title: Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity.
abstract: The success of clinically relevant immunotherapies requires reversing tumor-induced immunosuppression. Here we demonstrated that linear polyethylenimine-based (PEI-based) nanoparticles encapsulating siRNA were preferentially and avidly engulfed by regulatory DCs expressing CD11c and programmed cell death 1-ligand 1 (PD-L1) at ovarian cancer locations in mice. PEI-siRNA uptake transformed these DCs from immunosuppressive cells to efficient antigen-presenting cells that activated tumor-reactive lymphocytes and exerted direct tumoricidal activity, both in vivo and in situ. PEI triggered robust and selective TLR5 activation in vitro and elicited the production of hallmark TLR5-inducible cytokines in WT mice, but not in Tlr5-/- littermates. Thus, PEI is a TLR5 agonist that, to our knowledge, was not previously recognized. In addition, PEI-complexed nontargeting siRNA oligonucleotides stimulated TLR3 and TLR7. The nonspecific activation of multiple TLRs (specifically, TLR5 and TLR7) reversed the tolerogenic phenotype of human and mouse ovarian tumor-associated DCs. In ovarian carcinoma-bearing mice, this induced T cell-mediated tumor regression and prolonged survival in a manner dependent upon myeloid differentiation primary response gene 88 (MyD88; i.e., independent of TLR3). Furthermore, gene-specific siRNA-PEI nanocomplexes that silenced immunosuppressive molecules on mouse tumor-associated DCs elicited discernibly superior antitumor immunity and enhanced therapeutic effects compared with nontargeting siRNA-PEI nanocomplexes. Our results demonstrate that the intrinsic TLR5 and TLR7 stimulation of siRNA-PEI nanoparticles synergizes with the gene-specific silencing activity of siRNA to transform tumor-infiltrating regulatory DCs into DCs capable of promoting therapeutic antitumor immunity.
authors.affiliation: Department of Microbiology and Immunology, Dartmouth Medical School, Lebanon, New Hampshire, USA.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Cubillos-Ruiz
authors.forename: Xavier
authors.initials: X
authors.lastname: Engle
authors.forename: Uciane K
authors.initials: UK
authors.lastname: Scarlett
authors.forename: Diana
authors.initials: D
authors.lastname: Martinez
authors.forename: Amorette
authors.initials: A
authors.lastname: Barber
authors.forename: Raul
authors.initials: R
authors.lastname: Elgueta
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Nesbeth
authors.forename: Yvon
authors.initials: Y
authors.lastname: Durant
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Gewirtz
authors.forename: Charles L
authors.initials: CL
authors.lastname: Sentman
authors.forename: Ross
authors.initials: R
authors.lastname: Kedl
authors.forename: Jose R
authors.initials: JR
authors.lastname: Conejo-Garcia
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D018122:B7-1 Antigen / Q000502:physiology; D060890:B7-H1 Antigen; D003602:Cytotoxicity, Immunologic; D003713:Dendritic Cells / Q000276:immunology* / Q000502:physiology; D005260:Female; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D053594:Myeloid Differentiation Factor 88 / Q000502:physiology; D053758:Nanoparticles / Q000008:administration & dosage*; D010051:Ovarian Neoplasms / Q000276:immunology / Q000628:therapy*; D010455:Peptides / Q000502:physiology; D011094:Polyethyleneimine / Q000008:administration & dosage*; D034741:RNA, Small Interfering / Q000008:administration & dosage*; D013601:T-Lymphocytes / Q000276:immunology; D051198:Toll-Like Receptor 5 / Q000502:physiology*
chemical_list: D018122:B7-1 Antigen; D060890:B7-H1 Antigen; C498919:Cd274 protein, mouse; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D010455:Peptides; D034741:RNA, Small Interfering; D051198:Toll-Like Receptor 5; D011094:Polyethyleneimine