4-Hydroxytamoxifen induces a noncanonical ferroptosis in lung adenocarcinoma by targeting AKR1B10.

BACKGROUND: Lung adenocarcinoma (LUAD) remains a leading cause of cancer mortality, and current therapies are limited by drug resistance and toxicity. Ferroptosis offers an attractive strategy for cancer therapy, but classical ferroptosis is iron‑dependent. Repurposing approved drugs offers a rapid strategy to identify novel anti‑LUAD agents, yet the mechanism by which 4‑Hydroxytamoxifen (4‑OHT) exerts estrogen receptor-independent anti‑tumour effects remains unclear. METHODS: We performed a drug repurposing screen of 950 endogenous metabolites in LUAD cells. Anti‑tumour activity was validated in vitro and in vivo using LUAD cell lines and mouse models. Target identification and mechanistic studies employed LiP‑MS, pull-down SPR, CETSA, metabolomics, and enzyme activity assays. Clinical relevance was assessed via tissue microarrays and TCGA analysis. Drug synergy was quantified using the Chou-Talalay method. RESULTS: 4‑OHT inhibited LUAD cell proliferation with IC50 values of 3.86 ± 0.26 µM to 13.58 ± 0.55 µM independent of estrogen receptor. It triggered noncanonical ferroptosis characterised by GSH depletion (reduced by about 60%), GPX4 downregulation, lipid peroxidation (about 2.5-fold increase), and iron independence. Mechanistically, 4‑OHT directly bound AKR1B10 (KD(M) was 7.98e-06) and inhibited its enzymatic activity, leading to ACC1 degradation, lipid deficiency, and accumulation of toxic lipid‑derived carbonyls. AKR1B10 knockout abolished 4‑OHT‑induced cell death, while rescue restored sensitivity. Nanatinostat similarly targeted AKR1B10 and induced the same cell death modality. AKR1B10 upregulation in LUAD tissues correlated with reduced overall survival rates. CONCLUSION: This study demonstrates that 4‑OHT directly inhibits AKR1B10 enzymatic activity to induce a noncanonical ferroptosis in LUAD. AKR1B10 overexpression correlates with poor prognosis and chemoresistance in LUAD patients. Nonetheless, AKR1B10 inhibition warrants further investigation as a therapeutic strategy. HIGHLIGHTS: 4‑OHT directly inhibits AKR1B10 enzymatic activity to induce noncanonical ferroptosis in LUAD. AKR1B10 sustains LUAD survival by stabilising ACC1 and detoxifying reactive carbonyl species (RCSs). Nanatinostat similarly targets AKR1B10 and elicits the same cell death modality. AKR1B10 overexpression correlates with poor prognosis and chemoresistance in LUAD.