CircZNF609 promotes breast cancer cell growth, migration, and invasion by elevating p70S6K1 via sponging miR-145-5p

CircIQCH Contributes to the Progression of Breast Cancer by Elevating NFIB Through Decoying miR-139-5p

Circular RNAs (circRNAs) are implicated in the progression of breast cancer (BC). However, the explorations on circRNA IQ motif containing H (circIQCH) in BC progression remain limited. Functional experiments were conducted using in vitro and murine xenograft model assays, respectively. Dual-luciferase reporter assay and RIP assay detected the associations among circIQCH, miR-139-5p, and nuclear factor IB (NFIB). CircIQCH was upregulated in BC, and the silencing of circIQCH repressed BC cell growth, metastasis, and autophagy, arrested cell cycle, promoted cell apoptosis in vitro, and blocked tumor growth in vivo. CircIQCH positively modulated NFIB expression by sponging miR-139-5p. Moreover, the deletion of miR-139-5p abated the action of circIQCH deficiency on BC cell malignant behaviors. Overexpression of miR-139-5p repressed the malignant characteristics of BC cells, while these impacts were abolished by elevating NFIB. Collectively, CircIQCH functioned as an oncogene in BC through upregulating NFIB expression by sponging miR-139-5p.

CircZNF609 inhibited bladder cancer immunotherapy sensitivity via enhancing fatty acid uptake through IGF2BP2/CD36 pathway

Circular RNAs (circRNAs) are gaining attention for their involvement in immune escape and immunotherapy sensitivity regulation. CircZNF609 is a well-known oncogene in various solid tumours. Our previous research revealed its role in reducing the chemosensitivity of bladder cancer (BCa) to cisplatin. However, the underlying role of circZNF609 in BCa immune escape and immunotherapy sensitivity remains unknown. We conducted BCa cells-CD8 + T cells co-culture assays, cell line-derived xenograft and patient-derived xenograft mouse models with human immune reconstitution to further confirm the role of circZNF609 in BCa immune escape and immunotherapy sensitivity. Overexpression of circZNF609 promoted BCa immune escape in vitro and in vivo. Mechanistically, circZNF609 was bound to IGF2BP2, enhancing its interaction with the 3'-untranslated region of CD36. This increased the stability of the CD36 mRNA, leading to enhanced fatty acid uptake by BCa cells and fatty acid depletion within the tumour microenvironment. Additionally, the nuclear export of circZNF609 was regulated by DDX39B. CircZNF609 promoted immune escape and suppressed BCa immunotherapy sensitivity by regulating the newly identified circZNF609/IGF2BP2/CD36 cascade. Therefore, circZNF609 holds potential as both a biomarker and therapeutic target in BCa immunotherapy.

The Transcriptional Landscape of Coding and Noncoding RNAs in Recurrent and Nonrecurrent Colon Cancer

A number of patients with colon cancer with local or local advanced disease suffer from recurrence and there is an urgent need for better prognostic biomarkers in this setting. Here, the transcriptomic landscape of mRNAs, long noncoding RNAs, snRNAs, small nucleolar RNAs (snoRNAs), small Cajal body-specific RNAs, pseudogenes, and circular RNAs, as well as RNAs denoted as miscellaneous RNAs, was profiled by total RNA sequencing. In addition to well-known coding and noncoding RNAs, differential expression analysis also uncovered transcripts that have not been implicated previously in colon cancer, such as RNA5SP149, RNU4-2, and SNORD3A. Moreover, there was a profound global up-regulation of snRNA pseudogenes, snoRNAs, and rRNA pseudogenes in more advanced tumors. A global down-regulation of circular RNAs in tumors relative to normal tissues was observed, although only a few were expressed differentially between tumor stages. Many previously undescribed transcripts, including RNU6-620P, RNU2-20P, VTRNA1-3, and RNA5SP60, indicated strong prognostic biomarker potential in receiver operating characteristics analyses. In summary, this study unveiled numerous differentially expressed RNAs across various classes between recurrent and nonrecurrent colon cancer. Notably, there was a significant global up-regulation of snRNA pseudogenes, snoRNAs, and rRNA pseudogenes in advanced tumors. Many of these newly discovered candidates demonstrate a strong prognostic potential for stage II colon cancer.

CircZNF609 and circNFIX as possible regulators of glioblastoma pathogenesis via miR-145-5p/EGFR axis

Glioblastoma is a rare and deadly malignancy with a low survival rate. Emerging evidence has shown that aberrantly expressed circular RNAs (circRNAs) play a critical role in the initiation and progression of GBM tumorigenesis. The oncogenic function of circZNF609 and circNFIX is involved in several types of cancer, but the role and underlying mechanism of these circRNAs in glioblastoma remain unclear. In this study, we hypothesized that circZNF609 and circNFIX may regulate EGFR through sponging miR-145-5p. Herein, we assessed the expression levels of circZNF609, circNFIX, miR-145-5p, and EGFR using quantitative polymerase chain reaction in glioblastoma patients and normal brain samples. The results showed that circZNF609, circNFIX, and EGFR expression levels were upregulated and miR145-5p was downregulated (p = 0.001, 0.06, 0.002, and 0.0065, respectively), while there was no significant association between clinicopathological features of the patients and the level of these genes expression. We also found a significant inverse correlation between miR145-5p and the expression of cZNF609, cNFIX and EGFR (p = 0.0003, 0.0006, and 0.009, respectively). These findings may open a new window for researchers to better understand the potential pathways involved in GBM pathogenesis. In conclusion, it may provide a new potential pathway for the development of effective drugs for the treatment of GBM patients.

Bibliometric analysis of the research hotspots and trends of circular RNAs

Background and objective

Circular RNAs (circRNAs) have garnered considerable attention in the study of various human diseases due to their ubiquitous expression and potential biological functions. This study conducts a bibliometric and visualization-based analysis of circRNA-related research in diseases, aiming to reveal the current status, hotspots and emerging trends within the field.

Methods

Literature published between 2013 and 2022 and indexed in the Web of Science core databases was retrieved. Visualizations of publication volume, countries, authors, institutions, journals, references, and keywords were performed. Microsoft Excel (2021) was used to analyze and graph publication volume and growth trends. Additionally, CiteSpace (version 6.1.R6) and VOSviewer (version 1.6.18) were employed to visualize the bibliographic information.

Results

Between 2013 and 2022, a total of 4195 relevant articles on circRNA in the context of diseases were identified. These articles covered 56 countries, 2528 institutions, 19,842 authors and 698 journals, citing 85,541 references. The annual publication volume showed an exponential growth trend, with rapid development post-2017. China, the United States and Germany emerged as the top three contributors, demonstrating high publication volume and total citations. Notably, Nanjing Medical University exhibited the highest publication volume, boasting 291 articles. Burton B. Yang and Li Yang consistently ranked among the top 10 authors in terms of publication volume and citations, emerging as core contributors in this research field. The journal Bioengineered ranked first in terms of published articles (160), with an impact factor of 6.832, while Molecular Cancer garnered the highest impact factor (41.4), solidifying its position as a top journal in this field. Furthermore, high-frequency keywords included "expression" "proliferation" "biomarker" "microRNA" "cancer", signifying the prevailing research hotspots and principal themes of this field over the past decade. As of 2022, "biomarker", "prostate cancer","drug resistance","papillary thyroid carcinoma", etc. continued as keywords during the outbreak period. At present, the value of circRNA application is mainly reflected in the two aspects of biomarkers and therapeutic targets, and the prediction of accurate diagnosis and precise treatment based on big data analysis, especially in cancer, will become a hot spot of research in the future.

Conclusion

The trajectory of circRNA research from its biological origins to its applications in diseases has been delineated from 2013 to 2022. However, the transition to disease-specific applications and exploration of biological functions warrants further attention in future research endeavors.

Circular RNA-mediated miRNA sponge & RNA binding protein in biological modulation of breast cancer

Circular RNAs (circRNAs) and small non-coding RNAs of the head-to-junction circle in the construct play critical roles in gene regulation and are significantly associated with breast cancer (BC). Numerous circRNAs are potential cancer biomarkers that may be used for diagnosis and prognosis. Widespread expression of circRNAs is regarded as a feature of gene expression in highly diverged eukaryotes. Recent studies show that circRNAs have two main biological modulation models: sponging and RNA-binding. This review explained the biogenesis of circRNAs and assessed emerging findings on their sponge function and role as RNA-binding proteins (RBPs) to better understand how their interaction alters cellular function in BC. We focused on how sponges significantly affect the phenotype and progression of BC. We described how circRNAs exercise the translation functions in ribosomes. Furthermore, we reviewed recent studies on RBPs, and post-protein modifications influencing BC and provided a perspective on future research directions for treating BC.

CircZNF609 regulates pulmonary fibrosis via miR-145-5p/KLF4 axis and its translation function

BACKGROUND

Pulmonary fibrosis is a growing clinical problem that develops as a result of abnormal wound healing, leading to breathlessness, pulmonary dysfunction and ultimately death. However, therapeutic options for pulmonary fibrosis are limited because the underlying pathogenesis remains incompletely understood. Circular RNAs, as key regulators in various diseases, remain poorly understood in pulmonary fibrosis induced by silica.

METHODS

We performed studies with fibroblast cell lines and silica-induced mouse pulmonary fibrosis models. The expression of circZNF609, miR-145-5p, and KLF4 was determined by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. RNA immunoprecipitation (RIP) assays and m6A RNA immunoprecipitation assays (MeRIP), Western blotting, immunofluorescence assays, and CCK8 were performed to investigate the role of the circZNF609/miR-145-5p/KLF4 axis and circZNF609-encoded peptides in fibroblast activation.

RESULTS

Our data showed that circZNF609 was downregulated in activated fibroblasts and silica-induced fibrotic mouse lung tissues. Overexpression of circZNF609 could inhibit fibroblast activation induced by transforming growth factor-β1 (TGF-β1). Mechanically, we revealed that circZNF609 regulates pulmonary fibrosis via miR-145-5p/KLF4 axis and circZNF609-encoded peptides. Furthermore, circZNF609 was highly methylated and its expression was controlled by N6-methyladenosine (m6A) modification. Lastly, in vivo studies revealed that overexpression of circZNF609 attenuates silica-induced lung fibrosis in mice.

CONCLUSIONS

Our data indicate that circZNF609 is a critical regulator of fibroblast activation and silica-induced lung fibrosis. The circZNF609 and its derived peptides may represent novel promising targets for the treatment of pulmonary fibrosis.

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.

Non-coding RNAs' function in cancer development, diagnosis and therapy

While previous research on cancer biology has focused on genes that code for proteins, in recent years it has been discovered that non-coding RNAs (ncRNAs)play key regulatory roles in cell biological functions. NcRNAs account for more than 95% of human transcripts and are an important entry point for the study of the mechanism of cancer development. An increasing number of studies have demonstrated that ncRNAs can act as tumor suppressor genes or oncogenes to regulate tumor development at the epigenetic level, transcriptional level, as well as post-transcriptional level. Because of the importance of ncRNAs in cancer, most clinical trials have focused on ncRNAs to explore whether ncRNAs can be used as new biomarkers or therapies. In this review, we focus on recent studies of ncRNAs including microRNAs (miRNAs), long ncRNAs (lncRNAs), circle RNAs (circRNAs), PIWI interacting RNAs (piRNAs), and tRNA in different types of cancer and explore the application of these ncRNAs in the development of cancer and the identification of relevant therapeutic targets and tumor biomarkers. Graphical abstract drawn by Fidraw.

The m6A reader YTHDC1 and the RNA helicase DDX5 control the production of rhabdomyosarcoma-enriched circRNAs

N6-Methyladenosine (m⁶A) is well-known for controlling different processes of linear RNA metabolism. Conversely, its role in the biogenesis and function of circular RNAs (circRNAs) is still poorly understood. Here, we characterize circRNA expression in the pathological context of rhabdomyosarcoma (RMS), observing a global increase when compared to wild-type myoblasts. For a set of circRNAs, such an increase is due to the raised expression of the m⁶A machinery, which we also find to control the proliferation activity of RMS cells. Furthermore, we identify the RNA helicase DDX5 as a mediator of the back-splicing reaction and as a co-factor of the m⁶A regulatory network. DDX5 and the m⁶A reader YTHDC1 are shown to interact and to promote the production of a common subset of circRNAs in RMS. In line with the observation that YTHDC1/DDX5 depletion reduces RMS proliferation, our results provide proteins and RNA candidates for the study of rhabdomyosarcoma tumorigenicity.

PI3K/AKT/mTOR signaling pathway modulation by circular RNAs in breast cancer progression

The PI3K/Akt/mTOR signaling pathway is responsible for many cellular behaviors, including survival, growth, and proliferation. A newly identified RNA, circular RNA (circRNA), plays a crucial role in the regulation of gene expression. The upregulation of the PI3K/Akt pathway through dysregulated circRNAs promotes breast tumor initiation, growth, and progression. The dysregulation of PI3K/Akt-regulating circRNAs seems to be directly correlated with breast cancer clinical features, including overall survival, tumor size, cancer stage, and lymph node metastasis. In addition, targeting these circRNAs may be a promising option in cancer-targeted therapy. Understanding the molecular pathogenesis of the circRNA-PI3K/AKT axis may give the insight to develop new therapeutic and diagnostic approaches for breast cancer therapy. Here we reviewed the expression and functions of PI3K/AKT-regulating circRNAs, and their correlation with breast cancer clinical features. In addition, the potential of PI3K/AKT-regulating circRNAs as diagnostic/prognostic biomarkers or therapeutic targets was discussed.

Circular RNAs: biology and clinical significance of breast cancer

Circular RNAs (circRNAs) are novel noncoding RNAs with covalently closed-loop structures that can regulate eukaryotic gene expression. Due to their stable structure, circRNAs are widely distributed in the cytoplasm and have important biological functions, including as microRNA sponges, RNA-binding protein conjugates, transcription regulators, and translation templates. Breast cancer is among the most common malignant cancers diagnosed in women worldwide. Despite the development of comprehensive treatments, breast cancer still has high mortality rates. Recent studies have unmasked critical roles for circRNAs in breast cancer as regulators of tumour initiation, progression, and metastasis. Further, research has revealed that some circRNAs have the potential for use as diagnostic and prognostic biomarkers in clinical practice. Herein, we review the biogenesis and biological functions of circRNAs, as well as their roles in different breast cancer subtypes. Moreover, we provide a comprehensive summary of the clinical significance of circRNAs in breast cancer. CircRNAs are believed to be a hot focus in basic and clinical research of breast cancer, and innovative future research directions of circRNAs could be used as biomarkers, therapeutic targets, or novel drugs.Abbreviations: CeRNA: Competitive endogenous RNA; ciRNA: Circular intronic RNA; circRNA: Circular RNA; EIciRNA: Exon-intron circRNA; EMT: Epithelial-mesenchymal transition; IRES: Internal ribosome entry site; lncRNA: Long non-coding RNA; miRNA: MicroRNA; MRE: MiRNA response element; ncRNA: Non-coding RNA; RBP: RNA-binding protein; RNA-seq: RNA sequencing; RT-PCR: Reverse transcription-polymerase chain reaction.

