近日，Journal of Clinical Investigation在线刊登了院所邱录贵教授和湛凤凰教授课题组合作研究的关于染色体不稳定基因NEK2调控NF-κB信号通路参与MM骨病及硼替佐米耐药的作用机制这一研究成果：Destabilizing NEK2 overcomes resistance to proteasome inhibition in multiple myeloma。邱录贵教授和湛凤凰教授为本文共同通讯作者，郝牧研究员为共同第一作者。
课题组前期研究证实染色体不稳定基因NEK2在MM细胞尤其是治疗后耐药的MM克隆中表达显著增加，导致患者生存时间明显缩短。并且NEK2的表达水平与患者MM相关骨病严重程度呈正相关，NEK2通过激活NF-κB信号途径，上调MM细胞中细胞因子heparanase的表达并分泌到周围骨髓微环境中，促进微环境中破骨细胞的分化成熟，增加破骨细胞活性，抑制成骨细胞活化，参与骨髓瘤相关骨病的发生发展。研究首次提出治疗后残留的耐药MM克隆高水平表达NEK2蛋白是导致MM患者骨髓瘤骨病持续存在甚至加重的重要调控因子。相关研究成果已在2017年7月的Leukemia杂志上发表。
在此基础上，郝牧研究员等经过一系列深入研究阐明了MM细胞NEK2蛋白高表达以及NEK2蛋白激活NF-kB信号通路新的分子机制。研究发现NEK2蛋白质降解途径受到明显抑制：NEK2蛋白通过与去泛素化酶USP7相互结合，抑制蛋白酶体系统对NEK2的降解、稳定其表达；敲降USP7基因表达可明显增加NEK2高表达细胞对蛋白酶体抑制剂的敏感性，逆转细胞耐药。研究还发现NEK2是经典NF-κB信号通路新的激活剂：NEK2通过与PP1α蛋白直接结合并增强其磷酸化水平，从而激活AKT蛋白激酶，促进了IκBα蛋白磷酸化降解， p65蛋白从胞浆转入细胞核内促进下游基因的转录表达。NEK2通过调节IκBα蛋白磷酸化激活p65蛋白入核与heparanase启动子区结合，上调heparanase表达水平介导了骨髓瘤骨病的发生发展。
肿瘤细胞耐药是困扰临床治疗的关键问题，完全缓解后残留耐药MM细胞是疾病复发的根源。本研究阐明了MM细胞中高表达NEK2并参与MM细胞耐药及骨髓瘤骨病发病的分子机制。为靶向NEK2抑制其活性、促进其降解，从而逆转骨髓瘤骨病以及MM复发耐药提供重要的理论依据。
Abstract
Drug resistance remains the key problem in cancer treatment. It is now accepted that each myeloma patient harbors multiple subclones and subclone dominance may change over time. The coexistence of multiple subclones with high or low chromosomal instability (CIN) signature causes heterogeneity and drug resistance with consequent disease relapse. In this study, using a tandem affinity purification–mass spectrometry (TAP-MS) technique, we found that NEK2, a CIN gene, was bound to the deubiquitinase USP7. Binding to USP7 prevented NEK2 ubiquitination resulting in NEK2 stabilization. Increased NEK2 kinase levels activated the canonical NF-κB signaling pathway through the PP1α/AKT axis. Newly diagnosed myeloma patients with activated NF-κB signaling through increased NEK2 activity had poorer event-free and overall survivals based on multiple independent clinical cohorts. We also found that NEK2 activated heparanase, a secreted enzyme, responsible for bone destruction in an NF-κB–dependent manner. Intriguingly, both NEK2 and USP7 inhibitors showed great efficacy in inhibiting myeloma cell growth and overcoming NEK2-induced and -acquired drug resistance in xenograft myeloma mouse models.