Abstract
The effects of Dox (Dox), paclitaxel (Taxol), and serum starvation on the regulation of XIAP (X-linked inhibitor of apoptosis), Bcl-2 phosphorylation, and apoptosis were evaluated in human H460 non-small cell lung cancer cells. Protein kinases that responded to these treatments as prosurvival elements in signal transduction were identified by simultaneously screening phosphorylation of protein kinases in H460 cells cultured in serum-free medium or treated with Dox. We demonstrated that Dox and Taxol induced apoptosis through down-regulation of XIAP and phosphorylation of Bcl-2 in a concentration-dependent manner without changing expression of Bcl-xL in H460 cells. These effects were paralleled by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase protein. We identified that serum starvation and Dox reduced phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK), protein kinase C (PKC) alpha/beta and c-Jun NH(2)-terminal kinase. The MEK-specific inhibitor U0126 or PKC inhibitor staurosporine (STP) also down-regulated XIAP expression and induced apoptosis. Thus, our data suggest that apoptosis and down-regulation of XIAP induced by Dox exposure or serum starvation may be mediated through inactivation of the MEK/ERK and PKCalpha/beta pathways. In support of this we demonstrated that the cytotoxic effects of Dox when combined with U0126 or STP were enhanced, i.e., synergistic cytotoxic activities were demonstrated. The synergistic interaction of U0126 or STP with Dox was sequence- and concentration-dependent.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antineoplastic Agents / therapeutic use*
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Apoptosis / drug effects*
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Butadienes / pharmacology
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Carcinoma, Non-Small-Cell Lung / metabolism
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Carcinoma, Non-Small-Cell Lung / pathology*
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Caspases / metabolism
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Doxorubicin / therapeutic use
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Drug Synergism
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Drug Therapy, Combination
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Humans
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JNK Mitogen-Activated Protein Kinases
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Lung Neoplasms / metabolism
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Lung Neoplasms / pathology*
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Mitogen-Activated Protein Kinases / antagonists & inhibitors*
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Mitogen-Activated Protein Kinases / metabolism
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Nitriles / pharmacology
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Paclitaxel / therapeutic use
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Phosphorylation
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Poly(ADP-ribose) Polymerases / metabolism
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Protein Kinase C / antagonists & inhibitors
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Proteins / antagonists & inhibitors
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Signal Transduction
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Staurosporine / pharmacology
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / metabolism
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Tumor Cells, Cultured / pathology
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X-Linked Inhibitor of Apoptosis Protein
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bcl-X Protein
Substances
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Antineoplastic Agents
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BCL2L1 protein, human
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Butadienes
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Enzyme Inhibitors
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Nitriles
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Proteins
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Proto-Oncogene Proteins c-bcl-2
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U 0126
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X-Linked Inhibitor of Apoptosis Protein
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XIAP protein, human
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bcl-X Protein
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Doxorubicin
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Poly(ADP-ribose) Polymerases
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Protein Kinase C
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase Kinases
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Caspases
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Staurosporine
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Paclitaxel