Regulatory network of circRNA-miRNA-mRNA contributes to the histological classification and disease progression in gastric cancer

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

circHIPK3 nucleates IGF2BP2 and functions as a competing endogenous RNA

Circular RNAs represent a class of endogenous RNAs that regulate gene expression and influence cell biological decisions with implications for the pathogenesis of several diseases. Here, we disclose a novel gene-regulatory role of circHIPK3 by combining analyses of large genomics datasets and mechanistic cell biological follow-up experiments. Using time-course depletion of circHIPK3 and specific candidate RNA-binding proteins, we identify several perturbed genes by RNA sequencing analyses. Expression-coupled motif analyses identify an 11-mer motif within circHIPK3, which also becomes enriched in genes that are downregulated upon circHIPK3 depletion. By mining eCLIP datasets and combined with RNA immunoprecipitation assays, we demonstrate that the 11-mer motif constitutes a strong binding site for IGF2BP2 in bladder cancer cell lines. Our results suggest that circHIPK3 can sequester IGF2BP2 as a competing endogenous RNA (ceRNA), leading to target mRNA stabilization. As an example of a circHIPK3-regulated gene, we focus on the STAT3 mRNA as a specific substrate of IGF2BP2 and validate that manipulation of circHIPK3 regulates IGF2BP2-STAT3 mRNA binding and, thereby, STAT3 mRNA levels. Surprisingly, absolute copy number quantifications demonstrate that IGF2BP2 outnumbers circHIPK3 by orders of magnitude, which is inconsistent with a simple 1:1 ceRNA hypothesis. Instead, we show that circHIPK3 can nucleate multiple copies of IGF2BP2, potentially via phase separation, to produce IGF2BP2 condensates. Our results support a model where a few cellular circHIPK3 molecules can induce IGF2BP2 condensation, thereby regulating key factors for cell proliferation.

circHIPK3 nucleates IGF2BP2 and functions as a competing endogenous RNA

Circular RNAs (circRNAs) represent a class of widespread endogenous RNAs that regulate gene expression and thereby influence cell biological decisions with implications for the pathogenesis of several diseases. Here, we disclose a novel gene-regulatory role of circHIPK3 by combining analyses of large genomics datasets and mechanistic cell biological follow-up experiments. Specifically, we use temporal depletion of circHIPK3 or specific RNA binding proteins (RBPs) and identify several perturbed genes by RNA sequencing analyses. Using expression-coupled motif analyses of mRNA expression data from various knockdown experiments, we identify an 11-mer motif within circHIPK3, which is also enriched in genes that become downregulated upon circHIPK3 depletion. By mining eCLIP datasets, we find that the 11-mer motif constitutes a strong binding site for IGF2BP2 and validate this circHIPK3-IGF2BP2 interaction experimentally using RNA-immunoprecipitation and competition assays in bladder cancer cell lines. Our results suggest that circHIPK3 and IGF2BP2 mRNA targets compete for binding. Since the identified 11-mer motif found in circHIPK3 is enriched in upregulated genes following IGF2BP2 knockdown, and since IGF2BP2 depletion conversely globally antagonizes the effect of circHIPK3 knockdown on target genes, our results suggest that circHIPK3 can sequester IGF2BP2 as a competing endogenous RNA (ceRNA), leading to target mRNA stabilization. As an example of a circHIPK3-regulated gene, we focus on the STAT3 mRNA as a specific substrate of IGF2BP2 and validate that manipulation of circHIPK3 regulates IGF2BP2- STAT3 mRNA binding and thereby STAT3 mRNA levels. However, absolute copy number quantifications demonstrate that IGF2BP2 outnumbers circHIPK3 by orders of magnitude, which is inconsistent with a simple 1:1 ceRNA hypothesis. Instead, we show that circHIPK3 can nucleate multiple copies of IGF2BP2, potentially via phase separation, to produce IGF2BP2 condensates. Finally, we show that circHIPK3 expression correlates with overall survival of patients with bladder cancer. Our results are consistent with a model where relatively few cellular circHIPK3 molecules function as inducers of IGF2BP2 condensation thereby regulating STAT3 and other key factors for cell proliferation and potentially cancer progression.

Prediction of novel biomarkers for gastric intestinal metaplasia and gastric adenocarcinoma using bioinformatics analysis

Background & aim

The histologic and molecular changes from intestinal metaplasia (IM) to gastric cancer (GC) have not been fully characterized. The present study sought to identify potential alterations in signaling pathways in IM and GC to predict disease progression; these alterations can be considered therapeutic targets.

Materials & methods

Seven gene expression profiles were selected from the GEO database. Discriminate differentially expressed genes (DEGs) were analyzed by EnrichR. The STRING database, Cytoscape, Gene Expression Profiling Interactive Analysis (GEPIA), cBioPortal, NetworkAnalyst, MirWalk database, OncomiR, and bipartite miRNA‒mRNA correlation network was used for downstream analyses of selected module genes.

Results

Analyses revealed that extracellular matrix-receptor interactions (ITGB1, COL1A1, COL1A2, COL4A1, FN1, COL6A3, and THBS2) in GC and PPAR signaling pathway interactions (FABP1, APOC3, APOA1, HMGCS2, and PPARA and PCK1) in IM may play key roles in both the carcinogenesis and progression of underlying GC from intestinal metaplasia. IM enrichment indicated that this is closely related to digestion and absorption. The TF-hub gene regulatory network revealed that AR, TCF4, SALL4, and ESR1 were more important for hub gene expression. It was revealed that the development and prediction of GC may be affected by hsa-miR-29. It was found that PTGR1, C1orf115, CRYL1, ALDOB, and SULT1B1 were downregulated in GC and upregulated in IM. Therefore, they might have tumor suppressor activity in GC progression.

Conclusion

New potential biomarkers and pathways involved in GC and IM were identified that are important for the transformation of GC from IM to adenocarcinoma and can be therapeutic targets for GC.

Decoding the Versatile Landscape of Autophagic Protein VMP1 in Cancer: A Comprehensive Review across Tissue Types and Regulatory Mechanisms

Autophagy, a catabolic process orchestrating the degradation of proteins and organelles within lysosomes, is pivotal for maintaining cellular homeostasis. However, its dual role in cancer involves preventing malignant transformation while fostering progression and therapy resistance. Vacuole Membrane Protein 1 (VMP1) is an essential autophagic protein whose expression, per se, triggers autophagy, being present in the whole autophagic flux. In pancreatic cancer, VMP1-whose expression is linked to the Kirsten Rat Sarcoma Virus (KRAS) oncogene-significantly contributes to disease promotion, progression, and chemotherapy resistance. This investigation extends to breast cancer, colon cancer, hepatocellular carcinoma, and more, highlighting VMP1's nuanced nature, contingent on specific tissue contexts. The examination of VMP1's interactions with micro-ribonucleic acids (miRNAs), including miR-21, miR-210, and miR-124, enhances our understanding of its regulatory network in cancer. Additionally, this article discusses VMP1 gene fusions, especially with ribosomal protein S6 kinase B1 (RPS6KB1), shedding light on potential implications for tumor malignancy. By deciphering the molecular mechanisms linking VMP1 to cancer progression, this exploration paves the way for innovative therapeutic strategies to disrupt these pathways and potentially improve treatment outcomes.

Abnormal levels of expression of microRNAs in peripheral blood of patients with traumatic brain injury are induced by microglial activation and correlated with severity of injury

BACKGROUND

Microglia play a crucial role in regulating the progression of traumatic brain injury (TBI). In specific, microglia can self-activate and secrete various substances that exacerbate or alleviate the neuroimmune response to TBI. In addition, microRNAs (miRNAs) are involved in the functional regulation of microglia. However, molecular markers that reflect the dynamics of TBI have not yet been found in peripheral tissues.

METHODS

Paired samples of peripheral blood were collected from patients with TBI before and after treatment. Next-generation sequencing and bioinformatics analysis were used to identify the main pathways and biological functions of TBI-related miRNAs in the samples. Moreover, lipopolysaccharide-treated human microglia were used to construct a cellular immune-activation model. This was combined with analysis of peripheral blood samples to screen for highly expressed miRNAs derived from activated microglia after TBI treatment. Quantitative reverse-transcriptase polymerase chain reaction was used to determine the expression levels of these miRNAs, allowing their relationship with the severity of TBI to be examined. Receiver operating characteristic (ROC) curves were constructed to analyse the clinical utility of these miRNAs for determining the extent of TBI.

RESULTS

Sequencing results showed that 37 miRNAs were differentially expressed in peripheral blood samples from patients with TBI before and after treatment, with 17 miRNAs being upregulated and 20 miRNAs being downregulated after treatment. The expression profiles of these miRNAs were verified in microglial inflammation models and in the abovementioned peripheral blood samples. The results showed that hsa-miR-122-5p and hsa-miR-193b-3p were highly expressed in the peripheral blood of patients with TBI after treatment and that the expression levels of these miRNAs were correlated with the patients' scores on the Glasgow Coma Scale. ROC curve analysis revealed that abnormally high levels of expression of hsa-miR-122-5p and hsa-miR-193b-3p in peripheral blood have some clinical utility for distinguishing different extents of TBI and thus could serve as biomarkers of TBI.

CONCLUSION

Abnormally high levels of expression of hsa-miR-122-5p and hsa-miR-193b-3p in the peripheral blood of patients with TBI were due to the activation of microglia and correlated with the severity of TBI. This discovery may help to increase understanding of the molecular pathology of TBI and guide the development of new strategies for TBI therapy based on microglial function.

Hypoxia-induced circRNAs encoded by PPARA are highly expressed in human cardiomyocytes and are potential clinical biomarkers of acute myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) is a serious cardiovascular disease that adversely affects human health. Circular RNAs (circRNAs) are involved in the pathological and physiological processes of AMI, but the biological mechanism of their involvement and their clinical significance remain unknown. We aimed to identify circRNAs that are significantly associated with morbidity in the peripheral blood of patients with AMI and evaluate their diagnostic utility.

