Work

Living bacterial reactor potently activates tumor immunogenic ferroptosis via cysteine depletion and photothermal therapy

Year: 2026

Type: article

Abstract: Bacterial combination therapy offers immense promise for treating aggressive "cold" solid tumors, such as triple-negative breast cancer (TNBC). However, the clinical translatability of traditional genetic engineering is often hampered by operational complexity and genetic instability. Here, we developed A-SPB—a non-genetically engineered, multi-functional living bioreactor based on Shewanella oneidensis MR-1 (SO), surface-modified with Prussian blue (PB) nanoparticles and attenuated via deoxycholic acid (DA) treatment. This platform serves as an in situ metabolic factory that "hijacks" the sulfur-metabolism within the hypoxic tumor microenvironment. By actively depleting cysteine, A-SPB not only starves the glutathione (GSH) synthesis pathway but also generates hydrogen sulfide (H 2 S) to inhibit the transsulfuration bypass, leading to a dual-pronged collapse of the GSH/GPX4 antioxidant axis and triggering robust tumor ferroptosis. This metabolic sensitization is further amplified by the PB-mediated photothermal therapy (PTT), which generates localized hyperthermia and excessive reactive oxygen species (ROS). Notably, the PTT serves as a dual-functional "bio-switch": it promotes acute tumor ablation while simultaneously triggering bacterial self-lysis to ensure biosafety. This programmed lysis releases a synergistic cocktail of bacterial PAMPs and tumor-derived DAMPs, which effectively remodels the immunosuppressive TME and initiates a potent systemic antitumor immune response. By integrating metabolic reprogramming, sensitized ferroptosis, and on-demand immune activation through simple surface engineering, this study provides a highly translatable and safe paradigm for the next generation of living bacterial therapeutics. (A) A-SPB antitumor mechanisms. The potent therapeutic impact of the A-SPB system stems from a triple-mode cooperative mechanism designed for TNBC treatment: 1) Metabolic re-engineering: After localizing in the tumor, the A-SPB system operates as an internal reactor, consuming cysteine and yielding H 2 S within the TME. This combined action effectively blocks both GSH synthesis routes. The resulting glutathione peroxidase 4 (GPX4) suppression and subsequent LPO culminates in the powerful induction of ferroptosis within cancer cells. 2) Photothermal amplification: PBs-mediated PTT offers precise spatial and temporal control, destroying tumor tissue through localized heat and producing ROS, which significantly boosts the ferroptosis effect. 3) Immune remodeling: The bacteria undergo thermal lysis due to the heat, discharging microbe-derived antigens. These released antigens, along with existing tumor antigens, jointly trigger a specialized anti-tumor immune response and effectively reconfigure the inhibitory tumor environment.

Source: Materials Today Bio

DOI: 10.1016/j.mtbio.2026.102843