title: Uptake routes of tumor-antigen MAGE-A3 by dendritic cells determine priming of naïve T-cell subtypes.
abstract: Induction of tumor-antigen-specific T cells in active cancer immunotherapy is generally difficult due to the very low anti-tumoral precursor cytotoxic T cells. By improving tumor-antigen uptake and presentation by dendritic cells (DCs), this problem can be overcome. Focusing on MAGE-A3 protein, frequently expressed in many types of tumors, we analyzed different DC-uptake routes after additional coating the recombinant MAGE-A3 protein with either a specific monoclonal antibody or an immune complex formulation. Opsonization of the protein with antibody resulted in increased DC-uptake compared to the uncoated rhMAGE-A3 protein. This was partly due to Fcγ receptor-dependent internalization. However, unspecific antigen internalization via macropinocytosis also played a role. When analyzing DC-uptake of MAGE-A3 antigen expressed in multiple myeloma cell line U266, pretreatment with proteasome inhibitor bortezomib resulted in increased apoptosis compared to γ-irradiation. Bortezomib-mediated immunogenic apoptosis, characterized by elevated surface expression of hsp90, triggered higher phagocytosis of U266 cells by DCs involving specific DC-derived receptors. We further investigated the impact of antigen delivery on T-cell priming. Induction of CD8(+) T-cell response was favored by stimulating naïve T cells with either antibody-opsonized MAGE-A3 protein or with the bortezomib-pretreated U266 cells, indicating that receptor-mediated uptake favors cross-presentation of antigens. In contrast, CD4(+) T cells were preferentially induced after stimulation with the uncoated protein or protein in the immune complex, both antigen formulations were preferentially internalized by DCs via macropinocytosis. In summary, receptor-mediated DC-uptake mechanisms favored the induction of CD8(+) T cells, relevant for clinical anti-tumor response.
authors.affiliation: Department of Hematology/Oncology, University Medical Center Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany.
authors.forename: Ines
authors.initials: I
authors.lastname: Moeller
authors.forename: Giulio C
authors.initials: GC
authors.lastname: Spagnoli
authors.forename: Jürgen
authors.initials: J
authors.lastname: Finke
authors.forename: Hendrik
authors.initials: H
authors.lastname: Veelken
authors.forename: Leonora
authors.initials: L
authors.lastname: Houet
mesh_terms: D000936:Antigen-Antibody Complex / Q000276:immunology; D000951:Antigens, Neoplasm / Q000276:immunology* / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D045744:Cell Line, Tumor; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D005720:Gamma Rays / Q000627:therapeutic use; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000276:immunology / Q000532:radiotherapy; D009101:Multiple Myeloma / Q000188:drug therapy / Q000276:immunology / Q000532:radiotherapy; D009363:Neoplasm Proteins / Q000276:immunology* / Q000378:metabolism; D010873:Pinocytosis / Q000276:immunology; D011719:Pyrazines / Q000494:pharmacology; D012878:Skin Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000532:radiotherapy; D016896:Treatment Outcome
chemical_list: D000936:Antigen-Antibody Complex; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D001897:Boronic Acids; C072013:MAGEA3 protein, human; D009363:Neoplasm Proteins; D011719:Pyrazines; D000069286:Bortezomib