165. Enhanced Baculovirus-Mediated Transduction of Human Cancer Cells by Tumor- Homing Peptides

Abstract

Tumor cells and tumor vasculature both offer specific molecular targets that can be utilized for site-directed delivery of therapeutic genes. In order to achieve tumor-specific gene delivery, the tropism of baculovirus can be manipulated by modification of the virus envelope using baculovirus display technology. We genetically engineered a series of recombinant display viruses by fusing various tumor-homing peptides to the transmembrane anchor of vesicular stomatitis virus G-protein to establish more efficient and selective baculovirus vectors for targeted gene delivery into human cancer cells. The viruses were further equipped with a luciferase expression cassette, allowing transduction monitoring in mammalian cells by measuring luciferase activity. The fusion proteins were successfully incorporated into budded virions and these modified viruses showed significantly improved binding to both human breast carcinoma (MDA-MB-435) and hepatocarcinoma (HepG2) cells as measured by flow cytometry. Binding of the tumor-homing peptide displaying viruses to target cells was reduced to the level of the control virus by preincubating the cells with the corresponding soluble peptides. Moreover, a maximum of 7- and 24-fold increase in transgene expression was achieved for these cell lines, respectively. The enhanced binding and transduction strongly suggest that the displayed peptides dictated this behavior. Together, these results imply that the specificity and efficiency of baculovirus-mediated gene delivery can be notably enhanced in vitro when tumor-targeting ligands are used and therefore also highlight the potential of baculovirus vectors in cancer gene therapy in vivo. Tumor cells and tumor vasculature both offer specific molecular targets that can be utilized for site-directed delivery of therapeutic genes. In order to achieve tumor-specific gene delivery, the tropism of baculovirus can be manipulated by modification of the virus envelope using baculovirus display technology. We genetically engineered a series of recombinant display viruses by fusing various tumor-homing peptides to the transmembrane anchor of vesicular stomatitis virus G-protein to establish more efficient and selective baculovirus vectors for targeted gene delivery into human cancer cells. The viruses were further equipped with a luciferase expression cassette, allowing transduction monitoring in mammalian cells by measuring luciferase activity. The fusion proteins were successfully incorporated into budded virions and these modified viruses showed significantly improved binding to both human breast carcinoma (MDA-MB-435) and hepatocarcinoma (HepG2) cells as measured by flow cytometry. Binding of the tumor-homing peptide displaying viruses to target cells was reduced to the level of the control virus by preincubating the cells with the corresponding soluble peptides. Moreover, a maximum of 7- and 24-fold increase in transgene expression was achieved for these cell lines, respectively. The enhanced binding and transduction strongly suggest that the displayed peptides dictated this behavior. Together, these results imply that the specificity and efficiency of baculovirus-mediated gene delivery can be notably enhanced in vitro when tumor-targeting ligands are used and therefore also highlight the potential of baculovirus vectors in cancer gene therapy in vivo.