Abstract
Acadesine, 5-aminoimidazole-4-carboxamide (AICA) riboside, induced apoptosis in B-cell chronic lymphocytic leukemia (B-CLL) cells in all samples tested (n = 70). The half-maximal effective concentration (EC(50)) for B-CLL cells was 380 +/- 60 microM (n = 5). The caspase inhibitor Z-VAD.fmk completely blocked acadesine-induced apoptosis, which involved the activation of caspase-3, -8, and -9 and cytochrome c release. Incubation of B-CLL cells with acadesine induced the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK), indicating that it is activated by acadesine. Nitrobenzylthioinosine (NBTI), a nucleoside transport inhibitor, 5-iodotubercidin, an inhibitor of adenosine kinase, and adenosine completely inhibited acadesine-induced apoptosis and AMPK phosphorylation, demonstrating that incorporation of acadesine into the cell and its subsequent phosphorylation to AICA ribotide (ZMP) are necessary to induce apoptosis. Inhibitors of protein kinase A and mitogen-activated protein kinases did not protect from acadesine-induced apoptosis in B-CLL cells. Moreover, acadesine had no effect on p53 levels or phosphorylation, suggesting a p53-independent mechanism in apoptosis triggering. Normal B lymphocytes were as sensitive as B-CLL cells to acadesine-induced apoptosis. However, T cells from patients with B-CLL were only slightly affected by acadesine at doses up to 4 mM. AMPK phosphorylation did not occur in T cells treated with acadesine. Intracellular levels of ZMP were higher in B-CLL cells than in T cells when both were treated with 0.5 mM acadesine, suggesting that ZMP accumulation is necessary to activate AMPK and induce apoptosis. These results suggest a new pathway involving AMPK in the control of apoptosis in B-CLL cells and raise the possibility of using acadesine in B-CLL treatment.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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AMP-Activated Protein Kinases
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Adenosine / pharmacology
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Amino Acid Chloromethyl Ketones / pharmacology
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Aminoimidazole Carboxamide / analogs & derivatives*
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Aminoimidazole Carboxamide / antagonists & inhibitors
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Aminoimidazole Carboxamide / metabolism
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Aminoimidazole Carboxamide / pharmacology*
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Antimetabolites, Antineoplastic / pharmacology*
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Apoptosis / drug effects*
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B-Lymphocytes / drug effects*
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B-Lymphocytes / enzymology
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B-Lymphocytes / pathology
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Caspases / metabolism
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Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
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Cysteine Proteinase Inhibitors / pharmacology
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Humans
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Leukemia, Lymphocytic, Chronic, B-Cell / enzymology
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Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
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MAP Kinase Signaling System / drug effects
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Mitochondria / drug effects
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Multienzyme Complexes / metabolism*
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Neoplasm Proteins / metabolism*
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Neoplastic Stem Cells / drug effects*
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Neoplastic Stem Cells / enzymology
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Neoplastic Stem Cells / pathology
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein Serine-Threonine Kinases / metabolism*
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Ribonucleosides / antagonists & inhibitors
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Ribonucleosides / pharmacology*
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Ribonucleotides / metabolism
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T-Lymphocytes / drug effects
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T-Lymphocytes / enzymology
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Tubercidin / analogs & derivatives*
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Tubercidin / pharmacology
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / enzymology
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Tumor Cells, Cultured / pathology
Substances
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Amino Acid Chloromethyl Ketones
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Antimetabolites, Antineoplastic
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Cysteine Proteinase Inhibitors
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Enzyme Inhibitors
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Multienzyme Complexes
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Neoplasm Proteins
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Ribonucleosides
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Ribonucleotides
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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5-iodotubercidin
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Aminoimidazole Carboxamide
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acadesine
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Protein Serine-Threonine Kinases
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Cyclic AMP-Dependent Protein Kinases
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Mitogen-Activated Protein Kinases
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AMP-Activated Protein Kinases
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Caspases
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AICA ribonucleotide
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Adenosine
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Tubercidin