Advantages and limitations of particle-mediated transfection (gene gun) in cancer immuno-gene therapy using IL-10, IL-12 or B7-1 in murine tumor models

Background: Previous studies have shown that particle-mediated transfection (PMT; gene gun) is an efficient method of non-viral gene transfer. We have examined the advantages and limitations of PMT in cancer immunogene therapy using IL-10, IL-12 or B7-1, all of which have been shown to be effective in murine tumor models using retroviral vectors. Methods: Murine cell lines (MCA205, MCA207, NIH-3T3) were treated with in vitro PMT, liposome-mediated transfection (LMT) or retroviral transfection. In vivo PMT was also examined for in vivo experiments using C57BL/6. Results: Transfection efficiency and cytokine expression of PMT were similar to those of LMT, another non-viral approach, in culture when murine adherent cells were used. Tumor establishment of MCA205 was suppressed when they were transfected with the mIL-12 and/or mB7-1 gene using PMT in vitro. In a treatment of established tumor, vaccination with tumor cells transfected with an IL-12 gene suppressed tumor growth, whereas a B7-1 gene was not effective. When an IL-10 gene was used to supply a high level of expression for antitumor effects, neither in vitro nor in vivo PMT could suppress even tumor establishment. These failures appear to be caused by the characteristics of PMT which allows high, but transient, expression of transfected genes. Conclusions: Particle-mediated transfection is a useful non-viral transfection method in a system which does not require high-level gene expression for a prolonged time of period.