Objective: Interleukin-12 (IL-12) has potent anti-tumor activities through the activation of natural killer cells and cytotoxic T lymphocytes (CTLs). Gene therapy by the intratumoral injection of the IL-12 gene expect as an effective tumor therapy because of IL-12 locally release in tumor. Non-viral gene therapy has many advantages over gene therapy, including ease of plasmid DNA production, lower toxicity, and less costly method compared with viral vector system. Previously, we developed liposomal bubbles (Bubble liposomes (BLs)) containing the ultrasound imaging gas, perfluoropropane. When coupled with ultrasound exposure, BLs which induce cavitation can be used as novel gene delivery agents. In this study, we assessed the ability of this gene delivery system in cancer gene immunotherapy using IL-12 gene.
Methods: B6C3F1 mice were intradermally inoculated with mouse ovarian cancer cells (OV-HM cells) into flank. After 7, 9, 12, 14, 16, 19 days, BLs (2.5 ug) and mouse IL-12 cording plasmid DNA (10 ug) were injected into tumor, and ultrasound (1 MHz, 0.7 W/cm², 60 sec.) was transdermally exposed toward tumor. Anti-tumor effects were evaluated by measuring tumor volume.
Results and Discussion: The group of IL-12 gene delivery with Lipofectamine2000 as conventional lipofection method showed no apparent anti-tumor effect. In contrast, the group of IL-12 gene delivery with BLs and ultrasound exposure was dramatically suppressed tumor growth and complete regression occurred in 80 % of the tumor bearing mice. Therefore, we concluded that the combination of BLs and ultrasound exposure would be a good non-viral gene delivery system in cancer gene immunotherapy.