基于RNA测序技术的胃癌转移相关长链非编码RNA CASC19的功能鉴定与机制研究

Metastasis contributes to the poor prognosis and treatment failure of gastric cancer. There’s limited knowledge about the mechanisms under metastasis of gastric cancer, so as to be difficult in new drug development and effects promotion. Recently, we used RNA sequencing of gastric adenocarcinoma tissues with high or low metastatic trend to identify metastasis related lncRNA, combining cell migration model and analysis based on TCGA database, and then found lncRNA CASC19. In vitro experiments showed that up-regulation of CASC19 could increase the proliferation and migration of gastric cancer cells. So far, there’s no report about the function of CASC19 in cancer. We conceive that CASC19 may promote proliferation and metastasis of gastric cancer cells. In the present study, we’ll detect the expression of CASC19 in large gastric cancer samples and analyze its correlation with metastasis and prognosis. Furtherly, we’ll study the functions of CASC19 in regulating proliferation,apoptosis, EMT, metastasis and stemness of gastric cancer cells, and explore the mechanisms by studying its downstream target genes and combined proteins, by in vitro cell experiment and in vivo animal model. Completion of this study will clarify the expression of CASC19 and its function in gastric cancer, and will help us deeply understanding the mechanisms of carcinogenesis and development of gastric cancer, and may help to identify novel targets for treatment and new drug development.

胃癌预后差，转移是治疗失败的主要原因；而胃癌转移的机制仍未阐明，致使新药研发困难、疗效难以提高。我们前期采用RNA测序技术在高、低转移倾向胃癌组织中筛选转移相关长链非编码RNA（lncRNA），结合细胞迁移模型及 TCGA 数据库分析，发现 CASC19 高表达与转移密切相关，细胞学实验过表达CASC19可促进胃癌细胞的增殖与迁移。CASC19在肿瘤中的作用尚无报道，我们设想 CASC19 可能在胃癌中发挥促进增殖与转移的作用。本项目拟扩大样本量检测胃癌组织中CASC19表达并分析其与胃癌转移、预后等的相关性；通过细胞学与动物实验，进一步外源性改变CASC19并观察其对胃癌细胞的增殖与凋亡、EMT与转移、干细胞样特性的调控作用，并从下游基因及蛋白途径分析其机制。本项目的完成，将阐明CASC19在胃癌中的表达与生物学功能，有助于胃癌发生发展机制的深入理解、为胃癌治疗与新药研发提供新靶点。

本课题进一步探究了前期筛选的胃癌转移相关lncRNA CASC19在胃癌中的促进转移、增殖和免疫逃逸的功能及具体下游调控机制。在临床样本中我们验证了CASC19与更差的预后相关。通过体外实验证实了过表达CASC19有促进胃癌细胞增殖、抑制凋亡、促进转移的作用，体内小鼠肺转移模型实验验证了CASC19在体内对胃癌转移的促进作用。进一步发现CASC19在胃癌中可通过与DHX9结合来调控c-MYC的表达，进而激活c-MYC下游通路，促进胃癌的发展和转移。我们发现CASC19不仅可通过c-MYC上调PD-L1表达，还能够通过PD-L1调控发挥免疫逃逸机制，这说明CASC19在胃癌免疫微环境调控中起到了重要作用。总而言之，CASC19通过形成CASC19/DHX9复合体上调c-MYC促进胃癌发生与转移，并可参与PD-L1介导的免疫逃逸，这提示CASC19可作为提示胃癌早期转移和预后的标志物，参与免疫调控，并在免疫治疗方面有着潜在的临床价值。