The Role of Thoc1 in Normal Development and Cancer

描述（由申请人提供）：本申请的长期目标是了解TAD1基因的正常功能，并评估其作为癌症治疗和预后的分子靶点的潜在适用性。TTR1编码一种蛋白质（pTTR1），该蛋白质最近被鉴定为进化上保守的TREX复合物的组分。TREX是一个基因子集的有效转录延伸所必需的，并且它将延伸与RNA加工和核输出的过程物理耦合。TAP1的酵母直系同源物对于生存力不是必需的，但是该基因的缺失导致细胞寿命缩短、生长速率降低和对DNA损伤的敏感性增加。类似地，耗尽pTGF1的人癌细胞表现出降低的生长、活力和对遗传毒性化疗剂的抗性。相比之下，正常分化的细胞相对不受pTAD1丢失的影响。Thoc在正常发育和癌症中的生理需求尚未在多细胞生物体中进行体内评估。我们假设癌细胞的生长和生存能力独特地依赖于Thoc表达，特别是在存在DNA损伤的情况下。一般的实验方法提出的假设进行测试是测量的影响pThoc损失正常发展和恶性转化使用基因工程改造的Thoc等位基因和本地小鼠模型的乳腺癌。提出了4个具体目标：1）检测pTAD1缺失是否抑制体外恶性转化。2)确定pTGF1缺失是否影响正常乳腺发育。3)确定pTGF1缺失是否抑制体内乳腺癌发生。4)评估pTGF1水平是否影响乳腺癌对遗传毒性治疗的反应。癌细胞积累遗传和表观遗传改变，赋予它们不必要的增殖潜力，但也给它们带来独特的脆弱性。因此，有可能鉴定癌细胞而不是正常细胞的活力所需的基因。这种合成的致命遗传相互作用确定了潜在的治疗分子靶点，有望产生更大的癌细胞特异性。成功完成拟议的研究将提供TAD1是这样一个分子靶点的原理证明。由于pTHB1是新发现的TREX复合物的一个组成部分，它以一种新的作用机制发挥作用。基于靶向pT细胞1的治疗和诊断预计将产生新的临床反应，新的联合治疗的机会，和预后信息可能独立于目前使用的标准。这项拟议中的研究与人类健康高度相关，因为显然需要对癌细胞具有更高特异性的新分子靶向疗法。所提出的实验将确定pTHB1是否是开发新疗法和预后测试的有希望的靶点。

DESCRIPTION (provided by applicant): The long-term objectives of this application are to understand the normal function of the Thoc1 gene and to assess its potential suitability as a molecular target for cancer therapy and prognosis. Thoc1 encodes a protein (pThoc1) that has recently been identified as a component of the evolutionarily conserved TREX complex. TREX is required for the efficient transcriptional elongation of a subset of genes, and it physically couples elongation to the processes of RNA processing and nuclear export. The yeast orthologue of Thoc1 is not essential for viability, but loss of this gene causes reduced cellular lifespan, reduced growth rate, and increased sensitivity to DNA damage. Similarly, human cancer cells depleted of pThoc1 exhibit reduced growth, viability, and resistance to genotoxic chemotherapeutics. In contrast, normal differentiated cells are relatively unaffected by loss of pThoc1. The physiological requirements for Thoc in normal development and cancer have yet to be assessed in vivo in a multicellular organism. We hypothesize that cancer cells are uniquely dependent on Thoc expression for growth and viability, particularly in the presence of DNA damage. The general experimental approach proposed for testing the hypothesis is to measure the effects of pThoc loss on normal development and malignant transformation using genetically engineered Thoc alleles and autochthonous mouse models of breast cancer. 4 specific aims are proposed: 1) Test whether pThoc1 depletion inhibits malignant transformation in vitro. 2) Determine if pThoc1 depletion affects normal mammary gland development. 3) Ascertain whether pThoc1 depletion inhibits breast carcinogenesis in vivo. 4) Assess whether pThoc1 levels influence the response of breast cancer to genotoxic therapy. Cancer cells accumulate genetic and epigenetic alterations that endow them with unwanted proliferative potential, but also burden them with unique vulnerabilities. Thus, it is possible to identify genes that are required for the viability of cancer cells, but not normal cells. Such synthetic lethal genetic interactions identify potential molecular targets for therapy that promise to yield greater specificity for cancer cells. Successful completion of the proposed study will provide proof of principle that Thoc1 is such a molecular target. Since pThoc1 is a component of the newly discovered TREX complex, it functions with a novel mechanism of action. Therapies and diagnostics based on targeting pThoc1 are expected to yield novel clinical responses, opportunities for novel combination therapies, and prognostic information potentially independent of currently used criteria. The proposed research is highly relevant to human health because new molecularly targeted therapies with greater specificity for cancer cells are clearly needed. The experiments proposed will determine whether pThoc1 is a promising target for the development of new therapies and prognostic tests.