Abstract
Apoptin, a chicken anemia virus-derived protein, selectively induces apoptosis in transformed but not in normal cells, thus making it a promising candidate as a novel anticancer therapeutic. The mechanism of apoptin-induced apoptosis is largely unknown. Here, we report that contrary to previous assumptions, Bcl-2 and Bcl-xL inhibit apoptin-induced cell death in several tumor cell lines. In contrast, deficiency of Bax conferred resistance, whereas Bax expression sensitized cells to apoptin-induced death. Cell death induction by apoptin was associated with cytochrome c release from mitochondria as well as with caspase-3 and -7 activation. Benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, a broad spectrum caspase inhibitor, was highly protective against apoptin-induced cell death. Apoptosis induced by apoptin required Apaf-1, as immortalized Apaf-1-deficient fibroblasts as well as tumor cells devoid of Apaf-1 were strongly protected. Thus, our data indicate that apoptin-induced apoptosis is not only Bcl-2- and caspase dependent, but also engages an Apaf-1 apoptosome-mediated mitochondrial death pathway.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Chloromethyl Ketones / pharmacology
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Apoptosis*
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Apoptotic Protease-Activating Factor 1
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Breast Neoplasms / metabolism
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Breast Neoplasms / pathology
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Capsid Proteins / pharmacology*
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Caspase 3
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Caspase 7
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Caspase Inhibitors
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Caspases / metabolism
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Cysteine Proteinase Inhibitors / pharmacology
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Cytochromes c / metabolism
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Enzyme Activation
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Female
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Fibroblasts / cytology
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Fibroblasts / drug effects
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Fibroblasts / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Lymphoma, B-Cell / metabolism
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Lymphoma, B-Cell / pathology
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Male
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Mitochondria / metabolism
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Prostatic Neoplasms / metabolism
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Prostatic Neoplasms / pathology
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Proteins / antagonists & inhibitors
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Proteins / genetics
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Proteins / metabolism*
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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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RNA, Small Interfering / pharmacology
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Tumor Cells, Cultured
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bcl-X Protein / genetics
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bcl-X Protein / metabolism*
Substances
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APAF1 protein, human
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Amino Acid Chloromethyl Ketones
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Apoptotic Protease-Activating Factor 1
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Capsid Proteins
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors
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Intracellular Signaling Peptides and Proteins
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Proteins
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Proto-Oncogene Proteins c-bcl-2
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RNA, Small Interfering
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VP3 protein, Chicken anemia virus
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bcl-X Protein
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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Cytochromes c
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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