Department of Neurosurgery, the Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, Wuxi, China.
Department of Neurosurgery, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
Neuro Oncol. 2019 Oct 9;21(10):1284-1296. doi: 10.1093/neuonc/noz128.
Circular RNAs (circRNAs), a newly discovered type of endogenous noncoding RNA, have been proposed to mediate the progression of diverse types of tumors. Systematic studies of circRNAs have just begun, and the physiological roles of circRNAs remain largely unknown. Here, we focused on elucidating the potential role and molecular mechanism of circular forkhead box O3 (circFOXO3) in glioblastoma (GBM) progression.
First, we analyzed circFOXO3 alterations in GBM and noncancerous tissues through real-time quantitative reverse transcription PCR (qRT-PCR). Next, we used loss- and gain-of-function approaches to evaluate the effect of circFOXO3 on GBM cell proliferation and invasion. Mechanistically, fluorescent in situ hybridization, RNA pull-down, dual luciferase reporter, and RNA immunoprecipitation assays were performed to confirm the interaction between circFOXO3 and miR-138-5p/miR-432-5p in GBM. An animal model was used to verify the in vitro experimental findings.
CircFOXO3 expression was significantly higher in GBM tissues than in noncancerous tissues. GBM cell proliferation and invasion were reduced by circFOXO3 knockdown and enhanced by circFOXO3 overexpression. Further biochemical analysis showed that circFOXO3 exerted its pro-tumorigenic activity by acting as a competing endogenous RNA (ceRNA) to increase expression of nuclear factor of activated T cells 5 (NFAT5) via sponging both miR-138-5p and miR-432-5p. Notably, tumor inhibition by circFOXO3 downregulation could be reversed by miR-138-5p/miR-432-5p inhibitors in GBM cells. Moreover, GBM cells with lower circFOXO3 expression developed less aggressive tumors in vivo.
Our data demonstrate that circFOXO3 can exert regulatory functions in GBM and that ceRNA-mediated microRNA sequestration might be a potential strategy for GBM therapy.
环状 RNA（circRNAs）是一种新发现的内源性非编码 RNA，被认为可以介导多种类型肿瘤的进展。对 circRNAs 的系统研究才刚刚开始，circRNAs 的生理功能在很大程度上仍然未知。在这里，我们专注于阐明环状叉头框 O3（circFOXO3）在胶质母细胞瘤（GBM）进展中的潜在作用和分子机制。
首先，我们通过实时定量逆转录 PCR（qRT-PCR）分析 GBM 和非癌组织中 circFOXO3 的改变。接下来，我们使用缺失和功能获得方法来评估 circFOXO3 对 GBM 细胞增殖和侵袭的影响。通过荧光原位杂交、RNA 下拉、双荧光素酶报告基因和 RNA 免疫沉淀实验证实了 circFOXO3 与 miR-138-5p/miR-432-5p 在 GBM 中的相互作用。使用动物模型验证了体外实验结果。
circFOXO3 在 GBM 组织中的表达明显高于非癌组织。circFOXO3 敲低可降低 GBM 细胞的增殖和侵袭，而过表达则增强其增殖和侵袭。进一步的生化分析表明，circFOXO3 通过作为核因子活化 T 细胞 5（NFAT5）的竞争性内源性 RNA（ceRNA），通过海绵吸附 miR-138-5p 和 miR-432-5p 来增加 NFAT5 的表达，从而发挥其促肿瘤活性。值得注意的是，在 GBM 细胞中，circFOXO3 下调引起的肿瘤抑制作用可被 miR-138-5p/miR-432-5p 抑制剂逆转。此外，体内表达较低 circFOXO3 的 GBM 细胞形成的肿瘤侵袭性较小。
我们的数据表明，circFOXO3 可以在 GBM 中发挥调节功能，而 ceRNA 介导的 microRNA 隔离可能是 GBM 治疗的一种潜在策略。
