Embryonic Stem Cell Properties in Cancer

描述(申请人提供)：Wnt信号蛋白？-catenin的不适当激活会导致多种器官的癌症，包括~90%的结直肠癌。β-连环蛋白也被证明可以促进成体干细胞和胚胎干细胞的自我更新。几项研究表明，β-连环蛋白对干细胞的影响与其致癌能力直接相关；然而，将Tcf-连环蛋白对干细胞的影响与肿瘤形成联系起来的下游机制仍然是该领域的一个重要问题。为了让连环蛋白刺激肿瘤的形成和干细胞的自我更新，它与Tcf蛋白家族的成员结合，而Tcf家族的成员是Wnt-连环蛋白信号的DNA结合效应器。一种Tcf蛋白，Tcf3，在几种不同类型的干细胞(造血细胞、神经干细胞、胚胎干细胞、毛囊干细胞)中表达，这些干细胞对β-连环蛋白水平敏感。我们的初步研究表明，Tcf3在干细胞中作为连环蛋白的抑制因子发挥作用，这表明Tcf3可能具有肿瘤抑制因子样的功能。这项建议侧重于Tcf3在小鼠中的作用，特别是当它们与干细胞自我更新和肿瘤形成有关时。我们提出了两个特定的目标：(1)确定Tcf3在其高表达的器官(前列腺、结肠)和我们发现在TCF3+/-小鼠身上发生肿瘤的器官(子宫)中预防癌症的功能；(2)阐明Tcf3调控干细胞自我更新的下游分子机制。TCF3条件性基因敲除小鼠的下游机制检查(AIM 2)将用于确定小鼠缺陷的根本原因。拟议中的实验将对干细胞自我更新和肿瘤形成的潜在分子控制产生重要的新理解。如果他们证明Tcf3的缺失会导致肿瘤的形成，他们将识别出一种潜在的新的肿瘤抑制基因。如果他们揭示TCF3的缺失不会增加癌症的易感性，他们将找到安全的基于细胞的疗法的新途径，以促进干细胞的自我更新。与公共卫生相关：拟议的研究将阐明干细胞中的基因决定干细胞是否会产生更多干细胞、产生不同类型的细胞或停止分裂的基本机制。此外，使用小鼠进行的强大的基因实验将确定影响成年干细胞中这些基本机制的分子控制的缺陷如何导致子宫、结肠和前列腺等器官的恶性肿瘤。

DESCRIPTION (provided by applicant): Inappropriate activation of the Wnt-signaling protein, ¿-catenin causes cancer in a wide range of organs, including ~90% of colorectal cancers. ¿ -catenin has also been shown to promote self-renewal of adult stem cells and embryonic stem cells. Several studies suggest that effects of ¿ -catenin on stem cells are directly linked to its ability to cause cancer; however the downstream mechanisms connecting Tcf- ¿ -catenin effects on stem cells and tumor formation remain a significant question in the field. In order for ¿ -catenin to stimulate tumor formation and stem cell self-renewal, it binds to members of the Tcf family of proteins, which function as the DNA-binding effectors of Wnt- ¿ -catenin signaling. One Tcf protein, Tcf3, is expressed in several different types of stem cells (hematopoietic, neural, embryonic, hair follicle) that are sensitive to ¿-catenin levels. Our preliminary studies demonstrate that Tcf3 functions as an inhibitor of ¿ -catenin in stem cells, suggesting the possibility that Tcf3 has tumor suppressor-like functions. This proposal focuses on the effects of Tcf3 in mice specifically as they relate to stem cell self renewal and tumor formation. We propose two specific aims: (1) to determine the function of Tcf3 in preventing cancer in organs where it is highly expressed (prostate, colon) and in an organ (uterus) that we found to develop tumors in TCF3+/- mice, and (2) to elucidate the downstream molecular mechanisms used by Tcf3 that regulate stem cell self renewal. Examination of the downstream mechanisms (Aim 2) in TCF3 conditional knockout mice (Aim 1) will be used to determine the underlying cause of defects in mice. The proposed experiments will generate important new understanding into the underlying molecular controls of stem cell self renewal and tumor formation. Should they demonstrate that loss of Tcf3 leads to tumor formation, they will identify a potentially novel tumor suppressor gene. Should they reveal that loss of Tcf3 does not confer a susceptibility to cancer, they will identify new avenues for safe cell-based therapeutics to promote stem cell self renewal. PUBLIC HEALTH RELEVANCE: The proposed research will elucidate fundamental mechanisms by which genes in stem cells determine whether stem cells will make more stem cells, make different cell types, or stop dividing. In addition, powerful genetic experiments using mice will determine how defects affecting the molecular control of these fundamental mechanisms in adult stem cells could lead to malignancies in organs such as the uterus, colon and prostate.