胃癌中外周血CD45+CD33lowCD11bdim髓系细胞抑制CD8+T淋巴细胞功能的作用机制研究

CD8+T lymphocytes in the peripheral blood of gastric cancer (GC) play an important role in anti-GC. It is often inhibited that the function of CD8+T lymphocytes in the peripheral blood of GC patients. However, the underlying mechanism of this inhibition of the function of CD8+T lymphocytes in peripheral blood of GC patients is unknown. One cause of this inhibition is the myeloid cells with the potential of immunosuppression in the microenvironment. Previously, we found that CD45+CD33lowCD11bdim myeloid cells, was distinctively increased in peripheral blood of GC patients. Most importantly, this myeloid cells were negatively associated with IFN-γ-producing CD8+T lymphocytes, suggesting that this myeloid cell might be involved in the inhibition of CD8+T lymphocytes in peripheral blood of GC. Thus, we aim at CD45+CD33lowCD11bdim myeloid cells, and intend to investigate (1) the clinical significance of these myeloid cells in peripheral blood of GC; (2) the regulating mechanism of IL-6 and IL-8 in the degranulation activity, cell clustering and arginase Ⅰ(ARGⅠ) release of these myeloid cells; (3) the effector mechanism of ARGⅠin the inhibition of CD8+T lymphocytes by these myeloid cells; in terms of cell sorting, cell coculture and subcellular components separation. This study may provide new experimental evidence for the mechanism of the inhibition of CD8+T lymphocytes in peripheral blood of GC.

胃癌病人外周血CD8+T淋巴细胞是发挥抗肿瘤效应的重要细胞，但其功能往往被抑制，其机制尚不清楚。免疫抑制性髓系细胞可以抑制CD8+T淋巴细胞功能。我们前期发现，胃癌病人外周血特征性的出现了一群CD45+CD33lowCD11bdim髓系细胞；其与分泌IFN-γ的CD8+T淋巴细胞呈负相关；提示此髓系细胞很可能介导了胃癌病人外周血CD8+T淋巴细胞功能的抑制。因此，本项目拟以这群CD45+CD33lowCD11bdim髓系细胞为研究对象，通过细胞分选、细胞共培养及亚细胞成分分离等手段，研究：（1）这群髓系细胞在胃癌进程中的临床意义；（2）炎症因子IL-6、IL-8介导这群髓系细胞脱颗粒活动、细胞分群及精氨酸酶Ⅰ（ARGⅠ）释放的调控机制；（3）效应因子ARGⅠ介导这群髓系细胞抑制CD8+T淋巴细胞功能的效应机制。相关研究将为阐明胃癌病人外周血CD8+T淋巴细胞功能抑制的机制提供新的实验证据。

背景：中性粒细胞是肿瘤病人外周血及肿瘤微环境中重要的一类髓系细胞和主要组成部分，并且其在不同的肿瘤微环境中表现出不同的表型功能。但是，中性粒细胞在人胃癌中的性质、调控、功能以及临床意义并未完全阐明。.方法：流式细胞术检测105例胃癌病人外周血以及肿瘤组织中中性粒细胞的应答水平以及表型。Kaplan-Meier plot方法评估中性粒细胞应答水平与胃癌病人总体生存率的关系。分选、刺激以及培养中性粒细胞、T细胞来进行体外以及体内调控和功能学实验。.结果：相对于正常人外周血，胃癌病人外周血中中性粒细胞应答水平显著增高，并且中性粒细胞在胃癌病人肿瘤组织中显著浸润增高。这些肿瘤组织中浸润的中性粒细胞表现出CD54阳性的激活表型并且高表达免疫抑制性分子PD-L1。肿瘤可以激活中性粒细胞使其延长寿命并诱导其表达PD-L1，使其具有和肿瘤微环境中中性粒细胞相似的表型；并且这些中性粒细胞上CD54和PD-L1的表达水平呈正相关。同时，肿瘤组织中PD-L1阳性的中性粒细胞与疾病的进程呈正相关，而与胃癌病人的生存呈负相关。肿瘤分泌的GM-CSF可以通过JAK-STAT3通路来激活中性粒细胞并诱导其表达PD-L1。这些表达PD-L1的激活中性粒细胞能在体外显著抑制T细胞的正常免疫功能，并在体内促进肿瘤生长和进展；这些病理性效应可以通过阻断中性粒细胞上的PD-L1加以改善。.结论：我们的研究结果阐明了一个肿瘤激活的表达PD-L1的中性粒细胞参与胃癌免疫的新机制，同时也为基于干扰GM-CSF-PD-L1通路的胃癌免疫治疗提供了新思路。