Circular RNA hsa_circ_0001666 sponges miR‑330‑5p, miR‑193a‑5p and miR‑326, and promotes papillary thyroid carcinoma progression via upregulation of ETV4

Circular RNAs in EMT-driven metastasis regulation: modulation of cancer cell plasticity, tumorigenesis and therapy resistance

The non-coding RNAs comprise a large part of human genome lack of capacity in encoding functional proteins. Among various members of non-coding RNAs, the circular RNAs (circRNAs) have been of importance in the pathogenesis of human diseases, especially cancer. The circRNAs have a unique closed loop structure and due to their stability, they are potential diagnostic and prognostic factors in cancer. The increasing evidences have highlighted the role of circRNAs in the modulation of proliferation and metastasis of cancer cells. On the other hand, metastasis has been responsible for up to 90% of cancer-related deaths in patients, requiring more investigation regarding the underlying mechanisms modulating this mechanism. EMT enhances metastasis and invasion of tumor cells, and can trigger resistance to therapy. The cells demonstrate dynamic changes during EMT including transformation from epithelial phenotype into mesenchymal phenotype and increase in N-cadherin and vimentin levels. The process of EMT is reversible and its reprogramming can disrupt the progression of tumor cells. The aim of current review is to understanding the interaction of circRNAs and EMT in human cancers and such interaction is beyond the regulation of cancer metastasis and can affect the response of tumor cells to chemotherapy and radiotherapy. The onco-suppressor circRNAs inhibit EMT, while the tumor-promoting circRNAs mediate EMT for acceleration of carcinogenesis. Moreover, the EMT-inducing transcription factors can be controlled by circRNAs in different human tumors.

Hsa_circ_0092355 Accelerates Papillary Thyroid Cancer Progression by Regulating the miR-543/PDE5A Pathway

CircRNAs have been found to participate in the progression of various tumors. In the present study, we aimed to clarify the role of hsa_circ_0092355 in papillary thyroid cancer (PTC) cell development. RT-qPCR was used to determine the expression of hsa_circ_0092355, miR-543, and PDE5A. PTC cell proliferation was ascertained via a cell colony formation assay and the CCK-8 test. Western blotting was performed to examine the expression levels of PDE5A and apoptosis-associated proteins (Bcl-2 and Bax) in PTC cells. A scratch wound assay was performed to measure the migration of PTC cells. A mouse xenograft test was performed to assess the effects of hsa_circ_0092355 in vivo. RIP and dual-luciferase reporter assays confirmed the association between miR-543 and hsa_circ_0092355 or PDE5A. Associations between miR-543, hsa_circ_0092355, and PDE5A were evaluated using Pearson's correlation coefficient. Upregulation of hsa_circ_0092355 was observed in PTC tissues. The hsa_circ_0092355 knockdown blocked the proliferation and migration of PTC cells and induced apoptosis. Moreover, hsa_circ_0092355 knockdown blocked PTC xenograft tumor growth in vivo. The miR-543 inhibitor could reverse the changes induced by hsa_circ_0092355 knockdown by hsa_circ_0092355 targeting miR-543. Furthermore, miR-543 suppresses PTC progression by downregulating PDE5A expression. Our findings suggest that the PTC tumor promoter hsa_circ_0092355 may promote carcinogenesis by controlling the miR-543/PDE5A pathway.

CircPHGDH downregulation decreases papillary thyroid cancer progression through miR-122-5p/PKM2 axis

BACKGROUND

Although papillary thyroid carcinoma (PTC) has a favorable prognosis, it could affect patient life quality and become a serious threat because of invasion and metastasis. Many investigations have suggested that circular RNAs (circRNAs) are involved in different cancer regulations. Nevertheless, circRNAs role in invasive PTC remains unclear.

METHODS

In the present investigation, next-generation sequencing was applied to explore abnormal circRNA expression. The expression of circRNA phosphoglycerate dehydrogenase (circPHGDH) in PTC cell lines and tissues were examined. Then, we investigated regulatory mechanism and circPHGDH downstream targets using bioinformatics analysis and luciferase reporting analysis. Then transwell migration, Cell Counting Kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays were used for cells migration and proliferation analysis. In vivo metastasis and tumorigenesis assays were also employed to evaluate the circPHGDH role in PTC.

