KLF5-driven G6PD protects lung squamous cell carcinoma from ferroptosis by sustaining mitochondrial homeostasis and SLC7A11-dependent cystine uptake

AIMS: Lung squamous cell carcinoma (LUSC) is a highly aggressive malignancy with limited therapeutic options. Ferroptosis has emerged as a promising antitumor strategy. However, the metabolic determinants governing ferroptotic vulnerability in LUSC remain incompletely understood. We investigated glucose-6-phosphate dehydrogenase (G6PD) in this context. MATERIALS AND METHODS: In vitro models using small interfering RNA (siRNA)-mediated G6PD depletion, together with pharmacological studies using 6-aminonicotinamide (6-AN) and LUSC xenograft models, were employed to investigate the underlying mechanisms. KEY FINDINGS: G6PD was markedly upregulated in LUSC, and analysis of the Cancer Genome Atlas lung squamous cell carcinoma (TCGA-LUSC) cohort showed that elevated G6PD expression was associated with advanced clinicopathological features and poorer overall survival. While ferroptosis inducers (erastin and RSL3) did not alter G6PD mRNA, they robustly increased G6PD protein during ferroptotic stress. Genetic or pharmacological inhibition of G6PD significantly sensitized LUSC cells to RSL3-induced ferroptosis, evidenced by enhanced lipid peroxidation, glutathione depletion, and ferrostatin-1-reversible cell death. Mechanistically, G6PD inhibition led to mitochondrial ferrous iron accumulation, elevated reactive oxygen species, impaired respiration, and activation of PINK1/Parkin-dependent mitophagy, which further exacerbated ferroptotic injury. In vivo, combined treatment with 6-aminonicotinamide and RSL3 markedly suppressed LUSC xenograft growth and enhanced biochemical markers of ferroptotic stress. Furthermore, G6PD protects cells by positively regulating the cystine/glutamate antiporter SLC7A11 to maintain redox homeostasis. Upstream, the oncogenic factor Krüppel-like factor 5 (KLF5) directly activates G6PD transcription. SIGNIFICANCE: Our findings identify a KLF5-G6PD-SLC7A11 axis as a critical metabolic safeguard against ferroptosis in LUSC. Targeting G6PD disrupts mitochondrial homeostasis, enhances mitophagy-dependent oxidative stress, and sensitizes tumors to ferroptotic therapy, highlighting a promising therapeutic strategy for LUSC.