Serum hsa_circ_0000615 is a prognostic biomarker of sorafenib resistance in hepatocellular carcinoma

BACKGROUND

Circular RNAs (circRNAs) can shape tumor progression and chemoresistance. How specific circRNAs shape hepatocellular carcinoma (HCC) chemoresistance, however, remains to be fully elucidated.

METHODS

In total, serum samples were collected from 202 HCC patients that had completed four sorafenib chemotherapy cycles. Serum hsa_circ_0000615 levels in these patients were quantified via quantitative real-time polymerase chain reaction (qRT-PCR), with demographic details and survival outcomes being recorded for subsequent analyses.

RESULTS

We found hsa_circ_0000615 to be significantly upregulated in chemoresistant HCC patients relative to chemosensitive patients, with such upregulation being positively correlated with disease stage. Moreover, the area under the curve (AUC) value for hsa_circ_0000615 was moderately good, and high levels of hsa_circ_0000615 expression were associated with shorter overall survival among chemoresistant HCC patients.

CONCLUSION

Our results highlight hsa_circ_0000615 as a promising driver of sorafenib resistance in HCC patients, highlighting it as a promising target for the treatment of this deadly cancer type.

Non-coding RNA in rhabdomyosarcoma progression and metastasis

Rhabdomyosarcoma (RMS) is a soft tissue sarcoma of skeletal muscle differentiation, with a predominant occurrence in children and adolescents. One of the major challenges facing treatment success is the presence of metastatic disease at the time of diagnosis, commonly associated with the more aggressive fusion-positive subtype. Non-coding RNA (ncRNA) can regulate gene transcription and translation, and their dysregulation has been associated with cancer development and progression. MicroRNA (miRNA) are short non-coding nucleic acid sequences involved in the regulation of gene expression that act by targeting messenger RNA (mRNA), and their aberrant expression has been associated with both RMS initiation and progression. Other ncRNA including long non-coding RNA (lncRNA), circular RNA (circRNA) and ribosomal RNA (rRNA) have also been associated with RMS revealing important mechanistic roles in RMS biology, but these studies are still limited and require further investigation. In this review, we discuss the established roles of ncRNA in RMS differentiation, growth and progression, highlighting their potential use in RMS prognosis, as therapeutic agents or as targets of treatment.

Emerging Roles of Circ-ZNF609 in Multiple Human Diseases

Circular RNAs (circRNAs) are a special type of endogenous RNAs with extensive roles in multiple human diseases. They are formed by back-splicing of partial sequences of the parental precursor mRNAs. Unlike linear RNAs, their covalently closed loop structure without a 5′ cap and a 3′ polyadenylated tail confers on them high stability and they are difficult to be digested by RNase R. Increasing evidence has proved that aberrant expressions of many circRNAs are detected and that circRNAs exert essential biological functions in disease development and progression via acting as a molecular sponge of microRNA, interacting with proteins as decoys or scaffolds, or self-encoding small peptides. Circular RNA zinc finger protein 609 (circ-ZNF609) originates from exon2 of ZNF609, which is located at chromosome 15q22.31, and it has recently been proved that it can translate into a protein. Being aberrantly upregulated in various diseases, it could promote malignant progression of human tumors, as well as tumor cell proliferation, migration, and invasion. Here in this review, we concluded the biological functions and potential mechanisms of circ-ZNF609 in multiple diseases, which could be further explored as a targetable molecule in future accurate diagnosis and prognosis.

A novel circular RNA confers trastuzumab resistance in human epidermal growth factor receptor 2-positive breast cancer through regulating ferroptosis

HER2-positive breast cancer is an aggressive subtype of breast cancer, characterized by high malignancy and poor prognosis. Trastuzumab, the first HER2-targeted monoclonal antibody therapy, has a crucial role in a curative setting in HER2-positive breast cancer. However, frequent drug resistance inhibits its clinical efficacy. Herein, by performing circular RNA (circRNA) profiling, we identified a novel circRNA, circ-BGN, as a key contributor in trastuzumab resistance. Circ-BGN was evidently increased in trastuzumab-resistant breast cancer cells and tissues, linking to poor overall survival. Knockdown of circ-BGN inhibited breast cancer cell viability and notably restored its sensitivity to trastuzumab. Further, we found that circ-BGN could directly bind to OTUB1 and SLC7A11, enhancing OTUB1-mediated SLC7A11 deubiquitination and thereby inhibiting ferroptosis, a newly recognized form of cell death that is distinct from apoptosis, necrosis, and autophagy. Moreover, erastin, a small-molecule ferroptosis inducer, could effectively restore the anti-tumor effect of trastuzumab. Pre-clinically, the orthotopic tumor model showed that erastin significantly reduced tumor volume generated by trastuzumab-resistant breast cancer cells, which was more pronounced after combined circ-BGN knockdown. Collectively, our data reveal a novel circRNA controlling trastuzumab resistance via regulation of ferroptosis, providing a promising therapeutic strategy for trastuzumab-resistant breast cancer patients.

Circular RNAs Acting as miRNAs’ Sponges and Their Roles in Stem Cells

Circular RNAs (circRNAs), a novel type of endogenous RNAs, have become a subject of intensive research. It has been found that circRNAs are important players in cell differentiation and tissue homeostasis, as well as disease development. Moreover, the expression of circRNAs is usually not correlated with their parental gene expression, indicating that they are not only a steady-state by-product of mRNA splicing but a product of variable splicing under novel regulation. Sequence conservation analysis has also demonstrated that circRNAs have important non-coding functions. CircRNAs exist as a covalently closed loop form in mammalian cells, where they regulate cellular transcription and translation processes. CircRNAs are built from pre-messenger RNAs, and their biogenesis involves back-splicing, which is catalyzed by spliceosomes. The splicing reaction gives rise to three different types of intronic, exotic and exon–intron circular RNAs. Due to higher nuclease stability and longer half lives in cells, circRNAs are more stable than linear RNAs and have enormous clinical advantage for use as diagnostic and therapeutic biomarkers for disease. In recent years, it has been reported that circRNAs in stem cells play a crucial role in stem cell function. In this article, we reviewed the general feature of circRNAs and the distinct roles of circRNAs in stem cell biology, including regulation of stem cell self-renewal and differentiation. CircRNAs have shown unique expression profiles during differentiation of stem cells and could serve as promising biomarkers of these cells. As circRNAs play pivotal roles in stem cell regulation as well as the development and progression of various diseases, we also discuss opportunities and challenges of circRNA-based treatment strategies in future effective therapies for promising clinical applications.

