Objective To investigate methylation of the P15INK4B and p27kipl genes in human mantle cell lymphoma cell line Mino,to evaluate the effects of decitabine on demethylation of p15INK4B and p27kip1 genes and on apoptosis of Mino cells and its relative mechanism. Methods Mino cells were after treated with various concentration of decitabine, the cell viability, cell cycle distribution or the apoptosis of Mino cells was respectively analyzed by trypan dye-exclusion assay or flow cytometry.The mRNA and protein expression of p15INK4B 、p27kip1 and bcl-2 were studied by RT-PCR or Western blot, respectively.Methylation of the p15INK4B and p27kip1 genes in Mino cells were determined by PCR using the methylation specific primer(MSP).Results Decitabine significantly inhibit the cell growth,induced G1 arrest and promoted apoptosis of Mino cells. The expression of p15INK4B and p27kipl mRNA were both significantly increased,wheres bcl-2 mRNA was decreased, After treatment with 6.4,3.2,1.6 mmol/L decitabine for 72 h,the methylationg of p15INK4B gene were decreased to 25.2 ％ 、48.2 ％ and 65.0 ％respectively,in the meantime,the methylationg of p27kip1 gene was decreased to 20.21％ 、50.2 ％ and 70.0 ％. Conclusion The hp15INK4B and p27kip1 genes of Mino cells are methylated and down-regulated.Decitabine can inhibit the proliferation and induce the apoptosis of Mino cell lines,with the reduction of bcl-2 gene and demethylation of p15INK4B and p27kip1 genes.