The Circular RNA hsa_circ_0001445 Regulates the Proliferation and Migration of Hepatocellular Carcinoma and May Serve as a Diagnostic Biomarker. Dis Markers. 2018;2018:3073467. [PMID: 29785229 PMCID: PMC5896272 DOI: 10.1155/2018/3073467]

Small Extracellular Vesicle-Derived Circular RNA hsa_circ_0007386 as a Biomarker for the Diagnosis of Pleural Mesothelioma

Pleural mesothelioma (PM) is a highly aggressive tumor that is caused by asbestos exposure and lacks effective therapeutic regimens. Current procedures for PM diagnosis are invasive and can take a long time to reach a definitive result. Small extracellular vesicles (sEVs) have been identified as important communicators between tumor cells and their microenvironment via their cargo including circular RNAs (circRNAs). CircRNAs are thermodynamically stable, highly conserved, and have been found to be dysregulated in cancer. This study aimed to identify potential biomarkers for PM diagnosis by investigating the expression of specific circRNA gene pattern (hsa_circ_0007386) in cells and sEVs using digital polymerase chain reaction (dPCR). For this reason, 5 PM, 14 non-PM, and one normal mesothelial cell line were cultured. The sEV was isolated from the cells using the gold standard ultracentrifuge method. The RNA was extracted from both cells and sEVs, cDNA was synthesized, and dPCR was run. Results showed that hsa_circ_0007386 was significantly overexpressed in PM cell lines and sEVs compared to non-PM and normal mesothelial cell lines (p < 0.0001). The upregulation of hsa_circ_0007386 in PM highlights its potential as a diagnostic biomarker. This study underscores the importance and potential of circRNAs and sEVs as cancer diagnostic tools.

Exploring non-coding RNA mechanisms in hepatocellular carcinoma: implications for therapy and prognosis

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths in the world. The development and progression of HCC are closely correlated with the abnormal regulation of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Important biological pathways in cancer biology, such as cell proliferation, death, and metastasis, are impacted by these ncRNAs, which modulate gene expression. The abnormal expression of non-coding RNAs in HCC raises the possibility that they could be applied as new biomarkers for diagnosis, prognosis, and treatment targets. Furthermore, by controlling the expression of cancer-related genes, miRNAs can function as either tumor suppressors or oncogenes. On the other hand, lncRNAs play a role in the advancement of cancer by interacting with other molecules within the cell, which, in turn, affects processes such as chromatin remodeling, transcription, and post-transcriptional processes. The importance of ncRNA-driven regulatory systems in HCC is being highlighted by current research, which sheds light on tumor behavior and therapy response. This research highlights the great potential of ncRNAs to improve patient outcomes in this difficult disease landscape by augmenting the present methods of HCC care through the use of precision medicine approaches.

circSLCO1B7 suppresses the malignant progression of hepatocellular carcinoma via the miR-556-3p/DAB2IP axis

Circular RNAs (circRNAs) are noncoding RNAs with a circular colsed structure that play an important role in the occurrence and development of cancers. The functional mechanism of circRNAs as ceRNAs in hepatocellular carcinoma (HCC) and its effect on the invasion and metastasis of HCC need to be further studied. Five pairs of HCC tissues were selected for high-throughput sequencing, and 19 circRNAs with differential expression were obtained. The expression of circSLCO1B7 was obviously downregulated in 50 pairs of tumor tissues and plasma of HCC patients, which was closely related to the TNM stage, lymph node metastasis and tumor size. Cell functional experiments showed that circSLCO1B7 could inhibit cell growth, migration, invasion and promote cell apoptosis. In the regulatory mechanism, circSLCO1B7 sponged miR-556-3p to regulate the expression of the downstream target gene DAB2IP and induced the Epithelial-mesenchymal transition (EMT) progression. Our results indicated that circSLCO1B7 significantly inhibits the metastasis of HCC via the miR-556-3p/DAB2IP axis. Thus, circSLCO1B7 is a good candidate as a therapeutic target.

Recent advances of exosomal circRNAs in cancer and their potential clinical applications

Circular RNA (circRNA) is a type of non-coding RNA that forms a covalently closed, uninterrupted loop. The expression of circRNA differs among cell types and tissues, and various circRNAs are aberrantly expressed in a variety of diseases, including cancer. Aberrantly expressed circRNAs contribute to disease progression by acting as microRNA sponges, functional protein sponges, or novel templates for protein translation. Recent studies have shown that circRNAs are enriched in exosomes. Exosomes are spherical bilayer vesicles released by cells into extracellular spaces that mediate intercellular communication by delivering cargoes. These cargoes include metabolites, proteins, lipids, and RNA molecules. Exosome-mediated cell-cell or cell-microenvironment communications influence the progression of carcinogenesis by regulating cell proliferation, angiogenesis, metastasis as well as immune escape. In this review, we summarize the current knowledge about exosomal circRNAs in cancers and discuss their specific functions in tumorigenesis. Additionally, we discuss the potential value of exosomal circRNAs as diagnostic biomarkers and the potential applications of exosomal circRNA-based cancer therapy.

Circulating biomarkers for diagnosis and management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, but the prognosis of HCC patients is poor due to the difficulty of early diagnosis and high recurrence rate. Therefore, it is particularly important to seek effective methods for early diagnosis and early recurrence monitoring after treatment. Circulating biomarkers play an important role in the diagnosis, progression monitoring, and prognosis evaluation of HCC. In recent years, with the discovery of a variety of new biomarkers, the development of biomarkers-related models, and the emergence of liquid biopsy technology, the diagnosis and treatment of HCC have been greatly improved. This article reviews the latest research advances of biomarkers in the diagnosis and treatment of HCC, aiming to provide new ideas for improving the prognosis of HCC patients.

Review of novel functions and implications of circular RNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies, with high incidence and mortality. As the majority of HCC patients are diagnosed at an advanced stage and die of recurrence and metastasis, its pathology and new biomarkers are needed. Circular RNAs (circRNAs) are a large subclass of long non-coding RNAs (lncRNAs) with covalently closed loop structures and abundant, conserved, stable, tissue-specific expression in mammalian cells. CircRNAs exert multiple functions in HCC initiation, growth and progression, serving as promising biomarkers for diagnosis, prognosis and therapeutic targets for this disease. This review briefly describes the biogenesis and biological functions of circRNAs and elucidates the roles of circRNAs in the development and progression of HCC, especially regarding epithelial-mesenchymal transition (EMT), drug resistance and interactions with epigenetic modifications. In addition, this review highlights the implications of circRNAs as potential biomarkers and therapeutic targets for HCC. We hope to provide novel insight into the roles of circRNAs in HCC.

Liquid Biopsy for Lung Cancer: Up-to-Date and Perspectives for Screening Programs

Lung cancer is the deadliest cancer worldwide. Tissue biopsy is currently employed for the diagnosis and molecular stratification of lung cancer. Liquid biopsy is a minimally invasive approach to determine biomarkers from body fluids, such as blood, urine, sputum, and saliva. Tumor cells release cfDNA, ctDNA, exosomes, miRNAs, circRNAs, CTCs, and DNA methylated fragments, among others, which can be successfully used as biomarkers for diagnosis, prognosis, and prediction of treatment response. Predictive biomarkers are well-established for managing lung cancer, and liquid biopsy options have emerged in the last few years. Currently, detecting EGFR p.(Tyr790Met) mutation in plasma samples from lung cancer patients has been used for predicting response and monitoring tyrosine kinase inhibitors (TKi)-treated patients with lung cancer. In addition, many efforts continue to bring more sensitive technologies to improve the detection of clinically relevant biomarkers for lung cancer. Moreover, liquid biopsy can dramatically decrease the turnaround time for laboratory reports, accelerating the beginning of treatment and improving the overall survival of lung cancer patients. Herein, we summarized all available and emerging approaches of liquid biopsy-techniques, molecules, and sample type-for lung cancer.

Altered Expression of hsa_circ_0001445 and hsa_circ_0020397 in Breast Cancer Representing Associations with BMI and Reproductive Factors

BACKGROUND

Circular RNAs (circRNAs), one of the recent subclasses of non-coding RNAs (ncRNAs), show pivotal functions in regulation of gene expression and have significant roles in malignancies including breast cancer (BC). This study was aimed to assess the hsa_circ_0001445 and hsa_circ_0020397 expression and role in BC, as well as the potential circRNA/miRNA/mRNA crosstalk in these contexts.

METHODS

The expression of hsa_circ_0001445 and hsa_circ_0020397 in 50 breast tumors and 50 normal tissues adjacent to the tumors was investigated using quantitative real-time polymerase chain reaction (qRT-PCR). Finally, bioinformatics analyses were used to uncover hsa_circ_0001445, hsa_circ_0020397-miRNA-mRNA potential regulatory networks.

RESULTS

The hsa_circ_0001445 expression was considerably downregulated in malignant tissues compared to their normal counterparts (P=0.020), while the hsa_circ_0020397 showed an upregulated pattern (P<0.001). Additionally, it was observed that the higher expression of hsa_circ_0001445 was associated with hair dye avoidance (P=0.034) and normal body mass index (BMI) (P=0.016) while hsa_circ_0020397 over-expression had an important association with a lack of vitamin D consumption (P=0.039). On the other hand, lower expression of hsa_circ_0001445 was significantly associated with age at menarche ˂14 years (P=0.027). Our study also revealed that the two circRNAs have potential ability to regulate key mRNAs and miRNAs in competing endogenous RNA (ceRNA) networks.

CONCLUSION

It is suggested that hsa_circ_0001445 and hsa_circ_0020397 with two opposite roles may be involved in BC development through sponging some miRNAs regulating ceRNA networks. However, their molecular interactions should be validated by further functional studies.

Circular Sponge against miR-21 Enhances the Antitumor Activity of Doxorubicin against Breast Cancer Cells

Breast cancer is the most common type of cancer in women, with chemotherapy being the main strategy. However, its effectiveness is reduced by drug resistance mechanisms. miR-21 is upregulated in breast cancer that has been linked to drug resistance and carcinogenic processes. Our aim was to capture miR-21 with a circular sponge (Circ-21) and thus inhibit the carcinogenic processes and drug resistance mechanisms in which it participates. Proliferation, migration, colony formation, cell cycle, and poly [ADP-ribose] polymerase 1 (PARP-1) and vascular endothelial growth factor (VEGF) detection assays were performed with MCF7 breast cancer cells and MCF10A non-tumor cells. In addition, doxorubicin resistance tests and detection of drug resistance gene expression were performed in MCF7 cells. Reduction in proliferation, as well as migration and colony formation, increased PARP-1 expression, inhibition of VEGF expression and cell cycle arrest in G2/M phase were displayed in the Circ-21 MCF7, which were not observed in the MCF10A cells. Furthermore, in the MCF7 cells, the Circ-21 enhanced the antitumor activity of doxorubicin and decreased the expression of resistance genes: ABCA1, ABCC4, and ABCC5. Based on these results, the use of Circ-21 can be considered a first step for the establishment of an effective gene therapy in the treatment of breast cancer.

Non-coding RNAs in hepatocellular carcinoma: Insights into regulatory mechanisms, clinical significance, and therapeutic potential

Hepatocellular carcinoma (HCC) is a complex and heterogeneous malignancy with high incidence and poor prognosis. In addition, owing to the lack of diagnostic and prognostic markers, current multimodal treatment options fail to achieve satisfactory outcomes. Tumor immune microenvironment (TIME), angiogenesis, epithelial-mesenchymal transition (EMT), invasion, metastasis, metabolism, and drug resistance are important factors influencing tumor development and therapy. The intercellular communication of these important processes is mediated by a variety of bioactive molecules to regulate pathophysiological processes in recipient cells. Among these bioactive molecules, non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), account for a large part of the human transcriptome, and their dysregulation affects the progression of HCC. The purpose of this review is to evaluate the potential regulatory mechanisms of ncRNAs in HCC, summarize novel biomarkers from somatic fluids (plasma/serum/urine), and explore the potential of some small-molecule modulators as drugs. Thus, through this review, we aim to contribute to a deeper understanding of the regulatory mechanisms, early diagnosis, prognosis, and precise treatment of HCC.

The Emerging Roles and Clinical Potential of circSMARCA5 in Cancer

Circular RNAs (circRNAs) are a type of endogenous non-coding RNA and a critical epigenetic regulation way that have a closed-loop structure and are highly stable, conserved, and tissue-specific, and they play an important role in the development of many diseases, including tumors, neurological diseases, and cardiovascular diseases. CircSMARCA5 is a circRNA formed by its parental gene SMARCA5 via back splicing which is dysregulated in expression in a variety of tumors and is involved in tumor development with dual functions as an oncogene or tumor suppressor. It not only serves as a competing endogenous RNA (ceRNA) by binding to various miRNAs, but it also interacts with RNA binding protein (RBP), regulating downstream gene expression; it also aids in DNA damage repair by regulating the transcription and expression of its parental gene. This review systematically summarized the expression and characteristics, dual biological functions, and molecular regulatory mechanisms of circSMARCA5 involved in carcinogenesis and tumor progression as well as the potential applications in early diagnosis and gene targeting therapy in tumors.

Hsa_circ_0000098 is a novel therapeutic target that promotes hepatocellular carcinoma development and resistance to doxorubicin

Background

Circular RNA (circRNA) is crucial to the progression of hepatocellular cancer (HCC). In addition, Mitochondrial calcium uniporter regulatory factor 1 (MCUR1) is commonly overexpressed in HCC to increase cellular ATP levels. Due to the highly aggressive characteristics of HCC, it is essential to identify new diagnostic biomarkers and therapeutic targets that may facilitate the diagnosis of HCC and the development of effective anti-HCC treatments.

Methods

A series of in vitro and in vivo experiments were undertaken to investigate the biological importance and underlying mechanisms of circ_0000098 in HCC.

Results

The expression of circ_0000098 was higher in HCC tissues compared to paired adjacent tissues. According to the receiver-operating characteristic curves, circ_0000098 functioned as a potential diagnostic tumor marker in HCC. Our experiments indicated that circ_0000098 served as a key oncogenic circRNA to increase HCC cell proliferation and invasion in vitro and HCC progression in vivo. Furthermore, mechanistic investigation demonstrated that by sequestering miR-383 from the 3′-UTR of MCUR1, circ_0000098 positively regulated MCUR1 expression in HCC cells and finally promoted HCC progression. On the other hand, inhibiting circ_0000098 in HCC cells could diminish doxorubicin (DOX) resistance by decreasing P-glycoprotein (P-gp, MDR1) expression and intracellular ATP levels. Either downregulation of MCUR1 or overexpression of miR-383 improved DOX sensitivity in HCC cells. Subsequently, a short hairpin RNA targeting circ_0000098 (referred to as sh-1) and doxorubicin (DOX) were encapsulated into platelets (PLTs), referred to as DOX/sh-1@PLT. Activated DOX/sh-1@PLT through HCC cells resulted in the creation of platelet-derived particles that were capable of delivering the DOX/sh-1 combination into HCC cells and promoting intracellular DOX accumulation. Furthermore, our in vivo experiments showed that DOX/sh-1@PLT can effectively reduce P-gp expression, promote DOX accumulation, and reverse DOX resistance.

Conclusions

Our results demonstrated that circ_0000098 is an oncogenic circRNA that promotes HCC development through the miR-383/MCUR1 axis and targeting circ_0000098 with DOX/sh-1@PLT may be a promising and practical therapeutic strategy for preventing DOX resistance in HCC.

CircSMARCA5: A key circular RNA in various human diseases

Circular RNAs (circRNAs) are recognized as a novel type of single-stranded endogenous noncoding RNA molecule with the characteristics of tissue specificity, sequence conservation and structural stability. Accumulating studies have shown that circRNAs play a unique biological role in different kinds of diseases. CircRNAs can affect tumor proliferation, migration, metastasis and other behaviors by modulating the expression of downstream genes. CircSMARCA5, an example of a circRNA, is dysregulated in various noninfectious diseases, such as tumors, osteoporosis, atherosclerosis and coronary heart disease. Furthermore, recent studies have demonstrated that circSMARCA5 is associated with the occurrence and development of a variety of tumors, including gastric cancer, glioblastoma, hepatocellular carcinoma, multiple myeloma, colorectal cancer, breast cancer and osteosarcoma. Mechanistically, circSMARCA5 primarily acts as a sponge of miRNAs to regulate the expression of downstream genes, and can serve as a potential biomarker for the diagnosis of malignant tumors. This review summarizes the biological roles of circSMARCA5 and its molecular mechanism of action in various diseases. Moreover, the meta-analysis of some publications showed that the expression of circSMARCA5 was significantly correlated with the prognosis of patients and tumor TNM stage, showing that circSMARCA5 has the potential to be a prognostic marker.

Link of sorafenib resistance with the tumor microenvironment in hepatocellular carcinoma: Mechanistic insights

Sorafenib, a multi-kinase inhibitor with antiangiogenic, antiproliferative, and proapoptotic properties, is the first-line treatment for patients with late-stage hepatocellular carcinoma (HCC). However, the therapeutic effect remains limited due to sorafenib resistance. Only about 30% of HCC patients respond well to the treatment, and the resistance almost inevitably happens within 6 months. Thus, it is critical to elucidate the underlying mechanisms and identify effective approaches to improve the therapeutic outcome. According to recent studies, tumor microenvironment (TME) and immune escape play critical roles in tumor occurrence, metastasis and anti-cancer drug resistance. The relevant mechanisms were focusing on hypoxia, tumor-associated immune-suppressive cells, and immunosuppressive molecules. In this review, we focus on sorafenib resistance and its relationship with liver cancer immune microenvironment, highlighting the importance of breaking sorafenib resistance in HCC.

High-throughput circular RNA sequencing reveals the profiles of circular RNA in non-cirrhotic hepatocellular carcinoma

Background

Liver cirrhosis is a well-known risk factor for hepatocellular carcinoma (HCC). However, some HCC cases can also originate from non-cirrhotic livers. The aim of this study was to identify key circular RNAs (circRNAs) associated with the tumorigenesis of non-cirrhotic liver disease.

Methods

The differently expressed circRNAs between non-cirrhotic and cirrhotic HCCs were assessed with use of high-throughput circRNAs sequencing and validated with quantitative reverse transcription polymerase chain reaction (qRT-PCR). Potential biological functions of these dysregulated circRNAs were predicted with use of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. A circRNA-miRNA-mRNA regulation network was constructed as achieved with use of miRanda software and visualized using Cytoscape software. Biological functions of the four most prominent dysregulated circRNAs identified were confirmed by in vitro experiments. Moreover, possible translations of these dysregulated circRNAs were also predicted.

Results

A total of 393 dysregulated circRNAs were identified between non-cirrhotic and cirrhotic HCC, including 213 that were significantly up-regulated and 180 significantly down-regulated circRNAs. Expression levels of the six most prominent dysregulated circRNAs were further validated using qRT-PCR. Many tumor related miRNAs were involved in the circRNA-miRNA-mRNA networks, including miR-182-5p, miR-561-3p, miR-125a-5p, miR-145, miR-23b-3p and miR-30e-3p, and downstream mRNAs of dysregulated circRNAs were significantly related with biological processes involved in the progression of tumors, including proliferation, migration, differentiation, and focal adhesion. Results from the in vitro experiments demonstrated that the most prominent dysregulated circRNAs exerted notable effects upon the proliferation and migration of HCC cells. Finally, we also identified 19 dysregulated circRNAs having potential for the coding of functional peptides.

Conclusion

The results of this present study indicate that circRNAs may play important roles in tumorigenesis of non-cirrhotic HCC. Such findings provide some novel insights and pave the way for the development of future studies directed at investigating the initiation and treatment of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09909-2.

The potential of CircRNA1002 as a biomarker in hepatitis B virus-related hepatocellular carcinoma

Background

Although hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, there is a lack of effective diagnostic measures. Circular RNAs (circRNAs) can be used as biomarkers for monitoring the occurrence and development of HCC. However, a convenient and reliable serum circRNA biomarker is not currently available.

Materials & Methods

CircRNA expression profiles were explored using high-throughput sequencing technology, and targeted circRNAs and mRNAs were validated by quantitative reverse transcription PCR (RT-qPCR). The biological functions of circRNAs were investigated using Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Downstream miRNAs and mRNAs of dysregulated circRNAs were predicted using TargetScan, miRanda, and miRDB; then circRNA-miRNA-mRNA interaction networks were constructed based on sequencing data and the Cancer Genome Atlas (TCGA).

Results

A total of 50,327 circRNAs were identified, with 1,187 circRNAs significantly differentially expressed between hepatitis B virus (HBV)-related HCC and HBV asymptomatic carriers. Among these circRNAs, four (circRNA1002, circRNA7941, circRNA 39338, and circRNA44142) were validated by RT-qPCR as being statistically different either in HCC tissue or serum samples. circRNA1002 was significantly down-regulated in both HCC serum and tissue, indicating its reliability. Bioinformatics analysis showed that circRNA1002-associated genes were enriched in GO terms relating to hormone pathway and cell-cell interaction processes, which are involved in the progression of HCC.

Conclusion

Our circRNA analysis of HCC patients and HBV asymptomatic carriers showed that circRNA1002 may be a reliable serum biomarker for HCC. These results could provide an improved assay for the early detection of HCC.

Construction of endogenous RNA regulatory network for colorectal cancer based on bioinformatics

OBJECTIVES

The high morbidity and mortality of colorectal cancer (CRC) have posed great threats to human health. Circular RNA (circRNA) and microRNA (miRNA), acting as competing endogenous RNAs (ceRNAs), have been found to play vital roles in carcinogenesis. This paper aims to construct a circRNA/miRNA/mRNA regulatory network so as to explore the molecular mechanism of CRC.

