Progress and prospects of circular RNAs in Hepatocellular carcinoma: Novel insights into their function

CircDCAF8 promotes the progression of hepatocellular carcinoma through miR-217/NAP1L1 Axis, and induces angiogenesis and regorafenib resistance via exosome-mediated transfer

BACKGROUND

Circular RNAs (circRNAs), which are a new type of single-stranded circular RNA, have significant involvement in progression of many diseases, including tumors. Currently, multiple circRNAs have been identified in hepatocellular carcinoma (HCC). Our study aims to investigate the function and mechanism of circDCAF8 in HCC.

METHODS

The expression of circDCAF8 (hsa_circ_0014879) in HCC and para-carcinoma tissue samples was determined using quantitative real-time polymerase chain reaction (qRT-PCR). The biological function of circDCAF8 in HCC was confirmed by experiments conducted both in vitro and in vivo. And the relationship between circDCAF8, miR-217 and NAP1L1 was predicted by database and verified using qRT-PCR, RNA-binding protein immunoprecipitation (RIP) and dual-luciferase reporter assays. Exosomes isolated from HCC cells were utilized to assess the connection of exosomal circDCAF8 with HCC angiogenesis and regorafenib resistance.

RESULTS

CircDCAF8 is upregulated in HCC tissues and cell lines, and is linked to an unfavourable prognosis for HCC patients. Functionally, circDCAF8 was proved to facilitate proliferation, migration, invasion and Epithelial-Mesenchymal Transformation (EMT) in HCC cells. Animal examinations also validated the tumor-promoting characteristics of circDCAF8 on HCC. Besides, exosomal circDCAF8 promoted angiogenesis in HUVECs. Mechanistically, circDCAF8 interacted with miR-217 and NAP1L1 was a downstream protein of miR-217. CircDCAF8 promoted NAP1L1 expression by sponging miR-217. In addition, exosomes may transfer circDCAF8 from regorafenib-resistant HCC cells to sensitive cells, where it would confer a resistant phenotype.

CONCLUSION

CircDCAF8 facilitates HCC proliferation and metastasis via the miR-217/NAP1L1 axis. Meanwhile, circDCAF8 can promote angiogenesis and drive resistance to regorafenib, making it a viable therapeutic target for HCC patients.

hsa_circ_0000092 promotes hepatocellular carcinoma progression through up-regulating HN1 expression by binding to microRNA-338-3p

Circular RNAs (circRNAs) have been identified in diverse cancers for their role in regulating multiple cellular processes by antagonizing microRNAs (miRNAs or miRs). However, the role of circRNA hsa_circ_0000092 in hepatocellular carcinoma (HCC) still remains enigmatic. Therefore, we aimed to investigate the specific mechanism of hsa_circ_0000092 in HCC. Differentially expressed circRNAs associated to HCC were initially analysed. The expression of hsa_circ_0000092, miR-338-3p and HN1 in HCC tissues and cell lines was examined. Next, the interaction among hsa_circ_0000092, miR-338-3p and HN1 was determined by dual-luciferase reporter, RNA pull-down and northern blot assays. Subsequently, a series of mimic, inhibitor or siRNA plasmids were delivered into HCC cells to validate the effects of hsa_circ_0000092, miR-338-3p and HN1 in controlling cell proliferation, migration, invasion and angiogenesis in vitro. Furthermore, the role of hsa_circ_0000092 in tumour growth of HCC in vivo was assessed with hsa_circ_0000092 depleted with siRNA. The hsa_circ_0000092/miR-338-3p/HN1 axis was predicted to participate in the development of HCC. hsa_circ_0000092 and HN1 were highly expressed while miR-338-3p was poorly expressed in HCC tissues and cell lines. hsa_circ_0000092 could competitively bind to miR-338-3p to up-regulate HN1 expression. Moreover, depleted hsa_circ_0000092 or elevated miR-338-3p was shown to suppress HCC cell proliferation, migration, invasion and angiogenesis in vitro via down-regulation of HN1. Furthermore, silencing hsa_circ_0000092 was demonstrated to suppress tumour growth in HCC in vivo. The results of this study suggested that hsa_circ_0000092 impaired miR-338-3p-mediated HN1 inhibition to aggravate the development of HCC, indicating that hsa_circ_0000092 is a potential candidate marker and therapeutic target for HCC.

Exosome-transported circHDAC1_004 Promotes Proliferation, Migration, and Angiogenesis of Hepatocellular Carcinoma by the miR-361-3p/NACC1 Axis

Background and Aims

Hepatocellular carcinoma (HCC) is among the most common malignant tumors globally. Circular RNAs (circRNAs), as a type of noncoding RNAs, reportedly participate in various tumor biological processes. However, the role of circHDAC1_004 in HCC remains unclear. Thus, we aimed to explore the role and the underlying mechanisms of circHDAC1_004 in the development and progression of HCC.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect circHDAC1_004 expression (circ_0005339) in HCC. Sanger sequencing and agarose gel electrophoresis were used to determine the structure of circHDAC1_004. In vitro and in vivo experiments were used to determine the biological function of circHDAC1_004 in HCC. Herein, qRT-PCR, RNA immunoprecipitation, western blotting, and a luciferase reporter assay were used to explore the relationships among circHDAC1_004, miR-361-3p, and NACC1.

Results

circHDAC1_004 was upregulated in HCC and significantly associated with poor overall survival. circHDAC1_004 promoted HCC cell proliferation, stemness, migration, and invasion. In addition, circHDAC1_004 upregulated human umbilical vein endothelial cells (HUVECs) and promoted angiogenesis through exosomes. circHDAC1_004 promoted NACC1 expression and stimulated the epithelial-mesenchymal transition pathway by sponging miR-361-3p.

Conclusions

We found that circHDAC1_004 overexpression enhanced the proliferation, stemness, and metastasis of HCC via the miR-361-3p/NACC1 axis and promoted HCC angiogenesis through exosomes. Our findings may help develop a possible therapeutic strategy for HCC.

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.

Circ_0008285 knockdown represses tumor development by miR-384/RRM2 axis in hepatocellular carcinoma

INTRODUCTION AND OBJECTIVES

Circular RNA (circRNA) has attracted extensive attention in studies related to the malignant progression of cancer, including hepatocellular carcinoma (HCC). Therefore, its molecular mechanism in HCC needs to be further explored.

MATERIALS AND METHODS

The expression levels of circ_0008285, microRNA (miR)-384 and ribonucleotide reductase subunit M2 (RRM2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was analyzed using cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine assay, cell apoptosis was analyzed by flow cytometry, and cell migration and invasion were detected by transwell assay. Protein level was detected by western blot. The relationships between miR-384 and circ_0008285 or RRM2 were predicted by bioinformatics software and validated by dual luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

Circ_0008285 expression is elevated to HCC tissues and cell lines. Silencing of circ_0008285 inhibited the proliferation, migration and invasion of HCC cells but accelerated cell apoptosis in vitro and impeded HCC tumorigenesis in vivo. Mechanistically, circ_0008285 directly interacted with miR-384, and miR-384 silencing attenuated the effects of circ_0008285 interference on cell proliferation, migration, invasion, and apoptosis. RRM2 was a direct target of miR-384, and RRM2 overexpression reversed the effects of miR-384 overexpression on cell proliferation, migration, invasion, and apoptosis. In addition, circ_0008285 regulated RRM2 expression by sponging miR-384.

CONCLUSION

In this study, circ_0008285 could promote the malignant biological behaviors of HCC cells through miR-384/RRM2 axis and has the potential to become a therapeutic target for HCC, providing a new idea for targeted therapy of HCC.

Prognostic Values of BolA Family Member Expression in Hepatocellular Carcinoma

The BolA gene family member (BOLA1-3) plays an important role in regulating normal and pathological biological processes including liver tumorigenesis. However, their expression patterns as prognostic factors in hepatocellular carcinoma (HCC) patients have not to be elucidated. We examined the transcriptional expressions and survival data of BolA family member in patients with HCC from online databases including ONCOMINE, TCGA, UALCAN, Gene Expression Profiling Interactive Analysis (GEPIA), Kaplan-Meier plotter, SurvExpress, cBioPortal, and Exobase. Network molecular interaction views of BolA family members and their neighborhoods were constructed by the IntAct web server. In our research, we had found that the expression levels of BolA /2/3 mRNA were higher in HCC tissue than in normal liver tissues from TGCA databases. Moreover, the BolA family gene expression level is significantly associated with distinct tumor pathological grade, TMN stage, and overall survival (OS). The BolA family can be considered as prognostic risk biomarkers of HCC. A small number of BolA gene-mutated samples were detected in the HCC tissue. IntAct analysis revealed that BolA1/2/3 was closely associated with the GLRX3 expression in HCC, which is implicated in the regulation of the cellular iron homeostasis and tumor growth. Furthermore, prognostic values of altered BolAs and their neighbor GLRX3 gene in HCC patients were validated by SurvExpress analysis. In conclusion, the membrane BolA family identified in this study provides very useful information for the mechanism of hepatic tumorigenesis.

Novel Insight of CircRNAs in Cervical Cancer: Potential Biomarkers and Therapeutic Target

Cervical cancer (CC) is a prominent cancer around the globe, with a high incidence, and fatality rate. Numerous recent investigations have shown that various non-coding RNAs are associated with the progression of CC. Circular RNAs, a novel class of non-coding RNAs, have a single chain covalent closed-loop structure and are involved in cell growth and other physiological processes. These dysregulated circRNAs seem to have environment-specific functions. They have been demonstrated in certain studies to have a dual involvement in oncogene production and tumor inhibition in different cell settings. Simultaneously, some evidence indicates that circRNAs are abnormally expressed in CC and contributes to its progression. Thus, the distinctive expression profile of circRNAs is associated with the diagnosis, prognosis, and treatment outcomes of CC. We summarized numerous CC-specific circles and their function in revealing the molecular processes of carcinogenesis and progression in CC in this review. Taken together, these data suggest that circRNA may be used as an early detection biomarker and potential therapeutic target in patients with CC.

Circular RNA Circ-STIL Contributes to Cell Growth and Metastasis in Hepatocellular Carcinoma via Regulating miR-345-5p/AQP3 Axis

BACKGROUND

Circular RNAs (circRNAs) are implicated in the pathogenesis and development of hepatocellular carcinoma (HCC). However, the function and latent mechanism of circ-STIL in HCC have not been elucidated.

AIMS

This study was designed to explore the precise role and underlying molecular mechanism of circ-STIL in HCC advancement.

METHODS

The expression levels of circ-STIL, SCL/TAL1 interrupting locus (STIL), miR-345-5p and aquaporin-3 (AQP3) were measured by quantitative real-time polymerase chain reaction or western blot. Cell proliferation was assessed by 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay. Cell apoptosis was analyzed by flow cytometry. Transwell assay was conducted to analyze cell migratory and invasive capacities. The interactions among circ-STIL, miR-345-5p and AQP3 were confirmed by dual-luciferase reporter and RNA immunoprecipitation assays. Xenograft tumor model was established to analyze the role of circ-STIL in HCC in vivo.

RESULTS

Circ-STIL was upregulated in HCC tissues and cells. Circ-STIL knockdown inhibited HCC cell progression by reducing cell proliferation, migration and invasion and promoting cell apoptosis. MiR-345-5p was a direct target of circ-STIL, and AQP3 was targeted by miR-345-5p in HCC. Circ-STIL knockdown or miR-345-5p overexpression impeded cell malignant behaviors in HCC cells, and the effects could be reversed by miR-345-5p silence or AQP3 enhancement, respectively. Meanwhile, circ-STIL regulated AQP3 expression by sponging miR-345-5p. Besides, circ-STIL downregulation retarded HCC tumor growth in vivo.

CONCLUSION

Circ-STIL knockdown suppressed HCC development by regulating miR-345-5p/AQP3 pathway, which might provide a promising target for HCC therapy.

Hsa_circRNA_0088036 acts as a ceRNA to promote bladder cancer progression by sponging miR-140-3p

Circular RNAs (circRNAs) are a class of non-coding RNAs that play vital roles in cancer biology. However, the potential role of hsa_circRNA_0088036 in bladder cancer (BCa) remains unknown. Hsa_circRNA_0088036 was identified by microarray analysis and validated by quantitative real-time polymerase chain reaction. Functional assays were conducted to confirm the effects of hsa_circRNA_0088036 on the growth, migration, invasion, tumorigenesis, and metastasis of BCa cells. The luciferase reporter assay and RNA pull down assay were performed to investigate the interactions between hsa_circRNA_0088036, miR-140-3p, and forkhead box protein Q1 (FOXQ1). Upregulated expression of hsa_circRNA_0088036 in BCa tissues and cell lines was positively correlated with overall survival and clinicopathologic characteristics. Knockdown of hsa_circRNA_0088036 inhibited the growth, migration, and invasion of BCa cells both in vivo and in vitro. Mechanistically, hsa_circRNA_0088036 could directly interact with miR-140-3p and act as a miRNA sponge to modulate FOXQ1 expression. Knockdown of hsa_circRNA_0088036 inhibited the proliferation, migration, and metastasis of BCa cells via miR-140-3p/FOXQ1 signaling, suggesting that hsa_circRNA_0088036 is a potential biomarker and therapeutic target for BCa.

Epigenetic remodelling in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer, being the sixth most commonly diagnosed cancer and the fourth leading cause of cancer-related death. As other heterogeneous solid tumours, HCC results from a unique synergistic combination of genetic alterations mixed with epigenetic modifications.In HCC the patterns and frequencies of somatic variations change depending on the nearby chromatin. On the other hand, epigenetic alterations often induce genomic instability prone to mutations. Epigenetics refers to heritable states of gene expression without alteration to the DNA sequence itself and, unlike genetic changes, the epigenetic modifications are reversible and affect gene expression more extensively than genetic changes. Thus, studies of epigenetic regulation and the involved molecular machinery are greatly contributing to the understanding of the mechanisms that underline HCC onset and heterogeneity. Moreover, this knowledge may help to identify biomarkers for HCC diagnosis and prognosis, as well as future new targets for more efficacious therapeutic approaches.In this comprehensive review we will discuss the state-of-the-art knowledge about the epigenetic landscape in hepatocarcinogenesis, including evidence on the diagnostic and prognostic role of non-coding RNAs, modifications occurring at the chromatin level, and their role in the era of precision medicine.Apart from other better-known risk factors that predispose to the development of HCC, characterization of the epigenetic remodelling that occurs during hepatocarcinogenesis could open the way to the identification of personalized biomarkers. It may also enable a more accurate diagnosis and stratification of patients, and the discovery of new targets for more efficient therapeutic approaches.

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.

