A novel circular RNA circ_HN1/miR-628-5p/Ecto-5’-nucleotidase competing endogenous RNA network regulates gastric cancer development

The competing endogenous RNA (ceRNA) activity of circular RNAs (circRNAs) has been implicated in the development of gastric cancer. Here, we sought to explore the ceRNA function of circRNA Jupiter microtubule associated homolog 1 (circ_HN1) in gastric tumorigenesis. Circ_HN1, microRNA (miR)-628-5p, and NT5E expression levels were quantified by qRT-PCR and western blot. Dual-luciferase reporter assays were used to assess the direct relationship between miR-628-5p and circ_HN1 or NT5E. Our data showed that circ_HN1 expression was enhanced in human gastric cancer. Depletion of circ_HN1 impeded cell proliferation, spheroid formation, invasion, and migration and promoted apoptosis <i>in vitro</i>, as well as diminished tumor growth <i>in vivo</i>. NT5E was a downstream effector of circ_HN1 function. NT5E was targeted and inhibited by miR-628-5p through the perfect complementary site in NT5E 3ʹUTR, and circ_HN1 affected NT5E expression through miR-628-5p competition. Moreover, depletion of miR-628-5p reversed the effects of circ_HN1 silencing on regulating cell functional behaviors. Our findings identify a novel ceRNA network, the circ_HN1/miR-628-5p/NT5E axis, for the oncogenic activity of circ_HN1 in gastric cancer, highlighting circ_HN1 inhibition as a promising targeted treatment against gastric cancer.

环状RNA（circRNAs）的内源竞争RNA（ceRNA）活性已被证实参与胃癌的发生发展过程。本研究旨在探究环状RNA Jupiter微管相关同源物1（circ_HN1）在胃癌发生中的ceRNA调控功能。采用实时定量荧光PCR（qRT-PCR）与蛋白质印迹法（western blot）对circ_HN1、微小RNA（miR）-628-5p及NT5E的表达水平进行定量检测。通过双荧光素酶报告基因实验（dual-luciferase reporter assays）验证miR-628-5p与circ_HN1或NT5E之间的直接靶向互作关系。研究数据显示，circ_HN1在人类胃癌组织中表达显著上调。体外（in vitro）实验表明，敲低circ_HN1可显著抑制胃癌细胞的增殖、球体形成、侵袭与迁移能力，并促进细胞凋亡；体内（in vivo）实验则证实其可有效延缓肿瘤生长。NT5E是circ_HN1发挥致癌功能的下游效应分子。miR-628-5p可通过靶向结合NT5E 3'非翻译区（3'UTR）中的完美互补序列，对NT5E的表达进行抑制；而circ_HN1可通过竞争结合miR-628-5p，从而调控NT5E的表达水平。此外，敲低miR-628-5p可逆转circ_HN1沉默对胃癌细胞功能表型的调控作用。本研究鉴定出一条全新的ceRNA调控网络——circ_HN1/miR-628-5p/NT5E轴，阐明了circ_HN1在胃癌中发挥致癌活性的分子机制，提示靶向抑制circ_HN1有望成为胃癌治疗的潜在靶向策略。