title: The small-molecule Bcl-2 inhibitor HA14-1 interacts synergistically with flavopiridol to induce mitochondrial injury and apoptosis in human myeloma cells through a free radical-dependent and Jun NH2-terminal kinase-dependent mechanism.
abstract: Interactions between the cyclin-dependent kinase inhibitor flavopiridol and the small-molecule Bcl-2 antagonist HA14-1 were examined in human multiple myeloma cells. Whereas individual treatment of U266 myeloma cells with 10 micromol/L HA14-1 or 100 nmol/L flavopiridol had little effect, exposure of cells to flavopiridol (6 hours) followed by HA14-1 (18 hours) resulted in a striking increase in mitochondrial dysfunction (cytochrome c and Smac/DIABLO release; loss of mitochondrial membrane potential), activation of the caspase cascade, apoptosis, and diminished clonogenic survival. Similar findings were noted in other myeloma cell lines (e.g., MM.1S, RPMI8226, and NCI-H929) as well as in those resistant to dexamethasone and cytotoxic agents (e.g., MM.1R, 8226/Dox40, and 8226/LR5). Combined exposure to flavopiridol and HA14-1 was associated with down-regulation of Mcl-1 and Bcl-xL, Bid cleavage, and mitochondrial translocation of Bax. Flavopiridol/HA14-1-treated cells also exhibited a pronounced activation of Jun NH2-terminal kinase, a modest activation of p38 mitogen-activated protein kinase, and down-regulation of cyclin D1. Flavopiridol/HA14-1-induced apoptosis was associated with a marked increase in reactive oxygen species generation; moreover,both events were attenuated by the antioxidant N-acetyl-l-cysteine. Finally, in contrast to dexamethasone, flavopiridol/HA14-1-induced lethality was unaffected by exogenous interleukin-6 or insulin-like growth factor-I. Together, these findings indicate that flavopiridol and the small-molecule Bcl-2 antagonist HA14-1 cooperate to trigger oxidant injury, mitochondrial dysfunction, caspase activation, and apoptosis in human multiple myeloma cells and suggest that this approach may warrant further evaluation as an antimyeloma strategy.
authors.affiliation: Department of Medicine, Virginia Commonwealth University/Medical College of Virginia, Richmond, Virginia 23298, USA.
authors.forename: Xin-Yan
authors.initials: XY
authors.lastname: Pei
authors.forename: Yun
authors.initials: Y
authors.lastname: Dai
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D001578:Benzopyrans / Q000378:metabolism / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D045304:Cytochromes c / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009101:Multiple Myeloma / Q000473:pathology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D009570:Nitriles / Q000378:metabolism / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D001578:Benzopyrans; D002352:Carrier Proteins; C412403:DIABLO protein, human; D004791:Enzyme Inhibitors; D005419:Flavonoids; D005609:Free Radicals; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D009570:Nitriles; D010880:Piperidines; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C456800:ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate; D019938:Cyclin D1; C077990:alvocidib; D045304:Cytochromes c; D018844:Cyclin-Dependent Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases