Circular RNA and its mechanisms in disease: From the bench to the clinic

Insights into the Transcriptome of Human Cytomegalovirus: A Comprehensive Review

Human cytomegalovirus (HCMV) is a widespread pathogen that poses significant risks to immunocompromised individuals. Its genome spans over 230 kbp and potentially encodes over 200 open-reading frames. The HCMV transcriptome consists of various types of RNAs, including messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs), with emerging insights into their biological functions. HCMV mRNAs are involved in crucial viral processes, such as viral replication, transcription, and translation regulation, as well as immune modulation and other effects on host cells. Additionally, four lncRNAs (RNA1.2, RNA2.7, RNA4.9, and RNA5.0) have been identified in HCMV, which play important roles in lytic replication like bypassing acute antiviral responses, promoting cell movement and viral spread, and maintaining HCMV latency. CircRNAs have gained attention for their important and diverse biological functions, including association with different diseases, acting as microRNA sponges, regulating parental gene expression, and serving as translation templates. Remarkably, HCMV encodes miRNAs which play critical roles in silencing human genes and other functions. This review gives an overview of human cytomegalovirus and current research on the HCMV transcriptome during lytic and latent infection.

Network approach in liquidomics landscape

Tissue-based biopsy is the present main tool to explore the molecular landscape of cancer, but it also has many limits to be frequently executed, being too invasive with the risk of side effects. These limits and the ability of cancer to constantly evolve its genomic profile, have recently led to the need of a less invasive and more accurate alternative, such as liquid biopsy. By searching Circulating Tumor Cells and residues of their nucleic acids or other tumor products in body fluids, especially in blood, but also in urine, stools and saliva, liquid biopsy is becoming the future of clinical oncology. Despite the current lack of a standardization for its workflows, that makes it hard to be reproduced, liquid biopsy has already obtained promising results for cancer screening, diagnosis, prognosis, and risk of recurrence.Through a more accessible molecular profiling of tumors, it could become easier to identify biomarkers predictive of response to treatment, such as EGFR mutations in non-small cell lung cancer and KRAS mutations in colorectal cancer, or Microsatellite Instability and Mismatch Repair as predictive markers of pembrolizumab response.By monitoring circulating tumor DNA in longitudinal repeated sampling of blood we could also predict Minimal Residual Disease and the risk of recurrence in already radically resected patients.In this review we will discuss about the current knowledge of limitations and strengths of the different forms of liquid biopsies for its inclusion in normal cancer management, with a brief nod to their newest biomarkers and its future implications.

Circ_0001714 knockdown alleviates lipopolysaccharide-induced apoptosis and inflammation in renal tubular epithelial cells via miR-129-5p/TRAF6 axis in septic acute kidney injury

BACKGROUND

Circular RNAs (circRNAs) have been shown to play roles in regulating sepsis. Sepsis is a major cause of acute kidney injury (AKI). Herein, we aimed to investigate the role and mechanism of circ_0001714 in the progression of sepsis-induced AKI.

METHODS

Human HK-2 cells were exposed to lipopolysaccharide (LPS) for functional experiments. Quantitative real-time polymerase chain reaction and western blotting were used for expression analysis. Functional experiments were performed by using MTT assay, 5-ethynyl-2'-deoxyuridine assay, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). The binding between miR-129-5p and circ_0001714 or TRAF6 (TNF receptor associated factor 6) was validated using dual-luciferase reporter assay.

RESULTS

Circ_0001714 expression was higher in sepsis-AKI patients. HK-2 cells were exposed to LPS to imitate the injury of renal tubular epithelial cells during sepsis-AKI. LPS dose-dependently up-regulated circ_0001714, moreover, circ_0001714 silencing reversed LPS-evoked apoptosis and inflammation in HK-2 cells. Mechanistically, circ_0001714 sequestered miR-129-5p to up-regulate TRAF6 expression, implying the circ_0001714/miR-129-5p/TRAF6 feedback loop. MiR-129-5p was decreased, while TRAF6 was increased in sepsis-AKI patients and LPS-stimulated HK-2 cells. MiR-129-5p re-expression or TRAF6 silencing protected against LPS-induced HK-2 cell apoptosis and inflammation. Additionally, a series of rescue experiments showed that miR-129-5p inhibition reversed the inhibitory action of circ_0001714 knockdown on LPS-induced HK-2 cell injury. Furthermore, TRAF6 overexpression also attenuated the protective effects of miR-129-5p on HK-2 cells under LPS treatment.

CONCLUSION

Circ_0001714 silencing might alleviate LPS-induced apoptosis and inflammation via targeting miR-129-5p/TRAF6 axis in HK-2 cells.

CIRCTDRD9 CONTRIBUTES TO SEPSIS-INDUCED ACUTE LUNG INJURY BY ENHANCING THE EXPRESSION OF RAB10 VIA DIRECTLY BINDING TO MIR-223-3P

ABSTRACT

Background: The dysregulation of circular RNAs (circRNAs) is involved in various human diseases, including sepsis-induced acute lung injury (ALI). We aimed to investigate the role of circTDRD9 in the development of sepsis-induced ALI. Methods: Cell models of sepsis-induced ALI were established by treating A549 cells with LPS. The expression of circTDRD9, miR-223-3p, and RAB10 mRNA was measured by quantitative real-time PCR (qPCR). The levels of inflammatory factors were measured by ELISA. Oxidative stress-related indicators were monitored by using commercial detection kits. The expression of fibrosis-related proteins was detected by Western blot assay. Cell proliferation was assessed by EdU assay. The predicted binding relationship between miR-223-3p and circTDRD9 or RAB10 was verified by dual-luciferase reporter assay, RIP assay or pull-down assay. Results: CircTDRD9 was highly expressed in LPS-treated A549 cells. CircTDRD9 downregulation prevented LPS-induced inflammation, oxidative stress, cell proliferation inhibition, and cell fibrosis in A549 cells, whereas these effects were reversed by the inhibition of miR-223-3p, a target of circTDRD9. In addition, RAB10 was verified as a target of miR-223-3p, and RAB10 overexpression recovered LPS-induced inflammation, oxidative stress, cell proliferation inhibition, and cell fibrosis in A549 cells that were ameliorated by miR-223-3p restoration. Importantly, circTDRD9 positively regulated RAB10 expression by binding to miR-223-3p. Conclusion: CircTDRD9 overexpression was closely associated with LPS-induced ALI. CircTDRD9 contributed to LPS-induced ALI partly by upregulating RAB10 via binding to miR-223-3p.

CircZfp609 contributes to cerebral infarction via sponging miR-145a-5p to regulate BACH1

BACKGROUND

Circular RNAs (circRNA) have been reported to be involved in the progression of cerebral infarction. The purpose of this study was to reveal the role and potential molecular mechanism of circZfp609 (mmu_circ_0001797) in cerebral infarction.

METHODS

C57BL/6J mice was used to construct middle cerebral artery occlusion (MCAO) mice model, and primary mouse astrocytes were treated with oxygen-glucose deprivation/reperfusion (OGD/R) process. The circZfp609, microRNA (miR)-145a-5p and BTB and CNC homology 1 (BACH1) expression levels were detected by quantitative real-time PCR. Cell proliferation and apoptosis were assessed by cell counting kit 8 assay, EdU assay and flow cytometry. Western blot analysis was used to measure protein levels, and ELISA assay was utilized to detect the levels of inflammation factors. Lactate dehydrogenase (LDH) level was measured by LDH Assay Kit. Dual-luciferase reporter assay, RIP assay and RNA pull-down assay were used to evaluate RNA interaction.

RESULTS

CircZfp609 was upregulated in MCAO mice and OGD/R-induced astrocytes. Knockdown of circZfp609 promoted cell proliferation, while suppressed apoptosis and inflammation in OGD/R-induced astrocytes. CircZfp609 served as a sponge for miR-145a-5p, and miR-145a-5p inhibitor reversed the regulation of circZfp609 knockdown on OGD/R-induced astrocyte injury. BACH1 was a target of miR-145a-5p, and its overexpression abolished the inhibition effect of miR-145a-5p on OGD/R-induced astrocyte injury. Besides, circZfp609 downregulation also relieved the brain injury of MCAO mice through miR-145a-5p/BACH1 axis.

CONCLUSION

Our data showed that circZfp609 might promote cerebral infarction by regulating the miR-145a-5p/BACH1 pathway.

Circular RNA mediated gene regulation in human breast cancer: A bioinformatics analysis

Circular RNAs (circRNAs) are a new acknowledged class of RNAs that has been shown to play a major role in several biological functions both in physiological and pathological conditions, operating as critical part of regulatory processes, like competing endogenous RNA (ceRNA) networks. The ceRNA hypothesis is a recently discovered molecular mechanism that adds a new key layer of post-transcriptional regulation, whereby various types of RNAs can reciprocally influence each other's expression competing for binding the same pool of microRNAs, even affecting disease development. In this study, we build a network of circRNA-miRNA-mRNA interactions in human breast cancer, called CERNOMA, that is a bipartite graph with one class of nodes corresponding to differentially expressed miRNAs (DEMs) and the other one corresponding to differentially expressed circRNAs (DEC) and mRNAs (DEGs). A link between a DEC (or DEG) and DEM is placed if it is predicted to be a target of the DEM and shows an opposite expression level trend with respect to the DEM. Within the CERNOMA, we highlighted an interesting deregulated circRNA-miRNA-mRNA triplet, including the up-regulated hsa_circRNA_102908 (BRCA1 associated RING domain 1), the down-regulated miR-410-3p, and the up-regulated ESM1, whose overexpression has been already shown to promote tumor dissemination and metastasis in breast cancer.

