Circ_0000218 plays a carcinogenic role in colorectal cancer progression by regulating miR-139-3p/RAB1A axis

Circular RNA circRHOBTB3 inhibits ovarian cancer progression through PI3K/AKT signaling pathway

BACKGROUND

Circular RNAs (circRNAs) have emerged as significant regulators in human cancers. We aimed to explore the functional role of circular RNA RHOBTB3 (circRHOBTB3) in ovarian cancer.

METHODS

The expression of circRHOBTB3 was detected by real-time quantitative PCR (RT-qPCR). Then, the localization of circRHOBTB3 in ovarian cancer cells was identified by cell fractionation assay. Cell proliferation, migration and invasion were measured by cell counting kit-8 (CCK-8), transwell migration and invasion assays, respectively. The protein expression of N-cadherin, vimentin and E-cadherin was measured by western blot. And the glucose consumption and lactate production were detected by a glucose colorimetric assay kit and a lactic acid production detection kit, respectively. The involvement mRNA and protein expression of glucose transporter 1 (GLUT1), hexokinase-2 (HK2) and lactate dehydrogenase A (LDHA) were determined by RT-qPCR and western blot, respectively. Besides, lentivectors for short hairpin RNA (shRNA) against circRHOBTB3 (sh-circRHOBTB3) or pcDNA-circRHOBTB3 were used to downregulate or upregulate circRHOBTB3 expression in an animal tumor model. The protein expression of phosphoinositide 3-kinase (PI3K), phospho-PI3K (p-PI3K), protein kinase B (AKT), phospho-AKT (p-AKT), mammalian target of rapamycin (mTOR) and phospho-mTOR (p-mTOR) was examined by western blot. The activator (740Y-P) and inhibitor (LY294002) of PI3K/AKT pathway were used to evaluate the contribution of PI3K/AKT. CircRHOBTB3 was downregulated in ovarian cancer tissues and cells.

RESULTS

Functionally, circRHOBTB3 overexpression could markedly suppress cell proliferation, metastasis, and glycolysis, whereas the opposite results could be observed in the deletion of circRHOBTB3. Additionally, xenograft experiment also identified the above results. Finally, we observed that circRHOBTB3 inhibited the progression of ovarian cancer via inactivating PI3K/AKT signaling pathway.

CONCLUSIONS

CircRHOBTB3 exerted a suppressor role and inhibited the tumorigenesis by inactivating PI3K/AKT pathway in ovarian cancer.

Enterotoxigenic Bacteroides fragilis (ETBF) Enhances Colorectal Cancer Cell Proliferation and Metastasis Through HDAC3/miR-139-3p Pathway

Enterotoxigenic Bacteroides fragilis (ETBF) is believed to promote the malignant process of colorectal cancer (CRC), but the underlying molecular mechanism still needs to be revealed. CRC cells (SW480 and HCT-116) were treated with ETBF strain. Cell proliferation, invasion and, migration were evaluated by cell counting kit 8 assay, EdU assay, colony formation assay, transwell assay, and wound healing assay. Protein expression was analyzed by western blot. MicroRNA (miR)-139-3p and histone deacetylase 3 (HDAC3) expression levels in tissues and cells were determined by qRT-PCR. Xenograft tumor model was conducted to evaluate the effect of miR-139-3p on CRC tumor growth. ETBF treatment could promote CRC cell proliferation, invasion and migration. MiR-139-3p expression was decreased by ETBF, and its overexpression reversed the effect of ETBF on CRC cell progression. HDAC3 negatively regulated miR-139-3p expression, and its overexpression facilitated CRC cell behaviors via reducing miR-139-3p expression. Moreover, HDAC3 expression was increased by ETBF, and its knockdown also abolished ETBF-mediated CRC cell progression. Additionally, miR-139-3p overexpression could reduce CRC tumor growth in vivo. ETBF aggravated CRC proliferation and metastasis via the regulation of HDAC3/miR-139-3p axis. The discovery of ETBF/HDAC3/miR-139-3p axis may provide a new direction for CRC treatment.

LncRNA BANCR promotes oral squamous cell carcinoma progression via regulating Rab1A signaling

BACKGROUND

Long non-coding RNA BRAF-activated non-protein coding RNA plays bidirectional roles in human cancers. However, function and molecular mechanism of BRAF-activated non-protein coding RNA in oral squamous cell carcinoma still need to clarify further.

METHODS

Long non-coding RNA microarray assay, in situ hybridization staining, clinicopathological data analysis were performed to investigate expression pattern of BRAF-activated non-protein coding RNA in oral squamous cell carcinoma tissue samples. Constructing ectopically expressed BRAF-activated non-protein coding RNA in oral squamous cell carcinoma cells via plasmids or siRNAs, then changeable abilities of proliferation and motility of these cells were observed in vitro and in vivo. RNA-protein pulldown, RNA immunoprecipitation, and bioinformatics analyses were performed to explore potential pathways involved in BRAF-activated non-protein coding RNA-based regulation of malignant progression in oral squamous cell carcinoma.

RESULTS

BRAF-activated non-protein coding RNA was identified upregulated in oral squamous cell carcinoma tissue and correlated with nodal metastasis and clinical severity of patients. Overexpressed BRAF-activated non-protein coding RNA increased percentage of 5-ethynyl-2'-deoxyuridine-positive cells, viability, migration, and invasion rates of oral squamous cell carcinoma cells, while silenced BRAF-activated non-protein coding RNA could observe weakened effects in vitro. Xenograft tumor formed by BRAF-activated non-protein coding RNA-overexpressed cells had bigger volume, faster growth rates, higher weight, and more Ki67+ cells. Pulmonary metastasis induced by BRAF-activated non-protein coding RNA-silenced cells had fewer colony nodes, Ki67+ cells, and CD31+ blood vessels. Furthermore, BRAF-activated non-protein coding RNA was mainly localized in nucleus of oral squamous cell carcinoma cells and bound Ras-associated binding 1A. Silencing Ras-associated binding 1A could damage mobile ability and phosphorylation levels of nuclear factor-κB in oral squamous cell carcinoma cells induced by overexpressing BRAF-activated non-protein coding RNA. Opposite trend was also observed.

CONCLUSION

Acting as a promoter in oral squamous cell carcinoma metastasis, BRAF-activated non-protein coding RNA promotes oral squamous cell carcinoma cells proliferation and motility by regulating the BRAF-activated non-protein coding RNA/Ras-associated binding 1A complex, which activates nuclear factor-κB signaling pathway.

Hsa_circ_0040809 and hsa_circ_0000467 promote colorectal cancer cells progression and construction of a circRNA-miRNA-mRNA network

Objective: Circular RNAs (circRNAs) have been demonstrated to be closely involved in colorectal cancer (CRC) pathogenesis and metastasis. More potential biomarkers are needed to be searched for colorectal cancer (CRC) diagnosis and treatment. The objective of this study is to seek differentially expressed circRNAs (DEcircRNAs), test their roles in CRC and construct a potential competing endogenous RNA (ceRNA) network.

Methods: CircRNA microarrays were obtained from Gene Expression Omnibus, and differential expression was analyzed by R software. The relative expressions of DEcircRNAs were confirmed in CRC tissues and cell lines by qRT-PCR. MTs and Transwell experiments were performed for detecting the roles of circRNAs on CRC cell proliferation and migration, respectively. Targeted miRNAs of circRNAs and targeted mRNAs of miRNAs were predicted and screened by bioinformatics methods. A ceRNA network of DEcircRNAs was constructed by Cytoscape. To further verify the potential ceRNA network, the expressions of miRNAs and mRNAs in knockdown of DEcircRNAs CRC cells were detected by qRT-PCR.

Results: Two DEcircRNAs (hsa_circ_0040809 and hsa_circ_0000467) were identified and validated in CRC tissues and cell lines. The results of MTs and Transwell experiments showed that hsa_circ_0040809 and hsa_circ_0000467 promoted CRC proliferation and migration. Bioinformatics analysis screened 3 miRNAs (miR-326, miR-330-5p, and miR-330-3p) and 2 mRNAs (FADS1 and RUNX1), and a ceRNA network was constructed. In knockdown of hsa_circ_0040809 HCT-116 cells, the expression of miR-330-3p was significantly upregulated, while RUNX1 was significantly downregulated. In knockdown of hsa_circ_0000467 HCT-116 cells, the expressions of miR-326 and miR-330-3p were upregulated, while FADS1was downregulated.

Conclusion: We found that hsa_circ_0040809 and hsa_circ_0000467 were upregulated in CRC tissues and cell lines, and promoted CRC cell progression. A circRNA-miRNA-mRNA network based on hsa_circ_0040809 and hsa_circ_0000467 was constructed.

Hsa_circ_0001550 facilitates colorectal cancer progression through mediating microRNA-4262/nuclear casein kinase and cyclin-dependent kinase substrate 1 cascade

Background

Circular RNAs (circRNAs) play important roles in various malignancies, such as colorectal cancer (CRC). However, the function of hsa_circ_0001550 in CRC remains to be elucidated.

Methods

The expression levels of hsa_circ_0001550, microRNA (miR)‐4262, and nuclear casein kinase and cyclin‐dependent kinase substrate 1 (NUCKS1) were determined by real‐time qPCR. Cell biological behaviors were evaluated via colony formation assay, transwell assay, flow cytometry, and sphere formation assays. The target relationship was validated via dual‐luciferase reporter and RNA pull‐down assays. Protein expression was analyzed by western blot. Xenograft tumor model was adopted to evaluate hsa_circ_0001550 function in vivo.

Results

Hsa_circ_0001550 enrichment was enhanced in CRC tissue specimens and cell lines. Hsa_circ_0001550 absence hindered CRC cell proliferation, metastasis, stemness, and caused apoptosis. Hsa_circ_0001550 targeted miR‐4262, and hsa_circ_0001550 absence‐caused impacts were diminished by anti‐miR‐4262. MiR‐4262 targeted NUCKS1. Hsa_circ_0001550 had positive regulation on NUCKS1 expression. NUCKS1 overexpression overturned the influences of hsa_circ_0001550 silencingon CRC cell progression. Hsa_circ_0001550 interference notably blocked in vivo xenograft tumor growth.

Conclusion

Hsa_circ_0001550 facilitated CRC progression by binding to miR‐4262 to positively regulate NUCKS1 abundance.

MicroRNA-139, an Emerging Gate-Keeper in Various Types of Cancer

Mounting data show that MIR139 is commonly silenced in solid cancer and hematological malignancies. MIR139 acts as a critical tumor suppressor by tuning the cellular response to different types of stress, including DNA damage, and by repressing oncogenic signaling pathways. Recently, novel insights into the mechanism of MIR139 silencing in tumor cells have been described. These include epigenetic silencing, inhibition of POL-II transcriptional activity on gene regulatory elements, enhanced expression of competing RNAs and post-transcriptional regulation by the microprocessor complex. Some of these MIR139-silencing mechanisms have been demonstrated in different types of cancer, suggesting that these are more general oncogenic events. Reactivation of MIR139 expression in tumor cells causes inhibition of tumor cell expansion and induction of cell death by the repression of oncogenic mRNA targets. In this review, we discuss the different aspects of MIR139 as a tumor suppressor gene and give an overview on different transcriptional mechanisms regulating MIR139 in oncogenic stress and across different types of cancer. The novel insights into the expression regulation and the tumor-suppressing activities of MIR139 may pave the way to new treatment options for cancer.

UCK2 regulated by miR-139-3p regulates the progression of hepatocellular carcinoma cells

Objective: This study mainly explores how UCK2 impacts the progression of hepatocellular carcinoma (HCC). Methods: Mature miRNA and mRNA expression data along with the clinical data of HCC were provided by The Cancer Genome Atlas to mine differentially expressed miRNAs and mRNAs. Expression levels of UCK2 and miR-139-3p in HCC were tested through quantitative real-time PCR. How UCK2 and miR-139-3p impacted HCC cell activities were detected by Transwell, wound healing and cell proliferation approaches. Whether miR-139-3p could bind to UCK2 was detected by dual-luciferase assay. Results: This investigation found evidently high levels of UCK2 in both HCC tissue and cells and its marked association with poor prognosis. Overexpression of UCK2 could significantly promote the behaviors of HCC cells. In addition, poorly expressed miR-139-3p was inversely associated with UCK2. Dual-luciferase method also proved the association. The rescue experiment showed that miR-139-3p regulated cell behaviors in HCC through targeting UCK2. Conclusion: Highly expressed UCK2 was mediated by miR-139-3p to modulate cell behaviors in HCC. It is assumed that UCK2 is a possible target of HCC for cancer therapy purposes.

hsa_circ_0000218/hsa-miR-139-3p/SOX4 regulatory feedback circuit influences the proliferation and apoptosis of gastric cancer cells

Previous studies have reported that circular (circ)RNAs serve an important role in cancer progression, but the effects of hsa_circRNA_0000218 (circ_0000218) and its potential underlying mechanism in gastric cancer (GC) are not completely understood. In the present study, dual luciferase reporter and RNA pull down assays were performed to detect the relationship between microRNA (miR)-139-3p and circ_0000218, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect circ_0000218, miR-139-3p and SRY-box transcription factor 4 (SOX4) mRNA expression levels in GC and GES-1 cells. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry were used to detect cell proliferation and apoptosis, respectively. Western blotting was performed to assess cleaved-Caspase3 and Caspase3 expression levels in GC cells. circ_0000218 and SOX4 were highly expressed, whereas miR-139-3p was lowly expressed in GC cells. Moreover, circ_0000218 negatively regulated miR-139-3p in GC cells. circ_0000218 knockdown inhibited GC cell proliferation, promoted apoptosis and enhanced cleaved-Caspase3 expression in GC cells, whereas miR-139-3p knockdown reversed these effects. miR-139-3p overexpression inhibited proliferation and induced apoptosis in GC cells, but these effects were reversed by SOX4 overexpression. Collectively, the present study demonstrated that circ_0000218 upregulated SOX4 via downregulating miR-139-3p to promote GC progression.

Exosomal transfer of circ_0006174 contributes to the chemoresistance of doxorubicin in colorectal cancer by depending on the miR-1205/CCND2 axis

Exosomes are the mediators of intercellular signal transduction, and they have been involved in the carcinogenesis and chemoresistance of tumor cells. Herein, we intended to investigate whether circular RNA (circRNA) circ_0006174 can regulate chemoresistance of doxorubicin (DOX) in colorectal cancer via exosomes. Forty-one pairs of normal and CRC (DOX sensitive, n = 16; DOX resistant, n = 25) samples were collected. The resistant cell lines (LoVo/DOX and HCT116/DOX) were constructed by exposure of parental cell lines (LoVo and HCT116) to DOX. The detection of circ_0006174, microRNA-1205 (miR-1205), and cyclin D2 (CCND2) was performed by quantitative real-time polymerase chain reaction (qRT-PCR). Cell Counting Kit-8(CCK-8) was applied for determining the half of inhibitory concentration (IC50) of DOX and cell proliferation. The migration and invasion capacities were analyzed via transwell assay. Exosomes were extracted using ultracentrifugation. Protein levels were determined using western blot. Dual-luciferase reporter assay was used for affirming target interaction. In vivo experiment was performed by establishing xenograft models in mice. Circ_0006174 level was upregulated in DOX-resistant CRC tissues and cells. The downregulation of circ_0006174 inhibited DOX resistance, cell proliferation, migration, and invasion in DOX-resistant CRC cells. Interestingly, the abundant circ_0006174 was enriched in exosomes derived from DOX-resistant CRC cells. Furthermore, circ_0006174 could enhance DOX resistance via the exosomal intercellular transfer. Moreover, we validated the target relation of circ_0006174/miR-1205 or miR-1205/CCND2. The effect of exosomal circ_0006174 on DOX resistance was achieved by upregulating the miR-1205-mediated CCND2. In vivo, knockdown of circ_0006174 also enhanced tumor sensitivity to DOX by targeting miR-1205/CCND2 axis. Altogether, these findings unraveled that circ_0006174-enriched exosomes elevated DOX chemoresistance in CRC by the miR-1205/CCND2 axis. The exosomal circ_0006174 can be used as an available biomarker for the diagnosis of chemoresistance in CRC.

The Dual Role of Circular RNAs as miRNA Sponges in Breast Cancer and Colon Cancer

Breast cancer (BC) and colon cancer (CRC) are the two most deadly cancers in the world. These cancers partly share the same genetic background and are partially regulated by the same genes. The outcomes of traditional chemoradiotherapy and surgery remain suboptimal, with high postoperative recurrence and a low survival rate. It is, therefore, urgent to innovate and improve the existing treatment measures. Many studies primarily reported that the microRNA (miRNA) sponge functions of circular RNA (circRNA) in BC and CRC have an indirect relationship between the circRNA–miRNA axis and malignant behaviors. With a covalent ring structure, circRNAs can regulate the expression of target genes in multiple ways, especially by acting as miRNA sponges. Therefore, this review mainly focuses on the roles of circRNAs as miRNA sponges in BC and CRC based on studies over the last three years, thus providing a theoretical reference for finding new therapeutic targets in the future.

A circular RNA derived from FAT atypical cadherin 3 promotes lung cancer progression via forming a regulatory loop with oncogenic ELAV like RNA binding protein 1

Circular RNA (circRNA) is a covalently closed endogenous RNA that participates in disease progression. However, its role in lung cancer is largely undetermined. In the present study, we found an oncogenic circRNA in lung cancer, FAT atypical cadherin 3 (FAT3) circRNA (circ-FAT3) was remarkably upregulated in lung cancer in comparison to paired normal tissues. High circ-FAT3 was closely linked to larger tumor size, lymph node metastasis, later clinical stage as well as dismal outcome. Stable knockdown of circ-FAT3 inhibited cell proliferation and metastasis both in vitro and in vivo. RNA binding protein ELAV like RNA binding protein 1 (HuR) was found to bind to introns flanking circ-FAT3, promoting the cyclization and generation of circ-FAT3. Further, circ-FAT3 was able to sponge miR-136-5p by acting as a competing endogenous RNA (ceRNA), alleviating the repressive effect of miR-136-5p on HuR mRNA at the transcriptional and post-transcriptional levels. Moreover, circ-FAT3 expression in lung cancer tissues was strongly positively and negatively correlated with HuR and miR-136-5p expression, respectively. Overall, our data reveal the previously uncharacterized regulatory loop of circ-FAT3/miR-136-5p/HuR in lung cancer, and provide novel evidence for the importance of circRNA as a ceRNA in tumorigenesis.

CircRNAs: a family number of miRNA regulatory transcriptome in laryngeal carcinoma

Laryngeal carcinoma (LC) is a common head and neck cancer, which is the result of mutational changes due to gene dysregulation and etiological factors such as tobacco and smoking. A large number of patients received a poor prognosis due to diagnosis at an advanced stage. This highlights the need for definitive, early, and efficient diagnoses. With rapid development of high‐throughput sequencing, circular RNA (circRNA) has been reported to play a pivotal role in cancer. CircRNA functions as a microRNA (miRNA) sponge in the regulation of mRNA expression, forming circRNA‐miRNA regulatory axis. In this review, we described the axis in LC. The result indicated that CDR1as, hsa_circ_0042823, hsa_circ_0023028, circPARD3, hsa_circ_103862, hsa_circ_0000218, circMYLK, circCORO1C, hsa_circ_100290, circ‐CCND1, hsa_circ_0057481, circFLAN, and circRASSF2 expressed higher in LC, whereas, hsa_circ_0036722 and hsa_circ_0042666 expressed lower. The circRNAs regulated the target genes by sponging miRNAs and contributed to the pathogenesis of LC.

The effective function of circular RNA in colorectal cancer

Colorectal cancer (CRC) is the 3rd most common type of cancer worldwide. Late detection plays role in one-third of annual mortality due to CRC. Therefore, it is essential to find a precise and optimal diagnostic and prognostic biomarker for the identification and treatment of colorectal tumorigenesis. Covalently closed, circular RNAs (circRNAs) are a class of non-coding RNAs, which can have the same function as microRNA (miRNA) sponges, as regulators of splicing and transcription, and as interactors with RNA-binding proteins (RBPs). Therefore, circRNAs have been investigated as specific targets for diagnostic and prognostic detection of CRC. These non-coding RNAs are also linked to metastasis, proliferation, differentiation, migration, angiogenesis, apoptosis, and drug resistance, illustrating the importance of understanding their involvement in the molecular mechanisms of development and progression of CRC. In this review, we present a detailed summary of recent findings relating to the dysregulation of circRNAs and their potential role in CRC.

Circ_0087862 promotes the progression of colorectal cancer by sponging miR-142-3p and up-regulating BACH1 expression

Circular RNAs (circRNAs) feature prominently in regulating the malignant biological behaviors of colorectal cancer (CRC), including cell viability, cell cycle progression, apoptosis, migration, invasion, and so on. This study is performed to probe into the biological function and molecular mechanism of circ_0087862 in CRC. The expression profile of GSE138589 was available from Gene Expression Omnibus (GEO), and the differentially expressed circRNAs were analyzed by GEO2R. The expression of circ_0087862, miR-142-3p, and BACH1 mRNA in CRC tissues and cells was measured by qRT-PCR. CCK-8 assay was employed to determine the proliferation of CRC cells. Scratch wound healing and transwell assays were used to examine the migration and invasion of CRC cells. The targeting relationships between circ_0087862 and miR-142-3p, and between miR-142-3p and BACH1 3'UTR were verified by dual-luciferase reporter gene assay and RIP assay. BACH1 protein expression was probed by western blot. Circ_0087862 was highly expressed in CRC tissues and cell lines. Knocking down circ_0087862 significantly restrained the multiplication, migration and invasion of CRC cells. miR-142-3p inhibition weakened the impact of circ_0087862 knockdown on CRC cells. Circ_0087862 regulated BACH1 expressions by targeting miR-142-3p. Circ_0087862 regulates BACH1 expressions through sponging miR-142-3p, and promotes the proliferation, migration, and invasion of CRC cells.

Roles of circular RNAs in colorectal cancer

Colorectal cancer (CRC) is one of the most common types of malignant cancer worldwide and poses a significant burden on both the individual and healthcare systems. Despite advances in treatment options, advanced-stage CRC has a high mortality rate due to its heterogeneity, metastatic potential and/or delay in diagnosis. In recent years, an increasing number of studies have indicated that circular RNAs (circRNAs) serve important roles in several types of cancer, including CRC. Recent studies have revealed that circRNAs are aberrantly expressed in CRC tissues and function as oncogenic or tumor suppressive regulators of CRC carcinogenesis and development. Numerous circRNAs have been associated with the clinicopathological features of patients with CRC and have been considered as potential biomarkers for the diagnosis and prognosis of CRC, as well as targets for treatment. However, a deeper understanding of their potential function is required. In the present review, the current body of knowledge on the biogenesis and functions of CRC-associated circRNAs, and their potential value in clinical applications, such as in CRC diagnosis, prognosis and treatment, is discussed and summarized.

Circular RNA circEGFR regulates tumor progression via the miR-106a-5p/DDX5 axis in colorectal cancer

Recently, an increasing number of studies have reported that dysregulation of circular RNA (circRNA) expression plays critical roles in the progression of several cancers, including colorectal cancer (CRC). However, the detailed molecular mechanisms of circRNAs involvement in CRC remain largely unknown. Here, we confirmed that the level of circEGFR was significantly increased in CRC tissues compared to matched adjacent non-tumor tissues, and a high level of circEGFR was correlated with poor clinicopathological characteristics and poor prognosis in patients with CRC. Moreover, increased circEGFR expression promoted CRC cell proliferation, migration, and invasion in vitro. Mechanistically, circEGFR acted as a ceRNA for miR-106a-5p to relieve the repressive effect of miR-106a-5p on DDX5 mRNA. Moreover, circEGFR enhanced DDX5 expression, thereby upregulating p-AKT levels. Together, these findings showed that circEGFR promoted CRC cell proliferation, migration, and invasion through the miR-106a-5p/DDX5/AKT axis, and may serve as a promising diagnostic marker and therapeutic target for CRC patients.

Oncogenic Functions and Clinical Significance of Circular RNAs in Colorectal Cancer

Colorectal cancer (CRC) is ranked as the second most commonly diagnosed disease in females and the third in males worldwide. Therefore, the finding of new more reliable biomarkers for early diagnosis, for prediction of metastasis, and resistance to conventional therapies is an important challenge in overcoming the disease. The current review presents circular RNAs (circRNAs) with their unique features as potential prognostic and diagnostic biomarkers in CRC. The review highlights the mechanism of action and the role of circRNAs with oncogenic functions in the CRC as well as the association between their expression and clinicopathological characteristics of CRC patients. The comprehension of the role of oncogenic circRNAs in CRC pathogenesis is growing rapidly and the next step is using them as suitable new drug targets in the personalized treatment of CRC patients.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Function of circular RNAs in the pathogenesis of colorectal cancer

Circular RNAs (circRNAs) comprise a group of noncoding RNAs with a circular conformation being constructed by either classic spliceosome-mediated or lariat-kind of splicing. They have tissue and temporal specificity and are involved in different biological functions. A vast body of literature has demonstrated critical roles of circRNAs in the formation or progression of neoplasms. Hsa_circ_0066631, hsa_circ_0082096, ciRS-7, circMAT2B, circ_052666, circMBOAT2, circPACRGL and circ_0128846 are among up-regulated circRNAs in CRC. Instead, expression levels of circTADA2A, circ_022743, circ_004452, circ-FBXW7, circ0106714, circFNDC3B and circ_cse1 have been decreased in CRC samples. Finally, expression levels of circRNA-100876, hsa_circ_0002320, circNOL10, circ_0056618, circ_0060745, circ-0004277, hsa_circRNA_102958, circPPP1R12A, hsa_circ_0007534, circ_0079993 and hsa_circ_0005075 can be used for prediction of clinical outcome of patients CRC.

Circular RNA PTK2 Accelerates Cell Proliferation and Inhibits Cell Apoptosis in Gastric Carcinoma via miR-139-3p

BACKGROUND

Gastric carcinoma (GC) is one of the most common malignant tumors. Although increasing studies have indicated that circular RNAs function as ideal biomarkers for multiple cancers, only a few researches elucidated the correlation between circular RNA PTK2 (circPTK2) and human cancers.

