Circular RNA hsa_circ_0001982 Promotes Breast Cancer Cell Carcinogenesis Through Decreasing miR-143

Hsa_circ_0046263 Drives the Carcinogenesis and Metastasis of Non-Small Cell Lung Cancer Through the Promotion of NOVA2 by Absorbing Mir-940 as a Molecular Sponge

Background

Circular RNAs (circRNAs) have increasingly been investigated in different cancers due to their regulatory roles. In this study, hsa_circ_0046263 will be detailedly researched in non-small cell lung cancer (NSCLC).

Methods

The analyses of hsa_circ_0046263, microRNA-940 (miR-940), and neuro-oncological ventral antigen 2 (NOVA2) levels were administrated by quantitative real-time polymerase chain reaction (qRT-PCR). The proliferation detection was conducted using Cell Counting Kit-8 (CCK-8) and colony formation assays. Cell cycle and apoptosis were evaluated by flow cytometry. Transwell assay for migration and invasion was used to determine cell metastatic capacity. Overall protein levels were examined adopting Western blot. Target binding analysis was completed via dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. The effect of hsa_circ_0046263 on NSCLC in vivo was studied by xenograft model in mice.

Results

Hsa_circ_0046263 was overtly upregulated in NSCLC with important prognostic value. In vitro experiments indicated that hsa_circ_0046263 knockdown caused inhibitory effects on NSCLC cell proliferation, cell cycle, and metastasis but stimulative effect on apoptosis. Molecular mechanism analysis demonstrated that hsa_circ_0046263 served as a miR-940 sponge to act in the development of NSCLC. Moreover, miR-940 targeted NOVA2 and NOVA2 was regulated by hsa_circ_0046263/miR-940 axis. NOVA2 overexpression also neutralized the miR-940-mediated progression inhibition of NSCLC cells. In vivo assays suggested that hsa_circ_0046263 enhanced NSCLC tumorigenesis by targeting miR-940/NOVA2 axis.

Conclusion

Hsa_circ_0046263 was identified as a cancer-promoting factor in NSCLC via sponging miR-940 and upregulating NOVA2, which presented a clear mechanism of NSCLC occurrence and progression.

Plasma and local expressions of CircRNA CDR1as are linked with disease severity in patients with non-traumatic osteonecrosis of femoral head

Objective

To investigate the correlation of plasma and local expressions of Circ CDR1as with disease severity in patients with non-traumatic osteonecrosis of femoral head (ONFH).

Methods

Ninety-nine non-traumatic ONFH patients receiving surgery and 99 healthy individuals were enrolled in our study. Plasma and local Circ CDR1as were detected using real-time quantitative PCR (RT-qPCR). Radiographic progression was determined using Association Research Circulation Osseous (ARCO) classification system. Harris hip score (HHS) and visual analogue scale (VAS) were used to assess the clinical severity. Receiver operating characteristic (ROC) curve was carried out to evaluate the diagnostic value of plasma Circ CDR1as with regard to the radiographic severity.

Results

Plasma Circ CDR1as expressions were significantly higher in non-traumatic ONFH patients compared with healthy controls. In non-traumatic ONFH patients, there were no significant differences of CircCDR1as expressions between patients with alcohol-induced ONFH and steroid-induced ONFH. CircCDR1as in local necrotic tissue were significantly higher than adjacent non-affected tissue. Plasma and local Circ CDR1as expressions in patients with ARCO phase 4 were markedly upregulated compared with ARCO phase 3; plasma and local Circ CDR1as expressions in patients with ARCO phase 3 were markedly upregulated compared with ARCO phase 1/2. Plasma and local CircCDR1as expressions were positively associated with ARCO classification. In addition, plasma and local Circ CDR1as expressions were positively correlated with VAS and HHS scores. ROC curve analysis indicated that plasma Circ CDR1as may act as a decent marker for radiographic progression in non-traumatic ONFH patients.

Conclusions

Both plasma and local expressions of CircRNA CDR1as are linked with disease severity in patients with non-traumatic ONFH.

Circ_0008039 supports breast cancer cell proliferation, migration, invasion, and glycolysis by regulating the miR-140-3p/SKA2 axis

Circular RNAs (circRNAs) have been shown to modulate gene expression and participate in the development of multiple malignancies. The purpose of this study was to investigate the role of circ_0008039 in breast cancer (BC). The expression of circ_0008039, miR-140-3p, and spindle and kinetochore-associated protein 2 (SKA2) was detected by qRT-PCR. Cell viability, colony formation, migration, and invasion were evaluated using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, colony formation assay, and transwell assay, respectively. Glucose consumption and lactate production were measured using commercial kits. Protein levels of hexokinase II (HK2) and SKA2 were determined by western blot. The interaction between miR-140-3p and circ_0008039 or SKA2 was verified by dual-luciferase reporter assay. Finally, a mouse xenograft model was established to investigate the roles of circ_0008039 in BC in vivo. We found that circ_0008039 and SKA2 were upregulated in BC tissues and cells, while miR-140-3p was downregulated. Knockdown of circ_0008039 suppressed BC cell proliferation, migration, invasion, and glycolysis. Moreover, miR-140-3p could bind to circ_0008039 and its inhibition reversed the inhibitory effect of circ_0008039 interference on proliferation, migration, invasion, and glycolysis in BC cells. SKA2 was verified as a direct target of miR-140-3p and its overexpression partially inhibited the suppressive effect of miR-140-3p restoration in BC cells. Additionally, circ_0008039 positively regulated SKA2 expression by sponging miR-140-3p. Consistently, silencing circ_0008039 restrained tumor growth via increasing miR-140-3p and decreasing SKA2. In conclusion, circ_0008039 downregulation suppressed BC cell proliferation, migration, invasion, and glycolysis partially through regulating the miR-140-3p/SKA2 axis, providing an important theoretical basis for treatment of BC.

The decreased expression of hsa_circ_0043278 and its relationship with clinicopathological features of breast cancer

Background

Breast cancer is one of the most significant causes of death in women around the world. Circular RNAs (circRNAs), which are a novel class of conserved RNA molecules, are involved in the occurrence and development of various diseases, especially malignancies; however, researchers rarely report their roles in human breast cancer.

Methods

In the present study, the differentially expressed levels of circRNAs in human breast cancer tissues and paired noncancerous tissues were screened by circRNA microarray. Hsa_circ_0043278 was downregulated 43-fold in breast cancer and was selected for further analysis. The expression of hsa_circ_0043278 was verified in breast cancer specimens and paired noncancerous tissues by quantitative reverse transcription polymerized chain reaction (qRT-PCR) technique. The relationship between the expression of hsa_circ_0043278 and the clinicopathological features was analyzed.

Results

Among the 520 differentially expressed circRNAs, 292 significantly upregulated circRNAs and 228 downregulated circRNAs in the breast cancer tissues compared with the paired noncancerous tissues. The area under the receiver operating characteristic (ROC) curve of hsa_circ_0043278 was 0.690. The results of the bioinformatics prediction showed five target miRNAs that might be sponged by hsa_circ_0043278. The expression of hsa_circ_0043278 was associated with lymph node metastasis and histological type of the patient. Patients with lymph node metastasis have tumors with significantly downregulated expression of hsa_circ_0043278 (P=0.0201).

Conclusions

Our results suggest that hsa_circ_0043278 is downregulated and may play a key role in human breast cancer.

The circular RNAs differential expression profiles in the metastasis of salivary adenoid cystic carcinoma cells

In order to reveal circular RNAs (circRNAs) differential expression profiles and investigate the function and mechanism of circRNAs in the metastasis of salivary adenoid cystic carcinoma (SACC), microarray was used to detect differentially expressed circRNAs in SACC-83 and SACC-lung metastasis (LM) cell lines. Up-regulated circRNAs were analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to further predict their function. Expression of candidate circRNA and microRNA (miRNA) was determined using quantitative real-time polymerase chain reaction (qRT-PCR). Constructed circRNA-miRNA-mRNA co-expression network was based on TargetScan, miRanda databases. Wound healing and transwell assays were completed to examine the effects of hsa_circRNA_001982 and miR-181a-5p on cell migration and invasion. qRT-PCR confirmed hsa_circRNA_092556, hsa_circRNA_101379, and hsa_circRNA_001982 up-regulation in SACC-LM. miR-181a-5p was down-regulated in SACC-LM and correlated with up-regulated hsa_circRNA_001982. Wound healing and transwell assays indicated that silencing hsa_circRNA_001982 inhibited the migration and invasion of the SACC-LM cells. Furthermore, over-expression of hsa_circRNA_001982 promoted the migration and invasion of SACC-83 cells. Interestingly, up-regulation or down-regulation of miR-181a-5p led to the opposite result in wound healing and transwell assays. Overall, differential expression circRNA profiles in SACC-83 and SACC-LM cells may reveal potential targets and a novel mechanism of circRNAs in the metastasis of SACC. Moreover, the interaction of hsa_circRNA_001982/miR-181a-5p is closely related to the metastasis of SACC cells.

CircSEC31A Promotes the Malignant Progression of Non-Small Cell Lung Cancer Through Regulating SEC31A Expression via Sponging miR-376a

Background

Circular RNAs (circRNAs) have recently been shown as important regulators in the pathogenesis of non-small cell lung cancer (NSCLC). The purpose of this work was to explore the precise parts played by circRNA SEC31 homolog A (circSEC31A, hsa_circ_0001421) in NSCLC malignant progression.

Methods

The expression levels of circSEC31A, miR-376a and SEC31 homolog A (SEC31A) were gauged by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. Subcellular fractionation assay was used to determine the subcellular localization of circSEC31A, and RNase R assay was performed to assess the stability of circSEC31A. Cell migration and invasion were detected by transwell assay, and cell apoptosis was evaluated using flow cytometry. Measurement of glucose consumption, lactate production and adenosine triphosphate (ATP) level were done using corresponding assay kits. The targeted interactions among circSEC31A, miR-376a and SEC31A were confirmed by the dual-luciferase reporter and RNA pull-down assays. Animal studies were performed to observe the role of circSEC31A in tumor growth in vivo.

Results

Our data indicated that circSEC31A and SEC31A were upregulated in NSCLC tissues and cells. CircSEC31A knockdown suppressed NSCLC cell migration, invasion, glycolysis and promoted apoptosis in vitro, as well as hindered tumor growth in vivo. Mechanistically, circSEC31A directly interacted with miR-376a, and circSEC31A depletion regulated NSCLC cell malignant progression by miR-376a. Moreover, SEC31A was a functional target of miR-376a, and it mediated the regulatory impact of miR-376a overexpression on NSCLC cell progression. Furthermore, circSEC31A controlled SEC31A expression through acting as a miR-376a sponge.

Conclusion

Our findings first identified that the knockdown of circSEC31A suppressed NSCLC malignant progression at least partly through modulating SEC31A expression by acting as a miR-376a sponge, providing a novel molecular target of NSCLC therapy.

Circ_0072995 Promotes Cell Carcinogenesis via Up-Regulating miR-149-5p-Mediated SHMT2 in Breast Cancer

Background

Circ_0072995 is a novel identified circRNA and has been identified to involve in the metastasis of breast cancer. However, the detailed function and mechanism of circ_0072995 in the biological property of breast cancer cell remain vague.

Materials and Methods

The expression of circ_0072995, microRNA (miR)-149-5p and serine hydroxymethyltransferase 2 (SHMT2) mRNA was detected using quantitative real-time polymerase chain reaction. Western blot was used to detect the protein levels of SHMT2, hexokinase-2 (HK-2), lactate dehydrogenase a chain (LDHA), and glucose transporter 1 (GLUT1). Cell proliferation, apoptosis, migration, and invasion were analyzed using cell counting kit-8 assay, flow cytometry, caspase-3 activity analysis, cell adhesion assay and transwell assay, respectively. Glucose metabolism was calculated by measuring glucose uptake, lactate production, and adenosine triphosphate (ATP) levels. The interaction between miR-149-5p and circ_0072995 or SHMT2 was confirmed by dual-luciferase reporter assay. In vivo tumorigenesis was performed using the murine xenograft model.

Results

Circ_0072995 and SHMT2 were up-regulated in breast cancer tissues and cell lines, and knockdown of circ_0072995 or SHMT2 suppressed cell malignant properties and anaerobic glycolysis; importantly, SHMT2 overexpression attenuated the anticancer action of circ_0072995 knockdown in breast cancer. Besides, we also found circ_0072995 directly targeted miR-149-5p, thereby regulating its downstream gene SHMT2 by competitively binding to miR-149-5p. Additionally, xenograft analysis showed circ_0072995 silencing suppressed tumor growth via regulating SHMT2 and miR-149-5p in vivo.

Conclusion

This study demonstrated that circ_0072995 promoted cell malignant phenotypes and anaerobic glycolysis in breast cancer via up-regulating SHMT2 through sponging miR-149-5p, indicating a promising molecular target for breast cancer treatment.

Circular RNAs: Emerging Role in Cancer Diagnostics and Therapeutics

Circular RNAs (circRNAs) are rapidly coming to the fore as major regulators of gene expression and cellular functions. They elicit their influence via a plethora of diverse molecular mechanisms. It is not surprising that aberrant circRNA expression is common in cancers and they have been implicated in multiple aspects of cancer pathophysiology such as apoptosis, invasion, migration, and proliferation. We summarize the emerging role of circRNAs as biomarkers and therapeutic targets in cancer.

Circular RNA circABCC4 acts as a ceRNA of miR-154-5p to improve cell viability, migration and invasion of breast cancer cells in vitro

Breast cancer is one of the dominant cancers of women-related death universal. This inquiry aims to disclose the probable role of circABCC4 in breast cancer. The level of circABCC4 was discovered through qRT-PCR. The reactions of circABCC4 and miR-154-5p on the cell viability, apoptosis, migration as well as invasion were, respectively, inspected by CCK-8, flow cytometry, and transwell assays. The association betwixt circABCC4 and miR-154-5p was investigated. The accumulation of NF-κB and Wnt/β-catenin pathway proteins was discovered through Western blot. The expression of circABCC4 was far great in tumor tissues than in normal tissues. Knockdown of circABCC4 could subdue cell viability, migration, invasion, and enhance apoptosis in breast cancer cell lines. CircABCC4 negatively regulated the manifestation of miR-154-5p and shared binding sites with the latter. Suppression of miR-154-5p expression partially conversed the repressive effect of circABCC4 knockdown on breast cancer cell viability, migration, invasion, and NF-κB and Wnt/β-catenin pathways. CircABCC4 knockdown repressed breast cancer cells viability, migration, and invasion by up-regulating miR-154-5p via inhibiting NF-κB and Wnt/β-catenin signal pathways.

Circular RNA circ_C16orf62 Suppresses Cell Growth in Gastric Cancer by miR-421/Tubulin beta-2A Chain (TUBB2A) Axis

Background

Gastric cancer (GC) is the third leading cause of cancer-associated mortality in the world. Expression of circular RNA circ_C16orf62 is reported to be low in GC. The role and mechanism of circ_C16orf62 remain unclear.

Material/Methods

Expression levels of circ_C16orf62 and tubulin beta-2A chain (TUBB2A) in GC tissues and cells, and microRNA-421 (miR-421) level in GC cells were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The predominant cytoplasmic localization of circ_C16orf62 was identified by subcellular fractionation. The protein level of TUBB2A was detected by western blot assay. Cell proliferative ability, migration, and invasion were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation, and several transwell assaysy. The binding relationship between miR-421 and circ_C16orf62 or TUBB2A was predicted by starBase3.0 or Targetscan, and then verified by the dual-luciferase reporter assay. The biological role ofcirc_C16orf62 was examined by xenograft tumor model in vivo.

Results

Circ_C16orf62 andTUBB2A were downregulated in GC tissues and cells. Circ_C16orf62 was predominantly located in the cytoplasm of GC cells, and repressed proliferation, migration, and invasion of GC cells. Mechanistically, circ_C16orf62 worked as the miR-421 sponge to upregulate TUBB2A in GC, thereby hindering GC growth. Circ_C16orf62 repressed GC tumor growth in vivo.

Conclusions

These findings demonstrate that circ_C16orf62 impeded proliferation, migration, and invasion in vitro and retarded tumor growth in vivo by the miR-421/TUBB2A axis in GC, providing a potential therapeutic strategy for patients with GC.

Identification of circular RNAs in the ovarian follicles of Meishan and Duroc sows during the follicular phase

Circular RNAs (circRNAs) are a newly discovered class of endogenous non-coding RNAs that play an important role in growth and development by regulating gene expression and participating in a variety of biological processes. However, the role of circRNAs in porcine follicles remains unclear. Therefore, this study examined middle-sized ovarian follicles obtained from Meishan and Duroc sows at day 4 of the follicular phase. High-throughput RNA sequencing (RNA-seq) was utilized to construct circRNAs, and differential expression was identified. The findings were validated using reverse transcription PCR (RT-PCR) and DNA sequencing, GO and KEGG analyses were performed, and potential miRNA targets were identified. The RNA-seq identified a total of 15,866 circRNAs, with 244 differentially expressed in the Meishan relative to the Duroc (111 up-regulated and 133 down-regulated). The RT-PCR finding confirmed the RNA-seq results, and quantitative real-time PCR (qPCR) analysis examining a subset of the circRNAs showed that they are resistant to RNase R digestion. Bioinformatics analysis (GO and KEGG) showed that the host genes associated with the differentially expressed circRNAs are involved in reproduction and follicular development signaling pathways. Furthermore, many of the circRNAs were found to interact with miRNAs that are associated with follicular development. This study presents a new perspective for studying circRNAs and provides a valuable resource for further examination into the potential roles of circRNAs in porcine follicular development.

The circRNA circ_0000291 acts as a sponge of microRNA 326 to regulate E26 transformation-specific sequence-1 expression and promote breast cancer progression

Accumulating studies authenticate that circular RNAs (circRNAs) are involved in the progression of cancers. However, their role in breast cancer (BC) remains largely unknown. In this study, real-time polymerase chain reaction was employed to detect the circ_0000291 and miR-326 expressions in BC tissues and cells. The correlation between the expression level of circ_0000291 and clinicopathological parameters of BC patients was analyzed. Western blot was used to detect the expression of E26 transformation-specific sequence-1 (ETS1), E-cadherin, N-cadherin and Vimentin in BC cells. Cell proliferation was measured using the cell counting kit-8 assay and the bromodeoxyuridine assay. Cell migration and invasion were detected by Transwell assay. The interactions between circ_0000291 and miR-326, miR-326 and ETS1 were verified using bioinformatics prediction, the dual-luciferase reporter gene assay or/and RNA binding protein immunoprecipitation assay. We demonstrated that circ_0000291 was significantly upregulated in BC, and its high expression was positively correlated with T stage and local lymph node metastasis. Functional assays validated that circ_0000291 promoted BC cell proliferation, migration and invasion. The mechanism studies indicated that circ_0000291 could decoy miR-326 and in turn upregulate the expression of ETS1. In conclusion, circ_0000291 is the novel oncogenic circRNA and promotes BC progression via modulating the miR-326/ETS1 axis.

Circular RNA has_circ_0000034 accelerates retinoblastoma advancement through the miR-361-3p/ADAM19 axis

Retinoblastoma (RB) is an intraocular malignancy that mainly occurs in infants and young children under 5 years of age. Circular RNA hsa_circ_0000034 (circ_0000034) was reported to be upregulated in RB tissues. Nevertheless, the function and mechanism of circ_0000034 in RB are unclear. Expression of circ_0000034, microRNA-361-3p (miR-361-3p), and a disintegrin and metalloproteinase 19 (ADAM19) was examined via quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, migration, invasion, and apoptosis were determined though Cell Counting Kit-8 (CCK-8), transwell, or flow cytometry assays. Caspase-3 activity was detected using a caspase-3 activity assay kit. Some protein levels were examined using Western blot analysis. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, or RNA pull-down assay were performed to verify the relationship between circ_0000034 or ADAM19 and miR-361-3p. The function of circ_0000034 in vivo was confirmed via animal experiment. We verified that circ_0000034 expression was elevated in RB tissues and cells. Circ_0000034 silencing reduced RB growth in vivo, repressed viability, migration, invasion, and EMT, and induced apoptosis of RB cells in vitro. Circ_0000034 acted as a sponge for miR-361-3p, which targeted ADAM19 in RB cells. Furthermore, the inhibition of miR-361-3p restored circ_0000034 knockdown-mediated impacts on viability, migration, invasion, apoptosis, and EMT of RB cells. Moreover, ADAM19 overexpression abolished the influence of miR-361-3p mimic on viability, migration, invasion, apoptosis, and EMT of RB cells. Circ_0000034 expedited RB progression through upregulating ADAM19 via sponging miR-361-3p, which indicated that circ_0000034 might a target for RB therapy.

circRNA RNF111 regulates the growth, migration and invasion of gastric cancer cells by binding to miR‑27b‑3p

hsa_circ_0001982 [circRNA ring finger protein 111 (RNF111)] has been found to promote cancer growth; however, its role in gastric cancer (GC) remains unclear. The present study examined the effects of circR-RNF111 on the growth, migration and invasion of GC cells and aimed to elucidate the underlying molecular mechanisms. The expression levels of circR-RNF111 and miR-27b-3p in GC tissues and GC cell lines were detected by reverse transcription-quantitative PCR (RT-qPCR). StarBase v2.0 and dual-luciferase assay were used to predict and analyze the association between circR-RNF111 and miR-27b-3p. The effects of circR-RNF111 and miR-27b-3p on cell growth, apoptosis, migration and invasion were detected by cell counting kit-8 (CCK-8) assay, colony formation assay, flow cytometry, wound-healing assay and Transwell assay, respectively. In addition, western blot analysis was performed to determine the expression levels of genes related to cell apoptosis and epithelial-mesenchymal transition (EMT). The results revealed that circR-RNF111 and miR-27b-3p were closely related to the clinicopathological characteristics of GC, and that circR-RNF111 and miR-27b-3p negatively correlated and were abnormally expressed in GC. circR-RNF111 acted as a sponge of miR-27b-3p. The silencing of circR-RNF111 significantly inhibited GC cell viability, colony formation, migration and invasion, and exerted a pro-apoptotic effect. miR-27b-3p inhibitor promoted the proliferation, migration and invasion of GC cells, and inhibited cell apoptosis. In addition, circR-RNF111 silencing significantly decreased the expression levels of Bcl2, Vimentin and N-cadherin, and increased those of cleaved caspase-3 and E-cadherin. Furthermore, miR-27b-3p inhibition reversed the regulatory effects of circR-RNF111 silencing on the GC cells. On the whole, the findings of the present study demonstrate that circR-RNF111 is involved in the regulation of growth, migration and invasion of GC cells by binding to miR-27b-3p.

Circ_DCAF6 potentiates cell stemness and growth in breast cancer through GLI1-Hedgehog pathway

Circular RNAs (circRNAs) are extensively revealed as a malignant activator or suppressor in multiple pathological processes including cancer cell stemness and growth. However, the association of circ_DCAF6 with breast cancer (BC) cell growth and stemness has not been well depicted. In this research, qRT-PCR clarified the high level of circ_DCAF6 in BC cells. In functional aspects, BC cells presented suppressed proliferation and stemness in the absence of circ_DCAF6. The potential correlation of circ_DCAF6 with Hedgehog (Hh) pathway was unveiled utilizing its specific inhibitor or agonist in qRT-PCR and functional assays. Circ_DCAF6 positively mediated the expression of GLI1 and its facilitating impacts on BC cell proliferation and stemness required the participation of GLI1-dependent Hh signaling pathway. In depth, circ_DCAF6 post-transcriptionally upregulated GLI1 expression through sequestering miR-616-3p. Rescue experiments verified that the suppressive influence of circ_DCAF6 depletion or miR-616-3p upregulation on BC progression was reversed by GLI1 upregulation. In summary, a probable contribution of circ_DCAF6 to BC cell growth and stemness was elaborated. Circ_DCAF6 assisted in Hh signal pathway activation via the up-regulation of GLI1 by sponging miR-616-3p, generating new thoughts on future direction of antagonizing BC tumorigenesis and stem-like property.

Depletion of exosomal circLDLR in follicle fluid derepresses miR-1294 function and inhibits estradiol production via CYP19A1 in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder in reproductive women and is characterized by polycystic ovaries, hyperandrogenism and chronic anovulation. Abnormal folliculogenesis is considered as a common characteristic of PCOS. Our aim is to identify the altered circRNA expression profile in exosomes isolated from follicular fluid (FF) of PCOS patients to investigate the molecular function of exosomal circRNA, as a vital mediator in follicular microenvironment, in the aetiology and pathobiology of PCOS. In this study, the circRNA expression profile of FF exosomes were compared between PCOS and control patients by RNA sequencing (N=5 vs 5). Sixteen circRNAs showed significantly different expression. GO and KEGG pathway analyses indicated that their parental genes were enriched in PCOS-related pathways, including ovarian steroidogenesis, aldosterone synthesis and secretion, and Jak-STAT signaling. Among sixteen differentially expressed circRNAs, hsa_circ_0006877 (circLDLR) was processed from its parental LDLR (low density lipoprotein receptor) transcript, which participated in ovarian steroidogenesis. Its depletion in PCOS FF exosomes was further verified in an additional cohort (N=25 vs 25) by qRT-PCR. And a circLDLR-miR-1294-CYP19A1 competing endogenous RNA (ceRNA) network was predicted by cytoscape software, and confirmed by luciferase assay and correlative expression in the cumulus cells of PCOS patients. Mechanistically, the intercellular transfer of functional circLDLR assay and its withdrawal experiments in KGN cells showed that depleting circLDLR in exosomes increased miR-1294 expression and inhibited CYP19A1 expression in recipient cells, as well as reduced their estrogen (E2) secretion. Our findings revealed a ceRNA network of circLDLR and provided new information on abnormal follicle development in PCOS.

A Novel Circular RNA hsa_circRPPH1_015 Exerts an Oncogenic Role in Breast Cancer by Impairing miRNA-326-Mediated ELK1 Inhibition

Background: Breast cancer (BC) represents a heterogeneous disease with distinct subtypes and high tumor metastatic potentials. Recent researchers identify the implication of circular RNAs (circRNAs) in the initiation of BC. Herein, we uncover a novel circRNA hsa_circRPPH1_015 as a tumor promoter in BC.

Methods: A total of 86 paired cancerous and non-cancerous tissues were surgically resected and collected from BC patients. Cell proliferation, colony formation, and cell invasion were examined by Edu staining, clone formation assays, propidium iodide (PI)-labeled flow cytometry, and Transwell invasion assays. PCNA, Ki67, MMP-2, MMP-9, Cyclin D1, and CDK4 expression was assayed using Western blot analysis. RNA pull-down, dual-luciferase reporter gene assay, and RNA binding protein immunoprecipitation (RIP) assay were performed to investigate the relationships among hsa_circRPPH1_015, microRNA-326 (miR-326), and ELK1. The tumor growth of human BC MCF-7 cells in vivo was evaluated in nude mice by subcutaneous xenografts of MCF-7 cells.

Results: hsa_circRPPH1_015 expression was upregulated in BC tissues. Knockdown of hsa_circRPPH1_015 restrained the aggressive behavior of MCF-7. hsa_circRPPH1_015 could bind to miRNA-326 that negatively regulates ELK1. Elevation of miRNA-326 expression resulted in inhibition of cell proliferation, colony formation, and cell invasion of MCF-7. Disturbance of miRNA-326 or overexpression of ELK1 restored the proliferation and aggressiveness in hsa_circRPPH1_015-depleted MCF-7 cells. Tumor growth of MCF-7 cells in vivo was reduced in nude mice lack of endogenous hsa_circRPPH1_015 expression.

Conclusion: Overall, the present study demonstrates that hsa_circRPPH1_015 was an oncogene and unfavorable prognostic factor in BC, providing an exquisite therapeutic target for BC.

Circular RNA hsa_circ_0078607 suppresses ovarian cancer progression by regulating miR-518a-5p/Fas signaling pathway

BACKGROUND

Increasing researches have demonstrated the critical functions of circular RNAs (circRNAs) in the progression of malignant tumors, including ovarian cancer. In this study, we aim to investigate abnormally expression of hsa_circ_0078607 and the role of hsa_circ_0078607 during ovarian cancer pathogenesis.

METHODS

RT-PCR were used to detect the expression of circ_0078607 in ovarian cancer tissues. To determine the functional roles of circ_0078607 in ovarian cancer, cell proliferation and cell invasion assays were performed. Bioinformatics and luciferase reporter analysis were used to predict the target of circ_0078607.

RESULTS

In the present study, we first found that circ_0078607 was downregulated in ovarian cancer. Forced circ_0078607 expression significantly suppressed proliferation and promoted apoptosis of ovarian cancer cells. Mechanically, bioinformatics and luciferase reporter analysis identified miR-518a-5p as a direct target of circ_0078607, while Fas as a direct target of miR-518a-5p. MiR-518a-5p negatively regulated Fas in ovarian cancer cells, while overexpression of circ_0078607 could increase the expression of Fas inhibited by miR-518a-5p. Furthermore, overexpression of circ_0078607 could inhibit the proliferation and invasion of ovarian cancer cells caused by miR-518a-5p mimic.

CONCLUSION

The results of the present study revealed that circ_0078607 suppressed ovarian cancer progression by sponging oncogenic miR-518a-5p to induce Fas expression, which may provide new therapeutic approach for ovarian cancer.

Circ-RNF111 contributes to paclitaxel resistance in breast cancer by elevating E2F3 expression via miR-140-5p

Background

Circular RNAs (circRNAs) have been demonstrated to act as key regulators in the chemoresistance of human cancers, including breast cancer (BC). Here, we aimed to explore the role of circ‐RNF111 in paclitaxel (PTX) resistance of BC.

Methods

Quantitative real‐time polymerase chain reaction (qRT‐PCR) was employed to determine the expression of circ‐RNF111, microRNA‐140‐5p (miR‐140‐5p) and E2F transcription factor 3 (E2F3) mRNA. The half maximal inhibitory concentration (IC₅₀) of PTX, cell viability, colony formation and cell invasion were assessed by cell counting kit‐8 (CCK‐8) assay, colony formation assay and transwell assay, respectively. Glucose consumption and lactate production were determined by specific kits. A murine xenograft model was established to investigate the role of circ‐RNF111 in PTX resistance of BC in vivo. Dual‐luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the relationship between miR‐140‐5p and circ‐RNF111 or E2F3. Western blot assay was conducted to examine the protein level of E2F3.

Results

Circ‐RNF111 was upregulated in PTX‐resistant BC tissues and cells. Circ‐RNF111 knockdown restrained IC₅₀ of PTX, cell viability, colony numbers, cell invasion and glycolysis in PTX‐resistant BC cells in vitro and enhanced PTX sensitivity in vivo. MiR‐140‐5p was a target of circ‐RNF111 and miR‐140‐5p expression was negatively correlated with circ‐RNF111 expression in BC tissues. The effect of circ‐RNF111 knockdown on PTX resistance was rescued by miR‐140‐5p deletion. Additionally, miR‐140‐5p could interact with E2F3 and negatively regulate E2F3 expression. Moreover, miR‐140‐5p suppressed IC₅₀ of PTX, cell viability, colony numbers, cell invasion and glycolysis by targeting E2F3.

Conclusions

Circ‐RNF111 improved PTX resistance of BC by upregulating E2F3 via sponging miR‐140‐5p.

Circular RNA Gprc5a Promotes HCC Progression by Activating YAP1/TEAD1 Signalling Pathway by Sponging miR-1283

BACKGROUND

Circular RNA (circRNA) plays a critical role in tumorigenesis and tumor progression. Many studies indicate that circRNA Gprc5a is significantly upregulated and functions as an oncogene in a variety of cancers. However, the molecular mechanism of circGprc5a in liver cancer remains unclear.

METHODS

qRT-PCR was used to measure the expression levels of circGprc5a, miR-1283, YAP1 and TEAD1 mRNA in hepatocellular carcinoma (HCC) tissues or cells. YAP1 and TEAD1 protein levels were detected by Western blot. CCK-8 assay, cell colony formation, BrdU incorporation and Annexin V-FITC/PI assays were performed to analyze the effects of circGprc5a and miR-1283 on cell proliferation and apoptosis. The relationship between circGprc5a, miR-1283, YAP1 and TEAD1 was analyzed using bioinformatic analysis and luciferase. The tumor changes in mice were detected by in vivo experiments.

RESULTS

CircGprc5a was highly expressed in liver cancer, and closely related poor survival of patients with liver cancer. Knockout of circGprc5a inhibited proliferation of HCC and induced apoptosis. CircGprc5a activated the YAP1/TEAD1 signaling pathway by acting as a sponge for miR-1283. Furthermore, overexpression of miR-1283 abolished the promotion of circGprc5a on HCC cells. Therefore, miR-1283 expression correlated negatively with circGprc5a expression yet positively with the expression of YAP1/TEAD1 in liver cancer.

CONCLUSION

CircGprc5a promoted the development of HCC by inhibiting the expression of miR-1283 and activating the YAP1/TEAD1 signaling pathway.

Knockdown of circRAD18 Mitigates Breast Cancer Progression through the Regulation of miR-613/HK2 Axis

Background

Breast cancer (BC) remains the most prevalent malignancy and the leading cause of cancer death. Circular RNAs (circRNAs) have been discovered to serve as crucial regulators in BC. In the current work, we aimed to study the impact of circRAD18 (hsa_circ_0002453) on BC progression and mechanism governing it.

Materials and Methods

The expression levels of circRAD18, miR-613 and hexokinase 2 (HK2) mRNA were determined by quantitative real-time polymerase chain reaction (qRT-PCR). CircRAD18 identification was performed using RNase R digestion and actinomycin D assay. Cell viability, colony formation, apoptosis, migration, invasion and glycolysis were measured by Cell Counting Kit-8 assay, colony formation assay, flow cytometry, transwell analysis and extracellular acidification rate detection assay, respectively. Western blot was used to assess the levels of E-Cadherin, Vimentin, N-Cadherin and HK2 protein. The targeted interplay between miR-613 and circRAD18 or HK2 was detected by dual-luciferase reporter assay. Xenograft model assay was performed to observe the role of circRAD18 in vivo.

Results

CircRAD18 was highly expressed in BC tissues and cells. CircRAD18 depletion hindered BC cell malignant behaviors, as evidenced by the inhibition in cell viability, colony formation, migration, invasion, epithelial to mesenchymal transition and glycolysis, as well as the promotion in cell apoptosis. CircRAD18 directly interacted with miR-613, and miR-613 mediated the repressive effect of circRAD18 knockdown on BC cell malignant behaviors. Moreover, HK2 was a direct target of miR-613, and circRAD18 positively regulated HK2 expression via sponging miR-613. Additionally, circRAD18 knockdown repressed tumor growth in vivo by miR-613.

Conclusion

Our current work suggested that circRAD18 silencing suppressed BC cell malignant behaviors in vitro and tumor growth in vivo at least partly via the regulation of the miR-613/HK2 axis, highlighting that circRAD18 might be a promising therapeutic target for BC treatment.

circHMCU Promotes Proliferation and Metastasis of Breast Cancer by Sponging the let-7 Family

Circular RNA (circRNA), as a kind of novel identified non-coding RNA, has become the focus of attention for its vital physiological and pathological roles. However, the function and mechanism of circRNAs in the regulation of cancer progression are largely unknown. In the present study we found a circRNA termed circHMCU whose expression was associated with poor prognosis. It was upregulated in cell lines with high metastatic potential compared with its parental cell line and in breast cancer tissues compared with normal tissues. In vitro results proved that circHMCU could significantly promote proliferation, migration, and invasion abilities of breast cancer cells via affecting the G₁ phase cell cycle checkpoint and the epithelial-mesenchymal transition (EMT) pathway. Further in vivo studies showed that overexpression of circHMCU contributed to rapid proliferation and lung metastasis of breast cancer. For determination of the mechanisms, bioinformatics analysis revealed two complementary sequences within circHMCU for let-7 microRNAs, which was validated by a luciferase reporter assay. Finally, let-7 microRNAs could rescue the functions of circHMCU in breast cancer via suppressing the expression of MCY, HMGA2, and CCND1. Taken together, our findings demonstrated that circHMCU exerted oncogenic functions in breast cancer and could be a used as a novel biomarker in the diagnosis and prognosis of breast cancer.

Berberine attenuates Aβ42-induced neuronal damage through regulating circHDAC9/miR-142-5p axis in human neuronal cells

BACKGROUND

Berberine plays a neuroprotective role in neurodegenerative diseases, including Alzheimer's disease (AD). Circular RNAs (circRNAs) function as crucial players in AD pathogenesis. In the current work, we aimed to investigate whether circRNA histone deacetylase 9 (circHDAC9) was involved in the regulation of berberine in AD.

METHODS

Cell viability and apoptosis were determined by the Cell Counting Kit-8 (CCK-8) assay and flow cytometry, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to assess caspase-3 activity and the production of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α). The levels of circHDAC9 and miR-142-5p were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Subcellular fractionation assays were performed to evaluate the localization of circHDAC9. The direct interaction between circHDAC9 and miR-142-5p was confirmed by dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays.

RESULTS

Our data indicated that circHDAC9 was indeed a circular transcript and mainly localized in the cytoplasm. 42-residue β-amyloid (Aβ42) triggered a significant down-regulation in circHDAC9 and a striking up-regulation in miR-142-5p in human neuronal (HN) cells. Berberine relieved Aβ42-induced HN cell neurotoxicity. Moreover, berberine resulted in increased circHDAC9 expression and decreased miR-142-5p level in Aβ42-treated HN cells. Berberine alleviated Aβ42-induced neuronal damage in HN cells by up-regulating circHDAC9. Furthermore, circHDAC9 acted as a molecular sponge of miR-142-5p. CircHDAC9 overexpression alleviated Aβ42-induced HN cell neurotoxicity via miR-142-5p.

CONCLUSION

Our current study suggested that berberine protected HN cell from Aβ42-induced neuronal damage at least partly through regulating the circHDAC9/miR-142-5p axis, highlighting novel evidence for the neuroprotective effect of berberine in AD.

Hsa_circ_0061140 promotes endometrial carcinoma progression via regulating miR-149-5p/STAT3

Circular RNAs (circRNAs) are reported to participate in many diseases including tumorigenesis, which can modulate gene expression post-transcriptionally. Up to now, the detailed function of circRNAs in endometrial carcinoma (EC) progression are to be well established. hsa_circ_0061140 has been revealed to act as crucial regulators in several cancers. This current study was carried out to explore the function of hsa_circ_0061140 in EC development. Here, hsa_circ_0061140 expression was modulated using functional assays and we found loss of hsa_circ_0061140 significantly restrained EC cells progression. Moreover, we revealed hsa_circ_0061140 could act as a molecular sponge for miR-149-5p. STAT3 was predicted as a downstream target gene of miR-149-5p. As well known, miR-149-5p is reported to be involved in tumor growth and metastasis. Then, dual luciferase reporter experiment and RIP assay were carried out to evidence the direct binding association between hsa_circ_0061140 and miR-149-5p. miR-149-5p was able to negatively modulate STAT3 expression. Additionally, we proved hsa_circ_0061140 exhibited its oncogenic role due to the modulation of miR-149-5p and STAT3 axis. Taken these together, we suggested that hsa_circ_0061140 might act as an effective therapy to treat EC through functioning as a molecular sponge of miR-149-5p.

Non-coding RNAs: Key regulators of aerobic glycolysis in breast cancer

Although extensive research progress has been made in breast cancer in recent years, yet the morbidity and mortality rates of breast cancer are rising, making it the major disease that endangers women's health. Energy metabolism reprogramming is featured by a state termed "aerobic glycolysis" or the Warburg effect that glycolysis is preferred even under aerobic conditions in neoplastic diseases. Widely acknowledged as an emerging hallmark in cancers, this metabolic switch shows a sophisticated role in the pathogenesis of breast cancer. The regulating effect of non-coding RNAs (ncRNAs) composed of microRNAs, long non-coding RNAs and circular RNAs is closely related to the glycolysis in breast cancer. Therefore, understand the mechanisms of ncRNAs of aerobic glycolysis in breast cancer may provide new strategy for the disease.

A New World of Biomarkers and Therapeutics for Female Reproductive System and Breast Cancers: Circular RNAs

As one of the most recently (re)discovered types of non-coding RNAs (ncRNA), circular RNAs (circRNAs) differentiate from other ncRNAs by a specific biogenesis, high stability, and distinct functions. The biogenesis of circRNAs can be categorized into three mechanisms that permit the back-splicing reaction: exon-skipping, pairing of neighboring introns, and dimerization of RNA-binding proteins. Regarding their stability, circRNAs have no free ends, specific to linear RNA molecules, prompting a longer half-life and resistance to exonuclease-mediated activity by RNase R, bypassing the common RNA turnover process. Regarding their functions, circular transcripts can be categorized into four broad roles: miRNA sponging, protein binding, regulation of transcription, and coding for proteins and peptides. Female reproductive system (including mainly ovarian, corpus, and cervix uteri cancers) and breast cancers are the primary causes of death in women worldwide, accounting for over 1,212,772 deaths in 2018. We consider that a better understanding of the molecular pathophysiology through the study of coding and non-coding RNA regulators could improve the diagnosis and therapeutics of these cancers. Developments in the field of circRNA in regard to breast or gynecological cancers are recent, with most circRNA-related discoveries having been made in the last 2 years. Therefore, in this review we summarize the newly detected roles of circRNAs in female reproductive system (cervical cancer, ovarian cancer, and endometrial cancer) and breast cancers. We argue that circRNAs can become essential elements of the diagnostic and therapeutic tools for female reproductive system cancers in the future.

Circular RNA hsa_circ_0068033 Acts as a Diagnostic Biomarker and Suppresses the Progression of Breast Cancer Through Sponging miR-659

Purpose

Recently, dysregulated circular RNAs (circRNAs) have been associated with the progression of numerous malignant tumors. However, the mechanism through which circRNAs participate in breast cancer (BC) remains unclear. This study was designed to illustrate the role of hsa_circ_0068033 in BC.

Methods

We detected the expression levels of hsa_circ_0068033 in BC tissues using quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). A series of functional experiments were conducted to assess the function of hsa_circ_0068033 in BC development and the underlying mechanisms.

Results

The results suggested that the expression of hsa_circ_0068033 was downregulated in BC tissues, and its expression was markedly correlated with tumor size (P=0.021), and the Tumor, Node, and Metastasis stage (P=0.023). Receiver operating characteristic analysis showed that hsa_circ_0068033 testing yielded an area under the curve value of 0.8480 in discriminating BC from non-tumor controls. Functionally, in-vitro experiments demonstrated that overexpression of hsa_circ_0068033 could inhibit the growths, clone formation, invasion and migration of MCF-7 and MDA-MB-231 cells while activating the intrinsic apoptotic pathway to induce apoptosis. The xenograft experiment revealed that exogenous hsa_circ_0068033 is able to evidently reduce the tumorigenic ability of MDA-MB-231 cells in nude mice. Rescue assays further proved that hsa_circ_0068033 exerts biological functions by sponging miR-659.

Conclusion

Collectively, this study revealed for the first time that hsa_circ_0068033 acts as a tumor suppressor gene in BC, and the hsa_circ_0068033/miR-659 axis participates in the progression of BC.

CircRNA_103762 promotes multidrug resistance in NSCLC by targeting DNA damage inducible transcript 3 (CHOP)

BACKGROUND

CircRNAs have been found to play crucial roles in multiple tumor including non-small cell lung cancer (NSCLC). Here, we researched the correlation between circRNA_103762 and chemotherapy resistance.

METHODS

RT-PCR assay was performed to detect circRNA_103762 and DNA damage inducible transcript 3 (CHOP) expression. CCK8 assay was performed to examine cell proliferation and IC₅₀ of different drug. Migration and invasion assay was used to detect cell migration and invasion.

RESULTS

In our study, circRNA_103762 expression was upregulated in NSCLC tissues and cell. Knockdown of circRNA_103762 can inhibited cell proliferation, migration and invasion in NSCLC. In addition, downregulation of circRNA_103762 promoted CHOP expression and inhibited multidrug resistance (MDR) in NSCLC.

CONCLUSION

Together, we demonstrated that circRNA_103762 is upregulated in NSCLC and functions as an oncogene in NSCLC, and circRNA_103762 enhanced MDR by inhibited CHOP expression in NSCLC cells. These results will help us understand the MDR of NSCLC, providing better effective therapy strategies for patients.

Insights into the regulatory role of circRNA in angiogenesis and clinical implications

Angiogenesis is the physiological process of new blood vessel formation from existing capillary vessels or posterior capillary veins. Its dysfunction could result in a number of diseases, such as cardiovascular diseases and cancer, contributing to death and disability worldwide. Circular RNAs (circRNAs) are a class of novel identified RNA molecules with a special covalent loop structure without a 5' cap and 3' tail, which can lead to novel back-splicing or skipping events from precursor mRNAs. Accumulating evidence suggests that circRNA play critical roles in diseases; in particular, they are abundantly and abnormally expressed in angiogenesis-related diseases. In this review, we describe the role of circRNA under pathological conditions, discuss the association between circRNA and angiogenesis, classify the regulatory mechanisms and suggest that circRNA can be used as potential therapeutic targets for angiogenesis-related diseases under clinical evaluation.

Integrating random walk with restart and k-Nearest Neighbor to identify novel circRNA-disease association

CircRNA is a special type of non-coding RNA, which is closely related to the occurrence and development of many complex human diseases. However, it is time-consuming and expensive to determine the circRNA-disease associations through experimental methods. Therefore, based on the existing databases, we propose a method named RWRKNN, which integrates the random walk with restart (RWR) and k-nearest neighbors (KNN) to predict the associations between circRNAs and diseases. Specifically, we apply RWR algorithm on weighting features with global network topology information, and employ KNN to classify based on features. Finally, the prediction scores of each circRNA-disease pair are obtained. As demonstrated by leave-one-out, 5-fold cross-validation and 10-fold cross-validation, RWRKNN achieves AUC values of 0.9297, 0.9333 and 0.9261, respectively. And case studies show that the circRNA-disease associations predicted by RWRKNN can be successfully demonstrated. In conclusion, RWRKNN is a useful method for predicting circRNA-disease associations.

Exosome-transmitted circular RNA hsa_circ_0051443 suppresses hepatocellular carcinoma progression

Extracellular communication in the tumor microenvironment is critical. Results of qRT-PCR show that circ-0051443 is significantly lower in the plasma exosomes and tissues from patients with hepatocellular carcinoma (HCC) than healthy controls. Compared with the producer cells, circ-0051443 is mainly packaged into exosomes. A receiver operating characteristic curve (ROC) shows that the patients with HCC can be distinguished from the controls by exosomal circ-0051443. The role of exosomal circ-0051443 in HCC was determined by animal and cell analyses. Circ-0051443 is transmitted from normal cells to HCC cells via exosomes and suppresses the malignant biological behaviors by promoting cell apoptosis and arresting the cell cycle. Exosomal circ-0051443 decreases the weight and volume of the xenograft tumors in nude mice via BAK1 upregulation in these tumors. BAK1 expression is mediated by exosomal circ-0051443 through competitive bound to miR-331-3p. Therefore, exosomal circ-0051443 can serve as a predictor and potential therapeutic target for HCC.

Circular RNA; a new biomarker for breast cancer: A systematic review

Circular RNAs (circRNAs) were recently discovered as a looped subset of competing endogenous RNAs, with an ability to regulate gene expression by microRNA sponging. There are several studies on their potential roles in cancer development, such as colorectal cancer and basal cell carcinoma. However, there is still a significant gap in the knowledge about circRNA functions in breast cancer (BC) progression. The current study systematically reviewed circRNA biogenesis and their potential roles as a novel biomarker in BC on published studies of the MEDLINE®/PubMed, Cochrane®, and Scopus® databases. The obtained results showed a general dysregulation of circRNAs expression in BC cells with a cell-type and stage-specific manner. The potential connection between circRNAs and BC cell proliferation, apoptosis, metastasis, and chemotherapy sensitivity and resistance were discussed.

Circ_0001667 promotes breast cancer cell proliferation and survival via Hippo signal pathway by regulating TAZ

Background

Breast cancer is a most common type of cancer in women. Circular RNAs (circRNAs) are involved in cancer development and progression, but their roles and regulatory mechanisms are unclear in breast cancer. Our previous study indicated that has_circ_0001667 (circ_0001667) was up-regulated in breast cancer from the array and might play an oncogenic role, however, the roles of circ_0001667 were not known. This study was aimed to investigate the role and the underlying molecular mechanism of circ_0001667 in breast cancer.

Results

The real-time PCR result showed that circ_0001667 was overexpressed in breast cancer tissues or cell lines compared to the adjacent normal tissues or normal cells. There was a negative relationship between circ_0001667 levels and the life time of breast cancer patients. Meanwhile, the inhibition of circ_0001667 suppressed the proliferation and metastasis of human breast cancer cells. Further bioinformatical analysis indicated that circ_0001667 sponged miR-125a-5p to regulate TAZ expression by Targetscan and miRanda. Dual luciferase reporter assay and western blotting experiments revealed that circ_0001667 negatively regulated miR-125a-5p expression leading to promoting TAZ expression through Hippo signal pathway in breast cancer cells.

Conclusions

This study uncovered that circ_0001667 was a potential breast cancer prognostic marker, as well as a potential therapeutic target to inhibit breast cancer metastasis by circ_0001667/miR-125a-5p/TAZ axis.

Circular RNA circSLC26A4 Accelerates Cervical Cancer Progression via miR-1287-5p/HOXA7 Axis

Circular RNAs (circRNAs) are group of noncoding RNAs derived from back-splicing events. Accumulating evidence certifies the critical roles of circRNAs in human tumorigenesis. However, the role and biogenesis of circRNAs in cervical cancer are still unclear. Here, a novel identified circRNA, circSLC26A4, was found to be upregulated in cervical cancer tissue and cells. Clinically, the high expression of circSLC26A4 was related to the poor survival of cervical cancer patients. Functionally, cellular experiments indicated that circSLC26A4 knockdown repressed the proliferation, invasion, and tumor growth in vitro and in vivo. Furthermore, circSLC26A4 acted as the sponge of miR-1287-5p; moreover, miR-1287-5p targeted the 3′ UTR of HOXA7 mRNA. Mechanistically, RNA binding protein (RBP) quaking (QKI) was identified to interact with the QKI response elements (QREs) in SLC26A4 gene introns, thereby promoting circSLC26A4 biogenesis. In conclusion, these findings demonstrate that circSLC26A4 facilitates cervical cancer progression through the QKI/circSLC26A4/miR-1287-5p/HOXA7 axis, which might bring novel therapeutic strategies for cervical cancer.

Circ-TFCP2L1 Promotes the Proliferation and Migration of Triple Negative Breast Cancer through Sponging miR-7 by Inhibiting PAK1

CircRNAs are essential factors that have been verified to regulate various forms of carcinogenesis. However, the role of circRNAs in triple negative breast cancer (TNBC) tumourigenesis is not well clarified. In this study, we explored the circRNA expression profiles and possible modulation mechanism of circRNAs on triple negative breast cancer tumourigenesis. We used three pairs of triple negative breast cancer tissues and adjacent noncancerous tissues to perform a human circRNA microarray for screening of circRNA expression patterns in TNBC. The results showed that circ-TFCP2L1 was significantly up-regulated in TNBC tissues and cells, tending to have a shorter disease-free survival of TNBC patients. In vitro loss-of-function experiments showed that knockdown of circ-TFCP2L1 significantly suppressed the proliferation and migration of TNBC cells. Moreover, the results showed that the proliferation and migration capabilities and PAK1 expression in TNBC cells treated with si-circ-TFCP2L1 + miR-7 mimics were significantly suppressed compared with the normal group. Therefore, circ-TFCP2L1 was identified as a sponge of miR-7 functionally targeting PAK1 and further promoting the proliferation and migration of TNBC cells. Taken together, the results from our study reveal a novel regulatory mechanism and offer novel insight into the role of circ-TFCP2L1 in progression of triple negative breast cancer.

Circular RNAs Regulate Cancer Onset and Progression via Wnt/β-Catenin Signaling Pathway

Cancer remains to be a major challenge for public health providers, and is the second leading cause of death worldwide. Therefore, it is imperative to explore the mechanisms underlying cancer initiation and development, and design novel diagnostics and therapeutics. Circular RNAs (circRNAs), which exhibit a covalently closed loop structure, are involved in a variety of diseases, including cancer. The aberrant expression of circRNAs contributes to the initiation and development of various cancers by disrupting the interplay of specific signaling pathways, including the Wnt/β-catenin pathway, which controls a plethora of cellular processes that drive cancer development. The interactions between circRNAs (specifically expressed in different cancer tissues) and Wnt/β-catenin signaling pathway presents potential diagnostic biomarkers and novel therapeutic targets. In this review, we have summarized research discoveries on the functions of Wnt/β-catenin pathway-related circRNAs in the modulation of oncogenesis and progression of different types of cancer. We anticipate that our findings will contribute to the improvement or development of circRNAs-based strategies for cancer treatment.

Circular RNA circC3P1 restrains kidney cancer cell activity by regulating miR-21/PTEN axis and inactivating PI3K/AKT and NF- kB pathways

Kidney cancer (KC) seriously impacts public health. We detected the function and mechanism of circular RNA C3P1 (circC3P1) in KC cells. CCK-8, flow cytometry, migration, and invasion assay were respectively used to investigate the efficacies of circC3P1 and microRNA (miR)-21 on cell viability, apoptosis, migration, and invasion. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN), circC3P1, and miR-21 expression were changed by cell transfection and detected by quantitative reverse-transcription polymerase chain reaction. Moreover, the apoptosis/pathways-related proteins and proteins were detected by western blot analysis. Besides, the relation between PTEN and miR-21 was detected by luciferase assay. circC3P1 and PTEN were downregulated while miR-21 was upregulated in KC tissues. circC3P1 declined cell viability, migration, and invasion and caused apoptosis. Furthermore, circC3P1 negatively regulated miR-21; miR-21 mimic could reverse the efficacies of circC3P1. Besides, circC3P1 restrained the PI3K/AKT and NF-κB pathways by downregulating miR-21. Finally, PTEN was authenticated as a target of miR-21. circC3P1 restrained KC cell growth, migration, and invasion by regulating miR-21/PTEN axis and inactivating PI3K/AKT and NF-κB signaling pathways.

Circular RNAs: epigenetic regulators in cancerous and noncancerous skin diseases

The most frequent kind of malignancy in the universe is skin cancer, which has been categorized into non-melanoma and melanoma skin cancer. There are no complete information of the skin carcinogenesis process. A variety of external and internal agents contribute to the non-melanoma and melanoma skin cancer pathogenesis. These factors are epigenetic changes, X-rays, genetic, arsenic compounds, UV rays, and additional chemical products. It was found that there could be a relationship between the appearing novel and more suitable therapies for participants in this class of diseases and detection of basic molecular paths. A covalently closed loop structure bond connecting the 5' and 3' ends characterizes a new group of extensively expressed endogenous regulatory RNAs, which are called circular RNAs (circRNAs). Mammals commonly express circRNAs. They are of high importance in tumorigenesis. Multiple lines evidence indicated that a variety of circular RNAs are associated with initiation and development of skin-related diseases such as skin cancers. Given that different circular RNAs (hsa_circ_0025039, hsa_circRNA006612, circRNA005537, and circANRIL) via targeting various cellular and molecular targets (e.g., CDK4, DAB2IP, ZEB1, miR-889, and let-7c-3p) exert their effects on skin cancers progression. Herein, for first time, we summarized different circular RNAs in skin cancers and noncancerous diseases. Moreover, we highlighted crosstalk between circular RNAs and ceRNAs in cancerous conditions.

Circular RNAs in cancer: new insights into functions and implications in ovarian cancer

Circular RNAs (circRNAs) are a class of long non-coding RNAs (lncRNAs) which have a circular and closed loop structure. They are ubiquitous, stable, conserved and diverse RNA molecules with a range of activities such as translation and splicing regulation, which are able to interacting with RNA-binding proteins and specially miRNA sponge. The expression patterns of the circRNAs exhibited tissue specificity and also, step and stage specificity. Accumulating evidences approved the critical role of circular RNAs in many cancers such as ovarian cancer. Given that these molecules exert their effects through multiple cellular and molecular mechanisms (i.e., angiogenesis, apoptosis, growth, and metastasis) which are involved in cancer pathogenesis, circular RNAs, in particular, act by controlling cell proliferation in ovarian cancer, so that, it has been shown that the deregulation of these molecules is associated with initiation and progression of ovarian cancer. Therefore, they are attractive molecules which have introduced them as cancer biomarkers. Moreover, they could be used as new therapeutic candidates for developing novel treatment strategies. Here, for first time, we have provided a comprehensive review on the recent knowledge of circular RNAs and their pathological roles in the ovarian cancer.

Circular RNAs: A novel target among non‑coding RNAs with potential roles in malignant tumors (Review)

Circular RNAs (circRNAs) are a class of non-coding RNAs that are generated via alternative back-splicing, which connects the terminal 5′ and 3′ends. Due to their unique loop structure, circRNAs are resistant to ribonucleases and more stable than linear RNAs. In vivo, they are usually highly conserved and stably expressed in tissue/developmental-stage-specific manners. Generally, circRNAs function as microRNA sponges and splicing regulators, as well as in protein binding and transcription. Some circRNAs contain open reading frames with internal ribosomal entry site elements and can thus encode specific proteins. Previously, circRNAs were thought to be erroneous splicing products or by-products of mRNA splicing. With the development of the next-generation sequencing techniques, it has become increasingly clear that circRNAs are abundantly widespread in eukaryotes and that they play significant roles in malignant tumor progression. The present review briefly introduces the biogenesis and functions of circRNAs, as well as summarizes recent research in several common malignancies. The present review also addresses the prospects of circRNAs in clinical applications.

Connexin43 as a Tumor Suppressor: Proposed Connexin43 mRNA-circularRNAs-microRNAs Axis Towards Prevention and Early Detection in Breast Cancer

Breast cancer (BC) is a global public health burden, constituting the highest cancer incidence in women worldwide. Connexin43 (Cx43) is a member of a family of transmembrane proteins responsible in part for intercellular communication between adjacent breast epithelial cells, via gap junctions. Cx43 plays key role in mammary gland development and differentiation and its spatio-temporal perturbation contributes to tumorigenesis. Thus, Cx43 acts as a breast tumor-suppressor. Signaling pathways and phenotypes downstream of Cx43 mRNA loss/mis-localization in breast cells have been well-studied. However, axes parallel to Cx43 loss are less understood. microRNAs (miRNAs) are small endogenous non-coding RNAs that repress translation and circularRNAs (circRNAs) are a class of endogenous RNAs that originate from RNA splicing and act as miRNA "sponges". CircRNAs and miRNAs are dysregulated in cancers and are highly abundant and stable in the circulation. Thus, they present as attractive liquid biopsy cancer biomarkers. Here, an axis for Cx43 mRNA-circRNAs-miRNAs interactions along BC initiation (denoted by loss of breast epithelial polarity and development of hyperplastic phenotypes) is proposed to potentially serve as a signature biomarker toward BC early-onset detection and prevention.

Predicting human disease-associated circRNAs based on locality-constrained linear coding

Circular RNAs (circRNAs) are a new kind of endogenous non-coding RNAs, which have been discovered continuously. More and more studies have shown that circRNAs are related to the occurrence and development of human diseases. Identification of circRNAs associated with diseases can contribute to understand the pathogenesis, diagnosis and treatment of diseases. However, experimental methods of circRNA prediction remain expensive and time-consuming. Therefore, it is urgent to propose novel computational methods for the prediction of circRNA-disease associations. In this study, we develop a computational method called LLCDC that integrates the known circRNA-disease associations, circRNA semantic similarity network, disease semantic similarity network, reconstructed circRNA similarity network, and reconstructed disease similarity network to predict circRNAs related to human diseases. Specifically, the reconstructed similarity networks are obtained by using Locality-Constrained Linear Coding (LLC) on the known association matrix, cosine similarities of circRNAs and diseases. Then, the label propagation method is applied to the similarity networks, and four relevant score matrices are respectively obtained. Finally, we use 5-fold cross validation (5-fold CV) to evaluate the performance of LLCDC, and the AUC value of the method is 0.9177, indicating that our method performs better than the other three methods. In addition, case studies on gastric cancer, breast cancer and papillary thyroid carcinoma further verify the reliability of our method in predicting disease-associated circRNAs.

Analysis of the circular RNA transcriptome in the grade 3 endometrial cancer

Background/aims

Circular RNAs (circRNAs), a class of newly discovered endogenous noncoding RNAs, have shown large capabilities in gene regulation. Patients with the grade 3 endometrial cancer (EC) have a generally poor prognosis, and the specific role of circRNAs in the grade 3 EC remains unclear. This study aims to investigate the roles of circRNAs in the grade 3 EC.

