ABSTRACT
Germline mutations in ATM (encoding the DNA-damage signaling kinase, ataxia-telangiectasia-mutated) increase Familial Pancreatic Cancer (FPC) susceptibility, and ATM somatic mutations have been identified in resected human pancreatic tumors. Here we investigated how Atm contributes to pancreatic cancer by deleting this gene in a murine model of the disease expressing oncogenic Kras (KrasG12D). We show that partial or total ATM deficiency cooperates with KrasG12D to promote highly metastatic pancreatic cancer. We also reveal that ATM is activated in pancreatic precancerous lesions in the context of DNA damage and cell proliferation, and demonstrate that ATM deficiency leads to persistent DNA damage in both precancerous lesions and primary tumors. Using low passage cultures from primary tumors and liver metastases we show that ATM loss accelerates Kras-induced carcinogenesis without conferring a specific phenotype to pancreatic tumors or changing the status of the tumor suppressors p53, p16Ink4a and p19Arf. However, ATM deficiency markedly increases the proportion of chromosomal alterations in pancreatic primary tumors and liver metastases. More importantly, ATM deficiency also renders murine pancreatic tumors highly sensitive to radiation. These and other findings in our study conclusively establish that ATM activity poses a major barrier to oncogenic transformation in the pancreas via maintaining genomic stability.
Subject(s)
Ataxia Telangiectasia Mutated Proteins/deficiency , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/pathology , Animals , Biomarkers, Tumor , Carcinoma, Pancreatic Ductal/genetics , Carcinoma, Pancreatic Ductal/mortality , Carcinoma, Pancreatic Ductal/pathology , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p16/genetics , Cyclin-Dependent Kinase Inhibitor p16/metabolism , DNA Damage , Disease Models, Animal , Genomic Instability , Humans , In Situ Hybridization, Fluorescence , Mice , Mice, Knockout , Neoplasm Metastasis , Pancreatic Neoplasms/mortality , Radiation Tolerance/genetics , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolismABSTRACT
Transposon-based integration systems have been widely used for genetic manipulation of invertebrate and plant model systems. In the past decade, these powerful tools have begun to be used in vertebrates for transgenesis, insertional mutagenesis, and gene therapy applications. Sleeping Beauty (SB) is a member of Tc1/mariner class of transposases and is derived from an inactive form of the gene isolated from Atlantic salmon. SB has been used extensively in human cell lines and in whole animal vertebrate model systems such as the mouse, rat, and zebrafish. In this study, we describe the use of SB in the diploid frog Xenopus tropicalis to generate stable transgenic lines. SB transposon transgenes integrate into the X. tropicalis genome by a noncanonical process and are passed through the germline. We compare the activity of SB in this model organism with that of Tol2, a hAT (hobo, Ac1, TAM)-like transposon system.
