E3连接酶TRIM21泛素化调控GMPS/USP7介导多发性骨髓瘤硼替佐米耐药的作用及机制研究

Multiple myeloma (MM) is a hematological malignancy characterized by abnormal accumulation of clonal plasma cells in the bone marrow. Bortezomib, a proteasome inhibitor, is one of the most effective drugs for treatment of MM. However, primary and secondary resistance of bortezomib to MM still exist. A growing number of E3 ligases and related substrate proteins have emerged as crucial players in bortezomib resistance. Our previous study found that TRIM21, as a E3 ligase, can interact with guanosine monophosphate synthetase (GMPS) in myeloma cell lines, and high expression of TRIM21 were more senseitve to bortezomin treatment, while refractory MM patients expressed low expression of TRIM21. GMPS mediates deubiquitinase USP7 activity and deubiquitinating activity of USP7 is related to bortezomib resistance. This project works on various levels of cells, proteins and genes, to demonstrate the role and mechanism of E3 ubiquitin ligase TRIM21 in drug resistance of bortezomin in MM, to explore the regulation of TRIM21 on GMPS/USP7 and possible downstream substrate proteins, and to provide a theoretical basis for novel target of MM treatment by effectively intervening the interaction between TRIM21 and substrate proteins.

多发性骨髓瘤（MM）是单克隆浆细胞异常增生的恶性肿瘤，蛋白酶体抑制剂硼替佐米（Bor）是目前治疗MM的最有效药物之一，但大部分患者仍因耐药致疾病复发。已证实决定蛋白质降解特异性的E3连接酶与Bor耐药密切相关。我们的前期研究发现E3连接酶TRIM21在Bor耐药细胞株和复发原代骨髓瘤细胞中表达明显降低，敲除TRIM21可降低MM细胞对Bor敏感性，进一步实验发现TRIM21调控Bor耐药过程中与代谢酶鸟苷酸合成酶GMPS相互作用，后者是去泛素化酶USP7的主要调节因子，而抑制USP7活性能克服MM细胞对Bor耐药，但这三者在MM细胞Bor耐药中的具体功能和下游关键性底物蛋白尚未阐明。本项目拟深入探讨TRIM21泛素化调控GMPS/USP7并通过下游底物蛋白介导MM Bor耐药的作用及机制，寻求是否可通过有效调节TRIM21与底物蛋白的作用，克服甚至逆转Bor耐药，为探索MM治疗提供新思路。

多发性骨髓瘤是第二常见血液系统恶性疾病。尽管医疗水平的发展极大地提高了使患者的生存率，患者最终面临复发和耐药等问题。深入研究耐药机制对提高患者疗效和延长生存时间具有非常重要的理论和现实意义。本研究揭示了TRIM21对MM硼替佐米耐药具有重要作用。TRIM21低表达与耐药相关，过表达TRIM21增加MM对硼替佐米的敏感性促进细胞凋亡同时我们发现激活自噬途径也被激活。TRIM21 泛素化调控GMPS，影响USP7及其下游底物蛋白HDM2、PTEN、FOXO4、TSPYL5 等表达，从而介导多发性骨髓瘤硼替佐米耐药的发生机制。此外，我们从临床验证研究中获得了相似的结果。综上，本项目从分子、细胞，体内和体外实验等多个层面进行论证，阐明TRIM21作为抑癌分子在MM中发挥作用，并为MM的治疗提供了新的思路和分子靶点。