Circular RNA as a Novel Regulator and Promising Biomarker in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a prevalent metabolic and reproductive disorder that causes low fertility in females. Despite its detrimental effects on women's health, care for PCOS has been impeded by its undefined pathogenesis. Thus, there is an urgent need to explore novel biomarkers and therapeutic targets for the diagnosis and treatment of PCOS. Circular RNAs (circRNAs) are a class of noncoding RNAs with covalently closed cyclic structures, present in high abundance, and show development-stage specific expression patterns. Recent studies have demonstrated that circRNAs participate in PCOS progression by modulating various biological functions, including cell proliferation, apoptosis, and steroidogenesis. In addition, circRNAs are widely present in the follicular fluid of women with PCOS, indicating their potential as diagnostic biomarkers and therapeutic targets for PCOS. This review provides the current knowledge of circRNAs in PCOS, including their regulatory functions and molecular mechanisms, and explores their potential as diagnostic biomarkers and therapeutic targets.

CircDOCK7 facilitates the proliferation and adipogenic differentiation of chicken abdominal preadipocytes through the gga-miR-301b-3p/ACSL1 axis

BACKGROUND

Abdominal fat deposition depends on both the proliferation of preadipocytes and their maturation into adipocytes, which is a well-orchestrated multistep process involving many regulatory molecules. Circular RNAs (circRNAs) have emergingly been implicated in mammalian adipogenesis. However, circRNA-mediated regulation in chicken adipogenesis remains unclear. Our previous circRNA sequencing data identified a differentially expressed novel circRNA, 8:27,886,180|27,889,657, during the adipogenic differentiation of chicken abdominal preadipocytes. This study aimed to investigate the regulatory role of circDOCK7 in the proliferation and adipogenic differentiation of chicken abdominal preadipocytes, and explore its molecular mechanisms of competing endogenous RNA underlying chicken adipogenesis.

RESULTS

Our results showed that 8:27,886,180|27,889,657 is an exonic circRNA derived from the head-to-tail splicing of exons 19-22 of the dedicator of cytokinesis 7 (DOCK7) gene, abbreviated as circDOCK7. CircDOCK7 is mainly distributed in the cytoplasm of chicken abdominal preadipocytes and is stable because of its RNase R resistance and longer half-life. CircDOCK7 is significantly upregulated in the abdominal fat tissues of fat chickens compared to lean chickens, and its expression gradually increases during the proliferation and adipogenic differentiation of chicken abdominal preadipocytes. Functionally, the gain- and loss-of-function experiments showed that circDOCK7 promoted proliferation, G0/G1- to S-phase progression, and glucose uptake capacity of chicken abdominal preadipocytes, in parallel with adipogenic differentiation characterized by remarkably increased intracellular lipid droplet accumulation and triglyceride and acetyl coenzyme A content in differentiated chicken abdominal preadipocytes. Mechanistically, a pull-down assay and a dual-luciferase reporter assay confirmed that circDOCK7 interacted with gga-miR-301b-3p, which was identified as an inhibitor of chicken abdominal adipogenesis. Moreover, the ACSL1 gene was demonstrated to be a direct target of gga-miR-301b-3p. Chicken ACSL1 protein is localized in the endoplasmic reticulum and mitochondria of chicken abdominal preadipocytes and acts as an adipogenesis accelerator. Rescue experiments showed that circDOCK7 could counteract the inhibitory effects of gga-miR-301b-3p on ACSL1 mRNA abundance as well as the proliferation and adipogenic differentiation of chicken abdominal preadipocytes.

CONCLUSIONS

CircDOCK7 serves as a miRNA sponge that directly sequesters gga-miR-301b-3p away from the ACSL1 gene, thus augmenting adipogenesis in chickens. These findings may elucidate a new regulatory mechanism underlying abdominal fat deposition in chickens.

Development of a circHIPK3-based ceRNA network and identification of mRNA signature in breast cancer patients harboring BRCA mutation

Background

Exploring the regulatory network of competing endogenous RNAs (ceRNAs) as hallmarks for breast cancer development has great significance and could provide therapeutic targets. An mRNA signature predictive of prognosis and therapy response in BRCA carriers was developed according to circular RNA homeodomain-interacting protein kinase 3 (circHIPK3)-based ceRNA network.

Method

We constructed a circHIPK3-based ceRNA network based on GSE173766 dataset and identified potential mRNAs that were associated with BRCA mutation patients within this ceRNA network. A total of 11 prognostic mRNAs and a risk model were identified and developed by univariate Cox regression analysis and the LASSO regression analysis as well as stepAIC method. Genomic landscape was treated by mutect2 and fisher. Immune characteristics was analyzed by ESTIMATE, MCP-counter. TIDE analysis was conducted to predict immunotherapy. The clinical treatment outcomes of BRCA mutation patients were assessed using a nomogram. The proliferation, migration and invasion in breast cancer cell lines were examined using CCK8 assay and transwell assay.

Result

We found 241 mRNAs within the circHIPK3-based ceRNA network. An 11 mRNA-based signature was identified for prognostic model construction. High risk patients exhibited dismal prognosis, low response to immunotherapy, less immune cell infiltration and tumor mutation burden (TMB). High-risk patients were sensitive to six anti-tumor drugs, while low-risk patient were sensitive to 47 drugs. The risk score was the most effective on evaluating patients' survival. The robustness and good prediction performance were validated in The Cancer Genome Atlas (TCGA) dataset and immunotherapy datasets, respectively. In addition, circHIPK3 mRNA level was upregulated, and promoted cell viability, migration and invasion in breast cancer cell lines.

Conclusion

The current study could improve the understanding of mRNAs in relation to BRCA mutation and pave the way to develop mRNA-based therapeutic targets for breast cancer patients with BRCA mutation.

Functions of Circular RNA in Human Diseases and Illnesses

Circular RNAs (circRNAs) represent single-stranded RNA species that contain covalently closed 3' and 5' ends that provide them more stability than linear RNA, which has free ends. Emerging evidence indicates that circRNAs perform essential functions in many DNA viruses, including coronaviruses, Epstein-Barr viruses, cytomegalovirus, and Kaposi sarcoma viruses. Recent studies have confirmed that circRNAs are present in viruses, including DNA and RNA viruses, and play various important functions such as evading host immune response, disease pathogenesis, protein translation, miRNA sponges, regulating cell proliferation, and virus replication. Studies have confirmed that circRNAs can be biological signatures or pathological markers for autoimmune diseases, neurological diseases, and cancers. However, our understanding of circRNAs in DNA and RNA viruses is still limited, and functional evaluation of viral and host circRNAs is essential to completely understand their biological functions. In the present review, we describe the metabolism and cellular roles of circRNA, including its roles in various diseases and viral and cellular circRNA functions. Circular RNAs are found to interact with RNA, proteins, and DNA, and thus can modulate cellular processes, including translation, transcription, splicing, and other functions. Circular RNAs interfere with various signaling pathways and take part in vital functions in various biological, physiological, cellular, and pathophysiological processes. We also summarize recent evidence demonstrating cellular and viral circRNA's roles in DNA and RNA viruses in this growing field of research.

CIRC_0026466 KNOCKDOWN PROTECTS HUMAN BRONCHIAL EPITHELIAL CELLS FROM CIGARETTE SMOKE EXTRACT-INDUCED INJURY BY PROMOTING THE MIR-153-3P/TRAF6/NF-ΚB PATHWAY

ABSTRACT

Background: Considerable data have shown that circular RNAs (circRNAs) mediate the pathogenesis of chronic obstructive pulmonary disease (COPD). The study aims to analyze the function and mechanism of circ_0026466 in COPD. Methods: Human bronchial epithelial cells (16HBE) were treated with cigarette smoke extract (CSE) to establish a COPD cell model. Quantitative real-time polymerase chain reaction and Western blot were used to detect the expression of circ_0026466, microRNA-153-3p (miR-153-3p), TNF receptor associated factor 6 (TRAF6), cell apoptosis-related proteins, and NF-κB pathway-related proteins. Cell viability, proliferation, apoptosis, and inflammation were investigated by cell counting kit-8, EdU assay, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Oxidative stress was evaluated by lipid peroxidation malondialdehyde assay kit and superoxide dismutase activity assay kit. The interaction between miR-153-3p and circ_0026466 or TRAF6 was confirmed by dual-luciferase reporter assay and RNA pull-down assay. Results: Circ_0026466 and TRAF6 expression were significantly increased, but miR-153-3p was decreased in the blood samples of smokers with COPD and CSE-induced 16HBE cells when compared with controls. CSE treatment inhibited the viability and proliferation of 16HBE cells but induced cell apoptosis, inflammation, and oxidative stress, but these effects were attenuated after circ_0026466 knockdown. Circ_0026466 interacted with miR-153-3p and regulated CSE-caused 16HBE cell damage by targeting miR-153-3p. Additionally, TRAF6, a target gene of miR-153-3p, regulated CSE-induced 16HBE cell injury by combining with miR-153-3p. Importantly, circ_0026466 activated NF-κB pathway by targeting the miR-153-3p/TRAF6 axis. Conclusion: Circ_0026466 absence protected against CSE-triggered 16HBE cell injury by activating the miR-153-3p/TRAF6/NF-κB pathway, providing a potential therapeutic target for COPD.

