TheU2AF2/circRNA ARF1/miR-342-3p/ISL2feedback loop regulates angiogenesis in glioma stem cells

Background Glioma is the most common and lethal primary brain tumor in adults, and angiogenesis is one of the key factors contributing to its proliferation, aggressiveness, and malignant transformation. However, the discovery of novel oncogenes and the study of its molecular regulating mechanism based on circular RNAs (circRNAs) may provide a promising treatment target in glioma. Methods Bioinformatics analysis, qPCR, western blotting, and immunohistochemistry were used to detect the expression levels ofISL2, miR-342-3p, circRNA ARF1 (cARF1),U2AF2, andVEGFA. Patient-derived glioma stem cells (GSCs) were established for the molecular experiments. Lentiviral-based infection was used to regulate the expression of these molecules in GSCs. The MTS, EDU, Transwell, and tube formation assays were used to detect the proliferation, invasion, and angiogenesis of human brain microvessel endothelial cells (hBMECs). RNA-binding protein immunoprecipitation, RNA pull-down, dual-luciferase reporter, and chromatin immunoprecipitation assays were used to detect the direct regulation mechanisms among these molecules. Results We first identified a novel transcription factor related to neural development.ISL2was overexpressed in glioma and correlated with poor patient survival.ISL2transcriptionally regulatedVEGFAexpression in GSCs and promoted the proliferation, invasion, and angiogenesis of hBMECs viaVEGFA-mediatedERKsignaling. Regarding its mechanism of action, cARF1 upregulatedISL2expression in GSCs via miR-342-3p sponging. Furthermore,U2AF2bound to and promoted the stability and expression of cARF1, whileISL2induced the expression ofU2AF2, which formed a feedback loop in GSCs. We also showed that bothU2AF2and cARF1 had an oncogenic effect, were overexpressed in glioma, and correlated with poor patient survival. Conclusions Our study identified a novel feedback loop amongU2AF2, cARF1, miR-342-3p, andISL2in GSCs. This feedback loop promoted glioma angiogenesis, and could provide an effective biomarker for glioma diagnosis and prognostic evaluation, as well as possibly being used for targeted therapy.