Polymorphisms and expression pattern of circular RNA circ-ITCH contributes to the carcinogenesis of hepatocellular carcinoma

Identification of circRNA-disease associations via multi-model fusion and ensemble learning

Circular RNA (circRNA) is a common non-coding RNA and plays an important role in the diagnosis and therapy of human diseases, circRNA-disease associations prediction based on computational methods can provide a new way for better clinical diagnosis. In this article, we proposed a novel method for circRNA-disease associations prediction based on ensemble learning, named ELCDA. First, the association heterogeneous network was constructed via collecting multiple information of circRNAs and diseases, and multiple similarity measures are adopted here, then, we use metapath, matrix factorization and GraphSAGE-based models to extract features of nodes from different views, the final comprehensive features of circRNAs and diseases via ensemble learning, finally, a soft voting ensemble strategy is used to integrate the predicted results of all classifier. The performance of ELCDA is evaluated by fivefold cross-validation and compare with other state-of-the-art methods, the experimental results show that ELCDA is outperformance than others. Furthermore, three common diseases are used as case studies, which also demonstrate that ELCDA is an effective method for predicting circRNA-disease associations.

Involvement of CircRNAs in regulating The "New Generation of Cancer Hallmarks": A Special Depiction on Hepatocellular Carcinoma

The concept of 'Hallmarks of Cancer' is an approach of reducing the enormous complexity of cancer to a set of guiding principles. As the underlying mechanism of cancer are portrayed, we find that we gain insight and additional aspects of the disease arise. The understanding of the tumor microenvironment (TME) brought a new dimension and led to the discovery of novel hallmarks such as senescent cells, non-mutational epigenetic reprogramming, polymorphic microbiomes and unlocked phenotypic plasticity. Circular RNAs (circRNAs) are single-stranded, covalently closed RNA molecules that are ubiquitous across all species. Recent studies on the circRNAs have highlighted their crucial function in regulating the formation of human malignancies through a range of biological processes. The primary goal of this review is to clarify the role of circRNAs in the most common form of liver cancer, hepatocellular carcinoma (HCC). This review also addressed the topic of how circRNAs affect HCC hallmarks, including the new generation hallmarks. Finally, the enormous applications that these rapidly expanding ncRNA molecules serve in the functional and molecular development of effective HCC diagnostic biomarkers and therapeutic targets.

CircRNA-regulated glucose metabolism in ovarian cancer: an emerging landscape for therapeutic intervention

Ovarian cancer (OC) has the highest mortality rate among female reproductive system tumours, with limited efficacy of traditional treatments and 5-year survival rates that rarely exceed 40%. Circular RNA (circRNA) is a stable endogenous circular RNA that typically regulates protein expression by binding to downstream miRNA. It has been demonstrated that circRNAs play an important role in the proliferation, migration, and glucose metabolism (such as the Warburg effect) of OC and can regulate the expression of glucose metabolism-related proteins such as GLUT1 and HK2, promoting anaerobic glycolysis of cancer cells, increasing glucose uptake and ATP production, and affecting energy supply and biosynthetic substances to support tumour growth and invasion. This review summarises the formation and characteristics of circRNAs and focuses on their role in regulating glucose metabolism in OC cells and their potential therapeutic value, providing insights for identifying new therapeutic targets.

WNT/β-catenin signaling in hepatocellular carcinoma: The aberrant activation, pathogenic roles, and therapeutic opportunities

Hepatocellular carcinoma (HCC) is a liver cancer, highly heterogeneous both at the histopathological and molecular levels. It arises from hepatocytes as the result of the accumulation of numerous genomic alterations in various signaling pathways, including canonical WNT/β-catenin, AKT/mTOR, MAPK pathways as well as signaling associated with telomere maintenance, p53/cell cycle regulation, epigenetic modifiers, and oxidative stress. The role of WNT/β-catenin signaling in liver homeostasis and regeneration is well established, whereas in development and progression of HCC is extensively studied. Herein, we review recent advances in our understanding of how WNT/β-catenin signaling facilitates the HCC development, acquisition of stemness features, metastasis, and resistance to treatment. We outline genetic and epigenetic alterations that lead to activated WNT/β-catenin signaling in HCC. We discuss the pivotal roles of CTNNB1 mutations, aberrantly expressed non-coding RNAs and complexity of crosstalk between WNT/β-catenin signaling and other signaling pathways as challenging or advantageous aspects of therapy development and molecular stratification of HCC patients for treatment.

A spotlight on the interplay between Wnt/β-catenin signaling and circular RNAs in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the deadliest cancers due to multifocal development and distant metastasis resulting from late diagnosis. Consequently, new approaches to HCC diagnosis and treatment are required to reduce mortality rates. A large body of evidence suggests that non-coding RNAs (ncRNAs) are important in cancer initiation and progression. Cancer cells release many of these ncRNAs into the blood or urine, enabling their use as a diagnostic tool. Circular RNAs (CircRNAs) are as a members of the ncRNAs that regulate cancer cell expansion, migration, metastasis, and chemoresistance through different mechanisms such as the Wnt/β-catenin Signaling pathway. The Wnt/β-catenin pathway plays prominent roles in several biological processes including organogenesis, stem cell regeneration, and cell survival. Aberrant signaling of both pathways mentioned above could affect the progression and metastasis of many cancers, including HCC. Based on several studies investigated in the current review, circRNAs have an effect on HCC formation and progression by sponging miRNAs and RNA-binding proteins (RBPs) and regulating the Wnt/β-catenin signaling pathway. Therefore, circRNAs/miRNAs or RBPs/Wnt/β-catenin signaling pathway could be considered promising prognostic and therapeutic targets in HCC.

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.

Targeting a novel circITCH/miR-421/BTG1 axis is effective to suppress the malignant phenotypes in hepatocellular carcinoma (HCC) cells

Circular RNA-based competing endogenous RNA (ceRNA) networks contribute to the initiation and development of various types of cancer, including hepatocellular carcinoma (HCC). Although a novel circular RNA itchy E3 ubiquitin protein ligase (circITCH) is identified as a tumor suppressor in HCC, its detailed molecular mechanisms have not been fully delineated. The present study was designed to resolve this issue, and we firstly verified that circITCH suppressed the malignant phenotypes in HCC cells by regulating a novel miR-421/B-cell translocation gene 1 (BTG1) axis. Specifically, through performing the Real-Time qPCR analysis, we noticed that circITCH expression in HCC tumor tissues or cell lines were significantly lower than that in adjacent normal tissues or normal hepatocytes, and the expression levels of circITCH were negatively correlated with tumor size and TNM stage in HCC patients. Next, our functional experiments confirmed that overexpression of circITCH induced cell cycle arrest and apoptosis, and reduced cell viability and colony forming ability in Hep3B and Huh7 cells. Mechanically, bioinformatics analysis, RNA immunoprecipitation and luciferase reporter assay demonstrated that circITCH served as RNA sponges for miR-421 to elevate BTG1 levels in HCC cells. The rescuing experiments verified that upregulation of miR-421 promoted cell viability and colony formation, and reduced apoptosis, which were abrogated by overexpression of circITCH or BTG1. In conclusion, this study identified a novel circITCH/miR-421/BTG1 axis that restrained the development of HCC, and our findings provided novel biomarkers for the treatment of this disease.

Circular RNA ITCH increases sorafenib-sensitivity in hepatocellular carcinoma via sequestering miR-20b-5p and modulating the downstream PTEN-PI3K/Akt pathway

BACKGROUNDS

Sorafenib-resistance leads to poor prognosis and high mortality in advanced hepatocellular carcinoma (HCC), and this study aims to investigate the functional role of a circular RNA ITCH (circITCH) in regulating the sorafenib-resistance of HCC and its underlying mechanisms.

METHODS

The expression of circITCH in HCC tissues and cell lines were detected by performing quantitative real-time polymerase chain reaction. Sorafenib-resistant HCC cells were transfected with PLCDH-circITCH to upregulate circITCH and intervened with sorafenib, and MTT assay, flow cytometry and transwell assay were used to test the cell viability, apoptosis and migration ability, respectively. The downstream target of circITCH were explored by using bioinformatic analysis, dual luciferase reporter system and Western blot.

