TRAPPC4 Promotes GPX4 Stability to Drive Ferroptosis Resistance and Tumor Progression in Head and Neck Squamous Cell Carcinoma.

Head and neck squamous cell carcinoma (HNSCC) is often diagnosed at advanced stages, resulting in poor clinical outcomes. Ferroptosis resistance presents a major challenge in the treatment of HNSCC, highlighting the need to elucidate the mechanisms that enable HNSCC cells to evade ferroptosis. In this study, we conducted a genome-wide CRISPR-Cas9 knockout screen and identified trafficking protein particle complex subunit 4 (TRAPPC4) as a key regulator of ferroptosis resistance in HNSCC. Across a comprehensive set of experimental models, including HNSCC cell lines, patient-derived organoids, cell-derived xenografts, patient-derived xenografts, Trappc4 conditional knockout mice, and lymph node and lung metastasis models, TRAPPC4 promoted tumor progression by inhibiting ferroptosis. Mechanistically, TRAPPC4 decreased chromatin accessibility at a distal regulatory element upstream of TRIM55, thereby limiting FOS-dependent transcription. This repression reduced TRIM55-mediated GPX4 ubiquitination and degradation, resulting in GPX4 stabilization and ferroptosis resistance. Structure-based high-throughput virtual screening identified pitavastatin (PTV) calcium as a TRAPPC4-binding compound that promoted TRAPPC4 degradation. Notably, PTV calcium synergized with the ferroptosis inducer RSL3 to enhance ferroptotic activity and suppress HNSCC progression. These findings delineate a TRAPPC4-FOS-TRIM55-GPX4 signaling axis that drives ferroptosis resistance and tumor progression and highlight TRAPPC4 as a promising therapeutic target for ferroptosis-based intervention in HNSCC. SIGNIFICANCE: TRAPPC4 enables head and neck squamous cell carcinoma to resist ferroptosis by regulating TRIM55-mediated GPX4 degradation, providing a potential therapeutic target to inhibit cancer progression.