Abstract
Previous studies have shown that triggering multiple myeloma (MM) cells via CD40 induces IL-6-mediated autocrine growth as well as increased expression of cell surface adhesion molecules including CD11a, CD11b, CD11c, and CD18. In this study, we generated the 5E2 mAb which targets an antigen that is induced upon CD40 ligand (CD40L) activation of MM cells. Immunofluorescence, immunoprecipitation, and protein sequencing studies identified the target antigen of 5E2 mAb as the 86-kD subunit of the Ku autoantigen. We demonstrate that increased cell surface expression of Ku on CD40L-treated cells is due to migration of Ku from the cytoplasm to the cell surface membrane. Moreover, cell surface Ku on CD40L-treated MM cells mediates homotypic adhesion of tumor cells, as well as heterotypic adhesion of tumor cells to bone marrow stromal cells and to human fibronectin; and 5E2 mAb abrogates IL-6 secretion triggered by tumor cell adherence to bone marrow stromal cells. These data suggest that CD40L treatment induces a shift of Ku from the cytoplasm to the cell surface, and are the first to show that Ku functions as an adhesion molecule. They further suggest that cell surface Ku may play a role in both autocrine and paracrine IL-6-mediated MM cell growth and survival.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Amino Acid Sequence
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Animals
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Antibodies, Blocking / immunology
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Antibodies, Monoclonal / biosynthesis
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Antibodies, Monoclonal / immunology
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Antigens, CD / immunology
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Antigens, Nuclear*
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Autoantibodies / immunology*
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Blotting, Western
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Bone Marrow Cells / immunology
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Bone Marrow Cells / metabolism
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CD40 Antigens / immunology
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CD40 Ligand
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Cell Adhesion / immunology
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Cell Membrane / immunology
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Cell Membrane / metabolism
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Cell Nucleus / immunology
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Cell Nucleus / metabolism
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Cytoplasm / immunology
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Cytoplasm / metabolism
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DNA Helicases*
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DNA-Binding Proteins / immunology*
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DNA-Binding Proteins / isolation & purification
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DNA-Binding Proteins / metabolism*
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Fibronectins / metabolism
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Flow Cytometry
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Humans
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Interleukin-6 / metabolism
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Ku Autoantigen
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Membrane Glycoproteins / immunology
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Mice
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Mice, Inbred BALB C
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Molecular Sequence Data
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Multiple Myeloma / immunology*
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Multiple Myeloma / metabolism*
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Nuclear Proteins / immunology*
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Nuclear Proteins / isolation & purification
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Nuclear Proteins / metabolism*
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Precipitin Tests
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Stromal Cells / immunology
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Stromal Cells / metabolism
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Transfection
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Tumor Cells, Cultured
Substances
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Antibodies, Blocking
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Antibodies, Monoclonal
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Antigens, CD
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Antigens, Nuclear
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Autoantibodies
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CD40 Antigens
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DNA-Binding Proteins
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Fibronectins
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Interleukin-6
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Membrane Glycoproteins
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Nuclear Proteins
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CD40 Ligand
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DNA Helicases
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XRCC5 protein, human
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Xrcc6 protein, human
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Xrcc6 protein, mouse
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Ku Autoantigen