Molecular basis of androgen receptor mediated gene transcriptional repression

描述（由申请人提供）： 在我的博士前研究中，我与Lirim Shemshedini博士（托莱多大学）一起研究基因 前列腺癌 (PCa) 中雄激素受体 (AR) 的调节。我发表了研究c-Jun对AR反式激活的协同作用以及AR调节SGCα1、ETV1和MRP4基因在PCa中的作用的结果。在我的博士后培训中，我加入了贝斯以色列女执事医疗中心 (BIDMC)/哈佛医学院的 Steven Balk 实验室，专注于了解 AR 在致死性 PCa (CRPC) 中的作用，这种 PCa 会产生对雄激素剥夺疗法 (ADT) 的抵抗力。 Balk 实验室的研究重点是 PCa 和 AR，该实验室拥有多个来源的资金，包括 NIH R01 支持、前列腺癌 SPORE、DoD 前列腺癌计划和 PCF 挑战拨款。我最初的研究是研究 AR 和 HER 信号传导的串扰，然后我转向研究 PCa 中的 TMPRSS2:ERG 融合基因。使用融合阳性细胞系，我建立了明显模拟 CRPC 进展的异种移植模型。研究该模型得出了三个主要发现：（1）SOX9 被确定为融合阳性 PCa 中 TMPRSS2:ERG 的主要下游效应子； (2)瘤内雄激素合成增加介导肿瘤对ADT和CYP17A1抑制的抵抗； (3) CRPC中AR表达增加是由于解除了AR对其自身基因的抑制。 AR 在原发性 PCa 中发挥关键作用，并在 CRPC 中恢复其功能。与基因转录中公认的 AR 激活功能相比，人们对它的抑制功能知之甚少。该提案主要致力于阐明AR介导的基因转录抑制的分子机制。我的 2 年指导阶段的近期目标是探索 AR 通过结合其内含子 2 位点 (ARBS2) 并抑制基因转录介导其自身基因表达的分子基础和临床相关性。还将研究其他几个介导雄激素合成基因（HSD17B6 和 AKR1C3）表达的 AR 抑制基因位点。特别是，将鉴定染色质上的阻遏复合物及其导致 ARBS2 表观遗传修饰并调节其活性的作用。更重要的是，需要阐明将 AR 作为激活剂与阻抑剂区分开的任何独特机制。这些发现也将转化为临床治疗，以增强 ARBS2 的活性，但不影响 AR 激活的基因位点。对于包括3年独立阶段在内的长期目标，AR基因位点的发现将扩展到PCa细胞的整个基因组。利用下一代测序和高通量数据的生物信息学分析的优势，将鉴定PCa细胞中的全局AR介导的抑制元件并研究它们的功能。此外，AR相互作用的阻遏物复合物对基因转录和前列腺癌发生和进展的总体作用也将在提案阶段进行研究。目前的研究结果清楚地表明，我们尚未完全了解 AR 的功能，并且进一步新颖的作用机制可能有助于其对基因子集的调节。由于 AR 调节涉及许多细胞途径的大量基因，因此选择性靶向这些基因子集的潜在能力对于 PCa 和其他疾病的治疗具有广泛的影响。

DESCRIPTION (provided by applicant): In my pre-doctoral study, I worked with Dr. Lirim Shemshedini (University of Toledo) on studying gene regulation by androgen receptor (AR) in prostate cancer (PCa). I have published the results on studying the cooperative role of c-Jun on AR transactivation and the roles of AR regulated SGCα1, ETV1, and MRP4 genes in PCa. In my postdoctoral training, I joined Steven Balk lab at Beth Israel Deaconess Medical Center (BIDMC)/Harvard Medical School and focused on understanding roles of AR in the lethal form of PCa (CRPC) that develops the resistance to androgen deprivation therapy (ADT). Research in the Balk lab is focused on PCa and AR, and the lab has funding from multiple sources including NIH R01 support, a Prostate Cancer SPORE, DoD Prostate Cancer program, and PCF challenge grant. My initial study is on studying the crosstalk of AR and HER signaling and then I moved to the field of studying TMPRSS2:ERG fusion gene in PCa. Using fusion positive cell lines, I have established xenograft models that clearly mimic the progression of CRPC. Studying this model led to three major findings: (1) SOX9 was identified as the major downstream effector of TMPRSS2:ERG in fusion positive PCa; (2) increased intratumoal androgen synthesis mediates tumor resistance to ADT and CYP17A1 inhibition; (3) increased AR expression in CRPC is due to relieving AR suppression of its own gene. AR plays a pivotal role in primary PCa and regains its functions in CRPC. In contrast to the wellestablished AR activation function on gene transcription, its suppression function is poorly understood. This proposal mainly focuses on elucidating the molecular mechanisms of AR mediated gene transcriptional repression. My immediate goal of 2-yrs mentored phase will be to pursue the molecular basis and clinical relevance of AR mediated its own gene expression through binding of its intron 2 site (ARBS2) and repressing the gene transcription. Several other AR-repressed gene loci that mediate expression of androgen synthetic genes (HSD17B6 and AKR1C3) will also be studied. In particularly, the repressor complex on chromatin and their actions that results in the epigenetic modifications on ARBS2 and regulates its activity will be identified. More important, any distinct mechanism that separates AR as an activator versus a repressor needs to be elucidated. These findings will also be translated into clinical therapy to enhance the activity of ARBS2 but not affect AR activated gene loci. For the long-term goal, which includes the 3-yr independence phase, the findings on AR gene loci will be extended to the whole genome of PCa cells. Taking the advantages of next generation sequencing and bioinformatics analysis on high throughput data, the global AR-mediated suppressor elements will be identified in PCa cells and their functions will also be studied. Moreover, the global roles of AR interacted repressor complex on gene transcription and on prostate cancer initiation and progression will also be studied in the phase of proposal. Current findings clearly demonstrate that we do not yet fully understand how AR functions, and that further novel mechanisms of action may contribute to its regulation of subsets of genes. As AR regulates a large number of genes involved in many cellular pathways, the potential ability to selectively target subsets of these genes has broad implications for the therapy of PCa and other diseases.