Circular RNA ZNF609 promotes laryngeal squamous cell carcinoma progression by upregulating epidermal growth factor receptor via sponging microRNA-134-5p

Emerging evidence has revealed that aberrantly expressed circular RNAs (circRNAs) play vital roles in tumorigenesis and progression of diverse human malignancies. CircZNF609 was found to be involved in hepatocellular carcinoma, but the role and underlying mechanism of circZNF609 in laryngeal squamous cell carcinoma (LSCC) remain unclear. This study aimed to explore the molecular mechanism of circZNF609 in LSCC. qRT-qPCR was performed to detect the expression of circZNF609 and microRNA-134-5p (miR-134-5p) in LSCC. Colony formation assay, CCK-8 assay, BrdU incorporation assay, clone formation assay, transwell invasion assay and Western blot analysis were performed to evaluate LSCC cell proliferation, as well as the expression of proliferating cell nuclear antigen (PCNA) and MMP-2. Luciferase reporter assay, target gene prediction and screening were used to validate downstream target genes of circZNF609 and miR-134-5p. EGFR expression was detected by Western blot analysis and RT-qPCR. Nude mice were used to detect tumor changes. CircZNF609 was upregulated in LSCC and associated with poor survival of LSCC patients. Knockdown of circZNF609 inhibited LSCC proliferation, invasion and the expression of PCNA and matrix matalloproteinases-2 (MMP-2). CircZNF609 can regulate miR-134-5p to upregulate epidermal growth factor receptor (EGFR). In addition, knockdown of EGFR or overexpression of miR-134-5p could reverse the tumor-promoting effects of circZNF609 in LSCC. In LSCC tissues, circZNF609 was negatively correlated with miR-134-5p and positively correlated with EGFR. CircZNF609 promotes the progression of LSCC via the miR-134-5p/EGFR axis, which might be the therapeutic target of LSCC.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

Chimeric Peptides/Proteins Encoded by circRNA: An Update on Mechanisms and Functions in Human Cancers

The discovery of circular RNAs and exploration of their biological functions are increasingly attracting attention in cell bio-sciences. Owing to their unique characteristics of being highly conserved, having a relatively longer half-life, and involvement in RNA maturation, transportation, epigenetic regulation, and transcription of genes, it has been accepted that circRNAs play critical roles in the variety of cellular processes. One of the critical importance of these circRNAs is the presence of small open reading frames that enable them to encode peptides/proteins. In particular, these encoded peptides/proteins mediate essential cellular activities such as proliferation, invasion, epithelial-mesenchymal transition, and apoptosis and develop an association with the development and progression of cancers by modulating diverse signaling pathways. In addition, these peptides have potential roles as biomarkers for the prognosis of cancer and are being used as drug targets against tumorigenesis. In the present review, we thoroughly discussed the biogenesis of circRNAs and their functional mechanisms along with a special emphasis on the reported chimeric peptides/proteins encoded by circRNAs. Additionally, this review provides a perspective regarding the opportunities and challenges to the potential use of circRNAs in cancer diagnosis and therapeutic targets in clinics.

CircRNA ZNF609 promotes the growth and metastasis of thyroid cancer in vivo and in vitro by downregulating miR-514a-5p

Thyroid cancer (TC) often manifests in the form of a painless cervical mass or nodule and continues to increase in incidence. Currently, much less is known about its pathogenesis in TC cells. This study sought to figure out what role the circular RNA (circRNA) ZNF609/miR-514a-5p might play in TC development and metastasis. In this study, the detection of circ-ZNF609 and miR-514a-5p expressions was carried out by qRT-PCR in TC cell lines. Cell proliferation assessment is employed by cell counting kit-8 (CCK-8) assay, colony formation, Western blot and immunofluorescence. Cell invasion and migration measurement were conducted applying wound healing and transwell. The relationship between circ-ZNF609 and miR-514a-5p was subjected to prediction with bioinformatics analysis and validated with the aid of luciferase reporter assay. Furthermore, xenograft animal experiment was adopted to confirm the role of circ-ZNF609/miR-514a-5p in TC in vivo. The data indicated that circ-ZNF609 was highly expressed, while miR-514a-5p was downregulated in TC cells. Circ-ZNF609 knockdown prevented the malignant biological behaviors of TPC-1 and IHH-4 cells. Besides, circ-ZNF609 sponged miR-514a-5p and miR-514a-5p knockdown reversed the suppressed impacts of circ-ZNF609 knockdown on TC cell malignant biological behaviors. In addition, the silence of circ-ZNF6091 significantly repressed, whereas miR-514a-5p silencing promoted TC tumorigenesis in vivo. The findings highlighted the importance of circ-ZNF609 function in facilitating TC cell development and metastasis in vitro and in vivo via binding to miR-514a-5p.

CircFISH: A Novel Method for the Simultaneous Imaging of Linear and Circular RNAs

Simple Summary

Circular RNAs are a recently appreciated class of regulatory non-coding RNAs. Although a number of high-resolution methods have been developed for the imaging of RNAs in cells and tissues, there is no reliable method for the simultaneous imaging of circular RNAs distinctly from their linear counterparts. Here, we report circFISH as a simple and single-molecule resolution method that will simultaneously image linear and circular RNAs in fixed cells and tissues. We demonstrate that multiple circular RNAs can be imaged using circFISH. We also show the ability of circFISH to work seamlessly with protein and other organelle imaging. We optimized the method to work across sample types, making it a versatile tool for the functional characterization of circular RNAs.

Abstract

Circular RNAs (circRNAs) are regulatory RNAs which have recently been shown to have clinical significance in several diseases, including, but not limited to, various cancers, neurological diseases and cardiovascular diseases. The function of such regulatory RNAs is largely dependent on their subcellular localization. Several circRNAs have been shown to conduct antagonistic roles compared to the products of the linear isoforms, and thus need to be characterized distinctly from the linear RNAs. However, conventional fluorescent in situ hybridization (FISH) techniques cannot be employed directly to distinguish the signals from linear and circular isoforms because most circRNAs share the same sequence with the linear RNAs. In order to address this unmet need, we adapted the well-established method of single-molecule FISH by designing two sets of probes to differentiate the linear and circular RNA isoforms by virtue of signal colocalization. We call this method ‘circular fluorescent in situ hybridization’ (circFISH). Linear and circular RNAs were successfully visualized and quantified at a single-molecule resolution in fixed cells. RNase R treatment during the circFISH reduced the levels of linear RNAs while the circRNA levels remain unaltered. Furthermore, cells with shRNAs specific to circRNA showed the loss of circRNA levels, whereas the linear RNA levels were unaffected. The optimization of the in-situ RNase R treatment allowed the multiplexing of circFISH to combine it with organelle staining. CircFISH was found to be compatible with multiple sample types, including cultured cells and fresh-frozen and formalin-fixed tissue sections. Thus, we present circFISH as a versatile method for the simultaneous visualization and quantification of the distribution and localization of linear and circular RNA in fixed cells and tissue samples.

Circular RNA ZNF609/CKAP5 mRNA interaction regulates microtubule dynamics and tumorigenicity

Circular RNAs (circRNAs) are widely expressed in eukaryotes and are regulated in many biological processes. Although several studies indicate their activity as microRNA (miRNA) and protein sponges, little is known about their ability to directly control mRNA homeostasis. We show that the widely expressed circZNF609 directly interacts with several mRNAs and increases their stability and/or translation by favoring the recruitment of the RNA-binding protein ELAVL1. Particularly, the interaction with CKAP5 mRNA, which interestingly overlaps the back-splicing junction, enhances CKAP5 translation, regulating microtubule function in cancer cells and sustaining cell-cycle progression. Finally, we show that circZNF609 downregulation increases the sensitivity of several cancer cell lines to different microtubule-targeting chemotherapeutic drugs and that locked nucleic acid (LNA) protectors against the pairing region on circZNF609 phenocopy such effects. These data set an example of how the small effects tuned by circZNF609/CKAP5 mRNA interaction might have a potent output in tumor growth and drug response.

