MicroRNA-601 Enhances Osimertinib Sensitivity by Targeting Transient Receptor Potential Mucolipin 3 in Non-small Cell Lung Cancer Cells

Acquired resistance to tyrosine kinase inhibitors (TKIs), such as osimertinib, poses a major barrier to effective treatment of non-small cell lung cancer (NSCLC). Recent data suggest that lysosomal Ca²⁺ signaling, particularly via transient receptor potential mucolipin 3 (TRPML3; also known as MCOLN3), contributes to TKI resistance by promoting lysosomal exocytosis and drug efflux. Here, we investigated the regulatory role of microRNA-601 (miR-601) in modulating TRPML3 expression and its impact on osimertinib resistance in NSCLC. Bioinformatic predictions using the DIANA microT-CDS algorithm identified TRPML3 as a putative target of miR-601. Luciferase reporter assays confirmed direct binding of miR-601 to the TRPML3 3'-untranslated region. Functional assays were conducted with parental and osimertinib-resistant PC9 and HCC827 cells to evaluate the effects of miR-601 on TRPML3 expression, apoptosis, cell-cycle progression, and drug sensitivity. Osimertinib treatment led to a time-dependent miR-601 downregulation in NSCLC cells, and its basal expression remained suppressed in resistant sublines. miR-601 overexpression reduced TRPML3 protein levels, enhanced poly(ADP-ribose) polymerase cleavage, induced G0/G1 cell-cycle arrest, and restored osimertinib sensitivity. Similar effects were observed upon TRPML3 knockdown, supporting a TRPML3-dependent mechanism. Thus, miR-601 negatively regulates TRPML3 and modulated TKI responses in NSCLC cells. Restoring miR-601 expression may represent a promising therapeutic strategy for overcoming acquired osimertinib resistance by targeting TRPML3-mediated lysosomal signaling.