FBR-NDs: a ferroptosis-inducing nanocomplex for targeted breast cancer therapy via immune modulation and redox-responsive drug delivery.

BACKGROUND: The aim of this study was to develop and characterize a novel ferroptosis-inducing nanocomplex, FBR-NDs (Fe³⁺-BMS-1-R848 Nanodrugs), and to evaluate its anti-tumor effects in breast cancer cells through induction of ferroptosis and modulation of immune responses. METHODS: FBR-NDs were synthesized by nanoprecipitation, followed by characterization using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FT-IR) spectroscopy to confirm their structure and composition. Drug loading, release, and redox-responsive properties were assessed using ultraviolet-visible spectroscopy, and the drug release profile was evaluated under acidic pH and glutathione (GSH) conditions. In vitro growth inhibition of breast cancer cells (BT549 and MDA-MB-231) was assessed by cell viability, colony formation, and apoptosis assays. Ferroptosis was evaluated by measuring reactive oxygen species (ROS) levels, lipid peroxidation, mitochondrial morphology via electron microscopy, and expression of ferroptosis-related markers. In vivo anti-tumor efficacy was assessed in a 4T1 breast cancer mouse model, and immune responses were evaluated by flow cytometry, immunohistochemistry, and enzyme-linked immunosorbent assays. RESULTS: FBR-NDs demonstrated high drug loading efficiency and exhibited redox-responsive release behavior under acidic pH and GSH conditions. In vitro, FBR-NDs significantly inhibited breast cancer cell proliferation and induced ferroptosis, as evidenced by elevated ROS levels, lipid peroxidation, and mitochondrial damage. In vivo, FBR-NDs significantly reduced tumor growth, enhanced apoptosis, and induced ferroptosis in tumor tissues. Additionally, FBR-NDs treatment increased the infiltration of immune cells, including dendritic cells (DCs) and M1 macrophages, and promoted T-cell activation. Immunogenic cell death was observed, as evidenced by increased levels of high mobility group box 1 (HMGB1) and calreticulin in tumor tissues. CONCLUSION: FBR-NDs are a promising therapeutic strategy for breast cancer, combining ferroptosis induction with immune modulation. The ability to induce ferroptosis, enhance immune responses, and promote anti-tumor immunity makes FBR-NDs a potential candidate for cancer immunotherapy.