Effect of irradiation-induced wt-p53 positive circuit on cell life cycle,apoptosis and irradiation sensitivity of lung adenocarcinoma cells / 第三军医大学学报

ABSTRACT

Objective To study the effects of irradiation-induced wt-p53 positive feedback circuit on cell life cycle,apoptosis rate and irradiation sensitivity of adenocarcinoma of lung in vitro.Methods The therapeutic group pE6R4-p53-EGFP/H1299 cells and the other 3 control groups H1299(p53-/-) ,pE6-p53EGFP/H1299 and pR4-p53-EGFP/H1299 cells were irradiated with 8-Mev electron beam generated by a linear accelerator at a dose rate of 400 cGy/min and a source-skin distance(SSD) of 100 cm,12 h exposure to irradiation.The cell life cycle and the rate of apoptosis were analyzed by FCM.Mean lethal dose(Do) and sensitive enhancement ratio(SER) index were calculated from the irradiation dose-survival curve.Results In 12 h post 4-Gy 8MV-X-ray irradiation,FCM analysis showed that most cells in therapeutic group were arrested at G0/G1 stage(75.13?1.42) %,compared with the 3 control groups(38.47?0.87) %,(62.57? 0.76) %and(51.23?2.41) %,respectively.After irradiation,the cell apoptotic rate in each group was higher than that in the cells without irradiation.The apoptotic rate in the therapeutic group was(23.73? 0.21) %,which was 5.69,1.51 and 2.57 folds respectively higher in the 3 control groups(4.17?0.12) %,(15.67?0.32) %and(9.23?0.15) %.Do values were 0.91,1.073 and 1.413 Gy respectively in pE6R4-p53-EGFP/H1299,pE6-p53-EGFP/H1299 and H1299 cells.The SER,derived from Do values,was 2.63 and 1.34,respectively.Conclusion Irradiation up-regulates wt-p53 gene expression,regulates cell cycle and induces cell apoptosis.Thus this positive feedback circuit increases the sensitivity of lung adenocarcinoma to irradiation.