title: Noxa up-regulation and Mcl-1 cleavage are associated to apoptosis induction by bortezomib in multiple myeloma.
abstract: Targeting the ubiquitin-proteasome pathway has emerged as a potent anticancer strategy. Bortezomib, a specific proteasome inhibitor, has been approved for the treatment of relapsed or refractory multiple myeloma. Multiple myeloma cell survival is highly dependent on Mcl-1 antiapoptotic molecules. In a recent study, proteasome inhibitors induced Mcl-1 accumulation that slowed down their proapoptotic effects. Consequently, we investigated the role of Bcl-2 family members in bortezomib-induced apoptosis. We found that bortezomib induced apoptosis in five of seven human myeloma cell lines (HMCL). Bortezomib-induced apoptosis was associated with Mcl-1 cleavage regardless of Mcl-1L accumulation. Furthermore, RNA interference mediated Mcl-1 decrease and sensitized RPMI-8226 HMCL to bortezomib, highlighting the contribution of Mcl-1 in bortezomib-induced apoptosis. Interestingly, an important induction of Noxa was found in all sensitive HMCL both at protein and mRNA level. Concomitant to Mcl-1 cleavage and Noxa induction, we also found caspase-3, caspase-8, and caspase-9 activation. Under bortezomib treatment, Mcl-1L/Noxa complexes were highly increased, Mcl-1/Bak complexes were disrupted, and there was an accumulation of free Noxa. Finally, we observed a dissociation of Mcl-1/Bim complexes that may be due to a displacement of Bim induced by Noxa. Thus, in myeloma cells, the mechanistic basis for bortezomib sensitivity can be explained mainly by the model in which the sensitizer Noxa can displace Bim, a BH3-only activator, from Mcl-1, thus leading to Bax/Bak activation.
authors.affiliation: Institut National de la Sante et de la Recherche Medicale, UMR601, Nantes, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Gomez-Bougie
authors.forename: Soraya
authors.initials: S
authors.lastname: Wuillème-Toumi
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Ménoret
authors.forename: Valérie
authors.initials: V
authors.lastname: Trichet
authors.forename: Nelly
authors.initials: N
authors.lastname: Robillard
authors.forename: Moreau
authors.initials: M
authors.lastname: Philippe
authors.forename: Régis
authors.initials: R
authors.lastname: Bataille
authors.forename: Martine
authors.initials: M
authors.lastname: Amiot
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D001897:Boronic Acids; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; C498702:PMAIP1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; D034741:RNA, Small Interfering; D050998:bcl-2 Homologous Antagonist-Killer Protein; D000069286:Bortezomib