CircRNA circ_0072995 promotes the progression of epithelial ovarian cancer by modulating miR-147a/CDK6 axis

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.

Deregulated circRNAs in Epithelial Ovarian Cancer With Activity in Preclinical In Vivo Models: Identification of Targets and New Modalities for Therapeutic Intervention

Epithelial ovarian cancer (EOC) is associated with a dismal prognosis due to development of resistance to chemotherapy and metastasis in the peritoneal cavity and distant organs. In order to identify new targets and treatment modalities we searched the literature for up- and and down-regulated circRNAs with efficacy in preclinical EOC-related in vivo systems. Our search yielded circRNAs falling into the following categories: cisplatin and paclitaxel resistance, transmembrane receptors, secreted factors, transcription factors, RNA splicing and processing factors, RAS pathway-related components, proteolysis and cell-cycle regulation, signaling-related proteins, and circRNAs regulating proteins in additional categories. These findings can be potentially translated by validation and manipulation of the corresponding targets, inhibition of circRNAs with antisense oligonucleotides (ASO), small interfering RNAs (siRNA) or small hairpin RNA (shRNA) or by reconstituting their activity.

Dysregulated Expression Patterns of Circular RNAs in Cancer: Uncovering Molecular Mechanisms and Biomarker Potential

Circular RNAs (circRNAs) are stable, enclosed, non-coding RNA molecules with dynamic regulatory propensity. Their biogenesis involves a back-splicing process, forming a highly stable and operational RNA molecule. Dysregulated circRNA expression can drive carcinogenic and tumorigenic transformation through the orchestration of epigenetic modifications via extensive RNA and protein-binding domains. These multi-ranged functional capabilities have unveiled extensive identification of previously unknown molecular and cellular patterns of cancer cells. Reliable circRNA expression patterns can aid in early disease detection and provide criteria for genome-specific personalized medicine. Studies described in this review have revealed the novelty of circRNAs and their biological ss as prognostic and diagnostic biomarkers.

Circ_0070203 Promotes Epithelial-mesenchymal Transition in Ovarian Serous Cystadenocarcinoma through miR-370-3p/TGFβR2 Axis

INTRODUCTION

Circular RNAs (circRNAs) are important biological molecules associated with the pathogenesis of multiple cancers.

OBJECTIVE

This work aimed to investigate the function and molecular mechanism of circ_0070203 in high-grade serous ovarian cystadenocarcinoma (HGSOC).

METHODS

circRNA microarray was conducted to detect the circ_0070203 expression in HGSOC tissues. Bioinformatics analysis was used to find the binding sites between circ_0070203, miR- 370-3p and TGFβR2. Real-time quantitative reverse transcription PCR (RT-qPCR) was executed to detect the expressions of circ_0070203, miR-370-3p and TGFβR2 in HGSOC tissues and SKOV3 cells. Dual-luciferase reporter gene assay was used to validate the relationships between miR-370-3p and circ_0070203 or TGFβR2. Besides, transwell assays were conducted to assess the migrative, invasive abilities of ovarian cancer (OC) cells. Western blotting was adopted to detect the expression of epithelial-mesenchymal transition (EMT)-related proteins. The related patents were also studied during the research.

RESULTS

Circ_0070203 and TGFβR2 were upregulated, while miR-370-3p was downregulated in FIGO stage III-IV HGSOC tissues and SKOV-3 cell lines. circ_0070203 overexpression changed the expression of other EMT-related proteins and enhanced the migrative, invasive abilities of OC cells, while silencing circ_0070203 worked oppositely. Mechanistically, circ_0070203 could upregulate TGFβR2 expression in OC cells via sponging miR-370-3p.

CONCLUSION

Circ_0070203 could promote the epithelial-mesenchymal transition, invasion, and metastasis of HGSOC via regulating the miR-370-3p/TGFβR2 axis. Our findings provided a potential biomarker for HGSOC therapy.

The role of circRNAs in regulation of drug resistance in ovarian cancer

Ovarian cancer is one of the female reproductive system tumors. Chemotherapy is used for advanced ovarian cancer patients; however, drug resistance is a pivotal cause of chemotherapeutic failure. Hence, it is critical to explore the molecular mechanisms of drug resistance of ovarian cancer cells and to ameliorate chemoresistance. Noncoding RNAs (ncRNAs) have been identified to critically participate in drug sensitivity in a variety of human cancers, including ovarian cancer. Among ncRNAs, circRNAs sponge miRNAs and prevent miRNAs from regulation of their target mRNAs. CircRNAs can interact with DNA or proteins to modulate gene expression. In this review, we briefly describe the biological functions of circRNAs in the development and progression of ovarian cancer. Moreover, we discuss the underneath regulatory molecular mechanisms of circRNAs on governing drug resistance in ovarian cancer. Furthermore, we mention the novel strategies to overcome drug resistance via targeting circRNAs in ovarian cancer. Due to that circRNAs play a key role in modulation of drug resistance in ovarian cancer, targeting circRNAs could be a novel approach for attenuation of chemoresistance in ovarian cancer.

m6A-modified circNFIX promotes ovarian cancer progression and immune escape via activating IL-6R/JAK1/STAT3 signaling by sponging miR-647

BACKGROUND

Ovarian cancer (OC) is one of the most common gynecological malignant cancers. Our previous work confirmed that circNFIX acted as an oncogene in OC, which could promote malignant proliferation, metastasis and angiogenesis. However, the role and mechanism of circNFIX in OC immune escape remain unclear.

METHODS

The RNA and protein levels were determined by qRT-PCR and western blot assays. The malignant phenotypes were tested by cell count kit-8, EdU staining, flow cytometry and transwell assays. The immune cytokines levels were measured by ELISA analysis. Molecular interactions were verified employing RNA immunoprecipitation, meRIP and dual luciferase methods. In vivo validation was performed by xenograft tumor and lung metastasis model. Hematoxylin & eosin and immunohistochemistry staining were used to observe the pathological changes.

RESULTS

The levels of circNFIX, PD-L1, and IL-6R were upregulated in OC tissues and cell lines, while miR-647 was downregulated. Functional assays showed that loss of circNFIX suppressed the growth, metastasis and immune escape of OC cells both in vitro and in vivo. On the molecular level, the m6A modification of circNFIX was elevated in OC cells, and its expression was positively correlated to m6A modification and depended on IGF2BP1 ∼ 3 recognition. Moreover, circNFIX acted as a competing endogenous RNA for miR-647 to upregulate IL-6R expression, thereby activating JAK/STAT3 signaling and elevating PD-L1 expression. Rescue assays revealed that co-silencing of miR-647 reversed the antitumor effects of circNFIX knockdown on cell proliferation, metastasis and immune escape of OC cells.

CONCLUSION

This study provided a comprehensive understanding of the molecular mechanism about circNFIX in OC, demonstrating m6A activated-circNFIX accelerated OC development and immune escape via regulating miR-647/IL-6R/PD-L1 pathway.

Circ_0021573 acts as a competing endogenous RNA to promote the malignant phenotypes of human ovarian cancer cells

Circular RNAs (circRNAs) have been reported to be implicated in the tumorigenesis and progression of ovarian cancer. Here, the study was designed to explore the activity of human circ_0021573 in ovarian cancer pathogenesis and its regulation through the competing endogenous RNA (ceRNA) crosstalk. Circ_0021573, microRNA (miR)- 936, and cullin 4B (CUL4B) were quantified by qRT-PCR and western blot. Cell proliferation ability was detected by XTT, 5-Ethynyl-2'-Deoxyuridine (EdU), and colony formation assays. Cell apoptosis, migration, and invasion were assessed by flow cytometry, wound-healing, and transwell assays, respectively. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were used to evaluate the direct relationship between miR-936 and circ_0021573 or CUL4B 3'UTR. Xenograft studies were applied to assess the role of circ_0021573 in tumor growth. Our data showed that circ_0021573 expression is enhanced in human ovarian cancer. Inhibition of circ_0021573 impedes cell proliferation, migration, and invasion and promotes apoptosis in vitro, as well as diminishes tumor growth in vivo. Mechanistically, circ_0021573 contains a miR-936 binding site, and miR-936 is a relevant mediator of circ_0021573 regulation. MiR-936 direct targets and inhibits CUL4B. MiR-936-mediated suppression of CUL4B hinders cell proliferation, migration, and invasion and accelerates apoptosis in vitro.. These data suggested that circ_0021573 might promote the malignant phenotypes of ovarian cancer cells by functioning as a ceRNA for miR-936 to induce CUL4B, which provided a promising target for the prevention and inhibition of ovarian cancer.

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.

Insight on Non-Coding RNAs from Biofluids in Ovarian Tumors

Ovarian tumors are the most frequent adnexal mass, raising diagnostic and therapeutic issues linked to a large spectrum of tumors, with a continuum from benign to malignant. Thus far, none of the available diagnostic tools have proven efficient in deciding strategy, and no consensus exists on the best strategy between "single test", "dual testing", "sequential testing", "multiple testing options" and "no testing". In addition, there is a need for prognostic tools such as biological markers of recurrence and theragnostic tools to detect women not responding to chemotherapy in order to adapt therapies. Non-coding RNAs are classified as small or long based on their nucleotide count. Non-coding RNAs have multiple biological functions such as a role in tumorigenesis, gene regulation and genome protection. These ncRNAs emerge as new potential tools to differentiate benign from malignant tumors and to evaluate prognostic and theragnostic factors. In the specific setting of ovarian tumors, the goal of the present work is to offer an insight into the contribution of biofluid non-coding RNAs (ncRNA) expression.