RESULTS

CircITCH was significantly down-regulated in HCC tissues and cell lines, compared with their normal counterparts. Especially, in contrast with the sorafenib-sensitive HCC cells, continuous sorafenib treatment decreased the expression levels of circITCH in the sorafenib-resistant HCC cells. Overexpression of circITCH increased sorafenib-sensitivity, promoted cell apoptosis and reduced cell migration abilities in the sorafenib-resistant HCC cells. Mechanically, circITCH elevated PTEN expression to inactivate the PI3K/Akt signals through negatively regulating miR-20b-5p in HCC, and upregulating miR-20b-5p or inhibiting PTEN abolished the enhancing effect of circITCH overexpression on sorafenib-induced cytotoxicity in sorafenib-resistant HCC cells.

CONCLUSION

Taken together, this study proves that circITCH enhances sorafenib-sensitivity in sorafenib-resistant HCC cells via regulating the miR-20b-5p/PTEN/PI3K/Akt signaling cascade, which highlights the potential value of circITCH as a target for enhancing the sorafenib-sensitivity in HCC.

The potential value of plasma Circ-ITCH in hepatocellular carcinoma patients with current hepatitis C virus infection

BACKGROUND

There is an obvious need to diagnose hepatocellular carcinoma using novel non-invasive and sensitive biomarkers. Circular RNAs have recently attracted great interest as promising biomarkers and treatment targets. However, their function in hepatocellular carcinoma whose etiology related to hepatitis C has been rarely studied.

AIM OF WORK

The current study was conducted to analyze differential expression of circ-ITCH in plasma of Egyptian HCC patients with concomitant HCV infection, compared to normal control subjects, to investigate its correlation with liver function parameters, and to determine the possible diagnostic ability of circ-ITCH in plasma as a non-invasive marker, compared to its linear counterpart.

RESULTS

The results showed that the relative expression of circ-ITCH was significantly higher in the plasma of HCC patients (P<0.05). Moreover, when comparing its expression in the metastatic and non-metastatic subgroups, it was significantly higher in the non-metastatic HCC group compared to control group (P<0.05). Circ-ITCH was positively correlated with liver enzymes AST, ALT (P<0.001), also was significantly higher in HCC child C patients. To evaluate the potential diagnostic value of circ-ITCH in plasma, a ROC curve was generated, the AUC was 0.661, (95% CI: 0.5433-0.778) with a sensitivity and specificity 65% and 70% respectively.

CONCLUSION

The results revealed that circ-ITCH is-with no doubt-involved in the pathogenesis of HCC and its high level may be related to HCV infection, further researches in this area will certainly make great contributions in understanding. In conclusion our results suggested that circ-ITCH may be used as a noninvasive diagnostic marker and a promising therapeutic target for HCC.

CircRNA ITCH: Insight Into Its Role and Clinical Application Prospect in Tumor and Non-Tumor Diseases

CircRNA E3 ubiquitin protein ligase (ITCH) (circRNA ITCH, circ-ITCH), a stable closed-loop RNA derived from the 20q11.22 region of chromosome 20, is a new circRNA discovered in the cytoplasm in recent decades. Studies have shown that it does not encode proteins, but regulates proteins expression at different levels. It is down-regulated in tumor diseases and is involved in a number of biological activities, including inhibiting cell proliferation, migration, invasion, and promoting apoptosis. It can also alter disease progression in non-tumor disease by affecting the cell cycle, inflammatory response, and critical proteins. Circ-ITCH also holds a lot of promise in terms of tumor and non-tumor clinical diagnosis, prognosis, and targeted therapy. As a result, in order to aid clinical research in the hunt for a new strategy for diagnosing and treating human diseases, this study describes the mechanism of circ-ITCH as well as its clinical implications.

Hotspots and development frontiers of circRNA based on bibliometric analysis

Background and purpose

Circular RNAs (circRNAs) are a big group of members of the noncoding RNA family following long non-coding RNA and microRNA. They play a regulatory role in many biological processes. Analyzing their current research status and future development trends is conducive to a more comprehensive understanding of circRNAs and contributes to the dedication to the biological field.

Methods

The literature on circRNA from 2000 to 2021 in the Web of Science Core Collection of the Web of Science database with “circular RNA” as the subject was searched. R Studio's Bibliometrix package and biblioshiny software were used for publication trend analysis, citation analysis, keyword analysis, author analysis, research institution analysis, source analysis, country analysis, and collaboration analysis for all documents and highly cited documents.

Results

From 2000 to 2021, 3,186 circRNA-related articles were published worldwide, of which 193 were highly cited. The number of published articles had shown an explosive increase after 2013. These articles were mainly from Chinese research institutions and authors, but the country with the highest average number of citations per year in highly cited documents was Germany. Scientific research institutions came from countries represented by Germany, USA, China, Australia and Canada all had different degrees of cooperation. The theme and key points of the research had evolved over time from expression to the role and mechanism of circRNA in diseases, especially in cancer. CDR1as, circFOXO3, circHIPK3, circITCH, circMTO1, circSMARCA5 and circZNF609 are circRNAs that are mainly studied currently, their studies mainly involve cell biology, biological functions and cancer. The future research direction and trend would still be the application of circRNA in diseases.

Conclusion

The basic situation and development trend of circRNA related research we described provide a direction for future research.

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The study systematically analyzed all articles and highly cited (H-cited) articles related to circRNA published in the past 20 years based on bibliometric analysis;

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The main research content include main information, the number of articles published each year, the annual citations, the main keywords, the sources, the authors, the institutions and countries, the evolution and trend of the themes, the cooperation relationship of the studies, circRNAs that are mainly studied currently, etc.

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The article is going to describe the basic situation and development trend of circRNA related research and provide direction for research in this field by revealing these contents.

RNMFLP: Predicting circRNA-disease associations based on robust nonnegative matrix factorization and label propagation

Circular RNAs (circRNAs) are a class of structurally stable endogenous noncoding RNA molecules. Increasing studies indicate that circRNAs play vital roles in human diseases. However, validating disease-related circRNAs in vivo is costly and time-consuming. A reliable and effective computational method to identify circRNA-disease associations deserves further studies. In this study, we propose a computational method called RNMFLP that combines robust nonnegative matrix factorization (RNMF) and label propagation algorithm (LP) to predict circRNA-disease associations. First, to reduce the impact of false negative data, the original circRNA-disease adjacency matrix is updated by matrix multiplication using the integrated circRNA similarity and the disease similarity information. Subsequently, the RNMF algorithm is used to obtain the restricted latent space to capture potential circRNA-disease pairs from the association matrix. Finally, the LP algorithm is utilized to predict more accurate circRNA-disease associations from the integrated circRNA similarity network and integrated disease similarity network, respectively. Fivefold cross-validation of four datasets shows that RNMFLP is superior to the state-of-the-art methods. In addition, case studies on lung cancer, hepatocellular carcinoma and colorectal cancer further demonstrate the reliability of our method to discover disease-related circRNAs.

The functional roles of the circRNA/Wnt axis in cancer

CircRNAs, covalently closed noncoding RNAs, are widely expressed in a wide range of species ranging from viruses to plants to mammals. CircRNAs were enriched in the Wnt pathway. Aberrant Wnt pathway activation is involved in the development of various types of cancers. Accumulating evidence indicates that the circRNA/Wnt axis modulates the expression of cancer-associated genes and then regulates cancer progression. Wnt pathway-related circRNA expression is obviously associated with many clinical characteristics. CircRNAs could regulate cell biological functions by interacting with the Wnt pathway. Moreover, Wnt pathway-related circRNAs are promising potential biomarkers for cancer diagnosis, prognosis evaluation, and treatment. In our review, we summarized the recent research progress on the role and clinical application of Wnt pathway-related circRNAs in tumorigenesis and progression.

