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。大约32%的胰腺肿瘤可见LKB1位点的LOH，提示其参与胰腺肿瘤的发生。肿瘤抑制因子LKB1已被证明是mTOR（哺乳动物雷帕霉素靶点）信号的负调节因子，通过AMPK激活结节硬化复合体2 （TSC2）。据报道，mTOR信号通路在高比例的胰腺癌中被组成性激活。LKB1的种系突变导致Peutz-Jeghers综合征（PJS），这是一种以粘膜皮肤色素沉着和胃肠道错构瘤息肉为特征的疾病，其表现为mTOR信号失调。此外，PJS患者发生各种上皮瘤变的风险也显著增加。据估计，患胰腺癌的相对风险是普通人群的132倍。本研究的总体目标是建立一种通过LKB1缺乏导致mTOR失调的胰腺腺癌小鼠模型。这将通过产生LKB1和p53条件敲除基因纯合子的小鼠系来实现。基于我们之前的研究表明LKB1和p53的突变可以协同加速胃肠道错构瘤的发生，我们假设LKB1和p53的突变会协同加速肿瘤的发生，这些小鼠会发展为胰腺癌。在携带LKB1条件敲除、pdxre转基因和野生型p53的小鼠中进行的初步观察表明，胰腺腺泡到导管的化生发生在2-3月龄。化生是许多组织癌变的先兆。随着小鼠年龄的增长，它们会出现囊性畸形，类似于人类PJS患者的乳头内粘液瘤（IPMNs）以及零星病例。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为胰腺癌。假设胰腺特异性缺失p53，以及LKB1，将加速肿瘤发生过程，ipmn样结构将发展为胰腺腺癌。一旦产生具有胰腺特异性p53和LKB1缺失的小鼠，将评估这些小鼠胰腺中任何组织学变化的出现时间和发展。由于LKB1的失活已被证明会导致AMPK的失活，从而导致mTOR信号的失调，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腺癌，它们将作为一个有价值的新模型，用于开展针对mTOR途径的靶向治疗的未来研究。如果LKB1和p53的突变在肿瘤发生过程中协同作用，这些小鼠将成为研究LKB1和p53突变在胰腺腺癌中相互作用机制的一个令人兴奋的新模型。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。接近100%的胰腺癌患者会发生转移。mTOR通路的失调在胰腺腺癌中很常见。该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该疾病的靶点的潜力。第二个目标将是确定LKB1和p53突变是否在胰腺肿瘤发生中协同作用。LKB1和p53的突变先前在一项对息肉病小鼠模型的研究中被发现是合作的。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