Injectable SF-platform orchestrates GPX4-targeted ferroptosis-autophagy-immunogenic circuit for overcoming oxidative resistance in triple-negative breast cancer.

Background: Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, characterized by the absence of targeted therapies and poor clinical outcomes. The development of novel, effective therapeutic strategies is urgently required to improve patient prognosis. Ferroptosis, a regulated form of cell death, has recently emerged as a promising therapeutic approach for TNBC. Objectives: This study aims to evaluate the efficacy of an injectable silk fibroin (SF)-based platform in treating TNBC and to explore the underlying mechanisms involved. Methods: We engineered an injectable SF platform consisting of magnetic, thermoresponsive silk fibroin-based hydrogels (IMSFs) coupled with temporally controlled TAT-Beclin1 delivery. Ferroptosis induction was quantified using the C11-BODIPY probe and transmission electron microscopy (TEM). To investigate the molecular mechanisms, RNA sequencing, Western blotting, and co-immunoprecipitation were performed. Additionally, enzyme-linked immunosorbent assay (ELISA) and flow cytometry were used to assess immune responses. Results: In the presence of an alternating magnetic field (AMF), IMSFs induce localized hyperthermia (42-45 °C) and catalyze Fenton reaction-driven reactive oxygen species (ROS) generation through Fe²⁺/Fe³⁺ release. The resulting ROS synergize with sorafenib release to inhibit the Xc⁻ system via the AMPK-Beclin1-SLC7A11 axis, leading to the local suppression of glutathione peroxidase 4 (GPX4) activity and the initiation of a ferroptosis cascade. Temporal delivery of TAT-Beclin1 prevents premature activation of autophagy, which could otherwise dampen ferroptosis. Instead, this approach leverages autophagy-ferroptosis synergy to amplify immunogenic cell death (ICD). This, in turn, activates CD8⁺ T cells, triggering interferon-gamma (IFN-γ)-mediated downregulation of SLC7A11 and establishing a self-amplifying cascade of "ferroptosis-autophagy-immunity" loop that induces oxidative stress and leads to enhanced anti-tumor effects. Conclusion: The injectable SF platform, incorporating sequential therapeutic modules, demonstrates potent anti-tumor efficacy and holds significant promise for clinical translation in the treatment of TNBC.