The enhanced anti-angiogenic and antitumor effects of combining flk1-based DNA vaccine and IP-10

Abstract The purpose of the present study was to evaluate the anti-vasculature effects and the anti-tumor effects of attenuated Salmonella typhimurium vaccine strain encoding murine vascular endothelial growth factor (VEGF) receptor-2 (flk1) in combination with plasmid DNA vector encoding the murine interferon-induced protein of 10 kDa (IP-10 or CXCL10) gene. Mouse models of malignant melanoma (B16-F10) were treated with combining orally given attenuated S. typhimurium vaccine strain encoding flk1 with direct intratumoral injection of a non-viral plasmid DNA vector encoding the murine IP-10 gene. The volumes of tumors and survival of mice bearing B16-F10 tumors were observed. Cytolytic T lymphocyte (CTL) response was measured by cytotoxic assay, vessel density and tumor-cell proliferation were observed by immunostaining, and tumor apoptosis was determined by TUNEL staining. The results revealed the combination therapy groups showed more significantly inhibited tumor growth, apoptosis of tumor cells, and reduced neovascularization, cell proliferation, and developed a strong CTL response in these mice. In summary, the therapy of attenuated S. typhimurium vaccine strain encoding flk1 combined with the IP-10 gene has significant synergistic effect against tumors.