Oncolytic peptide LTX-315 enhances anti-melanoma immunity by inducing MyD88-dependent maturation of dendritic cells

Abstract

Abstract LTX-315 is a synthetic cationic oncolytic peptide with potent anticancer cytotoxicity. LTX-315 induces both immunogenic tumor cell death and the generation of tumor-specific immune response. Given the central role of dendritic cell (DC) maturation in the induction of antigen-specific immune responses, we investigated the effect of LTX-315 treatment on the maturation of tumor-infiltrating DCs (TiDCs) and the generation of anti-melanoma immunity. The results reveal that LTX-315 induces the maturation of DCs through three distinct mechanisms: 1) release of DAMPs/alarmins; 2) complexes of LTX-315 with nucleic acids that act immunostimulatory; and 3) direct induction of the maturation of both conventional and plasmacytoid DCs by triggering TLR7. Importantly, LTX-315-induced maturation of DCs in vitro and in vivo was dependent on the presence of the signal transducer MyD88 as well as distinct TLRs. Our data also substantiate the notion that reagents like LTX-315 with both tumor cell cytotoxic and immunostimulaing capacities are more effective immunotherapeutics.