Protein Kinase D in oncogenic oxidative stress signaling

描述（由申请人提供）：胰腺导管腺癌（PDAC）可能是迄今为止已知的最具侵袭性的癌症形式，其5年总生存率最低。PDAC中生长因子信号和K-ras突变的增加导致活性氧（ROS）的产生速率升高。ROS在细胞内信号级联反应中作为第二信使，诱导和维持致瘤表型。氧化应激激活和调节肿瘤细胞存活的保护性信号级联反应尚不清楚。了解这些保护性信号机制是非常重要的，因为它们的调节可能允许打破ROS稳态的平衡，使癌细胞对化疗诱导的细胞死亡敏感。我们的假设是氧化应激通过激活蛋白激酶d介导肿瘤细胞存活。具体来说，我们假设ros介导的PKD信号通过线粒体传递，而被这一途径激活的PKD通过转录因子FOXO3a调节存活。我们进一步假设，PKD的药理抑制增加了肿瘤细胞对ros介导的细胞死亡的敏感性。为了验证这一点，我们将：确定蛋白激酶D如何被募集到线粒体以响应ROS (Specific Aim 1)；表征肿瘤抑制因子FOXO3a作为ros激活PKD的细胞靶标（Specific Aim 2），表征新的PKD抑制剂及其在癌症治疗中的价值（Specific Aim 3）。这一建议的成功完成将有助于理解ROS-和pkd介导的PDAC细胞中的保护性信号。这将表明，在对生长因子，K- ras或其他ROS诱导剂的响应中，PKD作为PKD激活机制的第一步，通过DAG结合定位到线粒体。通过鉴定FOXO3a作为新的PKD靶点，将进一步剖析PKD在肿瘤细胞存活中的作用。最后，我们将描述新的pkd抑制化合物在使胰腺癌细胞对ROS和化疗诱导的细胞死亡敏感方面的价值。总的来说，我们的结果将为胰腺癌患者开发新的和更有效的治疗策略提供基础。

DESCRIPTION (provided by applicant): Pancreatic ductal adenocarcinoma (PDAC) is probably the most aggressive form of cancer known to date with the lowest overall 5-year survival rate. Increased growth factor signaling and K-ras mutations in PDAC lead to the generation of reactive oxygen species (ROS) at elevated rates. ROS act as second messengers in intracellular signaling cascades, which induce and maintain the oncogenic phenotype. Little is known about the protective signaling cascades that are activated by oxidative stress and regulate tumor cell survival. It is of great importance to understand these protective signaling mechanisms since their modulation may allow tipping the balance in ROS homeostasis to sensitize cancer cells to chemotherapeutics-induced cell death. It is our hypothesis that oxidative stress mediates tumor cell survival by activating Protein Kinase D. Specifically, we hypothesize that ROS-mediated PKD signaling is transmitted through the mitochondria and that PKD activated by this pathway regulates survival via the transcription factor FOXO3a. We further hypothesize that the pharmacological inhibition of PKD increases the sensitivity of tumor cells to ROS-mediated cell death. To test this we will: Determine how Protein Kinase D is recruited to the mitochondria in response to ROS (Specific Aim 1); Characterize the tumor suppressor FOXO3a as a cellular target for ROS-activated PKD (Specific Aim 2) and Characterize novel PKD inhibitors and their value for cancer therapy (Specific Aim 3). Successful completion of this proposal will contribute to the understanding of ROS- and PKD-mediated protective signaling in PDAC cells. It will show that in response to growth factors, K- ras or other inducers of ROS, as a first step in the PKD activation mechanisms, PKD is located to the mitochondria via DAG binding. It will further dissect PKD's role in tumor cell survival by identifying FOXO3a as a novel PKD target. Finally, we will characterize novel PKD-inhibiting compounds for their value in sensitizing pancreatic cancer cells to ROS- and chemotherapeutics-induced cell death. Overall our results will provide the basis for the development of novel and more potent therapeutic strategies for pancreatic cancer patients. PUBLIC HEALTH RELEVANCE: This proposal aims to understand a novel signaling mechanism which mediates pancreatic cancer cell survival in response to oxidative stress. We further will test if inhibiting a key enzyme in this pathway with a set of novel inhibitors will sensitize pancreatic cancer cells to chemotherapeutics.