Deletion of GPX8 Enhances Irradiation-Induced Ferroptosis Through m6A Hypomethylation-Mediated Upregulation of ACSL4 in Oral Cancer.

Abstract

Aims: Radioresistance limits the therapeutic efficacy of radiotherapy, and although ferroptosis contributes to radiation-induced tumor suppression, the upstream redox-epitranscriptomic mechanisms remain poorly defined. This study investigated how loss of the antioxidant enzyme glutathione peroxidase 8 (GPX8) influences susceptibility to ionizing radiation (IR), delineated the molecular pathway linking oxidative stress to ferroptosis, and evaluated the potential of GPX8 deletion as a radiosensitization strategy.

Results: We identify GPX8 as a previously unrecognized suppressor of ferroptosis whose deletion markedly amplifies IR-induced ferroptotic cell death. GPX8 deficiency increased reactive oxygen species accumulation, lipid peroxidation, labile iron levels, and ferroptosis-associated gene expression following irradiation. Mechanistic dissection revealed a novel redox-epitranscriptomic axis: oxidative stress induced by GPX8 loss downregulated the transcription factor E2F4, which in turn reduced zinc-finger CCCH-type containing 13 (ZC3H13) expression, leading to N⁶-methyladenine (m⁶A) hypomethylation and stabilization of acyl-CoA synthetase long-chain family member 4 (ACSL4) mRNA. Overexpression of E2F4 or ZC3H13 reversed ACSL4 upregulation, confirming pathway causality. ACSL4 knockdown diminished ferroptosis and rescued the hypersensitivity of GPX8-deficient cells to IR. In an orthotopic xenograft model, GPX8-knockout tumors displayed significantly enhanced radiosensitivity and elevated ferroptotic markers, effects mitigated by the ferroptosis inhibitor liproxstatin-1.

Innovation: This work uncovers a previously uncharacterized antioxidant-m⁶A-ferroptosis regulatory pathway and provides the first evidence that GPX8 modulates radiotherapy response by epitranscriptomic control of ACSL4 stability via the E2F4-ZC3H13 axis.

Conclusion: GPX8 deletion sensitizes oral cancer to irradiation by promoting ferroptosis through oxidative stress-driven suppression of E2F4 and ZC3H13, resulting in m⁶A hypomethylation and stabilization of ACSL4 mRNA. GPX8 thus represents a promising target for ferroptosis-based radiosensitization. Antioxid. Redox Signal. 45, 219-241.