AIM

To further explore the expression status, biological function, and regulatory mechanism of circPTK2 in GC.

METHODS

Bioinformatics analysis and function or mechanism experiments including RT-qPCR, flow cytometry, Western blot, luciferase reporter assay, and xenografts assays were applied to investigate the function of circPTK2 and miR-139-3p.

RESULTS

High expression of circPTK2 was presented in GC tissues and cells. The circPTK2 knockdown notably suppressed cell proliferation and promoted cell apoptosis in GC. In mechanism, circPTK2 served as a sponge of miR-139-3p. Inhibition of miR-139-3p could reverse circPTK2 silence-mediated effects on GC cell proliferation and apoptosis. Furthermore, the xenograft tumor model was established to investigate the role of circPTK2 in GC tumor growth. Experimental results delineated that the reduction in tumor growth in response to circPTK2 knockdown was partly recovered by miR-139-3p inhibitor.

CONCLUSIONS

CircPTK2 promotes GC development by sponging miR-139-3p, which may function as an effective gene target for managing GC.

Circular RNA circ_0000372 contributes to the proliferation, migration and invasion of colorectal cancer by elevating IL6 expression via sponging miR-495

Circular RNAs are thought to play a vital function in the progression of various cancers, including colorectal cancer (CRC). However, the biological function and mechanism of circ_0000372 in CRC are still not clear. The expression of circ_0000372 and microRNA (miR)-495 was examined by quantitative real-time PCR. Cell proliferation was evaluated using cell counting kit 8 and colony formation assays. Further, cell migration and invasion were assessed using transwell assay. Additionally, western blot analysis was used to detect the expression of proteins associated with proliferation, metastasis, Janus kinase 2 (JAK2)/signal transducers and activators of transcription (STAT3) signaling pathway and interleukin 6 (IL6). Dual-luciferase reporter assay and RNA immunoprecipitation assay were employed to verify the interaction between miR-495 and circ_0000372 or IL6. Furthermore, the effect of circ_0000372 on CRC tumor growth in vivo was explored using the mice xenograft models. Circ_0000372 was markedly upregulated in CRC, and its high expression was associated with the poor prognosis of CRC patients. Silenced circ_0000372 was able to suppress CRC cell proliferation, migration and invasion in vitro and CRC tumor growth in vivo. Bioinformatics prediction and experimental verification proposed that circ_0000372 could sponge miR-495, and miR-495 could target IL6. Besides, the JAK2/STAT3 signaling pathway activation could be regulated by circ_0000372, miR-495 and IL6. Rescue assay results confirmed that the inhibition effect of circ_0000372 knockdown on the proliferation and metastasis of CRC could be reversed by miR-495 inhibitor or IL6 overexpression. In short, we concluded that circ_0000372 promoted CRC progression by regulating the miR-495/IL6 axis, suggesting that circ_0000372 could be used as a new prognostic biomarker and therapeutic target for CRC.

Bioinformatic analysis reveals an exosomal miRNA-mRNA network in colorectal cancer

BACKGROUND

Exosomes play important roles in angiogenesis, drug resistance, and metastasis of colorectal cancer (CRC), but the underlying mechanism has seldom been reported. Herein, our study aimed to reveal an exosomal miRNA-mRNA network involved in CRC by performing bioinformatical analysis.

METHODS

The mRNA and miRNA data of colon adenocarcinoma and rectal adenocarcinoma were downloaded from The Cancer Genome Atlas (TCGA) database, and exosomal miRNAs data were downloaded from the GEO dataset GSE39833. The differential expression analysis was performed using "limma" and "edgeR". Target mRNAs of miRNAs were predicted using FunRich 3.1.3, miRNAtap and multiMiR. The candidate mRNAs and exosomal miRNAs were obtained by intersecting two groups of differentially expressed miRNAs and intersection of the differential expressed mRNAs and the target mRNAs, respectively. Key mRNAs and exosomal miRNAs were identified by the least absolute shrinkage and selection operator regression analysis, and used to construct the exosomal miRNA-mRNA network. The network verified was by receiver operating characteristic curve, GEPIA and LinkedOmics. Functional enrichment analysis was also performed for studied miRNAs and mRNAs.

RESULTS

A total of 6568 differentially expressed mRNAs and 531 differentially expressed miRNAs from TCGA data, and 166 differentially expressed exosomal miRNAs in GSE39833 dataset were identified. Next, 16 key mRNAs and five key exosomal miRNAs were identified from the 5284 candidate mRNAs and 61 candidate exosomal miRNAs, respectively. The exosomal miRNA-mRNA network with high connectivity contained 13 hub mRNAs (CBFB, CDH3, ETV4, FOXQ1, FUT1, GCNT2, GRIN2D, KIAA1549, KRT80, LZTS1, SLC39A10, SPTBN2, and ZSWIM4) and five hub exosomal miRNAs (hsa-miR-126, hsa-miR-139, hsa-miR-141, hsa-miR-29c, and hsa-miR-423). The functional annotation revealed that these hub mRNAs were mainly involved in the regulation of B cell receptor signaling pathway and glycosphingolipid biosynthesis related pathways. All hub mRNAs and hub exosomal miRNAs exhibited high diagnosis value for CRC. Furthermore, the association of the hub mRNAs with overall survival, stages, and MSI phenotype of CRC revealed their important roles in CRC progression.

CONCLUSION

This study constructed an exosomal miRNA-mRNA network which may play crucial roles in the carcinogenesis and progression of CRC, thus providing potential diagnostic biomarkers and therapeutic targets for CRC.

Comprehensive landscape and future perspectives of circular RNAs in colorectal cancer

Colorectal cancer (CRC) is a common hereditary tumor that is often fatal. Its pathogenesis involves multiple genes, including circular RNAs (circRNAs). Notably, circRNAs constitute a new class of noncoding RNAs (ncRNAs) with a covalently closed loop structure and have been characterized as stable, conserved molecules that are abundantly expressed in tissue/development-specific patterns in eukaryotes. Based on accumulating evidence, circRNAs are aberrantly expressed in CRC tissues, cells, exosomes, and blood from patients with CRC. Moreover, numerous circRNAs have been identified as either oncogenes or tumor suppressors that mediate tumorigenesis, metastasis and chemoradiation resistance in CRC. Although the regulatory mechanisms of circRNA biogenesis and functions remain fairly elusive, interesting results have been obtained in studies investigating CRC. In particular, the expression of circRNAs in CRC is comprehensively modulated by multiple factors, such as splicing factors, transcription factors, specific enzymes and cis-acting elements. More importantly, circRNAs exert pivotal effects on CRC through various mechanisms, including acting as miRNA sponges or decoys, interacting with RNA binding proteins, and even translating functional peptides. Finally, circRNAs may serve as promising diagnostic and prognostic biomarkers and potential therapeutic targets in the clinical practice of CRC. In this review, we discuss the dysregulation, functions and clinical significance of circRNAs in CRC and further discuss the molecular mechanisms by which circRNAs exert their functions and how their expression is regulated. Based on this review, we hope to reveal the functions of circRNAs in the initiation and progression of cancer and highlight the future perspectives on strategies targeting circRNAs in cancer research.

