NUDT21 regulates circRNA cyclization and ceRNA crosstalk in hepatocellular carcinoma

Genome-wide identification and functional analysis of circRNAs in Trichophyton rubrum conidial and mycelial stages

Background

Circular RNAs (circRNAs) are a group of noncoding RNAs that participate in gene expression regulation in various pathways. The essential roles of circRNAs have been revealed in many species. However, knowledge of circRNAs in fungi is still not comprehensive.

Results

Trichophyton rubrum (T. rubrum) is considered a model organism of human pathogenic filamentous fungi and dermatophytes. In this study, we performed a genome-wide investigation of circRNAs in T. rubrum based on high-throughput sequencing and ultimately identified 4254 circRNAs. Most of these circRNAs were specific to the conidial or mycelial stage, revealing a developmental stage-specific expression pattern. In addition, 940 circRNAs were significantly differentially expressed between the conidial and mycelial stages. PCR experiments conducted on seven randomly selected differentially expressed (DE-) circRNAs confirmed the circularized structures and relative expression levels of these circRNAs. Based on their genome locations, most circRNAs originated from intergenic regions, unlike those in plants and animals. Furthermore, we constructed circRNA-miRNA-mRNA regulatory networks that included 661 DE-circRNAs targeting 140 miRNAs and further regulating 2753 mRNAs. The relative expression levels of two randomly selected circRNA-miRNA-mRNA axes were investigated by qRT-PCR, and the competing endogenous RNA (ceRNA) network theory was validated. Functional enrichment analysis of the target genes suggested that they were significantly involved in posttranscriptional processes and protein synthesis as well as some small-molecule metabolism processes. CircRNAs are relatively more conserved in closely related dermatophytes but rarely conserved in distantly related species. Tru_circ07138_001 is a highly conserved circRNA that was conserved in all ten dermatophytes analyzed in our study and three distantly related species. Its host gene TERG_07138 was also highly conserved in two of these distantly related species Gallus gallus and Caenorhabditis elegans. The specific role of this circRNA deserves further exploration.

Conclusions

Our study is the first to provide a global profile of circRNAs in T. rubrum as well as dermatophytes. These results could serve as valuable resources for research on circRNA regulatory mechanisms in fungi and reveal new insights for further investigation of the physical characteristics of these significant human fungal pathogens.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08184-y.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Circular RNAs profiles of osteoarthritic synovium

Purposes: To identify the Circular RNAs (circRNAs) expression profile in the synovium of patients with Osteoarthritis (OA) and explore their potential regulatory mechanism. Methods: Transcriptome high-throughput sequencing was used to...

E2F3 promotes liver cancer progression under the regulation of circ-PRKAR1B

Liver cancer is one of the most lethal malignant tumors in the world. The high recurrence and mortality rate make it urgent for scientists and clinicians to find new targets for better treatment of liver cancer. Here, we found that circ-PRKAR1B expression was increased in the paired intrahepatic metastasis sample through high-throughput sequencing. Further experiments also confirmed its high expression both in carcinoma and metastasis when compared to the paired para-carcinoma and the paired carcinoma, respectively. Mechanism study showed that circ-PRKAR1B could promote liver cancer progression through the miR-432-5p/E2F3 pathway, and microRNA-432-5p could directly target the 3' untranslated region (UTR) of E2F3 mRNA to suppress its translation, thereby influencing liver cancer cell invasion and migration capacities. Clinical data obtained by using online databases based on The Cancer Genome Atlas (TCGA) samples and the clinicopathological data of liver cancer patients who underwent surgery in our hospital in the past 2 years also confirmed the significance of circ-PRKAR1B/miR-432-5p/E2F3 signaling in liver cancer progression. Animal experiments also indicated that targeting this newly identified signaling by overexpressing microRNA-432-5p could suppress the progression of liver cancer. Together, our study suggests that circ-PRKAR1B plays an important role in the regulation of liver cancer progression, and targeting this new circ-PRKAR1B/miR-432-5p/E2F3 signaling may help us find new treatment strategies to better suppress liver cancer progression.

CstF64-Induced Shortening of the BID 3'UTR Promotes Esophageal Squamous Cell Carcinoma Progression by Disrupting ceRNA Cross-talk with ZFP36L2

The majority of human genes have multiple polyadenylation sites, which are differentially used through the process of alternative polyadenylation (APA). Dysregulation of APA contributes to numerous diseases, including cancer. However, specific genes subject to APA that impact oncogenesis have not been well characterized, and many cancer APA landscapes remain underexplored. Here, we used dynamic analyses of APA from RNA-seq (DaPars) to define both the 3'UTR APA profile in esophageal squamous cell carcinoma (ESCC) and to identify 3'UTR shortening events that may drive tumor progression. In four distinct squamous cell carcinoma datasets, BID 3'UTRs were recurrently shortened and BID mRNA levels were significantly upregulated. Moreover, system correlation analysis revealed that CstF64 is a candidate upstream regulator of BID 3'UTR length. Mechanistically, a shortened BID 3'UTR promoted proliferation of ESCC cells by disrupting competing endogenous RNA (ceRNA) cross-talk, resulting in downregulation of the tumor suppressor gene ZFP36L2. These in vitro and in vivo results were supported by human patient data whereby 3'UTR shortening of BID and low expression of ZFP36L2 are prognostic factors of survival in ESCC. Collectively, these findings demonstrate that a key ceRNA network is disrupted through APA and promotes ESCC tumor progression.Significance: High-throughput analysis of alternative polyadenylation in esophageal squamous cell carcinoma identifies recurrent shortening of the BID 3'UTR as a driver of disease progression.

CircESRP1 inhibits clear cell renal cell carcinoma progression through the CTCF-mediated positive feedback loop

Circular RNA (circRNA), a closed continuous loop formed by back-splicing, has been confirmed to be implicated in a variety of human diseases including cancers. However, the underlying molecular mechanism of circRNA regulating the progression of renal cell carcinoma (RCC) remains largely unclear. In the present study, we identified a novel circular RNA, circESRP1, that derived from the ESRP1 gene locus at 8q22.1 exons. Lower expression of circESRP1 was found in clear cell RCC (ccRCC) tissues and cell lines. Besides, circESRP1 expression level showed inversely correlated with the advanced tumor size, TNM stage and distant metastasis of ccRCC. The expression level of circESRP1 exhibited a positive correlation with CTCF protein but negatively correlated with miR-3942 in 79 ccRCC tissues. In vivo experiments, we found that overexpression of circESRP1 effectively repressed xenograft tumor growth and inhibited c-Myc-mediated EMT progression. CircESRP1 acted as a sponge to competitively bind with miR-3942 as confirmed through RNA pull-down, RIP and dual-luciferase reporter assays. Moreover, CTCF, a downstream target of miR-3942, was validated to specifically promote the circESRP1 transcript expression and regulated by circESRP1/miR-3942 pathway to form a positive feedback loop. We also revealed that the circESRP1/miR-3942/CTCF feedback loop regulated the ccRCC cell functions via c-Myc mediated EMT process. This study provides a novel regulatory model of circRNA via forming a positive-feedback loop that perpetuates the circESRP1/miR-3942/CTCF axis, suggesting that this signaling may serve as a novel target for the treatment of ccRCC.

