Hsa_circ_0058124 promotes papillary thyroid cancer tumorigenesis and invasiveness through the NOTCH3/GATAD2A axis

Downregulation of sperm-associated antigen 5 inhibits melanoma progression by regulating forkhead box protein M1/A disintegrin and metalloproteinase 17/NOTCH1 signaling

Sperm-associated antigen 5 (SPAG5) has been identified as a driver in several type of cancers. In this study, we aimed to reveal the role of SPAG5 in melanoma and clarify whether FOXM1 (forkhead box protein M1) /ADAM17 (A disintegrin and metalloproteinase 17) /NOTCH1 signaling was involved. The expression of SPAG5 in malignant melanoma (MM) tissues and matched normal tissues was detected using qRT-PCR, immunohistochemistry and Western blotting. Cell viability was tested using CCK-8 (Cell Count Kit-8), colony formation and EdU staining. Cell migration and epithelial to mesenchymal transition (EMT) were measured using transwell chambers and immunofluorescent staining. Cell cycle distribution and tumorigenesis were assessed by flow cytometry and in vivo tumor-bearing experiments, respectively. The results demonstrated that the expression of SPAG5 was increased in MM tissues and cells. Downregulation of SPAG5 inhibited cell viability, migration, invasion and EMT, and induced a G1-phase arrest. In addition, downregulation of SPAG5 decreased the expression of FOXM1, thereafter inhibiting the expression of ADAM17, NOTCH1 and HES1. Furthermore, deletion of SPAG5 expression decreased the tumorigenesis of MM A375 cells. In conclusion, this study demonstrated that SPAG5 was overexpressed in MM. Downregulation of SPAG5 repressed MM cell growth and EMT, which might be induced by inactivation of the FOXM1/ADAM17/NOTCH1 signaling.

lncRNA ACTA2-AS1 inhibits malignant phenotypes of gastric cancer cells

Gastric cancer (GC) is one of the most common malignancies in digestive system. Accumulating evidence reveals the critical role of long noncoding RNAs (lncRNAs) in GC development. The study aimed to explore the functions and mechanism of lncRNA actin alpha 2, smooth muscle antisense RNA 1 (ACTA2-AS1) in GC. Reverse transcription-quantitative polymerase chain reaction analyses and subcellular fractionation assays showed that ACTA2-AS1 was lowly expressed in GC cells and was mainly distributed in the cytoplasm. Overexpressed ACTA2-AS1 inhibited GC cell viability, proliferation, migration, invasion, and epithelial-mesenchymal transition process, as suggested by cell counting kit-8 assays, colony formation assays, wound healing assays, Transwell assays and Western blot analyses. Mechanistically, ACTA2-AS1 served as a competing endogenous RNA (ceRNA) to bind with miR-378a-3p and thereby, antagonized the inhibitory effect of miR-378a-3p on the expression of messenger RNA phosphatidylinositol specific phospholipase C X domain containing 2 (PLCXD2). The binding capacity between miR-378a-3p and ACTA2-AS1 (or PLCXD2) was detected by RNA pulldown assays, luciferase reporter assays and RNA immunoprecipitation assays. Moreover, PLCXD2 knockdown rescued the inhibitory effect of ACTA2-AS1 overexpression on malignant behaviors of GC cells. Overall, ACTA2-AS1 inhibits malignant phenotypes of GC cells by acting as a ceRNA to target miR-378a-3p/PLCXD2 axis.

circCHST15 is a novel prognostic biomarker that promotes clear cell renal cell carcinoma cell proliferation and metastasis through the miR-125a-5p/EIF4EBP1 axis

Background

Circular RNAs (circRNAs) have been indicated as potentially critical mediators in various types of tumor progression, generally acting as microRNA (miRNA) sponges to regulate downstream gene expression. However, the aberrant expression profile and dysfunction of circRNAs in human clear cell renal cell carcinoma (ccRCC) need to be further investigated. This study mined key prognostic circRNAs and elucidates the potential role and molecular mechanism of circRNAs in regulating the proliferation and metastasis of ccRCC.

Methods

circCHST15 (hsa_circ_0020303) was identified by mining two circRNA microarrays from the Gene Expression Omnibus database and comparing matched tumor versus adjacent normal epithelial tissue pairs or matched primary versus metastatic tumor tissue pairs. These results were validated by quantitative real-time polymerase chain reaction and agarose gel electrophoresis. We demonstrated the biological effect of circCHST15 in ccRCC both in vitro and in vivo. To test the interaction between circCHST15 and miRNAs, we conducted a number of experiments, including RNA pull down assay, dual-luciferase reporter assay and fluorescence in situ hybridization.

Results

The expression of circCHST15 was higher in ccRCC tissues compared to healthy adjacent kidney tissue and higher in RCC cell lines compared to normal kidney cell lines. The level of circCHST15 was positively correlated with aggressive clinicopathological characteristics, and circCHST15 served as an independent prognostic indicator for overall survival and progression-free survival in patients with ccRCC after surgical resection. Our in vivo and in vitro data indicate that circCHST15 promotes the proliferation, migration, and invasion of ccRCC cells. Mechanistically, we found that circCHST15 directly interacts with miR-125a-5p and acts as a microRNA sponge to regulate EIF4EBP1 expression.

Conclusions

We found that sponging of miR-125a-5p to promote EIF4EBP1 expression is the underlying mechanism of hsa_circ_0020303-induced ccRCC progression. This prompts further investigation of circCHST15 as a potential prognostic biomarker and therapeutic target for ccRCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01449-w.

Circular RNA circ_0000644 promotes papillary thyroid cancer progression via sponging miR-1205 and regulating E2F3 expression

The dysregulation of circular RNAs (circRNAs) facilitates the tumorigenesis of papillary thyroid carcinoma (PTC). This study was targeted at determining the functions and mechanism of circ_0000644 in regulating PTC development. Circ_0000644, microRNA-1205 (miR-1205) and E2F transcription factor 3 (E2F3) expressions were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Actinomycin D (ActD) and Ribonuclease R (RNase R) assays were used to verify the circular characteristic of circ_0000644. After circ_0000644 was knocked down, PTC cell growth, migration, invasion and apoptosis were assessed by cell counting kit-8 (CCK-8) assay, Transwell assay and flow cytometry analysis, respectively. The regulating relationships among circ_0000644, E2F3 and miR-1205 were confirmed through RNA immunoprecipitation (RIP) assay and dual-luciferase reporter assay. Besides, the regulatory effects of circ_0000644 on the protein level of E2F3 was analyzed via Western blot. In PTC, circ_0000644 was highly expressed, and it was located mainly in the cytoplasm, and it had stable structure. The knockdown of circ_0000644 repressed PTC cell growth, migration, and invasion, and facilitated apoptosis. Circ_0000644 could directly interact with miR-1205 to repress the expression of miR-1205, and it served as a miR-1205 sponge to modulate E2F3 expression in PTC cells. Circ_0000644 up-regulates E2F3 expression via sponging miR-1205 to promote PTC progression.

Tumor Suppressive Circular RNA-102450: Development of a Novel Diagnostic Procedure for Lymph Node Metastasis from Oral Cancer

Circular RNAs (circRNAs), which form as covalently closed loop structures, have several biological functions such as regulation of cellular behavior by adsorbing microRNAs. However, there is limited information of circRNAs in oral squamous cell carcinoma (OSCC). Here, we aimed to elucidate the roles of aberrantly expressed circRNAs in OSCC. CircRNA microarray showed that circRNA-102450 was down-regulated in OSCC cells. Clinical validation of circRNA-102450 was performed using highly sensitive droplet digital PCR in preoperative liquid biopsy samples from 30 OSCC patients. Interestingly, none of 16 studied patients with high circRNA-102450 had regional lymph node metastasis (RLNM), whereas 4 of 14 studied patients (28.5%) with low expression had pathologically proven RLNM. Overexpressed circRNA-102450 significantly inhibited the tumor metastatic properties of cell proliferation, migration, and invasion. Furthermore, circRNA-102450 directly bound to, and consequently down-regulated, miR-1178 in OSCC cells. Taken together, circRNA-102450 has a tumor suppressive effect via the circRNA-102450/miR-1178 axis and may be a novel potential marker of RLNM in OSCC patients.

