Deciphering molecular mechanisms of Epithelial Plasticity

项目摘要/摘要 细胞可塑性，一种与上皮向间充质转化(EMT)相关的特征，有助于 对肿瘤细胞的存活、迁移、侵袭和治疗耐药的影响。在人类癌症中，肿瘤的发病率很高 分级、低分化和接受过EMT的患者预后较差，发生 转移到远处的器官。EMT是与肿瘤进展相关的共同特征，被认为 对某些肿瘤的癌细胞扩散起关键作用，如胰腺导管腺癌 (PDA)。PDA是一种致命性且鲜为人知的人类恶性肿瘤，其特征是激活 KRAS基因突变。此外，AXL是一种受体酪氨酸激酶(RTK)，与肿瘤有关 包括动脉导管未闭在内的多种癌症类型的进展、转移、治疗抵抗和EMT。在我的 论文研究发现，坦克结合蛋白1(TRAK-BIND KEATE 1，TBK1)是细胞外信号转导系统的关键下游效应因子。 突变的活性KRAS，在突变的KRAS-PDA中是Ax1驱动的EMT的中心。然而，机制是如何 TBK1驱动EMT尚未阐明。我们假设，TBK1通过激活AKT3来驱动EMT 下游转录网络的稳定性。我的数据显示AKT3被激活 Tbk1下游对AXL刺激的反应，从而导致AKT3与 AXL-TBK1依赖方式。为了完成我的论文，我将确立AKT3在驱动EMT中的作用 AX1和TBK1下游，目标如下：1)确定AKT3对AX1和TBK1驱动的必要性 EMT；2)评估参与TBK1下游的EMT转录因子；3)确定AKT3的作用 激活对EMT转录因子稳定性的影响。 尽管有重要证据表明EMT直接促进肿瘤进展，但有几项研究 提示对于动脉导管未闭和乳腺癌的转移扩散，EMT不是必需的。例如，大多数 众所周知，转移性病变表现出上皮特征，这一观察结果似乎与 EMT作为转移的先决条件。因此，EMT在癌症生物学中的重要性一直被认为是 被问话了。我推测，肿瘤内EMT程序的慢性激活可能取决于 肿瘤微环境中的旁分泌信号，决定肿瘤细胞是接受EMT还是 相遇了。因为这些细胞以可塑性状态存在，所以这些肿瘤细胞有可能很容易地恢复其 表型基于微环境特定的背景和因素。此外，目前的活体血统- 追踪技术并没有解决集体移民的重要性和/或EMT之间的争论 用于转移扩散。在我的博士后研究期间，我的目标是调查EMT在 利用体内谱系追踪、单细胞测序和有机化合物更好地了解转移 癌基因和组织特异性方式的上皮可塑性。了解这一过程将有助于 开发有效的转移癌治疗方法，并将指导未来转移的研究方向。

Project Summary/Abstract Cellular plasticity, a feature associated with epithelial-to-mesenchymal transition (EMT), contributes to tumor cell survival, migration, invasion, and therapy resistance. Across human cancer, tumors that are high grade, poorly differentiated, and have undergone EMT carry a worse prognosis with a high likelihood of metastasizing to distant organs. EMT is a common feature associated with tumor progression and is thought to be critical to cancer cell dissemination in some tumors, such as pancreatic ductal adenocarcinoma (PDA). PDA is a lethal and poorly understood human malignancy that is characterized by an activating mutation in KRAS. Additionally, AXL, a receptor tyrosine kinase (RTK), has been implicated in tumor progression, metastasis, therapy resistance, and EMT in multiple cancer types including PDA. During my dissertation studies, I have found that TANK-binding kinase 1 (TBK1), a critical downstream effector of mutant active KRAS, is central to AXL-driven EMT in KRAS-mutant PDA. However, the mechanism of how TBK1 drives EMT has yet to be elucidated. We hypothesize that TBK1 drives EMT via activation of AKT3 and the stability of downstream transcriptional networks. My data demonstrate that AKT3 is activated downstream of TBK1 in response to stimulation of AXL, which leads to the binding of AKT3 and Slug in an AXL-TBK1 dependent manner. To complete my dissertation, I will establish the function of AKT3 in driving EMT downstream of Axl and TBK1 with the following goals: 1) Establish the necessity of AKT3 for Axl and TBK1 driven EMT; 2) Evaluate EMT transcription factors engaged downstream of TBK1 and 3) Determine the effect of AKT3 activation on the stability of EMT transcription factors. Despite significant evidence that EMT directly contributes to tumor progression, several studies have suggested EMT is not required for the metastatic spread of PDA and breast cancer. For example, most metastatic lesions are known to exhibit epithelial features, an observation that seems to be at odds with EMT as a prerequisite for metastasis. As such, the importance of EMT in cancer biology h as been questioned. I hypothesize that the chronic activation of an EMT program within a tumor may depend on paracrine signals within the tumor microenvironment, dictating whether the tumor cells undergo EMT or MET. Because these cells exist in a plastic state, it is possible that these tumor cells readily revert their phenotype based on a microenvironment-specific context and factors. Additionally, current in vivo lineage- tracing technology has not settled the debate between the importance of collective m igration and/or EMT for metastatic dissemination. During my postdoctoral research, I aim to investigate the role of EMT in metastasis using in vivo lineage tracing, single-cell sequencing, and organoids to better understand epithelial plasticity in an oncogene- and tissue-specific manner. Understanding this process will aid in the development of effective metastatic cancer therapies and will direct future research directions in metastasis.