title: Development of a conditional liver tumor model by mifepristone-inducible Cre recombination to control oncogenic kras V12 expression in transgenic zebrafish.
abstract: Here we report a new transgenic expression system by combination of liver-specific expression, mifepristone induction and Cre-loxP recombination to conditionally control the expression of oncogenic kras(V12). This transgenic system allowed expression of kras(V12) specifically in the liver by a brief exposure of mifepristone to induce permanent genomic recombination mediated by the Cre-loxP system. We found that liver tumors were generally induced from multiple foci due to incomplete Cre-loxP recombination, thus mimicking naturally occurring human tumors resulting from one or a few mutated cells and clonal proliferation to form nodules. Similar to our earlier studies by both constitutive and inducible expression of the kras(V12) oncogene, hepatocellular carcinoma (HCC) is the main type of liver tumor induced by kras(V12) expression. Moreover, mixed tumors with hepatocellular adenoma and hepatoblastoma (HB) were also frequently observed. Molecular analyses also indicated similar increase of phosphorylated ERK1/2 in all types of liver tumors, but nuclear localization of β-catenin, a sign of malignant transformation, was found only in HCC and HB. Taken together, our new transgenic system reported in this study allows transgenic kras(V12) expression specifically in the zebrafish liver only by a brief exposure of mifepristone to induce permanent genomic recombination mediated by the Cre-loxP system.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543.|Department of Microbiology, Oregon State University, Corvallis, Oregon, USA, 97331.
authors.forename: Anh Tuan
authors.initials: AT
authors.lastname: Nguyen
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543.
authors.forename: Vivien
authors.initials: V
authors.lastname: Koh
authors.affiliation: Department of Microbiology, Oregon State University, Corvallis, Oregon, USA, 97331.
authors.forename: Jan M
authors.initials: JM
authors.lastname: Spitsbergen
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Gong
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D004195:Disease Models, Animal; D015870:Gene Expression; D018390:Gene Targeting; D011905:Genes, ras; D005822:Genetic Vectors / Q000235:genetics; D059765:Homologous Recombination; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System; D009928:Organ Specificity / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D060449:Wnt Signaling Pathway; D015027:Zebrafish
chemical_list: D011993:Recombinant Fusion Proteins