Role of MIF in myeloma bone homing and drug response

项目摘要 多发性骨髓瘤(MM)，以恶性浆细胞在骨髓(BM)聚集为特征， 是美国最常见的骨恶性肿瘤。虽然化疗是最有效的 在治疗过程中，大多数患者会复发并死于该病。治疗的主要原因 失败就是多药耐药的发展。骨髓微环境赋予多发性骨髓瘤化疗耐药性。 因此，推断BM如何创造对MM细胞友好的微环境并赋予抗性是关键 到克服耐药性和极大地提高患者的存活率。最近我们发现人类MM- 衍生的MIF(巨噬细胞移动抑制因子)调节MM细胞对BM的归巢或亲和力， 因此，他们对化疗的敏感性。人多发性骨髓瘤细胞高表达MIF及其表达 水平与患者的晚期疾病和较差的存活率呈正相关。令人惊讶的是，推倒 MM细胞中的MIF抑制其与骨髓基质细胞(BMSCs)的体外黏附，并导致 SCID小鼠的髓外肿瘤。更重要的是，MIF基因敲除的人多发性骨髓瘤细胞更敏感， 与对照细胞相比，由于化疗有效根除了SCID小鼠的化疗 宿主的髓外肿瘤而不是髓内肿瘤。抑制MM细胞中的MIF活性(细胞系和 MIF抑制剂(4-IPP)或中和单抗也会导致损害 SCID和SCID-Hu小鼠骨髓间充质干细胞体外黏附及髓外肿瘤的形成 影响肿瘤负担。MM-(Transwell)条件下的人BMSCs介导更强的黏附 对MM细胞，对化疗诱导的MM细胞提供更大的保护作用，并吸引 单核细胞数量多于MIF基因敲除的MM条件下的骨髓间充质干细胞。基于这些新发现，我们 假设MM细胞中高MIF通过增强MM细胞的亲和力而导致患者存活率较低 对于BM和通过将BM调节为MM友好的微环境，从而促进MM生长 以及存活和诱导抗药性。目的1将阐明MM来源的MIF的机制。 调节MM归巢到BM和亲和力。目标2将确定MM的重要性和机制- 衍生的MIF在条件BM中成为MM友好的微环境，Aim 3将确定和 验证MM表达MIF在MM患者中的作用。实现这些目标将提供 针对MIF开发新的有效策略以提高治疗效果的理由和工具 化疗的疗效。拟议的研究还将使我们更好地了解 多发性骨髓瘤归巢或转移至骨的潜在机制和多发性骨髓瘤调节微环境， 并可能通过动员多发性骨髓细胞为目前多发性骨髓瘤治疗的第一个实质性改进铺平道路 远离保护性的BM微环境。

Project Summary Multiple myeloma (MM), characterized by an accumulation of malignant plasma cells in the bone marrow (BM), is the most common bone malignancy in the United States. Although chemotherapy is the most effective treatment, the majority of patients experience relapse and die of the disease. The major cause of treatment failure is the development of multidrug resistance. The BM microenvironment confers MM chemoresistance. Deducing how the BM creates a microenvironment friendly to MM cells and confers resistance is thus the key to overcoming drug resistance and greatly improving patient survival. Recently we discovered that human MM- derived MIF (macrophage migration inhibitory factor) regulates the homing or affinity of MM cells for BM and, as a result, their sensitivity to chemotherapy. MIF is highly expressed by human MM cells and the expression levels positively correlate with advanced disease and poor survival in patients. Surprisingly, knocking down MIF in MM cells impaired their adhesion to BM stromal cells (BMSCs) in vitro and led to formation of extramedullary tumors in SCID mice. More importantly, MIF-knockdown human MM cells were more sensitive, compared with control cells, to chemotherapy in SCID mice because chemotherapy effectively eradicated extramedullary but not intramedullary tumors in the host. Inhibiting MIF activity in MM cells (cell lines and primary MM cells from patients) by the MIF inhibitor (4-IPP) or neutralizing mAbs also resulted in impaired adhesion to BMSCs in vitro and formation of extramedullary tumors in SCID and SCID-hu mice without affecting tumor burdens. Furthermore, MM-(transwell)-conditioned human BMSCs mediated stronger adhesion to MM cells, provided greater protection to MM cells against chemotherapy-induced apoptosis, and attracted more monocytes than MIF-knockdown MM-conditioned BMSCs. Based on these novel findings, we hypothesize that high MIF in MM cells contributes to poor patient survival by enhancing the affinity of MM cells for BM and by conditioning BM to become a MM-friendly microenvironment, leading to enhanced MM growth and survival and induction of drug resistance. Aim 1 will elucidate the mechanisms of MM-derived MIF in regulating MM homing to and affinity for BM. Aim 2 will determine the importance and mechanisms of MM- derived MIF in conditioning BM to become a MM-friendly microenvironment, and Aim 3 will determine and validate the role of MM-expressing MIF in patients with MM. Accomplishing these aims will provide the justification and tools for developing novel and effective strategies to target MIF to improve the therapeutic efficacy of chemotherapy. The proposed studies will also lead to a better understanding of the fundamental mechanisms underlying MM homing or metastasis to the bone and MM conditioning the microenvironment, and could pave the way to the first substantial improvements in current MM treatment by mobilizing MM cells away from the protective BM microenvironment.