The U2AF65/circNCAPG/RREB1 feedback loop promotes malignant phenotypes of glioma stem cells through activating the TGF-β pathway.

Glioma is the most aggressive and common malignant neoplasms in human brain tumors. Numerous studies have showed that glioma stem cells (GSCs)drive the malignant progression of gliomas. Recent studies have revealed that circRNAs can maintain stemness and promote malignant progression of glioma stem cells. We used bioinformatics analysis to identify circRNAs and potential RNA-binding proteins (RBPs) in glioma. qRT-PCR, western blotting, RNA FISH, RNA pull-down, RNA immunoprecipitation assay, ChIP, immunohistochemistry, and immunofluorescence methods were used to quantified the expression of circNCAPG, U2AF65, RREB1 and TGF-β1, and the underlying mechanisms between them. MTS, EDU, neurosphere formation, limiting dilution neurosphere formation and transwell assays examined the proliferation and invasive capability of GSCs, respectively. We identified a novel circRNA named circNCAPG was overexpressed and indicated the poor prognosis in glioma patients. Upregulating circNCAPG promoted the malignant progression of GSCs. RNA binding protein U2AF65 could stabilize circNCAPG by direct binding. Mechanically, circNCAPG interacted with and stabilized RREB1, as well as stimulated RREB1 nuclear translocation to activate TGF-β1 signaling pathway. Furthermore, RREB1 transcriptionally upregulated U2AF65 expression to improve the stability of circNCAPG in GSCs, which established a feedback loop involving U2AF65, circNCAPG and RREB1. Since circRNA is more stable than mRNA and can execute its function continuously, targeting circNCAPG in glioma may be a novel promising therapeutic.

Li H ，Jiang Y ，Hu J ，Xu J ，Chen L ，Zhang G ，Zhao J ，Zong S ，Guo Z ，Li X ，Zhao X ，Jing Z ... -  《Cell Death & Disease》

The U2AF2 /circRNA ARF1/miR-342-3p/ISL2 feedback loop regulates angiogenesis in glioma stem cells.

Jiang Y ，Zhou J ，Zhao J ，Zhang H ，Li L ，Li H ，Chen L ，Hu J ，Zheng W ，Jing Z ... -  《JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH》

CircKPNB1 mediates a positive feedback loop and promotes the malignant phenotypes of GSCs via TNF-α/NF-κB signaling.

Glioma stem cells (GSCs) are a special kind of cells in GBM showing tumor initiation, self-renewal, and multi-lineage differentiation abilities. Finding novel circRNAs related to GSCs is of great significance for the study of glioma. qPCR, western blotting, and immunohistochemistry were used to detect the expression levels of circKPNB1, SPI1, DGCR8, and TNF-α. The expression of these molecules in GSCs was regulated by lentiviral-based infection. RNA immunoprecipitation assay, RNA pull-down, dual-luciferase reporter, and chromatin immunoprecipitation assays were used to study the direct regulation mechanisms among these molecules. All the MTS, EDU, transwell, neurosphere formation assays, ELDA assays, and xenograft experiments were used to detect the malignant phenotype of GSCs. We found a novel circRNA circKPNB1 was overexpressed in GBM and associated with GBM patients' poor prognosis. CircKPNB1 overexpression can promote the cell viabilities, proliferation, invasion, neurospheres formation abilities, and stemness of GSCs. Mechanistically, circKPNB1 regulates the protein stability and nuclear translocation of SPI1. SPI1 promotes the malignant phenotype of GSCs via TNF-α mediated NF-κB signaling. SPI1 can also transcriptionally upregulate DGCR8 expression, and the latter can maintain the stability of circKPNB1 and forms a positive feedback loop among DGCR8, circKPNB1 and SPI1. Our study found circKPNB1 was a novel oncogene in GBM and of great significance in the diagnosis and prognosis prediction of GBM and maybe a novel target for molecular targeted therapy.

Jiang Y ，Zhao J ，Liu Y ，Hu J ，Gao L ，Wang H ，Cui D ... -  《Cell Death & Disease》

Propofol Represses Cell Growth and Metastasis by Modulating the Circular RNA Non-SMC Condensin I Complex Subunit G/MicroRNA-200a-3p/RAB5A Axis in Glioma.

Glioma is a common primary intracranial tumor, with high infiltration and aggression. Propofol (Pro) is associated with growth and metastasis in glioma. Meanwhile, circular RNA non-SMC condensin I complex subunit G (circNCAPG; hsa_circ_0007244) has been reported to be upregulated in glioma. This study explored the role and mechanism of circNCAPG in Pro-induced glioma progression. Cell viability was determined by cell counting kit-8 assay. Levels of circNCAPG, microRNA-200a-3p (miR-200a-3p), and member RAS oncogene family (RAB5A) were detected by real-time quantitative polymerase chain reaction. Colony number, apoptosis, migration, and invasion were analyzed by colony formation, flow cytometry, wound healing, and transwell assays. Matrix metallopeptidase 2, matrix metallopeptidase 9, and RAB5A protein levels were detected by Western blot assay. The binding relationship between miR-200a-3p and circNCAPG or RAB5A was predicted by starBase 2.0 and then verified by a dual-luciferase reporter and RNA immunoprecipitation assays. The biological roles of circNCAPG and Pro on glioma tumor growth were examined by the xenograft tumor model in vivo. Expression of circNCAPG and RAB5A was upregulated, and miR-200a-3p was decreased in glioma tissues and cells, while their expression presented an opposite trend in Pro-treated glioma cells. Moreover, circNCAPG overexpression could abolish Pro-mediated proliferation, apoptosis, migration, and invasion in glioma cells in vitro. Mechanically, circNCAPG could regulate RAB5A expression by sponging miR-200a-3p. Pro blocked glioma tumor growth in vivo by modulating circNCAPG. Pro could inhibit glioma cell growth and metastasis through the circNCAPG/miR-200a-3p/RAB5A axis, providing a promising therapeutic strategy for glioma treatment.

Zhang L ，Chen H ，Tian C ，Zheng D ... -  《-》

FMR1/circCHAF1A/miR-211-5p/HOXC8 feedback loop regulates proliferation and tumorigenesis via MDM2-dependent p53 signaling in GSCs.

Jiang Y ，Wang Z ，Ying C ，Hu J ，Zeng T ，Gao L ... -  《-》