NIR-II-Responsive Hybrid System Achieves Cascade-Augmented Antitumor Immunity via Genetic Engineering of Both Bacteria and Tumor Cells.

The combination of nanoparticles and tumor-targeting bacteria for cancer immunotherapy can overcome the shortcomings of poor nanoparticle accumulation, limited penetration, and restricted distribution. However, it remains a great challenge for the hybrid system to improve therapeutic efficacy through the simultaneous and controllable regulation of immune cells and tumor cells. Herein, a hybrid therapeutic platform is rationally designed to achieve immune cascade-augmented cancer immunotherapy. To construct the hybrids, photothermal nanoparticles responsive to light in the second near-infrared (NIR-II) region are conjugated onto the surface of engineered bacteria through pH-responsive Schiff base bonds. Taking advantage of the hypoxia targeting and deep penetration characteristics of the bacteria, the hybrids can accumulate at tumor sites. Then nanoparticles detach from the bacteria to realize genetic engineering of tumor cells, which induces tumor cell apoptosis and down-regulate the expression of programmed cell death ligand 1 to alleviate immunosuppressive tumor microenvironment. The mild photothermal heating can not only induce tumor-associated antigen release, but also trigger sustainable expression of cytokine interleukin-2. Notably, a synergistic antitumor effect is achieved between the process of p53 transfection and NIR-II light-activated genetic engineering of bacteria. This work proposes a facile strategy for the construction of hybrid system to achieve cascade-augmented cancer immunotherapy.