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

APC失活下游大肠癌发生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 该项目旨在了解细胞类型特异性和分子机制， APC肿瘤抑制因子的失活驱动结肠直肠癌的个体发生。APC突变， 绝大多数CRC，并且被广泛认为是大多数这些癌症的起始事件。 正因为如此，已经有大量的研究进入分子机制， APC的功能。APC是经典Wnt信号传导的公认负调节因子， 因此，大量证据表明，组成性Wnt途径 APC缺失下游的激活对于CRC的起始和维持是必需的。但我们 提供初步的数据和理由，表明这一机构的研究在很大程度上忽视了 这种肿瘤抑制因子的几个额外的重要功能，这些功能将代表 对CRC的预防措施和治疗干预有价值的观点。特别是最近的证据 来自我们小组和其他人的研究揭示了在APC丧失后激活的额外致癌途径， 也是启动和维持CRC所必需的。特别是，我们在先前的实验中证明了 资助期，Msi家族的RNA结合蛋白在Wnt中APC丢失后被激活， 在鼠和人CRC模型中，Msi活性是CRC所必需 启动和维持，且Msi功能单独获得足以将肠 上皮以Wnt非依赖性方式。在细胞水平上，我们发现Msi活动特异性地作用于 为了驱动静止（G 0）肠干细胞（ISC）的代谢活化导致细胞周期进入， 增殖和阻断其分化。相比之下，Msi活性没有可辨别的分子 对由Wnt途径活性驱动的活性ISC群体的影响，并且先前被认为是细胞- CRC中的原产地。以前的研究发现，这些静止的ISCs对经典Wnt不敏感， 在他们的休眠状态下的刺激途径。因此，我们假设APC的丢失可以启动 肿瘤发生通过混杂激活静止的肠干细胞通过Wnt- 独立的机制。我们认为APC的丢失启动了许多致癌途径 独立于经典Wnt途径活化（包括Msi诱导）。我们将测试APC是否 缺失可以通过将静止的ISC从G 0中驱动出来并进入细胞周期来启动CRC，从而建立 静止ISCs作为结直肠癌的细胞或起源。我们将使用一个 基因组和遗传技术的结合，最终目标是测试Wnt- APC缺失下游激活的独立途径是治疗干预的可行点， 《儿童权利公约》。

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.