Circular RNAs serve as miRNA sponges in breast cancer

Exploring the complex dimensions of Alzheimer's disease: The promising role of circular RNAs and their potential contributions

Circular RNAs (circRNAs) are multifunctional molecules that regulate gene expression at transcriptional and post-transcriptional levels. They are generated through the back-splicing of mRNA precursors and exhibit tissue-specific expression patterns. CircRNAs highly conserved among various species, exhibit significant abundance and dynamic expression within the nervous system, especially at synaptic sites. Research has shown varied distributions of circRNAs across different organs, including the brain, heart, liver, and lungs, with pronounced enrichment in the nervous system. Neurological disorders lead to alterations in gene expression, transcript profiles, and modifications of non-coding RNAs, including circRNAs. Alzheimer's disease is marked by the accumulation of amyloid-beta (Aβ) plaques and the presence of phosphorylated tau (P-tau) neurofibrillary tangles, both of which are key histological features that contribute to the pathophysiology of the disease. Notably, circRNAs cross the blood-brain barrier (BBB), presenting promising avenues for therapeutic interventions in neurological conditions like Alzheimer's disease (AD) due to their stability and the specificity of their expression in various tissues, circular RNAs are increasingly recognized as promising candidates for therapeutic intervention.

Genome-wide analysis of m6A-modified circRNAs in the mouse model of myocardial injury induced by obstructive sleep apnea

BACKGROUND

The peculiar expression of N6-methyladenosine (m6A) in Circular RNAs (circRNAs) is closely linked to the occurrence of many diseases. However, roles of m6A-modified circRNAs in OSA-induced cardiovascular disease are unknown. Here, we use bioinformatics analysis to investigate the expression profiles of m6A-modified circRNAs and reveal their potential functional roles in the mouse models of chronic intermittent hypoxia (CIH).

METHODS

Firstly, the expression profiles of m6A-modified circRNA in left ventricular tissue of the CIH mouse model were examined using circRNA microarray analysis. Then, the expression level of selected circrRNA was compared by folding change filtration, and the consistency between them and microarray results was verified by MeRIP-qPCR. GO analyses and KEGG analyses were conducted to predict the potential functions of these m6A-modified circRNAs. Finally, we conducted a ceRNA analysis, and a network was constructed to clarify the relationship between the selected circRNAs and miRNAs as well as the targeted genes.

RESULTS

In total, 255 circRNAs with m6A peaks in CIH-treated cardiac tissues were identified. 250 were up-regulated, 5 were down-regulated. The results of MeRIP-qPCR were consistent with the microarray results. 73 pathways were detected in the up-regulated transcripts and no relevant pathways were detected in the down-regulated transcripts. Finally, three circRNAs (mmu_circRNAs_22543, mmu_circRNAs_29768, and mmu_circRNAs_34841) were selected for ceRNA analysis, and the circRNA-miRNA-mRNA network was constructed.

CONCLUSION

Our findings are the first to show that m6A-modified circRNAs play a key role in OSA-induced cardiovascular disease. This study highlights the pivotal role of m6A-modified circRNAs in regulating gene expression and their potential implications in understanding the molecular pathogenesis of OSA-induced cardiac injury.

Protocol to infer and analyze miRNA sponge modules in heterogeneous data using miRSM 2.0

MicroRNA (miRNA) sponges synergistically modulate physiological and pathological processes in the form of modules or clusters. Here, we present a protocol for inferring and analyzing miRNA sponge modules in heterogeneous data using the R package miRSM 2.0. We describe steps for identifying gene modules, inferring miRNA sponge modules at multi-sample and single-sample levels, and performing modular analysis. From the perspective of computational biology, miRSM 2.0 has the potential to advance our understanding of the role of miRNA sponges in diseases. For complete details on the use and execution of this protocol, please refer to Zhang et al.1,2,3.

Comprehensive Analysis of circRNA-Related mRNAs as Prognostic Factors in Non-Smoking Women with Lung Adenocarcinoma

Background

Non-smoking women with lung adenocarcinoma(NSWLA) is a significant health problem globally; the carcinogenesis and prognostic signature remain poorly understood. Circular RNAs (circRNAs) are gradually implicated in cancer formation through sponging miRNAs to regulate mRNAs.

Methods

Tumor and paracancerous specimens from non-smoking women after lung adenocarcinoma surgery were collected for high-throughput sequencing of circRNA. miRNA and mRNA datasets were downloaded from TCGA. A circRNA-miRNA-mRNA network was built using differentially expressed circRNAs (DEcircRNAs), miRNAs (DEmiRNAs), and mRNAs (DEmRNAs). Following that, GSEA was applied to analyze the biological function of mRNAs in the ceRNA network. Utilizing the mRNAs associated with prognosis, we created an original prognostic risk score model. The expression of DEmRNA in the ceRNA network was verified by mRNA-seq and scRNA-seq data (GSE131907). The expression of BTBD3 and EIF4EBP2 was then verified by immunohistochemistry.

Results

16 pairs of adenocarcinoma tissues and their corresponding para-tumor samples were collected from thoracic surgery. We created a circRNA related ceRNA in NSWLA. The hsa_circ_0002346 regulation of the cancer cell proliferation may through the hsa_circ_0002346/miR-96-5p/EIF4EBP2 axis. Hsa_circ_0072309 may affect proliferation of lung adenocarcinoma and activate Nature Killer cells by targeting miR-32-5p to regulate PCMTD1 expression. Based upon mRNA (BTBD3, CFL2, EIF4EBP2, EVI5, PCMTD1, SYDE2) related to overall survival, we also created a predictive signature. According to mRNA-seq, scRNA-seq, and immunohistochemical data, the expression of BTBD3 and EIF4EBP2 was lower in tumor samples than in normal tissues nearby.

