Abstract:

Objective To investigate the role of microRNA-125b（miR-125b）increasing the killing activity of doxorubicin to hepatic cancer HepG2 stem cells and its mechanism. Methods HepG2 cells treated with miR-125b,doxorubicin and myeloid cell leukemia-1（MCL-1）plasmid. Flow cytometry was used to determine the proportions of HepG2 cells,3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide（MTT） method was used to determine cell vitalities,and cell apoptosis rate was determined by Annexin V staining method. Cell mitochondrial membrane potential was determined by JC-1 dyeing method,and western blotting was used to determine the target protein [MCL-1,cysteine aspartic acid specific protease-9（caspase-9） and cysteine aspartic acid specific protease-3（caspase-3）]. Results Single treatment of doxorubicin increased the proportion of HepG2 cells,however,the combined treatment with doxorubicin and miR-125b decreased it. The results of MTT method and flow cytometry showed that miR-125b could enrich the killing activity and cell apoptosis of doxorubicin to HepG2 cells. The results of JC-1 dyeing method showed that miR-125b enhanced the damage of mitochondria induced by doxorubicin. The results of western blotting indicated that miR-125b increased the activation of caspase-9 and caspase-3 in doxorubicin-treated HepG2 cells. MCL-1 plasmid impaired the synergistic effect of miR-125b on doxorubicin-induced cell death and apoptosis in HepG2 cells. Conclusions miR-125b increased the susceptibility of HepG2 cells to doxorubicin through down-regulating the expression of MCL-1.

Key words: MicroRNA-125b, Doxorubicin, Hepatic cancer, Cancer stem cells, Myeloid cell leukemia-1, Cell apoptosis