Bcl-2/Bcl-XL SiRNA Sensitisizes Cisplatin-resistant Human Lung Adenocarcinoma Cells A549/DDP To Cisplatin

Objective: To investigate the effect of Bcl-2 siRNA , Bcl-XL siRNA on apoptosis and drug sensitization in cisplatin-resistant human lung adenocarcinoma cell line A549/DDP and to determine the inhibitory effect of the Bcl-2 siRNA, Bcl-XL siRNA on the gene expression in cells A549/DDP.Method: Bcl-2 siRNA, Bcl-XL siRNA and negative siRNA plasmid vector were stably transfected into A549/DDP cells. Drug sensitivity of the cells to cisplatin (DDP) was analyzed with MTT and flow cytometry. Spontaneous apoptosis of cells was detected by AO/EB dyeing.RT-PCR, Immunofluorescence microscopy and Western-blot was used to detect the target gene expression.Result: MTT results showed that Bcl-2 siRNA, Bcl-XL siRNA transfectants had a higher cell inhibition rate than negative siRNA or untreated cells after treated with 0.2, 2 ,20, 200μg /ml DDP(13.31±1.23%, 12.65±1.70% vs. 2.18±0.65% vs. 2.16±0.80%; 16.52±1.02%, 15.13±1.14% vs. 3.05±1.05% vs. 2.85±0.76%; 46.19±0.89%, 49.24±0.48% vs. 28.15±0.65% vs. 27.26±0.85%; 54.51±1.02%, 58.75±0.45% vs. 31.18±0.79% vs. 33.27±1.23%), IC50 value of DDP in Bcl-2 siRNA,Bcl-XL siRNA transfected cells had significant lower value than that of negative siRNA or untreated cells. Moreover, Flow cytometry results demonstrated that Bcl-2 siRNA, Bcl-XL siRNA cells had increased apoptosis rate After addition 20μg /ml DDP(11.1±0.52%, 20±0.48% vs. 1.8±0.35% vs. 2.4±0.57% ). Spontaneous apoptosis of cells were significantly increased in Bcl-2 siRNA, Bcl-XL siRNA stable transfectants. The mRNA and protein expression level of Bcl-2/Bcl-XL in Bcl-2 siRNA/ Bcl-XL siRNA stable transfectants were obviously reduced compared with negative siRNA transfectants or untreated cells. moreover, Bcl-2 siRNA, Bcl-XL siRNA increased the activity of active caspase-3 and active PARP.Conclusion: siRNA targeting Bcl-2/Bcl-XL gene can sensitize cells to DDP and increase cell spontaneous apoptosis, specifically down-regulate Bcl-2/Bcl-XL expression, actived caspase-3 and PARP in A549/DDP cells. Bcl-2/Bcl-XL siRNA may be a potential therapy agent against human lung adenocarcinoma.