Circ_0007841 accelerates ovarian cancer development through facilitating MEX3C expression by restraining miR-151-3p activity

EIF4A3-Bound hsa_circ_0006847 Exerts a Tumor-Suppressive Role in Gastric Cancer

Numerous studies have shown that circular RNAs are associated with the occurrence and development of various cancers, but the biological functions and mechanisms of hsa_circ_0006847 (circASPHD1) in gastric cancer (GC) remain unclear. The expression of hsa_circ_0006847 in GC cell lines, tissue, and plasma from GC patients was assayed by quantitative real-time reverse transcription-polymerase chain reaction. Hsa_circ_0006847 expression in cells was downregulated or upregulated by transfected small interfering RNA (siRNA) or overexpression plasmid. The role of hsa_circ_0006847 in GC was investigated with Cell Counting Kit-8, EdU, Transwell, flow cytometry assays, and in a subcutaneous xenograft tumor model. In addition, the interaction of eukaryotic translation initiation factor 4A3 (EIF4A3) and hsa_circ_0006847 was determined with western blot, biotin-labeled RNA pull-down, and RNA immunoprecipitation assays. Co-immunoprecipitation and mass spectrometry were used to validate the combination of EIF4A3 and synaptopodin-2 (SYNPO2). The expression of hsa_circ_0006847 was decreased in GC tissues and cells and indicated poor survival and prognosis. Overexpression of hsa_circ_0006847 inhibited cell proliferation, migration, and invasion. Flow cytometry showed that upregulation of hsa_circ_0006847 resulted in promotion of apoptosis of GC cells and inhibited their progression through the G0/G1 phase. Downregulation of hsa_circ_0006847 expression had the opposite effects. Overexpression of hsa_circ_0006847 in subcutaneous tumor xenografts inhibited tumor growth. Mechanically, hsa_circ_0006847 promoted the binding of EIF4A3 to SYNPO2 by recruiting EIF4A3, which inhibited the growth of GC. The tumor suppressor activity of hsa_circ_0006847, inhibition of the occurrence and development of GC, was mediated by promotion of EIF4A3 and the binding of EIF4A3 to SYNPO2. The results support the study of hsa_circ_0006847 as a novel therapeutic target for the treatment of GC.

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.

Ubiquitylation of RUNX3 by RNA-binding ubiquitin ligase MEX3C promotes tumorigenesis in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most common pathological type of lung cancer, but the early diagnosis rate is low. The RNA-binding ubiquitin ligase MEX3C promotes tumorigenesis in several cancers but its mechanism of action in LUAD is unclear. In this study, the biological activity of MEX3C was assessed in LUAD. MEX3C and RUNX3 mRNA levels in the tissues of LUAD patients were determined using reverse transcription‑quantitative PCR. The involvement of MEX3C in the growth and metastasis of LUAD cells was measured by EdU assay, CCK-8, colony formation, Transwell assay, TUNEL, and flow cytometry. Expression of apoptosis and epithelial-mesenchymal transition related proteins were determined using western blotting analysis. LUAD cells transfected with si-MEX3C were administered to mice subcutaneously to monitor tumor progression and metastasis. We found that MEX3C is strongly upregulated in LUAD tissue sections, and involved in proliferation and migration. A549 and H1299 cells had significantly higher levels of MEX3C expression compared to control HBE cells. Knockdown of MEX3C dramatically decreased cell proliferation, migration, and invasion, and accelerated apoptosis. Mechanistically, we demonstrate MEX3C induces ubiquitylation and degradation of tumor suppressor RUNX3. Moreover, RUNX3 transcriptionally represses Suv39H1, as revealed by RNA pull-down and chromatin immunoprecipitation assays. The in vivo mice model demonstrated that knockdown of MEX3C reduced LUAD growth and metastasis significantly. Collectively, we reveal a novel MEX3C-RUNX3-Suv39H1 signaling axis driving LUAD pathogenesis. Targeting MEX3C may represent a promising therapeutic strategy against LUAD.