Circular RNA hsa_circ_0103552 Promotes Proliferation, Migration, and Invasion of Breast Cancer Cells through Upregulating Cysteine-Rich Angiogenic Inducer 61 (CYR61) Expression via Sponging MicroRNA-515-5p

Circular RNAs (circRNAs) exert a significant regulatory function on tumor progression. This work intends to probe into the biological function and regulatory mechanism of circRNA_0103552 (circ_0103552) in breast cancer carcinogenesis. In this study, circ_0103552, microRNA-515-5p (miR-515-5p), and cysteine-rich angiogenic inducer 61 (CYR61) mRNA expressions in breast cancer cells and tissues were determined by quantitative real-time polymerase chain reaction, followed by cell counting kit 8 and Transwell experiments to examine the multiplication, migration, and invasion of breast cancer cells. Circular RNA Interactome database and StarBase database were searched, and dual-luciferase reporter gene experiments were applied to verify the targeting relationship between circ_0103552 and miR-515-5p, and between miR-515-5p and CYR61, and Western blot was adopted to the regulatory function of circ_0103552 and miR-515-5p on CYR61 protein expression. Circ_0103552 expression was found to be remarkably up-modulated in breast cancer tissues and cells, and circ_0103552 overexpression facilitated the multiplication, migration, and invasion of breast cancer cells, while knocking down circ_0103552 induced the opposite effects. Mechanistically, circ_0103552 could sponge miR-515-5p and restrained its expression in breast cancer cells. MiR-515-5p could counteract the functions of circ_0103552 in breast cancer cells. Additionally, CYR61 was revealed to be a downstream target of miR-515-5p in breast cancer cells. In summary, this study shows that circ_0103552 up-modulates CYR61 expression by targeting miR-515-5p and thus facilitates the multiplication, migration, and invasion of breast cancer cells.

CircGSK3B promotes RORA expression and suppresses gastric cancer progression through the prevention of EZH2 trans-inhibition

BACKGROUND

Circular RNAs (circRNAs) are a class of non-coding RNA that play critical roles in the development and pathogenesis of various cancers. The circRNA circGSK3B (hsa_circ_0003763) has been shown to enhance cell proliferation, migration, and invasion in hepatocellular carcinoma. However, the specific functions and underlying mechanistic involvement of circGSK3B in gastric cancer (GC) have not yet been explored. Our study aimed to investigate the effect of circGSK3B on the progression of GC and to identify any potential mechanisms underlying this process.

METHODS

CircRNA datasets associated with GC were obtained from the PubMed, GEO, and ArrayExpress databases, and circRNAs were validated via RT-qPCR and Sanger sequencing. Biotin-labeled RNA pull-down, mass spectrometry, RNA immunoprecipitation, and in vitro binding assays were employed to determine proteins demonstrating interactions with circGSK3B. Gene expression regulation was assessed through RT-qPCR, chromatin immunoprecipitation, and western blot assays. Gain- and loss-of-function assays were used to analyze any effects of circGSK3B and its partner regulatory molecule (EZH2) on the proliferation, invasion, and migration abilities of GC cells both in vitro and in vivo.

RESULTS

CircGSK3B was mainly identified in the nucleus. This circRNA was present at a reduced concentration in GC tissues and cell lines. Overexpression of circGSK3B was shown to inhibit the growth, invasion, and metastasis of GC cells both in vitro and in vivo. Mechanistically, circGSK3B directly interacted with EZH2, acting to suppress the binding of EZH2 and H3K27me3 to the RORA promoter, and leading to an elevation in RORA expression and ultimately the suppression of GC progression.

CONCLUSIONS

CircGSK3B acts as a tumor suppressor, reducing EZH2 trans-inhibition and GC progression. This demonstrates the potential use of this RNA as a therapeutic target for GC.

Circ_0011058 facilitates proliferation, angiogenesis and radioresistance in papillary thyroid cancer cells by positively regulating YAP1 via acting as miR-335-5p sponge

BACKGROUND

Circular RNAs (circRNAs) are reported to be associated with multiple biological processes in human cancers. However, there are still numerous circRNAs whose functions remain unclear. The aim of this study was to investigate the role of circ_0011058 in papillary thyroid cancer (PTC).

METHODS

Quantitative real-time PCR (qPCR) was utilized to detect the expression of circ_0011058, microRNA-335-5p (miR-335-5p) and Yes-associated Protein 1 (YAP1). Cell proliferation was detected using cell counting kit-8 (CCK-8) assay and EdU assay. Cell apoptosis was detected by flow cytometry assay. Angiogenesis ability was assessed using tube formation assay. The expression of angiogenesis-related proteins and YAP1 protein was detected by western blot. Radioresistance was examined using colony formation assay. The binding relationship between miR-335-5p and circ_0011058 or YAP1 was verified by dual-luciferase reporter assay, pull-down assay and RIP assay. Xenograft models were constructed to ensure the role of circ_0011058.

RESULTS

Circ_0011058 expression was aberrantly elevated in PTC tissues and cells. The downregulation of circ_0011058 suppressed proliferation, angiogenesis and radioresistance in PTC cells. MiR-335-5p was defined as a target of circ_0011058, and miR-335-5p inhibition reversed the effects of circ_0011058 downregulation. In addition, YAP1 was a target of miR-335-5p, and circ_0011058 positively regulated YAP1 expression by targeting miR-335-5p. MiR-335-5p restoration inhibited proliferation, angiogenesis and radioresistance in PTC cells, while YAP1 overexpression abolished these effects. Animal study showed that circ_0011058 knockdown inhibited tumor growth in vivo.

CONCLUSION

Circ_0011058 promoted PTC cell proliferation, angiogenesis and radioresistance by upregulating YAP1 via acting as miR-335-5p sponge.

CircRNA: A novel potential strategy to treat thyroid cancer (Review)

Thyroid cancer (TC) is the most common type of endocrine cancer. Over the last 50 years, the global incidence of TC has been increasing. The survival rate of TC is higher than that of most other types of cancer, but it depends on numerous factors, including the specific type of TC and stage of the disease. Circular RNAs (circRNAs) are a new class of long noncoding RNA with a closed loop structure that have a critical role in the complex gene regulatory network that controls the emergence of TC. The most important function of circRNAs is their ability to specifically bind to microRNAs. In addition, the biological functions of circRNAs also include interactions with proteins, regulation of the transcription of genes and acting as translation templates. Based on the characteristics of circRNAs, they have been identified as potential biomarkers for the diagnosis of tumors. In the present review, the function and significance of circRNAs and their potential clinical implications for TC were summarized. Furthermore, possible treatment approaches involving the use of mesenchymal stem cells (MSCs) and exosomes derived from MSCs as carriers to load and transport circRNAs were discussed.

Circ_0000376 enhances the proliferation, metastasis, and chemoresistance of NSCLC cells via repressing miR-384

BACKGROUND

Non-small cell lung cancer (NSCLC) is the most common cancer worldwide. Circular RNAs (circRNAs) are recently identified as important gene regulators with critical roles in cancer biology. In this study, we focus on the effect of circ_0000376 targeting miR-384 on malignant phenotypes of NSCLC cells.

METHODS

Circ_0000376 and miR-384 expression in NSCLC tissue samples were measured using qRT-PCR. The association between pathological parameters and the circ_0000376 expression was analyzed as well. Human NSCLC cell lines A549 and NCI-H460 were used as cell models. CCK-8 and BrdU assay were used to assess the effect of circ_0000376 on NSCLC cell line proliferation and drug sensitivity. Transwell assay was conducted to detect the effect of circ_0000376 on migration and invasion. Further, luciferase reporter assay was employed to validate the targeting of miR-384 by circ_0000376.

RESULTS

Circ_0000376 expression in NSCLC clinical samples was up-regulated and this was linked to unfavorable pathological parameters. Circ_0000376 markedly accelerated the proliferation and metastasis, and enhanced chemoresistance of NSCLC cells. Mechanically, circ_0000376 overexpression could bind with miR-384 and repress its expression.

CONCLUSIONS

Circ_0000376 is a newly discovered oncogenic circRNA in NSCLC, and can be potentially regarded as a diagnostic biomarker and therapy target.

