Cytoskeletal Dynamics in Pancreatic Cancer Metastasis

描述(申请人提供)：胰腺癌是一种极具破坏性的疾病，预后极差。起源于导管的肿瘤占胰腺肿瘤的95%，有很强的侵袭周围实质和转移到远端器官的倾向。目前，支持这些关键过程的分子机制还不是很清楚。已知肌动蛋白细胞骨架在许多胰腺肿瘤中起重要作用，并对受体酪氨酸激酶家族的刺激做出动态反应。这是一项研究RTK激活肌动蛋白细胞骨架戏剧性重组的机制的建议，该重组改变了细胞的极性，导致细胞迁移、侵袭和转移。我们已经在这些细胞中发现了一个关键的调节细胞骨架复合体，由以下组成：在人类胰腺肿瘤中显著上调的名为Dynamin(Dyn2)的大型机械力化学GTP酶，肌动蛋白交联蛋白Cortactin，以及由RTK激活并结合和磷酸化Dy2和Cortactin的转化激酶Src。重要的是，我们已经证明这种复合体与肌动蛋白细胞骨架、细胞膜以及与胰腺癌有关的已知致癌蛋白相关联，形成支持侵袭过程的“信号平台”。我们最近的手稿和未发表的观察结果为本研究的中心假说提供了强有力的支持：主要是，Dy2-Cort-Src复合体与致癌蛋白1-Actinin和Rac一起被升高的RTK级联激活，介导肌动蛋白-质膜动力学，促进肿瘤胰腺导管细胞的侵袭和转移。这项建议将利用应用于胰腺肿瘤细胞系的最先进的光学和分子方法、人类肿瘤样本的组织微阵列(TMA)技术和体内动物模型来确定该蛋白质复合体增强胰腺肿瘤和转移的分子机制。该提案分为三个不同但相关的具体目标，它们将定义以下内容：第一，这些信号平台如何介导RTK从细胞表面大规模内化以改变细胞信号级联；第二，Dy2-Cort-Src复合体如何介导肿瘤细胞中主要的肌动蛋白重组，从而成为迁移和侵袭性的；第三，肿瘤细胞黏附复合体如何形成和增殖，以调节周围细胞外基质的降解，从而促进转移。这项研究将使分离的细胞与人类肿瘤密切相关，为理解胰腺肿瘤如此具有侵袭性、迁移性和致命性的分子机制提供新的信息。此外，它还描述了使用新近发现的药理抑制剂进行的临床前试验。 与公共卫生相关：胰腺癌因其侵袭性的扩散和转移而特别致命。这项提议将定义这些肿瘤细胞从胰腺转移到周围器官的一些核心机制，通过专注于在这些癌症中显著上调的特定“致癌”蛋白。

DESCRIPTION (provided by applicant): Pancreatic cancer is a devastating disease with an exceptionally poor prognosis. Tumors of ductular origin comprise 95% of pancreatic neoplasms and have strong tendencies to invade surrounding parenchyma and metastasize to distal organs. Currently, the molecular mechanisms that support these critical processes are poorly defined. It is known that the actin cytoskeleton plays an important role and responds dynamically to stimulation by a family of Receptor Tyrosine Kinases (RTKs) that are upregulated significantly in many pancreatic tumors. This is a proposal to study the mechanisms by which RTKs activate dramatic reorganization of the actin cytoskeleton, which alters cell polarity and leads to cell migration, invasion, and metastasis. We have identified a key regulatory cytoskeletal complex in these cells composed of; a large mechanochemical GTPase called dynamin (Dyn2) that is markedly upregulated in human pancreatic tumors, the actin crosslinking protein cortactin, and the transforming kinase Src, which is activated by RTKs and binds and phosphorylates both Dyn2 and cortactin. Importantly, we have shown that this complex associates with the actin cytoskeleton, cellular membranes, as well as known oncogenic proteins implicated in pancreatic cancer to form "signaling platforms" that support the invasive process. Our recent manuscripts and unpublished observations provide strong support for the CENTRAL HYPOTHESIS of this study: mainly, the Dyn2-Cort-Src complex, in concert with the oncogenic proteins 1-actinin and Rac, is activated by elevated RTK cascades to mediate actin-plasma membrane dynamics that promote invasion and metastasis of neoplastic pancreatic ductular cells. This proposal will utilize state-of-the-art optical and molecular methods applied to pancreatic tumor cell lines, tissue micro-array (TMA) technology of human tumor samples, and in vivo animal models to define the molecular mechanisms by which this protein complex potentiates pancreatic neoplasia and metastasis. This proposal is organized into three distinct but related specific aims that will define the following; first, how these signaling platforms mediate large-scale internalization of RTKs from the cell surface to alter cell signaling cascades; second, how the Dyn2-Cort-Src complex mediates major actin reorganization in tumor cells that become migratory and invasive; and third, how tumor cell adhesion complexes form and proliferate to mediate degradation of the surrounding extracellular matrix to facilitate metastasis. This study will make close correlations between isolated cells and human tumors to provide novel information toward understanding the molecular mechanisms that make pancreatic tumors so aggressive, migratory, and lethal. In addition, it describes pre-clinical trials using novel, recently identified pharmacological inhibitors. PUBLIC HEALTH RELEVANCE: Pancreatic cancers are particularly lethal due to the aggressive way they spread and metastasize. This proposal will define some of the central mechanisms by which these tumor cells move away from the pancreas to invade peripheral organs by focusing on specific "oncogenic" proteins that are markedly "upregulated" in these cancers.