Circ-PGAM1 promotes malignant progression of epithelial ovarian cancer through regulation of the miR-542-3p/CDC5L/PEAK1 pathway

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.

Deciphering the impact of circRNA-mediated autophagy on tumor therapeutic resistance: a novel perspective

Cancer therapeutic resistance remains a significant challenge in the pursuit of effective treatment strategies. Circular RNAs (circRNAs), a class of non-coding RNAs, have recently emerged as key regulators of various biological processes, including cancer progression and drug resistance. This review highlights the emerging role of circRNAs-mediated autophagy in cancer therapeutic resistance, a cellular process that plays a dual role in cancer by promoting both cell survival and death. Increasing evidence suggests that circRNAs can modulate autophagy pathways, thereby influencing the response of cancer cells to therapeutic agents. In this context, the intricate interplay between circRNAs, autophagy, and therapeutic resistance is explored. Various mechanisms are discussed through which circRNAs can impact autophagy, including direct interactions with autophagy-related genes, modulation of signaling pathways, and cross-talk with other non-coding RNAs. Furthermore, the review delves into specific examples of how circRNA-mediated autophagy regulation can contribute to resistance against chemotherapy and radiotherapy. Understanding these intricate molecular interactions provides valuable insights into potential strategies for overcoming therapeutic resistance in cancer. Exploiting circRNAs as therapeutic targets or utilizing them as diagnostic and predictive biomarkers opens new avenues for developing personalized treatment approaches. In summary, this review underscores the importance of circRNA-mediated autophagy in cancer therapeutic resistance and proposes future directions for research in this exciting and rapidly evolving field.

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.

Glucose metabolism reprogramming in gynecologic malignant tumors

The incidence and mortality of gynecological tumors are progressively increasing due to factors such as obesity, viral infection, unhealthy habits, as well as social and economic pressures. Consequently, it has emerged as a significant threat to women's health. Numerous studies have revealed the remarkable metabolic activity of tumor cells in glycolysis and its ability to influence malignant biological behavior through specific mechanisms. Therefore, it is crucial for patients and gynecologists to comprehend the role of glycolytic proteins, regulatory molecules, and signaling pathways in tumorigenesis, progression, and treatment. This article aims to review the correlation between abnormal glucose metabolism and gynecologic tumors including cervical cancer (CC), endometrial carcinoma (EC), and ovarian cancer (OC). The findings from this research will provide valuable scientific insights for early screening, timely diagnosis and treatment interventions while also aiding in the prevention of recurrence among individuals with gynecological tumors.

FOXA1 prolongs S phase and promotes cancer progression in non-small cell lung cancer through upregulation of CDC5L and activation of the ERK1/2 and JAK2 pathways

Non-small cell lung cancer (NSCLC) causes high mortality worldwide; however, its molecular pathways have not been fully investigated. The relationship between FOXA1 and CDC5L as well as their roles in NSCLC have not been comprehensively studied. Clinical tissues were collected from 78 NSCLC patients for clinical studies. The BEAS-2B human normal lung epithelial cell line and the A549, Calu-3, H526 and H2170 human NSCLC cell lines were used for in vitro studies. sh-FOXA1 and oe-CDC5L constructs were used to generate knockdown and overexpression models, respectively. The CCK-8 assay was used to analyze cell viability. The cell cycle and apoptosis were evaluated by flow cytometry analysis. The relationship between FOXA1 and CDC5L was demonstrated using dual-luciferase and ChIP assays. Gene levels were examined via immunohistochemistry, qRT-PCR and western blot analysis. FOXA1 levels were increased in NSCLC clinical tissues and cell lines. Depletion of FOXA1 increased the apoptosis rate and increased the proportion of cells in G2/M phase. In addition, we demonstrated that FOXA1 was directly bound to the promoter of CDC5L and that depletion of FOXA1 inhibited CDC5L expression. Overexpression of CDC5L induced ERK1/2 phosphorylation, induced JAK2 phosphorylation, inhibited cell apoptosis, prolonged S phase, and significantly reversed the effects of FOXA1 knockdown on the progression of NSCLC. The present study demonstrated that FOXA1 prolongs S phase and promotes NSCLC progression through upregulation of CDC5L and activation of the ERK1/2 and JAK2 pathways.

Knockdown of LncRNA DICER1-AS1 arrests the cell cycle, inhibits cell proliferation, and induces cell apoptosis by regulating CDC5L nuclear transfer in osteosarcoma

BACKGROUND

DICER1-AS1 is reported to promote the progression and disturb the cell cycle in osteosarcoma; however, its mechanism has rarely been studied.

MATERIALS AND METHODS

DICER1-AS1 expression levels were evaluated by qPCR and fluorescence in situ hybridization (FISH). The total, nuclear, and cytosolic levels of CDC5L were measured by western blotting and immunofluorescence (IF). Cell proliferation, apoptosis, and cell cycle analyses were conducted using the colony formation, CCK-8 assay, terminal transferase-mediated UTP nick end-labeling kit (TUNEL) assay, and flow cytometry. Levels of cell proliferation-, cell cycle-, and cell apoptosis-related proteins were determined by western blotting. RNA immunoprecipitation (RIP) and RNA pull-down assays were conducted to evaluate the relationship between DICER1-AS1 and CDC5L.

RESULTS

LncRNA DICER1-AS1 was highly expressed in samples of osteosarcoma tissue and in osteosarcoma cell lines. DICER1-AS1 knockdown inhibited cell proliferation, promoted cell apoptosis, and disturbed the cell cycle. Moreover, DICER1-AS1 was found to bind with CDC5L, and knockdown of DICER-AS1 inhibited the nuclear transfer of CDC5L. DICER1-AS1 knockdown also reversed the effects of CDC5L overexpression on cell proliferation, apoptosis, and the cell cycle. Moreover, CDC5L inhibition suppressed cell proliferation, promoted cell apoptosis, and disturbed the cell cycle, and those effects were further enhanced by DICER1-AS1 knockdown. Finally, DICER1-AS knockdown inhibited tumor growth and proliferation, and promoted cell apoptosis in vivo.

CONCLUSION

LncRNA DICER1-AS1 knockdown inhibits the nuclear transfer of CDC5L protein, arrests the cell cycle, and induces apoptosis to suppress the development of osteosarcoma. Our results suggest a novel target (DICER1-AS1) for treatment of osteosarcoma.

CircRNA PGAM1 Promotes the Migration and Invasion of Pancreatic Adenocarcinoma Cells by Activating the AKT/mTOR Signaling Pathway

Pancreatic adenocarcinoma (PAAD) is a lethal malignancy of the gastrointestinal tract. Circular RNA, an endogenous noncoding RNA, is considered a new regulatory molecule in tumorigenesis and development. Here, we aimed to investigate the role of circPGAM1 in PAAD. The PAAD cell line HPAC was transfected with OE-circPGAM1 to overexpress circPGAM1 and treated with AZD5363 to inhibit the AKT/mTOR pathway. Simultaneously, another PAAD cell line BxPC-3 was transfected with sh-circPGAM1 to silence circPGAM1. The GEPIA database was used to determine the expression of circPGAM1 in PAAD and its association with overall and disease-free survival. CircPGAM1 expression levels were determined in cell lines using reverse transcription-quantitative PCR. The cell counting kit-8, wound healing, and transwell assays were performed to determine cell migration and invasion. The protein expression levels of phosphorylated AKT and mTOR were determined using western blotting. CircPGAM1 was overexpressed in PAAD and related to poor prognosis. Silencing circPGAM1 inhibited migration and invasion of BxPC-3 cells, and overexpression of circPGAM1 showed the opposite effects. Overall, circPGAM1 promoted the migration and invasion of PAAD cells through the AKT/mTOR axis.

The mechanisms, functions and clinical applications of miR-542-3p in human cancers

MicroRNAs, as a major type of noncoding RNAs, have crucial roles in various functions during development. Available data have shown that miR-542-3p decreased in various types of cancers. MiR-542-3p is engaged in various cancer-related behaviors like glycolysis, metastasis, epithelial-to-mesenchymal transition (EMT), cell cycle, apoptosis, and proliferation via targeting at least 18 genes and some important signaling pathways like Wnt/β-catenin, Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and Janus kinase 2 (JAK2) signaling, and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling. Current studies have proposed that the level of miR-542-3p could be modulated by several upstream regulators like transcription factors, long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). In addition, the level of miR-542-3p or its related lncRNAs/circRNAs are correlated with poor prognosis and clinicopathological features of cancer-affected patients. Here, we have discussed the biogenesis, function, and regulation of miR-542-3p as well as its aberrant expression in various types of neoplastic cells. Moreover, we have discussed the prognostic value of miR-542-3p in cancer. Finally, we have added the underlying molecular mechanism of miR-542-3p in cancer pathogenesis.

Expression of circ-PHC3 enhances ovarian cancer progression via regulation of the miR-497-5p/SOX9 pathway

BACKGROUND

Accumulating studies have reported indispensable functions of circular RNAs (circRNA) in tumor progression through regulation of gene expression. However, circRNA expression profiles and functions in human ovarian carcinoma (OC) are yet to be fully established.

METHODS

In this research, deep sequencing of circRNAs from OC samples and paired adjacent normal tissues was performed to establish expression profiles and circ-PHC3 levels between the groups further compared using RT-qPCR. The effects of ectopic overexpression of miR-497-5p and SOX9 and siRNA-mediated knockdown of circ-PHC3 and an miR-497-5p inhibitor were explored to clarify the regulatory mechanisms underlying circ-PHC3 activity in OC proliferation and metastasis. Information from public databases and the luciferase reporter assay were further utilized to examine the potential correlations among circ-PHC3, miR-497-5p and SOX9.

RESULTS

Our results showed significant upregulation of circ-PHC3 in both OC cell lines and tissues. In the luciferase reporter assay, downregulation of circ-PHC3 led to suppression of metastasis and proliferation, potentially through targeted effects on the miR-497-5p/SOX9 axis in OC. SOX9 overexpression or miR-497-5p suppression rescued OC cell proliferation and invasion following silencing of circ-PHC3. Moreover, SOX9 inhibition induced restoration of OC cell invasion and proliferation under conditions of overexpression of miR-497-5p. Thus, circ-PHC3 appears to exert effects on cancer stem cell differentiation through regulation of the miR-497-5p/SOX9 axis.

CONCLUSION

Taken together, our findings suggest that circ-PHC3 enhances OC progression through functioning as an miR-497-5p sponge to promote SOX9 expression, supporting its potential as a promising candidate target for OC therapy.

Circ_0000471 suppresses the progression of ovarian cancer through mediating mir-135b-5p/dusp5 axis

BACKGROUND

Ovarian cancer (OC) is a common gynecologic cancer with high incidence and mortality. We attempted to investigate the role of circular RNA_0000471 (circ_0000471) in OC progression and its associated mechanism.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot assay were conducted to measure RNA and protein expression, respectively. Cell proliferation was analyzed by Cell Counting Kit-8 (CCK8) assay, colony formation assay, and 5-Ethynyl-2'-deoxyuridine (EdU) assay. Cell apoptosis was assessed by flow cytometry. Cell migration and invasion were analyzed by wound healing assay and transwell assay, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to verify the target relationships. Xenograft tumor model was established to assess the role of circ_0000471 on tumor growth in vivo.

RESULTS

Circ_0000471 expression was down-regulated in OC tissues and cell lines. Circ_0000471 overexpression blocked the proliferation, migration, and invasion and triggered the apoptosis of OC cells. Circ_0000471 served as a molecular sponge for microRNA-135b-5p (miR-135b-5p), and circ_0000471 overexpression-mediated anti-tumor influences in OC cells were largely reversed by the overexpression of miR-135b-5p. Dual specificity phosphatase 5 (DUSP5) was a target of miR-135b-5p, and miR-135b-5p silencing-induced anti-tumor effects were largely counteracted by the interference of DUSP5. Circ_0000471 increased DUSP5 expression by sponging miR-135b-5p in OC cells. Circ_0000471 overexpression restrained the growth of xenograft tumors in vivo.

CONCLUSION

Overexpression of circ_0000471 inhibited OC development by targeting miR-135b-5p/DUSP5 axis, indicating that circ_0000471 may be a new potential target for OC treatment.

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-PGAM1 Enhances Matrine Resistance of Non-Small Cell Lung Cancer via the miR-326/CXCR5 Axis

Background: Circular RNAs (circ-RNAs) have been demonstrated to influence initiation, drug resistance, and metastasis of tumors. However, the effects of circular-phosphoglycerate mutase 1 (circ-PGAM1) on matrine resistance in nonsmall cell lung cancer (NSCLC) remain unknown. Materials and Methods: The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to determine gene expression. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and cell colony formation assays were used to evaluate NSCLC apoptosis and cell proliferation after indicated treatments, respectively. Results: circ-PGAM1 was upregulated in human NSCLC cell lines (H1299 and A549) compared with the human normal lung epithelial (BEAS-2B) cells. circ-PGAM1 overexpression reversed the matrine treatment-induced inhibition on proliferation of NSCLC cells (A549 and H1299) and rescued the matrine treatment-stimulated apoptosis of these cells. miR-326 was demonstrated to interact with circ-PGAM1. circ-PGAM1 knockdown enhanced the antitumor effect of matrine on NSCLC cell proliferation and apoptosis, which was reversed by miR-326 inhibition. The authors also identified CXCR5 as a key downstream target of miR-326 in A549 cells. Conclusions: circ-PGAM1 enhances matrine resistance of NSCLC cells through the miR-326/CXCR5 axis. The authors' findings provide new insights into NSCLC-targeted therapy.

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.

Studies on the molecular level changes and potential resistance mechanism of Coreius guichenoti under temperature stimulation

In this study, we used transcriptome and proteome technology to analyze molecular level changes in tissues of Coreius guichenoti cultured at high temperature (HT) and low temperature (LT). We also screened for specific anti-stress genes and proteins and evaluated the relationships between them. We identified 201,803 unigenes and 10,623 proteins. Compared with the normal temperature (NT), 408 genes and 1,204 proteins were up- or down-regulated in brain tissues, respectively, at HT, and the numbers were 8 and 149 at LT. In gill tissues, the numbers were 101 and 1,745 at HT and 27 and 511 at LT. In gill tissues at both temperatures, the degree of down-regulation (average, HT 204.67-fold, LT 443.13-fold) was much greater than that of up-regulation (average, HT 28.69-fold, LT 17.68-fold). The protein expression in brain (average, up 52.67-fold, down 13.54-fold) and gill (average, up 73.02-fold, down 12.92-fold) tissues increased more at HT than at LT. The protein expression in brain (up 3.77-fold, down 4.79-fold) tissues decreased more at LT than at HT, whereas the protein expression in gill (up 8.64-fold, down 4.35-fold) tissues was up-regulated more at LT than at HT. At HT, brain tissues were mainly enriched in pathways related to metabolism and DNA repair; at LT, they were mainly enriched in cancer-related pathways. At both temperatures, gill tissues were mainly enriched in pathways related to cell proliferation, apoptosis, immunity, and inflammation. Additionally, Kyoto Encyclopedia of Genes and Genomes pathway analysis showed more differentially expressed proteins in gill tissues than in brain tissues at HT and LT, and temperature stimulation led to the strengthening of metabolic pathways in both tissues. Of the 96 genes we identified as potentially being highly related to temperature stress (59 from transcriptome and 38 from proteome data), we detected heat shock protein 70 in both the transcriptome and proteome. Our results improved our understanding of the differential relationship between gene expression and protein expression in C. guichenoti. Identifying important temperature stress genes will help lay a foundation for cultivating C. guichenoti, and even other fish species, that are resistant to HT or LT.

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.

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.

DNA and RNA Binding Proteins: From Motifs to Roles in Cancer

DNA and RNA binding proteins (DRBPs) are a broad class of molecules that regulate numerous cellular processes across all living organisms, creating intricate dynamic multilevel networks to control nucleotide metabolism and gene expression. These interactions are highly regulated, and dysregulation contributes to the development of a variety of diseases, including cancer. An increasing number of proteins with DNA and/or RNA binding activities have been identified in recent years, and it is important to understand how their activities are related to the molecular mechanisms of cancer. In addition, many of these proteins have overlapping functions, and it is therefore essential to analyze not only the loss of function of individual factors, but also to group abnormalities into specific types of activities in regard to particular cancer types. In this review, we summarize the classes of DNA-binding, RNA-binding, and DRBPs, drawing particular attention to the similarities and differences between these protein classes. We also perform a cross-search analysis of relevant protein databases, together with our own pipeline, to identify DRBPs involved in cancer. We discuss the most common DRBPs and how they are related to specific cancers, reviewing their biochemical, molecular biological, and cellular properties to highlight their functions and potential as targets for 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.