Tumor-Associated Fibroblast-Derived Exosomal circDennd1b Promotes Pituitary Adenoma Progression by Modulating the miR-145-5p/ONECUT2 Axis and Activating the MAPK Pathway

TAF participated in the progression of various cancers, including PA via the release of soluble factors. Exosomes belonged to extracellular vesicles, which were revealed as a crucial participator in intercellular communication. However, the expression pattern and effect of TAF-derived exosomes remained largely unknown in PA. In the present study, we performed in silico analysis based on public RNA-seq datasets to generate the circRNA/miRNA regulatory network. The qRT-PCR, Western blotting, RNA pull-down, and luciferase assay were performed to investigate the effect of TAF-derived exosomes. TAF-derived exosomal circDennd1b was significantly upregulated in PA and promoted the proliferation, migration, and invasion of PA cells via sponging miR-145-5p in PA cells. In addition, miR-145-5p directly regulated One Cut homeobox 2 (ONECUT2/OC2) expression and inhibited the promoting effect of ONECUT2 on PA. We further demonstrated that ONECUT2 transcriptionally increased fibroblast growth factor receptor 3 (FGFR3) expression, which further activates the mitogen-activated protein kinases (MAPK) pathway, thus promoting PA progression. Moreover, the suppression of TAFs by ABT-263 and ONECUT2 by CSRM617 inhibited the growth of PA. In conclusion, our study illustrated that TAF-derived exosomal circDennd1b affected PA progression via regulating ONECUT2 expression, which provides a potential therapeutic strategy against aggressive PA.

Role of Circ-ITCH Gene Polymorphisms and Its Expression in Breast Cancer Susceptibility and Prognosis

INTRODUCTION/OBJECTIVE

Breast cancer (BC) is the first leading cause of cancer-related mortality in females worldwide. We have investigated the correlation between circ-ITCH gene polymorphisms, circ-ITCH expression, and their effect on β-catenin levels and BC development.

METHODS

Participants included 62 BC and 62 controls matched in terms of age. The circ-ITCH polymorphisms rs10485505 and rs4911154 were genotyped using whole blood samples. In addition, mRNA expression analysis of circ-ITCH was performed on BC tissues. The β-catenin levels in serum samples were measured using ELISA.

RESULTS

The qRT-PCR results demonstrated that circ-ITCH was significantly downregulated in BC compared to normal healthy tissues. The genotype distribution of rs10485505 and rs4911154 were significantly associated with BC risk. For rs10485505, genotype CT and TT were significantly associated with an increased BC risk. In contrast, there was a significant association between rs4911154, genotypes GA and AA, and an increased BC risk. Regarding the rs10485505 genotype, carriers of the T allele frequently have a poor prognosis compared to carriers of the CC genotype. Serum β-catenin in the BC patients' group was significantly higher than in the control group. The relative expression levels of circ-ITCH were remarkably decreased in the BC samples of patients carrying the A allele at rs4911154 compared to patients with a GG genotype. Conversely, β-catenin protein levels were increased in patients carrying the A allele, while rs10485505 genotype carriers of the CT and TT genotypes showed downregulation of circ-ITCH expression fold compared to the CC genotype. Contrarily, β-catenin levels markedly increased in TT and CT genotypes compared with the CC genotype.

CONCLUSIONS

Our research showed that the rs10485505 polymorphism (T allele) and the rs4911154 polymorphism (A allele) are associated with the risk and prognosis of BC. This finding may be due to the effect on the level of circ-ITCH mRNA expression in BC tissues as well as the level of β-catenin in BC patients.

Vascular calcification in CKD: New insights into its mechanisms

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) and contributes to an increased risk of cardiovascular morbidity and mortality. However, effective therapies are still unavailable at present. It has been well established that VC associated with CKD is not a passive process of calcium phosphate deposition, but an actively regulated and cell-mediated process that shares many similarities with bone formation. Additionally, numerous studies have suggested that CKD patients have specific risk factors and contributors to the development of VC, such as hyperphosphatemia, uremic toxins, oxidative stress and inflammation. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in CKD-related VC, many questions remain unanswered. Moreover, studies from the past decade have demonstrated that epigenetic modifications abnormalities, such as DNA methylation, histone modifications and noncoding RNAs, play an important role in the regulation of VC. This review seeks to provide an overview of the pathophysiological and molecular mechanisms of VC associated with CKD, mainly focusing on the involvement of epigenetic modifications in the initiation and progression of uremic VC, with the aim to develop promising therapies for CKD-related cardiovascular events in the future.

Hsa_circ_0003528 promotes cell malignant transformation and immune escape via increasing oncogene PDL1 through sponging miR-511-3p in non-small cell lung cancer

BACKGROUND

Accumulating evidence suggests that circular RNAs (circRNAs) play important regulatory roles in non-small cell lung cancer (NSCLC). At present, we aimed to explore the regulatory role of has_circ_0003528 (circ_0003528) in NSCLC.

METHODS

Alterations of circ_0003528 expression in NSCLC samples and cell lines were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Impacts of circ_0003528 on NSCLC cell malignant transformation were analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, transwell invasion, and tube formation assays. Epithelial-mesenchymal transition (EMT)-related markers were detected with western blotting. Pro-inflammatory cytokines were detected by Enzyme-linked immunosorbent assay (ELISA). The regulation mechanism of circ_0003528 was verified by dual-luciferase reporter and RNA pull-down assays. The tumorigenesis role of circ_0003528 was verified by animal experiments.

RESULTS

Higher levels of circ_0003528 were obtained in NSCLC samples and cell lines, and patients with high circ_0003528 expression had a worse prognosis. Silence of circ_0003528 decreased xenograft growth in mouse models and induced cell apoptosis and repressed cell viability, proliferation, invasion, EMT, angiogenesis, and immune escape in NSCLC cells in vitro. Mechanistically, circ_0003528 controlled programmed cell death ligand 1 (PDL1) expression through interaction with miR-511-3p. The inhibiting impacts of circ_0003528 knockdown on NSCLC cell malignant transformation and immune escape were weakened after miR-511-3p silencing. Moreover, PDL1 overexpression partially counteracted miR-511-3p upregulation-mediated suppression on NSCLC cell malignant transformation and immune escape.

CONCLUSIONS

Circ_0003528 facilitated NSCLC cell malignant transformation and immune escape through regulation of the miR-511-3p/PDL1 axis, highlighting the oncogenic role of circ_0003528 in NSCLC.

OCRFinder: a noise-tolerance machine learning method for accurately estimating open chromatin regions

Open chromatin regions are the genomic regions associated with basic cellular physiological activities, while chromatin accessibility is reported to affect gene expressions and functions. A basic computational problem is to efficiently estimate open chromatin regions, which could facilitate both genomic and epigenetic studies. Currently, ATAC-seq and cfDNA-seq (plasma cell-free DNA sequencing) are two popular strategies to detect OCRs. As cfDNA-seq can obtain more biomarkers in one round of sequencing, it is considered more effective and convenient. However, in processing cfDNA-seq data, due to the dynamically variable chromatin accessibility, it is quite difficult to obtain the training data with pure OCRs or non-OCRs, and leads to a noise problem for either feature-based approaches or learning-based approaches. In this paper, we propose a learning-based OCR estimation approach with a noise-tolerance design. The proposed approach, named OCRFinder, incorporates the ideas of ensemble learning framework and semi-supervised strategy to avoid potential overfitting of noisy labels, which are the false positives on OCRs and non-OCRs. Compared to different noise control strategies and state-of-the-art approaches, OCRFinder achieved higher accuracies and sensitivities in the experiments. In addition, OCRFinder also has an excellent performance in ATAC-seq or DNase-seq comparison experiments.

CIRC_0012535 CONTRIBUTES TO LIPOPOLYSACCHARIDE-INDUCED FETAL LUNG FIBROBLAST APOPTOSIS AND INFLAMMATION TO REGULATE INFANTILE PNEUMONIA DEVELOPMENT BY MODULATING THE MIR-338-3P/IL6R SIGNALING

ABSTRACT

Background: Infantile pneumonia is a respiratory infection disease, seriously threatening the life of neonatal patients. Circular RNA (circRNA) dysregulation is reported to be involved in pneumonia pathogenesis. Circ_0012535 was previously displayed to be upregulated in blood samples of patients with community-acquired pneumonia. However, circ_0012535's role in this disorder remains unclear. We thus aim to unveil the functions of circ_0012535 in infantile pneumonia. Methods: Fetal lung fibroblasts (WI38) treated with LPS were used as pneumonia cell models. Expression analysis for circ_0012535, miR-338-3p and IL6R was performed using quantitative real-time polymerase chain reaction. Cell counting kit 88), 5-ethynyl-2'-deoxyuridine, and flow cytometry assays were implemented for cell function detection. The release of inflammatory factors, and superoxide dismutase activity and malonaldehyde content were ascertained using commercial kits. The putative binding between miR-338-3p and circ_0012535 or IL6R was validated by dual-luciferase analysis, RIP analysis, and pull-down analysis. Results: Circ_0012535 was highly expressed in LPS-treated WI38 cells. Knockdown of circ_0012535 recovered LPS-inhibited cell viability and proliferation and attenuated LPS-induced cell apoptosis, cell cycle arrest, inflammation, and oxidative stress. Circ_0012535 bound to miR-338-3p and negatively regulated miR-338-3p expression. Inhibition of miR-338-3p reversed the role of circ_0012535 knockdown, thereby recovering LPS-induced WI38 cell apoptosis and inflammation. MiR-338-3p bound to IL6R 3'UTR, and circ_0012535 shared miR-338-3p binding site with IL6R. IL6R overexpression reversed the role of miR-338-3p, thereby recovering LPS-induced WI38 cell apoptosis and inflammation. Conclusion: Circ_0012535 supported LPS-induced WI38 cell apoptosis and inflammation to promote the progression of infantile pneumonia, and circ_0012535 functioned partly by targeting the miR-338-3p/IL6R signaling.

CIRCULAR RNA CIRC_0099188 CONTRIBUTES TO LPS-INDUCED HPAEpiC CELL INJURY BY TARGETING THE MIR-1236-3P/HMGB3 AXIS

ABSTRACT

Purpose: This study is designed to explore the role and mechanism of circ_0099188 in LPS-engendered HPAEpiC cells. Methods: Circ_0099188, microRNA-1236-3p (miR-1236-3p), and high mobility group box 3 (HMGB3) levels were measured using real-time quantitative polymerase chain reaction. Cell viability and apoptosis were assessed using cell counting kit-8 (CCK-8) and flow cytometry assays. Protein levels of B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), cleaved-caspase 3, cleaved-caspase 9, and HMGB3 were determined using Western blot assay. IL-6, IL-8, IL-1β, and TNF-α levels were analyzed using enzyme-linked immunosorbent assays. After predicting using Circinteractome and Targetscan, the binding between miR-1236-3p and circ_0099188 or HMGB3 was verified using a dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays. Results: Circ_0099188 and HMGB3 were highly expressed, and miR-1236-3p was decreased in LPS-stimulated HPAEpiC cells. Also, the downregulation of circ_0099188 might overturn LPS-triggered HPAEpiC cell proliferation, apoptosis, and inflammatory response. Mechanically, circ_0099188 is able to affect HMGB3 expression by sponging miR-1236-3p. Conclusion: Circ_0099188 knockdown might mitigate LPS-induced HPAEpiC cell injury by targeting the miR-1236-3p/HMGB3 axis, providing an underlying therapeutic strategy for pneumonia treatment.

Exosomal circSPIRE1 mediates glycosylation of E-cadherin to suppress metastasis of renal cell carcinoma

Metastasis is the main cause of mortality in renal cell carcinoma (RCC). Circular RNAs (circRNAs) involvement in RCC metastasis has been described, although the underlying mechanisms remain unknown. We evaluated recurring lung-metastasis cases using patient-derived xenograft models and isolated a highly metastatic clone. CircSPIRE1 was identified as a metastasis-inhibiting circRNA in clinical cohort and xenograft models. Mechanistically, circSPIRE1 suppressed mesenchymal state through regulating ELAV like RNA binding protein 1-mRNA binding, and upregulating polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) and KH domain RNA binding protein (QKI) expression. GALNT3 promoted glycosylation and cytomembrane localization of E-cadherin. QKI formed a positive feedback loop to enhance circSPIRE1 expression. Meanwhile, exosomal circSPIRE1 suppressed angiogenesis and vessel permeability. Our work reveals a non-canonical route for circRNAs in RCC to suppress metastasis. Furthermore, a nanomedicine consisting of circSPIRE1 plasmid suppressed metastasis formation. In conclusion, circSPIRE1 may be a predictor of metastasis and a potential therapeutic target of metastatic RCC.

Intergenerational Perioperative Neurocognitive Disorder

Accelerated neurocognitive decline after general anesthesia/surgery, also known as perioperative neurocognitive disorder (PND), is a widely recognized public health problem that may affect millions of patients each year. Advanced age, with its increasing prevalence of heightened stress, inflammation, and neurodegenerative alterations, is a consistent contributing factor to the development of PND. Although a strong homeostatic reserve in young adults makes them more resilient to PND, animal data suggest that young adults with pathophysiological conditions characterized by excessive stress and inflammation may be vulnerable to PND, and this altered phenotype may be passed to future offspring (intergenerational PND). The purpose of this narrative review of data in the literature and the authors' own experimental findings in rodents is to draw attention to the possibility of intergenerational PND, a new phenomenon which, if confirmed in humans, may unravel a big new population that may be affected by parental PND. In particular, we discuss the roles of stress, inflammation, and epigenetic alterations in the development of PND. We also discuss experimental findings that demonstrate the effects of surgery, traumatic brain injury, and the general anesthetic sevoflurane that interact to induce persistent dysregulation of the stress response system, inflammation markers, and behavior in young adult male rats and in their future offspring who have neither trauma nor anesthetic exposure (i.e., an animal model of intergenerational PND).

Systematic analysis of circRNA-related ceRNA networks of black rockfish (Sebastes schlegelii) in response to Aeromonas salmonicides infection

Aeromonas salmonicides is a type of Gram-negative bacteria and has become the main fish pathogen in aquaculture because of its characteristics of worldwide distribution, broad host range and potentially devastating impacts. In the past years, studies have been focused to explore the regulatory roles of circRNA-miRNA-mRNA network in fish diseases. However, there are only few systematic studies linked to the anti-bacterial roles of circRNA-related ceRNA networks in the spleen immune system of black rockfish (Sebastes schlegelii). In this study, the whole-transcriptome sequencing (RNA-seq) was conducted in the black rockfish spleen with A. salmonicida challenging. The differentially expressed (DE) circRNAs were identified comprehensively for the following enrichment analysis. Interactions of miRNA-circRNA pairs and miRNA-mRNA pairs were predicted for the construction of circRNA-related ceRNA regulatory networks. Then, protein-protein interaction (PPI) analysis of mRNAs from these ceRNA networks were conducted. Finally, a total number of 39 circRNAs exhibited significantly differential expressions during A. salmonicida infection in the black rockfish spleen in 4338 identified circRNAs from 12 samples in 4 libraries. Functional enrichment analysis suggested that they were significantly enriched in several immune-related pathways, including Endocytosis, FoxO signaling pathway, Jak-STST signaling pathway, Herpes simplex infection, etc. Subsequently, 290 circRNA-miRNA-mRNA pathways (91 at 2 h, 142 at 12 h and 65 at 24 h) were constructed including 31 circRNAs, 50 miRNAs, and 156 mRNAs. In conclusion, the circRNA-related ceRNA networks were established, which will provide some novel insights in molecular mechanistic investigations of anti-bacterial immune response in teleost. Also, these findings will propose significant predictive values for the development of methods of treatment and prevention in black rockfish after bacterial infection in the future.

Mmu_circ_0000037 inhibits the progression of acute pancreatitis by miR-92a-3p/Pias1 axis

BACKGROUND

Acute pancreatitis (AP) is an inflammatory disease with high mortality. Previous study has suggested that circular RNAs are dysregulated and involved in the regulation of inflammatory responses in AP. This study aimed to investigate the function and regulatory mechanism underlying mmu_circ_0000037 in caerulein-induced AP cellular model.

METHODS

Caerulein-treated MPC-83 cells were used as an in vitro cellular model for AP. The expression levels of mmu_circ_0000037, microRNA (miR)-92a-3p, and protein inhibitor of activated STAT1 (Pias1) were detected by quantitative real-time polymerase chain reaction. Cell viability, amylase activity, apoptosis, and inflammatory response were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Amylase Assay Kit, flow cytometry, and enzyme-linked immunosorbent assays. The protein level was quantified by western blot analysis. The target interaction between miR-92a-3p and mmu_circ_0000037 or Pias1 were predicted by StarbaseV3.0 and validated by dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

Mmu_circ_0000037 and Pias1 levels were decreased, whereas miR-92a-3p expression was elevated in caerulein-induced MPC-83 cells. Overexpression of mmu_circ_0000037 protected MPC-83 cells from caerulein-induced the decrease of cell viability, as well as the promotion of amylase activity, apoptosis and inflammation. MiR-92a-3p was targeted by mmu_circ_0000037, and miR-92a-3p overexpression rescued the effect of mmu_circ_0000037 on caerulein-induced MPC-83 cell injury. Pias1 was confirmed as a target of miR-92a-3p and mmu_circ_0000037 regulated the expression of Pias1 by sponging miR-92a-3p.

CONCLUSION

Mmu_circ_0000037 relieves caerulein-induced inflammatory injury in MPC-83 cells by targeting miR-92a-3p/Pias1 axis, providing a theoretical basis for the treatment of AP.

Circular RNA suppression of vascular smooth muscle apoptosis through the miR-545-3p/CKAP4 axis during abdominal aortic aneurysm formation

BACKGROUND

Abdominal aortic aneurysms (AAA) are an important cause of cardiovascular deaths. The loss of vascular smooth muscle cells (VSMCs) has been reported to be related to the pathology of AAA. This study focused on investigating the function of circ_0002168 in VSMC apoptosis.

METHODS

Levels of genes and proteins were measured by quantitative real-time-polymerase chain reaction (qRT-PCR) and Western blot. The growth of VSMCs was determined by using cell counting kit-8 assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry and the evaluation of caspase-3 activity analysis, reactive oxygen species (ROS) production as well as lactate dehydrogenase (LDH) activity. The binding between miR-545-3p and circ_0002168 or Cytoskeleton-associated protein 4 (CKAP4) was confirmed by bioinformatics analysis, dual-luciferase reporter, RNA immunoprecipitation, and pull-down assays.

