A modular metalloprotein in situ vaccine for cancer immunotherapy in mouse models of breast cancer

Immunogenic cell death (ICD) is a promising approach for generating antitumor immune responses to treat patients with cancer. However, the stereotactic induction of ICD and spatiotemporal synchronized activation of the tumor-specific immune response pose two critical challenges. Here, we report the basic principles and systematic development of a modular metalloprotein platform designated the protease-activated PSTAGylated in situ tumor vaccine (PPTV). Ferritin was used as a vaccine framework, with its outer surface fused with an optimal mito-disrupt peptide and its inner cavity loaded with manganese ions (Mn 2+ ). Moreover, a protease-activated PSTAGylated prodrug strategy was developed to circumvent the major issues associated with ferritin, such as liver interception and drug leakage. We also demonstrated the activation of prodrugs in tumor lysates from patients. In subcutaneous and orthotopic tumor transplantation mouse models, the PPTV effectively codelivered mito-disrupt peptides and Mn 2+ into tumors, leading to a combined effect of ICD and cGAS-STING cyclic GMP–AMP synthase–stimulator of interferon genes (cGAS-STING) pathway activation, thereby achieving a potent antitumor immune response. The combined application of PPTV and anti–programmed death-ligand 1 resulted in the eradication of established tumors. These results underscore the applicability of the PPTV as an innovative in situ vaccine nanoplatform for establishing an antitumor immune response. This modular metalloprotein vaccine has clinical translational potential because of its simple generation and safety profile.