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

描述(申请人提供)：80%的致死性雄激素非依赖性前列腺癌(PCA)病例会发生骨转移，这说明有必要更好地了解调控PCA在骨骼中生长的机制。骨细胞旁分泌信号影响癌细胞归巢和适应骨骼的生长。Pca在骨中存活的一种可能方式是通过细胞经历神经内分泌分化(NED)的能力。神经内分泌分化(NE)的PCa细胞在晚期PCa中最常见，与雄激素非依赖性疾病相关，并支持疾病的进展。此外，NE-PCA细胞可以去分化，并在休眠和增殖状态之间转换，从而带来治疗后复发的风险。未分裂的、寿命长的NE PCA细胞可以逃避常规的放化疗并导致肿瘤潜伏期，但仍为重新进入细胞周期做好准备，以在复发期间促进肿瘤生长。骨髓基质细胞(BMSC)旁分泌信号诱导共培养的骨转移瘤细胞凋亡。然而，一组骨转移的PCA细胞可以避免细胞凋亡性死亡，并经历NED。提出了一种工作模型，在该模型中，转移的PCA细胞到达骨骼后，会遇到存在于那里的天然免疫系统构成的敌意微环境，从而触发大多数细胞中的PCA细胞死亡。然而，PCA细胞的一个亚群可以激活一个分子程序，促进PCA NED和细胞在骨骼中的存活。自噬--一种动态平衡的细胞生存过程--被骨髓间充质干细胞上调，有助于维持NE-PCa细胞处于跨分化状态。引导PCa细胞走向凋亡或走向NED的分子机制尚不清楚。了解这些机制将提供一个机会，以防止细胞进行NED，并使天平倾向于凋亡，从而极大地降低复发的几率。本项目的目的是证明BMSCs通过抑制雄激素受体(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，决定了PCa细胞在AR表达下调后是否经历凋亡或NED。利用显微镜、免疫印迹和表达载体等分子生物学手段，研究当AR表达和自噬被调控时，BMSC诱导的PCA和NED的凋亡和NED，提出了以下特定的目的：具体目的1：证实BMSC介导的AR抑制诱导PCA凋亡或PCANED。特定目标2：确定自噬是否保护PCa细胞免于凋亡，并在BMSC诱导的AR抑制反应中将这些细胞导向NED。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.