METHODS

High-throughput sequencing was used to screen for differentially expressed circRNAs in peripheral blood samples obtained from five patients with AMI and five sex- and age-matched healthy controls. A series of bioinformatics tools and databases were used to determine the biological functional classification and pathway enrichment of the circRNAs based on data obtained from sequencing. A hypoxia model was established and used to evaluate the effect of hypoxia on circRNA expression in human cardiomyocytes. A cytoplasmic separation assay and enzyme resistance assay were employed to identify the biological characteristics of circRNA. Polymerase chain reaction validity testing and receiver operating characteristic (ROC) curve analysis were used to evaluate the utility of circRNA assessments in the diagnosis of AMI.

RESULTS

A large number of circRNAs were found to be differentially expressed in the peripheral blood of patients with AMI, and significantly more of these circRNAs were highly expressed than lowly expressed. The genes encoding these circRNAs have a wide range of effects on various functions in the body. A hypoxic environment promoted the upregulation of circRNA expression in human cardiomyocytes, and hsa_circ_0116795 encoded by PPARA was highly expressed in the peripheral blood of the patients with AMI. In terms of biological characteristics, under physiological conditions, hsa_circ_0116795 (circ_PPARA) was mainly located in the cytoplasm of cardiomyocytes and found to be resistant to exonuclease. The ROC curve analysis showed that the expression levels of circ_PPARA in the peripheral blood of patients with AMI were significantly different from those in the peripheral blood of healthy controls.

CONCLUSION

A large number of abnormally expressed circRNAs are detectable in the peripheral blood of patients with AMI. In particular, circ_PPARA is highly expressed in human myocardial cells under hypoxic conditions, and its biological characteristics indicate that it could be employed as a biomarker for the early diagnosis of AMI.

Circ_0003356 suppresses gastric cancer growth through targeting the miR-668-3p/SOCS3 axis

BACKGROUND

Circular RNAs (circRNAs) have attracted extensive attention as therapeutic targets in gastric cancer (GC). Circ_0003356 is known to be downregulated in GC tissues, but its cellular function and mechanisms remain undefined.

AIM

To investigate the role of circ_0003356 in GC at the molecular and cellular level.

METHODS

Circ_0003356, miR-668-3p, and SOCS3 expression were assessed via quantitative real time-polymerase chain reaction (qRT-PCR). Wound healing, EdU, CCK-8, flow cytometry and transwell assays were used to analyze the migration, proliferation, viability, apoptosis and invasion of GC cells. The subcellular localization of circ_0003356 was monitored using fluorescence in situ hybridization. The interaction of circ_0003356 with miR-668-3p was confirmed using RIP-qRT-PCR, RNA pull-down, and dual luciferase reporter assays. We observed protein levels of genes via western blot. We injected AGS cells into the upper back of mice and performed immunohistochemistry staining for examining E-cadherin, N-cadherin, Ki67, and SOCS3 expressions. TUNEL staining was performed for the assessment of apoptosis in mouse tumor tissues.

RESULTS

Circ_0003356 and SOCS3 expression was downregulated in GC cells, whilst miR-668-3p was upregulated. Exogenous circ_0003356 expression and miR-668-3p silencing suppressed the migration, viability, proliferation, epithelial to mesenchy-mal transition (EMT) and invasion of GC cells and enhanced apoptosis. Circ_0003356 overexpression impaired tumor growth in xenograft mice. Targeting of miR-668-3p by circ_0003356 was confirmed through binding assays and SOCS3 was identified as a downstream target of miR-668-3p. The impacts of circ_0003356 on cell proliferation, apoptosis, migration, invasion and EMT were reversed by miR-668-3p up-regulation or SOCS3 down-regulation in GC cells.

CONCLUSION

Circ_0003356 impaired GC development through its interaction with the miR-668-3p/SOCS3 axis.

Circ_0058608 contributes to the progression and taxol resistance of non-small cell lung cancer by sponging miR-1299 to upregulate GBP1

Circular RNAs (circRNAs) act as key regulators in human cancers and chemoresistance. Here, we aimed to explore the role and mechanism of circ_0058608 in nonsmall cell lung cancer (NSCLC) and taxol resistance. The expression of circ_0058608, microRNA-1299 (miR-1299) and guanylate binding protein 1 (GBP1) mRNA was determined by quantitative real-time PCR. In-vitro and in-vivo assays were conducted using Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), colony formation, transwell assays, flow cytometry and animal xenograft experiments. The interaction between miR-1299 and circ_0058608 or GBP1 was confirmed by the dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Circ_0058608 was overexpressed in NSCLC tissues/cells and taxol-resistant NSCLC tissues/cells. Circ_0058608 knockdown inhibited NSCLC cell proliferation and metastasis and also suppressed tumor growth in vivo. Moreover, circ_0058608 knockdown increased taxol sensitivity by increasing taxol-induced apoptosis in taxol-resistant NSCLC cells. Moreover, circ_0058608 silencing enhanced taxol-induced tumor growth of NSCLC in vivo. MiR-1299 was a target of circ_0058608, and the effects of circ_0058608 knockdown on NSCLC cell progression and taxol resistance were reversed by miR-1299 inhibition. Additionally, miR-1299 could interact with GBP1, and miR-1299 suppressed NSCLC cell progression and taxol resistance by targeting GBP1. Furthermore, circ_0058608 could regulate GBP1 expression by sponging miR-1299. Circ_0058608 promoted the progression and taxol resistance of NSCLC by regulating the miR-1299/GBP1 axis.

Multi-Transcriptomic Analysis Reveals the Heterogeneity and Tumor-Promoting Role of SPP1/CD44-Mediated Intratumoral Crosstalk in Gastric Cancer

GC is a fatal disease with high heterogeneity and invasiveness. Recently, SPP1 has been reported to be involved in the tumor progression of multiple human cancers; however, the role of SPP1 in GC heterogeneity and whether it is associated with the invasiveness and mortality of GC remain unclear. Here, we combined multiple RNA sequencing approaches to evaluate the impact of SPP1 on GC. Through bulk RNA sequencing (bulk RNA-seq) and immunohistochemistry (IHC), we found that SPP1 was highly expressed in GC, and high levels of SPP1 were associated with macrophage infiltration, an advanced tumor stage, and higher mortality for advanced GC patients. Furthermore, through simultaneous single-cell and spatial analysis, we demonstrated that SPP1⁺ macrophages are tumor-specific macrophages unique to cancer and enriched in the deep layer of GC tissue. Cell-cell communication analysis revealed that SPP1/CD44 interactions between SPP1⁺ macrophages and their localized tumor epithelial cells could activate downstream target genes in epithelial cells to promote dynamic changes in intratumor heterogeneity. Moreover, these activated genes were found to be closely associated with poor clinical GC outcomes and with cancer-related pathways that promote GC progression, as shown by survival analysis and enrichment analysis, respectively. Collectively, our study reveals that tumor-specific SPP1⁺ macrophages drive the architecture of intratumor heterogeneity to evolve with tumor progression and that SPP1 may serve as a prognostic marker for advanced GC patients, as well as a potential therapeutic target for GC.

Understanding the Dual Roles of CircHIPK3 in Tumorigenesis and Tumor Progression

CircHIPK3 is a type of endogenous circular RNA, which contains a covalently closed circular structure and cannot encode protein or polypeptide. CircHIPK3 is unusually expressed in varieties of tumors and plays dual roles of tumor promotion or tumor inhibition in tumorigenesis and development of tumors by serving as the sponge for miRNA in multiple tumors. Here, we reviewed the differential expression, the dual functions, the regulation mechanism, and the network in a variety of tumors as well as the potential value for the diagnosis and treatment of tumors, which are of great significance for our comprehensive understanding of the roles and mechanisms of circHIPK3 in tumors.

The Diagnostic and Therapeutic Role of Circular RNA HIPK3 in Human Diseases

Circular RNAs (circRNAs) are a class of noncoding RNAs with closed-loop of single-stranded RNA structure. Although most of the circRNAs do not directly encode proteins, emerging evidence suggests that circRNAs play a pivotal and complex role in multiple biological processes by regulating gene expression. As one of the most popular circRNAs, circular homeodomain-interacting protein kinase 3 (circHIPK3) has frequently gained the interest of researchers in recent years. Accumulating studies have demonstrated the significant impacts on the occurrence and development of multiple human diseases including cancers, cardiovascular diseases, diabetes mellitus, inflammatory diseases, and others. The present review aims to provide a detailed description of the functions of circHIPK3 and comprehensively overview the diagnostic and therapeutic value of circHIPK3 in these certain diseases.

Network of miR-373/miR-520s-CD44 Axis Significantly Inhibits the Growth and Invasion of Human Glioblastoma Cells

BACKGROUND

The expression and regulation of microRNAs (miRNAs) play an important role in glioblastoma (GBM) tumorigenesis, progression and prognosis. Little is known about the role of the miRNA regulatory network of GBM risk-related genes in GBM growth and invasiveness.

METHODS

The UALCAN and Oncomine gene expression dataset were used to explore gene expression profiles in human GBM. The Kaplan-Meier method was performed to evaluate the prognostic values of the GBM-related genes. Multiple bioinformatics databases were analysed to predict the GBM-related genes targeted by miRNAs. A luciferase reporter assay and other molecular cell function experiments were conducted to reveal the mechanisms of interaction between the identified miRNAs and their targets.

RESULTS

The CD44 expression is significantly higher in GBM tissues than that in normal tissues, and negatively correlated with survival duration in GBM patients. In normal physiological conditions, CD44 expression is lower in various parts of the central nervous system than in other organ systems. The mRNA encoding CD44 is a direct target of miR-373 and miR-520s, and this finding was verified by molecular biology experiments. We further found that miR-373 and miR-520s expression was negatively associated with CD44 expression in GBM specimens, and that the miR-373 or miR-520s-CD44 interaction network significantly affected the growth and invasiveness of GBM cells.

CONCLUSION

The miR-373 and miR-520s exert their functions by suppressing CD44 expression in GBM cells, and their expression, together with that of CD44, could thus serve as a valuable biomarker of GBM prognosis.

Circ_0114428 promotes proliferation, fibrosis and EMT process of high glucose-induced glomerular mesangial cells through regulating the miR-185-5p/SMAD3 axis

Circular RNA (circRNA) has been confirmed to be the key regulators of diabetic nephropathy (DN) progression. However, the role of circ_0114428 in the DN progression remains unclear. Glomerular mesangial cells (GMCs) were treated with high glucose (HG) to mimic DN cell models in vitro. The expression levels of circ_0114428, microRNA (miR)-185-5p, and SMAD3 mRNA were examined by quantitative real-time PCR. Cell proliferation ability was detected by MTT assay, EdU staining and flow cytometry. The protein levels of proliferation marker, fibrosis markers, epithelial-mesenchymal transition (EMT) markers and SMAD3 were measured by western blot assay. The interaction between miR-185-5p and circ_0114428 or SMAD3 was confirmed via dual-luciferase reporter assay, RIP assay and RNA pull-down assay. Our data showed that circ_0114428 was upregulated in HG-induced GMCs. Circ_0114428 overexpression could aggravate the promotion effect of HG on the proliferation, fibrosis and EMT process of GMCs, while its knockdown had an opposite effect. In the terms of mechanisms, circ_0114428 could sponge miR-185-5p to regulate SMAD3. MiR-185-5p inhibitor could reverse the suppressive effect of circ_0114428 knockdown on the proliferation, fibrosis and EMT process in HG-induced GMCs. Also, SMAD3 overexpression abolished the inhibition of miR-185-5p on the proliferation, fibrosis and EMT process in HG-induced GMCs. Taken together, our data suggested that circ_0114428 might promote DN progression by regulating the miR-185-5p/SMAD3 axis.

Integrated analysis of the functions and clinical implications of exosome circRNAs in colorectal cancer

Background

Exosome circRNAs (Exo-circRNAs) regulate cancer progression and intercellular crosstalk in the tumor microenvironment. However, their biological functions and potential clinical importance in colorectal cancer (CRC) remain unknown.

Methods

We used exoRBase 2.0 data to identify significant differentially expressed Exo-circRNAs (Exo-DEcircRNAs) in CRC patients and healthy individuals. The least absolute shrinkage and selector operation algorithm, support vector machine-recursive feature elimination, and multivariate Cox regression analyses were used to select candidate Exo-circRNAs and constructed a diagnostic model. Quantitative reverse transcription-polymerase chain reaction analysis was performed to confirm the expression of Exo-circRNAs in the serum samples of patients. Furthermore, we constructed an exosome circRNA-miRNA-mRNA network for CRC. Upregulated target mRNAs in the exosome competing endogenous RNA (Exo-ceRNA) network were used for functional and pathway enrichment analyses. We identified 22 immune cell types in CRC patients using CIBERSORT. Correlation analysis revealed the relationship between Exo-ceRNA networks and immune-infiltrating cells. The relationship between target mRNAs and immunotherapeutic response was also explored. Finally, using the Kaplan–Meier survival curve, a prognostic upregulated target mRNA was screened. We constructed a survival-related Exo-ceRNA subnetwork and explored the correlation between the Exo-ceRNA subnetwork and immune-infiltrating cells.

Results

The constructed diagnostic model had a high area under the curve (AUC) value in both the training and validation sets (AUC = 0.744 and AUC = 0.741, respectively). qRT-PCR confirmed that the Exo-circRNAs were differentially expressed in CRC serum samples. We constructed Exo-ceRNA networks based on the interactions among seven upregulated Exo-DEcircRNAs, eight differentially expressed miRNAs, and twenty-two differentially expressed mRNAs in CRC. Functional enrichment analysis revealed that the upregulated target mRNAs were significantly enriched in cytoskeletal motor activity and the PI3K-Akt signaling pathway. Co-expression analysis showed a significant correlation between the Exo-ceRNA networks and immune cells. The significant correlation was observed between target mRNAs and the immunotherapeutic response. Additionally, based on the prognostic upregulated target gene (RGS2), we constructed a survival-related Exo-ceRNA subnetwork (Exosome hsa_circ_0050334-hsa_miR_182_5p-RGS2). CIBERSORT results revealed that the Exo-ceRNA subnetwork correlated with M2 macrophages (P = 4.6e-07, R = 0.31).

Conclusions

Our study identified an Exo-diagnostic model, established Exo-ceRNA networks, and explored the correlation between Exo-ceRNA networks and immune cell infiltration in CRC. These findings elucidated the biological functions of Exo-circRNAs and their potential clinical implications.

Hsa_circular RNA_0001013 exerts oncogenic effects in gastric cancer through the microRNA-136-TWSG1 axis

BACKGROUND

Gastric cancer (GC) is one of the leading malignancies of the digestive system. Circular RNAs (circRNAs) are well-established to play critical regulatory roles in GC development. The current study sought to explore the effects and regulatory mechanism of circ_0001013 in the course of GC.

METHODS

First, differential circRNAs and related mechanisms in GC were predicted by microarray analysis. Circ_0001013, microRNA (miR)-136, and TWSG1 expression patterns were subsequently detected in GC clinical samples and cells using RT-qPCR. The relationship among circ_0001013, miR-136, and TWSG1 was further assessed by dual-luciferase reporter assay, biotin-coupled probe pull-down assay, and biotin-coupled miRNA capture. Based on gain- and loss-of-function assays, GC cell proliferation, migration, invasion, and the cell cycle and apoptosis were also measured by 5-ethynyl-2'-deoxyuridine (EdU) assay, scratch test, Transwell assay, and flow cytometry, respectively. Moreover, the effect of circ_0001013 on tumor growth was detected by tumor xenografting in nude mice.

RESULTS

Circ_0001013 was predicted to be up-regulated in GC by microarray profiling, which was confirmed by RT-qPCR detection in GC tissues and cells. miR-136 was poorly expressed, and TWSG1 was highly expressed in GC tissues. Mechanistically, circ_0001013 bound to miR-136, which negatively targeted TWSG1 in the GC cells. Silencing circ_0001013 or TWSG1 or over-expressing miR-136 led to decreased GC cell proliferation, migration, invasion, and cell cycle arrest and enhanced apoptosis. Furthermore, silencing circ_0001013 resulted in diminished TWSG1 expression and inhibited transplanted tumor growth in the nude mice.

CONCLUSION

Collectively, our findings indicated that circ_0001013 increased TWSG1 expression by binding to miR-136, thereby exerting oncogenic effects in GC.

Upregulation of osteoprotegerin inhibits tert-butyl hydroperoxide-induced apoptosis of human chondrocytes

Necrosis of the femoral head (NFH) is an orthopedic disease characterized by a severe lack of blood supply to the femoral head and a marked increase in intraosseous pressure. NFH is associated with numerous factors, such as alcohol consumption and hormone levels. The present study focused on the expression levels of osteoprotegerin (OPG) in NFH and the effect of OPG overexpression on chondrocyte apoptosis. The results demonstrated that OPG expression was markedly decreased in the femoral head of patients with NFH compared with normal femoral heads. Lentivirus-mediated overexpression of OPG in human chondrocytes reversed the decrease in cell viability and the increase in reactive oxygen species production induced by an oxidative stress-inducing factor, tert-butyl hydroperoxide. Flow cytometry and TUNEL assays revealed that OPG overexpression inhibited the apoptosis of chondrocytes. In addition, it was revealed that OPG exerted its anti-apoptotic effect mainly by promoting Bcl-2 expression and Akt phosphorylation and inhibiting caspase-3 cleavage and Bax expression. The present study revealed that OPG may be an important regulator of NFH.

circIFITM1/miR-802/Foxp1 Axis Participates in Proliferation and Invasion of Lovo Cells

Objective. To explore the role of circIFITM1 and its potential molecular mechanism in colon cancer. Methods. The circIFITM1 in human samples and cell lines of colon cancer was measured via RT-PCR. The cyclicity of circIFITM1 was confirmed by agarose gel electrophoresis and Sanger sequencing, and the stability of circIFITM1 was confirmed by actinomycin D assay. The proliferative and invasive ability was detected by the CCK-8 assay and Transwell assay, respectively. RNA pull-down assay confirmed a combination of circIFITM1 and miRNA. Dual-luciferase reporter gene was used to detect the direct relationship between miRNA and the target gene. Results. circIFITM1 originated from the maternal gene IFITM1and had high stability. It was resistant to processing by actinomycin D. Upregulating circIFITM1 facilitated the proliferation and invasion of Lovo cells, while interfering with circIFITM1 expression inhibited them. circIFITM1 interacted with miR-802, and miR-802 targeted the 3 ${}^{\prime }$ UTR of FOXP1. The overexpression of circIFITM1 downregulated miR-802 and upregulated FOXP1. Conclusion. circIFITM1 facilitates the proliferative and invasive abilities via miR-802/FOXP1 in Lovo cells.

Construction of the miRNA-mRNA Regulatory Networks and Explore Their Role in the Development of Lung Squamous Cell Carcinoma

Purpose: MicroRNA (miRNA) binds to target mRNA and inhibit post-transcriptional gene expression. It plays an essential role in regulating gene expression, cell cycle, and biological development. This study aims to identify potential miRNA-mRNA regulatory networks that contribute to the pathogenesis of lung squamous cell carcinoma (LUSC).

Patients and Methods: MiRNA microarray and RNA-Seq datasets were obtained from the gene expression omnibus (GEO) databases, the cancer genome atlas (TCGA), miRcancer, and dbDEMC. The GEO2R tool, “limma” and “DEseq” R packages were used to perform differential expression analysis. Gene enrichment analysis was conducted using the DAVID, DIANA, and Hiplot tools. The miRNA-mRNA regulatory networks were screened from the experimentally validated miRNA-target interactions databases (miRTarBase and TarBase). External validation was carried out in 30 pairs of LUSC tissues by Real-Time Quantitative Reverse Transcription PCR (qRT-PCR). Receiver operating characteristic curve (ROC) and decision curve analysis (DCA) were conducted to evaluate the diagnostic value. Clinical, survival and phenotypic analysis of miRNA-mRNA regulatory networks were further explored.

