An androgen-regulated cytokine network controls prostate apoptosis

描述（由申请人提供）：前列腺癌（PrCa）的诊断和治疗是一个复杂的临床问题，在美国每年影响数百万男性，产生20万新诊断和27万死亡。大多数PrCa是局部的，生长缓慢；一小部分转移并导致死亡。由于前列腺癌起源于雄激素依赖性上皮，一些局部PrCa病例和大多数转移性PrCa病例通过雄激素剥夺疗法（ADT）治疗。ADT是一种比手术或放疗更具特异性的治疗方法，它能诱导局部和分散的前列腺上皮肿瘤细胞凋亡，而不是消融整个腺体并对周围结构造成损害。然而，雄激素除了调节前列腺上皮的生长和分化外，还具有全身性作用，因此ADT产生了相当大的副作用。此外，ADT经常失败。以选择性方式触发PrCa细胞凋亡的新型靶向治疗的发展提供了减少副作用和改善疾病进展控制的可能性。我们的总体目标是阐明雄激素戒断后前列腺细胞凋亡的机制，最终设计出选择性模拟ADT细胞凋亡效应的治疗方法。为了实现这一目标，我们在正常啮齿动物和模型前列腺细胞系中研究了雄激素戒断诱导的细胞凋亡（AWIA）。最近，我们开发了一种新的磁共振成像（CHESS-MRI）方案来量化前列腺退化，并发现肿瘤坏死因子（TNF）信号对于AWIA是必需的，但不是充分的。先前，我们发现FLIP，一种抑制TNF信号的caspase-8的无活性同源物，在雄激素停用后减少。FLIP和TNF的表达均受雄激素调控。另外两种细胞因子信号通路（由转化生长因子-b （TGFb）和胰岛素样生长因子1 （IGF1）触发）也与AWIA有关，相应的基因也受雄激素调控。我们将测试以下中心假设：雄激素戒断调节旁分泌作用细胞因子网络（TNF, TGFb, IGF1, IGFBP3），从而降低细胞内凋亡抑制剂FLIP的表达。净效应是触发TNF信号通路的凋亡臂。实验计划利用啮齿类动物AWIA模型和类似人类前列腺癌的前列腺特异性pten缺陷小鼠模型，结合CHESS-MRI对正常和肿瘤前列腺进行成像。目的1确定TNF、TGFb和IGFBP3在adt诱导的前列腺细胞凋亡中的作用，以及这些细胞因子是否协同诱导正常和致瘤性前列腺细胞凋亡。目的2研究TGFb和NF-kB串扰在雄激素剥夺诱导的FLIP下调中的作用。最后，Aim 3测试了FLIP的功能作用，在小鼠模型中确定FLIP下调是否可以与促凋亡细胞因子协同诱导正常前列腺和PrCa的凋亡和消退。

DESCRIPTION (provided by applicant): The diagnosis and treatment of prostate cancer (PrCa) is a complex clinical problem that affects millions of men each year in the US, producing >200,000 new diagnoses and >27,000 deaths. Most PrCa is localized and slow growing; a smaller fraction metastasizes and causes death. Since prostate cancer derives from androgen dependent epithelium, some cases of localized PrCa and most cases of metastatic PrCa are treated via androgen deprivation therapy (ADT). ADT is a more specific therapy than surgery or radiation, inducing apoptosis in both localized and dispersed prostate epithelial tumor cells, rather than ablating the entire gland and causing damage to surrounding structures. However, androgens have systemic effects beyond regulating the growth and differentiation of prostate epithelium and ADT therefore produces considerable side-effects. Moreover, ADT frequently fails. The development of novel, targeted therapies that trigger PrCa apoptosis in a selective manner offers the possibility of reduced side-effects and improved control of disease progression. Our overall goal is to elucidate the mechanism of prostate apoptosis in response to androgen withdrawal, to eventually design therapies that selectively mimic the apoptotic effects of ADT. To achieve this goal, we have investigated androgen withdrawal induced apoptosis (AWIA) in normal rodents and model prostate cell lines. Recently, we developed a novel magnetic resonance imaging (CHESS-MRI) protocol to quantitate prostate regression and found that tumor necrosis factor (TNF) signaling is required, but not sufficient, for AWIA. Previously, we showed that FLIP, an inactive homologue of caspase-8 that inhibits TNF signaling, decreases following androgen withdrawal. The expression of both FLIP and TNF are androgen regulated. Two other cytokine signaling pathways (triggered by transforming growth factor-b (TGFb) and insulin-like growth factor 1 (IGF1)) have also been implicated in AWIA, and the corresponding genes are also androgen regulated. We will test the following central hypothesis: androgen withdrawal regulates a network of paracrine-acting cytokines (TNF, TGFb, IGF1, IGFBP3) and thereby reduces the expression of the intracellular apoptosis inhibitor FLIP. The net effect is to trigger the apoptotic arm of the TNF signaling pathway. The experimental plan utilizes rodent AWIA models and a prostate-specific PTEN-deficient mouse model resembling human prostate cancer, in conjunction with CHESS-MRI to image both normal and tumorous prostates. Aim 1 determines the role of TNF, TGFb and IGFBP3 in ADT-induced prostate apoptosis and whether these same cytokines cooperate to induce apoptosis in normal and tumorigenic prostates. Aim 2 investigates the role of TGFb and NF-kB cross-talk in mediating androgen deprivation induced down-regulation of FLIP. Finally, Aim 3 tests the functional role of FLIP, determining if FLIP down-regulation can cooperate with pro- apoptotic cytokines to induce apoptosis and regression of normal prostate and PrCa in a murine model.