Five genes involved in circular RNA-associated competitive endogenous RNA network correlates with metastasis in papillary thyroid carcinoma

This study aimed to identify potential circular RNA (circRNA), microRNA (miRNA) and mRNA biomarkers as well as their underlying regulatory mechanisms in papillary thyroid carcinoma (PTC). Three microarray datasets from the Gene Expression Omnibus database as well as expression data and clinical phenotype from The Cancer Genome Atlas (TCGA) were downloaded, followed by differential expression, functional enrichment, protein-protein interaction (PPI), and module analyses. The support vector machine (SVM)-recursive feature elimination (RFE) algorithm was used to screen the key circRNAs. Finally, the mRNA-miRNA-circRNA regulatory network and competitive endogenous RNA (ceRNA) network were constructed. The prognostic value and clinical correlations of key mRNAs were investigated using TCGA dataset, and their expression was validated using the UALCAN database. A total of 1039 mRNAs, 18 miRNAs and 137 circRNAs were differentially expressed in patients with PTC. A total of 37 key circRNAs were obtained using the SVM-RFE algorithm, whereas 46 key mRNAs were obtained from significant modules in the PPI network. A total of 11 circRNA-miRNA pairs and 40 miRNA-mRNA pairs were predicted. Based on these interaction pairs, 46 circRNA-miRNA-mRNA regulatory pairs were integrated, of which 8 regulatory pairs in line with the ceRNA hypothesis were obtained, including two circRNAs (circ_0004053 and circ_0028198), three miRNAs (miR-199a-5p, miR-199b-5p, and miR-7-5p), and five mRNAs, namely APOA2, CCL20, LPAR5, MFGE8, and TIMP1. Survival analysis showed that LPAR5 expression was associated with patient survival. APOA2 expression showed significant differences between metastatic and non-metastatic tumors, whereas CCL20, LPAR5, MFGE8 and TIMP1 showed significant differences between metastatic and non-metastatic lymph nodes. Overall, we identified several potential targets and regulatory mechanisms involved in PTC. APOA2, CCL20, LPAR5, MFGE8, and TIMP1 may be correlated with PTC metastasis.

ceRNAs in Cancer: Mechanism and Functions in a Comprehensive Regulatory Network

Noncoding RNAs have been shown with powerful ability in post-transcriptional regulation, enabling intertwined RNA crosstalk and global molecular interaction in a large amount of dysfunctional conditions including cancer. Competing endogenous RNAs (ceRNAs) are those competitively binding with shared microRNAs (miRNAs), freeing their counterparts from miRNA-induced degradation, thus actively influencing and connecting with each other. Constantly updated analytical approaches boost outstanding advancement achieved in this burgeoning hotspot in multilayered intracellular communication, providing new insights into pathogenesis and clinical treatment. Here, we summarize the mechanisms and correlated factors under this RNA interplay and deregulated transcription profile in neoplasm and tumor progression, underscoring the great significance of ceRNAs for diagnostic values, monitoring biomarkers, and prognosis evaluation in cancer.

Noncoding RNAs link metabolic reprogramming to immune microenvironment in cancers

Altered metabolic patterns in tumor cells not only meet their own growth requirements but also shape an immunosuppressive microenvironment through multiple mechanisms. Noncoding RNAs constitute approximately 60% of the transcriptional output of human cells and have been shown to regulate numerous cellular processes under developmental and pathological conditions. Given their extensive action mechanisms based on motif recognition patterns, noncoding RNAs may serve as hinges bridging metabolic activity and immune responses. Indeed, recent studies have shown that microRNAs, long noncoding RNAs and circRNAs are widely involved in tumor metabolic rewiring, immune cell infiltration and function. Hence, we summarized existing knowledge of the role of noncoding RNAs in the remodeling of tumor metabolism and the immune microenvironment, and notably, we established the TIMELnc manual, which is a free and public manual for researchers to identify pivotal lncRNAs that are simultaneously correlated with tumor metabolism and immune cell infiltration based on a bioinformatic approach.

circAMOTL1L Suppresses Renal Cell Carcinoma Growth by Modulating the miR-92a-2-5p/KLLN Pathway

Accumulating evidence indicates that the dysregulation of circular RNAs (circRNAs) contributes to tumor progression; however, the regulatory functions of circRNAs in renal cell carcinoma (RCC) remain largely unknown. In this study, the function and underlying mechanism of circAMOTL1L in RCC progression were explored. qRT-PCR showed the downregulation of circAMOTL1L in RCC tissues and cell lines. The decrease in circAMOTL1L expression correlated with the tumor stage, metastasis, and poor prognosis in patients with RCC. Functional experiments revealed that circAMOTL1L inhibited cell proliferation and increased apoptosis in RCC cells. Subcutaneous implantation with circAMOTL1L-overexpressing cells in nude mice decreased the growth ability of the xenograft tumors. Mechanistically, circAMOTL1L served as a sponge for miR-92a-2-5p in upregulating KLLN (killin, p53-regulated DNA replication inhibitor) expression validated by bioinformatics analysis, oligo pull-down, and luciferase assays. Further, reinforcing the circAMOTL1L-miR-92a-2-5p-KLLN axis greatly reduced the growth of RCC in vivo. Conclusively, our findings demonstrate that circAMOTL1L has an antioncogenic role in RCC growth by modulating the miR-92a-2-5p-KLLN pathway. Thus, targeting the novel circAMOTL1L-miR-92a-2-5p-KLLN regulatory axis might provide a therapeutic strategy for RCC.

