Protein Kinase D in oncogenic oxidative stress signaling

描述(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，总体5年生存率最低。PDAC中生长因子信号的增加和K-ras突变导致活性氧物种(ROS)的产生速度加快。ROS在细胞内信号级联中扮演第二信使的角色，诱导和维持致癌表型。人们对氧化应激激活并调节肿瘤细胞存活的保护性信号级联知之甚少。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会打破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来调节肿瘤细胞的生存。具体地说，我们假设ROS介导的PKD信号是通过线粒体传递的，由这一途径激活的PKD通过转录因子FOXO3a来调节生存。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。为了测试这一点，我们将：确定蛋白激酶D如何被招募到线粒体以响应ROS(特定目标1)；表征肿瘤抑制基因FOXO3a作为ROS激活的PKD的细胞靶点(特定目标2)，并表征新的PKD抑制剂及其癌症治疗价值(特定目标3)。这一建议的成功完成将有助于理解ROS和PKD介导的PDAC细胞保护信号。这表明，在对生长因子、K-ras或其他ROS诱导剂的反应中，作为PKD激活机制的第一步，PKD通过DAG结合定位于线粒体。通过将FOXO3a确定为新的PKD靶点，它将进一步剖析PKD在肿瘤细胞生存中的作用。最后，我们将表征新的PKD抑制化合物在提高胰腺癌细胞对ROS和化疗诱导的细胞死亡的敏感性方面的价值。总体而言，我们的结果将为胰腺癌患者开发新的、更有效的治疗策略提供基础。 公共卫生相关性：这项建议旨在了解一种新的信号机制，该机制介导胰腺癌细胞在氧化应激下的生存。我们将进一步测试用一组新的抑制剂抑制这一途径中的一个关键酶是否会使胰腺癌细胞对化疗药物敏感。

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.