Results: We screened 5 miRNA and 10 mRNA expression datasets from GEO and identified 7 DE-miRNAs and 270 DE-mRNAs. After databases screening and correlation analysis, four pairs of miRNA-mRNA regulatory networks were screened out. The miRNA-mRNA network of miR-205-5p (up) and PTPRM (down) was validated in 30 pairs of LUSC tissues. MiR-205-5p and PTPRM have good diagnostic efficacy and are expressed differently in different clinical features and are related to tumor immunity.

Conclusion: The research identified a potential miRNA-mRNA regulatory network, providing a new way to explore the genesis and development of LUSC.

Hsa_circ_0000285 contributes to gastric cancer progression by upregulating FN1 through the inhibition of miR-1278

Background

Gastric cancer (GC) is one of the most severe cancers worldwide, particularly in China. Circular RNA (circRNA) plays an essential role in GC. Hsa_circ_0000285 regulates the progression of several cancers. However, its role in GC has not been reported. This study elucidated the molecular mechanism and role of hsa_circ_0000285 in GC progression.

Methods

GC cells were transfected with silencers of hsa_circ_0000285 and fibronectin 1 (FN1), an inhibitor of miR‐1278, and their negative controls (NC). Mice were injected with short hairpin (sh) RNAs targeting hsa_circ_0000285 or NC. The expression levels of hsa_circ_0000285, miR‐1278, and FN1 were assessed using western blotting and reverse transcription quantitative real‐time polymerase chain reaction (qRT‐PCR). Several assays were used to evaluate cell proliferation, invasion, and apoptosis. Tumor burden was also analyzed. The interactions between miR‐1278, hsa_circ_0000285, and FN1 were ascertained using dual‐luciferase reporter assays. An RNA immunoprecipitation (RIP) assay was used to assess the enrichment of hsa_circ_0000285 and miR‐1278 in GC.

Results

Hsa_circ_0000285 was significantly overexpressed in the GC tissues. Silencing hsa_circ_0000285 inhibited cell proliferation and invasion, promoted apoptosis, and inhibited tumor development. Hsa_circ_0000285 sponged miR‐1278. Inhibition of miR‐1278 in vitro reversed the effects of hsa_circ_0000285 silencing on GC progression. MiR‐1278 targeted FN1, and silencing FN1 neutralized the effects of miR‐1278 inhibitors on GC progression.

Conclusions

The hsa_circ_0000285/miR‐1278/FN1 axis regulated GC progression. In addition, it may serve as a potential therapeutic biomarker for GC.

Breast cancer derived exosomes promoted angiogenesis of endothelial cells in microenvironment via circHIPK3/miR-124-3p/MTDH axis

Circular RNAs (circRNAs) are important contents in exosomes, which can regulate peripheral cell functions, thus influencing the tumor microenvironment. This work investigated the mechanisms underlying the angiogenesis in peripheral human endothelial cells (ECs) mediated by the breast cancer (BC) cells derived exosomal circRNAs and aimed to explore the biomarkers for the anti-angiogenesis therapy for BC.The BC cell derived exosomes were extracted and the expression level and the circular formation of HIPK3 enclosed was determined. To examine the impact of this exosomal circRNA on ECs, cell viability and tube formation were determined in recipient cells co-cultured with exosomes or transfected with circHIPK3 and the related controls. Target microRNAs (miRNAs) for circHIPK3 and target genes for miRNAs were predicted and confirmed by multiple assays like dual luciferase reporter assay, western blot, and qPCR assays. The existence of the circHIPK3/miR-124-3p/MTDH axis were further confirmed with rescue experiment in mice xenograft model.HIPK3s were mainly in forms of circRNAs and were highly expressed in the BC cell derived exosomes, which could be absorbed by the recipient ECs. The cell viability and angiogenesis in ECs were enhanced when treated with circHIPK3s and decreased when treated with circHIPK3-si. Furthermore, MTDH was proved to be the responsible gene in this process which was regulated by miR-124-3p, the local miRNA sponged by the exosomal circHIPK3.circHIPK3 enclosed in the BC cell-derived exosomes enhanced MTDH expression in the endothelial cell by sponging miR-124-3p, favoring the tube formation in ECs, which might serve as a therapeutic target for anti-angiogenesis therapy for breast cancer.

Hsa_circRNA_0017620 regulated cell progression of non-small-cell lung cancer via miR-520a-5p/KRT5 axis

Background

CircRNA is a very important functional RNA that plays an important role in the development and metabolism of cancer. However, the study of circRNA in NSCLC has not been fully elucidated.

Methods

The expression of hsa_circ_0017620, SFMBT2, miR‐520a‐5p, and KRT5 was determined using qRT‐PCR. KRT5, Twist1, E‐cadherin, and Ki67 protein expression were measured with western blot. The positive expression rates of Ki67 and Vimentin were determined by immunohistochemistry assay. 5‐Ethynyl‐2’‐deoxyuridine (EdU), colony formation, and MTT assays were used to assess cell proliferation. Transwell migration and invasion assay were applied to determine cell migration and invasion. Dual‐luciferase reporter and RNA immunoprecipitation assays were used to verify the relationship among hsa_circ_0017620, miR‐520a‐5p, and KRT5. The animal experiment was used to ensure the effects of hsa_circ_0017620 on tumor growth in vivo.

Results

Hsa_circ_0017620 was upregulated in NSCLC cells and tissues. MiR‐520a‐5p had been verified to be a target miRNA of hsa_circ_0017620 and KRT5 had been verified to be a target mRNA of miR‐520a‐5p in NSCLC cells. Knockdown of hsa_circ_0017620 inhibited cell proliferation, migration, and invasion in NSCLC cells, which was reversed by downregulating miR‐520a‐5p or upregulating KRT5 in NSCLC. Overexpression of hsa_circ_0017620 had opposite effects in NSCLC. Moreover, hsa_circ_0017620 silencing inhibited tumor growth in vivo of NSCLC.

Conclusion

In this study, we found that hsa_circ_0017620 played an important role in NSCLC progression. Hsa_circ_0017620 regulated cell proliferation, invasion, and migration through targeting miR‐520a‐5p/KRT5 axis in NSCLC, providing a potential new target for the treatment and diagnosis of NSCLC.

Circ_0016760 Serves as a Cancer Promoter in Non-small Cell Lung Cancer Through miR-876-3p/NOVA2 Axis

Non-small cell lung cancer (NSCLC) is a serious threaten to human health globally. Circular RNAs (circRNAs) were testified to alter the progression of NSCLC. This work intended to investigate the functional role of circ_0016760 in NSCLC development and the potential mechanism. Expression of circ_0016760, microRNA (miR)-876-3p and NOVA alternative splicing regulator 2 (NOVA2) was determined via quantitative reverse transcription-PCT (qRT-PCR) or western blotting. Cell viability, clonogenicity and apoptosis were assessed by Cell Counting Kit-8 (CCK-8) assay, colony formation assay and flow cytometry, respectively. Transwell assay was performed to examine cell migration and invasion. Western blotting was also conducted to detect the levels of epithelial-to-mesenchymal transition (EMT)-related proteins. Role of circ_0016760 in vivo was evaluated via xenograft model assay. Moreover, the interaction between miR-876-3p and circ_0016760 or NOVA2 was verified by dual-luciferase reporter assay or RNA Immunoprecipitation (RIP) assay. Circ_0016760 and NOVA2 were upregulated, while miR-876-3p expression was decreased in NSCLC tissues and cells. Circ_0016760 depletion suppressed NSCLC cell proliferation and metastasis in vitro, as well as hampered tumor growth in vivo. Circ_0016760 acted as a sponge of miR-876-3p, and miR-876-3p could target NOVA2. Circ_0016760 might play vital roles in NSCLC by regulating miR-876-3p/NOVA2 axis. Circ_0016760 could promote the malignant development of NSCLC through miR-876-3p/NOVA2 axis, at least in part.

Variation in the co-expression profile highlights a loss of miRNA-mRNA regulation in multiple cancer types

Recent research provides insight into the ability of miRNA to regulate various pathways in several cancer types. Despite their involvement in the regulation of the mRNA via targeting the 3′UTR, there are relatively few studies examining the changes in these regulatory mechanisms specific to single cancer types or shared between different cancer types.

We analyzed samples where both miRNA and mRNA expression had been measured and performed a thorough correlation analysis on 7494 experimentally validated human miRNA-mRNA target-gene pairs in both healthy and tumoral samples.

We show how more than 90% of these miRNA-mRNA interactions show a loss of regulation in the tumoral samples compared with their healthy counterparts.

As expected, we found shared miRNA-mRNA dysregulated pairs among different tumors of the same tissue. However, anatomically different cancers also share multiple dysregulated interactions, suggesting that some cancer-related mechanisms are not tumor-specific. 2865 unique miRNA-mRNA pairs were identified across 13 cancer types, ≈ 40% of these pairs showed a loss of correlation in the tumoral samples in at least 2 out of the 13 analyzed cancers. Specifically, miR-200 family, miR-155 and miR-1 were identified, based on the computational analysis described below, as the miRNAs that potentially lose the highest number of interactions across different samples (only literature-based interactions were used for this analysis).

Moreover, the miR-34a/ALDH2 and miR-9/MTHFD2 pairs show a switch in their correlation between healthy and tumor kidney samples suggesting a possible change in the regulation exerted by the miRNAs. Interestingly, the expression of these mRNAs is also associated with the overall survival. The disruption of miRNA regulation on its target, therefore, suggests the possible involvement of these pairs in cell malignant functions.

The analysis reported here shows how the regulation of miRNA-mRNA interactions strongly differs between healthy and tumoral cells, based on the strong correlation variation between miRNA and its target that we obtained by analyzing the expression data of healthy and tumor tissue in highly reliable miRNA-target pairs. Finally, a go term enrichment analysis shows that the critical pairs identified are involved in cellular adhesion, proliferation, and migration.

LncRNA SND1-IT1 facilitates TGF-β1-induced epithelial-to-mesenchymal transition via miR-124/COL4A1 axis in gastric cancer

The transformation of tumor cells from an epithelial to a mesenchymal-like phenotype, designated as epithelial-to-mesenchymal transition (EMT), represents a key hallmark of human cancer metastasis, including gastric cancer (GC). However, a large set of non-coding RNAs have been studied for their functions that initiate or inhibit this phenotypic switch in GC cells by regulating oncogenes or tumor suppressors. In this paper, we aimed to identify lncRNA SND1-IT1, miR-124, and COL4A1 gene in the context of GC with a specific focus on their effects on transforming growth factor β1 (TGF-β1)-induced EMT. The study included 52 paired samples of lesion tissues and adjacent lesion-free tissues surgically resected from patients diagnosed with GC. HGC-27 cells were stimulated with exogenous TGF-β1 (2 ng/mL). Expression of lncRNA SND1-IT1, miR-124, and COL4A1 was determined by RT-qPCR. CCK-8 assays, Transwell assays, immunoblotting analysis of EMT-specific markers, and tumor invasion markers were performed to evaluate cell viability, migration, and invasion of cultured HGC-27 cells. Luciferase activity assay was employed to examine miR-124 binding with lncRNA SND1-IT1 and COL4A1, respectively. LncRNA SND1-IT1 was upregulated in GC tissues and cells. TGF-β1-stimulated EMT and regulated lncRNA SND1-IT1, miR-124, and COL4A1 expressions in HGC-27 cells. LncRNA SND1-IT1 knockdown tempered HGC-27 cell viability, migration and invasion. LncRNA SND1-IT1 participated in TGF-β1-stimulated EMT in GC by sponging miR-124. MiR-124 attenuated TGF-β1-stimulated EMT in GC by targeting COL4A1. These results primarily demonstrated TGF-β1 can regulate cancer cell migration, invasion and stimulate EMT through the SND1-IT1/miR-124/COL4A1 axis in GC.

Hsa_circ_0005230 is up-regulated and promotes gastric cancer cell invasion and migration via regulating the miR-1299/RHOT1 axis

Gastric cancer (GC) is one of the most common cancers in the world. Circular RNAs (circRNAs) are a class of non-coding RNAs that are widely expressed in eukaryotic cells. However, their role has been poorly understood in GC. This report aimed to explore the biological functions of hsa_circ_0005230 and its action mechanism in GC. This study validated that hsa_circ_0005230 was significantly up-regulated in 130 cases of GC tissues using qRT-PCR, and clinicopathological feature analysis revealed that its high expression was positively associated with histological grade, lymph node metastasis, TNM stages, and poor prognosis. In vitro, functional experiments showed that silencing hsa_circ_0005230 significantly decreased GC cell proliferation, invasion and migration capabilities. In addition, the major proteins of EMT (epithelial-mesenchymal transition) relevance have changed. In mechanism studies, bioinformatics analyses were used to predict the hsa_circ_0005230/miR-1299/RHOT1 axis and hsa_circ_0005230 may serve as a sponge for miR-1299 and indirectly regulate the expression of RHOT1. The regulated relationships between the molecules on the axis were verified using qRT-PCR and correlation analysis. Dual-luciferase reporter gene assay has been used to verify the binding site between miR-1299 and RHOT1. WB (Western blotting) and IHC (Immunohistochemical) were used to verify that RHOT1 may play the role of oncoprotein and affect the biological behavior of GC. Overall, hsa_circ_0005230 could enhance the EMT phenotype by promoting RHOT1 expression through sponging miR-1299, thus affecting the biological behavior of GC. Hsa_circ_0005230 can be easily identified as a potential diagnostic biomarker and assessment prognosis target for GC.

Knockdown of circRNA Paralemmin 2 Ameliorates Lipopolysaccharide-induced Murine Lung Epithelial Cell Injury by Sponging miR-330-5p to Reduce ROCK2 Expression

Previous data have reported the high expression of circRNA paralemmin 2 (circPALM2) in mice with acute lung injury (ALI). However, the role of circPALM2 in ALI pathogenesis remains unclear. The study aims to reveal the function of circPALM2 in ALI and the underlying mechanism. C57BL/6 J mice and murine lung epithelial-12 (MLE-12) cells were treated with lipopolysaccharide (LPS) to simulate ALI mouse and ALI cell models, respectively. Lung injury score and lung wet-to-dry ratio assays were used to evaluate the ALI mouse model. Quantitative real-time polymerase chain reaction and Western blot assays were implemented to analyze the expressions of circPALM2, microRNA-330-5p (miR-330-5p), rho-associated coiled-coil containing protein kinase 2 (ROCK2), and apoptosis-related markers. Cell viability, apoptosis, and the production of inflammatory cytokines were investigated by cell counting kit-8, flow cytometry, and enzyme-linked immunosorbent assays. The expressions of circPALM2 and ROCK2 were significantly increased, while miR-330-5p was decreased in ALI mice and LPS-induced MLE-12 cells compared with controls. LPS treatment inhibited cell viability but induced apoptosis, inflammatory cytokine production, and oxidative stress; however, these effects were attenuated after the combination of circPALM2 knockdown and LPS. CircPALM2 regulated LPS-caused MLE-12 cell damage by targeting miR-330-5p. Additionally, ROCK2, a target gene of miR-330-5p, participated in LPS-induced MLE-12 cell injury. Further, circPALM2 activated ROCK2 by associating with miR-330-5p. CircPALM2 modulated LPS-caused murine lung epithelial cell injury by the miR-330-5p/ROCK2 pathway, providing a therapeutic target for ALI.

CircRTN4IP1 regulates the malignant progression of intrahepatic cholangiocarcinoma by sponging miR-541-5p to induce HIF1A production

BACKGROUND

Recent studies indicate that circular RNA (circRNA) serves important roles in the development of intrahepatic cholangiocarcinoma (ICC). However, the role of circRNA reticulon 4 interacting protein 1 (circRTN4IP1) in ICC progression remains unknown.

METHODS

Expression of circRTN4IP1, microRNA-541-5p (miR-541-5p), hypoxia inducible factor 1 subunit alpha (HIF1A) and other indicated protein markers was detected by quantitative real-time polymerase chain reaction or Western blot. The functional effects of circRTN4IP1 knockdown in ICC cells were analyzed by cell counting kit-8, cell colony formation, flow cytometry analysis, Western blot, glucose and lactate kit assays. The positive expression rate of HIF1A was detected by immunohistochemistry assay. The interaction between miR-541-5p and circRTN4IP1 or HIF1A was identified by dual-luciferase reporter, RNA immunoprecipitation or RNA pull-down assays. Xenograft mouse model assay was performed to determine the effect of circRTN4IP1 depletion on tumor formation.

RESULTS

In contrast, ICC tissues and cells showed high expression of circRTN4IP1 and HIF1A, but low expression of miR-541-5p. Knockdown of circRTN4IP1 led to repression of cell proliferation and glucose metabolism, but promotion of cell apoptosis; however, circRTN4IP1 overexpression had opposite effects. In mechanism, circRTN4IP1 acted as a sponge for miR-541-5p, which was found to target HIF1A. MiR-541-5p inhibitors could remit circRTN4IP1 knockdown-mediated action. Also, HIF1A participated in the regulation of miR-541-5p in ICC progression. In support, circRTN4IP1 depletion impeded tumor formation in vivo.

CONCLUSION

CircRTN4IP1 knockdown inhibited ICC cell malignancy by miR-541-5p/HIF1A axis, providing us with a reliable target for the therapy of ICC.

Circ_0025039 acts an oncogenic role in the progression of non-small cell lung cancer through miR-636-dependent regulation of CORO1C

Non-small cell lung cancer remains the leading cause of cancer-related death worldwide. Circular RNA plays vital roles in NSCLC progression. This study is designed to reveal the role of circ_0025039 in NSCLC cell malignancy. The RNA expression of circ_0025039, microRNA-636 (miR-636), and coronin 1C was detected by quantitative real-time polymerase chain reaction. Protein expression was checked by Western blot analysis or immunohistochemistry assay. Cell proliferation, migration, invasion, tube formation ability, sphere formation capacity, and apoptosis were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine, transwell assay, tube formation assay, sphere formation assay, and flow cytometry analysis, respectively. Mouse model assay was conducted to reveal the effect of circ_0025039 silencing on tumor formation in vivo. The interaction between miR-636 and circ_0025039 or CORO1C was identified through dual-luciferase reporter and RNA pull-down assays. The expression of circ_0025039 and CORO1C was significantly increased, while miR-636 was decreased in NSCLC tissues and cells compared with controls. Circ_0025039 depletion repressed NSCLC cell proliferation, migration, invasion, tube-forming capacity, and sphere formation ability, but induced cell apoptosis. The neoplasm formation was repressed after circ_0025039 silencing. Additionally, circ_0025039 acted as a sponge for miR-636, which was found to target CORO1C. Importantly, the contribution of circ_0025039 to NSCLC progression was mediated by miR-636/CORO1C axis. Circ_0025039 silencing repressed NSCLC malignant progression by reducing CORO1C expression through miR-636, showing the possibility of circ_0025039 as a therapeutic target for NSCLC.

Circ-CREBBP promotes cell tumorigenesis and glutamine catabolism in glioma by regulating miR-375/glutaminase axis

Circular RNA CREB-binding protein (circ-CREBBP) has been reported to involve in the tumorigenesis of glioma. However, the role and underlying molecular mechanism of circ-CREBBP in glioma glutamine catabolism remain unclear. The expression of circ-CREBBP, microRNA (miR)-375 and glutaminase (GLS) was detected using quantitative real-time polymerase chain reaction and western blot. The 3‑(4, 5‑dimethylthiazol‑2‑y1)‑2, 5‑diphenyl tetrazolium bromide (MTT), colony formation, flow cytometry and transwell assays were used to determine the effects of them on glioma cell malignant biological behaviors in vitro. Glutamine metabolism was analyzed using assay kits. Murine xenograft model was established to investigate the role of circ-CREBBP in vivo. The binding interactions between miR-375 and circ-CREBBP or GLS were confirmed by the dual-luciferase reporter assay. Circ-CREBBP was highly expressed in glioma tissues and cells, and high expression of circ-CREBBP predicted poor prognosis. Circ-CREBBP knockdown suppressed cell proliferation, migration, invasion and glutamine metabolism while expedited cell apoptosis in glioma in vitro, as well as impeded tumor growth in vivo. Circ-CREBBP directly targeted miR-375, which was demonstrated to restrain glioma cell growth, motility and glutamine metabolism. Moreover, miR-375 inhibition reverted the anticancer effects of circ-CREBBP knockdown on glioma cells. GLS was a target of miR-375, GLS silencing or the treatment of GLS inhibitor bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES) impaired glioma cell malignant phenotypes and glutamine metabolism. Importantly, GLS up-regulation weakened the tumor-suppressive functions of miR-375 on glioma cells. Mechanistically, circ-CREBBP indirectly regulated GLS expression through sponging miR-375. In all, circ-CREBBP expedited glioma tumorigenesis and glutamine metabolism through miR-375/GLS axis, suggesting a promising target for combined glioma therapy.

CircRNAs as Potential Blood Biomarkers and Key Elements in Regulatory Networks in Gastric Cancer

Gastric cancer (GC) is the fifth most common type of cancer and the third leading cause of cancer death in the world. It is a disease that encompasses a variety of molecular alterations, including in non-coding RNAs such as circular RNAs (circRNAs). In the present study, we investigated hsa_circ_0000211, hsa_circ_0000284, hsa_circ_0000524, hsa_circ_0001136 and hsa_circ_0004771 expression profiles using RT-qPCR in 71 gastric tissue samples from GC patients (tumor and tumor-adjacent samples) and volunteers without cancer. In order to investigate the suitability of circRNAs as minimally invasive biomarkers, we also evaluated their expression profile through RT-qPCR in peripheral blood samples from patients with and without GC (n = 41). We also investigated the predicted interactions between circRNA-miRNA-mRNA and circRNA-RBP using the KEGG and Reactome databases. Overall, our results showed that hsa_circ_0000211, hsa_circ_0000284 and hsa_circ_0004771 presented equivalent expression profiles when analyzed by different methods (RNA-Seq and RT-qPCR) and different types of samples (tissue and blood). Further, functional enrichment results identified important signaling pathways related to GC. Thus, our data support the consideration of circRNAs as new, minimally invasive biomarkers capable of aiding in the diagnosis of GC and with great potential to be applied in clinical practice.

Potential Role of circRNA-HIPK3/microRNA-124a Crosstalk in the Pathogenesis of Rheumatoid Arthritis

BACKGROUND

Circular RNA-HIPK3 (CircHIPK3) has been shown to be aberrantly expressed in a variety of diseases, contributing to disease initiation and progression. The aim of the present study is to investigate the role of the circHIPK3 RNA/microRNA-124a interaction in the pathogenesis of rheumatoid arthritis (RA).

METHODS

This study included 79 RA patients and 30 control individuals. The patients involved were classified according to the disease activity score (DAS28) into mild (24 patients), moderate (24 patients), and severe (31 patients). Serum samples were collected to estimate the relative gene expression of circHIPK3 RNA and its target gene microRNA-124a by quantitative real time-PCR. Moreover, ELISA was used to detect the serum levels of monocyte chemoattractant protein-1 (MCP-1). Routine laboratory estimation of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor (RF) was also done.

RESULTS

In all grades of RA groups, there was a significantly substantial elevation of circHIPK3 RNA gene expression, with subsequent downregulation of miRNA-124a when compared to the control group. CircHIPK3 and microRNA-124a expression have been established to be inversely linked. Also, estimation of serum levels of MCP-1, ESR, CRP, and RF exhibited a significant increase in all grades of RA as compared to the control group.

CONCLUSION

CircHIPK3 and microRNA-124a might be regarded as key players in the pathogenesis of RA. The cross-talk between them appears to be responsible for inducing joint inflammation by increasing MCP-1 production. Targeting circHIPK3 and microRNA-124a, and their downstream adaptor molecules, poses a new challenge for RA therapy.

The Molecular Roles and Clinical Implications of Non-Coding RNAs in Gastric Cancer

Gastric cancer (GC) is one of the most common malignancies in the world. It is also the fifth most common cancer in China. In recent years, a large number of studies have proved that non-coding RNAs (ncRNAs) can regulate cell proliferation, invasion, metastasis, apoptosis, and angiogenesis. NcRNAs also influence the therapeutic resistance of gastric cancer. NcRNAs mainly consist of miRNAs, lncRNAs and circRNAs. In this paper, we summarized ncRNAs as biomarkers and therapeutic targets for gastric cancer, and also reviewed their role in clinical trials and diagnosis. We sum up different ncRNAs and related moleculars and signaling pathway in gastric cancer, like Bcl-2, PTEN, Wnt signaling. In addition, the potential clinical application of ncRNAs in overcoming chemotherapy and radiotherapy resistance in GC in the future were also focused on.

Comparative analysis of circular RNA enrichment methods

The circRNAs sequencing results vary due to the different enrichment methods and their performance is needed to systematic comparison. This study investigated the effects of different circRNA enrichment methods on sequencing results, including abundance and species of circRNAs, as well as the sensitivity and precision. This experiment was carried out by following four common circRNA enrichment methods: including ribosomal RNA depletion (rRNA-), polyadenylation and poly (A+) RNA depletion followed by RNase R treatment (polyA+RNase R), rRNA-+polyA+RNase R and polyA+RNase R+ rRNA-. The results showed that polyA+RNase R+ rRNA - enrichment method obtained more circRNA number, higher sensitivity and abundance among them; polyA+RNase R method obtained higher precision. The linear RNAs can be thoroughly removed in all enrichment methods except rRNA depletion method. Overall, our results helps researchers to quickly selection a circRNA enrichment of suitable for own study among many enrichment methods, and it provides a benchmark framework for future improvements circRNA enrichment methods.[Figure: see text].

Circular RNA circRAB31 acts as a miR-885-5psponge to suppress gastric cancer progressionvia the PTEN/PI3K/AKT pathway

Emerging evidence indicated that circular RNAs (circRNAs) play essential roles in cancer progression. A large number of circRNAs have been reported to modulate cancer carcinogenesis. However, the underlying mechanisms by which circRNAs regulate gastric cancer remain largely unclear. By using circRNA microarray, we identified that circRAB31 may serve as a tumor suppressor. circRAB31 was downregulated in gastric cancer tissues and gastric cancer cell lines compared with normal tissues and a human gastric epithelial cell line (GES-1). Overexpression of circRAB31 suppressed gastric cancer proliferation and metastasis in vitro and in vivo, whereas silencing of circRAB31 had the opposite effects. Bioinformatic analysis as well as pull-down and luciferase assays revealed that circRAB31 exerted tumor-suppressive functions by binding directly to miR-885-5p. In addition, we demonstrated that circRAB31 could suppress PI3K/AKT signaling via the phosphatase and tensin homologue (PTEN)-a downstream target gene of miR-885-5p. In summary, our results demonstrated that circRAB31 could serve as a sponge of miR-885-5p to regulate gastric cancer cell proliferation, migration, and invasion by affecting the PTEN/PI3K/AKT signaling.

Long Noncoding RNA NEAT1 Knockdown Ameliorates 1-Methyl-4-Phenylpyridine-Induced Cell Injury Through MicroRNA-519a-3p/SP1 Axis in Parkinson Disease

BACKGROUND

Parkinson disease is a neurodegenerative disease and is characterized by resting tremor, dementia, and gait disorder. Previous studies have indicated that long noncoding RNA participates in the regulation of the pathogenesis of Parkinson disease. The study aimed to reveal the effects of long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) on 1-methyl-4-phenylpyridine (MPP+)-induced human neuroblastoma cell injury and the underlying mechanism.

METHODS

The expressions of NEAT1, microRNA (miR)-519a-3p, and transcription factor specific protein 1 (SP1) were detected by quantitative real-time polymerase chain reaction. The protein expressions of SP1 and inflammation-related factors were determined by Western blot. Cell viability was determined by 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was investigated by flow cytometry analysis. The targeting relationship between miR-519a-3p and NEAT1 or SP1 was predicted by starBase online database and verified by a dual-luciferase reporter assay.

RESULTS

NEAT1 and SP1 expressions were significantly upregulated, whereas miR-519a-3p was downregulated in MPP+-treated neuroblastoma cells in a dose- and time-dependent manner when compared with control groups. NEAT1 knockdown restrained MPP+-induced repression of cell viability and promotion of cell apoptosis and inflammation. Additionally, NEAT1 served as a sponge of miR-519a-3p and regulated MPP+-caused cell injury by interacting with miR-519a-3p. Also, SP1, a target gene of miR-519a-3p, rescued miR-519a-3p-mediated actions under MPP+ treatment. Importantly, NEAT1 stimulated SP1 expression through interaction with miR-519a-3p.

CONCLUSIONS

NEAT1 silencing protected against MPP+-induced neuroblastoma cell injury by regulating the miR-519a-3p/SP1 pathway. This finding provides a novel direction for the development of therapeutic strategies for Parkinson disease.

CircPTK2 inhibits the tumorigenesis and metastasis of gastric cancer by sponging miR-134-5p and activating CELF2/PTEN signaling

BACKGROUND

CircRNAs are a new subset of noncoding RNAs formed by covalent closed loops and play crucial roles in the regulation of cancer gene expression. However, the roles and underlying mechanisms of circRNAs in gastric cancer (GC) remain indistinct. This study aimed to explore the role and mechanism of hsa_circ_0006421 (circPTK2) in GC.

