Abstract
Little knowledge exists about the mechanisms by which estrogen can impede chemotherapy-induced cell death of breast cancer cells. 17beta-Estradiol (E(2)) hinders cytotoxic drug-induced cell death in estrogen receptor-positive (ER(+)) breast cancer cells. We noted that the activity of the proapoptotic mixed lineage kinase 3 (MLK3) kinase was relatively higher in estrogen receptor-negative (ER(-)) breast tumors, suggesting that E(2) might inhibit MLK3 activity. The kinase activities of MLK3 and its downstream target, c-Jun NH(2)-terminal kinase, were rapidly inhibited by E(2) in ER(+) but not in ER(-) cells. Specific knockdown of AKT1/2 prevented MLK3 inhibition by E(2), indicating that AKT mediated this event. Furthermore, MLK3 inhibition by E(2) involved phosphorylation of MLK3 Ser(674) by AKT, attenuating the proapoptotic function of MLK3. We found that a pan-MLK inhibitor (CEP-11004) limited Taxol-induced cell death and that E(2) accentuated this limitation. Taken together, our findings indicate that E(2) inhibits the proapoptotic function of MLK3 as a mechanism to limit cytotoxic drug-induced death of ER(+) breast cancer cells.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Apoptosis / drug effects*
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Breast Neoplasms / drug therapy
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Breast Neoplasms / genetics
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Breast Neoplasms / pathology*
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Carcinoma / drug therapy
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Carcinoma / genetics
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Carcinoma / pathology*
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Cell Line, Tumor
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Cells, Cultured
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Down-Regulation / drug effects
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Drug Resistance, Neoplasm / drug effects
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Drug Resistance, Neoplasm / genetics
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Enzyme Activation / drug effects
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Estradiol / pharmacology*
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Estrogen Receptor alpha / genetics*
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Estrogen Receptor alpha / metabolism
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Estrogen Receptor alpha / physiology
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Female
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Humans
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JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
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JNK Mitogen-Activated Protein Kinases / metabolism
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MAP Kinase Kinase Kinases / antagonists & inhibitors*
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MAP Kinase Kinase Kinases / metabolism
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MAP Kinase Kinase Kinases / physiology
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Mice
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Mitogen-Activated Protein Kinase Kinase Kinase 11
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Models, Biological
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Proto-Oncogene Proteins c-akt / metabolism
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Receptors, Progesterone / genetics
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Receptors, Progesterone / metabolism
Substances
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Estrogen Receptor alpha
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Receptors, Progesterone
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Estradiol
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Proto-Oncogene Proteins c-akt
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JNK Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinases