In our tested cell cycle checkpoint proteins, the expression of p21, p27 and p53 were down-regulated in Msi1 over-expressing cervical cancer cells and up-regulated in the shRNA transfected cervical cancer cells, suggesting that the cell cycle transition from the G0/G1 phase to the S phase in cervical cancer cells might be regulated by Msi1 through p21, p27 and p53. This evidence concerns the gene CDKN1B and cervical carcinoma.