[Expression of RAD51 and MAX in pancreatic cancer rats]

To establish a model of pancreatic cancer induced by 7,12-dimethyl-benzathracene (DMBA) in SD rats, and to detect the expression levels of RAD51 and Myc-associated factor X (MAX) and their effect on carcinogenesis of rat pancreas.

Ninety SD rats were randomly divided into 3 groups: a model group, an intervention group, and a control group. DMBA was directly implanted into the parenchyma of rat pancreas (the model group and the intervention group). Rats in the intervention group were treated with 1 mL trichostatin A (TSA) saline solution (1 mug/mL) via ip weekly. Rats within 3~5 months in the model group and the intervention group were executed and observed by macrograph and under microscope. Meanwhile, the rats in the control group were executed at 5th month. The EnVision(TM) immunohistochemistry to assay the expression levels of RAD51 and MAX was used in conventional paraffin-embedded sections from the above pancreatic specimens.

The incidence of pancreatic cancer in the model group within 3-5 months was 48.7% (18/37), including 17 ductal adenocarcinomas and 1 fibrosarcoma. The incidence of pancreatic cancer in the intervention group within 3-5 months was 33.3%(12/36), including 11 ductal adenocarcinomas and 1 fibrosarcoma. The maximal diameter of mass in the model group was significantly higher than that in the intervention group (P<0.05). No pathological changes were found in pancreas of the control group and other extra-pancreatic main organs of the model group and the intervention group (such as the liver, biliary tract, gastrointestine tract, kidney, and lung). The positive rate of RAD51 was significantly higher in ductal adenocarcinoma in the model group, the intervention group, and the model group +the intervention group than those in corresponding groups of non-cancerous pancreatic tissues (P<0.01), but the positive rate of MAX expression was opposite to RAD51 expression(P<0.01). The positive tissues of RAD51 expression and/or negative tissues of MAX expression in non-cancerous tissues showed atypical-hyperplasia of ductal epitheli. Pancreas of the control group showed the negative expression of RAD51 and positive expression of MAX. Two cases of fibrosarcoma showed the negative expression of RAD51 and MAX.

DMBA directly implanted into the parenchyma of pancreas can obtain an ideal pancreatic cancer model with high incidence in a short time. The TSA might have an inhibitive effect on carcinogenesis and growth of rat pancreas. The over-expression of RAD51 and/or lose-expression might have important effect on carcinogenesis induced DMBA in rat pancreas.