The Role of the Epigenetic Regulator UHRF1 in Colon Tumorigenesis

项目总结 调节所有染色质模板化过程的正常DNA甲基化模式的改变是一个标志 癌症的威胁。整体DNA低甲基化和局部高甲基化导致恶性转化和 肿瘤抑制基因(TSG)的沉默。DNA超甲基化的特定模式尤其是 出现在近端结直肠癌(CRC)的一个亚类中。这些右侧结直肠肿瘤通常表现为 CpG岛甲基化表型(CIMP)，其中许多正常未甲基化的启动子CpG岛 甲基化的频率和一致性都很高。这些异常的DNA甲基化模式是如何 建立和传播仍不清楚，而治疗药物打算逆转DNA 目前，高甲基化不能满足结直肠癌患者的需求。一种具有吸引人的属性的蛋白质 可以解释DNA高甲基化在结直肠癌中是如何发生的，是E3连接酶和表观遗传调节因子uhrf1。Uhrf1 通过重新招募维持DNA甲基转移酶DNMT1来指导DNA甲基化 复制的DNA。有证据表明uhrf1过表达，其在DNA甲基化中的作用是 在许多癌症中被挪用，包括结直肠癌。这项建议的目标是定义 受高水平的uhrf1影响，并确定uhrf1参与的机制。 通过改变DNA甲基化水平和模式来治疗结直肠癌。目标1将确定与CRC关联最多的子类 Uhrf1高表达。这对于确定抑制uhrf1将 对治疗有好处。这一目标将使用原代人类结肠癌组织来分离uhrf1高表达的肿瘤。 具有表观遗传表型。目的2探讨uhrf1在结肠癌形成和维持中的作用。这 目的将利用小鼠肠道上皮细胞衍生的肠道器官的体外模型系统。这 系统允许精确控制肠道肿瘤的发病表型，以促进对 Uhrf1在肿瘤启动或维持中的作用及其DNA甲基化的变化 当然了。最后，Aim 3查询确定的其他基因靶点，以调控表观遗传介导的沉默 TSGS。这些靶点是通过全基因组筛选确定的，包括两个已知的表观遗传学 以前未知的调节TSG沉默的调节因子和蛋白质。随着DNA超甲基化的逆转 为了重新启动TSG，这个项目的一个长期目标是更好地了解 重新激活表观遗传沉默的TSG并使用该信息所需的机制 完善对结直肠癌的治疗。因此，这项提案将解决哪个遗传/表观遗传亚类以及在什么时候 在肿瘤的形成中，uhrf1是重要的，除了通过表观遗传学更好地理解tsg沉默。 修改。这与公共卫生有很高的相关性，因为CRC的流行和迫切需要 寻找潜在的治疗靶点来逆转结直肠癌中异常的DNA甲基化和TSG沉默。

PROJECT SUMMARY Alterations to the normal DNA methylation patterns that regulate all chromatin-templated processes is a hallmark of cancer. Global DNA hypomethylation and local hypermethylation contribute to malignant transformation and the silencing of tumor suppressor genes (TSGs). Specific patterns of DNA hypermethylation are particularly present in a subclass of proximal colorectal cancers (CRC). These right-sided colorectal tumors often present with the CpG Island Methylator Phenotype (CIMP) in which many normally unmethylated promoter CpG islands are hypermethylated with high consistency and frequency. How these abnormal DNA methylation patterns are established and propagated remains unclear, while therapeutic agents intended to reverse DNA hypermethylation do not currently meet the needs of CRC patients. One protein with appealing attributes that may explain how DNA hypermethylation occurs in CRC is the E3 ligase and epigenetic regulator UHRF1. UHRF1 directs DNA methylation through recruitment of the maintenance DNA methyltransferase DNMT1 to newly replicated DNA. Evidence suggests UHRF1 is overexpressed and its function in DNA methylation is misappropriated in many cancers, including CRC. The objective of this proposal is to define the subclass of CRCs influenced by high UHRF1 levels and determine the mechanism through which UHRF1 contributes to CRC by altering DNA methylation levels and patterns. Aim 1 will identify the subclass of CRC most associated with high UHRF1 expression. This is critical to determining the CRC context for which inhibition of UHRF1 would have therapeutic benefit. This Aim will use primary human colon tumor tissue to segregate UHRF1-high tumors with epigenetic phenotypes. Aim 2 addresses the role of UHRF1 in colon tumor formation and maintenance. This aim will utilize an ex vivo model system of intestinal organoids derived from mouse intestinal epithelia. This system allows for precise control of the onset of an intestinal tumor phenotype to facilitate understanding of the contribution of UHRF1 to either tumor initiation or maintenance and changes in DNA methylation during this course. Finally, Aim 3 queries other gene targets identified to regulate the epigenetic-mediated silencing of TSGs. These targets were determined through a genome-wide screen and include both known epigenetic regulators and proteins previously unknown to regulate TSG silencing. As reversal of DNA hypermethylation is necessary for reactivation of TSGs, a long-term goal of this project is to gain a better understanding of the mechanisms necessary for reactivating TSGs that have been epigenetically silenced and using that information to refine CRC treatments. Thus, this proposal will address in which genetic/epigenetic subclass and at what point in tumor formation UHRF1 is important, in addition to better understanding TSG silencing through epigenetic modifications. This has high relevance to public health given the prevalence of CRC and the critical need for identifying potential therapeutic targets to reverse abnormal DNA methylation and TSG silencing in CRC.