title: Hyperthermia restores apoptosis induced by death receptors through aggregation-induced c-FLIP cytosolic depletion.
abstract: TRAIL is involved in immune tumor surveillance and is considered a promising anti-cancer agent owing to its limited side effects on healthy cells. However, some cancer cells display resistance, or become resistant to TRAIL-induced cell death. Hyperthermia can enhance sensitivity to TRAIL-induced cell death in various resistant cancer cell lines, including lung, breast, colon or prostate carcinomas. Mild heat shock treatment has been proposed to restore Fas ligand or TRAIL-induced apoptosis through c-FLIP degradation or the mitochondrial pathway. We demonstrate here that neither the mitochondria nor c-FLIP degradation are required for TRAIL-induced cell death restoration during hyperthermia. Our data provide evidence that insolubilization of c-FLIP, alone, is sufficient to enhance apoptosis induced by death receptors. Hyperthermia induced c-FLIP depletion from the cytosolic fraction, without apparent degradation, thereby preventing c-FLIP recruitment to the TRAIL DISC and allowing efficient caspase-8 cleavage and apoptosis. Hyperthermia-induced c-FLIP depletion was independent of c-FLIP DED2 FL chain assembly motif or ubiquitination-mediated c-FLIP degradation, as assessed using c-FLIP point mutants on lysine 167 and 195 or threonine 166, a phosphorylation site known to regulate ubiquitination of c-FLIP. Rather, c-FLIP depletion was associated with aggregation, because addition of glycerol not only prevented the loss of c-FLIP from the cytosol but also enabled c-FLIP recruitment within the TRAIL DISC, thus inhibiting TRAIL-induced apoptosis during hyperthermia. Altogether our results demonstrate that c-FLIP is a thermosensitive protein whose targeting by hyperthermia allows restoration of apoptosis induced by TNF ligands, including TRAIL. Our findings suggest that combining TRAIL agonists with whole-body or localized hyperthermia may be an interesting approach in cancer therapy.
authors: 1] INSERM, UMR866, Dijon, F-21079 France [2] Faculty of Medicine and Pharmacy, Univ. Bourgogne, Dijon, F-21079 France.
authors: A
authors: A
authors: Morlé
authors: 1] INSERM, UMR866, Dijon, F-21079 France [2] Faculty of Medicine and Pharmacy, Univ. Bourgogne, Dijon, F-21079 France [3] Centre Georges-François Leclerc, Dijon, F-21000 France.
authors: C
authors: C
authors: Garrido
authors: 1] INSERM, UMR866, Dijon, F-21079 France [2] Faculty of Medicine and Pharmacy, Univ. Bourgogne, Dijon, F-21079 France [3] Centre Georges-François Leclerc, Dijon, F-21000 France.
authors: O
authors: O
authors: Micheau
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism*; D006801:Humans; D006979:Hyperthermia, Induced; D047468:Immunoprecipitation; D017354:Point Mutation / Q000235:genetics; D034741:RNA, Small Interfering; D053218:Receptors, Death Domain / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506387:Cflar protein, mouse; D034741:RNA, Small Interfering; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand