Mitochondrial Rewiring with Small-Molecule Drug-Free Nanoassemblies Unleashes Anticancer Immunity

The immunosuppressive tumor microenvironment (TME) remains a major obstacle to tumor control and causes suboptimal responses to immune checkpoint blockade (ICB) therapy. Thus, developing feasible therapeutic strategies that trigger inflammatory responses in the TME could improve the ICB efficacy. Mitochondria play an essential role in inflammation regulation and tumor immunogenicity induction. Herein, we report the discovery and characterization of a new class of previously unappreciated small molecules that can recapitulate aqueous self-assembly behavior, specifically target cellular organelles (e.g., mitochondria), and invigorate tumor cell immunogenicity. Mechanistically, this nanoassembly platform dynamically rewires mitochondria, induces endoplasmic reticulum stress, and causes apoptosis/paraptosis-associated immunogenic cell death. After treatment, stressed and dying tumor cells can act as prophylactic or therapeutic cancer vaccines. In preclinical mouse models of cancers with intrinsic or acquired resistance to programmed death-1 (PD-1) blockade, the local administration of nanoassemblies inflames the immunologically silent TME and synergizes with ICB therapy, generating potent antitumor immunity. This chemically programmed small-molecule immune enhancer acts like no other reported cytotoxic therapeutics and offers a promising new strategy for synchronous and dynamic tailoring of innate immunity to achieve traceless cancer therapy and overcome immunosuppression in cancers. Overall design: Mice bearing anti-PD-1-resistant MC38 tumors received intratumoral injections of vehicle (saline containing 5% DMSO) or mtDSN-2 (1 mg kg-1) every three days. After a total of three doses, tumors were collected, minced and dissociated (n = 3 mice or samples were pooled to control for biological variability).