Conclusion

The circRNA related mRNAs played an important role in predicting the overall survival of NSWLA. The circRNA in the ceRNA network might unravel the pathogenesis and be potential novel targets for NSWLA.

Exploring the impact of circRNAs on cancer glycolysis: Insights into tumor progression and therapeutic strategies

Cancer cells exhibit altered metabolic pathways, prominently featuring enhanced glycolytic activity to sustain their rapid growth and proliferation. Dysregulation of glycolysis is a well-established hallmark of cancer and contributes to tumor progression and resistance to therapy. Increased glycolysis supplies the energy necessary for increased proliferation and creates an acidic milieu, which in turn encourages tumor cells' infiltration, metastasis, and chemoresistance. Circular RNAs (circRNAs) have emerged as pivotal players in diverse biological processes, including cancer development and metabolic reprogramming. The interplay between circRNAs and glycolysis is explored, illuminating how circRNAs regulate key glycolysis-associated genes and enzymes, thereby influencing tumor metabolic profiles. In this overview, we highlight the mechanisms by which circRNAs regulate glycolytic enzymes and modulate glycolysis. In addition, we discuss the clinical implications of dysregulated circRNAs in cancer glycolysis, including their potential use as diagnostic and prognostic biomarkers. All in all, in this overview, we provide the most recent findings on how circRNAs operate at the molecular level to control glycolysis in various types of cancer, including hepatocellular carcinoma (HCC), prostate cancer (PCa), colorectal cancer (CRC), cervical cancer (CC), glioma, non-small cell lung cancer (NSCLC), breast cancer, and gastric cancer (GC). In conclusion, this review provides a comprehensive overview of the significance of circRNAs in cancer glycolysis, shedding light on their intricate roles in tumor development and presenting innovative therapeutic avenues.

Circ_0007445 inhibits trophoblast cell proliferation, migration and invasion by mediating the miR-4432/HTRA1 axis in preeclampsia

BACKGROUND

: Circular RNAs (circRNAs) have been shown to be extensively involved in preeclampsia progression. At present, the role of circ_0007445 in preeclampsia progression is not clear.

METHODS

A total of 30 preeclampsia patients and 30 normal pregnant women were recruited in our study. The function of trophoblast cells was explored to clarify the role and mechanism of circ_0007445 on the preeclampsia progression. The expression of circ_0007445, microRNA (miR)-4432 and high temperature requirement A1 (HTRA1) was analyzed by quantitative real-time PCR. The proliferation, migration and invasion of trophoblast cells were determined by cell counting kit 8 assay, EdU assay, colony formation assay, flow cytometry, and transwell assay. Protein expression was examined by western blot analysis. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were used to assess RNA interaction relationships.

RESULTS

Our data suggested that circ_0007445 had increased expression in preeclampsia patients. Knockdown of circ_0007445 enhanced trophoblast cell proliferation, migration and invasion. MiR-4432 was lowly expressed in preeclampsia patients, and it could be sponged by circ_0007445. MiR-4432 inhibitor overturned the promotion effects of circ_0007445 knockdown on trophoblast cell functions. HTRA1 was highly expressed in preeclampsia patients, and it could be targeted by miR-4432. HTRA1 overexpression could also reverse the proliferation, migration and invasion of trophoblast cells promoted by miR-4432 mimic. In addition, circ_0007445 positively regulated HTRA1 through targeting miR-4432.

CONCLUSION

:Our results suggested that circ_0007445 facilitated the development of preeclampsia by suppressing trophoblast cell function through miR-4432/HTRA1 axis.

Dysregulated Expression Patterns of Circular RNAs in Cancer: Uncovering Molecular Mechanisms and Biomarker Potential

Circular RNAs (circRNAs) are stable, enclosed, non-coding RNA molecules with dynamic regulatory propensity. Their biogenesis involves a back-splicing process, forming a highly stable and operational RNA molecule. Dysregulated circRNA expression can drive carcinogenic and tumorigenic transformation through the orchestration of epigenetic modifications via extensive RNA and protein-binding domains. These multi-ranged functional capabilities have unveiled extensive identification of previously unknown molecular and cellular patterns of cancer cells. Reliable circRNA expression patterns can aid in early disease detection and provide criteria for genome-specific personalized medicine. Studies described in this review have revealed the novelty of circRNAs and their biological ss as prognostic and diagnostic biomarkers.

Bladder-cancer-derived exosomal circRNA_0013936 promotes suppressive immunity by up-regulating fatty acid transporter protein 2 and down-regulating receptor-interacting protein kinase 3 in PMN-MDSCs

BACKGROUND

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is one of the causes of tumor immune tolerance and failure of cancer immunotherapy. Here, we found that bladder cancer (BCa)-derived exosomal circRNA_0013936 could enhance the immunosuppressive activity of PMN-MDSCs by regulating the expression of fatty acid transporter protein 2 (FATP2) and receptor-interacting protein kinase 3 (RIPK3). However, the underlying mechanism remains largely unknown.

METHODS

BCa-derived exosomes was isolated and used for a series of experiments. RNA sequencing was used to identify the differentially expressed circRNAs. Western blotting, immunohistochemistry, immunofluorescence, qRT-PCR, ELISA and Flow cytometry were performed to reveal the potential mechanism of circRNA_0013936 promoting the immunosuppressive activity of PMN-MDSC.

