Develop and Characterize a Novel Animal Model of Pancreatic Cancer

描述(由申请人提供)：真实模拟人类疾病的胰腺导管腺癌(PDAC)动物模型对于研究人员开发有效的早期诊断、预防和治疗策略是必要的。近年来，已经建立了几种PDAC的遗传小鼠模型，并极大地提高了我们对其生物学的理解。今天广泛使用的遗传模型是通过对胚胎胰腺或产生消化酶的成年细胞--胰腺腺泡细胞--进行基因改造而建立的。这些模型忠实地模拟了人类PDAC的发育，这一点是有争议的，因为人们普遍认为，在人类中，这种疾病是在一种不同类型的细胞--导管细胞内发展的。此外，PDAC是一种老年人的疾病，在儿童中没有发现。显然，基于成人胰管细胞遗传变化的遗传模型将为这种疾病的研究提供一个重要的模型。以前的尝试依赖于胰管特异的基因启动子而非胰腺特异的基因启动子(例如CK19)，但由于癌基因在所有CK19阳性细胞中的广泛表达是胚胎致死的，因此建立胰管特异模型的尝试失败了。在拟议的项目中，我们将开发一个小鼠模型，在该模型中，基因表达受到成年胰腺管细胞的特异性控制，而不是任何其他细胞。为了做到这一点，我们开发了一种新的策略，使用必须同时激活的两个基因启动子的组合。对于导管细胞的特异性，我们将使用特性良好的CK19启动子，该启动子在全身的导管细胞中都很活跃。对于胰腺特异性，我们将使用PDX1启动子，它在胚胎发育期间在胰腺前体细胞中表达。我们将这些启动子组装成一种结构，使导管细胞特异性启动子CK19受胰腺特异性启动子PDX1的控制。为了在时间上控制基因的表达，我们将利用我们的系统表达一种可以被药物他莫昔芬激活的分子。一旦被诱导，这种分子就能够激活或删除专门为此目的而设计的小鼠的基因，其中许多已经存在。该模型将首次实现对胰管细胞基因表达的特异性调控，这对许多生理和病理研究都是有用的。一旦建立了胰管特异性表达系统，我们将使用它来激活癌基因并抑制肿瘤抑制基因，以模仿通常在人类中发现的情况来产生PDAC。在这个模型中产生的PDAC的样本将与其他遗传小鼠模型的样本以及与人类疾病的样本进行比较。我们期望这种胰腺癌动物模型在临床上更具相关性，更适合于转化性研究。

DESCRIPTION (provided by applicant): Animal models of pancreatic ductal adenocarcinoma (PDAC) that faithfully mimic the human disease are necessary to allow researchers to develop effective early diagnosis, prevention, and treatment strategies. In recent years, several genetic mouse models of PDAC have been developed and have greatly improved our understanding of its biology. The genetic models in widespread usage today were developed by genetically altering either the embryonic pancreas or the adult cells that produce digestive enzymes, pancreatic acinar cells. That these models faithfully mimic the development of human PDAC is controversial because it is generally felt that in humans this disease develops within a different cell type, duct cells. Furthermore, PDAC is a disease of the elderly and is not found in children. Clearly, a genetic model based on genetical changes in adult pancreatic duct cells would provide an important model for investigation of this disease. Previous attempts to develop pancreatic duct-specific models relying on gene promoters that were duct specific but not pancreas specific (e.g. CK19) have failed because broad expression of oncogenes in all CK19-positive cells is embryonically lethal. In the proposed project, we will develop a mouse model in which gene expression is controlled specifically in adult pancreatic duct cells rather than any other cells. In order to do so, we have developed a novel strategy that uses a combination of two gene promoters that must be activated in tandem. For duct cell specificity, we will use the well-characterized CK19 promoter, which is active in duct cells throughout the body. For pancreatic specificity, we will use the PDX1 promoter, which is expressed in pancreatic precursor cells during embryonic development. We will assemble these promoters in a construct such that the duct cell- specific promoter CK19 is under the control of the pancreas-specific promoter PDX1. To control gene expression temporally, we will utilize our system to express a molecule that can be activated by a drug, tamoxifen. Once induced, this molecular is capable of activating or deleting genes in mice engineered specifically for this purpose, many of which are already available. This model will allow for the first time the specific regulation of pancreatic duct cell gene expression, which is useful for many physiological and pathological studies. Once the pancreatic duct-specific expression system is established, we will use it to activate an oncogene and inhibit a tumor suppressor to mimic the situation commonly found in humans to generate PDAC. Specimens of the PDAC that develops in this model will be compared with those from other genetic mouse models and with the human disease. We expect that this animal model of pancreatic cancer will be more clinically relevant and appropriate for translational research.