Pan-Cancer Transcriptome and Immune Infiltration Analyses Reveal the Oncogenic Role of Far Upstream Element-Binding Protein 1 (FUBP1)

Despite increasing evidence to support the relationship between FUBP1 and tumorigenesis in some types of cancers, there have been no analyses from a pan-cancer perspective. Here, we are the first to investigate the putative oncogenic role of FUBP1 in 33 cancer types based on The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Dysregulated FUBP1 expression was observed in most cancer types, and high FUBP1 expression suggests poor prognosis in cancers such as ACC, KICH, LIHC, LUAD, LUSC, SARC, CESC, and SKCM. Missense mutation is the most common type of FUBP1 mutation, and R430 in KH_4 is a predominant mutation site. Enhanced phosphorylation of FUBP1 at the S120 site has been observed in clear cell RCC, lung adenocarcinoma, and pediatric brain cancer specimens from African-American and Asian individuals. The expression of FUBP1 was found to be negatively correlated with the infiltration of CD8+ T lymphocytes in GBM, HNSC-HPV- and UCEC but positively correlated with that of tumor-associated fibroblasts in CESC, ESCA, HNSC, LIHC, LUAD, PAAD, and THYM. Furthermore, RNA splicing and spliceosome signaling were predominantly enriched in both GO and KEGG analyses of the functional mechanism of FUBP1. Briefly, this pan-cancer analysis comprehensively revealed the multifaceted characteristics and oncogenic role of FUBP1 in different human cancers.

3D-QSAR, Molecular Docking, and MD Simulations of Anthraquinone Derivatives as PGAM1 Inhibitors

PGAM1 is overexpressed in a wide range of cancers, thereby promoting cancer cell proliferation and tumor growth, so it is gradually becoming an attractive target. Recently, a series of inhibitors with various structures targeting PGAM1 have been reported, particularly anthraquinone derivatives. In present study, the structure–activity relationships and binding mode of a series of anthraquinone derivatives were probed using three-dimensional quantitative structure–activity relationships (3D-QSAR), molecular docking, and molecular dynamics (MD) simulations. Comparative molecular field analysis (CoMFA, r² = 0.97, q² = 0.81) and comparative molecular similarity indices analysis (CoMSIA, r² = 0.96, q² = 0.82) techniques were performed to produce 3D-QSAR models, which demonstrated satisfactory results, especially for the good predictive abilities. In addition, molecular dynamics (MD) simulations technology was employed to understand the key residues and the dominated interaction between PGAM1 and inhibitors. The decomposition of binding free energy indicated that the residues of F22, K100, V112, W115, and R116 play a vital role during the ligand binding process. The hydrogen bond analysis showed that R90, W115, and R116 form stable hydrogen bonds with PGAM1 inhibitors. Based on the above results, 7 anthraquinone compounds were designed and exhibited the expected predictive activity. The study explored the structure–activity relationships of anthraquinone compounds through 3D-QSAR and molecular dynamics simulations and provided theoretical guidance for the rational design of new anthraquinone derivatives as PGAM1 inhibitors.

CircSETDB1 knockdown inhibits the malignant progression of serous ovarian cancer through miR-129-3p-dependent regulation of MAP3K3

Background

Circular RNA (circRNA) is recently found to participate in the regulation of tumor progression, including ovarian cancer. However, the application of circRNA SET domain bifurcated histone lysine methyltransferase 1 (circSETDB1) as a therapeutic target in serous ovarian cancer (SOC) remains to be elucidated. Herein, circSETDB1 role in SOC malignant progression and underlying mechanism are revealed.

Methods

The expression of circSETDB1, microRNA-129-3p (miR-129-3p) and mitogen-activated protein kinase kinase kinase 3 (MAP3K3) messenger RNA (mRNA) was detected by quantitative real-time polymerase chain reaction. Protein abundance was determined by western blot analysis. Cell proliferation, apoptosis, invasion and migration were demonstrated by cell counting kit-8 and 5-Ethynyl-29-deoxyuridine assays, flow cytometry analysis, transwell invasion assay and wound-healing assay, respectively. The interaction between miR-129-3p and circSETDB1 or MAP3K3 was predicted by online database, and identified by mechanism assays. The effect of circSETDB1 knockdown on tumor formation in vivo was unveiled by mouse model experiment.

Results

CircSETDB1 and MAP3K3 expression were apparently upregulated, whereas miR-129-3p expression was downregulated in SOC tissues and cells in comparison with normal fallopian tube tissues or normal ovarian epithelial cells. CircSETDB1 knockdown inhibited cell proliferation, invasion and migration, but induced cell apoptosis in SOC cells. Additionally, miR-129-3p inhibitor impaired circSETDB1 silencing-mediated SOC malignant progression. MiR-129-3p repressed SOC cell processes via binding to MAP3K3. Furthermore, circSETDB1 knockdown suppressed tumor growth in vivo.

Conclusion

CircSETDB1 silencing repressed SOC malignant progression through miR-129-3p/MAP3K3 pathway. This study supports circSETDB1 as a new therapeutic target for SOC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00875-0.