The quantification of circular RNA 0007841 during induction therapy helps estimate the response and survival benefits to bortezomib-based regimen in multiple myeloma

OBJECTIVE

Circular RNA_0007841 (Circ_0007841) facilitates multiple myeloma (MM) progression and resistance of the bortezomib by experimental studies, while its clinical implication in MM patients is still unclear. This study intended to evaluate the longitudinal change and prognostic role of circ_0007841 expression in MM patients receiving bortezomib-based induction therapy.

METHODS

In this prospective study, bone marrow plasma cell (BMPC) samples were gained from 97 MM patients at diagnosis and after bortezomib-based induction therapy, and from 30 healthy controls (HCs) proposing BM donation. Then, circ_0007841 expression in BMPC samples was measured by reverse transcription-quantitative polymerase chain reaction. Additionally, MM patients were followed up for a median of 29.4 months.

RESULTS

Circ_0007841 expression was increased in MM patients compared to HCs (P < 0.001), but it was decreased after bortezomib-based induction therapy in MM patients (P < 0.001). Moreover, circ_0007841 expression at diagnosis was associated with the presence of t (4; 14) (P = 0.034), while its expression after bortezomib-based induction therapy was linked with higher revised international staging system stage (P = 0.025) in MM patients. Interestingly, circ_0007841 expression after bortezomib-based induction therapy was lower in MM patients who achieved complete remissions (P = 0.001) and overall responses (P = 0.002) compared to those who did not. Prognostically, circ_0007841 expression after bortezomib-based induction therapy (over the median vs. below the median) independently predicted shorter progression-free survival (hazard ratio (HR): 2.497, P = 0.002) and overall survival (HR: 3.107, P = 0.008) in MM patients.

CONCLUSION

Circ_0007841 quantification during induction therapy may reflect the response and survival benefits to bortezomib-based regimen in MM patients.

REG3A promotes proliferation and DDP resistance of ovarian cancer cells by activating the PI3K/Akt signaling pathway

This study explored the effect of Regenerating Islet-Derived 3-Alpha (REG3A) on ovarian cancer (OC) progression. REG3A expression was scrutinized in clinical tissues of 97 OC cases by quantitative real-time polymerase chain reaction (qRT-PCR). REG3A expression in OC cells and cisplatin (DDP) resistance OC cells was regulated by transfection. LY294002 (10 μM, inhibitor of the PI3K/Akt signaling pathway) was used to treat OC cells and DDP resistance OC cells. Cell counting kit-8 and methyl-thiazolyl-tetrazolium assays were applied for proliferation and DDP resistance detection. Flow cytometry was utilized for cell cycle and apoptosis analysis. The effect of REG3A on the OC cell in vivo growth was researched by establishing xenograft tumor model via using nude mice using nude mice. The expression of genes in clinical samples, cells and xenograft tumor tissues was investigated by qRT-PCR, Western blot and immunohistochemistry. As a result, REG3A was over-expressed in OC patients and cells, associating with dismal prognosis of patients. REG3A knockdown repressed proliferation, DDP resistance, induced cell cycle arrest and apoptosis of OC cells, and reduced the expression MDR-1, Cyclin D1, Cleaved caspase 3 proteins and the PI3K/Akt signaling pathway activity in OC cells. LY294002 treatment abrogated the promotion effect of REG3A on OC cell proliferation, apoptosis inhibition and DDP resistance. REG3A knockdown suppressed the in vivo growth of OC cells. Thus, REG3A promoted proliferation and DDP resistance of OC cells by activating the PI3K/Akt signaling pathway. REG3A might be a promising target for the clinical treatment of OC.

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.

Roles and mechanisms of CircRNAs in ovarian cancer

Ovarian cancer (OC) is one of the female malignancies with nearly 45% 5-year survival rate. Circular RNAs (circRNAs), a kind of single-stranded non-coding RNAs, are generated from the back-splicing of cellular housekeeping noncoding RNAs and precursor messenger RNAs. Recent studies revealed that circRNAs have different biological function, including sponging miRNAs, encoding micropeptides, regulating stability of cytoplasmic mRNAs, affecting transcription and splicing, via interacting with DNA, RNA and proteins. Due to their stability, circRNAs have the potential of acting as biomarkers and treatment targets. In this review, we briefly illustrate the biogenesis mechanism and biological function of circRNAs in OC, and make a perspective of circRNAs drug targeting immune responses and signaling pathways in OC. This article can provide a systematic view into the current situation and future of circRNAs in OC.

