Circular RNA 0001785 regulates the pathogenesis of osteosarcoma as a ceRNA by sponging miR-1200 to upregulate HOXB2

CircFLNA facilitates gastric cancer cell proliferation and glycolysis via regulating SOX5 by sponging miR-1200

BACKGROUND AND STUDY AIMS

Circular RNAs (circRNAs) are important regulators for gastric cancer (GC) progression. Our study aims to investigate the role and mechanism of circFLNA in GC progression.

PATIENTS AND METHODS

The levels of circFLNA, microRNA (miR)-1200 and SRY-box transcription factor 5 (SOX5) were examined using qRT-PCR. Flow cytometry, cell counting kit 8 assay and EdU assay were performed to measure cell proliferation and apoptosis. Cell glycolysis ability was assessed by examining glucose uptake and lactate produce. RNA interaction was determined using RNA pull-down assay and dual-luciferase reporter assay. Mice xenograft models were constructed to evaluate the regulation of circFLNA knockdown on GC tumor growth.

RESULTS

CircFLNA was upregulated in GC tissues. Functional experiments showed that circFLNA knockdown suppressed GC cell proliferation, inhibited glycolysis, and promoted apoptosis in vitro, as well as reduced GC tumor growth in vivo. CircFLNA sponged miR-1200, and miR-1200 targeted SOX5. MiR-1200 mimic reversed the promotion effect of circFLNA overexpression on GC cell growth and glycolysis, and SOX5 upregulation also abolished the inhibiting effect of miR-1200 mimic on GC cell growth and glycolysis.

CONCLUSION

Our data suggest that circFLNA might exert oncogenic role in GC development, which promoted GC proliferation and glycolysis through regulating miR-1200/SOX5 axis.

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Interaction of ncRNAs and the PI3K/AKT/mTOR pathway: Implications for osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, and is characterized by high heterogeneity, high malignancy, easy metastasis, and poor prognosis. Recurrence, metastasis, and multidrug resistance are the main problems that limit the therapeutic effect and prognosis of OS. PI3K/AKT/mTOR signaling pathway is often abnormally activated in OS tissues and cells, which promotes the rapid development, metastasis, and drug sensitivity of OS. Emerging evidence has revealed new insights into tumorigenesis through the interaction between the PI3K/AKT/mTOR pathway and non-coding RNAs (ncRNAs). Therefore, we reviewed the interactions between the PI3K/AKT/mTOR pathway and ncRNAs and their implication in OS. These interactions have the potential to serve as cancer biomarkers and therapeutic targets in clinical applications.

Osteosarcoma in a ceRNET perspective

Osteosarcoma (OS) is the most prevalent and fatal type of bone tumor. It is characterized by great heterogeneity of genomic aberrations, mutated genes, and cell types contribution, making therapy and patients management particularly challenging. A unifying picture of molecular mechanisms underlying the disease could help to transform those challenges into opportunities.This review deeply explores the occurrence in OS of large-scale RNA regulatory networks, denominated "competing endogenous RNA network" (ceRNET), wherein different RNA biotypes, such as long non-coding RNAs, circular RNAs and mRNAs can functionally interact each other by competitively binding to shared microRNAs. Here, we discuss how the unbalancing of any network component can derail the entire circuit, driving OS onset and progression by impacting on cell proliferation, migration, invasion, tumor growth and metastasis, and even chemotherapeutic resistance, as distilled from many studies. Intriguingly, the aberrant expression of the networks components in OS cells can be triggered also by the surroundings, through cytokines and vesicles, with their bioactive cargo of proteins and non-coding RNAs, highlighting the relevance of tumor microenvironment. A comprehensive picture of RNA regulatory networks underlying OS could pave the way for the development of innovative RNA-targeted and RNA-based therapies and new diagnostic tools, also in the perspective of precision oncology.

HOXB5 promotes the progression and metastasis of osteosarcoma cells by activating the JAK2/STAT3 signalling pathway

Objective

To investigate the involvement of the homeobox gene B5 (HOXB5) in the progression and metastasis of osteosarcoma.

Methods

The expression of HOXB5 in human osteosarcoma tissues and its correlation with clinical indicators were investigated using bioinformatics analysis and immunohistochemical labelling. Human osteosarcoma cells (HOS, MG63, U2OS, and Saos-2) and normal human osteoblasts (hFOB1.19) were cultivated. The expression of HOXB5 in these cells was detected using western blotting (WB) and RT‒PCR. Two cell lines exhibiting elevated HOXB5 expression were chosen and divided into three groups: the blank group (mock), control group (control) and transfection group (shHOXB5). The transfection group was infected with lentivirus expressing shRNAs targeting HOXB5. The transfection efficiency was detected by WB. Cell proliferation suppression was measured by CCK-8 and 5-ethynyl-2'-deoxyuridine (EdU) assays; the percentage of apoptotic cells was determined by flow cytometry; and cell migration and invasion were detected via the Transwell chamber test. WB was utilized to determine the protein expression of genes linked to metastasis (MMP2, MMP9), apoptosis (Bax, Bcl-2), and the JAK2/STAT3 pathway (JAK2, p-JAK2, STAT3, p-STAT3).

Results

In osteosarcoma tissues, HOXB5 expression was elevated and strongly correlated with distant metastasis. Silencing HOXB5 reduced the proliferation, migration and invasion of osteosarcoma cells; prevented the progression and metastasis of tumours in tumour-bearing nude mice; and reduced the activation of key proteins in the JAK2/STAT3 signalling pathway.

Conclusion

Through the JAK2/STAT3 signalling pathway, HOXB5 plays a crucial role in the malignant progression of osteosarcoma and is a promising target for osteosarcoma treatment.

Homeobox B2 promotes malignant behavior and contributes to the radioresistance of nasopharyngeal carcinoma by regulating forkhead box protein O1

Background: Nasopharyngeal carcinoma (NPC) is an epithelial tumor of the head and neck with heterogeneous racial and geographical distributions. Homeobox B2 (HOXB2) is a tumor promoter in many cancers. However, the biological role of HOXB2 in NPC has not been elucidated. Methods: Bioinformatics analysis was performed to identify the differentially expressed genes (DEGs) between samples of patients with radiosensitive and radioresistant NPC. qRT-PCR, western blotting and immunohistochemistry were used to detect the expression levels of the corresponding mRNA and proteins. Cell viability was detected by CCK-8 assay and colony-forming capability was evaluated using colony formation assays. Further, migration and invasion abilities were examined using wound-healing and transwell chamber assays, respectively. Cellular apoptosis after irradiation was assessed using flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Results: HOXB2 was identified as a potential regulator of radioresistance in NPC. Our in vitro results indicate that HOXB2 overexpression (HOXB2-OE) promoted malignant behaviors including invasion, migration, proliferation, and inhibited the irradiation-induced apoptosis of NPC cells. Consistent with these results, HOXB2 knockdown (HOXB2-sh) exhibited the opposite trends in these biological activities. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs were enriched in the FOXO signaling pathway. Mechanistically, western blotting showed that HOXB2-OE inhibited forkhead box protein O1 (FOXO1) expression in NPC cells. Thereafter, we transferred the FOXO1-OE plasmid to HOXB2-OE NPC cells and found that overexpression of FOXO1 reversed cell proliferation, migration, invasion, and radioresistance profiles promoted by HOXB2 overexpression. Conclusion: Our findings showed that HOXB2 acts as a tumor promoter in NPC, activating malignant behaviors and radioresistance of tumors via FOXO1 regulation. Moreover, the inactivation of HOXB2 or activation of FOXO1 are potential strategies to inhibit tumor progression and overcome radioresistance in NPC.

CircZCCHC2 decreases pirarubicin sensitivity and promotes triple-negative breast cancer development via the miR-1200/TPR axis

Triple-negative breast cancer (TNBC) has attracted attention due to its poor prognosis and limited treatment options. The mechanisms underlying the association between circular RNAs (circRNAs) and the occurrence and development of TNBC remain unclear. CircZCCHC2 is observed to be upregulated in TNBC cells, tissues, and plasma exosomes. Knockdown of circZCCHC2 inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition of TNBC cells in vitro and in vivo. Pirarubicin (THP) treatment downregulated circZCCHC2, and circZCCHC2 affected the sensitivity to THP. CircZCCHC2/miR-1200/translocated promoter region, the nuclear basket protein (TPR) pathway was cascaded and verified. It is demonstrated that circZCCHC2 plays a crucial role in the malignant progression of TNBC via the miR-1200/TPR axis, thereby activating the RAS-RAF-MEK-ERK pathway. The present results indicate that circZCCHC2 has the potential to serve as a novel prognostic biomarker for TNBC.