RESULTS

CircRNA_0013936 enriched in BCa-derived exosomes could promote the expression of FATP2 and inhibit the expression of RIPK3 in PMN-MDSCs. Mechanistically, circRNA_0013936 promoted the expression of FATP2 and inhibited the expression of RIPK3 expression via sponging miR-320a and miR-301b, which directly targeted JAK2 and CREB1 respectively. Ultimately, circRNA_0013936 significantly inhibited the functions of CD8+ T cells by up-regulating FATP2 through the circRNA_0013936/miR-320a/JAK2 pathway, and down-regulating RIPK3 through the circRNA_0013936/miR-301b/CREB1 pathway in PMN-MDSCs.

CONCLUSIONS

BCa-derived exosomal circRNA_0013936 promotes suppressive immunity by up-regulating FATP2 through the circRNA_0013936/miR-320a/JAK2 pathway and down-regulating RIPK3 through the circRNA_0013936/miR-301b-3p/CREB1 pathway in PMN-MDSCs. These findings help to find new targets for clinical treatment of human bladder cancer.

circNFIB decreases synthesis of arachidonic acid and inhibits breast tumor growth and metastasis

We identified circNFIB (hsa_circ_0086376) as a down-regulated circRNA in breast cancer but its effect is unclear. We aimed to explore the roles of circNFIB in breast cancer. The expression levels of circNFIB in breast cancer tissues and cells were detected. Both in vitro and in vivo experiments were used to assess the effects and mechanisms of circNFIB. circNFIB was down-regulated in 29 breast cancer tissues compared to adjacent normal tissues. circNFIB is a highly conserved circRNA and mainly located in cytoplasm of breast cancer cells. In vitro experiments showed that overexpression of circNFIB inhibited proliferation and invasion of breast cancer cells, whereas knockdown of circNFIB induced proliferation and invasion. Animal experiments indicated that circNFIB inhibited tumor growth and metastasis in vivo. Bioinformatics analysis showed that circNFIB contained an open reading frame (ORF) spanning its spliced junction, an internal ribosome entry site (IRES) and a N6-methyladenosine (m6A) site, suggesting circNFIB had the potential to encode a 56 amino acid (aa) protein, which was then confirmed by experiments. Metabonomics analysis results indicated that circNFIB may inhibit synthesis of arachidonic acid (AA) by regulating phospholipase. EIF4A3 and U2AF65 may regulate circNFIB expression by binding to the flanking sequence of circNFIB. In conclusion, circNFIB is a down-regulated circRNA in breast cancer tissues and encodes a 56 aa protein. circNFIB down-regulates AA in breast cancer cells, thus decreasing AA metabolites. Based on reported evidences of AA metabolites on cancer, we speculated that circNFIB may inhibit breast tumor growth and metastasis partly by inhibiting AA.

Exosome‑delivered miR‑486‑3p inhibits the progression of osteosarcoma via sponging CircKEAP1/MARCH1 axis components

Accumulating evidence shows that the disruption of competing endogenous RNA (ceRNA) networks plays a significant role in osteosarcoma (OS) initiation and progression. However, the specific roles and functions of the ceRNAs in OS remain unclear. First, differentially expressed microRNAs (DEMs) were identified by mining the E-MTAB-1136 and GSE28423 datasets. MiRWalk website was used to predict the target gene of miRNA. OS-associated circular RNA (circRNA) expression profiles were downloaded from the published microarray databases. Gene expression levels were assessed through reverse transcription-quantitative PCR and western blotting. The biological effects of circKEAP1, microRNA (miR)-486-3p and membrane-associated RINGCH finger protein 1 (MARCH1) in OS cells were investigated using Cell Counting Kit-8, Transwell, colony formation and wound healing assays. miR-486-3p was aberrantly downregulated in OS tissues and cell lines and was packed with exosomes. miR-486-3p overexpression was shown to inhibit OS cell progression and promoted cell cycle arrest in vitro. In addition, MARCH1 was identified as a direct downstream molecule of miR-486-3p in OS cells. circKEAP1 was found to be upregulated in OS tissues and cells. circKEAP1 was found to have binding sites with miR-486-3p. Mechanistically, circKEAP1 positively regulated MARCH1 expression by sponging miR-486-3p. Exosomal miR-486-3p inhibited the progression of OS by sponging the circKEAP1/MARCH1 axis. These findings may provide a promising treatment approach for OS.

Circular RNA DLGAP4 alleviates sevoflurane-induced neurotoxicity by regulating miR-9-5p/Sirt1/BDNF pathway

BACKGROUND

Sevoflurane is a widely used anesthetic in infants. However, long and repeated exposure to this drug can cause developmental neurotoxicity. This study aimed to investigate the role and mechanism of circular RNA DLGAP4 (circDLGAP4) in sevoflurane-induced neurotoxicity.

METHODS

Neonatal mice and mouse hippocampal neuronal cell line HT22 were used to construct sevoflurane-induced nerve injury models. The role of circDLGAP4 in sevoflurane-induced neurotoxicity was evaluated by gain-and/or loss-of-function methods. Pathological alterations in hippocampus were analyzed by hematoxylin-eosin and Tunel staining. Cell injury was assessed by cell viability and apoptosis, which was detected by CCK-8 and flow cytometry. The expression of circDLGAP4 and miR-9-5p was determined by real-time PCR. Sirt1 and BDNF levels were measured by Western blot. Productions of TNF-α and IL-6 were examined by ELISA. Dual-luciferase reporter assay and/or RNA pull-down assay were used to confirm the direct binding among circDLGAP4, miR-9-5p, and Sirt1. Rescue experiments were used to further verify the mechanism of circDLGAP4.

RESULTS

CircDLGAP4 expression was decreased by sevoflurane both in vivo and in vitro. Overexpression of circDLGAP4 elevated cell viability, reduced apoptosis and levels of TNF-α and IL-6, while circDLGAP4 knockdown showed the opposite effects in sevoflurane-induced HT22 cells. Mechanically, circDLGAP4 functioned via directly binding to and regulating miR-9-5p, followed by targeting the Sirt1/BDNF pathway. Additionally, circDLGAP4 upregulation relieved sevoflurane-induced nerve injury, reduced levels of TNF-α, IL-6 and miR-9-5p, but increased the expression of Sirt1 and BDNF in hippocampus.

CONCLUSIONS

Our studies found that circDLGAP4 relieved sevoflurane-induced neurotoxicity by sponging miR-9-5p to regulate Sirt1/BDNF pathway.

Hsa_circ_0136666 mediates the antitumor effect of curcumin in colorectal carcinoma by regulating CXCL1 via miR-1301-3p

BACKGROUND

This study investigate the anti-tumor effect of curcumin and whether its mediated by hsa_circ_0136666 through miR-1301-3p/CXCL1 in colorectal carcinoma (CRC). Through multiple experiments, we have drawn the conclusion that curcumin inhibited CRC development through the hsa_circ_0136666/miR-1301-3p/CXCL1 axis, hinting at a novel treatment option for curcumin to prevent CRC development.

AIM

To determine whether hsa_circ_0136666 involvement in curcumin-triggered CRC progression was mediated by sponging miR-1301-3p.

METHODS

Cell counting kit-8, colony-forming cell, 5-ethynyl-2'-deoxyuridine, and flow cytometry assays were carried out to determine cell proliferation, apoptosis, and cell cycle progression. Real-time quantitative polymerase chain reaction quantified hsa_circ_0136666, miR-1301-3p, and chemokine (C-X-C motif) ligand 1 (CXCL1), and western blot analysis determined CXCL1, B-cell lymphoma-2 (Bcl-2), and Bcl-2 related X protein (Bax) protein levels. CircBank or starbase software was first used for the prediction of miR-1301-3p binding with hsa_circ_0136666 and CXCL1, followed by RNA pull-down, RNA immunoprecipitation, and dual-luciferase reporter assay validation. In vivo experiments were implemented in a murine xenograft model.

RESULTS

Curcumin blocked CRC cell proliferation but boosted apoptosis. Moreover, elevated hsa_circ_0136666 Levels were observed in CRC cells, which were reduced by curcumin. In vitro, hsa_circ_0136666 overexpression abolished the antitumor activity of CRC cells. Mechanical analysis revealed the ability of hsa_circ_0136666 to sponge miR-1301-3p to modulate CXCL1 levels.

CONCLUSION

Curcumin inhibited CRC development through the hsa_circ_0136666/miR-1301-3p/CXCL1 axis, hinting at a novel treatment option for curcumin to prevent CRC development.

Circ_ZNF778_006 promoted ESCC progression by upregulating HIF-1α expression via sponging miR-18b-5p

In multiple malignant tumors, circular RNAs (circRNAs) are believed to play a crucial role. Our prior results demonstrated that circ_ZNF778_006 was significantly increased in esophageal squamous cell carcinoma (ESCC) tissues, but the roles of circ_ZNF778_006 in ESCC is still not clear. The expression of circ_ZNF778_006 was compared in different pathological grades of ESCC. And the expression levels of circ_ZNF778_006, miR-18b-5p, HIF-1α were analyzed by qRT-PCR and Western blot, respectively. Plasmid transfection techniques were applied to prepare ESCC cells with silenced or overexpressed genes (CircZNF778_006, miR-18b-5p). The CCK8 kit was used to determine cell proliferation, and the Transwell assay was used to measure the migration and invasion. The effects of circ_ZNF778_006 on tumor growth was investigated in vivo. Furthermore, luciferase reporter gene assay and RNA-binding protein immunoprecipitation (RIP) were performed to verify the targeting relationship between miR-18b-5p and circZNF778_006, miR-18b-5p and HIF-1α. The expression of circ_ZNF778_006 was positively correlated with pathological grade in ESCC. Circ_ZNF778_006 significantly inhibited sensitivity to 5-fluorouracil & cisplatin. It could promote the proliferation, invasion, migration in ESCC cells and accelerated tumor growth in vivo. Furthermore, circ_ZNF778_006 could upregulate the expression of HIF-1α via sponing miR-18b-5p. Circ_ZNF778_006 promoted ESCC progression by upregulating HIF-1α expression via sponging miR-18b-5p.

Hsa_circ_0052611 and mir-767-5p guide the warburg effect, migration, and invasion of BRCA cells through modulating SCAI

Noncoding RNAs are key regulators in the Warburg Effect, an emerging hallmark of cancer. We intended to investigate the role and mechanism of circular RNA hsa_circ_0052611 (circ_0052611) and microRNA (miR)-767-5p in breast cancer (BRCA) hallmarks, especially the Warburg Effect. Expression of circ_0052611 and SCAI was downregulated, and miR-767-5p was upregulated in human BRCA tissues and cells; moreover, circ_0052611 acted as a miR-767-5p sponge to modulate the expression of miR-767-5p-targeted SCAI. Functionally, re-expressing circ_0052611 suppressed migration, invasion, glucose uptake, lactate production, and extracellular acidification rate (ECAR) in BRCA cells, and promoted apoptotic rate. These effects were accompanied by decreased Vimentin, N-cadherin, Bcl-2, and LDHA, and increased E-cadherin and Bax. Consistently, exhausting miR-767-5p exerted similar effects in BRCA cells. High miR-767-5p could counteract the role of circ_0052611 overexpression, and low SCAI likewise blocked the role of miR-767-5p deletion. In vivo, upregulating circ_0052611 delayed tumor growth of BRCA cells by altering miR-767-5p and SCAI expression. circ_0052611/miR-767-5p/SCAI axis might boycott the malignancy of BRCA cells.

EXOSOMAL CIRCVMA21 DERIVED FROM ADIPOSE-DERIVED STEM CELLS ALLEVIATES SEPSIS-INDUCED ACUTE KIDNEY INJURY BY TARGETING MIR-16-5P

ABSTRACT

Background: Exosome from adipose-derived stem cells (ADSCs-Exo) has been shown to inhibit the progression of human diseases, including sepsis-related acute kidney injury (AKI). CircVMA21 is considered to be an important regulator for sepsis-related AKI. However, whether ADSCs-Exo affected sepsis-induced AKI by delivering circVMA21 is not clear. Methods: Adipose-derived stem cells were identified by alizarin red staining, oil red O staining, and flow cytometry. Exosome from adipose-derived stem cells was authenticated by transmission electron microscopy, nanoparticle tracking analysis, western blot analysis, and immunofluorescence assay. Cell apoptosis was assessed by flow cytometry, and inflammation cytokine levels were determined by ELISA. Lactate production was assessed using Lactate Acid Content Assay Kit. The expression levels of aerobic glycolysis-related markers, circVMA21 and miR-16-5p, was evaluated by quantitative real time-polymerase chain reaction. Dual-luciferase reporter assay and RIP assay were employed to detect RNA interaction. Animal experiments were used to evaluate the role of ADSCs-Exo on renal function and cell injury in LPS-induced AKI mice model. Results: Exosome from adipose-derived stem cells inhibited LPS-induced HK-2 cell apoptosis, inflammation, and aerobic glycolysis. Knockdown of exosomal circVMA21 derived from ADSCs enhanced HK-2 cell injury induced by LPS. In terms of mechanism, circVMA21 could serve as sponge for miR-16-5p. Besides, miR-16-5p inhibitor reversed the promotion effect of Exo-sh-circVMA21 on LPS-induced cell injury. In addition, ADSCs-Exo protected LPS-induced AKI in mice by increasing circVMA21 expression and decreasing miR-16-5p expression. Conclusion: Exosomal circVMA21 derived by ADSCs relieved LPS-induced AKI through targeting miR-16-5p, which provided a potential molecular target for treating sepsis-related AKI.

Hsa_circ_0005273 acts as a sponge of miR-509-3p to promote the malignant behaviors of breast cancer by regulating HMMR expression

BACKGROUND

Breast cancer (BC) is a common malignant tumor that threatens the health of women worldwide. Hsa_circ_0005273 has been identified as a carcinogenic factor in some solid tumors, including BC. However, the molecular mechanism of circ_0005273 in BC is poorly defined.

METHODS

The expression of circ_0005273, miR-509-3p, and hyaluronan-mediated motility receptor (HMMR) mRNA in BC was detected by quantitative real-time polymerase chain reaction. Cell proliferation, migration, invasion, and apoptosis were detected by 5-ethynyl-2'-deoxyuridine, transwell, and flow cytometry assays. The glycolysis level was detected via specific kits. Western blot was used to detect protein expression. Binding between miR-509-3p and circ_0005273 or HMMR was also verified by dual-luciferase reporter, RNA pull-down, and RNA immunoprecipitation assays. Xenograft tumor model was used to detect tumor changes in mice, and immunohistochemistry assay was employed to detect Ki-67 abundance.

RESULTS

Circ_0005273 was increased in BC tissues and cells. Circ_0005273 knockdown might inhibit BC cell proliferation, migration, invasion, glutamine metabolism, and induce apoptosis. Circ_0005273 was a miR-509-3p, and the repression role of circ_0005273 absence on BC cell development was weakened by miR-509-3p inhibitor or HMMR overexpression. Circ_0005273 up-regulated the expression of HMMR by sponging miR-509-3p. Additionally, circ_0005273 silencing might hinder tumor growth in vivo.

CONCLUSION

Circ_0005273 knockdown might repress BC cell malignant behaviors by regulating the miR-509-3p/HMMR axis, which might provide a potential therapeutic target for BC.

Circ_CSPP1 Regulates the Development of Non-small Cell Lung Cancer via the miR-486-3p/BRD9 Axis

In this study, we explored the role of circ_CSPP1 in non-small cell lung cancer (NSCLC) using NSCLC cell lines (A549 and H1299) and human bronchial epithelioid cells (16HBE). The differential expression of circ_CSPP1, miR-486-3p and BRD9 in NSCLC by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot in A549 cells, H1299 cells, 16HBE cells, NSCLC tissues and healthy lung tissues. Dual-luciferase reporter assay was conducted to verify the interaction between circ_CSPP1 and miR-486-3p or miR-486-3p and BRD9. The effect of circ_CSPP1/miR-486-3p/BRD9 axis on NSCLC cell proliferation was evaluated using cell counting kit-8 assay, colony formation assay, and 5-ethynyl-2'-deoxyuridine assay. Additionally, transwell assays were performed to evaluate the effect of circ_CSPP1/miR-486-3p/BRD9 axis on A549 and H1299 cell migration and invasion. The effect of circ_CSPP1 on tumor tumorigenesis of A549 cells in vivo was determined by xenograft tumor model and immunohistochemistry assay. Circ_CSPP1 and BRD9 expression were upregulated, while miR-486-3p expression was downregulated in tumor tissues of NSCCL patients and A549 and H1299 cells. Circ_CSPP1 specifically bound miR-486-3p, and miR-486-3p could target BRD9. Circ_CSPP1 upregulation promoted proliferation, invasion and migration of NSCLC cells, circ_CSPP1 knockdown or miR-486-3p upregulation had the opposite effects. Circ_CSPP1 knockdown-induced effects were reverted by miR-486-3p inhibition. Similarly, the effects of miR-486-3p upregulation on NSCLC cell proliferation, invasion and migration were reversed by BRD9 overexpression. In addition, circ_CSPP1 silencing inhibited tumor growth in nude mice. Circ_CSPP1 promoted A549 and H1299 cell malignancy by competitively inhibiting BRD9 and binding to miR-486-3p.

Circ-TRIO promotes TNBC progression by regulating the miR-432-5p/CCDC58 axis

Numerous studies have shown that circRNAs are aberrantly expressed in various cancers and play a significant role in tumor progression. However, the molecular mechanisms of circRNAs in triple-negative breast cancer (TNBC) remain ambiguous. By intersecting throughput data and qRT-PCR results from tissues and cell lines, circ-TRIO was identified as a potential oncogenic regulator of TNBC. Moreover, circ-TRIO expression was detected in TNBC tissues and was correlated with the recurrence and prognosis of TNBC patients. The circular characteristics of circ-TRIO were verified by RNase R and CHX assays. Functionally, the knockdown of circ-TRIO inhibited the proliferation, migration and invasion of TNBC cells, while the overexpression of circ-TRIO resulted in the opposite impacts. Mechanistically, a dual luciferase reporter assay and RNA immunoprecipitation were performed and indicated that circ-TRIO could combine with miR-432-5p to regulate the expression of coiled-coil domain containing 58 (CCDC58). In summary, our study illustrates that circ-TRIO plays an important role in the progression of TNBC by regulating the miR-432-5p/CCDC58 axis, which could broaden our insight into the underlying mechanisms and provide a novel prognostic marker of TNBC in the clinic.

CircRNA 0009043 suppresses non-small-cell lung cancer development via targeting the miR-148a-3p/DNAJB4 axis

Background

Circular RNAs (circRNAs) are important regulators of the development and progression of non-small-cell lung cancer (NSCLC) and many other malignancies. The functional importance of circ_0009043 in NSCLC, however, has yet to be established.

Methods

The expression of circ_0009043, miR-148a-3p, and DnaJ heat shock protein family (Hsp40) member B4 (DNAJB4) in NSCLC cells was assessed via qPCR. The proliferative activity of these cells was examined through EdU uptake and CCK-8 assays, while flow cytometry approaches were used to examine apoptotic cell death rates. Protein expression was measured through Western immunoblotting. Interactions between miR-148a-3p and circ_0009043 or DNAJB4 were detected through RNA immunoprecipitation (RIP) and dual-luciferase reporter assays. The in vivo importance of circ_0009043 as a regulator of oncogenic activity was assessed using murine xenograft models.

Results

Both NSCLC cells and tissue samples were found to exhibit circ_0009043 upregulation, and lower circ_0009043 expression levels were found to be related to poorer NSCLC patient overall survival. Knocking down circ_0009043 resulted in the enhancement of NSCLC cell proliferative activity and the suppression of apoptotic tumor cell death in vitro, while also driving more rapid in vivo tumorigenesis. Mechanistically, circ_0009043 was found to function as a molecular sponge that sequestered miR-148a-3p, which was in turn able to directly suppress DNAJB4 expression. When miR-148a-3p was overexpressed, this reversed the impact of knocking down circ_0009043 on the apoptotic death and proliferation of NSCLC cells. Conversely, miR-148a-3p inhibition resulted in the suppression of NSCLC cell apoptosis and the enhancement of tumor cell growth, while the downregulation of DNAJB4 reversed these changes.

Conclusion

Circ_0009043 acts as a tumor suppressor in NSCLC cells, promoting DNAJB4 upregulation via the sequestration of miR-148a-3p.

Screening of Human Circular RNAs as Biomarkers for Early Onset Detection of Alzheimer’s Disease

Circular RNAs (circRNAs) are a distinctive type of endogenous non-coding RNAs, and their regulatory roles in neurological disorders have received immense attention. CircRNAs significantly contribute to the regulation of gene expression and progression of neurodegenerative disorders including Alzheimer’s disease (AD). The current study aimed to identify circRNAs as prognostic and potential biomarkers in AD. The differentially expressed circRNAs among subjective cognitive decline, amnestic mild cognitive impairment, and age-matched normal donors were determined through Arraystar Human circRNA Array V2 analysis. The annotations of circRNAs-microRNA interactions were predicted by employing Arraystar’s homemade microRNAs (miRNA) target prediction tool. Bioinformatics analyses comprising gene ontology enrichment, KEGG pathway, and network analysis were conducted. Microarray analysis revealed the 33 upregulated and 11 downregulated differentially expressed circRNAs (FC ≥ 1.5 and p-values ≤ 0.05). The top 10 differentially expressed upregulated and downregulated circRNAs have been chosen for further expression validation through quantitative real-time PCR and subsequently, hsa-circRNA_001481 and hsa_circRNA_000479 were confirmed experimentally. Bioinformatics analyses determined the circRNA-miRNA-mRNA interactions and microRNA response elements to inhibit the expression of miRNAs and mRNA targets. Gene ontology enrichment and KEGG pathways analysis revealed the functional clustering of target mRNAs suggesting the functional verification of these two promising circRNAs. It is concluded that human circRNA_001481 and circRNA_000479 could be utilized as potential biomarkers for the early onset detection of AD and the development of effective therapeutics.

