Figure 1. Cisplatin resistance of CR-A549 and CR-PC9 cells. (A) After treatment with different concentrations of cisplatin (0–60 μM), viability of A549 and CR-A549 cells was detected by using MTT assays. *P<0.05 vs. A549 cells. (B) After treatment with different concentrations of cisplatin (0–60 μM), viability of PC9 and CR-PC9 cells was detected by using MTT assays. *P<0.05 vs. PC9 cells.