Circular RNAs in Blood

The Combination of circEPSTI1 and MIF Offers Diagnostic Value for Endometrial Cancer

Background

Circular RNAs (circRNAs) exhibit unique patterns of expression and high levels of stability in patient plasma samples such that they represent ideal non-invasive biomarkers that can be leveraged to detect a wide array of diseases including endometrial cancer (EC). This study was designed to identify circRNAs with potential diagnostic utility in serum samples from EC patients while also evaluating the utility of macrophage migration inhibitory factor (MIF) as a biomarker when screening for this form of cancer in the clinic.

Methods

Levels of circEPSTI1 and MIF were assessed in the plasma of EC patients and healthy subjects (n=186 each) through qPCR and ELISAs. The diagnostic utility of these biomarkers was assessed with receiver operating characteristic curve (ROC) analyses.

Results

Relative to healthy subjects, EC patient serum contained significantly elevated circEPSTI1 and MIF. An association was noted between circEPSTI1 expression in stages, histologic grade, and residual tumor. ROC curves confirmed that serum circEPSTI1 levels distinguished between controls and patients with EC with an Area of 0.835 and serum MIF levels distinguished between controls and patients with EC with an Area of 0.6646. When instead diagnosing patients based on the combination of MIF and circEPSTI1, the Area further rose to 0.8604.

Conclusion

Assessing the combination of circEPSTI1 and MIF may be a viable approach to reliably diagnosing EC.

Circular RNAs and their roles in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited treatment options. Circular RNAs (circRNAs) have emerged as a novel class of non-coding RNAs with diverse functions in cellular processes. This review paper aims to explore the potential involvement of circRNAs in the pathogenesis of IPF and their diagnostic and therapeutic implications. We begin by providing an overview of the epidemiology and risk factors associated with IPF, followed by a discussion of the pathophysiology underlying this complex disease. Subsequently, we delve into the history, types, biogenesis, and functions of circRNAs and then emphasize their regulatory roles in the pathogenesis of IPF. Furthermore, we examine the current methodologies for detecting circRNAs and explore their diagnostic applications in IPF. Finally, we discuss the potential utility of circRNAs in the treatment of IPF. In conclusion, circRNAs hold great promise as novel biomarkers and therapeutic targets in the management of IPF.

Exploring the Multifaceted Biologically Relevant Roles of circRNAs: From Regulation, Translation to Biomarkers

CircRNAs are a category of regulatory RNAs that have garnered significant attention in the field of regulatory RNA research due to their structural stability and tissue-specific expression. Their circular configuration, formed via back-splicing, results in a covalently closed structure that exhibits greater resistance to exonucleases compared to linear RNAs. The distinctive regulation of circRNAs is closely associated with several physiological processes, as well as the advancement of pathophysiological processes in several human diseases. Despite a good understanding of the biogenesis of circular RNA, details of their biological roles are still being explored. With the steady rise in the number of investigations being carried out regarding the involvement of circRNAs in various regulatory pathways, understanding the biological and clinical relevance of circRNA-mediated regulation has become challenging. Given the vast landscape of circRNA research in the development of the heart and vasculature, we evaluated cardiovascular system research as a model to critically review the state-of-the-art understanding of the biologically relevant functions of circRNAs. We conclude the review with a discussion of the limitations of current functional studies and provide potential solutions by which these limitations can be addressed to identify and validate the meaningful and impactful functions of circRNAs in different physiological processes and diseases.

Circ_0067934: a circular RNA with roles in human cancer

A circular RNA (circRNA) is a non-coding RNA (ncRNA) derived from reverse splicing from pre-mRNA and is characterized by the absence of a cap structure at the 5' end and a poly-adenylated tail at the 3' end. Owing to the development of RNA sequencing and bioinformatics approaches in recent years, the important clinical value of circRNAs has been increasingly revealed. Circ_0067934 is an RNA molecule of 170 nucleotides located on chromosome 3q26.2. Circ_0067934 is formed via the reverse splicing of exons 15 and 16 in PRKCI (protein kinase C Iota). Recent studies revealed the upregulation or downregulation of circ_0067934 in various tumors. The expression of circ_0067934 was found to be correlated with tumor size, TNM stage, and poor prognosis. Based on experiments with cancer cells, circ_0067934 promotes cancer cell proliferation, migratory activity, and invasion when overexpressed or downregulated. The potential mechanism involves the binding of circ_0067934 to microRNAs (miRNAs; miR-545, miR-1304, miR-1301-3p, miR-1182, miR-7, and miR-1324) to regulate the post-transcriptional expression of genes. Other mechanisms include inhibition of the Wnt/β-catenin and PI3K/AKT signaling pathways. Here, we summarized the biological functions and possible mechanisms of circ_0067934 in different tumors to enable further exploration of its translational applications in clinical diagnosis, therapy, and prognostic assessments.

