基于MIF/CD74信号通路探讨肿瘤微环境调控口腔鳞癌细胞EMT/MET可塑性和干性的分子机制

EMT is first acquired in the onset of transmigration in tumor metastasis and then reversed MET in the new colony, thus the all-encompassing has been termed EMT/MET plasticity. Recently, it has been reported that EMT/MET plasticity of cancer can endow different characteristics of cancer stem cells (CSC) in tumor metastatic cascade, and tumor-associated hypoxia and inflammation microenvironments may play a critical role in this process. Our previous data have shown that migration inhibitory factor (MIF), as a linking of hypoxia and inflammation, is one of important inflammation factors in hypoxia inducing EMT of oral squamous cell carcinoma (OSCC) detected by Cytokine Array. Yet, there are many uncharted territories in this field that we have to shed more light on. Thus, we hypotheses that tumor-associated hypoxia and inflammation microenvironments could mediate EMT/MET plasticity and stemness of OSCC through MIF/CD74 signaling pathway. In this project, we will investigate the molecular mechanisms of the following questions: 1) How do MIF/CD74 signaling pathway regulate EMT/MET plasticity and different stemness of OSCC; and how do EMT/MET plasticity endow different stemness of OSCC in this process? 2) To select the key genes, proteins, microRNAs and signaling pathways involved in the EMT/MET plasticity and different stemness mediated by MIF/CD74 pathway in tumor microenvironment; 3)In addition, what are the characteristics and significance of the energy programming in this process? The discoveries of this project in the tumor metastasis field will lead to better definition of MIF/CD74 signaling pathway affected by inflammation and hypoxia microenvironment and the molecular mechanisms by which it modifies metastatic niche formation. This should pave the way toward a better understanding of tumor-associated microenvironment contributing to EMT/MET plasticity and the origin of CSC, as well as novel therapeutics targets to eradicate subpopulation of therapy-refractory cancer cells with metastatic and stem cells capacities. They may even yield new therapeutic targets to the medication prevention of OSCC metastasis in the future.

最新研究认为：肿瘤细胞EMT/MET可塑性赋予肿瘤干细胞不同特性，参与肿瘤转移不同阶段，肿瘤缺氧和炎症微环境在这一过程中发挥关键作用。课题组前期研究发现：缺氧和炎症的共同节点蛋白- - 巨噬细胞移动抑制因子(MIF)，是缺氧诱导口腔鳞癌EMT转化的重要炎症因子。据此提出假设：MIF/CD74通路在缺氧和炎症微环境调控口腔鳞癌EMT/MET可塑性和干性中可能发挥重要作用。拟从肿瘤炎症和缺氧微环境整体角度，以MIF/CD74为切入点，以EMT/MET可塑性和干性为中轴线，探讨MIF/CD74通过哪些下游基因、蛋白和miRNAs及信号通路在转移不同阶段调控口腔鳞癌EMT或MET发生？决定哪些干性特征？其能量代谢重编程特点是什么？肿瘤微环境又在其中起何作用？结果将全面动态诠释口腔鳞癌炎症和缺氧微环境中MIF/CD74通路调控EMT/MET可塑性和干性促进转移的分子机制，为口腔鳞癌转移的防治提供新思路。

肿瘤细胞EMT/MET可塑性赋予肿瘤干细胞不同特性，参与肿瘤转移不同阶段，肿瘤缺氧和炎症微环境在这一过程中发挥关键作用。而缺氧和炎症的共同节点蛋白——巨噬细胞移动抑制因子(MIF)，是缺氧诱导口腔鳞癌EMT转化的重要炎症因子。据此提出假设：MIF/CD74通路在缺氧和炎症微环境调控口腔鳞癌EMT/MET可塑性和干性中可能发挥重要作用。本项目严格按照资助计划书进行，在体外细胞株、动物模型以及口腔鳞癌（Oral squamous cell carcinoma，OSCC）临床标本上，分别研究MIF/CD74信号通路在炎症和缺氧调控EMT/MET可塑性赋予口腔鳞癌细胞不同干性特征、增加侵袭转移潜能中的作用及其调控的关键分子。结果显示，在口腔鳞癌临床标本中MIF表达的升高与患者TNM分期、淋巴结转移和肿瘤复发密切相关。在体外细胞上，MIF升高促进了口腔鳞癌细胞增殖，抑制凋亡，增强迁移侵袭能力，促进肿瘤细胞EMT发生和肿瘤干性；MIF降低能促进口腔鳞癌细胞凋亡，抑制增殖，抑制迁移和侵袭能力，干扰肿瘤细胞的细胞周期进程。进一步实验发现，缺氧通过HIF-1α和HIF-2α促进肿瘤细胞分泌MIF，MIF促进了CD11b+Gr-1+ MDSCs的迁移活性。在肿瘤细胞中沉默HIF-1α或HIF-2α抑制了MIF的表达，但对CD11b+Gr-1+MDSCs的迁移无明显抑制。其机制是HIF-1α和HIF-2α的沉默导致NF-κB活性升高，促进了IL-6的表达，代偿了MIF降低对CD11b+Gr-1+ MDSCs迁移的影响。动物实验结果显示，给予IL-6中和抗体、MIF抑制剂或NF-κB抑制剂显著抑制了CD11b+Gr-1+ MDSCs的外周扩增和瘤内的募集，伴随着肿瘤微血管、淋巴管密度的降低以及肿瘤生长的抑制。研究结果将为靶向口腔鳞癌MIF/CD74信号通路药物联合常规化疗药物治疗口腔鳞癌提供了重要的理论和实验依据。