Abstract： Objective To investigate the effects of histone deacetylase 1 (HDAC1) gene silencing on cell cycle of pancreatic cancer cell line PaTu8988 and possible mechanism.Methods The PaTu8988 cells were routinely cultured and divided into control group,negative control siRNA group (c-siRNA),HDAC1 siRNA 15 nmol/L group and HDAC1 siRNA 30nmol/L group.After Liposomes 2000 transfection for 48 h,the Western blotting was used to detect the efficiency of HDAC1 gene silencing on protein levels and the expression of p21 protein.Cell cycle was evaluated by using flow cytometry.Results Compared with that of control group,the expression of HDAC1 protein in PaTu8988 cell of HDAC1 siRNA 30nmol/L group was significantly decreased,and the expression of p21 protein was significantly increased; the percentage of G2/M phase cells were significantly decreased[(21.48 ±3.67)％ vs.(28.28 ±2.94) ％,P＜0.05]; while the percentage of S phase cells were significantly increased[( 50.20 ± 6.85 ) ％ vs.( 32.49 ± 2.78 ) ％,P ＜ 0.05].Conclusions HDAC1 siRNA can efficiently and specifically inhibit the expression of HDAC1 in PaTu8988 cells,and can induce S phase cells arrest,which may be related with up-regulation of p21 protein expression.