Fig. 2

Overexpression of NSUN2 results in gefitinib resistance and tumor recurrence. a PC-9 cells stably transfected with wild type NSUN2 (NSUN2-WT), the double catalytic mutant NSUN2 (NSUN2-DM), or empty vector plasmid (Mock) were detected for NSUN2 expression by western blotting analysis. b PC-9-Mock, PC-9-NSUN2-WT, PC-9-NSUN2-DM cells were treated with gefitinib at gradient concentrations for 72 h and cell viability as well as gefitinib IC₅₀ were measured by CCK-8 assay. c PC-9-Mock, PC-9-NSUN2-WT, PC-9-NSUN2-DM cells were treated with gefitinib (1 µM) for 24 h and NSUN2 protein level was determined by western blotting analysis. d-f Tumor volume (d), tumor weight (e), and mice survival (f) of xenografts subcutaneously implanted with PC-9-Mock, PC-9-NSUN2-WT, PC-9-NSUN2-DM cells in BALB/c nude mice (n ≥ 6 per group). About two weeks after injection, mice were administrated with 25 mg/kg gefitinib or 0.5% CMC-Na via gavage once daily for consecutive 10 days (from day 15 to day 24). g Representative images of ki67 IHC staining and the quantitative H-scores of tumors obtained from tumor xenografts. Image magnification: 200 × (upper panel) and 400 × (lower panel). Data are means ± SD of two independent experiments. For (d), results were expressed as mean ± SEM. For Kaplan-Meier curve, p values were determined using a log-rank test (f). ns, not significant, *p < 0.05, **p < 0.01, ***p < 0.001. Mock, empty vector control; NSUN2-WT, wild type NSUN2; NSUN2-DM, the double catalytic mutant NSUN2.