Circ_0000518 contributes to breast cancer development depending on the regulation of miR-1258/ZEB1 axis

Breast cancer (BC) is a common malignancy in women. We aimed to investigate the role of circular RNA_0000518 (circRNA_0000518) in BC progression and its associated mechanism. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were utilized to measure RNA and protein expression. Cell proliferation was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and colony formation assay. Transwell assays were conducted to analyze cell motility. Intermolecular interaction was verified via dual-luciferase reporter assay and RNA-pull down assay. Circ_0000518 expression was up-regulated in BC tissues and cell lines. Circ_0000518 interference suppressed the proliferation, migration, invasion and glycolytic metabolism and promoted the apoptosis of BC cells. Circ_0000518 acted as a molecular sponge for microRNA-1258 (miR-1258), and circ_0000518 interference-mediated effects in BC cells were largely alleviated by the addition of anti-miR-1258. MiR-1258 interacted with the 3′ untranslated region (3′UTR) of zinc finger E-box binding homeobox 1 (ZEB1) in BC cells, and miR-1258 suppressed the malignant behaviors of BC cells partly through down-regulating ZEB1. Circ_0000518 interference significantly suppressed the growth of xenograft tumors in vivo. Circ_0000518/miR-1258/ZEB1 signaling cascade was identified in this study for the first time. Circ_0000518 contributed to BC progression by binding to miR-1258 to induce ZEB1 expression.乳腺癌（BC）是女性常见的恶性肿瘤。本研究旨在探讨环状RNA_0000518（circRNA_0000518）在乳腺癌进展中的作用及其相关分子机制。研究采用实时荧光定量聚合酶链式反应（RT-qPCR）与蛋白质印迹实验检测RNA与蛋白的表达水平；通过噻唑蓝（MTT）法与集落形成实验评估细胞增殖能力；利用Transwell实验分析细胞运动能力；借助双荧光素酶报告基因实验与RNA下拉实验验证分子间相互作用。实验结果显示，circRNA_0000518在乳腺癌组织与细胞系中表达上调。敲低circRNA_0000518可抑制乳腺癌细胞的增殖、迁移、侵袭与糖酵解代谢，并促进其凋亡。circRNA_0000518可作为微小RNA-1258（miR-1258）的分子海绵，而加入抗miR-1258可显著逆转敲低circRNA_0000518对乳腺癌细胞产生的上述生物学效应。miR-1258可与乳腺癌细胞中锌指E盒结合同源框1（ZEB1）的3′非编码区（3′UTR）结合，且miR-1258可通过下调ZEB1的表达，部分抑制乳腺癌细胞的恶性表型。体内实验表明，敲低circRNA_0000518可显著抑制异种移植瘤的生长。本研究首次发现了circRNA_0000518/miR-1258/ZEB1信号级联通路，circRNA_0000518可通过结合miR-1258以诱导ZEB1表达，进而促进乳腺癌进展。