283. Adeno-Associated Viral Vector Expression Angiostatin and IL-15 for Brain Cancer Gene Therapy

Abstract

Malignant brain tumors are extremely aggressive cancers currently lacking effective treatment modalities. Gene therapy represents a promising approach for this disease. Several of effective therapeutic genes for gene-based therapies of brain cancer mainly include prodrug activating enzyme genes, tumor suppressor genes, immune regulatory genes and genes for producing inhibitors of angiogenesis. Gene therapy with immune regulatory gene can elicit the specific remembered immune responses to seek and attack uninfected tumor cells, thus the method may complement and improve the weakness of gene therapy that to efficiently delivery the therapeutic gene into the most tumor cell. To study clinical tumor cases, it was found that more malignant tumor cells lose their surface expression of major histocompatibility complex (MHC) and the loss of MHC expression will lift the MHC-restriction for the cytotoxicity of the NK cells. Thus, the activities of the host cell-mediated cytotoxic immune effectors will be activated to suppress the growth of tumor. IL-15 was indicated that it has several different activities to activate T, B and NK cells. Therefore, IL-15 was utilized to prevent tumor growth and the results showed it could significantly suppress tumor growth. Therefore, we extend the study with several modifications to improve the immunotherapy. First, the separated angiostatin and IL-15 genes were constructed into the plasmid. Second, because the AAV gene delivery system is considered as the safest viral delivery system, the AAV viral vector was utilized to express angiostatin or IL-15 proteins. The AAV viral vectors that encode angiostatin or IL-15 proteins will be used to produce recombinant therapeutic AAV in cGMP laboratory at Tzu-Chi Hospital. The high quality and high titers recombinant AAVs were attempted to co-infect brain tumor cell (RG-2 rat glioma) and the results showed the combination of two genes could suppress the growth of subcutaneous RG-2 tumor.