Investigating a Wnt-telomere feedback loop in the colorectal adenoma-carcinoma sequence

研究结直肠腺瘤-癌序列中的 Wnt 端粒反馈环路

基本信息

批准号：
10232000
负责人：
Katrina Noel Estep
金额：
$ 4.6万
依托单位：
UNIVERSITY OF PENNSYLVANIA
依托单位国家：
美国
项目类别：
财政年份：
2021
资助国家：
美国
起止时间：
2021-03-01 至 2025-02-28
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10232000
关键词：
APC gene Address Apoptosis Benign Biological Assay Biopsy CRISPR/Cas technology Cancer Etiology Carcinoma Cell Line Cell Nucleus Cell Proliferation Cells Cessation of life Chromosomal Instability Chromosomes Collection Colon Colon Carcinoma Colonic Neoplasms Colorectal Adenocarcinoma Colorectal Adenoma Colorectal Cancer DNA Damage Dominant-Negative Mutation Down-Regulation Doxycycline Engineering Enzymes Epithelial Feedback Functional disorder Gene Expression Profiling Genes Genetic Processes Genetic Transcription Genotype Growth Human Intestines Knock-out Laboratories Length Lesion Link Maintenance Malignant Neoplasms Measures Mediating Methods MicroRNAs Modeling Molecular Monitor Mus Mutate Mutation Nude Mice Oncogenic Organoids Pathway interactions Polyps Primary Neoplasm Proteins Regulation Risk Sampling Signal Pathway Signal Transduction Stains TP53 gene Telomerase Telomere Capping Telomere Shortening Telomeric Repeat Binding Protein 2 Testing Tissue Sample Tissues Transgenes Tumor Cell Invasion Tumor Suppressor Proteins Up-Regulation WNT Signaling Pathway Xenograft procedure adenoma anti-cancer beta catenin carcinogenesis colon tumorigenesis colorectal cancer progression early onset colorectal cancer experimental study improved induced pluripotent stem cell insight intestinal crypt loss of function loss of function mutation mutant mutational status novel premalignant prevent response senescence stem cells subcutaneous telomere telomere loss tumor tumor growth tumor progression tumorigenesis tumorigenic

项目摘要

ABSTRACT: Colorectal adenocarcinoma (CRC) is a leading cause of cancer deaths globally. CRC tumorigenesis proceeds through a model of stepwise transformation of the colonic epithelium from benign adenoma to invasive carcinoma. This genetic process generally initiates from loss-of-function mutations in APC, which hyperactivate the Wnt signaling pathway, and requires eventual mutations in p53 for tumor progression and invasion. A majority of CRC cases is also characterized by chromosomal instability (CIN), which arises early and increases through tumor progression and which enables mutations that drive carcinogenesis. Despite enablement of transformation by CIN, the mechanisms by which CIN arises are not completely understood. A strong candidate contributor to CIN in early CRC is telomere dysfunction, which occurs when chromosome ends become shortened and uncapped and activate a DNA damage response (DDR) that leads to chromosome end-fusions. Telomere erosion and fusions have been observed in adenoma and carcinoma biopsies and have been shown to correlate with CIN, consistent with the possibility that telomeres may function as a driver of carcinogenesis. Given these observations, a deeper understanding of the mechanisms that regulate telomere capping and the consequences of telomere uncapping during CRC progression is needed. Our laboratory previously uncovered a novel feedback loop between telomere capping and Wnt signaling that contributes to homeostatic intestinal maintenance in mice and humans. Through this loop, loss of telomere capping leads to a broad suppression of Wnt pathway activity in intestinal crypt epithelia and underlying stroma. We determined that in mice this regulation involves p53- mediated expression miR-34a, a p53-activated microRNA which targets Wnt pathway components. Moreover, activation of the Wnt pathway reinforces telomere capping through upregulation of the shelterin protein TRF2. Thus, telomere capping and Wnt signaling in the gut are mutually supportive, and dysregulation of this feedback loop in CRC may be permissive for cells harboring dysfunctional telomeres. The study proposed herein aims to understand how oncogenic CRC mutations that might compromise Wnt-telomere feedback impact telomere status during CRC progression, as well as the extent to which perturbed telomere capping promotes tumor growth. My central hypothesis is that the regulatory loop between Wnt signaling and telomere capping is disrupted in CRC such that dysfunctional telomeres enhance, rather than inhibit, tumorigenesis. In Aim 1, I will use a human colonic organoid model to determine how APC and p53 mutations disrupt Wnt-telomere feedback. In Aim 2, I will characterize the relationship between these mutations and Wnt signaling/TRF2 expression in human CRC samples and determine whether induced telomere dysfunction in the setting of APC and p53 loss enhances organoid growth in murine xenografts. Taken together, these studies will provide unprecedented insight into telomere dysfunction as a driver of early CRC tumorigenesis and reveal new information about the mutational landscape of developing colon tumors.

