Abstract
Bcl-2 protein plays a critical role in inhibiting anticancer drug-induced apoptosis. We found that Bcl-2 overexpression is associated with a nearly 3-fold increase in cellular glutathione levels and with increased resistance to cell death after treatment with etoposide or SN-38, a derivative of camptothecin, in leukemia 697 cells with wild-type p53. Treatment of Bcl-2-overexpressing 697 cells (697-Bcl-2) with buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, reduced cellular glutathione levels and completely abolished Bcl-2-mediated drug resistance. Morphologic studies revealed that nonapoptotic cell death was induced in 697-Bcl-2 cells after treatment with BSO plus etoposide or SN-38. Activation of caspase-3/7 and cytochrome c release could not be detected in 697-Bcl-2 cells after these drug treatments. Notably, we showed that proteasome-mediated down-regulation of Puma and Noxa proteins occurs in 697-Bcl-2 cells after treatment with BSO plus topoisomerase inhibitor, although there is an increase in the protein levels of p53 in these 697-Bcl-2 cells. In contrast, parental 697 cells underwent typical apoptosis with up-regulation of Puma and Noxa proteins, followed by cytochrome c release and caspase-3/7 activation after treatment with topoisomerase inhibitor in the presence or absence of BSO. Our data suggest that BSO may possess a unique activity to overcome Bcl-2-mediated drug resistance by stimulating the signals that can bypass mitochondrial process in Bcl-2-overexpressing cells.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Antineoplastic Combined Chemotherapy Protocols / pharmacology
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Apoptosis Regulatory Proteins / biosynthesis
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Apoptosis Regulatory Proteins / genetics
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Buthionine Sulfoximine / administration & dosage
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Buthionine Sulfoximine / pharmacology
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Camptothecin / administration & dosage
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Camptothecin / analogs & derivatives
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Camptothecin / pharmacology
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Caspase 3
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Caspase 7
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Caspases / metabolism
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Cell Death / drug effects
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Cell Death / physiology
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Cell Line, Tumor
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DNA Topoisomerases, Type I / metabolism
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Drug Resistance, Multiple
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Drug Resistance, Neoplasm
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Enzyme Activation
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Etoposide / administration & dosage
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Etoposide / pharmacology
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Gene Expression Regulation, Leukemic / drug effects
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Glutathione / antagonists & inhibitors*
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Glutathione / biosynthesis*
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Humans
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Irinotecan
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Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / drug therapy*
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Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / enzymology
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Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / metabolism*
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Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / pathology
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Proto-Oncogene Proteins / biosynthesis
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors
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Proto-Oncogene Proteins c-bcl-2 / biosynthesis
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism*
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Topoisomerase I Inhibitors*
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Tumor Suppressor Protein p53 / biosynthesis
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Tumor Suppressor Protein p53 / genetics
Substances
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Apoptosis Regulatory Proteins
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BBC3 protein, human
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PMAIP1 protein, human
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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TP53 protein, human
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Topoisomerase I Inhibitors
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Tumor Suppressor Protein p53
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Buthionine Sulfoximine
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Etoposide
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Irinotecan
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CASP3 protein, human
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CASP7 protein, human
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Caspase 3
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Caspase 7
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Caspases
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DNA Topoisomerases, Type I
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Glutathione
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Camptothecin