NUDT21 Promotes Tumor Growth and Metastasis Through Modulating SGPP2 in Human Gastric Cancer

Gastric cancer is one of the major malignancies with poor survival outcome. In this study, we reported that NUDT21 promoted cell proliferation, colony formation, cell migration and invasion in gastric cancer cells. The expression levels of NUDT21 were found to be much higher in human gastric cancer tissues compared with normal gastric tissues. NUDT21 expression was positively correlated with tumor size, lymph node metastasis and clinical stage in gastric cancer patients. High level of NUDT21 was associated with poor overall survival (OS) rates in gastric cancer patients. The expression levels of NUDT21 were also much higher in gastric cancer tissues from patients with tumor metastasis compared with those of patients without tumor metastasis. Moreover, forced expression of NUDT21 in gastric cancer cells promoted tumor growth and cell proliferation in xenograft nude mice, and depletion of NUDT21 in gastric cancer cells restrained lung metastasis in vivo. Through high throughput RNA-sequencing, SGPP2 was identified to be positively regulated by NUDT21 and mediated the tumor promoting role of NUDT21 in gastric cancer cells. Therefore, NUDT21 played an oncogenic role in human gastric cancer cells. NUDT21 could be considered as a novel potential target for gastric cancer therapy.

The Mechanism and Clinical Significance of Circular RNAs in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant tumors worldwide. In view of the lack of early obvious clinical symptoms and related early diagnostic biomarkers with high specificity and sensitivity, most HCC patients are already at the advanced stages at the time of diagnosis, and most of them are accompanied by distant metastasis. Furthermore, the unsatisfactory effect of the follow-up palliative care contributes to the poor overall survival of HCC patients. Therefore, it is urgent to identify effective early diagnosis and prognostic biomarkers and to explore novel therapeutic approaches to improve the prognosis of HCC patients. Circular RNA (CircRNA), a class of plentiful, stable, and highly conserved ncRNA subgroup with the covalent closed loop, is dysregulated in HCC. Increasingly, emerging evidence have confirmed that dysregulated circRNAs can regulate gene expression at the transcriptional or post-transcriptional level, mediating various malignant biological behaviors of HCC cells, including proliferation, invasion, metastasis, immune escape, stemness, and drug resistance, etc.; meanwhile, they are regarded as potential biomarkers for early diagnosis and prognostic evaluation of HCC. This article reviews the research progress of circRNAs in HCC, expounding the potential molecular mechanisms of dysregulated circRNAs in the carcinogenesis and development of HCC, and discusses those application prospects in the diagnosis and prognosis of HCC.

Mechanisms Regulating Abnormal Circular RNA Biogenesis in Cancer

Simple Summary

Circular RNAs (circRNAs) are circular RNA molecules without a 5′ cap and a 3′ poly(A) tail structure, which play an important role in tumor development, invasion and metastasis, etc. However, the mechanism of circRNA dysregulation in cancer remains unclear. Different from the classic splicing of linear RNA, circRNA is formed by back-splicing and is regulated by many cis-acting elements and trans-acting proteins. Exploring how the dysregulation of cis-regulatory elements and trans-acting proteins in tumor cells affects the biogenesis of circRNA, which in turn affects the development and prognosis of cancer, is of great significance for circRNA to become a cancer biomarker and therapeutic target.

Abstract

Circular RNAs (circRNAs), which are a class of endogenous RNA with covalently closed loops, play important roles in epigenetic regulation of gene expression at both the transcriptional and post-transcriptional level. Accumulating evidence demonstrated that numerous circRNAs were abnormally expressed in tumors and their dysregulation was involved in the tumorigenesis and metastasis of cancer. Although the functional mechanisms of many circRNAs have been revealed, how circRNAs are dysregulated in cancer remains elusive. CircRNAs are generated by a “back-splicing” process, which is regulated by different cis-regulatory elements and trans-acting proteins. Therefore, how these cis and trans elements change during tumorigenesis and how they regulate the biogenesis of circRNAs in cancer are two questions that interest us. In this review, we summarized the pathways for the biogenesis of circRNAs; and then illustrated how circRNAs dysregulated in cancer by discussing the changes of cis-regulatory elements and trans-acting proteins that related to circRNA splicing and maturation in cancer.

Identification of cis-HOX-HOXC10 axis as a therapeutic target for colorectal tumor-initiating cells without APC mutations

Colorectal cancer (CRC) is one of the most common cancers worldwide, in which adenomatous polyposis coli (APC) mutations are frequently and uniquely observed. Here we find that cis-HOX (circular RNA stabilizing HOXC10) is robustly expressed in colorectal tumor-initiating cells (TICs). cis-HOX knockout decreases colorectal TIC numbers and impairs the self-renewal, tumorigenesis, and metastatic capacities of TICs, whereas cis-HOX overexpression drives colorectal TIC self-renewal and metastasis. Mechanistically, cis-HOX binds to HOXC10 mRNA to attenuate its decay through blocking the K-homology splicing regulatory protein (KSRP)-binding sequence of HOXC10 3' UTR. HOXC10 is highly expressed in colorectal tumors and TICs and triggers Wnt/β-catenin activation by activating FZD3 expression. HOXC10 inhibitor salinomycin exerts efficient therapeutic effects in APC-wild-type colorectal tumors, but not in tumors with APC nonsense mutations. Therefore, the cis-HOX-HOXC10 pathway drives colorectal tumorigenesis, stemness, and metastasis and serves as a potential therapeutic target for APC-wild-type colorectal tumors.

The Vital Roles of LINC00662 in Human Cancers

Long non-coding RNAs (lncRNAs) play crucial roles in many human diseases, particularly in tumorigenicity and progression. Although lncRNA research studies are increasing rapidly, our understanding of lncRNA mechanisms is still incomplete. The long intergenic non-protein coding RNA 662 (LINC00662) is a novel lncRNA, and accumulating evidence suggests that it is related to a variety of tumors in multiple systems, including the respiratory, reproductive, nervous, and digestive systems. LINC00662 has been shown to be upregulated in malignant tumors and has been confirmed to promote the development of malignant tumors. LINC00662 has also been reported to facilitate a variety of cellular events, such as tumor-cell proliferation, invasion, and migration, and its expression has been correlated to clinicopathological characteristics in patients with tumors. In terms of mechanisms, LINC00662 regulates gene expression by interacting with both proteins and with RNAs, so it may be a potential biomarker for cancer diagnosis, prognosis, and treatment. This article reviews the expression patterns, biological functions, and underlying molecular mechanisms of LINC00662 in tumors.

