Novel roles of microRNA in androgen receptor signaling

描述（由申请人提供）：雄激素受体（AR）在前列腺癌（CaP）的发生和发展中起着重要作用。初步数据显示，与良性前列腺相比，微rna Let-7c在CaP细胞和组织中的表达下调。Let-7c抑制AR表达，过表达Let-7c降低AR活性，提示Let-7c可能参与了CaP细胞的AR调节。其他研究表明，let-7c介导的AR抑制是通过c-myc进行的，c-myc是一种在前列腺癌中持续过表达的AR激活剂。此外，let-7c在体外和体内均能抑制CaP细胞的生长。此外，对人类前列腺标本的分析表明，Let-7c与AR表达呈负相关。这些数据表明，Let-7c在调节AR信号通路和CaP的发生进展中起着重要作用。本研究旨在了解一种新的microRNA (miRNA) Let-7c -myc介导的AR信号通路及其相互作用。本研究提出了三个具体目标。目的1是确定let-7c对细胞生长和雄激素反应的影响。我们将在雄激素应答的人前列腺癌细胞系中敲低Let-7c的表达，并评估这种下调对细胞生长和雄激素应答的影响。相反，我们将在去势抵抗性前列腺癌细胞中过表达Let-7c，以确定它是否可以抑制细胞生长并导致雄激素依赖状态的逆转。目的2是表征let-7c作为AR和c-myc的调制器。我们将描述let-7c介导的AR抑制的潜在机制以及c-myc在这一过程中的作用。我们将研究let-7c是否抑制AR表达及其转录功能，以及是否通过抑制c-myc实现。我们将确定let-7c是否直接靶向c-myc RNA，以及c-myc对AR启动子的募集是否受到影响。此外，我们将探讨let-7c在前列腺癌细胞中的表达是如何被调节的。目的3是确定let-7c、AR和c- myc表达与前列腺癌进展之间的关系。我们将在临床前列腺癌标本中检测Let-7c、AR和c-myc的关系，并确定这三种重要分子的水平是否与前列腺癌患者标本的疾病进展和去势抵抗相关。如果一个连接AR、c-myc和microrna的新途径被发现，它将更好地理解导致前列腺癌发生和进展的分子机制。

DESCRIPTION (provided by applicant): The androgen receptor (AR) plays an important role in the initiation and progression of prostate cancer (CaP). Preliminary data show that expression of microRNA Let-7c is downregulated in CaP cells and tissues compared to benign prostate. Let-7c suppresses AR expression and overexpression of let-7c reduces AR activity, suggesting that let-7c may contribute to AR modulation in CaP cells. Additional studies suggest that let-7c- mediated AR suppression is via c-myc, an AR activator that is consistently overexpressed in prostate cancer. In addition, let-7c decreases the growth of CaP cells in vitro and in vivo. Furthermore, analysis of specimens from human prostate indicates a reverse correlation between Let-7c and AR expression. These data suggest that Let-7c plays an important role in regulating AR signaling and the development and progression of CaP. This proposal is aimed at understanding a novel microRNA (miRNA) let-7c-myc- mediated AR signaling pathway and the interaction between them. Three specific aims are proposed to this study. Aim 1 is to determine the effect of let-7c on cell growth and androgen responsiveness. We will knockdown Let-7c expression in androgen- responsive human prostate cancer cell lines, and assess the effects of such downregulation on the growth and on the androgen responsiveness of the cells. Conversely, we will overexpress Let-7c in castration-resistant prostate cancer cells to determine whether it can suppress cell growth and cause a reversal to an androgen- dependent state. Aim 2 is to characterize let-7c as a modulator of AR and c-myc. We will characterize the potential mechanisms of let-7c-mediated AR suppression and the role of c-myc in this process. We will study whether let-7c suppresses AR expression and its transcriptional functions, and whether it is via suppression of c-myc. We will determine whether let-7c directly targets c-myc RNA and whether c-myc recruitment to AR promoter is affected. Furthermore, we will explore how let-7c expression is regulated in prostate cancer cells. Aim 3 is to determine the relationship between let-7c, AR, and c- myc expression and prostate cancer progression. We will test the relationship of Let-7c, AR and c-myc in clinical prostate cancer specimens, and determine whether the levels of these three important molecules correlate with disease progression and castration resistance in specimens from patients with prostate cancer. If a novel pathway that connects AR, c-myc, and microRNAs is identified, it will gain a better understanding of the molecular mechanisms leading to prostate cancer development and progression.