Apoptosis induced by the kinase inhibitor BAY 43-9006 in human leukemia cells involves down-regulation of Mcl-1 through inhibition of translation.
BAY 43-9006 is a kinase inhibitor that induces apoptosis in a variety of tumor cells. Here we report that treatment with BAY 43-9006 results in marked cytochrome c and AIF release into the cytosol, caspase-9, -8, -7, and -3 activation, and apoptosis in human leukemia cells (U937, Jurkat, and K562). Pronounced apoptosis was also observed in blasts from patients with acute myeloid leukemia. These events were accompanied by ERK1/2 inactivation and caspase-independent down-regulation of Mcl-1. Inducible expression of a constitutively active MEK1 construct did not prevent Mcl-1 down-regulation, suggesting that this event is not related to MEK/ERK pathway inactivation. Furthermore, BAY 43-9006 did not induce major changes in Mcl-1 mRNA levels monitored by real-time PCR or Mcl-1 promoter activity demonstrated by luciferase reporter assays, but it did enhance Mcl-1 down-regulation in actinomycin D-treated cells. Inhibition of protein synthesis by cycloheximide or proteasome function with MG132 and pulse-chase studies with [35S]methionine demonstrated that BAY 43-9006 did not diminish Mcl-1 protein stability, nor did it enhance Mcl-1 ubiquitination, but instead markedly attenuated Mcl-1 translation in association with the rapid and potent dephosphorylation of the eIF4E translation initiation factor. Finally, ectopic expression of Mcl-1 in leukemic cells markedly inhibited BAY 43-9006-mediated cytochrome c cytosolic release, caspase-9, -7, and -3 activation, as well as cell death, indicating that Mcl-1 operates upstream of cytochrome c release and caspase activation. Together, these findings demonstrate that BAY 43-9006 mediates cell death in human leukemia cells, at least in part, through down-regulation of Mcl-1 via inhibition of translation.
Rahmani
Mohamed
M
Departments of Medicine, Biochemistry, and Pharmacology, Virginia Commonwealth University, School of Medicine, Richmond, Virginia 23298.
Davis
Eric Maynard
EM
Bauer
Cheryl
C
Dent
Paul
P
Grant
Steven
S
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001557:Benzenesulfonates / Q000494:pharmacology*; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism; D045744:Cell Line, Tumor; D002845:Chromatography; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D017930:Genes, Reporter; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D019169:Jurkat Cells; D020014:K562 Cells; D007938:Leukemia / Q000188:drug therapy*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D011725:Pyridines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077157:Sorafenib; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D020298:U937 Cells; D025801:Ubiquitin / Q000737:chemistry
D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D004791:Enzyme Inhibitors; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D012333:RNA, Messenger; D025801:Ubiquitin; D009536:Niacinamide; D000077157:Sorafenib; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases