PROTAC-Engineered Protein/DNA Nanoantigen is a Potent Booster for Dendritic Cell Vaccines in Cancer Immunotherapy

The efficacy of dendritic cell (DC) vaccines in cancer immunotherapy is often limited by weak immunogenicity due to inefficient antigen cross-presentation (XPT). We previously combined a calcium carbonate (CaCO₃) delivery system with a proteolysis-targeting chimera (PROTAC) to enhance antigen degradation. Along this line, we developed a protein/DNA-integrated nanoantigen platform (HpOAC) co-loading CaCO₃ with a His-tagged ovalbumin (O) modified with the von Hippel-Lindau (VHL) E3 ligase-recruiting peptide ALAPYIP (HOA) and a eukaryotic plasmid encoding O-ALAPYIP (pOA). HpOAC promoted DC maturation and migration via Ca²⁺ release. Mechanistically, HOA provided an immediate antigen source, while pOA enabled sustained expression; both underwent ALAPYIP-mediated VHL recruitment, enhancing O ubiquitination and proteasomal degradation, thereby amplifying XPT. Consequently, HpOAC-DCs induced strong OT-I/OT-II T cell proliferation in vitro. In vivo, a single immunization with HpOAC-DCs significantly suppressed tumor growth and elicited durable antigen-specific T helper type 1 and cytotoxic T lymphocyte responses, outperforming single-antigen vaccines. Under a two-dose regimen, its anti-tumor efficacy was improved compared to non-PROTAC and in situ antigen vaccines. Thus, we constructed a PROTAC-enhanced, protein/DNA-integrated DC vaccine platform that synergizes immediate and sustained antigen supply with Ca²⁺-mediated adjuvanticity, offering a highly promising strategy for novel DC vaccine design.