Objective:To study  the expressive levels of EZH 2 and PTEN in pancreatic cancer and non-cancerous tissue, and the effects on carcinogenesis of rat pancreas.
Methods:dimethylbenzathracene (DMBA) was directly implanted into the parenchyma of rat pancreas (group A,group B). The rats of group B were treated with 1 mL trichostatin A (TSA) solution (1μg/mL) intravenously per weer 1 week after the model were set up. The rats of group A, B were killed within 3-5 months
 and the rats in the control (C group) were executed at 5 months to observe the develope of pancreatic cancer by macrograph and microscopy, The EnVision TM immunohistochemistry was used to assay the expression of EZH 2 and PTEN in above pancreatic specimens.
Results:(1) The incidence of pancreatic cancer within 3-5 months in group A was 48.7% (18/37), including 17 cases of ductal adenocarcinoma and 1 case of fibrosarcoma. The incidence of pancreatic cancer in group B was 33.3% (12/36), including 11 cases of ductal adenocarcinoma and 1 cases of fibrosarcoma. The mean maximal diameter of mass was significantly higher in  group A than that in group B (P＜0.05). No pathological changes were found in pancreas of group C or other main organs of group A and group B. (2) the positive rxpression rates of EZH 2  were significantly higher in ductal adenocarcinoma of group A + group B than those in non-cancerous pancreatic tissues (P＜0.01). The positive expression rate of PTEN was significantly lower in ductal adenocarcinoma in group A + group B than that in non-cancerous pancreatic tissues (P＜0.05). But no stastical difference was found among the positive rate of PTEN in ductal adenocarcinoma of group A or group B and in non-cancerous pancreatic tissues of group A or group B (P＞0.05). The non-cancerous pancreatic tissues with positive expression of EZH 2 and/or negative expression of PTEN showed mild to severe atypical hyperplasia of ductal epithelium. An inconsistency was found between the expression of EZH 2 and PTEN in ductal adenocarcinoma（P=0.045）. Pancreas of group C showed negative expression of EZH 2 and positive expression of PTEN. Two cases of fibrosarcoma showed negative expression of EZH 2 and PTEN.
Conclusions:By use of higher dose of DMBA  directly implanted into the parenchyma of pancreas,  high incidence  of pancreatic cancer can be obtained. TSA could have an inhibitive effect on carcinogenesis and growth of pancratic cancer. The activation of EZH 2 gene and inactivation of  PTEN gene might have key effects on  pancreas carcinogenesis induced by DMBA in rat.