YY1 and eIF4A3 are mediators of the cell proliferation, migration and invasion in cholangiocarcinoma promoted by circ-ZNF609 by targeting miR-432-5p to regulate LRRC1

Cholangiocarcinoma is a highly aggressive malignant tumor, and its incidence is increasing all over the world. More and more evidences show that the aberrant expression of circular RNAs play important roles in tumorigenesis and progression. Current studies on the expression and function of circRNAs in cholangiocarcinoma are scarce. In this study, circ-ZNF609 was discovered as a novel circRNA highly expressed in cholangiocarcinoma for the first time. The circ-ZNF609 expression is connected with the advanced TNM stage, lymphatic invasion and survival time in cholangiocarcinoma patients, and can be used as an independent prognostic factor for the patients. Circ-ZNF609 can promote the cholangiocarcinoma cells proliferation, migration and invasion in vitro, it can also catalyze the xenograft growth in vivo. The promoting effect of circ-ZNF609 on cholangiocarcinoma is achieved via oncogene LRRC1 up-regulation through targeting miR-432-5p by endogenous competitive RNA mechanism. In addition, transcription factor YY1 can bind to the promoter of ZNF609 to further facilitate the transcription of circ-ZNF609. RNA binding protein eIF4A3 can bind to the pre-mRNA of circ-ZNF609 which promotes the circ-ZNF609 circular formation. Overall, YY1/eIF4A3/circ-ZNF609/miR-432-5p/LRRC1 have a significant role in progression of cholangiocarcinoma, and circ-ZNF609 is expected to become a novel biomarker for targeted therapy and prognosis evaluation of cholangiocarcinoma.

Influence of dysregulated expression of circular RNA on the diagnosis and prognosis of breast cancer in Asia: a meta-analysis study

OBJECTIVE

Recent studies have reported a correlation between non-coding RNAs such as circular RNAs (circRNAs) and clinical value of various cancers. However, the diagnostic and prognostic role of circRNA in breast cancer remains controversial.

DESIGN

Systematic review and meta-analysis.

METHODS

Diagnostic efficacy was estimated by sensitivity, specificity and area under the curve (AUC). Pooled HRs with 95% CIs estimated overall survival (OS), and ORs with 95% CIs investigated clinical features.

RESULTS

By searching PubMed, Embase, Web of Science, CNKI and Cochrane Library, we obtained a total of 29 studies with 4405 patients. A shorter survival time was associated with high expression levels of tumour-promoter circRNAs (OS: HR=2.43, 95% CI 2.20 to 2.92, p<0.001), and tumour-suppressor circRNAs were related to a favourable prognosis (OS: HR=0.32, 95% CI 0.23 to 0.44, p<0.001). Furthermore, high expression levels of oncogenic circRNAs were associated with poor clinical outcomes; tumour-suppressor circRNAs showed the opposite result. As for the diagnostic role, the outcome indicated an AUC of 0.82 (95% CI 0.78 to 0.85), with 85% sensitivity and 86% specificity to distinguish patients with breast cancer from healthy controls.

CONCLUSION

Dysregulated expression of circRNA was related to diagnosis and prognosis in breast cancer, which indicated it might be a novel biomarker and a target of therapy for breast cancer.

PROSPERO REGISTRATION NUMBER

CRD42020207912.

The Diagnostic Value of Serum Exosomal Has_circ_0000615 for Breast Cancer Patients

Background

To explore the expression level of has_circ_0000615 in peripheral blood samples and evaluate its diagnostic value for breast cancer patients.

Methods

The peripheral blood samples of 95 breast cancer patients who underwent curative surgical resection and 95 age-matched healthy volunteers in our institutions from September 2019 to November 2020 were systematically collected. The expression level of has_circ_0000615 in the plasma was amplified and detected by qRT-PCR, and its correlation to clinicopathological characteristics of breast cancer patients were analyzed.

Results

Breast cancer patients had a significantly higher expression level of has_circ_0000615 in the plasma than healthy controls (P < 0.01), and its high expression was closely associated with advanced tumor stage (P=0.010), lymph node metastasis (P = 0.001) and high grade of recurrence risk (P=0.012). The receiver operator characteristic (ROC) curves showed that the area under curve (AUC) value, sensitivity and specificity of has_circ_0000615 for the diagnosis of non-metastatic breast cancer was 0.904 (95% CI: 0.863–0.944), 76.8% and 88.4%, respectively. Serum has_circ_0000615 expression had a better diagnostic efficiency than routine tumor biomarkers such as CA153, CA125 and CEA for distinguishing breast cancer patients from healthy individuals. TEM revealed that isolated exosomes from the culture medium of breast cancer cells had a disk-like appearance with a diameter of 80–200 nm vesicles, and the expression of exosome markers CD9 and CD81 was markedly increased. More importantly, the expression of has_circ_0000615 was detected in the exosomes and its expression level was markedly upregulated in breast cancer cell lines compared with normal ductal epithelial cells. The stability assay showed that there was no difference between RNA extraction at 0 hour and 24 hours in terms of the expression of has_circ_0000615 (P =0.327). Has_circ_0000615 might as exosomes be secreted into the circulating blood of breast cancer patients, resulting in a high expression level in plasma samples.

Conclusion

The detection of has_circ_0000615 might be a promising diagnostic method for breast cancer.

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

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

Circular RNA VANGL1 knockdown suppressed viability, promoted apoptosis, and increased doxorubicin sensitivity through targeting miR-145-5p to regulate SOX4 in bladder cancer cells

Background

Bladder cancer is a common malignancy in the world. It is reported that circular RNA VANGL1 (circ_VANGL1) was involved in bladder cancer progression. However, the functional role and molecular mechanism of circ_VANGL1 in bladder cancer were still unclear.

Methods

The levels of circ_VANGL1, microRNA-145-5p (miR-145-5p), and Sex-determining region Y-related high-mobility group box 4 (SOX4) in bladder cancer tissues and cells were determined by quantitative real-time polymerase chain (RT-qPCR). The relative protein expression was detected by western blot. Cell counting kit-8 (CCK8) and flow cytometry analysis were used to measure cell viability, IC₅₀ value, and apoptosis rate. The interaction between miR-145-5p and circ_VANGL1 or SOX4 was predicted by online software starBase v2.0 or Targetscan and verified by the dual-luciferase reporter assay. Besides, xenograft mice model was used to detect the effects of circ_VANGL1 in vivo.

Results

The level of circ_VANGL1 and SOX4 was increased, while miR-145-5p was decreased in bladder cancer tissues and cells. Knockdown of circ_VANGL1 suppressed viability, while promoted apoptosis and increased doxorubicin sensitivity in bladder cancer cells. Moreover, circ_VANGL1 acted as a sponge for miR-145-5p. In addition, miR-145-5p partially reversed the effects of miR-145-5p knockdown in T24 and J82 cells. SOX4 was a target of miR-145-5p and negatively regulated by miR-145-5p. Furthermore, miR-145-5p regulated SOX4 to affect cell progression in bladder cancer cells, including viability, apoptosis, and doxorubicin sensitivity. Besides, circ_VANGL1 suppressed tumor growth and enhanced the doxorubicin sensitivity in bladder cancer in vivo.

Conclusion

circ_VANGL1 mediated cell viability, apoptosis, and doxorubicin sensitivity by regulating miR-145-5p/SOX4 axis in bladder cancer, providing a potential therapeutic target for bladder cancer therapy.

The biogenesis, function and clinical significance of circular RNAs in breast cancer

Circular RNAs (circRNAs) are noncoding RNAs that form covalently closed loop structures. CircRNAs are dysregulated in cancer and play key roles in tumorigenesis, diagnosis, and tumor therapy. CircRNAs function as competing endogenous RNAs or microRNA sponges that regulate transcription and splicing, binding to proteins, and translation. CircRNAs may serve as novel biomarkers for cancer diagnosis, and they show potential as therapeutic targets in cancers including breast cancer (BC). In women, BC is the most common malignant tumor worldwide and the second leading cause of cancer death. Although evidence indicates that circRNAs play a critical role in BC, the mechanisms regulating the function of circRNAs in BC remain poorly understood. Here, we provide literature review aiming to clarify the role of circRNAs in BC and summarize the latest research. We provide a systematic overview of the biogenesis and biological functions of circRNAs, elaborate on the functional roles of circRNAs in BC, and highlight the value of circRNAs as diagnostic and therapeutic targets in BC.

