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Identification of RIP1 as a critical mediator of Smac mimetic-mediated sensitization of glioblastoma cells for Drozitumab-induced apoptosis.

ABSTRACT: This study aims at evaluating the combination of the tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL)-receptor 2 (TRAIL-R2)-specific antibody Drozitumab and the Smac mimetic BV6 in preclinical glioblastoma models. To this end, the effect of BV6 and/or Drozitumab on apoptosis induction and signaling pathways was analyzed in glioblastoma cell lines, primary glioblastoma cultures and glioblastoma stem-like cells. Here, we report that BV6 and Drozitumab synergistically induce apoptosis and reduce colony formation in several glioblastoma cell lines (combination index<0.1). Also, BV6 profoundly enhances Drozitumab-induced apoptosis in primary glioblastoma cultures and glioblastoma stem-like cells. Importantly, BV6 cooperates with Drozitumab to suppress tumor growth in two glioblastoma in vivo models including an orthotopic, intracranial mouse model, underlining the clinical relevance of these findings. Mechanistic studies reveal that BV6 and Drozitumab act in concert to trigger the formation of a cytosolic receptor-interacting protein (RIP) 1/Fas-associated via death domain (FADD)/caspase-8-containing complex and subsequent activation of caspase-8 and -3. BV6- and Drozitumab-induced apoptosis is blocked by the caspase inhibitor zVAD.fmk, pointing to caspase-dependent apoptosis. RNA interference-mediated silencing of RIP1 almost completely abolishes the BV6-conferred sensitization to Drozitumab-induced apoptosis, indicating that the synergism critically depends on RIP1 expression. In contrast, both necrostatin-1, a RIP1 kinase inhibitor, and Enbrel, a TNF?-blocking antibody, do not interfere with BV6/Drozitumab-induced apoptosis, demonstrating that apoptosis occurs independently of RIP1 kinase activity or an autocrine TNF? loop. In conclusion, the rational combination of BV6 and Drozitumab presents a promising approach to trigger apoptosis in glioblastoma, which warrants further investigation.

SUBMITTER: Cristofanon S

PROVIDER: S-EPMC4650534 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Identification of RIP1 as a critical mediator of Smac mimetic-mediated sensitization of glioblastoma cells for Drozitumab-induced apoptosis.

Cristofanon S S Abhari B A BA Krueger M M Tchoghandjian A A Momma S S Calaminus C C Vucic D D Pichler B J BJ Fulda S S

Cell death & disease 20150416

This study aims at evaluating the combination of the tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL)-receptor 2 (TRAIL-R2)-specific antibody Drozitumab and the Smac mimetic BV6 in preclinical glioblastoma models. To this end, the effect of BV6 and/or Drozitumab on apoptosis induction and signaling pathways was analyzed in glioblastoma cell lines, primary glioblastoma cultures and glioblastoma stem-like cells. Here, we report that BV6 and Drozitumab synergistically induce apoptosi ...[more]

PMID: 25880091

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Project description:As inhibitor of apoptosis (IAP) proteins can regulate additional signaling pathways beyond apoptosis, we investigated the effect of the second mitochondrial activator of caspases (Smac) mimetic BV6, which antagonizes IAP proteins, on non-apoptotic functions in glioblastoma (GBM). Here, we identify non-canonical nuclear factor-?B (NF-?B) signaling and a tumor necrosis factor-? (TNF?)/TNF receptor 1 (TNFR1) autocrine/paracrine loop as critical mediators of BV6-stimulated migration and invasion of GBM cells. In addition to GBM cell lines, BV6 triggers cell elongation, migration and invasion in primary, patient-derived GBM cells at non-toxic concentrations, which do not affect cell viability or proliferation, and also increases infiltrative tumor growth in vivo underscoring the relevance of these findings. Molecular studies reveal that BV6 causes rapid degradation of cellular IAP proteins, accumulation of NIK, processing of p100 to p52, translocation of p52 into the nucleus, increased NF-?B DNA binding and enhanced NF-?B transcriptional activity. Electrophoretic mobility shift assay supershift shows that the NF-?B DNA-binding subunits consist of p50, p52 and RelB further confirming the activation of the non-canonical NF-?B pathway. BV6-stimulated NF-?B activation leads to elevated mRNA levels of TNF? and additional NF-?B target genes involved in migration (i.e., interleukin 8, monocyte chemoattractant protein 1, CXC chemokine receptor 4) and invasion (i.e., matrix metalloproteinase-9). Importantly, inhibition of NF-?B by overexpression of dominant-negative I?B? superrepressor prevents the BV6-stimulated cell elongation, migration and invasion. Similarly, specific inhibition of non-canonical NF-?B signaling by RNA interference-mediated silencing of NIK suppresses the BV6-induced cell elongation, migration and invasion as well as upregulation of NF-?B target genes. Intriguingly, pharmacological or genetic inhibition of the BV6-stimulated TNF? autocrine/paracrine loop by the TNF?-blocking antibody Enbrel or by knockdown of TNFR1 abrogates BV6-induced cell elongation, migration and invasion. By demonstrating that the Smac mimetic BV6 at non-toxic concentrations promotes migration and invasion of GBM cells via non-canonical NF-?B signaling, our findings have important implications for the use of Smac mimetics as cancer therapeutics.

Dataset Information

Identification of RIP1 as a critical mediator of Smac mimetic-mediated sensitization of glioblastoma cells for Drozitumab-induced apoptosis.

Publications

Identification of RIP1 as a critical mediator of Smac mimetic-mediated sensitization of glioblastoma cells for Drozitumab-induced apoptosis.

Similar Datasets

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