RESULTS

The data showcased that circPHGDH expression increased in both PTC cell lines and tissues, which suggested that circPHGDH functions in PTC progression. circPHGDH downregulation suppressed PTC invasion and proliferation in both in vivo and in vitro experiments. Bioinformatics and luciferase reporter results confirmed that both microRNA (miR)-122-5p and pyruvate kinase M2 subtype (PKM2) were downstream targets of circPHGDH. PKM2 overexpression or miR-122-5p suppression reversed PTC cell invasion and proliferation post silencing circPHGDH by restoring aerobic glycolysis.

CONCLUSION

Taken together, our research found that circPHGDH downregulation reduced PTC progression via miR-122-5p/PKM2 axis regulation mediated by aerobic glycolysis.

Emerging roles of circular RNAs in regulating the hallmarks of thyroid cancer

Thyroid cancer is a prevalent endocrine malignancy with increasing incidence in recent years. Although most thyroid cancers grow slowly, they can become refractory, leading to a high mortality rate once they exhibit recurrence, metastasis, resistance to radioiodine therapy, or a lack of differentiation. However, the mechanisms underlying these malignant characteristics remain unclear. Circular RNAs, a type of closed-loop non-coding RNAs, play multiple roles in cancer. Several studies have demonstrated that circular RNAs significantly influence the development of thyroid cancers. In this review, we summarize the circular RNAs identified in thyroid cancers over the past decade according to the hallmarks of cancer. We found that eight of the 14 hallmarks of thyroid cancers are regulated by circular RNAs, whereas the other six have not been reported to be correlated with circular RNAs. This review is expected to help us better understand the roles of circular RNAs in thyroid cancers and accelerate research on the mechanisms and cure strategies for thyroid cancers.

Dual effects of circRNA in thyroid and breast cancer

CircRNA, the latest research hotspot in the field of RNA, is a special non-coding RNA molecule, which is unable to encode proteins and bind polyribosomes. As a regulatory molecule, circRNA participates in cancer cell generation and progression mainly through the mechanism of competitive endogenous RNA. In numerous regulated cancer organs, the thyroid and breast are both endocrine organs, and both are regulated by the hypothalamic pituitary gland axis. Thyroid cancer (TC) and breast cancer (BC) are both sexually prevalent in women and both are affected by hormones, thus they are intrinsically linked. In addition, recent epidemiological surveys have found that, early metastasis and recurrence of breast cancer remain the main cause of survival in breast cancer patients. Although at home and abroad, studies have shown that new targeted anti-tumor drugs with numerous tumor markers are gradually being used in the clinic, evidence for potential molecular mechanisms affecting its prognosis lacks clinical studies. Therefore, we search the relevant literature, and based on the latest domestic and international consensus, review the molecular mechanisms and regulation relevance of circRNA, compare the difference of the same circRNA in two tumors, to more deeply understand and lay the foundation for future clinical diagnostic, therapeutic and prognostic studies in large samples.

Four differentially expressed exosomal miRNAs as prognostic biomarkers and therapy targets in endometrial cancer: Bioinformatic analysis

Endometrial cancer (EC) is one of the most common gynecological malignancies worldwide. Accumulated evidence has demonstrated exosomes of cancer cells carry microRNAs (miRNAs) to nonmalignant cells to induce metastasis. Our study aimed to find possible biomarkers of EC. Data for miRNA expression related with exosome from EC patients were downloaded from The Cancer Genome Atlas database, and the miRNA expression profiles associated with exosomes of EC were downloaded from the National Center for Biotechnology Information. We used different algorithms to analyze the differential miRNA expression, infer the relative proportion of immune infiltrating cells, predict chemotherapy sensitivity, and comprehensively score each gene set to evaluate the potential biological function changes of different samples. The gene ontology analysis and Kyoto encyclopedia of genome genomics pathway analysis were performed for specific genes. A total of 13 differential miRNAs were identified, of which 4 were up-regulated. The 4 miRNAs, that is hsa-miR-17-3p, hsa-miR-99b-3p, hsa-miR-193a-5p, and hsa-miR-320d, were the hub exosomal miRNAs that were all closely related to the clinic phenotypes and prognosis of patients. This study preliminarily indicates that the 4 hub exosomal miRNAs (hsa-miR-17-3p, hsa-miR-99b-3p, hsa-miR-193a-5p, and hsa-miR-320d) could be used as prognostic biomarkers or therapy targets in EC. Further studies are required to make sure of their real feasibility and values in the EC clinic and the relative research.