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.

MEX3C-Mediated Decay of SOCS3 mRNA Promotes JAK2/STAT3 Signaling to Facilitate Metastasis in Hepatocellular Carcinoma

Tumor metastasis is one of the major causes of high mortality in patients with hepatocellular carcinoma (HCC). Sustained activation of STAT3 signaling plays a critical role in HCC metastasis. RNA binding protein (RBP)-mediated posttranscriptional regulation is involved in the precise control of signal transduction, including STAT3 signaling. In this study, we investigated whether RBPs are important regulators of HCC metastasis. The RBP MEX3C was found to be significantly upregulated in highly metastatic HCC and correlated with poor prognosis in HCC. Mechanistically, MEX3C increased JAK2/STAT3 pathway activity by downregulating SOCS3, a major negative regulator of JAK2/STAT3 signaling. MEX3C interacted with the 3'UTR of SOCS3 and recruited CNOT7 to ubiquitinate and accelerate decay of SOCS3 mRNA. Treatment with MEX3C-specific antisense oligonucleotide significantly inhibited JAK2/STAT3 pathway activation, suppressing HCC migration in vitro and metastasis in vivo. These findings highlight a novel mRNA decay-mediated mechanism for the disruption of SOCS3-driven negative regulation of JAK2/STAT3 signaling, suggesting MEX3C may be a potential prognostic biomarker and promising therapeutic target in HCC.

SIGNIFICANCE

This study reveals that RNA-binding protein MEX3C induces SOCS3 mRNA decay to promote JAK2/STAT3 activation and tumor metastasis in hepatocellular carcinoma, identifying MEX3C targeting as a potential approach for treating metastatic disease.

Circ_0008285 knockdown represses tumor development by miR-384/RRM2 axis in hepatocellular carcinoma

INTRODUCTION AND OBJECTIVES

Circular RNA (circRNA) has attracted extensive attention in studies related to the malignant progression of cancer, including hepatocellular carcinoma (HCC). Therefore, its molecular mechanism in HCC needs to be further explored.

MATERIALS AND METHODS

The expression levels of circ_0008285, microRNA (miR)-384 and ribonucleotide reductase subunit M2 (RRM2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was analyzed using cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine assay, cell apoptosis was analyzed by flow cytometry, and cell migration and invasion were detected by transwell assay. Protein level was detected by western blot. The relationships between miR-384 and circ_0008285 or RRM2 were predicted by bioinformatics software and validated by dual luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

Circ_0008285 expression is elevated to HCC tissues and cell lines. Silencing of circ_0008285 inhibited the proliferation, migration and invasion of HCC cells but accelerated cell apoptosis in vitro and impeded HCC tumorigenesis in vivo. Mechanistically, circ_0008285 directly interacted with miR-384, and miR-384 silencing attenuated the effects of circ_0008285 interference on cell proliferation, migration, invasion, and apoptosis. RRM2 was a direct target of miR-384, and RRM2 overexpression reversed the effects of miR-384 overexpression on cell proliferation, migration, invasion, and apoptosis. In addition, circ_0008285 regulated RRM2 expression by sponging miR-384.

CONCLUSION

In this study, circ_0008285 could promote the malignant biological behaviors of HCC cells through miR-384/RRM2 axis and has the potential to become a therapeutic target for HCC, providing a new idea for targeted therapy of HCC.

CircRNF144B/miR-342-3p/FBXL11 axis reduced autophagy and promoted the progression of ovarian cancer by increasing the ubiquitination of Beclin-1

