Polycomb -Independent Functions of EZH2 in Castration Resistant Prostate Cancer

描述（由申请人提供）：去势抵抗性前列腺癌（CRPC）仍然是一个主要的临床挑战，因为这个阶段的肿瘤在很大程度上是不可治愈的。包括我们在内的累积证据表明，甲基转移酶EZH 2是CRPC治疗的一个有希望的药物靶点。虽然EZH 2最为人所知的是其作为Polycomb抑制复合物2（PRC 2）的催化亚基的作用，PRC 2甲基化lys 27上的组蛋白H3以进行基因沉默，但已经表明EZH 2的其他功能。这与我们先前的工作一致，显示了EZH 2在CRPC中的特异性反式激活功能，这需要其酶活性和作为关键转录因子如雄激素受体（AR）的共激活剂的能力。通过鉴定针对EZH 2甲基转移酶活性的靶向抑制剂，我们能够评估CRPC细胞中EZH 2的药理学抑制的生物学效应。事实上，EZH 2抑制剂显著延缓了前列腺癌细胞的生长。有趣的是，CRPC细胞中的抑制剂没有上调EZH 2抑制基因的表达，而是显著下调EZH 2激活基因的水平。此外，AR甲基化通过EZH 2甲基转移酶活性调节。同时，我们的蛋白质组分析发现？catenin是AR信号传导的一种众所周知的调节因子，是与PRC 2复合物的其他组分不相关的EZH 2相互作用蛋白之一。所有这些令人信服的数据加强了我们的假设，即EZH 2发挥与AR信号传导相关的多梳独立功能，这对CRPC的发展至关重要。因此，我建议建立临床前模型，以测试EZH 2抑制剂单独或与AR拮抗剂联合治疗前列腺癌的疗效（目的1），并研究由EZH 2、AR以及β-catenin组成的转录网络对CRPC相关基因的调控（目的2）。我将进一步鉴定与EZH 2相互作用的新蛋白质，并确定其致癌功能（目的3）。我相信我们的研究将为这个领域增添一个全新的层面 的癌症研究，并提供了一个令人信服的基础，为临床实践的侵袭性实体瘤。

DESCRIPTION (provided by applicant): Castration resistant prostate cancer (CRPC) remains a major clinical challenge, as tumors at this stage are largely incurable. Cumulative evidence, including ours, suggests that the methyltransferase EZH2 represents a promising drug target for CRPC treatment. Although EZH2 is best known for its role as the catalytic subunit of Polycomb repressive complex 2 (PRC2), which methylates histone H3 on lys27 for gene silencing, additional functions of EZH2 have been indicated. It is in consistence with our prior work showing a specific transactivation function of EZH2 in CRPC, which requires its enzymatic activity and the ability as a co-activator for critical transcription factors such as the androgen receptor (AR). With the identification of targeted inhibitors against EZH2 methyltransferase activity, we were able to evaluate the biological effects of pharmacological inhibition of EZH2 in CRPC cells. Indeed, EZH2 inhibitor significantly retarded the growth of prostate cancer cells. Intriguingly, the inhibitor in CRPC cells didn't up-regulate the expression of EZH2-repressed genes, but instead significantly down-regulated the levels of EZH2-activated genes. Furthermore, AR methylation was modulated by EZH2 methyltransferase activity. Meanwhile, our proteomic analysis found ?-catenin, a well-known regulator of AR signaling, as one of EZH2-interacting proteins that are not associated with other components of PRC2 complex. All these compelling data reinforce our hypothesis that EZH2 exerts a polycomb-independent function linking to the AR signaling, which is critical for CRPC development. Therefore, I proposed to set up the preclinical models to test the efficacy of EZH2 inhibitor, either alone or combined with AR antagonists, in prostate cancer (Aim 1), and investigate the transcriptional network composed of EZH2, AR as well as �-catenin in regulation of CRPC- related genes (Aim 2). I will further identify novel proteins that interact with EZH2 and determine its oncogenic functions (Aim 3). I am confident that our research will add an entirely new dimension to the field of cancer research, and provide a compelling foundation for the clinical practice of aggressive solid tumors.