Immunotherapy for melanoma using nonviral plasmid DNA based approach

Abstract

Abstract Malignant melanoma is the deadliest form of skin cancer. New immunotherapy approaches including anti-CTLA4, anti-PD-1 and anti-PD1-L1 have improved this prognosis for several patients. While the results obtained with these therapies are encouraging, there is still a need to establish improved therapies. IL-12 is a potent cytokine mediating antitumor activity. However, it has only achieved modest antitumor effects in clinical trials, often accompanied by unacceptable adverse events. We evaluated if intratumoral delivery of a plasmid encoding IL-12 using gene electrotransfer (GET) could be used to induce an anti-tumor response. Effective protocols delivering plasmids with GET directly into tumors induced not only local immune response, but a systemic one as well. We have been evaluating the specific response following pIL-12 delivery as well as the potential to combine with checkpoint inhibitors to determine if the response could be further augmented. Using a B16F10 mouse melanoma model, we show that melanoma exhibited unique immune cell composition within the tumor microenvironment after intratumoral injection of pIL12 with GET. The total number of memory immune cells was markedly increased in pIL12 GET melanoma groups compared with control group. pIL12 GET displayed significant regulation of multiple immune cell types, including CD8+ cells, regulatory T cells and myeloid cells, which were induced to mount a CD8+ immune response. It was also observed that there was an increase in PD-1 expression following pIl-12 delivery. Taken together, these findings suggest a sequence of immune activity following pIL12 GET. Further, these results suggest that pretreatment or simultaneous treatment with IL-12 may augment anti-PD1 therapy.