Characterizing and targeting PRMT5 in autophagy for cancer treatment

摘要 乳腺癌是美国诊断最多的癌症，也是导致癌症死亡的第二大原因。 女人。三阴性乳腺癌(TNBC)占所有BC病例的15%至20%，是最严重的 预后和总存活率。尽管许多靶向药物正在进行临床试验，但没有一种有显著意义 提高了TNBC患者的存活率。因此，确定新的目标和有效战略，包括 对于TNBC患者来说，迫切需要联合治疗。PRMT5正在成为一种潜在的治疗方法 目标。已经开发了几种PRMT5抑制剂，目前正在进行临床试验评估， 包括BC早期的II期试验。与其他BC亚型相比，TNBC表现最强 PRMT5表达。在TNBC患者中，PRMT5的高表达与较低的生存率呈正相关。 尽管它与TNBC的进展有关，但PRMT5的调控及其分子机制 PRMT5促进TNBC仍然难以捉摸。此外，TNBC细胞系表现出不同的敏感性或抗性。 对PRMT5抑制剂的作用，但其作用机制尚不明确。初步研究表明：(1) PRMT5被E3泛素连接酶TRAF6泛素化，TRAF6对其激活和TNBC细胞起重要作用 增殖；(2)PRMT5抑制自噬诱导并催化ULK1精氨酸甲基化；以及(3) 自噬抑制使TNBC细胞对PRMT5抑制剂敏感。基于这些初步发现，我们建议 三个目的是检验我们的中心假设，即TRAF6、PRMT5和ULK1形成调节自噬的新轴 和TNBC进展，PRMT5和自噬抑制剂的联合是一种潜在的抗击策略 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 TRAF6调节PRMT5的激活。在目标2中，我们将定义PRMT5在自噬中的分子功能 通过使ULK1甲基化进行调控。在目标3中，我们将评估PRMT5和自噬的协同效应。 TNBC中的抑制剂。我们相信，我们提议的研究不仅将大大推进当前的 了解PRMT5的调控机制和生物学功能，也为研究PRMT5提供了理论基础 PRMT5和自噬抑制剂联合治疗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.