Abstract:

Objective To investigate the role of Ku70 in the chemoresistance of lung cancer and the potential of Ku70 small-interfering RNA (siRNA) as a therapy for reversal of cisplatin resistance in lung adenocarcinoma.Methods The Ku70 mRNA and protein expression levels were dectected by RT-PCR and Western blotting methods in human lung adenocarcinoma cells A549 and their cisplatin-resistant variant A549/DDP.The A549/DDP cells were divided into 3 groups:blank control,negative control group in which the cells were tranfected with nonspecific si-RNA（si-Scramble） and experiment group  in which the cells were transfected with Ku70-specific siRNA(si-Ku70).The cells  in negative control group and experiment group were transfected 48 h prior to treatment with cisplatin.The cell survival was assessed by MTT assay.The apoptotic rate was determined by  flow cytometry.The Caspase-3 activity was detected by spectrophotometer.Results  The Ku70 mRNA and protein expressions in A549/DDP cells were significantly elevated compared with the parental A549 cells（P<0.01）.The si-Ku70 down-regulated the mRNA and protein expressions of Ku70 in A549/DDP cells.After treated with different concentrations of cisplatin for 24 h,the cell viabilities of si-Ku70 cells were decreased significantly compared with  control group（P<0.01）.After treatment with 6 mg/l isplatin for 24 h,the apoptotic rates and the activites of Caspase-3 in experiment group were increased significantly compared with control group（P<0.01）.Conclusion The overexpression of Ku70 in cisplatin-resistant human lung adenocarcinoma cells suggests that Ku70 might be involved in the chemoresistance of lung cancer.Ku70-specific siRNA can down-regulate the expression of Ku70,promte apoptosis and reverse resistance to cisplatin in cisplatin-resistant A549/DDP cells.Ku70 may be a new target for reversal of chemoresistance of lung cancer.

Key words: lung adenocarcinoma；drug resistance；cisplatin；Ku70；apoptosis