Circ_0015756 promotes ovarian cancer progression via the miR-145-5p/PSAT1 axis

Circular RNA (circRNA) have been shown to exert vital functions in the pathological progressions of ovarian cancer (OC). Herein, this study aimed to investigate the role and mechanisms of circ_0015756 in OC progression. Levels of circ_0015756, microRNA (miR)- 145-5p and phosphoserine aminotransferase 1 (PSAT1) were detected using quantitative real-time polymerase chain reaction, Western blot or immunohistochemistry assays. Cell proliferation, apoptosis, migration and invasion were determined using cell counting kit-8, 5-Ethynyl-2'-Deoxyuridine (Edu) incorporation, flow cytometry, transwell and Western blot assays. The binding interaction between miR-145-5p and circ_0015756 or PSAT1 was confirmed by bioinformatics prediction and dual-luciferase reporter assay. Tumor formation assay in nude mice was performed to determine the tumor growth in vivo. Circ_0015756 was highly expressed in OC tissues and cells. Knockdown of circ_0015756 suppressed cancer cell growth, migration and invasion in vitro, as well as impeded tumor growth in vivo. In a mechanical study, circ_0015756 directly bound to miR-145-5p, and inhibition of miR-145-5p reversed the effects of circ_0015756 knockdown on OC cells. Moreover, miR-145-5p directly targeted PSAT1, and miR-145-5p weakened OC cell growth, migration and invasion via targeting PSAT1. Importantly, further studies confirmed that circ_0015756 could indirectly regulate PSAT1 expression via sponging miR-145-5p. In all, circ_0015756 accelerated OC tumorigenesis through regulating miR-145-5p/PSAT1 axis, providing a new therapeutic target for OC.

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.

Circ_0072995 drives cervical cancer development by regulating the miR-29a/WDR5 axis

Circular RNA_0072995 (Circ_0072995) is involved in the pathogenesis of cancers; however, no study has investigated its role in cervical cancer. Therefore, we aimed to investigate the function of circ_0072995 in cervical cancer. Normal human cervical epithelial cells (hCECs), HeLa cells, and forty female nude BALB/c mice were used. Immunohistochemistry, invasion assays, flow cytometric analysis, luciferase assays, and tumour volume measurements were performed to explore the potential mechanism. Circ_0072995 was significantly up-regulated in cancer tissues, and its level was markedly correlated with the International Federation of Gynecology and Obstetrics system (FIGO) staging. In vitro studies revealed that circ_0072995 interacts with miR-29a to induce WD repeat domain 5 (WDR5) expression and promotes the proliferation and invasion of cells, but inhibits apoptosis of cells. Knockdown of circ_0072995 or WDR5, or overexpression of miR-29a significantly inhibited tumour growth in vivo. In conclusion, circ_0072995 promoted cervical cancer development by inducing miR-29a-mediated WDR5 expression.Impact statementWhat is already known on this subject? Global Cancer Statistics 2020 estimated that there were 1 021,494 new cases of cervical cancer and 439 201 deaths from cervical cancer. Circ_0072995 was first shown to promote breast cancer development in 2018. Subsequent studies have revealed that circ_0072995 is also involved in the development of other cancers, including epithelial ovarian cancer and hepatocellular carcinoma. However, no studies have explored the association between circ_0072995 and cervical cancer.What do the results of this study add? We hypothesized that circ_0072995 drives cervical cancer development by sponging miRNAs and inducing the expression of key factors involved in tumorigenesis. Based on this hypothesis, we investigated the role of circ_0072995 in cervical cancer and paracancerous tissues and explored the underlying mechanism in both in vitro and in vivo studies.What are the implications of these findings for clinical practice and/or further research? For the first time, our study revealed the key role of WDR5 in cervical cancer progression regulated by circ_0072995. We first reported the promoting effects of circ_0072995 in cervical cancer development by inducing miR-29a mediated WDR5 expression and also revealed the therapeutic potential of circ_0072995, miR-29a, and WDR5 in cervical cancer.

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.

MicroRNA-147a Targets SLC40A1 to Induce Ferroptosis in Human Glioblastoma

Objective. Glioblastoma is one of the most common malignant tumors in the brain, and these glioblastoma patients have very poor prognosis. Ferroptosis is involved in the progression of various tumors, including the glioblastoma. This study aims to determine the involvement of microRNA (miR)-147a in regulating ferroptosis of glioblastoma in vitro. Methods. Human glioblastoma cell lines were transfected with the inhibitor, mimic and matched negative controls of miR-147a in the presence or absence of ferroptotic inducers. To knock down the endogenous solute carrier family 40 member 1 (SLC40A1), cells were transfected with the small interfering RNA against SLC40A1. In addition, cells with or without the miR-147a mimic treatment were also incubated with temozolomide (TMZ) to investigate whether miR-147a overexpression could sensitize human glioblastoma cells to TMZ chemotherapy in vitro. Results. We found that miR-147a level was decreased in human glioblastoma tissues and cell lines and that the miR-147a mimic significantly suppressed the growth of glioblastoma cells in vitro. In addition, miR-147a expression was elevated in human glioblastoma cells upon erastin or RSL3 stimulation. Treatment with the miR-147a mimic significantly induced ferroptosis of glioblastoma cells, and the ferroptotic inhibitors could block the miR-147a mimic-mediated tumor suppression in vitro. Conversely, the miR-147a inhibitor prevented erastin- or RSL3-induced ferroptosis and increased the viability of glioblastoma cells in vitro. Mechanistically, we determined that miR-147a directly bound to the 3 $\prime$ -untranslated region of SLC40A1 and inhibited SLC40A1-mediated iron export, thereby facilitating iron overload, lipid peroxidation, and ferroptosis. Furthermore, miR-147a mimic-treated human glioblastoma cells exhibited higher sensitivity to TMZ chemotherapy than those treated with the mimic control in vitro. Conclusion. We for the first time determine that miR-147a targets SLC40A1 to induce ferroptosis in human glioblastoma in vitro.

Prospect of exosomal circular RNAs in breast Cancer: presents and future

Implementing precision oncology for breast cancer (BC) is a critical method for improving patient outcomes, which relies on the use of reliable biomarkers to be effective and safe. exosomes represent a potential alternative for the diagnosis and therapy of BC, As a "liquid biopsy" and a novel source for biomarkers. Exosomes are nanoscale phospholipid bilayer vesicles released by most cells that contain a large payload of various RNA species that can alter recipient cell activity. Circular RNAs (circRNAs) were recently revealed as a looping subclass of competing endogenous noncoding RNAs (ceRNAs) capable of microRNA sponging to regulate gene expression. They provide critical regulatory functions in carcinogenesis, proliferation, invasion, metastasis, and treatment resistance, as well as cancer prognostic. However, there is still a major gap in our understanding of the role of circRNA in the advancement of BC. CircRNAs are abundant in exosomes, according to various studies, and exosomal circRNAs (exo-circRNAs) play a significant role in cancer biology. Exo-circRNAs can be picked up by nearby or distant cells, affecting many features of the target cells' pathophysiological states, thus boosting cell communication and tumor spread. In this review, we have briefly summarized the major properties and functions of exosomes. Then, we have focused on exo-circRNAs, discussing their potential roles in both driving and inhibiting BC, as well as for cancer diagnosis, prognosis, and monitoring.

Exosomal lncRNA HMMR-AS1 mediates macrophage polarization through miR-147a/ARID3A axis under hypoxia and affects the progression of hepatocellular carcinoma

BACKGROUND

At present, the role of lncRNA in different kinds of tumors has been widely reported, but its role with hypoxic environment and macrophage polarization is still unclear. Therefore, this study tried to clarify the role of exosomal lncRNA in tumor hypoxic environment and macrophage polarization in the process of hepatocellular carcinoma (HCC), and provide a basis for targeted therapy of HCC.

METHODS

Bioinformatics screening of differentially expressed lncRNA and mRNA was carried out through GEO database, and the expression of lncRNA HMMR-AS1 in tumor tissues was detected and verified in HCC tissues. The effects of HMMR-AS1 on proliferation, migration, apoptosis, and macrophage polarization were determined by in vitro and in vivo experiments. Perform luciferase reporter gene detection and RNA immunoprecipitation to reveal the interaction between HMMR-AS1, miR-147a, and ARID3A. At the same time, the JASPAR database and dual luciferase report were used to detect the relationship between HIF-1α and HMMR-AS1 transcription regulation. Finally, nanoparticle tracking technology, transmission electron microscopy, and western blot were used to detect the effect of hypoxic environment on exosome secretion.

RESULTS

LncRNA HMMR-AS1 was significantly up-regulated in HCC tissues and HCC cells and was related to the poor prognosis. Inhibiting the expression of HMMR-AS1 could significantly inhibit tumor growth in vitro and in vivo. Further study of the mechanism showed that HMMR-AS1 could competitively bind to miR-147a to prevent the degradation of ARID3A. Exosomes carrying HMMR-AS1 could promote the M2 polarization of macrophages mediated by this pathway and further accelerate the progression of HCC. In addition, in the hypoxic environment, HIF-1α promotes its transcription by binding to the HMMR-AS1 promoter and induces an increase in the number of exosomes secreted.

CONCLUSION

In summary, we first discovered and verified the role of lncRNA HMMR-AS1 in HCC. In terms of mechanism, the promotion of exosomal HMMR-AS1 competitive adsorption of miR-147a under hypoxic environment affects ARID3A-mediated macrophage polarization. These data provide a new direction for the research on the pathogenesis of HCC and the development of targeted therapy.

Long noncoding RNA (lncRNA) metallothionein 1 J, pseudogene (MT1JP) is downregulated in triple-negative breast cancer and upregulates microRNA-138 (miR-138) to downregulate hypoxia-inducible factor-1α (HIF-1α)

Triple-negative breast cancer (TNBC) is a highly invasive subtype of breast cancer. This study explored the molecular mechanism and influences of metallothionein 1 J, pseudogene (MT1JP), microRNA-138 (miR-138), and hypoxia-inducible factor-1α (HIF-1α) on TNBC cell proliferation and migration. We confirmed TNBC cases by immunohistochemistry (IHC) staining. The expression of MT1JP in two types of tissue collected from 78 TNBC patients was detected by performing real-time quantitative fluorescence PCR (RT-qPCR). To further evaluate the relationship among MT1JP, miR-138 and HIF-1α, expression vectors of MT1JP and HIF-1α, as well as miR-138 mimic and inhibitor, were delivered into BT-549 cells. We observed that MT1JP was downregulated in TNBC. MT1JP was positively correlated with miR-138 but negatively correlated with HIF-1α in TNBC tissues. In TNBC cells, upregulation of miR-138 and downregulation of HIF-1α were observed after overexpression of MT1JP. In addition, overexpression of miR-138 resulted in downregulation of HIF-1α but did not affect the expression of MT1JP. Decreased proliferation rate of TNBC cells was observed after overexpression of MT1JP and miR-138. HIF-1α increased cell proliferation and migration. HIF-1α also suppressed the role of MT1JP and miR-138 in TNBC cell proliferation and migration. In conclusion, our findings demonstrated that MT1JP inhibited TNBC by regulating the miR-138/HIF-1α axis, indicating that MT1JP might serve as a biomarker or target for TNBC treatment.

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.

Circular RNA SET domain protein 3 promotes nasopharyngeal carcinoma proliferation, cisplatin resistance, and protein kinase B / mammalian target of rapamycin pathway activation by modulating microRNA-147a expression

Circular RNA (circRNA) plays a crucial role in the establishment and progression of nasopharyngeal carcinoma (NPC). Understanding the role of circRNA in NPC is helpful to find new therapeutic targets for NPC. The purpose of this study was to explore the effects of circRNA SET domain protein 3 (circSETD3) on protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) signaling pathway and cisplatin (DDP) resistance to NPC and explore its downstream mechanism. The results showed that circSETD3 was upregulated in NPC tissues and was related to DDP resistance to NPC. Functional experiments revealed that circSETD3 knockdown inhibited NPC proliferation and increased DDP sensitivity and apoptosis rate. The promotion effect of circSETD3 overexpression on NPC proliferation and DDP resistance and inhibition effect on apoptosis was reversed by elevated miR-147a. CircSETD3 knockdown or miR-147a overexpression prevented Akt/mTOR pathway's activation. In terms of the mechanism, circSETD3 acted as a sponge for miR-147a. Xenotransplantation experiments showed that knockdown circSETD3 or DDP treatment could restrain tumor growth, and the effect of DDP was enhanced by knockdown of circSETD3. In conclusion, the results of this study confirm that circSETD3 promotes NPC proliferation and DDP resistance by regulating miR-147a, and circSETD3/miR-147a axis may serve as a potential therapeutic target for NPC in the future.

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.

circRNA-miRNA-mRNA in breast cancer

Among cancers, breast cancer has the highest incidence rate among women and poses a tremendous threat to women's health. Messenger RNA (mRNA), microRNA (miRNA) and circular RNA (circRNA) play vital roles in the progression of breast cancer through a variety of biological effects and mechanisms. Recently, the regulatory network formed by circRNAs, miRNAs and mRNAs has piqued attention and garnered interest. CircRNAs bind to miRNAs through a regulatory mechanism in which endogenous RNAs compete to indirectly regulate the expression of mRNA corresponding to downstream target genes of miRNAs, contributing to the progression of breast cancer. The circRNA-miRNA-mRNA axis may be a marker for the early diagnosis and prognosis of breast cancer and a potential breast cancer treatment target, providing unlimited possibilities for the development of breast cancer biomarkers and therapeutic strategies. This article reviews recent research progress on the circRNA-miRNA-mRNA axis as a regulatory network of competing endogenous RNAs in breast cancer. Herein, we focus on the mechanism and function of the circRNA-miRNA-mRNA axis in the occurrence and metastasis of breast cancer, and resistance to chemotherapy.

Notoginsenoside R1 alleviates high glucose-induced inflammation and oxidative stress in HUVECs via upregulating miR-147a

Endothelial dysfunction in atherosclerotic cardiovascular diseases has become one of the main characteristics in patients with diabetes mellitus, which is usually caused by abnormal inflammation and oxidative stress response. Presently, we focused on the role of Notoginsenoside R1 (NR1), a major component isolated from Panax notoginseng, in endothelial dysfunction caused by high glucose (HG). Human umbilical vein endothelial cells (HUVECs) were treated with HG and then dealt with NR1. Cell counting kit-8 assay and 5-bromo-2'-dexoyuridine assay were conducted to examine cell proliferation and viability. Flow cytometry was used to measure apoptosis. The angiogenesis of HUVECs was determined by tube formation assay. Moreover, the expressions of miR-147a, inflammatory cytokines (TNF-α, IL-6, and IL-10) and oxidative stress markers malondialdehyde, superoxide dismutase, and glutathione peroxidase were measured. The protein levels of MyD88/TRAF6/NF-κB axis, Bax, Bcl2, and Caspase3 were detected by Western blot. Furthermore, gain and loss of functional assays of miR-147a were performed to verify the role of miR-147a in NR1-mediated effects. Our data confirmed that NR1 (at 10-40 μM) reduces HG-induced HUVECs proliferation and viability inhibition, mitigates apoptosis, and enhances tube formation ability. Meanwhile, NR1 inhibited oxidative stress and inflammatory response and blocked the activation of the MyD88/TRAF6/NF-κB pathway induced by HG. In addition, NR1 promoted the expression of miR-147a, which targeted MyD88. Overexpression of miR-147a markedly inactivated MyD88/TRAF6/NF-κB pathway, while the miR-147a inhibitors reversed NR1-mediated protective effect in HG-induced HUVECs through activating MyD88/TRAF6/NF-κB pathway. In conclusion, NR1 relieves HG-induced endothelial cell injury by downregulating the MyD88/TRAF6/NF-κB pathway via upregulating miR-147a.

Circ_0072995 Promotes Proliferation and Invasion via Regulating miR-1253/EIF4A3 Signaling in HCC

Background

Hepatocellular carcinoma (HCC) is a major threat for human health. This work aimed to determine the potential function of circ_0072995 in HCC progression and its molecular mechanism.

Methods

qRT-PCR was conducted to analyze circ_0072995 expression. CCK8 and colony formation assays were utilized to detect cell proliferation. Transwell assay was performed to determine migration and invasion. Interactions among circ_0072995, miR-1253 and EIF4A3 (Eukaryotic Translation Initiation Factor 4A3) were predicted through bioinformatics methods and confirmed via luciferase reporter assay and RNA pulldown assay.

Results

circ_0072995 expression was upregulated in HCC tissues. Circ_0072995 high level was associated with poor prognosis. Circ_0072995 knockdown impaired proliferation, migration, invasion and survival. MiR-1253 was sponged by circ_0072995 and targeted EIF4A3 directly. Circ_0072995 inhibited miR-1253 to upregulate EIF4A3 level.

Conclusion

Circ_0072995 exerted tumorigenic roles to enhance HCC progression through activating EIF4A3 by sponging miR-1253.

CircRNA FUT10 regulates the regenerative potential of aged skeletal muscle stem cells by targeting HOXA9

Skeletal muscle is capable of repairing itself after injury to maintain the stability of its own tissue, but this ability declines with aging. Circular RNAs (circRNAs) are involved in cell aging. However, there is little research into their role and underlying mechanisms, especially in skeletal muscle stem cells (SkMSCs). In this study, we assessed circRNA FUT10 expression in aged and adult SkMSCs. We observed that circRNA FUT10 was upregulated in aged SkMSCs compared with that in adult SkMSCs. Furthermore, we identified putative miR-365-3p binding sites on circRNA FUT10, suggesting that this circRNA sponges miR-365a-3p. We also found that HOXA9 is a downstream target of miR-365a-3p and confirmed that miR-365a-3p can bind to circRNA FUT10 and the 3′-untranslated region of HOXA9 mRNA. This finding indicated that miR-365a-3p might serve as a “bridge” between circRNA FUT10 and HOXA9. Finally, we found that the circRNA FUT10/miR365a-3p/HOXA9 axis is involved in SkMSC aging. Collectively, our results show that the circRNA FUT10/miR365a-3p/HOXA9 axis is a promising therapeutic target and are expected to facilitate the development of therapeutic strategies to improve the prognosis of degenerative muscle disease.

