LAUSR

Chemoresistance is the crux of clinical treatment failure of small‐cell lung cancer (SCLC). Cancer stem cells play a critical role in therapeutic resistance of malignant tumors. Studies have shown that the role of erythropoietin‐producing hepatocellular A2 (EphA2) in tumors is complex. This study aimed to test the hypothesis that ligand‐independent activation of EphA2 modulates chemoresistance by enhancing stemness in SCLC. We verified that EphA2 was activated in chemoresistance sublines in a ligand‐independent manner rather than a ligand‐dependent manner. Ligand‐independent EphA2 enhanced the expression of stemness‐associated biomarkers (CD44, Myc, and SOX2), accelerated epithelial–mesenchymal transition (EMT) and reinforced self‐renewal to drive the chemoresistance of SCLC, while the P817H mutant EphA2 neutralized intrinsic function. Co‐immunoprecipitation (co‐IP) and GST‐pull down experiments were conducted to verify that EphA2 directly interacted with PRMT1. Moreover, EphA2 increased the expression and activity of PRMT1. Whereafter, PRMT1 interacted with and methylated SOX2 to induce stemness and chemoresistance in SCLC. Pharmacological inhibition of EphA2 showed a synergistic anti‐tumor effect with chemotherapy in preclinical models, including patient‐derived xenograft (PDX) models. These findings highlight, for the first time, that the EphA2/PRMT1/SOX2 pathway induces chemoresistance in SCLC by promoting stemness. EphA2 is a potential therapeutic target in SCLC treatment.