ESR1 mediated circ_0004018 suppresses angiogenesis in hepatocellular carcinoma via recruiting FUS and stabilizing TIMP2 expression

Angiogenesis has been certified to account for tumor pathobiology. Circular RNAs (circRNAs) have been demonstrated to be involved in angiogenesis-related diseases, including hepatocellular carcinoma (HCC). Nevertheless, the regulatory roles of most circRNAs remain obscure. This study aims to uncover the function of hsa_circ_0004018 on angiogenesis in HCC. Firstly, quantitative real-time RT-PCR (RT-qPCR) analyzed that circ_0004018 was definitely down-regulated in HCC. Western blot analysis was conducted to detect the protein level of fused protein in sarcoma (FUS) and TIMP metallopeptidase inhibitor 2 (TIMP2). Functional assays were carried out to assess the impacts of circ_0004018 on HCC. From the experimental results, we found that overexpression of circ_0004018 significantly inhibited angiogenesis in HCC. The regulatory mechanism of circ_0004018 in HCC was determined by chromatin immunoprecipitation (ChIP), luciferase reporter assays and RNA immunoprecipitation (RIP) assay. Therefore, we proved that estrogen receptor 1 (ESR1) mediated circ_0004018 regulated TIMP2 by recruiting FUS. A series of rescue assays verified that circ_0004018 participated in angiogenesis in HCC via modulating TIMP2. In summary, this paper disclosed that ESR1 activated circ_0004018 inhibited angiogenesis in HCC via binding to FUS and stabilizing TIMP2 expression.

H/ACA snoRNP Gene Family as Diagnostic and Prognostic Biomarkers for Hepatocellular Carcinoma

Background

The H/ACA small nucleolar ribonucleoprotein (snoRNP) gene family, including GAR1 ribonucleoprotein (GAR1), NHP2 ribonucleoprotein (NHP2), NOP10 ribonucleoprotein (NOP10), and dyskerin pseudouridine synthase 1 (DKC1), play important roles in ribosome biogenesis. However, the potential clinical value of the H/ACA snoRNP gene family in hepatocellular carcinoma (HCC) has not yet been reported.

Methods

Bioinformation databases were used to analyze the expression and roles of the H/ACA snoRNP gene family in HCC. Survival analysis, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes enrichment pathway (KEGG) analyses were performed using R software. Tumor Immune Estimation Resource (TIMER) was used to analyze the correlation between the expression of the H/ACA snoRNP gene family and immune infiltration in HCC. Finally, immunohistochemistry and Western blotting were performed to verify the protein expression of the H/ACA snoRNP gene family in HCC tissues and adjacent tissues.

Results

The expression of the H/ACA snoRNP gene family was significantly increased in HCC samples compared to normal tissues, and the area under the curve (AUC) of GAR1, NHP2, NOP10, and DKC1 was 0.898, 0.962, 0.884, and 0.911, respectively. Increased expression of the H/ACA snoRNP gene family was associated with poor prognosis in HCC patients (Hazard Ratio, HR = 1.44 [1.02-2.04], 1.70 [1.20-2.40], 1.53 [1.09-2.17], and 1.43 [1.02-2.03], respectively; log-rank P = 0.036, 0.003, 0.014, 0.039, respectively). GO and KEGG analyses showed that co-expressed genes were primarily enriched in ribosome biogenesis. In addition, upregulated expression of H/ACA snoRNP gene family was related to the infiltration of various immune cells and multiple T cell exhaustion markers in HCC patients. Immunohistochemical analysis and Western blotting showed that the protein expression of H/ACA snoRNP gene family was higher in HCC tissues than in adjacent tissues of clinical samples.

Conclusion

H/ACA snoRNP gene family expression was higher in HCC tissues than in normal or adjacent tissues and was highly associated with poor prognosis of HCC patients and, therefore, has the potential to serve as diagnostic and prognostic biomarkers for HCC.

Circ_0004018 suppresses cell proliferation and migration in hepatocellular carcinoma via miR-1197/PTEN/PI3K/AKT signaling pathway

Hepatocellular carcinoma (HCC) is a common type of primary liver cancer. Circular RNAs (circRNAs) have been demonstrated to be a crucial player in multiple cancers. However, a large number of circRNAs remain to be explored. Our study focused on investigating hsa_circ_0004018 in HCC. Firstly, we conducted quantitative reverse transcription PCR (RT-qPCR) to find that circ_0004018 was down-regulated in HCC cells. Western blot analysis was performed to detect the protein levels of phosphatase and tensin homologue (PTEN) and related factors of PI3K/AKT signaling pathway. From the results of functional assays, we found that overexpression of circ_0004018 significantly inhibited the proliferative and migratory capacities of HCC cells. The regulatory mechanism of circ_0004018 in HCC was determined by RNA immunoprecipitation (RIP), RNA pull-down, and luciferase reporter assays, thereby we knew that circ_0004018 regulated PTEN by sequestering microRNA-1197 (miR-1197) to modulate PI3K/AKT signaling pathway. Finally, rescue assays verified that circ_0004018 participated in modulation of cell proliferation and migration in HCC via sponging miR-1197 and regulating PTEN. In conclusion, circ_0004018 suppresses the proliferation and migration of HCC cells via sponging miR-1197 to inactivate the PTEN/PI3K/AKT signaling pathway.Abbreviations: HCC: Hepatocellular carcinoma; circRNAs: Circular RNAs; PTEN: Phosphatase and tensin homologue; miR-1197: microRNA-1197; ceRNA: competitive endogenous RNA; ATCC: American Type Culture Collection; EMEM: Eagle's Minimum Essential Medium; RT-qPCR: Quantitative real-time PCR; EdU: 5-ethynyl-20-deoxyuridine; FISH: Fluorescent in situ hybridization; RIP: RNA immunoprecipitation; 3'-UTR: 3'-untranslated region; Wt: wild-type; Mut; mutant type; gDNA: genomic DNA; Act D: Actinomycin D; PI3K: phosphatidylinositol-3-kinase; AKT: protein kinase; lncRNAs: long non-coding RNAs.

Circ_0091581 Promotes the Progression of Hepatocellular Carcinoma Through Targeting miR-591/FOSL2 Axis

BACKGROUND

Circular RNAs (circRNAs) have shown crucial regulatory roles in cancer biology. We aimed to uncover the role and underlying mechanism of circ_0091581 in hepatocellular carcinoma (HCC) progression.

METHODS

The abundance of circ_0091581, microRNA-591 (miR-591) and FOS like 2, AP-1 transcription factor subunit (FOSL2) was measured by quantitative real-time polymerase chain reaction. Cell viability, colony formation ability, and invasion ability were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay, and transwell invasion assay. The migration ability was analyzed by transwell migration assay and wound healing assay. Flow cytometry was used to evaluate the cell cycle and apoptosis of HCC cells. The interaction between miR-591 and circ_0091581 or FOSL2 was predicted by Circular RNA Interactome database or TargetScan database and confirmed by dual-luciferase reporter assay and RNA immune co-precipitation assay. FOSL2 protein expression was measured by Western blot assay. Xenograft tumor assay was conducted to analyze the role of circ_0091581 in HCC tumor growth in vivo.

RESULTS

Circ_0091581 was highly expressed in HCC tissue samples and cell lines in contrast to that in adjacent normal tissue samples and THLE-2 cell line. Circ_0091581 accelerated the viability, colony formation, metastasis, and cell cycle, while it impeded the apoptosis of HCC cells. MiR-591 bound to circ_0091581, and circ_0091581 knockdown-mediated effects in HCC cells were largely overturned by miR-591 silencing. FOSL2 was a target of miR-591, and FOSL2 overexpression largely reversed miR-591 accumulation-induced influences in HCC cells. FOSL2 protein expression was down-regulated by circ_0091581 silencing, and the addition of miR-591 inhibitor partly recovered the expression of FOSL2 in HCC cells. Circ_0091581 interference notably suppressed HCC tumor growth in vivo.

CONCLUSION

Circ_0091581 acted as an oncogene to enhance the viability, colony formation, metastasis and cell cycle and inhibit the apoptosis of HCC cells through targeting miR-591/FOSL2 axis.

