Restoration of Osimertinib sensitivity in lung cancer through BRD4 inhibitor-mediated depalmitoylation of mutant EGFR via APT1.

Non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations initially responds to the third-generation EGFR-tyrosine kinase inhibitor (TKI) Osimertinib. However, acquired resistance inevitably develops through various mechanisms, including secondary mutations and activation of bypass signaling pathways. Nuclear translocation of EGFR has been implicated in resistance to targeted therapies, but the molecular mechanisms linking EGFR subcellular localization to Osimertinib resistance remain poorly understood. Our findings suggested that CMPK2 mediates Osimertinib resistance independently of EGFR mutations. Importantly, BRD4 inhibitor NHWD870 significantly reversed this resistance by inhibiting the nuclear translocation of EGFR and subsequent transcriptional activation of CMPK2. Moreover, upregulated APT1-mediated depalmitoylation of EGFR at C19 site was observed in Osimertinib resistant cells. BRD4 inhibitor treatment efficiently repressed viability and proliferation of Osimertinib-resistant cells, with APT1 silencing additionally enhancing these inhibitory effects. In conclusion, BRD4 inhibitor inhibited APT1-mediated depalmitoylation modification of EGFR, resulting in reduction of nuclear EGFR and subsequent downregulation of CMPK2, enhancing Osimertinib sensitivity in NSCLC. This study provides a novel therapeutic strategy for overcoming Osimertinib resistance in NSCLC treatment.