Epigenetically driven GAS2L3 enforces non-canonical cell cycle progression to promote osimertinib resistance in lung adenocarcinoma
Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have markedly improved outcomes in EGFR-mutant lung adenocarcinoma (LUAD), yet acquired resistance to the third-generation inhibitor osimertinib remains inevitable. Although metabolic reprogramming is increasingly recognized as a driver of therapeutic resistance, the epigenetic consequences of lactate accumulation and their functional relevance in osimertinib resistance are poorly understood. Here we report that osimertinib-resistant LUAD cells exhibit enhanced glycolytic flux, increased intracellular lactate levels, and elevated histone H4 lysine 8 lactylation (H4K8la). Integrative transcriptomic analysis revealed significant enrichment of cell-cycle–associated pathways in resistant tumors, despite downregulation of canonical Cyclin B1 and Cyclin D1. Among the upregulated genes, GAS2L3 emerged as a prominent candidate. Genome-wide CUT&Tag profiling demonstrated enrichment of H4K8la at the GAS2L3 promoter, which was confirmed by ChIP–qPCR. Functionally, GAS2L3 overexpression accelerated S/G2–M progression and promoted proliferation under drug pressure, whereas its silencing induced cell-cycle arrest and restored osimertinib sensitivity both in vitro and in xenograft models. Notably, resistant cells displayed elevated P53 expression without induction of its canonical effector P21, indicating checkpoint uncoupling and a noncanonical mode of cell-cycle regulation. Mechanistically, glycolysis inhibition reduced H4K8la and GAS2L3 expression and partially re-sensitized resistant cells, while exogenous lactate restored H4K8la levels and resistance phenotypes, establishing a metabolically driven epigenetic circuit. Clinically, high GAS2L3 expression was associated with shorter progression-free survival in osimertinib-treated patients. Collectively, our findings identify a glycolysis–H4K8la–GAS2L3 axis that drives noncanonical cell-cycle reprogramming independently of classical Cyclin–CDK activation, thereby promoting acquired osimertinib resistance. These results uncover a metabolism-epigenetics–cell cycle interface that may represent a therapeutic vulnerability in EGFR-mutant LUAD.