Role of H2AX and ATM in Suppression of Thymic Lymphomas

描述(由申请人提供)：未成熟T细胞淋巴瘤占人类淋巴系统恶性肿瘤的很大一部分，是一个临床问题，因为它们通常对治疗具有抵抗力。其中许多肿瘤具有反复的染色体间易位和染色体内重排(缺失)，激活原癌基因，灭活抑癌基因，或创造新的癌基因融合基因。大多数人未成熟T细胞淋巴瘤的致癌易位可能是由于在V(D)J重组启动过程中T细胞受体(TCR)基因座引入的特定DNA双链断裂(DSB)的修复错误和/或其他基因组位置的更普遍的DSB引起的。在此背景下，缺乏可在人类未成熟T细胞淋巴瘤中失活的共济失调毛细血管扩张突变(ATM)肿瘤抑制蛋白的小鼠总是会患上胸腺淋巴瘤并伴有致癌的TCR基因易位。另一方面，组蛋白H_2AX缺乏或半缺失和P53肿瘤抑制基因缺乏的小鼠迅速和可复制地死于具有克隆性易位的未成熟T细胞淋巴瘤，这些淋巴瘤通常不涉及TCR基因，而是涉及更普遍的DSB。值得注意的是，在小鼠和人类中，H_2AX与ATM密切相关，在人类的一个染色体区域，在许多癌症中，该区域会发生改变。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检验我们的假设，即H2 AX的杂合或纯合突变将与ATM的丢失协同作用，增加易位和对包括胸腺淋巴瘤在内的肿瘤的易感性。为此，我们将使用顺序Gone-靶向来产生组合了H2AX和ATM突变的细胞和小鼠。其他实验将测试这一假设，即ATM和H2AX通过稳定被切割的TCR染色体Gone片段的突触复合体来防止V(D)J异常重组引起的易位。将使用几种新的方法来测试这一概念，包括容易由于V(D)J异常重组而导致频繁染色体易位的小鼠的产生。最后，我们还将利用易患胸腺淋巴瘤的小鼠模型来测试TCR位点增强子元件在致癌易位产生中的作用。在这个项目中与调查人员的频繁互动将极大地提高我们所概述的目标的实现。从长远来看，我们的研究，以及我们将建立的小鼠模型，应该会使我们更好地理解导致胸腺恶性肿瘤的分子途径，这些分子途径也很可能 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.