Weissman A M, Yang Y, Kitagaki J, Sasiela C A, Beutler J A, O'Keefe B R
Laboratory of Protein Dynamics and Signaling, National Cancer Institute at Frederick, P.O. Box. Bldg. 560, Frederick, MD 21702-1201, USA.
Ernst Schering Found Symp Proc. 2008(1):171-90. doi: 10.1007/2789_2008_108.
The ubiquitin conjugating system represents a rich source of potential molecular targets for cancer and other diseases. One target of great interest is the RING finger ubiquitin ligase (E3) Hdm2/Mdm2, which is frequently overexpressed in cancer and is a critical E3 for the tumor suppressor p53. For those 50% of tumors that express wild-type p53, agents that inhibit Hdm2 have great potential clinical utility. We summarize our ongoing efforts to identify inhibitors of Hdm2 E3 activity by high-throughput screening of both defined small molecules and natural product extracts. Employing a strategy using both enzymatic and cell-based assays, we have identified inhibitors that block the E3 activity of Hdm2, activate a p53 response, preferentially kill p53-expressing cells, and have the capacity to differentially cause death of transformed cells. Therefore, screening for inhibitors of Hdm2 ubiquitin ligase activity through in vitro assays represents a powerful means of identifying molecules that activate p53 in cancer cells to induce apoptosis. We also discuss the potential of inhibitors of ubiquitin-activating enzyme (E1) that were discovered during these screens. E1 inhibitors may similarly serve as the basis for novel therapeutics. Additionally, they represent unique tools for providing new insights into the ubiquitin conjugating system.
泛素缀合系统是癌症和其他疾病潜在分子靶点的丰富来源。一个备受关注的靶点是环状结构域泛素连接酶（E3）Hdm2/Mdm2，它在癌症中经常过度表达，并且是肿瘤抑制因子p53的关键E3。对于那些表达野生型p53的50%的肿瘤而言，抑制Hdm2的药物具有巨大的临床应用潜力。我们总结了我们正在进行的通过对特定小分子和天然产物提取物进行高通量筛选来鉴定Hdm2 E3活性抑制剂的工作。采用酶法和基于细胞的检测策略，我们已经鉴定出能够阻断Hdm2的E3活性、激活p53反应、优先杀死表达p53的细胞并且有能力差异性地导致转化细胞死亡的抑制剂。因此，通过体外检测筛选Hdm2泛素连接酶活性抑制剂是鉴定能够激活癌细胞中p53以诱导细胞凋亡的分子的有力手段。我们还讨论了在这些筛选过程中发现的泛素激活酶（E1）抑制剂的潜力。E1抑制剂可能同样作为新型疗法的基础。此外，它们是为泛素缀合系统提供新见解的独特工具。
