circLARP4 induces cellular senescence through regulating miR-761/RUNX3/p53/p21 signaling in hepatocellular carcinoma

The circular RNA circSLC16A10 alleviates diabetic retinopathy by improving mitochondrial function via the miR-761-5p/MFN2 axis

It has been demonstrated that circular RNAs (circRNAs) are associated with the development of diabetic retinopathy (DR). Nevertheless, the function of circSLC16A10 in the development of DR remains unclear. In order to investigate the role of circSLC16A10, we employed cell and animal models of DR. An analysis of a public database revealed that hsa_circSLC16A10 was expressed at lower levels in DR patients than in diabetic patients without DR or healthy controls. Additionally, the level of hsa_circSLC16A10 was lower in high glucose (HG)-exposed ARPE-19 cells and diabetic mice. hsa_circSLC16A10 was observed to be mainly distributed in the cytoplasm. Moreover, overexpression of hsa_circSLC16A10 alleviated HG-induced endoplasmic reticulum stress and cell apoptosis in vitro. Furthermore, overexpression of hsa_circSLC16A10 ameliorated HG-induced mitochondrial dysfunction, as evidenced by improvements in mitochondrial structure and function. hsa_circSLC16A10 acted as a hsa-miR-761-5p sponge to increase MFN2 expression. MFN2 knockdown or hsa-miR-761-5p overexpression partially reversed the protective effect of hsa_circSLC16A10 in vitro. The protective effect of mmu_circSLC16A10 against DR was confirmed in an animal model of DR. These findings indicate that circSLC16A10 may regulate DR progression by improving mitochondrial function via the miR-761-5p/MFN2 axis.

Circular RNAs in Cell Cycle Regulation of Cancers

Cancer has been one of the most problematic health issues globally. Typically, all cancers share a common characteristic or cancer hallmark, such as sustaining cell proliferation, evading growth suppressors, and enabling replicative immortality. Indeed, cell cycle regulation in cancer is often found to be dysregulated, leading to an increase in aggressiveness. These dysregulations are partly due to the aberrant cellular signaling pathway. In recent years, circular RNAs (circRNAs) have been widely studied and classified as one of the regulators in various cancers. Numerous studies have reported that circRNAs antagonize or promote cancer progression through the modulation of cell cycle regulators or their associated signaling pathways, directly or indirectly. Mostly, circRNAs are known to act as microRNA (miRNA) sponges. However, they also hold additional mechanisms for regulating cellular activity, including protein binding, RNA-binding protein (RBP) recruitment, and protein translation. This review will discuss the current knowledge of how circRNAs regulate cell cycle-related proteins through the abovementioned mechanisms in different cancers.

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

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

Bronchial arterial chemoembolization with Drug-Eluting beads plus sequential chemotherapy for the treatment of stage III and IV lung squamous cell carcinoma

PURPOSE

This retrospective study aimed to investigate the effectiveness and safety of bronchial arterial chemoembolization with drug-eluting beads (DEB-BACE) plus chemotherapy versus chemotherapy alone in patients with stage III and IV lung squamous cell carcinoma (LSCC) who are not appropriate candidates for radiochemotherapy.

MATERIALS AND METHODS

In this retrospective analysis, we screened all adult patients undergoing either DEB-BACE plus chemotherapy or chemotherapy alone for stage III or IV LCSS at authors' center from January 2018 to August 2021. Each 21-day chemotherapy cycle consisted of intravenous injection of gemcitabine (1.0 g/m2) on days 1 and 8 and cisplatin 75 (mg/m2) on day 1. The planned cycles were 4. DEB-BACE consisted of microcatheter infusion of CalliSpheres beads carrying cisplatin (75 mg/m2) and gemcitabine (1.0 g/m2), at 3 weeks prior to chemotherapy. The primary outcome was overall survival (OS). The secondary outcomes included progression-free survival (PFS), pulmonary response, and adverse events (AEs).

RESULTS

The final analysis included 95 patients in the chemotherapy group and 41 patients in the combination treatment group. The median OS was 14 months (95 % CI 11.0-17.0) in the chemotherapy group and 19 months (95 % CI 18.0-24.0) in the combination group (P = 0.015). In multivariate Cox regression analysis, DEB-BACE plus chemotherapy was associated with lower risk of death versus chemotherapy only (HR 0.16, 95 % CI 0.05-0.52; log rank test P = 0.003). The median PFS was 6 months (95 % CI 4.0-7.0) in the chemotherapy group and 8 months (95 % CI 6.0-8.0) in the combination group (P = 0.015). The pulmonary objective response rate (ORR) and disease control rate (DCR) were 48.4 % and 62.1 % in chemotherapy group versus 82.9 % and 90.2 % in combination group (P < 0.001 and = 0.001, respectively). AEs occurred in 133 patients (97.8 %). The rate of bone marrow suppression was 48.4 % (46/95) in the chemotherapy group versus 7.3 % (3/41) in the combination group (P < 0.001).

CONCLUSION

Compared with chemotherapy alone, DEB-BACE plus chemotherapy was associated with longer survival outcomes and lower rate of bone marrow suppression.

Recent research progress of circular RNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an extremely heterogeneous malignant tumor with a high morbidity and mortality. Circular RNAs (circRNAs) are noncoding RNAs with high stability, organ/tissue/cell-specific expression and are conserved across species. Accumulating evidence suggested that circRNAs play crucial roles as microRNA sponges, protein sponges, scaffolds, recruiters and could even polypeptide encoders. Many studies have since revealed that circRNAs were aberrantly expressed in HCC and acted as crucial modulators of HCC carcinogenesis and progression. Furthermore, circRNAs have also been identified as potential diagnostic and prognostic biomarkers for HCC. In this review, we thoroughly outline and evaluate the function of circRNAs in HCC development, with an emphasis on the specific molecular pathways by which they participated in the formation and progression of HCC, and we address their potential for serving as clinical biomarkers in HCC.

Emerging Role of Circular RNAs in Hepatocellular Carcinoma Immunotherapy

Hepatocellular carcinoma (HCC) is a highly fatal malignancy with limited therapeutic options and high recurrence rates. Recently, immunotherapeutic agents such as immune checkpoint inhibitors (ICIs) have emerged as a new paradigm shift in oncology. ICIs, such as programmed cell death protein 1 (PD-1) inhibitors, have provided a new source of hope for patients with advanced HCC. Yet, the eligibility criteria of HCC patients for ICIs are still a missing piece in the puzzle. Circular RNAs (circRNAs) have recently emerged as a new class of non-coding RNAs that play a fundamental role in cancer pathogenesis. Structurally, circRNAs are resistant to exonucleolytic degradation and have a longer half-life than their linear counterparts. Functionally, circRNAs possess the capability to influence various facets of the tumor microenvironment, especially at the HCC tumor-immune synapse. Notably, circRNAs have been observed to control the expression of immune checkpoint molecules within tumor cells, potentially impeding the therapeutic effectiveness of ICIs. Therefore, this renders them potential cancer-immune biomarkers for diagnosis, prognosis, and therapeutic regimen determinants. In this review, the authors shed light on the structure and functional roles of circRNAs and, most importantly, highlight the promising roles of circRNAs in HCC immunomodulation and their potential as promising biomarkers and immunotherapeutic regimen determinants.