METHODS

The sequencing data of circRNA from CRC were obtained from Gene Expression Omnibus (GEO). The differential circRNA was screened and its structure was identified by Cancer-specific CircRNA Database (CSCD); the sequencing data of miRNA and messenger RNA (mRNAs) were downloaded from The Cancer Genome Atlas (TCGA) database and the differentially expressed genes were screened; the corresponding miRNA of differential circRNAs were predicted by CircInteractome database; DIANA, Miranda, PicTar, and TargetScan databases were used to predict the target genes of different miRNAs; the target genes from Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were enriched by R language; String database combined with Cytoscape 3.7.2 software was used to construct protein-protein interaction (PPI) network and hub genes were screened; the expressions of mRNAs in the Top10 hub genes were verified in CRC. The network diagrams of circRNAs/miRNAs/mRNAs and circRNAs/miRNAs/Top10 hub mRNAs were constructed by Cytoscape3.7.2. Real-time PCR was used to examine the expression levels of hsa_circRNA_0065173, hsa-mir-450b, hsa-mir-582, adenylate cyclase 5 (ADCY5), muscarinic acetylcholine receptor M2 (CHRM2), cannabinoid receptor 1 (CNR1), and lysophosphatidic acid receptor 1 (LPAR1) in the CRC tissues and the adjacent normal tissues.

RESULTS

A total of 14 differential circRNAs were identified, and 8 were found in CSCD; 34 miRNAs targeted by circRNAs were obtained. The PPI network was constructed, and the Top10 hub genes were identified, which were CHRM2, melanin concentrating hormone receptor 2 (MCHR2), G-protein gamma 3 subunit (GNG3), neuropeptide Y receptor Y1 (NPY1R), CNR1, LPAR1, ADCY5, adenylate cyclase 2 (ADCY2), gamma 7 (GNG7) and chemokine 12 (CXCL12), respectively. The expressions of Top 10 hub genes were also verified, and the results showed that the Top 10 hub genes were down-regulated in CRC; the constructed network diagram showed that hsa_circRNA_0065173 may regulate ADCY5, CHRM2, and Hsa-mir-450b by modulating hsa-mir-450b and hsa-mir-582. CNR1 and LPAR1 genes might serve as potentially relevant targets for the treatment of CRC. Real-time PCR results showed that the expression levels of hsa_circRNA_0065173, ADCY5, CHRM2, CNR1 and LPAR1 in the CRC tissues were significantly reduced compared with the adjacent normal tissues (all P<0.05); the expression levels of hsa-mir-450b and hsa-miR-582 were significantly increased (both P<0.05).

CONCLUSIONS

In this study, a potential circRNAs/miRNAs/mRNAs network is successfully constructed, which provides a new insight for CRC development mechanism through ceRNA mediated by circRNAs.

The function and regulation network mechanism of circRNA in liver diseases

Circular RNA (circRNA), a new type of endogenous non-coding RNA, is abundantly present in eukaryotic cells, and characterized as stable high conservation and tissue specific expression. It has been generated increasing attention because of their close association with the progress of diseases. The liver is the vital organ of humans, while it is prone to acute and chronic diseases due to the influence of multiple pathogenic factors. Moreover, hepatocellular carcinoma (HCC) is the one of most common cancer and the leading cause of cancer death worldwide. Overwhelming evidences indicate that some circRNAs are differentially expressed in liver diseases, such as, HCC, chronic hepatitis B, hepatic steatosis and hepatoblastoma tissues, etc. Additionally, these circRNAs are related to proliferation, invasion, migration, angiogenesis, apoptosis, and metastasis of cell in liver diseases and act as oncogenic agents or suppressors, and linked to clinical manifestations. In this review, we briefly summarize the biogenesis, characterization and biological functions, recent detection and identification technologies of circRNA, and regulation network mechanism of circRNA in liver diseases, and discuss their potential values as biomarkers or therapeutic targets for liver diseases, especially on HCC.

Synthetic Circular miR-21 Sponge as Tool for Lung Cancer Treatment

Lung cancer is the most common cancer in the world and several miRNAs are associated with it. MiRNA sponges are presented as tools to inhibit miRNAs. We designed a system to capture miRNAs based on circular RNAs (circRNA). To demonstrate its usefulness, we chose miR-21, which is upregulated and implicated in lung cancer. We constructed a miR-21 sponge and inserted it into a vector that facilitates circular RNA production (Circ-21) to study its effect on growth, colony formation, and migration in lung cancer cell lines and multicellular tumor spheroids (MTS). Circ-21 induced a significant and time-dependent decrease in the growth of A549 and LL2 cells, but not in L132 cells. Furthermore, A549 and LL2 cells transfected with Circ-21 showed a lower number of colonies and migration than L132. Similar findings were seen in A549 and LL2 Circ-21 MTS, which showed a significant decrease in volume growth, but not in L132 Circ-21 MTS. Based on this, the miR-21 circular sponge may suppress the processes of tumorigenesis and progression. Therefore, our system based on circular sponges seems to be effective, as a tool for the capture of other miRNAs.

Potential Biomarkers for Liver Cancer Diagnosis Based on Multi-Omics Strategy

Liver cancer is the fourth leading cause of cancer-related death worldwide. Hepatocellular carcinoma (HCC) accounts for about 85%-90% of all primary liver malignancies. However, only 20-30% of HCC patients are eligible for curative therapy mainly due to the lack of early-detection strategies, highlighting the significance of reliable and accurate biomarkers. The integration of multi-omics became an important tool for biomarker screening and unique alterations in tumor-associated genes, transcripts, proteins, post-translational modifications and metabolites have been observed. We here summarized the novel biomarkers for HCC diagnosis based on multi-omics technology as well as the clinical significance of these potential biomarkers in the early detection of HCC.

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.

Diagnostic Accuracy of Circular RNAs in Different Types of Samples for Detecting Hepatocellular Carcinoma: A Meta-Analysis

The lack of accurate biomarkers impeded the screening, diagnosis and early treatment of hepatocellular carcinoma (HCC). As a result of the development of high-throughput transcriptome analysis techniques, circular RNAs, a newly discovered class of noncoding RNAs, were recognized as potential novel biomarkers. This meta-analysis was performed to update the diagnostic roles of circular RNAs for HCC. We acquired 23 articles from PubMed, Web of Science, EMBASE, and Cochrane Library databases up to September 2021. The overall sensitivity was 0.80 (95% CI: 0.77–0.84), and the specificity was 0.83 (95% CI: 0.79–0.85), with an AUC of 0.88 (0.85–0.91). Considering of the significant heterogeneity, studies were divided into four groups based on the control types. The circular RNAs in exosomes had a sensitivity of 0.69 (95% CI: 0.61–0.75), and a highest specificity of 0.91 (95% CI: 0.83–0.96). The pooled sensitivity of circular RNAs in serum/plasma was 0.84 (95% CI: 0.81–0.87), and the pooled specificity was 0.83 (95% CI: 0.79–0.86). The pooled sensitivity of circular RNAs distinguishing tumor tissue from chronic hepatitis/cirrhosis tissues was 0.56 (95% CI: 0.48–0.64), and specificity was 0.76 (95% CI: 0.67–0.82). When the controls were adjacent tissues, the sensitivity was 0.78 (95% CI: 0.70–0.84), and the specificity was 0.78 (95% CI: 0.71–0.85). Hsa_circ_0001445 with a pooled sensitivity of 0.81, a specificity of 0.76 and an AUC of 0.85 in two studies, might be a suitable diagnostic blood biomarker for HCC. Relying on function in HCC, the AUC of subgroups were 0.88 (95%CI: 0.84–0.90) (function group) and 0.87 (95%CI: 0.84–0.90) (unknown function group). As for only reported in HCC or not, these circular RNAs had an AUC of 0.89 (95%CI: 0.86–0.91) (only in HCC) and 0.85 (95%CI: 0.82–0.88) (not only in HCC). In conclusion, the results suggested that circular RNAs were acceptable biomarkers for detecting HCC, especially those circular RNAs existing in exosomes or serum/plasma.

New Circulating Circular RNAs with Diagnostic and Prognostic Potential in Advanced Colorectal Cancer

Circular RNAs (circRNAs) are a group of special endogenous long non-coding RNAs which are highly stable in the circulation, and, thus, more suitable as new biomarkers of colorectal cancer (CRC). The aim of our study was to explore the plasma expression levels of four circRNAs: has_circ_0001445, hsa_circ_0003028, hsa_circ_0007915 and hsa_circ_0008717 in patients with CRC and to evaluate their associations with clinicopathological characteristics and the clinical outcome of the patients. CircRNAs were extracted from patients’ plasma obtained prior to chemotherapy. Their expression levels were measured by qPCR and calculated applying the 2^−ΔΔCt method. The levels of all four circRNAs were significantly increased in the plasma of CRC patients. At the optimal cut-off values hsa_circ_0001445 and hsa_circ_0007915 in plasma could significantly distinguish between patients with or without metastatic CRC with 92.56% sensitivity and 42.86% specificity, and with 86.07% sensitivity and 57.14% specificity, respectively. The mean overall survival (OS) of patients with high/intermediate expression of hsa_circ_0001445 was 30 months, significantly higher in comparison with the mean OS of the patients with low expression—20 months (log-rank test, p = 0.034). In multivariate Cox regression analysis, the low levels of hsa_circ_0001445 were also associated with shorter survival (HR = 1.59, 95% CI: 1.02–2.47, p = 0.040). A prognostic significance of hsa_circ_0001445 for patients with metastatic CRC was established.

Diagnostic value of RNA for hepatocellular carcinoma: a network meta-analysis

Aim: The aim of this study was to evaluate the capacity of RNA in the diagnosis of hepatocellular carcinoma (HCC). Methods: A systematic review was conducted from PubMed, Cochrane Library, EMBASE and Web of Science databases via well-designed retrieval strategy. Subsequently, the network meta-analysis was performed by the STATA software. Results: Through statistical analysis, the three hypotheses of the network meta-analysis were established. In view of these hypotheses, the diagnostic efficacy of the three markers in HCC (HCC vs healthy people) may be consistent, and the cumulative ranking results showed such a trend: circular RNA >long noncoding RNA >microRNA. Conclusion: Circular RNA may be most effective for diagnosing HCC across the three types of RNA.

The Value of Circulating Circular RNA in Cancer Diagnosis, Monitoring, Prognosis, and Guiding Treatment

Liquid biopsy includes non-invasive analysis of circulating tumor-derived substances. It is a novel, innovative cancer screening tool that overcomes the limitations of current invasive tissue examinations in precision oncology. Circular RNA (circRNA) is a recent, novel, and attractive liquid biomarker showing stability, abundance, and high specificity in various diseases, especially in human cancers. This review focused on the emerging potential of human circRNA in body fluids as the liquid biopsy biomarkers for cancers and the methods used to detect the circRNA expression and summarized the construction of circRNA biomarkers in body fluids for treating human cancers and their limitations before they become part of routine clinical medicine. Furthermore, the future opportunities and challenges of translating circRNAs in liquid biopsy into clinical practices were explored.

Diagnostic Accuracy of Serum/Plasma Circular RNAs and the Combination of Circular RNAs and α-Fetoprotein for Detecting Hepatocellular Carcinoma: A Meta-Analysis

The lack of an accurate biomarker in hepatocellular carcinoma (HCC) has hindered early detection, diagnosis, and treatment. Circular RNAs (circRNAs), which can be used as novel biomarkers in liquid biopsies, have been brought to light as a result of the advances in research on molecular biomarkers and the progression of genomic medicine. We conducted a meta-analysis of the diagnostic accuracy of serum/plasma circRNAs or the combination of circRNAs and α-fetoprotein (AFP) in HCC. We identified eight studies that met the inclusion/exclusion criteria from PubMed, Web of Science, EMBASE, and Cochrane Library databases. The data were pooled, and the sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratio (+LR), and negative likelihood ratio (-LR) with 95% confidence intervals (CIs) were calculated. The areas under the summary receiver operator characteristic (SROC) curves (AUCs) were also calculated. The sensitivity of circRNAs was 0.82 (95% CI: 0.78-0.85), and the specificity was 0.82 (95% CI: 0.78-0.86). The sensitivity of AFP was 0.65 (95% CI: 0.61-0.68), and the specificity was 0.90 (95% CI: 0.85-0.93). The AUC was 0.89 (95% CI: 0.86-0.91) for circRNAs and 0.77 (95% CI: 0.74-0.81) for AFP. The sensitivity of the combination of circRNAs and AFP was 0.88 (95% CI: 0.84-0.92), specificity was 0.86 (95% CI: 0.80-0.91), and AUC was 0.94 (95% CI: 0.91-0.96). Additionally, a subgroup analysis was conducted based on the control groups used; the diagnostic accuracy was particularly high in the comparison of HCC vs. healthy controls. In summary, serum/plasma circRNAs are accurate biomarkers suitable for clinical use for detecting HCC, and the combination of circRNAs and AFP improved the diagnostic accuracy.

Advances in Multi-Omics Applications in HBV-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) specifically infects liver cells, leading to progressive liver cirrhosis and significantly increasing the risk of hepatocellular carcinoma (HCC). The maturity of sequencing technology, improvement in bioinformatics data analysis and progress of omics technologies had improved research efficiency. The occurrence and progression of HCC are affected by multisystem and multilevel pathological changes. With the application of single-omics technologies, including genomics, transcriptomics, metabolomics and proteomics in tissue and body fluid samples, and even the novel development of multi-omics analysis on a single-cell platform, HBV-associated HCC changes can be better analyzed. The review summarizes the application of single omics and combined analysis of multi-omics data in HBV-associated HCC and proposes the importance of multi-omics analysis in the type of HCC, which provide the possibility for the precise diagnosis and therapy of HBV-associated HCC.

Plasma circRNAs as Biomarkers in Cancer

The incidence and mortality of cancer are increasing each year. At present, the sensitivity and specificity of the blood biomarkers that were used in clinical practice are low, which make the detection rate of cancer decrease. With advances in bioinformatics and technology, some non-coding RNA as biomarkers can be easily detected through some traditional and new technologies. Circular RNAs (circRNAs) are non-coding RNAs, that is, they do not encode proteins, and have important regulatory functions. CircRNAs can remain stable in bodily fluids, such as in saliva, blood, urine, and especially plasma. The difference in the expression of plasma circRNAs between cancer patients and normal people may suggest that plasma circRNAs may play an important role in the occurrence and development of cancer. In this review, we summarized the clinical effect of plasma circRNAs in several high-incidence cancers. CircRNAs may be effective biomarkers for tumour diagnosis, treatment selection and prognosis evaluation.

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.

