Inhibition of extracellular signal-regulated kinase (ERK) mediates cell cycle phase independent apoptosis in vinblastine-treated ML-1 cells.
Chemotherapeutic agents induce alterations in intracellular signal transduction cascades that culminate in the initiation of the apoptotic program. Here, the relationship between the mitogen-activated protein kinase (MAPK) response and apoptosis in ML-1 cells treated with vinblastine and paclitaxel was investigated. We show that these compounds elicit different effects on MAPKs with vinblastine, but not paclitaxel, increasing both c-Jun-NH2-terminal kinase (JNK) and p38 activity. However, vinblastine and paclitaxel both induced apoptosis with similar kinetics, suggesting that increased JNK and p38 activity is not required for apoptosis that is induced by microtubule interfering agents. Strikingly, the abrogation of extracellular signal-regulated kinase (ERK)-signaling by the MAPK/ERK kinase (MEK)1/2 inhibitor PD098059 in combination with vinblastine robustly induced apoptosis in ML-1 cells at a rate much faster than treatment with vinblastine alone and occurred at all phases of the cell cycle. This apoptotic induction was attributed to JNK activation because: (a) non-JNK-activating concentrations of vinblastine failed to increase apoptosis in the presence of PD098059; (b) apoptosis induced by paclitaxel, which did not activate JNK, was not potentiated by PD098059; and (c) transduction of an inhibitor of JNK activity partially suppressed both JNK activity and apoptosis induced by vinblastine plus PD098059. Additionally, we found that the activation of JNK by vinblastine occurred upstream of effector caspase activation because treatment with a pan-specific caspase inhibitor (valine-alanine-aspartate-fluoromethylketone) resulted in complete abrogation of apoptosis with no effect on MAPK signaling. Taken together, these data suggest that inhibition of the MEK-->ERK signal transduction cascade alleviates cell cycle dependence for vinblastine-induced apoptosis by a mechanism that requires JNK activation.
Stadheim
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Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Xiao
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Eastman
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D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D061945:Caspase Inhibitors; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D004357:Drug Synergism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007951:Leukemia, Myeloid / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
D000972:Antineoplastic Agents, Phytogenic; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D014747:Vinblastine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D017239:Paclitaxel; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one