The human oncogene B-cell-specific Moloney murine leukemia virus integration 
site 1 (BMI-1) is a member of the mammalian Polycomb group family. The 
overexpression of BMI-1 is associated with human malignancies. In this study, 
the effects of knockdown of BMI-1 by shRNA-mediated RNA interference on cell 
cycle and possible downstream targets in human cervical adenocarcinoma HeLa 
cells were investigated. As a result, when the shRNA plasmid was stably 
introduced into the cell line, the mRNA and protein of BMI-1 were specifically 
down-regulated, and the cells increased in the phase of G1 and cells in S phase 
significantly decreased by flow cytometric analysis; the knockdown of BMI-1 
expression could lead to significant up-regulation of p16INK4a, HOXA9 and HOXC13 
mRNA expression, but hTERT and HOXB4 mRNA expression did not change 
significantly. In conclusion, RNAi-mediated knockdown of BMI-1 expression can 
induce cell-cycle arrest and up-regulate p16INK4a, HOXA9 and HOXC13 in HeLa 
cells. Our results suggest that targeting BMI-1 might be a therapeutic potential 
for the treatment of cancer.