Intelligent structure prediction and visualization analysis of non-coding RNA in osteosarcoma research

Background

Osteosarcoma (OS) is the most common bone malignant tumor in children and adolescents. Recent research indicates that non-coding RNAs (ncRNAs) have been associated with OS occurrence and development, with significant progress made in this field. However, there is no intelligent structure prediction and literature visualization analysis in this research field. From the perspective of intelligent knowledge structure construction and bibliometrics, this study will comprehensively review the role of countries, institutions, journals, authors, literature citation relationships and subject keywords in the field of ncRNAs in OS. Based on this analysis, we will systematically analyze the characteristics of the knowledge structure of ncRNAs in OS disease research and identify the current research hotspots and trends.

Methods

The Web of Science Core Collection (WoSCC) database was searched for articles on ncRNAs in OS between 2001 and 2023. This bibliometric analysis was performed using VOSviewers, CiteSpace, and Pajek.

Results

This study involved 15,631 authors from 2,631 institutions across 57 countries/regions, with a total of 3,642 papers published in 553 academic journals. China has the highest number of published papers in this research field. The main research institutions include Nanjing Medical University (n = 129, 3.54%), Shanghai Jiao Tong University (n = 128, 3.51%), Zhengzhou University (n = 110, 3.02%), and China Medical University (n = 109, 2.99%). Oncology Letters (n =139, 3.82%), European Review for Medical Pharmacological Sciences (120, 3.31%), and Molecular Medicine Reports (n = 95, 2.61%) are the most popular journals in this field, with Oncotarget being the most co-cited journal (Co-Citation = 4,268). Wei Wang, Wei Liu, and Zhenfeng Duan published the most papers, with Wang Y being the most co-cited author. "miRNA", "lncRNA" and "circRNA" are the main focuses of ncRNAs in OS studies. Key themes include "migration and invasion", "apoptosis and proliferation", "prognosis", "biomarkers" and "chemoresistance". Since 2020, hotspots and trends in ncRNA research in OS include "tumor microenvironment", "immune" and "exosome".

Conclusion

This study represents the first comprehensive bibliometric analysis of the knowledge structure and development of ncRNAs in OS. These findings highlight current research hotspots and frontier directions, offering valuable insights for future studies on the role of ncRNAs in OS.

Circular RNAs in osteosarcoma: An update of recent studies (Review)

Osteosarcoma (OS) prevailing in children and adolescents mainly occurs at the metaphysis of long bones. As it is associated with a high invasive and metastatic ability, resistance to chemotherapy, and a low 5‑year survival rate, the diagnosis and treatment of OS post a global healthy issue. Over the past decades, RNA biology has shed new light onto the pathogenesis of OS. As a type of non‑coding RNAs, circular RNAs (circRNAs) have been found to play crucial roles in cellular activities. Recently, a large number of circRNAs have been identified in OS and some of them have been validated to be functional in OS. In the present review, abnormally expressed and different types of circRNAs in OS are summarized. Functional studies on circRNAs have revealed that circRNAs can regulate gene expression at different levels, such as gene transcription, precursor mRNA splicing, miRNA sponges and translation into proteins/peptides. Mechanistic analyses on circRNAs show that circRNAs can regulate JAK‑STAT3, NF‑κB, PI3K‑AKT, Wnt/β‑catenin signaling pathways during the occurrence and development of OS. Furthermore, the potential clinical applications of circRNAs are also emphasized. The present review focus on the current knowledge on the functions and mechanisms of circRNAs in the pathogenesis of OS, aiming to provide new insight into the OS diagnosis and treatment of OS.

Cellular and Genetic Background of Osteosarcoma

Osteosarcoma describes a tumor of mesenchymal origin with an annual incidence rate of four to five people per million. Even though chemotherapy treatment has shown success in non-metastatic osteosarcoma, metastatic disease still has a low survival rate of 20%. A targeted therapy approach is limited due to high heterogeneity of tumors, and different underlying mutations. In this review, we will summarize new advances obtained by new technologies, such as next generation sequencing and single-cell sequencing. These new techniques have enabled better assessment of cell populations within osteosarcoma, as well as an understanding of the molecular pathogenesis. We also discuss the presence and properties of osteosarcoma stem cells-the cell population within the tumor that is responsible for metastasis, recurrence, and drug resistance.

Circular RNAs: implications of signaling pathways and bioinformatics in human cancer

Circular RNAs (circRNAs) form a class of endogenous single-stranded RNA transcripts that are widely expressed in eukaryotic cells. These RNAs mediate post-transcriptional control of gene expression and have multiple functions in biological processes, such as transcriptional regulation and splicing. They serve predominantly as microRNA sponges, RNA-binding proteins, and templates for translation. More importantly, circRNAs are involved in cancer progression, and may serve as promising biomarkers for tumor diagnosis and therapy. Although traditional experimental methods are usually time-consuming and laborious, substantial progress has been made in exploring potential circRNA-disease associations by using computational models, summarized signaling pathway data, and other databases. Here, we review the biological characteristics and functions of circRNAs, including their roles in cancer. Specifically, we focus on the signaling pathways associated with carcinogenesis, and the status of circRNA-associated bioinformatics databases. Finally, we explore the potential roles of circRNAs as prognostic biomarkers in cancer.

circRNA, a novel diagnostic biomarker for coronary heart disease

Objective

This study aimed to identify the potential diagnostic biomarkers of coronary heart disease (CHD) from exosome-derived circRNA.

Methods

The microarray data of circRNA derived from the exosomes of patients with CHD and mRNA in acute myocardial infarction was retrieved from exoRBase website and GEO database (GSE61144), respectively, to identify the differentially expressed genes (DEGs). Our findings detected the differentially expressed circRNAs and mRNAs and predicted their correlation with microRNAs using the microRNA target prediction website, thus ascertaining the corresponding circ-microRNA and micro-mRNAs. Then, we performed systematic Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis on the differentially expressed mRNA. Protein-Protein Interactions (PPI) of these DEGs were examined using STRING. The receiver operator characteristic (ROC) curve was used to validate the diagnostic efficacy of circRNA in patients with CHD. Finally, the RNAs identified in this study were verified by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

A total of 85 differentially expressed circRNAs (4 up-regulated and 81 down-regulated) were identified by screening the circRNAs in exosome of CHD patients. Based on the prediction data of circRNA, mRNA, and the corresponding microRNA, a ceRNA network was constructed, including 7 circRNA nodes, 5 microRNA nodes, and 2 mRNA nodes. Finally, validated by qRT-PCR testing, we found circRNA0001785, circRNA0000973, circRNA0001741, and circRNA0003922 to be the promising candidate for the effective prediction of CHD. These potential diagnostic markers can provide insight for further research on the occurrence of CHD or even acute coronary syndrome (ACS).

High expression of homeobox B2 predicts poor survival of colon adenocarcinoma by enhancing tumor proliferation and invasion

OBJECTIVE

Homeobox B2 (HOXB2) is known to be correlated with the development and prognosis of various cancers. However, its role in colon cancer remains unclear.

AIMS

In this study, we explored the prognostic value of HOXB2 in colon adenocarcinoma (COAD).

METHODS

A total of 264 colon adenocarcinoma cases were retrospectively enrolled to evaluate HOXB2 expression and clinical significance. Chi-square test was applied to identify relationship between clinical features and HOXB2 expression. The effect of HOXB2 expression and clinical features on the survival of COAD patients was evaluated using Kaplan-Meier and Cox regression analyses. Cellular assays and mice models were conducted to validate the tumor-related role of HOXB2 in COAD.

RESULTS

Higher expression of HOXB2 in COAD tissues was significantly associated with tumor size, invasion depth, and lymph node metastasis (all P < 0.05). Univariate and multivariate analyses showed that high expression of HOXB2 was significantly correlated with a poor overall survival. In vitro cellular assays combined with knockdown strategies demonstrated that HOXB2 can promote tumor proliferation and invasion of COAD, which was further confirmed by in vivo xenograft experiments.

CONCLUSIONS

HOXB2 may be a valuable biomarker and potential therapeutic target for the treatment of COAD.

Circular RNAs: typical biomarkers for bone-related diseases

Bone is a connective tissue that has important functions in the human body. Cells and the extracellular matrix (ECM) are key components of bone and are closely related to bone-related diseases. However, the outcomes of conventional treatments for bone-related diseases are not promising, and hence it is necessary to elucidate the exact regulatory mechanisms of bone-related diseases and identify novel biomarkers for diagnosis and therapy. Circular RNAs (circRNAs) are single-stranded RNAs that form closed circular structures without a 5' cap or 3' tail and polycyclic adenylate tails. Due to their high stability, circRNAs have the potential to be typical biomarkers. Accumulating evidence suggests that circRNAs are involved in bone-related diseases, including osteoarthritis, osteoporosis, osteosarcoma, multiple myeloma, intervertebral disc degeneration, and rheumatoid arthritis. Herein, we summarize the recent research progress on the characteristics and functions of circRNAs, and highlight the regulatory mechanism of circRNAs in bone-related diseases.

Non-coding RNAs as potential biomarkers in osteosarcoma

Osteosarcoma (OS) is a primary solid malignant tumor that occurs most frequently in the metaphysis of long bones. More likely to happen to children and adolescents. OS has high mortality and disability rate. However, the etiology and pathogenesis of OS have not been fully understood till now. Due to the lack of effective biomarkers, OS cannot be precisely detected in the early stage. With the application of next-generation and high-throughput sequencing, more and more abnormally expressed non-coding RNAs(ncRNAs) have been identified in OS. Growing evidences have suggested the ncRNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), have played an important role in the tumorigenesis and progression of OS. Thus, they can be served as novel biomarkers for diagnosis, treatment and prognosis. This review summarized the application of ncRNA as biomarkers in OS in detail, and discussed the limitation and future improvement of the potential biomarkers.

Relation between the circular and linear form of the Elongator Acetyltransferase Complex Subunit 3 in the progression of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer (BC) that hardly responds to common treatment. Recent studies show that circ-ELP3 (Elongator Acetyltransferase Complex Subunit 3 or hsa-circ-0001785) is involved in the pathogenesis of several malignancies. The present study aimed to evaluate the possible role of this circRNA in the progression of TNBC cells and the possible relation between the circular and linear forms of the ELP3. We evaluated the circ-ELP3 and its host gene expression level in clinical samples and breast cancer cell lines. Using an expression vector, hsa-circ-0001785 was upregulated to investigate its role on cancer cell progression. After a transient transfection, we evaluated possible alterations in the cell cycle progression, cell viability, and cell proliferation. Quantitative real-time polymerase chain reaction analyses verified that circ-ELP3 and its host gene were significantly upregulated in TNBC tissues and breast cancer cells. Overexpression of circ-ELP3 markedly increases the cell viability and proliferation and also the formation of colonies in transfected cells compared to the controls. Briefly, our results showed that Circ-ELP3 and its host gene were significantly upregulated in TNBC. Circ-ELP3 is involved in TNBC progression and may exert its effects by indirectly regulating of ELP3 expression.

Roles and mechanisms of miR-195-5p in human solid cancers

Cancer persists as a worldwide disease that contributes to high morbidity and mortality rates. As a class of non-coding RNA, microRNAs (miRNAs) are one kind of important regulators in cancer and frequently implicated in tumor development and progression. Emerging experiments have suggested that miRNA-195-5p (miR-195-5p) can regulate neoplastic processes in many pathways. For instance, miR-195-5p can not only regulate proliferation, migration and invasion of tumor cells but also promote tumor cell apoptosis. Furthermore, low expression of miR-195-5p could induce drug resistance. Our review focuses on the expression of miR-195-5p in various tumors and elucidates the related mechanisms of which miR-195-5p participates in tumor biology, as well as summarizes the roles of miR-195-5p in tumor progression. We believe that miR-195-5p might have potential utility as a novel diagnostic biomarker and therapeutic target for cancer.

Circ_0085315 promotes cell proliferation, invasion, and migration in colon cancer through miR-1200/MAP3K1 signaling pathway

Colon cancer (CC) is a common malignant tumor of the digestive tract. Circular RNAs (circRNAs) play important roles in the progression of CC. This study aimed to explore the role and mechanism of circRNA_0085315 in CC. In this study, we used qRT-PCR and Western blot assays to analyze the expressions of circRNA, miRNA, and mRNA as well as the expression of the related proteins. Luciferase reporter, RNA pull-down, and qRT-PCR assays were used to prove the relationship among circRNA, miRNA, and mRNA. CCK-8, colony formation, and transwell assays were used to perform the analysis of cell proliferation, migration, and invasion. Our results showed that the higher circRNA_0085315 expression led to the poorer prognosis of CC patients. The function of circRNA_0085315 as a ceRNA in competing with MAP3K1 mRNA to sponge miR-1200. CircRNA_0085315 sponged miR-1200 to promote cell proliferation, migration, and invasion and affected the expression of Ki67, MMP2, E-cadherin, and N-cadherin, but not circRNA_0085315-mut without the binding site of miR-1200. MAP3K1-overexpression or miR-1200 mimics prevented the suppression on the enhanced cell proliferation, migration, and invasion caused by circRNA_0085315-overexpression. circRNA_0085315 increased the phosphorylation levels of JNK, p38, and ERK1/2 by stimulating MAP3K1 up-regulation caused by miR-1200 inhibition. In conclusion, circRNA_0085315 serves as a ceRNA and promotes CC progression through the activation of the MAPK signaling pathway mediated via the miR-1200/MAP3K1 axis, suggesting that circRNA_0085315 may be a promising diagnostic and therapeutic target for CC.

Silencing of circ-CDK14 suppresses osteosarcoma progression through the miR-198/E2F2 axis

BACKGROUND

Osteosarcoma (OS) is the most common primary bone malignancy. Circular RNAs (circRNAs) have been implicated in OS pathogenesis. In the current study, we explored the precise role of circRNA cyclin dependent kinase 14 (circ-CDK14, hsa_circ_0001721) in OS progression.

METHODS

The levels of circ-CDK14, miR-198 and E2F transcription factor 2 (E2F2) were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Cell viability, apoptosis, migration and invasion were determined using the Cell Counting-8 Kit (CCK-8), flow cytometry and transwell assays, respectively. Glucose consumption, lactate production and adenosine triphosphate (ATP) level were gauged using the commercial assay kits. The direct relationship between miR-198 and circ-CDK14 or E2F2 was confirmed by dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation (RIP) assays. Animal studies were used to analyze the role of circ-CDK14 in vivo.

RESULTS

Our data revealed that circ-CDK14 was up-regulated and miR-198 was down-regulated in OS tissues and cell lines. Circ-CDK14 silencing suppressed OS cell viability, migration, invasion, and glycolysis and promoted cell apoptosis in vitro, as well as diminished tumor growth in vivo. Mechanistically, circ-CDK14 directly targeted miR-198. Moreover, miR-198 was a functional mediator of circ-CDK14 in regulating OS cell progression in vitro. E2F2 was a direct target of miR-198, and miR-198 overexpression regulated OS cell progression in vitro by down-regulating E2F2. Furthermore, circ-CDK14 regulated E2F2 expression by functioning as a sponge of miR-198 in OS cells.

CONCLUSION

Our findings demonstrate the inhibitory effect of circ-CDK14 silencing on OS progression by targeting the miR-198/E2F2 axis, establishing a strong rationale for decreasing circ-CDK14 as a novel therapeutic strategy for OS.

Integral Analyses of Competing Endogenous RNA Mechanisms and DNA Methylation Reveal Regulatory Mechanisms in Osteosarcoma

Background: Osteosarcoma (OS) is the most common primary malignant bone tumour in children and adolescents, with rapid growth, frequent metastasis, and a poor prognosis, but its pathogenesis has not been fully elucidated. Exploring the pathogenesis of OS is of great significance for improving diagnoses and finding new therapeutic targets.

Methods: Differentially expressed circRNAs (DECs), miRNAs (DEMs), methylated DNA sites (DMSs), and mRNAs (DEGs) were identified between OS and control cell lines. GSEA of DEGs and functional enrichment analysis of methylated DEGs were carried out to further identify potential biological processes. Online tools were used to predict the miRNA binding sites of DECs and the mRNA binding sites of DEMs, and then construct a circRNA-miRNA-mRNA network. Next, an analysis of the interaction between methylated DEGs was performed with a protein-protein interaction (PPI) network, and hub gene identification and survival analysis were carried out. The expression pattern of circRNA-miRNA-mRNA was validated by real-time PCR.

Results: GSEA and functional enrichment analysis indicated that DEGs and methylated DEGs are involved in important biological processes in cancer. Hsa_circ_0001753/has_miR_760/CD74 network was constructed and validated in cell lines. Low expression levels of CD74 are associated with poor overall survival times and show good diagnostic ability.

Conclusion: Methylated DEGs may be involved in the development of OS, and the hsa_circ_0001753/has_miR_760/CD74 network may serve as a target for the early diagnosis of and targeted therapy for OS.

The Circ_0001367/miR-545-3p/LUZP1 Axis Regulates Cell Proliferation, Migration and Invasion in Glioma Cells

Glioma is the most common primary intracranial malignant tumour in adults. It has a high incidence and poses a serious threat to human health. Circular RNA is a hotspot of cancer research. In this study, we aimed to explore the role of circ_0001367 in gliomagenesis and the underlying mechanism. First, qRT-PCR was conducted, which showed that circ_0001367 level was downregulated in glioma tissues and cells. Next, gain-of-function and loss-of-function assays were performed, which indicated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells. Subsequent bioinformatics analysis, dual-luciferase reporter assays, RNA immunoprecipitation assays and cell function assays demonstrated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells by absorbing miR-545-3p and thereby regulating the expression of leucine zipper protein (LUZP1). Finally, an in vivo experiment was conducted, which demonstrated that circ_0001367 inhibited glioma growth in vivo by modulating miR-545-3p and LUZP1. Taken together, the results of this study demonstrate that the circ_0001367/miR-545-3p/LUZP1 axis may be a novel target for glioma therapy.

Crosstalk between circRNAs and the PI3K/AKT signaling pathway in cancer progression

Circular RNAs (circRNAs), covalently closed noncoding RNAs, are widely expressed in eukaryotes and viruses. They can function by regulating target gene expression, linear RNA transcription and protein generation. The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays key roles in many biological and cellular processes, such as cell proliferation, growth, invasion, migration, and angiogenesis. It also plays a pivotal role in cancer progression. Emerging data suggest that the circRNA/PI3K/AKT axis modulates the expression of cancer-associated genes and thus regulates tumor progression. Aberrant regulation of the expression of circRNAs in the circRNA/PI3K/AKT axis is significantly associated with clinicopathological characteristics and plays an important role in the regulation of biological functions. In this review, we summarized the expression and biological functions of PI3K-AKT-related circRNAs in vitro and in vivo and assessed their associations with clinicopathological characteristics. We also further discussed the important role of circRNAs in the diagnosis, prognostication, and treatment of cancers.

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

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

CircNRIP1 Encapsulated by Bone Marrow Mesenchymal Stem Cell-Derived Extracellular Vesicles Aggravates Osteosarcoma by Modulating the miR-532-3p/AKT3/PI3K/AKT Axis

Emerging evidence indicates that extracellular vesicle (EV)-encapsulated circRNAs have the potential diagnostic and prognostic values for malignancies. However, the role of circNRIP1 in osteosarcoma remains unclear. We herein investigated the therapeutic potential of circNRIP1 delivered by bone marrow mesenchymal stem cell–derived EVs (BMSC-EVs) in osteosarcoma. The expression of circNRIP1 was examined in the clinical tissue samples of osteosarcoma patients, after which the downstream genes of circNRIP1 were bioinformatically predicted. Gain- and loss-of function assays were then performed in osteosarcoma cells with manipulation of circNRIP1 and miR-532-3p expression. EVs isolated from BMSCs were characterized and co-cultured with osteosarcoma cells to examine their effects on cell phenotypes, as reflected by CCK-8 and Transwell assays. Further, a mouse model of tumor xenografts was established for in vivo substantiation. circNRIP1 was upregulated in osteosarcoma tissues and cells. Overexpression of circNRIP1 promoted the proliferative, migratory, and invasive potential of osteosarcoma cells. Co-culture data showed that BMSC-EVs could transfer circNRIP1 into osteosarcoma cells where it competitively bound to miR-532-3p and weakened miR-532-3p’s binding ability to AKT3. By this mechanism, the PI3K/AKT signaling pathway was activated and the malignant characteristics of osteosarcoma cells were stimulated. In vivo experimental results unveiled that circNRIP1-overexpressing BMSC-EVs in nude mice resulted in enhanced tumor growth. In conclusion, the BMSC-EV-enclosed circNRIP1 revealed a new molecular mechanism in the pathogenesis of osteosarcoma, which might provide a novel therapeutic target for osteosarcoma.

Exosomal circular RNA circ_0074673 regulates the proliferation, migration, and angiogenesis of human umbilical vein endothelial cells via the microRNA-1200/MEOX2 axis

Circular RNAs (circRNAs) are implicated in the pathogenesis of gestational diabetes mellitus (GDM). The aim of this study was to investigate the roles and molecular mechanism underlying the effects of circ_0074673 in GDM. Exosomal morphology was visualized by transmission electron microscopy (TEM), while exosomal size and concentration were determined by nanoparticle tracking analysis (NTA). The expression of CD9 and CD63 was measured by western blotting. The levels of circ_0074673, miR-1200 and mesenchyme homeobox 2 (MEOX2) were determined by quantitative real-time polymerase chain reaction (qPCR). Cellular proliferation, migration, and angiogenesis were measured by Cell Counting Kit-8 (CCK-8), transwell, and tube formation assays, respectively. The binding relationship between circ_0074673 or MEOX2 and miR-1200 was evaluated by luciferase reporter assay, RNA-binding protein immunoprecipitation (RIP) assay and RNA-pull-down assay. The results showed that exosomal size and concentration were greater in the umbilical cord blood of patients with GDM than in that of the healthy controls. The expression of circ_0074673 was upregulated in exosomes from GDM and in human umbilical vein endothelial cells (HUVECs) co-cultured with exosomes. High glucose (HG) treatment suppressed cellular proliferation, migration, and angiogenesis. Circ_0074673 knockdown enhanced the proliferation, migration, and angiogenesis of HG treated HUVECs (HG-HUVECs). As circ_0074673 and MEOX2 directly bind to miR-1200, circ_0074673 silencing promoted the biological functions of HG-HUVECs by sponging miR-1200 and further targeting MEOX2. Altogether, the loss of exosomal circ_0074673 facilitated the proliferation, migration, and angiogenesis of HG-HUVECs via the miR-1200/MEOX2 axis, suggesting that circ_0074673 is a potential therapeutic target for GDM.

Research Progress on the Functions and Mechanism of circRNA in Cisplatin Resistance in Tumors

Cisplatin is a common chemotherapeutic drug that has been used to treat of numerous tumors, including testicular, lung, bladder, ovarian, liver and head and neck cancers. Although clinical chemotherapy based on cisplatin has shown a remarkable therapeutic effect, the resistance to cisplatin becomes increasingly obvious as a patient uses it for a prolonged period. It not only affects the prognosis of these tumors, but also causes the recurrence of cancer and decreases the overall survival rate. The development of cisplatin resistance involves several mechanisms, including DNA damage repair, ATP-binding cassette (ABC) transporter, autophagy, cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), and other related signaling pathways. Interestingly, these mechanisms have been found to be influenced by circular RNAs (circRNAs) to regulate tumor proliferation, invasion, chemosensitivity, and other biological behaviors in the tumor microenvironment (TME). In recent years, circRNAs in cisplatin resistance in tumors, especially lung cancer and gastric cancer, have gradually drawn peoples' attention. This review summarizes recent studies on the functions and mechanisms of circRNAs in cisplatin resistance. We emphasize that circRNA can be used as a promising target gene to improve drug resistance and therapeutic efficacy.

Long non‑coding RNA H19 regulates LASP1 expression in osteosarcoma by competitively binding to miR‑29a‑3p

A prevalent type of bone tumor, osteosarcoma (OS) is prone to pulmonary metastasis, which results in a high relapse risk and poor prognosis for patients. The progression of OS is significantly associated with the expression of long non‑coding (lnc)RNA H19. To the best of our knowledge, however, the exact molecular mechanism of this lncRNA has not been fully investigated. The present study verified the effect of H19 on the proliferation and invasion of osteosarcoma cells via in vivo and in vitro experiments, including Cell Counting Kit‑8, western blot, reverse transcription‑quantitative PCR, wound healing and Transwell assays. H19 was found to be overexpressed in OS compared with corresponding normal adjacent tissue. In addition, H19 served as a competing endogenous ncRNA targeting microRNA‑29a‑3p and activating LIM and SH3 domain protein 1 and modulating the OS cell phenotype. The results of the present study may improve understanding of OS pathogenesis.

A panel of miRNAs as prognostic markers for African-American patients with triple negative breast cancer

BACKGROUND

To investigate the global expression profile of miRNAs, their impact on cellular signaling pathways, and their association with poor prognostic parameters in African-American (AA) patients with triple negative breast cancer (TNBC).

METHODS

Twenty-five samples of AA TNBC patients were profiled for global miRNA expression and stratified considering three clinical-pathological parameters: tumor size, lymph node (LN), and recurrence (REC) status. Differential miRNA expression analysis was performed for each parameter, and their discriminatory power was determined by Receiver Operating Characteristic (ROC) curve analysis. KMplotter was assessed to determine the association of the miRNAs with survival, and functional enrichment analysis to determine the main affected pathways and miRNA/mRNA target interactions.

RESULTS

A panel of eight, 23 and 27 miRNAs were associated with tumor size, LN, and REC status, respectively. Combined ROC analysis of two (miR-2117, and miR-378c), seven (let-7f-5p, miR-1255b-5p, miR-1268b, miR-200c-3p, miR-520d, miR-527, and miR-518a-5p), and three (miR-1200, miR-1249-3p, and miR-1271-3p) miRNAs showed a robust discriminatory power based on tumor size (AUC = 0.917), LN (AUC = 0.945) and REC (AUC = 0.981) status, respectively. Enrichment pathway analysis revealed their involvement in proteoglycans and glycan and cancer-associated pathways. Eight miRNAs with deregulated expressions in patients with large tumor size, positive LN metastasis, and recurrence were significantly associated with lower survival rates. Finally, the construction of miRNA/mRNA networks based in experimentally validated mRNA targets, revealed nodes of critical cancer genes, such as AKT1, BCL2, CDKN1A, EZR and PTEN.

CONCLUSIONS

Altogether, our data indicate that miRNA deregulated expression is a relevant biological factor that can be associated with the poor prognosis in TNBC of AA patients, by conferring to their TNBC cells aggressive phenotypes that are reflected in the clinical characteristics evaluated in this study.

Circular RNA_CNST Promotes the Tumorigenesis of Osteosarcoma Cells by Sponging miR-421

Circular RNAs (circRNAs) act crucial roles in the progression of multiple malignancies including osteosarcoma (OS). But, the underlying mechanisms by which hsa_circ_0017311 (circCNST) contributes to the tumorigenesis of OS remain poorly understood. Our present study aimed to explore the role and mechanisms of circCNST in OS tumorigenesis. The differentially expressed circRNAs were identified by the Gene Expression Omnibus database. The association of circCNST with clinicopathological features and prognosis in patients with OS was analyzed by RNA fluorescence in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (PCR) analysis. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation assays, and a xenograft tumor model were conducted to assess the role of circCNST in OS cells in vitro and in vivo. CircCNST-specific binding with miR-421 was confirmed by FISH, luciferase gene report, and RNA immunoprecipitation assays. As a result, we found that the expression levels of circCNST were dramatically increased in OS tissues and cell lines as compared with the adjacent normal tissues, and it was associated with tumor size and poor survival in OS patients. Knockdown of circCNST repressed cell viability, colony formation, and xenograft tumor growth, while restored expression of circCNST reversed these effects. Furthermore, circCNST was colocalized with miR-421 in the cytoplasm and acted as a sponge of miR-421, which attenuated circCNST-induced proliferation-promoting effects in OS cells by targeting SLC25A3. In conclusion, our findings demonstrate that circCNST promotes the tumorigenesis of OS cells by sponging miR-421, and provides a potential biomarker for patients with OS.

Hsa_circ_0010220 regulates miR-198/Syntaxin 6 axis to promote osteosarcoma progression

•

hsa_circ_0010220 expression is increased in osteosarcoma.

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hsa_circ_0010220 knockdown represses cell proliferation, migration and invasion.

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hsa_circ_0010220 regulates Syntaxin 6 via miR-198.

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hsa_circ_0010220 silence decreases xenograft tumor growth.

Background

Circular RNAs (circRNAs) are a class of endogenous RNAs that are involved in osteosarcoma progression. Hsa_circ_0010220 (circ_0010220) is a circRNA generated by gene Rho Guanine Nucleotide Exchange Factor 10 Like (ARHGEF10L) and is upregulated in osteosarcoma, but its functional role in osteosarcoma is limited studied. This study aimed to illustrate the regulatory mechanism underlying circ_0010220 in osteosarcoma.

Methods

51 paired tumor and normal tissues were obtained from osteosarcoma patients. circ_0010220, microRNA (miR)-198 and Syntaxin 6 (STX6) abundances were examined by quantitative reverse transcription polymerase chain reaction and western blot. Cell proliferation, cell cycle, apoptosis, migration and invasion were analyzed via Cell Counting Kits-8 (CCK-8), colony formation, flow cytometry and transwell analyses. Target relationship was verified via dual-luciferase reporter analysis, RNA immunoprecipitation and pull-down. The in vivo function was analyzed using a xenograft model.

Results

Circ_0010220 was elevated in osteosarcoma tissues and cells, and was related to the lower survival rate of osteosarcoma patients. Circ_0010220 knockdown inhibited cell proliferation, migration and invasion, but induced cell cycle arrest and apoptosis in vitro. Besides, circ_0010220 silence curbed the growth of xenograft osteosarcoma tumors in vivo. Mechanistic research revealed that miR-198 is a target of circ_0010220, and directly targets STX6. Moreover, circ_0010220 upregulated the expression of STX6 by sponging miR-198 to regulate cell proliferation, migration, invasion, cell cycle, and apoptosis.

Conclusion

Circ_0010220 contributes to osteosarcoma progression through mediating miR-198/STX6 axis, which might be a novel therapeutic target for osteosarcoma therapy.

Circ_0056285 Regulates Proliferation, Apoptosis and Glycolysis of Osteosarcoma Cells via miR-1244/TRIM44 Axis

Background

Osteosarcoma (OS) is a common malignant bone cancer that occurs in adolescents and children. Circular RNAs (circRNAs) are important regulators of tumorigenesis and development. This study aimed to explore the role and molecular basis of circ_0056285 in OS.

Methods

The levels of circ_0056285, miR-1244 and tripartite motif containing 44 (TRIM44) were determined by quantitative real-time polymerase chain reaction or Western blot assay. Cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8) assay and colony formation assay. Cell apoptosis was assessed by flow cytometry and caspase 3and caspase 9 activity assay kits. Glucose uptake, lactate product and ATP level were examined using commercial kits. Hexokinase II (HK2) and lactate dehydrogenase A (LDHA) levels were measured by Western blot assay. The interaction among circ_0056285, miR-1244 and TRIM44 was confirmed by dual-luciferase reporter assay, RNA immunoprecipitation assay or RNA pull-down assay. Xenograft experiment was conducted to explore tumor growth in vivo. Exosomes were identified by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA) and Western blot. The diagnostic value of exosomal circ_0056285 was evaluated by receiver operating characteristic (ROC) curve.

Results

Circ_0056285 and TRIM44 were up-regulated, and miR-1244 was down-regulated in OS tissues and cells. Circ_0056285 silencing inhibited proliferation and glycolysis and promoted apoptosis in OS cells. Also, circ_0056285 knockdown hindered proliferation and accelerated apoptosis in OS cells by regulating miR-1244/TRIM44 axis. Circ_0056285 depletion impeded tumor growth in vivo. Furthermore, ROC curve showed that circ_0056285 might be a diagnostic biomarker in OS.

Conclusion

Circ_0056285 facilitated OS progression by sponging miR-1244 and increasing TRIM44 expression, providing a promising therapeutic target for OS.

miR‑139‑5p enhances cisplatin sensitivity in non‑small cell lung cancer cells by inhibiting cell proliferation and promoting apoptosis via the targeting of Homeobox protein Hox‑B2

The development of chemotherapeutic dug resistance hinders the clinical treatment of cancer. MicroRNAs (miRNAs/miRs) have been revealed to serve essential roles in the drug resistance of numerous types of cancer. miR‑139‑5p was previously reported to be associated with cisplatin (DDP) sensitivity in human nasopharyngeal carcinoma cells and colorectal cancer cells. However, the effect and underlying mechanism of miR‑139‑5p in DDP sensitivity in non‑small cell lung cancer (NSCLC) cells has not yet been fully elucidated. In the present study, the expression of miR‑139‑5p and Homeobox protein Hox‑B2 (HOXB2) in NSCLC tissues was examined by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting. Subsequently, the effect of miR‑139‑5p on the DDP sensitivity of NSCLC cells in vitro was investigated. Cell proliferation was examined using a Cell Counting Kit‑8 assay. Western blotting was used to evaluate the protein expression of HOXB2, phosphorylated (p)‑PI3K, p‑AKT, caspase‑3 and cleaved‑caspase‑3, and RT‑qPCR was used to evaluate the expression of miR‑139‑5p, and the mRNA expression levels of HOXB2, PI3K, AKT and caspase‑3. The apoptotic rate of the cells was detected using flow cytometry. miR‑139‑5p expression in NSCLC tissues was shown to be significantly lower compared with that in adjacent tissues. Additionally, miR‑139‑5p increased cell apoptosis and inhibited NSCLC cell proliferation induced by DDP in vitro via modulating the PI3K/AKT/caspase‑3 signaling pathway. Furthermore, HOXB2 was identified to be a target of miR‑139‑5p, and miR‑139‑5p was revealed to sensitize NSCLC cells to DDP via the targeting of HOXB2. Taken together, the results of the present study demonstrated that regulating the expression of miR‑139‑5p could provide a novel approach to reverse DDP resistance and increase chemosensitivity in the treatment of NSCLC.

Identification and Analysis of Three Hub Prognostic Genes Related to Osteosarcoma Metastasis

Osteosarcoma (OS) often occurs in children and often undergoes metastasis, resulting in lower survival rates. Information on the complexity and pathogenic mechanism of OS is limited, and thus, the development of treatments involving alternative molecular and genetic targets is hampered. We categorized transcriptome data into metastasis and nonmetastasis groups, and 400 differential RNAs (230 messenger RNAs (mRNAs) and 170 long noncoding RNAs (lncRNAs)) were obtained by the edgeR package. Prognostic genes were identified by performing univariate Cox regression analysis and the Kaplan-Meier (KM) survival analysis. We then examined the correlation between the expression level of prognostic lncRNAs and mRNAs. Furthermore, microRNAs (miRNAs) corresponding to the coexpression of lncRNA-mRNA was predicted, which was used to construct a competitive endogenous RNA (ceRNA) regulatory network. Finally, multivariate Cox proportional risk regression analysis was used to identify hub prognostic genes. Three hub prognostic genes (ABCG8, LOXL4, and PDE1B) were identified as potential prognostic biomarkers and therapeutic targets for OS. Furthermore, transcriptions factors (TFs) (DBP, ESX1, FOS, FOXI1, MEF2C, NFE2, and OTX2) and lncRNAs (RP11-357H14.16, RP11-284N8.3, and RP11-629G13.1) that were able to affect the expression levels of genes before and after transcription were found to regulate the prognostic hub genes. In addition, we identified drugs related to the prognostic hub genes, which may have potential clinical applications. Immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR) confirmed that the expression levels of ABCG8, LOXL4, and PDE1B coincided with the results of bioinformatics analysis. Moreover, the relationship between the hub prognostic gene expression and patient prognosis was also validated. Our study elucidated the roles of three novel prognostic biomarkers in the pathogenesis of OS as well as presenting a potential clinical treatment for OS.

CircRNA hsa_circ_0005909 Promotes Cell Proliferation of Osteosarcoma Cells by Targeting miR-338-3p/HMGA1 Axis

Objective

Osteosarcoma (OS) is the most common malignant bone tumor in the pediatric population. The main goal of this study is to investigate the role of hsa_circ_0005909 and the underlying signaling pathway involved in OS.

Methods

Cell proliferation was measured using a CCK-8 assay kit and clone formation assay. Change of RNA and protein expression was determined using RNA extract and quantitative real time PCR (RT-qPCR) assay and Western blotting, respectively. CircInteractome was used to predict the target of circRNA and starBase v2.0 was used to predict the target of miRNAs. Luciferase assay was used to confirm the predicted results from CircInteractome, starBase v2.0, and MirTarget2.

Results

Expression of circ_0005909 was upregulated in both OS tissues and cell lines. The predicted results from CircInteractome, starBase v2.0, and MirTarget2 demonstrated that circ_0005909 could sponge miR-338-3p and that HGMA1 was the direct target of miR-338-3p. Cell viability and cell clones were inhibited by knockdown of circ_0005909 but increased by dual inhibition of circ_0005909 and miR-338-3p. Phosphorylation of ERK, Akt, and PI3K was inhibited by sh-circ_0005909, while this inhibition was repressed by co-transfection of sh-circ_0005909 and HGMA1.

Conclusion

Expression of circ_0005909 was upregulated in both OS tissues and cell lines which upregulated expression of HGMA1 through sponging miR-338-3p, resulting in the activation of MAPK-ERK and PI3K-Akt signaling pathways to promote the development of OS.

Identification of a novel circRNA, hsa_circ_0065898, that regulates tumor growth in cervical squamous cell carcinoma

Background

Circular RNAs (circRNAs) were reported to play an important role in regulating tumor pathogenesis. The molecular mechanism of circRNAs in cervical squamous cell carcinoma (CSCC) remains poorly understood. We aimed to identify the circRNAs differentially expressed, and to investigate the role of a novel circRNA, hsa_circ_0065898, in regulating proliferation, migration, and invasion in CSCC.

Methods

The online Kaplan-Meier Plotter was used to analyze the relationship between miRNA expression and overall survival. Bioinformatics tools, such as R, Cytoscape, and Perl, were used to analyze the Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, protein-protein interaction (PPI) network, and regulatory network. The expression level of hsa_circ_0065898 in CSCC cell lines was evaluated using quantitative polymerase chain reaction in vitro. The cell counting kit-8 (CCK-8) and transwell assays were used to assess cell proliferation, migration, and invasion.

Results

circRNA expression data (GSE102686) was downloaded from the Gene Expression Omnibus database, and this included data from 5 CSCC patients and 5 normal tissues. 13 differentially expressed circRNAs were identified, which included 9 upregulated circRNAs and 4 downregulated circRNAs. GO enrichment analysis showed that the target genes of miRNAs associated with hsa_circ_0065898 were enriched in ubiquitin-protein transferase activity, ubiquitin-like protein transferase activity, core promoter sequence-specific DNA binding, mRNA 3’-UTR AU-rich region binding, core promoter binding, and so on. KEGG showed that the Hippo and p53 signaling pathways played significant role in the pathway network. Hsa_circ_0065898 was significantly overexpressed in the CSCC cell lines. Hsa_circ_0065898 facilitated cell proliferation, migration, and invasion in CSCC.

Conclusions

This study identified differentially expressed circRNAs and constructed the regulatory network of hsa_circ_0065898 targeting microRNAs and mRNAs. We demonstrated that hsa_circ_0065898 promoted CSCC cell proliferation, migration, and invasion. Hence, hsa_circ_0065898 might be useful as a biomarker for CSCC diagnosis and targeted therapy.

circCAMSAP1 promotes osteosarcoma progression and metastasis by sponging miR-145-5p and regulating FLI1 expression

Osteosarcoma is the most common primary malignant bone tumor in adolescents. While chemotherapy combined with surgery can improve the prognosis of some patients, chemo-resistance is still a huge obstacle in osteosarcoma treatment. Accumulating evidence demonstrates that circular RNAs (circRNAs) are involved in cancer progression and metastasis, but their specific role in osteosarcoma remains mostly undescribed. In this study, we performed circRNA deep sequencing and identified 88 distinct circRNAs from a human osteosarcoma cell lines group (143B, HOS, SJSA, and U2OS) and the human osteoblast hFOB 1.19 (control). We found that circCAMSAP1, also named hsa_circ_0004338, is significantly upregulated in human osteosarcoma tissues and cell lines, and it is positively correlated with osteosarcoma development. Silencing of circCAMSAP1 effectively suppresses osteosarcoma cell growth, apoptosis, migration, and invasion. Furthermore, we validated that circCAMSAP1 functions in osteosarcoma tumorigenesis through a circCAMSAP1/miR-145-5p/friend leukemia virus integration 1 (FLI1) pathway. FLI1 promotes osteosarcoma tumorigenesis and miR-145-5p suppresses FLI translation. circCAMSAP1 directly sequesters miR-145-5p in the cytoplasm and inhibits its activity to suppress osteosarcoma tumorigenesis. Moreover, the regulatory role of circCAMSAP1 upregulation was examined and validated in rats. In summary, our findings provide evidence that circCAMSAP1 act as a "microRNA sponge" and suggest a new therapeutic target of human osteosarcoma.

Circular RNAs in childhood-related diseases and cancers: A review

Research into the diagnosis, treatment and prevention of childhood-related diseases is the key to reducing their morbidity and mortality. Circular RNAs (circRNAs) play critical roles, both in physiology and pathology, and there is ample evidence to show that they play varying roles in tissue development and gene regulation. Studies on circRNAs in different childhood-related diseases have confirmed their great potential for disease prevention and treatment. These breakthroughs highlight the pathological role of circRNAs in cancers, as well as cardiovascular and hereditary childhood illnesses. In this review, we summarize the role of circRNAs in childhood-related diseases and cancer, and provide an update of the possible diagnostic and therapeutic application of circRNAs.

Circular RNA hsa_circ_0008003 facilitates tumorigenesis and development of non-small cell lung carcinoma via modulating miR-488/ZNF281 axis

As one of the most aggressive malignancies, non‐small cell lung carcinoma (NSCLC) has high risks of death. It has been demonstrated that circRNAs accelerate NSCLC progression, but the underlying molecular mechanisms of circRNAs in NSCLC were still obscure. In the first place, the circRNA microarray of NSCLC was investigated in this study, and hsa_circ_0008003 (circ‐0008003) was chosen as the research object. Then, it was unveiled that the expression of circ‐0008003 examined via qRT‐PCR was elevated in tumour tissues relative to the non‐tumour tissues, which was associated with TNM stage and lymphatic metastasis in NSCLC. Additionally, the prognosis of NSCLC patients with high circ‐0008003 level was poor. Besides, circ‐0008003 silencing dampened the invasion and proliferation of NSCLC cells. Next, according to the mechanistic studies, circ‐0008003 functioned as a ceRNA of ZNF281 in NSCLC by acting as the endogenous sponge for miR‐488, which was proved to be a tumour suppressor in NSCLC. Additionally, ZNF281 overexpression and miR‐488 suppression recovered the influences of repressed circ‐0008003 on NSCLC cellular processes. It was validated in this research that circ‐0008003 triggered tumour formation in NSCLC, which was adjusted via miR‐488/ZNF281 axis, casting a novel light on the resultful target for treating NSCLC and predicting the prognosis.

Circular RNA Circ-03955 Promotes Epithelial-Mesenchymal Transition in Osteosarcoma by Regulating miR-3662/Metadherin Pathway

Osteosarcoma is the most common primary malignant tumor, especially in children and adolescents. Circular RNAs (circRNAs) are found to play roles in the progression of osteosarcoma. However, the exact functions of circRNAs in osteosarcoma development still need to be clarified. We obtained differentially expressed circRNAs and miRNAs from a GSE99671 data set (GEO database). The gene co-expression network of ceRNAs and osteosarcoma-related genes was analyzed using the STRING database. qRT-PCR was used to detect the expression of circ-03955 and miR-3662. Transwell assays and flow cytometry were performed to detect phenotypic changes in cell function. A xenograft tumor model was established using BALB/c nude mice. Dual luciferase activity and RNA immunoprecipitation assays were performed to assess the relationship between circ-03955, miR-3662, and metadherin (MTDH). Immunohistochemistry, immunofluorescence, and Western blotting were used to assess protein expression levels. Circ-03955 was significantly upregulated, and miR-3662 was downregulated in osteosarcoma. Circ-03955 silencing inhibited the growth and metastasis of osteosarcoma. Mechanism analysis revealed that circ-03955 could bind to miR-3662, and the latter could target MTDH, leading to its suppressed expression and facilitating epithelial-mesenchymal transition (EMT). All these findings demonstrate that the presence of circ-03955 promotes EMT in osteosarcoma by acting as miR-3662 sponge-mediated MTDH expression.

N6-methyladenine modification in noncoding RNAs and its function in cancer

Non-coding RNAs are the main component of the extensive transcription results of the mammalian genome. They are not transcribed into proteins but play critical roles in regulating multiple biological processes and affecting cancer progression. m6A modification is one of the most abundant internal RNA modification of mammalian cells, and it involves almost all aspects of RNA metabolism. Recent research revealed tight correlations between m6A modification and ncRNAs and indicated the interaction between m6A and ncRNAs act a pivotal part in the development of cancer. The correlation between m6A modification and ncRNAs provides a new perspective for exploring the potential regulatory mechanism of tumor gene expression, and suggest that m6A modification and ncRNAs may be important prognostic markers and therapeutic targets for multiple cancers. In this review, we summarize the potential regulatory mechanisms between m6A methylation and ncRNAs, highlighting how their relationship affects biological functions in cancer.

Emerging Roles and Potential Biological Value of CircRNA in Osteosarcoma

Circular RNAs (circRNAs) are endogenous noncoding RNAs that are widely found in eukaryotic cells. They have been found to play a vital biological role in the development of human diseases. At present, circRNAs have been involved in the pathogenesis, diagnosis, and targeted treatment of multiple tumors. This article reviews the research progress of circRNAs in osteosarcoma (OSA) in recent years. The potential connection between circRNAs and OSA cell proliferation, apoptosis, metastasis, and chemotherapy sensitivity or resistance, as well as clinical values, is described in this review. Their categories and functions are generally summarized to facilitate a better understanding of OSA pathogenesis, and findings suggest novel circRNA-based methods may be used to investigate OSA and provide an outlook for viable biomarkers and therapeutic targets.

An update on the roles of circular RNAs in osteosarcoma

Osteosarcoma is the most common primary bone malignancy and is a neoplasm thought to be derived from the bone‐forming mesenchymal stem cells. Aberrant activation of oncogenes and inactivation of tumour suppressor genes by somatic mutations and epigenetic mechanisms play a pivotal pathogenic role in osteosarcoma. Aside from alterations in these protein‐coding genes, it has now been realized that dysregulation of non‐coding RNAs (ncRNAs), including microRNAs (miRNAs), long non‐coding RNAs (lncRNAs) and the recently discovered circular RNAs (circRNAs), is crucial to the initiation and progression of osteosarcoma. CircRNAs are single‐stranded RNAs that form covalently closed loops and function as an important regulatory element of the genome through multiple machineries. Recently, an increasing number of studies suggested that circRNAs also played critical roles in osteosarcoma. This review summarizes recent development and progression in circRNA transcriptome analysis and their functions in the modulation of osteosarcoma progression.

CircRNA circ-0038718 promotes hepatocellular carcinoma progression through sponging miR-139-3p

Hepatocellular Carcinoma (HCC) is the main histological subtype of liver malignancy with poor prognosis. A growing body of evidence showed that Circular RNAs (circRNAs) are related to HCC tumorigenesis and progression. In this study, we investigated the function and regulation of circ-0038718 in HCC. We found that circ-0038718 was frequently elevated in HCC specimens and cell lines. High expression levels of circ-0038718 were correlated with unfavorable prognosis in HCC patients. Furthermore, we demonstrated that knockdown of circ-0038718 attenuated HCC cell proliferation and metastatic abilities, while overexpression of circ-0038718 resulted the converse effect. Silencing circ-0038717 inhibited HCC xenograft tumor development in vivo. Mechanistically, circ-0038718 acted as the sponge of tumor-suppressive miR-139-3p to regulate HCC progression. Rescue experiments suggested the oncogenic activity of circ-0038718 was partially exerted via modulating miR-139-3p expression. Inhibition of miR-139-3p abrogated the regulatory effect of circ-0038718 in HCC cells. In summary, our results unveiled that circ-0038718 could serve as an crucial regulator of HCC progression and provide a potential therapeutic target for HCC treatment.

Biological significance of expression of circ_0001785 and miR-330-5p in colorectal cancer

BACKGROUND

The pathogenesis of colorectal cancer (CRC) has not been elucidated. Circular RNAs (circRNAs) are abnormally expressed in CRC and other tumors and can regulate the biological processes of cell proliferation, migration, and invasion. However, the specific mechanisms of action have not been fully elucidated. Therefore, exploration of new circRNA molecules and their possible mechanisms of action is of great significance to further reveal the pathogenesis of CRC.

AIM

To investigate the biological significance of expression of circ_0001785 and miR-330-5p in CRC.

METHODS

The expression levels of circ_0001785 and miR-330-5p in CRC tissues and adjacent tissues were detected by qRT-PCR. Pearson method was used to detect the correlation between circ_0001785 and miR-330-5p expression in CRC. According to the average values of circ_0001785 and miR-330-5p expression, patients were divided into 41 cases with high circ_0001785 expression, 39 with low circ_0001785 expression, 45 with high miR-330-5p expression, and 35 with low miR-330-5p expression. The correlation of the expression levels of circ_0001785 and miR-330-5p with the clinicopathological parameters of patients with CRC was observed. Human CRC cells SW480 were cultured in vitro, and si-NC, si-circ_0001785, si-circ_0001785 and anti-miR-NC, and si-circ_0001785 and anti-miR-330-5p were transfected into SW480 cells, respectively. The expression of circ_0001785 and miR-330-5p in transfected cells was detected by qRT-PCR. CCK-8 method was used to detect cell proliferation. Transwell assay was used to detect cell migration and invasion. The dual luciferase reporter assay was used to detect the targeting relationship between circ_0001785 and miR-330-5p. Western blot was used to detect the protein expression of MMP-2 and MMP-9.