LncRNA PCAT6 regulates the progression of pituitary adenomas by regulating the miR-139-3p/BRD4 axis

BACKGROUND

Dysregulated lncRNA PCAT6 was discovered in many cancers excluding pituitary adenomas (PA). Therefore, we explored the role of PCAT6 in PA in this research.

METHODS

Abnormally expressed miRNAs were analyzed by bioinformatics and RT-qPCR. The target and regulator of miR-139-3p were determined by bioinformatics, dual-luciferase reporter assay, or RIP. The correlation among PCAT6, miR-139-3p, and BRD4 was further analyzed. The viability, apoptosis, cell cycle distribution of PA cells, as well as their ability to invade, migrate, and proliferate, were tested after transfection through CCK-8, flow cytometry, transwell, wound healing, and colony formation assays. After construction of transplanted-tumor model in nude mice, cell apoptosis in the tumor was detected by TUNEL. The expressions of PCAT6, BRD4, miR-139-3p, and apoptosis-related factors in PA tissues, cells, or tumor tissues were detected by RT-qPCR, Western blot, or IHC.

RESULTS

PCAT6 and BRD4 were high-expressed but miR-139-3p was low-expressed in PA. Both the 3'-untranslated regions of PCAT6 and BRD4 mRNAs were demonstrated to contain a potential binding site for miR-139-3p. PCAT6 was positively correlated to BRD4, and miR-139-3p was negatively correlated to PCAT6 and BRD4. MiR-139-3p mimic, shPCAT6 and siBRD4 inhibited the viability, migration, invasion, and proliferation of PA cells while inducing apoptosis. MiR-139-3p mimic and shPCAT6 inhibited the cell cycle progression of PA cells, decreased the weight and volume of the xenotransplanted tumor, and reduced the levels of Bcl-2 and BRD4 while enhancing the levels of Bax, miR-139-3p, and Cleaved caspase-3. MiR-139-3p inhibitor caused the opposite effect of miR-139-3p mimic and further reversed the effect of shPCAT6 on on PA cells.

CONCLUSION

PCAT6 regulated the progression of PA via modulating the miR-139-3p/BRD4 axis, which might provide a novel biomarker for the prevention, diagnosis, and treatment of PA.

LncRNA CTBP1-AS2 Facilitates Gastric Cancer Progression via Regulating the miR-139-3p/MMP11 Axis

Background

This study aimed at probing into the effect of long non-coding RNA (lncRNA) C-terminal binding protein 1 antisense RNA 2 (CTBP1-AS2) on gastric cancer (GC) cell proliferation and apoptosis, and its regulatory function on miR-139-3p and MMP11.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to examine the expressions of CTBP1-AS2, miR-139-3p and MMP11 mRNA in GC cell lines and clinical specimens. Cell counting kit-8 (CCK-8) assay, flow cytometry and EdU assay were conducted to examine the effects of CTBP1-AS2 and miR-139-3p on GC cell proliferation and apoptosis. Western blot was applied for detecting the expressions of Bax, Bcl-2 and MMP11. A lung metastasis mouse model was used to evaluate metastasis of GC cells in vivo. Bioinformatics, dual-luciferase report assay, RIP and RNA pull-down assays were utilized to validate the targeted relationship between CTBP1-AS2 and miR-139-3p as well as the targeting relationship between miR-139-3p and MMP11.

Results

CTBP1-AS2 was highly expressed in GC, and its high expression was strongly associated with increased TNM stage, increased tumor size and low degree of differentiation of the tumor tissues. Meanwhile, CTBP1-AS2 promoted GC cell proliferation, metastasis and suppressed apoptosis, while miR-139-3p could weaken these effects. In addition, CTBP1-AS2 was identified as a molecular sponge for miR-139-3p, and MMP11 was verified as a target gene of CTBP1-AS2. CTBP1-AS2 could increase the expression of MMP11 via repressing miR-139-3p.

Conclusion

CTBP1-AS2 promotes GC cells and inhibits apoptosis by regulating the miR-139-3p/MMP11 molecular axis.

CircRNA circUGGT2 Contributes to Hepatocellular Carcinoma Development via Regulation of the miR-526b-5p/RAB1A Axis

Background

Hepatocellular carcinoma (HCC) is a common malignant tumor in the world. Circular RNA hsa_circ_0008274 (circUGGT2) is reported to be upregulated in HCC tissues. Notwithstanding, the role and regulatory mechanism of circUGGT2 in HCC are indistinct.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was implemented to examine the levels of circUGGT2, microRNA (miR)-526b-5p, and ras-related protein Rab-1A (RAB1A) mRNA in HCC tissues and cells. Cell proliferation and colony formation were assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) or colony formation assays. The levels of cyclin D1, proliferating cell nuclear antigen (PCNA), and RAB1A were detected with Western blotting. Cell cycle progression, migration, and invasion were evaluated by using flow cytometry or transwell assays. The relationship between circUGGT2 or RAB1A and miR-526b-5p was verified via dual-luciferase reporter and/or RNA pull-down assays. Xenograft assay was executed to confirm the role of circUGGT2 in vivo.

Results

We observed that circUGGT2 and RAB1A were upregulated while miR-526b-5p was downregulated in HCC tissues and cells. CircUGGT2 silencing suppressed tumor growth in vivo and curbed proliferation, colony formation, cell cycle progression, migration, and invasion of HCC cells in vitro. Mechanically, circUGGT2 regulated RAB1A expression via competitively binding to miR-526b-5p. Also, the inhibitory influence of circUGGT2 silencing on the malignancy of HCC cells was overturned by miR-526b-5p inhibitor. Furthermore, RAB1A overexpression reversed the suppressive influence of miR-526b-5p mimic on the malignancy of HCC cells.

Conclusion

CircUGGT2 silencing inhibited HCC development via modulating the miR-526b-5p/RAB1A axis, providing a possible target for HCC treatment.

