Abstract
The primary aim of this study was to elucidate the role of the estrogen receptor (ER), a transcription factor involved in the nicotine- and 17β-estradiol (E2)-mediated up-regulation of α9-nAChR gene expression. A real-time polymerase chain reaction (PCR) assay was used to quantify the α9-nAChR mRNA expression levels of surgically isolated (n=339) and laser-capture microdissected tissues (ER+ versus ER-, n= 6 per group). Chromatin immunoprecipitation (ChIP) and luciferase-promoter activity assays were used to investigate the ER-mediated transcriptional regulation of α9-nAChR gene expression. We observed that breast tumors with higher α9-nAChR mRNA expression levels (i.e., a mean fold ratio in the tumor/normal-paired samples of greater than tenfold) were associated with the lowest 5-year disease-specific survival rate (50%, dead/alive= 4/4, total = 8 patients, P= 0.006), in contrast to breast tumors with low levels (i.e., a mean fold ratio of less than onefold) of α9-nAChR expression (88%, dead/alive= 3/22, total= 25 patients). Furthermore, higher α9-nAChR mRNA expression levels were preferentially detected in ER+ tumor tissues in comparison to ER- tumor tissues (ER+ versus ER- patients: n=160 vs. 72; mean fold ratios of α9-nAChR expression = 11 ± 3 vs. 6.7 ± 2.3 fold, respectively). In vitro promoter-binding assays demonstrated that the ER is a major transcription factor that mediates nicotine- and E2-induced up-regulation of α9-nAChR gene expression in MCF-7 cells. In conclusion, our data indicate that the ER plays a central role in mediating α9-nAChR gene up-regulation in response to either nicotine or E2 stimulation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Breast Neoplasms / genetics
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Breast Neoplasms / metabolism*
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Breast Neoplasms / mortality
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Breast Neoplasms / pathology
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Cell Line, Tumor
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Cell Proliferation / drug effects
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Chromatin Immunoprecipitation
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Dose-Response Relationship, Drug
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Estradiol / pharmacology*
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Estrogen Receptor alpha / agonists*
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Estrogen Receptor alpha / metabolism
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Extracellular Signal-Regulated MAP Kinases / metabolism
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Female
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Genes, Reporter
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Humans
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Kaplan-Meier Estimate
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Middle Aged
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Nicotine / pharmacology*
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Nicotinic Agonists / pharmacology*
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Phosphorylation
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Prognosis
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Promoter Regions, Genetic
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Proto-Oncogene Proteins c-akt / metabolism
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RNA, Messenger / metabolism
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Receptor Cross-Talk*
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Receptors, Nicotinic / drug effects*
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Receptors, Nicotinic / genetics
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Receptors, Nicotinic / metabolism
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Signal Transduction
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Survival Rate
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Time Factors
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Transcription Factor AP-1 / metabolism
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Transfection
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Up-Regulation
Substances
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CHRNA9 protein, human
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ESR1 protein, human
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Estrogen Receptor alpha
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Nicotinic Agonists
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RNA, Messenger
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Receptors, Nicotinic
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Transcription Factor AP-1
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Estradiol
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Nicotine
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Proto-Oncogene Proteins c-akt
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Extracellular Signal-Regulated MAP Kinases