Engineered Bacterial Biohybrid-Mediated CD47-SIRPα Blockade and HSP90 Inhibition for Enhanced Immuno-Photothermal Therapy

Macrophage phagocytosis of tumor cells shows significant promise in cancer treatment. However, it faces great challenges due to the upregulation of antiphagocytosis molecules, such as CD47, on the surface of tumor cells. Merely reducing the level of CD47 is insufficient to induce phagocytosis of tumor cells because it lacks enough "eat me" signals. Here, we have developed an engineered bacterial biohybrid system (eVNP@AuNFs) to decrease the expression of CD47 and HSP90 proteins, achieving an enhanced immuno-photothermal combination therapy. The attenuated Salmonella VNP20009, capable of selectively accumulating in hypoxic tumor regions, was intracellularly genetically engineered with CD47 and HSP90 shRNA plasmids and an extracellularly adsorbed flower-like gold nanoparticle (AuNF) photothermal agent, forming an eVNP@AuNF bacterial hybrid. After administration into 4T1 tumor-bearing mice intravenously, the eVNP@AuNF bacterial hybrid could effectively accumulate in tumor tissues and release CD47 and HSP90 shRNA plasmids to reduce the expression of CD47 and HSP90 protein, leading to enhanced macrophage phagocytosis to tumor cells and an improved photothermal effect. Under further NIR-II laser irradiation, extracellular AuNFs of eVNP@AuNFs could photothermally induce immunogenic cell death, including surface calreticulin exposure and high-mobility group box 1 translocation, facilitating the infiltration of the "eat me" signal and multiple immune cells and enhancing tumor immunogenicity. The eVNP@AuNF bacterial hybrid could eradicate the primary tumor and elicit a systemic antitumor immunity response, inhibiting the recurrence of the tumor. This study presents a hybrid system involving bacteria, plasmids, and nanomaterials for tumor therapy, opening an avenue for hierarchical modulation of the tumor immune response.