Hepatic Stellate Cell: A Potential Target for Hepatocellular Carcinoma

Liver cancer is a leading cause of cancer-related death worldwide, in which hepatocellular carcinoma (HCC) accounts for the majority. Despite the progression in treatment, the prognosis remains extremely poor for HCC patients. The mechanisms of hepatocarcinogenesis are complex, of which fibrosis is acknowledged as the pre-cancerous stage of HCC. Approximately, 80-90% of HCC develops in the fibrotic or cirrhotic livers. Hepatic stellate cells (HSCs), the main effector cells of liver fibrosis, could secret various biological contents to maintain the liver inflammation. By decades, HSCs are increasingly correlated with HCC in the tumor microenvironment. In this review, we summarized the underlying mechanisms that HSCs participated in the genesis and progression of HCC. HSCs secrete various bioactive contents and regulate tumor-related pathways, subsequently contribute to metastasis, angiogenesis, immunosuppression, chemoresistance and cancer stemness. The study indicates that HSC plays vital roles in HCC progression, suggesting it as a promising therapeutic target for HCC treatment.

Circular RNA as An Epigenetic Regulator in Chronic Liver Diseases

Circular RNA (circRNA) is a type of non-coding RNA characterized by a covalently closed continuous loop. CircRNA is generated by pre-mRNA through back-splicing and is probably cleared up by extracellular vesicles. CircRNAs play a pivotal role in the epigenetic regulation of gene expression at transcriptional and post-transcriptional levels. Recently, circRNAs have been demonstrated to be involved in the regulation of liver homeostasis and diseases. However, the epigenetic role and underlying mechanisms of circRNAs in chronic liver diseases remain unclear. This review discussed the role of circRNAs in non-neoplastic chronic liver diseases, including alcoholic liver disease (ALD), metabolic-associated fatty liver disease (MAFLD), viral hepatitis, liver injury and regeneration, liver cirrhosis, and autoimmune liver disease. The review also highlighted that further efforts are urgently needed to develop circRNAs as novel diagnostics and therapeutics for chronic liver diseases.

Mechanisms and Clinical Trials of Hepatocellular Carcinoma Immunotherapy

Hepatocellular carcinoma (HCC), one of the most common and lethal tumors worldwide, is usually not diagnosed until the disease is advanced, which results in ineffective intervention and unfavorable prognosis. Small molecule targeted drugs of HCC, such as sorafenib, provided only about 2.8 months of survival benefit, partially due to cancer stem cell resistance. There is an urgent need for the development of new treatment strategies for HCC. Tumor immunotherapies, including immune check point inhibitors, chimeric antigen receptor T cells (CAR-T) and bispecific antibodies (BsAb), have shown significant potential. It is known that the expression level of glypican-3 (GPC3) was significantly increased in HCC compared with normal liver tissues. A bispecific antibody (GPC3-S-Fabs) was reported to recruit NK cells to target GPC3 positive cancer cells. Besides, bispecific T-cell Engagers (BiTE), including GPC3/CD3, an aptamer TLS11a/CD3 and EpCAM/CD3, were recently reported to efficiently eliminate HCC cells. It is known that immune checkpoint proteins programmed death-1 (PD-1) binding by programmed cell death-ligand 1 (PD-L1) activates immune checkpoints of T cells. Anti-PD-1 antibody was reported to suppress HCC progression. Furthermore, GPC3-based HCC immunotherapy has been shown to be a curative approach to prolong the survival time of patients with HCC in clinically trials. Besides, the vascular endothelial growth factor (VEGF) inhibitor may inhibit the migration, invasion and angiogenesis of HCC. Here we review the cutting-edge progresses on mechanisms and clinical trials of HCC immunotherapy, which may have significant implication in our understanding of HCC and its immunotherapy.

Circ-CSPP1 knockdown suppresses hepatocellular carcinoma progression through miR-493-5p releasing-mediated HMGB1 downregulation

BACKGROUND

Hepatocellular carcinoma (HCC) accounts for over 80% of primary liver cancers and leads to a high death rate. Research on circular RNAs (circRNAs) suggests that circRNAs are promising biomarkers for cancer treatment. This study aimed to explore the function of a novel circRNA (circ-CSPP1) in HCC.

METHODS

Circ-CSPP1 was obtained from the microarray data downloaded from the Gene Expression Omnibus (GEO) database. The expression of circ-CSPP1, miR-493-5p and high mobility group box 1 (HMGB1) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation, colony formation ability, migration and invasion were monitored using cell counting kit-8 (CCK-8) assay, colony formation assay, wound healing assay and transwell assay, respectively. The protein levels of CyclinD1, Vimentin, matrix metallopeptidase 9 (MMP-9) and HMGB1 were detected by western blot. Xenograft models were established to investigate the function of circ-CSPP1 in vivo. The association between miR-493-5p and circ-CSPP1 or HMGB1 was predicted by the online tool starBase and ensured by dual-luciferase reporter assay.

RESULTS

The expression of circ-CSPP1 and HMGB1 was elevated, while the expression of miR-493-5p was declined in HCC tissues and cells. Circ-CSPP1 knockdown not only depleted HCC cell proliferation, formation, migration and invasion in vitro but also inhibited tumor growth in vivo. MiR-493-5p was a target of circ-CSPP1, and HMGB1 was a target of miR-493-5p. Rescue experiments presented that miR-493-5p deficiency reversed the effects of circ-CSPP1 knockdown, and HMGB1 overexpression reversed the effects of miR-493-5p restoration. Circ-CSPP1 sponged miR-493-5p to regulate HMGB1 expression.

CONCLUSION

Knockdown of circ-CSPP1 suppressed HCC development both in vitro and in vivo by upregulation of miR-493-5p and downregulation of HMGB1, hinting that circ-CSPP1 participated in HCC pathogenesis.

Circular ribonucleic acid nei-like deoxyribonucleic acid glycosylase 3 governs the microribonucleic acid -3150b-3p/laminin subunit gamma 1 network to partially promote the development of hepatocellular carcinoma

AIM

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors, and its progression is implicated in the dysregulation of circular ribonucleic acids (RNAs). This study aimed to investigate the role of circular RNA nei-like DNA glycosylase 3 (circNEIL3) in HCC.

METHODS

Real-time quantitative PCR was used for expression analysis of circNEIL3, microRNA-3150b-3p (miR-3150b-3p) and laminin subunit gamma 1 (LAMC1) message RNA. MTT assay, colony formation assay, wound healing assay, transwell assay, and flow cytometry assay were performed for functional analyses on cell proliferation, migration, invasion, apoptosis, and cycle. The expression of marker proteins and LAMC1 protein was quantified by western blot. The interaction between miR-3150b-3p and circNEIL3 or LAMC1 was confirmed by dual-luciferase reporter assay or RNA immunoprecipitation assay. An animal study was performed to confirm the role of circNEIL3 in vivo.

RESULTS

CircNEIL3 was upregulated in tumor tissues and HCC cell lines. CircNEIL3 knockdown significantly suppressed HCC cell proliferation, migration and invasion and induced cell apoptosis and cell cycle arrest. MiR-3150b-3p was a target of circNEIL3, and its inhibition largely reversed the functional effects of circNEIL3 knockdown on cell behaviors. Moreover, LAMC1 served as a target of miR-3150b-3p, and its expression was elevated in HCC tissues and cells. LAMC1 overexpression recovered HCC cell proliferation, migration and invasion that were blocked by miR-3150b-3p restoration. Additionally, circNEIL3 knockdown inhibited tumor growth in mice.

CONCLUSION

CircNEIL3 dysregulation was responsible for the partial development of HCC by regulating the miR-3150b-3p/LAMC1 regulatory network.

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.