Bone Marrow Mesenchymal Stem Cells-derived Exosomal Long Non-coding RNA KLF3 antisense RNA 1 Enhances Autophagy to Protect Against Cerebral Ischemia/Reperfusion Injury Via ETS Variant Transcription Factor 4/Silent Information Regulator 1 Axis

Mesenchymal stem cells (MSCs)-derived exosomes are demonstrated to exert neuroprotective effects in stroke. We aimed to explore the role and mechanism of long non-coding RNA (lncRNA) KLF3 antisense RNA 1 (KLF3-AS1) in bone marrow mesenchymal stem cells-derived exosomes (BMSCs-Exos) in cerebral ischemia/reperfusion (I/R) injury. Exosomes were isolated from the culture medium of BMSCs. A mouse model of middle cerebral artery occlusion (MCAO) in vivo and a BV-2 cell model of oxygen and glucose deprivation/reoxygenation (OGD/RX) in vitro were established. Cell viability and apoptosis were detected using MTT assay, TUNEL staining and flow cytometry, respectively. Related proteins were determined with western blot and immunohistochemistry, while related RNAs were analyzed by RT-qPCR. Neurological deficit and cerebral infarct volume were evaluated by the modified neurological severity score (mNSS) and TTC staining, respectively. Our observations indicate that exosomes derived from BMSCs-preconditioned medium exerted neuroprotective effects, as indicated by the increased cell viability and the suppressed apoptosis in OGD/RX-suffered BV-2 cells. KLF3-AS1 expression was upregulated in BMSCs-Exos. Furthermore, KLF3-AS1 knockdown antagonized the protective effects of BMSCs-Exos. Mechanistically, BMSCs-Exos carrying KLF3-AS1 inhibited apoptosis via enhancing autophagy. KLF3-AS1 was found to recruit ETS variant transcription factor 4 (ETV4), which upregulated Sirt1 expression. Knockdown of KLF3-AS1 neutralized the protective effects of BMSCs-Exos on MCAO-induced brain injury, which was then reversed by the treatment with Sirt1 inhibitor EX527. We concluded that KLF3-AS1 derived from BMSCs-Exos promoted autophagy to alleviate I/R injury via ETV4/Sirt1 axis.

Identifying and analyzing the key genes shared by papillary thyroid carcinoma and Hashimoto's thyroiditis using bioinformatics methods

Background

Hashimoto's thyroiditis (HT) is a chronic autoimmune disease that poses a risk factor for papillary thyroid carcinoma (PTC). The present study aimed to identify the key genes shared by HT and PTC for advancing the current understanding of their shared pathogenesis and molecular mechanisms.

Methods

HT- and PTC-related datasets (GSE138198 and GSE33630, respectively) were retrieved from the Gene Expression Omnibus (GEO) database. Genes significantly related to the PTC phenotype were identified using weighted gene co-expression network analysis (WGCNA). Differentially expressed genes (DEGs) were identified between PTC and healthy samples from GSE33630, and between HT and normal samples from GSE138198. Subsequently, functional enrichment analysis was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Transcription factors and miRNAs regulating the common genes in PTC and HT were forecasted using the Harmonizome and miRWalk databases, respectively, and drugs targeting these genes were investigated using the Drug-Gene Interaction Database (DGIdb). The key genes in both GSE138198 and GSE33630 were further identified via Receiver Operating Characteristic (ROC) analysis. The expression of key genes was verified in external validation set and clinical samples using quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC).