RESULTS

Circ_0002168 decreased in the aortic tissues of patients with AAA. Functionally, ectopic overexpression of circ_0002168 dramatically induced proliferation and suppressed apoptosis in VSMCs. Mechanistically, circ_0002168 sequestered miR-545-3p to release CKAP4 expression via the ceRNA mechanism, indicating the circ_0002168/miR-545-3p/CKAP4 feedback loop in VSMCs. Increased miR-545-3p and a decreased CKAP4 expression were observed in patients with AAA. Rescue experiments showed that miR-545-3p reversed the protective effects of circ_0002168 on VSMC proliferation. Moreover, inhibition of miR-545-3p could restrain the apoptosis of VSMCs, which was abolished by CKAP4 silencing.

CONCLUSION

Circ_0002168 has a protective effect on VSMC proliferation by regulating the miR-545-3p/CKAP4 axis, adding further understanding of the pathogenesis of AAA and a potential therapeutic approach in AAA management.

Circular RNA CircCDKN2B−AS_006 Promotes the Tumor-like Growth and Metastasis of Rheumatoid Arthritis Synovial Fibroblasts by Targeting the miR−1258/RUNX1 Axis

Rheumatoid arthritis (RA) is an autoimmune polyarthritis in which synovial fibroblasts (SFs) play a major role in cartilage and bone destruction through tumor−like proliferation, migration, and invasion. Circular RNAs (circRNAs) have emerged as vital regulators for tumor progression. However, the regulatory role, clinical significance, and underlying mechanisms of circRNAs in RASF tumor−like growth and metastasis remain largely unknown. Differentially expressed circRNAs in synovium samples from patients with RA and patients with joint trauma were identified via RNA sequencing. Subsequently, in vitro and in vivo experiments were performed to investigate the functional roles of circCDKN2B−AS_006 in RASF proliferation, migration, and invasion. CircCDKN2B−AS_006 was upregulated in synovium samples from patients with RA and promoted the tumor-like proliferation, migration, and invasion of RASFs. Mechanistically, circCDKN2B−AS_006 was shown to regulate the expression of runt−related transcription factor 1 (RUNX1) by sponging miR-1258, influencing the Wnt/β−catenin signaling pathway, and promoting the epithelial−to−mesenchymal transition (EMT) in RASFs. Moreover, in the collagen−induced arthritis (CIA) mouse model, intra−articular injection of lentivirus−shcircCDKN2B−AS_006 was capable of alleviating the severity of arthritis and inhibiting the aggressive behaviors of SFs. Furthermore, the correlation analysis results revealed that the circCDKN2B−AS_006/miR−1258/RUNX1 axis in the synovium was correlated with the clinical indicators of RA patients. CircCDKN2B−AS_006 promoted the proliferation, migration, and invasion of RASFs by modulating the miR−1258/RUNX1 axis.

The critical role of circular RNAs in drug resistance in gastrointestinal cancers

Nowadays, drug resistance (DR) in gastrointestinal (GI) cancers, as the main reason for cancer-related mortality worldwide, has become a serious problem in the management of patients. Several mechanisms have been proposed for resistance to anticancer drugs, including altered transport and metabolism of drugs, mutation of drug targets, altered DNA repair system, inhibited apoptosis and autophagy, cancer stem cells, tumor heterogeneity, and epithelial-mesenchymal transition. Compelling evidence has revealed that genetic and epigenetic factors are strongly linked to DR. Non-coding RNA (ncRNA) interferences are the most crucial epigenetic alterations explored so far, and among these ncRNAs, circular RNAs (circRNAs) are the most emerging members known to have unique properties. Due to the absence of 5' and 3' ends in these novel RNAs, the two ends are covalently bonded together and are generated from pre-mRNA in a process known as back-splicing, which makes them more stable than other RNAs. As far as the unique structure and function of circRNAs is concerned, they are implicated in proliferation, migration, invasion, angiogenesis, metastasis, and DR. A clear understanding of the molecular mechanisms responsible for circRNAs-mediated DR in the GI cancers will open a new window to the management of GI cancers. Hence, in the present review, we will describe briefly the biogenesis, multiple features, and different biological functions of circRNAs. Then, we will summarize current mechanisms of DR, and finally, discuss molecular mechanisms through which circRNAs regulate DR development in esophageal cancer, pancreatic cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma.

Identification and characterization of CircRNA-associated CeRNA networks in moso bamboo under nitrogen stress

BACKGROUND

Nitrogen is a macronutrient element for plant growth and development. Circular RNAs (circRNAs) serve as pivotal regulators for the coordination between nutrient supply and plant demand. Moso bamboo (Phyllostachys edulis) is an excellent plant with fast growth, and the mechanism of the circRNA-target module in response to nitrogen remains unclear.

RESULTS

Deep small RNA sequencing results of moso bamboo seedlings under different concentrations of KNO₃ (N0 = 0 mM, N6 = 6 mM, N18 = 18 mM) were used to identify circRNAs. A total of 549 circRNAs were obtained, of which 309 were generated from corresponding parental coding genes including 66 new ones. A total of 536 circRNA-parent genes were unevenly distributed in 24 scaffolds and were associated with root growth and development. Furthermore, 52 differentially expressed circRNAs (DECs) were obtained, including 24, 33 and 15 DECs from three comparisons of N0 vs. N6, N0 vs. N18 and N6 vs. N18, respectively. Based on integrative analyses of the identified DECs, differentially expressed mRNAs (DEGs), and miRNAs (DEMs), a competitive endogenous RNA (ceRNA) network was constructed, including five DECs, eight DEMs and 32 DEGs. A regulatory module of PeSca_6:12,316,320|12,372,905-novel_miR156-PH02Gene35622 was further verified by qPCR and dual-luciferase reporter assays.

CONCLUSION

The results indicated that circRNAs could participate in multiple biological processes as miRNA sponges, including organ nitrogen compound biosynthesis and metabolic process regulation in moso bamboo. Our results provide valuable information for further study of circRNAs in moso bamboo under fluctuating nitrogen conditions.

Circular RNAs: New layer of complexity evading breast cancer heterogeneity

Advances in high-throughput sequencing techniques and bioinformatic analysis have refuted the "junk" RNA hypothesis that was claimed against non-coding RNAs (ncRNAs). Circular RNAs (circRNAs); a class of single-stranded covalently closed loop RNA molecules have recently emerged as stable epigenetic regulators. Although the exact regulatory role of circRNAs is still to be clarified, it has been proven that circRNAs could exert their functions by interacting with other ncRNAs or proteins in their own physiologically authentic environment, regulating multiple cellular signaling pathways and other classes of ncRNAs. CircRNAs have also been reported to exhibit a tissue-specific expression and have been associated with the malignant transformation process of several hematological and solid malignancies. Along this line of reasoning, this review aims to highlight the importance of circRNAs in Breast Cancer (BC), which is ranked as the most prevalent malignancy among females. Notwithstanding the substantial efforts to develop a suitable anticancer therapeutic regimen against the heterogenous BC, inter- and intra-tumoral heterogeneity have resulted in an arduous challenge for drug development research, which in turn necessitates the investigation of other markers to be therapeutically targeted. Herein, the potential of circRNAs as possible diagnostic and prognostic biomarkers have been highlighted together with their possible application as novel therapeutic targets.

Regulation of Glial Function by Noncoding RNA in Central Nervous System Disease

Non-coding RNAs (ncRNAs) are a class of functional RNAs that play critical roles in different diseases. NcRNAs include microRNAs, long ncRNAs, and circular RNAs. They are highly expressed in the brain and are involved in the regulation of physiological and pathophysiological processes of central nervous system (CNS) diseases. Mounting evidence indicates that ncRNAs play key roles in CNS diseases. Further elucidating the mechanisms of ncRNA underlying the process of regulating glial function that may lead to the identification of novel therapeutic targets for CNS diseases.

Silencing of circ-NT5C2 retards the progression of IL-1β-induced osteoarthritis in an in vitro cell model by targeting the miR-142-5p/NAMPT axis

Osteoarthritis (OA) is a degenerative disease that occurs mostly in the elderly, and its specific pathogenesis is still unknown, but recent studies have found that circular RNA generally display aberrant expression in OA. Our study explored the expression characteristics and mechanism of action of circ-NT5C2 in OA. Circ-NT5C2, microRNA-142-5p (miR-142-5p), and nicotinamide phosphoribosyltransferase (NAMPT) mRNA levels were measured using RT-qPCR. Western blot was employed to assess the protein level of NAMPT and extracellular matrix (ECM) production-related markers. The viability, proliferation, apoptosis and inflammation were examined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Relationship between miR-142-5p and circ-NT5C2 or NAMPT was demonstrated by dual-luciferase reporter system and RNA immunoprecipitation assay. We reported that circ-NT5C2 and NAMPT were greatly upregulated, and miR-142-5p level was constrained in OA tissues and in a cell model. Circ-NT5C2 silencing alleviated IL-1β-induced inhibitory effects on chondrocyte proliferation and ECM generation, meanwhile the promotional role of IL-1β on chondrocyte apoptosis and inflammation was also weakened. The targeting relationship of miR-142-5p with either circ-NT5C2 or NAMPT was confirmed. Knockdown of miR-142-5p reversed the suppressive effects of circ-NT5C2 silencing on the OA progression in vitro, and NAMPT overexpression also attenuated the effects of miR-142-5p upregulation in an OA cell model. Collectively, circ-NT5C2 accelerated the OA process by targeting the miR-142-5p/NAMPT axis. This study provides valuable information to find a better treatment for OA.

Circvrk1 downregulation attenuates brain microvascular endothelial cell damage induced by oxygen-glucose deprivation through modulating the miR-150-5p/MLLT1 axis

The pivotal regulatory role of circular RNAs (circRNAs) in ischemic stroke (IS) has been expounded. The study aimed to probe the exact role and underlying mechanism of circVRK1 in oxygen-glucose deprivation (OGD)-induced human brain microvascular endothelial cells (HBMECs) injury. HBMECs challenged by OGD were used as in vitro models of IS. Quantitative real-time PCR was used to examine the levels of circVRK1, vaccinia-related kinase 1 (VRK1), miR-150-5p and MLLT1 mRNA. Cell viability, migration angiogenesis ability and death were evaluated by Cell counting kit-8 assay, transwell assay, wound-healing assay, tube formation assay and flow cytometry analysis. All the protein levels were monitored by western blot assay. Enzyme-linked immunosorbent assay was conducted for examining cell oxidative stress. Dual-luciferase reporter assay, RIP assay and RNA pull-down assay were performed to verify the combination between miR-150-5p and circVRK1 or MLLT1. CircVRK1 was upregulated in OGD-treated HBMECs. CircVRK1 knockdown alleviated OGD-caused effects on HBMECs migration, angiogenesis, death, inflammatory response and oxidative stress. Furthermore, circVRK1 could sponge miR-150-5p, and miR-150-5p silencing also mitigated the impact of circVRK1 deficiency on OGD-evoked injury. Besides, MLLT1 acted as a molecular target of miR-150-5p, and the protective influence of miR-150-5p on OGD-induced cell damage was overturned by MLLT1 introduction. CircVRK1 knockdown weakened OGD-evoked injury in HBMECs through modulating miR-150-5p/MLLT1 pathway, and this might supply new insights and probable targets for IS treatment.

Molecular regulation of hypoxia through the lenses of noncoding RNAs and epitranscriptome

Cells maintain homeostasis in response to environmental stress through specific cell stress responses. Hypoxic stress, well known to be associated with diverse solid tumors, is one of the main reasons for cancer-related mortality. Although cells can balance themselves well during hypoxic stress, the underlying molecular mechanisms are not well understood. The enhanced appreciation of diverse roles played by noncoding transcriptome and epigenome in recent years has brought to light the involvement of noncoding RNAs and epigenetic modifiers in hypoxic regulation. The emergence of techniques like deep sequencing has facilitated the identification of large numbers of long noncoding RNAs (lncRNAs) that are differentially regulated in various cancers. Similarly, proteomic studies have identified diverse epigenetic modifiers such as HATs, HDACs, DNMTs, polycomb groups of proteins, and their possible roles in the regulation of hypoxia. The crosstalk between lncRNAs and epigenetic modifiers play a pivotal role in hypoxia-induced cancer initiation and progression. Besides the lncRNAs, several other noncoding RNAs like circular RNAs, miRNAs, and so forth are also expressed during hypoxic conditions. Hypoxia has a profound effect on the expression of noncoding RNAs and epigenetic modifiers. Conversely, noncoding RNAs/epigenetic modifies can regulate the hypoxia signaling axis by modulating the stability of the hypoxia-inducible factors (HIFs). The focus of this review is to illustrate the molecular orchestration underlying hypoxia biology, especially in cancers, which can help in identifying promising therapeutic targets in hypoxia-induced cancers. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry.

Circular RNA expression profile identifies circMGEA5 as a novel metastasis-promoting factor and potential biomarker in osteosarcoma

Osteosarcoma (OS) is associated with a high incidence of lung metastasis, which leads to a high risk of cancer death. Circular RNA (circRNA), a novel class of noncoding RNA, is emerging as a key player in human cancer. Herein, we explored the role of circMGEA5 in OS metastasis by conducting circRNA expression microarray. CircMGEA5 was significantly upregulated in metastatic OS tissues compared to primary tissues. High circMGEA5 was positively related with shorter overall and disease-free survival time. Knockdown of circMGEA5 suppressed OS cell migration, invasion, and epithelial-mesenchymal transition (EMT). Mechanistically, circMGEA5 acted as a competing endogenous RNA (ceRNA) to directly sponge miR-153-3p and miR-8084, resulting in increasing ZEB1 and Snail expression, respectively, thereby inducing EMT and metastasis. In turn, ZEB1 and Snail were capable to bind to circMGEA5 promoter, activating circMGEA5 transcription, thus forming a positive feedback loop. Furthermore, we established the tail vein injection model and found that circMGEA5 depletion remarkably reduced lung metastasis nodules generated by OS cells. In sum, our findings, for the first time, reveal the metastasis-promoting role of circMGEA5 in OS. Targeting of this newly identified ceRNA axis may be crucial in the development of novel therapies for metastatic OS patients.

Hsa_circ_0046430 promotes the progression of colorectal cancer by targeting miR-6785-5p/SRCIN1 axis as a ceRNA

The correlation among circular RNAs (circRNAs), microRNAs, and messenger RNAs have gained increasing attention in recent years. However, the mechanism of such discoveries in colorectal cancer (CRC) is not yet elucidated. The present study aimed to clarify whether the novel circRNAs regulate the prognosis-related genes through the competing endogenous RNAs (ceRNA). An analysis of the Weighted Gene Co-Expression Network Analysis was conducted to screen a module-trait circRNAs, and other big data mining technologies were used to predict the related microRNAs and the downstream genes. Prognosis-related gene model was built using the Cox regression analysis for the 138 messenger RNAs associated with hsa circ 0046430. The qRT-PCR was adopted to verify ceRNA network. Immunohistochemistry verified the correlation between SRCIN1 and patient prognosis. In summary, these results demonstrated that hsa_circ_0046430 is a tumor-related circRNA based on the clinical characteristics module of Weighted Gene Co-Expression Network Analysis. The prognostic risk score signature model analysis indicated that CRC risk was independently related to the risk score and SRCIN1 was independently associated with overall survival. Therefore, the hsa_circ_0046430/miR-6785-5p/SRCIN1 axis was constructed. Hsa_circ_0046430/miR-6785-5p/SRCIN1 axis relative expression level was determined by qRT-PCR. Immunohistochemical staining further validated that SCRIN1 was significantly higher in cancer than in adjacent normal tissues. Our study identified and primarily validated the hsa_circ_0046430/miR-6785-5p/SRCIN1 regulatory axis impacted on CRC prognosis, suggesting novel biomarkers and therapeutic targets for CRC patients. Further in-depth studies are essential to confirm the underlying ceRNA mechanism.

Autophagy-mediated circHIPK2 promotes lipopolysaccharide-induced astrocytic inflammation via SIGMAR1

Circular RNAs (circRNAs) are a subclass of noncoding RNAs and widely involve in the occurrence of multiple human diseases. It is an urgent task to clarify circRNA upstream regulation mechanism and seek their biofunction. Our previous study has confirmed that circular RNA HIPK2 (circHIPK2) promotes astrocyte activation via SIGMAR1, sigma non-opioid intracellular receptor 1, in a mouse model of single high-dose lipopolysaccharide (LPS) injection. However, what mechanism circHIPK2 is regulated by and whether it is involved in the inflammatory response of astrocytes remain unclear. In this study, we reported that circHIPK2 and SIGMAR1 were significantly increased in mouse prefrontal cortex after multiple intraperitoneal injection of LPS, with the elevation of inflammatory mediators. Knockdown circHIPK2 in primary astrocytes suppressed the SIGMAR1 expression and inflammation. Pretreatment of autophagy inducer rapamycin on astrocytes suppressed the circHIPK2 expression and inactivated inflammatory response. These results implied that autophagy inducer rapamycin could suppress astrocytic inflammation by inactivating circHIPK2-SIGMAR1 axis. Autophagy may be a promising upstream administrator of circHIPK2 and therapeutic target for central nervous system inflammation.

Novel circRNA-miRNA-mRNA networks regulated by maternal exercise in fetal hearts of pregestational diabetes

BACKGROUND

Maternal exercise lowers the incidence of congenital heart defects (CHDs) induced by pregestational diabetes. However, the molecular mechanisms underlying the beneficial effects of maternal exercise remain unclear. The present study aimed to identify circular RNA (circRNA), microRNA (miRNA) and mRNA networks that are regulated by maternal exercise in fetal hearts of pregestational diabetes.

METHODS

Pregestational diabetes was induced in adult C57BL/6 female mice by streptozotocin. The expression profiles of circRNAs, miRNAs and mRNAs in E10.5 fetal hearts of offspring of control and diabetic mothers with or without exercise were analyzed using next generation sequencing. circRNA-miRNA-mRNA networks in fetal hearts were mapped and key candidate transcripts were verified by qPCR analysis.

RESULTS

Pregestational diabetes dysregulated the expression of 206 circRNAs, 66 miRNAs and 391 mRNAs in fetal hearts. Maternal exercise differentially regulated 188 circRNAs, 57 miRNAs and 506 mRNAs in fetal hearts of offspring of pregestational diabetes. A total of 5 circRNAs, 12 miRNAs, and 28 mRNAs were incorporated into a final maternal exercise-associated regulatory network in fetal hearts of offspring of maternal diabetes. Notably, maternal exercise normalized the dysregulated circ_0003226/circ_0015638/miR-351-5p and circ_0002768/miR-3102-3p.2-3p pairs in fetal hearts of pregestational diabetes.

