Strike Mitochondria By Enzyme-Instructed Self-Assembled Peptides for Effective Immunogenic Anti-Tumor Therapy.

Introduction: Immunogenic cell death (ICD) plays a crucial role in cancer immunotherapy in disrupting the immunosuppressive tumor microenvironment (TME). However, key bottlenecks remain, including the lack of precise and efficient ICD induction at the tumor site and poor synergy with other therapeutic mechanisms for tumor suppression. Methods: To tackle these bottlenecks, this study developed a legumain-instructed self-assembling peptide PSK, with legumain highly expressed in tumors. Its mechanism is as follows: first, via sequence design, it specifically binds to programmed cell death ligand 1 (PD-L1), which highly expressed on tumor cells, mediating its selective uptake by tumor cells. Subsequently, catalyzed cleavage by legumain in the TME triggers its in-situ self-assembly into nanoaggregates, prolonging its retention at the tumor site. Finally, the PSK targets the mitochondria of tumor cells, enabling precise organelle-level action. Results: In vitro and in vivo experiments showed that PSK exerts synergistic anti-tumor effects through a dual mechanism: it targets mitochondria to disrupt membrane potential and induce dysfunction, thereby triggering tumor cell ICD and releasing damage-associated molecular patterns (DAMPs) to activate immunity; meanwhile, it binds to PD-L1 to downregulate its expression, reducing tumor immune escape. As an enzyme-responsive in-situ self-assembling peptide drug, PSK exhibits high tumor cell selectivity, effectively inhibits tumor growth, and has no obvious systemic toxicity. Discussion: The development of PSK provides a new approach for anti-tumor peptide drug research and precision tumor therapy. With its design featuring tumor specificity, enzyme responsiveness, and dual-action mechanism, this peptide is expected to address key challenges in ICD-based cancer immunotherapy.