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.
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.
Pei
Xin-Yan
XY
Department of Medicine, Virginia Commonwealth University/Medical College of Virginia, Richmond, Virginia 23298, USA.
Dai
Yun
Y
Grant
Steven
S
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
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