Circ_0072995 Promotes Ovarian Cancer Progression Through Regulating miR-122-5p/SLC1A5 Axis

Ovarian cancer is a common cancer affecting women with high morbidity and mortality globally. Circular RNAs (circRNAs) have been found play vital roles in multifarious cancers, including OC. This study aims to explore the biological role and underlying mechanism of circ_0072995 in OC progression. Circ_0072995 was upregulated in OC tissues and cells in a stable structure. Functional experiments indicated that circ_0072995 knockdown suppressed cell proliferation, migration, invasion and accelerated cell apoptosis of OC cells. Mechanistically, miR-122-5p was a direct target of circ_0072995, and its knockdown reversed the effects of circ_0072995 silence on inhibition of OC cell progression. Meanwhile, SLC1A5 was a downstream target gene of miR-122-5p, and miR-122-5p overexpression inhibited the progression of OC cells by targeting SLC1A5. Moreover, circ_0072995 positively regulated SLC1A5 expression via sponging miR-122-5p. Circ_0072995 could play oncogenic role in tumorigenesis and malignant development of OC by regulating miR-122-5p/SLC1A5 axis, providing a novel approach for OC treatment.

Tumor-derived exosomal circRNA_102481 contributes to EGFR-TKIs resistance via the miR-30a-5p/ROR1 axis in non-small cell lung cancer

Exosomes are messengers for intercellular communication and signal transduction. Circular RNA (circRNA) abnormal expression and regulation are involved in the occurrence and development of a variety of tumors. In the present study, exosomes in the serum of five patients with non-small cell lung cancer (NSCLC) were isolated before and after EGFR-TKIs resistance, and the circRNA expression profile was screened using a circRNA microarray. The effects of the exosome circRNA_102481 on cell proliferation and apoptosis were analyzed. The interaction between miR-30a-5p and circRNA_102481 or ROR1 was predicted by starBase software, and was confirmed by RNA pull-down and dual-luciferase reporter assays. The results showed that exosomes containing circRNA_102481 were significantly up-regulated in NSCLC with EGFR-TKIs resistance (p<0.05), and that circRNA_102481 was mainly secreted by EGFR-TKIs resistance cell via exosomes (p<0.05). Both circRNA_102481 silencing and si-circRNA_102481 transported by exosomes could inhibit EGFR-TKIs resistance cell proliferation and promote cell apoptosis and circRNA_102481 overexpression could promote EGFR-TKIs sensitive cell proliferation and inhibit cell apoptosis in vitro (p<0.05). CircRNA_102481 served as a miR-30a-5p sponge to regulate ROR1 expression (p<0.05). Furthermore, the expression of circRNA_102481 in exosomes was associated with TNM stage, tumor differentiation status, brain metastasis, and PFS and OS duration. Therefore, it was concluded that tumor-derived exosomal circRNA_ 102481 could contribute to EGFR-TKIs resistance via the microRNA-30a-5p/ROR1 axis in NSCLC. Exosomal circRNA_102481 may serve as a novel diagnostic biomarker and a therapeutic target for EGFR-TKIs resistance in NSCLC.

Circular RNA ZNF609 promotes the malignant progression of glioma by regulating miR-1224-3p/PLK1 signaling

Objective: Previous studies have demonstrated that circular RNAs (circRNAs) play vital roles in pathological process of various diseases, including tumors. This study aimed at exploring the role and mechanism of circRNA RNA ZNF609 (circ-ZNF609) in the occurrence and development of glioma. Materials and methods: Real-time quantitative PCR (qRT-PCR) was applied to measure the expression of circ-ZNF609, miRNA-1224-3p (miR-1224-3p) and Polo-like kinase 1 (PLK1) in glioma tissues and cell lines. Furthermore, the association between circ-ZNF609 and clinical features of glioma was analyzed. CCK8 assay, EdU assay and Transwell assay were conducted to detect the effect of circ-ZNF609, miR-1224-3p and PLK1 on proliferation, migration and invasion in glioma cells. Then, we investigated the underlying mechanism of circ-ZNF609 by bioinformatics analysis, luciferase reporter assay, RNA immunoprecipitation (RIP), qRT-PCR and western blotting assay. Results: Circ-ZNF609 was confirmed prominently upregulated in glioma. Inhibition of circ-ZNF609 could obviously suppress glioma cell proliferation, migration and invasion, while overexpression of circ-ZNF609 promoted glioma growth and metastasis. In vivo, xenotransplanted tumor model also showed that overexpression of circ-ZNF609 could promote in vivo glioma growth. Mechanistically, circ-ZNF609 could promote PLK1 expression via binding to miR-1224-3p, circ-ZNF609/miR-1224-3p/PLK1 was shown responsible for circ-ZNF609 promoting glioma growth and metastasis. Conclusion: Together, our results revealed that circ-ZNF609 elevates glioma growth and metastasis via enforcing PLK1 expression by competitively binding miR-1224-3p, suggesting that circ-ZNF609 might be an underlying therapeutic target for glioma.

