Tcf/Lef-b-catenin in T cell identity and cancer

 描述（由申请人提供）：免疫缺陷（遗传性或获得性）和淋巴细胞恶性肿瘤是两种主要的免疫疾病，对公众健康构成严重威胁。首先，成人T细胞的损失（例如由于化疗或衰老）严重损害细胞免疫。不同的CD 4+和CD 8 + T细胞身份是如何建立和维持的，目前仍然是一个悬而未决的问题。其次，急性T细胞淋巴母细胞性白血病/淋巴瘤（T-ALL）是由胸腺中发育中的T细胞转化诱导的。需要阐明有助于T-ALL启动和增殖的因素/途径，以改善诊断和开发新的靶向治疗。 Tcf 1和Lef 1转录因子在T细胞发育中具有重要作用。我们还表明，Tcf 1的功能作为一个肿瘤抑制剂，通过抑制Lef 1和Notch在早期胸腺细胞的表达。Tcf 1和Lef 1与Wnt-β-连环蛋白途径最显著相关;然而，关于β-连环蛋白在T细胞发育和恶性肿瘤中的生理作用的长期争议仍未解决. 通过将Tcf 1和Lef 1条件性靶向于CD 4 + CD 8+双阳性（DP）胸腺细胞，我们发现Tcf 1/Lef 1双缺陷的CD 8 + T细胞显示出不适当的CD 4+谱系基因表达，包括CD 4辅助受体本身、CD 40配体、Rogt和Foxp 3，而无需预先活化。我们假设Tcf 1和Lef 1通过表观遗传学沉默CD 4+相关基因来封闭CD 8 + T细胞的身份。我们已经产生了一个真正的β-连环蛋白无效突变体和另一个小鼠品系，其中Tcf 1长同种型被消融，因此Tcf 1-β-连环蛋白相互作用被消除。有了这些新的工具，我们将测试Tcf 1和Lef 1使用β-连环蛋白依赖和β-连环蛋白独立的机制来调节胸腺细胞的成熟和转化的假设。我们的具体目标是：具体目标1。探讨Tcf 1和Lef 1调节CD 8 + T细胞特性的机制。具体目标2。阐明β-catenin及其与Tcf 1/Lef 1相互作用在T细胞发育和恶性肿瘤中的作用。 这些研究将确定第一个转录因子及其与表观遗传机制的相互作用，表观遗传机制负责调节CD 8 + T细胞的身份。新的动物模型将确保前所未有的清晰度，以解决长期存在的争议β-连环蛋白。这些结果将为免疫细胞的身份和Wnt-β-catenin通路的参与建立新的范式。这些信息将确定将造血祖细胞或iPS细胞定向为具有所需抗原特异性的成熟T细胞的关键调控点，从而有助于改善免疫重建和靶向的基于细胞的癌症治疗。

 DESCRIPTION (provided by applicant): Immunodeficiencies (inherited or acquired) and lymphocyte malignancy are two major immune disorders that pose grave threats to public health. Firstly, loss of T cells in adults (e.g. due to chemotherapy or ageing) severely compromises cellular immunity. How the distinct CD4+ and CD8+ T cell identities are established and maintained remains an unanswered puzzling question at present. Secondly, acute T cell lymphoblastic leukemia/lymphomas (T-ALLs) is induced by the transformation of developing T cells in the thymus. Elucidation of factors/pathways contributing to initiation and propagation of T-ALLs is required to improve diagnosis and develop novel targeted therapies. Tcf1 and Lef1 transcription factors are well documented to have essential roles in T cell development. We also showed that Tcf1 functions as a tumor suppressor by restraining Lef1 and Notch expression in early thymocytes. Tcf1 and Lef1 are most notably associated with the Wnt-ß-catenin pathway; however, the long- standing controversies regarding the physiological roles of ß-catenin in T cell development and malignancy remain unresolved. By conditionally targeting both Tcf1 and Lef1 at CD4+CD8+ double positive (DP) thymocytes, we found that Tcf1/Lef1 double deficient CD8+ T cells showed inappropriate expression of CD4+ lineage genes including the CD4 coreceptor itself, CD40 ligand, Rorgt and Foxp3 without prior activation. We hypothesize that Tcf1 and Lef1 seal off CD8+ T cell identity by epigenetically silencing CD4+-associated genes. We have generated a true ß-catenin null mutant and another mouse strain where Tcf1 long isoforms are ablated and hence Tcf1-ß- catenin interaction is abrogated. With these new tools, we will test the hypothesis that Tcf1 and Lef1 use both ß-catenin-dependent and -independent mechanisms to regulate thymocyte maturation and transformation. Our specific aims are: Specific Aim 1. To investigate the mechanisms by which Tcf1 and Lef1 regulate CD8+ T cell identity. Specific Aim 2. To elucidate the requirements of ß-catenin and its interaction with Tcf1/Lef1 in T cell development and malignancy. These studies will identify the first transcription factors and their interaction with epigenetic machinery that re responsible for regulation of CD8+ T cell identity. The new animal models will ensure unprecedented clarity to resolve the long-standing controversies over ß-catenin. The outcomes will establish new paradigms in immune cell identity and the involvement of Wnt-ß-catenin pathway. The information will identify critical regulatory points in directing hematopoietic progenitors or iPS cells to mature T cells with desired antigen specificity and thus help improve immune reconstitution and targeted, cell-based cancer therapy.