Non-coding RNAs' function in cancer development, diagnosis and therapy

While previous research on cancer biology has focused on genes that code for proteins, in recent years it has been discovered that non-coding RNAs (ncRNAs)play key regulatory roles in cell biological functions. NcRNAs account for more than 95% of human transcripts and are an important entry point for the study of the mechanism of cancer development. An increasing number of studies have demonstrated that ncRNAs can act as tumor suppressor genes or oncogenes to regulate tumor development at the epigenetic level, transcriptional level, as well as post-transcriptional level. Because of the importance of ncRNAs in cancer, most clinical trials have focused on ncRNAs to explore whether ncRNAs can be used as new biomarkers or therapies. In this review, we focus on recent studies of ncRNAs including microRNAs (miRNAs), long ncRNAs (lncRNAs), circle RNAs (circRNAs), PIWI interacting RNAs (piRNAs), and tRNA in different types of cancer and explore the application of these ncRNAs in the development of cancer and the identification of relevant therapeutic targets and tumor biomarkers. Graphical abstract drawn by Fidraw.

Nucleus-localized circSLC39A5 suppresses hepatocellular carcinoma development by binding to STAT1 to regulate TDG transcription

Accumulating evidence indicates that circular RNAs (circRNAs) are inextricably linked to cancer development. However, the function and mechanism of nucleus-localized circRNAs in hepatocellular carcinoma (HCC) still require investigation. Here, qRT-PCR and receiver-operating characteristic curve were used to detect the expression and diagnostic potential of circSLC39A5 for HCC. The biological function of circSLC39A5 in HCC was investigated in vitro and in vivo. Nucleoplasmic separation assay, fluorescence in situ hybridization, RNA pulldown, RNA immunoprecipitation, the HDOCK Server, the NucleicNet Webserver, crosslinking-immunoprecipitation, MG132 treatment, and chromatin immunoprecipitation were utilized to explore the potential molecular mechanism of circSLC39A5 in HCC. The results showed that circSLC39A5 was downregulated in both HCC tissues and plasma and was associated with satellite nodules and lymph node metastasis/vascular invasion. CircSLC39A5 was stably expressed in plasma samples under different storage conditions, showing good diagnostic potential for HCC (AUC = 0.915). CircSLC39A5 inhibited proliferation, migration, and invasion, facilitated the apoptosis of HCC cells, and was associated with low expression of Ki67 and CD34. Remarkably, circSLC39A5 is mainly localized in the nucleus and binds to the transcription factor signal transducer and activator of transcription 1 (STAT1), affecting its stabilization and expression. STAT1 binds to the promoter of thymine DNA glycosylase (TDG). Overexpression of circSLC39A5 elevates TDG expression and reverses the increase of proliferating cell nuclear antigen (PCNA) expression and the overactive cell proliferation caused by TDG silencing. Our findings uncovered a novel plasma circRNA, circSLC39A5, which may be a potential circulating diagnostic marker for HCC, and the mechanism by which nucleus-localized circSLC39A5 exerts a transcriptional regulatory role in HCC by affecting STAT1/TDG/PCNA provides new insights into the mechanism of circRNAs.

Multiple Roles of the RUNX Gene Family in Hepatocellular Carcinoma and Their Potential Clinical Implications

Hepatocellular carcinoma (HCC) is one of the most frequent cancers in humans, characterised by a high resistance to conventional chemotherapy, late diagnosis, and a high mortality rate. It is necessary to elucidate the molecular mechanisms involved in hepatocarcinogenesis to improve diagnosis and treatment outcomes. The Runt-related (RUNX) family of transcription factors (RUNX1, RUNX2, and RUNX3) participates in cardinal biological processes and plays paramount roles in the pathogenesis of numerous human malignancies. Their role is often controversial as they can act as oncogenes or tumour suppressors and depends on cellular context. Evidence shows that deregulated RUNX genes may be involved in hepatocarcinogenesis from the earliest to the latest stages. In this review, we summarise the topical evidence on the roles of RUNX gene family members in HCC. We discuss their possible application as non-invasive molecular markers for early diagnosis, prognosis, and development of novel treatment strategies in HCC patients.

Going circular: history, present, and future of circRNAs in cancer

To date, thousands of highly abundant and conserved single-stranded RNA molecules shaped into ring structures (circRNAs) have been identified. CircRNAs are multifunctional molecules that have been shown to regulate gene expression transcriptionally and post-transcriptionally and exhibit distinct tissue- and development-specific expression patterns associated with a variety of normal and disease conditions, including cancer pathogenesis. Over the past years, due to their intrinsic stability and resistance to ribonucleases, particular attention has been drawn to their use as reliable diagnostic and prognostic biomarkers in cancer diagnosis, treatment, and prevention. However, there are some critical caveats to their utility in the clinic. Their circular shape limits their annotation and a complete functional elucidation is lacking. This makes their detection and biomedical application still challenging. Herein, we review the current knowledge of circRNA biogenesis and function, and of their involvement in tumorigenesis and potential utility in cancer-targeted therapy.

Circular SERPINA3 and its target microRNA-944 as potential biomarkers in hepatitis C virus-induced hepatocellular carcinoma in Egyptian population

Background

The most prevalent cancer in Egypt is hepatocellular carcinoma (HCC) mainly due to the infection with the hepatitis C virus. So it is critical to find sensitive biomarkers for early diagnosis of HCC and avoid post-operation tumor recurrence. Therefore, this research was designed to demonstrate the circSERPINA3 role in the regulation of microRNA-944 gene expression in HCV-related HCC cases and compare these results with circSERPINA3 and microRNA-944 gene expression levels in HCV-infected patients.

Methodology

Study participants were divided into three groups: healthy controls, HCV- infected, and HCV-induced HCC patients. The gene expression levels of circSERPINA3 and microRNA-944 were evaluated using Real-Time qPCR. Then the immunoblotting procedure was applied to measure the serum levels of MDM2 and E-cadherin besides, the serum concentration levels of glypican-3 and alpha-fetoprotein were measured by sandwich ELISA.

Results

The gene expression level of circSERPINA3 was significantly upregulated in both HCV-infected and HCC patients causing suppression of the antitumor effect of miR-944 and showing a lower 1-year survival rate than the participants who had low circSERPINA3 gene expression levels. Subsequently, the miR-944 downstream protein, MDM2 was remarkably upregulated, exaggerating the metastasis and oxidative stress in HCC cases. Additionally, the results confirmed the downregulation of microRNA-944 improved the progression of viral hepatitis C cases to hepatocarcinogenesis through the significantly increased serum level of the metastatic marker, E-cadherin. Although alpha-fetoprotein is a common diagnostic marker used in the diagnosis of HCC, our results showed that glypican-3 had greater sensitivity and specificity and positively correlated to the IGF-1 signaling pathway of HCC cases. Moreover, the gene expression levels of circSERPINA3 and E-cadherin in both the HCV and HCV-induced HCC were significantly positively correlated.

Conclusion

circSERPINA3 and miR-944 were sensitive molecular markers for early diagnosis of HCC and could be prospective treatment targets for HCV-infected patients to avoid tumor recurrence in HCC cases.

