Although there is strong evidence that thyroid tumors occur more frequently in females than in males, few studies have investigated the role sex hormones play in thyroid carcinogenesis, especially the role of estrogen (E2). This laboratory has previously shown that estrogen receptors (ERs) exist in thyroid papillary carcinoma cells. Continuing along this line of research, we studied the role of E2 and its receptors on the regulation of human thyroid cancer. / In conclusion, we have demonstrated (1) a novel mechanism by which E2 contributes to the proliferation and growth of thyroid cancer cells, (2) that E2 influences the expression of ERalpha and ERbeta differently, causing an imbalance between them, which may change the biological behavior of thyroid cancer cells, giving them the ability to proliferate and resist apoptosis by influencing the level of ERK1/2 activity and subsequently the ratio of anti-apoptotic Bcl-2 to pro-apoptotic Bax, and (3) that the subcellular localization of ERalpha and ERbeta may be a factor that contributes to the differing pathogeneses of papillary and anaplastic thyroid cancers. / To further clarify the mechanism by which E2 promotes cellular proliferation in thyroid cancer cells, we studied the localization of ERalpha and ERbeta in both KAT5 and anaplastic carcinoma cells (FRO) by immunofluorescence staining and by immunoblotting of the proteins in subcellular fractions. Cell proliferation and apoptosis were examined together with the expression of selected apoptotic proteins such as Bax, AIF and cytochrome c. We showed that the subcellular localization of ERalpha and ERbeta differed in papillary and anaplastic thyroid cancer. E2 administration led to an increase in the level of ERalpha in the nuclei of papillary cancer cells while the levels of ERbeta remained unchanged. However, the level of mitochondrial ERbeta surpassed that of ERalpha in anaplastic cancer cells. We also showed that E2 affected caspase-dependent and/or independent apoptosis via ERs in thyroid cancers. / We first studied the molecular pathways by which E2 promotes cellular proliferation in thyroid cancer cells using a human thyroid cancer cell line (KAT5) treated with E2, a selective E2 alpha receptor (ERalpha) agonist (PPT), a selective E2 beta receptor (ERbeta) agonist (DPN), an ERalpha antagonist (MPP), an E2 antagonist (ICI182780) and siRNA, which blocks ERalpha and ERbeta, by MTT assay, DNA fragmentation ELISA, BrdU cell proliferation assay and Western blot. We found that E2 and PPT gradually promoted cell proliferation by increasing the expression of ERalpha and by up-regulating the expression of Bcl-2 and pERK1/2. In contrast, we found that DPN had a negative effect on cell growth by enhancing the expression of ERbeta and Bax and by down-regulating pERK1/2 expression. At the same time, blocking ERalpha significantly reduced the E2-mediated Bcl-2 and pERK1/2 expression. On the other hand, blocking ERbeta markedly enhanced their expression. These results suggest that E2 regulates cellular growth of KAT5 cells by an ER-ERK1/2-MAPK pathway and also that E2 affects mitochondrial homeostasis. / Zeng, Qiang. / "September 2007." / Adviser: George Gong Chen. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4616. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 136-154). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344099 |
| Date | January 2007 |
| Contributors | Zeng, Qiang, Chinese University of Hong Kong Graduate School. Division of Surgery. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xiv, 154 p. : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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