Wnt/b-catenin signaling in T-cell transformation

描述（由申请方提供）：正常胸腺细胞发育中涉及的分子或信号级联的表达失调已显示可导致转化。也许最引人注目的例子是频繁检测到Notch激活突变作为人类和小鼠T细胞转化中的启动或协同事件。功能丧失和获得的研究都表明，Wnt/β-连环蛋白信号传导在胸腺细胞成熟中起重要作用，特别是在双阴性（DN）到双阳性（DP）的转变过程中。最近的证据表明，条件性胸腺细胞特异性稳定的<$-连环蛋白的发展过渡期从双阳性（DP）的单阳性（SP）胸腺细胞阶段和DP胸腺细胞转化的倾向。通过β-连环蛋白的T细胞转化需要Rag活性，其在该发育阶段达到峰值，以及额外的次级遗传事件。一致的次级事件是c-Myc的转录上调，其活性是转化所需的。有趣的是，Notch受体以及靶标的表达在具有稳定的β-连环蛋白的DP胸腺细胞中降低，并且在转化的细胞中保持低水平，表明Notch活化对于β-连环蛋白诱导的转化不是必需的或选择的。因此，β-连环蛋白激活可能提供了一种不依赖于Notch激活的T细胞转化机制。拟议的研究将探索连环蛋白在人类T细胞转化病因学中的潜在作用，特别是在没有显示Notch激活的情况下，并将研究所涉及的分子机制。最初将研究转化的T细胞对β-连环蛋白的依赖性。这些细胞需要β-连环蛋白活性的维持将允许确定β-连环蛋白在转化的T细胞中的表达特征，并使得能够询问来自初级样品的微阵列数据以获得该途径失调的迹象。平行研究将评估T细胞淋巴细胞性淋巴瘤的组织学材料，以寻找活化的核连环蛋白的证据。与合作的活动将通过逆转录病毒插入诱变来探索T细胞转化中的β-连环蛋白，而通过分析淋巴瘤和预转化的胸腺细胞的基因组完整性来检查染色体缺陷的潜在Rag依赖性积累。这些方法将评估β-连环蛋白的失调激活是否在病因学上与人类T细胞转化相关，并研究这种活性是否构成这些疾病靶向治疗的合适候选者。 相关性：负责T细胞成熟的细胞信号失调通常会导致白血病。一种叫做2-连环蛋白的信号蛋白的不适当激活会导致小鼠T细胞的转化。本文提出的研究旨在调查2-catenin是否在人类T细胞白血病中被不适当地激活，以及激活的2-catenin转化T细胞所需的其他变化。通过这种方式，这一建议将促进目前对T细胞白血病病因的理解，并将为专门治疗的设计提供新的目标。

DESCRIPTION (provided by applicant): Deregulated expression of molecules or signaling cascades involved in normal thymocyte development has been shown to lead to transformation. Perhaps the most striking example is the frequent detection of Notch activating mutations as initiating or cooperating events in human and mouse T-cell transformation. Both loss and gain of function studies have indicated that Wnt/¿-catenin signaling plays essential roles in thymocyte maturation and in particular during the double negative (DN) to double positive (DP) transition. More recent evidence indicates that conditional thymocyte specific stabilization of ¿-catenin stalls the developmental transition from the double-positive (DP) to the single-positive (SP) thymocyte stage and predisposes DP thymocytes to transformation. T-cell transformation by ¿-catenin requires Rag activity, which peaks at this developmental stage, as well as additional secondary genetic events. A consistent secondary event is the transcriptional upregulation of c-Myc, whose activity is required for transformation. Interestingly, the expression of Notch receptors as well as targets is reduced in DP thymocytes with stabilized ¿-catenin and remains low in the transformed cells indicating that Notch activation is not required or selected for in ¿-catenin induced transformation. Thus, ¿-catenin activation may provide a mechanism for T-cell transformation that does not depend on Notch activation. The proposed research will explore the potential role of ¿-catenin in the etiology of human T-cell transformation, in particular cases that do not show Notch activation, and will investigate the molecular mechanism involved. Initially the dependence of transformed T-cells on ¿-catenin will be investigated. Such cells that require ¿-catenin activity for their maintenance will permit determination of the expression signature of ¿-catenin in transformed T-cells and enable the interrogation of microarray data from primary samples for signs of deregulation of this pathway. Parallel studies will evaluate histologic material from T-cell lymphocytic lymphoma for evidence of activated nuclear ¿-catenin. Events that cooperate with ¿-catenin in T cell transformation will be explored by retroviral insertional mutagenesis, while the potential Rag dependent accumulation of chromosomal defects will be examined in lymphomas and pretransformed thymocytes by analysis of their genomic integrity. These approaches will evaluate whether deregulated activation of ¿-catenin is etiologically linked to human T cell transformation and investigate whether this activity constitutes a suitable candidate for targeted therapy of these conditions. Relevance: Deregulation of cell signals that are responsible for the maturation of T-cells frequently leads to leukemia. The inappropriate activation of a signaling protein called 2-catenin causes transformation of T-cells in mice. Research proposed here aims at investigating whether 2-catenin is inappropriately activated in human T-cell leukemias and what other changes are required for the transformation of T-cells with activated 2-catenin. In this way this proposal will promote current understanding about the causes of T-cell leukemia and will provide new targets for the design of specialized therapies.