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

Abstract

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 of ISL2, miR-342–3p, circRNA ARF1 (cARF1), U2AF2, and VEGFA. 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. ISL2 was overexpressed in glioma and correlated with poor patient survival. ISL2 transcriptionally regulated VEGFA expression in GSCs and promoted the proliferation, invasion, and angiogenesis of hBMECs via VEGFA-mediated ERK signaling. Regarding its mechanism of action, cARF1 upregulated ISL2 expression in GSCs via miR-342–3p sponging. Furthermore, U2AF2 bound to and promoted the stability and expression of cARF1, while ISL2 induced the expression of U2AF2, which formed a feedback loop in GSCs. We also showed that both U2AF2 and cARF1 had an oncogenic effect, were overexpressed in glioma, and correlated with poor patient survival. Conclusions Our study identified a novel feedback loop among U2AF2, cARF1, miR-342–3p, and ISL2 in 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.

Circular RNA circASPM Promotes the Progression of Glioblastoma by Acting as a Competing Endogenous RNA to Regulate miR-130b–3p/E2F1 Axis

“…We then veri ed the stability of circASPM using RNase R assays. RNase R assays are commonly used to con rm RNAs' circular structure because it can degrade linear RNAs with short 3′-tails, whereas it cannot degrade circRNAs (35). After RNase R disposition, ASPM mRNA expression was signi cantly decreased in GSC11 and GSC18 cells, while circASPM was unaffected (Fig.…”

“…We then cultured patient-derived GSCs cell line and used RNase R assays to prove that circASPM was stable after verifying that the cell lines culture worked well (35). Subsequently, we performed gain-offunction assays and loss-of-function assays to analyze the biological role of circASPM in GBM progression.…”

MicroRNAs and Stem-like Properties: The Complex Regulation Underlying Stemness Maintenance and Cancer Development

“…In glioma stem cells, circATP5B competitively sponges miR-185-5p, upregulating the expression of the homeobox gene HOXB5, which induces the proliferation of glioma stem cells through JAK2/STAT3 signaling [258]. In the same context, the circRNA cARF1 competitively binds to miR-342-3p, upregulating the expression of the transcription factor ISL2, which induces the expression of U2AF2 and causes an oncogenic effect [259]. In human liver cancer, the circRNA CircMEG3 inhibits the growth of the liver cancer stem cells repressing the expression of the m6A methyltransferase METTL3 and Cbf5, which in turn represses the telomerase activity [260].…”

Hsa_circ_0091581 promotes glioma progression by regulating RMI1 via sponging miR-1243-5p

“…International Publisher biomarker of lymph node metastasis in thyroid cancer [14]; hsa_circ_0003829 may act as a diagnostic predictor in oral squamous cell carcinoma [15]. In glioma, accumulating evidence indicates that circRNAs are closely associated with glioma progression [1,16,17]; however, progress of the sequencing technology resulted in identification of additional circRNAs, and the relationships between circRNAs and glioma progression require further investigation.…”

“…Glioma is a pervasive malignancy and the main cause of cancer-related deaths worldwide [1]. Glioblastoma multiforme (GBM), WHO Ⅳ grade glioma, is characterized by the presence of poorly differentiated stromal cells around focal necrosis and capillary proliferation [2,3].…”