Objective  To explore the silence of B-cell specific Moloney murine leukaemia virus insertion site 1 (Bmi-1) by RNA interference on the proliferation of human leukemia cell line K562 and its mechanisms.   Methods  Small interfering RNA (siRNA) targeting Bmi-1 gene was designed and double-stranded siRNA was chemically synthesized. After doublestranded siRNA was transfected into K562 cells with Lipofectamine 2000

the proliferation of K562 cells was detected by MTT colorimetry

cell cycle was determined by flow cytometry

and the expression of Bmi-1 and P16 were analyzed by Western blotting.   Results  The siRNA targeting human Bmi-1 gene effectively prolonged the double time of K562 cells

increased the percentage of cells at G

1

phase

and the expression of Bmi-1 was significantly down-regulated but the expression of P16 was up-regulated.   Conclusion  The siRNA targeting human Bmi-1 gene inhibits the proliferation of K562 cells

and up-regulates the expression of P16 in the cells.