title: Heat shock protein 70 surface-positive tumor exosomes stimulate migratory and cytolytic activity of natural killer cells.
abstract: Detergent-soluble membrane vesicles are actively released by human pancreas (Colo-/Colo+) and colon (CX-/CX+) carcinoma sublines, differing in their capacity to present heat shock protein 70 (Hsp70)/Bag-4 on their plasma membranes. Floating properties, acetylcholine esterase activity, and protein composition characterized them as exosomes. An enrichment of Rab-4 documented their intracellular transport route from early endosomes to the plasma membrane. After solubilization, comparable amounts of cytosolic proteins, including tubulin, Hsp70, Hsc70, and Bag-4, but not ER-residing Grp94 and calnexin, were detectable in tumor-derived exosomes. However, with respect to the exosomal surface, only Colo+/CX+ but not Colo-/CX- derived exosomes were Hsp70 membrane positive. Therefore, concomitant with an up-regulated cell surface density of activation markers, migration and Hsp70 reactivity of natural killer (NK) cells was stimulated selectively by Hsp70/Bag-4 surface-positive exosomes, but not by their negative counterparts and tumor cell lysates. Moreover, the exosome-mediated lytic activity of NK cells was blockable by Hsp70-specific antibody. As already shown for TKD stimulation, NK cells preincubated with Hsp70 surface-positive exosomes initiated apoptosis in tumors through granzyme B release. In summary, our data provide an explanation how Hsp70 reactivity in NK cells is induced by tumor-derived exosomes.
authors.affiliation: Department of Hematology and Oncology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Gastpar
authors.forename: Mathias
authors.initials: M
authors.lastname: Gehrmann
authors.forename: Maria A
authors.initials: MA
authors.lastname: Bausero
authors.forename: Alexzander
authors.initials: A
authors.lastname: Asea
authors.forename: Catharina
authors.initials: C
authors.lastname: Gross
authors.forename: Josef A
authors.initials: JA
authors.lastname: Schroeder
authors.forename: Gabriele
authors.initials: G
authors.lastname: Multhoff
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000276:immunology*; D003110:Colonic Neoplasms / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D022162:Cytoplasmic Vesicles / Q000276:immunology / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D053804:Granzymes; D018840:HSP70 Heat-Shock Proteins / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D010190:Pancreatic Neoplasms / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D010446:Peptide Fragments / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000276:immunology / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C116906:BAG4 protein, human; D018840:HSP70 Heat-Shock Proteins; D010446:Peptide Fragments; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases