Genetic pathways of replicative senescence and its function in tumorigenesis

描述（由申请人提供）：为了维持组织稳态和正常功能，需要替换或修复受损细胞。在哺乳动物中，这样的过程需要大量的细胞增殖。这种大规模增殖的结果是突变的积累，其中一些可能针对致癌基因。为了抑制癌前细胞的增殖和生存，有效的肿瘤抑制机制必须发挥作用，其中之一就是衰老。衰老限制了细胞的增殖能力，从而阻碍了肿瘤发生所必需的多种突变的积累。此外，异常致癌激活、DNA损伤或氧化应激也可激活衰老，提供防止处于肿瘤转化风险的细胞增殖的故障安全机制。克服衰老是癌细胞获得的基本特性。尽管其重要性，衰老的分子调控知之甚少，许多关键的监管机构仍然不明。我们的长期目标是了解衰老的分子调控及其在肿瘤发生中的作用。我们最近已经确定Smurf2是一种新的衰老调节因子。其表达响应于人成纤维细胞中的端粒缩短而上调，并且这种升高的表达足以诱导衰老。我们的初步研究发现，Smurf2的下调延缓了人类成纤维细胞的衰老，而Smurf2缺陷的小鼠胚胎成纤维细胞在培养中是永生的。我们假设Smurf2通过其调节p16和p21衰老通路的能力来调节衰老，因此Smurf2可能在肿瘤发生中起重要作用。在这个提议中，我们将描述Smurf2在衰老调节和肿瘤发生中的功能，具有三个特定的目标。在目的1中，我们将描述Smurf2在p16衰老途径调节中的功能。在目标2中，我们将研究Smurf2调节p21衰老途径的机制。在目标3中，我们将研究Smurf2的功能及其在肿瘤发生中对衰老的调节。这些研究将为Smurf2在肿瘤发生中的功能提供直接证据。此外，这些研究将确定衰老途径中的新遗传成分，并为衰老如何调节提供新的见解，这是实现癌症治疗中衰老的伟大前景的重要一步。

DESCRIPTION (provided by applicant): To maintain tissue homeostasis and normal functions, damaged cells need to be replaced or repaired. In mammals, such process requires extensive cell proliferation. A consequence of this massive proliferation is the accumulation of mutations, some of which may target cancer causing genes. To constrain the proliferation and survival of precancerous cells, potent tumor suppression mechanisms must be functional, one of which is senescence. Senescence limits proliferative capacity of cells, thus impeding the accumulation of multiple mutations that are necessary for tumorigenesis. Furthermore, aberrant oncogenic activation, DNA damage or oxidative stress can also activate senescence, providing a failsafe mechanism that prevents the proliferation of cells at risk for neoplastic transformation. Overcoming senescence is an essential property acquired by cancer cells. Despite its importance, the molecular regulation of senescence is poorly understood, and many of the critical regulators remain unidentified. Our long-term goal is to understand the molecular regulation of senescence and its function in tumorigenesis. We recently have identified Smurf2 as a novel regulator of senescence. Its expression is up-regulated in response to telomere shortening in human fibroblasts, and such elevated expression is sufficient to induce senescence. Our preliminary studies have found that down-regulation of Smurf2 postpones senescence in human fibroblasts, whereas mouse embryonic fibroblasts deficient in Smurf2 are immortal in culture. We hypothesize that Smurf2 regulates senescence through its ability to modulate the p16 and p21 senescence pathways, and that consequently Smurf2 might play an important role in tumorigenesis. In this proposal, we will characterize the function of Smurf2 in senescence regulation and tumorigenesis with three specific aims. In Aim 1, we will characterize the function of Smurf2 in regulation of the p16 senescence pathway. In Aim 2, we will study the mechanism by which Smurf2 regulates the p21 senescence pathway. In Aim 3, we will investigate the function of Smurf2 and its regulation of senescence in tumorigenesis. These studies will provide direct evidence for a function of Smurf2 in tumorigenesis. Furthermore, these studies will identify new genetic components in the senescence pathways, and provide new insight into how senescence is regulated, an important step towards the fulfillment of the great promise of senescence in cancer treatment.