Curcumin suppresses the malignancy of non-small cell lung cancer by modulating the circ-PRKCA/miR-384/ITGB1 pathway

BACKGROUND

Curcumin exerts a suppressive effect in tumor growth by acting as a modulator of multiple molecular targets. Circular RNA hsa_circ_0007580 (circ-PRKCA) accelerates the tumorigenesis of non-small cell lung cancer (NSCLC). However, whether curcumin can regulate circ-PRKCA to inhibit NSCLC progression is unclear.

METHODS

Cell viability, colony formation, apoptosis, migration, and invasion were analyzed using Cell Counting Kit-8 (CCK-8), plate clone, flow cytometry, or transwell assay. Expression of circ-PRKCA, microRNA (miR)-384, and ITGB1 mRNA (integrin subunit beta 1) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Curcumin repressed NSCLC growth through regulating circ-PRKCA expression was validated by xenograft assay. The targeting relationship between circ-PRKCA or ITGB1 and miR-384 was verified by dual-luciferase reporter assay. The level of ITGB1 protein was measured by western blotting.

RESULTS

Circ-PRKCA and ITGB1 expression were elevated in NSCLC tissues and cells, but miR-384 had an opposing tendency. After curcumin treatment, the expression tendency of circ-PRKCA, miR-384, and ITGB1 in NSCLC cells was overturned. Furthermore, curcumin impeded viability, colony formation, migration, invasion, and accelerated apoptosis of NSCLC cells, but these impacts were partially reversed by circ-PRKCA elevation, miR-384 downregulation, or ITGB1 overexpression. Also, the inhibitory effect of curcumin on xenograft tumor was further enhanced after circ-PRKCA knockdown. Notably, circ-PRKCA regulated ITGB1 expression through sponging miR-384 in curcumin-treated NSCLC cells.

CONCLUSIONS

Curcumin inhibited NSCLC growth through downregulating circ-PRKCA, which regulated ITGB1 expression by adsorbing miR-384. This study provided a new mechanism to understand how curcumin inhibited the progression of NSCLC.

Circ_0000527 Promotes Retinoblastoma Progression through Modulating miR-98-5p/XIAP Pathway

Purpose: Retinoblastoma (RB) is an intraocular malignancy that often occurs in childhood. Circular RNAs (circRNAs) play crucial roles in regulating the malignant phenotypes of various tumors. This study aimed to explore the role and potential mechanism of circ_0000527 in RB.Methods: The levels of circ_0000527, microRNA-98-5p (miR-98-5p) and X-linked inhibitor of apoptosis (XIAP) were determined by qRT-PCR or western blot. Cell proliferation was detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and colony formation assays. Cell apoptosis, migration and invasion were evaluated by flow cytometry, transwell and scratch assays. Xenograft assay was conducted to analyze tumor growth in vivo. The binding relationship between miR-98-5p and circ_0000527 or XIAP was verified by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.Results: Circ_0000527 and XIAP levels were increased, while miR-98-5p level was reduced in RB tissues and cells. Silencing of circ_0000527 suppressed the proliferation, migration and invasion of RB cells and promoted apoptosis. In addition, knockdown of circ_0000527 inhibited tumor growth in xenograft mice. Besides, circ_0000527 sponged miR-98-5p to regulate RB cell progression, and miR-98-5p targeted XIAP to mediate RB cell development. Moreover, circ_0000527 modulated XIAP expression via sequestering miR-98-5p.Conclusion: Circ_0000527 facilitated RB progression via regulating miR-98-5p/XIAP axis, which provided a promising therapeutic target for RB.

CircRNA in cancer: Fundamental mechanism and clinical potential

Circular RNAs (CircRNAs) are a class of single-stranded noncoding RNAs that are formed in a circular conformation via non-canonical splicing or back-splicing events. Aberrant expressions of many circRNAs are observed in diverse cancers, indicating their crucial roles in tumorigenesis and tumor development. Recently, several pieces of evidence have revealed that many circRNAs are involved in the promotion or suppression of cancers to varying degrees via different molecular mechanisms. Here in this review, we present a summary of the characteristics, types, biogenesis, and functions of circRNAs, and outline a series of the most recently studied circRNAs and their functional mechanisms in multiple cancer types with future perspectives. With great advances in nucleic acid-based therapeutic tools, circRNAs could be further explored as targetable molecules in future cancer treatments.0.

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.