Molecular basis of androgen receptor mediated gene transcriptional repression

描述（由申请人提供）：博士期间在美国托莱多大学Lirim Shemshedini实验室开始研究雄激素受体（AR）在前列腺癌中的功能。在这段时间的研究中，我主要关注AR共激活因子和AR靶基因在前列腺癌（PCa）中的作用。发表了c-Jun在AR转激活中的协同作用以及AR调控的SGC¿1、ETV1、MRP4基因在PCa中的作用研究结果。在我获得博士学位后，我加入了贝斯以色列女执事医疗中心(BIDMC)/哈佛医学院的史蒂文·巴尔克实验室。该癌症生物学项目由血液学肿瘤学部门管理，该部门由参与患者护理，临床，转化和基础癌症研究的大型教师组成。Balk实验室的研究重点是前列腺癌和AR，该实验室的资金来自多个来源，包括NIH R01支持，前列腺癌孢子和国防部前列腺癌项目来源。在实验室里，我继续研究AR在致死性前列腺癌中的作用，这种前列腺癌会对雄激素剥夺疗法（ADT）产生耐药性。这种癌症被称为去势抵抗性前列腺癌，简称CRPC。我最初的研究方向是HER信号对AR的调控，后来转入了PCa中TMPRSS2:ERG融合基因的研究领域。使用融合阳性细胞系，我建立了异种移植模型，可以清楚地模拟CRPC的进展。该模型的研究有两个主要发现：(1)瘤内雄激素合成增加，介导肿瘤对ADT和CYP17A1抑制的抵抗；(2) CRPC中AR表达升高是由于AR抑制自身基因所致。AR在原发性前列腺癌中起关键作用，并在CRPC中恢复其功能。与已知的AR对基因转录的激活作用相反，其抑制作用尚不清楚。本文主要研究AR介导的基因转录抑制的分子机制。我的2年指导期的直接目标将是通过结合其内含子2位点（ARBS2）和抑制基因转录来追求AR介导其自身基因表达的分子基础和临床相关性。其他几个介导雄激素合成基因（HSD17B6和AKR1C3）表达的ar抑制基因位点也将被研究。特别是，染色质上的抑制复合物及其作用将导致ARBS2的表观遗传修饰并调节其活性。更重要的是，任何区分AR作为激活剂和抑制剂的独特机制都需要阐明。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年独立期在内的长期目标，AR基因位点的发现将扩展到PCa细胞的全基因组。利用下一代测序和高通量数据的生物信息学分析的优势，将在PCa细胞中鉴定全局ar介导的抑制元件并研究其功能。此外，AR相互作用抑制复合物在基因转录和前列腺癌发生和发展中的全局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，并且进一步的新作用机制可能有助于其对基因亚群的调节。由于AR调节了参与许多细胞通路的大量基因，因此选择性靶向这些基因亚群的潜在能力对PCa和其他疾病的治疗具有广泛的意义。

DESCRIPTION (provided by applicant): I started to study androgen receptor (AR) functions in prostate cancer in Lirim Shemshedini lab (University of Toledo) during my Ph.D.. In this period of study, I mainly focused on the roles of AR coactivators and AR target genes 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 SGC¿1, ETV1, and MRP4 genes in PCa. After I received my Ph.D., I joined Steven Balk lab at Beth Israel Deaconess Medical Center (BIDMC)/Harvard Medical School. This Cancer Biology Program is administratively housed within the Hematology-Oncology Division, which comprises a large faculty involved in patient care, clinical, translational, and basic cancer research. 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, and DoD Prostate Cancer program sources. In the lab, I continued to study the roles of AR in the lethal form of PCa that develops the resistance to androgen deprivation therapy (ADT). This form of cancer is called castration resistant prostate cancer, or CRPC. My initial study is focusing on AR regulation by 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 two major findings: (1) increased intratumoal androgen synthesis that mediates tumor resistance to ADT and CYP17A1 inhibition; (2) increased AR expression in CRPC is due to AR suppression of its own gene. AR plays a pivotal role in primary PCa and regains its functions in CRPC. In contrast to the well- established 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.