Role of H2AX and ATM in Suppression of Thymic Lymphomas

描述（由申请方提供）：未成熟T细胞淋巴瘤占人类淋巴恶性肿瘤的很大一部分，并且是一个临床问题，因为它们通常对治疗具有抗性。这些肿瘤中的许多具有复发性染色体间易位和染色体内重排（缺失），其激活原癌基因、抑制肿瘤抑制基因或产生新的致癌融合基因。人类未成熟T细胞淋巴瘤的大多数致癌性易位可能是由于在V（D）J重组启动期间在T细胞受体（TCR）位点引入的特异性DNA双链断裂（DSB）的修复错误和/或在其他基因组位置的更一般的DSB引起的。在这种情况下，小鼠缺乏共济失调毛细血管扩张突变（ATM）肿瘤抑制蛋白，它可以在人类未成熟T细胞淋巴瘤失活，总是发展胸腺淋巴瘤与致癌TCR基因座易位。另一方面，组蛋白H2 AX缺陷或单倍不足且p53肿瘤抑制因子缺陷的小鼠快速且可重复地死于具有克隆易位的未成熟T细胞淋巴瘤，所述克隆易位通常不涉及TCR基因座，而是涉及更一般的DSB。值得注意的是，H2 AX在小鼠和人的染色体区域中与ATM密切相关，该区域在人类中在大量癌症中发生改变。在这个应用中，我们建议阐明导致与T细胞淋巴瘤相关的染色体易位的机制。这项工作的一个主要目标将是测试我们的假设，即H2 AX的杂合或纯合突变将与ATM的丢失协同作用，以增加易位和肿瘤易感性，包括胸腺淋巴瘤。为此目的，我们将使用连续的gone靶向来产生具有组合的H2 AX和ATM突变的细胞和小鼠。其他实验将检验ATM和H2 AX通过稳定裂解的TCR染色体片段的突触复合物来防止由异常V（D）J重组引起的易位的假设。将采用几种新的方法来测试这一概念，包括产生小鼠，这将是容易频繁的染色体易位导致异常V（D）J重组。最后，我们还将利用胸腺淋巴瘤易感小鼠模型来测试TCR基因座增强子元件在致癌易位产生中的作用。在这个项目中与研究人员的频繁互动将大大提高我们所概述的目标的实现。从长远来看，我们的研究和我们将产生的小鼠模型，应该会导致更好地理解导致胸腺恶性肿瘤的分子途径， 参与了许多其他类型癌症的发展。

DESCRIPTION (provided by applicant): Immature T cell lymphomas account for a significant portion of human lymphoid malignancies and are a clinical problem as they are typically resistant to treatment. Many of these tumors harbor recurrent inter-chromosomal translocations and intra-chromosomal rearrangements (deletions) that activate proto-oncogenes, inactivate tumor suppressor genes, or create novel oncogenic fusion genes. Most oncogenic translocations of human immature T cell lymphomas likely arise through errors in the repair of specific DNA double strand breaks (DSBs) introduced at T cell receptor (TCR) loci during initiation of V(D)J recombination and/or more general DSBs at other genomic locations. In this context, mice deficient for the Ataxia Telangiectasia mutated (ATM) tumor suppressor protein, which can be inactivated in human immature T cell lymphomas, invariably develop thymic lymphoma with oncogenic TCR locus translocations. On the other hand, mice deficient or haplo-insufficient for histone H2AX and deficient for the p53 tumor suppressor rapidly and reproducibly succumb to immature T cell lymphomas with clonal translocations that, frequently, do not involve TCR loci and, instead, involve more general DSBs. Notably, H2AX is closely linked to ATM in both mice and man in a chromosomal region that in man is altered in a large number of cancers. In this application, we propose to elucidate mechanisms that lead to chromosomal translocations associated with T cell lymphomas. A major goal of this work will be to test our hypothesis that heterozygous or homozygous mutations of H2AX will function synergistically with loss of ATM to increase translocations and predisposition to tumors including thymic lymphomas. For this purpose, we will use sequential gone-targeting to generate cells and mice with combined H2AX and ATM mutations. Other experiments will test the hypothesis that ATM and H2AX prevent translocations resulting from aberrant V(D)J recombination by functioning to stabilize synaptic complexes of cleaved TCR chromosomal gone segments. Several novel approaches will be employed to test this notion, including the generation of mice which will be prone to frequent chromosomal translocations resulting from aberrant V(D)J recombination. Finally, we will also exploit thymic lymphoma-prone mouse models to test the role of TCR locus enhancer elements in the generation of oncogenic translocations. Frequent interaction with investigators in this program will greatly enhance the accomplishment of our goals as outlined. In the long term, our studies, and the mouse models that we will generate, should lead to a greater understanding of the molecular pathways which lead to thymic malignancies and which also are likely involved in the development of many other types of cancer.