Circular RNA CircITCH (has-circ-0001141) suppresses hepatocellular carcinoma (HCC) progression by sponging miR-184

Aberrant expression of circular RNA (circRNA) is involved in the occurrence of various diseases and tumor development, in which plays a vital role, including hepatocellular carcinoma (HCC). Nevertheless, the regulation mechanism and biological function of circITCH in hepatocellular carcinoma (HCC) remain unclear. The expression level of circular RNA itchy E3 ubiquitin protein ligase (circ-ITCH) was identified and validated by real-time polymerase-chain reaction (RT-qPCR) in HCC cell lines. The stability of circITCH was confirmed by Ribonuclease R (RNase R) assay. Subsequently, through silencing and overexpression of circITCH to investigate the functional roles of circITCH in HCC proliferation, invasion, and apoptosis. We also carried out bioinformatics analysis, luciferase reporter assays to define the relationship between microRNA (miR)-184 and circITCH. Moreover, xenograft mouse models and immunohistochemistry were employed to assess the function of circITCH in HCC. CircITCH (hsa_circ_0001141) was a stable circRNA and downregulated in HCC cells. Overexpression of circITCH inhibited cell proliferation, migration, invasion, and promoted apoptosis in vitro and in vivo, whereas knockdown of circITCH had the opposite effects. Mechanistically, miR-184 could be sponged by circITCH, and its overexpression could mitigate the suppressive effects of circITCH overexpression on HCC progression. Through biological website to predict the target genes of miR-184 may be combined. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to investigate mRNAs with significant functional enrichment and pathways, also which its relationship with HCC-related pathway and immune cells. Our findings reveal that circITCH served as a repressor to restrain HCC malignancy via miR-184. Therefore, circITCH may serve as a potential prognostic marker and therapeutic target for HCC.

Abbreviations: HCC: hepatocellular carcinoma; CircRNA: Circular RNA; miRNA: MicroRNA; Circ-ITCH: circular RNA itchy E3 ubiquitin protein ligase; RT-qPCR: real-time polymerase-chain reaction; RNase R: Ribonuclease R; CeRNA: competing endogenous RNAs; SiRNA: small interfering RNA

The roles of E3 ligases in Hepatocellular carcinoma

Hepatocarcinogenesis is a complex multistep biological process involving genetic and epigenetic alterations that are accompanied by activation of oncoproteins and inactivation of tumor suppressors, which in turn results in Hepatocellular carcinoma (HCC), one of the common tumors with high morbidity and mortality worldwide. The ubiquitin-proteasome system (UPS) is the key to protein degradation and regulation of physiological and pathological processes, and E3 ligases are key enzymes in the UPS that contain a variety of subfamily proteins involved in the regulation of some common signal pathways in HCC. There is growing evidence that many structural or functional dysfunctions of E3 are engaged in the development and progression of HCC. Herein, we review recent research advances in HCC-associated E3 ligases, describe their structure, classification, functional roles, and discuss some mechanisms of the abnormal activation or inactivation of the HCC-associated signal pathway due to the binding of E3 to known substrates. In addition, given the success of proteasome inhibitors in the treatment of malignant cancers, we characterize the current knowledge and future prospects for targeted therapies against aberrant E3 in HCC.

ITCH E3 Ubiquitin Ligase downregulation compromises hepatic degradation of branched-chain amino acids

Objective

Metabolic syndrome, obesity, and steatosis are characterized by a range of dysregulations including defects in ubiquitin ligase tagging proteins for degradation. The identification of novel hepatic genes associated with fatty liver disease and metabolic dysregulation may be relevant to unravelling new mechanisms involved in liver disease progression

Methods

Through integrative analysis of liver transcriptomic and metabolomic obtained from obese subjects with steatosis, we identified itchy E ubiquitin protein ligase (ITCH) as a gene downregulated in human hepatic tissue in relation to steatosis grade. Wild-type or ITCH knockout mouse models of non-alcoholic fatty liver disease (NAFLD) and obesity-related hepatocellular carcinoma were analyzed to dissect the causal role of ITCH in steatosis

Results

We show that ITCH regulation of branched-chain amino acids (BCAAs) degradation enzymes is impaired in obese women with grade 3 compared with grade 0 steatosis, and that ITCH acts as a gatekeeper whose loss results in elevation of circulating BCAAs associated with hepatic steatosis. When ITCH expression was specifically restored in the liver of ITCH knockout mice, ACADSB mRNA and protein are restored, and BCAA levels are normalized both in liver and plasma

Conclusions

Our data support a novel functional role for ITCH in the hepatic regulation of BCAA metabolism and suggest that targeting ITCH in a liver-specific manner might help delay the progression of metabolic hepatic diseases and insulin resistance.

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ITCH expression is reduced in liver during NAFLD.

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Transcriptomics analysis of liver in obese women highlighted the interplay between ITCH and genes involved in BCAA degradation.

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Modulation of ITCH in models of metabolic hepatic diseases supported the association between ITCH and BCAA metabolism.

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Targeting ITCH in a liver specific manner might help to delay the progression of metabolic hepatic diseases and insulin resistance.

Emerging roles of circular RNAs in liver cancer

Hepatocellular carcinoma and cholangiocarcinoma are the most common primary liver tumours, whose incidence and associated mortality have increased over recent decades. Liver cancer is often diagnosed late when curative treatments are no longer an option. Characterising new molecular determinants of liver carcinogenesis is crucial for the development of innovative treatments and clinically relevant biomarkers. Recently, circular RNAs (circRNAs) emerged as promising regulatory molecules involved in cancer onset and progression. Mechanistically, circRNAs are mainly known for their ability to sponge and regulate the activity of microRNAs and RNA-binding proteins, although other functions are emerging (e.g. transcriptional and post-transcriptional regulation, protein scaffolding). In liver cancer, circRNAs have been shown to regulate tumour cell proliferation, migration, invasion and cell death resistance. Their roles in regulating angiogenesis, genome instability, immune surveillance and metabolic switching are emerging. Importantly, circRNAs are detected in body fluids. Due to their circular structure, circRNAs are often more stable than mRNAs or miRNAs and could therefore serve as promising biomarkers - quantifiable with high specificity and sensitivity through minimally invasive methods. This review focuses on the role and the clinical relevance of circRNAs in liver cancer, including the development of innovative biomarkers and therapeutic strategies.

Lidocaine Inhibits Hepatocellular Carcinoma Development by Modulating circ_ITCH/miR-421/CPEB3 Axis

BACKGROUND

Lidocaine plays an anticancer role in hepatocellular carcinoma. Nevertheless, the mechanism of lidocaine in hepatocellular carcinoma remains largely unclear.

AIMS

This study aims to assess the function of lidocaine and explore the potential regulatory mechanism.

METHODS

Hepatocellular carcinoma cells were challenged via lidocaine. Cell proliferation, apoptosis, migration, and invasion were detected via colony formation, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, flow cytometry, Western blot, and transwell analyses. Circular RNA itchy E3 ubiquitin protein ligase (circ_ITCH), microRNA-421 (miR-421), and cytoplasmic polyadenylation element-binding protein 3 (CPEB3) abundances were detected via quantitative reverse transcription polymerase chain reaction or Western blot. The relationship between miR-421 and circ_ITCH or CPEB3 was tested via dual-luciferase reporter analysis. The role of circ_ITCH in lidocaine-challenged cell growth in vivo was assessed via xenograft model.

RESULTS

Lidocaine inhibited hepatocellular carcinoma cell proliferation by decreasing colony formation and cell viability. Lidocaine suppressed hepatocellular carcinoma cell migration and invasion and promoted apoptosis. circ_ITCH and CPEB3 levels were decreased in hepatocellular carcinoma tissues and cells, and were restored in cells via lidocaine treatment. circ_ITCH knockdown weakened the suppressive effect of lidocaine on hepatocellular carcinoma development, which was abolished via CPEB3 overexpression. circ_ITCH could modulate CPEB3 by competitively binding with miR-421. miR-421 knockdown mitigated the effect of circ_ITCH silence in lidocaine-challenged cells. circ_ITCH knockdown increased xenograft tumor growth.

CONCLUSIONS

Lidocaine represses hepatocellular carcinoma cell proliferation, migration, and invasion and promotes apoptosis via regulating circ_ITCH/miR-421/CPEB3 axis, indicating a new insight into the mechanism of lidocaine in hepatocellular carcinoma.

Involvement of the circular RNA/microRNA/glucose-6-phosphate dehydrogenase axis in the pathological mechanism of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death worldwide with high mortality. The incidence of HCC is increasing in China. Abnormal activation of glucose-6-phosphate dehydrogenase (G6PD) exists in all malignant tumors, including HCC, and is closely related to the development of HCC. In addition, the differential expression of non-coding RNAs is closely related to the development of HCC. This systematic review focuses on the relationship between G6PD, HCC, and non-coding RNA, which form the basis for the circRNA/miRNA/G6PD axis in HCC. The circular RNA (circRNA)/microRNA (miRNA)/G6PD axis is involved in development of HCC. We proposed that non-coding RNA molecules of the circRNA/miRNA/G6PD axis may be novel biomarkers for the pathological diagnosis, prognosis, and targeted therapy of HCC.

CircITCH: A Circular RNA With Eminent Roles in the Carcinogenesis

Circular RNAs (circRNAs) are a group of long non-coding RNAs with enclosed structure generated by back-splicing events. Numerous members of these transcripts have been shown to affect carcinogenesis. Circular RNA itchy E3 ubiquitin protein ligase (circITCH) is a circRNA created from back splicing events in ITCH gene, a protein coding gene on 20q11.22 region. ITCH has a role as a catalyzer for ubiquitination through both proteolytic and non-proteolytic routes. CircITCH is involved in the pathetiology of cancers through regulation of the linear isoform as well as serving as sponge for several microRNAs, namely miR-17, miR-224, miR-214, miR-93-5p, miR-22, miR-7, miR-106a, miR-10a, miR-145, miR-421, miR-224-5p, miR-197 and miR-199a-5p. CircITCH is also involved in the modulation of Wnt/β-catenin and PTEN/PI3K/AKT pathways. Except from a single study in osteosarcoma, circITCH has been found to exert tumor suppressor role in diverse cancers. In the present manuscript, we provided a comprehensive review of investigations that reported function of circITCH in the carcinogenesis.

Rs4911154 of circ-ITCH aggravated tumor malignancy of thyroid nodules via the circ-ITCH/miR-22-3p/CBL axis

Recent evidence revealed an inhibitory effect of circ-ITCH on the progression of papillary thyroid cancer via affecting the circ-ITCH/miR-22-3p/CBL axis. Rs4911154, an SNP located in circ-ITHC, was previously reported to be significantly associated with an increased risk of hepatocellular carcinoma. Ultrasound testing was used to evaluate the doubling time of thyroid nodules. 202 patients diagnosed with thyroid nodule disorders were divided into three groups according to their genotypes at rs4911154. We found that the A allele was correlated with a shortening doubling time of thyroid nodules. Moreover, the A allele contributed to reduced expression of circ-ITCH/CBL and increased expression of miR-22-3p. Besides, decreased tissue apoptosis was linked to the A allele. Luciferase assays indicated that miR-22-3p could effectively suppress the luciferase activities of CBL and circ-ITCH. Furthermore, manual up-regulation of miR-22-3p effectively suppressed the expression of CBL, while CBL siRNA apparently abolished circ-ITCH induced CBL upregulation, reduced proliferation and increased apoptosis of K1 and TPC-1 cells. A signaling pathway of circ-ITCH/miR-22-3p/CBL axis was established to explain the effect of SNP of circ-ITCH in thyroid tumor malignancy. Compared with the G allele, the A allele in rs4911154 contributed to the malignancy of thyroid nodules with decreased doubling time and down-regulated CBL expression.

Inflammation-Related circRNA Polymorphism and Ischemic Stroke Prognosis

CircRNAs belong to a novel class of noncoding RNAs that are generated by exons of genes by alternative mRNA splicing and involved in pathophysiological processes of ischemic stroke by regulating neuro-inflammation. A total of 982 patients were enrolled in our study for stroke recovery analysis. The aim of our study was to first explore the association between the inflammation-related circRNA polymorphism and functional outcome 3 months after ischemic stroke by using multivariate logistic regression model. Next, we further investigated the role of circRNA polymorphism in predicting stroke recurrence by using Cox proportional hazard regression model. Five circRNA polymorphisms were genotyped by using polymerase chain reaction and ligation detection reaction method. We identified circ-STAT3 (signal transducer and activator of transcription) rs2293152 GG genotype to be associated with poorer recovery 90 days after stroke (OR = 1.452, 95% CI: 1.165-4.362, p = 0.016). After adjusting for confound factors, the association for rs2293152 with 3 months outcome after IS was stronger, suggesting a mechanism that rs2293152 is an independent risk factor for stroke recovery (OR = 2.255, 95% CI: 1.034-2.038, p = 0.031). However, no other circRNA polymorphisms (circ-DLGAP4 rs41274714, circ-TRAF2 rs10870141, circ-ITCH rs10485505, rs4911154) were associated with functional outcome 3 months after stroke in any genetic models. Subgroup analysis revealed that the negative effect of rs2293152 GG genotype was greater in female and older patients, subjects with history of hypertension. Additionally, all the circRNA polymorphisms were not correlated with recurrent risk of ischemic stroke. Our results indicated that circ-STAT3 might be a novel biomarker for predicting functional outcome after stroke and an important contributor to the ischemic stroke recovery.

CircRNA circ-ITCH improves renal inflammation and fibrosis in streptozotocin-induced diabetic mice by regulating the miR-33a-5p/SIRT6 axis

Diabetic nephropathy (DN) seriously affects the people's life and health in China. This study aimed to investigate the effect of circRNA circ-ITCH on improving DN by regulating the miR-33a-5p/SIRT6 axis and the possible mechanism of action. High glucose (HG)-induced rat mesangial cells (RMCs) were used to simulate the DN in vitro. Reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis were conducted to detect the gene or protein expression. Cell Counting Kit-8 (CCK-8) and wound healing assays were performed to estimate the cell viability and migration capability. Immunofluorescence and enzyme-linked immunosorbent assay (ELISA) were used to detect the α-Smooth Muscle Actin (α-SMA) expression and levels of inflammatory factors. The potential associations between circ-ITCH and miR-33a-5p, miR-33a-5p and SIRT6 in RMCs were measured via dual-luciferase reporter assay. Streptozotocin (STZ) was used to induce the diabetic mice. Blood glucose and serum insulin of mice were determined by corresponding kits, and blood urea nitrogen (BUN) and serum creatinine (SCr) were measured using an automatic biochemical analyzer. Hematoxylin and eosin (H&E) staining and periodic acid-Schiff (PAS) staining were applied to observe the degree of pathological injury and fibrosis of renal tissues. The results of the present study revealed that circ-ITCH expression was obviously decreased in HG-induced RMCs. In addition, circ-ITCH overexpression inhibited the viability, migration, fibrosis and inflammatory response of HG-induced RMCs. Further experiments confirmed that miR-33a-5p may be a direct target of circ-ITCH and SIRT6 may be a direct target of miR-33a-5p. Notably, the miR-33a-5p mimic or shRNA-SIRT6 were discovered to reverse the inhibitory effects of circ-ITCH on the proliferation, migration, fibrosis and inflammatory response of HG-induced RMCs. Furthermore, circ-ITCH overexpression ameliorated renal inflammation and fibrosis in STZ-induced diabetic mice. In conclusion, circ-ITCH alleviated renal inflammation and fibrosis in STZ-induced diabetic mice by regulating the miR-33a-5p/SIRT6 axis.Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Author 1 Given name: [ChunYang] Last name [Xu]. Author 2 Given name: [DingBo] Last name [Xu]. Author 3 Given name: [YongHua] Last name [Liu]. Author 4 Given name: [Juanjuan] Last name [Jiang]. Also, kindly confirm the details in the metadata are correct.ok.

Current Molecular Biology and Therapeutic Strategy Status and Prospects for circRNAs in HBV-Associated Hepatocellular Carcinoma

Circular RNAs (circRNAs) are newly classified noncoding RNA (ncRNA) members with a covalently closed continuous loop structure that are involved in immune responses against hepatitis B virus (HBV) infections and play important biological roles in the occurrence and pathogenesis of HCC progression. The roles of circRNAs in HBV-associated HCC (HBV-HCC) have gained increasing attention. Substantial evidence has revealed that both tissue and circulating circRNAs may serve as potential biomarkers for diagnostic, prognostic and therapeutic purposes. So far, at least four circRNA/miRNA regulatory axes such as circRNA_101764/miR-181, circRNA_100338/miR-141-3p, circ-ARL3/miR-1305, circ-ATP5H/miR-138-5p, and several circulating circRNAs were reported to be associated with HBV-HCC development. Notably, TGF/SMAD, JAK/STAT, Notch and Wnt/β-catenin signaling pathways may play pivotal roles in this HBV-driven HCC via several circRNAs. Moreover, in non-HBV HCC patients or HCC patients partially infected by HBV, numerous circRNAs have been identified to be important regulators impacting the malignant biological behavior of HCC. Furthermore, the role of circRNAs in HCC drug resistance has become a focus of research with the aim of reversing chemoresistance and immune resistance. Herein, we review the molecular biology of circRNAs in HBV-HCC and their potential in therapeutic strategies.