CircCAMSAP1 promotes hepatocellular carcinoma progression through miR-1294/GRAMD1A pathway

Hepatocellular carcinoma (HCC) is one of the most common cancers with high prevalence and mortality, and it has brought huge economic and health burden for the world. It is urgent to found novel targets for HCC diagnosis and clinical intervention. Circular RNA (circRNA) has been reported to participate in many cancer progressions including HCC, suggesting that circRNA might paly essential role in HCC initiation and progression. Our study aims to found that potential circRNA participates in HCC development and its underlying molecular mechanisms. We obtained three pairs of HCC tissues and its adjacent normal tissues data from GEO DataSets. MTT, cell colony, EdU, wound-healing, transwell invasion and mouse xenograft model assays were used to demonstrate the biological functions of circCAMSAP1 in HCC progression. Furthermore, we conducted bioinformatics analysis, AGO2-RIP, RNA pull-down and luciferase reporter assays to assess the association of circCAMSAP1-miR-1294-GRAMD1A axis in HCC cells. The expression of circCAMSAP1 was up-regulated in HCC tissues compared with its adjacent normal tissues. Up-regulation of circCAMSAP1 promoted HCC biological functions both in vitro and in vivo. The promotive effects of circCAMSAP1 on HCC progression function through miR-1294/GRAMD1A pathway. CircCAMSAP1 was up-regulated in HCC tissues, and circCAMSAP1 up-regulated GRAMD1A expression to promote HCC proliferation, migration and invasion through miR-1294. CircCAMSAP1 might be a potential prognosis and therapeutic target for HCC.

Hsa_circ_0008537 facilitates liver carcinogenesis by upregulating MCL1 and Snail1 expression via miR‑153‑3p

The biological functions of circular RNAs in liver tumorigenesis have been well demonstrated by a number of studies. Nevertheless, to the best of our knowledge, the role and mechanism of action of hsa_circ_0008537 (circ_0008537) in liver cancer pathogenesis remain undetermined. In the present study, circ_0008537 expression was associated with the GLI3 gene and was markedly increased in liver cancer tissue specimens and cells. High expression levels of circ_0008537 exhibited a poor prognosis. In addition, circ_0008537 overexpression resulted in an increased proliferation, migration and invasion of liver cancer cells, whereas circ_0008537 knockdown exhibited opposite effects. circ_0008537 acted as a sponge of microRNA-153-3p (miR-153-3p), and a negative correlation was observed between circ_0008537 and miR-153-3p expression in liver cancer. Transfection with miR-153-3p further abolished the effects of circ_0008537 on the malignant behavior of liver cancer cells. Furthermore, circ_0008537 indirectly affected the expression levels of pro-survival protein myeloid cell leukemia 1 (MCL1) and snail family zinc finger 1 (Snail1) via miR-153-3p in liver cancer cells. In conclusion, the data indicated that circ_0008537 facilitated liver carcinogenesis by indirectly regulating miR-153-3p and leading to the release of MCL1 and Snail1.

Circ_LDLR Knockdown Suppresses Progression of Hepatocellular Carcinoma via Modulating miR-7/RNF38 Axis

Background

Hepatocellular carcinoma (HCC) is a horrible malignancy derived from liver. Circular RNAs (circRNAs) act important roles in the pathogenesis and progression of human diseases, including HCC. The current assay intended to investigate the function of circRNA low-density lipoprotein receptor (circ_LDLR) in HCC and clarify the underlying mechanism.

Materials and Methods

Expression of circ_LDLR, microRNA (miR)-7 and ring finger protein 38 (RNF38) was determined by quantitative real-time PCR (qRT-PCR) or Western blot analysis. Flow cytometry was used to detect cell cycle distribution and apoptosis. Cell colony formation ability and viability were examined by colony formation and methyl thiazolyl tetrazolium (MTT) assays, respectively. Levels of cell proliferation and epithelia-mesenchymal transition (EMT) biomarker proteins were analyzed via Western blot assay. Cell migration and invasion were monitored by Transwell assay, and target relationship between miR-7 and circ_LDLR or RNF38 was validated by dual-luciferase reporter assay. Xenograft model was established to explore the role of circ_LDLR in vivo.

Results

Expression of circ_LDLR and RNF38 was upregulated, but miR-7 expression was downregulated in HCC tissues and cells. Circ_LDLR knockdown significantly inhibited cell proliferation, migration, invasion and EMT in HCC cells. Circ_LDLR acted as a sponge of miR-7, and interference of miR-7 could attenuate circ_LDLR knockdown-induced inhibitory effects on malignant behaviors of HCC cells. Besides, miR-7 also repressed cell proliferation and metastasis of HCC cells, by targeting RNF38. Depletion of circ_LDLR could suppress tumor growth in vivo.

Conclusion

Depletion of circ_LDLR restrained HCC cell proliferation, metastasis and tumorigenesis through the regulation on miR-7/RNF38 axis, affording a promising therapeutic target for HCC.

Circular RNA circRIMS1 Acts as a Sponge of miR-433-3p to Promote Bladder Cancer Progression by Regulating CCAR1 Expression

Circular RNAs (circRNAs), a subclass of noncoding RNAs, are reportedly involved in the progression of various diseases. However, the exact role of circRIMS1, also termed hsa_circ_0132246, in human bladder cancer remains unknown. By performing RNA sequencing comparing bladder cell lines and normal uroepithelial cells, circRIMS1 was selected as a research object. We further verified by qRT-PCR that circRIMS1 is upregulated in both bladder cancer tissue and cell lines. Proliferation, colony-formation, Transwell migration, invasion, apoptosis, western blotting, and in vivo experiments were utilized to clarify the roles of circRIMS1, microRNA (miR)-433-3p, and cell cycle and apoptosis regulator 1 (CCAR1). For mechanistic investigation, RNA pulldown, fluorescence in situ hybridization (FISH), and luciferase reporter assay confirmed the binding of circRIMS1 with miR-433-3p. Inhibition of circRIMS1 suppressed the proliferation, migration, and invasion of bladder cancer cells both in vitro and in vivo. Moreover, the circRIMS1/miR-433-3p/CCAR1 regulatory axis was confirmed to be responsible for the biological functions of circRIMS1. Taken together, our research demonstrated that circRIMS1 promotes tumor growth, migration, and invasion through the miR-433-3p/CCAR1 regulatory axis, representing a potential therapeutic target and biomarker in bladder cancer.

hsa_circ_0004018 suppresses the progression of liver fibrosis through regulating the hsa-miR-660-3p/TEP1 axis

Efforts have been made in the prevention and treatment of liver fibrosis. The inhibition or depletion of the hepatic stellate cells (HSCs) has been considered as a potential approach. Recently, there are numbers of studies about the role of the circular RNA in the disease progression. However, the role of circular RNA in the regulation of HSCs and the progression of liver fibrosis remained elusive. In this study, we constructed a CCl4-induced liver fibrosis mouse model and overexpressed hsa_circ_0004018 in HSCs. Then, salvianolic acid B was used to treat HSCs in vitro. We found that hsa_circ_0004018 is downregulated in liver fibrogenesis. Luciferase reporter assay was performed to verify the interaction of hsa_circ_0004018, hsa-miR-660-3p and TEP1. It showed that hsa_circ_0004018 may act as a sponge of hsa-miR-660-3p, which can target and downregulate the expression of TEP1. hsa_circ_0004018 expressing lentivirus was used to investigate the in-vivo function of hsa_circ_0004018 in CCl4-induced liver fibrosis mice. We also reveal that the hsa_circ_0004018/hsa-miR-660-3p/TEP1 axis contributes to the proliferation and activation of HSCs. In addition, the overexpression of hsa_circ_0004018 alleviated the progression of liver fibrosis. In conclusion, our study highlights hsa_circ_0004018 as a potential biomarker and therapeutic target for liver fibrosis.

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.

Piplartine attenuates the proliferation of hepatocellular carcinoma cells via regulating hsa_circ_100338 expression

Researches have pointed that piplartine inhibits the proliferation of hepatocellular carcinoma (HCC) cells, however, the underlying mechanisms has not been well defined. Currently, more and more studies have pointed out that circRNAs can regulate tumor cell proliferation, involve in the tumorigenesis mechanism of various tumors. In this study, we explored whether piplartine may participate in the development of HCC through the regulation of ability of HCC cell proliferation by circRNA. Based on the chip analysis, we selected candidate circRNAs that are highly correlated with HCC. CircRNA expression in OSCC cells treated with piplartine was detected by qRT-PCR. We found that only the expression of hsa_circ_100338 (circ-100338) was observably reduced. The expression characteristics of circ-100338 in HCC cell lines were also verified by qRT-PCR. Subsequently, whether or notcirc-100338 can regulate ZEB1 via competitively binding to miR-141-3p was determined by the RIP assay and dual luciferase reporter gene assay. The effect of the circ-100338/miR-141-3p/ZEB1 axis on the proliferation of HCC cell was tested by EdU and CCK-8 assay. Results showed that circ-100338 expression was observably increased in HCC cell lines. Simultaneously, circ-100338 can regulate the expression of ZEB1by competitively binding to miR-141-3p. Moreover high expression of circ-100338 can stimulate the proliferation of HCC cells. Our current study revealed that circ-100338 played as a ceRNA in promoting the progression of HCC by sponging miR-141-3p, while piplartine can participate in the development of HCC by inhibiting the expression of circ-100338.

Circular RNA hsa_circ_0056836 functions an oncogenic gene in hepatocellular carcinoma through modulating miR-766-3p/FOSL2 axis

BACKGROUND

Circular RNA (circRNA) remains a tumour-related factor in various biological cells and plays regulatory roles in gene expression. It is a type of non-coding RNA, whereas the function of human circRNA in hepatocellular carcinoma (HCC) is still not clear yet. Our investigation used the HCC cell line to uncover the biological function of hsa_circ_0056836 in the development and progression of hepatocellular carcinoma.

RESULTS

The present study showed that hsa_circ_0056836 revealed high expressions in HCC cell lines and tissues compared with corresponding controls. Silencing of Hsa_circ_0056836 decreased cell migration, proliferation and invasion. Silencing of hsa_circ_0056836 inhibited the development of HCC in xenograft nude mice. Mechanistically, we found that hsa_circ_0056836 directly bound to miR-766-3p, thereby alleviating the targeted inhibition of Fos-related antigen 2 (FOSL2). The results of this study indicated that hsa_circ_0056836 is a novel oncogenic RNA of vast potential as a tumor biomarker.

CONCLUSION

In summary, the hsa_circ_0056836 / miR-766-3p / FOSL2 axis may serve as a promising strategy for HCC treatment.

METHOD

First, the expressions of hsa_circ_0056836 in HCC tissues and corresponding para-cancerous tissues as well as in HCC cell lines and normal hepatocytes THLE-3 were detected by RT-PCR. Subcellular localization of hsa_circ_0056836 was confirmed by FISH. To detect the association between hsa_circ_0056836 and miR-766-3p, AGO2-RIP and Luciferase reporter assay were adopted. Loss of function study was applied to assess the role of hsa_circ_0056836 in HCC and to determine tumorigenesis in nude mice.

Circ_0001955 facilitates hepatocellular carcinoma (HCC) tumorigenesis by sponging miR-516a-5p to release TRAF6 and MAPK11

Circular RNAs (circRNAs) have been increasingly demonstrated to function as novel promising therapeutic RNA molecules for diverse human diseases, including cancer. Although the important role of circRNAs has been well documented in HCC, the complex mechanisms of circRNAs in HCC need to be elucidated. Here, a novel circRNA circ_0001955 was identified from three GSE datasets (GSE7852, GSE94508, and GSE97322) as a differentially expressed circRNA between HCC and normal samples. We revealed that circ_0001955, TRAF6 and MAPK11 levels were increased, while miR-516a-5p levels were decreased in HCC tumor tissues compared to adjacent normal tissues. Knockdown of circ_0001955 repressed HCC tumor growth in vitro and in vivo, while overexpression of circ_0001955 exhibited the opposite effect. Circ_0001955 was identified as a sponge for miR-145-5p and miR-516a-5p, and TRAF6 and MAPK11 were demonstrated to be two target genes of miR-516a-5p. In conclusion, circ_0001955 facilitated HCC tumorigenesis by sponging miR-516a-5p to release TRAF6 and MAPK11 expression.

Abnormal regulation of non-coding RNAs plays a role in development and progression of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an aggressive tumor with a poor prognosis. Non-coding RNAs (ncRNAs) are RNAs transcribed from the genome but not translated into protein. In recent years, ncRNAs have been recognized to be key factors in tumorigenesis because of their ability to regulate multiple targets, cell proliferation, differentiation, apoptosis, and development. In this review, we discuss the pathological significance of ncRNAs (microRNAs, long-chain non-coding RNAs, and cyclic RNAs) in the development and progression of HCC. We also discuss the potential role of ncRNAs in the diagnosis and treatment of HCC.

Circular RNA PIP5K1A promotes colon cancer development through inhibiting miR-1273a

BACKGROUND

Circular RNAs (circRNAs) are considered to be highly stable due to the closed structure, which are predominately correlated with the development and progression of a wide variety of cancers. Colon cancer is one of the most common malignancies worldwide. A recent study demonstrated the upregulated expression of circPIP5K1A in non-small cell lung cancer. However, few studies have investigated the relationship between circ_0014130 level and colon cancer. Therefore, elucidating the underlying mechanisms of circPIP5K1A’s role may help with the identification of novel diagnostic and therapeutic targets for colon cancer.

AIM

To investigate the status of circPIP5K1A in colon cancers and its effects on the modulation of cancer development.

METHODS

The expression level of circPIP5K1A in tissue and serum samples from colon cancer patients, as well as human colonic cancer cell lines was detected by real-time quantitative reverse transcription-polymerase chain reaction. Following the transfection of specifically synthesized small interfering RNA (siRNA) into colon cell lines, we used Hoechst staining assay to measure the ratio of cell death in the absence of circPIP5K1A. Moreover, we also used the Transwell assay to assess the migratory function of colon cells overexpressing circPIP5K1A. Additionally, we employed a series of bioinformatics prediction programs to predict the potential of circPIP5K1A-targeted miRNAs and mRNAs. The miR-1273a vector was constructed, and then transfected with or without circPIP5K1A vector into colon cancer cells. Afterwards, the expression of activator protein 1 (AP-1), interferon regulating factor 4 (IRF-4), caudal type homeobox 2 (CDX-2), and zinc finger of the cerebellum 1 (Zic-1) was detected by western blotting.

RESULTS

CircPIP5K1A was significantly upregulated in colon cancer tissue relative to their adjacent normal tissues. Knockdown of circPIP5K1A in colon cancer cells impaired cell viability and suppressed cell invasion and migration, while enforced expression of circPIP5K1A exhibited the opposite effects on cell migration. Bioinformatics prediction program predicted that the association of circPIP5K1A with miR-1273a, as well as AP-1, IRF-4, CDX-2, and Zic-1. Subsequent studies showed that overexpression of circPIP5K1A augmented the expression of AP-1 but attenuated the expression of IRF-4, CDX-2, and Zic-1. Reciprocally, overexpression of miR-1273a abrogated the oncogenic function of circPIP5K1A in colon cancers.