The Potential of Serum Exosomal hsa_circ_0028861 as the Novel Diagnostic Biomarker of HBV-Derived Hepatocellular Cancer

Hepatitis B virus (HBV)-derived hepatocellular cancer (HCC) is a serious threat to human health, especially in China. There is no highly sensitive and specific HCC biomarker at present, which makes it difficult to detect HCC at the early stage. Serum exosomal circular RNAs (circRNAs) have been reported as novel diagnostic and prognostic biomarkers of cancers. In the present study, we aimed to explore the diagnostic performance of serum exosomal circRNAs for HBV-derived HCC screening. At first, many circRNAs were found to be differentially expressed in the serum exosomes of HCC individuals by microarray analysis. The validation of dysregulated circRNAs by qRT-PCR revealed that serum exosomal hsa_circ_0028861 was decreased in HCC compared to chronic HBV and cirrhosis. Then, hsa_circ_0028861 was identified as a novel biomarker for HCC diagnosis with an area under the ROC curve (AUC) of 0.79 for discriminating HCC from chronic HBV and cirrhosis individuals. Hsa_circ_0028861 was capable of detecting small (AUC = 0.81), early-stage (AUC = 0.82) and AFP-negative [AFP (-)] (AUC = 0.78) tumors as well. The combination of hsa_circ_0028861 and AFP exhibited better diagnostic ability (AUC = 0.86 for discriminating HCC from chronic HBV and cirrhosis). Moreover, bioinformatics prediction suggested that hsa_circ_0028861 might influence HCC progression by regulating its targeted microRNAs (miRNAs) and downstream tumor-related signaling pathways. Collectively, our study reveals a novel diagnostic tool for HBV-derived HCC.

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.

Diagnostic and Prognostic Value of Circulating CircRNAs in Cancer

Cancer has been regarded as one of the leading causes of mortality worldwide. Diagnostic and prognostic biomarkers with high sensitivity and specificity for cancer play a crucial role in preventing or treating cancer. Circular RNAs (circRNAs), which hold great potential for the management of cancer patients due to their abundance, stable property, and high specificity in serum, plasma, and other body fluids, can be used as non-invasive and blood-based biomarkers in cancer diagnosis and prognosis. There are four types of circRNAs including exonic circRNAs (ecircRNA), intronic circRNAs, exon-intron circRNAs (EIciRNA), and intergenic circRNAs. CircRNAs can act as miRNA sponges, affect protein translation, interplay with RNA binding proteins, regulate protein recruitment, and modulate protein scaffolding and assembly. Therefore, the multifunctionalities of circRNAs make them ideal for detecting and predicting cancer. Indeed, circRNAs manifest high sensitivity and specificity in more than ten types of cancer. This review aims to consolidate the types and functions of circRNAs, as well as discuss the diagnostic and prognostic value of circulating circRNAs in cancer.

Peripheral Blood Genetic Biomarkers for the Early Diagnosis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has high mortality. Biomarkers related to HCC, such as alpha-fetoprotein, and imaging technology, such as ultrasound and computed tomography, have been used to screen and monitor HCC, but HCC is still difficult to diagnose effectively in the early stage due to the low sensitivity of the above mentioned traditional methods. There is an urgent need for noninvasive biomarkers to facilitate the screening and early diagnosis of HCC. With the advancement of next-generation sequencing, genetic biomarkers are becoming the core of cancer diagnosis. Genetic biomarkers such as peripheral blood circulating tumor DNA, microRNAs, long noncoding RNAs, circular RNAs, and exosomes have become the focus of early HCC diagnostics. HCC genetic biomarkers have been implemented in clinical practice. In this review, we describe the available literature on peripheral blood genetic biomarkers in the diagnosis of early HCC.

Exosomal circRNAs: A new star in cancer

As a disease that seriously endangers human health, cancer still lacks effective treatment because of its complicated mechanism of action. Currently, an emerging class of RNAs, named circular RNAs (circRNAs), has been found to be closely related to cancer. CircRNAs have a stable closed loop structure which would be hardly degraded in blood or body fluids. Exosomes are found naturally in a variety of cells, mediating cell-to-cell communication, or participating in multiple processes of tumor development. Researchers have found that abnormally expressed circRNAs may be associated with the occurrence and development of malignancies. As a kind of exosome-derived non-coding RNAs, exosomal circRNAs have also played important roles in cancer progression and acted as diagnostic and prognostic biomarkers for cancer, and thus arousing more and more attention. This article reviews the functions, mechanisms and values of the exosomal circRNAs in tumors in order to provide new ideas and novel biomarkers for the diagnosis and treatment of cancer.

Exosomal circRNAs as novel cancer biomarkers: Challenges and opportunities

Identifying high specificity and sensitivity biomarkers has always been the focus of research in the field of non-invasive cancer diagnosis. Exosomes are extracellular vesicles with a lipid bilayer membrane that can be released by all types of cells, which contain a variety of proteins, lipids, and a variety of non-coding RNAs. Increasing research has shown that the lipid bilayer can effectively protect the nucleic acid in exosomes. In cancers, tumor cell-derived exosomal circRNAs can act on target cells or organs through the transport of exosomes, and then participate in the regulation of tumor development and metastasis. Since exosomes exist in various body fluids and circRNAs in exosomes exhibit high stability, exosomal circRNAs have the potential as biomarkers for early and minimally invasive cancer diagnosis and prognosis judgment. In this review, we summarized circRNAs and their biological roles in cancers, with the emerging value biomarkers in cancer diagnosis, disease judgment, and prognosis observation. In addition, we briefly compared the advantages of exosomal circRNAs as biomarkers and the current obstacles in the exosome isolation technology, shed light to the future development of this technology.

Circular RNA hsa_circ_0001445 in plasma as a novel biomarker for osteoporosis in postmenopausal women

Background: The present study evaluated the potential of hsa_circ_0001445 as a biomarker in plasma for postmenopausal patients with osteoporosis (OPO). Materials & methods: The expression levels of hsa_circ_0001445 in plasma were detected in healthy controls, patients with osteopenia (OPE) and patients with OPO by using quantitative reverse-transcriptase PCR. Results: The expression levels of hsa_circ_0001445 in plasma were much lower in OPO patients compared with OPE patients and healthy controls. Its expression was positively correlated with the T-score and was negatively correlated with β-isomerized C-terminal telopeptides (β-CTx). It could distinguish OPE or/and OPO patients from healthy controls. Moreover, its expression was significantly upregulated in the plasma of OPO patients after anti-osteoporotic treatment. Conclusion: Hsa_circ_0001445 in plasma may be a novel potential diagnostic biomarker for OPO.

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."

Construction of circRNA-Associated ceRNA Network Reveals Novel Biomarkers for Esophageal Cancer

Objective

Esophageal cancer (ESCC) is reported to be the eighth most common malignant tumors worldwide with high mortality. However, the functions of majority circRNAs in ESCC requires to be further explored.

Methods

This study identified differently expressed circRNAs in 3 paired ESCC using RNA-sequencing method. The interactions among circRNAs, miRNAs, and mRNAs were predicted using bioinformatics analysis.

Results

In this study, using RNA-sequencing method and integrated bioinformatics analysis, 418 overexpressed circRNAs and 637 reduced circRNAs in ESCC sample were identified. Based on the mechanism that circRNAs could play as ceRNAs to modulate targets expression, circRNA-miRNA and circRNA-miRNA-mRNA networks were constructed in this study. Based on the network analysis, 7 circRNAs, including circ_0002255, circ_0000530, circ_0001904, circ_0001005, circ_0000513, circ_0000075, and circ_0001121, were identified as key circRNAs in ESCC. We found that circ_0002255 was related to the regulation of substrate adhesion-dependent cell spreading. circ_0001121 was involved in regulating nucleocytoplasmic transport. circ_0000513 played a key role in regulating Adherens junction, B cell receptor signaling pathway. Meanwhile, we observed circ_0000075 was involved in regulating zinc II ion transport, transition metal ion homeostasis, and angiogenesis.

