FAT1 Promotes EGFR-TKI Resistance in Non-Small Cell Lung Cancer Cells by Inducing Mitochondrial Autophagy

EGFR-TKIs improve NSCLC outcomes, but acquired resistance persists. The role of mitochondrial homeostasis remains unclear. TKI-resistant NSCLC models were established. Mitochondrial function, ROS, and mitophagy were assessed in resistant versus parental cells and after FAT1 knockdown. Mechanisms were explored via protein interaction and ubiquitination assays. In vivo studies validated therapeutic relevance. Resistant NSCLC cells demonstrated enhanced mitochondrial function, marked by elevated mitochondrial mass, increased membrane potential, higher ATP production and mitophagy, and reduced ROS levels. FAT1 was significantly upregulated in these cells and correlated with heightened drug resistance, enhanced proliferation and migration, and inhibited apoptosis. FAT1 deficiency decreased mitochondrial function and disrupted mitophagy, resulting in ROS accumulation and restored TKI sensitivity. Treatment with the ROS scavenger NAC reversed TKI resistance. Chloroquine-induced autophagy inhibition also counteracted resistance. Mechanistically, FAT1 recruited USP38 to deubiquitinate PINK1, preventing K48-linked ubiquitin-mediated degradation and promoting PINK1 stability. In vivo , FAT1 knockdown improved the antitumor effect of osimertinib, inhibiting tumor growth and decreasing PINK1 and Ki67 expression. FAT1 drives TKI resistance by stabilizing PINK1 via USP38, enhancing mitophagy and reducing ROS. Targeting the FAT1–USP38–PINK1 axis represents a promising strategy to overcome resistance in NSCLC.