Circular RNAs in hepatocellular carcinoma: Recent advances

Circular RNAs (circRNAs) have covalently closed loop structures at both ends, exhibiting characteristics dissimilar to those of linear RNAs. Emerging evidence suggests that aberrantly expressed circRNAs play crucial roles in hepatocellular carcinoma (HCC) by affecting the proliferation, apoptosis and invasive capacity of HCC cells. Certain circRNAs may be used as biomarkers to diagnose and predict the prognosis of HCC. Therefore, circRNAs are expected to become novel biomarkers and therapeutic targets for HCC. Herein, we briefly review the characteristics and biological functions of circRNAs, focusing on their roles in HCC to provide new insights for the early diagnosis and targeted therapy of HCC.

Circ_0000442 functions as a tumor repressor in breast cancer by impacting miR-1229-3p and upregulating ZBTB1

A variety of circular RNAs (circRNAs) have tumor-regulatory roles in breast cancer (BC). Circ_0000442 was reported to inhibit the progression of BC, and this study was designed to explore the novel functional mechanism of circ_0000442 in BC. The expression analysis for circ_0000442, microRNA-1229-3p (miR-1229-3p) and zinc finger and BTB domain containing 1 (ZBTB1) was performed using the quantitative real-time polymerase chain reaction (qRT-PCR). Dual-luciferase reporter assay was used to affirm the target interaction. Cell proliferation was examined using Edu assay and colony formation assay. Cell migration and invasion were assessed by transwell assay. Flow cytometry was applied for the detection of cell apoptosis. Glycolysis was analyzed using the detection kits to measure the glucose consumption and lactate production. The protein expression levels were determined by western blot. The role of circ_0000442 in BC in vivo was explored using tumor xenograft assay. Circ_0000442 expression was downregulated and miR-1229-3p expression was upregulated in BC tissues and cells. Circ_0000442 directly interacted with miR-1229-3p. Circ_0000442 repressed proliferation, migration, invasion and glycolysis but promoted apoptosis in BC cells. The anti-tumor role of circ_0000442 was attributed to the sponge effect on miR-1229-3p. ZBTB1 was a downstream target for miR-1229-3p. Downregulation of miR-1229-3p blocked the malignant behaviors in BC cells by elevating the expression of ZBTB1. Circ_0000442 regulated the ZBTB1 level by targeting miR-1229-3p, and it inhibited tumor growth of BC in vivo by mediating the miR-1229-3p/ZBTB1 axis. All evidence unraveled that circ_0000442 impeded the progression of BC by sponging miR-1229-3p to evoke the ZBTB1 expression upregulation.

Circular RNA Expression Profiles and Bioinformatic Analysis in Mouse Models of Obstructive Sleep Apnea-Induced Cardiac Injury: Novel Insights Into Pathogenesis

Circular RNAs (circRNAs) participate in the development of various kinds of diseases. However, the function and roles of circRNAs in obstructive sleep apnea (OSA)-induced cardiovascular disease remain poorly understood. Therefore, we sought to explore the circRNA expression profiles and predict their functions in OSA-induced cardiac injury with the use of bioinformatics analysis. The model of OSA was established in mouse treated by chronic intermittent hypoxia (CIH) exposure. Then, we screened the circRNA profile using circRNA microarray. By comparing circRNA expression in three matched pairs of CIH-treated cardiac tissues and controls, differentially expressed circRNAs were identified in the CIH groups. Comparison of the selected circRNAs expression levels was performed between qRT-PCR and microarray. Meanwhile, we employed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses to predict the functions of these selected circRNAs. Finally, we constructed a circRNA-miRNA-mRNA network based on the target prediction. It was found that a total of 124 circRNAs were differentially expressed in CIH-treated cardiac tissues (p ≤ 0.05, fold-change ≥ 1.5). Among them, 23 circRNAs were significantly down-regulated, and the other 101 were up-regulated. Then, ten circRNAs were randomly selected to validate the reliability of the microarray results by using qRT-PCR. Next, we conducted the GO and KEGG pathway analysis to explore the parental genes functions of differentially expressed circRNA. Finally, two significantly differentially expressed circRNAs (mmu_circRNA_014309 and mmu_circRNA_21856) were further selected to create a circRNA-miRNA-mRNA regulation network. Our study did first reveal that the differentially expressed circRNAs played a vital role in the pathogenesis of OSA-induced cardiac damage. Thus, our findings bring us closer to unraveling the pathophysiologic mechanisms and eliciting novel therapeutic targets for the treatment of OSA-associated cardiovascular diseases.

Clinicopathologic and prognostic roles of circular RNA plasmacytoma variant translocation 1 in various cancers

OBJECTIVE

To explore the clinicopathologic and prognostic significance of circular RNA plasmacytoma variant translocation 1 (circPVT1) in various cancers.

METHODS

Several databases were searched for eligible studies published before March 01, 2021. The pooled odds ratios (ORs) with 95% confidence interval (95% CI) were calculated to assess the association between circPVT1 expression and prognostic outcomes of tumor including age, gender, clinical stage, tumor size, metastasis and overall survival. Begg's funnel plots and Egger's test were used to evaluate the publication bias. The robustness of our results was assessed using sensitivity analysis.

RESULTS

Ten studies comprising a total of 878 patients with cancer were included in this meta-analysis. The results showed that the high expression of circPVT1 was significantly related to clinical stage (OR=3.44, 95% CI: 2.40-4.94, P<0.05), tumor size (OR=2.29, 95% CI: 1.38-3.79, P<0.05), metastasis (OR=2.97, 95% CI: 2.06-4.28, p<0.05) and overall survival of cancer (OR=3.30, 95% CI: 2.26-4.84, p<0.05), but not associated with age and gender of patients with tumor. No publication bias was found.

CONCLUSIONS

High expression of circPVT1 may predict an advanced clinical stage and poor prognosis of tumor, suggesting that circPVT1 may serve as a potential prognostic marker in cancers.

Time to infer miRNA sponge modules

Inferring competing endogenous RNA (ceRNA) or microRNA (miRNA) sponge modules is a challenging and meaningful task for revealing ceRNA regulation mechanism at the module level. Modules in this context refer to groups of miRNA sponges which have mutual competitions and act as functional units for achieving biological processes. The recent development of computational methods based on heterogeneous data provides a novel way to discern the competitive effects of miRNA sponges on human complex diseases. This article aims to provide a comprehensive perspective of miRNA sponge module discovery methods. We first review the publicly available databases of cancer-related miRNA sponges, as the miRNA sponges involved in human cancers contribute to the discovery of cancer-associated modules. Then we review the existing computational methods for inferring miRNA sponge modules. Furthermore, we conduct an assessment on the performance of the module discovery methods with the pan-cancer dataset, and the comparison study indicates that it is useful to infer biologically meaningful miRNA sponge modules by directly mapping heterogeneous data to the competitive modules. Finally, we discuss the future directions and associated challenges in developing in silico methods to infer miRNA sponge modules. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Small Molecule-RNA Interactions Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

Circ_0001667 knockdown blocks cancer progression and attenuates adriamycin resistance by depleting NCOA3 via releasing miR-4458 in breast cancer

Accumulating evidence suggests that developmental chemoresistance in cancers is closely associated with the dysregulation of circular RNA transcriptions. The objective of this study is to disclose the role of circ_0001667 and provide a potential functional mechanism in breast cancer. Quantitative real-time PCR was applied for the analysis of circ_0001667, microRNA-4458 (miR-4458) and nuclear receptor coactivator 3 (NCOA3) expression. In adriamycin (ADM)-resistant cell lines, we investigated cell proliferation using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay and colony formation assay. Cell migration and cell invasion were determined by transwell assay. The protein levels of multi-drug resistance-1, matrix metalloproteinases-9, cleaved-caspase3, cleaved-caspase9 and NCOA3 were detected by western blot. ADM resistance was ascertained by IC50 value using MTT assay. Cell apoptosis was checked by flow cytometry assay. The putative relationship between miR-4458 and circ_0001667 and NCOA3 was validated by pull-down assay, dual-luciferase reporter assay or RNA Immunoprecipitation assay. Circ_0001667 knockdown inhibited MCF-7/ADM and MDA-MB-231/ADM cell proliferation, migration, invasion and ADM resistance. MiR-4458 was a target of circ_0001667, and its expression was decreased in ADM-resistant tumor tissues and cells. MiR-4458 inhibition reversed the effects of circ_0001667 knockdown. In depth, NCOA3 was a target of circ_0001667, and circ_0001667 knockdown weakened NCOA3 expression by releasing miR-4458. MCF-7/ADM and MDA-MB-231/ADM cell proliferation, migration, invasion, and ADM resistance inhibited by miR-4458 restoration were recovered by NCOA3 overexpression. Circ_0001667 knockdown also repressed tumor growth and ADM resistance in vivo. Circ_0001667 knockdown blocks cancer progression and attenuates ADM resistance by depleting NCOA3 via releasing miR-4458 in breast cancer.

CircWAC induces chemotherapeutic resistance in triple-negative breast cancer by targeting miR-142, upregulating WWP1 and activating the PI3K/AKT pathway

BACKGROUND

Chemotherapeutic resistance is the main cause of clinical treatment failure and poor prognosis in triple-negative breast cancer (TNBC). There is no research on chemotherapeutic resistance in TNBC from the perspective of circular RNAs (circRNAs).

METHODS

TNBC-related circRNAs were identified based on the GSE101124 dataset. Quantitative reverse transcription PCR was used to detect the expression level of circWAC in TNBC cells and tissues. Then, in vitro and in vivo functional experiments were performed to evaluate the effects of circWAC in TNBC.

RESULTS

CircWAC was highly expressed in TNBC and was associated with worse TNBC patient prognosis. Subsequently, it was verified that downregulation of circWAC can increase the sensitivity of TNBC cells to paclitaxel (PTX) in vitro and in vivo. The expression of miR-142 was negatively correlated with circWAC in TNBC. The interaction between circWAC and miR-142 in TNBC cells was confirmed by RNA immunoprecipitation assays, luciferase reporter assays, pulldown assays, and fluorescence in situ hybridization. Mechanistically, circWAC acted as a miR-142 sponge to relieve the repressive effect of miR-142 on its target WWP1. In addition, the overall survival of TNBC patients with high expression of miR-142 was significantly better than that of patients with low expression of miR-142, and these results were verified in public databases. MiR-142 regulated the expression of WWP1 and the activity of the PI3K/AKT pathway. It was confirmed that WWP1 is highly expressed in TNBC and that the prognosis of patients with high WWP1 expression is poor.

CONCLUSIONS

CircWAC/miR-142/WWP1 form a competing endogenous RNA (ceRNA) network to regulate PI3K/AKT signaling activity in TNBC cells and affect the chemosensitivity of cells.