Conclusion

We thought this study could provide novel biomarkers for the prognosis of ESCC.

Overexpression of circ_0001445 decelerates hepatocellular carcinoma progression by regulating miR-942-5p/ALX4 axis

Circular RNAs (circRNAs) have been verified to have essential regulatory roles in diverse human cancers, including hepatocellular carcinoma (HCC). In this study, we aimed to explore the roles of circ_0001445 in HCC. Herein, circ_0001445 was decreased and miR-942-5p was increased in HCC tissues and cells. Circ_0001445 overexpression or miR-942-5p inhibition repressed cell cycle process, migration, invasion, epithelial-mesenchymal transition and glycolysis in HCC cells. Mechanistically, circ_0001445 could promote ALX4 expression through targeting miR-942-5p. Moreover, miR-942-5p overexpression reversed the inhibitory effect of circ_0001445 on HCC cell progression. The effect of miR-942-5p on HCC cell development was rescued following the elevation of ALX4. In addition, circ_0001445 overexpression restrained tumorigenesis in vivo. In conclusion, circ_0001445 played a negative role in HCC progression by modulating miR-942-5p/ALX4 axis, which might provide a novel target for HCC therapy.

Identification of plasma hsa_circ_0008673 expression as a potential biomarker and tumor regulator of breast cancer

OBJECTIVE

Cell-free circular RNAs (circRNAs) are stable and abundantly exist in body fluids. In this study, we aimed to investigate plasma cell-free circRNAs as a novel class of biomarkers for the diagnosis of breast cancer (BC).

METHODS

Differentially expressed circRNAs from 6 normal and 6 BC plasma samples were detected by microarray. Hsa_circ_0008673 was then screened and validated in the plasma of 102 normal and 378 BC samples. A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value. The correlations between hsa_circ_0008673 expression and demographic characteristics, tumor features, and prognosis were analyzed. The effects of hsa_circ_0008673 on BC cell proliferation and metastasis were also measured.

RESULTS

Of the top ten up-regulated (hsa_circ_0008673, hsa_circ_0008500, hsa_circ_0005260, hsa_circ_0003423, hsa_circ_0119881, hsa_circ_0000987, hsa_circ_0007386, hsa_circ_0000091, hsa_circ_0016601, and hsa_circ_0008549) and top ten down-regulated (hsa_circ_0000826, hsa_circ_0072697, hsa_circ_0004587, hsa_circ_0000471, hsa_circ_0007786, hsa_circ_0001417, hsa_circ_0005982, hsa_circ_0001566, hsa_circ_0003823, and hsa_circ_0003823) circRNAs from microarray, hsa_circ_0008673 was the most significantly up-regulated circRNA in BC, and represented a good diagnostic value. Hsa_circ_0008673 was remarkably down-regulated after breast mastectomy. Hsa_circ_0008673 expression was associated with larger tumor size, distant metastasis, positive estrogen receptor (ER) status, and positive progesterone receptor (PR) status. Additionally, hsa_circ_0008673 could serve as a prognostic predicator of overall survival (OS) and disease-specific survival (DSS). Cell assays proved that hsa_circ_0008673 knockdown contributed to inhibition of tumor cell proliferation and migration.

CONCLUSION

Plasma cell-free hsa_circ_0008673 was up-regulated in BC, which was associated with poorer prognosis and promoted tumor proliferation and metastasis. Hsa_circ_0008673 is a promising biomarker for tumor diagnosis and prognostic assessment of BC patients.

Circular RNA is a popular molecule in tumors of the digestive system (Review)

Most tumors of the digestive system, including esophageal, gastric, liver and colorectal cancer, are malignant tumors that are associated with rates of high morbidity and mortality. The lack of effective methods for early diagnosis is an important cause of poor prognosis for these malignancies. Circular RNAs (circRNAs) belong to a family of endogenous, covalently closed non‑coding RNAs that are characterized as having no 5' cap structures or 3' poly‑A tails. Shortly following discovery, circRNAs were considered to be a product of mis‑splicing and have no significant biological function. However, in recent years, accumulating evidence is demonstrating that they serve key roles in tumorigenesis and have the potential to serve as diagnostic markers. The present article summarizes the biogenesis and function of circRNAs and reviews their role in seven common types of tumor of the digestive system whilst exploring their potential as tumor markers and the significant roles they can serve in the digestive system, in addition to providing a referencing point for future studies of digestive system malignancies.

Diagnostic Role of Dysregulated Circular RNA hsa_circ_0036722 in Laryngeal Squamous Cell Carcinoma

Purpose

Dysregulated circular RNAs (circRNAs) have been shown to play important roles in various cancers, and could serve as diagnostic biomarkers. However, research focusing on the roles of the circRNAs in laryngeal squamous cell carcinoma (LSCC) is limited. This research aimed to explore the expressions of hsa_circ_0036722 in LSCCs and its diagnostic significance.

Materials and Methods

The expression levels of the circular RNA, hsa_circ_0036722, and its parental gene, RHCG, in 41 pairs of LSCC tissues and paired adjacent normal tissues were validated with quantitative real-time polymerase chain reaction (qRT-PCR). The diagnostic values of hsa_circ_0036722 alone and combined with RHCG in LSCC were evaluated using receiver operating characteristic (ROC) curves. Bioinformatics analysis predicted likely cross-talk between hsa_circ_0036722 and RHCG. Then, qRT-PCR and luciferase reporter assay were used to examine the effect of hsa_circ_0036722 on miR-1248 and miR‑1248 on RHCG expression. CCK-8 assays were conducted to investigate their effects on LSCC cell line.

Results

Hsa_circ_0036722 and RHCG were downregulated in LSCC tissues (P < 0.0001). The expression level of hsa_circ_0036722 was significantly correlated with the differentiation level of LSCC (P = 0.018). The area under the ROC curve of hsa_circ_0036722 was 0.838, which reached 0.859 when hsa_circ_0036722 was combined with RHCG as a biomarker. Mechanistically, hsa_circ_0036722 could directly sponge miR-1248 to antagonize its inhibitory effect on RHCG. And downregulation of hsa_circ_0036722 could promote the proliferation of LSCC cell line through upregulating miR-1248.

Conclusion

Our results indicated that hsa_circ_0036722 was downregulated in LSCC, which regulate the function of RHCG in LSCC via inhibiting miR-1248, and it could serve as a potential diagnostic marker for LSCC.

Serum-derived three-circRNA signature as a diagnostic biomarker for hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is a common tumor characterized by high morbidity and mortality rates. The importance of circRNA in cancer diagnosis has been established. The study aimed to identify differentially-expressed circRNAs (DECs) in human blood exosomes from patients with HCC and to investigate their diagnostic value.

Methods

The circRNA expression profiles of HCC and normal human blood samples were downloaded and processed from the exoRBase database. At the cutoff criteria of a fold change (FC) > 2.0 and P < 0.05, DECs were screened utilizing the limma package in the R software. A receiver operator characteristic curve (ROC) was used to study its diagnostic value. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis was performed to confirm the three-circRNAs expression in the blood samples with HCC. Various bioinformatics tools were used to characterize the potential biological pathways induced by circRNAs.

