Role of Slowly Cycling Stem Cells in Cancer

缓慢循环干细胞在癌症中的作用

• 批准号: 8435340
• 负责人: David T Breault
• 金额: $ 17.79万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8435340
• 关键词: Cells; Development; Enzymes; Exhibits; Gene Expression; Genome; Injury; Intestinal Cancer; Intestines; Label; Malignant Neoplasms; MicroRNAs; Molecular; Molecular Profiling; Mutation; Pathway interactions; Pattern; Play; Population; Positioning Attribute; Process; Repression; Resistance; Role; Signal Transduction; Stem cells; System; Telomerase; Tissues; Villus; adenoma; base; cancer stem cell; cell type; comparative; human DICER1 protein; insight; intestinal epithelium; research study; response; screening; tumor

DESCRIPTION (provided by applicant): The intestinal epithelium is maintained by a population of rapidly cycling (Lgr5+) intestinal stem cells (ISCs). It has been postulated, however, that slowly cycling ISCs must also be present in the intestine to protect the genome from accumulating deleterious mutations and allow for response to tissue injury. We have identified a population of slowly cycling ISCs that is marked by telomerase (mTert) expression. mTert+ cells are rare single cells that distribute in a pattern along the crypt-villus axis similar to long-term label-retaining cells and are resistant to tissue injury. Lineage-tracing studies demonstrate that mTert+ cells give rise to all differentiated intestinal cell types and persist long term. Moreover, mTert-expressing cells appear to contribute to intestinal lineage development through both Lgr5-dependent and Lgr5- independent pathways. In order to investigate their role in intestinal cancer we stabilized ?-catenin within mTert+ cells, which resulted in their dramatic (1,500-fold) activation. Surprisingly, however, continuous canonical Wnt signaling in these cells did not give rise to intestinal adenoma formation, even after 6 months. This result stands in stark contrast to the effect seen following stabilization of ?-catenin within rapidly cycling Lgr5+ ISCs, which generate extensive adenomas within 4 weeks. Our studies support the concept that slowly cycling and rapidly cycling ISCs exhibit distinctly different responses to tumor initiating signals. We hypothesize that the lack of adenoma formation in mTert+ cells is due to a mechanism of "enforced quiescence" regulating these slowly cycling ISCs, which is lacking in rapidly cycling Lgr5+ ISCs. In order to better define the mechanisms leading to adenoma formation or repression, these studies will investigate the gene expression profiles of mTert- and Lgr5-expressing ISCs in the presence or absence of stabilized ?-catenin. To determine the role of microRNAs (miRNAs) in adenoma formation and repression we will perform global analysis of their expression patterns in the presence or absence of stabilized ?-catenin in mTert- and Lgr5-expressing ISCs. To determine whether miRNAs play a functional role in the repression of adenoma formation following stabilization of ?-catenin in mTert-expressing ISCs we will delete Dicer, the critical miRNA processing enzyme, within these cells to establish whether inactivation of this regulatory system results in adenoma formation. Similarly, we will delete Dicer in Lgr5-expressing ISCs to determine whether miRNAs have a functional role in the induction of adenoma formation. The results will generate new insight into the mechanisms underlying adenoma initiation in intestinal stem cells.

描述（由申请人提供）：肠上皮由快速循环（Lgr5+）肠干细胞（ISC）群体维持。然而，据推测，缓慢循环的 ISC 也必须存在于肠道中，以保护基因组免于积累有害突变，并对组织损伤做出反应。我们已经鉴定出一群缓慢循环的 ISC，其特征是端粒酶 (mTert) 表达。 mTert+ 细胞是罕见的单细胞，沿着隐窝-绒毛轴以类似于长期标记保留细胞的模式分布，并且对组织损伤具有抵抗力。谱系追踪研究表明，mTert+ 细胞可产生所有分化的肠道细胞类型并长期存在。此外，表达 mTert 的细胞似乎通过 Lgr5 依赖性和 Lgr5 独立途径促进肠道谱系发育。为了研究它们在肠癌中的作用，我们稳定了 mTert+ 细胞内的 β-连环蛋白，这导致它们显着（1,500 倍）激活。然而，令人惊讶的是，即使在 6 个月后，这些细胞中持续的经典 Wnt 信号传导也没有引起肠腺瘤的形成。这一结果与快速循环的 Lgr5+ ISC 中β-连环蛋白稳定后所观察到的效果形成鲜明对比，后者在 4 周内产生广泛的腺瘤。我们的研究支持这样的概念：缓慢循环和快速循环的 ISC 对肿瘤起始信号表现出明显不同的反应。我们假设 mTert+ 细胞中缺乏腺瘤形成是由于调节这些缓慢循环的 ISC 的“强制静止”机制，而快速循环的 Lgr5+ ISC 缺乏这种机制。为了更好地确定导致腺瘤形成或抑制的机制，这些研究将研究在存在或不存在稳定的β-连环蛋白的情况下表达 mTert 和 Lgr5 的 ISC 的基因表达谱。为了确定 microRNA (miRNA) 在腺瘤形成和抑制中的作用，我们将在表达 mTert 和 Lgr5 的 ISC 中存在或不存在稳定的 β-连环蛋白的情况下对其表达模式进行全局分析。为了确定表达 mTert 的 ISC 中 β-连环蛋白稳定后 miRNA 是否在抑制腺瘤形成中发挥功能性作用，我们将删除这些细胞内的关键 miRNA 加工酶 Dicer，以确定该调节系统的失活是否会导致腺瘤形成。同样，我们将删除表达 Lgr5 的 ISC 中的 Dicer，以确定 miRNA 是否在诱导腺瘤形成中具有功能性作用。这些结果将为肠道干细胞中腺瘤发生的机制提供新的见解。