Circ-DENND4C up-regulates TCF4 expression to modulate hepatocellular carcinoma cell proliferation and apoptosis via activating Wnt/β-catenin signal pathway

circDENND4C serves as a sponge for miR-200b to drive non-small cell lung cancer advancement by regulating MMP-9 expression

Introduction

Lung cancer has a higher incidence and mortality rate than other cancers, especially non-small cell lung cancer (NSCLC), accounting for 85% of the cases. The role of the circDENND4C/miR-200b/matrix metalloproteinase-9 (MMP-9) regulatory axis in NSCLC remains largely unknown.

Methods

NSCLC cell lines were used to examine the expression of circDENND4C, miR-200b, and MMP-9 via qRT-PCR or Western blot. The target relationship of circDENND4C, miR-200b, and MMP-9 was examined by RNA fluorescence in situ hybridization (RNA-FISH), immunofluorescence (IF), dual-luciferase reporter system, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot. Then, a cell count kit-8 (CCK-8) experiment, flow cytometry, and migration/invasion assays were performed to assess the biological function of circDENND4C, miR-200b, and MMP-9 by transfecting with their overexpression or knockout plasmids in A549 cells. Finally, the proteins related to cell adhesion and tight junction were further tested by Western blot and IF.

Results

circDENND4C and MMP-9 were found to be highly expressed in NSCLC cell lines, while miR-200b was lowly expressed in NSCLC cell lines. Moreover, circDENND4C could sponge miR-200b to target MMP-9. Subsequently, it was observed that knockdown of circDENND4C and MMP-9 or the upregulation of miR-200b repressed cell proliferation and cell cycle progression, increased cell apoptosis, and hindered cell migration and invasion. Finally, it was also found that the circDENND4C/miR-200b/MMP-9 regulatory axis might be involved with cell adhesion and tight junction to influence tumor metastasis.

Conclusions

Altogether, our study reveals a novel regulatory loop in which the circDENND4C/miR-200b/MMP-9 axis may modulate NSCLC progression, indicating potential biomarkers for the diagnosis or treatment of NSCLC.

Circ DENND4C inhibits pyroptosis and alleviates ischemia-reperfusion acute kidney injury by exosomes secreted from human urine-derived stem cells

Acute kidney injury (AKI) is a disease characterised by acute onset, high mortality, and poor prognosis, and is mainly caused by ischemia-reperfusion (I/R). Human urine-derived stem cells (USCs) exhibit antioxidant, anti-inflammatory, and anti-apoptotic cytoprotective effects. Previously, we found that exosomes from USCs had the ability to inhibit apoptosis and protect kidneys from I/R injury. This study aimed to investigate the role of USC-derived exosomes (USC-Exos) in reducing pyroptosis and alleviating I/R-AKI. Models of HK-2 cells hypoxia-reoxygenation (H/R) and I/R kidney injury was established in Sprague Dawley rats to simulate AKI in vitro and in vivo. USC-Exos were isolated using ultracentrifugation and identified via electron microscopy and western blotting. USC-Exos were co-cultured with HK-2 cells and injected into rats via the tail vein. The expression of pyroptosis-related molecules (GSDMD, caspase-1, and NLRP-3) was verified using PCR and western blotting. Changes in renal function were reflected in the serum creatinine, urea, and cystatin C levels. The degree of renal injury was determined using haematoxylin and eosin and immunohistochemical staining. The levels of IL-1β and IL-18 were detected using enzyme-linked immunosorbent assay (ELISA) to verify the role of USC-Exos in pyroptosis. Differentially expressed circRNAs in I/R rat kidneys were screened by transcriptome sequencing, and a dual-luciferase experiment was used to verify the interaction between upstream and downstream molecules. Ischemia-reperfusion resulted in significantly impaired renal function and expression of pyroptosis molecules, and significantly increased concentrations of inflammatory factors. These effects were reversed by injecting USC-Exos. Circ DENND4C was the most significantly decreased circRNA in I/R rat renal tissue, and knock-down of circ DENND4C can aggravate AKI in vivo and in vitro. DAVID(http://david.abcc.ncifcrf.gov) website showed that miR 138-5p/FOXO3a is a potential downstream target of circ DENND4C. Knock-down of circ DENND4C in HK-2 cells resulted in increased expression of miR 138-5p and increased miR 138-5p can reverse the regulation of FOXO3a. Dual-luciferase assay verified the reverse interaction between circ DENND4C, miR 138-5p, and FOXO3a. Exosomes promote cell proliferation and inhibit the activation of NLR family pyrin domain containing 3 through the circ DENND4C/miR 138-5p/FOXO3a pathway, thereby reducing pyroptosis and AKI. Circ DENND4C may be a potential therapeutic target for AKI.

Crosstalk Between circRNA and Tumor Microenvironment of Hepatocellular Carcinoma: Mechanism, Function and Applications

Hepatocellular carcinoma (HCC) is one of the most common aggressive tumors in the world. Despite the availability of various treatments, its prognosis remains poor due to the lack of specific diagnostic indicators and the high heterogeneity of HCC cases. CircRNAs are noncoding RNAs with stable and highly specific expression. Extensive research evidence suggests that circRNAs mediate the pathogenesis and progression of HCC through acting as miRNA sponges, protein modulators, and translation templates. Tumor microenvironment (TME) has become a hotspot of immune-related research in recent years due to its effects on metabolism, secretion and immunity of HCC. Accordingly, understanding the role played by circRNAs in TME is important for the study of HCC. This review will discuss the crosstalk between circRNAs and TME in HCC. In addition, we will discuss the current deficiencies and controversies in research on circRNAs and predict future research directions.

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.

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.

Lipid Deposition Profiles Influence Foreign Body Responses

Fibrosis remains a significant cause of failure in implanted biomedical devices and early absorption of proteins on implant surfaces has been shown to be a key instigating factor. However, lipids can also regulate immune activity and their presence may also contribute to biomaterial-induced foreign body responses (FBR) and fibrosis. Here it is demonstrated that the surface presentation of lipids on implant affects FBR by influencing reactions of immune cells to materials as well as their resultant inflammatory/suppressive polarization. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) is employed to characterize lipid deposition on implants that are surface-modified chemically with immunomodulatory small molecules. Multiple immunosuppressive phospholipids (phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin) are all found to deposit preferentially on implants with anti-FBR surface modifications in mice. Significantly, a set of 11 fatty acids is enriched on unmodified implanted devices that failed in both mice and humans, highlighting relevance across species. Phospholipid deposition is also found to upregulate the transcription of anti-inflammatory genes in murine macrophages, while fatty acid deposition stimulated the expression of pro-inflammatory genes. These results provide further insights into how to improve the design of biomaterials and medical devices to mitigate biomaterial material-induced FBR and fibrosis.

Hsa_circ_0016070/micro‐340‐5p Axis Accelerates Pulmonary Arterial Hypertension Progression by Upregulating TWIST1 Transcription Via TCF4/β‐Catenin Complex

Background

Hypoxia is considered a major leading cause of pulmonary hypertension (PH). In this study, the roles and molecular mechanism of circ_0016070 in PH were studied.

Methods and Results

The expression of circ_0016070 in serum samples, human pulmonary artery smooth muscle cells and hypoxia/monocrotaline‐treated rats was determined by real‐time quantitative polymerase chain reaction. Cell viability, migration, and apoptosis were analyzed by Cell Counting Kit‐8, wound healing, flow cytometry, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assays, respectively. The molecular interactions were validated using RNA immunoprecipitation, chromatin immunoprecipitation, and dual luciferase reporter assays. The levels of phenotype switch‐related proteins were evaluated by Western blot and immunohistochemistry. The pathological characteristics were assessed using hematoxylin and eosin staining. circ_0016070 was highly expressed in the serum samples, hypoxia‐induced pulmonary artery smooth muscle cells and pulmonary arterial tissues of PH rats. Downregulation of circ_0016070 ameliorated the excessive proliferation, migration, vascular remodeling, and phenotypic transformation but enhanced cell apoptosis in the PH rat model. In addition, micro (miR)‐340‐5p was verified as a direct target of circ_0016070 and negatively regulated TCF4 (transcription factor 4) expression. TCF4 formed a transcriptional complex with β‐catenin to activate TWIST1 (Twist family bHLH transcription factor 1) expression. Functional rescue experiments showed that neither miR‐340‐5p inhibition nor TWIST1 or TCF4 upregulation significantly impeded the biological roles of circ_0010670 silencing in PH.

Conclusions

These results uncovered a novel mechanism by which circ_0016070 play as a competing endogenouse RNA of miR‐340‐5p to aggravate PH progression by promoting TCF4/β‐catenin/TWIST1 complex, which may provide potential therapeutic targets for PH.

CircLIFR suppresses hepatocellular carcinoma progression by sponging miR-624-5p and inactivating the GSK-3β/β-catenin signaling pathway

Circular RNAs have been reported to play essential roles in the tumorigenesis and progression of various cancers. However, the biological processes and mechanisms involved in hepatocellular carcinoma (HCC) remain unclear. Initial RNA-sequencing data and qRT-PCR results in our cohort showed that hsa_circ_0072309 (also called circLIFR) was markedly downregulated in HCC tissues. Kaplan-Meier analysis indicated that higher levels of circLIFR in HCC patients correlated with favorable overall survival and recurrence-free survival rates. Both in vitro and in vivo experiments indicated that circLIFR inhibited the proliferation and invasion abilities of HCC cells. We therefore conducted related experiments to explore the mechanism of circLIFR in HCC. Fluorescence in situ hybridization results revealed that circLIFR was mainly located in the cytoplasm, and RNA immunoprecipitation assays indicated that circLIFR was significantly enriched by Ago2 protein. These results suggested that circLIFR may function as a sponge of miRNAs to regulate HCC progression. We further conducted bioinformatics prediction as well as dual-luciferase reporter assays, and the results of which showed that circLIFR could sponge miR-624-5p to stabilize glycogen synthase kinase 3β (GSK-3β) expression. Loss and gain of function experiments demonstrated that regulation of the expression of miR-624-5p or GSK-3β markedly affected HCC progression induced by circLIFR. Importantly, we also proved that circLIFR could facilitate the degradation of β-catenin and prevent its translocation to the nucleus in HCC cells. Overall, our study demonstrated that circLIFR acts as a tumor suppressor in HCC by regulating miR-624-5p and inactivating the GSK-3β/β-catenin signaling pathway.

CircMTO1 suppresses hepatocellular carcinoma progression via the miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling pathway and epithelial-to-mesenchymal transition

CircRNA mitochondrial tRNA translation optimization 1 (circMTO1) functions as a tumor suppressor usually and is related to the progression of many tumors, including hepatocellular carcinoma (HCC). CircMTO1 is downregulated in HCC as compared to adjacent nontumor tissue, which may suppress the HCC progression by certain signal pathways. However, the underlying signal pathway remains largely unknown. The interactions between circMTO1 and miR-541-5p were predicted through bioinformatics analysis and verified using pull-down and dual-luciferase reporter assays. CCK-8, transwell, and apoptosis assays were performed to determine the effect of miR-541-5p on HCC progression. Using bioinformatic analysis, dual-luciferase reporter assay, RT-qPCR, and western blot, ZIC1 was found to be the downstream target gene of miR-541-5p. The regulatory mechanisms of circMTO1, miR-541-5p, and ZIC1 were investigated using in vitro and in vivo rescue experiments. The results depicted that silencing circMTO1 or upregulating miR-541-5p expression facilitated HCC cell proliferation, migration, and invasion and inhibited apoptosis. CircMTO1 silencing upregulated the expression of downstream ZIC1 regulators of the Wnt/β-catenin pathway markers, β-catenin, cyclin D1, c-myc, and the mesenchymal markers N-cadherin, Vimentin, and MMP2, while the epithelial marker E-cadherin was downregulated. MiR-541-5p knockdown had the opposite effect and reversed the effect of circMTO1 silencing on the regulation of downstream ZIC1 regulators. Intratumoral injection of miR-541-5p inhibitor suppressed tumor growth and reversed the effect of circMTO1 silencing on the promotion of tumor growth in HCC. These findings indicated that circMTO1 suppressed HCC progression via the circMTO1/ miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling and epithelial-to-mesenchymal transition, making it a novel therapeutic target.

