Ductal origin of pancreatic adenocarcinomas induced by conditional activation of a human Ha- ras oncogene in rat pancreas

Abstract

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.

Upregulation and redistribution of integrin α6β4 expression occurs at an early stage in pancreatic adenocarcinoma progression

“…32 Moreover, recent mouse and rat models have shown the importance of Ras mutations in pancreatic adenocarcinoma development. 33,34 The hepatocyte growth factor receptor, c-Met, is another molecule of interest found to be upregulated in early PanIN lesions and pancreatic adenocarcinomas. 35,36 c-Met is known to cooperate with integrin a6b4 to enhance the migratory and invasive potential of cancer cells in vitro.…”

Novel immunohistochemical marker, integrin αVβ3, for BOP-induced early lesions in hamster pancreatic ductal carcinogenesis

“…Consequently, a number of candidates of prognostic and/or predictive markers have been established (9,10). Examples expressed in early lesions show potential for the development of novel diagnostic and preventive strategies.Chemically induced and transgenic animal models for pancreatic ductal carcinogenesis have been the target of investigation of the impact of environmental factors and the role of specific gene alterations in multistage carcinogenesis (11)(12)(13)(14)(15). Among the models established thus far, the N-nitrosobis(2-oxopropyl)amine (BOP)-induced hamster model is the first and most widely utilized based on similarities to human diseases in the morphological characteristics of, not only advanced cancers, but also early ductal lesions, as well as pivotal genetic alterations, including K-ras and p16 (13,(16)(17)(18).…”

In vivo 18F-fluorodeoxyglucose-positron emission tomography/computed tomography imaging of pancreatic tumors in a transgenic rat model carrying the human KRASG12V oncogene

“…The preparation and inoculation of the adenoviruses was performed as previously described (9). In brief, a Cre-recombinase expressing adenovirus was amplified in HEK293 cells and then purified using the Vivapure AdenoPACK (Vivascience, Hannover, Germany) (17).…”

“…By focusing on human pancreatic adenocarcinomas that express a high frequency of KRAS mutation, a transgenic rat model carrying the human HRAS G12V or KRAS G12V oncogene was established (8,9). The activation of the target transgene is attained by the injection of a Cre recombinase (Cre)-carrying adenovirus into the pancreatic ducts of the animal via the …”

“…In this model, the transgenic rats usually develop pre-neoplastic and neoplastic pancreatic lesions within two weeks of the viral inoculation (10). These lesions in the transgenic rats exhibit morphological similarities to those observed in human pancreatic lesions, including PDAC (11) and intraepithelial neoplasias (PanINs) (9). Due to the position of the tumors within the abdominal cavity, laparotomy is the only technique that is able to determine the existence and size of pancreatic tumors within the transgenic rats following virus inoculation, as the tumors cannot be visually assessed from surface scans of the affected rats.…”