The emerging power and promise of non-coding RNAs in chronic pain

Chronic pain (CP) is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage lasting longer than 3 months. CP is the main reason why people seek medical care and exerts an enormous economic burden. Genome-wide expression analysis has revealed that diverse essential genetic elements are altered in CP patients. Although many possible mechanisms of CP have been revealed, we are still unable to meet all the analgesic needs of patients. In recent years, non-coding RNAs (ncRNAs) have been shown to play essential roles in peripheral neuropathy and axon regeneration, which is associated with CP occurrence and development. Multiple key ncRNAs have been identified in animal models of CP, such as microRNA-30c-5p, ciRS-7, and lncRNA MRAK009713. This review highlights different kinds of ncRNAs in the regulation of CP, which provides a more comprehensive understanding of the pathogenesis of the disease. It mainly focuses on the contributions of miRNAs, circRNAs, and lncRNAs to CP, specifically peripheral neuropathic pain (NP), diabetic NP, central NP associated with spinal cord injury, complex regional pain syndrome, inflammatory pain, and cancer-induced pain. In addition, we summarize some potential ncRNAs as novel biomarkers for CP and its complications. With an in-depth understanding of the mechanism of CP, ncRNAs may provide novel insight into CP and could become new therapeutic targets in the future.

CircSEMA4B inhibits the progression of breast cancer by encoding a novel protein SEMA4B-211aa and regulating AKT phosphorylation

PI3K/AKT signaling pathway plays an important role in regulating the tumorigenesis, recurrence, and metastasis of breast cancer (BC). In this study, we discovered a circRNA with protein-coding potential, which we named circSEMA4B. CircSEMA4B could encode a novel protein, SEMA4B-211aa. Both circSEMA4B and SEMA4B-211aa were remarkably downregulated in BC tissues and cell lines. Low expression of circSEMA4B was positively associated with TNM stage, tumor size, lymph node metastasis, and distant metastasis of BC patients. The functional investigation showed that circSEMA4B and SEMA4B-211aa could significantly inhibit the proliferation and migration of BC in vivo and in vitro. Of note, SEMA4B-211aa inhibited the generation of PIP3 by binding to p85, thereby inhibiting the phosphorylation of AKT (Thr308). CircSEMA4B inhibited the phosphorylation of AKT (Ser473) through miR-330-3p/PDCD4 axis. Taken together, circSEMA4B is a novel negative regulator of PI3K/AKT signaling pathway, providing novel mechanistic insights into the underlying mechanisms of BC.

Emerging Roles of Circ-ZNF609 in Multiple Human Diseases

Circular RNAs (circRNAs) are a special type of endogenous RNAs with extensive roles in multiple human diseases. They are formed by back-splicing of partial sequences of the parental precursor mRNAs. Unlike linear RNAs, their covalently closed loop structure without a 5′ cap and a 3′ polyadenylated tail confers on them high stability and they are difficult to be digested by RNase R. Increasing evidence has proved that aberrant expressions of many circRNAs are detected and that circRNAs exert essential biological functions in disease development and progression via acting as a molecular sponge of microRNA, interacting with proteins as decoys or scaffolds, or self-encoding small peptides. Circular RNA zinc finger protein 609 (circ-ZNF609) originates from exon2 of ZNF609, which is located at chromosome 15q22.31, and it has recently been proved that it can translate into a protein. Being aberrantly upregulated in various diseases, it could promote malignant progression of human tumors, as well as tumor cell proliferation, migration, and invasion. Here in this review, we concluded the biological functions and potential mechanisms of circ-ZNF609 in multiple diseases, which could be further explored as a targetable molecule in future accurate diagnosis and prognosis.

Detection of Embryonic Trisomy 21 in the First Trimester Using Maternal Plasma Cell-Free RNA

Prenatal trisomy 21 (T21) screening commonly involves testing a maternal blood sample for fetal DNA aneuploidy. It is reliable but poses a cost barrier to universal screening. We hypothesized maternal plasma RNA screening might provide similar reliability but at a lower cost. Discovery experiments used plasma cell-free RNA from 20 women 11−13 weeks tested by RNA and miRNA microarrays followed by qRT-PCR. Thirty-six mRNAs and 18 small RNAs of the discovery cDNA were identified by qPCR as potential markers of embryonic T21. The second objective was validation of the RNA predictors in 998 independent pregnancies at 11−13 weeks including 50 T21. Initial analyses identified 9−15 differentially expressed RNA with modest predictive power (AUC < 0.70). The 54 RNAs were then subjected to machine learning. Eleven algorithms were trained on one partition and tested on an independent partition. The three best algorithms were identified by Kappa score and the effects of training/testing partition size and dataset class imbalance on prediction were evaluated. Six to ten RNAs predicted T21 with AUCs up to 1.00. The findings suggest that maternal plasma collected at 11−13 weeks, tested by qRT-PCR, and classified by machine learning, may accurately predict T21 for a lower cost than plasma DNA, thus opening the door to universal screening.

hsa_circ_0068631 promotes breast cancer progression through c-Myc by binding to EIF4A3

Breast cancer (BC) is one of the most common malignancies among women worldwide with a high incidence of recurrence and metastasis. In this study, we demonstrate that hsa_circ_0068631, a circRNA generated from the transferrin receptor (TFRC), is upregulated in BC tissues and cell lines. Knockdown of hsa_circ_0068631 inhibited the proliferation and migration of BC cells in vitro and in vivo. Mechanistically, an RNA pull-down assay and RNA immunoprecipitation assay revealed that eukaryotic translation initiation factor 4A3 (EIF4A3) could bind to hsa_circ_0068631 and c-Myc mRNA. Additionally, the expression of hsa_circ_0068631 was positively correlated with c-Myc, and the upregulation of hsa_circ_0068631 was a crucial factor for the dysregulation of c-Myc. Through an actinomycin D assay, we confirmed that the mRNA stability of c-Myc was influenced by hsa_circ_0068631 and EIF4A3. Furthermore, hsa_circ_0068631 could recruit EIF4A3 to increase c-Myc mRNA stability. Rescue assays manifesting depletion of c-Myc rescued the promotive effect of hsa_circ_0068631 overexpression on biological activities in BC. In conclusion, to our knowledge, this study is the first to unveil the role of hsa_circ_0068631 and the hsa_circ_0068631/EIF4A3/c-Myc axis in BC, providing a new target for BC treatment.

Dental pulp stem cell-derived small extracellular vesicle in irradiation-induced senescence

Small extracellular vesicles (sEV) facilitate signaling molecule transfer among cells. We examined the therapeutic efficacy of human dental pulp stem cell-derived sEV (hDPSC-sEV) against cellular senescence in an irradiated-submandibular gland mouse model. Seven-week-old mice were exposed to 25 Gy radiation and randomly assigned to control, phosphate-buffered saline (PBS), or hDPSC-sEV groups. At 18 days post-irradiation, saliva production was measured; histological and reverse transcription-quantitative PCR analyses of the submandibular glands were performed. The salivary flow rate did not differ significantly between the PBS and hDPSC-sEV groups. AQP5-expressing acinar cell numbers and AQP5 expression levels in the submandibular glands were higher in the hDPSC-sEV group than in the other groups. Furthermore, compared with non-irradiated mice, mice in the 25 Gy + PBS group showed a high senescence-associated-β-galactosidase-positive cell number and upregulated senescence-related gene (p16^INK4a, p19^Arf, p21) and senescence-associated secretory phenotypic factor (MMP3, IL-6, PAI-1, NF-κB, and TGF-β) expression, all of which were downregulated in the hDPSC-sEV group. Superoxide dismutase levels were lower in the PBS group than in the hDPSC-sEV group. In summary, hDPSC-sEV reduced inflammatory cytokine and senescence-related gene expression and reversed oxidative stress in submandibular cells, thereby preventing irradiation-induced cellular senescence. Based on these results, we hope to contribute to the development of innovative treatment methods for salivary gland dysfunction that develops after radiotherapy for head and neck cancer.

Identification of circRNA_001846 as putative non-small cell lung cancer biomarker

CircRNAs play diverse roles in the regulation of oncogenic processes, yet the roles of these circRNAs in non-small cell lung cancer (NSCLC) remain to be fully clarified. Herein, patterns of circRNA expression in NSCLC tissues and paracancerous tissues were assessed, and the relationships between these circRNAs and NSCLC patient clinical findings were assessed. NSCLC tissues were evaluated using a circRNA microarray approach, with Quantitative real‑time polymerase chain reaction (qPCR) qPCR being used to validate candidate circRNA expression levels in NSCLC patients peripheral blood samples. GEO2R was used to analyze the array data. SPSS23.0, GraphPad Prism, and Sigmaplot were utilized for statistical analyses. Overall, 114 circRNAs that were differentially expressed in NSCLC tissue relative to paracancerous tissue levels were identified, of which 77 and 37 were downregulated and upregulated, respectively. CircRNA_001846 were then chosen based on its differential expression score. Consistent with array findings, serum samples from NSCLC patients exhibited circRNA_001846 upregulation relative to those from healthy individuals. The circRNA_001846 was associated with tumor differentiation, lymph node metastasis, and node metastasis stage. Receiver operating characteristic (ROC) curves analyses revealed that levels of circRNA_001846 in the serum were capable of differentiating between individuals diagnosed with NSCLC and controls at a cut off of 3.9496, yielding respective sensitivity and specificity values of 78.2% and 81.1%, with an area under the curve (AUC) value of 0.872. When combined with carcinoembryonic antigen (CEA), this circRNA achieved an improved AUC value of 0.925. CircRNA_001846 may represent a promising diagnostic biomarker for NSCLC.

Circular RNAs as Novel Diagnostic Biomarkers and Therapeutic Targets in Kidney Disease

Circular RNAs (circRNAs) are a novel type of non-coding RNAs that have aroused growing attention in this decade. They are widely expressed in eukaryotes and generally have high stability owing to their special closed-loop structure. Many circRNAs are abundant, evolutionarily conserved, and exhibit cell-type-specific and tissue-specific expression patterns. Mounting evidence suggests that circRNAs have regulatory potency for gene expression by acting as microRNA sponges, interacting with proteins, regulating transcription, or directly undergoing translation. Dysregulated expression of circRNAs were found in many pathological conditions and contribute to the pathogenesis and progression of various disorders, including renal diseases. Recent studies have revealed that circRNAs may serve as novel reliable biomarkers for the diagnosis and prognosis prediction of multiple kidney diseases, such as renal cell carcinoma (RCC), acute kidney injury (AKI), diabetic kidney disease (DKD), and other glomerular diseases. Furthermore, circRNAs expressed by intrinsic kidney cells are shown to play a substantial role in kidney injury, mostly reported in DKD and RCC. Herein, we review the biogenesis and biological functions of circRNAs, and summarize their roles as promising biomarkers and therapeutic targets in common kidney diseases.