Circular RNAs (circRNAs) can regulate autophagy and ovarian cancer (OC) progression. However, autophagy-associated circRNAs involved in OC progression are largely unknown. Bioinformatics, RNA sequencing, and qRT-PCR were conducted to detect circRNF144B expression in OC as well as its relationship with patient prognosis. Functional experiments were used to determine the effects of circRNF144B on the proliferation, mobility and autophagy of OC. Double luciferase reporter assays, immunoprecipitation, and ubiquitination detection were performed to determine the molecular mechanisms of circRNF144B in autophagy and OC progression. CircRNF144B was elevated in OC tissues with low autophagy levels, and associated with poor prognosis. CircRNF144B promoted the malignant biological properties of OC cells, and inhibited the autophagy. Mechanistically, circRNF144B acts as a sponge for miR-342-3p and inhibits miR-342-3p-induced degradation of lysine demethylase 2 A (FBXL11) mRNA, leading to elevated FBXL11 protein levels. Elevated FBXL11 promoted the ubiquitination and degradation of Beclin-1, thus inhibiting autophagy. In conclusion, CircRNF144B increased FBXL11 level by sponging miR-342-3p, whereas elevated FBXL11 promoted the ubiquitination and protein degradation of Beclin-1, thus suppressing autophagy flux and promoting OC progression. Thus, circRNF144B may be an effective target for OC therapy.

New insights into the role of circular RNAs in ovarian cancer

Ovarian cancer (OC) is one of the most aggressive tumors in women and has a poor prognosis and the highest mortality rate. Circular RNAs (circRNAs) are a type of endogenous non-coding RNAs that have recently attracted interest in cancer research. Increasing evidence has demonstrated that circRNAs play an oncogenic or suppressive role in tumorigenesis and progression, and show tissue- or developmental-stage-specific expression. Due to high stability, conservation, abundance, and specificity, circRNAs are considered promising biomarkers for the diagnosis and prognosis of cancer. Herein, we have summarized the expression profiles of circRNAs in OC tissues, serums, and cell lines. Moreover, we discuss how circRNAs participate in the regulation of multiple biological processes in OC, including cell proliferation, apoptosis, migration, invasion, autophagy, epithelial-to-mesenchymal transition, glucose metabolism, angiogenesis, immune response, and chemotherapy resistance, by sponging microRNAs and interacting with proteins.

Effects of Circ_0109046 Regulating Mir-338-3p on the Malignant Behavior of A2780 Cells

Objective

The objective is to explore the action and mechanism of circ_0109046 on the malignant phenotypes of ovarian cancer cells.

Methods

Circ_0109046 and miR-338-3p expression were detected by quantitative real-time polymerase chain reaction (qRT-PCR). In vitro assays were conducted to investigate the action of circ_0109046 and miR-338-3p on ovarian cancer cell growth and metastasis. Western blotting was utilized to investigate the contents of apoptosis-related markers. The binding between circ_0109046 and miR-338-3p was validated using dual-luciferase reporter assay.

Results

Circ_0109046 was increased, while miR-338-3p content was decreased in ovarian cancer tissues. Deficiency of circ_0109046 or the upregulation of miR-338-3p was observed to weaken cell proliferative, migratory, and invasive abilities and elevated cell apoptosis rate in ovarian cancer. Circ_0109046 targetedly suppressed miR-338-3p. Down-regulation of miR-338-3p was able to reverse the repressing impacts of circ_0109046 silencing on ovarian cancer growth and mobility.

Conclusion

Circ_0109046 silencing impaired the proliferation, migration, and invasion of ovarian cancer cells through negatively regulating miR-338-3p in vitro, indicating the potential implication of circ_0109046 in ovarian cancer progression.

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 ribonucleic acid nucleoporin 98 knockdown alleviates high glucose-induced proliferation, fibrosis, inflammation and oxidative stress in human glomerular mesangial cells by regulating the microribonucleic acid-151-3p-high mobility group AT-hook 2 axis

AIMS/INTRODUCTION

This study aimed to investigate the role and mechanism of circular ribonucleic acid nucleoporin 98 (circNUP98) in diabetic nephropathy (DN).

MATERIALS AND METHODS

Human glomerular mesangial cells (HMCs) were stimulated with high glucose (HG) to imitate the growth environment of cells under the DN condition. Levels of genes and proteins were tested by quantitative reverse transcription polymerase chain reaction and western blot. Cell proliferation, apoptosis and inflammatory response were analyzed by using cell counting kit-8, flow cytometry and enzyme-linked immunosorbent assay analysis, respectively. Oxidative stress and fibrosis were evaluated by detecting the activity of reactive oxygen species, malondialdehyde, superoxide dismutase, fibronectin and collagen IV. The binding interaction between microribonucleic acid (miR)-151-3p and high mobility group AT-hook 2 (HMGA2) or circNUP98 was confirmed using dual-luciferase reporter, pull-down and ribonucleic acid immunoprecipitation assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy, nanoparticle tracking analysis and western blot.