Results

In total, 690 and 1945 DEGs were associated with PTC and HT, respectively; of these, 56 were shared and exhibited excellent predictive accuracy in the GSE138198 and GSE33630 cohorts. Notably, four genes, Alcohol Dehydrogenase 1B (ADH1B), Active BCR-related (ABR), alpha-1 antitrypsin (SERPINA1), and lysophosphatidic acid receptor 5 (LPAR5) were recognized as key genes shared by HT and PTC. Subsequently, EGR1 was identified as a common transcription factor regulating ABR, SERPINA1, and LPAR5 expression. These findings were confirmed using qRT-PCR and immunohistochemical analysis.

Conclusion

Four (ADH1B, ABR, SERPINA1, and LPAR5) out of 56 common genes exhibited diagnostic potential in HT and PTC. Notably, this study, for the first time, defined the close relationship between ABR and HT/PTC progression. Overall, this study provides a basis for understanding the shared pathogenesis and underlying molecular mechanisms of HT and PTC, which might help improve patient diagnosis and prognosis.

CircRTN1 stimulates HMGB1 to regulate the malignant progression of papillary thyroid cancer by sponging miR-101-3p

BACKGROUND

The important role played by circular RNA (circRNA) in promoting the progression of papillary thyroid cancer (PTC) is attracting ever more attention among medical researchers. However, what the precise contribution is of circRTN1 in PTC progression remains unclear. The study was designed to analyze the role and mechanism of circRTN1 in regulating PTC progression.

METHODS

Human PTC cell lines (TPC-1 and IHH-4) and human thyroid normal cells (Nthy-ori 3-1) were used for in vitro assays. mRNA or protein expression of circRTN1, miR-101-3p, and high mobility group box 1 (HMGB1) were detected by quantitative real-time polymerase chain reaction or western blot. Cell proliferation was investigated by cell counting kit-8 assay, cell colony formation assay, and 5-ethynyl-2'-deoxyuridine assay. Wound-healing assay and transwell invasion assay were conducted to evaluate cell migration and invasion. Dual-luciferase reporter assay and RNA immunoprecipitation assay were applied to verify the target relations between circRTN1, miR-101-3p, and HMGB1. A xenograft tumor model was established to demonstrate the effect of circRTN1 on tumor formation in vivo. An immunohistochemistry assay was used to detect protein expression of HMGB1, ki-67, E-cadherin, and vimentin.

RESULTS

In comparison with healthy thyroid tissues and cells, PTC tissues and cells displayed high circRTN1 RNA expression and high HMGB1 mRNA and protein expression but low miR-101-3p expression. Silencing of circRTN1 suppressed PTC cell proliferation, migration, and invasion in vitro. MiR-101-3p was a target of circRTN1, and the knockdown of miR-101-3p relieved circRTN1 absence-mediated suppressive effects on PTC cell malignancy. HMGB1 was identified as a target gene of miR-101-3p, and overexpressed HMGB1 almost reverted the inhibitory impacts induced by miR-101-3p mimic in PTC cells. Moreover, circRTN1 silencing hampered tumor formation in vivo.

CONCLUSION

CircRTN1 depletion impeded PTC cell malignancy via the miR-101-3p/HMGB1 pathway, which provided a possible circRNA-targeted therapeutic strategy for PTC.

A Review and In Silico Analysis of Tissue and Exosomal Circular RNAs: Opportunities and Challenges in Thyroid Cancer

Simple Summary

Thyroid cancer is the most common endocrine neoplasm. Recently, knowledge of the molecular genetic changes of thyroid cancer has dramatically improved. Understanding the roles of these molecular changes in thyroid cancer tumorigenesis and progression is essential in developing a successful treatment strategy and improving disease outcomes. As a family of non-coding RNAs, circular RNAs (circRNAs) have been involved in several aspects of the physiological and pathological processes of the cells. The roles of circRNAs in cancer development and progress are evident. In the current review, we aimed to explore the clinical potential of circRNAs as potential diagnostic, prognostic, and therapeutic targets in thyroid cancer. Furthermore, screening the genome-wide circRNAs and performing functional enrichment analyses for all associated dysregulated circRNAs in thyroid cancer have been done. Given the unique advantages circRNAs have, such as superior stability, higher abundance, and presence in different body fluids, this family of non-coding RNAs could be promising diagnostic and prognostic biomarkers and potential therapeutic targets for thyroid cancer.