Early pregnancy prediction of spontaneous preterm birth before 32 completed weeks of pregnancy using plasma RNA: transcriptome discovery and initial validation of an RNA panel of markers

OBJECTIVE

To compare the second-trimester plasma cell-free (PCF) transcriptome of women who delivered at term with that of women with spontaneous preterm birth (sPTB) at or before 32 weeks of gestation and identify/validate PCF RNA markers present by 16 weeks of gestation.

DESIGN

Prospective case-control study.

SETTING

Academic tertiary care centre.

POPULATION

Pregnant women with known outcomes prospectively sampled.

METHODS

PCF RNAs extracted from women at 22-24 weeks of gestation (five sPTB up to 32 weeks and five at term) were hybridised to gene expression arrays. Differentially regulated RNAs for sPTB up to 32 weeks were initially selected based on P value compared with control (P < 0.01) and fold change (≥1.5×). Potential markers were then reordered by narrowness of distribution. Final marker selection was made by searching the Metacore™ database to determine whether the PCF RNAs interacted with a reported set of myometrial Preterm Initiator genes. RNAs were confirmed by quantitative reverse transcription polymerase chain reaction and tested in a second group of 40 women: 20 with sPTB up to 32 weeks (mean gestation 26.5 weeks, standard deviation ±2.6 weeks), 20 with spontaneous term delivery (40.1 ± 0.9 weeks) sampled at 16-19+5  weeks of gestation.

MAIN OUTCOME MEASURE

Identification of PCF RNAs predictive of sPTB up to 32 weeks.

RESULTS

Two hundred and ninety-seven PCR RNAs were differentially expressed in sPTB up to 32 weeks of gestation. Further selection retained 99 RNAs (86 mRNAs and 13 microRNAs) and five of these interacted in silica with seven Preterm Initiator genes. Four of five RNAs were confirmed and tested on the validation group. The expression of each confirmed PCF RNA was significantly higher in sPTB up to 32 weeks of gestation. In vitro study of the four mRNAs revealed higher expression in placentas of women with sPTB up to 32 weeks and the potential to interfere with myometrial quiescence.

CONCLUSIONS

The PCF RNA markers are highly associated with sPTB up to 32 weeks by 16 weeks of gestation.

TWEETABLE ABSTRACT

Women destined for spontaneous preterm birth can be identified by 16 weeks of gestation with a panel of maternal plasma RNAs.

Circular RNAs and their role in renal cell carcinoma: a current perspective

Circular RNAs (circRNAs) are a new class of long non-coding RNAs, that results from a special type of alternative splicing referred to as back-splicing. They are widely distributed in eukaryotic cells and demonstrate tissue-specific expression patterns in humans. CircRNAs actively participate in various important biological activities like gene transcription, pre-mRNA splicing, translation, sponging miRNA and proteins, etc. With such diverse biological functions, circRNAs not only play a crucial role in normal human physiology, as well as in multiple diseases, including cancer. In this review, we summarized our current understanding of circRNAs and their role in renal cell carcinoma (RCC), the most common cancer of kidneys. Studies have shown that the expression level of several circRNAs are considerably varied in RCC samples and RCC cell lines suggesting the potential role of these circRNAs in RCC progression. Several circRNAs promote RCC development and progression mostly via the miRNA/target gene axis making them ideal candidates for novel anti-cancer therapy. Apart from these, there are a few circRNAs that are significantly downregulated in RCC and overexpression of these circRNAs leads to suppression of RCC growth. Differential expression patterns and novel functions of circRNAs in RCC suggest that circRNAs can be utilized as potential biomarkers and therapeutic targets for RCC therapy. However, our current understanding of the role of circRNA in RCC is still in its infancy and much comprehensive research is needed to achieve clinical translation of circRNAs as biomarkers and therapeutic targets in developing effective treatment options for RCC.

CircRNAs and their regulatory roles in cancers

Circular RNAs (circRNAs), a novel type of non-coding RNAs (ncRNAs), have a covalently closed circular structure resulting from pre-mRNA back splicing via spliceosome and ribozymes. They can be classified differently in accordance with different criteria. As circRNAs are abundant, conserved, and stable, they can be used as diagnostic markers in various diseases and targets to develop new therapies. There are various functions of circRNAs, including sponge for miR/proteins, role of scaffolds, templates for translation, and regulators of mRNA translation and stability. Without m7G cap and poly-A tail, circRNAs can still be degraded in several ways, including RNase L, Ago-dependent, and Ago-independent degradation. Increasing evidence indicates that circRNAs can be modified by N-6 methylation (m6A) in many aspects such as biogenesis, nuclear export, translation, and degradation. In addition, they have been proved to play a regulatory role in the progression of various cancers. Recently, methods of detecting circRNAs with high sensitivity and specificity have also been reported. This review presents a detailed overview of circRNAs regarding biogenesis, biomarker, functions, degradation, and dynamic modification as well as their regulatory roles in various cancers. It’s particularly summarized in detail in the biogenesis of circRNAs, regulation of circRNAs by m6A modification and mechanisms by which circRNAs affect tumor progression respectively. Moreover, existing circRNA detection methods and their characteristics are also mentioned.