Specific and sensitive detection of CircRNA based on netlike hybridization chain reaction

Circular RNA (circRNA), as a new class of biomarker, plays an important role in the occurrence and development of cancer. However, the limitations of detection methods in recent years have severely restricted the related research of circRNA. Here, we have developed an effective circRNA detection method based on the thermostatic netlike hybridization chain reaction (HCR). It combines reverse transcription-rolling circle amplification (RT-RCA) with well-designed netlike HCR to achieve dual selection and dual signal amplification, which can eliminate the interference of linear isomers. This two-dimensional netlike HCR is composed of an ingeniously designed trigger chain and two hairpin fuel probes, which can generate a stable network structure with RT-RCA products containing multiple sets of repeats at a constant temperature, thereby producing enhanced fluorescent signals. Systematic studies reveal that the optimized netlike HCR system has higher detection efficiency for DNA strands containing multiple sets of repetitive sequences, can detect circRNA as low as 0.1 pM, and has excellent selectivity. By using human tumor cell lines and tissues, it has been verified that the netlike HCR-based method can accurately detect specific circRNA in real biological samples without RNase R enrichment, which provides a simple and useful platform for detecting low-abundance circRNA. Furthermore, the proposed strategy is also a potential method for detecting some genes containing repetitive sequences, such as telomere DNA, centromere DNA and ribosomal DNA (rDNA).

The Regulation Network and Clinical Significance of Circular RNAs in Breast Cancer

Breast cancer is one of the most common malignant tumors in women worldwide. Circular RNA (circRNA) is a class of structurally stable non-coding RNA with a covalently closed circular structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been discovered and have proven to be clinically significant in the development and progression of breast cancer. Importantly, several regulators of circRNA biogenesis have been discovered. Here, we systematically summarize recent progress regarding the network of regulation governing the biogenesis, degradation, and distribution of circRNAs, and we comprehensively analyze the functions, mechanisms, and clinical significance of circRNA in breast cancer.

Identification of RNA binding protein interacting with circular RNA and hub candidate network for hepatocellular carcinoma

The interaction between RNA binding protein (RBP) and circular RNA (circRNA) is important for the regulation of tumor progression. This study aimed to identify the RBP-circRNA network in hepatocellular carcinoma (HCC). 22 differentially expressed (DE) circRNAs in HCC were screened out from Gene Expression Omnibus (GEO) database and their binding RBPs were predicted by Circular RNA Interactome. Among them, 17 DERBPs, which were commonly dysregulated in HCC from The Clinical Proteomic Tumor Analysis Consortium (CPTAC), The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) projects, were utilized to construct the RBP-circRNA network. Through survival analysis, we found TARDBP was the only prognostic RBP for HCC in CPTAC, TCGA and ICGC projects. High expression of TARDBP was correlated with high grade, advanced stage and low macrophage infiltration of HCC. Additionally, gene set enrichment analysis showed that dysregulated TARDBP might be involved in some pathways related to the HCC pathogenesis. Therefore, a hub RBP-circRNA network was generated based on TARDBP. RNA immunoprecipitation and RNA pull-down confirmed that hsa_circ_0004913 binds to TARDBP. These findings indicated certain RBP-circRNA regulatory network potentially involved in the pathogenesis of HCC, which provides novel insights into the mechanism study and biomarker identification for HCC.

CPSF4 regulates circRNA formation and microRNA mediated gene silencing in hepatocellular carcinoma

CircRNAs play essential roles in various physiological processes and involves in many diseases, in particular cancer. Global downregulation of circRNA expression has been observed in hepatocellular carcinoma (HCC) in many studies. Previous studies revealed that the pre-mRNA 3' end processing complex participates in circRNA cyclization and plays an important role in HCC tumorigenesis. Therefore, we explored the role of CPSF4, for 3' end formation and cleavage, in circRNA formation. Clinical research has shown that CPSF4 expression is upregulated in HCC and that high expression of CPSF4 is associated with poor prognosis in HCC patients. Mechanistic studies have demonstrated that CPSF4 reduces the levels of circRNAs, which possess a polyadenylation signal sequence and this decrease in circRNAs reduces the accumulation of miRNA and disrupts the miRNA-mediated gene silencing in HCC. Experiments in cell culture and xenograft mouse models showed that CPSF4 promotes the proliferation of HCC cells and enhances tumorigenicity. Moreover, CPSF4 antagonizes the tumor suppressor effect of its downstream circRNA in HCC. In summary, CPSF4 acts as an oncogene in HCC through circRNA inhibition and disruption of miRNA-mediated gene silencing.

Hsa_circ_0001982 promotes the progression of breast cancer through miR-1287-5p/MUC19 axis under hypoxia

Background

Breast cancer (BC) is the most commonly malignant tumor among women worldwide. Many studies have reported that circular RNAs (circRNAs) were participated in the regulation of multiple cancers development. However, the mechanism underlying hsa_circ_0001982 in breast cancer development is still unclear.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the levels of circ_0001982, microRNA-1287-5p (miR-1287-5p), and mucin 19 (MUC19) in BC tissues and cells under hypoxia. Moreover, glycolysis was evaluated by glucose consumption, lactic acid production, and hexokinase II (HK2) protein levels. The protein levels of cyclin D1, proliferating cell nuclear antigen (PCNA), and HK2 were determined by western blot assay. Cell proliferation, migration, and invasion were assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-h-tetrazolium bromide (MTT) and transwell assays, respectively. The relationship between miR-1287-5p and circ_0001982 or MUC19 was predicted using starbase v3.0 or Targetscan, and verified by dual-luciferase reporter assay and RNA binding protein immunoprecipitation (RIP) assay. The xenograft model in nude mice was established to examine the effect of circ_0001982 in vivo.

Results

The levels of circ_0001982 and MUC19 were upregulated, while miR-1287-5p was downregulated in BC tissues and cells under hypoxia. Knockdown of circ_0001982 hindered glycolysis, cell viability, migration, and invasion of BC cells under hypoxia. Mechanistic studies discovered that circ_0001982 could act as a sponge for miR-1287-5p to enhance MUC19 expression in BC cells. In addition, circ_0001982 silencing reduced xenograft tumor growth by regulating miR-1287-5p/MUC19 axis.

Conclusion

Circ_0001982 affected BC cells glycolysis, proliferation, migration, and invasion through miR-1287-5p/MUC19 axis under hypoxia.

Comprehensive analysis of the competing endogenous circRNA-lncRNA-miRNA-mRNA network and identification of a novel potential biomarker for hepatocellular carcinoma

BACKGROUND

The competing endogenous RNAs (ceRNAs) hypothesis has received increasing attention as a novel explanation for tumorigenesis and cancer progression. However, there is still a lack of comprehensive analysis of the circular RNA (circRNA)-long non-coding RNA (lncRNA)-miRNA-mRNA ceRNA network in hepatocellular carcinoma (HCC).

METHODS

RNA sequencing data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database were employed to identify Differentially Expressed mRNAs (DEmRNAs), DElncRNAs, and DEcircRNAs between HCC and normal tissues. Candidates were identified to construct networks through a comprehensive bioinformatics strategy. A prognostic mRNA signature was established based on data from TCGA database and validated using data from the GEO database. Then, the HCC prognostic circRNA-lncRNA-miRNA-mRNA ceRNA network was established. Finally, the expression and function of an unexplored hub gene, deoxythymidylate kinase (DTYMK), was explored through data mining. The results were examined using clinical samples and in vitro experiments.

RESULTS

We constructed a prognostic signature with seven target mRNAs by univariate, lasso and multivariate Cox regression analyses, which yielded 1, 3 and 5-year AUC values of 0.797, 0.733 and 0.721, respectively, indicating its sensitivity and specificity in the prognosis of HCC. Moreover, the prognostic signature could be validated in GSE14520. The prognostic ceRNA network of 21 circRNAs, 15 lncRNAs, 5 miRNAs, and 7 mRNAs was established according to the targeting relationship between 7 hub mRNAs and other RNAs. Our experiment results indicated that the depletion of DTYMK inhibited liver cancer cell proliferation and invasion.

CONCLUSIONS

The network revealed in this study may help comprehensively elucidate the ceRNA mechanisms driving HCC, and provide novel candidate biomarkers for evaluating the prognosis of HCC.

Circular RNA PLEC acts as a sponge of microRNA-198 to promote gastric carcinoma cell resistance to paclitaxel and tumorigenesis

Gastric carcinoma (GC) is one of the most frequent types of malignancy worldwide. Resistance to paclitaxel (PTX) has become an obstacle to the prognosis of GC, and the underlying mechanism is not clear. A previous study identified GC-related circRNAs via microarray analysis and bioinformatics analysis, and we discovered that circPLEC (hsa_circ_104722) was markedly upregulated in GC tissues and cells. The molecular mechanism of circPLEC in PTX-resistant GC cells still needs to be explored. In the present study, qRT-PCR demonstrated that circPLEC was upregulated in PTX-resistant GC tissues and cells, indicating that circPLEC boosts the PTX resistance of GC. circPLEC downregulation weakened GC resistance to PTX and tumorigenesis, migration and invasion and promoted the apoptosis of PTX-resistant GC cells. MiR-198 inhibitor reversed the effect of circPLEC downreguAlation in PTX-resistant GC cells, and MUC19 downregulation weakened GC resistance to PTX and tumorigenesis and improved the apoptosis of PTX-resistant GC cells. In summary, circPLEC acts as a sponge of miR-198 to promote the PTX resistance and tumorigenesis of GC cells by regulating MUC19 expression.

The VIM-AS1/miR-655/ZEB1 axis modulates bladder cancer cell metastasis by regulating epithelial-mesenchymal transition

BACKGROUND

Invasive bladder tumors cause a worse prognosis in patients and remain a clinical challenge. Epithelial-mesenchymal transition (EMT) is associated with bladder cancer metastasis. In the present research, we attempted to demonstrate a novel mechanism by which a long noncoding RNA (lncRNA)-miRNA-mRNA axis regulates EMT and metastasis in bladder cancer.

METHODS

Immunofluorescence (IF) staining was used to detect Vimentin expression. The protein expression of ZEB1, Vimentin, E-cadherin, and Snail was investigated by using immunoblotting assays. Transwell assays were performed to detect the invasive capacity of bladder cancer cells. A wound healing assay was used to measure the migratory capacity of bladder cancer cells.

RESULTS

Herein, we identified lncRNA VIM-AS1 as a highly- expressed lncRNA in bladder cancer, especially in metastatic bladder cancer tissues and high-metastatic bladder cancer cell lines. By acting as a ceRNA for miR-655, VIM-AS1 competed with ZEB1 for miR-655 binding, therefore eliminating the miR-655-mediated suppression of ZEB1, finally promoting EMT in both high- and low-metastatic bladder cancer cells and enhancing cancer cell metastasis.

CONCLUSIONS

In conclusion, the VIM-AS1/miR-655/ZEB1 axis might be a promising target for improving bladder cancer metastasis via an EMT-related mechanism.

Downregulation of NUDT21 contributes to cervical cancer progression through alternative polyadenylation

Nudix Hydrolase 21 (NUDT21), an alternative polyadenylation (APA)-regulatory protein, exhibits tumor-suppressive effects. However, its role in cervical cancer (CxCa) remains unknown. In the present study, we found that NUDT21 expression was reduced in CxCa tissues and cells, and NUDT21 levels were highly associated with the clinical prognosis of patients with CxCa. Knockdown of NUDT21 promoted CxCa cell proliferation, migration, and invasion in vitro, as well as tumorigenesis and lung metastasis in vivo. Overexpression of NUDT21 produces the opposite effects. Moreover, we performed polyadenylation site sequencing (PAS-Seq) and identified 457 transcripts with lengthened 3' untranslated regions (3' UTRs) upon NUDT21 overexpression. In particular, NUDT21 modulated the expression of several genes involved in fatty acid metabolism and the Wnt and NF-κB signaling pathways in CxCa development. Taken together, our study demonstrated that the APA regulatory effect of NUDT21 is an important mechanism for CxCa suppression.

Circular RNA expression profile in human primary multiple intracranial aneurysm

Primary multiple intracranial aneurysm (MIA) is a vascular disease that frequently leads to fatal vascular rupture and subarachnoid hemorrhage. However, the epigenetic regulation associated with MIA has remained largely elusive. Circular RNAs (circRNAs) serve important roles in cardiovascular diseases; however, their association with MIA has remained to be investigated. The present study initially aimed to explore novel mechanisms of MIA through examining circRNA expression profiles. Comprehensive circRNA expression profiles were detected by RNA sequencing (RNA-Seq) in human peripheral blood mononuclear cells. The RNA-Seq results were validated by reverse transcription-quantitative PCR. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested the functions of these circRNAs. A competing endogenous RNA network was constructed to reveal the circRNA-microRNA-mRNA relationship. Among the 3,328 differentially expressed circRNAs between the MIA and matched control groups, 60 exhibited significant expression changes (|log2 fold change|≥2; P<0.05). Among these 60 circRNAs, 20 were upregulated, while the other 40 were downregulated. A number of downregulated circRNAs were involved in inflammation. The most significant KEGG pathway was ‘leukocyte transendothelial migration’. The circRNAs Homo sapiens (hsa)_circ_0135895, hsa_circ_0000682 and hsa_circ_0000690, which were also associated with the above-mentioned pathway, were indicated to be able to regulate protein tyrosine kinase 2, protein kinase Cβ and integrin subunit αL, respectively. To the best of our knowledge, the present study was the first to perform a circRNA sequencing analysis of MIA. The results specifically predicted the regulatory role of circRNAs in the pathogenesis of MIA. ‘Leukocyte transendothelial migration’ may be critical for the pathogenesis of MIA.

Reduced expression of circRNA novel_circ_0005280 and its clinical value in the diagnosis of non-small cell lung cancer

Background

Circular RNAs (circRNAs) are a class of novel RNAs with important biologic functions. The aberrant expression of circRNAs has been implicated in human diseases; however, the clinical significance of circRNAs in non-small cell lung cancer (NSCLC) is still unclear. The aim of the present study was to evaluate the expression and clinical implications of novel_circ_0005280 in patients with NSCLC.

Methods

We evaluated differential circRNA expression in cancer and adjacent normal tissues from 3 patients with NSCLC via RNA sequencing. Among these circRNAs, 17 and 64 circRNAs showed higher and lower expressions, respectively. Novel_circ_0005280 expression in cancer tissues (n=41) was examined using quantitative real-time polymerase chain reaction, and the results are presented in the form of paired graph and scatter graph and its correlation with clinicopathological features and patient prognosis was analyzed by drawing receiver-operating characteristic (ROC) curve and Kaplan-Meier survival analysis.

Results

Novel_circ_0005280 expression was significantly decreased in NSCLC tumor tissues (n=41, obtained via biopsies), compared with adjacent normal tissues (n=27). Novel_circ_0005280 expression was correlated with tumor diameter and age. The area under the receiver-operating characteristic curve, cutoff, sensitivity, and specificity of novel_circ_0005280 were 0.944, 10.23, 85.2%, and 95.1%, respectively. Low novel_circ_0005280 expression was associated with a worse prognosis.

Conclusions

Novel_circ_0005280 may be a useful biomarker for the diagnosis and prognosis of NSCLC.

Circular RNA profiling identifies circ102049 as a key regulator of colorectal liver metastasis

Circular RNA (circRNA) plays an essential role in the development and progression of various cancers. However, the functions and mechanisms of circRNA in colorectal liver metastasis have not been fully elucidated. We performed circRNA microarray analysis to screen differentially expressed circRNA in the pathology of colorectal liver metastasis. Quantitative real-time PCR was used to detect the expression of hsa_circ_102049 (circ102049) in colorectal cancer (CRC) samples. CRC cells were transfected with circ102049 overexpression vector or small interfering (si)RNA to assess the effects of circ102049 in vitro. Bioinformatics analysis, fluorescence in situ hybridization, RNA immunoprecipitation, RNA pull-down and luciferase reporter assays were conducted to confirm the relationship of circ102049, miR-761, miR-192-3p and FRAS1. The mechanism by which circ102049 recruits and distributes DGCR8 protein in the cytoplasm was also investigated. We found that circ102049 was highly expressed in primary CRC tumors with liver metastasis and closely correlated with the prognosis of patients with CRC. Circ102049 significantly enhanced the adhesion, migration and invasion abilities of CRC cells, and promoted CRC progression via a micro (mi)R-761/miR-192-3p-FRAS1-dependent mechanism. Notably, due to the distribution of DGCR8 protein, circ102049 may also indirectly reduce the levels of mature miR-761 and miR-192-3p in the cytoplasm. In addition, the role of circ102049 in promoting colorectal liver metastasis was confirmed in vivo. Our findings provide new evidence that circ102049 may be a potential prognostic factor in CRC, and that the circ102049-miR-761/miR-192-3p-FRAS1 axis may be an anti-metastatic target for CRC patients.

Regulation of circular RNAs act as ceRNA in a hypoxic pulmonary hypertension rat model

To explore potential critical genes and identify circular RNAs (circRNAs) that act as the competitive endogenous RNA (ceRNA) in a hypoxic pulmonary hypertension (HPH) rat model. Constructed rat model, and a bioinformatics method was used to analyse differentially expressed (DE) genes and construct a circRNA-miRNA-mRNA ceRNA regulatory network. Then, qRT-PCR was used to verify. The significant DEcircRNAs/DEmiRNAs/DEmRNAs was showed, and a ceRNA network with 8 DEcircRNAs, 9 DEmiRNAs and 46 DEmRNAs were constructed. The functional enrichment suggested the inflammatory response, NF-κB signalling, MAPK cascade and Toll-like receptor were associated with HPH. Further assessment confirmed that circ_002723, circ_008021, circ_016925 and circ_020581 could have a potential ceRNA mechanism by sponging miR-23a or miR-21 to control downstream target gene and be involved in the pathophysiology of HPH. The qRT-PCR validation results were consistent with the RNA-Seq results. This study revealed potentially important genes, pathways and ceRNA regulatory networks in HPH.

Circ_0016760 Acts as a Sponge of MicroRNA-4295 to Enhance E2F Transcription Factor 3 Expression and Facilitates Cell Proliferation and Glycolysis in Nonsmall Cell Lung Cancer

Background: Circular RNAs (circRNAs) have been validated as important regulators of nonsmall cell lung cancer (NSCLC), but the role and potential mechanism of circ_0016760 in NSCLC remain largely unclear. Materials and Methods: Quantitative real-time polymerase chain reaction was performed to detect the levels of circ_0016760, microRNA-4295 (miR-4295), and E2F transcription factor 3 (E2F3). The cell proliferation was measured by methyl-thiazolyl diphenyl-tetrazolium bromide assay. The protein levels of proliferating cell nuclear antigen and E2F3 were examined by Western blot. Xenograft mice model was constructed to explore the effect of circ_0016760 on tumor growth in vivo. The relationship among circ_0016760, miR-4295, and E2F3 was evaluated using dual-luciferase reporter assay. Glucose consumption of NSCLC cells was assessed by the glucose assay kit. Results: Circ_0016760 and E2F3 expression levels were upregulated in NSCLC tissues and cells, while miR-4295 was downregulated. Circ_0016760 could bind to miR-4295, and negatively modulate its expression in NSCLC cells. Besides, miR-4295 directly targeted E2F3 and inversely regulated E2F3 expression. More importantly, Circ_0016760 facilitated proliferation and glycolysis of NSCLC cells by increasing E2F3 by sponging miR-4295 as well as promoted the tumor growth in vivo. Conclusion: Circ_0016760 served as a growth-promoting circRNA in NSCLC by facilitating cell proliferation and glycolysis by regulating the miR-4295/E2F3 axis, providing a novel potential target for NSCLC treatment.