Down-regulation of circITCH promotes osteosarcoma development and resistance to doxorubicin via the miR-524/RASSF6 axis

BACKGROUND

Osteosarcoma (OS) is a malignant bone cancer, in which circular RNAs (circRNAs) act as important modulators. The present study aimed to explore the functional role of circRNA itchy E3 ubiquitin protein ligase (circITCH) in the development and doxorubicin (DXR) resistance of OS and the possible mechanistic pathway.

METHODS

A quantitative real-time polymerase chain reaction or western blot assays were exploited to analyze the expression of circITCH, miR-524 and Ras association domain family member 6 (RASSF6). Cell viability and half-maximal inhibitory concentration (IC₅₀ ) value of DXR were monitored using a cell counting kit-8 assay. Cell migration, invasion and apoptosis were determined via a transwell assay and flow cytometry. The target interaction among circITCH, miR-524 and RASSF6 was validated by dual-luciferase reporter and RNA immunoprecipitation assays. A xenograft model of MG-63/DXR cells stably expressing circITCH in nude mice was established for assessing the role of circITCH in vivo.

RESULTS

Down-regulation of circITCH and RASSF6, as well as the up-regulation of miR-524, was revealed in OS by investigating 40 paired OS tissue and normal tissue samples. Overexpression of circITCH lowered the cell viability, IC₅₀ value of DXR, migration and invasion, whereas it facilitated apoptosis of OS cells. circITCH sponged miR-524 to up-regulate RASSF6, causing OS progression inhibition and DXR resistance reduction. Additionally, circITCH up-regulation reduced tumor growth in vivo.

CONCLUSIONS

Transduction with circITCH represses OS progression and promotes DXR sensitivity by the miR-524/RASSF6 axis, providing a new perspective for therapeutic intervention.

The role of circular RNAs in the development of hepatocellular carcinoma

Circular RNAs (circRNAs) are a group of regulatory non-coding transcripts, which partake in the pathobiology of hepatocellular carcinoma (HCC). Numerous micro-array based investigations have discovered aberrant expression of circRNAs in HCC samples in comparison with para-cancerous sections. Furthermore, a number of in vitro and in vivo experimentations have aimed at understanding the molecular pathways of circRNAs contribution in the evolution of HCC. CircRNAs have interplay with a number of transcription factors such as ZEB1 that possibly mediates the effects of these transcripts in the epithelial-mesenchymal transition. Moreover, circRNAs functionally interact with miRNAs. CircRNA_0000502/ miR-124, circ_0001955/ miR-145-5p, circ_0001955/ miR-516a-5p and hsa_circ_0001955/miR-145-5p are examples of such interactions in the context of HCC. CircRNAs not only predict the course of HCC, but also, they can differentiate HCC samples from non-malignant liver tissues. In this review article, we have provided an inclusive summary of researches that quantified circRNAs profile in HCC. We also provide evidence for application of circRNAs as HCC biomarkers.

Characterization of the small RNA transcriptomes of cell protrusions and cell bodies of highly metastatic hepatocellular carcinoma cells via RNA sequencing

Increasing evidence suggest that hepatocellular carcinoma (HCC) HCCLM3 cells initially develop pseudopodia when they metastasize, and microRNAs (miRNAs/miRs) and circular RNAs (circRNAs) have been demonstrated to serve important roles in the development, progression and metastasis of cancer. The present study aimed to isolate the cell bodies (CBs) and cell protrusions (CPs) from HCCLM3 cells, and screen the miRNAs and circRNAs associated with HCC infiltration and metastasis in CBs and CPs. The Boyden chamber assay has been confirmed to effectively isolate the CBs and CPs from HCCLM3 cells via observation of microtubule immunofluorescence, DAPI staining and nuclear protein H3 western blotting. Following high-throughput sequencing of the successfully isolated CBs and CPs, 64 pairs of miRNAs, including 23 pairs of upregulated genes and 41 pairs of downregulated genes, and 260 sets of circRNAs, including 127 upregulated genes and 133 downregulated genes, were significantly differentially expressed, using the following criteria: HP/HB ratio, fold change ≥|1.5|, P<0.05). PCR analysis verified that changes in the expression levels of hsa-let-7a-5p, hsa-let-7c-3p, hsa-miR-30c-5p, hsa_circ_0059580, hsa_circ_0067475, hsa_circ_0002100 and hsa_circ_00072309 were consistent with the sequencing results. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed to analyze the functions and roles of the differentially expressed miRNAs and circRNAs. The interaction maps between miRNAs and circRNAs were constructed, and signaling pathway maps were analyzed to determine the molecular mechanism and regulation of the differentially expressed miRNAs and circRNAs. Taken together, the results of the present study suggest that the Boyden chamber assay can be used to effectively isolate the somatic CBs and CPs of HCC, which can be used to screen the miRNAs and circRNAs associated with invasion and metastasis of HCC.

Genome-wide identification and characterization of circular RNA in resected hepatocellular carcinoma and background liver tissue

Circular RNA (circRNA) is a type of non-coding RNA known to affect cancer-related micro RNAs and various transcription factors. circRNA has promise as a cancer-related biomarker because its circular structure affords high stability. We found using high-throughput sequencing that seven candidate circRNAs (hsa_circ_0041150, hsa_circ_0025624, hsa_circ_0001020, hsa_circ_0028129, hsa_circ_0008558, hsa_circ_0036683, hsa_circ_0058087) were downregulated in HCC. The expression of these circRNAs was examined by quantitative PCR in 233 sets of HCC and matched background normal liver tissues, and correlations between candidate circRNA expression and prognosis were evaluated. The results of quantitative PCR showed that expression of hsa_circ_0041150, hsa_circ_0001020 and hsa_circ_0008558 was significantly lower in HCC than in background normal liver tissues. Kaplan–Meier analysis revealed that low expression of hsa_circ_0001020, hsa_circ_0036683, and hsa_circ_0058087 was associated with poor recurrence-free (RFS) and overall survival (OS) in HCC. Additionally, multivariate analysis revealed that low hsa_circ_0036683 expression was a significant prognostic factor, independent from other clinicopathological features, for inferior RFS and OS. There was no significant association between the expression of these circRNAs and hepatitis B/C status or cirrhosis. This study therefore identified circRNAs as potential prognostic markers for patients who undergo curative surgery for HCC and highlighted hsa_circ_0036683 as the most useful biomarker.

The Role of circRNAs in Human Papillomavirus (HPV)-Associated Cancers

Circular RNAs (circRNAs) are a new class of "non-coding RNAs" that originate from non-sequential back-splicing of exons and/or introns of precursor messenger RNAs (pre-mRNAs). These molecules are generally produced at low levels in a cell-type-specific manner in mammalian tissues, but due to their circular conformation they are unaffected by the cell mRNA decay machinery. circRNAs can sponge multiple microRNAs or RNA-binding proteins and play a crucial role in the regulation of gene expression and protein translation. Many circRNAs have been shown to be aberrantly expressed in several cancer types, and to sustain specific oncogenic processes. Particularly, in virus-associated malignancies such as human papillomavirus (HPV)-associated anogenital carcinoma and oropharyngeal and oral cancers, circRNAs have been shown to be involved in tumorigenesis and cancer progression, as well as in drug resistance, and some are useful diagnostic and prognostic markers. HPV-derived circRNAs, encompassing the HPV E7 oncogene, have been shown to be expressed and to serve as transcript for synthesis of the E7 oncoprotein, thus reinforcing the virus oncogenic activity in HPV-associated cancers. In this review, we summarize research advances in the biogenesis of cell and viral circRNAs, their features and functions in the pathophysiology of HPV-associated tumors, and their importance as diagnostic, prognostic, and therapeutic targets in anogenital and oropharyngeal and oral cancers.