METHODS

The differential expression of circRNAs between GC tissues and adjacent normal tissues were identified by a circRNA expression profiling. Associations of circPTK2 or miR-134-5p expression with clinicopathological characteristics and prognosis of GC patients were analyzed by chi-square of Fisher's exact tests and Kaplan-Meier analysis. CCK8, colony formation, EdU assays and animal models were performed to assess the effects of circPTK2 on proliferation and invasion of GC cells. CircPTK2-specific probes were used to purify the RNA pulled down from the circPTK2, and enrichment of circPTK2 and miR-134-5p was detected by qRT-PCR. The effects of circPTK2 on miR-134-5p expression and CELF2/PTEN signaling were examined by qRT-PCR and Western blotting analysis.

RESULTS

Low expression of circPTK2 and high expression of miR-134-5p were related to the poor survival, and high expression of miR-134-5p was related to the tumor recurrence in GC patients. Overexpressing circPTK2 suppressed the proliferation, colony formation, DNA synthesis and cell invasion as well as xenograft tumor growth and lung metastasis in vitro and in vivo, whereas silencing circPTK2 had the opposite effects. Moreover, circPTK2 was negatively correlated and co-localized with miR-134-5p in the cytoplasm of GC tissue cells. circPTK2 bound to and sponged miR-134-5p in GC cells, and miR-134-5p facilitated cell growth and invasion but attenuated circPTK2 induced tumor suppressive effects and CELF2/PTEN signaling activation in GC cells.

CONCLUSIONS

circPTK2 functions as a tumor suppressor in GC by sponging miR-134-5p and activating the CELF2/PTEN axis.

Pepsinogen C expression-related lncRNA/circRNA/mRNA profile and its co-mediated ceRNA network in gastric cancer

The expression of pepsinogen C (PGC) is considered an ideal negative biomarker of gastric cancer, but its pathological mechanisms remain unclear. This study aims to analyze competing endogenous RNA (ceRNA) networks related to PGC expression at a post-transcriptional level and build an experimental basis for studying the role of PGC in the progression of gastric cancer. RNA sequencing technology was used to detect the differential expression (DE) profiles of PGC-related long non-coding (lnc)RNAs, circular (circ)RNAs, and mRNAs. Ggcorrplot R package and online database were used to construct DElncRNAs/DEcircRNAs co-mediated PGC expression-related ceRNA networks. In vivo and in vitro validations were performed using quantitative reverse transcription-PCR (qRT-PCR). RNA sequencing found 637 DEmRNAs, 698 DElncRNAs, and 38 DEcircRNAs. The PPI network of PGC expression-related mRNAs consisted of 503 nodes and 1179 edges. CFH, PPARG, and MUC6 directly interacted with PGC. Enrichment analysis suggested that DEmRNAs were mainly enriched in cancer-related pathways. Eleven DElncRNAs, 13 circRNAs, and 35 miRNA-mRNA pairs were used to construct ceRNA networks co-mediated by DElncRNAs and DEcircRNAs that were PGC expression-related. The network directly related to PGC was as follows: SNHG16/hsa_circ_0008197-hsa-mir-98-5p/hsa-let-7f-5p/hsa-let-7c-5p-PGC. qRT-PCR validation results showed that PGC, PPARG, SNHG16, and hsa_circ_0008197 were differentially expressed in gastric cancer cells and tissues: PGC positively correlated with PPARG (r = 0.276, P = 0.009), SNHG16 (r = 0.35, P = 0.002), and hsa_circ_0008197 (r = 0.346, P = 0.005). PGC-related DElncRNAs and DEcircRNAs co-mediated complicated ceRNA networks to regulate PGC expression, thus affecting the occurrence and development of gastric cancer at a post-transcriptional level. Of these, the network directly associated with PGC expression was a SNHG16/hsa_circ_0008197-mir-98-5p/hsa-let-7f-5p/hsa-let-7c-5p - PGC axis. This study may form a foundation for the subsequent exploration of the possible regulatory mechanisms of PGC in gastric cancer.

The Use of circRNAs as Biomarkers of Cancer

CircRNAs are a subclass of lncRNAs that have been found to be abundantly present in a wide range of species, including humans. CircRNAs are generally produced by a noncanonical splicing event called backsplicing that is dependent on the canonical splicing machinery, giving rise to circRNAs classified into three main categories: exonic circRNA, circular intronic RNA, and exon-intron circular RNA. Notably, circRNAs possess functional importance and display their functions through different mechanisms of action including sponging miRNAs, or even being translated into functional proteins. In addition, circRNAs also have great potential as biomarkers, particularly in cancer, thanks to their high stability, tissue type and developmental stage specificity, and their presence in biological fluids, which make them promising candidates as noninvasive biomarkers. In this chapter, we describe the most commonly used techniques for the study of circRNAs as cancer biomarkers, including high-throughput techniques such as RNA-Seq and microarrays, and other methods to analyze the presence of specific circRNAs in patient samples.

Circ_0062270 upregulates EPHA2 to facilitate melanoma progression via sponging miR-331-3p

BACKGROUND

Circular RNA (circRNA) has been confirmed to play a vital role in melanoma progression.

OBJECTIVE

The regulatory function of circ_0062270, a novel circRNA, in melanoma progression is unclear.

METHODS

Relative expression levels of circ_0062270 and microRNA (miR)-331-3p were determined using qRT-PCR. Cell counting kit 8 assay, EdU staining and flow cytometry were used to measure cell proliferation, cell cycle distribution and apoptosis. The protein levels of proliferation, apoptosis and metastasis-related markers, as well as EPH receptor A2 (EPHA2), were tested using western blot analysis. Besides, cell migration and invasion were evaluated using transwell assay. Meanwhile, the interaction between miR-331-3p and circ_0062270 or EPHA2 was confirmed by dual-luciferase reporter assay or RIP assay. Additionally, tumor xenograft models were constructed to investigate the function of circ_0062270 on melanoma tumor growth in vivo.

RESULTS

The expression of circ_0062270 was increased in melanoma tissues and cells. Knockdown of circ_0062270 inhibited proliferation, promoted apoptosis, and repressed metastasis in melanoma. Moreover, circ_0062270 could serve as miR-331-3p sponge, and miR-331-3p could target EPHA2. Furthermore, miR-331-3p inhibitor and EPHA2 overexpression reversed the inhibitory effect of circ_0062270 silencing on melanoma progression. In addition, silenced circ_0062270 also could inhibit melanoma tumor growth in vivo.

CONCLUSION

Circ_0062270 accelerated the progression of melanoma through regulating the miR-331-3p/EPHA2 axis, suggesting that circ_0062270 might be a novel potential therapeutic target for melanoma.

CircRNA circFOXK2 facilitates oncogenesis in breast cancer via IGF2BP3/miR-370 axis

Metastasis is the leading cause of breast cancer (BC)-related deaths. Circular RNAs (circRNAs) have emerged as essential regulators for cancer progression and metastasis. Therefore, the objective of this study was to investigate the role of circRNAs in BC metastasis and related mechanism. In this study, we established the BC cell line with high or low potential of metastasis. RNA sequencing, migration and invasion assay, Fluorescence in situ hybridization, luciferase report assay, circRNA pulldown, and transmission electron microscopy were performed to elucidate the molecular mechanism. The results showed that circRNA circFOXK2 was significantly increased in BC cells with high metastatic ability, and the upregulation of circFOXK2 was correlated with poor clinicopathological characteristics. Functional experiments demonstrated that overexpression of circFOXK2 promoted migration and invasion of BC cells. Also. circFOXK2 could act with IGF2BP3, an RNA-binding protein, and miR-370 to synergistically promote BC metastasis. Moreover, miR-370 could be transferred through exosomes to enhance the metastatic ability of recipient cells. In conclusion, circFOXK2 functions as a key regulator in BC metastasis, and the role of circFOXK2 on BC metastasis is tightly associated with the involvement of IGF2BP3 and miR-370. CircFOXK2 might serve as a potential biomarker for the diagnosis and treatment of BC.

Immune-Related Nine-MicroRNA Signature for Predicting the Prognosis of Gastric Cancer

Recent findings have demonstrated the superiority and utility of microRNAs (miRNAs) as new biomarkers for cancer diagnosis, therapy, and prognosis. In this study, to explore the prognostic value of immune-related miRNAs in gastric cancer (GC), we analyzed the miRNA-expression profiles of 389 patients with GC, using data deposited in The Cancer Genome Atlas database. Using a forward- and backward-variable selection and multivariate Cox regression analyses model, we identified a nine-miRNA signature (the “ImmiRSig,” consisting of miR-125b-5p, miR-99a-3p, miR-145-3p, miR-328-3p, miR-133a-5p, miR-1292-5p, miR-675-3p, miR-92b-5p, and miR-942-3p) in the training cohort that enabled the division of patients into high- and low-risk groups with significantly different survival rates. The ImmiRSig was successfully validated with an independent test cohort of 193 GC patients. Univariate and multivariate Cox regression analyses indicated that the ImmiRSig would serve as an independent prognostic factor after adjusting for other clinical covariates. Pending further prospective validation, the identified ImmiRSig appears to have significant clinical importance in terms of improving outcome predictions and guiding personalized treatment for patients with GC. Finally, significant associations between the ImmiRSig and the half-maximal inhibitory concentrations of chemotherapeutic agents were observed, suggesting that ImmiRSig may predict the clinical efficacy of chemotherapy.

Downregulating circRNA_0044516 Inhibits Cell Proliferation in Gastric Cancer Through miR-149/Wnt1/β-catenin Pathway

BACKGROUND

Circular RNAs (circRNAs) play important roles in the progression of gastric cancer (GC). The Wnt1/β-catenin pathway can promote the proliferation of GC cells. This study aimed to explore whether circRNA_0044516 can regulate the proliferation of GC cells by modulating the Wnt1/β-catenin pathway.

