TGM2-TUFM promotes acquired resistance to EGFR-TKIs in EGFR-mutated NSCLC through p62-mediated lipophagy

BACKGROUND: Acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) remains the leading cause of treatment failure in advanced non-small cell lung cancer (NSCLC) patients harboring sensitizing EGFR mutations. This study aims to investigate the underlying resistance mechanisms in EGFR-mutated NSCLC. METHODS: Analyze the differential genes in the transcriptome sequencing data of EGFR-TKi-sensitive and -resistant cell lines, and use the GDC database to analyze the prognosis. qRT‒PCR, western blotting, and immunohistochemistry were used to detect the expression of TGM2 in EGFR-TKI-sensitive and -resistant NSCLC cells and tissue samples. The effects and molecular mechanisms of TGM2 on EGFR-TKI resistance were verified by CCK-8, flow cytometry, western blotting, mouse xenograft models, gene enrichment analysis, and mass spectrometry. RESULTS: Our study found that TGM2 was highly expressed in EGFR-TKI-resistant NSCLC cells and tissue samples. Its increased expression was associated with shorter survival time in NSCLC patients. Transglutaminase 2 (TGM2) overexpression renders EGFR-sensitive mutated NSCLC cells resistant to EGFR-TKIs in culture and in murine xenograft models. Mechanistically, we determined that TGM2 promotes lipophagy and fatty acid oxidation (FAO) by inhibiting the ubiquitin-mediated degradation of elongation factor Tu, mitochondrial (TUFM), thereby contributing to drug resistance in NSCLC. Furthermore, we found that TGM2 promotes the formation of p62 (sequestosome 1) bodies through TUFM, and these p62 bodies bind to lipid droplets (LDs)-associated protein perilipin 2 (PLIN2) to enhance lipophagy, revealing a novel pathway for TGM2-facilitated LD breakdown. Notably, treatment with the autophagy inhibitor chloroquine (CQ) and the FAO inhibitor etomoxir reversed TGM2-mediated EGFR-TKI resistance. CONCLUSIONS: Our study revealed that TGM2 is a potential therapeutic target or biomarker for predicting acquired EGFR-TKI resistance in EGFR-mutated NSCLC.