Circular RNAs: A Promising Biomarker for Endometrial Cancer

Endometrial cancer (EC) is one of the most common malignant tumors of the female reproductive tract. EC patients have high morbidity and mortality rates and remain an important cause of cancer-related morbidity and mortality worldwide. More and more studies have shown that a large number of non-coding RNAs (such as microRNAs and long non-coding RNAs) are associated with the occurrence of diseases. Circular RNAs (circRNAs) is an endogenous non-coding RNA. It has a unique covalent structure. Many studies in recent years have found circRNAs differential expression in a variety of tumor tissues compared to matched normal tissues. In endometrial carcinoma, there also are multiple circRNAs differentially expressed and therefore circRNAs perhaps can be used as a diagnostic and prognosis biomarkers of EC. In this review, we described the biogenesis, function and characteristics of circRNAs, and the circRNAs with potential influence and clinical significance on the development of EC were summarized. Adenocarcinoma is the most common form of EC, so this review focuses on endometrioid adenocarcinoma.

CircRNA Circ-ITCH Inhibits the Proliferation and Invasion of Glioma Cells Through Targeting the miR-106a-5p/SASH1 Axis

Circ-ITCH, a novel circRNA, was generated from several exons of itchy E3 ubiquitin protein ligase (ITCH). Recently, circ-ITCH has been demonstrated to be involved in cancer development. However, there have been few investigations on the specific role of circ-ITCH in glioma. In this study, we performed quantitative real-time polymerase chain reaction analysis and identified that circ-ITCH was significantly downregulated in glioma tissues and cell lines. The function assays showed that upregulation of circ-ITCH inhibited glioma cell proliferation and invasion in vitro as well as reduced cell growth in vivo. Moreover, miR-106a-5p was found serving as a target of circ-ITCH and miR-106a-5p mimics could reverse the inhibitory effect of circ-ITCH on glioma cell proliferation and invasion. We also revealed that circ-ITCH increased SASH1 expression by sponging miR-106a-5p in glioma cells. In addition, SASH1 downregulation could abrogate the suppressive effect of circ-ITCH on glioma progression. Taken together, our results suggested that circ-ITCH could suppress glioma cell proliferation and invasion via regulating the miR-106a-5p/SASH1 axis, elucidating a novel molecular target for glioma treatment.

The Prognostic and Predictive Significance of circRNA CDR1as in Tumor Progression

Cerebellar degeneration-related protein 1 antisense (CDR1as) is an important member of the circRNAs family, also known as cirs-7. Its main function in vivo is to act as a mir-7 sponge. Accumulated studies show that CDR1as is closely related to various diseases, especially cancer. Our analysis show that CDR1as expression in human cancer is significantly associated with poor overall survival (hazard ratio [HR] = 2.50, 95% confidence interval [CI] = 2.06–3.04; p < 0.00001) and that high CDR1as expression is associated with the tumor node metastasis stage (odds ratio [OR] = 2.13, 95% CI = 1.63–2.78; p < 0.00001), and distant metastasis (OR = 3.50, 95% CI = 1.90–6.64; p < 0.00001). Furthermore, the results reveal the prognostic significance of CDR1as in neoplasms of the digestive system (HR = 1.69, 95% CI = 2.14–2.71; p < 0.001), colorectal cancer (HR = 1.34, 95% CI = 1.96–2.85; p < 0.001), and non-small cell lung cancer (HR = 2.40, 95% CI = 3.42–4.83; p = 0.008). In this study, we summarize in detail the latest research findings and demonstrate the function and regulatory mechanism of CDR1as in various cancer processes, and its potential as a biomarker for cancer prevention and prognosis.

Prognostic and Clinicopathological Significance of Circular RNA circ-ITCH Expression in Cancer Patients: A Meta-analysis

Circular RNAs are a class of RNAs with a covalently closed configuration, and several members of them have been reported to be capable of regulating various biological processes and predicting the outcome of disease. Among them, circular RNA circ-ITCH has been identified to be aberrantly expressed and associated with disease progression in diverse cancers. However, the correlation of circ-ITCH expression with clinicopathological features, as well as the prognosis of cancers, remains inconclusive. Therefore, a meta-analysis was performed to investigate the clinical significance of circ-ITCH in cancers by systematically summarizing all eligible literatures. Up to August 31, 2020, relevant articles were searched in PubMed, Web of Science, Cochrane library, Embase, CNKI, and Wanfang databases. Pooled hazard ratios (HRs) and odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated. A total of 1604 patients from 14 studies were included in this meta-analysis. The results showed that cancer patients with low circ-ITCH expression were more susceptible to develop lymph node metastasis (OR = 2.25, 95% CI: 1.67-3.02, p ≤ 0.01), larger tumor size (OR = 3.01, 95% CI: 2.01-4.52, p ≤ 0.01), advanced TNM stage (OR = 2.82, 95% CI: 1.92-4.14, p ≤ 0.01), and poor overall survival (OS) (HR = 2.45, 95% CI: 2.07-2.90, p ≤ 0.01, univariate analysis; HR = 2.69, 95% CI: 1.82-3.96, p ≤ 0.01, multivariate analysis). Thus, low circ-ITCH expression was significantly associated with aggressive clinicopathological features and unfavorable outcome in various cancers. Therefore, circ-ITCH may serve as a molecular therapy target and a prognostic marker in human cancers.

Circular RNAs in body fluids as cancer biomarkers: the new frontier of liquid biopsies

Cancer is a leading cause of death worldwide, particularly because of its high mortality rate in patients who are diagnosed at late stages. Conventional biomarkers originating from blood are widely used for cancer diagnosis, but their low sensitivity and specificity limit their widespread application in cancer screening among the general population. Currently, emerging studies are exploiting novel, highly-accurate biomarkers in human body fluids that are obtainable through minimally invasive techniques, which is defined as liquid biopsy. Circular RNAs (circRNAs) are a newly discovered class of noncoding RNAs generated mainly by pre-mRNA splicing. Following the rapid development of high-throughput transcriptome analysis techniques, numerous circRNAs have been recognized to exist stably and at high levels in body fluids, including plasma, serum, exosomes, and urine. CircRNA expression patterns exhibit distinctly differences between patients with cancer and healthy controls, suggesting that circRNAs in body fluids potentially represent novel biomarkers for monitoring cancer development and progression. In this study, we summarized the expression of circRNAs in body fluids in a pan-cancer dataset and characterized their clinical applications in liquid biopsy for cancer diagnosis and prognosis. In addition, a user-friendly web interface was developed to visualize each circRNA in fluids (https://mulongdu.shinyapps.io/circrnas_in_fluids/).

Circular RNAs: Promising biomarkers for cancer diagnosis and prognosis

Circular RNAs (circRNAs), a group of non-coding RNA characterized by the presence of covalent bonds linking 3' and 5' ends, act as miRNA sponges to participate in the tumorigenesis. Being stable, conserved and cell- or tissue-specific, circRNAs have shown their potentials as molecular markers for cancer. Convenient and noninvasive approaches may be developed based on the roles of circRNAs to diagnose or predict the prognosis of tumors. Although most of the potential mechanisms are not entirely clear, circRNAs have shown a universal and critical role in regulating cellular processes of cancers. This review summarized the classification, formation, characteristics, detection, and biological functions of circRNAs. We proposed the possibility of using circRNAs as biomarkers for cancer diagnosis, treatment and prognosis.

ncRNAVar: A Manually Curated Database for Identification of Noncoding RNA Variants Associated with Human Diseases

While variants of noncoding RNAs (ncRNAs) have been experimentally validated as a new class of biomarkers and drug targets, the discovery and interpretation of relationships between ncRNA variants and human diseases become important and challenging. Here we present ncRNAVar (http://www.liwzlab.cn/ncrnavar/), the first database that provides association data between validated ncRNA variants and human diseases through manual curation on 2650 publications and computational annotation. ncRNAVar contains 4565 associations between 711 human disease phenotypes and 3112 variants from 2597 ncRNAs. Each association was reviewed by professional curators, incorporated with valuable annotation and cross references, and designated with an association score by our refined score model. ncRNAVar offers web applications including association prioritization, network visualization, and relationship mapping. ncRNAVar, presenting a landscape of ncRNA variants in human diseases and a useful resource for subsequent software development, will improve our insight of relationships between ncRNA variants and human health.

