Role of RecQ Helicases to Prevent Senescence By c-Myc

描述(申请人提供)：避免衰老是肿瘤细胞的基本属性。我们正计划确定WRN和潜在相关的RecQ解旋酶在避免癌基因诱导的衰老中所起的作用。我们将特别关注c-Myc癌基因，因为我们已经证明c-Myc刺激WRN基因的转录，更重要的是，WRN蛋白是避免c-Myc过表达诱导细胞衰老所必需的。WRN功能突变的丧失会导致人类早衰症，Werner综合征(WS)，其症状类似自然衰老的方面。来自WS患者的细胞也表现出提前衰老，表明机体表型可能是由于细胞加速衰老所致。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剧。事实上，初步数据表明，WRN缺陷细胞对c-Myc过度表达的衰老反应是由于DNA损伤和由此产生的细胞检查点反应。在这个建议中，我们计划检验这一假设，从而定义WRN和c-Myc相互依赖的机制。这些实验将涉及使用来自WS患者的细胞(可从商业上获得)以及各种方法来干扰正常人类成纤维细胞和人类癌细胞系中WRN的功能/或表达。最后，为了评估WRN在体内肿瘤发展中的作用，我们将使用建立的c-Myc诱导的小鼠淋巴瘤模型和WRN基因敲除小鼠。最终，我们的目标是为开发WRN抑制剂提供一种合理的方法，用于癌症的新治疗方法。我们的建议与衰老相关，提供了关于WRN基本功能的信息，WRN是一个明显与生物衰老有关的基因，它也对癌症至关重要，因为它定义了细胞如何在致癌刺激下绕过衰老。这项拨款建议集中在我们之前的工作支持的假设上，即一种与人类衰老有关的基因，称为沃纳综合征基因，也参与了肿瘤细胞的“老化”过程。事实上，众所周知，我们体内的细胞也会衰老。老年细胞最终停止分裂，这种情况被称为不可逆转的细胞周期停滞。这与肿瘤细胞的生长不相容，因此癌细胞已经设计出避免衰老的方法。我们之前的工作表明，当正常细胞携带激活的癌症基因时，WRN基因的存在对于避免正常细胞的衰老是必要的。现在我们想直接测试抑制人类癌症细胞系中WRN功能是否会导致肿瘤细胞老化或停止生长。如果是这样，可以建议使用WRN功能的药物抑制剂来治疗癌症。

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.