CircUBAP2 Promotes MMP9-Mediated Oncogenic Effect via Sponging miR-194-3p in Hepatocellular Carcinoma

Cardiomyocyte-derived small extracellular vesicle: a new mechanism driving diabetic cardiac fibrosis and cardiomyopathy

Rationale: Diabetic cardiomyopathy is one of the major diabetic cardiovascular complications in which fibrosis plays a critical pathogenetic role. However, the precise mechanisms by which diabetes triggers cardiac fibrosis in the heart remain elusive. Small extracellular vesicles (sEVs) play an important role in the cellular communication. Nevertheless, whether and how diabetes may adversely alter sEVs-mediated cardiomyocyte-fibroblast communication, promoting diabetic cardiac fibrosis and contributing to diabetic cardiomyopathy, has not been previously investigated. Methods and results: High-fat diet (HFD)-induced and genetic (db/db) type 2 diabetic models were utilized. Cardiomyocyte sEVs (Myo-sEVs) were isolated by ultracentrifugation. Normal cardiomyocyte-derived Myo-sEVs attenuated diabetic cardiac fibrosis in vitro and in vivo and improved cardiac diastolic function. In contrast, diabetic cardiomyocyte-derived Myo-sEVs significantly exacerbated diabetic cardiac fibrosis and worsened diastolic function. Unbiased miRNA screening analysis revealed that miR-194-3p was significantly reduced in diabetic Myo-sEVs. Additional in vitro and in vivo experiments demonstrated that miR-194-3p is a novel upstream molecule inhibiting TGFβR2 expression and blocking fibroblast-myofibroblast conversion. Administration of miR-194-3p mimic or agomiR-194-3p significantly reduced diabetic cardiac fibrosis in vitro and in vivo, and attenuated diabetic cardiomyopathy. Conclusion: Our study demonstrates for the first time that cardiomyocyte-derived miR194-3p inhibits TGFβ-mediated fibroblast-to-myofibroblast conversion, acting as an internal break against cardiac fibrosis. Diabetic downregulation of sEV-mediated miR-194-3p delivery from cardiomyocytes to fibroblasts contributes to diabetic cardiac fibrosis and diabetic cardiomyopathy. Pharmacological or genetic restoration of this system may be a novel therapy against diabetic cardiomyopathy.

MicroRNAs in Hepatocellular Carcinoma Pathogenesis: Insights into Mechanisms and Therapeutic Opportunities

Hepatocellular carcinoma (HCC) presents a significant global health burden, with alarming statistics revealing its rising incidence and high mortality rates. Despite advances in medical care, HCC treatment remains challenging due to late-stage diagnosis, limited effective therapeutic options, tumor heterogeneity, and drug resistance. MicroRNAs (miRNAs) have attracted substantial attention as key regulators of HCC pathogenesis. These small non-coding RNA molecules play pivotal roles in modulating gene expression, implicated in various cellular processes relevant to cancer development. Understanding the intricate network of miRNA-mediated molecular pathways in HCC is essential for unraveling the complex mechanisms underlying hepatocarcinogenesis and developing novel therapeutic approaches. This manuscript aims to provide a comprehensive review of recent experimental and clinical discoveries regarding the complex role of miRNAs in influencing the key hallmarks of HCC, as well as their promising clinical utility as potential therapeutic targets.

The novel circFKBP8/miR-432-5p/E2F7 cascade functions as a regulatory network in breast cancer

BACKGROUND

Circular RNAs (circRNAs) are capable of affecting breast cancer (BC) development. However, the role and underneath mechanism of circFKBP8 (also known as hsa_circ_0000915) in BC remain largely unknown.

METHODS

Expression analyses were performed using quantitative real-time polymerase chain reaction (qRT-PCR), western blot, and immunohistochemistry (IHC) assays. Effects on cell functional phenotypes were determined by assessing cell proliferation, migratory capacity, invasion, and stemness in vitro. The relationship between microRNA (miR)-432-5p and circFKBP8 or E2F transcription factor 7 (E2F7) was examined by RNA pull-down, dual-luciferase reporter, and RNA immunoprecipitation (RIP) assays. Xenograft assays were used to identify the function of circFKBP8 in vivo.

RESULTS

CircFKBP8 was presented at high levels in BC tissues and cells. High circFKBP8 expression was associated with worse overall survival in BC patients. CircFKBP8 suppression inhibited BC cell proliferation, migratory capacity, invasion and stemness in vitro. CircFKBP8 suppression blocked xenograft tumor growth in vivo. Mechanistically, circFKBP8 functioned as a miR-432-5p sponge to modulate E2F7 expression. CircFKBP8 modulated BC cell malignant behaviors by miR-432-5p, and miR-432-5p affected these cell phenotypes through E2F7.

CONCLUSION

Our observations prove that circFKBP8 promotes BC malignant phenotypes through the miR-432-5p/E2F7 cascade, offering a promising therapeutic and prognostic target for BC.

Periodontitis promotes hepatocellular carcinoma in Stelic Animal model (STAM) mice

Periodontitis is a prevalent oral inflammatory disease that leads to alveolar bone loss and may exert an adverse impact on systemic health. Periodontal disease may be associated with hepatocellular carcinoma (HCC); however, the mechanism of such an association is unknown. In this study, Stelic Animal model (STAM) mice, a model of nonalcoholic steatohepatitis (NASH)-HCC, were induced to develop periodontitis and subjected to histopathological and immunological analyses. HCC progression was greater in STAM mice with experimental periodontitis compared with that in STAM mice without experimental periodontitis. Tumor necrosis factor-α (TNFα), matrix metalloproteinase-9 (MMP9), collagen 1, and angiopoietin-like protein 2 (ANGPTL2) gene expression was significantly increased in the liver of the periodontitis group. ANGPTL2 was previously reported to be involved in the pathogenesis of periodontitis, and HCC and ANGPTL2 protein tended to be more abundant in the pocket epithelium of STAM mice with experimental periodontitis than in control STAM mice. ANGPTL2 levels in the serum of STAM mice with experimental periodontitis tended to be higher than in control STAM mice. Our results indicate that ANGPTL2 is produced in chronically inflamed periodontal tissue and then travels to the liver via the bloodstream where it accumulates to promote the progression of hepatocellular carcinoma.

miR-194-3p regulates epithelial-mesenchymal transition in embryonic epicardial cells via p120/β-catenin signaling

The epicardium is integral to cardiac development and facilitates endogenous heart regeneration and repair. While miR-194-3p is associated with cellular migration and invasion, its impact on epicardial cells remains uncharted. In this work we use gain-of-function and loss-of-function methodologies to investigate the function of miR-194-3p in cardiac development. We culture embryonic epicardial cells in vitro and subject them to transforming growth factor β (TGF-β) treatment to induce epithelial-mesenchymal transition (EMT) and monitor miR-194-3p expression. In addition, the effects of miR-194-3p mimics and inhibitors on epicardial cell development and changes in EMT are investigated. To validate the binding targets of miR-194-3p and its ability to recover the target gene-phenotype, we produce a mutant vector p120-catenin-3'UTR-MUT. In epicardial cells, TGF-β-induced EMT results in a notable overexpression of miR-194-3p. The administration of miR-194-3p mimics promotes EMT, which is correlated with elevated levels of mesenchymal markers. Conversely, miR-194-3p inhibitor attenuates EMT. Further investigations reveal a negative correlation between miR-194-3p and p120-catenin, which influences β-catenin level in the cell adhesion pathway. The suppression of EMT caused by the miR-194-3p inhibitor is balanced by silencing of p120-catenin. In conclusion, miR-194-3p directly targets p120-catenin and modulates its expression, which in turn alters β-catenin expression, critically influencing the EMT process in the embryonic epicardial cells via the cell adhesion mechanism.

Aspartame carcinogenic potential revealed through network toxicology and molecular docking insights

The research employed network toxicology and molecular docking techniques to systematically examine the potential carcinogenic effects and mechanisms of aspartame (L-α-aspartyl-L-phenylalanine methyl ester). Aspartame, a commonly used synthetic sweetener, is widely applied in foods and beverages globally. In recent years, its safety issues, particularly the potential carcinogenic risk, have garnered widespread attention. The study first constructed an interaction network map of aspartame with gastric cancer targets using network toxicology methods and identified key targets and pathways. Preliminary validation was conducted through microarray data analysis and survival analysis, and molecular docking techniques were employed to further examine the binding affinity and modes of action of aspartame with key proteins. The findings suggest that aspartame has the potential to impact various cancer-related proteins, potentially raising the likelihood of cellular carcinogenesis by interfering with biomolecular function. Furthermore, the study found that the action patterns and pathways of aspartame-related targets are like the mechanisms of known carcinogenic pathways, further supporting the scientific hypothesis of its potential carcinogenicity. However, given the complexity of the in vivo environment, we also emphasize the necessity of validating these molecular-level findings in actual biological systems. The study introduces a fresh scientific method for evaluating the safety of food enhancers and provides a theoretical foundation for shaping public health regulations.

Circ_0003945: an emerging biomarker and therapeutic target for human diseases

Due to the rapid development of RNA sequencing techniques, a circular non-coding RNA (ncRNA) known as circular RNAs (circRNAs) has gradually come into focus. As a distinguished member of the circRNA family, circ_0003945 has garnered attention for its aberrant expression and biochemical functions in human diseases. Subsequent studies have revealed that circ_0003945 could regulate tumor cells proliferation, migration, invasion, apoptosis, autophagy, angiogenesis, drug resistance, and radio resistance through the molecular mechanism of competitive endogenous RNA (ceRNA) during tumorigenesis. The expression of circ_0003945 is frequently associated with some clinical parameters and implies a poorer prognosis in the majority of cancers. In non-malignant conditions, circ_0003945 also holds considerable importance in diseases pathogenesis. This review aims to recapitulate molecular mechanism of circ_0003945 and elucidates its potential as a diagnostic and therapeutic target in neoplasms and other diseases.

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.

New insight into circRNAs: characterization, strategies, and biomedical applications

Circular RNAs (circRNAs) are a class of covalently closed, endogenous ncRNAs. Most circRNAs are derived from exonic or intronic sequences by precursor RNA back-splicing. Advanced high-throughput RNA sequencing and experimental technologies have enabled the extensive identification and characterization of circRNAs, such as novel types of biogenesis, tissue-specific and cell-specific expression patterns, epigenetic regulation, translation potential, localization and metabolism. Increasing evidence has revealed that circRNAs participate in diverse cellular processes, and their dysregulation is involved in the pathogenesis of various diseases, particularly cancer. In this review, we systematically discuss the characterization of circRNAs, databases, challenges for circRNA discovery, new insight into strategies used in circRNA studies and biomedical applications. Although recent studies have advanced the understanding of circRNAs, advanced knowledge and approaches for circRNA annotation, functional characterization and biomedical applications are continuously needed to provide new insights into circRNAs. The emergence of circRNA-based protein translation strategy will be a promising direction in the field of biomedicine.

MicroRNA-194-3p impacts autophagy and represses rotavirus replication via targeting silent information regulator 1

BACKGROUND

Rotavirus (RV) is the main cause of serious diarrhea in infants and young children worldwide. Numerous studies have demonstrated that RV use host cell mechanisms to motivate their own stabilization and multiplication by degrading, enhancing, or hijacking microRNAs (miRNAs). Therefore, exploring the molecular mechanisms by which miRNAs motivate or restrain RV replication by controlling different biological processes, including autophagy, will help to better understand the pathogenesis of RV development. This study mainly explored the effect of miR-194-3p on autophagy after RV infection and its underlying mechanism of the regulation of RV replication.

METHODS

Caco-2 cells were infected with RV and used to measure the expression levels of miR-194-3p and silent information regulator 1 (SIRT1). After transfection with plasmids and RV infection, viral structural proteins, RV titer, cell viability, and autophagy-linked proteins were tested. The degree of acetylation of p53 was further investigated. A RV-infected neonatal mouse model was constructed in vivo and was evaluated for diarrhea symptoms and lipid droplet formation.

RESULTS

The results showed that miR-194-3p was reduced but SIRT1 was elevated after RV infection. Elevation of miR-194-3p or repression of SIRT1 inhibited RV replication through the regulation of autophagy. The overexpression of SIRT1 reversed the effects of miR-194-3p on RV replication. The upregulation of miR-194-3p or the downregulation of SIRT1 repressed RV replication in vivo. MiR-194-3p targeted SIRT1 to decrease p53 acetylation.

CONCLUSION

These results were used to determine the mechanism of miR-194-3p in RV replication, and identified a novel therapeutic small RNA molecule that can be used against RV.

Decoding hepatocarcinogenesis from a noncoding RNAs perspective

Being a leading lethal malignancy worldwide, the pathophysiology of hepatocellular carcinoma (HCC) has gained a lot of interest. Yet, underlying mechanistic basis of the liver tumorigenesis is poorly understood. The role of some coding genes and their respective translated proteins, then later on, some noncoding RNAs (ncRNAs) such as microRNAs have been extensively studied in context of HCC pathophysiology; however, the implication of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) in HCC is indeed less investigated. As a subclass of the ncRNAs which has been elusive for long time ago, lncRNAs was found to be involved in plentiful cellular functions such as DNA, RNA, and proteins regulation. Hence, it is undisputed that lncRNAs dysregulation profoundly contributes to HCC via diverse etiologies. Accordingly, lncRNAs represent a hot research topic that requires prime focus in HCC. In this review, the authors discuss breakthrough discoveries involving lncRNAs and circRNAs dysregulation that have contributed to the contemporary concepts of HCC pathophysiology and how these concepts could be leveraged as potential novel diagnostic and prognostic HCC biomarkers. Further, this review article sheds light on future trends, thereby discussing the pathological roles of lncRNAs and circRNAs in HCC proliferation, migration, and epithelial-to-mesenchymal transition. Along this line of reasoning, future recommendations of how these targets could be exploited to achieve effective HCC-related drug development is highlighted.

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.

IL-17 induces non-small cell lung cancer metastasis via GCN5-dependent SOX4 acetylation enhancing MMP9 gene transcription and expression

Interleukin-17 (IL-17), a potent proinflammatory cytokine, can trigger the metastasis of non-small cell lung cancer (NSCLC). However, the underlying mechanism involved in IL-17-induced NSCLC cell metastasis remains unclear. In this study, we found that not only the expression of IL-17, IL-17RA, and/or general control nonrepressed protein 5 (GCN5), SRY-related HMG-BOX gene 4 (SOX4), and matrix metalloproteinase 9 (MMP9) was increased in the NSCLC tissues and in the IL-17-stimulated NSCLC cells, but also IL-17 treatment could enhance NSCLC cell migration and invasion. Further mechanism exploration revealed that IL-17-upregulated GCN5 and SOX4 could bind to the same region (-915 to -712 nt) of downstream MMP9 gene promoter driving its gene transcription. In the process, GCN5 could mediate SOX4 acetylation at lysine 118 (K118, a newly identified site) boosting MMP9 gene expression as well as cell migration and invasion. Moreover, the SOX4 acetylation or MMP9 induction and metastatic nodule number in the lung tissues of the BALB/c nude mice inoculated with the NSCLC cells stably infected by corresponding LV-shGCN5 or LV-shSOX4, LV-shMMP9 plus IL-17 incubation were markedly reduced. Overall, our findings implicate that NSCLC metastasis is closely associated with IL-17-GCN5-SOX4-MMP9 axis.

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.

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

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

Mechanism underlying circRNA dysregulation in the TME of digestive system cancer

Circular RNAs (circRNAs) are a new series of noncoding RNAs (ncRNAs) that have been reported to be expressed in eukaryotic cells and have a variety of biological functions in the regulation of cancer pathogenesis and progression. The TME, as a microscopic ecological environment, consists of a variety of cells, including tumor cells, immune cells and other normal cells, ECM and a large number of signaling molecules. The crosstalk between circRNAs and the TME plays a complicated role in affecting the malignant behaviors of digestive system cancers. Herein, we summarize the mechanisms underlying aberrant circRNA expression in the TME of the digestive system cancers, including immune surveillance, angiogenesis, EMT, and ECM remodelling. The regulation of the TME by circRNA is expected to be a new therapeutic method.

The potential of mecciRNA in hepatic stellate cell to regulate progression of nonalcoholic hepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) occupies a substantial proportion of chronic liver disease worldwide, of which pathogenesis needs further research. Recent studies have demonstrated the significant roles of circular RNAs (circRNAs) in NASH, while the function of a novel type of circRNAs, namely mitochondria-encoded circRNAs (mecciRNAs), remains elusive. Therefore, we aimed to investigate their potential to regulate the progression of NASH in this study.

METHODS

GSE134146 was used to screen for differentially expressed mecciRNAs in NASH, while GSE46300 was used to identify NASH-related genes. To establish the mecciRNA-miRNA-mRNA networks, circMINE and miRNet databases were used for predicting downstream targets. Then, consensus clustering analysis was used to determine immune subtypes of NASH. Finally, we successfully validated our findings in vitro (LPS-treated hepatic stellate cells [HSCs]) and in vivo (MCD-diet mice) NASH models.

RESULTS

We confirmed that circRNomics balance is disrupted in HSCs of NASH, while two mecciRNAs (hsa_circ_0089761 and hsa_circ_0089763) could function as competing for endogenous RNAs (ceRNAs) to regulate fibrosis-related signals. Furthermore, we constructed two ceRNA networks based on mecciRNAs for the first time. Cell and animal NASH models validated our findings that c-MYC and SMAD2/3 were upregulated in HSCs, while THBS1 and p-STAT3 were upregulated in hepatocytes. Moreover, we identified 21 core genes by overlapping the differentially expressed genes (NASH vs. Normal) with mecciRNA-targeted genes. According to their expression profiles, NASH patients could be divided in 2 different clusters, in which proinflammatory signals (TNF and IL-17 pathways) are significantly activated in Cluster 1.

CONCLUSION

We successfully established two novel mecciRNA-miRNA-mRNA networks in HSCs and hepatocytes, which were further confirmed by in vitro and in vivo models. Meanwhile, the novel immunotyping model revealed the heterogeneity of NASH, thereby might guiding treatment options. Altogether, our study brought a distinct perspective on the relationship between mecciRNAs and NASH.

Investigations of nitazoxanide molecular targets and pathways for the treatment of hepatocellular carcinoma using network pharmacology and molecular docking

Nitazoxanide has been investigated for colorectal cancer and breast cancer. However, its molecular targets and pathways have not yet been explored for hepatocellular carcinoma (HCC) treatment. Utilizing a network pharmacology approach, nitazoxanide’s potential targets and molecular pathways for HCC treatment were investigated. HCC targets were extracted from the GeneCards database. Potential targets of nitazoxanide were predicted using Swiss Target Prediction and Super Pred. Intersecting targets were analyzed with VENNY online tool. Using Cytoscape, a protein-protein interaction (PPI), cluster, and core targets-pathways networks were constructed. Using the Database for Annotation, Visualization and Integrated Discovery (DAVID), gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted. The nitazoxanide was molecularly docked with anti-HCC core targets by employing Auto Dock Vina. A total of 168 potential targets of nitazoxanide, 13,415 HCC-related targets, and 153 intersecting targets were identified. The top eight anti-HCC core targets were identified: SRC, EGFR, CASP3, MMP9, mTOR, HIF1A, ERBB2, and PPARG. GO enrichment analysis showed that nitazoxanide might have anti-HCC effects by affecting gene targets involved in multiple biological processes (BP) (protein phosphorylation, transmembrane receptor protein tyrosine kinase (RTKs) signaling pathway, positive regulation of MAP kinase activity, etc.). KEGG pathways and core targets-pathways network analysis indicated that pathways in cancer and proteoglycans in cancer are two key pathways that significantly contribute to the anti-HCC effects of nitazoxanide. Results of molecular docking demonstrated the potential for active interaction between the top eight anti-HCC core targets and nitazoxanide. Our research offers a theoretical basis for the notion that nitazoxanide may have distinct therapeutic effects in HCC, and the identified pharmacological targets and pathways might function as biomarkers for HCC therapy.

