Molecular Mediators of Pancreatic Cancer Invasion and Progression

描述(申请人提供)：转移性胰腺癌是一种致命的疾病。虽然大多数关键的遗传和表观遗传改变多年来已为人所知，但到目前为止，这还没有产生有用的治疗方法。我们最重要的目标是找出 PDAC基因表达，可用于开发有效的治疗方法。为此，我们最近一直在关注转录因子FOXM1，它在PDAC中急剧增加。为了了解这种高表达的重要性，我们开发了基因工程的PDAC细胞系，以过表达FOXM1。这些细胞系均表现出显著的生长和转移能力。在一个补充的方法中，我们减少了FOXM1在许多PDAC细胞中的表达，并观察到这些细胞的侵袭性降低。最近，我们发现人PDAC细胞几乎完全表达FOXM1的一种剪接形式，称为FoxM1C，这在正常组织中没有观察到。根据我们的初步研究，我们推测在PDAC癌变过程中，miRNA的表达异常导致FOXM1的过度表达及其下游侵袭和转移关键靶基因的异常表达，从而增强了PDAC细胞的恶性潜能，导致PDAC患者预后不良。因此，FOXM1是PDAC的一个恶性生物标志物和治疗靶点。为了验证我们的假设，我们提出了以下三个具体目标。目的：1.探讨胰腺癌中FOXM1表达异常的分子机制。FOXM1在PDAC中的过度表达是众所周知的，但其潜在的机制尚不清楚。我们最近利用一种基于计算机的算法来筛选针对FOXM1的可能的microRNAs(在正常胰腺和胰腺癌的miRNA表达的计算机分析和微阵列分析中都是如此)，并初步鉴定了3个与FOXM1相关的microRNAs。有趣的是，这三种基因在胰腺癌中都表达下调。我们期望这些microRNAs因果地调节FOXM1的表达和功能，并显示出预后价值。目的#2.确定FOXM1表达在胰腺癌侵袭和转移中的调节作用。已知人胰腺癌细胞过度表达uPAR，其表达水平与FOXM1的表达水平直接相关。UPAR表达改变对胰腺癌侵袭转移的调控作用。因此，我们希望确定uPAR是否是FOXM1的一个新的重要下游靶点和功能介体。我们认为FOXM1亚型调控胰腺癌细胞中uPAR的表达和功能，这一新的途径在胰腺癌的侵袭和转移中是必不可少的。目的#3.探讨FOXM1亚型在胰腺癌侵袭转移中的临床意义。FOXM1由3种异构体组成：FoxM1A、FoxM1B和FoxM1C，最近又发现了另外两种异构体，并暂时命名为FoxM1B1和FoxM1B2。这些异构体在胰腺癌中的表达和功能尚不完全清楚。我们的初步研究表明，胰腺癌细胞主要表达FoxM1C，这种形式具有独特的特性。我们预计，FoxM1C形式与特别侵袭性的疾病有关，不同FOXM1亚型的表达变化，包括FoxM1B1和FoxM1B2到FoxM1B，直接影响胰腺癌的生长和转移。

DESCRIPTION (provided by applicant): Metastatic pancreatic cancer is a lethal disease. While most of the critical genetic and epigenetic alterations have been known for years, to date this has not resulted in useful therapeutics. Our most important goal is to identify alterations in PDAC gene expression that can be utilized to develop effective therapies. To this end we have recently been focusing on the transcription factor FoxM1, which is drastically increased in PDAC. To understand the importance of this elevated expression we have developed PDAC cell lines genetically engineered to over-express FoxM1. These cell lines uniformly exhibit greatly elevated growth and metastasis. In a complimentarily approach, we have reduced FoxM1 expression in numerous PDAC cells and observed a reduction in the aggressive nature of these cells. Recently, we discovered that human PDAC cells almost exclusively express a splice form of FoxM1 called FoxM1C, which is not observed in normal tissues. Based on our preliminary studies, we postulate that during PDAC carcinogenesis, dysregulated miRNA expression leads to overexpression of FoxM1 and dysregulated expression of its downstream target genes key to invasion and metastasis, resulting in an enhanced malignant potential of PDAC cells and cause poor prognosis of PDAC patients. Thus, FoxM1 is a malignant biomarker and therapeutic target in PDAC. To test our hypothesis, we propose the following three specific aims. Aim #1. Investigate the molecular mechanisms underlying the dysregulated FoxM1 expression in pancreatic cancer. The overexpression of FoxM1 in PDAC is well established, while the underlying mechanisms are unknown. We have recently utilized a computer based algorithm to screen for possible microRNAs that target FoxM1 (both in silico analysis and microarray analysis of miRNA expression in normal pancreas vs. pancreatic cancer) and have tentatively identified 3 FoxM1-related microRNAs. Interestingly, all three are down-regulated in pancreatic cancer. We expect that those microRNAs causally regulate FoxM1 expression and function and exhibit prognostic values. Aim #2. Determine the regulatory role of FoxM1 expression in pancreatic cancer invasion and metastasis. Human pancreatic cancer cells are known to overexpress uPAR and its expression levels directly correlate with those of FoxM1. Altered expression of uPAR regulates invasion and metastasis of pancreatic cancer. Therefore, we wish to determine whether uPAR is a novel important downstream target and functional mediator of FoxM1. We expect that FoxM1 isoforms regulate the expression and function of uPAR in pancreatic cancer cells and this novel pathway is essential to pancreatic cancer invasion and metastasis. Aim #3. Determine the clinical significance of FoxM1 isoforms in human pancreatic cancer invasion and metastasis. FoxM1 consists of 3 isoforms: FoxM1A, FoxM1B, and FoxM1C, and most recently, two additional isoforms are identified and provisionally named as FoxM1B1 and FoxM1B2. The expression and functions of those isoforms in pancreatic cancer are not completely known. Our preliminary studies have indicated that pancreatic cancer cells predominantly express FoxM1C and that this form has unique properties. We expect that the FoxM1C form is associated with particularly aggressive disease and altered expression of different isoforms of FoxM1, including FoxM1B1 and FoxM1B2 to FoxM1B, directly impact on pancreatic cancer growth and metastasis.