MDSCs介导MDS骨髓衰竭和恶性克隆免疫逃逸的作用及机制

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem/progenitor cell (HSPC) malignancies which are characterized by the gradual amplification of the malignant clone and the ineffective hematopoiesis of the normal HSPC. it is the most difficult problems in Department of Hemotology. MDS often show significant reduction in peripheral blood cells, but it is obvious hyperproliferative in bone marrow. We found the Ki-67 expression rate is very low in myeloid and erythroid by analysis of proliferation index. It represented ineffective proliferation. myeloid-derived suppressor cells (MDSCs) have significant immune suppression function. In our previous work, we found that MDSCs were significantly increased in the bone marrow of the MDS patients and could inhibit hematopoiesis. According to preliminary studies and the latest literatures, we hypothesized that MDSCs may involve in the normal hematopoietic failure and malignant clone progression of MDS. Interferon regulatory factor -8 (IRF-8) plays an important role in the regulation of the myeloid differentiation and its down-regulation which triggered by the tumor might participate in the increase of MDSCs. In this project we plan to investigate the relationship between IRF8 and MDSCs and uncover the pathogenesis of the MDSCs on the development and progression of the MDS, such as the ineffective hematopoiesis of the normal HSPC and the immune escape of the malignant clones, as well as explore the novel treatment strategies for MDS through inducing the MDSCs differentiation.

MDS是恶性克隆逐渐扩增伴随正常造血衰竭的髓系肿瘤，是血液科治疗最棘手的难题之一。MDS常表现为全血细胞减少，但其骨髓常常是增生明显活跃，我们通过增殖指数分析，发现MDS的粒系、红系的Ki-67表达率明显减低，表现为无效增殖。MDSC为骨髓来源的抑制性细胞，具有显著的免疫抑制功能，在前期研究中我们发现MDS患者的骨髓中MDSCs明显增多，并且可直接抑制造血，根据前期研究及最新文献，我们推测MDSCs可能参与了MDS的正常造血衰竭和MDS恶性克隆的发生、发展。干扰素调节因子-8（IRF-8），对于正常造血系统的髓系分化调控起着重要作用，MDSCs增多可能与肿瘤诱导的IRF-8表达下调有关，本项目拟通过对IRF-8的干预及研究，探讨MDS患者来源的MDSCs增高的机制，以及MDSCs对正常造血的影响和恶性克隆的逃逸机制。并通过MDSCs的诱导分化，探寻MDS新的治疗手段。

本项目总共对31例初治的MDS患者通过流式细胞学进行MDSCs细胞数量的检测，分析了MDSCs的比例与MDS的亚型、原始细胞计数及血红蛋白水平的相关性，发现MDS患者的MDSCs细胞数量明显高于正常人，但与MDS的亚型无明显相关性，并且与Hb的水平呈负相关。对12例MDS患者进行了治疗前后MDSCs细胞比例的检测，我们发现对目前治疗有效的患者，贫血改善，血红蛋白提高超过20g/L，MDSCs细胞比例明显下降，而血液学无改善的患者，MDSCs细胞比例变化不明显，提示MDSCs的数量与患者治疗疗效呈负相关。通过磁珠分选的MDSCs（3例MDS患者）与正常健康人的骨髓单个核细胞以1:1共培养，发现BFU-E,CFU-E和CFU-GM均不同程度下降，可以看到MDSCs可明显抑制红系及粒-单核细胞集落形成单位，但是所做的样本较少，未能作出统计学分析。还研究了全反式维甲酸（ATRA）对MDSCs增殖及分化的影响，发现不同浓度的ATRA未能明显诱导MDSCs的增殖和凋亡。通过prestoblue的方法检测ATRA对MDSCs增殖的影响，发现ARTA对MDSCs细胞的增殖活性无明显影响，未能检测到IRF-8水平的变化。在项目中，我们尝试研究IDO抑制剂BMS-986205对MDS骨髓来源的MDSCs，通过prestoblue的方法，初步看到BMS-986205可以诱导MDSCs的凋亡，提示IDO信号通路可能参与了MDSCs免疫抑制的机制。