Molecular basis of androgen receptor mediated gene transcriptional repression

描述(申请人提供)：我在博士期间开始在托莱多大学的Lirim Shemshedini实验室研究前列腺癌的雄激素受体(AR)功能。在这段时间里，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。我已经发表了关于c-jun在AR反式激活中的协同作用以及AR调节的SGC1、ETV1和MRP4基因在前列腺癌中的作用的研究结果。在我获得博士学位后，我加入了贝丝以色列女执事医学中心(BIDMC)/哈佛医学院的Steven Balk实验室。这个癌症生物学项目由血液肿瘤科负责管理，该科由一大批从事患者护理、临床、转化和基础癌症研究的教职员工组成。巴尔克实验室的研究重点是PCA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计划来源。在实验室里，我继续研究AR在对雄激素剥夺疗法(ADT)产生抵抗力的致命性前列腺癌中的作用。这种癌症被称为耐阉割前列腺癌，简称CRPC。我最初的研究重点是HER信号对AR的调控，然后我进入了研究TMPRSS2：ERG融合基因在前列腺癌中的领域。利用融合阳性细胞系，我已经建立了明显模拟CRPC进展的异种移植模型。对这一模型的研究导致了两个主要发现：(1)肿瘤内雄激素合成增加，介导了肿瘤对ADT和CYP17A1的抑制；(2)CRPC中AR表达的增加是由于其自身基因的AR抑制。AR在初级PCa中起着关键作用，并在CRPC中恢复其功能。与AR对基因转录的激活作用不同，人们对其抑制作用知之甚少。这一建议主要集中在阐明AR介导的基因转录抑制的分子机制。我在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)并抑制基因转录而介导其自身基因表达的分子基础和临床意义。其他几个调节雄激素合成基因(HSD17B6和AKR1C3)表达的AR抑制基因位点也将被研究。特别是，染色质上的阻遏复合体及其导致ARBS2的表观遗传修饰并调节其活性的作用将被识别。更重要的是，任何将AR区分为激活剂和抑制物的不同机制都需要阐明。这些发现也将被转化为临床治疗，以增强ARBS2的活性，而不影响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基因位点的研究结果将扩展到PCa细胞的整个基因组。利用下一代测序和高通量数据生物信息学分析的优势，将在PCa细胞中鉴定由AR介导的全局抑制元件，并研究它们的功能。此外，AR相互作用的抑制子复合体在基因转录和前列腺癌发生和发展中的全球作用也将在提案阶段进行研究。目前的发现清楚地表明，我们还没有完全了解AR是如何发挥作用的，进一步的新的作用机制可能有助于它对基因亚集的调节。由于AR调节许多细胞通路中涉及的大量基因，因此选择性地靶向这些基因亚群的潜在能力对前列腺癌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.