title: PolyI:C-Induced, TLR3/RIP3-Dependent Necroptosis Backs Up Immune Effector-Mediated Tumor Elimination In Vivo.
abstract: Double-stranded RNA directly acts on fibroblast and myeloid lineages to induce necroptosis as in TNFα. Here, we investigated whether this type of cell death occurred in cancer cells in response to polyinosinic-polycytidylic acid (polyI:C) and the pan-caspase inhibitor z-Val-Ala-Asp fluromethyl ketone (zVAD). We found that the colon cancer cell line CT26 is highly susceptible to necroptosis, as revealed by staining with annexin V/propidium iodide. CT26 cells possess RNA sensors, TLR3 and MDA5, which are upregulated by interferon (IFN)-inducing pathways and linked to receptor-interacting protein kinase (RIP) 1/3 activation via TICAM-1 or MAVS adaptor, respectively. Although exogenously added polyI:C alone marginally induced necroptosis in CT26 cells, a combined regimen of polyI:C and zVAD induced approximately 50% CT26 necroptosis in vitro without secondary effects of TNFα or type I IFNs. CT26 necroptosis depended on the TLR3-TICAM-1-RIP3 axis in the tumor cells to produce reactive oxygen species, but not on MDA5, MAVS, or the caspases/inflammasome activation. However, the RNA-derived necroptosis was barely reproduced in vivo in a CT26 tumor-implanted Balb/c mouse model with administration of polyI:C + zVAD. Significant shrinkage of CT26 tumors was revealed only when polyI:C (100 μg) was injected intraperitoneally and zVAD (1 mg) subcutaneously into tumor-bearing mice that were depleted of cytotoxic T lymphocytes and natural killer cells. The results were confirmed with immune-compromised mice with no lymphocytes. Although necroptosis-induced tumor growth retardation appears mechanistically complicated and dependent on the injection routes of polyI:C and zVAD, anti-caspase reagent directed to tumor cells will make RNA adjuvant immunotherapy more effective by modulating the formation of the tumoricidal microenvironment and dendritic cell-inducing antitumor immune system.
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan. Department of Hematology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Takemura
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Takaki
authors.affiliation: Division of Hematopoiesis, Center for AIDS Research, Kumamoto University, Kumamoto, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Okada
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shime
authors.affiliation: Department of Tumor Immunology, Research Institute, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Akazawa
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oshiumi
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Misako
authors.initials: M
authors.lastname: Matsumoto
authors.affiliation: Department of Hematology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Teshima
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan. seya-tu@pop.med.hokudai.ac.jp.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D064593:Heterografts; D006801:Humans; D051379:Mice; D009369:Neoplasms / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology; D011070:Poly I-C / Q000276:immunology* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D051196:Toll-Like Receptor 3 / Q000378:metabolism*; D047368:Tumor Burden
chemical_list: D009842:Oligopeptides; D017382:Reactive Oxygen Species; D051196:Toll-Like Receptor 3; C517629:benzyloxycarbonyl-valyl-alanyl-aspartic acid; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C485615:Ripk3 protein, mouse; D011070:Poly I-C