METHODS

The expression of circRNA_0044516, miR-149, Wnt1, and β-catenin in GC tissues or cells was detected by qRT-PCR and western blot. Cell viability and apoptosis were measured by CCK-8 and flow cytometry assays, respectively. The interaction between circRNA_0044516 and miR-149 was determined by luciferase reporter and RNA pull-down assays.

RESULTS

Upregulated circRNA_0044516 was found in GC tissues and cell lines. Downregulating circRNA_0044516 inhibited the viability and promoted apoptosis of GC cells. CircRNA_0044516 targeted miR-149, and its downregulation elevated miR-149 level in GC cells. Mechanistically, silencing circRNA_0044516 reduced the protein level of Wnt1 and β-catenin through miR-149, and finally suppressed viability and contributed to apoptosis of GC cells. Moreover, circRNA_0044516 knockdown inhibited the tumor growth of HGC-27 cells in nude mice.

CONCLUSIONS

Our results indicated an important role of circRNA_0044516 in GC and elucidated that downregulation of circRNA_0044516 inhibits the proliferation of GC cells through miR-149/Wnt1/β-catenin.

Knockdown of circBFAR inhibits proliferation and glycolysis in gastric cancer by sponging miR-513a-3p/hexokinase 2 axis

The relationship between circular RNAs (circRNAs) and many types of cancer has been of great interest. A novel circRNA, circBFAR, has been identified, but the functions of circBFAR and its underlying mechanism in gastric cancer (GC) have not been reported. This study was designed to investigate the role of circBFAR in GC and its downstream miRNA targets. Quantitative real-time polymerase reaction was used to detect the expression of circBFAR and miRNAs. Cell counting kit-8 and EdU were used to detect the proliferation of GC cells. Measurement of the extracellular acidification rate, oxygen consumption rate and lactate acid production were performed to assess the glycolysis levels. The results showed that circBFAR exhibited higher expression in GC tissues and cell lines. circBFAR was proven to promote GC proliferation by targeting the miR-513a-3p/hexokinase 2 (HK2) axis. Inhibition of circBFAR also led to a significant decrease in the glycolysis levels. In this study, we found a circBFAR/miR-513a-3p/HK2 axis in GC and revealed the relationship between circBFAR and glycolysis for the first time. circBFAR may serve as a novel target of GC individualized therapy.

Comprehensive Bioinformatics Analysis of mRNA Expression Profiles and Identification of a miRNA-mRNA Network Associated with the Pathogenesis of Low-Grade Gliomas

Purpose

Low-grade glioma is the most common type of primary intracranial tumour, and the overall survival of patients with low-grade glioma (LGG) has shown no significant improvement over the past few decades. Therefore, it is crucial to understand the precise molecular mechanisms involved in the carcinogenesis of LGG.

Methods

To investigate the regulatory mechanisms of mRNA–miRNA networks related to LGG, in the present study, a comprehensive analysis of the genomic landscape between low-grade gliomas and normal brain tissues from the GEO and TCGA datasets was first conducted to identify differentially expressed genes (DEGs) and differentially expressed miRNAs in LGG. Following a series of analyses, including WGCNA, GO and KEGG analyses, PPI and key model analyses, and survival analysis of the DEGs with clinical phenotypes, the potential key genes were screened and identified, and the related miRNA–mRNA networks were subsequently constructed through miRWalk 3.0. Finally, the potential miRNA–mRNA networks were further validated in CGGA (Chinese Glioma Genome Atlas) datasets and clinical specimens by qRT-PCR.

Results

In our results, six hub genes, MELK, NCAPG, KIF4A, NUSAP1, CEP55, and TOP2A, were ultimately identified. Two regulatory pathways, miR-495-3p-TOP2A and miR-1224-3p-MELK, that regulate the pathogenesis of LGG were ultimately identified. Furthermore, the expression of miR-495-3p-TOP2A and miR-1224-3p-MELK in solid tissues was validated by qRT-PCR.

Conclusion

Our study identified hub genes and related miRNA–mRNA regulatory pathways that contribute to the carcinogenesis of LGG, which may help us reveal the mechanisms underlying the development of LGG.

The role of circRNA derived from RUNX2 in the serum of osteoarthritis and its clinical value

Background

Circular RNA (circRNA) has been shown to affect the pathological process of osteoarthritis (OA) and is expected to become a potential marker for disease diagnosis. This study aimed to investigate the association between circRNA derived from the gene of runt‐related transcription factor 2 (RUNX2) and OA risk.

Methods

The expression profile of RUNX2‐derived circRNAs in serum of OA patients was detected. Then, the cytological localization of screened differential circRNAs was studied. Luciferase (LUC) reporter assay was used to identify the microRNA (miRNA) sponge capacity of the circRNAs. Bioinformatics analysis was used to construct the functional pathway of this circRNA‐miRNAs network. And then, the diagnostic value of RUNX2‐derived circRNAs in OA was evaluated.

Results

RUNX2‐derived hsa_circ_0005526 (circ_RUNX2) is significantly highly expressed in OA serum and mainly located in the cytoplasm within the cartilage cell by sponging multiple miRNAs (miR‐498, miR‐924, miR‐361‐3p, and miR‐665). Bioinformatics analysis showed ECM‐receptor interaction pathway ranked the most significant pathway of circ_RUNX2‐miRNAs regulatory network in KEGG database. The ROC curve showed that there may be good diagnostic value of serum circ_RUNX2 in OA.

Conclusion

RUNX2‐derived circ_RUNX2 may be involved in OA development via ECM‐receptor interaction pathways and may be used as potential clinical indicator of OA.

CircASXL1 knockdown represses the progression of colorectal cancer by downregulating GRIK3 expression by sponging miR-1205

BACKGROUND

Colorectal cancer (CRC) is a common aggressive tumor that poses a heavy burden to human health. An increasing number of studies have reported that circular RNA (circRNA) is involved in the progression of CRC. In this study, the special profiles of circASXL1 (circ_0001136) in CRC progression were revealed.

METHODS

The expression of circASXL1, microRNA-1205 (miR-1205), and glutamate ionotropic receptor kainate type subunit 3 (GRIK3) mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein expression was determined by Western blot or immunohistochemistry. Cell colony-forming ability was investigated by colony formation assay. Cell cycle and apoptosis were demonstrated using cell-cycle and cell-apoptosis analysis assays, respectively. Cell migration and invasion were detected by wound-healing and transwell migration and invasion assays, respectively. The binding sites between miR-1205 and circASXL1 or GRIK3 were predicted by circBank or miRDB online database, and identified by dual-luciferase reporter assay. The impact of circASXL1 on tumor formation in vivo was investigated by in vivo tumor formation assay.

RESULTS

CircASXL1 and GRIK3 expression were apparently upregulated, and miR-1205 expression was downregulated in CRC tissues and cells relative to control groups. CircASXL1 knockdown inhibited cell colony-forming ability, migration and invasion, whereas induced cell arrest at G0/G1 phase and cell apoptosis in CRC cells; however, these effects were attenuated by miR-1205 inhibitor. Additionally, circASXL1 acted as a sponge for miR-1205, and miR-1205 was associated with GRIK3. Furthermore, circASXL1 silencing hindered tumor formation by upregulating miR-1205 and downregulating GRIK3 expression.

CONCLUSION

CircASXL1 acted an oncogenic role in CRC malignant progression via inducing GRIK3 through sponging miR-1205. Our findings provide a theoretical basis for studying circASXL1-directed therapy for CRC.

Tumor Suppressive Effects of miR-124 and Its Function in Neuronal Development

MicroRNA-124 (miR-124) is strongly expressed in neurons, and its expression increases as neurons mature. Through DNA methylation in the miR-124 promoter region and adsorption of miR-124 by non-coding RNAs, miR-124 expression is known to be reduced in many cancer cells, especially with high malignancy. Recently, numerous studies have focused on miR-124 due to its promising tumor-suppressive effects; however, the overview of their results is unclear. We surveyed the tumor-suppressive effect of miR-124 in glial cell lineage cancers, which are the most frequently reported cancer types involving miR-124, and in lung, colon, liver, stomach, and breast cancers, which are the top five causes of cancer death. Reportedly, miR-124 not only inhibits proliferation and accelerates apoptosis, but also comprehensively suppresses tumor malignant transformation. Moreover, we found that miR-124 exerts its anti-tumor effects by regulating a wide range of target genes, most notably STAT3 and EZH2. In addition, when compared to the original role of miR-124 in neuronal development, we found that the miR-124 target genes that contribute to neuronal maturation share similarities with genes that cause cancer cell metastasis and epithelial-mesenchymal transition. We believe that the two apparently unrelated fields, cancer and neuronal development, can bring new discoveries to each other through the study of miR-124.

Hsa_circ_0003829 serves as a potential diagnostic predictor for oral squamous cell carcinoma

Objective

Increasing evidence suggests that circular RNAs (circRNAs) play a major role in tumorigenesis and cancer progression. This study aimed to identify aberrant expression of hsa_circ_0003829 in oral squamous cell carcinoma (OSCC) and to explore its clinical significance.

Methods

We conducted a prospective clinical study to examine the expression pattern of hsa_circ_0003829 in 60 paired OSCC and normal clinical samples and in cell lines using real-time quantitative polymerase chain reaction. We also evaluated the diagnostic value of hsa_circ_0003829 in OSCC based on receiver operating characteristic (ROC) curve analysis, and examined the relationships between hsa_circ_0003829 expression and clinicopathological features in patients with OSCC. We further used bioinformatics software CircInteractome (https: //Circinteractome.nia.nih.gov/) to predict circRNA–microRNA interactions.

Results

Hsa_circ_0003829 was significantly downregulated in OSCC compared with adjacent normal tissues. The area under the ROC curve was 0.81. Low expression levels of hsa_circ_0003829 in OSCC tissues were negatively correlated with lymph node metastasis status and TNM stage.

Conclusions

Downregulated expression of has_circ_0003829 suggests that this may be a key circRNA in OSCC, and may serve as a prospective biomarker for the diagnosis of OSCC.