2003 Fiscal Year Final Research Report Summary
Mechanisms of the regulation of estrogen receptor function in acquisition of resistance to estrogen-ablation of breast cancer
| Project/Area Number |
13671169
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Endocrinology
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| Research Institution | Radiation Effects Research Foundation |
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Principal Investigator |
EGUCHI Hidetaka Radiation Effects Research Foundation, Department of Radiobiology/Molecular Epidemiology, Research Scientist, 放射線生物学・分子疫学部, 研究員 (00260232)
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| Co-Investigator(Kenkyū-buntansha) |
MASAMURA Shigeru Tokyo Dental College Ichikawa General Hospital, Department of Surgery, Associate Professor, 市川総合病院外科, 助教授 (40190342)
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| Project Period (FY) |
2001 – 2003
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| Keywords | breast cancer / estrogen receptor |
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| Research Abstract |
We have studied the involvement of estrogen receptor (ER) α in the acquisition of resistance against estrogen-ablation using breast cancer cells MCF-7B that show estrogen-dependent cell growth and its derivative MCF-7D cells that are established by long time culture under estrogen depleted condition. Intracellular concentration of estrone and estradiol (E2) did not differ among MCF-7B and MCF-7D cells, suggesting that intracellular biosynthesis of estrogen is not related to the resistance. Next, we evaluated the transcription activities of ERα in these cells. Transient transfection of reporter gene possessing estrogen responsive element (ERE) in front of the promoter has been performed to examine the transcription activity of ERα under various concentrations of E2. Notably, MCF-7D cells showed transcription activity of endogenous ERα even in the absence of E2. Transient transfection of chimeric genes of ERα transactivation domain AF-1 or AF-2 with GAL4 DNA binding domain (DBD) revealed that both of these domains contribute to the enhancement of ERα activity in MCF-7D cells under estrogen depleted condition. In order to investigate this activation mechanism, we established stable transformants expressing these chimeric genes. In MCF-7D cells, both AF-1 and AF-2 domains were activated by the addition of E2, and the activated activity was efficiently inhibited by pure anti-estrogen ICI182,780. Moreover, DNA-pull down experiment using DNA fragment containing ERE as scaffold demonstrated that protein complexes involved in the transcriptional using DNA fragment containing ERE as scaffold demonstrated that protein complexes involved in the transcriptional regulation differed among these cells. In addition, we also showed that constitutively activated MAP kinase directly activated the ERα in MCF-7D cells, and that membrane-associated ERα is involved in the activation of MAP kinase.
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Research Products
(12 results)