Circ_0006528 Contributes to Paclitaxel Resistance of Breast Cancer Cells by Regulating miR-1299/CDK8 Axis

Background

Circular RNAs (circRNAs) have been reported to be involved in regulating the development of breast cancer. Paclitaxel (PTX) can be used for the chemotherapy of breast cancer. The study aimed to explore the role and mechanism of circ_0006528 in PTX-resistant breast cancer progression.

Methods

The levels of circ_0006528, microRNA-1299 (miR-1299) and cyclin-dependent kinase 8 (CDK8) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). RNase R treatment was used to confirm that the circ_0006528 was a circular RNA. PTX resistance and cell proliferation were determined by Cell counting kit-8 (CCK-8) assay. Cell apoptosis, migration and invasion were analyzed by flow cytometry and Transwell assays, respectively. The levels of all proteins were examined by Western blot. The interaction between circ_0006528 and miR-1299 or CDK8 was predicted by online database confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Xenograft mice model was constructed to reveal the role of circ_0006528 on tumor growth in vivo.

Results

Circ_0006528 was significantly up-regulated and miR-1299 was down-regulated in PTX-resistant breast cancer tissues and cells compared with control groups. CDK8 protein expression was dramatically upregulated in PTX-resistant breast cancer tissues and cells as compared to control groups. Loss-of-function experiments revealed that circ_0006528 knockdown decreased IC50 value of PTX and restrained proliferation, migration, invasion and autophagy, whereas induced apoptosis of PTX-resistant breast cancer cells in vitro. The inhibitory effects of sh-circ_0006528 on the progression of PTX-resistant breast cancer cells were reversed by decreasing miR-1299 or increasing CDK8 expression. Furthermore, circ_0006528 could modulate CDK8 expression by sponging miR-1299. Circ_0006528 silencing impeded the growth of PTX-resistant tumors by regulating miR-1299/CDK8 axis in vivo.

Conclusion

Circ_0006528 partially contributed to PTX resistance of breast cancer cells through up-regulating CDK8 expression by sponging miR-1299.

Circular RNA MYLK Promotes Hepatocellular Carcinoma Progression Through the miR29a/KMT5C Signaling Pathway

Purpose

This study aimed to investigate the functions of the circular RNA circMYLK (hsa_circ_0002768) in the development of hepatocellular carcinoma (HCC) and to identify the underlying mechanisms of the circMYLK/miR29a/KMT5C axis.

Materials and Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to explore the expressions of circMYLK, miR-29a and KMT5C in HCC tissues and cells. A potential miRNA (miR-29a) regulated by circMYLK was also explored, and the target relationship between miR-29a and KMT5C was confirmed. FISH, qRT-PCR, Western blotting, and dual-luciferase reporter assays were used to examine the circMYLK/miR29a/KMT5C signaling pathways involved in HCC development. Additionally, HCC cells were implanted into nude mice subcutaneously to test the role of circMYLK in tumor growth.

Results

circMYLK was determined to be significantly upregulated in HCC tissues and cells. Suppression of circMYLK repressed HCC cell proliferation, migration, and invasion while increasing apoptosis. In addition, FISH, qRT-PCR, and Western blotting, as well as dual-luciferase reporter assays, revealed that circMYLK could bind to miR-29a. In rescue experiments, miR-29a had the potential to eliminate the inhibitory effect of circMYLK knockdown in HCC. Moreover, miR-29a was found to target the KMT5C gene, which was positively regulated by circMYLK. Finally, a nude mouse tumorigenicity assay showed that injection of circMYLK siRNA into nude mice drastically suppressed xenograft tumor formation in vivo.

Conclusion

Our current study demonstrated that circMYLK promotes HCC progression by acting as a competing endogenous RNA of miR-29a, which regulates the downstream oncogene KMT5C.

CFIm25 in Solid Tumors: Current Research Progress

Cleavage factor I m25 is a newly discovered solid tumor-related gene, however, its precise role in cancer pathogenesis has not yet been characterized. Alternative polyadenylation is an RNA-processing mechanism that generates distinct 3′-termini on messenger RNAs, producing messenger RNA isoforms. Different factors influence the initiation and development of this process. As a key factor in alternative polyadenylation, cleavage factor I m25 plays an important role in messenger RNA maturation and cell signal transduction. Moreover, by regulating the process of alternative polyadenylation, it can inhibit the proliferation, invasion, and metastasis of a variety of tumors. Cleavage factor I m25 also acts as an oncogene in select tumors. The present review focuses on the role of cleavage factor I m25 in solid tumors and treatment. Due to the lack of current knowledge regarding the mechanisms of action and regulation of cleavage factor I m25 and alternative polyadenylation, it is necessary to further examine their role in cancer as well as in other diseases.

Emerging Roles of RNA 3'-end Cleavage and Polyadenylation in Pathogenesis, Diagnosis and Therapy of Human Disorders

A crucial feature of gene expression involves RNA processing to produce 3′ ends through a process termed 3′ end cleavage and polyadenylation (CPA). This ensures the nascent RNA molecule can exit the nucleus and be translated to ultimately give rise to a protein which can execute a function. Further, alternative polyadenylation (APA) can produce distinct transcript isoforms, profoundly expanding the complexity of the transcriptome. CPA is carried out by multi-component protein complexes interacting with multiple RNA motifs and is tightly coupled to transcription, other steps of RNA processing, and even epigenetic modifications. CPA and APA contribute to the maintenance of a multitude of diverse physiological processes. It is therefore not surprising that disruptions of CPA and APA can lead to devastating disorders. Here, we review potential CPA and APA mechanisms involving both loss and gain of function that can have tremendous impacts on health and disease. Ultimately we highlight the emerging diagnostic and therapeutic potential CPA and APA offer.

