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，每年影响美国数百万男性，导致超过 200,000 例新诊断和超过 27,000 例死亡。大多数 PrCa 是局部的且生长缓慢；一小部分转移并导致死亡。由于前列腺癌源自雄激素依赖性上皮，因此一些局限性 PrCa 病例和大多数转移性 PrCa 病例通过雄激素剥夺疗法 (ADT) 进行治疗。 ADT 是一种比手术或放疗更具特异性的疗法，可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之外还具有全身作用，因此 ADT 会产生相当大的副作用。而且，ADT经常失败。以选择性方式触发 PrCa 细胞凋亡的新型靶向疗法的开发提供了减少副作用和改善对疾病进展的控制的可能性。 我们的总体目标是阐明前列腺细胞凋亡响应雄激素撤退的机制，最终设计出选择性模仿 ADT 细胞凋亡效应的疗法。为了实现这一目标，我们研究了正常啮齿动物和模型前列腺细胞系中的雄激素撤退诱导细胞凋亡（AWIA）。最近，我们开发了一种新型磁共振成像 (CHESS-MRI) 方案来定量前列腺退化，并发现肿瘤坏死因子 (TNF) 信号传导对于 AWIA 是必需的，但还不够。此前，我们发现 FLIP（一种抑制 TNF 信号传导的 caspase-8 无活性同源物）会在雄激素撤退后减少。 FLIP 和 TNF 的表达均受雄激素调节。另外两种细胞因子信号传导途径（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 相关，并且相应的基因也受雄激素调节。 我们将检验以下中心假设：雄激素撤退调节旁分泌作用细胞因子（TNF、TGFb、IGF1、IGFBP3）网络，从而减少细胞内凋亡抑制剂 FLIP 的表达。最终效果是触发 TNF 信号通路的凋亡臂。 该实验计划利用啮齿动物 AWIA 模型和类似于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。目标 1 确定 TNF、TGFb 和 IGFBP3 在 ADT 诱导的前列腺细胞凋亡中的作用，以及这些相同的细胞因子是否协同诱导正常和致瘤性前列腺细胞凋亡。目标 2 研究 TGFb 和 NF-kB 串扰在介导雄激素剥夺诱导的 FLIP 下调中的作用。最后，目标 3 测试了 FLIP 的功能作用，确定 FLIP 下调是否可以与促凋亡细胞因子配合，在小鼠模型中诱导正常前列腺和 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.