Abstract 4434: Development of pancreatic ductal adenocarcinoma (PDAC) by the expression of temperature-sensitive SV40 large T antigen (tsTAg) and K-ras G12D on pancreatic epithelial linage cells
Authors: Yamaguchi Takashi , Ikehara Sanae , Hashimoto MIka , Sato Ami , Nakanishi Hayao , Ikehara Yuzuru 
Published: August 2012

Abstract
Based on studies using genetically engineered mouse (GEM) models producing pancreatic ductal adenocarcinoma (PDAC), pancreatic intraepithelial neoplasia (PanIN) - PDAC linear pathway has been proposed. Whereas the positive association between the carcinogenesis and the engineered genetic abnormalities K-ras, Ink4a/Arf, Trp53, and Smad4, it has been pointed out the oversimplification on the postulated carcinogenesis steps. Indeed, there should be various routes leading to PDAC on the etiological heterogeneity, and it remains controversial whether PanIN-1 lesions are required for development of PDAC in view of the pathogenesis. In order to increase knowledge about the routes leading to PDAC, we generated GEM harboring loxP-μgeo-stop-loxP-tsTAg (LbsL-tsTAg); loxP-stop-loxP-K-rasG12D; Pdx1-Cre (TKC) alleles that express temperature-sensitive SV40 T antigen (tsTAg) and K-rasG12D on epithelial cells in pancreas. The tsTAg has been widely used to generate immortalized cells by inhibiting tumor suppressor molecules, P53 and Rbs (Rb1, Rbl1, Rbl2), and we previously reported the generation of GEM with LbsL-tsTAg and the success to establish the immortalized lymphatic endothelial cells using this mice (Yamaguchi T. et al, FEBS J. Vol.275: p1988-1998, 2008). In TKC mice, PDAC foci appeared at 5th days after birth without PanIN-1 lesions, and showed rapid progression and invasion into duodenum, resulting in death within 3 weeks. On the contrary, though tsTAg-expressing TC mice develop neither PDAC nor PanIN, dysplastic feature appeared on acinar cells at 15-20 weeks after birth. In in vitro assay, the characteristics of the established PDAC cell lines from TKC mice was compared with the immortalized cell lines expressing Cytokeratin 19 (Ck19, pancreatic ductal cell marker) from TC mice. PDAC cells were positive for Ck19 and formed atypical gland structures in collagen gel 3D culture the same as in subcutaneous transplanted tumor in nude mice, while the Ck19 positive immortalized cell lines from TC mice formed ductal structures in collagen gel similar to either intralobular or interloblar pancreatic ducts. The expression of Tacstd2, SerpinB2, and microRNA-200 group genes were upregulated in PDAC cells more than the Ck19 positive immortalized cell lines, which were commonly in human PDAC. These results suggest that PDAC can develop without PanIN-1 lesion under the given conditions as TKC mice, and that constitutive active mutation of K-ras plays an important role for lineage addiction to show ductal phenotype. Our newly established mice models and in vitro assay systems are feasible not only to establish molecular taxonomy of PDAC, but also to develop biomarkers for early detection, and help to discover the therapeutic target molecules.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4434. doi:1538-7445.AM2012-4434