title: Targeting Toll-like receptor 7/8 enhances uptake of apoptotic leukemic cells by monocyte-derived dendritic cells but interferes with subsequent cytokine-induced maturation.
abstract: Therapeutic vaccination with dendritic cells (DC) is an emerging investigational therapy for eradication of minimal residual disease in acute myeloid leukemia. Various strategies are being explored in manufacturing DC vaccines ex vivo, e.g., monocyte-derived DC (MoDC) loaded with leukemia-associated antigens (LAA). However, the optimal source of LAA and the choice of DC-activating stimuli are still not well defined. Here, loading with leukemic cell preparations (harboring both unknown and known LAA) was explored in combination with a DC maturation-inducing cytokine cocktail (CC; IL-1β, IL-6, TNF-α, and PGE(2)) and Toll-like receptor ligands (TLR-L) to optimize uptake. Since heat shock induced apoptotic blasts were more efficiently taken up than lysates, we focused on uptake of apoptotic leukemic cells. Uptake of apoptotic blast was further enhanced by the TLR7/8-L R848 (20-30%); in contrast, CC-induced maturation inhibited uptake. CC, and to a lesser extent R848, enhanced the ability of MoDC to migrate and stimulate T cells. Furthermore, class II-associated invariant chain peptide expression was down-modulated after R848- or CC-induced maturation, indicating enhanced processing and presentation of antigenic peptides. To improve both uptake and maturation, leukemic cells and MoDC were co-incubated with R848 for 24 h followed by addition of CC. However, this approach interfered with CC-mediated MoDC maturation as indicated by diminished migratory and T cell stimulatory capacity, and the absence of IL-12 production. Taken together, our data demonstrate that even though R848 improved uptake of apoptotic leukemic cells, the sequential use of R848 and CC is counter-indicated due to its adverse effects on MoDC maturation.
authors.affiliation: Department of Hematology, Cancer Center Amsterdam, VU Institute for Cancer and Immunology, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands. w.vandenancker@vumc.nl
authors.forename: Willemijn
authors.initials: W
authors.lastname: van den Ancker
authors.forename: Marvin M
authors.initials: MM
authors.lastname: van Luijn
authors.forename: Jurjen M
authors.initials: JM
authors.lastname: Ruben
authors.forename: Theresia M
authors.initials: TM
authors.lastname: Westers
authors.forename: Hetty J
authors.initials: HJ
authors.lastname: Bontkes
authors.forename: Gert J
authors.initials: GJ
authors.lastname: Ossenkoppele
authors.forename: Tanja D
authors.initials: TD
authors.lastname: de Gruijl
authors.forename: Arjan A
authors.initials: AA
authors.lastname: van de Loosdrecht
mesh_terms: D017951:Antigen Presentation / Q000187:drug effects; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000276:immunology; D019496:Cancer Vaccines; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D004705:Endocytosis / Q000187:drug effects; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007167:Immunotherapy; D015470:Leukemia, Myeloid, Acute / Q000276:immunology* / Q000473:pathology / Q000628:therapy*; D008213:Lymphocyte Activation / Q000187:drug effects; D009000:Monocytes / Q000473:pathology; D010446:Peptide Fragments / Q000378:metabolism; D051199:Toll-Like Receptor 7 / Q000819:agonists; D051200:Toll-Like Receptor 8 / Q000819:agonists
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D019496:Cancer Vaccines; D016207:Cytokines; D000949:Histocompatibility Antigens Class II; D007093:Imidazoles; D010446:Peptide Fragments; C495348:TLR7 protein, human; C495349:TLR8 protein, human; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; C045084:invariant chain; C402365:resiquimod