Pancreatic cancer is a leading cause of cancer-related mortality in the United States, with an estimated 31,000 deaths in 2004. Many commonly occurring genetic alterations have been identified in this disease; however, the precise molecular mechanisms by which these mutations induce pancreatic tumors remain poorly understood. Thus, model systems, including mouse models that elucidate these mechanisms are greatly needed. This application therefore proposes the generation of a novel mouse model for pancreatic ductal adenocarcinoma (PDAC) through the somatic delivery of avian retroviruses encoding the mouse polyoma virus middle T antigen (PyMT) to transgenic mice engineered to express the retroviral receptor, TVA, specifically within the pancreatic duct epithelium. PyMT is a potent transforming oncoprotein that stimulates Ras- and PI3-kinase-mediated signaling pathways, thus mimicking two common events in PDAC. To identify the cooperating genetic lesions required for tumor formation, PyMT-encoding retroviruses will be delivered to mice in which the p53 or Ink4a/Arftumor suppressor gene loci, or both, are deleted within the pancreas. The induced tumors will be analyzed for tumor grade, ability to metastasize, the expression of pancreatic progenitor cell markers, and lineage specific markers. Furthermore, the activation status of the notch and hedgehog signaling pathways, recently shown to be activated in the majority of pancreatic cancers, will be determined and correlated with the initiating genetic lesions. Thus, the relationship between initiating genetic lesions, tumor grade, and the activation of important signaling pathways in PDAC will be ascertained. PyMT stimulates signaling through the Ras^ and PI3-kinase/Akt-induced signaling pathways. To identify the contributions of these pathways to tumor initiation and progression, Viruses encoding PyMT mutants attenuated for signaling through these pathways will be delivered to transgenic bearing tumor suppressor gene mutations. In addition, to determine whether sustained activation of the Ras and Akt signaling pathways is required for tumor cell growth and survival, cell lines isolated from PyMT-induced tumors will be treated with inhibitors of the Ras-responsive MAP kinase pathway or the PI3-kinase/Akt pathway. Thus, the contributions of the Ras and Akt signaling pathways to tumor initiation, progression, and tumor cell maintenance will be elucidated using this novel mouse model. Therefore, the experiments described in this proposal will contribute to an increased understanding of the molecular features of pancreatic cancer, potentially enhancing the development of effective targeted therapies. Such an advance would benefit public health by reducing the mortality associated with this disease. ? ? ?