Wnt/β-Catenin Signaling as a Driver of Hepatocellular Carcinoma Progression: An Emphasis on Molecular Pathways

Liver cancers cause a high rate of death worldwide and hepatocellular carcinoma (HCC) is considered as the most common primary liver cancer. HCC remains a challenging disease to treat. Wnt/β-catenin signaling pathway is considered a tumor-promoting factor in various cancers; hence, the present review focused on the role of Wnt signaling in HCC, and its association with progression and therapy response based on pre-clinical and clinical evidence. The nuclear translocation of β-catenin enhances expression level of genes such as c-Myc and MMPs in increasing cancer progression. The mutation of CTNNB1 gene encoding β-catenin and its overexpression can lead to HCC progression. β-catenin signaling enhances cancer stem cell features of HCC and promotes their growth rate. Furthermore, β-catenin prevents apoptosis in HCC cells and increases their migration via triggering EMT and upregulating MMP levels. It is suggested that β-catenin signaling participates in mediating drug resistance and immuno-resistance in HCC. Upstream mediators including ncRNAs can regulate β-catenin signaling in HCC. Anti-cancer agents inhibit β-catenin signaling and mediate its proteasomal degradation in HCC therapy. Furthermore, clinical studies have revealed the role of β-catenin and its gene mutation (CTNBB1) in HCC progression. Based on these subjects, future experiments can focus on developing novel therapeutics targeting Wnt/β-catenin signaling in HCC therapy.

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.

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.

Circ_0000345 Protects Endothelial Cells From Oxidized Low-Density Lipoprotein-Induced Injury by miR-129-5p/Ten-Eleven Translocation Axis

ABSTRACT

Circular RNAs have shown regulatory functions in atherosclerosis (AS) progression. Here, we explored the role and working mechanism of circ_0000345 in the AS cell model in vitro. Quantitative real-time polymerase chain reaction was applied to measure the enrichment of circ_0000345, microRNA-129-5p (miR-129-5p), and ten-eleven translocation-2 (TET2) messenger RNA. Cell Counting Kit 8 assay was used to analyze cell viability of human umbilical vein endothelial cells (HUVECs). Flow cytometry was conducted to assess cell apoptosis and cell cycle progression. The target relationship between miR-129-5p and circ_0000345 or TET2 was verified by the dual-luciferase reporter assay. The Western blot assay was used to analyze the protein level of TET2. Circ_0000345 abundance was reduced in serum samples of AS patients and AS cell model compared with their matching counterparts. Circ_0000345 overexpression promoted cell viability and cell cycle progression and hampered cell apoptosis in HUVECs induced by oxidized low-density lipoprotein. MiR-129-5p was a target of circ_0000345 and circ_0000345 attenuated ox-LDL-induced damage in HUVECs through sponging miR-129-5p. MiR-129-5p bound to the 3' untranslated region (3'UTR) of TET2, and miR-129-5p functioned in ox-LDL-induced HUVECs by targeting TET2. Circ_0000345 enhanced TET2 messenger RNA and protein expression through sponging miR-129-5p in HUVECs. Circ_0000345 attenuated ox-LDL-mediated injury in HUVECs through targeting miR-129-5p/TET2 axis. Increasing the levels of circ_0000345 and TET2 might be a novel insight into AS treatment.

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 gastrointestinal cancer: Current knowledge, biomarkers and targeted therapy (Review)

Circular RNAs (circRNAs) are a type of endogenous non‑coding RNAs that are connected at the 3' and 5' ends by exon or intron cyclization, which forms a covalently closed loop. They are stable, well conserved, exhibit specific expression in mammalian cells and can function as microRNA (miRNA or miR) sponges to regulate the target genes of miRNAs, which influences biological processes. Such as tumor proliferation, invasion, metastasis, apoptosis and tumor stage. circRNAs represent promising candidates for clinical diagnosis and treatment. In the present review, the biogenesis, classification and functions of circRNAs in tumors are briefly summarized and discussed. In addition, the participation of circRNAs in signal transduction pathways regulating gastrointestinal cancer cellular functions is highlighted.