The Role Of DNA Damage In Epirubicin Resistance-Breast Cancer Cell

ObjectiveWe detected the difference of the the DNA damage and DNA damage repair between MDA and epirubicin(EPI)resistance EPI-R cell.We explored the mechanisms and revealed the potential roles of DNA damage in the EPI resistance of breast cancer cells.Methods1.Breast cancer MDA was used us parental cells,EPI-R cells were established as EPI resistant cells.2.DNA damage and DNA damage repair related protein were detected by Western Blotting.3.The percentage of Comet tail DNA and tail length were detected by Comet assay.4.Reactive oxygen species(ROS)levels was tested by Flow cytometry.5.The cell activity of MDA and EPI-R cell and ATM specific inhibitor KU55933 treated EPI-R containing medium were measured by MTT.Results1.Detection of DNA damage: compared to the parental cell,EPI-R cell were treaed with different concentration of epirubicin,the DNA damage protein of ? H2 AX,the percentage of Comet tail DNA and tail length and levels of reactive oxygen species(ROS)reduced.(p < 0.05).2.Detection of DNA damage repair: compared to the parental cell,EPI-R cell were treaed with the epirubicin,the DNA repair protein levels of ATM,p-ATM,Chk2 increased,the protein levels of p53 and p-p53 reduced(p < 0.05).3.Inhibition of ATM expression in EPI-R cells: ATM specific inhibitor KU55933 have no effect on EPI-R cell activity in the EPI-R containing medium.Compared to the EPI treated EPI-R cells,combination of ATM specific inhibitor KU55933 ATM inhibitor KU55933 and EPI treated EPI-R cell,the DNA damage protein increased;the percentage of Comet tail DNA and tail length increased;ROS levels increased(p < 0.05).4.the sensitivity of EPI-R to the epirubicin increased after pretreatment with ATM inhibitor KU55933(p < 0.05).Conclusion1.Compared to the parental cells,EPI-R cells are treated with different concentration of epirubicin,the DNA damage protein of ? H2 AX,the percentage of Comet tail DNA and tail length,the levels of reactive oxygen species(ROS)reduced,suggestting DNA damage reduced in EPI-R cells.2.Compared to the parental cells,EPI-R cells are treated with epirubicin,the DNA repair protein levels of ATM,p-ATM,Chk2 increased,the protein levels of p53 and p-p53 reduced,indicating that DNA damage repair activity increased in EPI-R following epirubicin treatment.3.Inhibition of DNA repair activity,increases the DNA damage,can increase the sensitivity of EPI resistant EPI-R cells to EPI in breast cancer.