Dysregulation of tumour microenvironment driven by circ-TPGS2/miR-7/TRAF6/NF-κB axis facilitates breast cancer cell motility

Tumour microenvironment (TME) is frequently remodelled and deregulated in cancer development and progression. The underlying mechanisms are complex, multifactorial and largely unknown. Circular RNA (circRNA) is an endogenous RNA with a covalently closed loop that plays critical roles in the pathological and physiological processes of the organism. Here, we identified a TME-associated circRNA, circ-TPGS2, which promoted breast cancer (BC) cell dissemination via altering TME. High circ-TPGS2 was observed in metastatic BC tissues and cell lines in comparison to respective normal controls, which was linked to poor overall and recurrence-free survival. Overexpression of circ-TPGS2 notably promoted cell migration, while silencing of circ-TPGS2 resulted in an opposite trend. Moreover, circ-TPGS2 increased pro-inflammatory chemokine production and evoked tumour-associated inflammation by recruiting neutrophils via autocrine and paracrine manners. In terms of mechanism, circ-TPGS2 acted as a sponge of miR-7 and elevated TRAF6, leading to p65 phosphorylation and nuclear translocation, ultimately activating NF-κB signalling. In addition, p65 was abundantly occupied on circ-TPGS2 promoter, activating circ-TPGS2 transcription, thus, forming a positive feedback loop that amplified the pro-metastasis effect of circ-TPGS2. Taken together, our data for the first time reveal the biological implication of circ-TPGS2 in BC, it triggers TME reshaping that facilitates BC metastasis through the miR-7/TRAF6/NF-κB signalling cascade.

Emerging role of circular RNAs in breast cancer

Circular RNAs (cirRNAs) are generally considered as non-coding RNAs which can act as molecular sponges for miRNAs, exert regulatory roles in transcription or splicing, and interplay with RNA binding proteins. These single-stranded transcripts can affect tumor growth, the metastatic ability of cancer cells, stemness properties, and resistance to therapeutic options. Recent investigations have shown the crucial effects of circrNAs in the evolution of breast cancer. Signature of circRNAs in breast cancer samples has been mostly assessed through microarray-based methods revealing up-regulation of some circRNAs such as circ-TFF1, circACAP2, circ-TFCP2L1, hsa_circ_0000519, circDENND4C, circPLK1 and circRNA_069718, while down-regulation of other circRNAs such as hsa_circ_0000375, circYap, hsa_circ_0025202, circTADA2A-E6, circASS1 and circRNA_BARD1 in breast cancer samples. Mechanistically, these transcripts mainly affect breast cancer tumorigenesis via serving as sponges for miRNAs. In the current manuscript, we explore the results of researches that appraised the role of circRNAs in breast cancer.

Role of circular RNAs in colorectal tumor microenvironment

Circular RNAs (circRNAs) are a class of endogenous noncoding RNA, which were previously considered as a byproduct of RNA splicing error. Numerous studies have demonstrated the altered expression of circRNAs in organ tissues during pathological conditions and their involvements in disease pathogenesis and progression, including cancers. In colorectal cancer (CRC), multiple circRNAs have been identified and characterized as "oncogenic", given their involvements in the downregulation of tumor suppressor genes and induction of tumor initiation, progression, invasion, and metastasis. Additionally, other circRNAs have been identified in CRC and characterized as "tumor suppressive" based on their ability of inhibiting the expression of oncogenic genes and suppressing tumor growth and proliferation. circRNAs could serve as potential diagnostic and prognostic biomarkers, and therapeutic targets or vectors to be utilized in cancer therapies. This review briefly describes the dynamic changes of the tumor microenvironment inducing immunosuppression and tumorigenesis, and outlines the biogenesis and characteristics of circRNAs and recent findings indicating their roles and functions in the CRC tumor microenvironment. It also discusses strategies and technologies, which could be employed in the future to overcome current cancer therapy challenges associated with circRNAs.

CircRNA ZNF609 Knockdown Represses the Development of Non-Small Cell Lung Cancer via miR-623/FOXM1 Axis

Background

The dysregulated circular RNAs (circRNAs) are relevant to the development of non-small cell lung cancer (NSCLC). Nevertheless, the function and mechanism of circRNA zinc finger protein 609 (circZNF609) in NSCLC development remain uncertain.

Methods

Sixty-two NSCLC patients were recruited. circZNF609, microRNA-623 (miR-623) and forkhead box M1 (FOXM1) abundances were measured via quantitative reverse transcription polymerase chain reaction or Western blot. Cell viability, apoptosis, migration and invasion were analyzed via cell counting kit-8 (CCK8), flow cytometry, caspase3 activity, transwell assay and Western blot. The interaction between miR-623 and circZNF609 or FOXM1 was analyzed via dual-luciferase reporter analysis, RNA immunoprecipitation and pull-down. The function of circZNF609 on cell growth in vivo was tested via xenograft model.

Results

circZNF609 abundance was enhanced in NSCLC tissues and cells. High expression of circZNF609 indicated the lower overall survival. circZNF609 interference restrained cell viability, migration and invasion and increased apoptosis. miR-623 was targeted via circZNF609. FOXM1 was targeted via miR-623 and regulated via circZNF609. miR-623 knockdown or FOXM1 overexpression mitigated the role of circZNF609 silence in NSCLC development. circZNF609 knockdown decreased NSCLC xenograft tumor growth.

Conclusion

circZNF609 knockdown repressed NSCLC development via regulating miR-623 and FOXM1.

Advancement and properties of circular RNAs in prostate cancer: An emerging and compelling frontier for discovering

Prostate cancer (PC) is the most common carcinoma among men worldwide which results in 26% of leading causes of cancer-related death. However, the ideal and effective molecular marker remains elusive. CircRNA, initially observed in plant-infected viruses and Sendai virus in 1979, is generated from pre-mRNA back-splicing and comes in to play by adequate expression. The differential expression in prostate tissues compared with the control reveals the promising capacity in modulating processes including carcinogenesis and metastasis. However, the biological mechanisms of regulatory network in PC needs to systemically concluded. In this review, we enlightened the comprehensive studies on the definite mechanisms of circRNAs affecting tumor progression and metastasis. What's more, we validated the potential clinical application of circRNAs serving as diagnostic and prognostic biomarker. The discussion and analysis in circRNAs will broaden our knowledge of the pathogenesis of PC and further optimize the current therapies against different condition.

Circular RNAs in Human Cancer

Circular RNAs (circRNAs) are a class of endogenous single-stranded covalently closed RNAs, primarily produced from pre-mRNAs via non-canonical back-splicing. circRNAs are highly conserved, stable, and expressed in tissue- and development-specific pattern. circRNAs play essential roles in physiological process as well as cancer biology. By the advances of deep sequencing and bioinformatics, the number of circRNAs have increased explosively. circRNAs function as miRNA/protein sponge, protein scaffold, protein recruitment, enhancer of protein function, as well as templates for translation involved in the regulation of transcription/splicing, translation, protein degradation, and pri-miRNA processing in human cancers and contributed to the pathogenesis of cancer. Numerous circRNAs may function in diverse manners. In this review, we survey the current understanding of circRNA functions in human cancer including miRNA sponge, circRNA-protein interaction, and circRNA-encoded protein, and summarize available databases for circRNA annotation and functional prediction.

