Intratumoral expression of IL-12 and CD40 ligand (CD154) from plasmids generates antitumor responses that eliminate tumoral T regs.

Intratumoral immunotherapy (ITIT) strives to generate effective antitumor immunity by directly stimulating the immune system in tumors to reverse local tumor-mediated immune suppression. expression of Interleukin-12 (IL-12) using plasmid transfection as an intratumoral cancer immunotherapy entered Phase II clinical trials for metastatic melanoma but to limited clinical success. We sought to improve the efficacy of IL-12 electroporation by the addition of a CD154 (CD40 ligand)- expressing plasmid to the IL-12 encoding plasmid treatment and assessing efficacy against solid tumors. Mice with intradermal B16F10 melanoma or MC38 murine colon carcinoma tumors received 2 weekly intratumoral (IT) injections of plasmids encoding IL-12 and CD154, followed by electroporation. The addition of CD154 to IL-12 was superior to IL-12 alone and resulted in frequent tumor clearance of treated tumors, marked by an increase in CD8 T cells and a drastic reduction in T regulatory cells in the tumor microenvironment. Tumor treatment responses were abrogated in mice which lack conventional DC1 cells (BatF3 KO) or lack CD8 T cells. These findings highlight the potential of adding CD154 to IL-12 plasmid electroporation as a cancer immunotherapy and suggest that other combinations would be therapeutically valuable.