CONCLUSION

Overall, our data demonstrate the oncogenic role of circPIP5K1A-miR-1273a axis in regulation of colon cancer development, which provides a novel insights into colon cancer pathogenesis.

Circular RNA expression and circPTPRM promotes proliferation and migration in hepatocellular carcinoma

Circular RNAs (circRNAs) play a critical role during hepatocellular carcinoma (HCC) development. CircRNA PTPRM (circPTPRM) has not been reported to cause disease and its role in HCC is unclear. This study explored circRNA expression and the function of circPTPRM in HCC. RNA sequencing (RNA-seq) was performed on 3 randomly selected pairs of HCC tissues and their corresponding adjacent non-tumor tissues. Three differentially expressed circRNAs, circPTPRM, circSMAD2 and circPTBP3 were selected and verified by real-time quantitative reverse transcription-polymerase chain reactions in 30 pairs of tissue samples, In vitro cultured hepatoma cells, and normal liver cells. Clinical data analysis was performed to select target circRNAs. Anti-target circRNA siRNAs were transfected into hepatoma cell lines, and the biological behavior of hepatoma cells following silencing of the target circRNA were detected by cell proliferation, plate cloning, and transwell assays. There were 86 differentially expressed circRNAs from RNA-seq, of which 53 were significantly upregulated and 33 were significantly downregulated in HCC. CircPTPRM expression was significantly upregulated in HCC tissue (p = 0.023) based on the analysis of 30 paired samples. CircPTPRM expression positively correlated with HCC recurrence and metastasis (p = 0.039). CircPTPRM silencing reduced HCC cell proliferation, migration and invasion. CircRNAs were differentially expressed in HCC samples. CircPTPRM was significantly upregulated in HCC and may function during the tumorigenesis and metastasis of HCC.

CircRNA_101505 sensitizes hepatocellular carcinoma cells to cisplatin by sponging miR-103 and promotes oxidored-nitro domain-containing protein 1 expression

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and a leading cause of cancer-related deaths worldwide. Emerging studies have shown that circular RNAs (circRNAs) are differentially expressed in HCC and play an important role in HCC pathogenesis and metastasis. However, the mechanism of circRNA in the chemoresistance of HCC remains unclear. In this study, we aimed to investigate the role of circRNA in cisplatin resistance of HCC. We identified a novel circRNA circRNA_101505 that was decreased in cisplatin-resistant HCC tissues and cell lines, and associated with a poor survival outcome. Gain-of-function investigations showed that overexpression of circRNA_101505 suppressed cancer cell growth in vivo and in vitro, and enhanced cisplatin toxicity in HCC cells. Mechanistic studies found that circRNA_101505 could sensitize HCC cells to cisplatin by sponging miR-103, and thereby promoting oxidored-nitro domain-containing protein 1 (NOR1) expression. In conclusion, the significant inhibitory effects indicate circRNA_101505 to be a potential therapeutic target for HCC treatment. Our findings provide significant evidence to further elucidate the therapeutic use of circRNA in HCC.

hsa_circ_0091570 acts as a ceRNA to suppress hepatocellular cancer progression by sponging hsa-miR-1307

Alterations in circular RNA (circRNA) expression have a vital impact on the biological processes in cancer. Moreover, the expression pattern and roles of circRNAs in hepatocellular cancer (HCC) remain unclear. This study performed qRT-PCR to determine the regulated circRNAs in HCC tissues and cell lines. CCK8, 5-ethynyl-2'-deoxyuridine (EdU) assay, colony formation, cell cycle assay, apoptotic assay, transwell, and wound healing assay were conducted to assess the function of hsa_circ_0091570 or miR-1307 on cell proliferation, apoptosis, and migration in vitro. Mouse xenograft models were used to measure the functions of hsa_circ_0091570 in vivo. The decreased expression of hsa_circ_0091570 was associated with the pathological staging of HCC patients. Furthermore, inhibition of hsa_circ_0091570 promoted cell proliferation and migration, blocked cell apoptosis in HCC cell lines, and promoted tumor growth in the mouse xenograft model. RNA immunoprecipitation assay verified the interaction of hsa_circ_0091570 and miR-1307. The miR-1307 inhibitor inhibited the function induced by hsa_circ_0091570 siRNA. Overall, hsa_circ_0091570 sponge miR-1307 as a ceRNA and regulate ISM1 expression by exerting functional roles in HCC.

High-Throughput Sequencing Strategy for miR-146b-regulated circRNA Expression in Hepatic Stellate Cells

BACKGROUND This study was designed to detect and analyze miR-146b-mediated circular RNA (circRNA) expression in hepatic stellate cells. MATERIAL AND METHODS The experiment was divided into a control group and a siRNA-miR-146b group. The interference efficiency of siRNA-miR-146b was confirmed by real-time quantitative reverse transcription PCR (qRT-PCR) and the cells were collected, and total RNA was collected for high flux sequencing. The miRNA-targeted carcass were predicted. Finally, the expression of 5 circRNAs was verified by qRT-PCR. RESULTS miR-146b expression in the siRNA-miR-146b group was significantly lower than that in the control group. The quality of the original sequencing data and the processed data satisfied with the analysis, and the expression of circRNAs was modulated after the reduction of miR-146b. Among them, 18 circRNAs were upregulated, while 77 circRNAs were downregulated in the miR-146b group compared with the control group. The gene prediction showed that hsa_circ1887 was the largest contact point in miRNA and circRNA regulatory networks. qRT-PCR showed that rno-circRNA-469, rno-circRNA-1138, rno-circRNA-2168 and rno-circRAN-1907 were significantly reduced, while circRNA-1984 was significantly promoted in the siRNA-miR-146b group compared with the control group, which were consistent with the measurements by high-throughput sequencing technique. CONCLUSIONS miR-146b could regulate the expression of circRNAs in HSCs, which might take part in the formation and development of hepatic fibrosis.

Hsa_circ_101280 promotes hepatocellular carcinoma by regulating miR-375/JAK2

In this study, we sought to predict the effects of a certain circular RNA (circRNA), hsa_circ_101280 (also known as hsa_circ_0100929 and hsa_circ_SLAIN1), on hepatocellular carcinoma (HCC) cells and to determine the potential mechanism. After screening differentially expressed circRNAs in HCC tissues through Gene Expression Omnibus data analysis, hsa_circ_101280 was found to be highly expressed, and its high expression was verified in HCC cell lines with qRT-PCR along with the low expression of its downstream miRNA miR-375. Colony formation and flow cytometry assays showed that both hsa_circ_101280 silencing and miR-375 overexpression restrained proliferation and promoted apoptosis in HCC cells. JAK2 was identified as a downstream mRNA target of miR-375 by RNA pull-down and dual-luciferase reporter gene assays, its expression in HCC cell lines were positively regulated by hsa_circ_101280 and negatively by miR-375 expression. Furthermore, the silencing of hsa_circ_101280 significantly inhibited the growth of HCC xenografts in nude mice, with the downregulated expression of JAK2. Overall, both the in vitro and in vivo studies revealed that hsa_circ_101280 largely facilitated the tumorigenesis of HCC, characterized by the promoted proliferation and suppressed apoptosis of HCC cells, by sponging miR-375 and upregulating JAK2.

