结肠癌肿瘤微环境中pDCs通过PD-L1信号通路调控肿瘤进展和转移的作用及机制研究

Although plasmacytoid dendritic cells (pDCs) play an important role in antiviral immune responses, their role in the tumor microenvironment remains controversial. With the increasing incidence of primary and recurrence of colon cancer, the function of pDCs is particularly unclear. Our previous study on 20 colon cancer patients showed that the number of pDCs (T-pDCs) in the tumor microenvironment of patients with colon cancer was significantly higher than that of the relatively normal tumor distal tissues pDCs (D-pDCs), this is positively correlated with malignancy grade and metastasis. Furtherly, the RNA-Seq analysis showed that PD-L1 is a gene with a significant difference in expression, which is highly expressed on T-pDCs. Further patient specimens study verified PD-L1 also has a positive correlation with malignant grade and tumor metastasis. Therefore, this project will use cancer patients and colon cancer mice model to investigate the role of PD-L1 in the regulation of T-pDCs in promoting tumor progression, metastasis, and immune escape. Our study will be expected to explore a new mechanism of T-pDCs in promoting tumor progression and metastasis in colon cancer microenvironment，and provide innovative treatment for the immunotherapy of metastatic and recurrent colon cancer.

浆细胞样树突状细胞（pDCs）在抗病毒免疫应答中扮演重要角色，但在肿瘤微环境中的功能研究尚存争议。在发病率和复发率逐年上升的结肠癌中，pDCs的功能尚不清楚。我们前期收集了20例结肠癌病人结肠组织分析发现，结肠癌病人肿瘤微环境中pDCs（T-pDCs）的数量明显高于相对正常的肿瘤远端组织pDCs（D-pDCs），与恶性程度和转移呈正相关。进一步RNA-Seq结果显示，PD-L1是一个具有显著表达差异的基因，在T-pDCs上高表达。通过患者标本验证了PD-L1也与肿瘤的恶性级别和转移呈正相关。因此，本项目将应用结肠癌病人和结肠癌模型鼠研究T-pDCs通过PD-L1调控Treg和CD8+T细胞的数量和功能改变进而影响结肠癌进展和转移，促进肿瘤的免疫逃逸的机制。本研究有望发现结肠癌肿瘤微环境中T-pDCs促进肿瘤进展、转移的新机制。为转移和复发性结肠癌的免疫治疗提供新的思路和方向。

浆细胞样树突状细胞（pDCs）在抗病毒免疫应答中扮演重要角色，但在肿瘤微环境中的功能研究尚存争议。在发病率和复发率逐年上升的结肠癌中，pDCs的功能尚不清楚。本项目应用结肠癌病人和结肠癌模型鼠研究肿瘤相关pDCs（T-pDCs）的分布、表型和功能改变，阐明免疫检查点蛋白程序性细胞死亡受体-配体1（PD-L1）表达在T-pDCs上的功能。收集临床80例结肠癌病人的样本，分为肿瘤，肿瘤旁（距肿瘤区2-5cm）和肿瘤远端（距肿瘤区5cm以上），用于流式、q-PCR及免疫组化等相关检测。成功建立小鼠原位结肠癌肿瘤模型，用于体内实验。结果显示，T-pDCs和PD-L1+ T-pDCs的数量明显高于肿瘤近端和远端组织，分别与肿瘤的病理分期呈正相关，与Tregs细胞的比例呈正相关，与CD8+T细胞的比例呈负相关。小鼠模型进一步验证pDCs通过PD-L1调控Treg细胞的数量和功能改变进而影响肿瘤的进展。另外，肿瘤微环境中3型天然淋巴细胞（T-ILC3s）的比例低于肿瘤远端，与肿瘤的病理分期呈负相关，与T-pDCs的比例呈负相关。应用RNA-Seq 分析T-pDCs和T-ILC3s在基因水平的差异，筛选并验证差异基因及其功能，明确T-pDCs通过上调凋亡相关蛋白的表达诱导T-ILC3s凋亡。本研究有望发现结肠癌肿瘤微环境中T-pDCs促进肿瘤进展、转移的新机制。为转移和复发性结肠癌的免疫治疗提供新的思路和方向。