title: Targeting Mcl-1 for multiple myeloma (MM) therapy: drug-induced generation of Mcl-1 fragment Mcl-1(128-350) triggers MM cell death via c-Jun upregulation.
abstract: Myeloid cell leukemia-1 (Mcl-1, HGNC: 6943), a pro-survival member of the Bcl-2 family, plays a crucial role in Multiple Myeloma (MM) pathogenesis and drug resistance, thus representing a promising therapeutic target in MM. A novel strategy to inhibit Mcl-1 activity is the induction of ubiquitin-independent Mcl-1 degradation. Our own and other previous studies have demonstrated caspase-dependent generation of a 28kDa Mcl-1 fragment, Mcl-1(128-350), which inhibits MM cell proliferation and survival. Here, we show that similar to bortezomib, the novel proteasome inhibitors carfilzomib and ixazomib, as well as staurosporine and adaphostin, induce the generation of Mcl-1(128-350) in MM cells. Next, the molecular sequelae downstream of Mcl-1(128-350), which mediate its pro-apoptotic activity, were delineated. Surprisingly, we observed nuclear accumulation of drug-induced or exogenously overexpressed Mcl-1(128-350), followed by elevated mRNA and protein levels of c-Jun, as well as enhanced AP-1 reporter activity. Moreover, drug-induced AP-1 activity was blocked after introducing a point mutation into the highly conserved Mcl-1 caspase-cleavage site Asp127, but not Asp157. Consequently, drug-triggered cell death was significantly decreased in MM cells transfected with Mcl-1 D127A, but not with Mcl-1 D157A. Consistent with these data, treatment with bortezomib triggered c-Jun upregulation followed by apoptosis in Mcl-1(wt/wt), but not Mcl-1(Δ/null) murine embryonic fibroblasts (MEFs). Transfection of a plasmid carrying Mcl-1(wt) into Mcl-1(Δ/null) MEFs restored bortezomib-induced Mcl-1 fragmentation, c-Jun upregulation and AP-1 reporter activity. Finally, our data indicate that drug-induced generation of a pro-apoptotic Mcl-1 fragment followed by c-Jun upregulation may also be a novel therapeutic approach in other tumor entities.
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Fengjuan
authors.initials: F
authors.lastname: Fan
authors.affiliation: Functional Genomics of Cancer Unit, Division of Molecular Oncology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Tonon
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Muhammad Hasan
authors.initials: MH
authors.lastname: Bashari
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Sonia
authors.initials: S
authors.lastname: Vallet
authors.affiliation: Functional Genomics of Cancer Unit, Division of Molecular Oncology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Antonini
authors.affiliation: Section Multiple Myeloma, Department of Internal Medicine V, National Center for Tumor Diseases (NCT), University of Heidelberg, Heidelberg, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Goldschmidt
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Schulze-Bergkamen
authors.affiliation: St. Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Opferman
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Sattler
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Anderson
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Jäger
authors.affiliation: Medical Oncology, National Center for Tumor Diseases (NCT), University of Heidelberg and German Cancer Research Center (DKFZ), Heidelberg, Germany. Electronic address: klaus.podar@nct-heidelberg.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Podar
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D005455:Fluorescent Antibody Technique; D006801:Humans; D051379:Mice; D009101:Multiple Myeloma / Q000188:drug therapy*; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000235:genetics* / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009842:Oligopeptides; D010446:Peptide Fragments; D016755:Proto-Oncogene Proteins c-jun; C524865:carfilzomib
keywords: Apoptosis; Glioblastoma; MEFs; Mcl-1; Multiple myeloma; c-Jun