Characterization of Epigenetic Targets in Prostate Cancer

描述（由申请人提供）：组蛋白甲基转移酶（HMT酶）是染色质修饰剂，在正常发育以及癌症等疾病中发挥重要作用。在我们的研究小组发现EZH 2过表达并与前列腺癌进展和预后不良相关之后（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EZH 2抑制剂用于临床用途。然而，直接靶向EZH 2被认为是有问题的，因为它也在干细胞维持中起作用，并在骨髓疾病中充当肿瘤抑制因子。最近，我们对多种癌症（包括原发性和转移性前列腺肿瘤）的转录组和蛋白质表达分析揭示了另一种HMTase MMSET的过表达，其抑制了EZH 2的表达、功能和临床属性（2）。发现与通过组蛋白H3 K27三甲基化介导的基因沉默相关的EZH 2在MMSET的上游协同表达和起作用，MMSET介导与活性转录相关的H3 K36二甲基化。鉴于MMSET作为EZH 2介导的肿瘤发生的效应子的高表达和功能意义，以及观察到MMSET通过调节AR信号传导和基因表达在前列腺癌中起关键作用，我们假设MMSET可能代表前列腺癌中的重要治疗靶点。在治疗靶向MMSET的努力中，我们已经鉴定了一种先导探针化合物，3-羟基-2-喹喔啉硫醇（MCTP 39），一种含有巯基的肼苯哒嗪（已知的表观遗传药物）异构体，发现其在体内减弱MMSET酶活性。此外，显示MCTP 39特异性地抑制过表达MMSET的癌细胞系的生长和侵袭特性。在这里，我们提出进行以下具体目标：1）MMSET在前列腺癌中的综合功能研究; 2）阐明MMSET在AR信号传导中的作用; 3）表征先导MMSET抑制剂化合物MCTP 39。成功完成本提案中概述的目标将提高对MMSET作用及其在AR介导的前列腺癌进展中的重要性的理解，并可能产生一种有前途的小分子抑制剂，可进一步开发用于临床。所建议的项目和支持的初步数据是根据申请人的原始想法构思的。Chinnaiyan博士在密歇根州转化病理学中心提供的跨学科环境，具有应用高通量技术和生物信息学方法研究癌症突变景观并确定相关生物标志物和治疗靶点的丰富经验，是支持申请人科学职业目标的理想环境。申请人的大量初步数据证明了这一点，这些数据导致了多篇第一作者和合著者在高影响力期刊上发表论文。Chinnaiyan博士对申请人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人转变为癌症生物学领域的独立研究者，特别是将基于基因组的发现转化为临床应用是必不可少的。

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.