CONCLUSION

Maternal exercise reverses the dysregulated circ_0003226/circ_0015638/miR-351-5p and circ_0002768/miR-3102-3p.2-3p pairs, and partially normalizes circRNA, miRNA, and mRNA expression profiles in fetal hearts of pregestational diabetes. These findings shed new light on the potential mechanisms of the beneficial effects of maternal exercise on the developing heart in diabetic pregnancies.

CircVAPA contributes to hyper-proliferation and inflammation of keratinocytes through miR-125b-5p/sirt6 axis in psoriasis

Psoriasis is an autoimmune skin disease with abnormal keratinocyte hyperproliferation. The important roles of circular RNAs (circRNAs) in various inflammatory diseases have been revealed. The present study aimed to investigate the roles of circVAPA and its molecular mechanisms in psoriasis. Quantitative real-time polymerase chain reaction was performed to measure the RNA expression. Enzyme-linked immunosorbent assays were employed to examine the production of inflammatory factors. Cell-counting kit-8, EDU and flow cytometry assay were conducted to examine the cell viability, proliferation and apoptosis respectively. Dual-luciferase reporter assay and ribonucleoprotein immunoprecipitation (RIP) were conducted to verify the target relationship between miR-125b-5p and circVAPA or Sirt6. Herein our findings showed increased expression of circVAPA and Sirt6 and decreased level of miR-125b-5p in psoriatic lesional tissues and M5-stimulated keratinocytes. Mechanistically, circVAPA knockdown significantly suppressed the promotion of M5 on cell viability, proliferation, and inflammation of HaCaT cells. circVAPA was verified to interact with miR-125b-5p, while inhibition of miR-125b-5p counteracted circVAPA knockdown-mediated effects in M5-stimulated HaCaT cells. Sirt6 was confirmed as a target of miR-125b-5p, and miR-125b-5p overexpression inhibited cell growth and inflammation partly by targeting Sirt6 in M5-stimulated HaCaT cells. Moreover, circVAPA was featured as a competing endogenous RNA by directly sponging miR-125b-5p to up-regulate the expression of Sirt6. CircVAPA participate in the progression of psoriasis through miR-125b-5p/sirt6 axis by regulating proliferation and inflammation of keratinocytes, highlighting a potential therapeutic target for psoriasis.

circ_0001274 Competitively Binds miR-143-3p to Upregulate VWF Expression to Improve Acute Traumatic Coagulopathy

Accumulating evidence has noted the circRNA-microRNA- (circRNA-miRNA-) mRNA competing endogenous RNA (ceRNA) regulatory network in disease development and progression. The current study explored the ceRNA network in acute traumatic coagulopathy (ATC). Potential ATC-related genes were screened, and upstream miRNAs and circRNAs of VWF (the candidate target) were assayed through database searching and high-throughput sequencing technology. circ_0001274/miR-143-3p/VWF ceRNA regulatory network was constructed and validated. The expression of circ_0001274/miR-143-3p/VWF was determined in the peripheral blood samples from ATC patients and ATC mouse models. Online database and circRNA sequencing analysis results identified VWF as a key gene in ATC as supported by assays and that VWF was lowly expressed in ATC patients and mice. Further experiments demonstrated that miR-143-3p could target and inhibit VWF, and circ_0001274 could competitively sponge miR-143-3p. Functionally, circ_0001274 could competitively sequester miR-143-3p to upregulate VWF expression, potentially improving ATC. Our study highlights the critical role of circ_0001274/miR-143-3p/VWF axis in improving ATC.

The Intricate Role of Non-Coding RNAs in Sepsis-Associated Disseminated Intravascular Coagulation

Disseminated Intravascular Coagulation (DIC) is a type of tissue and organ dysregulation in sepsis, due mainly to the effect of the inflammation on the coagulation system. Unfortunately, the underlying molecular mechanisms that lead to this disorder are not fully understood. Moreover, current biomarkers for DIC, including biological and clinical parameters, generally provide a poor diagnosis and prognosis. In recent years, non-coding RNAs have been studied as promising and robust biomarkers for a variety of diseases. Thus, their potential in the diagnosis and prognosis of DIC should be further studied. Specifically, the relationship between the coagulation cascade and non-coding RNAs should be established. In this review, microRNAs, long non-coding RNAs, and circular RNAs are studied in relation to DIC. Specifically, the axis between these non-coding RNAs and the corresponding affected pathway has been identified, including inflammation, alteration of the coagulation cascade, and endothelial damage. The main affected pathway identified is PI3K/AKT/mTOR axis, where several ncRNAs participate in its regulation, including miR-122-5p which is sponged by circ_0005963, ciRS-122, and circPTN, and miR-19a-3p which is modulated by circ_0000096 and circ_0063425. Additionally, both miR-223 and miR-24 were found to affect the PI3K/AKT pathway and were regulated by lncGAS5 and lncKCNQ1OT1, respectively. Thus, this work provides a useful pipeline of inter-connected ncRNAs that future research on their impact on DIC can further explore.

Circ VRK1/microRNA-17/PTEN axis modulates the angiogenesis of human brain microvascular endothelial cells to affect injury induced by oxygen-glucose deprivation/reperfusion

BACKGROUND

Circular RNAs (circRNAs) can act as microRNA (miRNA) sponges, thus regulating gene expression. The role of circRNAs in the process of oxygen-glucose deprivation/reoxygenation (OGD/R) is unclear. Here, we explored the mechanism underlying Circ VRK1 in human brain microvascular endothelial cells (HBMVECs) injury induced by OGD/R.

METHODS

The OGD/R cell model was established in HBMVECs. The microarray was applied to detect differentially expressed circRNAs, followed by subcellular fractionation assay. Colony formation assay, flow cytometry, ELISA, tube formation, Transwell and western blot assays were performed for loss-of-function assay. HE staining, TTC staining, immunohistochemistry and western blot were performed in an established mouse model. The relationships between Circ VRK1 and miR-17, and between miR-17 and PTEN were detected by bioinformatics and dual-luciferase assays. Rescue experiments were conducted in vitro and in vivo, and PI3K/AKT activity was detected by Western Blot.

RESULTS

Circ VRK1, predominantly present in the cytoplasm of cells, was upregulated in the HBMVECs exposed to OGD/R. Circ VRK1 downregulation decreased proliferation, migration, tube formation, inflammatory factors and oxidative stress, while increased apoptosis in HBMVECs. Moreover, Circ VRK1 silencing reduced neurological damage, cerebral infarct size, CD34-positive cell counts and VEGF expression in mice. Circ VRK1 mediated PTEN expression and the PI3K/AKT pathway by targeting miR-17. Deletion of miR-17 inhibited the effects of Circ VRK1 siRNA, and silencing of PTEN suppressed the effects of miR-17 inhibitor.

CONCLUSION

Circ VRK1 was upregulated during OGD/R. Circ VRK1 downregulation regulates PTEN expression by targeting miR-17, thereby promoting PI3K/AKT pathway activity to alleviate OGD/R injury.

Circular RNA in Retina: A Potential Biomarker and Therapeutic Target

Circular RNA (circRNA) is a newly discovered noncoding RNA, which forms a closed ring with more than 200 bases in length. CircRNA is formed by back splicing of precursor RNA, and its expression abundance in body fluid is up to 10 times that of homologous linear transcripts. Recently, novel activities for circRNA in various diseases have emerged, ranging from cancer therapy and neurodegenerative diseases. Here, we reviewed the literature on the biogenesis of circRNA and its relationship with retinal diseases in recent years. We first described the mechanism, existing form and main function of circRNA. Next, we also pinpoint that circRNA has great value in the diagnosis and treatment of retinal diseases represented by retinoblastoma, retinal degeneration, and diabetic retinopathy. By this review, we hope to explore more possibilities of circRNA in clinical diagnosis and treatment.

Recent Advances of Circular RNAs as Biomarkers for Osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor in young adult, which is prone to early metastasis and poor prognosis. The current treatment methods need to be improved. Circular RNA is a covalently blocked circular, non-coding RNA that plays an essential role in the occurrence, development, clinical diagnosis, and treatment of various diseases. Recently, an increasing number of circRNAs have been identified in osteosarcoma. Understanding its role in osteosarcoma is conducive to the early detection, diagnosis, and treatment of osteosarcoma. In this paper, we reviewed the mechanism of action of circular RNA in the occurrence and development of osteosarcoma and its clinical application in recent years.

Identification of pathological-related and diagnostic potential circular RNAs in Stanford type A aortic dissection

Introduction

Stanford type A aortic dissection (TAAD) is one of the lethal macrovascular diseases caused by the invasion of blood into the media layer of ascending aortic wall. Inflammation, smooth muscle dysfunction, and extracellular matrix (ECM) degradation were regarded as the major pathology in affected tissue. However, the expression pattern and its regulation especially through circular RNAs (circRNAs) as an overall characteristic of TAAD molecular pathology remain unclear.

Methods

We employed CIRCexplorer2 to identify circRNAs based on the RNA sequencing (RNA-seq) data of human ascending aortic tissues to systematically assess the role of circRNA in the massive alterations of gene expression in TAAD aortas. The key circRNAs were determined by LASSO model and functionally annotated by competing endogenous RNAs (ceRNA) network and co-analysis with mRNA profile. The expression level and diagnostic capability of the 4 key circRNAs in peripheral serum were confirmed by real-time polymerase chain reaction (RT-PCR).