Disruption of PD-1 Enhanced the Anti-tumor Activity of Chimeric Antigen Receptor T Cells Against Hepatocellular Carcinoma

Cancer immunotherapy has made unprecedented breakthrough in the fields of chimeric antigen receptor-redirected T (CAR T) cell therapy and immune modulation. Combination of CAR modification and the disruption of endogenous inhibitory immune checkpoints on T cells represent a promising immunotherapeutic modality for cancer treatment. However, the potential for the treatment of hepatocellular carcinoma (HCC) has not been explored. In this study, the gene expressing the programmed death 1 receptor (PD-1) on the Glypican-3 (GPC3)-targeted second-generation CAR T cells employing CD28 as the co-stimulatory domain was disrupted using the CRISPR/Cas9 gene-editing system. It was found that, in vitro, the CAR T cells with the deficient PD-1 showed the stronger CAR-dependent anti-tumor activity against native programmed death 1 ligand 1-expressing HCC cell PLC/PRF/5 compared with the wild-type CAR T cells, and meanwhile, the CD4 and CD8 subsets, and activation status of CAR T cells were stable with the disruption of endogenous PD-1. Additionally, the disruption of PD-1 could protect the GPC3-CAR T cells from exhaustion when combating with native PD-L1-expressing HCC, as the levels of Akt phosphorylation and anti-apoptotic protein Bcl-xL expression in PD-1 deficient GPC3-CAR T cells were significantly higher than those in wild-type GPC3-CAR T cells after coculturing with PLC/PRF/5. Furthermore, the in vivo anti-tumor activity of the CAR T cells with the deficient PD-1 was investigated using the subcutaneous xenograft tumor model established by the injection of PLC/PRF/5 into NOD-scid-IL-2Rγ-/- (NSG) mice. The results indicated that the disruption of PD-1 enhanced the in vivo anti-tumor activity of CAR T cells against HCC, improved the persistence and infiltration of CAR T cells in the NSG mice bearing the tumor, and strengthened the inhibition of tumor-related genes expression in the xenograft tumors caused by the GPC3-CAR T cells. This study indicates the enhanced anti-tumor efficacy of PD-1-deficient CAR T cells against HCC and suggests the potential of precision gene editing on the immune checkpoints to enhance the CAR T cell therapies against HCC.

Global microarray profiling identified hsa_circ_0064428 as a potential immune-associated prognosis biomarker for hepatocellular carcinoma

BACKGROUND

Increasing evidence has shown that circular RNAs (circRNAs) are involved tumourigenesis and metastasis of hepatocellular carcinoma (HCC); however, progression about its function in HCC is relatively slow. Here, we aimed to investigate whether plasma circRNAs could reflect the tumour-infiltrating lymphocytes (TILs) in HCC tumour tissues and serve as prognosis biomarker for HCC.

METHODS

Tissue samples of patients with HCC were subjected to immunohistochemistry staining against CD8 to examine the TILs. Then, we investigated the expression profile of circRNAs by microarray between plasma of patients with HCC with high TILs and low TILs, and the differentially expressed circRNAs were validated with qRT-PCR. Statistical analysis was performed with SPSS software and GraphPad Prism.

RESULTS

We have demonstrated that patients with HCC with high TILs exhibit a significant better overall survival, suggesting clinical outcome could be predicted by TILs. Global circRNA microarray between plasma of patients with HCC with high TILs and low TILs successfully identified six differentially expressed novel circRNAs. Among them, the expression of hsa_circ_0064428 was significantly reduced in patients with HCC with high TILs but increased in patients with low TILs. Moreover, hsa_circ_0064428 was negatively correlated with patient's survival, tumour size and metastasis.

CONCLUSION

These findings together imply that hsa_circ_0064428 could be considered as a potential HCC prognosis biomarker. Future in-depth research is required to further illustrate the involvement of hsa_circ_0064428 in HCC tumourigenesis and metastasis.

Circular RNAs: Characteristics, Function and Clinical Significance in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC patients are commonly diagnosed at an advanced stage, for which highly effective therapies are limited. Moreover, the five-year survival rate of HCC patients remains poor due to high frequency of tumor metastasis and recurrence. These challenges give rise to the emergent need to discover promising biomarkers for HCC diagnosis and identify novel targets for HCC therapy. Circular RNAs (circRNAs), a class of long-overlook non-coding RNA, have been revealed as multi-functional RNAs in recent years. Growing evidence indicates that circRNA expression alterations have a broad impact in biological characteristics of HCC. Most of these circRNAs regulate HCC progression by acting as miRNA sponges, suggesting that circRNAs may function as promising diagnostic biomarkers and ideal therapeutic targets for HCC. In this review, we summarize the current progress in studying the functional role of circRNAs in HCC pathogenesis and present their potential values as diagnostic biomarkers and therapeutic targets. In-depth investigations on the function and mechanism of circRNAs in HCC will enrich our knowledge of HCC pathogenesis and contribute to the development of effective diagnostic biomarkers and therapeutic targets for HCC.

Prospects of Noncoding RNAs in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a global health problem and one of the most common malignant tumors. Recent studies have shown that noncoding RNAs (ncRNAs) contribute to the pathogenesis of hepatocellular carcinoma (HCC). These RNAs may be involved in a variety of pathological processes such as cell proliferation, apoptosis, angiogenesis, invasion, and metastasis. In addition, abnormal expression of ncRNAs in HCC may provide potential prognostic or diagnostic biomarkers. This review provides an overview of the role and potential applications of ncRNAs, miRNAs, lncRNAs, circRNAs, and snoRNAs in liver cancer.

CircRNAs as biomarkers of cancer: a meta-analysis

Background

The expression of circular RNA (circRNA) may affect tumor progression. However, there have been no systemic meta-analysis for cancer diagnosis by using circRNAs in clinical till now. Herein, we aimed to collect and examined all the evidence on the potential role of circRNA as novel biomarker in human cancers.

Methods

A comprehensive search strategy was used to search relevant literatures in the databases of PubMed, Embase, and the Web of Science from 2015 to August 2017. The correlation between circRNA expression and the diagnostic accuracy of tumor markers was analyzed. The methodological quality of each study was assessed by quality assessment for the diagnostic accuracies of the eligible studies (QUADAS-2). Statistical analysis was performed by applying the STATA (version 12.0) software.

Results

The present meta-analysis included 1752 patients with circRNA expression data of tumor and paired adjacent non-tumorous tissues from 17 publications (19 studies). The pooled sensitivity, specificity, positive likelihood ratios (PLR), negative likelihood ratios (NLR), and diagnostic OR (DOR) with their 95% confidential intervals (95%CIs), and AUC values were 0.72 (0.67–0.76), 0.74 (0.69–0.78), 2.80 (2.40–3.10), 0.38 (0.33–0.44), 7.00 (6.00–9.00), and 0.79, respectively. Subgroup analyses showed that the expression of circRNA in tissues of hepatocellular carcinoma (HCC) group was more prone to be detected than other tumor types, with a high values of the specificity, DOR, and AUC.

Conclusions

circRNAs might be suitable as diagnostic biomarkers for tumors, especially in HCC diagnosis. Further prospective studies on the diagnostic value of circRNAs from the different tumors are needed in the future.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4213-0) contains supplementary material, which is available to authorized users.

The novel roles of circular RNAs in metabolic organs

Circular RNAs (circRNAs) with a covalently closed loop structure which was different with linear RNAs, recently re-merged as novel regulator and exerted function in multiple biological processes. Through deep RNA sequencing (RNA-seq) technology coupled with bioinformatic analyses, a number of circRNAs has been identified. Moreover, circRNAs exhibit tissue- and development-specific expression indicating their potential biological significance. Actually, function of circRNAs as miRNA sponge has been well demonstrated in some diseases, besides, circRNAs also could function as RNA binding protein sponge and regulate alternative splicing and gene transcription. Notably, Emerging evidences showed that circRNAs played a pivotal role on the development of diseases including atherosclerotic vascular disease, neurological disorders and liver diseases, and served as diagnostic or predictive biomarkers of some diseases. This review mainly discusses the current advance of circRNAs as regulator involved in many diseases, and highlights circRNAs which have been well elucidated biological and pathogenic mechanism.