Circular RNA Circ_0067934 Attenuates Ferroptosis of Thyroid Cancer Cells by miR-545-3p/SLC7A11 Signaling

Ferroptosis is an emerging programmed cell death distinguished from apoptosis and autophagy and plays essential roles in tumorigenesis. Thyroid cancer is a prevalent endocrine tumor, but the molecular mechanism of ferroptosis during thyroid cancer development remains unclear. Here, we identified the critical function of circular RNA circ_0067934 in repressing ferroptosis of thyroid cancer cells. Our data showed that the ferroptosis activator erastin decreased thyroid cancer cell viabilities, while the circ_0067934 shRNA further attenuated erastin-inhibited cell viabilities. The silencing of circ_0067934 enhanced the levels of ferroptosis-related markers, including Fe2+, iron, and ROS in the cells. The knockdown of circ_0067934 induced thyroid cancer cell apoptosis and repressed thyroid cancer cell proliferation in vitro and in vivo. Circ_0067934 upregulated the expression of the ferroptosis-negative regulator SLC7A11 by sponging and inhibiting miR-545-3p in thyroid cancer cells. The overexpression of SLC7A11 or the inhibitor of miR-545-3p reversed circ_0067934 silencing-regulated thyroid cancer cell proliferation. Therefore, we concluded that Circ_0067934 attenuated ferroptosis of thyroid cancer cells by miR-545-3p/SLC7A11 signaling. Circ_0067934 may serve as a potential therapeutic target by regulating ferroptosis for the treatment of thyroid cancer.

Circ_0072088 promotes progression of hepatocellular carcinoma by activating JAK2/STAT3 signaling pathway via miR-375

Circular RNAs feature prominently in cancer development. Nonetheless, the role of circ_0072088 in hepatocellular carcinoma (HCC) remains unclear. GEO databases (GSE97332, GSE108724, GSE36915, and GSE33006) were used to screen out the differentially expressed circRNAs, miRNAs, and mRNA in HCC. The expressions of circ_0072088, miR-375, and Janus Kinase 2 (JAK2) mRNA in HCC tissue and cell lines were determined with quantitative real-time polymerase chain reaction. RNase R treatment assay was used to measure the stability of circ_0072088, and subcellular fraction assay was used to detect the localization of circ_0072088. Cell counting kit-8 assay, flow cytometry, and Transwell assay were used to measure proliferation, apoptosis, migration, and invasion of HCC cells. RNA immunoprecipitation and dual-luciferase reporter gene assay were employed for investigating the binding sequence between circ_0072088 and miR-375, as well as miR-375 and JAK2 3'UTR. Western blot assay was used to detect the expression of JAK2 and p-STAT3 after circ_0072088 and miR-375 were selectively regulated. Circ_0072088 and JAK2 mRNA expressions were highly expressed in HCC tissues and cell lines while miR-375 expression was remarkably downregulated. Circ_0072088 was resistant to RNase R treatment and mainly located in the cytoplasm of HCC cells. The transfection of circ_0072088 overexpression plasmid or miR-375 inhibitors promoted the proliferation, migration, and invasion, and inhibited the apoptosis of HCC cells, whereas transfection of circ_0072088 siRNA or miR-375 mimics exerted opposite effects. Besides, miR-375 was confirmed as a target of circ_0072088 and miR-375 could further downregulate the expression of JAK2. MiR-375 mimics could reverse the upregulation of JAK2 and p-STAT3 protein induced by circ_0072088 overexpression. Circ_0072088 can enhance the proliferation, migration, and invasion, and impede apoptosis of HCC cells. Mechanistically, circ_0072088 activates JAK2/STAT3 signaling pathway by serving as a molecular sponge of miR-375.

The Role of Notch3 Signaling in Cancer Stemness and Chemoresistance: Molecular Mechanisms and Targeting Strategies

Aberrant Notch signaling profoundly affects cancer progression. Especially the Notch3 receptor was found to be dysregulated in cancer, where its expression is correlated with worse clinicopathological features and poor prognosis. The activation of Notch3 signaling is closely related to the activation of cancer stem cells (CSCs), a small subpopulation in cancer that is responsible for cancer progression. In addition, Notch3 signaling also contributes to tumor chemoresistance against several drugs, including doxorubicin, platinum, taxane, epidermal growth factor receptor (EGFR)–tyrosine kinase inhibitors (TKIs) and gemcitabine, through complex mechanisms. In this review, we mainly focus on discussing the molecular mechanisms by which Notch3 modulates cancer stemness and chemoresistance, as well as other cancer behaviors including metastasis and angiogenesis. What’s more, we propose potential treatment strategies to block Notch3 signaling, such as non-coding RNAs, antibodies and antibody-drug conjugates, providing a comprehensive reference for research on precise targeted cancer therapy.

Circular RNA 0102049 suppresses the progression of osteosarcoma through modulating miR-520g-3p/PLK2 axis

Circular RNAs (circRNAs) are a type of non-coding RNAs generated from back splicing to enhance or inhibit the progression of multiple human cancers including osteosarcoma (OS). Although circ_0102049 has been found to be highly expressed in OS cell lines, the role and specific mechanism of circ_0102049 in OS remains unclear. Here, we found that silence of circ_0102049 could significantly exacerbate the tumorigenesis of OS in vivo through sponging microRNA-520g-3p. Polo-like kinase 2 (PLK2) was predicted to be a target of miR-520g-3p, and luciferase reporter assay revealed that overexpression of miR-520g-3p dramatically suppressed the expression of PLK2, whereas miR-520g-3p inhibitor promoted the PLK2 expression. Moreover, the silence of circ_0102049 could markedly promote the proliferation, invasion, migration and cell-cycle promotion while inhibiting the apoptosis of OS cell line MG63 cells in vitro through regulating miR-520g-3p/PLK2 axis. Taken together, the present study indicated that circ_0102049 suppressed the progression of osteosarcoma via modulating miR-520g-3p/PLK2/TAp73 axis, providing a potential therapeutic target for OS.

Circular RNA circWDR27 Promotes Papillary Thyroid Cancer Progression by Regulating miR-215-5p/TRIM44 Axis

Purpose

This study was to explore the biological roles and underlying mechanism of circRNA WD repeat domain 27 (circWDR27).

Methods

The expression of circWDR27, microRNA-215-5p (miR-215-5p) and tripartite motif containing 44 (TRIM44) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony formation assays were employed to detect cell proliferation. Flow cytometry was used to determine cell apoptosis and cell cycle distribution. Cell migration and invasion abilities were examined by wound healing and transwell assays. The protein levels of matrix metalloproteinase 2 (MMP2), MMP9 and TRIM44 were analyzed by Western blot assay. The relationship between miR-215-5p and circWDR27 or TRIM44 was predicted by bioinformatics tools and confirmed using dual-luciferase reporter assay. Mouse xenograft model was established to examine the role of circWDR27 in vivo.

Results

CircWDR27 and TRIM44 were highly expressed while miR-215-5p was lowly expressed in PTC tissues and cells. Knockdown of circWDR27 suppressed cell proliferation and metastasis and induced cell cycle arrest and apoptosis in PTC cells. Moreover, miR-215-5p was a direct target of circWDR27, and its inhibition reversed the suppressive effect of circWDR27 knockdown on PTC cell progression. In addition, miR-215-5p directly targeted TRIM44, and miR-215-5p exerted its anti-cancer role in PTC cells by targeting TRIM44. Furthermore, circWDR27 positively regulated TRIM44 expression by sponging miR-215-5p. Importantly, knockdown of circWDR27 suppressed tumor growth in vivo by upregulating miR-215-5p and downregulating TRIM44.

Conclusion

CircWDR27 accelerates PTC progression via regulating miR-215-5p/TRIM44 axis, providing a potential therapeutic target for PTC.

Advances of circular RNAs in thyroid cancer: An overview

Circular RNA (circRNA) is a general term for a type of single-stranded RNAs, they are primarily generated via exon back-splice process in precursor mRNAs (pre-mRNAs). circRNAs refer to an emerging type of endogeneity-correlated closed molecules of RNA in a covalent manner. They mainly function as microRNA sponges, protein brackets, and regulatory element in transcription and splicing process. Recently, it has also starting been noticed that they serve as extraordinary models involved in polypeptides producing process. Although circRNAs have been extensively studied, their function in thyroid carcinoma is still lacking. Thus, we present the latest advances in circRNA research and summarize their fundamental rules of regulating process as well as the mechanism. More importantly, We mainly review the role and mechanism of circRNA in thyroid cancer, which provides an emerging perspective and theoretically supports the treatment of thyroid cancer.

Circular RNA circ-NCOR2 accelerates papillary thyroid cancer progression by sponging miR-516a-5p to upregulate metastasis-associated protein 2 expression

Objective

Papillary thyroid cancer (PTC) is one of the most prevalent endocrine malignancies and the fifth most common cancer in women. Circular RNAs (circRNAs) have been shown to play vital functions in cancers, but few studies have focused on the functions and mechanism of dysregulated circRNAs in PTC.

