MnO-melittin nanoparticles serve as an effective anti-tumor immunotherapy by enhancing systemic immune response.

Cancer vaccines are viewed as a promising immunotherapy to eradicate malignant tumors and aim to elicit the patients' own tumor-specific immune response against tumor cells. However, few cancer vaccines have been applied due to the low immunogenicity of antigen and invalidation of adjuvant. Herein, we designed a tumor microenvironment (TME) responsive MnO-melittin nanoparticles (M-M NPs). The M-M NPs consumed glutathione and produced •OH via Fenton-like reaction in the mimic TME, specifically caused tumor cell death in vitro, activated cGAS-STING pathway in vitro and promoted the maturation of antigen-presenting cells in vitro and in vivo to elicit systemic anti-tumor immune response including the augmentation of tumor-specific T cells and more productions of pro-inflammatory cytokines and chemokines, which all were stronger than MnO NPs and melittin. The anti-tumor effects of M-M NPs were evaluated in three subcutaneous tumor models and the B16-F10 lung metastasis model and the tumor growth and lung metastasis were more obviously inhibited in the M-M NPs treated mice, compared with MnO NPs and melittin treatments. More importantly, only M-M NPs promoted the MHC-I cross-dressing by dendritic cells to prime tumor-specific CD8 T cells and remarkably suppressed the growth of left tumors if express cognate antigen while treating on the right in the bilateral tumor model. Our findings proposed a strategy to enhance the cancer vaccine efficiency which showed great therapeutic effect on tumor immunotherapy.