Gene Expression Signatures of a Preclinical Mouse Model during Colorectal Cancer Progression under Low-Dose Metronomic Chemotherapy

Understanding the molecular signatures of colorectal cancer progression under chemotherapeutic treatment will be crucial for the success of future therapy improvements. Here, we used a xenograft-based mouse model to investigate, how whole transcriptome signatures change during metastatic colorectal cancer progression and how such signatures are affected by LDM chemotherapy using RNA sequencing. We characterized mRNAs as well as non-coding RNAs such as microRNAs, long non-coding RNAs and circular RNAs in colorectal-cancer bearing mice with or without LDM chemotherapy. Furthermore, we found that circZNF609 functions as oncogene, since over-expression studies lead to an increased tumor growth while specific knock down results in smaller tumors. Our data represent novel insights into the relevance of non-coding and circRNAs in colorectal cancer and provide a comprehensive resource of gene expression changes in primary tumors and metastases. In addition, we present candidate genes that could be important modulators for successful LDM chemotherapy.

Anti-antioxidant impacts of circZNF609 silence in HaCaT cells through regulating miR-145

Background: CircZNF609 (cZNF609) is previously revealed as an essential mediator in oxidative stress. This paper determined the role of cZNF609 in skin oxidative damage to evaluate its importance in pressure ulcer.Methods: HaCaT cells treated by H₂O₂ were considered as a cell model of pressure ulcer. The role of cZNF609 in the model was checked by conducting CCK-8 assay, FITC-PI double-staining, ROS detection and Western blot. The downstream gene and signalling of cZNF609 were studied by utilizing qRT-PCR and Western blot.Results: HaCaT cells were remarkably damaged by H₂O₂, as evidenced by the viability loss, apoptosis and ROS generation. It was coupled with the elevated expression of p53, p16, Bax and the activated forms of caspase-3 and PARP. Meanwhile, cZNF609 was high-expressed in response to H₂O₂. The oxidative stress driven by H₂O₂ was alleviated by transfection with cZNF609 specific siRNA. Further, the anti-antioxidant impacts of cZNF609 silence were impeded by miR-145 silence. The inhibition of JNK and p38MAPK pathways induced by cZNF609 silence was impeded by miR-145 silence.Conclusion: The protective function of cZNF609 silence in H₂O₂-injured HaCaT cells was revealed in vitro. Silence of cZNF609 exhibited its impact possibly through regulating miR-145, and JNK and p38MAPK pathways.

CircZNF609 promotes cell proliferation, migration, invasion, and glycolysis in nasopharyngeal carcinoma through regulating HRAS via miR-338-3p

Circular RNA zinc finger protein 609 (circZNF609) has been reported to involve in nasopharyngeal carcinoma (NPC) tumorigenesis regulation. However, the role and the molecular mechanism of circZNF609 in NPC remain unclear. Levels of circZNF609, microRNA (miR)-338-3p, and GTPase HRas (HRAS) were detected by quantitative real-time polymerase chain reaction or Western blot. Cell proliferation, migration, and invasion were analyzed using cell counting kit-8 assay, colony formation assay, and transwell assay, respectively. Glucose metabolism was calculated by measuring glucose consumption, lactate production, adenosine triphosphate (ATP) levels, and HK2 activity. The interaction between miR-338-3p and circZNF609 or HRAS was analyzed by the dual-luciferase reporter assay. In vivo experiment was conducted using the murine xenograft model. CircZNF609 was elevated in NPC tissues and cell lines, and high circZNF609 expression had a poor prognosis. CircZNF609 knockdown suppressed NPC progression in vitro by inhibiting cell proliferation, migration, invasion, and glycolysis and hindered tumor growth in vivo. MiR-338-3p directly bound to circZNF609 and HRAS, and circZNF609 knockdown repressed NPC cell malignant properties by binding to miR-338-3p. MiR-338-3p was low in NPC, and miR-338-3p restoration performed anti-tumor effects in cells of NPC by targeting HRAS. Importantly, circZNF609 acted as a competing endogenous RNA of miR-338-3p to regulate HRAS. CircZNF609 knockdown suppressed cell tumorigenesis in NPC via regulating miR-338-3p/HRAS axis, suggesting a novel therapeutic strategy for NPC.

FUS-induced circular RNA ZNF609 promotes tumorigenesis and progression via sponging miR-142-3p in lung cancer

Circular RNAs (circRNAs) have been associated with lung cancer (LC), one of the most common cancers, but the underlying molecular mechanisms of the specific correlation with LC carcinogenesis remain unveiled. Quantitative real-time polymerase chain reaction was applied to examine the level of circZNF609. LC cells were transfected with silenced circZNF609 by siRNAs, and cell proliferation, migration, and apoptosis were evaluated to reflect the influences of circZNF609 knockdown in LC. Biotin-coupled circRNA capture, FISH and luciferase reporter assays were performed to study the relationship between circZNF609 and miR-142-3p. In current work, it was discovered that circZNF609 functioned as an onco-circRNA, which exhibited high expression as well as facilitated the proliferation and migration in LC cells. Next, we discovered that FUS RNA-binding protein, which could bind to the ZNF609 pre-mRNA, induced circZNF609 formation, and increased circZNF609 expression in LC. Furthermore, circZNF609 was verified to sponge and sequester miR-142-3p; circZNF609 enhanced LC cell proliferative and migrative ability via targeting miR-142-3p. Finally, G protein subunit beta 2 (GNB2) was figured out to involve in circZNF609/miR-142-3p axis-induced LC development. Conclusively, the results indicated that FUS-induced circZNF609 exerts promotional effects on LC cell proliferation and migration through modulation of the miR-142-3p/GNB2 axis, which could offer new insight for understanding LC.

CircZNF609 is involved in the pathogenesis of focal segmental glomerulosclerosis by sponging miR-615-5p

As a set of distinct syndromes, focal segmental glomerulosclerosis (FSGS) is the most common cause of adult nephrotic syndrome with diverse mechanisms. We recently found that expression of the circular RNA circZNF609 is increased in renal biopsies of lupus nephritis patients. In the present study, we aimed to determine whether circZNF609 participates in the pathogenesis of FSGS in mice given Adriamycin. In FSGS mice, circZNF609 was upregulated while miR-615-5p was downregulated in FSGS mice analyzed by qPCR and fluorescence in situ hybridization (FISH). Expression of podocyte proteins Wilms tumor 1 (WT1) and podocin were decreased, while expression of collagen 1 (COL1) and transforming growth factor-beta1 (TGF-β1) were increased on Western blotting. Renal circZNF609 levels were positively correlated and miR-615-5p levels were negatively correlated with the degree of podocyte injury and renal fibrosis. Importantly, circZNF609 and miR-615-5p co-localized to glomeruli and tubules on FISH. Perfect match seeds were found between circZNF609 and miR-615-5p and COL1 mRNA, leading us to explore mechanisms of circZNF609 in bovine serum albumin (BSA) stimulating HK-2 cells, which model the toxicity of proteinuria on tubular cells. In vitro studies, circZNF609 increased and miR-615-5p decreased after BSA treatment and were negatively correlated with each other. COL1 and TGF-β1 were both upregulated and negatively correlated with miR-615-5p. Lastly, circZNF609 expression increased in glomeruli and tubules of FSGS patient renal biopsies. We conclude that circZNF609 may play an important role in FSGS by sponging miR-615-5p.

Circular RNA ZNF609 Promoted Hepatocellular Carcinoma Progression by Upregulating PAP2C Expression via Sponging miR-342-3p

Background

Emerging evidence has revealed that circular RNAs (circRNAs) participated in hepatocellular carcinoma (HCC) development. However, the roles of most circRNAs have not been studied.

