title: Identification of DR5 as a critical, NF-κB-regulated mediator of Smac-induced apoptosis.
abstract: Smac mimetic promotes apoptosis by neutralizing inhibitor of apoptosis (IAP) proteins and is considered as a promising cancer therapeutic. Although an autocrine/paracrine tumor necrosis factor-α (TNFα) loop has been implicated in Smac mimetic-induced cell death, little is yet known about additional factors that determine sensitivity to Smac mimetic. Using genome-wide gene expression analysis, we identify death receptor 5 (DR5) as a novel key mediator of Smac mimetic-induced apoptosis. Although several cell lines that are sensitive to the Smac mimetic BV6 die in a TNFα-dependent manner, A172 glioblastoma cells undergo BV6-induced apoptosis largely independently of TNFα/TNFR1, as the TNFα-blocking antibody Enbrel or TNFR1 knockdown provide little protection. Yet, BV6-stimulated nuclear factor-κB (NF-κB) activation is critically required for apoptosis, as inhibition of NF-κB by overexpression of dominant-negative IκBα superrepressor (IκBα-SR) blocks BV6-induced apoptosis. Unbiased genome-wide gene expression studies in IκBα-SR-overexpressing cells versus vector control cells reveal that BV6 increases DR5 expression in a NF-κB-dependent manner. Importantly, this BV6-stimulated upregulation of DR5 is critically required for apoptosis, as transient or stable knockdown of DR5 significantly inhibits BV6-triggered apoptosis. In addition, DR5 silencing attenuates formation of a RIP1/FADD/caspase-8 cytosolic cell death complex and activation of caspase-8, -3 and -9. By identifying DR5 as a critical mediator of Smac mimetic-induced apoptosis, our findings provide novel insights into the determinants that control susceptibility of cancer cells to Smac mimetic.
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstr. 3a, 60528 Frankfurt, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Eckhardt
authors.forename: S
authors.initials: S
authors.lastname: Roesler
authors.forename: S
authors.initials: S
authors.lastname: Fulda
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D008954:Models, Biological; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand