Ectopic and over-expression of G protein-coupled receptor (GPCR) have been reported to induce tumor formation. Mas protein is a member of GPCR family and was originally isolated from human epidermoid carcinoma. It was demonstrated that mas mRNA was abundantly expressed in human and rat brains by in situ hybridization and RNase protection assays. However, cellular mechanism that leads to such tumorigenic transformation is still an open question. / In order to identify the cellular mechanism of mas-induced tumor formation, a full-length mas cDNA was cloned into a mammalian expression vector pFRSV with dihydrofolate reductase gene as a selection marker. Detailed analyses of mas-transfected cell lines by Southern blot, Northern blot and tumorigenicity assay indicated that tumorigenicity of mas-transfected cells depended on the sites of chromosomal integration and the levels of mas expression. These results suggest that overexpression of mas is not sufficient to induce tumor formation. In line with the ability of mas-transfected cells Mc0M80 to form solid tumor in nude mice, MTT cell proliferation assay indicated that the mas-transfected cells Mc0M80 proliferated faster than vector-transfected cells. Moreover, mas-transfected cells Mc0M80 exhibited significantly increased anchorage-independent growth. Furthermore, mas-transfected cells Mc0M80 showed higher percentage cells in G2/M phase but lower in S-phase in comparison with vector-transfected cells. / Interestingly, Southern blot analysis of individual xenografted tumor tissue indicated that tumor was composed of cells not only derived from injected mas-transfected CHO cells but also cells from mouse tissues. The presence of mouse stromal cells in the tumor was confirmed by immunohistochemistry and in situ hybridization. Previously our laboratory had identified some up- and down-regulated genes in mas-transfected cells by fluorescent differential display (FluoroDD). Northern blot showed that these differential expressed genes were up- or down-regulated in mas-transfected cells and tumor samples, which might play an important role in cancerous growth. / Taken together, these results suggest that over-expression of GPCR mas up-regulated tumor-related genes, resulting in promoting excessive cell growth and tumorigenic transformation. In addition, when the tumor mass formed they secreted some growth factor(s) which altered the migration of mouse stromal cells into tumor mass. The interactions of transformed cells and stromal cells further aggravate the tumorigenicity process. / To complement our fluorescent differential display study and to compare changes of gene expression when transformed cells were exposed to the microenvironment in nude mice, protein expression profiles of mas over-expressing cells as well as tumor tissues were analyzed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry. The 2D-PAGE analysis showed that a similar but distinct protein expression profiles in mas-transfected cells and in mas-induced tumor. Mass spectrometry analysis identified several cancerous growth-related proteins and they are involved in processes such as cell signaling, energy metabolism, transcription and translation and cytoskeleton organization. / Lin Wenzhen. / "December 2005." / Adviser: Cheung Wing Tai. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6381. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 222-240). / 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. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_343716 |
| Date | January 2005 |
| Contributors | Lin, Wenzhen., 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 (xxi, 240 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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