Exosomal hsa_circ_0017252 attenuates the development of gastric cancer via inhibiting macrophage M2 polarization

Gastric cancer (GC) is an aggressive malignant tumor of the digestive system, with high morbidity rates. We previously demonstrated that miR-17-5p can modify tumorigenesis in GC. In addition, other studies have shown that circRNAs can regulate GC progression by sponging various miRNAs. However, the association between circRNAs and miR-17-5p in GC has not yet been explored. Hence, this study aimed to explore the possible interactions between various circRNAs and miR-17-5p using a dual-luciferase assay. CCK-8 was used to determine cell viability, and a Transwell assay was used to measure cell invasion and migration. Gene expression was assessed using quantitative reverse transcription PCR (RT-qPCR), and exosomes were identified using transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Annexin V/PI staining was also used to detect cell apoptosis. These investigations collectively revealed that miR-17-5p is a target of the circRNA hsa_circ_0017252 and hsa_circ_0017252 is significantly downregulated in GC tissues. In addition, the overexpression of hsa_circ_0017252 inhibited GC cell migration by sponging of miR-17-5p, and GC cell-secreted exosomal hsa_circ_0017252 effectively inhibited macrophage M2-like polarization, which in turn suppressed GC cell invasion. Notably, exosomes containing hsa_circ_0017252 also suppressed GC tumor growth in vivo. Thus, our data suggest that the overexpression of hsa_circ_0017252 suppresses GC malignancy by sponging miR-17-5p. In addition, exosomal hsa_circ_0017252 excreted from GC cells attenuated GC progression by suppressing macrophage M2-like polarization. These findings improve our basic understanding of GC and open a novel avenue for developing more effective GC treatments.

Circular RNA UBAP2 facilitates the cisplatin resistance of triple-negative breast cancer via microRNA-300/anti-silencing function 1B histone chaperone/PI3K/AKT/mTOR axis

Circular RNAs (CircRNAs) have attracted increasing attention in the diagnosis and treatment of human cancers. CircUBAP2 has been identified to promote the progression of triple-negative breast cancer (TNBC), but the function of circUBAP2 in the cisplatin (DDP) resistance of TNBC remains obscure. Our investigation showed that circUBAP2 was significantly upregulated in DDP-resistant TNBC and TNBC sensitivity to DDP could be enhanced by silencing of circUBAP2. Moreover, circUBAP2 was revealed to be a ceRNA for miR-300 to upregulate the expression of anti-silencing function 1B histone chaperone (ASF1B). The effect of circUBAP2/miR-300/ASF1B axis on DDP resistance of TNBC was evaluated by rescue experiments, which demonstrated that circUBAP2 inhibited TNBC sensitivity to DDP through miR-300/ASF1B axis. Furthermore, it was discovered that ASF1B activated PI3K/AKT/mTOR signaling to facilitate the DDP resistance of TNBC cells. In summary, this research revealed a novel regulatory mechanism that circUBAP2 functioned as ceRNA of miR-300 to upregulate ASF1B, which further triggered the PI3K/AKT/mTOR (PAM) signaling to enhance the DDP resistance of TNBC.

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.

Hsa_circ_0003945 promotes progression of hepatocellular carcinoma by mediating miR-34c-5p/LGR4/β-catenin axis activity

