title: Lectin binding to surface Ig variable regions provides a universal persistent activating signal for follicular lymphoma cells.
abstract: The vast majority of cases of follicular lymphoma (FL), but not normal B cells, acquire N-glycosylation sites in the immunoglobulin variable regions during somatic hypermutation. Glycans added to sites are unusual in terminating at high mannoses. We showed previously that the C-type lectins, dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) and mannose receptor, bound to FL surface immunoglobulin (sIg), generating an intracellular Ca(2+) flux. We have now mapped further intracellular pathways activated by DC-SIGN in a range of primary FL cells with detection of phosphorylated ERK1/2, AKT, and PLCγ2. The SYK inhibitor (tamatinib) or the BTK inhibitor (ibrutinib) each blocked phosphorylation. Activation by DC-SIGN occurred in both IgM(+) and IgG(+) cases and led to upregulation of MYC expression, with detection in vivo observed in lymph nodes. Unlike cells of chronic lymphocytic leukemia, FL cells expressed relatively high levels of sIg, unchanged by long-term incubation in vitro, indicating no antigen-mediated downregulation in vivo. In contrast, expression of CXCR4 increased in vitro. Engagement of sIg in FL cells or normal B cells by anti-Ig led to endocytosis in vitro as expected, but DC-SIGN, even when cross-linked, did not lead to significant endocytosis of sIg. These findings indicate that lectin binding generates signals via sIg but does not mediate endocytosis, potentially maintaining a supportive antigen-independent signal in vivo. Location of DC-SIGN in FL tissue revealed high levels in sinusoidlike structures and in some colocalized mononuclear cells, suggesting a role for lectin-expressing cells at this site.
authors.affiliation: Cancer Research UK Centre, Cancer Sciences Unit, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom;
authors.forename: Adam
authors.initials: A
authors.lastname: Linley
authors.affiliation: Barts Cancer Institute, Queen Mary, University of London, John Vane Science Centre, Charterhouse Square, London, United Kingdom; and.
authors.forename: Sergey
authors.initials: S
authors.lastname: Krysov
authors.affiliation: Vita-Salute San Raffaele University, Pathology and Lymphoid Malignancies Unit, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Maurilio
authors.initials: M
authors.lastname: Ponzoni
authors.affiliation: Cancer Research UK Centre, Cancer Sciences Unit, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom;
authors.forename: Peter W
authors.initials: PW
authors.lastname: Johnson
authors.affiliation: Cancer Research UK Centre, Cancer Sciences Unit, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom;
authors.forename: Graham
authors.initials: G
authors.lastname: Packham
authors.affiliation: Cancer Research UK Centre, Cancer Sciences Unit, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom;
authors.forename: Freda K
authors.initials: FK
authors.lastname: Stevenson
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D020013:Calcium Signaling; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism; D007135:Immunoglobulin Variable Region / Q000276:immunology / Q000378:metabolism*; D037181:Lectins, C-Type / Q000276:immunology / Q000378:metabolism*; D008224:Lymphoma, Follicular / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D020935:MAP Kinase Signaling System; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism; D051966:Phospholipase C gamma / Q000276:immunology / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000276:immunology / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000276:immunology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D015815:Cell Adhesion Molecules; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D037181:Lectins, C-Type; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D051966:Phospholipase C gamma; D051057:Proto-Oncogene Proteins c-akt; D016271:Proto-Oncogene Proteins c-myc; D019718:Receptors, CXCR4; D011956:Receptors, Cell Surface; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C527276:CXCR4 protein, human; C489427:MYC protein, human; C535150:MAPK1 protein, human