Role of RecQ Helicases to Prevent Senescence By c-Myc

描述（由申请人提供）：避免衰老是肿瘤细胞的基本特性。我们计划确定WRN和潜在相关的RecQ解旋酶在避免癌基因诱导的衰老中所发挥的作用。特别是，我们将集中在c-Myc癌基因，因为我们已经表明，c-Myc刺激WRN基因的转录，更重要的是，WRN蛋白是必要的，以避免c-Myc过表达诱导的细胞衰老。WRN的功能丧失突变导致人类过早早衰症，Werner综合征（WS），其症状模仿自然衰老的方面。来源于WS患者的细胞也显示出过早衰老，表明生物体表型可能是由于加速的细胞衰老。我们假设WRN功能是避免肿瘤细胞衰老所必需的，因此可能是癌症治疗的一个有吸引力的治疗靶点。WRN蛋白参与DNA复制过程中产生的异常结构的DNA修复，并因导致DNA复制阻断的药物而加重。事实上，初步数据表明，WRN缺陷细胞在c-Myc过表达时的衰老反应是由于DNA损伤和由此产生的细胞检查点反应。在本提案中，我们计划测试这一假设，从而定义WRN和c-Myc共同依赖的机制。这些实验将涉及使用来源于WS患者的细胞（可商购获得）以及干扰正常人成纤维细胞和人癌细胞系中WRN的功能/或表达的多种方法。最后，为了评估WRN在体内肿瘤发展中的作用，我们将在小鼠中采用建立的c-Myc诱导的淋巴瘤模型以及WRN敲除小鼠。最终，我们的目标是提供一个合理的开发WRN抑制剂，用于癌症的新治疗方法。我们的建议与衰老有关，提供了WRN基本功能的信息，WRN是一种明显与生物体衰老有关的基因，通过定义细胞如何在致癌刺激下绕过衰老，它对癌症也很重要。这项拨款提案的重点是我们以前的工作所支持的假设，即参与人类衰老的基因，称为沃纳综合征基因，也参与肿瘤细胞的“衰老”过程。事实上，众所周知，我们身体中的细胞也会老化。老细胞最终停止分裂，这种情况被称为不可逆的细胞周期停滞。这与肿瘤细胞的生长不相容，因此癌细胞设计了避免衰老的方法。我们以前的工作表明，WRN基因的存在是必要的，以避免正常细胞老化时，他们携带激活的癌基因。现在我们想直接测试抑制人类癌症细胞系中的WRN功能是否会导致肿瘤细胞衰老或停止生长。如果是这样的话，WRN功能的药物抑制剂可以用于治疗癌症。

DESCRIPTION (provided by applicant): The avoidance of senescence is an essential property of tumor cells. We are planning to determine the role played by the WRN and potentially related RecQ helicases in the avoidance of oncogene-induced senescence. In particular, we will focus on the c-Myc oncogene as we have shown that c-Myc stimulates transcription of the WRN gene and more important, that the WRN protein is required to avoid cellular senescence induced by c-Myc overexpression. Loss of function mutations of WRN causes a human premature progeria, Werner Syndrome (WS), whose symptoms mimic aspects of natural aging. Cells derived from WS patients also show premature senescence, indicating that the organismal phenotype might be due to accelerated cellular senescence. We hypothesize that WRN function is required for the avoidance of senescence of tumor cells and thus may represent an attractive therapeutic target for cancer treatment. WRN protein participates in DNA repair of abnormal structures generated during DNA replication and aggravated by drugs that cause a DNA replication block. Indeed the preliminary data indicate that the senescence response of WRN deficient cells upon c-Myc overexpression is due to DNA damage and resultant cellular checkpoint responses. In this proposal we plan to test this hypothesis, thus defining the mechanisms of WRN and c-Myc co-dependence. These experiments will involve use of cells derived from WS patients (commercially available) as well as a variety of approaches to interfere with function/or expression of WRN in normal human fibroblasts and in human cancer cell lines. Finally, to assess the role of WRN in tumor development in vivo we will employ an established c-Myc induced lymphoma model in mice together with WRN knock-out mice. Ultimately, our goal is to provide a rational to develop WRN inhibitors to be employed in new therapeutic approaches for cancer. Our proposal is relevant to aging providing information on the basic function of WRN, a gene clearly implicated in organismal aging, and it is also of importance for cancer by defining how cells bypass senescence under oncogenic stimulation. This grant proposal focus on the hypothesis, supported by our previous work, that a gene involved in human aging, called the Werner Syndrome gene, is also involved in the "aging" process of tumor cells. In fact, it is known that cells in our body also age. Old cells eventually stop dividing, a condition referred to as irreversible cell-cycle arrest". This is incompatible with tumor cell growth and thus cancer cells have devised ways of avoiding aging. Our previous work demonstrated that the presence of WRN gene was necessary to avoid aging of normal cells when they carry an activated cancer gene. Now we would like to directly test if inhibition of WRN function in cell lines derived from human cancers will cause tumor cells to age or to stop growing. If so, drug inhibitors of WRN function could be proposed for the treatment of cancer.