ZNF598 promotes glioblastoma progression and temozolomide resistance by facilitating MFN1-mediated mitochondrial quality control

Glioblastoma (GBM) is the most aggressive primary brain tumor and frequently develops intrinsic or acquired resistance to temozolomide (TMZ). Mitochondrial quality control (MQC) is essential for tumor cell survival and therapeutic adaptation, yet its upstream regulatory mechanisms in GBM remain poorly defined. Here, we identify zinc finger protein 598 (ZNF598), an E3 ubiquitin ligase with RNA-binding capacity, as a critical regulator of MQC and TMZ resistance in GBM. Analysis of public datasets revealed that ZNF598 expression is significantly elevated in TMZ-resistant GBM cells and human glioma tissues, correlating with adverse patient prognosis. Functionally, ZNF598 knockdown suppressed GBM cell proliferation, induced apoptosis, and disrupted mitochondrial homeostasis, as reflected by reduced ATP production and mtDNA copy numbers, elevated reactive oxygen species, loss of mitochondrial membrane potential, and mitochondrial fragmentation. ZNF598 silencing suppressed tumor growth in subcutaneous and intracranial orthotopic xenograft models and markedly enhanced TMZ sensitivity in vitro and in subcutaneous xenografts. Mechanistically, ZNF598 associated with mitofusin 1 (MFN1) mRNA and maintained its stability, thereby sustaining MFN1 expression and MFN1-mediated mitochondrial fusion. Notably, this regulation was independent of the E3 ubiquitin ligase activity of ZNF598, as the catalytically inactive ZNF598C29A mutant restored MFN1 mRNA stability, MFN1 protein abundance, and mitochondrial function in ZNF598-depleted cells. Restoration of MFN1 partially rescued mitochondrial dysfunction and apoptosis induced by ZNF598 knockdown. Furthermore, screening of the Genomics of Drug Sensitivity in Cancer dataset identified the BET inhibitor RVX208, which rapidly reduced ZNF598 mRNA and protein levels, phenocopied the mitochondrial dysfunction and apoptosis caused by ZNF598 suppression, and increased TMZ responsiveness at least partly through ZNF598 downregulation. These findings establish ZNF598 as a pivotal upstream regulator of MFN1-mediated MQC and a key determinant of TMZ response in GBM, highlighting the ZNF598–MFN1 axis as a promising therapeutic target for overcoming TMZ resistance.