Methods

CircZNF609, miR-342-3p and RAP2C expressions were assessed by qPCR or Western blot. Loss-of-function experiments were performed using si-circZNF609 transfection, followed by CCK-8 assay, flow cytometry, wound healing assay and transwell assay. Informatic tools and rescue experiments were carried out to investigate the underlying mechanisms.

Results

We showed that circZNF609 was overexpressed in HCC tissues and cells, as well as associated with poor clinical characteristics. Depletion of circZNF609 restrained HCC cell viability, migration and invasion while enhanced cell apoptosis. As to mechanism, miR-342-3p was sponged by circZNF609, and RAP2C was targeted by miR-342-3p. The effects on HCC cells induced by si-circZNF609 could be reversed by miR-342-3p inhibitor or RAP2C. In vivo, circZNF609 knockdown inhibited tumorigenesis of HCC mice, confirming the findings in vitro.

Conclusion

CircZNF609 was highly expressed in HCC tissues and driven HCC progression by sponging miR-342-3p and upregulating RAP2C. This study may provide new potential therapeutic targets for HCC treatment.

Silence of FOXD2-AS1 inhibited the proliferation and invasion of esophagus cells by regulating miR-145-5p/CDK6 axis

This study aimed to investigate the function of long non-coding RNA FOXD2 adjacent opposite strand RNA 1 (lncRNA FOXD2-AS1) during the progression of esophagus cancer (EC) and explore its underlying molecular mechanisms. The level of FOXD2-AS1 in EC tissues and paracancerous tissues was detected by using RT-qPCR; ROC curve was used to evaluate the diagnostic value of FOXD2-AS1 for EC. In addition, CCK8 assay and immunofluorescence staining assay were used to detect the proliferation of Eca-109 and TE-1 cells. To investigate the function of FOXD2-AS1 on cell apoptosis and cell cycle, flow cytometry was performed. To detect the invasion ability of EC cells, transwell invasion assay was performed. Starbase3.0 and Targetscan were used to predict the target genes of FOXD2-AS1 and miR-145-5p, and protein expressions were detected with western blot. We found FOXD2-AS1 was significantly upregulated in EC tissues compared with adjacent normal tissues, which was positively correlated with clinicopathological parameters of patients with EC. Downregulation of FOXD2-AS1 inhibited the proliferation and invasion by inducing apoptosis of EC cells. Moreover, FOXD2-AS1 may regulate the expression of CDK6 by targeting miR-145-3p. Meanwhile, silencing of FOXD2-AS1 caused G1 phase arrest of EC cells by reducing the expression of CDK6. In conclusion, silening FOXD2-AS1 significantly inhibited the proliferation and invasion of EC cells by regulating the miR-145-5p/CDK6 axis. Therefore, FOXD2-AS1 might be used as diagnostic biomarker and therapeutic target for EC.

CircRNA ZNF609 in peripheral blood leukocytes acts as a protective factor and a potential biomarker for coronary artery disease

Background

Circular RNAs (circRNAs) have been reported to aberrantly express in coronary artery disease (CAD). Due to their special structures, circRNAs have the potential to be specific and stable markers. We conducted this study to explore circZNF609's function in atherosclerosis and to evaluate its predictive values for CAD.

Methods

About 330 CAD patients and 209 controls were enrolled and the expression of circZNF609 in peripheral blood leukocytes (PBLs) was detected by quantitative real time polymerase chain reaction (RT-PCR). Spearman correlation, multivariate regression, multivariate logistic regression and receiver operating characteristic curve (ROC) were performed. Moreover, circZNF609 was overexpressed in mice macrophage RAW264.7 to investigate its influence on inflammatory cytokines. Finally, bioinformatics analysis was executed to excavate the potential downstream pathway of circZNF609.

Results

The expression level of circZNF609 in PBLs of CAD patients was significantly decreased compared with the controls (the fold changes of 0.4133, P<0.0001). The logistic regression analysis showed that decreased circZNF609 expressions were independently associated with increased risks of CAD. The area under the ROC curve was 0.761 (95% CI: 0.721-0.800, P<0.0001). Furthermore, the circZNF609 expression level was correlated with C-reactive protein (r=-0.138, P=0.026) and lymphocyte counts (r=0.16, P=0.01). After overexpression of circZNF609 in RAW264.7 cells, the expression level of IL-6 (P<0.001) and TNF-α (P<0.01) were significantly decreased and IL-10 was significantly increased (P<0.001). Bioinformatics analysis suggested that the abnormal expression of circZNF609 might probably sponge miRNA to modulate the inflammation cytokines.

Conclusions

CircRNA ZNF609 played an anti-inflammatory role and was an independent protective factor for CAD. It represented a moderate diagnostic value and might provide a new therapeutic target for CAD.

Circular RNAs in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a geographical distributed epithelial tumor of head and neck, which is prevalent in east Africa and Asia, especially southern China. Moreover, NPC has an unfavorable clinical effect and is prone to metastasis at an advanced stage. Although the recovery rate of patients has been improved due to concurrent chemoradiotherapy, poor curative effects and low overall survival remain key issues. The precise mechanisms and pivotal regulators of NPC remain still unclear. To improve the therapeutic efficacy, we focused on related-NPC circular RNAs (circRNAs). CircRNAs are a unique type of endogenous non-coding RNAs (ncRNAs) with a covalent closed-loop structure. Their expression is rich, stable and conservative. Different circRNA have specific tissue and developmental stages and can be detected in body fluids. In addition, circRNAs are involved in multiple pathological processes, especially in cancers. In recent years, using high-throughput indicator technology and bioinformatics technology, a large number of circRNAs have been identified in NPC cells and verified to have biological functions and mechanisms of action. This article aims to provide a retrospective review of the latest research on the proliferation and migration of related-NPC circRNA. Specifically, we focused on the roles and mechanisms of circRNAs in the development and progression of NPC.

CONCLUSION

CircRNA can act as an oncogene or tumor suppressor gene and participate in NPC progression (e.g., proliferation, apoptosis, migration, and invasion). In short, circRNAs have potential as biomarkers for the diagnosis, prognosis and treatment of NPC.

CircZNF609 enhances hepatocellular carcinoma cell proliferation, metastasis, and stemness by activating the Hedgehog pathway through the regulation of miR-15a-5p/15b-5p and GLI2 expressions

Emerging evidence has revealed that aberrantly expressed circular RNAs (circRNAs) play vital roles in tumorigenesis and progression of diverse human malignancies. Although an existing literature has elucidated the regulatory role of circZNF609 in breast cancer, the crucial function that circZNF609 exerted on hepatocellular carcinoma (HCC) remains unclear. Herein, we determined to explore the molecular mechanism of circZNF609 in HCC. In this study, circZNF609 was conspicuously overexpressed and featured with loop structure in HCC. Functional tests revealed that decreased expression of circZNF609 suppressed cell proliferation, metastasis and stemness, whereas induced cell apoptosis in HCC. Subsequent molecular mechanism assays indicated that circZNF609 contributed to HCC progression through activation of Hedgehog pathway. Moreover, circZNF609 was found to be negatively correlated with miR-15a-5p/15b-5p but positively correlated with GLI2. Moreover, there was a negative correlation between miR-15a-5p/15b-5p and GLI2. Rescue experiments testified that GLI2 overexpression could recover circZNF609 depletion-mediated function on HCC development while miR-15a-5p/15b-5p inhibition could partially rescue circZNF609 silencing-mediated effect on HCC progression. Final experiments in vivo further elucidated the suppressive function of circZNF609 knockdown on the tumorigenesis of HCC. Briefly, circZNF609 enhances HCC cell proliferation, metastasis, and stemness by activating the Hedgehog pathway through the regulation of miR-15a-5p/15b-5p and GLI2 expressions.