Role of circRNAs in neurodevelopment and neurodegenerative diseases

With the rapid development of sequencing technology, scientists have been able to study and acquire a better understanding of non-coding RNAs (ncRNAs). Circular RNAs (circRNAs), a unique class of ncRNAs with a special loop structure, have been found to possess modulatory properties with respect to various biological processes, such as interacting with nucleic acids or proteins. In addition to their tissue-specific expression and high conservation across species, circRNAs are abundant and dynamically expressed in the nervous system, especially in nerve synapse, indicating their potential regulation in synaptic plasticity or neuronal disorders. In this review, we discuss the characteristics of circRNAs and their common biological functions, as well as their significant role in neurodevelopment, drug addiction and neurodegenerative diseases, aiming to guide further disease diagnoses and efficient therapy.

The Roles of CircRNAs in Bladder Cancer: Biomarkers, Tumorigenesis Drivers, and Therapeutic Targets

Bladder cancer (BCa) is the most prevalent malignancy of the urinary system. Circular RNAs (circRNAs), a novel subtype of non-coding RNAs, play a crucial role in physiological and developmental processes. CircRNAs mainly function as regulators of splicing process and transcription, microRNA sponges, and protein brackets. Recent advances in understanding the pathogenesis of BCa have led to the identification of an abundance of dysregulated circRNAs associated with BCa. These aberrantly expressed circRNAs eventually lead to abnormalities in biological, genetic, and epigenetic information. In this review, we introduce the potential of circRNAs as biomarkers for BCa diagnosis and prognosis. Notably, diverse mechanisms have been proposed for circRNAs driving carcinogenesis, including increasing cell proliferation, promoting invasive and migratory capacity, enhancing endothelial–mesenchymal transition, sustaining stemness, and enabling resistance to chemotherapy. Importantly, a full understanding of circRNA mechanisms is needed to mine promising therapeutic approaches for targeting BCa. In this paper, we present the latest advances in circRNAs and systemically summarize the characteristics and mechanisms of circRNAs in BCa, providing potential perspectives for BCa treatment.

Circular RNAs: Novel Players in the Oxidative Stress-Mediated Pathologies, Biomarkers, and Therapeutic Targets

Oxidative stress (OxS) is a wildly described cause of damage to macromolecules, resulting in abnormal physiological conditions. In recent years, a few studies have shown that oxidation/antioxidation imbalance plays a significant role in developing diseases involving different systems and organs. However, the research on the circular RNA (circRNA) roles in OxS is still in its very infancy. Therefore, we hope to provide a comprehensive overview of the recent research that explored the function of circRNAs associated with OxS and its role in the pathogenesis of different diseases that affect different body systems like the nervous system, cardiovascular system, kidneys, and lungs. It provides the possibilities of using these circRNAs as superior diagnostic and therapeutic options for OxS associated with these disease conditions.

The Roles of Host Noncoding RNAs in Mycobacterium tuberculosis Infection

Tuberculosis remains a major health problem. Mycobacterium tuberculosis, the causative agent of tuberculosis, can replicate and persist in host cells. Noncoding RNAs (ncRNAs) widely participate in various biological processes, including Mycobacterium tuberculosis infection, and play critical roles in gene regulation. In this review, we summarize the latest reports on ncRNAs (microRNAs, piRNAs, circRNAs and lncRNAs) that regulate the host response against Mycobacterium tuberculosis infection. In the context of host-Mycobacterium tuberculosis interactions, a broad and in-depth understanding of host ncRNA regulatory mechanisms may lead to potential clinical prospects for tuberculosis diagnosis and the development of new anti-tuberculosis therapies.

Tumor-derived exosomal circRNA_102481 contributes to EGFR-TKIs resistance via the miR-30a-5p/ROR1 axis in non-small cell lung cancer

Exosomes are messengers for intercellular communication and signal transduction. Circular RNA (circRNA) abnormal expression and regulation are involved in the occurrence and development of a variety of tumors. In the present study, exosomes in the serum of five patients with non-small cell lung cancer (NSCLC) were isolated before and after EGFR-TKIs resistance, and the circRNA expression profile was screened using a circRNA microarray. The effects of the exosome circRNA_102481 on cell proliferation and apoptosis were analyzed. The interaction between miR-30a-5p and circRNA_102481 or ROR1 was predicted by starBase software, and was confirmed by RNA pull-down and dual-luciferase reporter assays. The results showed that exosomes containing circRNA_102481 were significantly up-regulated in NSCLC with EGFR-TKIs resistance (p<0.05), and that circRNA_102481 was mainly secreted by EGFR-TKIs resistance cell via exosomes (p<0.05). Both circRNA_102481 silencing and si-circRNA_102481 transported by exosomes could inhibit EGFR-TKIs resistance cell proliferation and promote cell apoptosis and circRNA_102481 overexpression could promote EGFR-TKIs sensitive cell proliferation and inhibit cell apoptosis in vitro (p<0.05). CircRNA_102481 served as a miR-30a-5p sponge to regulate ROR1 expression (p<0.05). Furthermore, the expression of circRNA_102481 in exosomes was associated with TNM stage, tumor differentiation status, brain metastasis, and PFS and OS duration. Therefore, it was concluded that tumor-derived exosomal circRNA_ 102481 could contribute to EGFR-TKIs resistance via the microRNA-30a-5p/ROR1 axis in NSCLC. Exosomal circRNA_102481 may serve as a novel diagnostic biomarker and a therapeutic target for EGFR-TKIs resistance in NSCLC.

Circular RNAs and Hepatocellular Carcinoma: New Epigenetic Players With Diagnostic and Prognostic Roles

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. Due to the lack of potent diagnosis and prognosis biomarkers and effective therapeutic targets, the overall prognosis of survival is poor in HCC patients. Circular RNAs (circRNAs) are a class of novel endogenous non-coding RNAs with covalently closed loop structures and implicated in diverse physiological processes and pathological diseases. Recent studies have demonstrated the involvement of circRNAs in HCC diagnosis, prognosis, development, and drug resistance, suggesting that circRNAs may be a class of novel targets for improving HCC diagnosis, prognosis, and treatments. In fact, some artificial circRNAs have been engineered and showed their therapeutic potential in treating HCV infection and gastric cancer. In this review, we introduce the potential of circRNAs as biomarkers for HCC diagnosis and prognosis, as therapeutic targets for HCC treatments and discuss the challenges in circRNA research and chances of circRNA application.

Circular RNA circHECTD1 facilitates glioma progression by regulating the miR-296-3p/SLC10A7 axis

Glioma is the most common type of primary brain tumor. Treatment options for recurrent gliomas include surgery, chemotherapy, and radiation therapy, but the clinical outcome is usually limited. In recent years, circular RNAs have been found to play a vital role in several human cancers. Gene Expression Omnibus database was utilized to verify the differentially expressed circRNAs. Then we detected that the expression of circular RNA circHECTD1 was significantly increased. The expression and function of circHECDT1 has not yet been reported in glioma. Then we confirmed that the level of circHECTD1 was significantly increased both in glioma tissues and cell lines, which is negatively correlated with the overall survival of patients. Knockdown of circHECTD1 inhibited proliferation and invasion in vitro, and also reduced the growth of tumor and prolonged the prognosis in vivo. Knockdown of circHECTD1 significantly elevated the miR-296-3p expression in LN229 and T98G cells. Luciferase reports and RNA immunoprecipitation data indicated that miR-296-3p was a direct target of circHECTD1 and that the miR-296-3p expression negatively regulated SLC10A7. Rescue experiments showed that the overexpression of SLC10A7 could impede the effects of circHECTD1 silencing on the proliferation and invasion of glioma cells. In this study, we identified that circHECTD1 regulates SLC10A7 by interacting with miR-296-3p in glioma cells. In conclusion, this study investigated a novel biomarker panel consisting of the circHECTD1/miR-296-3p/SLC10A7 axis, which is critical for glioma tumorigenesis and invasiveness and may represent a novel therapeutic target for intervening in glioma progression.

Microarray and Bioinformatics Analysis of Circular RNA Differential Expression in Newborns With Acute Respiratory Distress Syndrome

Previous studies pointed out that a variety of microRNAs (miRNAs) are involved in the pathogenesis of neonatal acute respiratory distress syndrome (NARDS) and play different roles in the pathological process. However, there have been few studies reporting the connection between circular RNA (circRNA) and NARDS, so the expression profile of circRNAs in newborns with acute respiratory distress syndrome remains largely unknown. In the present study, 10 samples obtained from remaining clinical blood samples of newborns hospitalized in a neonatal ward of the First Affiliated Hospital of Nanjing Medical University from January 2020 to October 2020 were divided into the "NARDS" group and "non-NARDS" group according to the Montelux standard and then were analyzed in microarray, and 10 other samples collected from the same place and from January 1, 2021 to August 31, 2021, were used to do RT-qPCR experiment. circRNA expression profiles, in which 741 circRNAs were downregulated and 588 were upregulated, were screened with circRNA high-throughput sequencing. Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of parent genes of the differentially expressed circRNAs revealed that these circRNAs may be related to the process of protein synthesis and metabolism in NARDS. Moreover, five circRNAs-hsa_circ_0058495, hsa_circ_0000367, hsa_circ_0005389, hsa_circ_0059571, and hsa_circ_0006608-were selected randomly among the top 10 circRNAs of the downregulated or upregulated expression profiles. Then, bioinformatics tools were used to predict correlative miRNA and its target genes, which were also subjected to the same bioinformatics analysis for further study. The top 30 enriched KEGG pathway analyses of the 125 target genes suggested that these target genes are widely involved in the synthesis and secretion of endocrine hormones, and the top 30 enriched GO terms based on the 125 target genes are also focused on the protein and DNA processing. Thus, the present results show that circRNAs could promote the inflammation of NARDS which may provide a new therapeutic direction and it can be used as molecular markers for early diagnosis of NARDS, but further molecular biology verification is needed to define the specific role of differentially expressed circRNAs in NARDS.

Correlation between serum circRNA and thyroid micropapillary carcinoma with cervical lymph node metastasis

The study aims to characterize the circular RNA (circRNA) expression profile that is functionally related with the invasiveness of papillary thyroid microcarcinoma (PTMC).A total of 13 pairs of female patients with non-invasive PTMC or lymph node metastasis PTMC (PTMC (L)) were included and the serum RNA was obtained. CircRNA microarray was performed to identify the circRNA expression profile. Real time-PCR was used to verify circRNA expression. Bioinformatic approaches were adopted to annotate the function of differentially expressed circRNAs and construct the circRNA-miRNA-mRNA network.In total, 400 significantly upregulated and 290 significantly downregulated circRNAs were identified in PTMC (L) compared with PTMC. Among them, 10 circRNAs were selected and validated by real time-PCR. Putative microRNAs (miRNAs) that could bind to the differentially expressed circRNAs were predicted. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of target genes of the differentially expressed circRNAs revealed that these circRNAs may play an important role in lymph node metastasis. Finally, circRNA targeted miRNAs were predicted and a circRNA-miRNA-mRNA network was constructed for hsa_circRNA_404686.Our results showed that several circRNAs, such as hsa_circRNA_404686, may serve as promising diagnostic marker for PTMC (L) in female.

The role of non-coding RNA network in atherosclerosis

Atherosclerosis is the primary culprit of cardiovascular and cerebrovascular diseases. Also, atherogenesis and the development of atherosclerosis involve endothelial cells, monocytes/macrophages, smooth myocytes, and others. Increasingly, studies have found that non-coding RNA (ncRNA) which can regulate apoptosis, pyroptosis, autophagy, proliferation, and monocyte migration participates in atherogenesis and progress of atherosclerosis by the above. The ncRNA networks may be essential in regulating the complicated process of atherosclerosis. Accordingly, this review delves into the regulatory roles of ncRNA, which were introduced previously. The answer above is particularly crucial to explain further the regulatory mechanism of ncRNA in cardiovascular disorders. Furthermore, we discuss the possibility and related research of ncRNAs as a biomarker and therapeutic target for the prevention, diagnosis, and treatment of atherosclerosis.

Circular RNAs in renal cell carcinoma: implications for tumorigenesis, diagnosis, and therapy

Renal cell carcinoma (RCC) is the most common malignant kidney tumor and has a high incidence rate. Circular RNAs (circRNAs) are noncoding RNAs with widespread distribution and diverse cellular functions. They are highly stable and have organ- and tissue-specific expression patterns. CircRNAs have essential functions as microRNA sponges, RNA-binding protein- and transcriptional regulators, and protein translation templates. Recent reports have shown that circRNAs are abnormally expressed in RCC and act as important regulators of RCC carcinogenesis and progression. Moreover, circRNAs have emerged as potential biomarkers for RCC diagnosis and prognosis and targets for developing new treatments. However, further studies are needed to better understand the functions of circRNAs in RCC. In this review, we summarize and discuss the recent research progress on RCC-associated circRNAs, with a focus on their potential for RCC diagnosis and targeted therapy.

Circular RNA circNRIP1 promotes migration and invasion in cervical cancer by sponging miR-629-3p and regulating the PTP4A1/ERK1/2 pathway

Emerging evidence indicates that circRNAs play essential roles in tumorigenesis and development. However, the role of circRNAs in cervical cancer (CC) remains unclear. CircRNA microarrays performed on the immortal cervical cell line H8 and the cervical cancer cell line SiHa were used to identify a circRNA, termed circNRIP1 (hsa_circ_0004771), which was upregulated in SiHa. QRT-PCR confirmed that circNRIP1 was upregulated in CC tissues, where its expression was correlated with lymphovascular space invasion. Besides, both in vitro and in vivo experiments demonstrated that circNRIP1 promotes cell proliferation, migration, and invasion. Additionally, we found that miR-629-3p induced tumor suppression by regulating PTP4A1 and the ERK1/2 pathway. Finally, we confirmed that circNRIP1 exerts its effect, at least partially, by sponging miR-629-3p and thereby regulating the PTP4A1/ERK1/2 pathway. Therefore, circNRIP1 may be useful as a potential prognostic biomarker and therapeutic target in CC patients.

Prospective Advances in Non-coding RNAs Investigation

Non-coding RNAs (ncRNAs) play significant roles in numerous physiological cellular processes and molecular alterations during pathological conditions including heart diseases, cancer, immunological disorders and neurological diseases. This chapter is focusing on the basis of ncRNA relation with their functions and prospective advances in non-coding RNAs particularly miRNAs investigation in the cardiovascular disease management.The field of ncRNAs therapeutics is a very fascinating and challenging too. Scientists have opportunity to develop more advanced therapeutics as well as diagnostic approaches for cardiovascular conditions. Advanced studies are critically needed to deepen the understanding of the molecular biology, mechanism and modulation of ncRNAs and chemical formulations for managing CVDs.

Circ-IGF1R inhibits cell invasion and migration in non-small cell lung cancer

BACKGROUND

Circular RNA (circRNA) is a novel molecular marker and target candidate that is closely associated with tumor invasion and migration. The mechanism of action of hsa_circ_0005035 (circ-IGF1R) in non-small cell lung cancer remains unclear. In this study, we aimed to study the mechanism of action of circ-IGF1R in lung cancer.

METHODS

We screened circ-IGF1R, one of the most notable differential expressions, from the Gene Expression Omnibus database, GSE104854, for further research. The expression level of circ-IGF1R was examined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in five different lung cancer cell lines and 50 pairs of lung cancer and adjacent tissues. Wound-healing and Transwell assays were used for verifying the biological function of circ-IGF1R. The effect of overexpressing circ-IGF1R on the transcriptome of whole lung cancer cells was explored in lung cancer cell lines using RNA-seq.

