<p>Nasopharyngeal carcinoma (NPC) is a malignant tumor with high metastatic potential. Tumor necrosis factor receptor-associated factor 4 (TRAF4) has been identified as an oncogene in various cancers; however, its specific role and molecular mechanism in NPC progression, particularly regarding oxidative stress regulation, remain largely unexplored. In this study, TRAF4 and SETDB1 expression levels were analyzed in NPC cell lines using RT-qPCR and Western blotting. Loss-of-function and gain-of-function assays were performed to evaluate cell proliferation and apoptosis in vitro. The regulatory interaction between TRAF4 and SETDB1 was investigated via co-immunoprecipitation and ubiquitination assays. Mitochondrial function was assessed using MitoSOX, JC-1, and MitoTracker staining to monitor reactive oxygen species (ROS) generation and membrane potential. TRAF4 was significantly upregulated in NPC cell lines compared to immortalized nasopharyngeal epithelial cells. Silencing TRAF4 markedly inhibited NPC cell proliferation and induced apoptosis. Mechanistically, TRAF4 functioned as a critical stabilizer of SETDB1; TRAF4 depletion reduced SETDB1 protein levels by altering its ubiquitination status. Furthermore, SETDB1 knockdown triggered mitochondrial dysfunction, characterized by ROS accumulation, membrane potential collapse, and Cytochrome c release, which could be reversed by the ROS scavenger N-acetyl-L-cysteine (NAC). Importantly, overexpression of SETDB1 rescued the proliferation inhibition and mitochondrial apoptosis induced by TRAF4 silencing. Our findings demonstrate that TRAF4 promotes NPC progression by stabilizing SETDB1 to suppress ROS-dependent mitochondrial apoptosis, highlighting the TRAF4/SETDB1 axis as a promising therapeutic target for NPC treatment.</p>