新鉴定食管癌驱动基因RPS15在ESCC进展中的功能及机制研究

The translation of RNA into protein is a complex, fundamental cellular process that occurs on ribosomes. Ribosomes are mainly composed of rRNA and ribosomal protein RP. In recent years, somatic RP mutations have been found in many types of cancer, but the mechanism remains unknown. We analyzed the whole genome sequence of esophageal cancer patients and found a new mutation site R47P in RPS15 in ESCC. The results of IHC showed that the expression of RPS15 was positively correlated with the occurrence and metastasis of ESCC. Further experiments confirmed that overexpression of RPS15 or RPS15 R47P promotes the proliferation and metastasis of ESCC cells, especially RPS15 R47P mutation promotes esophageal cancer progression. We speculate that RPS15 and R47P mutation may drive the development of esophageal cancer. These findings lead to the proposal that RPS15 is a master molecule that determines the development of ESCC. In this project, we are going to investigate the roles and the underlying mechanisms of RPS15 and R47P mutation contributing to ESCC occurrence and metastasis. Hopefully, we can uncover new roles and mechanisms of RPS15 in the progression of ESCC. This study would contribute to the understanding of the metastasis of ESCC at both the cellular and molecular levels and advance the development of prognostic and therapeutic strategies.

RNA翻译成蛋白质是发生在核糖体上的一个复杂的，基础的细胞过程。核糖体主要由rRNA和核糖体蛋白RP构成。近年来，在多种类型癌症中都发现了体细胞RP突变，然而其具体机制尚存未知。本课题组对508对食管鳞癌样本进行全基因组测序分析，发现了RPS15在食管肿瘤患者中的新的突变位点R47P。前期结果发现RPS15的表达与食管癌的发生和转移成正相关；进一步细胞生物学功能实验证实过表达RPS15或R47P突变后能促进食管癌细胞的增殖和转移，尤其是 R47P突变更能促进食管癌的进展，推测RPS15及R47P突变可能在食管癌的发生发展过程中扮演驱动基因的重要角色。本课题组拟对RPS15与食管癌临床特征的相关性、食管癌进展中的功能进行系统深入研究；寻找RPS15及其R47P位点突变影响的下游相关信号通路，以期揭示RPS15在食管癌进展中的重要作用机理，为开发RPS15在食管癌诊断与治疗的应用提供线索。

食管癌是全球高发的恶性肿瘤，食管鳞癌（ESCC）是食管癌一类主要的组织学亚型。目前除了传统治疗方式外，尚无有效的精准医疗技术。究其原因，主要是目前对ESCC分子机制及驱动事件认知尚不足，缺乏有效生物标志物或分子分类来预测患者受益。本课题研究发现，核糖体小亚基RPS15的高表达与淋巴结转移能力呈显著正相关，且高水平的RPS15表达与ESCC患者的无进展生存期有关，是ESCC患者转移和预后不良的独立危险因素。体外细胞增殖实验和体内裸鼠皮下瘤实验均证明RPS15在体内外促进了ESCC细胞的增殖，体外Transwell实验和体内肺转移和淋巴结转移实验同样证明RPS15的高表达促进了食管鳞癌的转移。联合核糖体组测序和转录组测序发现，RPS15的高表达促进了翻译相关的核心核糖体蛋白的翻译效率，同时也提高了E2F通路和p38/MAPK通路与细胞增殖、转移和周期相关的蛋白的翻译效率，尤其是p38/MAPK通路的MKK6和p38。研究发现，RPS15可以和IGF2BP1的KH3-4结构域结合，通过识别mRNA上的m6A修饰（N6-methyladenosine）位点结合稳定下游靶基因的表达。进一步筛选发现叶酸通过促进RPS15的降解，抑制了RPS15高表达对ESCC细胞增殖能力的促进作用，与单药治疗相比，叶酸联合DDP对肿瘤细胞生长的抑制作用更强。综上，我们的研究首次揭示了RPS15对ESCC进展的促进作用，并且提出叶酸载带顺铂在改善食管鳞癌患者预后方面的潜力。