Role of circular RNAs in digestive system malignancies

Gastrointestinal malignancies have very high morbidity and mortality worldwide, seriously endangering human life and health. However, there are still many challenges in their early diagnosis and effective treatment. Circular RNAs (circRNAs) are a new class of endogenous long non-coding RNAs characterized by covalently closed loops. Because they do not have a 5' cap structure and a 3' poly(A) tail, circRNAs have higher stability, abundance, and evolutionary conservation than linear RNAs. CircRNAs are expressed in a tissue- or developmental stage-specific manner. These features produce various potential biological functions of circRNAs, such as acting as sponges of microRNAs (miRNAs; circRNAs bind to miRNAs to eliminate the inhibitory effect of miRNAs on their target genes and play a role of competing endogenous RNAs) or forming RNA protein complexes through RNA binding proteins, participating in the regulation of protein functions. In recent years, more and more studies have shown that circRNAs play a vital role in the occurrence and development of digestive system tumors. At the same time, their enormous potential as a biomarker and therapeutic target is also evolving. In this review, we summarize the latest research progress of circRNAs in digestive system malignancies.

CircTLK1 promotes the proliferation and metastasis of renal cell carcinoma by sponging miR-136-5p

BACKGROUND

Circular RNAs (circRNAs), a novel type of noncoding RNA (ncRNA), are covalently linked circular configurations that form via a loop structure. Accumulating evidence indicates that circRNAs are potential biomarkers and key regulators of tumor development and progression. However, the precise roles of circRNAs in renal cell carcinoma (RCC) remain unknown.

METHODS

Through circRNA high-throughput sequencing of RCC cell lines, we identified the circRNA TLK1 (circTLK1) as a novel candidate circRNA derived from the TLK1 gene. qRT-PCR detected the mRNA, circRNA and miRNA expression levels in RCC tissues and cells. Loss-of function experiments were executed to detect the biological roles of circTLK1 in the RCC cell phenotypes in vitro and in vivo. RNA-FISH, RNA pull-down, dual-luciferase reporter, western blot and immunohistochemistry assays were used to investigate the molecular mechanisms underlying the functions of circTLK1.

RESULTS

circTLK1 is overexpressed in RCC, and expression is positively correlated with distant metastasis and unfavorable prognosis. Silencing circTLK1 significantly inhibited RCC cell proliferation, migration and invasion in vitro and in vivo. circTLK1 was mainly distributed in the cytoplasm and positively regulated CBX4 expression by sponging miR-136-5p. Forced CBX4 expression reversed the circTLK1 suppression-induced phenotypic inhibition of RCC cells. Moreover, CBX4 expression was positively correlated with VEGFA expression in RCC tissues. CBX4 knockdown significantly inhibited VEGFA expression in RCC cells.

CONCLUSION

Collectively, our findings demonstrate that circTLK1 plays a critical role in RCC progression by sponging miR-136-5p to increase CBX4 expression. circTLK1 may act as a diagnostic biomarker and therapeutic target for RCC.

Transcription activation of circ-STAT3 induced by Gli2 promotes the progression of hepatoblastoma via acting as a sponge for miR-29a/b/c-3p to upregulate STAT3/Gli2

BACKGROUND

Hepatoblastoma (HB) is a common liver malignancy in children. Our previous study has disclosed the crucial role of STAT3 (signal transducer and activator of transcription 3) in HB.

AIM OF THE STUDY

Present study was designed to study the circular RNA (circRNA) STAT3 in HB.

METHODS

Gel electrophoresis revealed the circular characteristics of circ-STAT3. Function assays like EdU, transwell and sphere formation assay disclosed the function of circ-STAT3 in HB cells. Mechanism assays including ChIP, RIP, RNA pull down assay demonstrated the macular mechanism underlying circ-STAT3.

RESULTS

Circ_0043800, which was originated from STAT3, was up-regulated in HB tissues and cells. More importantly, silencing of circ-STAT3 led to the inhibition on HB cell growth, migration and stem-cell characteristics. Circ_0043800 was predominantly located in the cytoplasm of HB cells. Then, circ_0043800 was found to up-regulate STAT3 via sponging miR-29a/b/c-3p. Besides, we identified that STAT3 overexpression partially rescued silenced circ_0043800, while miR-29a/b/c-3p inhibition completely rescued silenced circ_0043800 on HB cellular biological behaviors. Subsequently, Gli2 (GLI family zinc finger 2) was identified as another target of miR-29a/b/c-3p. Circ_0043800 served as a competing endogenous RNA (ceRNA) to up-regulate both Gli2 and STAT3 via sponging miR-29a/b/c-3p. Moreover, we figured out that Gli2 overexpression completely rescued silenced circ_0043800 on HB cell malignant behaviors. After that, we discovered that Gli2 transcriptionally activated circ_0043800. The in-vivo assays further revealed that circ_0043800 promoted HB tumor growth by up-regulation of Gli2 and STAT3.

CONCLUSION

Gli2-induced circ_0043800 served as the ceRNA to promote HB by up-regulation of STAT3 and Gli2 at a miR-29a/b/c-3p dependent manner.

CircRNA-PTN Sponges miR-326 to Promote Proliferation in Hepatocellular Carcinoma

Background

Mounting evidences reveal that circular RNAs (circRNAs) are critical to regulate biological behavior and process of tumor. Our objective is to explore the role of circRNA-PTN (circPTN) and explain the exact mechanism in hepatocellular carcinoma (HCC).

Methods

Real-time polymerase chain reaction assay was used to detect the level of circPTN and miR-326. The proliferation of cell was measured by CCK-8 assay and EdU assay. Western blot assay was performed to assess ErbB/PI3K expression. Luciferase and RNA pull-down assays were carried out to confirm the interaction between circPTN and miR-326.

Results

Our results indicated that circPTN was upregulated in human hepatocellular carcinoma tumor tissues and cell lines, compared with paratumor tissues and immortalized normal liver cell line. circPTN could significantly promote HCC tumor growth according to gain-and loss-of-function assays. Additionally, we determined that circPTN acted as a sponge through interacting with miR-326. Overexpression of miR-326 could rescue the cell proliferation inhibition and ErbB/PI3K downregulation in HCC cells by circPTN. Besides, the effects of miR-326 on HCC were missing when circPTN binding sites were mutated.

Conclusion

Our study indicates that circPTN acts as an oncogenic factor via sponging miR-326 in HCC.