Abstract:

Objective: To transfer the pEgr1-TRAIL recombinant plasmid into human breast cancer MCF-7 cells and to combine with ionizing radiation,and to discuss the changes of related gene and protein expressions of death receptor pathway in breast cancer MCF-7 cells. Methods: The MCF-7 cells were divided into empty plasmid,pEgr1-TRAIL plasmid,4.0 Gy X-ray,empty plasmid+4.0 Gy X-ray, and pEgr1 TRAIL+4.0 Gy X-ray groups.Real-time PCR method was used to detect the expression levels of DR4,caspase-9,and caspase-6 mRNA in the MCF-7 cells in various groups;Western blotting method was used to detect the relative expression levels of DR4,caspase-9,and caspase-6 protein in the MCF-7 cells in various groups. Results: Compared with control group, the mRNA expression levels of DR4,caspase-9 and caspase-6 in MCF-7 cells in the other groups began to rise 4 h after 4.0 Gy X-ray irradiation(P<0.01),and they reached to the highest levels 8 h later,then reduced to the level of pre-irradiation 24 h later.The order of these mRNA expression levels from high to low in various groups was pEgr1-TRAIL+4.0 Gy X-ray group>empty plasmid+4.0 Gy X-ray group >pEgr1-TRAIL plasmid group >empty plasmid group >4.0 Gy X-ray group>control group;the expression levels of RD4,caspase-9,and caspase-6 mRNA in the MCF-7 cells in pEgr1-TRAIL+4.0 Gy X-ray group were higher than those in other groups (P<0.01).The relative expression levels of DR4,caspase-9 and caspase-6 proteins began to rise 6 h after irradiation, and reached the peak 12 h later; the relative expression levels of those protein 48 h later were still higher than those 6 h after irrdiation.The order of these protein expression levels from high to low in various group was pEgr1 TRAIL+4.0 Gy X-ray group >empty plasmid+4.0 Gy X-ray group >4.0 Gy X-ray group >pEgr1-TRAIL plasmid group >empty plasmid group >control group.The relative expression levels of DR4,caspase-9,and caspase-6 proteins in the MCF-7 cells in pEgr1-TRAIL+4.0 Gy X-ray group were higher than those in the other groups. Conclusion: pEgr1-TRAIL recombinant plasmid combined with radiation can kill and induce the apoptosis of MCF-7 cells,and its effect is better than recombinant plasmid or ionizing radiation used alone.

Key words: pEgr1-TRAIL recombinant plasmid, ionizing radiation, MCF-7 cell, death receptor pathway