Mouse Model of Pancreatic Tumorigenesis with Dysregulation of mTOR

描述（由申请人提供）：胰腺癌是美国男性和女性癌症死亡的第四大常见原因。它是最致命的癌症之一，大多数患者在一年内死亡。LKB 1位点的洛缺失见于约32%的胰腺肿瘤，提示其参与胰腺肿瘤的发生。肿瘤抑制因子LKB 1已被证明是通过AMPK激活结节性硬化症复合体2（TSC 2）的mTOR [哺乳动物雷帕霉素靶蛋白]信号传导的负调节因子。据报道，mTOR信号通路在高比例的胰腺癌中被组成性激活。LKB 1的种系突变导致Peutz-Jeghers综合征（PJS），这是一种以皮肤粘膜色素沉着过度和胃肠道错构瘤性息肉为特征的疾病，其显示mTOR信号转导失调。此外，PJS患者发生各种上皮瘤形成的风险也显著增加。据估计，胰腺癌的相对风险是一般人群的132倍。本提案的总体目标是开发一种通过LKB 1缺陷导致mTOR失调的胰腺癌小鼠模型。这将通过产生对于LKB 1和p53的条件性敲除基因纯合的小鼠品系来实现。基于我们以前的研究表明LKB 1和p53突变可以协同加速胃肠道错构瘤的肿瘤发生，我们假设LKB 1和p53突变将协同加速肿瘤发生，这些小鼠将发展为胰腺癌。在携带LKB 1条件性敲除、PDXCre转基因和野生型p53的小鼠中的初步观察表明，胰腺腺泡-导管化生在2-3月龄时发生。在许多组织中，化生是癌症的先兆。随着小鼠年龄的增长，它们会出现囊性畸形，类似于在患有PJS的人类以及散发病例中观察到的乳头内粘液性肿瘤（IPMN）。IPMN被认为是胰腺癌的前体，然而，由于IPMN样结构的扩张，这些小鼠不能存活足够长的时间来发展胰腺癌。据推测，除了LKB 1之外，胰腺特异性缺失p53将加速肿瘤发生的过程，并且IPMN样结构将进展为胰腺癌。一旦产生胰腺特异性缺失p53和LKB 1的小鼠，将评估这些小鼠胰腺中任何组织学变化的出现和发展的时间。由于LKB 1的失活已被证明会导致AMPK的失活，导致mTOR信号转导的失调，我们假设我们将在这些小鼠的胰腺癌背景下观察到mTOR的失调。mTOR是癌症治疗和预防的靶点。如果这些小鼠发展为胰腺癌，它们将作为一种有价值的新模型，用于进行针对mTOR通路的靶向治疗的未来研究。如果LKB 1和p53突变在肿瘤发生过程中协同作用，这些小鼠将成为研究LKB 1和p53突变在胰腺癌中相互作用机制的令人兴奋的新模型。公共卫生相关性：胰腺癌是美国男性和女性癌症死亡的第四大常见原因。几乎100%的胰腺癌患者会发生转移。mTOR通路的失调在胰腺癌中很常见。这种小鼠模型将有助于研究mTOR通路的失调及其作为预防和治疗这种疾病的靶点的潜力。第二个目标是确定LKB 1和p53突变是否在胰腺肿瘤发生中协同作用。LKB 1和p53的突变先前被发现在对息肉病小鼠模型的研究中合作。1

DESCRIPTION (provided by applicant): Pancreatic cancer is the fourth most common cause of cancer mortality in men and women in the United States. It is one of the most lethal cancers, with most patients dying within a year. LOH at the LKB1 locus is seen in approximately 32% of pancreatic tumors suggesting its involvement in pancreatic tumorigenesis. The tumor suppressor LKB1 has been shown to be a negative regulator of mTOR [mammalian target of rapamycin] signaling via AMPK activation of the tuberous sclerosis complex 2 (TSC2). The mTOR signaling pathway has been reported to be constitutively activated in a high proportion of pancreatic cancers. Germline mutations in LKB1 cause Peutz-Jeghers syndrome (PJS), a disorder characterized by mucocutaneous hyperpigmentation and gastrointestinal hamartomatous polyps which display dysregulation of mTOR signaling. In addition, patients with PJS also have a dramatically increased risk for development of a variety of epithelial neoplasias. The relative risk for pancreatic cancer has been estimated to be 132 times that of the general population. The overall goal of this proposal is to develop a mouse model for pancreatic adenocarcinoma with dysregulation of mTOR via deficiency in LKB1. This will be accomplished by generating a mouse line that is homozygous for the conditional knockout genes of LKB1 and p53. Based on our previous studies demonstrating that mutations in LKB1 and p53 can cooperate to accelerate the tumorigenesis of gastrointestinal hamartomas, we hypothesize that mutations in LKB1 and p53 will cooperate to accelerate tumorigenesis and that these mice will develop pancreatic cancer. Preliminary observations in mice carrying the LKB1 conditional knockout, the PDXCre transgene, and wild type p53 indicate that pancreatic acinar-to-ductal metaplasia develops at 2-3 months of age. Metaplasia is a harbinger of cancer in many tissues. As the mice age, they develop cystic malformations that resemble the intrapapillary mucinous neoplasms (IPMNs) seen in humans with PJS as well as sporadic cases. IPMNs are considered precursors of pancreatic cancer, however these mice do not survive long enough to develop pancreatic cancer due to the expansion of the IPMN-like structures. It is hypothesized that pancreas specific deletion of p53, in addition to LKB1, will accelerate the process of tumorigenesis and the IPMN-like structures will progress to pancreatic adenocarcinoma. Once mice with pancreas specific deletion of p53 and LKB1 have been generated, the timing of appearance and the development of any histological changes in the pancreata of these mice will be assessed. Because inactivation of LKB1 has been shown to result in inactivation of AMPK, leading to dysregulation of mTOR signaling, we hypothesize that we will observe dysregulation of mTOR in the context of the pancreatic cancer in these mice. mTOR is a target for cancer therapy and prevention. If these mice develop pancreatic adenocarcinoma, they will serve as a valuable new model for conducting future studies on targeted therapy directed toward the mTOR pathway. If mutations in LKB1 and p53 cooperate in the process of tumorigenesis, these mice will serve as an exciting new model for studying the mechanisms by which LKB1 and p53 mutations interact in pancreatic adenocarcinoma. PUBLIC HEALTH RELEVANCE: Pancreatic cancer is the fourth most common cause of cancer mortality in men and women in the United States. Close to 100% of the patients with pancreatic cancer develop metastasis. Dysregulation of the mTOR pathway is common in pancreatic adenocarcinoma. This mouse model will be useful in studying the dysregulation of the mTOR pathway and its potential as a target for prevention and treatment of this disease. A secondary goal will be to determine if mutations in LKB1 and p53 cooperate in pancreatic tumorigenesis. Mutations in LKB1 and p53 were previously found to cooperate in a study on a mouse model of polyposis. 1