LEF/TCF Function in Adult Stem Cell Fate and Tumorigenesis

描述（由申请人提供）：本提案的长期目标是了解特定的遗传变化如何导致成体上皮干细胞内的异常命运决定和生长调节，以及这些变化如何促进干细胞形成肿瘤。LEF/TCF家族转录因子在干细胞介导的皮肤稳态中发挥重要作用。我们已经证明，人类皮脂腺肿瘤与由显性阴性的Lef-1基因诱导的小鼠肿瘤相似，我们最近在皮脂腺皮肤肿瘤中发现了Lef-1基因的突变。此外，TCF-4突变发生在很大比例的结肠癌中。因此，我们的假设是，LEF/TCF突变导致干细胞命运的异常决定和生长，从而促进皮肤皮脂腺肿瘤的形成。具体目的：(1)确定LEF-1失调促进人皮肤多能干细胞肿瘤发生的细胞机制。(2)确定一种新的皮脂腺肿瘤细胞系的细胞和分子特性，该细胞系显示缺乏LEF-1信号。(3)调查人类皮脂腺皮肤肿瘤中LEF/TCF突变的谱和发生率及其与肿瘤形态的关系。为了实现这些目标，我们将使用一种新的系统分离人皮肤成体上皮干细胞，并研究由改变的LEF-1信号引起的细胞变化。我们将使用体外分析，以及分子和生化测试来表征新的皮脂腺肿瘤细胞系。最后，将通过几种分子技术筛选大型皮脂腺肿瘤档案组织库，以确定LEF-1， TCF-3和TCF-4基因的突变。相关性：Muir-Torre综合征是一种基因遗传的DNA修复缺陷，患者可发展为许多皮脂腺皮肤肿瘤，并具有结肠癌的高风险。大约25%的眼睑皮脂腺肿瘤患者需要切除眼睛。这项工作将为皮脂腺皮肤肿瘤的发病机制提供重要的见解，可能导致预防或治疗这些肿瘤的新方法，并可能对成人上皮干细胞引起的其他癌症有更广泛的影响。

DESCRIPTION (provided by applicant): The long-term objectives of this proposal are to understand how specific genetic changes cause abnormal fate determination and growth regulation within adult epithelial stem cells and how these changes promote tumor formation from stem cells. The LEF/TCF family of transcription factors play an essential role in stem cell-mediated skin homeostasis. We have shown that human sebaceous tumors are similar to mouse tumors induced by a dominant negative Lef-1 gene and we recently identified mutations within the LEF-1 gene of sebaceous skin tumors. In addition, TCF-4 mutations occur in a significant proportion of colon cancers. Thus, our HYPOTHESIS is that LEF/TCF mutations cause abnormal stem cell fate determination and growth that promotes the formation of sebaceous tumors of the skin. Specific Aims: (1) Determine the cellular mechanisms by which dysregulated LEF-1 promotes tumorigenesis in multi-potent stem cells of human skin. (2) Determine the cellular and molecular properties of a new sebaceous tumor cell line showing deficient LEF-1 signaling. (3) Survey the spectrum and incidence of LEF/TCF mutations in human sebaceous skin tumors and correlate with tumor morphology. In order to accomplish these aims, we will use a novel system to isolate adult epithelial stem cells of human skin and study the cellular changes induced by altered LEF-1 signaling. We will use in vitro assays, as well as molecular and biochemical tests to characterize a new sebaceous tumor cell line. Lastly, a large archival tissue bank of sebaceous tumors will be screened by several molecular techniques to identify mutations within the LEF-1, TCF-3 and TCF-4 genes. Relevance: Patients with Muir-Torre syndrome, a genetically inherited defect of DNA repair, develop many sebaceous skin tumors and are at a high risk of colon cancer. Sebaceous tumors of the eyelid require removal of the eye in almost 25% of patients. This work should provide significant insights into the pathogenesis of sebaceous skin tumors, may lead to new ways of preventing or treating these tumors and may have broader implications for other cancers arising from adult epithelial stem cells.