Abstract
Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder maintained by cancer stem cells. To target this population, we investigated the mechanism of action of BMS-214662, developed as a farnesyl transferase inhibitor (FTI) and unique in inducing apoptosis in these cells. By contrast, a related congener and equally effective FTI, BMS-225975 does not induce apoptosis, indicating a novel mechanism of action. BMS-214662 significantly and selectively induced apoptosis in primitive CD34(+)38(-) CML compared with normal cells. Apoptosis proceeded via the intrinsic pathway: Bax conformational changes, loss of mitochondrial membrane potential, generation of reactive oxygen species, release of cytochrome c, and caspase-9/3 activation were noted. Up-regulation of protein kinase Cbeta (PKCbeta), down-regulation of E2F1, and phosphorylation of cyclin A-associated cyclin-dependent kinase 2 preceded these changes. Cotreatment of CML CD34(+) and CD34(+)38(-) cells with PKC modulators, bryostatin-1, or hispidin markedly decreased these early events and the subsequent apoptosis. None of these events was elicited by BMS-214662 in normal CD34(+) cells or by BMS-225975 in CML CD34(+) cells. These data suggest that BMS-214662 selectively elicits a latent apoptotic pathway in CML stem cells that is initiated by up-regulation of PKCbeta and mediated by Bax activation, providing a molecular framework for development of novel therapeutics.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ADP-ribosyl Cyclase 1 / metabolism
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Antigens, CD34 / metabolism
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Apoptosis / drug effects*
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Benzodiazepines / pharmacology*
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Bryostatins / pharmacology
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Caspases / metabolism
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Cyclin A / metabolism
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Cyclin-Dependent Kinase 2 / metabolism
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E2F1 Transcription Factor / metabolism
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Farnesyltranstransferase / antagonists & inhibitors
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Humans
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Imidazoles / pharmacology*
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In Vitro Techniques
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / enzymology
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / immunology
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
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Membrane Glycoproteins / metabolism
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Microscopy, Electron, Transmission
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Mitochondria / drug effects
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Neoplastic Stem Cells / drug effects*
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Neoplastic Stem Cells / immunology
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Neoplastic Stem Cells / pathology
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Protein Kinase C / metabolism*
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Protein Kinase C beta
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bcl-2-Associated X Protein / metabolism
Substances
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Antigens, CD34
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BAX protein, human
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Bryostatins
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Cyclin A
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E2F1 Transcription Factor
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E2F1 protein, human
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Enzyme Inhibitors
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Imidazoles
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Membrane Glycoproteins
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bcl-2-Associated X Protein
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Benzodiazepines
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bryostatin 1
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Farnesyltranstransferase
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Protein Kinase C
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Protein Kinase C beta
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CDK2 protein, human
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Cyclin-Dependent Kinase 2
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CD38 protein, human
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ADP-ribosyl Cyclase 1
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Caspases
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7-cyano-2,3,4,5-tetrahydro-1-(1H-imidazol-4-ylmethyl)-3-(phenylmethyl)-4-(2-thienylsulfonyl)-1H-1,4-benzodiazepine