Circular RNAs in gastrointestinal cancer: Current knowledge, biomarkers and targeted therapy (Review)

Circular RNAs (circRNAs) are a type of endogenous non‑coding RNAs that are connected at the 3' and 5' ends by exon or intron cyclization, which forms a covalently closed loop. They are stable, well conserved, exhibit specific expression in mammalian cells and can function as microRNA (miRNA or miR) sponges to regulate the target genes of miRNAs, which influences biological processes. Such as tumor proliferation, invasion, metastasis, apoptosis and tumor stage. circRNAs represent promising candidates for clinical diagnosis and treatment. In the present review, the biogenesis, classification and functions of circRNAs in tumors are briefly summarized and discussed. In addition, the participation of circRNAs in signal transduction pathways regulating gastrointestinal cancer cellular functions is highlighted.

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

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

CircRNA Circ_0001721 Promotes the Progression of Osteosarcoma Through miR-372-3p/MAPK7 Axis

Background

Osteosarcoma (OS) is the most common bone tumor. Many studies have reported that circular RNAs (circRNAs) play an important role in the development of a variety of human cancers. However, the underlying mechanism of circ_0001721 in regulating osteosarcoma progression remains unknown.

Materials and Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the levels of circ_0001721, miR-372-3p, and mitogen-activated protein kinase 7 (MAPK7) in osteosarcoma tissues and cells. Besides, glycolysis was investigated by glucose consumption, lactate production and hexokinase II (HK2) protein level. Cell proliferation and apoptosis were determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and flow cytometry, separately. Cell migration and invasion were determined by transwell assay. Moreover, the protein levels of HK2 and epithelial-to-mesenchymal transition (EMT) markers were determined by Western blot analysis. The relationship between miR-372-3p and circ_0001721 or MAPK7 was predicated by starbase v3.0 and confirmed by dual-luciferase reporter assay or RNA binding protein immunoprecipitation (RIP) assay. Murine xenograft model was established to investigate the role of circ_0001721 in vivo.

Results

The levels of circ_0001721 and MAPK7 were upregulated in osteosarcoma tissues and cells, while miR-372-3p was downregulated. Knockdown of circ_0001721 inhibited glycolysis, cell proliferation, cell migration, invasion and epithelial-to-mesenchymal transition (EMT), and promoted apoptosis. Circ_0001721 was validated as a sponge of miR-372-3p and mediated glycolysis, cell proliferation, apoptosis, migration, invasion, and EMT of osteosarcoma cells through miR-372-3p. MAPK7 was a target of miR-372-3p and overexpression of MAPK7 attenuated anti-cancer role of miR-372-3p in OS cells. Further studies revealed that circ_0001721 regulates MAPK7 expression via sponging miR-372-3-p. Finally, knockdown of circ_0001721 inhibited tumor progression in vivo.

Conclusion

Circ_0001721 promoted osteosarcoma development through the miR-372-3p/MAPK7 axis.

Circular RNAs: A New Piece in the Colorectal Cancer Puzzle

Colorectal cancer (CRC) is the third most fatal type of malignancy, worldwide. Despite the advances accomplished in the elucidation of its molecular base and the existing CRC biomarkers introduced in the clinical practice, additional research is required. Circular RNAs (circRNAs) constitute a new RNA type, formed by back-splicing of primary transcripts. They have been discovered during the 1970s but were characterized as by-products of aberrant splicing. However, the modern high-throughput approaches uncovered their widespread expression; therefore, several questions were raised regarding their potential biological roles. During the last years, great progress has been achieved in the elucidation of their functions: circRNAs can act as microRNA sponges, transcription regulators, and interfere with splicing, as well. Furthermore, they are heavily involved in various human pathological states, including cancer, and could serve as diagnostic and prognostic biomarkers in several diseases. Particularly in CRC, aberrant expression of circRNAs has been observed. More specifically, these molecules either inhibit or promote colorectal carcinogenesis by regulating different molecules and signaling pathways. The present review discusses the characteristics and functions of circRNA, prior to analyzing the multifaceted role of these molecules in CRC and their potential value as biomarkers and therapeutic targets.

Circular RNA circLPAR3 Facilitates Esophageal Squamous Cell Carcinoma Progression Through Upregulating HMGB1 via Sponging miR-375/miR-433

Background

Circular RNAs (circRNAs) are critical regulators of many diseases, including esophageal squamous cell carcinoma (ESCC). A recent study has shown that circLPAR3 is highly expressed in ESCC, but its role and mechanism in ESCC are still unclear.

Methods

The expression levels of circLPAR3, microRNA-375 (miR-375), miR-433, and high-mobility group box 1 (HMGB1) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The circular characteristic and localization of circLPAR3 were identified by Ribonuclease R (RNase R) and nuclear-cytoplasmic separation assay. Also, cell proliferation was detected by cell counting kit-8 (CCK-8) and colony formation assays. Cell migration and invasion were tested by transwell assay. Moreover, Western blot (WB) analysis was used to test the levels of proliferation and metastasis-related protein, as well as the HMGB1 protein. Besides, mice xenograft models were constructed to assess the effect of circLPAR3 on ESCC tumor growth in vivo. In addition, dual-luciferase reporter and RNA pull-down assays were used to identify the mechanism of circLPAR3.

Results

CircLPAR3 was upregulated in ESCC tissues and cells, and its high expression was related to the poor prognosis of ESCC patients. CircLPAR3 was a stable cyclic transcript, mainly located in the cytoplasm, and its knockdown hindered the proliferation, migration and invasion of ESCC cells and inhibited ESCC tumor growth in vivo. MiR-375/miR-433 could be sponged by circLPAR3, and their inhibitors could reverse the suppression effect of silenced circLPAR3 on ESCC progression. HMGB1 could be targeted by miR-375/miR-433, and its overexpression also could invert the inhibition effect of circLPAR3 knockdown on ESCC progression.

Conclusion

CircLPAR3 might play an oncogenic role in ESCC through sponging miR-375/miR-433 to promote HMGB1 expression, which might provide a theoretical basis for circLPAR3 to become a biomarker for ESCC therapy.

Circ_0000218 plays a carcinogenic role in laryngeal cancer through regulating microRNA-139-3p/Smad3 axis

BACKGROUND

Laryngeal squamous cell carcinoma (LSCC) accounts for about 85%-90% of all cases of laryngeal cancer. So far, the role and molecular mechanism of circular RNA 0,000,218 (circ_0000218)/microRNA (miR)-139-3p in laryngeal cancer are not clear. The present study aimed to investigate the role and regulatory mechanism of circ_0000218/miR-139-3p in laryngeal cancerin vitro and in vivo.

METHODS

quantitative real time polymerase chain reaction (qRT-PCR) was used to detect the expression of circ_0000218/miR-139-3p in LSCC cells. Dual luciferase reporter assay and RNA immunoprecipitation (RIP) assay were used to confirm binding sites between miR-139-3p and smad family member 3 (Smad3), and circ_0000218 and miR-139-3p. Cell Counting Kit-8 (CCK-8) and cell apoptosis analysis were used to detect cell viability and apoptosis. Xenograft experiment was performed to show in vivo effect of circ_0000218/miR-139-3p on the growth of LSCC.

