髓系抑制性细胞（MDSC）参与鼻咽癌免疫耐受的作用和调控机制

The tumor microenvironment of nasopharyngeal carcinoma (NPC) are always accompanied with chronic inflammatory response. Our previous study revealed that some cytokines with high expression level in tumor microenvironment can induce the generation and function of different tumor-infiltrating lymphocytes(TIL) subsets,additionally the murine-derived suppressor cells (MDSC) were expanded in tumor site and perperial blood which alter the clinical progression of NPC patients. However, the mechanism of immune escape of NPC is still unclear. We proposed the hypothesis that the EBV-psotivie NPC tumor cells can induce the accumulation of myeloid-derived suppressor cells (MDSC) in tumor microenvironments and the MDSC contribute to the immune escape of NPC tumor mediated the interaction between the tumor cells,cytotoxic T cells (CTL), regulatory T cells (Treg) and MDSC. We have found that the increase of MDSC number in the peripheral blood related to that of health controls, additional the density of MDSC was also increased in NPC tumor tissues compared to non-tumor nasopharyngeal tissues, furthermore, the NPC tumor cell lines could induce the generation of MDSC from PBMC of health controls in vitro in our preliminary experiments. Next, we will analyze the association of the numbers of MDSC in peripheral blood and NPC tumor tissues and the clinical pathological parameters prognosis of NPC patients; explore the molecular mechanism of EBV and EBV-positive NPC tumor cell lines to induce the MDSC, reveal the suppression of MDSC to other TIL subsets in NPC; and determine the impact of MDSC to the adoptive immunotherapy of TIL in NPC. We expect to find out the negative immune regulation targets and mechanisms in NPC tumor microenvironments mediated by the cross talk between MDSC and EBV-positive NPC tumor cells, and evaluate the impact of MDSC to the TIL immunotherapy in NPC.

我们前期工作发现鼻咽癌（NPC）患者外周血和肿瘤组织中髓系抑制性细胞（MDSC）的数目增高，并提示与肿瘤的免疫逃逸和临床进程有相关性，但MDSC介导NPC肿瘤微环境发生免疫耐受的原因和作用机制尚不清楚。本项目在相关研究的基础上探讨新近发现的MDSC通过与NPC细胞和其它TIL细胞亚群如Treg和效应淋巴细胞（CTL）的相互作用介导NPC免疫逃逸的分子机制。我们首先分析NPC患者中MDSC的临床相关性，并通过细胞共培养实验分析NPC细胞从CD33(+)PBMC诱导MDSC分化的作用和分子调控机理；其次通过相关免疫实验分析 MDSC对CTL细胞增殖和抗原特异性杀伤NPC细胞的抑制作用、和对Treg分化和抑制功能的影响及这些细胞相互作用的分子调控靶点；最后从动物模型分析MDSC对NPC抗原特异性TIL免疫治疗的干扰。预期发现MDSC参与NPC免疫逃逸的调控靶点，对完善NPC免疫治疗策略有重要意义

本项目主要研究了髓源性抑制细胞（Myeloid-derived suppressor cell， MDSC）在鼻咽癌患者中的分布、功能特点、临床相关性，以及肿瘤相关MDSC对鼻咽癌微环境免疫耐受的作用，对鼻咽癌疾病进展的影响，以及鼻咽癌细胞及其表达的EBV抗原对MDSC亚群扩增的影响及调控机制，探讨了鼻咽癌发生、发展中肿瘤细胞与MDSC之中的交互对话，筛查其预后相关的生物标志及治疗靶点。我们主要发现以下结果：1.MDSC在鼻咽癌患者的外周血及肿瘤组织中扩增，且与患者的不良预后相关。2.鼻咽癌细胞通过表达LMP1，上调COX-2等分子，促进鼻咽癌糖酵解，激活炎性小体和NF-kb信号通路，促进MDSC分化相关细胞因子IL-6、IL-1beta和GM-CSF分泌，诱导肿瘤相关MDSC分化及扩增。3.另一方面，鼻咽癌细胞通过分泌外泌体（exosome）富集miR-24抑制STING分子表达和I型干扰素信号通路，促进STAT3磷酸化，诱导MDSC分化及扩增.4.鼻咽癌相关MDSC不仅可以抑制T细胞增殖及分化，且可促进鼻咽癌细胞发生EMT转化，导致鼻咽癌在NOD/SCID的移植瘤模型中肺转移增加。总的说来，我们的研究揭示了EBV抗原表达、鼻咽癌细胞与免疫抑制细胞MDSC之间的相互作用关系及其MDSC在鼻咽癌扩增的分子调控机制，有望发现新的免疫治疗靶点。