Oxidative modification of G-quadruplex triggers CLIC4-associated mitochondrial dysfunction to promote glioblastoma progression.

Glioblastoma is the most aggressive form of primary brain tumor, characterized with poor prognosis and resistance to conventional therapies. Increasing evidence points to oxidative stress and redox dysregulation as important contributors to glioblastoma progression. Previously, chloride intracellular channel protein 4 (CLIC4), a redox-sensitive protein, has been implicated in cancer biology. However, its roles in glioblastoma remain poorly understood. Here, we found that CLIC4 expression is upregulated in glioblastoma tissues and cell lines, and is positively correlated with tumor malignancy and poor survival outcomes in patients with glioblastoma. Gene silencing of CLIC4 significantly reduces glioblastoma cell viability, migration, and proliferation in vitro and suppress tumor growth in vivo. Mechanistically, CLIC4 appears to maintain redox homeostasis by regulating mitochondrial functions, including membrane potential, mass, ROS production, and the activity of complexes III and IV. Moreover, a G-quadruplex (G4) structure located in CLIC4 promoter region is related to CLIC4 upregulation by oxidative stress in glioblastoma. This G4 structure can be readily oxidized to a parallel conformation, thereby enhancing its binding with DHX36 protein to promote gene transcription. Collectively, these findings position CLIC4 as a pivotal modulator of oxidative stress in glioblastoma and a potential target for developing therapeutic approaches for the treatment of glioblastoma.