HDAC6 promotes osimertinib resistance evolution in non-small cell lung cancer by activating EGFR degradation through the ubiquitin-proteasome pathway.

Osimertinib is the standard first-line treatment for patients with non-small cell lung cancer (NSCLC) harboring EGFR-sensitive mutations. However, drug resistance inevitably develops, highlighting the critical need for strategies to overcome this resistance and prolong therapeutic efficacy. Understanding the mechanisms underlying drug resistance is essential, and drug-resistant cell models serve as valuable tools for investigating acquired resistance. In this study, we establish an osimertinib resistance evolution model in vitro by continuous high-dose drug induction and identify cell lines exhibiting "permanent" resistance to osimertinib (osimertinib resistant, OR). Transcriptome sequencing (RNA-seq), gain- and loss-of-function assay, including lentiviral-mediated overexpression and RNAi knockdown, pharmacological inhibition, and protein degradation analysis reveal significant alterations in genes associated with epigenetic regulation, notably a marked upregulation of histone deacetylase 6 (HDAC6) in OR cells. Knockdown of HDAC6 or pharmacological inhibition of HDAC6 restores the sensitivity of OR cells to osimertinib, whereas overexpression of HDAC6 in sensitive cells reduces drug efficacy and accelerates the onset of resistance. Furthermore, we find that HDAC6 upregulation promotes EGFR degradation, thereby contributing to resistance. Collectively, our findings demonstrate the utility of drug resistance evolution models in identifying key resistance factors. HDAC6 plays a pivotal role in osimertinib resistance, and targeting HDAC6 may represent a novel therapeutic strategy to overcome resistance and enhance treatment efficacy.