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Glioblastoma is a rare and deadly malignancy with a low survival rate. Emerging evidence has shown that aberrantly expressed circular RNAs (circRNAs) play a critical role in the initiation and progression of GBM tumorigenesis. The oncogenic function of circZNF609 and circNFIX is involved in several types of cancer, but the role and underlying mechanism of these circRNAs in glioblastoma remain unclear. In this study, we hypothesized that circZNF609 and circNFIX may regulate EGFR through sponging miR-145-5p . Herein, we assessed the expression levels of circZNF609 , circNFIX, miR-145-5p , and EGFR using quantitative polymerase chain reaction in glioblastoma patients and normal brain samples. The results showed that circZNF609 , circNFIX, and EGFR expression levels were upregulated and miR145-5p was downregulated (p = 0.001, 0.06, 0.002, and 0.0065, respectively), while there was no significant association between clinicopathological features of the patients and the level of these genes expression. We also found a significant inverse correlation between miR145-5p and the expression of cZNF609 , cNFIX and EGFR (p = 0.0003, 0.0006, and 0.009, respectively). These findings may open a new window for researchers to better understand the potential pathways involved in GBM pathogenesis. In conclusion, it may provide a new potential pathway for the development of effective drugs for the treatment of GBM patients.

Background Circular RNA nuclear factor I X (circNFIX) has been reported to play an important role in glioma progression. However, the mechanism by which circNFIX participates in glioma progression remains poorly understood. Methods GERIA online were used to analyze the abnormally expressed genes in glioma tissues. The expression levels of circNFIX, microRNA (miR)-378e and Ribophorin-II (RPN2) were measured by quantitative real-time polymerase chain reaction or western blot. Cell cycle distribution, apoptosis, glycolysis, migration and invasion were determined by flow cytometry, special kit and trans-well assays, respectively. The target association between miR-378e and circNFIX or RPN2 was confirmed by luciferase reporter assay, RNA immunoprecipitation and pull-down. Xenograft model was established to investigate the role of circNFIX in vivo. Results The expression of circNFIX was enhanced in glioma tissues and cells compared with matched controls and high expression of circNFIX indicated poor outcomes of patients. Knockdown of circNFIX led to arrest of cell cycle, inhibition of glycolysis, migration and invasion and promotion of apoptosis in glioma cells. circNFIX was a sponge of miR-378e. miR-378e overexpression suppressed cell cycle process, glycolysis, migration and invasion but promoted apoptosis. miR-378e silence abated the suppressive role of circNFIX knockdown in glioma progression. RPN2 as a target of miR-378e was positively regulated via circNFIX by competitively sponging miR-378e. Silencing circNFIX decreased glioma xenograft tumor growth by regulating miR-378e/RPN2 axis. Conclusion Knockdown of circNFIX inhibits progression of glioma in vitro and in vivo by increasing miR-378e and decreasing RPN2, providing a novel mechanism for understanding the pathogenesis of glioma.

Ovarian cancer (OC) is a gynecological cancer with high mortality. OC‐derived exosomal circRNAs can regulate angiogenesis. This study aims to explore the role and mechanism of exosomal circRNA nuclear factor I X (CircNFIX) derived from OC cells in angiogenesis. Quantitative real‐time polymerase chain reaction was employed to evaluate the levels of circNFIX, miR‐518a‐3p, and tripartite motif protein 44 (TRIM44) in OC and adjacent tissues. Exosomes from the ovarian surface epithelial cell (HOSEpiC) and OC cells (SKOV3 or OVCAR3) were isolated by differential centrifugation. Exosomes were cocultured with the human umbilical vein endothelial cells (HUVECs). The angiogenesis capacity was analyzed by Tube formation assay. 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2‐H‐tetrazolium bromide (MTT) and Transwell assays were used to determine the cell viability and migration ability. The dual‐luciferase report, RNA immunoprecipitation (RIP), and RNA pull‐down assays were applied to validate the gene's interaction. CircNFIX and TRIM44 expression were higher and miR‐518a‐3p was lower in OC tissues than in the adjacent tissues. Upregulated circNFIX and TRIM44 were significantly correlated with the tumor size and International Federation of Gynecology and Obstetrics (FIGO) stage of OC patients. HUVECs treated OC‐derived exosomes had higher proliferation, migration, and angiogenesis capacities than the control group. While OC‐derived exosomal circNFIX silencing restrained HUVECs' proliferation, migration, and angiogenesis, compared with the OC‐derived exosomes group. OC‐derived exosomal circNFIX positively regulated TRIM44 expression by targeting miR‐518a‐3p in HUVECs. OC‐derived exosomal circNFIX promoted angiogenesis by regulating the Janus‐activated kinase/signal transducer and activator of transcription 1 (JAK/STAT1) pathway via miR‐518a‐3p/TRIM44 axis in HUVECs.