Methods

Quantitative reverse transcription PCR was used to measure circ-NCOR2 levels in PTC tissues and cell lines. The functions of circ-NCOR2 in PTC were examined by analysis using the cell counting kit-8, clone forming, flow cytometry, and Transwell experiments. Bioinformatic analysis and dual luciferase reporter gene testing were used to identify the mechanisms of circ-NCOR2.

Results

Circ-NCOR2 overexpression was observed in PTC tissues and cells. Silenced or overexpressed expression of circ-NCOR2 strikingly attenuated or facilitated, respectively, the growth, migration, and invasion of PTC cells. Mechanistically, miR-615a-5p was identified as the target of circ-NCOR2. Moreover, circ-NCOR2 enhanced the expression of metastasis-associated protein 2 (MTA2) by sponging miR-615a-5p, thereby facilitating PTC cell progression.

Conclusions

Taken together, our findings reveal a novel circ-NCOR2/miR-615a-5p/MTA2 axis in PTC, which could become a potential therapeutic target for this disease.

Emerging Roles of Circular RNAs in Thyroid Cancer

Thyroid cancer (TC) has the highest incidence among endocrine malignancies. Thus, it is essential to achieve a deep understanding of various mechanisms of development and progression of TC. circRNAs are recognized by multiple studies as being dysregulated in TC. Accumulating evidences have revealed that circRNAs serve as regulatory molecules involved in various biological processes in TC, including cell proliferation, apoptosis, invasion/migration, metabolism, and chemoresistance. Furthermore, circRNA can also serve as an effective tool in TC researches of diagnosis, prognosis, and treatments. Thus, this review is to outline the characteristics of circRNAs, generalize their categories and functions, and highlight the expression of circRNAs in TC. Meanwhile, we are expecting to achieve a comprehensive understanding of new therapies based on circRNAs in treating or preventing TC.

The emerging function and clinical significance of circRNAs in Thyroid Cancer and Autoimmune Thyroid Diseases

Thyroid cancer (TC) is one of the most common malignant tumors, with high morbidity and mortality rates worldwide. The incidence of TC, especially that of papillary thyroid carcinoma (PTC); has increased rapidly in recent decades. Autoimmune thyroid disease (AITD) is closely related to TC and has an estimated prevalence of 5%. Thus, it is becoming increasingly important to identify potential diagnostic biomarkers and therapeutic targets for TC and AITD. Circular RNAs (circRNAs) are a class of non-coding RNAs with covalently bonded circular structures that lack 5'-3' polarity and polyadenylated tails. Several circRNAs play crucial roles in the development of various diseases, including TC and AITD, and could be important new biomarkers and/or targets for the diagnosis and therapy of such disorders. Although there are four subtypes of TC, research on circRNA has largely focused on its connection to PTC. Therefore, this review mainly summarizes the relationships between circRNAs and PTC and AITD, including the molecular mechanisms underlying these relationships. In particular, the functions of “miRNA sponges” and their interactions with proteins and RNA are discussed. The possible targeting of circRNAs for the prevention, diagnosis, and treatment of TC and AITD is also described. CircRNAs could be potential biomarkers of TC and AITD, although validation will be required before they can be implemented in clinical practice.

circ-PSD3 promoted proliferation and invasion of papillary thyroid cancer cells via regulating the miR-7-5p/METTL7B axis

Papillary thyroid cancer (PTC) is a common tumor malignancy of the endocrine system worldwide. Recently, circular RNAs (circRNAs) have been reported to participate in diverse pathological processes, especially in tumorigenesis. However, the functional role and mechanism of circRNA pleckstrin and Sec7 domain containing 3 (circ-PSD3) in PTC are still unclear. In this study, qRT-PCR results showed that circ-PSD3 was significantly upregulated in PTC tissues and cell lines. Meanwhile, circ-PSD3 overexpression was positively associated with larger tumor size, TNM stage, and lymph node metastasis. Knockdown of circ-PSD3 suppressed the proliferation and invasion of PTC cells. Besides, circ-PSD3 interacted with miR-7-5p to reduce its expression, and methyltransferase like 7B (METTL7B) was verified as a target gene of miR-7-5p. Functionally, inhibition of circ-PSD3 impeded PTC cell proliferation and invasion via targeting miR-7-5p to downregulate METTL7B expression. Taken together, silencing of circ-PSD3 hampered the proliferation and invasion of PTC cells via upregulating the inhibitory effect of miR-7-5p on METTL7B expression. Therefore, circ-PSD3 could be a potential diagnostic biomarker or molecular treatment target for PTC.

Regulation of cell signaling pathways by circular RNAs and microRNAs in different cancers: Spotlight on Wnt/β-catenin, JAK/STAT, TGF/SMAD, SHH/GLI, NOTCH and Hippo pathways

Groundbreaking discoveries in molecular oncology have leveraged our understanding altogether to a new level. Mapping of plethora of cell signaling pathways has enabled researchers to drill down deep into the intermeshed regulatory networks which crosstalk to promote carcinogenesis and metastasis. More importantly, discovery of non-coding RNAs has added new layers of complexity to already complicated nature of cell signaling pathways. The discovery of circular RNAs (circRNAs) has opened the door to an ever-widening understanding of cellular processes that are controlled or influenced by circRNAs. In this review, we have summarized most recent advancements in our understanding related to interplay between circular RNAs and microRNAs for the regulation of NOTCH, Wnt/β-catenin, Hippo, SHH/GLI, JAK/STAT and TGF/SMAD pathways in different cancers.

Increased Expression of hsa_circ_0002111 and Its Clinical Significance in Papillary Thyroid Cancer

Circular RNA (circRNA) is a newly discovered non-coding RNA. Recent reports suggest that circRNAs are key regulators of tumorigenesis because of their special structure. In order to investigate the role of hsa_circ_0002111 in papillary thyroid cancer (PTC), we use quantitative real-time polymerase chain reaction (qRT-PCR) to determine the expression pattern of hsa_circ_0002111 in 82 paired PTC and adjacent non-cancerous thyroid tissues. Cell counting kit-8, colony formation, and transwell assays were conducted to assess the effect of hsa_circ_0002111 on PTC cell proliferation, migration, and invasion. We found that the expression of hsa_circ_0002111 was significantly up-regulated in PTC tissues compared with adjacent non-cancerous tissues (P < 0.0001). Expression of hsa_circ_0002111 was also associated with advanced TNM stage and lymph-node metastasis of patients with PTC. The area under the receiver operating characteristic curve was 0.833. Further, cell function assays showed that hsa_circ_0002111 inhibition significantly suppressed the proliferation and invasion abilities of PTC cells in vitro. In conclusions, the study findings show that the over-expression of hsa_circ_0002111 promotes PTC, and thus hsa_circ_0002111 may be a potential diagnostic biomarker and therapeutic target for PTC.

hsa_circ_0001018 promotes papillary thyroid cancer by facilitating cell survival, invasion, G1/S cell cycle progression, and repressing cell apoptosis via crosstalk with miR-338-3p and SOX4

We identified a novel interactome, circ_0001018/miR-338-3p/SOX4, in papillary thyroid cancer (PTC), and we intended to confirm the regulatory relationship between the three and to study the effects of the three in PTC. The bioinformatics method was used to screen out the circular RNA and mRNA of interest. A cellular fractionation assay and fluorescence in situ hybridization (FISH) assay were conducted to prove that circ_0001018 and CCT4 (the host gene of circ_0001018) mRNA primarily localized in the cytoplasm of PTC cell lines. By qRT-PCR analysis, the expression of circ_0001018 and SOX4 mRNA was found upregulated while the expression of miR-338-3p was found downregulated in PTC tissues and cells. circ_0001018 silence significantly inhibited the tumor growth in xenografted nude mice. A series of cytological experiments such as a Cell Counting Kit-8 (CCK-8) assay, a 5-ethynyl-2′-deoxyuridine (EdU) assay, cell cycle profiling, wound healing, a transwell assay, and cell apoptosis were conducted and showed that circ_0001018 and SOX4 promoted cell proliferation, migration, and invasion, inhibited cell apoptosis, and reduced the cell cycle arrest at the G₁ phase in PTC cells. Compared with circ_0001018 and SOX4, miR-338-3p held the opposite function. The regulatory relationship between circ_0001018 and miR-338-3p, and between miR-338-3p and SOX4 mRNA, was validated using a luciferase reporter gene assay and/or RNA immunoprecipitation (RIP assay). Our findings showed that circ_0001018 acted as the tumor promoter via sponging miR-338-3p to elevate SOX4 expression level in PTC. Importantly, this novel circ_0001018/miR-338-3p/SOX4 axis has the potential to be considered as a therapy target for PTC.

