title: 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 TNFα-blocking antibody, do not interfere with BV6/Drozitumab-induced apoptosis, demonstrating that apoptosis occurs independently of RIP1 kinase activity or an autocrine TNFα loop. In conclusion, the rational combination of BV6 and Drozitumab presents a promising approach to trigger apoptosis in glioblastoma, which warrants further investigation.
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Cristofanon
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: B A
authors.initials: BA
authors.lastname: Abhari
authors.affiliation: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tuebingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Krueger
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Tchoghandjian
authors.affiliation: Institute of Neuropathology, Goethe-University, Frankfurt, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Momma
authors.affiliation: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tuebingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Calaminus
authors.affiliation: Genentech, Inc, South San Francisco, CA, USA.
authors.forename: D
authors.initials: D
authors.lastname: Vucic
authors.affiliation: Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tuebingen, Germany.
authors.forename: B J
authors.initials: BJ
authors.lastname: Pichler
authors.affiliation: 1] Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany [2] German Cancer Consortium (DKTK), Heidelberg, Germany [3] German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Fulda
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D045744:Cell Line, Tumor; D005909:Glioblastoma / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C548876:drozitumab