RESULTS

Circ_0000218 was highly expressed in LSCC cells. miR-139-3p, lower expressed in LSCC cells, was negatively regulated by circ_0000218 in LSCC cells. Besides, the findings suggested that circ_0000218 silencing inhibited the LSCC cell viability and promoted apoptosis by negatively regulating miR-139-3p expression. Furthermore, the data indicated that miR-139-3p inhibited the viability of LSCC cells and promoted apoptosis, and these effects were reversed by Smad3 over-expression. In addition, the in vivo effects of circ_0000218/miR-139-3p on LSCC were consistent with the in vitro study.

CONCLUSIONS

circ_0000218 inhibition inhibited the growth of LSCC by targeting miR-139-3p/Smad3 axis. Our present study provided a new target for laryngeal cancer treatment.

Circular RNA is a popular molecule in tumors of the digestive system (Review)

Most tumors of the digestive system, including esophageal, gastric, liver and colorectal cancer, are malignant tumors that are associated with rates of high morbidity and mortality. The lack of effective methods for early diagnosis is an important cause of poor prognosis for these malignancies. Circular RNAs (circRNAs) belong to a family of endogenous, covalently closed non‑coding RNAs that are characterized as having no 5' cap structures or 3' poly‑A tails. Shortly following discovery, circRNAs were considered to be a product of mis‑splicing and have no significant biological function. However, in recent years, accumulating evidence is demonstrating that they serve key roles in tumorigenesis and have the potential to serve as diagnostic markers. The present article summarizes the biogenesis and function of circRNAs and reviews their role in seven common types of tumor of the digestive system whilst exploring their potential as tumor markers and the significant roles they can serve in the digestive system, in addition to providing a referencing point for future studies of digestive system malignancies.

The function and mechanism of circular RNAs in gastrointestinal tumours

Gastrointestinal tumours are tumours that originate in the digestive tract and have extremely high morbidity and mortality. The main categories include: oesophageal, gastric, and colorectal cancers. Circular RNAs are a new class of non‐coding RNAs with a covalent closed‐loop structure without a 5’ cap or a 3’ poly A tail, which can encode a small amount of polypeptide. Recent studies have shown that circRNAs are involved in multiple biological processes during the development of gastrointestinal tumours including proliferation, invasion and metastasis, radio‐ and chemoresistance, and inflammatory responses. Also, the clinical and pathological characteristics of the patient, such as staging and lymph node metastasis, are closely associated with the expression level of circRNAs. Further investigation of the function and the role of circRNAs in the development of gastrointestinal tumours will provide new directions for its clinical diagnosis and treatment.

Circ_100565 promotes proliferation, migration and invasion in non-small cell lung cancer through upregulating HMGA2 via sponging miR-506-3p

Background

Circular RNAs (circRNAs) play a vital role in the development of various cancers. Circ_100565 was found to be a highly expressed circRNA in non-small cell lung cancer (NSCLC) tissues screened by microarray profiles of circRNAs. However, the role of circ_100565 in NSCLC still remains unknown.

Methods

Microarray analysis was used to screen for differentially expressed circRNAs in NSCLC tissues. The expression levels of circ_100565, microRNA-506-3p (miR-506-3p) and high mobility group AT-hook 2 (HMGA2) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was detected by cell counting kit-8 (CCK-8) and colony formation assays. Transwell assay was used to determine the migration and invasion of cells. Besides, Western blot (WB) analysis was performed to assess the levels of proliferation and metastasis-related proteins and HMGA2 protein. Moreover, animal experiments were used to confirm the effect of circ_100565 on NSCLC tumor growth in vivo. In addition, the interaction between miR-506-3p and circ_100565 or HMGA2 was confirmed by dual-luciferase reporter, RNA immunoprecipitation (RIP) assay or biotin-labeled pull-down assay.

Results

Circ_100565 was upregulated in NSCLC, and its high expression was positively associated with the poor overall survival of NSCLC patients. Silencing of circ_100565 suppressed the proliferation, migration and invasion of NSCLC cells in vitro and reduced the tumor growth of NSCLC in vivo. Circ_100565 could sponge miR-506-3p, and miR-506-3p could target HMGA2. Moreover, miR-506-3p inhibitor or HMGA2 overexpression could reverse the inhibition effect of circ_100565 knockdown on NSCLC progression.

Conclusion

Circ_100565 increased HMGA2 expression to promote proliferation, migration and invasion in NSCLC via absorbing miR-506-3p. Our findings provided a new biomarker for NSCLC therapy.

CircFAT1 Suppresses Colorectal Cancer Development Through Regulating miR-520b/UHRF1 Axis or miR-302c-3p/UHRF1 Axis

Background: It was reported that circular RNAs (circRNAs) exerted important functions in various human cancers. However, the function of circFAT1 was less known. The purpose of this study was to reveal the functional mechanism of circFAT1 in colorectal cancer (CRC). Materials and Methods: Quantitative real-time polymerase chain reaction and Western blot assay were used to detect the levels of genes. Cell proliferation ability was assessed by 3-(4, 5-dimethyl-2-thiazoyl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry was used to investigate cell apoptosis rate. The glucose consumption and lactate production were determined using related kits. Furthermore, the interaction between circFAT1 or ubiquitin-like PHD and RING finger domain-containing protein 1 (UHRF1) and miR-520b or miR-302c-3p was predicted by starbase3.0, and then confirmed by the dual-luciferase reporter assay. Besides, xenograft experiment was performed to analyze the effect of circFAT1 on tumor growth in vivo. Results: The levels of circFAT1 and UHRF1 were increased, as well as the levels of miR-520b and miR-302c-3p were decreased in CRC tissues and cells. CircFAT1 knockdown suppressed cell proliferation, cycle, and glycolysis as well as induced apoptosis. Interestingly, circFAT1 was a sponge of miR-520b and miR-302c-3p, and miR-520b and miR-302c-3p could target UHRF1. Both miR-520b overexpression and miR-302c-3p overexpression inhibited CRC cell growth. Furthermore, both miR-520b knockdown and miR-302c-3p depletion weakened the effect of circFAT1 knockdown on the growth of CRC cells. Besides, circFAT1 depletion repressed tumor growth in vivo. Conclusion: The authors' findings suggested that circFAT1 upregulated UHRF1 to affect CRC cell proliferation, apoptosis, and glycolysis through targeting miR-520b and miR-302c-3p, providing theoretical basis for the treatment of CRC.