Circular RNAs in hepatocellular carcinoma: biogenesis, function, and pathology

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Both genetic and environmental factors through a multitude of underlying molecular mechanisms participate in the pathogenesis of HCC. Recently, numerous studies have shown that circular RNAs (circRNAs), an emerging class of non-coding RNAs characterized by the presence of covalent bonds linking 3' and 5' ends, play an important role in the initiation and progression of cancers, including HCC. In this review, we outline the current status of the field of circRNAs, with an emphasis on the functions and mechanisms of circRNAs in HCC and its microenvironment. We also summarize and discuss recent advances of circRNAs as biomarkers and therapeutic targets. These efforts are anticipated to throw new insights into future perspectives about circRNAs in basic, translational and clinical research, eventually advancing the diagnosis, prevention and treatment of HCC.

LARP4A and LARP4B in cancer: The new kids on the block

Recent developments have mounted a stunning body of evidence underlying the importance of RNA binding proteins (RBPs) in cancer research. In this minireview we focus on LARP4A and LARP4B, two paralogs belonging to the superfamily of La-related proteins, and provide a critical overview of current research, including their roles in cancer pathogenesis and cell proliferation, migration, cell cycle and apoptosis. We highlight current controversies surrounding LARP4A and LARP4B and conclude that their complex roles in tumorigenesis are cell-, tissue- and context-dependent, warning that caution must be exercised before categorising either protein as an oncoprotein or tumour-suppressor. We also reveal that LARP4A and LARP4B have often been confused with one another, adding uncertainty in delineating their functions. We suggest that further functional and mechanistic studies of LARP4 proteins present significant challenges for future investigations to recognise the vital contributions of these RBPs in cancer research.

Research progress of circular RNA molecules in aging and age-related diseases

Circular RNAs (circRNAs) are a class of single-chain endogenous closed circular RNAs that do not have a poly(A) tail at the 3' end and a cap structure at the 5' end and are connected end-to-end by covalent bonds. CircRNAs, which are pervasive, diverse, stable, and conversed, have functions in transcriptional control and protein translation and play vital roles in modulating cell senescence, individual aging, as well as the occurrence and development of age-related diseases. Studies in recent years were reviewed from aspects including the biosynthesis mechanisms, classification, expression, biomedical functions, associations with aging and age-related diseases, and potential clinical applications of circRNAs. It will provide the theoretic basis for exploring the molecular biological mechanisms of aging, using circRNA as the therapeutic target to delay aging, and finding therapeutic strategies to prevent and treat age-related diseases.

The RUNX Family, a Novel Multifaceted Guardian of the Genome

The DNA repair machinery exists to protect cells from daily genetic insults by orchestrating multiple intrinsic and extrinsic factors. One such factor recently identified is the Runt-related transcription factor (RUNX) family, a group of proteins that act as a master transcriptional regulator for multiple biological functions such as embryonic development, stem cell behaviors, and oncogenesis. A significant number of studies in the past decades have delineated the involvement of RUNX proteins in DNA repair. Alterations in RUNX genes cause organ failure and predisposition to cancers, as seen in patients carrying mutations in the other well-established DNA repair genes. Herein, we review the currently existing findings and provide new insights into transcriptional and non-transcriptional multifaceted regulation of DNA repair by RUNX family proteins.

Circ-Vps41 positively modulates Syp and its overexpression improves memory ability in aging mice

INTRODUCTION

Age is an established risk factor for neurodegenerative disorders. Aging-related cognitive decline is a common cause of memory impairment in aging individuals, in which hippocampal synaptic plasticity and hippocampus-dependent memory formation are damaged. Circular RNAs (circRNAs) have been reported in many cognitive disorders, but their role in aging-related memory impairment is unclear.Methods: In this study, we aimed to investigate the effects of circ-Vps41 on aging-related hippocampus-dependent memory impairment and explore the potential mechanisms. Here, D-galactose was used to produce a conventional aging model resulting in memory dysfunction.

RESULTS

Circ-Vps41 was significantly downregulated in D-galactose-induced aging in vitro and in vivo. The overexpression of circ-Vps41 could upregulate synaptophysin (Syp), thereby promoting the synaptic plasticity and alleviating cognitive impairment in aging mice. Mechanistically, we found that circ-Vps41 upregulated Syp expression by physically binding to miR-24-3p. Moreover, the miR-24-3p mimics reversed the circ-Vps41 overexpression-induced increase in Syp expression.

DISCUSSION

Overexpression of circ-Vps41 alleviated the synaptic plasticity and memory dysfunction via the miR-24-3p/Syp axis. These findings revealed circ-Vps41 regulatory network and provided new insights into its potential mechanisms for improving aging-related learning and memory impairment.

circRNA-MSR regulates the expression of FBXO21 to inhibit chondrocyte autophagy by targeting miR-761 in osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease and is the most prevalent and disabling form of arthritis worldwide. Autophagy plays a vital role in OA. This study aimed to explore whether covalently closed circular RNA MSR (circRNA-MSR) could affect the F-box Only Protein 21 (FBXO21) expression by targeting microRNA-761 (miR-761), thereby affecting the autophagy in OA chondrocytes. Clinical OA tissues were collected, and circRNA-MSR, miR-761, and FBXO21 expressions were detected via quantitative real-time polymerase chain reaction (qRT-PCR). An in vitro OA model was constructed by treating C28/I2 cells with LPS and treating them with overexpression or knockdown vector of circRNA-MSR, miR-761, and FBXO21, and autophagy inhibitor 3-MA. Fluorescence in situ hybridization (FISH) determined the location of circRNA-MSR and miR-761. Dual-luciferase assay assessed circRNA-MSR and miR-761, along with the bindings of miR-761 and FBXO21. Cell viability was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. LC3 II/I, p62 and beclin 1 expressions were detected via the western blot. circRNA-MSR and FBXO21 levels were elevated in OA, but miR-761 level was inhibited. Suppressing circRNA-MSR promoted the autophagy of LPS-treated cells. circRNA-MSR could bind to miR-761 and inhibit its expression. MiR-761 inhibition reversed the promoted autophagy caused by circRNA-MSR knockdown in LPS-treated C28/I2 cells. Moreover, miR-761 could target FBXO21 and inhibit its expression. FBXO21 overexpression reversed the increased autophagy caused by miR-761 overexpression in LPS-treated C28/I2 cells. circRNA-MSR could affect FBXO21 level via targeting miR-761, thereby repressing autophagy in OA chondrocytes, providing a new target and strategy for OA treatment.

Downregulation of miR-761 ameliorates radiation-induced pulmonary fibrosis by regulating PGC-1α

Background: Radiation-induced pulmonary fibrosis (RIPF) is a serious complication in patients treated with transthoracic irradiation. To date, there are no effective drugs for RIPF treatment. In this study, we attempted to explore the function of miR-761 in RIPF, further investigate its potential mechanism and evaluate its effectiveness in the treatment of RIPF. Methods: qRT-PCR analysis was used to detect miR-761 and peroxisome proliferator-activated receptor gamma (PPARg) coactivator-1 (PGC-1α) expression. Western Blot (WB) assay was applied to verify the regulation of PGC-1α by miR-761 and the expression of fibrosis-related proteins. Gel contraction assay was performed to demonstrate the level of fibroblast activation in vitro. A mouse RIPF model was used to validate the anti-fibrotic effect of Antagomir761. Bioinformatics analysis and dual-luciferase reporter assays were utilized to confirm the regulation relationship between miR-761 and PGC-1α. Results: The results showed that miR-761 was significantly elevated in irradiated mice lungs and fibroblasts. Overexpression of miR-761 in vitro promoted fibroblast activation. Whereas inhibition of miR-761 attenuated the degree of RIPF and inhibited fibroblast activation. Mechanistically, PGC-1α was a direct and functional target of miR-761, overexpression of PGC-1α inhibited irradiation-induced fibroblast activation, and knockdown of PGC-1α caused miR-761 inhibitor loses its anti-activation ability in irradiated cells. Conclusion: Our findings demonstrated that miR-761 regulated RIPF by targeting PGC-1α. Inhibition of miR-761 restored PGC-1α expression and attenuated RIPF damage, and miR-761 was a potential target for preventing the development of RIPF.

Prp19 Facilitated p21-Dependent Senescence of Hepatocellular Carcinoma Cells

Introduction

Evidence suggests that the role of senescence in the development of cancer is context-dependent. An orthologue of human pre-mRNA processing factor 19 (Prp19) attenuates the senescence of human endothelial cells. Prp19 has been reported to be involved in the progression of hepatocellular carcinoma (HCC). This work aims to investigate the effect of Prp19 on the senescence of HCC.

Materials and Methods

Senescence of L02 cells and HCC cells under different stimuli was detected through cell cycle analysis, SA-β-gal staining, and senescence associated secretory phenotype analysis. The relationship between Prp19 and senescence-related proteins was evaluated using real-time RT-PCR, western blot assay, and immunohistochemistry. Subcutaneous xenograft tumors in nude mice were used to evaluate the role of Prp19 on senescence in vivo. Data analysis was carried out using GraphPad Prism 6.

Results

Prp19 facilitated the senescence of L02 cells and HCC cells under different stresses. Prp19 positively modulated p21 expression in the mRNA level. Downregulation of Prp19 promoted the growth of subcutaneous xenograft tumors generated by HCC cell lines.

Conclusions

Prp19 may promote senescence of HCC cells via regulating p21 expression.

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.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

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.

Dissecting the Role of Circular RNAs in Sarcomas with Emphasis on Osteosarcomas

Circular RNAs (circRNAs) are single-stranded RNAs generated from exons back-splicing from a single pre-mRNA, forming covalently closed loop structures which lack 5'-3'-polarity or polyadenylated tail. Ongoing research depicts that circRNAs play a pivotal role in tumorigenesis, tumor progression, metastatic potential and chemoresistance by regulating transcription, microRNA (miRNA) sponging, RNA-binding protein interactions, alternative splicing and to a lesser degree, protein coding. Sarcomas are rare malignant tumors stemming from mesenchymal cells. Due to their clinically insidious onset, they often present at advanced stage and their treatment may require aggressive chemotherapeutic or surgical options. This review is mainly focused on the regulatory functions of circRNAs on osteosarcoma progression and their potential role as biomarkers, an area which has prompted lately extensive research. The attributed oncogenic role of circRNAs on other mesenchymal tumors such as Kaposi Sarcoma (KS), Rhabdomyosarcoma (RMS) or Gastrointestinal Stromal Tumors (GISTs) is also described. The involvement of circRNAs on sarcoma oncogenesis and relevant emerging diagnostic, prognostic and therapeutic applications are expected to gain more research interest in the future.

Circular RNAs in cell cycle regulation: Mechanisms to clinical significance

Circular RNAs (circRNAs), a type of non‐coding RNA, are single‐stranded circularized molecules characterized by high abundance, evolutionary conservation and cell development‐ and tissue‐specific expression. A large body of studies has found that circRNAs exert a wide variety of functions in diverse biological processes, including cell cycle. The cell cycle is controlled by the coordinated activation and deactivation of cell cycle regulators. CircRNAs exert mutifunctional roles by regulating gene expression via various mechanisms. However, the functional relevance of circRNAs and cell cycle regulation largely remains to be elucidated. Herein, we briefly describe the biogenesis and mechanistic models of circRNAs and summarize their functions and mechanisms in the regulation of critical cell cycle modulators, including cyclins, cyclin‐dependent kinases and cyclin‐dependent kinase inhibitors. Moreover, we highlight the participation of circRNAs in cell cycle‐related signalling pathways and the clinical value of circRNAs as promising biomarkers or therapeutic targets in diseases related to cell cycle disorder.

Circular RNA La-related protein 4 inhibits cell proliferation, migration, and invasion and sponges microRNA-367 in non-small cell lung cancer

This study aimed to investigate the effect of circular RNA (circRNA) La-related protein 4 (LARP4) on inhibiting the malignant progression of non-small cell lung cancer (NSCLC) cells. CircRNA LARP4 expression in a human normal lung epithelial cell line and NSCLC cell lines was detected by reverse transcription-quantitative polymerase chain reaction. CircRNA LARP4 overexpression and control overexpression plasmids were transfected into NCI-H1650 cells; circRNA LARP4 knockdown and control knockdown plasmids were transfected into A549 cells. CircRNA LARP4 and microRNA (miR)-367 expressions, cell proliferation, apoptosis, migration, and invasion after transfection were investigated. Moreover, the luciferase reporter assay was used to explore the interaction between circRNA LARP4 and miR-367. CircRNA LARP4 was decreased in NSCLC cell lines (including A549, NCI-H1650, NCI-H1299, and HCC827 cells) compared to BEAS-2B cells. In NCI-H1650 cells, circRNA LARP4 overexpression inhibited cell proliferation, migration, and invasion, while promoting apoptosis. In A549 cells, circRNA LARP4 knockdown increased cell proliferation, migration, and invasion, while decreasing apoptosis. Moreover, miR-367 was decreased by the overexpression of circRNA LARP4, but increased by the knockdown of circRNA LARP4; and further luciferase reporter assay revealed that circRNA LARP4 could directly bind to miR-367. In conclusion, circRNA LARP4 is downregulated, suppresses cell proliferation, migration, and invasion, and acts as a sponge of oncogene miR-367 in NSCLC.

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.

Regulation of RUNX proteins by long non-coding RNAs and circular RNAs in different cancers

RUNX proteins have been shown to behave as "double-edge sword" in wide variety of cancers. Discovery of non-coding RNAs has played linchpin role in improving our understanding about the post-transcriptional regulation of different cell signaling pathways. Several new mechanistic insights and distinct modes of cross-regulation of RUNX proteins and non-coding RNAs have been highlighted by recent research. In this review we have attempted to provide an intricate interplay between non-coding RNAs and RUNX proteins in different cancers. Better conceptual and mechanistic understanding of layered regulation of RUNX proteins by non-coding RNAs will be helpful in effective translation of the laboratory findings to clinically effective therapeutics.

Circular RNAs in Hepatocellular Carcinoma: Emerging Functions to Clinical Significances

Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver and carries high morbidity and mortality. Diagnosing HCC at an early stage is challenging. Therefore, finding new, highly sensitive and specific diagnostic biomarkers for the diagnosis and prognosis of HCC patients is extremely important. Circular RNAs (circRNAs) are a class of non-coding RNAs with covalently closed loop structures. They are characterized by remarkable stability, long half-life, abundance and evolutionary conservation. Recent studies have shown that many circRNAs are expressed aberrantly in HCC tissues and have important regulatory roles during the development and progression of HCC. Hence, circRNAs are promising biomarkers for the diagnosis and prognosis of HCC. This review: (i) summarizes the biogenesis, categories, and functions of circRNAs; (ii) focuses on current progress of dysregulated expression of circRNAs in HCC with regard to regulation of the tumor hallmarks, “stemness” of cancer cells, and immunotherapy; (iii) highlights circRNAs as potential biomarkers and therapeutic targets for HCC; and (iv) discusses some of the challenges, questions and future perspectives of circRNAs research in HCC.

The Latest Overview of circRNA in the Progression, Diagnosis, Prognosis, Treatment, and Drug Resistance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the main causes of tumor-related deaths worldwide. Due to the lack of obvious early symptoms and the lack of sensitive screening indicators in the early stage of HCC, the vast majority of patients are diagnosed with advanced or metastatic HCC, resulting in dissatisfactory treatment result. Therefore, it is urgent to determine effective and sensitive diagnostic and prognostic indicators and to determine new therapeutic targets. Circular RNA (circRNA) is a type of non-coding RNA that has been neglected for a long time. In recent years, it has been proved to play an important role in the development of many human diseases. Increasing evidence shows that change in circRNA expression has an extensive effect on the biological behavior of HCC. In this study, we comprehensively tracked the latest progress of circRNA in the pathogenesis of HCC, and reviewed its role as a biomarker for diagnosis and prognosis prediction in patients with HCC. In addition, we also summarized the potential of circRNA as therapeutic target in HCC and its relationship with HCC drug resistance, providing clues for the clinical development of circRNA-based therapeutic strategies.

The Roles of circRNAs in Liver Cancer Immunity

Circular RNAs (circRNAs) are stable covalently closed non-coding RNAs (ncRNAs). Many studies indicate that circRNAs are involved in the pathological and physiological processes of liver cancer. However, the functions of circRNAs in liver cancer immunity are less known. In this review, we summarized the functions of circRNAs in liver cancer, including proliferative, metastasis and apoptosis, liver cancer stemness, cell cycle, immune evasion, glycolysis, angiogenesis, drug resistance/sensitizer, and senescence. Immune escape is considered to be one of the hallmarks of cancer development, and circRNA participates in the immune escape of liver cancer cells by regulating natural killer (NK) cell function. CircRNAs may provide new ideas for immunotherapy in liver cancer.

Recent Update on the Role of Circular RNAs in Hepatocellular Carcinoma

After being overlooked for decades, circular RNAs (circRNAs) have recently generated considerable interest. circRNAs play a role in a variety of normal and pathological biological processes, including hepatocarcinogenesis. Many circRNAs contribute to hepatocarcinogenesis through sponging of microRNAs (miRs) and disruption of cellular signaling pathways that play a part in control of cell proliferation, metastasis and apoptosis. In most cases, overexpressed circRNAs sequester miRs to cause de-repressed translation of mRNAs that encode oncogenic proteins. Conversely, low expression of circRNAs has also been described in hepatocellular carcinoma (HCC) and is associated with inhibited production of tumor suppressor proteins. Other functions of circRNAs that contribute to hepatocarcinogenesis include translation of truncated proteins and acting as adapters to regulate influence of transcription factors on target gene expression. circRNAs also affect hepatocyte transformation indirectly. For example, the molecules regulate immune surveillance of cancerous cells and influence the liver fibrosis that commonly precedes HCC. Marked over- or under-expression of circRNA expression in HCC, with correlating plasma concentrations, has diagnostic utility and assays of these RNAs are being developed as biomarkers of HCC. Although knowledge in the field has recently surged, the myriad of described effects suggests that not all may be vital to hepatocarcinogenesis. Nevertheless, investigation of the role of circRNAs is providing valuable insights that are likely to contribute to improved management of a serious and highly aggressive cancer.

Circular RNAs in Human Cancer

Circular RNAs (circRNAs) are a class of endogenous single-stranded covalently closed RNAs, primarily produced from pre-mRNAs via non-canonical back-splicing. circRNAs are highly conserved, stable, and expressed in tissue- and development-specific pattern. circRNAs play essential roles in physiological process as well as cancer biology. By the advances of deep sequencing and bioinformatics, the number of circRNAs have increased explosively. circRNAs function as miRNA/protein sponge, protein scaffold, protein recruitment, enhancer of protein function, as well as templates for translation involved in the regulation of transcription/splicing, translation, protein degradation, and pri-miRNA processing in human cancers and contributed to the pathogenesis of cancer. Numerous circRNAs may function in diverse manners. In this review, we survey the current understanding of circRNA functions in human cancer including miRNA sponge, circRNA-protein interaction, and circRNA-encoded protein, and summarize available databases for circRNA annotation and functional prediction.

Circ_0008450 downregulates Runx3 to promote the proliferation and epithelial-mesenchymal transition of human keratinized epithelial cells

Keloid is an extremely common and often overlooked benign neoplastic disease, but its consequences should not be underestimated. Therefore, a deep exploration of the pathological mechanism of keloid becomes very essential. After 22 samples were collected from each patient's keloid tissues and normal skin tissues, circ_0008450 and Runx3 expression was tested by qRT-PCR. When primary human keratinized epithelial cells were transfected by sh-circ_0008450 or sh-Runx3, cell proliferation, apoptosis, migration, and EMT process were assessed by CCK-8, BrdU assay, apoptosis assay, migration assay, and Western blot. Finally, transfection was performed to explore the effect of circ_0008450 on the TGF-β/Smad signal pathway by adopting western blot. Circ_0008450 was highly expressed in keratinized epithelial tissues. After the transfection of sh-circ_0008450 into primary human keratinized epithelial cells, cell proliferation, migration, and EMT process were inhibited, and apoptosis was stimulated. Moreover, circ_0008450 silence-induced above changes were partly reversed by transfecting sh-Runx3. In addition, transfecting sh-circ_0008450 could repress TGF-β/Smad pathway, while transfecting sh-Runx3 activated the above pathway. Circ_0008450 down-regulated Runx3 to promote the proliferation and EMT process of human keratinized epithelial cells. This discovery may be related to the activation of the TGF-β/Smad pathway.

Circular RNAs in liver diseases: Mechanisms and therapeutic targets

Circular RNAs (circRNAs) are formed from the genome through diverse back splicing and feature the closed loop. circRNAs are widely available in a variety of cells and characterized by conservation, structural stability, high abundance and tissue-specific or developmental-specific expression. Recent studies have shown that circRNAs are closely related to liver diseases, such as metabolic-associated fatty liver disease, hepatitis, liver cirrhosis and hepatocellular carcinoma. circRNAs play an important role in the progression of liver diseases, are potential diagnostic and prognostic markers, and have translational value in therapy. This article reviews the research on circRNAs in liver diseases, with a view to providing a theoretical basis and new ideas for future research and treatment of liver diseases.

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."

The emerging roles of non-coding competing endogenous RNA in hepatocellular carcinoma

Accumulating evidence has emerged revealing that noncoding RNAs (ncRNAs) play essential roles in the occurrence and development of hepatocellular carcinoma (HCC). However, the complicated regulatory interactions among various ncRNAs in the development of HCC are not entirely understood. The newly discovered mechanism of competing endogenous RNAs (ceRNAs) uncovered regulatory interactions among different varieties of RNAs. In recent years, a growing number of studies have suggested that ncRNAs, including long ncRNAs, circular RNAs and pseudogenes, play major roles in the biological functions of the ceRNA network in HCC. These ncRNAs can share microRNA response elements to affect microRNA affinity with target RNAs, thus regulating gene expression at the transcriptional level and both physiological and pathological processes. The ncRNAs that function as ceRNAs are involved in diverse biological processes in HCC cells, such as tumor cell proliferation, epithelial-mesenchymal transition, invasion, metastasis and chemoresistance. Based on these findings, ncRNAs that act as ceRNAs may be promising candidates for clinical diagnosis and treatments. In this review, we discuss the mechanisms and research methods of ceRNA networks. We also reviewed the recent advances in studying the roles of ncRNAs as ceRNAs in HCC and highlight possible directions and possibilities of ceRNAs as diagnostic biomarkers or therapeutic targets. Finally, the limitations, gaps in knowledge and opportunities for future research are also discussed.

MicroRNA-761 modulates foam cell formation and inflammation through autophagy in the progression of atherosclerosis

Macrophage-derived foam cells formation is the initial stage of atherosclerosis, and lipid-laden macrophage accumulation is also considered as the symbol of unstable plaque. Autophagy is a subcellular process responsible for the degradation of damaged organelles and aggregated proteins in cells (Grootaert in Oxid Med Cell Longev: 7687083, 2018). Macrophage autophagy plays an important role in atherosclerosis under various stress conditions, and microRNAs are involved in this complicated process. The present study was programmed to explore the effects of microRNA-761 on macrophage-derived foam cell formation, focusing on the role of autophagy in this pathological process. The differentiated human THP-1 macrophages were used in the study. THP-1-derived macrophages were treated with miR-761 mimics or inhibitors and cultured with oxidized low-density lipoprotein to mimic the lipid-rich environment in blood vessel. The expression of miR-761 and mRNA levels of IL-1β and IL-18 were analyzed by quantitative real-time PCR. The effect of miR-761 on autophagy was evaluated by the protein levels of Beclin1, p62/SQSTM1, microtubule-associated protein light chain 3, mammalian target of rapamycin (mTOR), and unc-51-like autophagy activating kinase 1 (ULK1), determined by immunoblot and autophagic flux detected by fluorescent staining. The secretion of IL-1β and IL-18 was tested by enzyme-linked immunosorbent reaction kit. Lipid accumulation in foam cells was detected by oil red "O" staining. We demonstrated that miR-761 was able to repress foam cell formation and reduce the production of atherogenic inflammatory cytokines IL-1β and IL-18 in an autophagy-dependent manner in atherosclerosis, possibly via mTOR-ULK1 signaling pathway. In summary, we described an athero-protective function of miR-761 in macrophages incubated with excess ox-LDL and identified an important novel modulator of mTOR signaling and autophagy in macrophage-derived foam cells. This finding may provide a potential target for the prevention and early treatment in high-risk group of atherosclerosis.

Circular RNA La-Related Protein 4 Inhibits Nonsmall Cell Lung Cancer Cell Proliferation While Promotes Apoptosis Through Sponging microRNA-21-5p

Background: This study aimed to investigate the function of circular RNA La-related protein 4 (circ-LARP4) on nonsmall cell lung cancer (NSCLC) progression. Materials and Methods: Circ-LARP4 overexpression and circ-LARP4 short hairpin RNA (shRNA) plasmids were transfected into NCI-H1650 cells and NCI-H1299 cells respectively. In rescue experiment, microRNA (miR)-21-5p overexpression and miR-21-5p shRNA plasmids were transfected into circ-LARP4 overexpression-treated NCI-H1650 cells and circ-LARP4 knockdown-treated NCI-H1650 cells, respectively. Circ-LARP4 and miR-21-5p expression levels were detected by reverse transcription-quantitative polymerase chain reaction. Cell proliferation and apoptosis were investigated by cell counting kit-8 assay and annexin V/propidium iodide assay. The interaction between circ-LARP4 and miR-21-5p was further explored by luciferase reporter assay. Results: Circ-LARP4 expression was decreased in NSCLC cell lines (including NCI-H1299, NCI-H522, NCI-H23, NCI-H358, and NCI-H1650) compared with human normal lung epithelial cell line. Circ-LARP4 overexpression inhibited cell proliferation while promoted apoptosis in NCI-H1650 cells, whereas circ-LARP4 knockdown increased cell proliferation while decreased apoptosis in NCI-H1299 cells. Meanwhile, miR-21-5p was negatively regulated by circ-LARP4, whereas circ-LARP4 was not affected by miR-21-5p in NCI-H1650 and NCI-H1299 cells. In rescue experiment, miR-21-5p overexpression attenuated the effect of circ-LARP4 overexpression on decreasing cell proliferation and increasing apoptosis in NCI-H1650 cells, whereas miR-21-5p knockdown attenuated the effect of circ-LARP4 knockdown on promoting cell proliferation and suppressing apoptosis in NCI-H1299 cells. Further luciferase reporter assay revealed that circ-LARP4 could directly bind to miR-21-5p. Conclusions: Circ-LARP4 is decreased and suppresses cell proliferation while promoted apoptosis by sponging miR-21-5p in NSCLC.

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.

Circular RNA La-related RNA-binding protein 4 correlates with reduced tumor stage, as well as better prognosis, and promotes chemosensitivity to doxorubicin in breast cancer

OBJECTIVE

We aimed to evaluate the correlation of circular RNA La-related RNA-binding protein 4 (circ-LARP4) with tumor characteristics and prognosis, and its effect on chemosensitivity in breast cancer.

METHODS

Circ-LARP4 from tumor and adjacent tissues of 283 female breast cancer patients underwent resection was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Tumor features, disease-free survival (DFS), and overall survival (OS) were recorded. In vitro, circ-LARP4 in human normal mammary epithelial cells (HMEC) and breast cancer cell lines was detected by RT-qPCR. MCF-7 and MDA-MB-231 cells were transfected with circ-LARP4 overexpression plasmid (as OE-Circ group) and control overexpression plasmid (as OE-Control group). Relative cell viability under different concentrations of doxorubicin was measured.

RESULTS

Circ-LARP4 was decreased in tumor tissues than adjacent tissues (P < .001). Tumor circ-LARP4 negatively correlated with tumor size (P = .001), T stage (P = .009), N stage (P = .006), and TNM stage (P < .001), whereas positively correlated with DFS (P = .004) and OS (P < .001). In vitro, circ-LARP4 was decreased MCF-7, BT474, MDA-MB-231, and MDA-MB-468 cell lines than HMEC (all P < .001). Relatively cell viability of MCF-7 cells (at 20 nmol/L [P < .05], 40 nmol/L [P < .01], 80 nmol/L [P < .05] of doxorubicin) and MDA-MB-231 cells (at 120 nmol/L [P < .05], 240 nmol/L [P < .05] of doxorubicin) was decreased in OE-Circ group than OE-Control group. IC50 value of doxorubicin was decreased in OE-Circ group than OE-Control group in MCF-7 and MDA-MB-231 cell lines (both P < .01).

