LukS-PV targets human C5aR1 to reprogram tumor-associated macrophages and potentiate immunotherapy in hepatocellular carcinoma

Abstract Background Immune checkpoint inhibitors (ICIs) benefit only a subset of patients with hepatocellular carcinoma (HCC), largely because of an immunosuppressive tumor microenvironment enriched with M2-like tumor-associated macrophages (TAMs). C5aR1 is highly expressed on HCC TAMs, but no C5aR1-targeted cancer therapy has been approved. LukS-PV, a Staphylococcus aureus Panton-Valentine leukocidin component, is a natural ligand for human C5aR1. However, whether LukS-PV can reprogram TAMs and enhance immunotherapy in HCC remains unclear. Methods To define the therapeutic potential and mechanism of LukS-PV, subcutaneous and immunotherapy-refractory hydrodynamic tail vein injection-induced spontaneous HCC models were established in humanized C5AR1 knock-in mice and wild-type controls. Macrophage depletion experiments were conducted to assess the contribution of macrophages to LukS-PV-mediated antitumor activity. These models were used to evaluate LukS-PV alone and in combination with PD-1 blockade. Single-cell RNA sequencing was performed to characterize the cellular composition and immune landscape of tumor tissues. Flow cytometry and immunofluorescence were used for validation in vivo. In vitro macrophage-polarization assays were performed for functional validation. Transcriptomic and molecular analyses were further conducted to investigate the signaling mechanisms associated with LukS-PV treatment. Results LukS-PV significantly suppressed HCC growth in h C5AR1 mice but not in wild-type controls, supporting a human C5aR1-dependent mechanism in this experimental system. LukS-PV reshaped the tumor immune landscape by shifting TAMs from immunosuppressive M2-like phenotypes toward inflammatory M1-like states. This macrophage reprogramming was accompanied by increased CD8⁺T-cell infiltration, enhanced effector activation and reduced T-cell exhaustion. Mechanistically, LukS-PV inhibited C5aR1-dependent PI3K/AKT signalling in macrophages, suppressing the GSK3β/CREB/IL-10 axis while promoting NF-κB-associated inflammatory activation. Reduced TAM-derived IL-10 contributed to suppression of HCC progression and restoration of CD8⁺T-cell effector function. Consistent with this immune remodeling, LukS-PV enhanced the antitumor efficacy of PD-1 blockade. Conclusion LukS-PV targets human C5aR1 to reprogram immunosuppressive TAMs and enhance responsiveness to PD-1 blockade. These findings identify LukS-PV-mediated C5aR1 targeting as a promising translational strategy to overcome immunotherapy resistance in HCC.