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信号的非调控表达已被证明会导致转化。也许最引人注目的例子是在人类和小鼠的T细胞转化中频繁检测到Notch激活突变作为启动或协同事件。功能丧失和功能获得的研究表明，Wnt/β-catenin信号在胸腺细胞成熟，特别是在双阴性(DN)向双阳性(DP)的转变过程中发挥着重要作用。更新的证据表明，胸腺细胞特异性的条件性稳定-连环蛋白阻碍了胸腺细胞从双阳性(DP)到单阳性(SP)的发育转变，并使DP胸腺细胞易于转化。通过连环蛋白转化T细胞需要RAG活性，在这个发育阶段达到顶峰，以及额外的次要遗传事件。一个一致的次要事件是c-Myc的转录上调，它的活性是转化所必需的。有趣的是，在稳定的连环蛋白的DP胸腺细胞中，Notch受体和靶分子的表达减少，并且在转化的细胞中保持较低的水平，这表明Notch的激活不是连环蛋白诱导转化所必需或选择的。因此，-连环蛋白的激活可能为T细胞的转化提供了一种不依赖于Notch激活的机制。这项拟议的研究将探索-连环蛋白在人类T细胞转化的病因学中的潜在作用，特别是在没有表现出Notch激活的情况下，并将研究涉及的分子机制。首先，将研究转化的T细胞对β-连环蛋白的依赖性。这类需要连环蛋白活性以维持其功能的细胞将允许确定转化的T细胞中连环蛋白的表达特征，并能够从原始样本中询问微阵列数据，以寻找这一途径放松调控的迹象。平行研究将评估T细胞淋巴细胞性淋巴瘤的组织学资料，以寻找激活的核连环蛋白的证据。在T细胞转化中与连环蛋白协同作用的事件将通过逆转录病毒插入突变来探索，而潜在的依赖于RAG的染色体缺陷的积累将通过对其基因组完整性的分析在淋巴瘤和转化前的胸腺细胞中进行检测。这些方法将评估解除调节的连环蛋白的激活是否在病因学上与人类T细胞转化有关，并调查这种活性是否构成这些疾病的靶向治疗的合适候选者。 相关性：导致T细胞成熟的细胞信号失控经常导致白血病。一种名为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。这项研究旨在研究2-连环蛋白在人类T细胞白血病中是否被不适当地激活，以及在激活了2-连环蛋白的T细胞转化过程中还需要哪些其他变化。通过这种方式，这项建议将促进目前对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靶点。

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.