Circ-UBAP2 functions as sponges of miR-1205 and miR-382 to promote glioma progression by modulating STC1 expression

Background

Circular RNAs (circRNAs) exert vital functions in glioma pathogenesis. CircRNA ubiquitin‐associated protein 2 (circ‐UBAP2, hsa_circ_0008344) has been illuminated as a tumor driver in glioma. Nevertheless, the mechanisms underlying the oncogenic regulation of circ‐UBAP2 in glioma are still undefined.

Methods

Circ‐UBAP2, miR‐1205, miR‐382, and GPRC5A were quantified using qRT‐PCR and western blot. Cell viability was detected using a CCK‐8 assay. Cell migration and invasion were measured using the would‐healing and transwell assays. Flow cytometry and colony formation assay were applied to evaluate cell apoptosis and colony formation, respectively. The xenograft model assays were used to examine the impact of circ‐UBAP2 on tumorigenic effect in vivo. Direct relationships among circ‐UBAP2, miR‐1205, miR‐382, and GPRC5A were confirmed using dual‐luciferase reporter assays.

Results

Circ‐UBAP2 expression was upregulated in glioma. The reduced level of circ‐UBAP2 hampered cell proliferation, migration, invasion, and enhanced apoptosis in vitro and weakened tumor growth in vivo. Mechanistically, circ‐UBAP2 directly bound to miR‐1205 and miR‐382. miR‐1205 and miR‐382 mediated the regulation of circ‐UBAP2 silencing on glioma cell behaviors. Moreover, GPRC5A was a functional target of miR‐1205 and miR‐382 in regulating glioma cell behaviors. Furthermore, circ‐UBAP2 mediated GPRC5A expression through miR‐1205 or miR‐382 in glioma cells.

Conclusion

Our current findings identified that circ‐UBAP2 silencing impeded glioma malignant progression partially by downregulating GPRC5A through targeting miR‐1205 and miR‐382.

Progression Risk Assessment of Post-surgical Papillary Thyroid Carcinoma Based on Circular RNA-Associated Competing Endogenous RNA Mechanisms

Background: Accurate risk assessment of post-surgical progression in papillary thyroid carcinoma (PTC) patients is critical. Exploring key differentially expressed mRNAs (DE-mRNAs) regulated by differentially expressed circular RNAs (circRNAs) via the ceRNA mechanism could help establish a novel assessment tool. Methods: ceRNA network was established based on differentially expressed RNAs and correlation analysis. DE-mRNAs within the ceRNA network associated with progression-free interval (PFI) of PTC were identified to construct a prognostic ceRNA regulatory subnetwork. least absolute shrinkage and selection operator (LASSO)-Cox regression was applied to identify hub DE-mRNAs and establish a novel DE-mRNA signature in predicting PFI of PTC. Results: Six hub DE-mRNAs, namely, CLCNKB, FXBO27, FXYD6, RIMS2, SPC24, and CDKN2A, were identified to be most significantly related to the PFI of PTC, and a prognostic DE-mRNA signature was proposed. A nomogram incorporating the DE-mRNA signature and clinical parameters was established to improve the progression risk assessment in post-surgical PTC, which was superior to the American Thyroid Association risk stratification system and distant Metastasis, patient Age, Completeness of resection, local Invasion, and tumor Size (MACIS) score American Joint Committee on Cancer staging system. Conclusions: Based on the circRNA-associated ceRNA RNA mechanism, a DE-mRNA signature and prognostic nomogram was established, which may improve the progression risk assessment in post-surgical PTC.

Vitamin C sensitizes BRAFV600E thyroid cancer to PLX4032 via inhibiting the feedback activation of MAPK/ERK signal by PLX4032

BACKGROUND

BRAFV600E mutation is the most common mutation in thyroid cancer. It strongly activates MAPK/ERK pathway and indicates an invasive subtype of thyroid cancer. PLX4032 is a selective oral inhibitor of the BRAFV600 kinase although with limited effect in treating this panel of thyroid cancer, due to the feedback activation of MAPK/ERK as well as PI3K/AKT pathways. It was investigated that Vitamin C plays a positive role in inhibiting these pathways in thyroid cancer. However, whether Vitamin C could enhance the antitumor effect of PLX4032 remains largely unclear.

METHODS

The antitumor efficacy of combination therapy with PLX4032 and Vitamin C on BRAF^MT thyroid cancer cell was assessed by the MTT assay, EdU assay and colony formation, Chou-Talalay way was employed to analyze the synergistic effect. Flow cytometry were employed to assess cells' apoptosis and cell cycle arrest in response to combination therapy. Xenograft models were used to test its in vivo antitumor activity. Western blot and IHC were applied to investigate the mechanism underlying synergistic effect.

RESULTS

PLX4032 or Vitamin C monotherapy was mildly effective in treating BRAF^MT thyroid cancer cell and xenografts model. The combination therapy significantly inhibited cancer cell proliferation and tumor growth in nude mice, and induced cell apoptosis and cell cycle arrest compared to either monotherapy. PLX4032 monotherapy induced feedback activation of MAPK/ERK as well as PI3K/AKT pathway; while combination therapy significantly relieved this feedback.

CONCLUSION

Vitamin C promotes the antitumor effect of PLX4032 in BRAF^MT thyroid cancer cell and xenografts model via relieving the feedback activation of MAPK/ERK as well as PI3K/AKT pathway. PLX4032/Vitamin C combination may be a potential therapeutic approach to treat BRAF^MT thyroid cancer.

CircRNA_104565 Promoted Cell Proliferation in Papillary Thyroid Carcinoma by Sponging miR-134

BACKGROUND

Thyroid cancer is one of the most common cancers with rising incidence worldwide, and papillary thyroid carcinoma (PTC) accounts for 80-85% of thyroid malignancy. Although it has been reported that many genes relate to the carcinogenesis of PTC, the molecular mechanisms remain mostly unclear.

METHODS

QRT-PCR assay was performed to detect circRNA_104565, miR-134 and ELF2 expression. CCK8 assay was exercised to examine cell proliferation. Western blot was used to detect ELF2 expression.

RESULTS

We found that circRNA_104565 was highly expressed in PTC tissue and cell and promoted cell proliferation in vitro and in vivo. In addition, circRNA_104565 promoted cell proliferation in PTC by regulating the miR-134/ELF2 axis.

CONCLUSION

Hence, revealing the function of circRNA_104565 in PTC is important for understanding the molecular mechanism of carcinogenesis and providing new biomarkers or therapeutic targets for PTC.

Circ_SMAD4 promotes gastric carcinogenesis by activating wnt/β-catenin pathway

Objectives

Circular RNAs (circRNAs) are essential participants in tumour progression. This study focused on investigating the mechanism of a novel functional circRNA in gastric cancer (GC).

Methods

Gene expression was detected by qRT‐PCR or Western blot. Survival curves were generated via Kaplan‐Meier method. In vitro and in vivo assays were used to investigate the impact of circ_SMAD4 on GC cell growth and tumorigenesis. Agarose gel electrophoresis assay, RNase R treatment and Sanger sequencing were utilized for confirming the circular structure of circ_SMAD4. Relationship between molecules was monitored by a series of mechanical experiments, as needed.

Results

Circ_SMAD4 expression was potentiated in GC. Circ_SMAD4 depletion impeded GC cell growth in vitro and restrained tumorigenesis in vivo. Mechanically, nuclear circ_SMAD4 recruited TCF4 to facilitate CTNNB1 transcription, while cytoplasmic circ_SMAD4 sequestered miR‐1276 to prevent the silence of CTNNB1 mRNA, leading to activation of Wnt/β‐catenin pathway. Rescue experiments validated that circ_SMAD4 depended on miR‐1276/TCF4‐regulated CTNNB1 to elicit accelerating effects on GC cell growth.

Conclusion

Circ_SMAD4 facilitated GC tumorigenesis by activating CTNNB1‐dependent Wnt/β‐catenin pathway. Hopefully, the findings could provide new clues for improving GC prognosis and treatment.

