[Exploration of relationship between the expression level of DNA polymerase beta and 60Co gamma-ray radiosensitivity].

Objective To explore the relationship between the expression level of DNA polymerase β(polβ) and 60Coγ-ray radiosensitivity and provide a basis on improving the efficiency of radiotherapy theoretically.Methods polβ wild-type cells(polβ+/+),polβ null cells(pol β-/-) and polβ overexpressed cells(polβ oe) were applied as a model system.The radiosensitivity of 60Coγ-ray on the cell was detected by MTT assay and clone formation assay.The DCFH-DA fluorescent probe was used to examine the cellular ROS after 60Coγ-rays radiation.Results MTT assay showed that after radiation by 60Coγ-rays followed with 72 h incubation,the cell viabilities in the three kinds of cells decreased significantly with a dose-response relationship(r+/+=-0.976,r-/-=-0.977,roe=-0.982,P0.05).In addition,the viability of polβ-/-cell was lower than those of other two kinds of cells at the same dose(P0.05).Likewise,the colony number and colony formation rate in all tested cells also decreased after exposure to 60Coγ-rays.The ROS level in the three kinds of cells was enhanced after treatment with 60Coγ-ray,and the ROS level in polβ-/-cells was much higher than that in the other two kinds of cells(P0.05).Conclusion Cell death caused by 60Coγ-ray may associated with the DNA oxidative damage mediated by ROS;Overexpression of polβ could protect against oxidative DNA damage,thus the cell apoptosis/death,thereby leading to reducing the radiosensitivity of 60Coγ-rays,while null of DNA polβ could increase radiosensitivity of 60Coγ-rays by compromising the DNA repair.