Effect of Ku80 re-expression on cell apoptosis in hepatocellular carcinoma SMMC7721 cells

Objective To investigate the effect of Ku80 re-expression on cell apoptosis in hepatocellular carcinoma (HCC) SMMC7721 cells. Methods PcDNA3. 1 ( + )-myc-his-Ku80 and pcDNA3. 1( + )-myc-his expressive plasmids were transfected into Ku80 deficient SMMC7721 HCC cells. The cell apoptotic rates were analyzed by facial action coding system (FACS). The expression of cell apoptosis related regulators were analyzed by Western blotting. Cell apoptotic levels in xenograft tumor tissue were detected by TUNEL assay. Results The Western blotting analysis confirmed that Ku80-transfected cells expressed high protein levels of Ku80,whereas the vector-transfected and the parental SMMC7721 cells lacked Ku80 expression. FACS analysis indicated that, the apoptotic rates in SMMC7721, vector-transfected cells and the two Ku80-expressing clones were (9.44 ±1.52)％, (9.26 ±1.72)％ ; (1.81 ±0. 15)％ and (1.83 ±0. 25) ％, respectively. There was a significant difference in cell apoptotic rate between Ku80-expressing clones group and SMMC7721 or vector-transfected cells group ( P ＜ 0. 05 ). TUNEL assay also showed that,the cell apoptotic rates in tumor tissue derived from SMMC7721, vector-transfected cells and the two Ku80-expressing clones were (9. 3 ± 2. 0) ％, ( 10. 0 ± 2. 1 ) ％ ; (3.5 ± 1.0) ％ and (3.6 ± 1.1 ) ％, respectively. There was a significant difference in cell apoptotic rate between Ku80-expressing clones group and SMMC7721 or Vector-transfected cells group (P ＜0. 05). Western blotting further confirmed that levels of cleaved PARP-1, active Caspase-3 and cleaved Caspase-9 significantly increased in the Ku80-expressing clones compared with vector-transfected or parental SMMC7721 cells,whereas the expression levels of bcl-2 decreased. The expression level of bax remained unchanged. Conclusion Ku80 re-expression slightly induces cell apoptosis in SMMC7721 cells in vitro and in vivo. Key words: Ku80; Human hepatocellular carcinoma; Cell apoptosis