This study developed a novel antibody-toxin conjugate, CD47-LLO, which targets CD47 and utilizes Listeriolysin O (LLO) to enhance tumor antigen presentation and activate the innate immune cGAS-STING pathway, significantly boosting anti-tumor immune responses. The conjugate demonstrates potent therapeutic effects in both local and metastatic tumor models, with further efficacy enhancement observed when combined with immune checkpoint blockade therapy, offering an innovative strategy for cancer immunotherapy.
Literature Overview
The article "An antibody-toxin conjugate targeting CD47 linked to the bacterial toxin listeriolysin O for cancer immunotherapy" published in Nature Cancer reviews mechanisms of CD47-targeted antibody-toxin conjugates in promoting tumor cell phagocytosis and antigen presentation. The research reveals that CD47-LLO enhances tumor cell phagocytosis by macrophages while releasing LLO to disrupt phagolysosomal membranes, improving cytosolic antigen presentation efficiency and activating T-cell immune responses. In vivo studies demonstrate significant inhibition of breast cancer and melanoma growth, with enhanced efficacy when combined with PD1 blockade therapy. Single-cell sequencing further identifies CD47-LLO-induced pro-inflammatory tumor-associated macrophage (TAM) polarization and T-cell infiltration patterns, providing new directions for cancer immunotherapy.
Background Knowledge
CD47 is a "don't eat me" signal expressed on tumor cells that binds to SIRPα on macrophages to inhibit phagocytosis. Anti-CD47 antibodies have been widely explored to enhance tumor immunogenicity. However, antigen presentation efficiency is limited by phagolysosomal membrane integrity, hindering cytosolic antigen release for MHC I presentation and cGAS-STING activation. LLO, a phagolysosomal membrane-disrupting toxin from Listeria monocytogenes, forms pores in acidic environments to facilitate cytosolic release of bacterial DNA and antigens. This study conjugates LLO with CD47 antibodies, enabling phagocytes to activate LLO post-engulfment for improved tumor antigen release and presentation, thereby enhancing T-cell immune responses. The research team evaluated CD47-LLO's impact on tumor microenvironment using murine tumor models, flow cytometry, confocal microscopy, and single-cell sequencing, establishing a new technical framework for cancer immunotherapy and theoretical basis for antibody-toxin conjugate (ATC) development.
Research Methods and Experiments
The research team constructed a CD47-LLO conjugate by linking anti-CD47 antibodies with LLO toxin through click chemistry. The conjugate releases LLO in reducing phagolysosomal environments via disulfide bond cleavage, disrupting phagolysosomal membranes to facilitate cytosolic antigen release and MHC I presentation. Phagocytosis efficiency, antigen presentation, T-cell activation, and tumor microenvironment immune characteristics were evaluated using flow cytometry, confocal microscopy, transmission electron microscopy, and single-cell RNA sequencing. In vivo therapeutic effects were tested in local and metastatic breast cancer/melanoma models, with synergy assessed through combination therapy with PD1 blockers.
Key Conclusions and Perspectives
Research Significance and Prospects
This study establishes novel conceptual frameworks for antibody-toxin conjugates (ATC) in cancer immunotherapy. CD47-LLO's dual mechanism - targeting immune checkpoint CD47 and enhancing antigen presentation - provides effective tumor immunostimulation strategies. Future research may explore alternative phagocytic checkpoint-toxin conjugation approaches and expand this technical platform to other cancer types and personalized tumor vaccines, advancing precision immunotherapy.
Conclusion
CD47-LLO represents an innovative antibody-toxin conjugate strategy that enhances anti-tumor T-cell immunity through CD47 targeting and phagolysosomal membrane disruption. The study validates CD47-LLO's monotherapy and combination therapy efficacy across multiple tumor models, revealing induced pro-inflammatory immune microenvironments and tumor-specific immune memory. Despite systemic inflammation and anti-LLO antibody generation, the conjugate demonstrates favorable safety profiles and clinical translation potential. CD47-LLO provides a new approach for improving tumor immunogenicity and overcoming current phagocytic checkpoint limitations, with its platform technology broadly applicable for next-generation antibody-toxin conjugate development in cancer immunotherapy.
