Pak1 - PIN Pathway in Breast Cancer Progression

描述（由申请人提供）：乳腺癌是美国最常见的恶性肿瘤之一，影响九分之一的女性。乳腺癌进展为更恶性行为的分子机制目前还不完全清楚，据信涉及由生长因子激活的信号通路的失调及其受体。btors。例如，EGF家族配体对人表皮生长因子受体的过表达或过度活化通常与人乳腺癌的侵袭性临床过程、降低的无病存活率和转移有关。尽管有关生长因子及其受体的信息显著增长，但在理解这些细胞表面启动途径的下游靶点调节乳腺癌进展的机制方面的进展仍然难以捉摸。如下所述，我们最近的工作表明，生长因子刺激p21激活激酶（Pak 1），丝氨酸/苏氨酸激酶，在细胞运动，侵袭和存活中起着重要作用，所有这些都是正常乳腺发育和肿瘤形成所需的。我们的初步研究首次发现PIN是Pak 1和生长因子信号传导的生理底物，Pak 1-PIN通路可能与乳腺癌向更具侵袭性表型的进展密切相关。在这里，我们建议调查的分子机制，PIN参与提高细胞存活率的发展，解除管制的G1-S转换和乳腺癌细胞的致瘤表型。最近的研究表明，动力蛋白轻链-8（DLCS）/NOS的蛋白抑制剂（PIN）是一种新的Pak 1-介导蛋白，生长因子和Pak 1促进内源性Pak 1和PIN的相互作用，PIN是Pak 1及其上游激活剂如heregulin和EGF的生理底物，PIN在MCF 10AT进展模型中上调，并且在来自MMTVHER 2小鼠和人的乳腺肿瘤中上调，PIN过表达促进生长刺激、锚定独立性和细胞周期进程，Pak 1信号传导是PIN表达所需且足够的，Pak 1信号传导还调节其底物的表达。我们的工作假设是，“Pak 1活性的失调刺激PIN的表达和磷酸化，因此，有助于提高细胞存活率，细胞周期进展和锚定独立性，以及乳腺肿瘤细胞的肿瘤发生; PIN的这些表型效应可能由Pak 1对PIN的Ser 88磷酸化控制。“为了解决这些假设，我们的具体目标是确定：（1）Pak 1-PIN相互作用的功能意义和Pak 1调节乳腺癌细胞中PIN表达的机制;（2）PIN及其Ser 88磷酸化对与乳腺癌细胞进展相关的表型变化的影响;（3）PIN转基因表达对乳腺生物学、生长发育及早期肿瘤发生的影响;（4）PIN和Pak 1在乳腺癌多阶段发病过程中的表达特点及意义。浸润性乳腺癌患者。这些研究将独特地定义PIN及其上游Pak 1激酶调节乳腺癌细胞存活、有丝分裂和肿瘤发生的机制。我们提出的研究是重要的，因为这项研究可能形成新的进展，在确定新的分子靶点，检测，预防和治疗乳腺癌，通过确定PIN作为一个关键的调节结节的基础。

DESCRIPTION (provided by applicant): Breast cancer is one of the most common malignancies in the United States, affecting one in nine women. The molecular mechanisms underlying the progression of breast cancer to more malignant behavior are not completely understood at the present time and are believed to involve deregulation of signaling pathways activated by growth factors and their rece!btors. For example, overexpression or overactivation of the human epidermal growth factor receptors by EGF family of ligands is frequently associated with an aggressive clinical course, decreased disease-free survival, and metastasis in human breast cancer. Despite the remarkable growth of information about growth factors and its receptors, the progress in understanding the mechanism by which downstream target(s) of these cell surface-initiated pathways regulate breast cancer progression remains elusive. As described below, our recent work indicate that growth factor-stimulation of p21-activated kinase (Pak1), a serine/threonine kinase, plays a significant role in the cell motility, invasiveness and survival, all of which are required for both normal mammary gland development and tumor formation. Our preliminary studies have discovered for the first time that PIN is a physiological substrate of Pak1 and of growth factor signaling and that Pak1-PIN pathway may be closely involved in breast cancer progression to more invasive phenotypes. Here we propose to investigate the molecular mechanism by which PIN participates in the development of enhanced cell survival, deregulated G1-S transition and tumorigenic phenotypes in breast cancer cells. Recent studies suggest that dynein light chain-8 (DLCS)/Protein Inhibitor of NOS (PIN) is a novel Pak1-intercating protein, growth factors and Pakl promotes interaction of endogenous Pakl and PIN, PIN is a physiologic substrate of Pak1 and its upstream activators such as heregulin and EGF, PIN is upregulated in MCF10AT progression model, and in mammary tumors from MMTVHER2 mice and human, PIN overexpression promotes growth-stimulation, anchorage-independence, and cell cycle progression, and Pak1 signaling is required and sufficient for PIN expression, and Pak1 signaling also regulates the expression of its substrate. Our working hypothesis is that "deregulation of Pak1 activity stimulates the expression and phosphorylation of PIN, and consequently, contributes to an enhanced cell survival, cell cycle progression and anchorage-independence, and tumorigenesis of breast tumor cells; these phenotypic effects of PIN might be controlled by Ser 88 phosphorylation of PIN by Pak1 ." To address these hypotheses, our specific aims are to determine: (1) The functional significance of Pak1-PIN interaction and the mechanism of Pak1 regulation of PIN expression in breast cancer cells; (2) The influence of PIN and its Ser 88 phosphorylation on the phenotypic changes associated with the progression of breast cancer cells; (3) The influence of PIN transgene expression on the biology, development and the early stages of tumorigenesis in mammary gland; and (4) The expression characteristics and significance of PIN and Pak1 during multi-step pathogenesis of breast carcinoma and in-patients with invasive breast cancer. These studies will uniquely define the mechanisms through which PIN and its upstream Pak1 kinase regulate survival, mitogenesis and tumorigenesis of breast cancer cells. Our proposed research is significant as this research might form the basis for new advances in identifying novel molecular targets, detecting, preventing and treating breast cancer, by identifying PIN as a key regulatory nodule.