CtBP Promoted P4HB Mediates SLC7A11 Maturation to Confer Ferroptosis Resistance in Triple-Negative Breast Cancer

Background Triple-negative breast cancer (TNBC) is characterized by aggressive clinical behaviour and frequent resistance to chemotherapy. While ferroptosis—an iron-dependent form of cell death driven by lipid peroxidation—holds promise as a therapeutic strategy, its efficacy is often limited by adaptive resistance mechanisms that remain incompletely understood. C-terminal binding protein (CtBP) is an oncogene associated with poor prognosis in TNBC; however, whether CtBP confers resistance to oxidative stress and ferroptosis, thereby contributing to its oncogenic function, remains unknown. Methods We utilized both in vitro cell lines and in vivo mouse models to investigate the role of CtBP in regulating oxidative stress and ferroptosis sensitivity. Integrative analyses, including transcriptomics, metabolomics, and clinical data interrogation, were employed to elucidate the mechanisms underlying CtBP-mediated resistance. Key mechanistic findings were further validated in clinical TNBC specimens using protein correlation analysis. Results We identified CtBP as a stress-inducible gene that is essential for ferroptosis resistance in TNBC. Mechanistically, CtBP promotes resistance by transcriptionally upregulating Protein Disulfide Isomerase Family A Member 3 (P4HB). P4HB, localized to the endoplasmic reticulum (ER), functions as a chaperone to facilitate the correct folding and membrane maturation of SLC7A11, the catalytic subunit of the system xc− cystine/glutamate antiporter pivotal for glutathione (GSH) biosynthesis. We demonstrated that P4HB-mediated SLC7A11 maturation relies on its disulfide isomerase activity and ER retention signal (KDEL). Depletion of either CtBP or P4HB impaired SLC7A11 membrane trafficking, lead to accumulation of lipid peroxides and sensitization to ferroptosis. Conversely, P4HB overexpression restored SLC7A11 function and ferroptosis resistance in CtBP-deficient cells. Furthermore, significant positive correlations among CtBP, P4HB, and SLC7A11 expressions in clinical samples underscore the critical role of CtBP/P4HB/SLC7A11 axis in driving cancer aggressiveness. In vivo, targeting the CtBP/P4HB/SLC7A11 axis sensitized TNBC xenografts to the ferroptosis inducer RSL3, significantly suppressing tumor growth and lung metastasis. Conclusions This study identifies the CtBP/P4HB/SLC7A11 axis as a critical mediator of ferroptosis resistance in TNBC. These findings highlight this pathway as a potent therapeutic target to overcome resistance and enhance the efficacy of ferroptosis-inducing regimens in TNBC treatment.