title: Conditional transformation of mouse pancreatic epithelial cells: an in vitro model for analysis of genetic events in pancreatocarcinogenesis.
abstract: Pancreatic ductal adenocarcinomas arise through the accumulation of certain genetic alterations including ras, p16, p53, and DPC4. We found that activation of ras and inactivation of p53 could cooperatively induce in vitro tumorigenicity in conditionally immortalized pancreatic epithelial (IMPE) cells. IMPE cells were established from transgenic mice bearing a temperature-sensitive mutant SV40 Large T (LT) antigen. IMPE cells grew continuously under permissive conditions (33 degrees C with interferon-gamma), but rapidly suffered growth arrest under non-permissive conditions (39 degrees C without interferon-gamma). The cells showed strong expression of E-cadherin and beta-catenin as epithelial markers, and cytokeratin 19, a specific ductal cell marker. Cell proliferation under permissive conditions was associated with down-regulation of p21 expression through inactivation of p53 after overexpression of LT antigen. Intriguingly, the shift from the permissive to non-permissive culture conditions caused G2/M arrest of IMPE cells. Although the cells did not form colonies when cultured in soft agar without activation of ras, cells with ras activation via an adenovirus vector formed colonies under permissive conditions. These findings suggest that activation of ras and inactivation of p53 can cooperatively induce anchorage-independent growth of IMPE cells. This cell line might be useful for studying the processes involved in pancreatocarcinogenesis.
authors.affiliation: Department of Surgery and Basic Surgical Science, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Koizumi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Koji
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Eiji
authors.initials: E
authors.lastname: Toyoda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kami
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Mori
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Doi
authors.forename: Robert
authors.initials: R
authors.lastname: Whitehead
authors.forename: Masayuki
authors.initials: M
authors.lastname: Imamura
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D004847:Epithelial Cells / Q000473:pathology; D005434:Flow Cytometry; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008854:Microscopy, Electron; D010179:Pancreas / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction