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; 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）：肠上皮由快速骑自行车（LGR5+）肠道干细胞（ISC）的种群维持。但是，已经假设，肠道中还必须存在缓慢的循环ISC，以保护基因组免受有害突变的积累并允许对组织损伤的反应。我们已经确定了以端粒酶（MTERT）表达为特征的缓慢骑自行车的人群。 MTERT+细胞是稀有的单细胞，沿着隐裂宽轴的模式分布，类似于长期标记的细胞，并且对组织损伤具有抗性。谱系追踪研究表明，MTERT+细胞会引起所有分化的肠细胞类型并长期持续。此外，通过LGR5依赖性和LGR5独立途径，表达MTERT的细胞似乎有助于肠道谱系的发育。为了研究它们在肠癌中的作用，我们稳定了MTERT+细胞中的 - 蛋白酶，这导致了它们的戏剧性（1,500倍）激活。然而，令人惊讶的是，即使在6个月后，这些细胞中连续的典型Wnt信号传导也不会引起肠道腺瘤的形成。该结果与迅速循环的LGR5+ ISC稳定后看到的效果形成了鲜明的对比，后者在4周内会产生广泛的腺瘤。我们的研究支持这样的概念，即缓慢骑自行车和快速循环的ISC对肿瘤启动信号的反应明显不同。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，该机制在快速循环的LGR5+ ISC中缺乏。为了更好地定义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？ - 卡替宁的情况下，将MTERT和LGR5表达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，我们将在存在或不存在稳定的MTERT和LGR5表达ISC中对其表达模式进行全局分析。为了确定miRNA在表达mTERT的ISC中稳定腺瘤后是否在抑制腺瘤形成中起功能作用，我们将在这些细胞中删除关键miRNA加工酶的dicer，以确定在腺瘤形成中这种调节系统结果是否灭活。同样，我们将在表达LGR5的ISC中删除DICER，以确定miRNA在诱导腺瘤形成中是否具有功能作用。结果将产生对肠道干细胞中腺瘤启动的机制的新见解。