Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Pathology

Supervisor

Dr.WeiPing Min

Abstract

RNAi has great potential in future therapeutics as it has the ability to regulating many disease-related genes. However, many barriers prevent practical applications. To overcome the barriers, the specific targeting, efficient delivery system, the validated gene and the potent siRNA sequence are all vital important. The studies throughout this thesis have been focued on examining the validation of three RNAi therapies for two different disease models: allergic contact dermatitis and melanoma. For allergic contact dermatitis, I developed and tested a novel topical delivery system for siRNAs targeting TNFα (siTNFα) and MyD88 siRNA (siMyD88). While siRNAs applied without the transdermal enhancer are ineffective, treatment with combined siMyD88 and siTNFα significantly attenuated contact hypersensitivity (CHS) symptoms in mice, and did so better than treatment with siMyD88 or siTNFα as single agents. This is the first demonstration of topical gene silencing of TNFα and MyD88 to treat allergic reactions, highlighting a potential clinical use of RNAi therapy for skin and allergic diseases. For melanoma, I examined two RNAi therapies using liposomes attached to mannose and folate ligand, respectively. We developed a novel DC (dendritic cell)-targeted siRNA delivery system using mannosed liposomes (Man-lipo) with encapsulated IDO siRNA (Man-lipo-siIDO), which preferentially knocks down IDO in DCs. Mice treated with Man-lipo-siIDO had a delayed time of onset of implanted murine melanomas, increased survival time, reduced tumour size, and increased reactivity of T cells from spleen and lymph nodes against melanoma antigens. This study supports the concept that Man-lipo-siIDO has potential for development as an immune-targeting therapeutic anticancer agent. We constructed a liposomal folate receptor-targeting siRNA delivery system. Compared to controls (non-treatment mice, mice treated with Folate-lipo-siScramble, or with non-folate-lipo-siBRAF), mice treated with Folate-lipo-siBRAF had reduced tumour volume, lower tumour weight, and reduced expression of PCNA and vascular networks in tumour tissue. This study highlights the potential of Folate-lipo-siBRAF for development as an anticancer therapeutic agent. In conclusion, the therapies for allergic dermatitis that use topical delivery of siTNFα and siMyD88, for melanoma using the Man-lipo-siIDO or the Folate-lipo-siBRAF, have the potential to be effective RNAi therapies to treat allergic dermatitis and melanoma.


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