Abstract

Thyroid cancer (TC) is the most common endocrine tumor. The genetic and epigenetic molecular alterations of TC have become more evident in recent years. However, a deeper understanding of the roles these molecular changes play in TC tumorigenesis and progression is essential in developing a successful treatment strategy and improving patients’ prognoses. Circular RNAs (circRNAs), a family of non-coding RNAs, have been implicated in several aspects of carcinogenesis in multiple cancers, including TC. In the current review, we aimed to explore the clinical potential of circRNAs as putative diagnostic, prognostic, and therapeutic targets in TC. The current analyses, including genome-wide circRNA screening and functional enrichment for all deregulated circRNA expression signatures, show that circRNAs display atypical contributions, such as sponging for microRNAs, regulating transcription and translation processes, and decoying for proteins. Given their exceptional clinical advantages, such as higher stability, wider abundance, and occurrence in several body fluids, circRNAs are promising prognostic and theranostic biomarkers for TC.

Function and Clinical Significance of Circular RNAs in Thyroid Cancer

Thyroid cancer (TC) is the leading cause and mortality of endocrine malignancies worldwide. Tumourigenesis involves multiple molecules including circular RNAs (circRNAs). circRNAs with covalently closed single-stranded structures have been identified as a type of regulatory RNA because of their high stability, abundance, and tissue/developmental stage-specific expression. Accumulating evidence has demonstrated that various circRNAs are aberrantly expressed in thyroid tissues, cells, exosomes, and body fluids in patients with TC. CircRNAs have been identified as either oncogenic or tumour suppressor roles in regulating tumourigenesis, tumour metabolism, metastasis, ferroptosis, and chemoradiation resistance in TC. Importantly, circRNAs exert pivotal effects on TC through various mechanisms, including acting as miRNA sponges or decoys, interacting with RNA-binding proteins, and translating functional peptides. Recent studies have suggested that many different circRNAs are associated with certain clinicopathological features, implying that the altered expression of circRNAs may be characteristic of TC. The purpose of this review is to provide an overview of recent advances on the dysregulation, functions, molecular mechanisms and potential clinical applications of circRNAs in TC. This review also aimes to improve our understanding of the functions of circRNAs in the initiation and progression of cancer, and to discuss the future perspectives on strategies targeting circRNAs in TC.

The interaction between ETS transcription factor family members and microRNAs: A novel approach to cancer therapy

In cancer biology, ETS transcription factors promote tumorigenesis by mediating transcriptional regulation of numerous genes via the conserved ETS DNA-binding domain. MicroRNAs (miRNAs) act as posttranscriptional regulators to regulate various tumor-promoting or tumor-suppressing factors. Interactions between ETS factors and miRNAs regulate complex tumor-promoting and tumor-suppressing networks. This review discusses the progress of ETS factors and miRNAs in cancer research in detail. We focused on characterizing the interaction of the miRNA/ETS axis with competing endogenous RNAs (ceRNAs) and its regulation in posttranslational modifications (PTMs) and the tumor microenvironment (TME). Finally, we explore the prospect of ETS factors and miRNAs in therapeutic intervention. Generally, interactions between ETS factors and miRNAs provide fresh perspectives into tumorigenesis and development and novel therapeutic approaches for malignant tumors.

CircNRIP1 Exerts Oncogenic Functions in Papillary Thyroid Carcinoma by Sponging miR-653-5p and Regulating PBX3 Expression

Background

Circular RNA circ_0004771 (termed circNRIP1) was identified by RNA-Seq previously and was elevated in papillary thyroid carcinoma (PTC) tissues. A series of studies also showed that circNRIP1 was upregulated in some tumors and could promote the malignant progression of tumors. This research intended to focus on the role of circNRIP1 in PTC progression and explore the mechanisms underlying circNRIP1 functions.

