Controlled pyroptosis of engineered macrophages enables in situ biphasic antitumor via the release of oncolytic bacteria and inflammatory signals

Engineered macrophage-based therapies offer promising potential for cancer treatment but are limited by slow, uncontrolled drug release and the risk of macrophage reprogramming into tumor-promoting phenotypes. Here, we developed a thermally induced macrophage autolysis release system, the macrophage-microbe encapsulation bomb (MME-Bomb), which combines engineered macrophages loaded with indocyanine green (ICG)-encapsulated nanoparticles and antitumor attenuated Salmonella typhimurium strain. This system utilizes photothermally triggered pyroptosis to induce controlled macrophage rupture within the tumor microenvironment, releasing intracellular bacteria to stimulate prolonged antitumor immunity. By integrating light-responsive biomodulation, our approach enables site-specific activation of engineered cells, enhancing the rapid delivery of therapeutic agents and maximizing the synergy between macrophage-based and bacterial therapies. In preclinical cancer models, MME-Bomb significantly reduces the tumor burden and improves survival outcomes, both alone and in combination with checkpoint inhibitors. This innovative strategy offers a versatile and precise framework for advancing cancer immunotherapies. Overall design: A total of 1×10^6 4T1 cells were orthotopically inoculated into the mammary fat pads of 6-week-old female BALB/c mice to establish primary breast tumor. When tumor volumes reached approximately 60-90 mm^3, mice were randomly allocated into experimental groups. The cohorts received intratumoral injections of either saline or engineered cells (5.0×10^5 cells per mouse). Tumors in the engineered cells+NIR group were locally exposed to 980 nm NIR irradiation (1.5 W/cm^2), while other groups remained untreated. To mitigate spatial heterogeneity, entire tumors were homogenized and thoroughly mixed prior to RNA extraction. The extracted RNA was then subjected to RNA sequencing.