Gadd45beta in JNK Signaling, Apoptosis, and Cancer

描述(申请人提供)：除了协调免疫和炎症反应，核因子-kappaB/Rel转录因子控制细胞生存。这种抗细胞凋亡的功能对于肿瘤的发生、癌症的化疗耐药以及对抗肿瘤坏死因子受体诱导的杀伤是至关重要的。通过功能筛选，我们发现Gadd4513/myd 118是核因子-kappaB对肿瘤坏死因子α诱导的细胞凋亡保护作用的关键介质。Gadd45β的细胞保护涉及抑制JNK级联反应，而这种抑制是核因子-kappaB控制细胞死亡的中心。事实上，Gadd45a的表达依赖于核因子-kappaB，纠正了核因子-kappaB缺失细胞的凋亡缺陷，对依赖核因子-kappaB的生存是必不可少的。然而，核因子-kappaB在肿瘤发生和抗癌治疗抵抗中的保护作用的基础仍然知之甚少。同样，Gadd45β在细胞凋亡过程中控制的步骤(S)，以及Gadd45β抑制JNK信号转导的机制尚不清楚。这项提案有三个具体目标，将解决这些问题。在目标1中，我们将通过体内和体外相结合的方法，系统地研究Gadd45β对BJAB细胞中Fas诱导的通路的影响，重点放在两个主要的检查点：视盘和线粒体。我们还将评估JNK级联的靶向与Gadd45β控制Fas诱导的杀伤的相关性。在目标2中，我们将确定Gadd45β抑制JNK途径的机制以及Gadd45β特异性抑制该途径的基础。我们将首先评估新发现的Gadd45beta与JNK级联组件之间相互作用的重要性。如果有必要，我们将使用层析方法，确定与JNK抑制和细胞保护相关的Gadd451a的额外靶点。在目标3中，通过使用RAS转化和乳腺癌模型系统，我们将解决Gadd45β的作用和JNK通路在依赖于核因子？B的肿瘤发生中的靶向。我们还将对Gadd45β在人类原发肿瘤中的表达进行系统分析，重点关注那些依赖NF-kappaB生存的肿瘤。最后，我们检测了Gadd451a对化疗药物的抗凋亡活性对肿瘤细胞抗癌治疗的意义。这些研究的目标是确定Gadd45beta是否像核因子-kappaB一样代表癌症治疗的靶点。

DESCRIPTION (provided by applicant): In addition to coordinating immune and inflammatory responses, NF-kappaB/Rel transcription factors control cell survival. This anti-apoptotic function is crucial to oncogenesis, cancer chemoresistance, and to antagonize TNF-R-induced killing. Using a functional screen, we have identified Gadd4513/Myd 118 as a pivotal mediator of the NF-kappaB protective activity against apoptosis by TNFalpha. Cytoprotection by Gadd45beta involves the inhibition of the JNK cascade, and this inhibition is central to the control of cell death by NF-kappaB. Indeed, Gadd45a expression depends on NF-kappaB, corrects the apoptotic defect of NF-kappaB null cells, and is essential to NF-kappaB-dependent survival. However, the bases for the NF-kappaB protective functions in oncogenesis and resistance to anti-cancer therapy remain poorly understood. Likewise, the step(s) controlled by Gadd45beta during apoptosis, and the mechanisms by which Gadd45beta inhibits JNK signaling are not known. This proposal has three Specific Aims, which will address these issues. In Aim 1, by combining an in vivo and an in vitro approach, we will systematically examine the impact of Gadd45beta on Fas-induced pathways in BJAB cells, focusing on two major checkpoints: the DISC and the mitochondria. We will also assess the relevance of the targeting of the JNK cascade to the control of Fas-induced killing by Gadd45beta. In Aim 2, we will determine the mechanisms by which Gadd45beta suppresses the JNK pathway and the bases for the specific inhibition of this pathway by Gadd45beta. We will begin by assessing the significance of newly discovered interactions between Gadd45beta and components of the JNK cascade. If necessary, by using chromatographic methods, we will identify the additional targets of Gadd451a that are relevant to JNK inhibition and cytoprotection. In Aim 3, by using the Ras transformation and breast cancer model systems, we will address the roles of Gadd45beta and the targeting of the JNK pathway in NF-?B-dependent tumorigenesis. We will also perform a systematic analysis of Gadd45beta expression in primary human tumors, focusing on those tumors that depend on NF-kappaB for their survival. Finally, we examine the significance of the Gadd451a anti-apoptotic activity against chemotherapy drugs to the resistance of tumor cells to anti-cancer treatment. The goal of these studies is to determine whether, like NF-kappaB, Gadd45beta represents a target for cancer therapy.