CONCLUSION

Circ-LARP4 was a potential prognostic biomarker, which might improve the management of breast cancer.

CircLARP4 Suppresses Cell Proliferation, Invasion and Glycolysis and Promotes Apoptosis in Non-Small Cell Lung Cancer by Targeting miR-135b

Background

CircLARP4 is reported to act as a tumor suppressor in some cancers. However, the detailed roles and molecular basis of circLARP4 in non-small cell lung cancer (NSCLC) tumorigenesis are still unclear. The aim of the study is to explore the potential roles and molecular basis of circLARP4 in NSCLC tumorigenesis.

Materials and Methods

qRT-PCR was taken to detect circLARP4 and miR-135b expressions. MTT assay, transwell invasion assay and flow cytometry analysis were applied to evaluate cell proliferation, invasion and apoptosis, respectively. Glycolysis was assessed by measuring hexokinase2 (HK2) expression, glucose consumption and lactate production. Association between circLARP4 and miR-135a was examined by luciferase reporter and RIP assays. The changes of the phosphatase and tension homolog (PTEN)/protein kinase B (AKT)/hypoxia-inducible factor-1α (HIF-1α) pathway were evaluated by Western blot. The nude mouse xenograft models were applied to verify the regulation of circLARP4 in vivo.

Results

CircLARP4 was decreased in NSCLC tissues and cells. CircLARP4 overexpression blocked cell proliferation and invasion, and facilitated apoptosis in NSCLC cells. Meanwhile, circLARP4 overexpression suppressed glycolysis in NSCLC cells, as evidenced by the reduced HK2, glucose consumption and lactate production levels. Further analyses proved a downregulation of miR-135b by circLARP4 in a ceRNA-dependent manner in NSCLC cells. CircLARP4-mediated tumor suppression on NSCLC progression was partially overturned by overexpressing miR-135b. Moreover, we confirmed that circLARP4 had antitumor effect on xenograft tumors and downregulated miR-135b. Furthermore, circLARP4 overexpression inhibited the PTEN/AKT/HIF-1α pathway in NSCLC cells and xenograft tumors by downregulating miR-135b.

Conclusion

Our findings suggested that circLARP4 suppressed NSCLC progression by sponging miR-135b through inactivation of the PTEN/AKT/HIF-1α pathway, which broadens our understanding concerning the roles of circLARP4 in NSCLC tumorigenesis.

The long noncoding RNA Arrl1 inhibits neurite outgrowth by functioning as a competing endogenous RNA during neuronal regeneration in rats

The intrinsic regeneration ability of neurons is a pivotal factor in the repair of peripheral nerve injury. Therefore, identifying the key modulators of nerve regeneration may help improve axon regeneration and functional recovery after injury. Unlike for classical transcription factors and regeneration-associated genes, the function of long noncoding RNAs (lncRNAs) in the regulation of neuronal regeneration remains mostly unknown. In this study, we used RNA-Seq-based transcriptome profiling to analyze the expression patterns of lncRNAs and mRNAs in rat dorsal root ganglion (DRG) following sciatic nerve injury. Analyses using the lncRNA-mRNA co-expression network, gene ontology enrichment, and Kyoto Encyclopedia of Genes and Genomes pathway databases indicated that the lncRNA Arrl1 decreases neurite outgrowth after neuronal injury. shRNA-mediated Arrl1 silencing increased axon regeneration both in vitro and in vivo and improved functional recovery of the sciatic nerve. Moreover, inhibiting an identified target gene of Arrl1, cyclin-dependent kinase inhibitor 2B (Cdkn2b), markedly promoted neurite outgrowth of DRG neurons. We also found that Arrl1 acts as a competing endogenous RNA that sponges a Cdkn2b repressor, microRNA-761 (miR-761), and thereby up-regulates Cdkn2b expression during neuron regeneration. We conclude that the lncRNA Arrl1 affects the intrinsic regeneration of DRG neurons by derepressing Cdkn2b expression. Our findings indicate a role for an lncRNA-microRNA-kinase pathway in the regulation of axon regeneration and functional recovery following peripheral nerve injury in rats.

CircRNA_0005075 suppresses carcinogenesis via regulating miR-431/p53/epithelial-mesenchymal transition axis in gastric cancer

This study was aimed to explore the expression and biological function of circRNA_0005075 in gastric cancer (GC) progression and its underlying mechanism. First, the expression level of circRNA_0005075 and microRNA-431 (miR-431) in GC tissues were detected with the quantitative real-time polymerase chain reaction. In addition, after down-regulated the circRNA_0005075 expression by plasmid transfection in GC cells, the Cell Counting Kit-8 (CCK-8), EDU, transwell assay were conducted to evaluate the function of circRNA_0005075 or miR-431 on cell proliferation, metastasis in vitro. Moreover, p53 and Epithelial-mesenchymal transition (EMT) pathway related proteins were also measured with western blotting. Then, our data revealed that CircRNA_0005075 was found to be significantly up-regulated in GC tissues as well as GC cell lines, and the GC patients with higher CircRNA_0005075 expression were more likely to have poor outcomes. Down-regulation of CircRNA_0005075 could significantly suppress the GC cell proliferation and cell metastasis ability, while the addition of miR-431 inhibitors could counteract this effect. Importantly, we discovered that the silencing of circRNA_0005075 could weaken the micro-RNA sponge function for miR-431, and then upregulate the expression of p53 and forbid the EMT signalling pathway, and finally suppress the tumourigenesis of GC. To sum up, CircRNA_0005075 could inhibit cell growth and metastasis of GC through regulating the miR-431/p53/EMT axis. SIGNIFICANCE OF THE STUDY: The research clearly elucidated the potential role and relative regulatory mechanism of circRNA_0005075 in gastric cancer (GC) progression. Briefly, circRNA_0005075 could directly inhibit the expression level of miR-431, then regulate the p53/Epithelial-mesenchymal transition axis, and finally inhibit cell growth and metastasis in GC. Consequently, circRNA_0005075 might act as an oncogene in the GC procession, which provides a promising way for the treatment of GC.

lncRNA-TINCR Functions as a Competitive Endogenous RNA to Regulate the Migration of Mesenchymal Stem Cells by Sponging miR-761

Mounting evidences have indicated that terminal differentiation-induced lncRNA (TINCR) contributes to various cellular processes, such as proliferation, apoptosis, autophagy, migration, invasion, and metastasis. However, the function of TINCR in regulating migration of MSCs is largely unknown. In this study, the effects of TINCR on the migration of rat MSCs from the bone marrow were studied by Transwell assays and wound healing assays. Our results suggested that TINCR positively regulated migration of rMSCs. miR-761 mimics suppressed rMSC migration, whereas miR-761 inhibitor promoted migration. Target prediction analysis tools and dual-luciferase reporter gene assay identified Wnt2 as a direct target of miR-761. miR-761 could inhibit the expression of Wnt2. Further, the investigation about the function of TINCR in miR-761-induced migration of rMSCs was completed. These results demonstrated that TINCR took part in the regulation of miR-761-induced migration in rMSCs through the regulation of Wnt2 and its Wnt2 signaling pathway. Taken together, our results demonstrate that lncRNA-TINCR functions as a competitive endogenous RNA (ceRNA) to regulate the migration of rMSCs by sponging miR-761 which modulates the role of Wnt2. These findings provide evidence that lncRNA-TINCR has a chance to serve as a potential target for enhancing MSC homing through the miR-761/Wnt2 signaling pathway.

