Abstract: To measure the changes of the radiosensitivity in human lung adenocarcinoma A549 cells transfected with pEgr1-hsTRAIL plasmid and the effect on death receptor (DR) 4 and DR5 expressions,and to explore the radiosensitizing effect of pEgr1-hsTRAIL plasmid and possible mechanism on inducing apoptosis.Methods There were normal control,pEgr1-hsTRAIL,6 Gy X-rays,and pEgr1-hsTRAIL + 6 Gy X-rays groups in the experiment.After the A549 cells were transfected with liposome,and irradiated with X-rays,colony formation assay was used to measure the radiosensitivity,and reverse transcription PCR (RT-PCR) was performed to detect the  DR4 and DR5 mRNA expressions,and Western blotting was applied to determine the DR4 and DR5 protein expressions.Results The D0 values of  A549 cells in normal control  group and pEgr1-hsTRAIL group were 3.26 and 1.91 Gy,respectively,it indicated that pEgr1-hsTRAIL plasmid could enhance the radiosensitivity in A549 cells.The RT-PCR results showed that as compared with normal control group,the DR4 and DR5 mRNA expression levels  in pEgr1-hsTRAIL group had no significant change,but those in 6 Gy X-rays group were increased significantly (P<0.05),and those in pEgr1-hsTRAIL + 6 Gy X-rays group were also increased significantly (P<0.05);the DR5 mRNA expression level in pEgr1-hsTRAIL + 6 Gy X-rays  group was higher than that in 6 Gy X-rays group (P<0.05).The Western blotting results showed that the DR4 and DR5 protein expressions in pEgr1-hsTRAIL group did not change obviously  compared with  normal control group,but those in 6 Gy X-rays and pEgr1-hsTRAIL + 6 Gy X-rays  groups were increased,and the DR5 protein expression in pEgr1-hsTRAIL +6 Gy X-rays group was increased mostly.Conclusion The recombinant plasmid pEgr1-hsTRAIL can enhance the radiosensitivity of A549 cells,and has the enhancing effect on DR5 expression induced by radiation,but no same effect on DR4 expression.

Key words: early growth response protein 1, lung adenocarcinoma, human secreted TNF-related apoptosis-inducing ligand, radiosensitivity, apoptosis