ATM inhibition restores IFN-γ sensitivity and induces ferroptosis in NSCLC via DNA damage response.

Cancer immunotherapy has demonstrated remarkable clinical success across diverse tumor types. Nevertheless, durable responses occur in only a subset of patients, and both primary and acquired resistance remain major challenges. Interferon-γ (IFN-γ), a key effector cytokine in anti-tumor immunity, is often neutralized by tumor cells through mechanisms that attenuate its activity. In this study, we examined the regulation of IFN-γ responsiveness in two human NSCLC cell lines, PC-9 and A549. PC-9 cells exhibited greater resistance to IFN-γ treatment compared with A549 cells. Transcriptomic analysis revealed that IFN-γ-resistant PC-9 cells were enriched in genes associated with the homologous recombination (HR) DNA repair pathway following exposure to IFN-γ. Given the critical role of the serine/threonine kinase ataxia telangiectasia mutated (ATM) in detecting DNA double-strand breaks and coordinating HR repair, we investigated whether ATM contributes to IFN-γ resistance by using the ATM inhibitor KU-55933. Inhibition of ATM restored IFN-γ sensitivity by inducing ferroptosis in NSCLCs. Mechanistically, the combination of IFN-γ treatment and ATM inhibition elicited a robust DNA damage response and disrupted glutathione metabolism, reducing the GSH/GSSG ratio and thereby promoting ferroptosis through increased susceptibility to oxidative stress. These findings highlight the pivotal role of DNA damage response pathways in mediating the anti-tumor effects of IFN-γ.