Circular RNAs as biomarkers and therapeutic targets in cancer

Circular RNAs (circRNAs) are a class of single-stranded closed non-coding RNA molecules (ncRNAs), which are formed as a result of reverse splicing of mRNAs. Despite their relative abundance, an interest in understanding their regulatory importance is rather recent. High stability, abundance and evolutionary conservation among species underline some of their important traits. CircRNAs perform a variety of cellular functions ranging from miRNA and proteins sponges to transcriptional modulation and splicing. Additionally, most circRNAs are expressed aberrantly in pathological conditions suggesting their possible exploitation as diagnostic biomarkers. Their covalent closed cyclic structure resulting in resistance to RNases further makes them suitable as cancer biomarkers. Studies involving human tumors have verified differences in the expression profiles of circRNAs, indicating a regulatory role in cancer pathogenesis and metastasis. As endogenous competitive RNA, circRNAs can regulate tumor proliferation and invasion. Further, some circRNAs located in the nucleus can regulate transcription of genes by binding to RNA polymerase II. In this review, we elaborate the characteristics, functions and mechanisms of action of circRNAs in cancer. We also discuss the possibility of using circRNAs as potential therapeutic targets and biomarkers for cancer.

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

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

CircHIPK3 Promotes Thyroid Cancer Tumorigenesis and Invasion through the Mirna-338-3p/RAB23 Axis

Objective：Thyroid cancer is a common type of endocrine malignancy, and its incidence has been steadily increasing in many regions of the world. Numerous studies have found that the circRNAs in various cancer types are aberrantly expressed, which could be potential biological diagnostic markers and therapeutic targets. The purpose of this study was to investigate the role of circHIPK3 in the development and progression of thyroid cancer and its mechanism. Subject and Methods：qRT-PCR was used to detect the relative expression levels of circHIPK3 in thyroid cancer cell lines (K1, CAL-62, TPC1), human thyroid normal cells (Nthy-ori 3-1), 10 pairs of thyroid cancer tissues and corresponding adjacent normal tissues. CCK-8 and Transwell assays were used to detect the proliferation and metastasis ability of cells. The targeted relationships between circHIPK3-miR-338-3p and miR-338-3p-RAB23 were predicted by bioinformatics analysis and verified by dual-luciferase reporter assays. Results and Conclusion: The downregulation of circHIPK3 significantly reduced the migration, invasion and proliferation of thyroid carcinoma. Then, we demonstrated that circHIPK3 up-regulated the expression of its target gene RAB23 by sponging miR-338-3p to promote the tumorigenesis and invasiveness of thyroid cancer. This study is the first to find that circHIPK3 plays the role of oncogenetic circRNA in thyroid cancer, which may provide new insights into how circRNA affects the progression of thyroid cancer. Our study also showed that circHIPK3 could be a novel biomarker for thyroid cancer.

Circ_PSD3 promotes the progression of papillary thyroid carcinoma via the miR-637/HEMGN axis

AIMS

In the present study, we aimed to uncover the potential functions of circular RNA (circRNA) pleckstrin and Sec7 domain containing 3 (circ_PSD3) in papillary thyroid carcinoma (PTC) development.

MAIN METHODS

The abundance of circ_PSD3, PSD3 messenger RNA (mRNA), microRNA-637 (miR-637) and hemogen (HEMGN; EDAG-1) mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Flow cytometry was employed to measure cell cycle progression and cell apoptosis. Western blot assay was used to examine protein expression. The proliferation ability and motility of PTC cells were analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and transwell assays, respectively. The interaction between miR-637 and circ_PSD3 or HEMGN was tested by dual-luciferase reporter assay. Animal experiments were used to explore the role of circ_PSD3 in PTC progression in vivo.

KEY FINDINGS

Circ_PSD3 was aberrantly up-regulated in PTC tumor tissues compared with adjacent normal tissues. Circ_PSD3 and HEMGN promoted the cell cycle progression, proliferation and metastasis and impeded the apoptosis of PTC cells. MiR-637 was a direct target of circ_PSD3, and miR-637 directly interacted with HEMGN mRNA in PTC cells. Circ_PSD3 silencing-induced effects in PTC cells were partly attenuated by the addition of anti-miR-637 or HEMGN overexpression plasmid. Circ_PSD3/miR-637/HEMGN regulated the activity of PI3K/Akt signal pathway in PTC cells. Circ_PSD3 silencing inhibited the tumor growth in vivo.

SIGNIFICANCE

Circ_PSD3 promoted the progression of PTC through regulating miR-637/HEMGN axis and activating PI3K/Akt signaling. Circ_PSD3/miR-637/HEMGN signaling axis might be a potential target for PTC therapy.

The Research Progression and Clinical Significance of Circular RNAs in Head and Neck Cancers

With rapid development of science technique and molecular research, a large number of circular RNAs (circRNAs) were discovered. CircRNAs that are a heterogeneous endogenous group of non-coding RNA not only are abundantly and diffusely expressed in mammals but also participate in many biological processes, such as in tumor ingenuity and progress. CircRNAs have rarely open reports in the head and neck cancers (HNC), which are an aggressive malignant tumor with unsatisfactory overall survival rates. The diagnostics and treatments continue to improve while the survival rate of HNC patients has no more obvious improvement. Recent studies that are aimed at exploring the molecular mechanisms of occurrence and progression of circRNAs in HNC provide a valuable insight into potential novel diagnostic and therapeutic approaches. In this review, we summarize the increasing number of published researches on the research progression of circRNAs in HNC, as well as their possible clinical implications on HNC.

Circ_0058124 Aggravates the Progression of Papillary Thyroid Carcinoma by Activating LMO4 Expression via Targeting miR-370-3p

Background

Thyroid cancer is the most common malignant tumor in the endocrine system. Papillary thyroid carcinoma (PTC) accounts for the vast majority of cases in this cancer. Recently, the vital role of circular RNA (circRNA) has been acknowledged in various cancers, and this study aimed to investigate the role of circ_0058124 and related mechanism of its action in PTC.

Materials and Methods

The expression of circ_0058124, miR-370-3p and LIM domain only (LMO4) was detected by qRT-PCR in tissue samples (PTC tissues or normal tissues, n=20) and cell lines (non-cancer cell line, Nthy-ori 3–1, and PTC cell lines, IHH-4 and TPC-1). For functional analysis, cell proliferation was investigated using CCK-8 assay and colony formation assay. Cell migration and invasion were determined using transwell assay, and cell migration was also assessed by wound healing assay. Cell apoptosis was monitored by flow cytometry assay. For mechanism analysis, the interaction between miR-370-3p and circ_0058124 or LMO4 predicted by the bioinformatics analysis was validated by dual-luciferase reporter assay or RIP assay. The effect of circ_0058124 on tumor growth in vivo was identified by establishing the Xenograft model.

Results

The expression of circ_0058124 was enhanced in PTC tissues and cells. Circ_0058124 knockdown inhibited viability, colony formation, migration and invasion and promoted apoptosis of PTC cells. Besides, circ_0058124 knockdown also blocked tumor growth in vivo. miR-370-3p was a target of circ_0058124, and circ_0058124 regulated the expression of LMO4, a target of miR-370-3p, by targeting miR-370-3p. Rescue experiments presented that miR-370-3p inhibition reversed the inhibitory effects of circ_0058124 knockdown on PTC development, and LMO4 overexpression reversed the effect of miR-370-3p restoration on PTC development.

Conclusion

Circ_0058124 promoted the development of PTC by mediating the miR-370-3p/LMO4 axis, and circ_0058124, functioned as an oncogene in PTC, might be used as a promising biomarker for PTC diagnosis and treatment.

Non-coding RNA in thyroid cancer - Functions and mechanisms

Thyroid cancer is the most common endocrine malignant tumor, and its incidence has increased significantly in the past few years. A growing number of noncoding RNAs (ncRNAs) have shown abnormal expression patterns in human thyroid cancer in recent studies. Depending on size, ncRNAs are usually subdivided into two categories: short ncRNAs and long ncRNAs (longer than 200 nucleotides). Short ncRNAs include microRNAs (miRNAs), PIWI-interacting RNAs, small nucleolar RNAs, and endogenous small interfering RNAs, which have been extensively studied due to their roles in developmental and tumor biology. Compared to that of short ncRNAs, the involvement of lncRNAs in human cancers, especially in thyroid cancer, is not as well studied. Here, we reviewed the roles and clinical significance of miRNAs, lncRNAs, and circular RNA in thyroid development, tumorigenesis, and metastasis to offer a new approach to thyroid cancer treatment.

