Indexed: 11/17/2022] Open
Abstract
Preeclampsia is a pregnancy-specific disorder involving placental abnormalities. Elevated placental Sialic acid immunoglobulin-like lectin (Siglec)-6 expression has been correlated with preeclampsia. Siglec-6 is a transmembrane receptor, expressed predominantly by the trophoblast cells in the human placenta. It interacts with sialyl glycans such as sialyl-TN glycans as well as binds leptin. Siglec-6 overexpression has been shown to influence proliferation, apoptosis, and invasion in the trophoblast (BeWo) cell model. However, there is no direct evidence that Siglec-6 plays a role in preeclampsia pathogenesis and its signaling potential is still largely unexplored. Siglec-6 contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) and an ITIM-like motif in its cytoplasmic tail suggesting a signaling function. Site-directed mutagenesis and transfection were employed to create a series of Siglec-6 expressing HTR-8/SVneo trophoblastic cell lines with mutations in specific functional residues to explore the signaling potential of Siglec-6. Co-immunoprecipitation and inhibitory assays were utilized to investigate the association of Src-kinases and SH-2 domain-containing phosphatases with Siglec-6. In this study, we show that Siglec-6 is phosphorylated at ITIM and ITIM-like domains by Src family kinases. Phosphorylation of both ITIM and ITIM-like motifs is essential for the recruitment of phosphatases like Src homology region 2 containing protein tyrosine phosphatase 2 (SHP-2), which has downstream signaling capabilities. These findings suggest Siglec-6 as a signaling molecule in human trophoblasts. Further investigation is warranted to determine which signaling pathways are activated downstream to SHP-2 recruitment and how overexpression of Siglec-6 in preeclamptic placentas impacts pathogenesis.
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Robida PA, Rische CH, Morgenstern NBB, Janarthanam R, Cao Y, Krier-Burris RA, Korver W, Xu A, Luu T, Schanin J, Leung J, Rothenberg ME, Wechsler JB, Youngblood BA, Bochner BS, O’Sullivan JA. Functional and Phenotypic Characterization of Siglec-6 on Human Mast Cells. Cells 2022; 11:1138. [PMID: 35406705 PMCID: PMC8997871 DOI: 10.3390/cells11071138] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/21/2022] [Accepted: 03/23/2022] [Indexed: 12/12/2022] Open
Abstract
Mast cells are tissue-resident cells that contribute to allergic diseases, among others, due to excessive or inappropriate cellular activation and degranulation. Therapeutic approaches to modulate mast cell activation are urgently needed. Siglec-6 is an immunoreceptor tyrosine-based inhibitory motif (ITIM)-bearing receptor selectively expressed by mast cells, making it a promising target for therapeutic intervention. However, the effects of its engagement on mast cells are poorly defined. Siglec-6 expression and endocytosis on primary human mast cells and mast cell lines were assessed by flow cytometry. SIGLEC6 mRNA expression was examined by single-cell RNAseq in esophageal tissue biopsy samples. The ability of Siglec-6 engagement or co-engagement to prevent primary mast cell activation was determined based on assessments of mediator and cytokine secretion and degranulation markers. Siglec-6 was highly expressed by all mast cells examined, and the SIGLEC6 transcript was restricted to mast cells in esophageal biopsy samples. Siglec-6 endocytosis occurred with delayed kinetics relative to the related receptor Siglec-8. Co-crosslinking of Siglec-6 with FcεRIα enhanced the inhibition of mast cell activation and diminished downstream ERK1/2 and p38 phosphorylation. The selective, stable expression and potent inhibitory capacity of Siglec-6 on human mast cells are favorable for its use as a therapeutic target in mast cell-driven diseases.
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Affiliation(s)
- Piper A. Robida
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
| | - Clayton H. Rische
- McCormick School of Engineering, Northwestern University, Evanston, IL 60208, USA;
| | - Netali Ben-Baruch Morgenstern
- Division of Allergy and Immunology, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA; (N.B.-B.M.); (M.E.R.)
| | - Rethavathi Janarthanam
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL 60611, USA;
| | - Yun Cao
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
| | - Rebecca A. Krier-Burris
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
| | - Wouter Korver
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - Alan Xu
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - Thuy Luu
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - Julia Schanin
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - John Leung
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - Marc E. Rothenberg
- Division of Allergy and Immunology, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA; (N.B.-B.M.); (M.E.R.)
| | - Joshua B. Wechsler
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL 60611, USA;
| | - Bradford A. Youngblood
- Allakos, Inc., Redwood City, CA 94065, USA; (W.K.); (A.X.); (T.L.); (J.S.); (J.L.); (B.A.Y.)
| | - Bruce S. Bochner
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
| | - Jeremy A. O’Sullivan
- Division of Allergy and Immunology, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (P.A.R.); (Y.C.); (R.A.K.-B.); (J.B.W.); (B.S.B.)
