Targeting the Plk1/Pdcd4/mTORC2 Signaling to Treat Castration-Resistant Prostate Cancer

标题：靶向Plk1/Pdcd4/mTORC2信号转导治疗去势抵抗性前列腺癌 摘要 雄激素受体（AR）信号传导对于前列腺癌（PCa）的发展至关重要，包括去势- 耐药前列腺癌（CRPC）。因此，雄激素信号传导抑制剂（ASI），如阿比特龙和 Enzalutamide正在成为CRPC的一线治疗药物。然而，ASI的有限成功使其 迫切需要开发治疗对ASI不再有反应的CRPC患者的方法。程序性细胞 死亡4（Pdcd4）是一种肿瘤抑制因子，已证明其抑制肿瘤进展， 化学抗性此外，Pdcd4是调节PCa生长的雄激素抑制蛋白， 去势抵抗因此，了解Pdcd 4的调控机制具有重要的临床意义， 因为它将揭示克服ASI抗性的新方法。Polo样激酶1（Plk1），一种关键的调节因子， 细胞周期相关事件是PCa治疗的记录目标。值得注意的是，我们以前证明， Plk1的抑制增强了ASI的功效。这项研究的长期目标是确定可药物化的 信号通路，为不再有反应的CPRC患者提供有效的治疗选择 到ASIs。目的是确定Plk 1在调节Pdcd 4中的作用，并利用这些途径作为一种新的途径。 CRPC的治疗靶点。我们的数据显示，1）Pdcd4增强了对恩杂鲁胺的敏感性， 抑制mTORC 2（雷帕霉素复合物2的哺乳动物靶标）和AR表达; 2）Plk 1 Pdcd4的磷酸化导致其蛋白质降解;和3）显性负性Pdcd4肽（TAT-1）， RBD）克服了PCa中的ASI抗性。基于这些观察，我们的目标是测试中心假设， Pdcd4的Plk1相关磷酸化导致其降解，这导致随后的Pdcd4的激活。 mTORC2，最终有助于AR信号传导和ASI抗性的激活。我们的假设将被验证 通过追求三个特定目的-（1）证明Pdcd4激活mTORC2的缺失有助于ASI （2）剖析Pdcd4的Plk1磷酸化如何调节其作为肿瘤抑制因子的功能;以及 (3)分析Pdcd4的Plk1磷酸化的临床意义。这些相辅相成的目标将是 完成使用生化分析的信号中间体和采用遗传策略， 培养系统、诱导型PCa小鼠模型、患者来源的异种移植物（PDX）和人PCa样品。的 这项研究的基本原理是，它将探讨Plk 1相关活性对Pdcd 4的重要性，并检查 TAT-RBD肽是否是治疗AS I耐药CRPC的新方法。这一贡献意义重大 因为，如果阳性，拟议研究的结果将支持立即进行TAT-RBD肽的临床试验 治疗对ASI无反应的CRPC。多PI团队由Plk1（X. Liu）和Pdcd4（Yang），以及前列腺癌病理学（Allison）和生物统计学（Chen），将能够 及时完成研究工作。

Title: Targeting the Plk1/Pdcd4/mTORC2 signaling to treat castration-resistant prostate cancer Abstract Androgen receptor (AR) signaling is essential for development of prostate cancer (PCa), including castration- resistant prostate cancer (CRPC). Consequently, androgen signaling inhibitors (ASIs), such as abiraterone and enzalutamide, are becoming the first line treatment for CRPC. However, the limited success of ASIs makes it urgent to develop approaches to treat CRPC patients who are no longer responsive to ASIs. Programmed cell death 4 (Pdcd4) is a tumor suppressor, which has been demonstrated to inhibit tumor progression and chemoresistance. Furthermore, Pdcd4 is an androgen-repressed protein that regulates PCa growth and castration resistance. As such, it will be of clinical significance to understand the regulation mechanism of Pdcd4, as it will reveal novel approaches to overcome ASI resistance. Polo-like kinase 1 (Plk1), a critical regulator of cell cycle-related events, is a documented target for PCa treatment. Of note, we previously demonstrated that inhibition of Plk1 enhances the efficacy of ASIs. The long-term goals of this study are to identify druggable signaling pathways that offer effective treatment options for patients with CPRC who are no longer responsive to ASIs. The objective is to define the role of Plk1 in regulating Pdcd4 and to exploit these pathways as a novel therapeutic target for CRPC. Our data show that 1) Pdcd4 enhances the sensitivity to enzalutamide due to inhibition of mTORC2 (the mammalian target of rapamycin complex 2) and AR expression; 2) Plk1 phosphorylation of Pdcd4 results in its protein degradation; and 3) the dominant negative Pdcd4 peptide (TAT- RBD) overcomes ASI resistance in PCa. Based on these observations, we aim to test the central hypothesis that Plk1-associated phosphorylation of Pdcd4 results its degradation, which causes subsequent activation of the mTORC2, eventually contributing to activation of AR signaling and ASI resistance. Our hypothesis will be tested by pursuing three Specific Aims - (1) to demonstrate that loss of Pdcd4 to activate mTORC2 contributes to ASI resistance; (2) to dissect how Plk1 phosphorylation of Pdcd4 regulates its function as a tumor suppressor; and (3) to analyze clinical significance of Plk1 phosphorylation of Pdcd4. These complementary aims will be accomplished using biochemical analyses of signaling intermediates and employing genetic strategies with culture systems, inducible PCa mouse models, patient-derived xenograft (PDX) and human PCa samples. The rationale for the research is that it will probe the importance of Plk1-associated activity to Pdcd4 and to examine whether TAT-RBD peptide is a novel approach to treat ASI-resistant CRPC. This contribution is significant because, if positive, the results of the proposed study will support an immediate clinical trial for TAT-RBD peptide to treat CRPC that not respond to ASIs. The multiple-PI team, consisted of complementary expertise on Plk1 (X. Liu) and Pdcd4 (Yang), as well as prostate cancer pathology (Allison) and biostatistics (Chen), will be able to finish the proposed research in a timely manner.