RESULTS

CircNUP98 expression was higher in the serum of DN patients and HG-stimulated HMCs. Functionally, circNUP98 knockdown alleviated HG-induced proliferation, fibrosis, inflammatory response and oxidative stress in HMCs. Mechanistically, circNUP98 directly sponged miR-151-3p, which targeted HMGA2. Rescue experiments showed that miR-151-3p reversed the inhibitory effects of circNUP98 knockdown on HG-induced HMC dysfunction. Furthermore, miR-151-3p re-expression also led to an inhibition of the aforementioned biological behaviors, which was attenuated by HMGA2 upregulation. Besides that, CircNUP98 was found to be packaged into exosomes of DN, and exosomal circNUP98 possessed diagnostic value for DN patients.

CONCLUSION

CircNUP98 knockdown alleviates HG-induced proliferation, fibrosis inflammation and oxidative stress in HMCs by regulating the miR-151-3p-HMGA2 axis, which might provide a potential approach for DN therapeutics.

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.

Circ_0007841 knockdown confers cisplatin sensitivity to ovarian cancer cells by down-regulation of NFIB expression in a miR-532-5p-dependent manner

Cisplatin (DDP) is first-line management for ovarian cancer (OC). Previous data have suggested that circular RNA_0007841 (circ_0007841) regulates OC progression; however, there is no data on its role in the sensitivity of OC cells to DDP. RNA expression of circ_0007841, microRNA-532-5p (miR-532-5p) and nuclear factor I B (NFIB) was detected by quantitative real-time polymerase chain reaction in OC patient samples and OC cell lines. Protein expression was checked by Western blotting analysis. Cell viability, proliferation, cell apoptotic rate, migration and invasion were investigated by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-diphenytetrazoliumromide, 5-Ethynyl-29-deoxyuridine, flow cytometry analysis, scratch test and transwell assays, respectively. The interactions among circ_0007841, miR-532-5p and NFIB were identified by a dual-luciferase reporter assay. Xenograft mouse model assay was performed to determine the effect of circ_0007841 on DDP sensitivity in vivo. Circ_0007841 and NFIB expression were upregulated, whereas miR-532-5p was downregulated in DDP-resistant OC tissues and cells compared with controls. Circ_0007841 silencing improved DDP sensitivity, inhibited cell proliferation, invasion and migration, but induced cell apoptosis in DDP-resistant OC cells. Circ_0007841 acted as a miR-532-5p sponge and regulated DDP resistance and OC cell malignancy through miR-532-5p in DDP-resistant OC cells. Besides, the overexpression of NFIB, a target of miR-532-5p, remitted miR-532-5p-mediated effects in DDP-resistant OC cells. Circ_0007841 depletion conferred DDP sensitivity to DDP-resistant OC cells in vivo. Further, circ_0007841 was secreted from DDP-resistant OC cells through being packaged into exosomes. Circ_0007841 conferred DDP resistance to DDP-resistant OC cells through the miR-532-5p/NFIB axis, suggesting the potential of circ_0007841 as a therapeutic target for OC.

Circ_0061140 Contributes to the Malignant Progression in Ovarian Cancer Cells by Mediating the RAB1A Level Through Sponging miR-361-5p

