巨噬细胞迁移抑制因子MIF调控多发性骨髓瘤细胞骨髓归巢机制的研究

Multiple myeloma (MM),the second most common hematologic malignancy, is a cancer of antibody-producing plasma cells in bone marrow (BM). Although progress has been made in its treatment, MM remains an incurable disease. The main reasons for lack of cure are evasion from cytotoxic effects of therapies through oncogenic mutations, clonal selection, and BM microenvironment support. Although the BM microenvironment has been shown to confer or increase (or both) chemotherapeutic resistance in numerous studies and mechanisms have been outlined, little is known about what attracts and keeps MM cells in the BM. Our preliminary studies suggest that macrophage migration inhibitory factor (MIF) plays an important role in MM BM homing. MM cells, either MM cell lines and primary MM cells, express high levels of MIF. MIF knocked-down (KD) MM cells exhibited impaired BM homing in vivo in MM mouse models, including human MM SCID model and murine 5-TGM1 MM C57BL/KaLwRij mouse model. In addition, our findings suggest that MIF regulates MM BM homing by controlling adhesion molecules expression on MM cells. Most importantly, we find that MM cells without BM homing capability are more sensitive to chemotherapeutics. Based on these novel and exciting preliminary findings, we hypothesize that MIF regulates MM BM homing, and MIF-targeting therapy will inhibit MM homing to the BM microenvironment to significantly improve the efficacy of chemotherapy in MM patients. To test our hypotheses, we plan to compare gene expression profiles in control-KD MM cells and MIF-KD MM cells, and analyze the differentially regulated gene set, such as adhesion molecules, chemokine receptors. Positive findings will be further investigated in MM mouse models as described in our preliminary studies. Next, we will examine MIF inhibition strategy in vivo using MIF inhibitors and/or MIF neutralization antibody. At last, we will develop MIF inhibition/chemotherapy combined therapy for MM treatment and test the combined therapy in the MM mouse model.

多发性骨髓瘤（Multiple Myeloma）在造血系统恶性肿瘤中发病率位居第二，其表现为恶性浆细胞在骨髓内异常增殖。由于骨髓微环境的保护作用，位于骨髓内的骨髓瘤细胞不能被化疗药物完全根除，导致该病目前尚不能治愈。通过预研，我们发现巨噬细胞迁移抑制因子（MIF）在骨髓瘤细胞骨髓定居中发挥重要作用。更为有意义的是，通过干扰MIF功能可干扰骨髓瘤细胞骨髓归巢；且游离于骨髓外的骨髓瘤细胞对化疗药物高度敏感。以此为基础，本课题组拟开展MIF调控骨髓瘤细胞骨髓归巢的机制研究；并开发以MIF为靶点，配合化疗进行骨髓瘤联合治疗的全新治疗手段。具体而言，我们拟研究MIF下游调控骨髓瘤细胞骨髓归巢的信号传递通路，并在骨髓瘤动物模型（骨髓瘤SCID模型和鼠5-TGM1骨髓瘤C57BL/KaLwRij模型）中进行验证。同时，我们将在骨髓瘤动物模型上优化MIF抑制手段，探求与化疗药物的最佳联合治疗方案。

多发性骨髓瘤（Multiple myeloma, MM）是一种发生于骨髓的浆细胞恶性肿瘤，现阶段依然无法治愈。骨髓瘤为什么会自发归巢（Homing）到骨髓，其机制尚不清楚。通过本项目，我们研究了MIF因子在MM骨髓归巢调控中的作用。首先，我们通过分析6项独立基因表达谱研究了MM中MIF的表达，及其临床意义。MIF的表达还进一步通过ELISA法在蛋白水平加以了确认。为了研究MIF对MM骨髓归巢的影响，我们采用了人MM的小鼠移植模型以及肿瘤体内发光技术。对于MIF调控MM骨髓归巢的分子机制，我们也进行了深入研究，采用了诸如Chromatin immunoprecipitation（CHIP）实验在内的一些技术。通过上述实验，我们发现：1）MM骨髓内有高水平表达的MIF（骨髓穿刺样品中MIF水平: 健康人群 = 10.72 ± 5.788 ng/ml, n = 5; MM患者 = 1811 ± 248.7 ng/ml, n = 10; p < .001）；2）MM患者骨髓内MIF水平与患者预后相关，MIF水平高，患者预后差（Kaplan-Meier test for MM OS: 87 MIFhigh patients, 86 MIFlow patients, p = .02）；3）MIF敲低的MM细胞（MIF-KD）在实验鼠体内表现出骨髓归巢受干扰，多见髓外肿瘤形成；4）机制研究发现MIF可通过CXCR4受体影响MM细胞，调控MM细胞粘附因子表达改变，从而调控MM细胞在骨髓内的粘附与骨髓归巢；5）MIF及其下游细胞粘附作用与MM的化疗耐药性有关联。MIF-KD细胞（或MM细胞使用MIF抑制剂4-IPP后）由于粘附作用下降，对药物敏感性上升，更容易被化疗药物所杀灭。综上所述，我们的研究证实了MIF对MM骨髓归巢的调控作用。一项重要的发现是MIF抑制可能上调MM的药敏。