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

• 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
• 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

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。 CRC肿瘤发生 通过从良性腺瘤到侵入性的结肠上皮逐步转化的模型进行进行 癌。这种遗传过程通常是从APC中的功能丧失突变引起的，该突变过度活化 Wnt信号通路，需要p53中的最终突变，以进行肿瘤的进展和侵袭。多数 CRC病例的特征也有染色体不稳定性（CIN），该病例早期出现并通过 肿瘤进展并实现驱动癌变的突变。尽管启用了转型 通过CIN，尚未完全理解CIN出现的机制。强大的候选人贡献者 早期CRC中的CIN是端粒功能障碍，当染色体末端缩短并且 未封闭并激活导致染色体终止伴侣的DNA损伤反应（DDR）。端粒 在腺瘤和癌活检中已经观察到侵蚀和融合，并已证明是相关的 与CIN一起，与端粒可能充当癌变的可能性一致。鉴于这些 观察结果，对调节端粒封盖的机制有更深入的了解和后果 需要在CRC进展过程中进行端粒解胶。我们的实验室以前发现了一种新颖的反馈 在端粒封盖和Wnt信号之间有助于稳态肠道维护的循环 和人类。通过此循环，端粒封盖的丢失会导致对Wnt途径活动的广泛抑制 在肠道隐窝上皮和基础基质中。我们确定在小鼠中，该调节涉及p53- 介导的表达miR-34a，一种靶向WNT途径成分的P53激活的microRNA。而且， Wnt途径的激活通过庇护素蛋白TRF2的上调加强了端粒上限。 因此，肠道中的端粒封盖和Wnt信号是相互支持的，并且反馈失调 CRC中的循环可能对具有功能失调端粒的细胞允许。本文提出的研究旨在 了解可能损害Wnt-Telomere反馈影响端粒的致癌CRC突变 CRC进展过程中的状态以及扰动端粒限制的程度促进肿瘤 生长。我的中心假设是，Wnt信号传导和端粒封盖之间的调节循环是 在CRC中破坏，使功能失调的端粒增强而不是抑制肿瘤发生。在AIM 1中，我会 使用人类结肠类器官模型来确定APC和p53突变如何破坏Wnt-Telomere的反馈。 在AIM 2中，我将表征这些突变与Wnt信号传导/TRF2表达之间的关系 人类CRC样品并确定在APC和p53损失的情况下诱导的端粒功能障碍是否 增强了鼠异种移植物中的器官生长。综上所述，这些研究将提供前所未有的 深入了解端粒功能障碍是早期CRC肿瘤发生的驱动力，并揭示有关该的新信息 发生结肠肿瘤的突变景观。