Abstract
Objective To establish a model of pancreatic cancer induced by dimethylbenzanthracene(DMBA)in Sprague-Dawely(SD)rats,and detect the expression levels of insulin-like growth factor1(IGF-1)and its receptor(IGF-1R)and their effects on the carcinogenesis of rat pancreas.Methods DMBA was directly implanted into the parenchyma of rat pancreas(group A and group B).The rats in group B were treated with 1 ml trichostatin A(TSA)saline solution(1 mg/L)via intraperitoneally weekly.The carcinogenesis of rats executed within 3-5 months in groups A and group B was observed by macrograph and under microscopy.Meanwhile,the rats in the control group(group C)were executed in 5 months.The EnVisionTM immunohistochemistry for detecting the expression levels of IGF-1 and IGF-1R was used in conventionally paraffin-embedded sections from above pancreatic specimens.Results (1)The incidence of pancreatic cancer in group A within 3-5 months was 48.7 %(18/37),including 17 cases of pancreatic ductal adenocarcinoma and 1 case of fibrosarcoma.The incidence of pancreatic cancer in group B within 3-5 months was 33.3%(12/36),including 11 cases of pancreatic ductal adenocarcinoma and 1 case of fibrosarcoma.The maximal diameter of mass was larger in group A than in group B(P ＜0.05).No pathological changes were found in pancreas of group C and other main organs of all groups.(2)The positive expression rate of IGF-1 and IGF-1R in groups A and B was significiantly higher in ductal adenocarcinoma than in non-cancerous pancreatic tissues(P ＜ 0.01).The positive expression rate of IGF-1 and 1GF-1R in group A was significantly higher in ductal adenocarcinoma than in non-cancerous pancreatic tissues(P ＜0.05),but no statistically significant difference was found in group B(P ＞ 0.05).The positive cases of IGF-1 and/or IGF-1R in non-cancerous pancreatic tissues showed mild-to-severe atypical hyperplasia of ductal epithelia.Pancreatic tissues and fibrosarcoma in group C showed negative expression of IGF-1 and IGF-1 R.Conclusion DMBA directly implanted into the parenchyma of pancreas can obtain an ideal pancreatic cancer model with high incidence in a short time.TSA may have inhibitive effects on carcinogenesis in rat pancreas possibly by inhibiting the expression of IGF-1 and IGF-1 R.IGF-1 and IGF-1R might have important promotive effects on carcinogenesis induced by DMBA in rat pancreas. Key words: Pancreatic neoplasms; Insulin-like growth factor-1
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