Carcinogenesis Advance Access originally published online on June 13, 2006
Carcinogenesis 2006 27(12):2497-2510; doi:10.1093/carcin/bgl090
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Ductal origin of pancreatic adenocarcinomas induced by conditional activation of a human Ha-ras oncogene in rat pancreas
1 Department of Molecular Toxicology, Nagoya City University Graduate School of Medical Sciences 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
2 Experimental Pathology and Chemotherapy Division, National Cancer Center Research Institute, 5-1-1 Tsukiji Chuo-ku, Tokyo 104-0045, Japan
3 Section for Studies on Metastasis, National Cancer Center Research Institute, 5-1-1 Tsukiji Chuo-ku, Tokyo 104-0045, Japan
4 Laboratory of Molecular Genetics, Institute of Medical Science, University of Tokyo, 4-6-1 Shiroganedai Minato-ku, Tokyo 108-8639, Japan
5 Present address: Second Department of Pathology, Kansai Medical University, 10–15 Fumizono-cho, Moriguchi Osaka, Japan
6 Cancer Prevention Basic Research Project, National Cancer Center Research Institute Tokyo, Japan
*To whom correspondence and requests for reprints should be addressed. Tel: +81 52 853 8991; Fax: +81 52 853 8996; Email: htsuda{at}med.nagoya-cu.ac.jp
Pancreatic ductal adenocarcinoma is one of the most debilitating malignancies in humans. Currently, radiation and chemotherapy are ineffective, with median survival times after treatment of <12 months. Animal models that reflect the human condition and can be used to explore screening and therapeutic approaches are clearly desirable. One feature of human pancreatic adenocarcinoma is an exceedingly high frequency of K-ras mutation. The present study was conducted to determine if targeted activation of a human oncogenic-ras transgene in rat pancreas would induce carcinomas correspondent to human pancreatic ductal adenocarcinomas. We established transgenic (Hras250) rats in which expression of a human Ha-rasG12V oncogene is regulated by the Cre/lox system. Targeted pancreatic activation of the transgene was accomplished by injection of Cre-carrying adenovirus into the pancreatic ducts and acini through the common bile duct. Adenoviral infection of injected animals was exclusive to the pancreas; infected cells could be identified in duct, intercalated duct, centroacinar and, less frequently, acinar cells, but not in endocrine islet cells. Four weeks after injection, proliferative lesions in the duct epithelium, intercalated ducts and centroacinar cells, but not acinar cells, were widespread. Tumorigenesis in other tissues was not observed. Most lesions, including atypical duct proliferative lesions, PanIN-like lesions and carcinomas, were positive for cytokeratins 19 and 7, cyclooxygenase 2 and MMP-7 but negative for amylase and chymotrypsin. Many adenocarcinoma lesions were positive for EGF and EGFR. Duct epithelial and atypical duct proliferative lesions and carcinoma lesions were all positive for transduced Ha-rasG12V oncogene expression. The cytogenesis of pancreatic ductal type carcinoma was depicted. This model exhibits important similarities to the human disease and promises to advance our understanding of the behavior of pancreas adenocarcinomas and expedite screening and therapy.