BACKGROUND Circular RNAs (circRNAs) have recently emerged as a new family of noncoding RNAs that are involved in the causation and progression of various cancers. However, the roles of circRNAs in the tumorigenesis of gastric cancer (GC) are still largely unknown. METHODS The expression profiles of circRNAs in GC were identified in open GEO database and were evaluated at the mRNA level in clinical GC samples compared with paired non-tumorous tissues. Kaplan-Meier survival curve was used to analyze the correlation of circRNA and patients' prognosis. Subsequently, the circular structures of candidate circRNAs were validated by Sanger sequencing, divergent primer PCR, and RNase R treatments. Gain- and loss-of-function analyses were performed to evaluate the functional significance of it in GC initiation and progression. Dual-luciferase reporter and RNA pull-down assays were used to identify the microRNA (miRNA) sponge mechanism of circRNAs. RESULTS The expression of circRHOBTB3 was lower in GC tissues and cell lines. Downregulation of circRHOBTB3 was significantly correlated with poor differentiation and unfavorable prognosis in patients with GC. Overexpression of circRHOBTB3 in GC cells led to decreased proliferation and induced G1/S arrest in vitro, accompanied with inhibited xenograft tumor growth in vivo, while the opposite effects were achieved in circRHOBTB3-silenced cells. Furthermore, we demonstrated that circRHOBTB3 acts as a sponge for miR-654-3p and verified that p21 is a novel target of miR-654-3p. CONCLUSION Taken together, this study revealed that circRHOBTB3 might function as competing endogenous RNA (ceRNA) for miR-654-3p, which could contribute to growth inhibition of GC through activating p21 signaling pathway. Our data suggested that circRHOBTB3 would serve as a novel promising diagnosis marker and therapeutic target for GC.

中文翻译：

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环状RNA circRHOBTB3充当miR-654-3p抑制胃癌生长的海绵。

背景技术环状RNA（circRNA）最近作为一种新的非编码RNA家族出现了，它们参与了各种癌症的病因和发展。但是，circRNA在胃癌（GC）肿瘤发生中的作用仍是未知之数。方法在开放的GEO数据库中鉴定circRNA在GC中的表达谱，并在临床GC样品中与配对的非肿瘤组织进行mRNA水平评估。用Kaplan-Meier生存曲线分析circRNA与患者预后的相关性。随后，通过Sanger测序，差异引物PCR和RNase R处理验证了候选circRNA的环状结构。进行了功能获得和功能丧失分析以评估其在GC启动和进展中的功能意义。使用双荧光素酶报告基因和RNA下拉测定法来鉴定circRNA的microRNA（miRNA）海绵机制。结果circRHOBTB3在GC组织和细胞株中的表达较低。circRHOBTB3的下调与GC患者的不良分化和不良预后显着相关。GC细胞中circRHOBTB3的过表达导致体外增殖减少和G1 / S阻滞，并在体内抑制异种移植肿瘤的生长，而在circRHOBTB3沉默的细胞中却获得了相反的效果。此外，我们证明了circRHOBTB3充当miR-654-3p的海绵，并证实p21是miR-654-3p的新型靶标。结论综上所述，这项研究表明circRHOBTB3可能充当miR-654-3p的竞争内源RNA（ceRNA），可能通过激活p21信号通路来抑制GC的生长。我们的数据表明circRHOBTB3将作为GC的一种新的有希望的诊断标志物和治疗靶标。