Circular RNAs: Emerging Role in Cancer Diagnostics and Therapeutics

Circular RNAs (circRNAs) are rapidly coming to the fore as major regulators of gene expression and cellular functions. They elicit their influence via a plethora of diverse molecular mechanisms. It is not surprising that aberrant circRNA expression is common in cancers and they have been implicated in multiple aspects of cancer pathophysiology such as apoptosis, invasion, migration, and proliferation. We summarize the emerging role of circRNAs as biomarkers and therapeutic targets in cancer.

The Potential of Circular RNAs as Cancer Biomarkers

Circular RNA (circRNA) is a covalently closed RNA structure that has several proposed functions related to cancer development. Recently, cancer-specific and tissue-specific circRNAs have been identified by high-throughput sequencing and are curated in publicly available databases. CircRNAs have features that are ideal properties of biomarkers, including conservation, abundance, and stability in plasma, saliva, and urine. Many circRNAs with predictive and prognostic significance in cancer have been described, and functional mechanisms for some circRNAs have been suggested. CircRNA also has great potential as a noninvasive biomarker for early cancer detection, although further investigation is necessary before clinical application is feasible.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Role of circular RNAs in digestive system tumors

Circular RNAs (circRNAs), a class of endogenous closed-loop noncoding RNAs, are expressed widely in all kinds of eukaryotic cells and have the characteristics of stable structure, high conservation, cell specificity, and tissue specificity. Several studies have revealed that circRNAs are closely related to the occurrence and development of cardiovascular system diseases, nervous system diseases, tumors, and other diseases. Recently, more and more studies have indicated that circRNAs have good clinical efficacy in the diagnosis and treatment of digestive system tumors, and they are expected to become biomarkers for early diagnosis and new therapeutic targets for the development of novel anticancer drugs. Therefore, it has become a hot topic of the current and future development direction in clinical research. circRNAs play a dual role in the pathological evolution of digestive system tumors, wherein they acting as miRNA sponges could play significant roles in carcinogenesis and anticarcinogenesis. This paper reviews the biological characteristics of circRNAs, summarizes the research progress of circRNAs in digestive system tumors, and discusses the potential use of circRNAs as targets for prevention, diagnosis, and treatment of digestive system tumors in the future.

Silencing circular RNA hsa_circ_009755 promotes growth and metastasis of oral squamous cell carcinoma

OBJECTIVE

Oral squamous cell carcinoma (OSCC) is a common and rampant malignancy of the head and neck. However, its pathogenesis remains unclear. In this study, we have investigated the effects of circular RNA hsa_circ_009755 on proliferation, migration, invasion, and apoptosis in OSCC cells in vitro.

METHOD

Eight pairs of OSCC and normal adjacent tissues were selected to detect the differential expression of circRNAs by high-throughput sequencing. circRNA hsa_circ_009755 expression was determined by quantitative real-time polymerase chain reaction in OSCC tissues and cell lines. CCK-8, wound healing, Transwell, and flow cytometry assays were used to determine OSCC cell proliferation, migration, invasion, and apoptosis, respectively.

RESULT

The expression of hsa_circ_009755 was low in OSCC tissues and three OSCC cell lines. Silencing hsa_circ_009755 significantly enhanced the proliferation, migration, and invasion and suppressed the apoptosis of OSCC cells.

CONCLUSION

Therefore, hsa_circ_009755 may be important in the tumorigenesis of OSCC.

Circular RNAs: New players in thyroid cancer

The prevalence of thyroid cancer the most frequent endocrine malignancy, is rapidly increasing. Most of thyroid cancers are relatively indolent, however, some cases still possess a risk of developing into lethal types of thyroid cancer. Regarding its multistep tumorigenesis, the determination of the underlying mechanisms is a vital issue for thyroid cancer therapy. Circular RNAs (circRNAs) are a type of non-coding RNAs with a closed loop structure. Numerous circRNAs have been identified in cancerous tissues. Mounting data recommends that the biological activities of circRNAs, such as serving as microRNA or ceRNAs sponges, interacting with proteins, modulating gene translation and transcription, suggesting that circRNAs will be potential targets as well as agents for the prognosis and diagnosis of diseases, including cancer. Given that circular RNAs acts as oncogenes or tumor suppressors in the thyroid cancer. Several studies documented that circular RNAs via microRNA and protein sponges could regulate a sequences of cellular and molecular mechanisms e.g., apoptosis, angiogenesis, tumor growth, and invasion that are involved in thyroid cancer pathogenesis. Herein, we summarized the role of circular RNAs as therapeutic and diagnostic biomarkers in the thyroid cancer. Moreover, we highlighted the role of these molecules in the pathogenesis of various cancers.

Current Status of Research on the Role of Circular RNAs in Hepatocellular Carcinoma and Clinical Implications

The latest statistics show that rates of morbidity and mortality for hepatocellular carcinoma are gradually increasing over time. Accumulating evidence indicates that circular RNAs (circRNAs) participate in the regulation of gene transcription and translation and exert a crucial role in endogenous RNA network. circRNAs are implicated in the pathogenesis of numerous tumors including hepatocellular carcinoma (HCC), gastric carcinoma and bladder cancer. Of note, the effect of circRNAs in HCC has drawn increasing public attention. Previous studies revealed that the function of circRNAs mainly consists of sponges of miRNA and RNA-binding proteins, alternative splicing of pre-mRNAs, transcriptional and translational regulators, and potential to encode proteins. In addition, recent research data indicate that the expression level of circRNAs is closely correlated with metastasis, invasion, and occurrence of HCC in patients. These findings imply that circRNAs may be useful as biomarkers for diagnosis and prediction of prognosis of HCC. In this review, we have systemically summarized current viewpoints regarding the role of circRNAs expression in HCC to provide an important reference illustrating the underlying mechanism of HCC.

Protein-Related Circular RNAs in Human Pathologies

Circular RNAs (circRNAs) are a distinct family of RNAs derived from alternative splicing which play a crucial role in regulating gene expression by acting as microRNA (miRNA) and RNA binding protein (RBP) sponges. However, recent studies have also reported the multifunctional potential of these particles. Under different conditions, circRNAs not only regulate protein synthesis, destination, and degradation but can serve as protein scaffolds or recruiters and are also able to produce short peptides with active biological functions. circRNAs are under ongoing investigation because of their close association with the development of diseases. Some circRNAs are reportedly expressed in a tissue- and development stage-specific manner. Furthermore, due to other features of circRNAs, including their stability, conservation, and high abundance in bodily fluids, they are believed to be potential biomarkers for various diseases, including cancers. In this review, we focus on providing a summary of the current knowledge on circRNA-protein interactions. We present the properties and functions of circRNAs, the possible mechanisms of their translation abilities, and the emerging functions of circRNA-derived peptides in human pathologies.

Circular RNA ITCH suppresses proliferation, invasion, and glycolysis of ovarian cancer cells by up-regulating CDH1 via sponging miR-106a

Background

Accumulating data suggested that circular RNAs (circRNAs) played important roles in the development of human cancer. However, the potential mechanism of circRNAs in ovarian cancer remains unclear.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the levels of circRNA itchy E3 ubiquitin protein ligase (circ-ITCH), microRNA-106a (miR-106a) and E-cadherin (CDH1). Cell Counting Kit-8 (CCK-8) and Transwell assay were carried out to measure cell proliferation and invasion. Glucose consumption, lactate production, and ATP level were assessed by the glucose, lactate, and ATP assay kits, respectively. Cell apoptosis was detected by Flow cytometry. The binding sites were predicted by StarBase v.2.0 or microT-CDS and verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assays. CDH1 protein level was determined by western blot. The functional role of circ-ITCH was measured by xenograft tumor model in vivo.

