Toxicity assay of cisplatin on dsP21-322 transfected A549 cells. (A) Human lung cancer A549 cells transfected with mock, scramble dsRNA or dsP21-322 was treated by cisplatin with concentrations ranging from 0.5 μg/ml to 10 μg/ml for 48 h. The IC50 of dsP21-322 treated cells was decreased to 1.23 μg/ml compared with those of mock and scramble dsRNA transfected groups (4.15 μg/ml and 3.84 μg/ml respectively). (B) Transiently transfected A549 cells were treated with 5 μg/ml cisplatin, drug sensitivity analysis was performed with MTT assays. Data represent the mean + SE of three independent experiments. * p < 0.05.