title: RNAi screen of the druggable genome identifies modulators of proteasome inhibitor sensitivity in myeloma including CDK5.
abstract: The molecular target(s) cooperating with proteasome inhibition in multiple myeloma (MM) remain unknown. We therefore measured proliferation in MM cells transfected with 13 984 small interfering RNAs in the absence or presence of increasing concentrations of bortezomib. We identified 37 genes, which when silenced, are not directly cytotoxic but do synergistically potentiate the growth inhibitory effects of bortezomib. To focus on bortezomib sensitizers, genes that also sensitized MM to melphalan were excluded. When suppressed, the strongest bortezomib sensitizers were the proteasome subunits PSMA5, PSMB2, PSMB3, and PSMB7 providing internal validation, but others included BAZ1B, CDK5, CDC42SE2, MDM4, NME7, RAB8B, TFE3, TNFAIP3, TNK1, TOP1, VAMP2, and YY1. The strongest hit CDK5 also featured prominently in pathway analysis of primary screen data. Cyclin-dependent kinase 5 (CDK5) is expressed at high levels in MM and neural tissues with relatively low expression in other organs. Viral shRNA knockdown of CDK5 consistently sensitized 5 genetically variable MM cell lines to proteasome inhibitors (bortezomib and carfilzomib). Small-molecule CDK5 inhibitors were demonstrated to synergize with bortezomib to induce cytotoxicity of primary myeloma cells and myeloma cell lines. CDK5 regulation of proteasome subunit PSMB5 was identified as a probable route to sensitization.
authors.affiliation: Division of Hematology-Oncology, Mayo Clinic, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA.
authors.forename: Yuan Xiao
authors.initials: YX
authors.lastname: Zhu
authors.forename: Rodger
authors.initials: R
authors.lastname: Tiedemann
authors.forename: Chang-Xin
authors.initials: CX
authors.lastname: Shi
authors.forename: Holly
authors.initials: H
authors.lastname: Yin
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Schmidt
authors.forename: Laura A
authors.initials: LA
authors.lastname: Bruins
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Keats
authors.forename: Esteban
authors.initials: E
authors.lastname: Braggio
authors.forename: Chris
authors.initials: C
authors.lastname: Sereduk
authors.forename: Spyro
authors.initials: S
authors.lastname: Mousses
authors.forename: A Keith
authors.initials: AK
authors.lastname: Stewart
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D001897:Boronic Acids / Q000008:administration & dosage / Q000494:pharmacology; D000069286:Bortezomib; D051360:Cyclin-Dependent Kinase 5 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D053263:Gene Regulatory Networks; D015894:Genome, Human / Q000187:drug effects; D057166:High-Throughput Screening Assays; D006801:Humans; D046228:Microarray Analysis; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology; D034622:RNA Interference / Q000502:physiology; D034741:RNA, Small Interfering / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D034741:RNA, Small Interfering; D000069286:Bortezomib; D051360:Cyclin-Dependent Kinase 5; C495905:CDK5 protein, human; C088874:PSMB5 protein, human; D046988:Proteasome Endopeptidase Complex