Results

Circ-ITCH was down-regulated in ovarian cancer and positively correlated with 5-year overall survival of patients with ovarian cancer. RNase R digestion assay confirmed that circ-ITCH was more stable than its linear mRNA form. Moreover, circ-ITCH was mainly distributed in the cytoplasm of ovarian cancer cells.Functionally, circ-ITCH overexpression hindered proliferation, invasion, glycolysis and promoted apoptosis of ovarian cancer cells. Besides, circ-ITCH overexpression inhibited ovarian cancer cell progression by targeting miR-106a. Additionally, CDH1 was a target of miR-106a, and the protein level of CDH1 was negatively regulated by miR-106a. Similarly, CDH1 knockdown recovered the inhibition effects of miR-106a inhibitor or circ-ITCH overexpression on the progression of ovarian cancer cells. Importantly, circ-ITCH up-regulated the protein level of CDH1 by sponging miR-106a in ovarian cancer cells. Circ-ITCH overexpression suppressed the growth of ovarian cancer cells in vivo.

Conclusion

Circ-ITCH suppressed proliferation, invasion, glycolysis, and promoted apoptosis of ovarian cancer cells by modulating the miR-106a/CDH1 axis.

Circular RNA circ-CSPP1 regulates CCNE2 to facilitate hepatocellular carcinoma cell growth via sponging miR-577

Objective

Circ-centro-some/spindle pole-associated protein (CSPP1) has been confirmed to be characterized in diverse human malignancies and its ectopic expression may regulate tumor progression and development. However, in hepatocellular carcinoma (HCC), its biological role, clinical significance and molecular mechanism are still unclear.

Methods

Circ-CSPP1 expression and its prognostic values in HCC tissues were detected by qRT-PCR or in situ hybridization (ISH), and enriched by using Rnase R. The functional experiments (Circ-CSPP1 was overexpressed or knocked down) were performed in HCC cells. The HCC cell growth was analyzed by CCK-8 assay, transwell, wound healing and colony formation assays. The interation between circ-CSPP1 and miR-577/miR-577 and cyclin E2 (CCNE2) were determined by dual luciferase assay or RNA binding protein immunoprecipitation (RIP) assay. The RNA fluorescence in situ hybridization (FISH) assay was used to detect the subcellular distribution. Finally, an in vivo nude mouse tumor model was constructed.

Results

In HCC patients and cells, circ-CSPP1 was aberrantly expressed, and its upregulation predicted poor prognosis, and closely correlated with tumor size and TNM stage. Circ-CSPP1 resisted RnaseR digestion, indicating it is a circular RNA structure. Moreover, overexpression of circ-CSPP1 promoted HCC cell viability, colony formation, migration, and invasion in vitro. Knockdown of circ-CSPP1 showed contrary results. Circ-CSPP1 acts as a miR-577 sponge and positively regulated the target of miR-577, CCNE2. Besides, miR-577 inhibitor rescued the suppressive effects of circ-CSPP1 knockdown on HCC cell growth, whereas was completely reversed by silencing of CCNE2. Finally, the in vivo experiments confirmed that circ-CSPP1 knockdown regulated xenograft tumor volume and downregulated CCNE2, p-Rb, E2F1 and c-myc expression.

Conclusion

These findings revealed that circ-CSPP1 contributed to HCC progression by positively regulating CCNE2 via miR-577, thus established its potential as new a prognostic and therapeutic marker for HCC patients.

Upregulation of Circular RNA Itchy E3 Ubiquitin Protein Ligase Inhibits Cell Proliferation and Promotes Cell Apoptosis Through Targeting MiR-197 in Prostate Cancer

Objective:

This study aimed to investigate the effect of circular RNA itchy E3 ubiquitin protein ligase on cell proliferation and apoptosis and to explore its target micro-RNAs in prostate cancer cells.

Methods:

Circular RNA itchy E3 ubiquitin protein ligase expression in human prostate cancer cells and normal prostate epithelial cells was determined by real time-quantitative polymerase chain reaction assay. Circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids (circular RNA itchy E3 ubiquitin protein ligase(+) group and control overexpression plasmids group were transfected with PC-3 cells. Rescue experiment was performed by transfection of circular RNA itchy E3 ubiquitin protein ligase overexpression and micro-197 overexpression plasmids (circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids/micro RNA (+) group) into PC-3 cells. Cell Counting Kit-8 and annexin V/propidium iodide assays were conducted to evaluate cell proliferation and apoptosis, respectively. Western blot was performed to determine the expressions of apoptotic-related markers.

Results:

Circular RNA itchy E3 ubiquitin protein ligase expression was decreased in DU 145, 22RV1, VCaP, and PC-3 cells compared to RWPE cells. In PC-3 cells, cell proliferation rate was reduced in circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids group compared to control overexpression plasmids group at 48 hours and 72 hours. Cell apoptosis rate was elevated in circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids group compared to control overexpression plasmids group at 48 hours, and Western blot showed the similar results. Micro RNA-197 but not micro RNA-31 or micro RNA-432 was the target micro-RNA of circular RNA itchy E3 ubiquitin protein ligase. In rescue experiments, cell proliferation rate was elevated, but apoptosis rate was reduced in circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids/micro RNA (+) group compared to circular RNA itchy E3 ubiquitin protein ligase overexpression plasmids group, indicating that circular RNA itchy E3 ubiquitin protein ligase upregulation inhibited cell proliferation but promoted apoptosis through downregulating micro RNA-197.

Conclusion:

Circular RNA itchy E3 ubiquitin protein ligase upregulation suppresses cell proliferation but promotes apoptosis through targeting micro RNA-197 in prostate cancer. Our study may provide a new insight for the treatment of prostate cancer.

Downregulated circular RNA itchy E3 ubiquitin protein ligase correlates with advanced pathologic T stage, high lymph node metastasis risk and poor survivals in prostate cancer patients

OBJECTIVE

This study aimed to explore the correlation of circular RNA itchy E3 ubiquitin protein ligase (circ-ITCH) with pathological features as well as its predictive value on prognosis in prostate cancer patients.

METHODS

Three hundred and twenty-four patients with prostate cancer underwent radical prostatectomy were consecutively included in this retrospective study, and patients' specimens of tumor as well as paired adjacent tissues were collected for detection of circ-ITCH expression. Patients' baseline characteristics and survival data were obtained from follow-up records, and correlation of circ-ITCH with patients' pathological features and survival was determined.

RESULTS

Circ-ITCH expression was decreased in tumor tissue compared with paired adjacent tissues (P< 0.001), and it presented with good value in distinguishing tumor tissues from paired adjacent tissues with area under curve (AUC) of 0.812 (95%CI: 0.780-0.845). Circ-ITCH low expression was associated with advanced pathologic T stage (P= 0.002) and high risk of lymph node metastasis (P= 0.047) in prostate cancer patients. As for prognosis, patients with circ-ITCH high expression had longer disease-free survival (DFS) (P< 0.001) and overall survival (OS) (P< 0.001). Additionally, circ-ITCH (high vs. low) independently predicted better survival, while Gleason score (> 7 vs. ⩽ 7) and surgical margin status (positive vs. negative) independently predicted worse survival in prostate patients underwent radical prostatectomy.

CONCLUSIONS

Circ-ITCH is downregulated in prostate cancer tissues, and its low expression correlates with advanced pathologic T stage, high lymph mode metastasis risk and poor survival in prostate cancer patients underwent radical prostatectomy.

Circular RNA Circ-ITCH Inhibits the Malignant Behaviors of Cervical Cancer by microRNA-93-5p/FOXK2 Axis

Growing evidence has been demonstrated that circular RNA circ-ITCH plays an important role in the development of several cancers. However, the role of circ-ITCH in cervical cancer has not been evaluated. The aim of the present study was to investigate the biological function of circ-ITCH in cervical cancer both in vitro and in vivo. Our results showed that circ-ITCH was lowly expressed in both human cervical cancer tissues and cell lines. Overexpression of circ-ITCH in HeLa cells significantly suppressed cell proliferation, migration, and invasion. A xenograft tumor model was established to evaluate the role of circ-ITCH in vivo. The results showed that overexpression of circ-ITCH significantly inhibited tumorigenesis of cervical cancer. Mechanism investigations proved that circ-ITCH executed its tumor suppressive activity through sponging microRNA-93-5p (miR-93-5p) and regulating the expression of forkhead box K2 (FOXK2). These findings suggest that circ-ITCH may be a therapeutic target for the management of cervical cancer.