核糖体蛋白RPL32调控p53在肺癌细胞增殖中的作用及机制研究

Accumulating evidences indicate that the ribosomal proteins are closely related to tumorigenesis. Our previous study have shown that the expression of the ribosomal protein RPL32 was inversely correlated with the prognosis of lung cancer patients. RPL32 knockdown significantly decreased the proliferation of lung cancer cells. Preliminary studies suggest that this phenomenon is caused by decreased degradation of p53 protein via MDM2-mediated ubiquitination, which is RPL32 ribosomal function independent. Using RPL32 as bait, we screened and confirmed that C1QBP might interact with RPL32, and C1QBP knockdown could also induce p53 accumulation. To further investigate the role and mechanism of RPL32 in regulating p53 through interacting with C1QBP, the following experiments will be conducted: 1) To investigate the amino acid site of RPL32 and C1QBP interaction and study the p53 ubiquitination mechanism regulated by C1QBP; 2) To cross Rpl32fl/fl and p53fl/fl mice with LSL-KrasG12D mice that could develop spontaneous lung cancer to clarify the RPL32-C1QBP-p53 signal axis in the development of lung cancer in vivo; 3) To further verify the relationship between RPL32 and its related pathways and the prognosis of patients with lung cancer on extended clinical specimens. The proposed studies will demonstrate RPL32 may be a new target for the diagnosis and treatment of lung cancer.

研究表明核糖体蛋白与肿瘤密切相关，我们前期发现核糖体蛋白RPL32的表达与肺癌患者的预后呈负相关，敲降RPL32导致肺癌增殖下降，初步研究提示该现象并非依赖RPL32核糖体功能的改变，而是MDM2介导的p53泛素化降解减少导致的。以RPL32为诱饵，我们筛选并证实C1QBP是其互作蛋白，敲降C1QBP也可以导致p53聚集。为深入研究RPL32通过与C1QBP互作调控p53在肺癌中的作用及机制，我们将开展以下工作：1.明确参与RPL32与C1QBP互作的氨基酸位点，探索C1QBP下游通路调控p53泛素化的分子机制；2.用已有的Rpl32fl/fl、p53fl/fl小鼠与LSL-KrasG12D自发肺癌小鼠杂交，阐明RPL32-C1QBP-p53信号轴在肺癌发生发展中的作用及机制；3.扩大临床样本，验证RPL32及其相关通路与肺癌患者预后的关系。本研究将证实RPL32可能是肺癌诊疗的新靶点。

核糖体蛋白RPL32是核糖体大亚基组成蛋白，前期发现RPL32的非核糖体功能可能与肺癌的发生发展相关。在该研究中，我们进一步证实敲降（除）RPL32可以显著抑制肺癌细胞的增殖。RPL32的N端，C1QBP (p32)的C端分别参与RPL32和p32的互作。我们发现敲降RPL32导致的肺癌增殖抑制是p53依赖的，敲降RPL32后，发生细胞核内易位的RPL5和RPL11可以竞争性地结合MDM2，与MDM2结合的p53减少，最终导致p53聚集，共敲RPL5或RPL11可以逆转敲降RPL32导致的p53聚集。在小鼠肺癌PDX模型中发现，抑制RPL32可以显著抑制移植瘤的增殖。此外，我们通过对收集的25例肺癌患者的手术标本的免疫组化检测，结合临床数据分析，进一步证实RPL32的表达与肺癌患者的预后呈负相关。本项目研究了抑制RPL32抑制肺癌增殖的具体机制，进一步证实RPL32可能是肺癌诊疗的新靶点。