GPX4 and FSP1 Coinhibition Uncovers a Therapeutic Vulnerability in Oral Squamous Cell Carcinoma

ABSTRACT Background Ferroptosis, an iron‐dependent form of regulated cell death driven by lipid peroxidation, has recently emerged as a therapeutic vulnerability in resistant cancers. While glutathione peroxidase 4 (GPX4) has been established as a central ferroptosis suppressor, ferroptosis suppressor protein 1 has been identified as a parallel pathway that reduces ubiquinone to ubiquinol, thereby preventing lipid peroxidation. The upregulated expression of FSP1 has been linked to therapy resistance in several cancers; however, its clinical and biological significance in oral squamous cell carcinoma (OSCC) remains largely unknown. Methods To address this gap, we herein combined bioinformatic analyses of The Cancer Genome Atlas with functional studies on OSCC cell lines and xenograft models. Survival was analyzed using the expression of GPX4 and FSP1. Functional assays included pharmacological inhibition, CRISPR/Cas9 knockout, and rescue with cell death inhibitors. Results GPX4 expression showed no survival association, whereas high FSP1 expression correlated with poor long‐term outcomes, establishing its prognostic value in OSCC. Mechanistically, GPX4 inhibition induced the compensatory upregulation of FSP1, conferring ferroptosis resistance. GPX4‐deficient cells were highly sensitive to FSP1 inhibition, confirming dual dependency. Dual blockade suppressed proliferation in vitro, whereas systemic iFSP1 failed to significantly reduce xenograft growth, underscoring drug‐delivery limitations. Conclusions FSP1 acts as both a prognostic biomarker and compensatory survival factor in OSCC. Combined GPX4/FSP1 targeting represents a promising therapeutic strategy; however, translation will require innovative delivery systems and integration with redundant ferroptosis‐regulatory pathways.