Aryl hydrocarbon and estrogen receptor Alpha crosstalk in human breast and endometrial cancer cell lines /
Ishikawa human endometrial cancer cells express the estrogen receptor alpha (ERα); this study examined the aryl hydrocarbon receptor (AhR) expression and inhibitory AhR-ERα crosstalk in this cell line. The presence of AhR and Arnt was verified by sucrose density gradients and Western blot analyses....
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765106271&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Ishikawa human endometrial cancer cells express the estrogen receptor alpha (ERα); this study examined the aryl hydrocarbon receptor (AhR) expression and inhibitory AhR-ERα crosstalk in this cell line. The presence of AhR and Arnt was verified by sucrose density gradients and Western blot analyses. CYP1A1-dependent ethoxyresorufin O-deethylase (EROD) activity and AhR-responsive chloramphenicol acetyltransferase (CAT) reporter constructs verified AhR functionality. The AhR ligands TCDD, benzo[a]pyrene (BaP) or 6-methyl-1,3,8-trichlorodibenzofuran inhibited 17β-estradiol (E2)-induced cell proliferation and E2-responsive CAT reporter constructs. In contrast, 17β-estradiol or progesterone did not inhibit EROD activity induced by TCDD in Ishikawa cells. However, E2 did significantly inhibit TCDD-induced EROD activity in ECC-1 human endometrial cancer cells suggesting that these interactions were cell context dependent. TCDD is an environmental toxin that has been shown to disrupt multiple endocrine signaling pathways. T47D human breast carcinoma and MCF-7 human breast adenocarcinoma cancer cell lines express functional ERα, AhR, and Arnt. Treatment of these cells with TCDD resulted in a rapid decrease of immunoreactive ERα protein in the absence of E2, and co-treatment with both TCDD plus E2 resulted in a greater decrease in ERα protein levels. TCDD-induced degradation of ERα was blocked by several proteasome inhibitors but not by protease inhibitors. TCDD and other AhR ligands suppress E2-induced responses in rodent uterus and mammary tumors and in human breast cancer cells. TCDD induced proteasome-dependent degradation of ERα in ZR-75 (carcinoma), T47D, and MCF-7 human breast cancer cell lines. ERα levels in the mouse uterus and breast cancer cells were significantly lower after co-treatment with E2 plus TCDD than after treatment with TCDD or E2 alone. TCDD alone or in combination with E2 increased formation of ubiquitinated forms of ERα. Both coimmunoprecipitation and mammalian two hybrid assays demonstrate that TCDD induces interaction of the AhR with ERα in the presence or absence of E2. In contrast E2 does not induce AhR-ERα interactions. |
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| Item Description: | Vita. "Major Subject: Toxicology". |
| Physical Description: | xii, 238 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 171-237). |