RESULTS

The expression level of circ_0001785 in CRC tissues and cell lines was significantly increased (P < 0.05), and the expression level of miR-330-5p was significantly decreased (P < 0.05). circ_0001785 expression was negatively correlated with miR-330-5p expression (r = -0.985, P < 0.0001). The expression levels of circ_0001785 and miR-330-5p were closely related to the degree of differentiation, lymph node metastasis, and TNM stage (P < 0.05). Compared with the si-NC group, the cell viability and the protein levels of MMP-2 and MMP-9 in the si-circ_0001785 group were significantly reduced (P < 0.05), and the number of migrating and invading cells was significantly reduced (P < 0.05). The dual luciferase reporter assay confirmed that circ_0001785 could target and bind to miR-330-5p. Down-regulation of miR-330-5p expression reduced the effect of interference with circ_0001785 expression on the proliferation, migration, and invasion of SW480 cells.

CONCLUSION

The expression of circ_0001785 is up-regulated in CRC, while the expression of miR-330-5p is down-regulated. Interfering with the expression of circ_0001785 inhibits the proliferation, migration, and invasion of CRC cells by up-regulating the expression of miR-330-5p.

A novel identified circular RNA, circ_0000491, aggravates the extracellular matrix of diabetic nephropathy glomerular mesangial cells through suppressing miR‑101b by targeting TGFβRI

Circular RNAs (circRNAs) have crucial roles in various diseases; however, the mechanisms of action underlying circRNAs in the occurrence and development of diabetic nephropathy (DN) remains largely unknown. The present study investigated the differentially expressed circRNAs in the DN mice kidney cortex using circRNA sequencing and elucidated the role of circRNAs in mesangial cells. It was revealed that 40 circRNAs were unconventionally expressed, including 18 upregulated circRNAs and 22 downregulated circRNAs. Furthermore, circ_0000491 levels were significantly augmented in both DN mice and high glucose (HG, 30 mM)-induced mouse mesangial cells (MES13 cells). Knockdown of circ_0000491 significantly suppressed the increase of vimentin, fibronectin and α-smooth muscle actin, as well as collagen type I, III and IV, whilst reversing the decrease of E-cadherin in HG-induced MES13 cells. It was further revealed that circRNA_0000491 sponged miR-101b and that miR-101b directly targets TGFβRI. In addition, the expression levels of miR-101b were negatively associated with the transcriptional level of circRNA_0000491 and miR-101b inhibitors reversed the suppression of extracellular matrix (ECM)-associated protein synthesis mediated by knocking-down circRNA_0000491. In conclusion, the present study investigated the circRNA_0000491/miR-101b/TGFβRI axis in ECM accumulation and fibrosis-associated protein expression levels of mesangial cells, which suggested that circRNA_0000491 may be beneficial for the development of an effective therapeutic target for DN.

Circular RNA circ_0026359 Enhances Cisplatin Resistance in Gastric Cancer via Targeting miR-1200/POLD4 Pathway

Human gastric cancer is one of the most common malignant tumors with a poor prognosis. Cisplatin (CDDP) is a well-known first-line chemotherapeutic drug. Acquired resistance retards the clinical application of CDDP in gastric cancer. In this study, circular RNA circ_0026359 was demonstrated to be overexpressed in gastric cancer tissues/cells compared with normal gastric tissues/cells and was overexpressed in CDDP-resistant gastric cancer tissues/cells compared with CDDP-sensitive gastric cancer tissues/cells. High levels of circ_0026359 were associated with low overall survival (OS) and relapse-free survival (RFS) rates in gastric cancer patients. circ_0026359 was examined to promote CDDP resistance in gastric cancer cells. circ_0026359 directly interacted and negatively regulated miR-1200. POLD4 was a direct target of miR-1200. miR-1200/POLD4 pathway mediated the promoting role of circ_0026359 in CDDP resistance of gastric cancer. circ_0026359 could be used as a potential target for CDDP-resistant gastric cancer therapy.

Circular RNA hsa_circ_0005909 modulates osteosarcoma progression via the miR-936/HMGB1 axis

Background

Osteosarcoma (OS) is the most common bone malignant tumor in children, youth, and adolescents. Circular RNA hsa_circ_0005909 (circ_0005909) is involved in the progression of OS. Nevertheless, there are few reports on the role and mechanism of circ_0005909 in OS.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was executed to examine the expression of circ_0005909, miR-936, and High Mobility Group Box 1 (HMGB1) mRNA in OS tissues and cells. Cell viability, colony formation, migration, and invasion were evaluated by Cell Counting Kit-8 (CCK-8), cell colony formation, or transwell assays. Cell epithelial-mesenchymal transition (EMT) and HMGB1 protein levels were assessed through western blot analysis. The role of circ_0005909 on tumor growth in vivo was verified by xenograft assay. The relationship between circ_0005909 or HMGB1 and miR-936 was confirmed with the dual-luciferase reporter or RNA pull-down assays.

Results

Circ_0005909 level was upregulated in OS tissues and cells. OS patients with high circ_0005909 expression had a lower survival rate. Circ_0005909 inhibition reduced tumor growth in vivo and constrained cell viability, colony formation, migration, invasion, and EMT of OS cells in vitro. Furthermore, circ_0005909 served as a sponge for miR-936 and the repressive impacts of circ_0005909 silencing on malignant behaviors of OS cells were abolished by miR-936 inhibitors. Also, HMGB1 acted as a target for miR-936 and was modulated by circ_0005909 via miR-936. Additionally, HMGB1 overexpression restored the inhibitory influence on the malignant behaviors of OS cells mediated by circ_0005909 inhibition.

Conclusions

Circ_0005909 inhibition impeded the progression of OS via downregulating HMGB1 via sponging miR-936.

LINC00662 promotes cell viability and metastasis in esophageal squamous cell carcinoma by sponging miR-340-5p and upregulating HOXB2

Background

Previous studies have shown that lncRNA LINC00662 plays an important role in pathogenesis of malignancies. The purpose of this study was to elucidate the regulatory mechanism of LINC00662 in esophageal squamous cell carcinoma (ESCC).

Methods

In this study, the regulatory mechanism of LINC00662 was investigated by RT‐qPCR. MTT, transwell and dual luciferase reporter assays.

Results

Upregulation of LINC00662 was found in ESCC and associated with worse clinical outcomes in ESCC patients. More importantly, knockdown of LINC00662 restrained cell proliferation, migration and invasion in ESCC. In addition, LINC00662 acts as a molecular sponge for miR‐340‐5p in ESCC, and miR‐340‐5p directly targets HOXB2. HOXB2 expression can be positively regulated by LINC00662 in ESCC. Furthermore, HOXB2 downregulation or miR‐340‐5p overexpression weakened the carcinogenesis of LINC00662 in ESCC.

Conclusions

LncRNA LINC00662 promotes the progression of ESCC by upregulating HOXB2 by sponging miR‐340‐5p.

Emerging landscape of circular RNAs as biomarkers and pivotal regulators in osteosarcoma

Osteosarcoma represents the most prevailing primary bone tumor and the third most common cancer in children and adolescents worldwide. Among noncoding RNAs, circular RNAs (circRNAs) refer to a unique class in the shape of a covalently closed continuous loop with neither 5' caps nor 3'-polyadenylated tails, which are generated through back-splicing. Recently, with the development of whole-genome and transcriptome sequencing technologies, a growing number of circRNAs have been found aberrantly expressed in multiple diseases, including osteosarcoma. circRNA are capable of various biological functions including miRNA sponge, mediating alternatives, regulating genes at posttranscriptional levels, and interacting with proteins, indicating a pivotal role of circRNA in cancer initiation, progression, chemoresistance, and immune response. Moreover, circRNAs have been thrust into the spotlight as potential biomarkers and therapeutic targets in osteosarcoma. Herein, we briefly summarize the origin and biogenesis of circRNA with current knowledge of circRNA in tumorigenesis of osteosarcoma, aiming to elucidate the specific role and clinical implication of circRNAs in osteosarcoma.