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

Abstract

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.

Nuclear Translocation of SIRT4 Mediates Deacetylation of U2AF2 to Modulate Renal Fibrosis Through Alternative Splicing-mediated Upregulation of CCN2

“…6C, D ), supporting the idea that acetylation of U2AF2 is responsible for fibrotic reaction under TGF-β1. Additionally, a recent study showed that U2AF2 can directly bind and stabilize circNCAPG, which participates in the nuclear translocation of ras responsive element binding protein 1, thereby activating the TGF-β pathway and promoting glioma progression 47 . Taking this into consideration, we speculate that U2AF2 may be a positive feedback regulator of TGF-β1, although further investigations are required to ascertain this.…”

Cancer stem cells in brain tumors: From origin to clinical implications

“…Absence of Miat leads to differentiation of tumorigenic stem‐cell like MB cells and differentiation of tumorigenic stem‐cell like MB cells into a non‐tumorigenic state 76 . Most recently, circular RNAs has also been demonstrated to regulate pluripotency and tumor cell growth in brain tumor, such as circNDC80, circNCAPG, circRPPH1, and circKPNB1 77–80 . Taken together, these findings suggest that ncRNAs not only affect the function of non‐CSCs but also regulate the function of CSCs.…”

Comprehensive Analysis of WGCNA - Derived Cancer Associated Fibroblasts Model For Prognosis, Immune Features, and Candidate Drug Development in LUSC

“…Tumor tissue from LUSC patients was xed in 10% formalin at 4°C overnight and embed in para n. 5-µm sections were incubated with primary and secondary antibodies (Abcepta Biotech Ltd. Co.) successively [32] .…”