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

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

Circ_0000527 promotes the progression of retinoblastoma by regulating miR-646/LRP6 axis

Background

Researches validate that circular RNAs (circRNAs) are dysregulated in a variety of malignancies and play an important role in regulating the malignant phenotype of tumor cells. Nevertheless, the role of circ_0000527 in retinoblastoma (RB) and its regulatory mechanisms remain largely unknown.

Methods

Real-time PCR (RT-PCR) was used to detect circ_0000527 and miR-646 expression in RB tissues and cells. The LRP6 expression in RB cells was detected by Western blot. The relationship between circ_0000527 expression and the clinicopathological parameters of RB patients was analyzed. Cell proliferation, apoptosis and metastasis were monitored by cell counting kit-8 (CCK-8), flow cytometry, and Transwell assay. The dual-luciferase reporter gene assay and RIP assay were employed to verify the targeting relationship between circ_0000527 and miR-646, miR-646 and LRP6.

Results

Circ_0000527 was highly expressed in both RB and RB cell lines, whose high expression level and degree of differentiation were significantly correlated with the increase in cTNM staging level. Overexpression of circ_0000527 contributed to RB cell proliferation, migration, invasion and suppressed cell apoptosis, while knocking down circ_0000527 inhibited the above malignant biological behavior. The underlying mechanism suggested that functioning as a endogenous competitive RNA, circ_0000527 directly targeted miR-646 and positively regulated LRP6 expression.

Conclusion

Circ_0000527 enhances the proliferation and metastasis of RB cells by modulating the miR-646/LRP6 axis.

EMT related circular RNA expression profiles identify circSCYL2 as a novel molecule in breast tumor metastasis

Substantial evidence indicates that circular RNAs (circRNAs) play vital roles in several diseases, especially in cancer development. However, the functions of circRNAs in breast cancer metastasis remain to be investigated. This study aimed to identify the key circRNAs involved in epithelial mesenchymal transition (EMT) of breast cancer and evaluated their molecular function and roles in pathways that may be associated with tumor metastasis. An EMT model was constructed by treating breast cancer cells MCF‑7 and MDA‑MB‑231 with transforming growth factor‑β1. High‑throughput RNA sequencing was used to identify the differentially expressed circRNAs in EMT and blank groups of two cells, and reverse transcription‑quantitative PCR was used to validate the expression of circSCYL2 in human breast cancer tissues and cells. The effects of circSCYL2 on breast cancer cells were explored by transfecting with plasmids and the biological roles were assessed using transwell assays. EMT groups of breast cancer cells exhibited the characteristics of mesenchymal cells. Furthermore, the present study found that 7 circRNAs were significantly upregulated in both the MCF‑7 EMT and MDA‑MB‑231 EMT groups, while 16 circRNAs were significantly downregulated. The current study identified that circSCYL2 was downregulated in breast cancer tissues and cell lines, and that circSCYL2 overexpression inhibited cell migration and invasion. This study provides expression profiles of circRNAs in EMT groups of breast cancer cells. circSCYL2, which is downregulated in breast cancer tissues and cells, may play an important role in breast cancer EMT progression.

A Combination of circRNAs as a Diagnostic Tool for Discrimination of Papillary Thyroid Cancer

Background and Aim

Circular RNAs (circRNAs) have been highlighted to exert essential biological functions in papillary thyroid cancer (PTC). The purpose of this study was explore diagnostic utility of circRNAs in PTC patients.

Patients and Methods

The distinctive expression profile of serum circRNAs was determined by individual quantitative real-time PCR (qRT-PCR) in two independent cohorts of 113 PTC patients, 80 thyroid nodules, and 111 healthy controls (HCs). A combination of circRNAs (circRNA-based combination index) was constructed by logistic regression.

Results

Individual qRT-PCR identification showed that two circRNAs (circRAPGEF5 and hsa_circ_0058124) were significantly up-regulated in PTC patients compared with HCs and thyroid nodules. Receiver-operating characteristic (ROC) curve analysis suggested that a combination of circRNAs was superior to individual circRNA in distinguishing PTC patients from HCs and thyroid nodules with area under ROC curve of more than 0.80. Furthermore, the combination of circRNAs increased significantly after systematic treatment, suggesting that it could monitor PTC dynamics. Additionally, the combination of circRNAs was independently correlated with PTC presence.

Conclusion

The combination of these altered circRNAs was correlated with PTC and may serve as a novel diagnostic approach.

Metastatic propagation of thyroid cancer; organ tropism and major modulators

Thyroid cancer, as the most prevalent endocrine malignancy, comprises nearly 1% of all cancers in the world. The metastatic propagation of thyroid cancer is under the control of a number of modulating processes and factors such as signaling pathways and their components, cell division regulators, metabolic reprogramming factors, extracellular matrix remodelers, epithelial to mesenchymal transition modulators, epigenetic mechanisms, hypoxia and cytokines. Identifying the exact molecular mechanisms of these dysregulated processes could help to discover the key targets for therapeutic purposes and utilizing them as diagnostic, prognostic and predictors of the clinical course of patients. In this review article, we describe different aspects of thyroid cancer metastasis by focusing on defective genes and pathways involved in its metastatic spread.

CircRNAs: potency of protein translation and feasibility of novel biomarkers and therapeutic targets for head and neck cancers

Circular RNAs (circRNAs), a new star noncoding RNA (ncRNA), show stability, conservation, abundance, and tissue and stage specificity. They act as key regulators of biological processes. They target the mRNAs of many other different genes or signaling pathways, and closely link associated genes into regulatory networks. Growing evidence has demonstrated that circRNAs may play an important role in the carcinogenesis, progression and chemoradiation resistance of many cancers including head and neck cancers (HNC). CircRNA, like other ncRNA, such as miRNA, lncRNA, usually is considered to be non-protein coding transcript. However, recent studies indicated that abnormal translation of circRNAs may be involved in human diseases. In this review, we collected the origin, classification, characteristics, function of circRNAs, exosmal circRNAs, and then synthesize current study results to highlight aberration of circRNAs in various types of HNC, and try to clarify the molecular mechanisms of circRNAs affecting the pathogenesis and progression of HNC, as well as pay particular attention to provide a new avenue to the diagnosis and treatment strategy for HNC.

Hsa_circ_0102272 serves as a prognostic biomarker and regulates proliferation, migration and apoptosis in thyroid cancer

BACKGROUND

Accumulating evidence shows that circRNAs comprise a class of non-coding RNA exhibiting tremendous potential for cancer diagnosis and prognosis and they are also implicated in the pathogenesis of carcinogenesis. The present study aimed to investigate abnormally expressed circRNAs in thyroid cancer (TC).

MATERIALS AND METHODS

Five pairs of TC tissues and adjacent nornal specimens were used to analyze abnormal circRNA expression using high-throughput sequencing. MTT and Annexin V-fluorescein isothiocyanate/propidium iodide assays were performed to evaluate cell proliferation and apoptosis in vitro. Cell migration and invasion were detected by a Transwell assay conducted in vitro.

RESULTS

Fifty-four circRNAs, including 19 down-regulated and 35 up-regulated, were significantly aberrantly expressed in TC tissues compared to para-carcinoma tissues. Both sequencing and quantitative reverse transcriptse-polymersase chain reaction analysis corroborated that hsa_circ_0102272 was dramatically elevated in TC tissues and cell lines compared to the control group. Patients with high expression of hsa_circ_0102272 showed significantly short overall survival and progression-free survival compared to those patients with hsa_circ_0102272 low expression. In vitro experiments confirmed that knockdown of hsa_circ_0102272 could restrain cell proliferation, migration and invasion, as well as facilitate apoptosis of TC cells in vitro.

CONCLUSIONS

Hsa_circ_0102272 displays oncogenic function via repressing malignant biological properties and serves as a prognostic biomarker in TC patients.

Circular RNA CircPRMT5 Accelerates Proliferation and Invasion of Papillary Thyroid Cancer Through Regulation of miR-30c/E2F3 Axis

Background

The role of circular RNA (circRNA) in papillary thyroid cancer (PTC) is largely unknown. This study aims to determine the function and mechanism of circPRMT5 in the regulation of PTC development.

Methods

PTC tissues and cell lines were used to determine circPRMT5 expression via quantitative real-time polymerase chain reaction. Small interfering RNA (siRNA) was utilized to knock down circPRMT5. Proliferation was analyzed through CCK8 and colony formation assays. Transwell assay was performed to determine cell migration and invasion. Luciferase assay and RIP assay were carried out to analyze the interaction between circPRMT5 and miR-30c.

