Role of Androgen Receptor in Bone Metastatic Prostate Cancer Apoptosis and NED

描述（由申请人提供）：80%的致死性雄激素非依赖性前列腺癌（PCa）病例发生骨转移，说明需要更好地了解前列腺癌在骨中的生长调节机制。骨细胞旁分泌信号影响癌细胞的归巢和适应骨中的生长。骨内前列腺癌存活的一个可能途径是通过细胞进行神经内分泌分化（NED）的能力。神经内分泌分化（NE） PCa细胞在晚期PCa中最为普遍，与雄激素非依赖性疾病相关，并支持疾病进展。此外，NE - PCa细胞可以去分化并在休眠和增殖状态之间切换，这增加了治疗后复发的风险。非分裂、长寿命的NE - PCa细胞可以逃避常规的放化疗，导致肿瘤潜伏期，但在复发期间仍能重新进入细胞周期，促进肿瘤生长。骨髓基质细胞（BMSC）旁分泌信号诱导共培养骨转移性前列腺癌细胞凋亡。然而，骨转移性PCa细胞亚群可以避免凋亡细胞死亡并发生NED。本文提出了一种工作模型，其中转移性前列腺癌细胞到达骨后，会遇到由先天免疫系统构成的敌对微环境，从而引发大多数细胞的前列腺癌细胞死亡。然而，前列腺癌细胞的一个亚群可以激活一个分子程序，促进前列腺癌NED和骨细胞存活。自噬-一个稳态的细胞生存过程-在前列腺癌细胞中被骨髓间充质干细胞上调，并帮助维持NE前列腺癌细胞处于转分化状态。指导前列腺癌细胞走向凋亡或NED的分子机制尚不清楚。了解这些机制将提供一个干预的机会，以防止细胞发生NED，并将平衡向凋亡倾斜，大大减少复发的几率。本项目旨在证明骨髓间充质干细胞通过抑制雄激素受体（雄激素受体，AR）表达的共同机制促进细胞凋亡或NED，并进一步证明自噬是一种细胞变阻器，通过下调AR表达来决定PCa细胞是发生凋亡还是NED。利用分子生物学工具，如显微镜、western blot和表达载体来表征当AR表达和自噬被调节时，bmsc诱导的PCa凋亡和NED，提出以下具体目标：具体目标1：证明bmsc介导的AR抑制诱导PCa凋亡或PCa NED。特异性目的2：确定自噬是否保护PCa细胞免于凋亡，并在骨髓间充质干细胞诱导的AR抑制中引导这些细胞向内NED发展。具体目的3：剖析BMSC旁分泌信号抑制PCa AR表达的机制。

DESCRIPTION (provided by applicant): Bone metastasis occurs in 80% of lethal androgen independent prostate cancer (PCa) cases, illustrating the need to better understand the mechanisms that regulate PCa growth in the bone. Bone cell paracrine signals affect cancer cell homing and adaption to growth in the bone. One likely means of PCa survival in bone is through the ability of cells to undergo neuroendocrine differentiation (NED). Neuroendocrine differentiated (NE) PCa cells are most prevalent in advanced PCa, correlate with androgen independent disease, and support disease progression. Furthermore, the NE PCa cells can de-differentiate and switch between dormant and proliferative states posing a risk for relapse after treatment. Non-dividing, long-lived NE PCa cells can evade conventional chemo-radiation therapy and contribute to tumor latency, yet remain primed for re-entry into the cell cycle to contribute to tumor growth during recurrence. Bone marrow stromal cell (BMSC) paracrine signaling induces apoptosis in co-cultured bone metastatic PCa cells. However, a subpopulation of the bone metastatic PCa cells can avoid apoptotic cell death and undergo NED. A working model is proposed in which upon arrival to the bone, metastatic PCa cells encounter a hostile microenvironment posed by the innate immune system present there that triggers PCa cell death in the majority of cells. A subpopulation of the PCa cells, however, can activate a molecular program that promotes PCa NED and cell survival in bone. Autophagy - a homeostatic, cell survival process - is up- regulated in PCa cells by BMSCs and helps maintain NE PCa cells in a trans-differentiated state. The molecular mechanisms that direct PCa cell fate either towards apoptosis or towards NED remain unclear. Understanding these mechanisms would provide an opportunity to intervene to prevent cells from undergoing NED and tip the balance toward apoptosis, greatly reducing the odds of relapse. This project aims to demonstrate that BMSCs promote either apoptosis or NED through a common mechanism that involves the repression of androgen receptor (AR) expression, and furthermore, show that autophagy is a cellular rheostat that determines whether a PCa cell undergoes apoptosis or NED following down regulation of AR expression. Using molecular biology tools such as microscopy, western blot, and expression vectors to characterize BMSC-induced PCa apoptosis and NED when AR expression and autophagy are modulated, the following specific aims are proposed: Specific Aim 1: Demonstrate that BMSC-mediated AR repression induces PCa apoptosis or PCa NED. Specific Aim 2: Determine if autophagy protects PCa cells from apoptosis and directs these cells towards NED in response to BMSC-induced AR repression. Specific Aim 3: Dissect the mechanism by which BMSC paracrine signaling represses PCa AR expression.