Circular RNA LARP4 correlates with decreased Enneking stage, better histological response, and prolonged survival profiles, and it elevates chemosensitivity to cisplatin and doxorubicin via sponging microRNA-424 in osteosarcoma

BACKGROUND

This study aimed to evaluate the association of circular RNA La-related RNA-binding protein 4 (circ-LARP4) with clinical features and prognosis in osteosarcoma patients, and further explore its effect on chemosensitivity in osteosarcoma cells.

METHODS

Seventy-two osteosarcoma patients with Enneking stage IIA-IIB who underwent resection were consecutively enrolled, and then, tumor tissues and non-tumor tissues were obtained. Circ-LARP4 in tumor tissue/non-tumor tissue was detected by quantitative polymerase chain reaction. After circ-LARP4 overexpression and negative control overexpression plasmid transfection, relative cell viability (%) was evaluated by Cell Counting Kit-8 in MG63 cells treated by different concentrations of cisplatin, methotrexate, and doxorubicin, and IC50 was calculated.

RESULTS

Circ-LARP4 was downregulated in tumor tissue compared with non-tumor tissue and had a good value in distinguishing tumor tissue from non-tumor tissue with an area under curve of 0.829 (95% CI: 0.762-0.859). Meanwhile, tumor circ-LARP4 was negatively correlated with the Enneking stage. After resection, circ-LARP4 high expression patients showed an increased tumor cell necrosis rate to adjuvant chemotherapy compared to circ-LARP4 low expression patients, and circ-LARP4 high expression correlated with prolonged disease-free survival and overall survival. In vitro experiments revealed that circ-LARP4 overexpression elevated the chemosensitivity of MG63 cells to cisplatin and doxorubicin but not methotrexate, with decreased cisplatin IC50 and doxorubicin IC50 concentrations than negative control. Besides, miR-424 overexpression attenuated the chemosensitivity in circ-LARP4 overexpression-treated MG63 cells.

CONCLUSION

Circ-LARP4 high expression correlates with decreased Enneking stage and prolonged survival profiles, and it elevates chemosensitivity to cisplatin and doxorubicin via sponging miR-424 in osteosarcoma.

RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC1 and TP53 pathways and regulatory miRs as therapeutic targets in hepatocellular carcinoma

Introduction: Hepatocellular carcinoma (HCC) is a significant problem globally because of viral infections and the increasing incidence of obesity and fatty liver disease. However, it is difficult to treat because its inherent genetic heterogeneity results in activation of numerous signaling pathways. Kinases have been targeted for decades with varying results, but the development of therapeutic resistance is a major challenge.Areas covered: The key roles of the RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC1, TP53 microRNAs (miRs) as therapeutic targets are discussed and we suggests novel approaches for targeting miRs or their downstream targets to combat HCC. We performed literature searches using the Medline Database from 2000 to the present.Expert opinion: The involvement of RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC and TP53 pathways as drivers of the disease and drug resistance is a challenge. Moreover, miRs regulate the expression of key genes in these pathways. What we and others are proposing is the prospect of targeting miRs and their downstream targets to improve conventional approaches to treat HCC. Combination approaches are often promising because multiple signaling pathways are deregulated due to diverse mutations and events.

CircRNAs: From anonymity to novel regulators of gene expression in cancer (Review)

Circular RNAs (circRNAs) are a group of non‑coding RNAs, formed mostly through a unique backsplicing mechanism. Originally proposed to be a by‑product from errors in splicing, recent studies have shown they exhibit a range of roles in regulating gene expression, including sponging of microRNAs (miRNAs), interactions with RNA‑binding proteins and regulation of transcription. Though research is still in its infancy, evidence suggests circRNA levels are tightly regulated in the cell, reinforced by dysregulated circRNAs levels being implicated in a range of diseases, including cancer and viral infection. There is growing interest in circRNAs playing specific roles in cancers, either oncogenic or as tumour suppressors, with particular focus on their potential as novel biomarkers. This review will provide an overview of circRNA biogenesis and regulation, and their potential roles in the cell, with a focus on their dysregulation in cancer.

Downregulation of miR-552 in hepatocellular carcinoma inhibits cell migration and invasion, and promotes cell apoptosis via RUNX3

Research conducted previously has indicated that microRNAs (miRs) have potential effects on the pathogenesis of hepatocellular carcinoma (HCC). The biological functions of miR-552 have been well documented in colon cancer; however, the role of miR-552 in HCC remains unclear. The present study evaluated the effects of miR-552 in HCC physiology, using HCC cell lines as model. An miR-552 inhibitor was transfected into HCC cell lines to knock down the expression of miR-552. Reverse transcription-quantitative PCR and western blot analysis were used to detect the expression of miR-552 and Runt-related transcription factor 3 (RUNX3), respectively. MTT assay was used to analyze cell viability, whilst Transwell and wound-healing assay were used to investigate cell migration. Flow cytometry was performed to measure cell apoptosis. The direct association between RUNX3 and miR-552 was evaluated using dual luciferase reporter assay. The expression of miR-552 was significantly elevated in HCC tumor tissues compared with the adjacent healthy samples. Additionally, transfection with the miR-552 inhibitor decreased cell viability and migration. miR-552 knockdown also increased HCC cell apoptosis in vitro. In conclusion, these results suggest that miR-552 has an oncogenic function in HCC and is a potential biomarker for detecting HCC.

MicroRNA-519c-3p promotes tumor growth and metastasis of hepatocellular carcinoma by targeting BTG3

Tumor recurrence and metastasis after surgical resection are the major causes for the cancer-related death of hepatocellular carcinoma (HCC). Thus, better understanding the mechanisms involved in tumor progression will benefit to improve HCC treatment. Accumulating evidence demonstrates that microRNAs (miRNAs) play critical roles in the development and progression of HCC. However, the function of miR-519c-3p in HCC and its related mechanism remain unexplored. Here, we reported that miR-519c-3p was strongly overexpressed in HCC tissues, which was significantly correlated with poor prognosis and clinicopathological features including tumor size ≥5 cm, vascular invasion and advanced tumor-node-metastasis (TNM) stages (III + IV). Furthermore, the elevated levels of miR-519c-3p were observed in HCC cell lines. Subsequently, gain- or loss-of-function assays demonstrated that miR-519c-3p promoted HCC cell proliferation, migration as well as invasion in vitro, and facilitated the growth and metastasis of HCC cells in vivo. Mechanistically, B-cell translocation gene 3 (BTG3) was identified as a direct downstream target of miR-519c-3p. The level of BTG3 mRNA was downregulated in HCC and negatively correlated with miR-519c-3p expression. Western blotting confirmed that BTG3 was negatively regulated by miR-519c-3p in HCC cells. Luciferase reporter assays illustrated the direct interaction between miR-519c-3p and the 3'UTR of BTG3 mRNA. Recuse experiments demonstrated that BTG3 mediated the promoting effects of miR-519c-3p on the proliferation and motility of HCC cells. Collectively, our results suggest that miR-519c-3p functions as a tumor promotor in regulating the growth and metastasis of HCC by targeting BTG3, and potentially serves as a novel therapeutic target for HCC.