多发性骨髓瘤是浆细胞异常增生的恶性肿瘤。迄今为止，仅可用沙利度胺、来那度胺等几种药物进行治疗，但其治疗的分子机制尚未阐明，且几乎所有病人都对这些药物有抗药性。最近研究发现沙利度胺是一种泛素连接酶的抑制剂，并抑制CRBN蛋白的泛素化。我们的预实验显示来那度胺也抑制CRBN的泛素化。根据预实验结果我们推测：来那度胺治疗多发性骨髓瘤的机制极有可能与蛋白泛素化有直接关联。为证实这一假说，本课题将采用申请人新建立的蛋白泛素化位点鉴定技术，结合定量蛋白质组学及生物化学方法来探索来那度胺治疗多发性骨髓瘤的分子机制。通过定量蛋白质组学和泛素化位点鉴定技术找到调控肿瘤细胞凋亡的关键蛋白泛素化；应用定点突变和生物化学方法验证关键蛋白的泛素化，揭示其在治疗多发性骨髓瘤过程中的分子机制。通过这些研究，期望为这一疾病的治疗提供新靶点，并设计新化合物对疾病进行有效治疗，从而避免或减轻病人对药物的抗药性，并降低副作用。

Multiple myeloma (MM) is a B-cell malignancy characterized by abnormal growth of plasma cells. Currently, multiple myeloma is incurable although it can be treated clinically by thalidomide, lenalidomide, pomalidomide, or the combination of several drugs. However, the exact molecular mechanisms which are responsible for the treatment of this disease are not known yet. Recently, it has been found that thalidomide inhibits the activity of an E3 ubiquitin ligase complex, DCX(CRBN), composing of DNA damage binding protein 1, Cullin 4A, X-Box protein, and cereblon (CRBN). Thalidomide suppresses the ubiquitination of CRBN, an adaptor protein which recognizes the substrates of the E3 ligase. Our preliminary experiments demonstrated that lenalidomide, a more potent anti-myeloma drug and an analogue of thalidomide, also suppresses the ubiquitination of CRBN. This finding suggests that it is highly likely that the treatment of multiple myeloma by lenalidomide is directly linked to protein ubiquitination...In this application, we will use our newly developed technology, ubiquitin remnant immunoaffinity profiling, quantitative proteomics, and biochemical approaches to study the molecular mechanisms of lenalidomide in the treatment of multiple myeloma. Using quantitative proteomics, we will reveal the dynamics of protein ubiquitination and discover the ubiquitination events which are differentially regulated in the treatment of multiple myeloma by lenalidomide. We will further validate these ubiquitination events using mutagenesis and biochemical approaches, and identify key events which are responsible for the killing of myeloma cells during disease treatment. Through this study we will unravel the molecular mechanisms in the treatment of multiple myeloma by lenalidomide. The expected finding from this project can help us pave a new avenue to design novel therapeutic drugs or approaches for the treatment of myeloma, and thus to avoid drug resistance and reduce side effects that thalidomide and lenalidomide have in multiple myeloma patients.