SOX2-MYC Axis: Transcriptional Repression of the MYC Oncogene by SOX2

SOX2-MYC 轴：SOX2 对 MYC 癌基因的转录抑制

• 批准号: 10673740
• 负责人: A. ANGIE RIZZINO
• 金额: $ 7.68万
• 依托单位: UNIVERSITY OF NEBRASKA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10673740
• 关键词: 3-Dimensional; Acceleration; Address; Binding; Cell Cycle; Cell Line; Cell Proliferation; Cell Survival; Cells; Chromatin Loop; Chromatin Structure; Clinical; Complex; Data Analyses; Development; Distal; Down-Regulation; Doxycycline; Engineering; Enhancers; Failure; Gene set enrichment analysis; Genes; Genetic Transcription; Goals; Growth; Human; LNCaP; Link; MYC gene; Malignant Neoplasms; Molecular; Organ; Play; Population; Positioning Attribute; Proliferating; Prostate; Proteins; RNA; Recurrent Malignant Neoplasm; Recurrent tumor; Residual state; Resistance; Response Elements; Role; Structure; Testing; Transactivation; Tumor Cell Line; WNT Signaling Pathway; Work; anticancer research; beta catenin; c-myc Genes; cancer recurrence; cancer therapy; cell growth; cell type; chromatin immunoprecipitation; chromosome conformation capture; conventional therapy; fetal stem cell; gene repression; histone modification; in vivo; medulloblastoma; neoplastic cell; new therapeutic target; novel; promoter; response; small molecule inhibitor; stem cells; transcription factor; transcriptome; transcriptome sequencing; tumor; tumor growth

ABSTRACT A wide array of strategies and small molecule inhibitors have been identified that target actively proliferating tumor cells. However, quiescent tumor cells are largely resistant to conventional therapies used to eliminate proliferating tumor cells. Hence, quiescent tumor cells pose a major clinical challenge and a significant unmet need in the treatment of cancer, because quiescent cells represent a residual population of tumor cells that can drive tumor recurrence. To address this unmet need, we have been studying the transcription factor SOX2, whose elevated expression has been shown to restrict the proliferation of many different tumor cell types as well as the proliferation of normal fetal stem cells. Our work has established that elevating SOX2 from an inducible promoter in multiple tumor cell types invariably leads to growth inhibition. Moreover, we determined that elevating SOX2 in vivo leads to a reversible state of tumor growth arrest, where tumor growth resumes when SOX2 returns to endogenous levels. To determine how SOX2 restricts tumor cell growth, we examined how elevating SOX2 alters the transcriptome in different tumor cell types. These studies demonstrated that elevation of SOX2 downregulates MYC expression and the expression of MYC target genes. To extend these findings, we performed a MYC rescue study and determined that failure to downregulate MYC when SOX2 is elevated is deleterious to the cells. Thus, this newly discovered SOX2:MYC axis appears to play a critical role in growth inhibition when SOX2 is elevated. Equally important, we determined that elevating SOX2 downregulates MYC at the transcriptional level. The studies proposed here seek to determine how elevating SOX2 decreases MYC transcription. In proliferating cells, MYC transcription is dependent on multiple distal enhancers that activate the MYC promoter via chromatin loops whose formation is dependent on the binding of β-catenin to Wnt Response Elements (WREs) present in each MYC enhancer. Importantly, SOX2 has been shown to interfere with Wnt signaling by its interaction with β-catenin via the R1 transactivation domain of SOX2, which we recently determined is required to inhibit tumor cell growth and downregulate MYC. Based on these findings, we hypothesize that elevating SOX2 downregulates MYC expression by interfering with the function of transcription factors that promote the formation of critical long-range enhancer-promoter interactions required to drive MYC transcription. This hypothesis will be tested by two Specific Aims. Aim 1 will determine how elevating SOX2 alters the 3-D chromatin structure of the MYC locus. Aim 2 will determine whether elevating SOX2 alters the binding of transcription factors to MYC enhancers, changes histone modifications found at active MYC enhancers, and/or blocks the formation of the transcription preinitiation complex at the MYC promoter. Understanding how elevating SOX2 downregulates MYC would be highly significant, because little is known about the links between these two master regulators. Ultimately, we believe our studies will lead to the discovery of novel druggable targets to eradicate quiescent tumor cells implicated in cancer recurrence.

摘要 已经确定了一系列以积极增殖为靶点的策略和小分子抑制剂 肿瘤细胞。然而，静止的肿瘤细胞在很大程度上对用来消除 不断增殖的肿瘤细胞。因此，静止的肿瘤细胞构成了一个重大的临床挑战和重大的未满足的 在癌症治疗中需要，因为静止细胞代表了残留的肿瘤细胞群，可以 会导致肿瘤复发。为了解决这一未得到满足的需求，我们一直在研究转录因子SOX2， 它的高表达也被证明限制了许多不同类型的肿瘤细胞的增殖 作为正常胎儿干细胞的增殖。我们的工作已经确定，将SOX2从可诱导的 在多种肿瘤细胞类型中，启动子总是会导致生长抑制。此外，我们确定，提升 SOX2在体内导致肿瘤生长停滞的可逆状态，当SOX2恢复时，肿瘤生长恢复 达到内源性水平。为了确定SOX2如何限制肿瘤细胞的生长，我们研究了SOX2是如何升高的 改变不同类型肿瘤细胞的转录组。这些研究表明，SOX2的升高 下调MYC的表达和MYC靶基因的表达。为了扩大这些发现，我们 执行了MYC救援研究，并确定在SOX2升高时未能下调MYC是 对细胞有害。因此，这个新发现的SOX2：MYC轴似乎在生长中起着关键作用 SOX2升高时的抑制作用。同样重要的是，我们确定升高SOX2会下调MYC的表达 在转录水平上。这里提出的研究试图确定升高SOX2如何降低MYC 抄写。在增殖细胞中，MYC转录依赖于多个远端增强子，这些增强子激活 MYC启动子通过染色质环的形成依赖于β-连环蛋白与Wnt反应的结合 存在于每个MYC增强剂中的元素(Wre)。重要的是，SOX2已被证明干扰WNT 通过SOX2的R1反式激活结构域与β-连环蛋白相互作用的信号转导，我们最近 决心是必须的，以抑制肿瘤细胞生长和下调MYC。基于这些发现，我们 SOX2上调通过干扰转录功能下调MYC表达的假说 促进形成驱动MYC所需的关键长程增强子-启动子相互作用的因素 抄写。这一假设将通过两个具体目标进行检验。目标1将决定SOX2浓度升高的变化 MYC基因座的三维染色质结构。目标2将确定提升SOX2是否会改变绑定 转录因子到MYC增强子，改变在活性MYC增强子中发现的组蛋白修饰，和/或 阻断MYC启动子上转录预起始复合体的形成。了解如何提升 SOX2下调MYC将具有非常重要的意义，因为人们对这些之间的联系知之甚少 两个主要监管者。最终，我们相信我们的研究将导致发现新的可用药靶点来 根除与癌症复发有关的静止肿瘤细胞。