Accumulating evidence suggests that circular RNAs (circRNAs) play essential roles in regulating cancer progression, but many circRNAs in hepatocellular carcinoma (HCC) remain unknown. Dysregulated circRNAs in HCC were identified through bioinformatics analysis of Gene Expression Omnibus data sets. Quantitative real‐time PCR (qRT‐PCR), Sanger sequencing, RNase R digestion and actinomycin D treatment were conducted to confirm the characterization of circRNAs. CCK‐8, wound‐healing and Transwell assays were performed to assess the functional roles of Hsa_circ_0003945 (Circ_0003945) in HCC cell lines. Subcellular fractionation and fluorescence in situ hybridization (FISH) were performed to locate Circ_0003945 in HCC cells. Dual‐luciferase reporter assay was executed to verify the binding of Circ_0003945 to microRNAs (miRNAs) or the miRNAs to their target genes. In this study, we found that Circ_0003945 was upregulated in HCC tissue, and higher Circ_0003945 expression was positively correlated with tumour size and tumour stage. Furthermore, high plasma levels of circulating Circ_0003945 were confirmed in HCC patients compared with those in non‐HCC groups. The functional experiments revealed that overexpression or knockdown of Circ_0003945 promoted or attenuated tumour growth and migration, respectively. Mechanistically, Circ_0003945 might exert as a miR‐34c‐5p sponge to upregulate the expression of leucine‐rich repeat‐containing G protein‐coupled receptor 4 (LGR4), activating the β‐catenin pathway, and finally facilitating HCC progression. Additionally, a β‐catenin activator could reverse the effect of Circ_0003945 knockdown. In conclusion, Circ_0003945 exerts a tumour‐promoting role in HCC cells by regulating the miR‐34c‐5p/LGR4/β‐catenin axis, which may be a potential target for HCC therapy.

Methyltransferase-Like 3-Mediated m6A Methylation of Hsa_circ_0058493 Accelerates Hepatocellular Carcinoma Progression by Binding to YTH Domain-Containing Protein 1

Circular RNAs (circRNAs) are highly correlated with the progression and prognosis of hepatocellular carcinoma (HCC). In addition, mounting evidence has revealed that N6-methyladenosine (m6A) methylation, a common RNA modification, is involved in the progression of malignancies. In this research, a novel circRNA, hsa_circ_0058493, was proven to be upregulated in HCC, which was correlated with the prognosis of HCC patients. Experimentally, hsa_circ_0058493 knockdown suppressed the growth and metastasis of HCC cells in vivo and in vitro. On the contrary, the overexpression of hsa_circ_0058493 in HCC cells had the opposite effect in vitro. Mechanistic experiments revealed that hsa_circ_0058493 contained m6A methylation sites and that methyltransferase-like 3 (METTL3) mediated the degree of methylation modification of hsa_circ_0058493. Furthermore, YTH domain-containing protein 1 (YTHDC1) could bind to hsa_circ_0058493 and promote its intracellular localization from the nucleus to the cytoplasm. In addition, both si-METTL3 and si-YTHDC1 suppressed HCC cell growth and metastasis, whereas rescue experiments confirmed that overexpression of hsa_circ_0058493 inverted the inhibitory effects of si-METTL3 and si-YTHDC1 on HCC cells. Taken together, this study explored the oncogenic role of m6A-modified hsa_circ_0058493 and found to accelerate HCC progression via the METTL3-hsa_circ_0058493-YTHDC1 axis, indicating a potential therapeutic target for this deadly disease.

Circular RNAs: characteristics, biogenesis, mechanisms and functions in liver cancer

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies globally. Despite aggressive and multimodal treatment regimens, the overall survival of HCC patients remains poor. MAIN: Circular RNAs (circRNAs) are noncoding RNAs (ncRNAs) with covalently closed structures and tissue- or organ-specific expression patterns in eukaryotes. They are highly stable and have important biological functions, including acting as microRNA sponges, protein scaffolds, transcription regulators, translation templates and interacting with RNA-binding protein. Recent advances have indicated that circRNAs present abnormal expression in HCC tissues and that their dysregulation contributes to HCC initiation and progression. Furthermore, researchers have revealed that some circRNAs might serve as diagnostic biomarkers or drug targets in clinical settings. In this review, we systematically evaluate the characteristics, biogenesis, mechanisms and functions of circRNAs in HCC and further discuss the current shortcomings and potential directions of prospective studies on liver cancer-related circRNAs.

CONCLUSION

CircRNAs are a novel class of ncRNAs that play a significant role in HCC initiation and progression, but their internal mechanisms and clinical applications need further investigation.