Methods

RT-PCR or western blot determined circNRIP1, miR-653-5p, and pre-B-cell leukemia homeobox 3 (PBX3) expression. EdU, CCK-8, Tunel, and transwell assays determined cell proliferation, apoptosis, invasion, and migration, respectively. Luciferase reporter assay, RNA immunoprecipitation (RIP), and RNA pull down assays clarified the target relation between miR-653-5p and circNRIP1 or PBX3. Xenograft models were applied to explore the role of circNRIP1 in vivo.

Results

circNRIP1 significantly increased in PTC tissues and PTC cell lines than that in normal ones. Higher circNRIP1 expression was associated with the TNM stage and poorer overall survival. circNRIP1 knockdown attenuated the malignant progression of PTC, specifically by inhibiting proliferation and invasion/migration and promoting apoptosis. circNRIP1 was a miR-653-5p sponge; miR-653-5p knockdown reversed the suppressive role of circNRIP1 silence in PTC progression. PBX3, a target of miR-653-5p, was positively medicated through circNRIP1 via competitively sponging miR-653-5p. Knockdown of circNRIP1 attenuated the PTC tumor progression via miR-653-5p/PBX3 axis.

Conclusion

Silencing of circNRIP1 suppressed PTC development via miR-653-5p elevation and PBX3 reduction, providing a novel perspective for understanding PTC pathogenesis.

Circular RNA 0001666 inhibits colorectal cancer cell proliferation, invasion and stemness by inactivating the Wnt/β-catenin signaling pathway and targeting microRNA-1229

A previous bioinformatics study suggested that circular RNA 0001666 (circ_0001666) and its target microRNA (miR)-1229 were associated with colorectal cancer (CRC) pathogenesis. However, the role of this interaction in the regulation of CRC cell malignancy remains unclear. Thus, the aim of the present study was to examine the interaction between circ_0001666 and miR-1229, and its effects on CRC cell malignancy. circ_0001666 overexpression or knockdown plasmids were transfected into the HT-29 and HCT-116 cell lines. In addition, in rescue experiments, circ_000166 or miR-1229 overexpression plasmids were transfected into the HT-29 cell line, either alone or in combination. Following transfection, cell proliferation, apoptosis, invasion and the number of CD133⁺ cells were analyzed. The protein expression level of proteins in the Wnt/β-catenin pathway was also examined. In both HT-29 and HCT-116 cell lines, circ_0001666 overexpression increased apoptosis, whilst inhibiting cell proliferation and invasion, and reducing the frequency of CD133⁺ cells. By contrast, circ_0001666 knockdown reduced apoptosis, but increased cell proliferation and the number of CD133⁺ cells. However, cell invasion remained unaffected. In addition, circ_0001666 expression levels negatively regulated those of miR-1229, whereas miR-1229 expression did not affect circ_0001666, in both the HT-29 and HCT-116 cell lines. Furthermore, a luciferase reporter assay confirmed that miR-1229 directly bound to circ_0001666. In the HT-29 cell line, miR-1229 overexpression activated the Wnt/β-catenin pathway, and promoted cell proliferation, invasion and stemness, while suppressing cell apoptosis. In addition, miR-1229 overexpression reversed the effects of circ_0001666 overexpression. In conclusion, circ_0001666 suppresses CRC cell proliferation, invasion and stemness by inhibiting the Wnt/β-catenin signaling pathway by targeting miR-1229, and may represent a potential target for CRC treatment.

