去泛素化酶USP13促进MCL1稳定性和肿瘤发展的机制研究

MCL1 is an important anti-apoptotic protein, which is highly expressed in a variety of human cancers. Because of its crucial role in promoting tumor survival, how to inhibit MCL1 has been extensively investigated. In the current study, we have focused on the deubiquitinases, which presumably can regulate MCL1 protein stability. Using a siRNA library screen to individually target each of the 84 deubiquitinases, we identified USP13 to be able to increase the half-life and therefore the protein abundance of MCL1 in lung and ovarian cancer cells. Additionally, USP13 significantly reduced sensitivity to ABT-263, a small molecule antagonist of the pro-survival proteins BCL-2, BCL-xL and BCL-w. We propose this project to further study the biological functions of USP13 in tumor progression, as well as its regulatory role in MCL1 ubiquitination and degradation. Furthermore, we will determine the impact of USP13-MCL1 pathway on drug response to BCL-2 inhibitors. These studies will expand our understanding of MCL1 regulation, provide a rationale to target USP13 in cancer, and facilitate clinical development of BH3 mimetics.

MCL1是重要的抑凋亡蛋白，在多种癌症中普遍高表达并促进肿瘤生存，如何抑制其活性是亟需解决的关键问题。本项目聚焦调控MCL1蛋白稳定性的去泛素化酶，通过针对去泛素化酶家族84个成员的siRNA文库筛选，我们发现USP13可在肺癌与卵巢癌中延长MCL1半衰期，上调其蛋白水平，并能够介导对BCL-2抑制剂的耐药。本课题将进一步研究USP13在肿瘤发展中的生物学功能，确定USP13对MCL1泛素化和稳定性的调控作用，并深入探讨USP13-MCL1通路对BCL-2抑制剂敏感性的影响。这些研究将增加我们对MCL1调控机制的理解，建立以USP13为肿瘤分子靶点的理论基础，并有望指导BCL-2小分子抑制剂的临床应用。

MCL1是抗凋亡BCL-2家族蛋白的关键成员，BCL-2家族蛋白经常在多种癌症中失调。MCL1的独特之处在于它常被泛素化并降解，去泛素化酶（DUB）例如USP9X，可以通过去除多聚泛素链从而维持MCL1表达。但是，USP9X主要在大脑和免疫系统中表现出组织特异性表达。在这项研究中，我们通过无偏好性的DUBs的siRNA筛选，确定了第二种去泛素酶USP13调节肺癌和卵巢癌细胞中MCL1的稳定性。 USP13和MCL1都表现出基因组扩增，并且在肺癌和卵巢癌标本中，蛋白表达水平上调。在机理上，我们发现USP13与MCL1相互作用，通过去泛素化使其稳定。使用CRISPR/ Cas9系统敲除USP13能够抑制异种移植裸鼠中的肿瘤生长，我们进一步发现，USP13的遗传或药理抑制作用大大降低了MCL1蛋白的丰度，并显著提高了肿瘤细胞对靶向BCL-2和BCL-XL的BH3类似物抑制剂的敏感性。总的来说，我们揭示出USP13是一种新型的去泛素化酶，可以调节各种实体瘤中的MCL1表达，因此USP13可能是治疗各种恶性肿瘤的潜在分子靶标。