title: The multikinase inhibitor sorafenib potentiates TRAIL lethality in human leukemia cells in association with Mcl-1 and cFLIPL down-regulation.
abstract: Interactions between the multikinase inhibitor sorafenib and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) were examined in malignant hematopoietic cells. Pretreatment (24 h) of U937 leukemia cells with 7.5 micromol/L sorafenib dramatically increased apoptosis induced by sublethal concentrations of TRAIL/Apo2L (75 ng/mL). Similar interactions were observed in Raji, Jurkat, Karpas, K562, U266 cells, primary acute myelogenous leukemia blasts, but not in normal CD34+ bone marrow cells. Sorafenib/TRAIL-induced cell death was accompanied by mitochondrial injury and release of cytochrome c, Smac, and AIF into the cytosol and caspase-9, caspase-3, caspase-7, and caspase-8 activation. Sorafenib pretreatment down-regulated Bcl-xL and abrogated Mcl-1 expression, whereas addition of TRAIL sharply increased Bid activation, conformational change of Bak (ccBak) and Bax (ccBax), and Bax translocation. Ectopic Mcl-1 expression significantly attenuated sorafenib/TRAIL-mediated lethality and dramatically reduced ccBak while minimally affecting levels of ccBax. Similarly, inhibition of the receptor-mediated apoptotic cascade with a caspase-8 dominant-negative mutant significantly blocked sorafenib/TRAIL-induced lethality but not Mcl-1 down-regulation or Bak/Bax conformational change, indicating that TRAIL-mediated receptor pathway activation is required for maximal lethality. Sorafenib/TRAIL did not increase expression of DR4/DR5, or recruitment of procaspase-8 or FADD to the death-inducing signaling complex (DISC), but strikingly increased DISC-associated procaspase-8 activation. Sorafenib also down-regulated cFLIP(L), most likely through a translational mechanism, in association with diminished eIF4E phosphorylation, whereas ectopic expression of cFLIP(L) significantly reduced sorafenib/TRAIL lethality. Together, these results suggest that in human leukemia cells, sorafenib potentiates TRAIL-induced lethality by down-regulating Mcl-1 and cFLIP(L), events that cooperate to engage the intrinsic and extrinsic apoptotic cascades, culminating in pronounced mitochondrial injury and apoptosis.
authors.affiliation: Department of Medicine, Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
authors.forename: Roberto R
authors.initials: RR
authors.lastname: Rosato
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Almenara
authors.forename: Stefanie
authors.initials: S
authors.lastname: Coe
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001557:Benzenesulfonates / Q000008:administration & dosage / Q000494:pharmacology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000096:biosynthesis / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000378:metabolism*; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis; D000077157:Sorafenib; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000494:pharmacology*; D020298:U937 Cells; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494772:BAK1 protein, human; C494826:BAX protein, human; D001557:Benzenesulfonates; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053418:Death Domain Receptor Signaling Adaptor Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505653:TNFSF10 protein, human; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D009536:Niacinamide; D000077157:Sorafenib; D053181:Caspase 8