RBM15 facilitates osimertinib resistance of lung adenocarcinoma through m6A-dependent epigenetic silencing of SPOCK1.

Lung cancer is the leading cause of cancer-related mortality globally. N6-methyladenosine (m6A) is the most abundant modification in mammalian mRNA and is involved in the biological regulation of tumors, including lung cancer. However, the role of m6A-related proteins, such as RNA-binding motif protein 15 (RBM15), in lung cancer progression remains largely unknown. Our study indicated that RBM15 is significantly overexpressed in lung adenocarcinoma, serving as an independent prognostic factor for poor outcomes and facilitating tumor cell proliferation and migration. RBM15 was markedly elevated in patients with EGFR mutations, correlating with a poorer prognosis, while it had negligible prognostic value in EGFR wild-type patients. As EGFR-tyrosine kinase inhibitors (TKIs) are the standard treatment for patients with EGFR mutations, we subsequently determined that RBM15 drives osimertinib resistance via a novel mechanism: enhancing m6A modification of cwcv- and kazal-like domains proteoglycan 1 (SPOCK1) mRNA, promoting epithelial-mesenchymal transition-mediated osimertinib resistance through a bypass activation pathway. These findings were validated in osimertinib-resistant H1975 cells and organoids from patients with osimertinib-resistant lung adenocarcinoma. Furthermore, the RBM15-SPOCK1 axis was activated in drug-tolerant persister cells, indicating that early targeting of RBM15 during EGFR-TKI treatment could dramatically extend the patient response and benefit from TKI therapy. Our results emphasize the critical role of RBM15 in reversing EGFR-TKI resistance and propose it as a promising therapeutic target for prolonging TKI treatment benefits in patients with lung adenocarcinoma.