Nanovaccine-based immunotherapy has been considered as a major pillar to stimulate the host immune system to recognize and eradicate tumor cells as well as establish a long-term immune memory to prevent tumor relapse and metastasis. However, the weak specificity and low cross-presentation of antigens, as well as the immunosuppressive microenvironments of tumor tissues, are still the major obstacles on exerting the therapeutic performance of tumor nanovaccines sufficiently. Herein, we design and construct cytosine guanine dinucleotide (CpG) oligodeoxynucleotide (ODN)-loaded aluminum hydroxyphosphate nanoparticles covered by Fe-Shikonin metal-phenolic networks (MPNs) (Alum-CpG@Fe-Shikonin NPs) as personalized in situ nanovaccines for antitumor immunity. Upon internalization by tumor cells, the shell of Fe-Shikonin MPNs will disassemble into Fe2+ and Shikonin to elicit the immunogenic cell death of tumor cells through ferroptosis and necroptosis. Then, dying tumor cell-released autologous tumor cell lysates will be absorbed by Alum NPs and codelivered with CpG ODN to professional antigen-presenting cells temporally and spatially to activate multistep cascade antitumor immune responses, including dendritic cell maturation, antigen cross-presentation, natural killer cell and cytotoxic T lymphocyte infiltrations, and tumor-associated macrophage repolarization. Benefiting from the synergistic effects of Alum NPs, CpG ODN, and Fe-Shikonin MPNs, our Alum-CpG@Fe-Shikonin NPs exhibit drastic cytotoxicity and accurate selectivity on eradicating primary tumor, strong abscopal effect on inhibiting distant tumor, and a long-term immune memory effect on preventing tumor metastasis and recurrence. Because our report provides a feasible strategy to in situ make full use of autologous tumor cell lysates, which present an entire spectrum of the patient's personal epitopes without complicated ex vivo processes, such as extraction, purification, and sequencing, it may promote the development of personalized nanovaccines for antitumor immunity.
Keywords: Shikonin; immunoadjuvants; immunogenic cell death; metal-phenolic networks; nanovaccines; tumor immunotherapy.