Utility Of Plasma circBNC2 As A Diagnostic Biomarker In Epithelial Ovarian Cancer

The closed loop of the circCLIP2/miR-361-3p/STAT2 signaling axis regulates the progression of cervical cancer

BACKGROUND

Circular RNAs (circRNAs) are involved in tumorigenesis and the progression of cancer through various pathways. However, the detailed regulatory mechanisms of circRNAs in cervical cancer are not fully understood. The present study was designed to explore the biological functions and potential mechanisms of circCLIP2 (has_circ_0001717) in cervical cancer.

METHODS

The expression profiles of circRNAs in cancerous and adjacent normal tissues of cervical cancer patients were examined using RNA sequencing. Gain- and loss-of-function experiments were carried out to determine the biological functions of circCLIP2 in the proliferation, invasion, migration and apoptosis of cervical cancer cells. qRT-PCR was also used to evaluate the expression of circCLIP2, miR-361-3p and STAT2 in cervical cancer cells. The protein levels of STAT2 were determined by western blotting.

RESULTS

CircCLIP2 was identified as the most down-regulated molecule in the cancerous tissues of cervical cancer patients compared to the adjacent normal tissues. Moreover, the levels of circCLIP2 was decreased in cervical cancer patients with metastasis and advanced tumour stage, and patients with high-circCLIP2-expression exhibited poorer survival rate. In addition, over-expression of circCLIP2 suppressed the proliferation, invasion and migration of cervical cancer cells, whereas cell apoptosis was enhanced. Moreover, down-regulated circCLIP2 functioned as the sponge of miR-361-3p, which reduced the expression of STAT2. Furthermore, knockdown of STAT2 inhibited the expression of circCLIP2 at the transcriptional level.

CONCLUSION

The circCLIP2/miR-361-3p/STAT2 signalling could mediate the progression of cervical cancer. CircCLIP2 may become a novel target for the diagnosis and treatment of cervical cancer.

Role of circular RNA as competing endogenous RNA in ovarian cancer (Review)

Circular RNA (circRNA), a type of non‑coding RNA, plays a regulatory role in biological processes. The special loop structure of circRNA makes it highly stable and specific in diseased tissues and cells, especially in tumors. Competing endogenous RNAs (ceRNAs) compete for the binding of microRNA (miRNA) at specific binding sites and thus regulate gene expression. ceRNAs play an important role in various diseases and are currently recognized as the most prominent mechanism of action of circRNAs. circRNAs can modulate the proliferation, migration, invasion and apoptosis of tumor cells through the ceRNA mechanism. With further research, circRNAs may serve as novel markers and therapeutic targets for ovarian cancer (OC). In the present review, the research progress of circRNAs as ceRNAs in OC was summarized, focusing on the effects of the circRNA/miRNA/mRNA axis on the biological functions of OC cells through mediating pivotal signaling pathways. The role of circRNAs in the diagnosis, prognostic assessment and treatment of OC was also discussed in the present review.

New insight into circRNAs: characterization, strategies, and biomedical applications

Circular RNAs (circRNAs) are a class of covalently closed, endogenous ncRNAs. Most circRNAs are derived from exonic or intronic sequences by precursor RNA back-splicing. Advanced high-throughput RNA sequencing and experimental technologies have enabled the extensive identification and characterization of circRNAs, such as novel types of biogenesis, tissue-specific and cell-specific expression patterns, epigenetic regulation, translation potential, localization and metabolism. Increasing evidence has revealed that circRNAs participate in diverse cellular processes, and their dysregulation is involved in the pathogenesis of various diseases, particularly cancer. In this review, we systematically discuss the characterization of circRNAs, databases, challenges for circRNA discovery, new insight into strategies used in circRNA studies and biomedical applications. Although recent studies have advanced the understanding of circRNAs, advanced knowledge and approaches for circRNA annotation, functional characterization and biomedical applications are continuously needed to provide new insights into circRNAs. The emergence of circRNA-based protein translation strategy will be a promising direction in the field of biomedicine.

The role and mechanism of circ-BNC2 on the malignant progression of oral squamous cell carcinoma

BACKGROUND

Circular RNAs (circRNAs) play a key part in the progression of oral squamous cell carcinoma (OSCC). However, the role of circ-BNC2 (circRNA ID hsa_circ_0086414) in OSCC progression is still unclear.

METHODS

Plasmid transfection was used to induce overexpression of circ-BNC2. RNA expression of circ-BNC2, microRNA-142-3p (miR-142-3p) and GNAS complex locus (GNAS) was detected by quantitative real-time polymerase chain reaction. Protein expression was assessed by western blot assay or immunohistochemistry assay. Cell proliferation was investigated by 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay and flow cytometry analysis. Cell migratory and invasive abilities and cell apoptosis were assessed by transwell assay and flow cytometry analysis, respectively. Oxidative stress was evaluated by superoxide dismutase activity detection assay, lipid peroxidation malondialdehyde assay and cellular reactive oxygen species assay. The binding relationship between miR-142-3p and circ-BNC2 or GNAS was proved by dual-luciferase reporter assay and RNA immunoprecipitation assay. The impacts of circ-BNC2 overexpression on tumor growth in vivo were unveiled by a xenograft mouse model assay.

RESULTS

Circ-BNC2 expression was downregulated in OSCC tissues and cells when compared with adjacent healthy tissues and normal human oral keratinocytes. Circ-BNC2 overexpression repressed the proliferation, migration and invasion of OSCC cells but induced cell apoptosis and oxidative stress. Additionally, circ-BNC2 overexpression inhibited tumor growth in vivo. Furthermore, circ-BNC2 bound to miR-142-3p, and miR-142-3p targeted GNAS. MiR-142-3p mimic attenuated circ-BNC2 overexpression-mediated effects on the proliferation, migration, invasion, apoptosis and oxidative stress of OSCC cells. The regulation of miR-142-3p in OSCC cell tumor properties involved GNAS. Further, circ-BNC2 introduction promoted GNAS expression by inhibiting miR-142-3p.

CONCLUSION

Circ-BNC2 suppressed OSCC malignant progression by upregulating GNAS expression in a miR-142-3p-dependent manner, which suggested that circ-BNC2 might be a novel target for OSCC therapy.

Circular RNA circBNC2 facilitates glycolysis and stemness of hepatocellular carcinoma through the miR-217/high mobility group AT-hook 2 (HMGA2) axis

Hepatocellular cancer (HCC) accounts for approximately 90% of primary liver carcinoma and is a significant health threat worldwide. Circular RNA basonuclin 2 (circBNC2) is implicated with the progression of several cancers. However, its roles in carcinogenesis and glycolysis are still unclear in HCC. In this study, the levels of circBNC2 and high mobility group AT-hook 2 (HMGA2) were highly expressed, while these of miR-217 were poorly expressed in HCC tissues and cells. Upregulation of circBNC2 was related to poor prognosis and tumor node metastasis (TNM) stage. Knockdown of circBNC2 inhibited the HCC progression. Moreover, knockdown of circBNC2 suppressed the levels of Ras, ERK1/2, PCNA, HK2, and OCT4. Notably, circBNC2 functioned as a molecular sponge of microRNA 217 (miR-217) to upregulate the HMGA2 expression. The inhibitory effects of the circBNC2 silence on the growth and stemness of HCC cells, and levels of PCNA, HK2 and OCT4 were aggravated by the miR-217 overexpression, but neutralized by the HMGA2 overexpression. Besides, silencing of circBNC2 blocked the tumor growth through upregulating the expression of miR-217 and downregulating the levels of HMGA2, PCNA2, HK2 and OCT4 in vivo. Thus, the current data confirmed that circBNC2 sponged miR-217 to upregulate the HMGA2 level, thereby contributing to the HCC glycolysis and progression. These findings might present novel insight into the pathogenesis and treatment of HCC.

Characterization of cell-type specific circular RNAs associated with colorectal cancer metastasis

Colorectal cancer (CRC) is the most common gastrointestinal malignancy and a leading cause of cancer deaths in the United States. More than half of CRC patients develop metastatic disease (mCRC) with an average 5-year survival rate of 13%. Circular RNAs (circRNAs) have recently emerged as important tumorigenesis regulators; however, their role in mCRC progression remains poorly characterized. Further, little is known about their cell-type specificity to elucidate their functions in the tumor microenvironment (TME). To address this, we performed total RNA sequencing (RNA-seq) on 30 matched normal, primary and metastatic samples from 14 mCRC patients. Additionally, five CRC cell lines were sequenced to construct a circRNA catalog in CRC. We detected 47 869 circRNAs, with 51% previously unannotated in CRC and 14% novel candidates when compared to existing circRNA databases. We identified 362 circRNAs differentially expressed in primary and/or metastatic tissues, termed circular RNAs associated with metastasis (CRAMS). We performed cell-type deconvolution using published single-cell RNA-seq datasets and applied a non-negative least squares statistical model to estimate cell-type specific circRNA expression. This predicted 667 circRNAs as exclusively expressed in a single cell type. Collectively, this serves as a valuable resource, TMECircDB (accessible at https://www.maherlab.com/tmecircdb-overview), for functional characterization of circRNAs in mCRC, specifically in the TME.

Role of circular RNA and its delivery strategies to cancer - An overview

With the passage of years and the progress of research on ribonucleic acids, the range of forms in which these molecules have been observed grows. One of them, discovered relatively recently, is circular RNA - covalently closed circles (circRNA). In recent years, there has been a huge increase in the interest of researchers in this group of molecules. It entailed a significant increase in the state of knowledge about them, which in turn caused a dramatic change in their perception. Rather than seeing circular RNAs as curiosities that represent a minor information noise in a cell or a result of RNA misprocessing, they came to be regarded as a common, essential, and potentially extremely useful group of molecules. Nevertheless, the current state of the art of circRNA is full of white cards. A lot of valuable information has been obtained from high-throughput methods to study whole transcriptomes, but many issues related to circular RNAs still need to be clarified. Presumably, each answer obtained will raise several new questions. However, circRNAs have a wealth of potential applications, including therapeutic applications.

CircBNC2 affects epithelial ovarian cancer progression through the miR-223-3p/ LARP4 axis

Epithelial ovarian cancer (EOC) is one of the most serious cancer. Circular RNA BNC2 (circBNC2) expression was decreased in EOC tissues. However, the molecular mechanism of circBNC2 remains unknown. The expression of circBNC2, microRNA-223-3p (miR-223-3p), and La-related proteins 4 ( LARP4 ) were detected by quantitative real-time fluorescence PCR (qRT-PCR). A series of in-vitro experiments were designed to explore the function of circBNC2 in EOC cells and the regulatory mechanism between circBNC2 and miR-223-3p and LARP4 in EOC cells. Western blot examined the protein levels of Snail1, Slug, and LARP4 . The relationship between miR-223-3p and circBNC2 or LARP4 was verified by Dual-luciferase reporter assays. The xenotransplantation model was established to study the role of circBNC2 in vivo . The expression of circBNC2 and LARP4 was decreased in EOC tissues, while the expression of miR-223-3p was increased. CircBNC2 can sponge miR-223-3p, and LARP4 is the target of miR-223-3p. In-vitro complement experiments showed that overexpression of circBNC2 significantly decreased the malignant behavior of EOC, while co-transfection of miR-223-3p mimics partially upregulated this change. In addition, LARP4 knockdown increased the proliferation, migration, and invasion of EOC cells inhibited by miR-223-3p inhibitor. Mechanically, circBNC2 regulates LARP4 expression in EOC cells by spongy miR-223-3p. In addition, in-vivo studies have shown that overexpression of circBNC2 inhibits tumor growth. Overexpression of circBNC2 decreased proliferation, migration, and invasion of EOC cells by regulating the miR-223-3p/ LARP4 axis, suggesting that circBNC2/miR-223-3p/ LARP4 axis may be a potential regulatory mechanism for the treatment of EOC.

Through the Looking Glass: Updated Insights on Ovarian Cancer Diagnostics

Epithelial ovarian cancer (EOC) is the deadliest gynaecological malignancy and the eighth most prevalent cancer in women, with an abysmal mortality rate of two million worldwide. The existence of multiple overlapping symptoms with other gastrointestinal, genitourinary, and gynaecological maladies often leads to late-stage diagnosis and extensive extra-ovarian metastasis. Due to the absence of any clear early-stage symptoms, current tools only aid in the diagnosis of advanced-stage patients, wherein the 5-year survival plummets further to less than 30%. Therefore, there is a dire need for the identification of novel approaches that not only allow early diagnosis of the disease but also have a greater prognostic value. Toward this, biomarkers provide a gamut of powerful and dynamic tools to allow the identification of a spectrum of different malignancies. Both serum cancer antigen 125 (CA-125) and human epididymis 4 (HE4) are currently being used in clinics not only for EOC but also peritoneal and GI tract cancers. Screening of multiple biomarkers is gradually emerging as a beneficial strategy for early-stage diagnosis, proving instrumental in administration of first-line chemotherapy. These novel biomarkers seem to exhibit an enhanced potential as a diagnostic tool. This review summarizes existing knowledge of the ever-growing field of biomarker identification along with potential future ones, especially for ovarian cancer.

Diagnostic value of circN4BP2L2 in type I and type II epithelial ovarian cancer

BACKGROUND

CircN4BP2L2 was previously identified to be significantly decreased in epithelial ovarian cancer (EOC) and was associated with disease progression. The aim of this study was to evaluate the diagnostic value of plasma circN4BP2L2 using the unifying model of type I and type II EOC.

METHODS

A total of 540 plasma samples were obtained from 180 EOC patients, 180 benign ovarian cyst patients, and 180 healthy volunteers. CircN4BP2L2 was assessed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cancer antigen 125 (CA125) and human epididymis protein 4 (HE4) were assessed using enzyme-linked immunosorbent assay (ELISA). Receiver operating curve (ROC), the area under the curve (AUC), sensitivity and specificity were estimated.

RESULTS

Low level of circN4BP2L2 was associated with advanced tumor stage (p < 0.01) in type I EOC. Decreased circN4BP2L2 was associated with lymph node metastasis (LNM) (p = 0.04) in type II EOC. The expression level of circN4BP2L2 in type I was similar to that in type II. CircN4BP2L2 could significantly separate type I or type II from benign or normal cohort (p < 0.01). Early-stage type I or type II EOC vs. benign or normal cohort could also be distinguished by circN4BP2L2 (p < 0.01).

CONCLUSION

CircN4BP2L2 might serve as a promising diagnostic biomarker for both type I and type II EOC. The diagnostic safety for circN4BP2L2 in early-stage type I or type II EOC is also acceptable. Further large-scale well-designed studies are warranted to investigate whether circN4BP2L2 is specific for all histologic subgroups.

Circular RNAs in Epithelial Ovarian Cancer: From Biomarkers to Therapeutic Targets

Epithelial ovarian cancer (EOC) is the most lethal gynecological cancer, and more than 70% of patients are diagnosed at advanced stages. Despite the application of surgery and chemotherapy, the prognosis remains poor due to the high relapse rate. It is urgent to identify novel biomarkers and develop novel therapeutic strategies for EOC. Circular RNAs (circRNAs) are a class of noncoding RNAs generated from the "back-splicing" of precursor mRNA. CircRNAs exert their functions via several mechanisms, including acting as miRNA sponges, interacting with proteins, regulating transcription, and encoding functional proteins. Recent studies have identified many circRNAs that are dysregulated in EOC and may be used as diagnostic and prognostic markers. Increasing evidence has revealed that circRNAs play a critical role in ovarian cancer progression by regulating various cellular processes, including proliferation, apoptosis, metastasis, and chemosensitivity. The circRNA-based therapy may be a novel strategy that is worth exploring in the future. Here, we provide an overview of EOC and circRNA biogenesis and functions. We then discuss the dysregulations of circRNAs in EOC and the possibility of using them as diagnostic/prognostic markers. We also summarize the role of circRNAs in regulating ovarian cancer development and speculate their potential as therapeutic targets.

The emerging roles and potential applications of circular RNAs in ovarian cancer: a comprehensive review

Ovarian cancer (OC) is among the most common human malignancies and the first cause of deaths among gynecologic cancers. Early diagnosis can help improving prognosis in those patients, and accordingly exploring novel molecular mechanisms may lead to find therapeutic targets. Circular RNAs (circRNAs) comprise a group of non-coding RNAs in multicellular organisms, which are identified with characteristic circular structure. CircRNAs have been found with substantial functions in regulating gene expression through interacting with RNA-binding proteins, targeting microRNAs, and transcriptional regulation. They have been found to be involved in regulating several critical processes such as cell growth, and death, organ development, signal transduction, and tumorigenesis. Accordingly, circRNAs have been implicated in a number of human diseases including malignancies. They are particularly reported to contribute to several hallmarks of cancer leading to cancer development and progression, although a number also are described with tumor-suppressor function. In OC, circRNAs are linked to regulation of cell growth, invasiveness, metastasis, angiogenesis, and chemoresistance. Notably, clinical studies also have shown potentials in diagnosis, prediction of prognosis, and therapeutic targets for OC. In this review, I have an overview to the putative mechanisms, and functions of circRNAs in regulating OC pathogenesis in addition to their clinical potentials.

Circular RNA circ-BNC2 (hsa_circ_0008732) inhibits the progression of ovarian cancer through microRNA-223-3p/ FBXW7 axis

Background

Circular RNAs (circRNAs) are reported to be key regulators in the progression of human cancers. This work focuses on the function and molecular mechanism of circRNA-BNC2 (circ-BNC2) (also known as hsa_circ_0008732) in ovarian cancer (OC).

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to detect circ-BNC2, microRNA-223-3p (miR-223-3p) and F-box and WD repeat domain containing 7 (FBXW7) mRNA expressions in OC tissues and cells. Besides, cell counting kit 8 (CCK-8), transwell assay and cell cycle assays were executed to assess the proliferative, migrative, invasive abilities, and cell cycle progression of OC cells, respectively. Dual-luciferase reporter gene assay and RNA pull-down assay were used to validate the targeting relationships between miR-223-3p and circ-BNC2 or FBXW7. Western blot was adopted to determine FBXW7 protein levels in OC cells.

Results

Circ-BNC2 expression was downregulated in OC tissues and cell lines, which was associated with higher FIGO stage and lymph node metastasis of OC patients. Circ-BNC2 overexpression repressed the proliferation, migration, invasion of OC cells and induced cell cycle arrest, while silencing circ-BNC2 worked oppositely. Mechanistically, circ-BNC2 could upregulate FBXW7 expression in OC cells via sponging miR-223-3p.

Conclusion

Circ-BNC2 suppresses the progression of OC via regulating miR-223-3p / FBXW7 axis. Our findings provided potential biomarker for OC therapy.

Plasma circRNA microarray profiling identifies novel circRNA biomarkers for the diagnosis of ovarian cancer

Background

Circular RNA (circRNA), a class of RNA with a covalent closed circular structure that widely existed in serum and plasma, has been considered an ideal liquid biopsy marker in many diseases. In this study, we employed microarray and qRT-PCR to evaluate the potential circulating circRNAs with diagnostic efficacy in ovarian cancer.

Methods

We used microarray to explore the circRNA expression profile in ovarian cancer patients’ plasma and quantitative real-time (qRT)-PCR approach to assessing the candidate circRNA’s expression. Then the receiver operating characteristic (ROC) curve was employed to analyze the diagnostic values of candidate circRNAs. The diagnostic model circCOMBO was a combination of hsa_circ_0003972 and hsa_circ_0007288 built by binary logistic regression. Then bioinformatic tools were used to predict their potential mechanisms.

Results

Hsa_circ_0003972 and hsa_circ_0007288 were downregulated in ovarian cancer patients’ plasma, tissues, and cell lines, comparing with the controls. Hsa_circ_0003972 and hsa_circ_0007288 exhibited diagnostic values with the Area Under Curve (AUC) of 0.724 and 0.790, respectively. circCOMBO showed a better diagnostic utility (AUC: 0.781), while the combination of circCOMBO and carbohydrate antigen 125 (CA125) showed the highest diagnostic value (AUC: 0.923). Furthermore, the higher expression level of hsa_circ_0007288 in both plasma and ovarian cancer tissues was associated with lower lymph node metastasis potential in ovarian cancer.

Conclusions

Our results revealed that hsa_circ_0003972 and hsa_circ_0007288 may serve as novel circulating biomarkers for ovarian cancer diagnosis.

Supplementary information

The online version contains supplementary material available at 10.1186/s13048-022-00988-0.

Potential clinical utility of liquid biopsies in ovarian cancer

BACKGROUND

Ovarian cancer (OC) is the most lethal gynecologic malignancy worldwide. One of the main challenges in the management of OC is the late clinical presentation of disease that results in poor survival. Conventional tissue biopsy methods and serological biomarkers such as CA-125 have limited clinical applications. Liquid biopsy is a novel sampling method that analyzes distinctive tumour components released into the peripheral circulation, including circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), cell-free RNA (cfRNA), tumour-educated platelets (TEPs) and exosomes. Increasing evidence suggests that liquid biopsy could enhance the clinical management of OC by improving early diagnosis, predicting prognosis, detecting recurrence, and monitoring response to treatment. Capturing the unique tumour genetic landscape can also guide treatment decisions and the selection of appropriate targeted therapies. Key advantages of liquid biopsy include its non-invasive nature and feasibility, which allow for serial sampling and longitudinal monitoring of dynamic tumour changes over time. In this review, we outline the evidence for the clinical utility of each liquid biopsy component and review the advantages and current limitations of applying liquid biopsy in managing ovarian cancer. We also highlight future directions considering the current challenges and explore areas where more studies are warranted to elucidate its emerging clinical potential.

Emerging role of circular RNAs in the pathogenesis of ovarian cancer

Ovarian cancer is a female malignancy with high fatality-to-case ratio, which is due to late detection of cancer. Understanding the molecular mechanisms participating in these processes would facilitate design of therapeutic modalities and identification of novel tumor markers. Recent investigations have shown contribution of circular RNAs (circRNAs) in the evolution of ovarian cancer. These transcripts are produced through a back-splicing mechanism. The enclosed configuration of circRNAs protects them from degradation and potentiates them as biomarkers. Several circRNAs such as circMUC16, circRNA_MYLK, circRNA-UBAP2, circWHSC1, hsa_circ_0013958, circFGFR3, hsa_circRNA_102958 and circ_0072995 have been found to be up-regulated in this cancer, acting as oncogenes. On the other hand, circ-ITCH, circPLEKHM3, circ_100395, circ_0078607, circATRNL1, circHIPK3, circRHOBTB3, circEXOC6B, circ9119 and CDR1as are among down-regulated circRNAs in ovarian cancer. Expression levels of circCELSR1, circ_CELSR1, circATL2, circNRIP1, circTNPO3 and hsa_circ_0000714 have been shown to affect resistance of ovarian cancer cells to chemotherapy. Moreover, circ_100395, circFGFR3, circ_0000554, circCELSR1, circ-PTK2, circLNPEP, circ-CSPP1, circ_0000745, circ_100395 and circPLEKHM3 have been shown to regulate epithelial-mesenchymal transition and metastatic ability of ovarian cancer cells. In the current review, we explain the roles of circRNAs in the evolution and progression of ovarian cancer.

A Rapid and Affordable Screening Tool for Early-Stage Ovarian Cancer Detection Based on MALDI-ToF MS of Blood Serum

Ovarian cancer is a worldwide health issue that grows at a rate of almost 250,000 new cases every year. Its early detection is key for a good prognosis and even curative surgery. However, current medical examination methods and tests have been inefficient in detecting ovarian cancer at the early stage, leading to preventable death. So far, new screening tests based on molecular biomarker analysis techniques have not resulted in any substantial improvement in early-stage diagnosis and increased survival. Thus, whilst there remains clear potential to improve outcomes through early detection, novel approaches are needed. Here, we postulated that MALDI-ToF-mass-spectrometry-based tests can be a solution for effective screening of ovarian cancer. In this retrospective cohort study, we generated and analyzed the mass spectra of 181 serum samples of women with and without ovarian cancer. Using bioinformatics pipelines for analysis, including predictive modeling and machine learning, we found distinct mass spectral patterns composed of 9–20 key combinations of peak intensity or peak enrichment features for each stage of ovarian cancer. Based on a scoring algorithm and obtained patterns, the optimal sensitivity for detecting each stage of cancer was 95–97% with a specificity of 97%. Scoring all algorithms simultaneously could detect all stages of ovarian cancer at 99% sensitivity and 92% specificity. The results further demonstrate that the matrix and mass range analyzed played a key role in improving the mass spectral data quality and diagnostic power. Altogether, with the results reported here and increasing evidence of the MS assay’s diagnostic accuracy and instrument robustness, it has become imminent to consider MS in the clinical application for ovarian cancer screening.

Plasma circN4BP2L2 is a promising novel diagnostic biomarker for epithelial ovarian cancer

BACKGROUND

Circular RNAs (circRNAs) are more stable than linear RNA molecules, which makes them promising diagnostic biomarkers for diseases. By circRNA-sequencing analysis, we previously found that circN4BP2L2 was significantly decreased in epithelial ovarian cancer (EOC) tissues, and was predictive of disease progression. The aim of this study was to evaluate the diagnostic value of plasma circN4BP2L2 in EOC.

METHODS

Three hundred seventy-eight plasma samples were acquired prior to surgery. Samples were obtained from 126 EOC patients, 126 benign ovarian cyst patients, and 126 healthy volunteers. CircN4BP2L2 was assessed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cancer antigen 125 (CA125) and human epididymis protein 4 (HE4) were assessed using enzyme-linked immunosorbent assay (ELISA). EOC cells were transfected with small interference RNAs (siRNAs) and cell proliferation, migration, invasion, cell cycle and cell apoptosis were performed to assess the effect of circN4BP2L2 in EOC. Receiver operating curve (ROC), the area under the curve (AUC), sensitivity and specificity were estimated.

RESULTS

Plasma circN4BP2L2 was significantly downregulated in EOC patients. Decreased circN4BP2L2 was significantly associated with advanced tumor stage, worse histological grade, lymph node metastasis and distant metastasis in EOC. CircN4BP2L2 inhibited tumor cell migration and invasion in vitro. CircN4BP2L2 could significantly separate EOC from benign (AUC = 0.82, P <  0.01) or normal (AUC = 0.90, P <  0.01) cohort. Early stage EOC vs benign (AUC = 0.81, P <  0.01) or normal (AUC = 0.90, P <  0.01) cohort could also be distinguished by circN4BP2L2. In discrimination between EOC cohort and benign or normal cohort, circN4BP2L2 performed equally well in both pre- and post-menopausal women. The combination of circN4BP2L2, CA125 and HE4 showed high sensitivity and specificity in detecting EOC cases.

CONCLUSIONS

Plasma circN4BP2L2 is significantly downregulated in EOC and might serve as a promising novel diagnostic biomarker for EOC patients, especially in early stage EOC cases. CircN4BP2L2 might act as an adjunct to CA125 and HE4 in detecting EOC. Further large-scale studies are warranted to verify our results.

The potential of using blood circular RNA as liquid biopsy biomarker for human diseases

Circular RNA (circRNA) is a novel class of single-stranded RNAs with a closed loop structure. The majority of circRNAs are formed by a back-splicing process in pre-mRNA splicing. Their expression is dynamically regulated and shows spatiotemporal patterns among cell types, tissues and developmental stages. CircRNAs have important biological functions in many physiological processes, and their aberrant expression is implicated in many human diseases. Due to their high stability, circRNAs are becoming promising biomarkers in many human diseases, such as cardiovascular diseases, autoimmune diseases and human cancers. In this review, we focus on the translational potential of using human blood circRNAs as liquid biopsy biomarkers for human diseases. We highlight their abundant expression, essential biological functions and significant correlations to human diseases in various components of peripheral blood, including whole blood, blood cells and extracellular vesicles. In addition, we summarize the current knowledge of blood circRNA biomarkers for disease diagnosis or prognosis.

Circular RNA-Is the Circle Perfect?

Circular RNA (circRNA) is a distinct class of non-coding RNA produced, in principle, using a back-splicing mechanism, conserved during evolution, with increased stability and a tissue-dependent expression. Circular RNA represents a functional molecule with roles in the regulation of transcription and splicing, microRNA sponge, and the modulation of protein–protein interaction. CircRNAs are involved in essential processes of life such as apoptosis, cell cycle, and proliferation. Due to the regulatory role (upregulation/downregulation) in pathogenic mechanisms of some diseases (including cancer), its potential roles as a biomarker or therapeutic target in these diseases were studied. This review focuses on the importance of circular RNA in cancer.

Dysregulated expression of circular RNAs serve as diagnostic and prognostic markers in ovarian and cervical cancer: A PRISMA-compliant systematic review and meta-analysis

INTRODUCTION

Recent studies have reported a connection between non-coding RNAs such as circular RNAs (circRNAs) and the prognosis of various cancers. However, the mechanism of circRNA in ovarian cancer and cervical cancer has not been consistent. We evaluated the diagnostic and prognostic roles of circRNAs in ovarian and cervical cancer by meta-analysis.

METHODS

Pooled hazard ratios with 95% confidence intervals were to estimate overall survival. Diagnostic efficacy was estimated by sensitivity, specificity and area under curve.

RESULTS

By searching PubMed, Embase, the Web of Science databases, and other sources, we obtained a total of 22 studies with 2059 patients from Asia population. High expression levels of oncogenic circRNAs were significantly associated with poor prognoses both in ovarian and cervical cancer. However, elevated expression levels of tumor-suppressor circRNAs were linked with favorable survival time in ovarian cancer. As for diagnostic role, the area under the curve value in ovarian cancer and cervical cancer is 0.89 and 0.93, respectively.

CONCLUSIONS

CircRNAs have the prospect of becoming a promising biomarker for diagnosis and prognosis of ovarian and cervical cancer. Accordingly, circRNAs might be novel indicators and targets of therapy for ovarian and cervical cancer.

CircRNAs as potent biomarkers in ovarian cancer: a systematic scoping review

More powerful prognostic and diagnostic tools are urgently needed for identifying and treating ovarian cancer (OC), which is the most fatal malignancy in women in developed countries. Circular RNAs (circRNAs) are conservative and stable looped molecules that can regulate gene expression by competing with other endogenous microRNA sponges. This discovery provided new insight into novel methods for regulating genes that are involved in many disorders and cancers. This review focuses on the dysregulated expression of circRNAs as well as their diagnostic and prognostic values in OC. We found that studies have identified twenty-one downregulated circRNAs and fifty-seven upregulated ones. The results of these studies confirm that circRNAs might be potent biomarkers with diagnostic, prognostic and therapeutic target value for OC. We also consider the connection between circRNAs and OC cell proliferation, apoptosis, metastasis, and chemotherapy resistance and sensitivity.

A Comprehensive Overview of circRNAs: Emerging Biomarkers and Potential Therapeutics in Gynecological Cancers

Circular RNA (circRNA) is a highly conserved, stable and abundant non-coding RNA (ncRNA). Also, some circRNAs play an essential part in the progression of human cancers. CircRNA is different from traditional linear RNA. CircRNA has a closed circular structure, so it is resistant to exonuclease-mediated degradation and is more stable than linear RNA. Numerous studies have found that many circRNAs can act as a microRNA (miRNA) sponge, interact with RNA-binding proteins, regulate gene transcription, affect alternative splicing and be translated into proteins. Recently, some studies have also indicated that circRNA participates in the progression of gynecological cancers. In addition, circRNA can act as a promising biomarker for the diagnosis of gynecological tumors. Additionally, they can also play a key role in the prognosis of gynecological tumors. Furthermore, to our delight, circRNA may be a potential therapeutic target in gynecological cancers and widely used in clinical practice. This article reviews the functions and related molecular mechanisms of circRNAs in gynecological tumors, and discusses their potential as biomarkers for diagnostic and prognostic and therapeutic targets for gynecological cancers.

Expression and clinical significance of circular RNAs related to immunity and inflammation in patients with rheumatoid arthritis

The aim of this study was to investigate the changes in and clinical significance of circular RNAs (circRNAs) expression related to immunity and inflammation in patients with rheumatoid arthritis (RA). We analyzed the circRNAs related to immunity and inflammation in peripheral blood mononuclear cells (PBMCs) from three RA patients and three healthy controls using high-throughput sequencing and bioinformatics analysis. Subsequently, four differentially expressed circRNAs were verified by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). We selected hsa_circ_0003353 for functional phenotype analysis in fibroblast-like synoviocytes (FLS) according to correlation tests and logistic regression analysis. The results identified and verified the expression of circRNAs (0003353, 0005732, 0072428, 0091685) that were significantly changed in PBMCs from RA patients. ROC analysis suggested that these circRNAs have significant value in RA diagnosis. Spearman analysis revealed that significant relationships between these circRNAs and clinical indicators as well as SPP. The logistic regression analysis showed that clinical indicators and SPP were risk factors for hsa_circ_0003353 expression, which is worthy of further investigation. As predicted, hsa_circ_0003353 had significantly higher expression in RA-FLS. The cell proliferation, migration, invasion, apoptosis, and inflammatory cytokine production of RA-FLS showed significant alterations after hsa_circ_0003353 suppression and overexpression. Our results indicate that hsa_circ_0003353 may play an essential role in promoting immunity, inflammation, synovial invasion, and joint destruction and that hsa_circ_0003353 may act as a biomarker of RA.

Circular RNAs in body fluids as cancer biomarkers: the new frontier of liquid biopsies

Cancer is a leading cause of death worldwide, particularly because of its high mortality rate in patients who are diagnosed at late stages. Conventional biomarkers originating from blood are widely used for cancer diagnosis, but their low sensitivity and specificity limit their widespread application in cancer screening among the general population. Currently, emerging studies are exploiting novel, highly-accurate biomarkers in human body fluids that are obtainable through minimally invasive techniques, which is defined as liquid biopsy. Circular RNAs (circRNAs) are a newly discovered class of noncoding RNAs generated mainly by pre-mRNA splicing. Following the rapid development of high-throughput transcriptome analysis techniques, numerous circRNAs have been recognized to exist stably and at high levels in body fluids, including plasma, serum, exosomes, and urine. CircRNA expression patterns exhibit distinctly differences between patients with cancer and healthy controls, suggesting that circRNAs in body fluids potentially represent novel biomarkers for monitoring cancer development and progression. In this study, we summarized the expression of circRNAs in body fluids in a pan-cancer dataset and characterized their clinical applications in liquid biopsy for cancer diagnosis and prognosis. In addition, a user-friendly web interface was developed to visualize each circRNA in fluids (https://mulongdu.shinyapps.io/circrnas_in_fluids/).

Circular RNAs as biomarkers and therapeutic targets in cancer

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

Plasma and local expressions of CircRNA CDR1as are linked with disease severity in patients with non-traumatic osteonecrosis of femoral head

Objective

To investigate the correlation of plasma and local expressions of Circ CDR1as with disease severity in patients with non-traumatic osteonecrosis of femoral head (ONFH).

Methods

Ninety-nine non-traumatic ONFH patients receiving surgery and 99 healthy individuals were enrolled in our study. Plasma and local Circ CDR1as were detected using real-time quantitative PCR (RT-qPCR). Radiographic progression was determined using Association Research Circulation Osseous (ARCO) classification system. Harris hip score (HHS) and visual analogue scale (VAS) were used to assess the clinical severity. Receiver operating characteristic (ROC) curve was carried out to evaluate the diagnostic value of plasma Circ CDR1as with regard to the radiographic severity.

Results

Plasma Circ CDR1as expressions were significantly higher in non-traumatic ONFH patients compared with healthy controls. In non-traumatic ONFH patients, there were no significant differences of CircCDR1as expressions between patients with alcohol-induced ONFH and steroid-induced ONFH. CircCDR1as in local necrotic tissue were significantly higher than adjacent non-affected tissue. Plasma and local Circ CDR1as expressions in patients with ARCO phase 4 were markedly upregulated compared with ARCO phase 3; plasma and local Circ CDR1as expressions in patients with ARCO phase 3 were markedly upregulated compared with ARCO phase 1/2. Plasma and local CircCDR1as expressions were positively associated with ARCO classification. In addition, plasma and local Circ CDR1as expressions were positively correlated with VAS and HHS scores. ROC curve analysis indicated that plasma Circ CDR1as may act as a decent marker for radiographic progression in non-traumatic ONFH patients.

Conclusions

Both plasma and local expressions of CircRNA CDR1as are linked with disease severity in patients with non-traumatic ONFH.

Candidate RNA biomarkers in biofluids for early diagnosis of ovarian cancer: A systematic review

Ovarian cancer is often diagnosed in an advanced stage and is associated with a high mortality rate. It is assumed that early detection of ovarian cancer could improve patient outcomes. Unfortunately, effective screening methods for early diagnosis of ovarian cancer are still lacking. Extracellular RNAs circulating in human biofluids can reliably be measured and are emerging as potential biomarkers in cancer. In this systematic review, we present 75 RNA biomarkers detectable in human biofluids that have been studied for early diagnosis of ovarian cancer. The majority of these markers are microRNAs identified using RT-qPCR or microarrays in blood-based fluids. A handful of studies used RNA-sequencing and explored alternative fluids, such as urine and ascites. Candidate RNA biomarkers that were more abundant in biofluids of ovarian cancer patients compared to controls in at least two independent studies include miR-21, the miR-200 family, miR-205, miR-10a and miR-346. Amongst the markers confirmed to be lower in at least two studies are miR-122, miR-193a, miR-223, miR-126 and miR-106b. While these biomarkers show promising diagnostic potential, further validation is required before implementation in routine clinical care. Challenges related to biomarker validation and reflections on future perspectives to accelerate progress in this field are discussed.

The emerging roles of circular RNAs in ovarian cancer

Circular RNA (circRNA) is a novel class of regulatory noncoding RNA (ncRNA) molecules with a unique covalently closed loop structure. Next-generation sequencing shows that thousands of circRNAs are widely and stably expressed in multiple eukaryotes. As novel regulatory ncRNAs, circRNAs possess several specific molecular functions, including regulating gene transcription and translation, acting as miRNA sponges, and interacting with functional proteins. Ovarian cancer (OvCa) is one of the most aggressive malignant diseases affecting the lives of thousands of women worldwide, and the majority of OvCa cases are diagnosed at advanced stages. Accumulating evidence has revealed the significant roles of circRNAs in the occurrence and progression of OvCa, indicating the function of circRNAs as promising biomarkers and their therapeutic relevance in this disease. This review aims to summarize the mechanisms by which circRNAs mediate OvCa progression as well as their diagnostic and prognostic values in OvCa.

The Expression, Functions and Mechanisms of Circular RNAs in Gynecological Cancers

Circular RNAs (circRNAs) are covalently closed, endogenous non-coding RNAs and certain circRNAs are linked to human tumors. Owing to their circular form, circRNAs are protected from degradation by exonucleases, and therefore, they are more stable than linear RNAs. Many circRNAs have been shown to sponge microRNAs, interact with RNA-binding proteins, regulate gene transcription, and be translated into proteins. Mounting evidence suggests that circRNAs are dysregulated in cancer tissues and can mediate various signaling pathways, thus affecting tumorigenesis, metastasis, and remodeling of the tumor microenvironment. First, we review the characteristics, biogenesis, and biological functions of circRNAs, and describe various mechanistic models of circRNAs. Then, we provide a systematic overview of the functional roles of circRNAs in gynecological cancers. Finally, we describe the potential future applications of circRNAs as biomarkers for prognostic stratification and as therapeutic targets in gynecological cancers. Although the function of most circRNAs remains elusive, some individual circRNAs have biologically relevant functions in cervical cancer, ovarian cancer, and endometrial cancer. Certain circRNAs have the potential to serve as biomarkers and therapeutic targets in gynecological cancers.