活体显微成像法分析中性粒细胞在肿瘤微环境的动态和作用机制

Neutrophils are the most abundant immune cells in the peripheral blood and play important roles in innate immunity. Recent studies suggest that a significant number of neutrophils are found in tumor microenvironment in many different types of cancer. The detailed cellular events that are involved in the recruitment of neutrophils from blood into tumor tissue are still not clear. In addition, how neutrophils interact with other immune cells in the same tumor microenvironment to affect tumor growth is not well studied. To solve these questions, in this proposed research, we will first use intravital imaging to visualize the whole process when neutrophils are being recruited to tumor site and identify the molecular mechanisms that mediate neutrophil recruitment. We will also reveal how tumor associated neutrophils and macrophages are interacting with each other spatially and temporally, identify the factors that are released by neutrophils to mediate this interaction. This project will provide a step stone for understanding the roles of neutrophils in tumor microenvironment and shed light on potential therapeutic strategies for cancer.

作为人体外周血中数量最多的免疫细胞，中性粒细胞在浸润肿瘤微环境的免疫细胞中同样占有很大比例。然而中性粒细胞从外周血中进入肿瘤微环境过程中所发生的细胞事件还不是十分清楚。另外，中性粒细胞与其他免疫细胞在肿瘤微环境中相互作用共同调节肿瘤发展的机制也有待阐明。本课题将应用活体显微光学成像技术，使用中性粒细胞特异性表达荧光蛋白的转基因小鼠，对上述问题进行深入研究。我们将使用结肠癌细胞肝转移小鼠模型，通过活体显微成像为中性粒细胞被召集到肿瘤组织的这一过程提供可视化动态信息，并解析介导此过程的分子机制。另外，通过系统性分析肿瘤相关中性粒细胞产生的特异性因子，揭示中性粒细胞-巨噬细胞的相互作用和空间位置关系，阐明中性粒细胞-巨噬细胞的相互作用网络对肿瘤发展的促进机制。

本项目按申请书中研究计划已经全部完成。在多种动物模型中完成了对中性粒细胞调控肿瘤转移机制的研究，明确了肿瘤相关中性粒细胞通过分泌趋化因子CCL7，招募单核细胞进入肿瘤转移灶，形成促进肿瘤转移微环境的机制。我们在此基础上还对课题进行了进一步的延伸，利用体外筛选体系寻找靶向肿瘤相关中性粒细胞的小分子化合物，并发现FDA批准药物双硫仑能有效抑制肿瘤相关中性粒细胞的增殖与分化。在多种肿瘤转移模型中，给予双硫仑能有效抑制肿瘤转移。目前已经发现该小分子的下游靶标，正在进行进一步验证。