抽象的：结直肠腺癌（CRC）是全球癌症死亡的主要原因。结直肠癌肿瘤发生通过结肠上皮从良性腺瘤逐步转变为侵袭性腺瘤的模型进行癌。这种遗传过程通常始于 APC 的功能丧失突变，该突变过度激活 Wnt 信号通路，并且需要 p53 最终突变才能促进肿瘤进展和侵袭。多数 CRC 病例的另一个特点是染色体不稳定性 (CIN)，它出现较早，并随着时间的推移而增加肿瘤进展并导致突变导致癌变。尽管实现转型 CIN 的发生机制尚不完全清楚。强有力的候选人贡献者早期 CRC 中的 CIN 是端粒功能障碍，当染色体末端缩短且脱帽并激活 DNA 损伤反应 (DDR)，从而导致染色体末端融合。端粒在腺瘤和癌活检中观察到侵蚀和融合，并已被证明与与 CIN 相关，这与端粒可能作为致癌驱动因素的可能性一致。鉴于这些观察，更深入地了解调节端粒加帽的机制及其后果 CRC进展期间需要端粒脱帽。我们的实验室之前发现了一种新颖的反馈端粒加帽和 Wnt 信号之间的环有助于小鼠肠道稳态的维持和人类。通过这个循环，端粒加帽的丧失会导致 Wnt 通路活性的广泛抑制在肠隐窝上皮和下面的基质中。我们确定在小鼠中这种调节涉及 p53- miR-34a 介导的表达，这是一种 p53 激活的 microRNA，靶向 Wnt 通路成分。而且， Wnt 通路的激活通过上调庇护蛋白 TRF2 来增强端粒加帽。因此，端粒加帽和肠道中的 Wnt 信号传导是相互支持的，并且这种反馈的失调 CRC 中的环可能允许含有功能失调端粒的细胞。本文提出的研究旨在了解可能损害 Wnt 端粒反馈的致癌 CRC 突变如何影响端粒 CRC进展期间的状态，以及端粒加帽扰动促进肿瘤的程度生长。我的中心假设是 Wnt 信号传导和端粒加帽之间的调节环路是 CRC 中的端粒被破坏，导致功能失调的端粒增强而不是抑制肿瘤发生。在目标 1 中，我将使用人类结肠类器官模型来确定 APC 和 p53 突变如何破坏 Wnt 端粒反馈。在目标 2 中，我将描述这些突变与 Wnt 信号/TRF2 表达之间的关系人类 CRC 样本并确定在 APC 和 p53 丢失的情况下是否会诱导端粒功能障碍增强小鼠异种移植物中的类器官生长。总而言之，这些研究将提供前所未有的深入了解端粒功能障碍作为早期 CRC 肿瘤发生的驱动因素，并揭示有关端粒功能障碍的新信息发展中的结肠肿瘤的突变景观。