RNAi-mediated silencing of the Bmi-1 gene causes growth inhibition and enhances doxorubicin-induced apoptosis in MCF-7 cells oleh Xiang-mei Wu, Xing Liu, You-quan Bu, Joyeeta Sengupta, Hong-juan Cui, Fa-ping Yi, Tao Liu, Chen-fu Yuan, Yan-yan Shi, Fang-zhou Song