title: Apaf-1/cytochrome c-independent and Smac-dependent induction of apoptosis in multiple myeloma (MM) cells.
abstract: Smac, a second mitochondria-derived activator of caspases, promotes caspase activation in the cytochrome c (cyto-c)/Apaf-1/caspase-9 pathway. Here, we show that treatment of multiple myeloma (MM) cells with dexamethasone (Dex) triggers the release of Smac from mitochondria to cytosol and activates caspase-9 without concurrent release of cyto-c and Apaf-1 oligomerization. Smac binds to XIAP (an inhibitor of apoptosis protein) and thereby, at least in part, eliminates its inhibitory effect on caspase-9. Interleukin-6, a growth factor for MM, blocks Dex-induced apoptosis and prevents release of Smac. Taken together, these findings demonstrate that Smac plays a functional role in mediating Dex-induced caspase-9 activation and apoptosis in MM cells.
authors.affiliation: Jerome Lipper Multiple Myeloma Center, Department of Adult Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: D
authors.initials: D
authors.lastname: Chauhan
authors.forename: T
authors.initials: T
authors.lastname: Hideshima
authors.forename: S
authors.initials: S
authors.lastname: Rosen
authors.forename: J C
authors.initials: JC
authors.lastname: Reed
authors.forename: S
authors.initials: S
authors.lastname: Kharbanda
authors.forename: K C
authors.initials: KC
authors.lastname: Anderson
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D053477:Apoptotic Protease-Activating Factor 1; D002352:Carrier Proteins; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D009101:Multiple Myeloma / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: C506592:APAF1 protein, human; D051017:Apoptosis Regulatory Proteins; D053477:Apoptotic Protease-Activating Factor 1; D002352:Carrier Proteins; D003574:Cytochrome c Group; C412403:DIABLO protein, human; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases