circFBLIM1 act as a ceRNA to promote hepatocellular cancer progression by sponging miR-346

Upregulated circ_0005576 facilitates cervical cancer progression via the miR-153/KIF20A axis

Circular RNAs (circRNAs) are a novel group of noncoding RNAs characterized by a covalently closed loop. An increasing evidence suggests that deregulated circRNAs exert their essential regulatory roles in oncogenesis. However, little is explored on the biological role of novel circRNAs in cervical cancer (CC) progression. In the present study, we analyzed two GSE microarrays to screen for CC-specific circRNAs and found two circRNAs both expressed in CC cells and tissues. Among them, circ_0005576 was significantly overexpressed in both CC tissues and cell lines. Furthermore, upregulated circ_0005576 was positively associated with advanced FIGO stage, lymph node metastasis, but was negatively related with overall survival of CC patients. Additionally, circ_0005576 knockdown induced a suppressed cell growth, colony formation and metastasis of HeLa and SiHa cells. Mechanistically, circ 0005576 was mainly located in the cytoplasm and served as a sponge of miR-153-3p to increase kinesin family member 20A (KIF20A) expression. Rescue assays further validated the effects of circ_0005576/miR-153-3p/KIF20A axis on CC proliferation, migration and invasion. In conclusion, our research reveals a novel circ_0005576/miR-153-3p/KIF20A axis promoting CC progression, which may suggest a new insight into the pathogenesis of CC.

Circular RNA circRHOT1 promotes hepatocellular carcinoma progression by initiation of NR2F6 expression

Background

Increasing evidence has revealed a close relationship between non-coding RNAs and cancer progression. Circular RNAs (circRNAs), a recently identified new member of non-coding RNAs, are demonstrated to participate in diverse biological processes, such as development, homeostatic maintenance and pathological responses. The functions of circRNAs in cancer have drawn wide attention recently. Until now, the expression patterns and roles of circRNAs in hepatocellular carcinoma (HCC) have remained largely unknown.

Methods

Bioinformatics method was used to screen differentially expressed novel circRNAs in HCC. Northern blotting, qRT-PCR, in situ hybridization (ISH) and RNA-FISH were utilized to analyzed the expression of circRHOT1 in HCC tisues.CCK8, colony formation, EdU assays were used to analyze proliferation of HCC cells. Transwell assay was utilized to analyze HCC cell migration and invasion. FACS was used for apoptosis analysis. Xenograft experiments were used to analyze tumor growth in vivo. Mass spectrum, RNA pulldown, RIP and EMSA was utilized to test the interaction between circRHOT1 and TIP60. RNA-sequencing method was used to analyze the downstream target gene of circRHOT1.

Results

We identified circRHOT1 (hsa_circRNA_102034) as a conserved and dramatically upregulated circRNA in HCC tissues. HCC patients displaying high circRHOT1 level possessed poor prognosis. Through in vitro and in vivo experiments, we demonstrated circRHOT1 significantly promoted HCC growth and metastasis. Regarding the mechanism, we conducted a RNA pulldown with a biotin-labeled circRHOT1-specific probe and found that circRHOT1 recruited TIP60 to the NR2F6 promoter and initiated NR2F6 transcription. Moreover, NR2F6 knockout inhibited growth, migration and invasion, whereas rescuing NR2F6 in circRHOT1-knockout HCC cells rescued the proliferation and metastasis abilities of HCC cells.

Conclusion

Taken together, circRHOT1 inhibits HCC development and progression via recruiting TIP60 to initiate NR2F6 expression, indicating that circRHOT1 and NR2F6 may be potential biomarkers for HCC prognosis.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-1046-7) contains supplementary material, which is available to authorized users.

Identification of circRNA-miRNA-mRNA regulatory network in gastric cancer by analysis of microarray data

Background

Evidence is increasingly indicating that circular RNAs (circRNAs) are closely involved in tumorigenesis and cancer progression. However, the function of circRNAs in gastric cancer (GC) are still unknown. Here, we aimed to determine the regulatory mechanism of circRNAs in GC.

Methods

Expression profiles of circRNAs were downloaded from four Gene Expression Omnibus (GEO) microarray datasets. Expression profiles of miRNAs and mRNAs were collected from The Cancer Genome Atlas (TCGA) database. We used the robust rank aggregation method to identify differentially expressed circRNAs (DEcircRNAs) and a ceRNA network was constructed based on circRNA–miRNA pairs and miRNA–mRNA pairs. Functional and pathway enrichment analyses were performed and interactions between proteins were predicted using Cytoscape. Aa subnetwork regulatory module was built using the MCODE plugin.

Results

A total of eight DEcircRNAs, 240 DEmiRNAs, and 4578 DEmRNAs were identified. The circRNA–miRNA–mRNA network was constructed based on seven circRNAs, 33 miRNAs, 69 mRNAs in GC. GO and KEGG pathway analysis indicated DEmRNAs might be associated with GC onset and progression. A PPI network was established and four hub genes (MCM4, KIF23, MCM8, and NCAPD2) were determined from the network. Then a circRNA–miRNA-hub gene subnetwork was constructed based on the four DEcircRNAs, three DEmiRNAs, and four DEmRNAs.

Conclusions

Our findings provide a deeper understanding the circRNA-related competing endogenous RNA regulatory mechanism in GC pathogenesis.

Circular RNAs in hepatocellular carcinoma: Biomarkers, functions and mechanisms

Hepatocellular carcinoma (HCC), a leading cause of cancer-related death with high invasive and metastatic potential, has a low survival rate. To improve the survival and quality of life in HCC patients, it is urgently needed to explore novel biomarkers for early diagnosis and prognosis of HCC, as well as therapeutic strategies. Circular RNAs (circRNAs) are a class of highly conserved, stable and abundant non-coding RNAs (ncRNAs) that can regulate gene expression at transcriptional or post-transcriptional levels. Recently, some circRNAs are identified to be potential biomarkers for HCC diagnosis and prognosis. Furthermore, some circRNAs are found to play oncogenic or suppressive roles in HCC progression by regulating various biological processes, including cell proliferation, migration, invasion and metastasis, epithelial-mesenchymal transition (EMT), as well as apoptosis. In this review, we summarize recent findings of deregulated circRNAs, their functions and molecular mechanisms in HCC, and discuss their potential roles as diagnostic biomarkers, prognostic biomarkers, as well as therapeutic targets for HCC.

LncRNA NBAT1 suppresses cell proliferation and migration via miR-346/GSK-3β axis in renal carcinoma

Long non-coding RNA (LncRNA) neuroblastoma associated transcript 1 (NBAT1) was demonstrated to be significantly downregulated in renal carcinoma (RCC) cells. However, the function and mechanism of NBAT1 in RCC is poorly understood. The expression of NBAT1 and glycogen synthase kinase-3β (GSK-3β)-mediated Wnt/β-catenin-related proteins were measured by quantitative real-time PCR (qRT-PCR) and western blotting in RCC cell lines. Cell viability, migration, and invasion were estimated by CCK-8 and Transwell assay. The association of miR-346 with GSK-3β expression was verified using luciferase assay. NBAT1 was significantly downregulated in RCC cells, and inhibited RCC cell proliferation, migration, and invasion. Furthermore, NBAT1 negatively regulated miR-346 expression. In addition, miR-346 overexpression and the knockdown of GSK-3β, a direct target of miR-346 could overturn the inhibitory effect of NBAT1 on Wnt/β-catenin signaling and cell proliferation, migration, and invasion. NBAT1 functioned as an endogenous sponge by competing for miR-346 binding to GSK-3β and therefore alleviated RCC cells.

Circular RNA sequencing reveals the molecular mechanism of the effects of acupuncture and moxibustion on endometrial receptivity in patients undergoing infertility treatment

The present study aimed to determine the profile of differentially expressed circular RNAs (circRNAs) in infertile patients treated with acupuncture and moxibustion and verify the role of acupuncture and moxibustion in altering endometrial receptivity (ER). High‑throughput RNA sequencing and bioinformatics analysis of samples from six pairs of patients treated with or without acupuncture and moxibustion were conducted. The reliability of high‑throughput RNA sequencing was validated using reverse transcription‑quantitative PCR. The most significant circRNA functions and pathways were selected by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. A circRNA‑miR‑mRNA interaction network was constructed to determine the connection between circRNAs, microRNAs (miRs), and mRNAs. High‑throughput RNA sequencing identified 2,653 circRNAs. A total of 86 circRNAs was differentially expressed, of which 57 were upregulated and 29 were downregulated, between the acupuncture and moxibustion group and the control group. In the GO analysis, the identified BP terms were chromatin modification, positive regulation of transcription from RNA polymerase II promoter involved in unfolded protein response, oxidative DNA demethylation, regulation of transcription from RNA polymerase II promoter in response to hypoxia, and regulation of smooth muscle cell differentiation. The identified CC terms were nucleoplasm, nucleolus, nucleus, histone acetyltransferase complex, and annulate lamellae. The identified MF terms were methylcytosine dioxygenase activity, chromatin binding, zinc ion binding, histone binding, and protein binding. In the KEGG pathway analysis, the identified pathways were protein processing in endoplasmic reticulum, degradation of aromatic compounds, shigellosis, mTOR signaling pathway, bacterial invasion of epithelial cells, and prostate cancer. Circ‑SFMBT2, circ‑BACH1, and circ‑LPAR1 were significantly upregulated (P<0.05) and associated with numerous miRs and mRNAs. Acupuncture and moxibustion could impact ER by regulating the expression of circRNAs.

CircABCC2 Regulates Hepatocellular Cancer Progression by Decoying MiR-665

Background: Numerous studies have shown that circular RNAs (circRNAs) play vital roles in tumor progression. However, how circRNAs function in hepatocellular cancer (HCC) remains mostly unclear.

Methods: We analyzed HCC circRNA expression via a microarray, and the expression of an upregulated circRNA, circABCC2, was detected. We next explored the function of circABCC2 in HCC via a series of experiments. We performed RNA immunoprecipitation (RIP) and luciferase assays to explore the competing endogenous RNA (ceRNA) function of circABCC2 in HCC.

Results: qRT-PCR verified that circABCC2 was overexpressed in HCC. Inhibition of circABCC2 suppressed HCC cell proliferation and invasion, but promoted apoptosis. Luciferase assays and RIP showed that circABCC2 and ABCC2 could directly bind to miR-665 and that circABCC2 could regulate ABCC2 expression by sponging miR-665.

Conclusions: In summary, circABCC2 regulates ABCC2 expression and HCC progression by sponging miR-665. circABCC2 could be used as a biomarker and therapeutic target in HCC.

Circular RNA SMARCA5 inhibits gastric cancer progression through targeting the miR-346/ FBXL2 axis

Circular RNA (circRNA) SMARCA5 (circSMARCA5) is a cancer-related circRNA that has been observed to be involved in the progression of several types of cancer. However, the role of circSMARCA5 in gastric cancer has not been reported. In the present study, we aimed to explore the function and mechanism of circSMARCA5 in gastric cancer. Our results showed that circSMARCA5 expression was significantly decreased in human gastric cancer tissues and cell lines. Further in vitro investigations demonstrated that overexpression of circSMARCA5 in SGC7901 cells inhibited cell proliferation, migration and invasion. Luciferase reporter assays proved that circSMARCA5 acted as a sponge for miroRNA-346 (miR-346) and regulated the expression of F-Box and leucine rich repeat protein 2 (FBXL2). Furthermore, transfection of miR-346 mimics into cells overexpressing circSMARCA5 blocked the function of circSMARCA5. Finally, we found that knockdown FBXL2 significantly reversed the effects of miR-346 inhibitor on gastric cell proliferation, migration and invasion. Collectively, circSMARCA5 exhibited a tumor suppressor-like activity in gastric cancer via regulating the miR-346/FBXL2 axis.

Circular RNA (circRNA) SMARCA5 (circSMARCA5) is a cancer-related circRNA that has been observed to be involved in the progression of several types of cancer.

circMAN1A2 could serve as a novel serum biomarker for malignant tumors

Novel diagnostic and prognostic biomarkers of cancers are needed to improve precision medicine. Circular RNAs act as important regulators in cancers at the transcriptional and posttranscriptional levels. The circular RNA circMAN1A2 is highly expressed in nasopharyngeal carcinoma according to our previous RNA sequencing data; however, the expression and functions of circMAN1A2 in cancers are still obscure. Therefore, in this study, we evaluated the expression of circMAN1A2 in the sera of patients with nasopharyngeal carcinoma and other malignant tumors and analyzed its correlations with clinical features and diagnostic values. The expression levels of circMAN1A2 were detected by quantitative real-time PCR, and the correlations of clinical features with circMAN1A2 expression were analyzed by χ² tests. Receiver operating characteristic curves were used to evaluate the clinical applications of circMAN1A2. The results showed that circMAN1A2 was upregulated in nasopharyngeal carcinoma, oral cancer, thyroid cancer, ovarian cancer, and lung cancer, with areas under the curves of 0.911, 0.779, 0.734, 0.694, and 0.645, respectively, indicating the good diagnostic value of circMAN1A2. Overall, our findings suggested that circMAN1A2 could be a serum biomarker for malignant tumors, providing important insights into diagnostic approaches for malignant tumors. Further studies are needed to elucidate the mechanisms of circMAN1A2 in the pathogenesis of cancer.

Biogenesis and Function of Circular RNAs in Health and in Disease

Circular RNAs (circRNAs) are a class of non-coding RNA that were previously thought to be insignificant byproducts of splicing errors. However, recent advances in RNA sequencing confirmed the presence of circRNAs in multiple cell lines and across different species suggesting a functional role of this RNA species. CircRNAs arise from back-splicing events resulting in a circular RNA that is stable, specific and conserved. They can be generated from exons, exon-introns, or introns. CircRNAs have multifaceted functions. They are likely part of the competing endogenous RNA class. They can regulate gene expression by sponging microRNAs, binding proteins or they can be translated into a protein themselves. CircRNAs have been associated with health and disease, some with disease protective effects, some with disease promoting functions. The widespread expression and disease regulatory mechanisms endow circRNAs to be used as functional biomarkers and therapeutic targets for a variety of different disorders. In this concise article we provide an overview of the association of circRNAs with various diseases including cancer, cardiovascular and kidney disease as well as cellular senescence. We conclude with an assessment of the current status and future outlook of this new field of research that carries immense potential with respect to diagnostic and therapeutic approaches of a variety of diseases.

The emerging roles and functions of circular RNAs and their generation

Circular RNAs (circRNAs) are closed long non-coding RNAs, in which the 5’ and 3’ termini are covalently linked by back-splicing of exons from a single pre-mRNA. Emerging evidence indicates that circRNAs are broadly expressed in mammalian cells and show cell type- or tissue-specific expression patterns. Importantly, circRNAs have been shown to participate in regulating various biological processes. Functionally, circRNAs can influence cellular physiology through various molecular mechanisms, such as serving as a decoy for microRNAs or RNA-binding proteins to modulate gene expression or translation of regulatory proteins. The biogenesis of circRNAs is known to be tightly regulated by cis- (intronic complementary sequences) and/or trans-factors (splicing factors) that constitute a cell- and context-dependent regulatory layer in the control of gene expression. However, our understanding of the regulation and function of circRNAs is still limited. In this review, we summarize the current progress in elucidating the functional roles, mechanisms and biogenesis of circRNAs. We also discuss the relationship between regulation and formation of circRNAs.

Competing endogenous RNA network and prognostic nomograms for hepatocellular carcinoma patients who underwent R0 resection

The prognosis of hepatocellular carcinoma (HCC) after R0 resection is unsatisfactory due to the high rate of recurrence. In this study, we investigated the recurrence-related RNAs and the underlying mechanism. The long noncoding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) expression data and clinical information of 247 patients who underwent R0 resection patients with HCC were obtained from The Cancer Genome Atlas. Comparing the 1-year recurrence group (n = 56) with the nonrecurrence group (n = 60), we detected 34 differentially expressed lncRNAs (DElncRNAs), five DEmiRNAs, and 216 DEmRNAs. Of these, three DElncRNAs, hsa-mir-150-5p, and 11 DEmRNAs were selected for constructing the competing endogenous RNA (ceRNA) network. Next, two nomogram models were constructed based separately on the lncRNAs and mRNAs that were further selected by Cox and least absolute shrinkage and selection operator regression analysis. The two nomogram models that showed a high prediction accuracy for disease-free survival with the concordance indexes at 0.725 and 0.639. Further functional enrichment analysis of DEmRNAs showed that the mRNAs in the ceRNA network and nomogram models were associated with immune pathways. Hence, we constructed a hsa-mir-150-5p-centric ceRNA network and two effective nomogram prognostic models, and the related RNAs may be useful as potential biomarkers for predicting recurrence in patients with HCC.

CircDLST promotes the tumorigenesis and metastasis of gastric cancer by sponging miR-502-5p and activating the NRAS/MEK1/ERK1/2 signaling

Background

Accumulating evidence shows that, the dysregulation of circular RNAs (circRNAs) is associated with the progression of multiple malignancies. But, the underlying mechanisms by which has_circ_0032627 (circDLST) contributed to gastric cancer (GC) remain undocumented.

Methods

The expression and cellular localization of circDLST and its association with clinicopathological characteristics and prognosis in patients with GC was analysed by using fluorescence in situ hybridization. Gain- and loss-of-function experiments as well as a subcutaneous xenograft tumor model and a liver metastasis model from orthotopic implantation of GC tissues were conducted to assess the role of circDLST in GC cells. CircDLST specific binding with miR-502-5p was confirmed by dual luciferase gene report, RNA immunoprecipitation (RIP) assays and RIP-miRNA expression profiling. qRT-PCR and Western blot analysis was used to detect the effects of circDLST on miR-502-5p-mediated NRAS/MEK1/ERK1/2 signaling in GC cells.

Results

The expression levels of circDLST were dramatically elevated in GC tissues as compared with the adjacent normal tissues, and acted as an independent prognostic factor of poor survival in patients with GC. Knockdown of circDLST inhibited the cell viability, colony formation, DNA synthesis, cell invasion and liver metastasis in vitro and in vivo, whereas overexpression of circDLST had the opposite effects. Furthermore, circDLST was co-localized with miR-502-5p in the cytoplasm of GC cells, and acted as a sponge of miR-502-3p in GC cells, which abrogated the tumor promoting effects of circDLST by inactivating the NRAS/MEK1/ERK1/2 signaling in GC cells.

Conclusion

CircDLST promotes the tumorigenesis and metastasis of GC cells by sponging miR-502-5p to activate the NRAS/MEK1/ERK1/2 signaling.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-1015-1) contains supplementary material, which is available to authorized users.

Comprehensive analysis of differentially expressed profiles and reconstruction of a competing endogenous RNA network in papillary renal cell carcinoma

Long noncoding RNAs (lncRNAs) function as competing endogenous RNAs (ceRNAs). ceRNA networks may serve important roles in various tumors, as demonstrated by an increasing number of studies; however, papillary renal cell carcinoma (PRCC)-associated ceRNA networks mediated by lncRNAs remain unknown. Increased knowledge of ceRNA networks in PRCC may aid the identification of novel targets and biomarkers in the treatment of PRCC. In the present study, a comprehensive investigation of mRNA, lncRNA, and microRNA (miRNA) expression in PRCC was conducted using sequencing data from The Cancer Genome Atlas. Differential expression (DE) profiles of mRNAs, lncRNAs and miRNAs were evaluated, with 1,970 mRNAs, 1,201 lncRNAs and 96 miRNAs identified as genes with significantly different expression between PRCC and control paracancerous tissues. Based on the identified DEmRNAs, a protein-protein interaction network was generated using the STRING database. Furthermore, a ceRNA network for PRCC was determined using a targeted assay combined with the DE of miRNAs, mRNAs and lncRNAs, enabling the identification of important lncRNA-miRNA and miRNA-mRNA pairs. Analysis of the ceRNA network led to the extraction of a subnetwork and the identification of lncRNA maternally expressed 3 (MEG3), lncRNA PWRN1, miRNA (miR)-508, miR-21 and miR519 as important genes. Reverse transcription-quantitative polymerase chain reaction analysis was conducted to validate the results of the bioinformatics analyses; it was revealed that lncRNA MEG3 expression levels were downregulated in PRCC tumor tissues compared with adjacent non-tumor tissues. In addition, survival analysis was conducted to investigate the association between identified genes and the prognosis of patients with PRCC, indicating the potential involvement of 13 mRNAs, 15 lncRNAs and six miRNAs. In conclusion, the present study may improve understanding of the regulatory mechanisms of ceRNA networks in PRCC and provide novel insight for future studies of prognostic biomarkers and potential therapeutic targets.

Upregulated circ RNA hsa_circ_0000337 promotes cell proliferation, migration, and invasion of esophageal squamous cell carcinoma

Background

As a new class of endogenous ncRNAs, circRNAs have been recently verified to be involved in the carcinogenesis and progression of human cancers. In the current study, we attempted to explore the potential function of a candidate circRNA (hsa_circ_0000337) in esophageal squamous cell carcinoma (ESCC).

Patients and methods

The altered expression of hsa_circ_0000337 was validated in clinical samples from 48 patients with ESCC. The human esophageal carcinoma cell lines KYSE-150 and TE-1, and the normal human esophageal epithelial cell line (HET-1A) were applied for functional analysis of hsa_circ_0000337. Cell proliferation was measured using the Cell Counting Kit-8 assay and the colony formation assay. Cell invasion and migration were detected by Transwell and wound healing assays, respectively. We further performed bioinformatic analysis and luciferase reporter assays to explore the role of hsa_circ_0000337 as a miRNA sponge.

Results

hsa_circ_0000337 was significantly upregulated in ESCC tissues compared to adjacent normal-appearing tissues (P<0.0001). In our in vitro experiment, the expression of hsa_circ_0000337 was higher in TE-1 compared to the normal human esophageal epithelial cell line HET-1A (P<0.001), but was not significantly different in KYSE-150 (P>0.05). Knockdown of hsa_circ_0000337 significantly inhibited cell proliferation, migration, and invasion in TE-1 and KYSE-150 cell lines. Bioinformatics predicted and luciferase reporter assay verified that hsa_circ_0000337 could bind to miR-670-5p, a ncRNA involved in carcinogenesis. It is estimated that 21 genes are regulated by miR-670-5p.

Conclusion

hsa_circ_0000337 was found to be an upregulated circRNA that is related to ESCC and promotes the progression of disease by regulating cell proliferation, migration, and invasion. These findings suggest that this circRNA could be a promising diagnostic biomarker and potential therapeutic target.

CircSETD3 (Hsa_circ_0000567) acts as a sponge for microRNA-421 inhibiting hepatocellular carcinoma growth

Background

Circular RNAs (circRNAs) play important roles in tumourigenesis and tumour progression. However, the expression profiles and functions of circRNAs in hepatocellular carcinoma (HCC) are largely unclear.

Methods

The expression profiles of circRNAs in HCC were identified through microarray analysis and were validated through quantitative reverse transcription polymerase chain reaction (qRT-PCR). Survival curves were plotted using the Kaplan-Meier method and compared using the log-rank test. The circular structure of candidate circRNA was confirmed through Sanger sequencing, divergent primer PCR, and RNase R treatments. Proliferation of HCC cells was evaluated in vitro and in vivo. The microRNA (miRNA) sponge mechanism of circRNAs was demonstrated using dual-luciferase reporter and RNA immunoprecipitation assays.

Results

CircSETD3 (hsa_circRNA_0000567/hsa_circRNA_101436) was significantly downregulated in HCC tissues and cell lines. Low expression of circSETD3 in HCC tissues significantly predicted an unfavourable prognosis and was correlated with larger tumour size and poor differentiation of HCC in patients. In vitro experiments showed that circSETD3 inhibited the proliferation of HCC cells and induced G1/S arrest in HCC cells. In vivo studies revealed that circSETD3 was stably overexpressed in a xenograft mouse model and inhibited the growth of HCC. Furthermore, we demonstrated that circSETD3 acts as a sponge for miR-421 and verified that mitogen-activated protein kinase (MAPK)14 is a novel target of miR-421.

Conclusion

CircSETD3 is a novel tumour suppressor of HCC and is a valuable prognostic biomarker. Moreover, circSETD3 inhibits the growth of HCC partly through the circSETD3/miR-421/MAPK14 pathway.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1041-2) contains supplementary material, which is available to authorized users.

Upregulated circular RNA circ_0030235 predicts unfavorable prognosis in pancreatic ductal adenocarcinoma and facilitates cell progression by sponging miR-1253 and miR-1294

Accumulating evidence indicated that dysregulated circular RNAs (circRNAs) could play pivotal roles in cancer biology. A recent study demonstrated that circ_0030235 expression is upregulated in human pancreatic ductal adenocarcinoma (PDAC) by high-throughput circRNA microarray. In the current work, we aimed to elucidate the clinical significance, prognostic value, functional roles and mechanism of circ_0030235 in PDAC. Quantitative real time-PCR was used to detect circ_0030235 expression in PDAC tissue specimens and cell lines. The clinical significance of circ_0030235 was evaluated by Fisher's exact test, Kaplan-Meier curves, and Cox regression analysis. Cell growth, apoptosis, and metastatic properties were then explored after circ_0030235 knockdown/overexpression. Dual luciferase reporter assay was applied to detect the mechanisms of circ_0030235. As a result, the data documented that circ_0030235 was upregulated in PDAC cell lines and cancerous tissues compared with HPDE and matched normal tissue specimens, respectively. Overexpression of circ_0030235 in tumor samples is related to higher tumor stage and positive lymph node invasion. Additionally, analyses documented that high expression of circ_0030235 was associated with poor prognosis for PDAC patients. Knockdown of circ_0030235 by siRNAs inhibited cell growth, migratory and invasive potential, and promoted cell apoptosis. On the contrary, overexpression of circ_0030235 caused the opposite effect. Mechanistically, circ_0030235 directly sponges miR-1253 and miR-1294 in PDAC cells. What's more, the oncogenic properties of circ_0030235 was partly dependent on its suppression on miR-1253 and miR-1294. Overall, the results showed that circ_0030235 might act as an effective therapeutic target and indicate dismal prognosis for PDAC.

The circRNA circAGFG1 acts as a sponge of miR-195-5p to promote triple-negative breast cancer progression through regulating CCNE1 expression

Background

In recent years, circular RNAs (circRNAs), a new star of non-coding RNA, have been emerged as vital regulators and gained much attention for involvement of initiation and progression of diverse kinds of human diseases, especially cancer. However, regulatory role, clinical significance and underlying mechanisms of circRNAs in triple-negative breast cancer (TNBC) still remain largely unknown.

Methods

Here, the expression profile of circRNAs in 4 pairs of TNBC tissues and adjacent non-tumor tissues was analyzed by RNA-sequencing. Quantitative real-time PCR and in situ hybridization were used to determine the level and prognostic values of circAGFG1 in two TNBC cohorts. Then, functional experiments in vitro and in vivo were performed to investigate the effects of circAGFG1 on tumor growth and metastasis in TNBC. Mechanistically, fluorescent in situ hybridization, dual luciferase reporter assay, RNA pull-down and RNA immunoprecipitation experiments were performed to confirm the interaction between circAGFG1 and miR-195-5p in TNBC.

Results

We found that circAGFG1 was evidently up-regulated in TNBC, and its level was correlated with clinical stage, pathological grade and poor prognosis of patients with TNBC. The results indicated that circAGFG1 could promote TNBC cell proliferation, mobility and invasion as well as tumorigenesis and metastasis in vivo. Mechanistic analysis showed that circAGFG1 may act as a ceRNA (competing endogenous RNA) of miR-195-5p to relieve the repressive effect of miR-195-5p on its target cyclin E1 (CCNE1).

Conclusions

Our findings suggest that circAGFG1 promotes TNBC progression through circAGFG1/miR-195-5p/CCNE1 axis and it may serve as a new diagnostic marker or target for treatment of TNBC patients.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0933-7) contains supplementary material, which is available to authorized users.

