Characterization of Epigenetic Targets in Prostate Cancer

描述(申请人提供)：组蛋白甲基转移酶(HMTase)是染色质修饰物，在正常发育和癌症等疾病中发挥重要作用。随着我们小组发现EZH2过度表达并与前列腺癌进展和不良预后相关(1)，它已成为癌症中研究最充分的HMTase，多个研究小组和制药公司正在寻求开发用于临床的EZH2抑制剂。然而，直接靶向EZH2被认为是有问题的，因为它也在干细胞维持中发挥作用，并在髓系疾病中扮演肿瘤抑制因子的角色。最近，我们对包括原发癌和转移性前列腺癌在内的多种癌症的转录组和蛋白质表达分析显示，另一种HMTase MMSET过度表达，与EZH2的表达、功能和临床特征相平行(2)。EZH2与组蛋白H3K27三甲基化介导的基因沉默有关，它在MMSET的上游协同表达并发挥作用，MMSET介导H3K36的二甲基化与激活转录相关。鉴于MMSET作为EZH2介导的肿瘤发生的效应因子的高表达和功能意义，以及观察到MMSET通过调节AR信号和基因表达在前列腺癌中发挥关键作用，我们推测MMSET可能是前列腺癌的一个重要治疗靶点。为了针对MMSET进行治疗，我们已经确定了一种先导探针化合物，3-羟甲基-2-喹恶啉硫醇(MCTP39)，这是一种含有肼(已知的表观遗传药物)的异构体的硫醇，被发现在体内可以减弱MMSET的酶活性。此外，MCTP39被证明对过度表达MMSET的癌细胞株的生长和侵袭特性具有抑制作用。在这里，我们建议开展以下具体目标：1)MMSET在前列腺癌中的综合功能研究；2)阐明MMSET在AR信号转导中的作用；3)鉴定先导MMSET抑制剂化合物MCTP39。成功完成这项提案中概述的目标将提高对MMSET的作用及其在AR介导的前列腺癌进展中的重要性的理解，并可能产生一种有希望的小分子抑制剂，可进一步开发用于临床。建议的项目和支持的初步数据是根据申请者的原始想法构思的。Chinnaiyan博士在密歇根翻译病理学中心提供的跨学科环境是支持申请者科学职业目标的理想环境，该中心拥有应用高通量技术和生物信息学方法研究癌症突变图景和识别相关生物标记物和治疗靶点的丰富经验。申请者广泛的初步数据就是例证，这些数据导致在高影响力期刊上发表了多篇第一作者和合著者的论文。Chinnaiyan博士对申请者的职业目标给予了全力支持，并鼓励他将来将这些项目转移到他的独立实验室。总体而言，NIH独立之路奖对于申请者转变为癌症生物学领域的独立调查者是不可或缺的，特别是在将基于基因组的发现转化为临床应用方面。

DESCRIPTION (provided by applicant): Histone methyltransferases (HMTases) are chromatin modifiers that play an important role in normal development as well as in diseases such as cancer. Following the discovery by our group that EZH2 is overexpressed and associates with prostate cancer progression and poor prognosis (1), it has become the most well-studied HMTase in cancer with multiple research groups and pharmaceutical companies in pursuit of developing EZH2 inhibitors for clinical use. However, direct targeting of EZH2 is deemed problematic since it also has a role in stem cell maintenance and acts as a tumor suppressor in myeloid diseases. More recently, our transcriptome and protein expression analysis across multiple cancers including primary and metastatic prostate tumors revealed overexpression of another HMTase, MMSET, that paralleled EZH2 expression, function and clinical attributes (2). EZH2, which is associated with gene silencing mediated through histone H3K27 trimethylation, was found to be coordinately expressed and function upstream of MMSET, which mediates H3K36 dimethylation associated with active transcription. Given the high expression and functional significance of MMSET as an effector of EZH2-mediated oncogenesis as well as the observation that MMSET plays a critical role in prostate cancer by regulating AR signaling and gene expression, we hypothesize that MMSET potentially represents an important therapeutic target in prostate cancer. In an effort to therapeutically target MMSET we have identified a lead probe compound, 3-hydraxino-2-quinoxalinethiol (MCTP39), a thiol group containing isomer of hydralazine (a known epigenetic drug), that was found to attenuate MMSET enzymatic activity in vivo. Further, MCTP39 was shown to inhibit growth and invasive properties specifically of cancer cell lines that overexpress MMSET. Here, we propose to carry out the following Specific Aims: 1) Integrative functional study of MMSET in prostate cancer; 2) Elucidation of the role of MMSET in AR signaling; 3) Characterization of a lead MMSET inhibitor compound MCTP39. Successful completion of the Aims outlined in this proposal will improve understanding of the role of MMSET and its importance in AR-mediated prostate cancer progression, and may yield a promising small molecule inhibitor that could be further developed for clinical use. The proposed projects and the supporting preliminary data were conceived based on the applicant's original ideas. The cross-disciplinary environment provided by Dr. Chinnaiyan at the Michigan Center of Translational Pathology, which has vast experience applying high-throughput technologies and bioinformatics approaches for studying the mutational landscape of cancer and identifying associated biomarkers and therapeutic targets, serves as an ideal environment for supporting the applicant's scientific career goals. This is exemplified by the applicant's extensive preliminary data that has led to multiple first author and co-author papers in high impact journals. Dr. Chinnaiyan has extended his full support towards the applicants' career goals and has encouraged him to transfer these projects to his independent lab in the future. Overall, an NIH Pathway to Independence Award will be indispensable for the applicant to transition into an independent investigator in the field of cancer biology specifically in translating genome-based discoveries into clinical applications.