Abstract： Objective To detect the methylation status of ppENK and its role in the pathogenesis of pancreatic carcinoma.Methods The ppENK methylation status in human tissues of pancreatic cancer,pancreatic carcinoma cell lines and normal pancreas was detected by methylation-specific RT-PCR(MSP).The association of methylation status of ppENK gene with clinicopathological parameters was analyzed. The expression of ppENK mRNA was detected by RT-PCR.Two pancreatic carcinoma cell lines (PANC1,AsPC1 ) were treated with demethylating agent (5-aza-dC).The cell growth was measured by MTT.Apoptosis and cell cycle was analyzed by flow cytometry.The expression of DNMT3a was measured by Western blot.Results ppENK mRNA was expressed in normal pancreas.And methylation of ppENK was not detected in normal pancreas.Methylation of ppENK was detected in 90.3％ (28/31) of pancreatic carcinoma tissue,and there were no correlation between methylated ppENK with clinicopathological features of pancreatic carcinoma.There was no ppENK mRNA expression in SW1990,PANC1,PC3,AsPC1,PuPan-1,and ppENK was methylated.Methylated ppENK was associated with no ppENK mRNA expression.After 5-Aza-dC treatment,PANC1,AsPC1 was demethylated and ppENK mRNA expression was reversed.The proliferation of PANC1 and AsPC1 was inhibited in a dose dependent manner.The apoptotic rates of PANC1 and AsPC1 were increased [ (31.57 ± 6.76)％ts (3.21 ±1.43)％,P =0.002,(16.6 ±8.22)％ vs (3.82 ±1.71)％,P=0.058];the expression of DNMT3a protein was decreased; the PANC1 cells of G1 phase significantly increased [ (67.87 ± 2.72 ) ％ vs (54.57 ± 7.18) ％,P =0.040 ],but PANC1 cells of S phase significantly decreased [ ( 22.37 ± 4.31 )％ vs (33.73 ± 4.63)％,P =0.036 ].But the percentage of G1,S phase in AsPC1 cell line was not significantly changed ( P =0.236,0.075 ).Conclusions ppENK demethylation is an important molecular event in inducing ppENK expression inhibition,which can inhibit pancreatic cancer proliferation,promote apoptosis,arrest cell cycle at G1 and decrease the expression of DNMT3a protein.