Results

CircPRMT5 expression was upregulated in PTC tissues and cell lines. And circPRMT5 level was positively linked with advanced stage and lymph node metastasis. CircPRMT5 knockdown inhibited proliferation, migration and invasion while inducing apoptosis. CircPRMT5 worked as a competing endogenous RNA for miR-30c. By inhibiting miR-30c, circPRMT5 promoted the expression of E2F3.

Conclusion

Our findings demonstrate that circPRMT5 acts as an oncogenic circRNA to promote PTC progression via regulating miR-30c/E2F3 axis.

FAM225A facilitates colorectal cancer progression by sponging miR-613 to regulate NOTCH3

Colorectal cancer (CRC) is a fatal disease ranking the third among the commonplace cancer types around the world. It is extremely significant to exploit effective treatments against CRC. FAM225A was proved to influence cell progression and forecast unfavorable prognosis in nasopharyngeal carcinoma. The role and function mechanism of FAM225A are still unclear in CRC. In this research, FAM225A was discovered presenting much higher expression in CRC tissues and cell lines. In addition, depleting FAM225A was capable of inhibiting cell proliferation, migration, and epithelial‐to‐mesenchymal transition (EMT) progress, and enhancing cell apoptosis ability. Furthermore, miR‐613 exerted important effects as a mediator between FAM225A and NOTCH3. NOTCH3 was negatively correlated with miR‐613, whereas was positively associated with FAM225A. Via competitively binding with miR‐613, FAM225A positively regulated NOTCH3 expression. FAM225A facilitated CRC occurrence and development through positively regulating NOTCH3 expression by binding with miR‐613. In a word, FAM225A/miR‐613/NOTCH3 axis may play a tumor‐facilitator in CRC cell progression. These data manifested the pivotal effect of FAM225A/miR‐613/NOTCH3 pathway in CRC cell proliferation, apoptosis, and migration process. The findings may provide some theoretical basis and different perspective for CRC treatment.

Correction to: Hsa_circ_0058124 promotes papillary thyroid cancer tumorigenesis and invasiveness through the NOTCH3/GATAD2A axis

In the original publication of this manuscript [1], the Fig. 6a invasion si-hsa_circ_0058124_2# group (row 2 right and row 3 right) and Fig. 9c TPC-1 clone formation assay control group (row 1 left) were misplaced and need to be revised. The updated figures are shown below.

CircRNA ZNF609 Knockdown Suppresses Cell Growth via Modulating miR-188/ELF2 Axis in Nasopharyngeal Carcinoma

Background

Circular RNAs (circRNAs) and microRNAs (miRNAs) have been reported to act as the important regulators in nasopharyngeal carcinoma (NPC). CircRNA ZNF609 (circ-ANF609) and miR-188 have been, respectively, reported to play a pro-cancer and anti-cancer role in NPC. The purpose of this study is to reveal the functional relation of circ-ZNF609 and miR-188 in NPC development.

Methods

The transcription level and protein level of genes were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot assay, respectively. Cell proliferation was analyzed using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Furthermore, flow cytometry analysis was used to assess cell cycle transition and cell apoptosis rate. Besides, the interaction between miR-188 and circ-ZNF609 or E74-like factor 2 (ELF2) was predicted by starbase or microT-CDS, and then confirmed by the dual luciferase reporter assay and RIP assay.

Results

Circ-ZNF609 and ELF2 levels were increased and miR-188 level was decreased in NPC. Circ-ZNF609 knockdown significantly inhibited cell proliferation and cell cycle transition, as well as accelerated apoptosis in NPC cells. Interestingly, circ-ZNF609 directly bound to miR-188. Circ-ZNF609 regulated NPC cell growth through modulating miR-188 expression. In addition, miR-188 suppressed NPC cell growth via directly targeting ELF2. Finally, we confirmed that circ-ZNF609 mediated miR-188 level to modulate ELF2 expression.

Conclusion

Our findings demonstrated that circ-ZNF609 depletion-repressed proliferation and cell cycle transition, and induced apoptosis of NPC cells via modulation of miR-188/ELF2 axis, providing potential targets for the therapy of NPC.

CircRNA hsa_circ_0013958 may contribute to the development of ovarian cancer by affecting epithelial-mesenchymal transition and apoptotic signaling pathways

BACKGROUND

CircRNA plays an important role in the development of tumors, but its mechanism of action in ovarian cancer is still unclear.

METHODS

The expression level of hsa_circ_0013958 in 45 pairs of ovarian cancer tissues and cells was quantified by qRT-PCR, further revealing whether it is related to clinicopathological features and diagnostic value. Next, the effects of hsa_circ_0013958 on the proliferation, migration, invasion, and apoptosis of A2780 and OVCAR-3 cells were detected by CCK-8 assay, Transwell assay, and flow cytometry, respectively. Last, the expression levels of epithelial-mesenchymal transition-related proteins (E-cadherin and Vimentin) and apoptosis-related proteins (Bcl-2 and Bax) were detected by Western blotting.

RESULTS

Hsa_circ_0013958 was highly expressed in ovarian cancer tissues and cells, and its expression was closely related to patient FIGO stage and lymph node metastasis. Further, in vitro studies showed that knockdown of hsa_circ_0013958 suppressed proliferation, migration, and invasion of ovarian cancer cells but elevated the cell apoptotic rate. The expression levels of both epithelial-mesenchymal transition-related proteins and apoptosis-related proteins were also changed.

CONCLUSIONS

Hsa_circ_0013958 may contribute to the development of ovarian cancer by affecting epithelial-mesenchymal transition and apoptotic signaling pathways.

Biological Roles and Mechanisms of Circular RNA in Human Cancers

Circular RNA (circRNA) is an intriguing class of RNA with covalently closed-loop structure and is highly stable and conservative. As new members of the ncRNAs, the function, mechanism, potential diagnostic biomarker, and therapeutic target have raised increased attention. Most circRNAs are presented with characteristics of abundance, stability, conservatism, and often exhibiting tissue/developmental-stage-specific manner. Over 30,000 circRNAs have been identified with their unique structures to maintain stability more easily than linear RNAs. An increased numbers of circRNAs are dysregulated and involved in several biological processes of malignance, such as tumorigenesis, growth, invasion, metastasis, apoptosis, and vascularization. Emerging evidence suggests that circRNAs play important roles by acting as miRNA sponge or protein scaffolding, autophagy regulators, and interacting with RNA-binding protein (RBP), which may potentially serve as a novel promising biomarker for prevention, diagnosis and therapeutic target for treatment of human cancer with great significance either in scientific research or clinic arena. This review introduces concept, major features of circRNAs, and mainly describes the major biological functions and clinical relevance of circRNAs, as well as expressions and regulatory mechanisms in various types of human cancer, including pathogenesis, mode of action, potential target, signaling regulatory pathways, drug resistance, and therapeutic biomarkers. All of which provide evidence for the potential utilities of circRNAs in the diagnosis and treatment of cancer.

A Comprehensive Analysis Identified the Key Differentially Expressed Circular Ribonucleic Acids and Methylation-Related Function in Pheochromocytomas and Paragangliomas

We investigated differentially expressed circular RNAs (circRNAs) and their potential functions in pheochromocytomas and paragangliomas (PCC/PGLs). Expression levels of circRNAs in tumor and adjacent normal tissues from seven PCC/PGL patients were analyzed through RNA sequencing. Real-time PCR was conducted to verify the key candidates identified in the sequencing data. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the functions of these circRNAs. A total of 367 circRNAs were found differentially expressed between tumor and normal samples. The top three histone methylation-related circRNAs (hsa_circ_0000567, hsa_circ_0002897, and hsa_circ_0004473) and their target microRNAs (miRNAs) were identified and validated. We then mapped the circRNA-miRNA-messenger RNA (mRNA) coding-noncoding gene co-expression (CNC) networks to show the potential binding relationships between circRNAs and their targets in PCC/PGLs. The top five mRNAs, 88 miRNAs, and 132 circRNAs related to pathogenesis were utilized to map the CNC network, and we observed that the interactions of these candidates with their target miRNAs regulated histone methylation and further mediated PCC/PGL pathogenesis. This study is the first to provide the whole profile of differentially expressed circRNAs in PCC/PGLs. Our data indicate that altered circRNAs may control the pathogenesis of PCC/PGLs by regulating histone methylation processes, highlighting their role as potential biomarkers.