The effect of Ku80 re-expression on the DNA double-strand breaks in hepatocellular carcinoma cells

Objective To investigate the effect of Ku80 re-expression on DNA double-strand breaks in HCC cells.Methods γ-H2AX and Ku80 expressive levels in HCC tissues and corresponding liver tissues were analyzed by the Western blotting.PcDNA3.1 ( + )-myc-his-Ku80 and pcDNA3.1 ( + )myc-his expressive plasmids were transfected into Ku80 deficient SMMC7721 to generate Ku80-expressing SMMC7721 stable clones through G418 screen.γ-H2AX assay was used to quantify the numbers of γ-H2AX foci in the nuclei of Ku80-expressing clones and control cells,while Western blotting was used to compare the γ-H2AX expressive levels in Ku80-expressing clones and control cells.Results The γ-H2AX expressions in HCC tissues were higher than those in the corresponding adjacent liver tissues (31/40,77.5％ ),while Ku80 expressions were found to be decreased or lost in HCC tissues compared with adjacent liver tissues (30/40,75％ ) ; Significant correlation was found between the decreased expression of Ku80 and increased γ-H2AX in HCC( P ＜0.05 ).The Western blotting analysis confirmed that Ku80-transfected clones expressed high protein levels of Ku80,whereas vector-transfected clone and the parental SMMC7721 cells lacked Ku80 expression.γ-H2AX assay indicated that the numbers of γ-H2AX foci in the nuclei of Ku80-expressing clone cells were significantly decreased compared with SMMC7721 cells or the vector-transfected cells.Western blotting further confirmed that the expression levels of γ-H2AX were decreased in the Ku80expressing cells compared with SMMC7721 or the vector-transfected cells.Conclusion Ku80 re-expression was able to decrease DNA double-strand breaks levels of hepatocellular carcinoma cells. Key words: Ku80; human hepatocellular carcinoma; γ-H2AX; DNA double- strand breaks