Wnt/b-catenin signaling in T-cell transformation

描述（由申请人提供）：正常胸腺细胞发育过程中涉及的分子或信号级联表达失调已被证明会导致转化。也许最引人注目的例子是Notch激活突变作为人类和小鼠t细胞转化的启动或合作事件的频繁检测。功能的丧失和获得研究表明，Wnt/¿-catenin信号在胸腺细胞成熟过程中起着重要作用，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，有条件的胸腺细胞特异性稳定¿-catenin延缓了从双阳性（DP）到单阳性（SP）胸腺细胞的发育转变，并使DP胸腺细胞更易转化。-catenin转化t细胞需要Rag活性，Rag活性在这个发育阶段达到顶峰，还需要额外的二次遗传事件。一致的次要事件是c-Myc的转录上调，其活性是转化所必需的。有趣的是，Notch受体和靶点的表达在稳定的-catenin诱导的DP胸腺细胞中减少，并且在转化的细胞中保持低水平，这表明Notch激活不是-catenin诱导的转化所需要或选择的。因此，-catenin激活可能提供了一种不依赖于Notch激活的t细胞转化机制。这项拟议的研究将探索¿-catenin在人类t细胞转化的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。首先，转化t细胞对¿-catenin的依赖性将被研究。这种需要-catenin活性维持的细胞将允许在转化的t细胞中确定-catenin的表达特征，并允许对来自主要样本的微阵列数据进行查询，以寻找该途径解除监管的迹象。平行研究将评估来自t细胞淋巴细胞淋巴瘤的组织学材料，以寻找活化核¿-连环蛋白的证据。在T细胞转化过程中，与¿-catenin合作的事件将通过逆转录病毒插入突变来探索，而潜在的Rag依赖性染色体缺陷的积累将通过分析其基因组完整性来研究淋巴瘤和转化前胸腺细胞。这些方法将评估¿-catenin的失调控激活是否与人类T细胞转化在病因学上有关，并研究这种活性是否构成针对这些疾病的靶向治疗的合适候选。

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.