Elucidating the Role of SMAD4 in Colorectal Cancer

项目摘要/摘要 结肠癌是美国与癌症相关的死亡的第二大原因，也是最好的- 以实体肿瘤的常见基因突变为特征。然而，知识差距存在于 对这些癌症基因图谱下游的基本了解。例如，肿瘤抑制因子 Smad4基因在大约57%的结肠肿瘤中发生突变，并与结肠癌的不良预后有关 然而，对其在结肠癌中的分子机制仍知之甚少。另外， 而约70%的结肠癌遵循典型的WNT驱动的腺瘤到癌的途径，大约 20%的人遵循“锯齿状肿瘤路径”--通常是由功能获得型BRAF突变驱动的，并且有最差的 结肠癌的预后。该提案的主要目标将集中在阐明 结肠癌中的肿瘤抑制基因Smad4。假设Smad4在转录过程中起关键作用。 在调节WNT途径中发挥调节作用，并且是锯齿状肿瘤途径中的关键调节因子。这个 理论基础是基于初步研究揭示的：1)Smad4与基因组的调节区结合 也受？-catenin结合--最常见的突变信号通路的转录效应因子 结肠癌，WNT途径；和2)Smad4的缺失，当与BRAF的激活结合时，可以触发 在小鼠体内形成锯齿状肿瘤最快可达1个月。目标1将使用表观基因组学方法来绘制 Smad4与连接蛋白在DNA结合水平上的相互作用--详述它们的第一个交叉点 结肠癌基因组上的通路。Aim 2将使用新的鼠标模型来确定Smad4如何 抑制锯齿状癌从增生性病变到不典型增生的转变。目标3将使用最新的- ART肿瘤器官模型系统以确定Smad4如何抑制锯齿状癌症转移。目标是 是为了检验以下假设：1)Smad4通过重定向连接蛋白直接调节WNT信号通路 与RUNX3协同的肿瘤抑制基因靶点，从而影响癌症的发展，以及2) Smad4抑制锯齿状肿瘤进展所需的关键信号通路，并 转移。拟议的研究具有重要意义，因为它们将确定一种常见的 突变的肿瘤抑制基因，并为未被研究但更致命的结肠提供了新的视角 癌症肿瘤类型。这些研究将在癌症研究领域产生广泛影响，并将揭示新的 识别和治疗锯齿状肿瘤患者的目标。在Michael Verzi博士和 罗纳德·哈特，这项提议的培训计划将为我过渡到独立做好准备，1)继续 增强我的表观基因组学技能，2)开发新的模型系统来解决结肠中的关键问题 癌症领域，以及3)加强建立和维护我自己的独立研究计划所需的技能。 对于我的博士后来说，罗格斯大学的遗传学系一直是一个杰出的机构 训练，当我向独立过渡时，我将从环境中受益良多。

Project Summary/Abstract Colon cancer is the 2nd-leading cause of cancer-related deaths in the United States and is one of the best- characterized solid tumors in terms of its common genetic mutations. However, knowledge gaps exist in the basic understanding of these cancers downstream of their genetic profile. For instance, the tumor-suppressor gene SMAD4 is mutated in approximately 57% of all colon tumors, and is associated with poor prognosis in patients, yet there is still little understanding of its molecular mechanisms in colon cancer. Additionally, while ~70% of colon cancers follow the typical WNT-driven adenoma-to-carcinoma pathway, approximately 20% follow the “serrated tumor pathway”- often driven by gain-of-function BRAF mutations and have the worst prognosis of colon cancers. The proposal’s main objective will focus on elucidating the mechanistic role of the tumor suppressor SMAD4 in colon cancers. The hypothesis is that SMAD4 plays a critical transcriptional regulatory role in regulating the WNT pathway and is a key regulator in the serrated tumor pathway. The rationale is based on preliminary studies that reveal: 1) that SMAD4 binds to regulatory regions of the genome also bound by ß-catenin – the transcriptional effector of the most commonly mutated signaling pathway in colon cancer, the WNT pathway; and 2) SMAD4 loss, when combined with activation of BRAF, can trigger serrated tumor formation as rapidly as 1 month in mice. Aim 1 will use epigenomic approaches to map the interaction of SMAD4 with ß-catenin at the level of DNA-binding - detailing the first intersection of these pathways on the colon cancer genome. Aim 2 will use new mouse models to determine how SMAD4 suppresses the serrated cancer transition from hyperplastic lesions to dysplasias. Aim 3 will use state-of-the- art tumor organoid model systems to determine how SMAD4 suppresses serrated cancer metastasis. The goal is to test the hypotheses that 1) SMAD4 directly regulates the WNT-signaling pathway by redirecting ß-catenin to tumor-suppressive gene targets in coordination with RUNX3, thus impacting cancer development, and 2) that SMAD4 suppresses key signaling pathways that are required for serrated tumor progression and metastasis. The proposed studies are significant in that they will identify the regulatory targets of a commonly mutated tumor-suppressor gene and present a new perspective on an understudied, but more deadly, colon cancer tumor type. These studies would have broad impacts in the cancer research field, and will reveal new targets to identify and treat patients with serrated tumors. With the co-mentorship of Drs. Michael Verzi and Ronald Hart, this proposal's training plan will prepare me for a transition to independence by 1) continuing to enhance my epigenomics skillset, 2) develop novel model systems to address critical questions in the colon cancer field, and 3) fortify the skills required to establish and maintain my own independent research program. The Department of Genetics at Rutgers University has been an outstanding institution for my postdoctoral training, and I will benefit greatly from the environment as I transition towards independence.