Development of a Novel Htertc27 Based Cancer: Gene Therapy

This dissertation, "Development of a Novel HTERTC27 Based Cancer: Gene Therapy" by Yi, Gao, 高毅, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled "Development of a Novel hTERTC27 based Cancer Gene Therapy" Submitted by GAO Yi for the degree of Doctor of Philosophy at The University of Hong Kong in February 2007 Glioblastoma multiforme (GBM) is the most common and malignant primary tumors found in the human central nervous system. Despite surgery, chemotherapy, and radiotherapy, GBMs are almost always fatal, with a median survival rate of approximate a year. Therefore, there is a critical need to develop novel therapeutic approaches for this disease. Gene therapy, the use of genes or other nucleic acids as drugs, is a powerful new treatment strategy which can be developed to treat GBMs. We have previously constructed a 27 kDa polypeptide (hTERTC27) encoding the C-terminus domain of human telomerase reverse transcriptase (hTERT) and shown that hTERTC27 has potent anti-tumor activities in vitro in hTERT positive cancer cell lines and in vivo in nude mice xenograft, suggesting that hTERTC27 might be an ideal candidate for developing into a broadband therapeutic drug for cancers. My project aims to establish an hTERTC27-based cancer gene therapy using adeno-associated virus (AAV) plus adenovirus (Adv) cocktail vector system developed in our laboratory. To achieve this goal, I established a platform of large scale rAAV-hTERTC27 and rAdv-hTERTC27 productions and conducted pre-clinical studies using a nude mice GBM (U87-MG cells) xenograft model. Furthermore, I also developed a novel cancer gene therapy strategy by combining the novel anti-cancer gene hTERTC27 therapy with anti-angiogenesis, immunomodulatory and pro-apoptotic gene therapy to furnish the best performance of the treatment. In this study, I first showed that intratumoral injection of rAAV-hTERTC27 is highly effective in reducing tumor growth of the subcutaneously transplanted GBM. Histological studies and microarray data suggested that hTERTC27 exerts its anti-tumor effect through complex mechanisms including apoptosis, immune responses, etc. Using optical in vivo imaging, I demonstrated, for the first time, that adenovirus can enhance the transduction efficiency of rAAV by altering the expression pattern and magnitude of rAAV in vivo. These novel findings also suggested that combining rAAV-hTERTC27 with a rAdv vector, in particular a therapeutic dose of rAdv-hTERTC27, can elicit a significant enhancement on the anti-tumor effect. Moreover, my result of the hTERTC27 based combination therapy showed that hTERTC27 gene therapy in combination with other anti-cancer strategies, including anti-angiogenic gene (vastatin and HGFK1) therapy, immunomodulatory gene (hIL-2 and hGM-CSF) therapy, and pro-apoptotic gene (p53) therapy, can lead to significantly increased anti-tumor effect using rAAV+rAdv cocktail vector system in U87-MG nude mice xenograft model. Most importantly, 20% of mice in the rAAV-hTERTC27+rAAV-vastatin+rAdv-null treatment group, 33% of mice in the rAAV-hTERTC27+rAdv-hTERTC27 treatment group, and 38% of mice in the rAAV-hTERTC27+rAdv-hIL-2 treatment group achieved complete tumor regression. In conclusion, this study demonstrates a novel and efficient hTERTC27 based cancer gene therapy strategy for GBM treatment. Further investigations will definitely contribute to the translation of this promising experimental system into clinical practice. (443 words) DOI: 10.5353/th_b3955779 Subjects: Glioblastoma multif