A "CPApoptosis" nano-actuator switches immune-off solid tumors to immune-on for fueling T-cell- based immunotherapy

Background: Most anticancer agents induce tumor apoptosis, but they often lack immunogenicity and display limited success when combined with mainstream immunotherapies, thus killing cancer cells through multiple cell death modalities as well as switching immune-off tumors to immune-on is a strategy with great promise. To this end, we developed a CPApoptosis (cuproptosis, pyroptosis, apoptosis) nano-actuator for immunologically cold solid tumors. Methods: In this study, elesclomol (ES), a mitochondrial targeting copper transporter, was encapsulated within bacterial outer membrane vesicles (OMVs). These OMVs were then surface-modified via metal-phenolic self-assembly using Cu²⁺ and tannic acid (TA). Results: The Cu²⁺ and ES were released from the OMVs in a pH-dependent manner. OMV activated the non-canonical pyroptotic pathway, leading to cell membrane rupture. Cu²⁺ on the one hand was transported to the mitochondria for cuproptosis facilitated by ES, on the other hand, Cu²⁺ was reduced into Cu⁺ by TA, which catalyzed ROS production to induce oxidative apoptosis. Simultaneously, TA degraded glutathione (GSH), sensitizing cells to cuproptosis. The multifactorial cell death mechanisms led to the release of immunogenic factors from lysed tumor cells, stimulating dendritic cell maturation and recruiting cytotoxic T cells. This immune response was further amplified by αPD-L1 antibody treatment. Conclusion: The CPApoptosis nano-actuator represents a promising approach to enhance current cancer therapies, inducing both tumor cell death and a robust immune response, with the potential for long-lasting protective effects.