In vivo electroporation-mediated transfer of interleukin-12 and interleukin-18 genes induces significant antitumor effects against melanoma in mice

Direct intratumoral transfection of cytokine genes was performed by means o f the in vivo electroporation as a novel therapeutic strategy for cancer. P lasmid vectors carrying the firefly luciferase, interleukin (IL)-12 and IL- 18 genes were injected into established subcutaneous B16-derived melanomas followed by electric pulsation. When plasmid vectors with Epstein-Barr viru s (EBV) nuclear antigen 1 (EBNA1) gene were employed, the expression levels of the transgenes were significantly higher in comparison with those obtai ned with conventional plasmid vectors. In consequence of the transfection w ith IL-12 and IL-18 genes, serum concentrations of the cytokines were signi ficantly elevated, while interferon (IFN)-gamma also increased in the sera of the animals. The IL-12 gene transfection resulted in significant suppres sion of tumor growth, while the therapeutic effect was further improved by co-transfection with IL-12 and IL-18 genes. Repetitive co-transfection with IL-12 and IL-18 genes resulted in significant prolongation of survival of the animals. Natural killer (NK) and cytotoxic T lymphocyte (CTL) activitie s were markedly enhanced in the mice transfected with the cytokine genes. T he present data suggest that the cytokine gene transfer can be successfully achieved by in vivo electroporation, leading to both specific and nonspeci fic antitumoral immune responses and significant therapeutic outcome.