title: Cooperative TRAIL production mediates IFNα/Smac mimetic-induced cell death in TNFα-resistant solid cancer cells.
abstract: Smac mimetics antagonize IAP proteins, which are highly expressed in several cancers. Recent reports indicate that Smac mimetics trigger a broad cytokine response and synergize with immune modulators to induce cell death. Here, we identify a differential requirement of TRAIL or TNFα as mediators of IFNα/Smac mimetic-induced cell death depending on the cellular context. Subtoxic concentrations of Smac mimetics cooperate with IFNα to induce cell death in various solid tumor cell lines in a highly synergistic manner as determined by combination index. Mechanistic studies show that IFNα/BV6 cotreatment promotes the formation of a caspase-8-activating complex together with the adaptor protein FADD and RIP1. Assembly of this RIP1/FADD/caspase-8 complex represents a critical event, since RIP1 silencing inhibits IFNα/BV6-induced cell death. Strikingly, pharmacological inhibition of paracrine/autocrine TNFα signaling by the TNFα scavenger Enbrel rescues HT-29 colon carcinoma cells, but not A172 glioblastoma cells from IFNα/BV6-induced cell death. By comparison, A172 cells are significantly protected against IFNα/BV6 treatment by blockage of TRAIL signaling through genetic silencing of TRAIL or its cognate receptor TRAIL receptor 2 (DR5). Despite this differential requirement of TNFα and TRAIL signaling, mRNA and protein expression is increased by IFNα/BV6 cotreatment in both cell lines. Interestingly, A172 cells turn out to be resistant to exogenously added recombinant TNFα even in the presence of BV6, whereas they display a high sensitivity towards TRAIL/BV6. In contrast, BV6 efficiently sensitizes HT-29 cells to TNFα while TRAIL only had limited efficacy. This demonstrates that a differential sensitivity towards TRAIL or TNFα determines the dependency on either death receptor ligand for IFNα/Smac mimetic-induced cell death. Thus, by concomitant stimulation of both death receptor systems IFNα/Smac mimetic combination treatment is an effective strategy to induce cell death in TNFα- or TRAIL-responsive cancers.
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Roesler
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.|German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Ines
authors.initials: I
authors.lastname: Eckhardt
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wolf
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.|German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Fulda
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D016898:Interferon-alpha / Q000494:pharmacology*; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D009842:Oligopeptides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: C582180:BV6 peptide; D016898:Interferon-alpha; D009842:Oligopeptides; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; C532637:SMAC peptide; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha
keywords: Smac; TRAIL; apoptosis; cell death; interferon