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

描述（由申请人提供）：骨转移发生在80%的致死性雄激素非依赖性前列腺癌（PCa）病例中，说明需要更好地了解调节PCa在骨中生长的机制。骨细胞旁分泌信号影响癌细胞归巢和适应骨中的生长。PCa在骨中存活的一种可能方式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转换，从而造成治疗后复发的风险。非分裂的、长寿命的NE PCa细胞可以逃避常规的化学-放射疗法并有助于肿瘤潜伏期，但仍然准备好重新进入细胞周期以有助于复发期间的肿瘤生长。骨髓基质细胞（BMSC）旁分泌信号在共培养的骨转移性前列腺癌细胞中诱导凋亡然而，骨转移性PCa细胞的亚群可以避免凋亡性细胞死亡并经历NED。提出了一种工作模型，其中在到达骨骼后，转移性PCa细胞遇到由先天免疫系统引起的不利微环境，该先天免疫系统在大多数细胞中触发PCa细胞死亡。然而，PCa细胞的亚群可以激活促进PCa NED和细胞在骨中存活的分子程序。自噬-一种稳态的细胞存活过程-在PCa细胞中被BMSC上调，并有助于维持NE PCa细胞处于转分化状态。指导PCa细胞命运朝向凋亡或朝向NED的分子机制仍不清楚。了解这些机制将提供一个干预的机会，以防止细胞经历NED，并使平衡向凋亡倾斜，大大降低复发的几率。该项目旨在证明BMSCs通过一种共同的机制促进细胞凋亡或NED，该机制涉及雄激素受体（AR）表达的抑制，此外，还表明自噬是一种细胞变阻器，决定了PCa细胞在AR表达下调后是否发生细胞凋亡或NED。使用分子生物学工具，如显微镜，蛋白质印迹和表达载体，以表征骨髓基质细胞诱导的前列腺癌细胞凋亡和NED时，AR表达和自噬的调制，提出了以下具体目标：具体目标1：证明骨髓基质细胞介导的AR抑制诱导前列腺癌细胞凋亡或前列腺癌NED。具体目标二：确定自噬是否保护PCa细胞免于凋亡，并将这些细胞导向NED以响应BMSC诱导的AR抑制。具体目标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.