A Non-Canonical Core Transcriptional Regulatory Circuit Orchestrates Chromatin Reprogramming to Drive Osimertinib Resistance in Non-Small Cell Lung Cancer.

Osimertinib resistance represents a major therapeutic challenge in non-small cell lung cancer (NSCLC), yet the underlying epigenetic mechanisms remain incompletely understood. Through integrated epigenomic and transcriptomic profiling, we identified a resistance-specific, non-canonical transcriptional circuit driven by the coordinated action of three core components: ID3, SMAD3, and NR2F2. These transcription factors form protein complexes that co-bind to shared enhancers or promoters, reciprocally enhancing each other's transcriptional activity and that of their downstream targets. Mechanistically, ID3 mediates the chromatin residence of the SMAD3-NR2F2 complex through its non-canonical function as a structural co-factor. This rewires the transcriptional program of resistant cells to ultimately drive resistance via direct upregulation of HIF2A, a dual-function hub that concurrently promotes neuroendocrine differentiation and suppresses ferroptosis. Functional studies confirmed that disrupting this circuit or inhibiting its downstream effector HIF2A restored Osimertinib sensitivity in resistant models. Our study elucidates a novel epigenetic paradigm through which a non-canonical, self-reinforcing transcriptional circuit co-opts lineage plasticity and cell death evasion to drive Osimertinib resistance, thereby establishing a therapeutically actionable target for overcoming this aggressive phenotype.