Methods

In the current study, we screened the expression profiles of circRNAs taken from two women with the grade 3 EC and adjacent non-cancerous endometrial tissue using circRNAs sequencing. Bioinformatic analyses were applied to study these differentially expressed circRNAs. Quantitative reverse transcription polymerase chain reaction (qRT‐PCR) of six dysregulated circRNAs was performed to validate the sequencing results. Bioinformatic analyses, including the negative correlation network analyses of circRNAs–microRNAs (miRNAs)–messenger RNAs (mRNAs) and the Cytoscape, were used to delineate the interaction of circRNAs/miRNAs of the entire network.

Results

Data of circRNA sequencing showed a significant change in 75,928 unique circRNAs (P<0.05). The upregulated hsa_circ_0039569 and hsa_circ_0001610 and downregulated hsa_circ_0000437, hsa_circ_0001776, and hsa_circ_0009043 were validated by qRT-PCR analysis. Using bioinformatical methods, we found that hsa_circ_0039569 has the MRE of hsa-miR-542-3p and hsa-let-7c-5p. Hsa-miR-542-3p and hsa-let-7c-5p were downregulated in the grade 3 EC validated by qRT-PCR analysis. In the clinicopathological parameters, the expression level of hsa_circ_0039569 was significantly correlated with tumor differentiation (P=0.001).

Conclusion

This is the first study demonstrated that there were a lot of differences between the tissue of the grade 3 EC and adjacent non-cancerous endometrial in circRNA expression and may offer novel molecular candidates for diagnosis and clinical treatment of the grade 3 EC.

Fusion of multiple heterogeneous networks for predicting circRNA-disease associations

Circular RNAs (circRNAs) are a newly identified type of non-coding RNA (ncRNA) that plays crucial roles in many cellular processes and human diseases, and are potential disease biomarkers and therapeutic targets in human diseases. However, experimentally verified circRNA-disease associations are very rare. Hence, developing an accurate and efficient method to predict the association between circRNA and disease may be beneficial to disease prevention, diagnosis, and treatment. Here, we propose a computational method named KATZCPDA, which is based on the KATZ method and the integrations among circRNAs, proteins, and diseases to predict circRNA-disease associations. KATZCPDA not only verifies existing circRNA-disease associations but also predicts unknown associations. As demonstrated by leave-one-out and 10-fold cross-validation, KATZCPDA achieves AUC values of 0.959 and 0.958, respectively. The performance of KATZCPDA was substantially higher than those of previously developed network-based methods. To further demonstrate the effectiveness of KATZCPDA, we apply KATZCPDA to predict the associated circRNAs of Colorectal cancer, glioma, breast cancer, and Tuberculosis. The results illustrated that the predicted circRNA-disease associations could rank the top 10 of the experimentally verified associations.

The emerging role of circular RNAs in breast cancer

Breast cancer (BCa) is one of the most frequently diagnosed cancers and leading cause of cancer deaths among females worldwide. Circular RNAs (circRNAs) are a new class of endogenous regulatory RNAs characterized by circular shape resulting from covalently closed continuous loops that are capable of regulating gene expression at transcription or post-transcription levels. With the unique structures, circRNAs are resistant to exonuclease RNase R and maintain stability more easily than linear RNAs. Recently, an increasing number of circRNAs are discovered and reported to show different expression in BCa and these dysregulated circRNAs were correlated with patients’ clinical characteristics and grade in the progression of BCa. CircRNAs participate in the bioprocesses of carcinogenesis of BCa, including cell proliferation, apoptosis, cell cycle, tumorigenesis, vascularization, cell invasion, migration as well as metastasis. Here we concentrated on biogenesis and function of circRNAs, summarized their implications in BCa and discussed their potential as diagnostic and therapeutic targets for BCa.

Circular RNAs in Cancer

Circular RNAs (circRNAs) are a class of single-stranded closed RNA molecules that are formed by precursor mRNA back-splicing or skipping events of thousands of genes in eukaryotes as covalently closed continuous loops. High-throughput sequencing and bioinformatics approaches have uncovered the broad expression of circRNAs across species. Their high stability, abundance, and evolutionary conservation among species points to their distinct properties and diverse cellular functions as efficient microRNAs and protein sponges; they also play important roles in modulating transcription and splicing. Additionally, most circRNAs are aberrantly expressed in pathological conditions and in a tissue-specific manner such as development and progression of cancer. Herein, we highlight the characteristics, functions, and mechanisms of action of circRNAs in cancer; we also provide an overview of recent progress in the circRNA field and future application of circRNAs as cancer biomarkers and novel therapeutic targets.

Regulatory mechanisms and clinical perspectives of circRNA in digestive system neoplasms

A new star, circular RNA (circRNA), is a class of noncoding RNA with a stable cyclic structure. Exonic circRNA mainly exists in the eukaryotic cytoplasm. Intronic circRNAs (ciRNA) and exonic circRNAs with introns (EIciRNA) are found in the nucleus. Recent evidences showed the functional diversity of circRNAs, which could be microRNA (miRNA) sponges, interact with protein or translate into small peptide. Due to the change of human eating habits, digestive cancer remains one of the most common cancers worldwide and it is prone to metastasis. Increasing studies have found a number of circRNAs using RNA sequencing technology and displayed double roles of circRNA in digestive cancer. In this review, we surveyed the biogenesis and regulation of circRNAs, discussed circRNA functions and clinical applications (especially circRNAs in exosome) in digestive cancers, which implied that circRNAs could be as potential biomarkers in diagnosis and treatment of digestive cancers in the future.

SP1 induced lncRNA CASC11 accelerates the glioma tumorigenesis through targeting FOXK1 via sponging miR-498

The biological functions of long noncoding RNAs (lncRNAs) in the glioma have gained much attention in recent researches. However, the deepgoing mechanism by which lncRNA regulates the gliomagenesis is still ambiguous. In this work, we found that lncRNA CASC11 was significantly up-regulated in the glioma specimens and cells, and the ectopic overexpression indicated the poor prognosis of glioma patients. CASC11 expression could be activated by the transcription factor SP1. In vivo and vitro, the knockdown of CASC11 impaired the proliferation, migration and tumor growth of glioma cells. In mechanical experiments, the miR-498 was found to target the 3'-UTR of lncRNA CASC11 and FOXK1 mRNA. Taken together, the data suggest the regulation of SP1/CASC11/miR-498/FOXK1 in the gliomagenesis, which might provide a potential therapeutic strategy for glioma.

Hsa_circ_0004370 promotes esophageal cancer progression through miR-1294/LASP1 pathway

Circular RNAs (circRNAs) formed by back-splicing play multiple roles in the occurrence and development of cancer. Here, we found that hsa_circ_0004370 was up-regulated in both esophageal cancer (EC) tissues and cell lines. Loss function of hsa_circ_0004370 by si-RNA significantly suppressed proliferation and invasion and promoted apoptosis in both EC cell lines. The sponging of miR-1294 by hsa_circ_0004370 was bioinformatically predicted and subsequently verified by luciferase reporter assay and RNA immunoprecipitation assay. Further, hsa_circ_0004370 involved in the up-regulation of LASP1 by sponging miR-1294. Besides, the inhibition of the down-regulated hsa_circ_0004370 on cell malignant behaviors was rescued by miR-1294 inhibitor. Finally, this rescue effect was abrogated by suppressing the expression of LASP1. The results present here suggest that hsa_circ_0004370 functions as an oncogene on cell proliferation, apoptosis, and invasion via miR-1294/LASP1 axis.

Expression of circular RNAs in gynecological tumors: A systematic review

BACKGROUND

The rapid development of bioinformatic technology is boosting the discovery of components hiding in the darkness. As a type of universal, conservative, tissue-specific and stable molecules, circular RNA (circRNA) is a class of endogenous non-coding RNA that has no 5' cap and 3' poly(A) tail and forms a covalently closed continuous loop. At present, 3 types of circRNAs including exonic circRNA (ecRNA), intronic circRNA (ciRNA), and axon-intronic circRNA have been reported. Nowadays informatic technology and high-throughput sequencing have verified the abundance of endogenous circRNAs in eukaryocytes, with predominantly expressed in the cell cytoplasm. Their unique sequences endow them with special functions, such as miRNA sponge, selective transcription or splicing, and attaching to RNA-binding proteins.

DATA SOURCES

This review was based on articles published in PubMed databases up to January, 2019, with the following keywords: "circular RNA", "database", and "reproductive tumor" (Flow chart).

OBJECTIVES

Original articles and reviews on the topics were selected.

RESULTS

Studies have uncovered the interplay between circRNAs and the development of ovarian epithelial tumors, ovarian carcinoma, and cervical carcinoma, which suggesting the potential of circRNAs as biomarkers or therapeutic targets for human diseases.

CONCLUSIONS

Circular RNA has been found to play a role in gynecological tumors diseases. Meanwhile, we reviewed the studies on how CircularRNA participate in gynecological tumors, which provides a basis for the study of CircularRNA in gynecological tumors.