We aimed to study the regulatory roles and mechanism of circular nuclear factor IX (circNFIX) in cancer growth and stemness properties of ovarian cancer (OC). CircNFIX and SH3RF3 levels in OC tissues and cells were tested by quantitative real‐time PCR. RNase R treatment quantified circNFIX RNA stability. Molecular interaction among circNFIX, LIN28B, and SH3RF3 was predicted by bioinformatics software and validated through RNA immunoprecipitation (RIP) assay. The gain‐ or loss‐experiments of circNFIX on capabilities of metastasis and stemness in vitro were assessed using Cell Counting Kit‐8, Transwell, western blot, and sphere‐formation assays. CircNFIX and SH3RF3 were markedly elevated in OC tissues and OC cells. Knocking down circNFIX repressed the proliferation, migration, invasion, and stemness properties of A2780 and SKOV3 cells. The RIP assay verified the direct binding relationship between LIN28B, circNFIX, and SH3RF3. Additionally, overexpression of circNFIX elevated the SH3RF3 expression, while this effect was reversed by LIN28B silence. Rescue experiments demonstrated that the overexpression of SH3RF3 reversed the knockdown of circNFIX on OC cells' proliferation, metastasis, and stemness properties. CircNFIX improved the mRNA stability and translation of SH3RF3 via recruiting LIN28B, thus promoting the proliferation, invasion, and stemness properties of OC cells in vitro.

Non-small cell lung cancer (NSCLC) remains the most commonly diagnosed malignancy and the leading cause of cancer death worldwide. Circular RNAs (circRNAs) have been demonstrated to play critical roles in human carcinogenesis, including NSCLC. However, it is still unclear whether circRNA nuclear factor I X (circNFIX) is implicated in the molecular pathogenesis of NSCLC. The expression levels of circNFIX, miR-212-3p and a disintegrin and metalloproteinases 10 (ADAM10) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. Cell viability was gauged by the Cell Counting Kit-8 (CCK-8) assay, and cell migration and invasion were determined by transwell assays. Glucose uptake and lactate product were determined using the assay kits. Targeted relationships among circNFIX, miR-212-3p and were verified by dual-luciferase reporter and RNA pulldown assays. Additionally, the xenograft model assays were carried out to analyze the role of circNFIX in tumor growth in vivo. Our data revealed that circNFIX was overexpressed in NSCLC and predicted poor prognosis of NSCLC patients. CircNFIX knockdown suppressed NSCLC cell viability, migration, invasion and glycolysis in vitro and hampered tumor growth in vivo. Mechanistically, CircNFIX acted as a molecular sponge of miR-212-3p, and the repressive effect of circNFIX knockdown on NSCLC cell malignant progression was mediated by miR-212-3p. Moreover, was a direct target of miR-212-3p, and circNFIX influenced expression by sponging miR-212-3p in NSCLC cells. Furthermore, the silencing of hindered NSCLC cell viability, migration, invasion and glycolysis in vitro. Our findings first identified that the knockdown of circNFIX, a highly expressed circRNA in NSCLC, exerted a repressive role in NSCLC malignant progression at least in part through targeting the miR-212-3p/ axis, illuminating a novel understanding of circRNA regulation in NSCLC.

Myocardial infarction is the leading cause of death worldwide, and cardiomyocyte apoptosis during myocardial infarction and reperfusion is a significant factor of poor prognosis. As important regulatory molecules, biofimctions of circRNAs in the pathogenesis of myocardial infarction remain elusive. To confirm the expression level and biological function of circNFIX in cardiomyocytes upon oxidative stress. Divergent polymerase chain reaction and Sanger sequencing were performed to verify the circular structure. The stability of circNFIX was confirmed by RNase R treatment and actinomycin D assay. In order to simulate oxidative stress during myocardial infarction, H9c2 cells were subjected to hydrogen peroxide and hypoxia stimulation. In vivo, mouse models of myocardial ischemia were established. The biological function of circNFIX in cardiomyocytes was investigated through loss- and gain-of-function assays, and cardiomyocyte apoptosis level was detected by the terminal deoxyribonucleotidyl transferase-mediated TdT-mediated dUTP nick end labeling assay and Western blot. CircNFIX is abundant, conserved, and stable in H9c2 cells. The expression of circNFIX was significantly downregulated in cardiomyocytes subjected to oxidative stress. Enforced CircNFIX promotes H9c2 cells apoptosis induced by hydrogen peroxide, in sharp contrast to circNFIX knockdown. In this study, we found that circNFIX served as a pro-apoptosis factor in cardiomyocyte apoptosis. CircNFIX possesses potential to be the biomarker and therapeutic target in myocardial infarction.