Identifier

etd-04062006-102829

Degree

Master of Science (MS)

Department

Biomedical and Veterinary Medical Sciences - Comparative Biomedical Sciences

Document Type

Thesis

Abstract

In the last twenty years, interferon-α (IFN-α) has gained success as an immunotherapy for treating such cancers as hairy cell leukemia, malignant melanoma, and renal cell cancer. Our goal was to improve the effectiveness of IFN-α therapy by genetically modified the IFN-α gene to encode a tumor-targeting peptide fused to a functional IFN-α protein. To ensure the targeting peptide worked, a genetically modified reporter gene encoding a secreted alkaline phosphatase (SEAP) gene and different mini-peptides were used to determine distribution and targeting ability. The DNA fragment encoding the most effective peptide was selected to modify the IFN-α gene construct for therapeutic trials. This fusion gene encoded the peptide with the amino acid sequence of C-D-G-R-C, and demonstrated a higher localization of the genetically modified gene product in the tumor local area. Tumor volume and animal survival was measured over several weeks to compare the anti-tumor effects of the IFN-α to CDGRC-IFN-α treatments. Results indicate an increase in therapeutic efficacy due to treatment with the CDGRC-IFN-α gene over the wild-type IFN-α gene. Flow cytometry was performed and it was determined that both of the tumor targeted gene products, CDGRC-SEAP and CNGRC-SEAP share a high affinity for the receptor, Aminopeptidase N (CD13). In order to determine the mechanism responsible for the enhanced anti-tumor effect by CDGRC-IFN-α gene therapy, the T cell infiltration, subsequent CTL activity, and tumor vessel density were confirmed through immunostaining. An increase in number of CD8+ T cells was seen, as well as an increase in activity of cytotoxic T cells. Decreased vessel density in CDGRC-IFN-α treated animals suggest that this therapy enhanced anti-angiogenisis. A high level of non-specific activity was detected in the CTL assay, suggesting involvement of other immune cells, such as NK cells. Overall, this study describes the first example of using a genetically modified immunostimulatory gene encoding tumor-targeted IFN-α for treating tumors. This novel concept may have the potential for increasing therapeutic efficacy of several current cancer treatments.

Date

2006

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Shulin Li

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