THEM6 modulates carboplatin sensitivity by regulating ferroptosis through FDFT1 in triple-negative breast cancer.

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with poor prognosis, as chemotherapy resistance leads to relapse in many patients. Carboplatin addition improves treatment response, but challenges persist.

Methods: To identify novel targets for TNBC, we analyzed differentially expressed proteins in patients treated with neoadjuvant chemotherapy. Cell viability was assessed using CCK-8 and colony formation assays. In vivo effects were studied in an orthotopic xenograft model using THEM6 overexpression cells. ROS, iron levels, MDA, and mitochondrial ultrastructure were assessed. Protein expression was analyzed by Western blotting and RT-PCR, and FDFT1 ubiquitination was evaluated.

Results: We identified THEM6 (co-downregulated) and PGRMC1 (co-upregulated) as survival-associated proteins. THEM6 overexpression enhanced carboplatin sensitivity in vitro and in vivo, reducing tumor weight and volume. THEM6-induced sensitivity was linked to ferroptosis, as the ferroptosis inhibitor Fer-1 reversed the effect, while apoptosis, necrosis, and autophagy inhibitors had no impact. THEM6 overexpression reduced GPX4 and SLC7A11, while increasing ACSL4. TEM revealed mitochondrial damage, and iron, MDA, and ROS levels were elevated in treated cells. Mechanistically, THEM6 stabilized FDFT1 by inhibiting its K48-linked ubiquitination, prolonging its protein half-life, and promoting ferroptosis. FDFT1 knockdown reversed THEM6-induced sensitivity to carboplatin.

Conclusions: Our findings suggest that THEM6 enhances carboplatin sensitivity in TNBC by promoting ferroptosis through regulation of FDFT1. THEM6 may serve as a novel therapeutic target to improve TNBC treatment outcomes.