AR and GDNF signaling tune growth and differentiation in the developing prostate

项目摘要/摘要 雄激素受体(AR)介导的前列腺发育中断已被证明使人类和啮齿动物易患前列腺癌，前列腺癌是男性主要的泌尿系统疾病。在人类和啮齿动物中，前列腺由胚胎的泌尿生殖窦(UGS)形成。AR被认为控制了诱导性UGS间充质细胞中形态发生基因的表达，进而促进了前列腺上皮的增殖和分化。然而，AR调节的形态发生基因的性质和AR控制前列腺形成的机制尚不清楚。本实验室已鉴定出胶质细胞源性神经营养因子及其受体(GfR-α-1)是小鼠前列腺和尿路中雄激素抑制基因。与AR介导的对胶质细胞源性神经营养因子信号的抑制一致，通过受体酪氨酸激酶Ret和非受体α家族的GDNF-GFRSrc-1信号通路可能有助于抑制前列腺的形态发生。本研究的目的是阐明GDNF信号在前列腺发育中的作用，并确定其受AR信号的调节。这项拟议的研究具有重要意义，因为它将导致对负责前列腺发育的中央发育途径的彻底理解，包括AR和GDNF信号通路之间的串扰。这样的理解将为泌尿生殖系统疾病的病因学提供关键线索，并从机制上洞察前列腺癌中重新出现的关键发育事件。识别调节前列腺发育的信号节点将为未来治疗老年男性病理性前列腺细胞增殖和分化的药物发现策略和治疗机会提供信息。本实验室用创新的UGS器官培养发表的初步结果表明，在无雄激素的情况下，GDNF促进表达GFRα1的UGS间充质和上皮细胞的增殖。与RET在诱导性间充质中的定位一致，抑制RET选择性地阻断GDNF诱导的间充质细胞的增殖。我们还表明，雄激素诱导发育中的前列腺上皮细胞的增殖和分化，而GDNF抑制雄激素的作用。此外，AR可减少胶质细胞源性神经营养因子及其受体α-1的转录，而胶质细胞源性神经营养因子信号转导途径可降低AR的转录水平。因此，我们的假设是，GDNF信号通过RET介导的和RET非依赖的途径调节不同类型的前列腺细胞的生长和分化，AR和GDNF信号的相互下调发挥协调前列腺发育的作用。为了验证这一假设，本文提出了三个具体目标。目的1将阐明GDNF信号在前列腺发育中控制细胞增殖的机制。目的2将推断GDNF信号调节前列腺形成过程中细胞分化的机制。目标3将研究AR和GDNF信号通路在前列腺发育中的串扰。为了实现这些目标，我们将使用跨学科的方法，通过UGS器官培养和互补的小鼠模型来评估AR和GDNF信号通路的前列腺发育和功能串扰。

PROJECT SUMMARY/ABSTRACT Disruption of androgen receptor (AR)-mediated prostate development has been shown to predispose humans and rodents to prostate neoplasia, a leading urologic disease in men. In humans and rodents, the prostate gland forms from the embryonic urogenital sinus (UGS). AR is thought to control the expression of morphogenetic genes in inductive UGS mesenchyme, which in turn promotes proliferation and differentiation of the prostatic epithelium. However, the nature of the AR-regulated morphogenetic genes and the mechanisms whereby AR controls prostate formation are not understood. Our laboratory has identified glial cell line-derived neurotrophic factor (GDNF) and it receptor (GFRα1) as androgen-repressed genes in the UGS and prostate of mice. Consistent with AR-mediated suppression of GDNF signaling, GDNF-GFRα1 signaling via receptor tyrosine kinase RET and non-receptor Src family kinases may serve to inhibit prostate morphogenesis. The goal of this proposed research is to elucidate the function of GDNF signaling in prostate development and determine its regulation by AR signaling. This proposed research is significant because it will lead to a thorough understanding of the central developmental pathways responsible for prostate development, including crosstalk between AR and GDNF signaling pathways. Such understanding will provide crucial clues to the etiology of urogenital disorders and mechanistic insight into key developmental events that reemerge in prostate neoplasia. Identification of signaling nodes that regulate prostate development will inform future drug discovery strategies and therapeutic opportunities for treatment of pathologic prostate cell proliferation and differentiation in the aging male. Preliminary results published from our laboratory using innovative UGS organ culture demonstrate that in the absence of androgen, GDNF increases proliferation of UGS mesenchymal and epithelial cells, which express GFRα1. Consistent with RET localization in the inductive mesenchyme, inhibition of RET selectively blocks GDNF-induced proliferation of mesenchymal cells. We also show that androgen induces proliferation and then differentiation of epithelial cells in the developing prostate, whereas GDNF inhibits the effects of androgen. Further, AR reduces transcription of Gdnf and Gfrα1 while GDNF signaling lessens AR transcription. Therefore, our hypothesis is that GDNF signaling via RET-mediated and RET-independent pathways regulates growth and differentiation of distinct prostate cell types and that reciprocal down-regulation of AR and GDNF signaling functions to orchestrate prostate development. To test this hypothesis, three specific aims are proposed. Aim 1 will elucidate mechanisms whereby GDNF signaling controls cell proliferation in prostate development. Aim 2 will deduce mechanisms whereby GDNF signaling regulates cyto-differentiation in prostate formation. Aim 3 will examine crosstalk between AR and GDNF signaling pathways in prostate development. To achieve these aims, we will use interdisciplinary approaches to assess prostate development and functional crosstalk of AR and GDNF signaling pathways using UGS organ culture and complementary mouse models.