Characterizing and targeting PRMT5 in autophagy for cancer treatment

摘要 乳腺癌是美国最常见的癌症，也是癌症死亡的第二大原因 妇女三阴性乳腺癌（TNBC）占所有BC病例的15%至20%，并且具有最严重的 预后和总体生存率。尽管许多靶向药物正在进行临床试验，但没有一种药物具有显著的 提高了TNBC患者的生存率。因此，确定新的目标和有效的战略，包括 联合疗法是TNBC患者迫切需要的。PRMT 5正在成为一种潜在的治疗方法 目标已经开发了几种PRMT 5抑制剂，目前正在临床试验中进行评估， 包括早期BC的第二阶段试验。与其他BC亚型相比，TNBC显示出最强的 PRMT 5表达。PRMT 5高表达与TNBC患者的较差生存率正相关。 尽管PRMT 5与TNBC进展相关，但PRMT 5调节和调节TNBC进展的分子机制仍然存在。 PRMT 5促进TNBC仍然难以捉摸。此外，TNBC细胞系显示出不同的敏感性或抗性， PRMT 5抑制剂，但机制尚未确定。初步研究表明：（1） PRMT 5被E3泛素连接酶TRAF 6泛素化，这对于其活化和TNBC细胞增殖是重要的。 （2）PRMT 5抑制自噬诱导并催化ULK 1精氨酸甲基化;和（3） 自噬抑制使TNBC细胞对PRMT 5抑制剂敏感。基于这些初步发现，我们建议 三个目的是测试我们的中心假设，即TRAF 6，PRMT 5和ULK 1形成一个新的轴来调节自噬 和TNBC进展，PRMT 5和自噬抑制剂的组合是对抗TNBC进展的潜在策略。 TNBC。为了验证我们的假设，我们提出了三个目标。在目标1中，我们将定义 TRAF 6调节PRMT 5活化。在目标2中，我们将定义PRMT 5在自噬中的分子功能 通过甲基化ULK 1进行调节。在目标3中，我们将评估PRMT 5和自噬的协同作用。 TNBC中的抑制剂。我们相信，我们建议的研究不仅将大大推进目前的 了解PRMT 5的调节机制和生物学功能，还提供了一个基本原理， 在一些实施方案中，本发明提供PRMT 5和自噬抑制剂的组合以治疗TNBC。

Abstract Breast cancer (BC) is the most diagnosed cancer and the second leading cause of cancer death in American women. Triple negative breast cancer (TNBC) accounts for 15% to 20% of all BC cases and has the worst prognosis and overall survival. Although many targeted agents are ongoing clinical trials, none have significantly improved the survival in TNBC patients. Thus, the identification of novel targets and effective strategies, including combination therapies, are urgent needed for TNBC patients. PRMT5 is emerging as a potential therapeutic target. Several PRMT5 inhibitors have been developed and are currently being evaluated in clinical trials, including a phase II trial for early-stage BC. Compared to other BC subtypes, TNBC displays the strongest PRMT5 expression. High PRMT5 expression is positively correlated with poorer survival rate in TNBC patients. Despite its association with TNBC progression, PRMT5 regulation and the molecular mechanisms by which PRMT5 promotes TNBC remain elusive. Moreover, TNBC cell lines display differential sensitivity or resistance to PRMT5 inhibitors, but the mechanisms have yet to be defined. Our preliminary studies demonstrate that: (1) PRMT5 is ubiquitinated by E3 ubiquitin ligase TRAF6, which is important for its activation and TNBC cell proliferation; (2) PRMT5 suppresses autophagy induction and catalyzes ULK1 arginine methylation; and (3) autophagy inhibition sensitizes TNBC cells to PRMT5 inhibitor. Based on these preliminary findings, we propose three aims to test our central hypothesis that TRAF6, PRMT5, and ULK1 form a novel axis to regulate autophagy and TNBC progression, and combination of PRMT5 and autophagy inhibitors is a potential strategy to combat TNBC. To validate our hypothesis, we propose three Aims. In Aim 1, we will define the mechanism through which TRAF6 regulates PRMT5 activation. In Aim 2, we will define the molecular function of PRMT5 in autophagy regulation by methylating ULK1. In Aim 3, we will evaluate the synergistic effect of PRMT5 and autophagy inhibitors in TNBC. We believe that our proposed studies will not only substantially advance current understanding of regulatory mechanism and biological function of PRMT5, but also provide a rationale for combination of PRMT5 and autophagy inhibitors to treat TNBC.