Hsa_circ_0001666 promotes non-small cell lung cancer migration and invasion through miR-1184/miR-548I/AGO1 axis

Accumulating evidence has revealed that the dysregulation of circular RNAs (circRNAs) plays crucial roles in the occurrence and progression of cancers. However, the aberrant expression profile and dysfunction of circRNAs in non-small cell lung cancer (NSCLC) have not been fully explored. Herein, we discovered that a circRNA, hsa_circ_0001666 (circ0001666), was highly expressed in NSCLC tissues and cell lines, and it was positively correlated with NSCLC tumor pathological grade and lymph node metastasis. Moreover, Kaplan-Meier survival analysis implied that NSCLC patients with high circ0001666 expression were negatively correlated with favorable survival. Functionally, circ0001666 could promote migration and invasion of NSCLC cells in vitro and in vivo. Mechanistically, circ0001666 could act as a sponge to miR-1184/miR-548I and upregulate the expression of AGO1, thereby promoting the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR signaling pathway in NSCLC cells. Collectively, these findings demonstrated that circ0001666 could serve as an oncogene to promote the migration and invasion of NSCLC via a novel miR-1184/miR-548I/AGO1 axis, which might be a promising therapeutic target for NSCLC treatment.

A Novel Circular RNA CircRFX3 Serves as a Sponge for MicroRNA-587 in Promoting Glioblastoma Progression via Regulating PDIA3

An increasing number of studies have indicated that circular RNAs (circRNAs) participate in the progression of numerous tumors. However, the functions of circRNAs in glioblastoma (GBM) remain largely unknown. In this study, we focused on a novel circRNA (hsa_circRFX3_003) that was spliced from RFX3, which we named circRFX3. We confirmed that the expression of circRFX3 was substantially increased in GBM cell lines and clinical GBM tissues. The results of a series of overexpression and knockdown assays indicated that circRFX3 could boost the proliferation, invasion, and migration of GBM cells. By performing dual-luciferase reporter gene and RNA pull-down assays, we verified that circRFX3 could sponge microRNA-587 (miR-587) to exercise its function as a competing endogenous RNA (ceRNA) in the development of GBM. In addition, PDIA3 was proven to be a downstream target of miR-587 and to regulate the Wnt/β-catenin pathway. In conclusion, circRFX3 could act as a cancer-promoting circRNA to boost the development of GBM and regulate the miR-587/PDIA3/β-catenin axis. This study might provide a novel target for the treatment of GBM with molecular therapy.

Hsa_circ_0001666 suppresses the progression of colorectal cancer through the miR-576-5p/PCDH10 axis

BACKGROUND

Though circular RNAs, new non-coding RNA classes have demonstrated that they have an essential role in the initiation as well as development of CRC (colorectal cancer), whereas in CRC the function and mechanism of hsa_circ_0001666 are less known.

METHODS

Hsa_circ_0001666 was identified by bioinformatics analysis of a circRNA microarray from the GEO database, and its expression in both CRC cell lines and tissues was analysed. A series of in vitro along with in vivo experiments were carried out for exploring the hsa_circ_0001666 functions, including transwell, wound healing, flow cytometry, colony formation, Edu, CCK-8, soft agar colony formation, tumor xenografts and lung/liver metastasis in mice. RNA pull-down, RIP (RNA immunoprecipitation), luciferase reporter assay, FISH (fluorescence in situ hybridization) and rescue experiments were used for determining the correlation among hsa_circ_0001666, miR-576-5p and PCDH10.

RESULTS

Hsa_circ_0001666 was downregulated in both CRC cell lines along with tumour tissues. A higher expression level of hsa_circ_0001666 indicated a better clinical prognosis in patients with CRC. Hsa_circ_0001666 knockdown significantly supported CRC cell proliferation along with invasion and inhibited cell apoptosis in vitro. Hsa_circ_0001666 knockdown accelerated the CRC growth and metastasis in vivo. Moreover, the mechanistic study showed that hsa_circ_0001666, acting as 'ceRNA' of miR-576-5p, prevented PCDH10 downregulation, as well as suppressed EMT and stemness of CRC cells, and the Wnt/β-catenin signalling pathway. Inhibiting miR-576-5p or overexpressing PCDH10 could reverse phenotypic changes caused by knocking down of hsa_circ_0001666.

CONCLUSIONS

Hsa_circ_0001666 suppresses CRC progression through the miR-576-5p/PCDH10 axis and may provide a new insight for the diagnosis and treatment of CRC.

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.