CUHK electronic theses & dissertations collection

Insulin-like growth factor I (IGF-I) is a polypeptide protein hormone similar to insulin. It plays an important role in growth and anabolic effects in life. Most circulating IGF-I is bound to high-affinity insulin-like growth factor binding protein-3 (IGFBP-3), to form a complex (IGF-I/IGFBP-3) that can treat growth hormone insensitivity syndrome (GHIS) and can lower plasma glucose in diabetic patients. Its side effects can be reduced without affecting the therapeutic efficacy. Human insulin-like growth factor binding protein 3 (hIGFBP-3) alone is an anti-tumor agent. It has been shown to have anti-proliferation effect on numerous cancer cells, such as breast, prostate and liver cancers.Our previous study has demonstrated that recombinant hIGF-I (rhIGF-I) and hIGFBP-3 (rhIGFBP-3) could be synthesized in transgenic tobacco plant. In the present study, we propose to establish an efficient bioreactor platform for mass production of hIGF-I and hIGFBP-3 in rice, as rice grain contains 8-15% of protein by dry weight. In order to enhance rhIGF-I and rhIGFBP-3 stability and yield, and to control their glycosylation, various constructs were designed and transformed into rice by Agrobacterium-mediated transformation. Protein targeting signal sequence (KDEL) was fused to direct the target proteins to specific compartments in rice grain for glycosylation in the Golgi apparatus or for stable accumulation without complex glycan processing in the endoplasmic reticulum. These expression constructs were driven by seed-specific glutelin promoter (Gt1pro). Western blot analysis showed that the rhIGF-I and rhIGFBP-3 were successfully expressed in transgenic rice grains. Biological activity of rhIGF-I was evidenced by the induction of membrane ruffling in L6 rat skeletal muscle cells, while rhIGFBP-3 was effective in inhibiting the effect of IGF-I on membrane ruffling of L6 cell. Moreover, rhIGFBP-3 was also found to inhibit the growth of human breast cancer MCF-7 cells. Biological activity results showed that the active expression levels of rhIGF-I and rhIGFBP-3 were found to be 10 ug and 7.36 ug per 1 g of rice seed respectively. These findings suggested that both rice-produced rhIGF-I and rhIGFBP-3 were biologically active.Cheung, Chun Kai."September 2007."Adviser: Peter Tong Chun Yip.Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4555.Thesis (Ph.D.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (p. 209-243).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