Androgen Control of TGF-beta signaling

描述（由申请人提供）：转化生长因子- β (tgf - β)是25 kDa的多功能自分泌/旁分泌肽，具有抑制上皮细胞生长和凋亡的有效活性。在前列腺中，tgf - β蛋白及其受体的表达在雄激素消融后被诱导，与该组织中伴随发生的凋亡细胞死亡相一致。前列腺细胞在癌变过程中失去对雄激素的依赖，并对tgf - β反应产生抗性，其机制尚不明确。进一步支持tgf - β在前列腺中的抑瘤作用的研究来自于我们通过显性阴性TbetaRII的逆转录病毒转导，在两种非致瘤性细胞系（NRP-152和DP-153）中消融tgf - β信号，并显示对tgf - β反应的丧失引发恶性转化。tgf - β受体表达缺失是tgf - β耐药的多种潜在机制之一。其他途径可能涉及某些癌基因的激活，这些癌基因在不同水平上拦截tgf - β信号。我们最近报道DHT可以通过AR和Smad3之间的关联直接阻断tgf - β信号，导致LNCaP和NRP-154前列腺上皮细胞中Smad3的转录失活。我们利用emsa提供了证据，表明AR的抑制作用是通过阻断Smad3与靶基因的Smad结合元件（SBE）的结合来实现的。在此，我们拟研究：1)DHT/AR对tgf - β（或活性Smad3）诱导的生长停滞和凋亡的影响，2)DHT/AR对tgf - β诱导基因的表达，3)AR与Smad3结合背后的结构/功能基础，4)AR共激活剂通过AR作为Smad3的共同调节剂的可能功能，以及5)AR与Smad3在各种非致瘤性和致瘤性细胞系中相互作用的差异。我们相信这些研究肯定会对前列腺癌的治疗干预产生影响。

DESCRIPTION (provided by applicant): Transforming growth factor-betas (TGF-betas) are 25 kDa multifunctional autocrine/paracrine peptides with potent activity on growth suppression and apoptosis of epithelial cells. In the prostate, expression of TGF-beta protein and their receptors are induced upon androgen ablation, coincident with apoptotic cell death that occurs concomitantly in this tissue. Prostatic cells lose dependence on androgens and become resistant to TGF-beta responses during carcinogenesis, through mechanisms that remain to be defined. Further support for a tumor suppressor role of TGF-beta in the prostate comes from studies where we ablated TGF-beta signaling in two non-tumorigenic cell lines (NRP-152 and DP-153) by retroviral transduction of a dominant-negative TbetaRII, and showed the consequent loss of response to TGF-beta triggers malignant transformation. Loss of TGF-beta receptor expression is one of many potential mechanisms of TGF-beta resistance. Other pathways may involve activation of certain oncogenes that intercept TGF-beta signals at various levels. We have recently reported that DHT can directly block TGF-beta signaling through an association between AR and Smad3, leading to the transcriptional inactivation of Smad3 in LNCaP and NRP-154 prostatic epithelial cells. We provide evidence using EMSAs that AR's inhibitory effect is through blocking the binding of Smad3 to Smad Binding Elements (SBE) of target genes. Here we propose to investigate:1) the effects of DHT/AR on growth arrest and apoptosis induced by TGF-beta (or active Smad3), 2) expression of TGF-beta inducible genes by DHT/AR, 3) the structure/functional basis behind the binding of AR to Smad3, 4) possible function of AR co-activators as co-regulators or Smad3 through AR, and 5) differences in the interaction of AR with Smad3 in various nontumorigenic and tumorigenic cell lines. We believe these studies will most certainly impact on the therapeutic intervention of prostate cancer.