Amiloride synergizes with EGFR PROTACs and inhibitors to overcome therapeutic resistance in NSCLC.

Lung cancer remains the leading cause of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) accounting for most cases. Among NSCLC patients, approximately 15-30 % harbor activating mutations in the Epidermal Growth Factor Receptor (EGFR), making them eligible for treatment with tyrosine kinase inhibitors (TKIs) like osimertinib, which has shown significant therapeutic benefits. However, acquired resistance to these therapies remains a major challenge in improving long-term clinical outcomes, underscoring the urgent need for novel strategies to address treatment resistance. In this study, we investigated the therapeutic potential of Amiloride (MK-870), a sodium channel inhibitor, as an adjuvant to EGFR-targeted therapies for NSCLC. Our findings demonstrate that MK-870 exhibits synergistic effects with EGFR PROTACs and small-molecule inhibitors, significantly enhancing antitumor activity in NSCLC cell lines. We identified α-ENaC (encoded by SCNN1A) as a key regulator of EGFR stability, with high α-ENaC expression correlating with reduced sensitivity to EGFR. MK-870 achieves dual downregulation of EGFR at both transcriptional and protein levels via targeted inhibition of sodium channel proteins. Furthermore, MK-870 enhances lysosomal activity in multiple NSCLC cell lines and EGFR-overexpressing NIH/3 T3 cells-a phenomenon potentially linked to its inhibition of sodium‑hydrogen exchanger (NHE) to promote cellular acidification. Mechanistically, the resultant acidification promotes apoptosis while simultaneously enhancing lysosome-mediated degradation of EGFR proteins by PROTAC molecules. Collectively, MK-870 synergizes with EGFR-targeting agents through coordinated modulation of sodium channel proteins and NHE-mediated pH homeostasis. These novel insights highlight MK-870 as a promising adjuvant for overcoming EGFR-targeted therapeutic resistance in NSCLC, offering a new avenue for improving patient outcomes in this challenging disease.