title: Glucocorticoid receptor-induced MAPK phosphatase-1 (MPK-1) expression inhibits paclitaxel-associated MAPK activation and contributes to breast cancer cell survival.
abstract: Glucocorticoid receptor (GR) activation has recently been shown to inhibit apoptosis in breast epithelial cells. We have previously described a group of genes that is rapidly up-regulated in these cells following dexamethasone (Dex) treatment. In an effort to dissect the mechanisms of GR-mediated breast epithelial cell survival, we now examine the molecular events downstream of GR activation. Here we show that GR activation leads to both the rapid induction of MAPK phosphatase-1 (MKP-1) mRNA and its sustained expression. Induction of the MKP-1 protein in the MCF10A-Myc and MDA-MB-231 breast epithelial cell lines was also seen. Paclitaxel treatment resulted in MAPK activation and apoptosis of MDA-MB-231 breast cancer cells, and both processes were inhibited by Dex pretreatment. Furthermore, induction of MKP-1 correlated with the inhibition of extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) activity, whereas p38 activity was minimally affected. Blocking Dex-induced MKP-1 induction using small interfering RNA increased ERK1/2 and JNK phosphorylation and decreased cell survival. ERK1/2 and JNK inactivation was associated with Ets-like transcription factor-1 (ELK-1) dephosphorylation. To explore the gene expression changes that occur downstream of ELK-1 dephosphorylation, we used a combination of temporal gene expression data and promoter element analyses. This approach revealed a previously unrecognized transcriptional target of ELK-1, the human tissue plasminogen activator (tPA). We verified the predicted ELK-1--> tPA transcriptional regulatory relationship using a luciferase reporter assay. We conclude that GR-mediated MAPK inactivation contributes to cell survival and that the potential transcriptional targets of this inhibition can be identified from large scale gene array analysis.
authors.affiliation: Department of Medicine and the Committee on Cancer Biology, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Travis
authors.initials: T
authors.lastname: Pew
authors.forename: Min
authors.initials: M
authors.lastname: Zou
authors.forename: Diana
authors.initials: D
authors.lastname: Pang
authors.forename: Suzanne D
authors.initials: SD
authors.lastname: Conzen
mesh_terms: D020816:Amino Acid Motifs; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D001940:Breast / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D015536:Down-Regulation; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000096:biosynthesis; D048052:Mitogen-Activated Protein Kinase 3 / Q000096:biosynthesis; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D017239:Paclitaxel / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011485:Protein Binding; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection; D050807:ets-Domain Protein Elk-1; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; D017874:Immediate-Early Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D008156:Luciferases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; D010959:Tissue Plasminogen Activator; D017239:Paclitaxel