Cell type and molecular determinants of colorectal cancer initiation downstream of APC inactivation

APC失活后结直肠癌起始下游的细胞类型和分子决定因素 项目摘要 结直肠癌(CRC)是全球癌症相关死亡的主要原因。的长期目标是 本项目旨在了解细胞类型的特异性和分子机制，通过 APC抑癌基因的失活推动了结直肠癌的个体发生。APC基因发生突变 绝大多数的结直肠癌，被广泛认为是大多数此类癌症的始动事件。 正因为如此，人们通过大量的研究对分子机制进行了研究 哪个APC起作用。APC是规范的Wnt信号的一个公认的负调节因子 途径，因此存在大量证据表明，构成Wnt途径 APC丢失下游的激活对于CRC的启动和维护是必要的。然而，我们 提供初步数据和理由，表明这项研究在很大程度上被忽视了 这个肿瘤抑制因子的几个额外的重要功能，这些功能将代表 对结直肠癌的预防和治疗干预有价值的要点。具体地说，最近的证据 我们和其他人发现了APC丢失后激活的额外致癌途径 对于启动和维护CRC也是必要的。特别是，我们在前面的 MSI家族的RNA结合蛋白在Wnt-APC丢失时被激活的资金周期- 在小鼠和人结直肠癌模型中，MSI活性是结直肠癌所必需 启动和维持，仅MSI功能获得就足以改变肠道 上皮细胞以不依赖于WNT的方式。在细胞水平上，我们发现MSI的活动是特殊的 为了推动静止的(在G0中)肠道干细胞(ISCs)的代谢激活，导致细胞周期进入， 增殖，分化受阻。相反，MSI活性没有可识别的分子 对由Wnt途径活性驱动的活跃的ISC群体的影响，以前认为是细胞- 原产于中国。先前的研究发现，这些静止的ISCs对经典性WNT是难治性的 处于休眠状态的通路刺激。因此，我们假设APC的损失可能会引发 通过Wnt-2对静止的肠道干细胞进行异位激活的肿瘤发生 独立的机制。我们认为APC缺失启动了许多致癌途径 不依赖于典型的Wnt通路激活(包括MSI诱导)。我们将测试APC是否 Lost可通过将静止的ISCs赶出G0进入细胞周期来启动CRC，从而建立 静止的ISCs在结直肠癌中作为细胞或来源。我们将使用一个 基因组和基因技术的结合，最终目标是测试Wnt- APC丢失下游激活的独立通路是进行治疗干预的可行点 CRC。

Cell type and molecular determinants of colorectal cancer initiation downstream of APC inactivation Project Summary Colorectal cancer (CRC) is a leading cause of cancer-related deaths globally. The long-term objective of this project is to understand the cell type specificity and molecular mechanisms through which inactivation of the APC tumor suppressor drives the ontogeny of colorectal cancer. APC is mutated in the vast majority of CRC and is broadly considered the initiating event in most of these cancers. Because of this, there has been a large amount of research into the molecular mechanisms through which APC functions. APC is a well-established negative regulator of the canonical Wnt signaling pathway, and consequently a wealth of evidence exists demonstrating that constitutive Wnt pathway activation downstream of APC loss is necessary for initiation and maintenance of CRC. However, we provide preliminary data and rationale suggesting that this body of research has largely overlooked several additional important functions of this tumor suppressor, and that such functions will represent valuable points for preventative action and therapeutic intervention in CRC. Specifically, recent evidence from our group and others has uncovered additional oncogenic pathways activated upon APC loss that are also necessary for initiation and maintenance of CRC. In particular, we demonstrated in the prior funding period that the Msi family of RNA binding proteins are activated upon APC loss in a Wnt- independent manner in both murine and human CRC models, that Msi activity is necessary for CRC initiation and maintenance, and that Msi gain of function alone is sufficient to transform the intestinal epithelium in a Wnt-independent manner. At the cellular level, we found that Msi activity acts specifically to drive metabolic activation of quiescent (in G0) intestinal stem cells (ISCs) resulting in cell cycle entry, proliferation, and a block in their differentiation. In contrast, Msi activity has no discernable molecular effect on the active ISC population driven by Wnt pathway activity and previously posited to be the cell- of-origin in CRC. Previous studies have found that these quiescent ISCs are refractory to canonical Wnt pathway stimulation in their dormant state. Thus, we hypothesize that loss of APC can initiate tumorigenesis through promiscuous activation of quiescent intestinal stem cells via Wnt- independent mechanisms. We propose that APC loss initiates a number of oncogenic pathways independent of the canonical Wnt pathway activation (including Msi induction). We will test whether APC loss can initiate CRC by driving quiescent ISCs out of G0 and into the cell cycle, thus establishing quiescent ISCs as a cell-or-origin in colorectal cancer. We will address this hypothesis using a combination of genomic and genetic techniques with the ultimate goal of testing whether Wnt- independent pathways activated downstream of APC loss are viable points for therapeutic intervention in CRC.