Fig. 1.

Discovery and validation of enhanced expression of BCAT1 in TKI-resistant lung cancer. a Workflow of the SILAC assay to identify differentially expressed proteins between third-generation EGFR TKI-resistant clones and parental cells. Ribbon representation of the experimental structure of BCAT1 (PDB ID 7NTR⁴²) is shown on the right. b Common differentially expressed proteins in both ASK120067-resistant strains (67R) and osimertinib-resistant strains (AZDR). Red dots: up-regulated overlapping proteins; blue dots: down-regulated overlapping proteins. c Pathway enrichment analysis of differentially expressed overlapping proteins in TKI-resistant cells compared to the parental cells. The top 10 enriched pathways in TKI-resistant cells versus parental NCI-H1975 cells are shown. d Diagram of BCAT-catalyzed reversible BCAAs metabolism. e, f BCAT1 protein levels and relative mRNA levels (n = 5) in the indicated tumor cells were determined by Western blot assay (e) and RT‒qPCR (f). g BCAT1 expression levels in the indicated tumor tissues were determined by Western blot assay (n = 5) and are shown as representative images (left) and a quantitative graph (right). *p < 0.05, **p < 0.01, ***p < 0.001. Data are expressed as the mean ± SD