Ovarian cancer (OC) progression is related to many functional molecules, including circular RNAs (circRNAs). Hsa_circ_0061140 (circ_0061140) promoted cell growth and metastasis in OC. The aim of this study was to explore a specific functional mechanism of circ_0061140. Reverse transcription-quantitative polymerase chain reaction was performed for expression analysis of circ_0061140, microRNA-361-5p (miR-361-5p), and Ras-like protein in rat brain 1A (RAB1A). Cell proliferation was determined using Cell Counting Kit-8 assay, EdU assay, and colony formation assay. The migration and invasion were assessed through transwell assay. Tube formation assay was used for angiogenesis analysis. Cell apoptosis was evaluated using flow cytometry. The protein levels of epithelial-to-mesenchymal transition (EMT) markers and RAB1A were detected via western blot. Target analysis was performed by dual-luciferase reporter assay and RNA immunoprecipitation assay. In vivo research was conducted using xenograft model. The circ_0061140 level was upregulated in OC samples and cells. Downregulation of circ_0061140 impeded proliferation, migration, invasion, EMT, and angiogenesis of OC cells. Circ_0061140 directly interacted with miR-361-5p to act as a miRNA sponge. The miR-361-5p inhibition reversed the si-circ_0061140-induced anti-tumor function in OC cells. RAB1A was a downstream target of miR-361-5p, and miR-361-5p served as a tumor repressor in OC via inhibiting the level of RAB1A. Circ_0061140 could increase the RAB1A expression by sponging miR-361-5p in OC cells. Circ_0061140 also facilitated tumorigenesis in vivo through targeting the miR-361-5p/RAB1A axis. All results demonstrated that circ_0061140 promoted OC development by inhibiting miR-361-5p to upregulate the expression of RAB1A.

Circ_SEC61A1 contributes to the progression of multiple myeloma cells via regulating miR-660-5p/CDK6 axis

BACKGROUND

Circular RNAs (circRNAs) have been reported to play critical roles in the malignant progression of diverse human cancers, including multiple myeloma (MM). This study aimed to explore the functional role and underlying mechanism of circ_SEC61A1 in MM progression.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) assay was performed to detect the expression levels of circ_SEC61A1, microRNA (miR)-660-5p and cyclin-dependent kinase 6 (CDK6) mRNA. The localization of circ_SEC61A1 in MM cells was tested by the subcellular fractionation location assay. Actinomycin D assay was conducted to determine the characteristics of circ_SEC61A1. Cell proliferation was evaluated by colony formation assay, 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay and 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Western blot assay was exploited to examine the expression of proteins. Cell migration and invasion were tested via transwell assay, and cell apoptosis was measured by flow cytometry analysis. Dual-luciferase reporter assay was utilized to confirm the interaction between miR-660-5p and circ_SEC61A1 or CDK6.

RESULTS

Circ_SEC61A1 level was increased in MM tissues and cells. Circ_SEC61A1 was a stable circRNA and mainly located in cytoplasm. Circ_SEC61A1 silence restrained the proliferation, metastasis and expedited the apoptosis in MM cells. CDK6 was identified as the target of miR-660-5p, and circ_SEC61A1 sponged miR-660-5p to positively regulate CDK6 expression. The inhibitory impacts of circ_SEC61A1 knockdown on the progression of MM cells were mitigated by miR-660-5p inhibition. MiR-660-5p overexpression blocked the malignant phenotypes of MM cells by targeting CDK6.

CONCLUSION

Our study manifested that circ_SEC61A1 could accelerate MM progression at least partially through modulating miR-660-5p/CDK6 axis.

Circular RNAs and their role in renal cell carcinoma: a current perspective

Circular RNAs (circRNAs) are a new class of long non-coding RNAs, that results from a special type of alternative splicing referred to as back-splicing. They are widely distributed in eukaryotic cells and demonstrate tissue-specific expression patterns in humans. CircRNAs actively participate in various important biological activities like gene transcription, pre-mRNA splicing, translation, sponging miRNA and proteins, etc. With such diverse biological functions, circRNAs not only play a crucial role in normal human physiology, as well as in multiple diseases, including cancer. In this review, we summarized our current understanding of circRNAs and their role in renal cell carcinoma (RCC), the most common cancer of kidneys. Studies have shown that the expression level of several circRNAs are considerably varied in RCC samples and RCC cell lines suggesting the potential role of these circRNAs in RCC progression. Several circRNAs promote RCC development and progression mostly via the miRNA/target gene axis making them ideal candidates for novel anti-cancer therapy. Apart from these, there are a few circRNAs that are significantly downregulated in RCC and overexpression of these circRNAs leads to suppression of RCC growth. Differential expression patterns and novel functions of circRNAs in RCC suggest that circRNAs can be utilized as potential biomarkers and therapeutic targets for RCC therapy. However, our current understanding of the role of circRNA in RCC is still in its infancy and much comprehensive research is needed to achieve clinical translation of circRNAs as biomarkers and therapeutic targets in developing effective treatment options for RCC.