Polycomb -Independent Functions of EZH2 in Castration Resistant Prostate Cancer

描述(由申请人提供)：抗去势前列腺癌(CRPC)仍然是一个主要的临床挑战，因为肿瘤在这个阶段基本上是无法治愈的。包括我们在内的累积证据表明，甲基转移酶EZH2是治疗CRPC的一个有前途的药物靶点。尽管EZH2最为人所知的是它作为多梳抑制复合体2(PRC2)的催化亚单位，它使Lys27上的组蛋白H3甲基化，从而使基因沉默，但EZH2的其他功能已经被指出。这与我们之前的工作一致，表明EZH2在CRPC中具有特定的反式激活功能，这需要它的酶活性和作为关键转录因子(如雄激素受体(AR))的辅助激活剂的能力。通过确定抑制EZH2甲基转移酶活性的靶向抑制剂，我们能够评估EZH2在CRPC细胞中的药理抑制的生物学效应。事实上，EZH2抑制剂显著抑制了前列腺癌细胞的生长。有趣的是，CRPC细胞中的抑制剂并没有上调EZH2抑制基因的表达，而是显著下调了EZH2激活基因的水平。此外，AR甲基化受EZH2甲基转移酶活性的调节。同时，我们的蛋白质组学分析发现，众所周知的AR信号调节因子？-catenin是一种与EZH2相互作用的蛋白质，与PRC2复合体的其他成分没有关联。所有这些令人信服的数据支持了我们的假设，即EZH2发挥着与AR信号无关的多梳独立功能，这对CRPC的发育至关重要。因此，我建议建立临床前模型，以检测EZH2抑制剂单独或联合AR拮抗剂对前列腺癌的疗效(目标1)，并研究由EZH2、AR以及�-catenin组成的转录网络在调控CRPC相关基因中的作用(目标2)。我将进一步鉴定与EZH2相互作用的新蛋白质，并确定其致癌功能(目标3)。我相信，我们的研究将为这一领域增添一个全新的维度 为癌症研究提供了令人信服的基础，为侵袭性实体肿瘤的临床实践提供了令人信服的基础。

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.