Epigenetic Reprogramming of AR Function in CRPC

表观遗传学改变被认为在癌症的发生和肿瘤的发展中发挥重要作用，包括CRPC的发展。包括我们自己在内的几个研究小组的工作表明，雄激素受体(AR)在CRPC中继续发挥着关键作用。此外，我们实验室最近在雄激素依赖型前列腺癌和CRPC模型中定义AR周期的工作表明，AR被招募到CRPC中不同的基因组位置，在那里它执行不同的转录程序。这些CRPC选择性AR结合位点含有活性转录增强子特有的表观遗传染色质标记，并调控一系列细胞周期调控基因，包括CRPC生长所需的CDK1、CCNB1、CDC20和UBE2C。这些相同的基因在真实的CRPC病例中过度表达。 组蛋白甲基转移酶EZH2是一种已知的通过H3K27甲基化在基因沉默中发挥作用的组蛋白甲基转移酶，在CRPC中上调。在初步研究中，我们发现EZH2可以募集到CRPC选择性AR靶基因的顺式调控元件，如CDK1和UBE2C，在前列腺癌细胞中与AR形成复合体。令人惊讶的是，EZH2直接上调了CRPC细胞中的这些AR靶点，而不是雄激素依赖型前列腺癌细胞中的这些AR靶点。此外，EZH2是CRPC细胞生长所必需的。 因此，本研究将检验的总体假设是，表观遗传调控因子EZH2对CRPC中的AR功能进行重新编程，以刺激CRPC依赖AR的生长所需的一组细胞周期调控基因的诱导。|n目标1我们将分析CRPC细胞中依赖于EZH2的基因表达谱和循环；在目标2中，我们将确定AR和EZH2之间相互作用在调节特定的由AR上调的CRPC基因亚群中的机制；在目标3中，我们将利用Biospecimen和动物模型Core来分析CRPC异种移植模型中的基因表达、表观染色质修饰、EZH2和AR循环以及DNase I超敏反应，以验证细胞培养的结果。

Epigenetie alterations have been hypothesized to play important roles in carcinogenesis and tumor progression, including the development of CRPC. Work from several groups including our own demonstrates a continued critical role for the androgen receptor (AR) in CRPC. In addition, recent work from our lab defining the AR cistromes in a model of androgen-dependent prostate cancer and CRPC has shown that AR is recruited to distinct genomic sites in CRPC where it executes a distinct transcriptional program. These CRPC selective AR binding sites harbor epigenetie chromatin marks characteristic of active transcriptional enhancers and regulate a set of cell cycle regulatory genes including CDK1, CCNB1, CDC20 and UBE2C that are required for CRPC growth. These same genes are over-expressed in authentic cases of CRPC. EZH2, a SET domain histone methyltransferase known to play a role in gene silencing through H3K27 methylation is up-regulated in CRPC. In preliminary studies we have found that EZH2 can be recruited to the cis-regulatory elements of CRPC selective AR target genes such as CDK1 and UBE2C, forming a complex with AR in prostate cancer cells. Surprisingly, EZH2 directly up-regulates these AR targets in CRPC cells but not in androgen-dependent prostate cancer cells. In addition EZH2 is required for the growth of CRPC cells. Thus the overall hypothesis that will be tested in this study is that the epigenetie regulator EZH2 reprograms AR function in CRPC to stimulate the induction of a set of cell cycle regulatory genes required for the AR dependent growth of CRPC. |n Aim 1 we will analyze EZH2-dependent gene expression profiles and cistromes in CRPC cells; in Aim 2 we will determine the mechanisms underlying the interaction between AR and EZH2 in modulating the specific subset of genes up-regulated in CRPC by AR; and in Aim 3 we will utilize the Biospecimen and Animal Models Core to profile gene expression, epigenetie chromatin modifications, EZH2 and AR cistromes and DNAse I hypersensitivity in xenograft models of CRPC in order to validate the findings from cell culture.