A.The viability of A549 cells following 48 h of CTEO treatment was detected by CCK-8 assay. B. A549 cells were cultured with different concentrations (0–200 μg/mL) of CTEO for varied time points). Cell viability was determined by CCK-8 assay. C. The viability of HBE cells following 48 h of CTEO treatment was detected by CCK-8 assay. D. The colony formation of A549 cells was determined with colony formation assay after exposure to different concentrations of CTEO (0, 20, 40 and 60 μg/mL) and colonies were allowed to grow for 10 days. E, F. Western blotting analysis of PCNA protein expression after CTEO treatment, and quantification. Values represent mean ± SD of three independent experiments. *P < 0.05, **P < 0.01, and ***P < 0.001.