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Awoyemi T, Tannetta D, Zhang W, Kandzija N, Motta-Mejia C, Fischer R, Heilig R, Raiss S, Redman C, Vatish M. Glycosylated Siglec-6 expression in syncytiotrophoblast-derived extracellular vesicles from preeclampsia placentas. Biochem Biophys Res Commun 2020; 533:838-844. [PMID: 32998819 DOI: 10.1016/j.bbrc.2020.09.081] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 09/19/2020] [Indexed: 01/26/2023]
Abstract
INTRODUCTION Preeclampsia (PE) is associated with an exaggerated maternal systemic inflammatory response. Throughout gestation, the placenta releases extracellular vesicles through the syncytiotrophoblast layer (STB) into the maternal circulation and this is increased in PE. Expression of Siglec-6, a transmembrane receptor of molecular weight 50 KDa, is upregulated in PE placental tissue. METHODS Here we investigated respective abundance of Siglec-6 in PE -and normal pregnancy- (NP) derived placental lysates (PL) and syncytiotrophoblast-derived extracellular vesicles (STBEV). STBEV from PE and NP placentas were isolated through dual-lobe placental perfusion and serial ultracentrifugation. Siglec-6 was characterized by immunohistochemistry, immunoblotting, mass spectrometry (MS), and deglycosylation. RESULTS Immunoblotting revealed the expected Siglec-6 (50 KDa) band present in both PE and NP PL, however an additional heavier band was observed at 70 KDa only in PE PL, but not in NP. When interrogating STBEV we saw an absence of the expected 50 KDa band but the 70 KDa was present predominantly only in the PE STBEV. Deglycosylation of PL and STBEV from PE showed that the 70 KDa and the 50 KDa bands were reduced to 48 KDa, suggesting glycosylation. Both 48 KDa and 70 KDa bands were subjected to MS, confirming Siglec-6 expression in both. DISCUSSION Our data shows that the inability to detect Siglec-6 in circulation might be due to the placenta secreting STBEV carrying a modified glycosylated form of Siglec-6 with a 70 KDa molecular weight, significantly and uniquely upregulated in PE STBEV.
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Affiliation(s)
- Toluwalase Awoyemi
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Dionne Tannetta
- School of Pharmacy, University of Reading, Reading, United Kingdom
| | - Wei Zhang
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Neva Kandzija
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Carolina Motta-Mejia
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Roman Fischer
- Discovery Proteomics Facility, Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, United Kingdom
| | - Raphael Heilig
- Discovery Proteomics Facility, Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, United Kingdom
| | - Sina Raiss
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Christopher Redman
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Manu Vatish
- Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, United Kingdom.
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Yu Y, Blokhuis BRJ, Diks MAP, Keshavarzian A, Garssen J, Redegeld FA. Functional Inhibitory Siglec-6 Is Upregulated in Human Colorectal Cancer-Associated Mast Cells. Front Immunol 2018; 9:2138. [PMID: 30294327 PMCID: PMC6159741 DOI: 10.3389/fimmu.2018.02138] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 08/30/2018] [Indexed: 12/31/2022] Open
Abstract
Mast cells (MC) accumulate in colorectal cancer (CRC) and the relationship between MC density and cancer progression has been well recognized. MC can be either pro-tumor or anti-tumor players, depending on the local factors present in the tumor microenvironment. Upon malignant transformation, cancer cells express high levels of sialic acids on cell membrane or by secretion. Siglecs are a family of immunoglobulin-like receptors that bind sialic acids and each subtype has a distinct pattern of expression on immune cells. Among them, Siglec-6 is expressed predominately by MC. However, the function of Siglec-6 in MC is largely unexplored and whether it is expressed by CRC-associated MC remains unknown. In this study, we explored the function of Siglec-6 in CD34+ derived human MC. MC activation was initiated by IgE crosslinking with or without preincubation of anti-Siglec-6 Ab. Siglec-6 engagement significantly attenuated IgE-dependent MC degranulation as measured by ß-hexosaminidase release and CD63 expression. Interestingly, the production of GM-CSF was also shown reduced upon Siglec-6 engagement. To mimic the milieu of CRC, we cultured primary human MC with colon cancer cells or under hypoxia and Siglec-6 was then measured on these conditioned MC. Coculture with colon cancer cells (HT29 and Caco2) induced upregulation of Siglec-6 on MC. In comparison, normal colon cells (CCD841) had no effect. Also, a time-dependent increase of Siglec-6 by MC was observed under 1% O2. Immunohistochemistry of CRC tissue showed expression of Siglec-6 by MC in submucosa. Lectin immunochemistry revealed the presence of actual ligands for Siglec-6 in human CRC tissues. Together, our findings illustrate that Siglec-6 is a functionally inhibitory receptor on MC and suggest that Siglec-6 expression may be relevant for MC activity in the tumor microenvironment of CRC.
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MESH Headings
- Antigens, CD/immunology
- Antigens, CD/metabolism
- Antigens, CD34/immunology
- Antigens, CD34/metabolism
- Antigens, Differentiation, Myelomonocytic/immunology
- Antigens, Differentiation, Myelomonocytic/metabolism
- Biopsy
- Caco-2 Cells
- Cell Transformation, Neoplastic/immunology
- Cell Transformation, Neoplastic/metabolism
- Coculture Techniques
- Colorectal Neoplasms/immunology
- Colorectal Neoplasms/pathology
- Gene Expression Regulation, Neoplastic/immunology
- HT29 Cells
- Humans
- Lectins/immunology
- Lectins/metabolism
- Mast Cells/immunology
- Mast Cells/metabolism
- Primary Cell Culture
- Tumor Microenvironment/immunology
- Up-Regulation
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Affiliation(s)
- Yingxin Yu
- Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Bart R. J. Blokhuis
- Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Mara A. P. Diks
- Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Ali Keshavarzian
- Division of Digestive Diseases and Nutrition, Department of Internal Medicine, Rush University Medical Center, Chicago, IL, United States
| | - Johan Garssen
- Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
- Nutricia Research, Utrecht, Netherlands
| | - Frank A. Redegeld
- Division of Pharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
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