Background and purpose: The pro-oncogene Bmi-1 is a member of the polycomb- group family

can regulation of the proliferation and self-renewal of normal and tumor stem cells. In recent years

Bmi-1 has been found that it is overexpressed in varieties of human malignant tumors. The study aimed to observe the effects of Bmi-1-siRNA on the growth capacity of lung cancer cell line A549 in vivo and in vivo

and explore its mechanism. Methods: The most effective one as a target sequence was chosen from four Bmi-1 siRNA sequences which were designed by our lab

and one random sequence was chosen as a negative control. In short

the chemically synthesized siRNA and control sequences were connected to a retrovirus expressing vector

pSUPERretro-Neo plasmid

and then transfected into A549 cells. The stably transfected cells were cultured and passed. The level of mRNA and protein of Bmi-1 in A549 cells were assessed by RT-PCR and Western blot respectively. The proliferations of A549 cells in vivo was analyzed with MTT

trypan blue exclusion and plate colony forming methods. Flow cytometry was used for cell cycle analysis. The potency of tumorigenesis was observed in nude mouse through hypodermic inoculation of A549 cells. The expressions of cyclin D

p21/27

p-AKT and PTEN were analyzed by Western blot. Results: Compared to A549-ctr and A549-wt cells

Bmi-1 mRNA and protein levels all significantly reduced in A549-Bmi-1-siRNA cells. Bmi-1-siRNA inhibited the growth

colony formation in vitro and tumorigenesis in vitro of A549 cells

and the interference cells cell cycle arrested in G1 phase. In A549-Bmi-1-siRNA cells

p-AKT and cyclinD1 expression were down-regulated while p21/p27 and PTEN were up-regulated. Conclusion: Silencing Bmi-1 gene inhibits the proliferation of A549 cells through G1 phase arrest

which involves the downregulation of cyclin D/p-AKT and upregulation of p21/p27/PTEN.