A positive-feedback loop suppresses TNBC tumour growth by remodeling tumour immune microenvironment and inducing ferroptosis.

Triple-negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer due to poor immunogenicity and limited immune cell infiltration, efficient therapeutics are still deficiency. Ferroptosis, a reactive oxygen species (ROS)-reliant cell death, can enhance cellular immunogenicity and then active immune system. To sustain a long-term "hot" tumour immune microenvironment (TIME), an immune-modulator is indispensable. Metformin (MET), a commonly used oral drug for type 2 diabetes, has played a vital role in fostering an immunostimulatory environment. Herein, we confirm the TIME can be remodeled by MET and further promotes ferroptosis via upregulating cellular concentration of l-Glutamine. In light of this, we have design a self-assembled MET-loaded Fe-doped polydopamine nanoparticle (Fe-PDA-MET NP) that can disorder the cellular redox homeostasis and induce robust ferroptosis under 808 nm irradiation, resulting in a strong immune response. Based on the function of MET, there is a marked increase in the infiltration of activated CD8 T cells and NK cells, which subsequently augments ferroptosis to a greater extent. Taken together, Fe-PDA-MET NPs activate a ferroptotic positive-feedback loop for effectively control TNBC progression, which offers a promising therapeutic modality to enhance the immunogenicity and reshape the TIME.