Results

Compared with the normal samples, seven up-regulated and five down-regulated circRNAs were determined in the HCC samples. ROC analyses demonstrated that hsa_circ_0004001, hsa_circ_0004123, hsa_circ_0075792, and a combination of the three biomarkers exhibited higher sensitivity and specificity. The qRT-PCR confirmed that the three circRNAs were upregulated in the blood samples with HCC. Chi squared tests implied that the expression of three circRNAs was positively correlated with the TNM stage and tumor size. The circRNAs participated in VEGF/VEGFR, PI3K/Akt, mTOR, and Wnt signaling pathways by targeting miRNAs.

Conclusions

The study established the existence of seven up-regulated and five down-regulated circRNAs in HCC. Additionally, hsa_circ_0004001, hsa_circ_0004123, hsa_circ_0075792, and a combination of the three were utilized as valuable diagnostic biomarkers in HCC.

Circular RNAs: Promising Molecular Biomarkers of Human Aging-Related Diseases via Functioning as an miRNA Sponge

Circular RNAs (circRNAs) are a new class of noncoding single-stranded RNAs that differ from linear microRNAs (miRNAs), since they form covalently closed loop structures without free 3′ poly(A) tails or 5′ caps. circRNAs are the competitive endogenous RNAs (ceRNAs) by binding to miRNA through miRNA response elements (MREs) (i.e., “miRNA sponge”), thereby reducing the quantity of miRNA available to target mRNA, subsequently promoting mRNA stability or protein expression, which involves the initiation and progress of human diseases. Owing to these features of abundance, stability, conservative property, and tissue and stage specificity, widely distributing in the extracellular space and in various bodily fluids, circRNAs can be considered as potential biomarkers for various diseases. Here, we reviewed the promising circRNAs being disease biomarkers, focused on their regulatory function by acting as miRNA sponges, and described their roles in cancer, cardiovascular or neurodegenerative diseases, osteoarthritis, rheumatoid arthritis, diabetes, and other human aging-related diseases, which provide a new direction for pathogenesis, diagnosis, and treatment of human aging-related diseases.

Regulatory Roles of Circular RNAs in Coronary Artery Disease

Coronary artery disease (CAD) is a cardiac disorder caused by abnormal structure or function of the coronary artery, which leads to myocardial ischemia and hypoxia. CAD is a major cause of morbidity and mortality worldwide. Although there are currently effective drug therapies, there is a pressing need to find novel molecular therapeutic targets for CAD. The development of molecular biology technology has allowed the recognition of circular RNAs (circRNAs) as a novel class of noncoding RNAs that regulate gene function. The pathological roles of circRNAs in CAD have not, however, been comprehensively summarized. In this article, we review published research linking circRNAs to CAD and summarize the regulatory roles of circRNAs in the pathogenesis of coronary atherosclerosis, myocardial infarction, ischemia/reperfusion injury, and ischemic heart failure.

The mechanistic, diagnostic and therapeutic novel nucleic acids for hepatocellular carcinoma emerging in past score years

Despite The Central Dogma states the destiny of gene as 'DNA makes RNA and RNA makes protein', the nucleic acids not only store and transmit genetic information but also, surprisingly, join in intracellular vital movement as a regulator of gene expression. Bioinformatics has contributed to knowledge for a series of emerging novel nucleic acids molecules. For typical cases, microRNA (miRNA), long noncoding RNA (lncRNA) and circular RNA (circRNA) exert crucial role in regulating vital biological processes, especially in malignant diseases. Due to extraordinarily heterogeneity among all malignancies, hepatocellular carcinoma (HCC) has emerged enormous limitation in diagnosis and therapy. Mechanistic, diagnostic and therapeutic nucleic acids for HCC emerging in past score years have been systematically reviewed. Particularly, we have organized recent advances on nucleic acids of HCC into three facets: (i) summarizing diverse nucleic acids and their modification (miRNA, lncRNA, circRNA, circulating tumor DNA and DNA methylation) acting as potential biomarkers in HCC diagnosis; (ii) concluding different patterns of three key noncoding RNAs (miRNA, lncRNA and circRNA) in gene regulation and (iii) outlining the progress of these novel nucleic acids for HCC diagnosis and therapy in clinical trials, and discuss their possibility for clinical applications. All in all, this review takes a detailed look at the advances of novel nucleic acids from potential of biomarkers and elaboration of mechanism to early clinical application in past 20 years.

The Regulatory Functions of Circular RNAs in Digestive System Cancers

Circular ribonucleic acids (circRNAs), which are a type of covalently closed circular RNA, are receiving increasing attention. An increasing amount of evidence suggests that circRNAs are involved in the biogenesis and development of multiple diseases such as digestive system cancers. Dysregulated circRNAs have been found to act as oncogenes or tumour suppressors in digestive system cancers. Moreover, circRNAs are related to ageing and a wide variety of processes in tumour cells, such as cell apoptosis, invasion, migration, and proliferation. Moreover, circRNAs can perform a remarkable multitude of biological functions, such as regulating splicing or transcription, binding RNA-binding proteins to enable function, acting as microRNA (miRNA) sponges, and undergoing translated into proteins. However, in digestive system cancers, circRNAs function mainly as miRNA sponges. Herein, we summarise the latest research progress on biological functions of circRNAs in digestive system cancers. This review serves as a synopsis of potential therapeutic targets and biological markers for digestive system cancer.

Correlation between the expressions of circular RNAs in peripheral venous blood and clinicopathological features in hepatocellular carcinoma

Background

Recent studies have reported that circular RNAs (circRNAs) are involved in the development of hepatocellular carcinoma (HCC). This study evaluated the expression of preoperative peripheral venous blood circRNAs in HCC patients and their predictive ability for microvascular invasion (MVI).

Methods

Seven circRNAs (circMTO1, circ-10720, circZKSCAN1, cSMARCA5, circHIPK3, circSETD3 and ciRS-7) were screened from the literature as circRNAs with reported biological functions in HCC. The expression levels of seven circRNAs in preoperative blood samples and HCC tissues were detected by quantitative reverse transcription polymerase chain reaction. The correlations between the circRNA expressions in blood and the clinicopathological factors of HCC patients were analyzed. The risk factors of MVI were analyzed by univariate and multivariate logistic regression. The functional role of circSETD3 in cell migration and invasion was evaluated by wound healing and Transwell assays in vitro.

Results

The expressions of all seven circRNAs were measured in peripheral venous blood samples. The venous expression levels of circHIPK3 and circMTO1 were significantly associated with gender, while circ-10720 and circMTO1 levels were significantly correlated with gross vascular invasion. Furthermore, circMTO1 and cSMARCA5 levels were significantly associated with alpha-fetoprotein level and ciRS-7 was significantly associated with satellite nodules. Importantly, low venous circSETD3 expression was significantly associated with prothrombin induced by vitamin K absence or antagonist-II (PIVKA-II) level, MVI, gross vascular invasion, and liver capsule. Furthermore, venous circSETD3 expression had predictive ability for MVI. Knockdown of circSETD3 promoted cell invasion and metastasis in vitro.

Conclusions

CircRNAs were stably present in peripheral venous blood and associated with multiple clinicopathological characteristics of HCC patients. Venous circSETD3 was an independent risk factor of MVI and shows ability to predict MVI in HCC patients before surgery.