Pak1 Signaling and Targets in Breast Cancer Progression

描述(申请人提供)：乳腺癌的进展是由非调控的增殖、获得不适当的侵袭性和有丝分裂缺陷，以及其他表型变化所推动的。已知的导致乳腺癌细胞向更具侵袭性表型发展的一个分子是p21-激活激酶1(Pak1)，它是一种由各种细胞表面或细胞内信号激活的结节状激酶。尽管在过去的十年里，关于Pak1生物学的新信息有了显著的增长，但我们仍然不知道Pak1如何参与确保S期进展和受控的有丝分裂的基本调控事件，以及它如何显著影响乳腺癌中的多倍体状态。本项目的目的是首次阐明和确定Pak1的信号依赖刺激在G1向S的转变和有丝分裂进程中在生理性和异常细胞增殖中的重要作用。这些研究旨在为在细胞周期进程的两个关键点上PAK1失调的效应提供一个分子解释。此外，我们将使用功能相关的遗传小鼠模型来检验这一假设，即E2F1和HSF1转录因子是在G1/S相变和有丝分裂期间pak1功能的决定因素。最后，我们将评估这些新兴分子在乳腺癌进展中的预后意义。提出这项建议的理据，是根据由R01-CA090970-09号文件支持的创新科技署化验所的多项研究结果而提出，我们现正申请续期。这些结果表明，Pak1信号分别通过E2F1和HSF1在控制细胞从G1向S的转变和有丝分裂进程中发挥内在作用，E2F1和HSF1可能是乳腺癌细胞中Pak1功能的新决定因素。我们的可检验假设是：PAC1信号的解除调节刺激E2F1和HSF1依赖的通路；因此，PAC1信号的解除调节导致乳腺癌细胞从G1到S的非调节的转变和有丝分裂的进展。为了解决这些假说，我们的具体目标是：(1)通过定义Pak1磷酸化对E2FS功能的影响，研究Pak1调控G1-S进程的机制；(2)确定HSF1在活化的Pak1核积累和乳腺癌细胞有丝分裂进程中的作用；(3)在相关的生理模型系统中，研究E2F1或HSF1作为Pak1功能的决定因素在G1/S转换和有丝分裂进程中的作用。我们建议的研究具有重要意义，因为我们在这里获得的知识可能首次揭示Pak1信号依赖的E2F家族和HSF1转录因子的调控，从而定义Pak1在乳腺癌细胞从G1到S的转变和有丝分裂过程中的新功能。此外，这项工作是创新的，因为我们将开始了解pak1调控在S期和有丝分裂中起作用的基因子集转录的原理。

DESCRIPTION (provided by applicant): Breast cancer progression is driven by deregulated proliferation, the acquisition of inappropriate invasiveness and mitotic defects, in addition to other phenotypic changes. One molecule known to cause progression of breast cancer cells to more invasive phenotypes is p21-activated kinase 1 (Pak1), a nodular kinase activated by a variety of cell surface or intracellular signals. Despite the remarkable growth of new information on the biology of Pak1 in the last decade, we still do not know how Pak1 participates in essential, regulatory events which ensure S-phase progression and controlled mitosis and how it could significantly influence the status of polyploidy in breast cancer The purpose of this project is to clarify and define for the first time the significant role of signal-dependent stimulation of Pak1 in the G1-to-S transition and in mitotic progression, in both physiological and aberrant cell proliferation. These studies are designed to offer a molecular explanation for the well-documented effect of Pak1 dysregulation at two critical points in cell cycle progression. In addition, we will test the hypothesis that E2F1 and HSF1 transcriptional factors are determinants of Pak1 functions at the G1/S phase transition and during mitosis using functionally relevant, genetic mouse models. And finally, we will evaluate and the prognostic significance of these emerging molecules in breast cancer progression. The rationale for this proposal is drawn from a number of findings from the PI's laboratory supported by R01-CA090970-09, for which we are seeking renewal. These findings to suggest that Pak1 signaling plays an inherent role in controlling the G1-to-S phase transition and mitotic progression via E2F1 or HSF1 respectively, and that E2F1 and HSF1 might be novel determinants of Pak1 functions in breast cancer cells. Our testable hypotheses are: Deregulation of Pak1 signaling stimulates E2F1- and HSF1-dependent pathways; and consequently, deregulation of Pak1 signaling confers deregulated G1-to-S-transition and mitotic progression in breast cancer cells. To address these hypotheses, our Specific Aims are to: To address these hypotheses, our Specific Aims are to: (1) Investigate the mechanism by which Pak1 regulates the G1-to-S progression by defining the impact of Pak1-phosphorylation upon the functions of E2Fs; (2) Determine the role of HSF1 in the nuclear accumulation of activated Pak1 and in mitotic progression of breast cancer cells; and (3) To study the role of E2F1 or HSF1 as determinant of Pak1 function in the G1/S transition and mitotic progression in physiological relevant model systems. Our proposed research is significant as the knowledge gained here may reveal Pak1 signaling-dependent regulation of the E2F family and HSF1 transcriptional factors for the first time, and thus, defining novel Pak1 functions in the G1-to-S-transition and mitotic progression of breast cancer cells. Additionally, this work is innovative because we will start understanding the principles by which Pak1 regulates transcription of a subset of genes with roles in the S-phase and mitosis.