Circular RNA TMEM87A promotes cell proliferation and metastasis of gastric cancer by elevating ULK1 via sponging miR-142-5p (miRNA)

Background:Circular RNAs (circRNAs) act as vital regulators of gene expression in a variety of cancers. However, the role of circRNAs in gastric cancer (GC) remains largely unexplored. Herein, we identified that circTMEM87A sponges miR-142-5p to promote GC progression through up-regulating ULK1 expression. Methods:The expression of circTMEM87A in GC was determined by RNA sequencing and quantitative real-time PCR (qRT-PCR). The effects of knockdown or exogenous expression of circTMEM87A on GC cell phenotypes were evaluated both in vitro and in vivo. The interacting miRNA of circTMEM87A was predicted by bioinformatics and confirmed by RNA pull-down, dual-luciferase reporter assay and fluorescence in situ hybridization (FISH). The mechanism by which circTMEM87A/miR-142-5p/ULK1 axis promotes GC was determined by western blot, GFP/mRFP-LC3 puncta analysis, transmission electron microscope (TEM). Results:CircTMEM87A was dramatically elevated in GC tissues and cell lines, and high circTMEM87A expression was closely correlated with poor prognosis of GC patients. Knockdown of circTMEM87A suppressed cell growth, migration, invasion and induced apoptosis in vitro, as well as inhibited GC tumorigenicity and lung metastasis potential in vivo. Meanwhile, circTMEM87A overexpression had the opposite effects. Furthermore, we demonstrated that circTMEM87A could act as a sponge of miR-142-5p to regulate ULK1 expression and GC progression. Conclusions:Our findings suggest that circTMEM87A functions as an oncogene through the miR-142-5p/ULK1 axis in GC. CircTMEM87A might be a prognostic biomarker as well as a promising therapeutic target for GC. Overall design: microRNA expression profiles involved in Gastric cancer progression

研究背景：环状RNA（Circular RNAs, circRNAs）在多种癌症中均作为基因表达的关键调控因子发挥功能。然而，环状RNA在胃癌（Gastric Cancer, GC）中的作用仍有待深入探究。本研究证实，circTMEM87A可通过吸附miR-142-5p，上调ULK1的表达，进而促进胃癌进展。
研究方法：通过RNA测序与实时荧光定量聚合酶链反应（quantitative real-time PCR, qRT-PCR）检测胃癌组织中circTMEM87A的表达水平。分别在体外与体内实验中，评估敲低或过表达circTMEM87A对胃癌细胞表型的影响。通过生物信息学预测circTMEM87A的靶向miRNA，并借助RNA pull-down、双荧光素酶报告基因实验以及荧光原位杂交（fluorescence in situ hybridization, FISH）验证其相互作用。采用蛋白质印迹法、GFP/mRFP-LC3斑点分析以及透射电子显微镜（transmission electron microscope, TEM），阐明circTMEM87A/miR-142-5p/ULK1轴促进胃癌进展的具体分子机制。
研究结果：胃癌组织与细胞系中circTMEM87A的表达水平显著升高，且高表达circTMEM87A与胃癌患者的不良预后密切相关。体外实验中，敲低circTMEM87A可抑制胃癌细胞的增殖、迁移与侵袭能力，并诱导细胞凋亡；体内实验中则可抑制胃癌的成瘤能力与肺转移潜能。而过表达circTMEM87A则可产生相反的生物学效应。此外，本研究证实circTMEM87A可通过吸附miR-142-5p调控ULK1的表达，进而影响胃癌进展。
研究结论：本研究结果表明，circTMEM87A在胃癌中通过miR-142-5p/ULK1轴发挥致癌基因的功能。circTMEM87A有望成为胃癌的预后生物标志物与潜在治疗靶点。
整体实验设计：涉及胃癌进展的microRNA表达谱数据集