Results

The 4 key circRNAs, namely circPTGR1 (chr9:114341075-114348445[-]), circNOX4 (chr11:89069012-89106660[-]), circAMN1 (chr12:31854796-31862359[-]) and circUSP3 (chr15:63845913-63855207[+]), demonstrated a high power to discriminate between TAAD and control tissues, suggesting that these molecules stand for a major difference between the tissues at gene regulation level. Functionally, the ceRNA network of circRNA-miRNA-mRNA predicted by the online databases, combining gene set enrichment analysis (GSEA) and cell component prediction, revealed that the identified circRNAs covered all the aspects of primary TAAD pathology, centralized with increasing inflammatory factors and cells, and ECM destruction and loss of vascular inherent cells along with the circRNAs. Importantly, we validated the high concentration and diagnostic capability of the 4 key circRNAs in the peripheral serum in TAAD patients.

Discussion

This study reinforces the vital status of circRNAs in TAAD and the possibility of serving as promising diagnostic biomarkers.

Circular RNAs in extracellular vesicles: Promising candidate biomarkers for schizophrenia

As one of common and severe mental illnesses, schizophrenia is difficult to be diagnosed exactly. Both its pathogenesis and the causes of its development are still uncertain because of its etiology complexity. At present, the diagnosis of schizophrenia is mainly based on the patient's symptoms and signs, lacking reliable biomarkers that can be used for diagnosis. Circular RNAs in extracellular vesicles (EV circRNAs) can be used as promising candidate biomarkers for schizophrenia and other diseases, for they are not only high stability and disease specificity, but also are rich in contents and easy to be detected. The review is to focus on the research progress of the correlation between circRNAs and schizophrenia, and then to explores the possibility of EV circRNAs as new biomarkers for the schizophrenia diagnosis.

Regulatory effects of circular RNA on hypoxia adaptation in chicken embryos

The Tibetan chicken, a native breed of the Tibetan plateau, is adapted to the high-altitude and hypoxic environment of the plateau. As endogenous molecules, circular RNAs (circRNAs) have been shown to play an important role in the adaptation to hypoxic environments and regulation of angiogenesis. In this study, highland Tibetan and lowland Chahua chicken eggs were incubated in a hypoxic environment and the chorionic allantoic membrane was collected for Ribo-Zero RNA sequencing. A total of 1,414 circRNAs, mostly derived from exons, were identified. Of these, 93 differentially expressed circRNAs were detected between Tibetan and Chahua chickens. Combined with the differentially expressed miRNAs and mRNAs identified in our previous study, we identified four circRNAs (circBRD1, circPRDM2, circPTPRS, and circDENND4C). These circRNAs may act as competing endogenous RNA (ceRNA) to upregulate APOA1 expression by absorbing novel_miR_589, thereby regulating angiogenesis and affecting hypoxia adaptation in chicken embryos. The regulatory circRNAs/novel_miR_589/APOA1 axis provides valuable evidence for a better understanding of the specific functions and molecular mechanisms of circRNAs in plateau hypoxia adaptation in Tibetan chickens.

Dysregulation of circRNA-0076906 and circRNA-0134944 is Correlated with Susceptibility to Osteoporosis and Osteoporotic Fracture in Postmenopausal Females from the Chinese Han Population

Introduction

Many circRNAs, such as circRNA-0076906 and circRNA-0134944, have been reported to participate in the pathogenesis of osteoporosis via sponging miRNAs in postmenopausal female patients. In this study, we aimed to study potential signaling pathways underlying the role of certain circRNAs, miRNAs and their target genes in the pathogenesis of osteoporotic fracture in postmenopausal females.

Methods

Quantitative real-time PCR was performed to analyze the expression of circRNAs, miRNAs and their targets genes. Luciferase assays were carried out to explore the regulatory relationship between circ_0076906/miR-548i/OGN and circ_0134944/miR-630/TLR4.

Results

Osteoporosis and fracture were positively correlated to the expression of circ_0134944, miR-548i and TLR4, but negatively correlated to the expression of circ_0076906, miR-630 and OGN in the peripheral blood and bone tissue samples of postmenopausal women. Luciferase activities of wild-type circ_0076906 and OGN were inhibited by miR-548i, and the luciferase activities of wild-type circ_0134944 and TLR4 were suppressed by miR-630 in MG-63 and U-2 OS cells. Inhibition of circ_0076906 expression in MG-63 and U-2 OS cells activated the expression of miR-548i and inhibited the expression of OGN. Moreover, the overexpression of circ_0134944 in MG-63 and U-2 OS cells suppressed the expression of miR-630 and enhanced the expression of TLR4.

Conclusion

This study implied that the dysregulation of circRNA-0076906 and circRNA-0134944 modulated their specific signaling and thus contributed to the severity of osteoporosis, increasing the risk of osteoporotic fracture.

MicroRNA-125a-3p Modulate Amyloid β-Protein through the MAPK Pathway in Alzheimer's Disease

BACKGROUND

MicroRNA (miR)-125a-3p is reported to play an important role in some central nervous system diseases, such as Alzheimer's disease (AD). However, a study has not been conducted on the mechanism of miR-125a-3p in the pathological process of AD.

METHODS

First, we assessed the expression of miR-125a-3p in AD cohort. Subsequently, we altered the expressions of miR-125a-3p to assess its role in cell viability, cell apoptosis, amyloid-β (Aβ) metabolism, and synaptic activity. Finally, we identified its potential mechanism underlying AD pathology.

RESULTS

This study unveiled the potential function of miR-125a-3p through modulating amyloid precursor protein processing. Additionally, miR-125a-3p influenced cell survival and activated synaptic expression through the modulation of Aβ metabolism in the mitogen-activated protein kinase (MAPK) pathway via fibroblast growth factor receptor 2.

CONCLUSION

Our study indicates that targeting miR-125a-3p may be an applicable therapy for AD in the future. However, more in vitro and in vivo studies with more samples are needed to confirm these results.

CircUSP39/miR-362-3p/TRAF3 Axis Mediates Hypoxia/Reoxygenation-Induced Cardiomyocyte Oxidative Stress, Inflammation, and Apoptosis

Accumulating evidence suggested that aberrantly regulated circular RNA (circRNA) is a critical contributor to cardiovascular diseases, including acute myocardial infarction (AMI). However, the role and molecular mechanism of circUSP39 in AMI development remain unclear.Candidate circRNAs were screened from the Gene Expression Omnibus (GEO) database (GSE160717) and analyzed using the GEO2R tool. Hypoxia/reoxygenation (H/R) -induced AC16 cells were used to investigate the function of circUSP39 in H/R injury of cardiomyocytes. Quantitative real-time PCR (qRT-PCR) was employed to test RNA levels in H/R-induced AC16 cells. Cell Counting Kit-8, enzyme-linked immunosorbent assay, flow cytometry, and western blot (WB) assay were used to determine cell viability, oxidative stress, inflammatory factor levels, and cell apoptosis. RNA immunoprecipitation, RNA pull-down, and dual-luciferase reporter assay were conducted to validate the interactions between circRNA ubiquitin-specific peptidase 39 (circUSP39), miR-362-3p, and tumor necrosis factor receptor-associated factor 3 (TRAF3).In H/R-induced AC16 cells, the expression levels of circUSP39 and TRAF3 were upregulated whereas miR-362-3p expression was downregulated. CircUSP39 silencing markedly enhanced cell viability and superoxide dismutase activity but mitigated malondialdehyde level, secretion of inflammatory factors (IL-6, TNF-α, IL-1β, and MCP-1), and cell apoptosis in H/R-induced AC16 cells. CircUSP39 expedited H/R-induced AC16 cell injury by sponging miR-362-3p to increase the expression of TRAF3.CircUSP39 could facilitate H/R-induced cardiomyocyte oxidative stress, inflammation, and apoptosis by the miR-362-3p/TRAF3 axis, elucidating that it might be a therapeutic target for AMI.

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

Hsa_circ_0007380 silencing restrains the growth and enhances radiosensitivity in esophagus cancer by miR-644a/Spindlin 1 axis

Circular RNAs are frequently dysregulated and show important regulatory function of tumorigenesis in cancers. Hsa_circ_0007380 was found to be elevated in human radioresistant esophageal cancer cells. Here, this study aimed to investigate the action and mechanism of hsa_circ_0007380 in esophageal cancer carcinogenesis and radiosensitivity. Quantitative real-time PCR and western blotting were performed to detect levels of genes and proteins. Functional experiments were conducted using MTT assay, EdU assay, clonogenic survival assay, flow cytometry and murine xenograft model assay, respectively. The binding between miR-644a and hsa_circ_0007380 or spindlin1 (SPIN1) was validated using dual-luciferase activity assay. Hsa_circ_0007380 was highly expressed in esophagus cancer tissues and cells, knockdown of hsa_circ_0007380 suppressed esophagus cancer cell proliferation, induced apoptosis and enhanced radiosensitivity in vitro, and the same effects were also confirmed in nude mice. Mechanistically, hsa_circ_0007380 sequestered miR-644a to release SPIN1 expression, implying the hsa_circ_0007380/miR-644a/SPIN1 competing endogenous RNA network esophagus cancer cells. miR-644a was decreased in esophagus cancer, re-expression of miR-644a restrained cell growth and conferred radiosensitivity in esophagus cancer, which were reversed by SPIN1 overexpression. Besides that, inhibition of miR-644a abolished the promoting action of hsa_circ_0007380 knockdown on esophagus cancer apoptosis and radiosensitivity. Hsa_circ_0007380 silencing impedes cell growth and reinforces radiosensitivity in esophagus cancer by miR-644a/SPIN1 axis, suggesting a promising therapeutic target for esophagus cancer combined treatment.