泛素连接酶基因CUL4B在癌基因诱导细胞衰老中的作用机制及其对肿瘤发生的影响

Oncogene-induced senescence (OIS) serves as a robust barrier to cell transformation and cancer development. Therefore, gaining insight into how the OIS is regulated is important for understanding tumorigenesis. We previously found that loss-of-function mutation in human CUL4B cause X-linked mental retardation. CUL4B functions as a “scaffold” in cullin-RING-based E3 ubiquitin ligases (CRLs) and regulates diverse cellular processes including transcription, signal transduction and development. Our previous studies showed that CUL4B plays important roles in regulation of cell cycle, DNA replication and tumorigenesis. However, the exact mechanism of tumorgenesis regulation by CUL4B is still poorly understood. More recently, we found that CUL4B was overexpressed in lung cancers and knockdown of CUL4B in Ras mutant lung cancer cells inhibits cell growth in vitro and in vivo. Interestingly, we further showed that knockdown of CUL4B promote Ras induced senescence in NHF cells. These findings suggest that CUL4B plays a novel role in tumorigenesis regulation via OIS. In this proposed study, we will characterize the role of CUL4B in OIS using cellular and mouse model in vitro and in vivo and further identify the mechanism by which CUL4B regulates this process. In addition, we will also explore the role of CUL4B in tumorigenesis via OIS. This study will advance our understanding of the biological functions of CUL4B and help to develop new tumor markers and anticancer targets.

癌基因诱导的细胞衰老是防止细胞恶性转化和抑制肿瘤发生的重要屏障。本课题组前期发现CUL4B基因突变可导致X连锁智力低下综合征。作为E3泛素连接酶复合物的支架蛋白，CUL4B通过泛素化底物蛋白而参与调控多个生物学过程。我们过去的研究显示CUL4B在细胞周期、DNA复制和肿瘤中发挥着重要的调控功能。但目前对CUL4B调控肿瘤发生的机制了解较少。我们最新的研究结果显示CUL4B在肺癌中表达上调，干扰其表达可抑制Ras突变的肺癌细胞增殖和成瘤能力，并且抑制CUL4B表达可促进Ras诱导的NHF细胞衰老。这些结果提示CUL4B可能通过调控癌基因诱导的细胞衰老而影响肿瘤的发生。为此，本课题拟利用癌基因诱导衰老的细胞和小鼠模型并结合临床标本验证，分析CUL4B在癌基因诱导细胞衰老及肿瘤发生中的作用并明确其调控机制，为进一步认识CUL4B的功能，筛选新的肿瘤标志物和抗肿瘤靶点提供理论基础。

本项目拟明确CUL4B对癌基因诱导细胞衰老的影响并揭示其相关调控机制，研究CUL4B在肿瘤中的作用，为进一步认识CUL4B的功能，筛选新的肿瘤标志物和抗肿瘤靶点提供理论基础。在本项目资助下，我们研究发现CUL4B促进癌基因诱导的细胞衰老，抑制癌基因突变以及化学物质乌拉坦诱导的肺癌发生。机制分析显示，CUL4B可以通过抑制miR-372，促进p21蛋白表达，促进癌基因诱导的细胞衰老。另外，我们还发现，CUL4B在胃癌，肺癌和膀胱癌细胞内高表达，并且CUL4B可以通过促进H2KA119单泛素化修饰，进而表观遗传调控miR-125a、miR-194以及miR-372/373的表达，促进肿瘤细胞的增殖，转移，耐药以及干性维持。对CUL4B的表达调控研究我们还发现，CUL4B在肺癌细胞内受到p53-miR-194的调控。p53能够激活miR-194的转录，进而miR-194结合CUL4B的3‘UTR，抑制CUL4B的表达。这也是首次揭示CUL4B在肿瘤细胞中的表达调控机制。在本课题的资助下，我们还分析了天然小分子化合物汉黄芩素和小檗碱在肾细胞癌以及银屑病治疗中的作用和机制。以上研究结果对于进一步了解CUL4B功能以及作用机制，开发相关疾病治疗的新药物和新疗法提供实验数据和理论支撑。