CircRNA has_circ_0006427 suppresses the progression of lung adenocarcinoma by regulating miR-6783-3p/DKK1 axis and inactivating Wnt/β-catenin signaling pathway

Recently, circular RNAs (circRNAs) are identified as a novel class of noncoding RNAs playing important roles in human malignant tumors. However, the regulatory function of circRNA in lung adenocarcinoma (LUAD) is still largely unknown. Present study aimed to explore the role of circ_0006427 in LUAD progression. Firstly, the downregulation of circ_0006427 in LUAD tissues and cell lines was revealed by microarray analysis and qRT-PCR analysis. And we also confirmed the circ_0006427 as a prognostic target in LUAD patients. Functionally, overexpression of circ_0006427 effectively suppressed cell proliferation, migration and invasion. Mechanistically, circ_0006427 was found to be predominantly located in the cytoplasm of LUCA cell, and was further revealed to positively regulate DKK1 in LUAD by sponging miR-6783-3p. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis and western blot analysis revealed that circ_0006427 inactivated Wnt/β-catenin signaling pathway by upregulating DKK1. At last, rescue assays proved the function of circ_0006427/miR-6783-3p/DKK1 axis in LUAD progression. In conclusion, our study revealed that circ_0006427 suppressed lung adenocarcinoma progression through regulating miR-6783-3p/DKK1 axis.

CircRNA circRNA_102171 promotes papillary thyroid cancer progression through modulating CTNNBIP1-dependent activation of β-catenin pathway

Background

As a type of recently discovered noncoding RNA, circular RNAs (circRNAs) exert pivot biological functions in diverse cancers. However, the role of circRNA_102171 in papillary thyroid cancer (PTC) has not been investigated. Our study was focused on the functional investigation toward circRNA_102171 in PTC progression. And we also aimed to reveal its potential molecular mechanism.

Methods

The expression pattern of circRNA_102171 was determined using quantitative polymerase chain reaction (qPCR) in PTC samples and cell lines. Cell proliferation was examined utilizing CCK8, colony formation and EdU incorporation assays. Apoptosis was analyzed by Annexin V/PI staining and FACS detection. Cell migration and invasion was measured using Transwell assay. Tumor growth in vivo was determined through a xenograft assay. RNA-pulldown, RNA-IP (RIP) and RNA-EMSA were used to analyze the interaction between circRNA_102171 and CTNNBIP1.

Results

CircRNA_102171 expression was upregulated in tumor tissues and cell lines. CircRNA_102171 silencing suppressed PTC cell proliferation, migration and invasion while promoting apoptosis. CircRNA_102171 knockdown inhibited PTC growth in vivo. CircRNA_102171 interacted with CTNNBIP1 to block its interaction with the β-catenin/TCF3/TCF4/LEF1 complex, leading to activation of Wnt/β-catenin pathway.

Conclusions

CircRNA_102171 overexpression promotes PTC progression through activating Wnt/β-catenin pathway in a CTNNBIP1-dependent way.

A two‑circRNA signature predicts tumour recurrence in clinical non‑functioning pituitary adenoma

Clinical non‑functioning pituitary adenoma (NFPA) accounts for >30% of all pituitary adenomas, and the recurrence rate is notably high. The ability to predict tumour recurrence during initial surgery will aid in determining if adjunctive therapy is required to reduce recurrence. With the aim of developing a circular RNA (circRNA) signature to improve prognosis prediction in NFPA, the present study examined the circRNA expression profiles in 73 patients with NFPA from Beijing Tiantan Hospital using high‑throughput RNA chip technology. The dataset was randomly separated into a training group and a test group using an R program. In the training group (n=37), a Cox proportional hazards regression model was used to analyse the genes associated with the recurrence and progression‑free survival (PFS) of patients with NFPA. Meanwhile, a random survival forest algorithm, Kaplan‑Meier and receiver operating characteristic curve (ROC) analyses were used to determine the multi‑circRNA signature with the largest area under the ROC curve (AUROC) and verify its efficacy in the test group (n=36). In the training and test groups, the signatures of two circRNAs (hsa_circ_0000066 and hsa_circ_0069707) were specifically associated with the PFS of patients with NFPA (log‑rank P<0.05). Furthermore, the two‑circRNA signature had a high prediction accuracy for tumour recurrence, with an AUROC of 0.87 and 0.67 in the training and test groups, respectively; and the discriminative power of the signature was greater compared with that of age. The present study is the first to suggest a circRNA signature with a clinical application value for predicting recurrence/progression in patients with NFPA.