Abstract:

Abstract:Objective
To study the effects of the cotreatment of cadmium chloride (CdCl2) and Smac over-expression on proliferation and apoptosis of hepatocellular carcinoma cells,SMMC-7721,and provide an experimental basis for the Smac-based tumor gene therapy and the development of cadmium as the antihepatoma drug.Methods SMMC-7721 were divided into five groups,which were control,pcDNA3.1+,pcDNA3.1+-hSmac,single CdCl2-treated and CdCl2 plus Smac groups respectively. The cells in control group had no transfection or CdCl2 treatment,while those in pcDNA3.1+ and pcDNA3.1+-hSmac groups were transfected with null vector pcDNA3.1+ or pcDNA3.1+-hSmac respectively through lipofectamine-mediated method,and those in CdCl2-treated groups were exposed to CdCl2 at the concentration of 10,20 and 30  μmol·L^-1 respectively,and those in CdCl2 plus Smac groups were transfected with pcDNA3.1+-hSmac firstly,and then treated with CdCl2 after transfection for 24 h.MTT assay was used to determine the effect of Smac over-expression and CdCl2 on proliferation,and both AO/EB fluorescence staining and FCM with Annexin Ⅴ and PI double-staining methods for apoptosis.Results The  MTT results showed that compared with control group,except for  the null-vector pcDNA3.1+ group,the inhibitory rates in the rest groups were increased significantly (P<0.01 or P<0.001).In  single CdCl2-treated groups,the inhibitory rate was increased with the increasing of treatment doses,whereas,each Smac coupled group presented significantly higher inhibitory rate than the corresponding single CdCl2-treated group (P<0.001).AO/EB staining manifested that the  cells in control group were in good condition,while those in pcDNA3.1+-hSmac,30  μmol·L^-1 CdCl2 treatment,and CdCl2 plus Smac groups appeared the  morphological changes of apoptosis,especially in the last group.Furthermore,the results acquired by FCM showed that the apoptotic rate in pcDNA3.1+-hSmac group was increased significantly when compared with control and pcDNA3.1+ groups respectively (P<0.001).However,the apoptotic rate in CdCl2 pluse Smac group was the highest,which was significantly higher than that in single 30  μmol·L^-1 CdCl2-treated group (P<0.001).Conclusion CdCl2 has cytotoxicity to SMMC-7721 cells.It could inhibit cellular proliferation in a dose-dependent manner,and induce apoptosis.Smac over-expression  could inhibit cellular proliferation and slightly induce apoptosis independently.

Key words: cadmium chloride;Smac;apoptosis;proliferation;liver neoplasms;SMMC-7721