RESULTS

The expression level of circ-IGF1R was notably lower in lung cancer tissues and lung cancer cell lines than in the adjacent normal tissues and cells (P < 0.0001). In addition, the expression level of circ-IGF1R was associated with larger tumors (T2/T3/T4) and lymph node metastasis (N1/ N2/N3) (P < 0.05). The overexpression of circ-IGF1R significantly inhibited the invasion and migration of the lung cancer cells. The potential network of circ-IGF1R-miR-1270-VANGL2 was preliminarily determined, and the expression patterns of miR-1270 and VANGL2 were verified in lung cancer cell lines.

CONCLUSION

Circ-IGF1R may inhibit lung cancer invasion and migration through a potential network of circ-IGF1R-miR-1270-VANGL2.

Functions of circular RNAs and their potential applications in gastric cancer

Introduction: In recent years, circular RNAs (circRNAs) have emerged in the field of RNA research and their biological functions are now being gradually identified. circRNAs are divided into three categories: exonic circular RNAs (ecircRNAs), exon-intron circular RNAs (EIciRNAs), and intronic circular RNAs (ciRNAs). The circular structure of circRNAs confers unique biological characteristics upon them, such as enhanced stability over linear RNAs.Areas covered: circRNAs function to competitively bind with microRNAs (miRNAs) and proteins, participate in protein coding, regulate transcription, and form pseudogenes after reverse transcription. In gastric cancer, the circRNA-miRNA-mRNA axis is the most studied mechanisms underlying gastric cancer occurrence and development. Some specific and sensitive circRNAs, such as hsa_circ_102958, hsa_circ_0000520, and hsa_circ_0001017 may have potential diagnostic potential in early-stage gastric cancer. Abnormal expression of some circRNAs, including circ-LMTK2, circ-PSMC3, and circ-DLST are associated with the development of gastric cancer. Other circRNAs, such as hsa_circ_0001368, circ-ZFR, and circ-ERBB2, may also play important roles in gastric cancer treatment.Expert opinion: Exploring the roles of circRNAs in gastric cancer occurrence and development will help us to elucidate the functions of circRNAs and develop potential tools for early diagnosis and effective treatment of gastric cancer.

Circ_0006332 promotes growth and progression of bladder cancer by modulating MYBL2 expression via miR-143

In this study, we analyzed the role of circular RNAs in the growth and progression of bladder cancer. Direct Sanger sequencing and quantitative RT-PCR analysis showed that circ_0006332 was significantly upregulated in bladder cancer tissues. Sequencing analysis showed that circ_0006332 is generated from splicing of exons 8 and 9 of the MYBL2 transcript. Fluorescence in situ hybridization analysis showed that circ_0006332 was localized to the cytoplasm of bladder cancer cells. Dual luciferase reporter assays showed that miR-143 specifically bound to circ_0006332 and the 3’UTR of MYBL2. High expression of circ_006332 correlated with tumor-node-metastasis stages and muscular invasion in bladder cancer patients. Knockdown of circ_0006332 in bladder cancer cells decreased proliferation, colony formation and invasiveness. Circ_0006332 knockdown increased E-cadherin levels and decreased Vimentin, CCNB1 and P21 protein expression. This suggests that circ_0006332 promotes epithelial–mesenchymal transition and cell cycle progression. In vivo experiments in nude mice showed that circ_0006332 knockdown bladder cancer cells form significantly smaller tumors than the controls. Our study demonstrates that circ_0006332 promotes the growth and progression of bladder cancer by modulating MYBL2 expression by acting as a sponge for miR-143. Circ_0006332 is thus a potential early diagnostic marker of bladder cancer.

Serum circSETDB1 is a promising biomarker for predicting response to platinum-taxane-combined chemotherapy and relapse in high-grade serous ovarian cancer

Purpose

Circular RNAs (circRNAs) are emerging as promising biomarkers for various human malignancies. However, the application of circRNAs as non-invasive biomarkers in high-grade serous ovarian cancer (SOC) remains to be elucidated. Here, we aim to investigate the feasibility of using serum circSETDB1, a tumor-promoting circRNA generated from the SET domain bifurcated histone lysine methyltransferase 1 (SETDB1), known to be upregulated in SOC，as a biomarker for detecting SOC progression, predicting relapse, and evaluating the effectiveness of SOC treatment.

Methods

Serum circSETDB1 levels were measured using quantitative real-time RCR in 60 SOC patients (18 primary chemoresistance, 42 primary chemosensitive) and 60 healthy volunteers. Progression-free survival curve was calculated by Kaplan-Meier analysis. Diagnostic value was analyzed using receiver operating characteristic curve (ROC) method.

Results

Serum circSETDB1 expression is upregulated in SOC patients. Higher levels of circSETDB1 are positively associated with advanced clinical stage, lymph node metastasis of SOC patients. Notably, serum circSETDB1 levels are significantly increased in primary chemoresistance patients. Patients with higher levels of circSETDB1 have a shorter progression-free survival time. In addition, diagnostic value analyses revealed that serum circSETDB1 can distinguish patients with SOC from healthy volunteers as well as patients with primary chemoresistance from those with primary chemosensitivity.

Conclusion

Our data suggest that serum circSETDB1 may serve as a novel non-invasive biomarker for detecting SOC progression and predicting response to chemotherapy and relapse in high-grade serous ovarian cancer.