Merbarone, a catalytic inhibitor of DNA topoisomerase II, induces apoptosis in CEM cells through activation of ICE/CED-3-like protease.
Merbarone (5-[N-phenyl carboxamido]-2-thiobarbituric acid) is an anticancer drug that inhibits the catalytic activity of DNA topoisomerase II (topo II) without damaging DNA or stabilizing DNA-topo II cleavable complexes. Although the cytotoxicity of the complex-stabilizing DNA-topo II inhibitors such as VP-16 (etoposide) has been partially elucidated, the cytotoxicity of merbarone is poorly understood. Here, we report that merbarone induces programmed cell death or apoptosis in human leukemic CEM cells, characterized by internucleosomal DNA cleavage and nuclear condensation. Treatment of CEM cells with apoptosis-inducing concentrations of merbarone caused activation of c-Jun NH2-terminal kinase/stress-activated protein kinase, c-jun gene induction, activation of caspase-3/CPP32-like protease but not caspase-1, and the proteolytic cleavage of poly(ADP-ribose) polymerase. Treatment of CEM cells with a potent inhibitor of caspases, Z-Asp-2. 6-dichlorobenzoyloxymethyl-ketone, inhibited merbarone-induced caspase-3/CPP32-like activity and apoptosis in a dose-dependent manner. These results indicate that the catalytic inhibition of topo II by merbarone leads to apoptotic cell death through a caspase-3-like protease-dependent mechanism. These results further suggest that c-Jun and c-Jun NH2-terminal kinase/stress-activated protein kinase signaling may be involved in the cytotoxicity of merbarone.
Division of Developmental Therapeutics, Cancer Center, College of Medicine, University of Illinois at Chicago, USA.
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Khélifa
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Beck
D017209:Apoptosis; D001216:Asparagine / Q000031:analogs & derivatives / Q000494:pharmacology; D029742:Caenorhabditis elegans Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D016758:Genes, jun / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013858:Thiobarbiturates / Q000494:pharmacology*; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured
D029742:Caenorhabditis elegans Proteins; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D013858:Thiobarbiturates; D059005:Topoisomerase II Inhibitors; C117865:benzyloxycarbonyl-asparagine; D001216:Asparagine; D011065:Poly(ADP-ribose) Polymerases; D011494:Protein Kinases; D048056:Mitogen-Activated Protein Kinase 9; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans; C089403:protease resembling ICE; C045459:merbarone