Neuroblastoma is one of the most common solid tumors in patients below the age of 15. In this PhD project, the possible anti-tumor effects of the soy isoflavones on neuroblastoma cells have been investigated. A number of aspects of neuroblastoma cancer cell biology, including cell proliferation, cell cycle regulation, cell differentiation and apoptosis, intracellular signaling mechanisms, tumor invasiveness and metastatic properties, have been examined. Furthermore, novel antitumor properties of the soy isoflavones on neuroblastoma have also been quested for, hoping that through this PhD project, a better understanding of the potential anti-tumor effects of soy isoflavones on neuroblastoma cells can be obtained. In Chapter Three, we have demonstrated that the major soy isoflavones daidzein and genistein exerted potent anti-proliferative effect on murine neuroblastoma Neuro-2a (BU-1) cells. These two compounds were shown to modulate cell cycle distribution in BU-1 cells in different ways, possible through their differential effects on the expression of cell cycle regulatory proteins such as cyclins and cyclin-dependent kinase inhibitors. The anti-tumor effect of daidzein was found to be fairly specific to tumor cells, as daidzein only exhibited little, if any, direct cytotoxicity to normal murine cells such as bone marrow cells, macrophages, and thymocytes. Furthermore, the anti-proliferative effect of daidzein was unlikely to be attributed to its direct cytotoxicity to the BU-1 cells, but might be coupled with its ability to trigger the apoptosis and differentiation in the neuroblastoma cells. Our results show that daidzein could induce DNA fragmentation, ultrastructural changes, and the enrichment of cytoplasmic mono- and oligo-nucleosomes in the treated-BU-1 cells. Moreover, daidzein was shown to induce neuronal differentiation in the BU-1 cells, as indicated by morphological changes, and increased expression of the neuronal differentiation marker microtubule-associated protein-2, and acetylcholine esterase activity. In addition, we have also demonstrated that the signals of daidzein might be mediated by the estrogen receptor and nuclear factor-kappa B pathways. In Chapter Four, daidzein was shown to exert a differential an proliferative effect on three human neuroblastoma cell lines, including SK-N-DZ and SH-SY5Y. The most sensitive cell line, LA-N-1, was chosen for further mechanistic studies. It was found that daidzein-induced growth-inhibitory effect was coupled with the induction of neurite outgrowth and altered mRNA expression of the N-myc-related transcription factors. Moreover, daidzein was observed to modulate the invasiveness and metastatic properties of LA-N-1 cells, as indicated by the reduction of colony-forming ability, cell migratory ability, in vivo tumorigenicity, tumor vascularity, and angiogenic factors expression. Our results clearly suggest that the major soy isoflavone daidzein can exert its pleiotropic anti-tumor effects on both marine and human neuroblastoma cells. In Chapter Five, we isolated two stable actively proliferating subclones from the human neuroblastoma SH-SY5Y cells. We compared the sensitivities of the parental SH-SY5Y cells and the active subclones to the growth inhibition exerted by a number of conventional cancer chemotherapeutic agents and the soy isoflavone derivatives. We found that the major soy isoflavones daidzein and genistein were rather selective to the active subclones and this phenomenon was not observed with other chemotherapeutic agents. The anti-tumor action mechanisms of genistein on the most active subclone, designated as SH-SY5Y cl.6 cells, were examined in detail. It was found that genistein could induce apoptosis in SH-SY5Y cl.6 cells, as indicated by the induction of ultrastructural changes, phosphatidylserine externalization, and cytoplasmic enrichment of mono- and oligo-nucleosomes. The genistein-induced apoptosis in SH-SY5Y cl.6 cells was found to be both mitochondria and caspases-dependent, as mitochondrial membrane depolarization, cytosolic release of apoptotic mitochondrial factors and activation of caspase-3 were observed. To sum up, our results show that the major soy isoflavones, particularly daidzein and genistein, exhibit pleiotropic anti-tumor effects on both murine and human neuroblastoma cells, and they are also selective to the actively proliferating human neuroblastoma cells. (Abstract shortened by UMI.) / Lo, Fai-Hang. / "September 2007." / Adviser: Leung Kwok-Nam. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0949. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 255-287). / 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_344066 |
| Date | January 2007 |
| Contributors | Lo, Fai-Hang., Chinese University of Hong Kong Graduate School. Division of Biochemistry. |
| 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 (xxv, 287 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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