1. CircSETDB1 expression was increased in SOC tissues and cells.

2. CircSETDB1 silencing repressed the malignancy of SOC cells.

3. CircSETDB1 mediated SOC malignant progression by interacting with miR-129-3p.

4. MAP3K3 served as a target gene of miR-129-3p.

5. CircSETDB1 knockdown inhibited tumor formation in vivo.

Caseinolytic protease P (CLPP) activated by ONC201 inhibits proliferation and promotes apoptosis in human epithelial ovarian cancer cells by inducing mitochondrial dysfunction

Background

Caseinolytic protease P (CLPP) is a mitochondrial specific protein which has been reported to be related to tumor cell apoptosis. This study aims to explore the roles of CLPP in human epithelial ovarian cancer (EOC).

Methods

We determined CLPP expression in paracancerous tissues and cancer tissues obtained from 20 EOC patients, and also in 4 EOC cell lines, and one normal ovarian cell line (IOSE-80). We knocked CLPP expression down in SK-OV-3 and A2780 cells and overexpressed it in SW626 and OVcar3 cells. The effect of CLPP expression on cell proliferation, mitochondrial membrane potential, and apoptosis was then assessed by flow cytometry assay. Furthermore, the effect of ONC201 (agonist of CLPP) on the EOC cell lines was also investigated.

Results

The CLPP expression was markedly down-regulated in EOC cancer tissues, and the Kaplan-Meier Plotter database revealed its low expression was linked to poor prognosis in EOC patients. Low expression of CLPP up-regulated the expression of NADH: ubiquinone oxidoreductase subunit A12 (NDUFA12), succinate dehydrogenase complex flavoprotein subunit A (SDHA), and succinate dehydrogenase complex iron sulfur subunit B (SDHB), which are key members of the mitochondrial respiratory chain, and these up-regulated proteins further led to the increase of mitochondrial membrane potential, cell proliferation promotion and neoplasm metastasis. Conversely, while overexpression of CLPP led to the opposite results, including inducing the decrease of mitochondrial membrane potential and apoptosis. In addition, stimulation with ONC201 enhanced the function of CLPP in SW626 and OVcar3 cells, and silencing of CLPP could neutralize the effect of ONC201.

Conclusions

Our findings suggest that CLPP mediated mitochondrial dysfunction inhibits the proliferation and migration of EOC cells.

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_002178 as a ceRNA promotes the development of colorectal cancer by regulating miR-542-3p/CREB1

OBJECTIVE

Colorectal cancer (CRC) is a malignant tumor commonly found in the digestive tract. This study aimed to explore the effect of circRNA_002178 as a competing endogenous RNA in the development of CRC by regulating the miR-542-3p/cAMP response element binding protein 1 (CREB1) axis and its molecular mechanism.

METHODS

The relative expressions of circ_002178, miR-542-3p, and CREB1 in patients' cell lines and CRC tissues were measured using Western blot and qRT-PCR. The localization and expression of circ_002178 were determined using fluorescence in situ hybridization and nucleocytoplasmic separation tests. The targeting relationships among circ_002178, miR-542-3p, and CREB1 were validated using RNA immunoprecipitation and dual luciferase reporter assays. The cells' proliferation, invasion, and colony forming ability were tested using CCK8, Transwell, and Clone formation assays, respectively. The cellular glucose consumption, lactification, and adenosine triphosphate (ATP) production were measured using glucose uptake colorimetric assay kits, lactate colorimetric assay kits and ATP assay kits, respectively.

RESULTS

The circ_002178 and CREB1 expressions were up-regulated in the CRC cells and tissues, and the miR-542-3p expression was down-regulated (all P<0.05). The circ_002178 knockdown inhibited the proliferation, invasion, colony formation, and glycolysis of the CRC cells in vitro, but the overexpression of circ_002178 induced the opposite result (both P<0.05). Our molecular mechanism study revealed that circ_002178, as the molecular sponge of miR-542-3p, promotes CREB1 expression. The downregulation of miR-542-3p or the overexpression of CREB1 is able to partly weaken the inhibition of CRC cells through the circ_002178 knockdown.

CONCLUSION

circ_002178 promotes the invasion, proliferation, colony formation, and glycolysis of CRC cells by regulating the miR-542-3p/CREB1 axis, thus driving the development of CRC.

CDC5L promotes early chondrocyte differentiation and proliferation by modulating pre-mRNA splicing of SOX9, COL2A1, and WEE1

Ossification of the posterior longitudinal ligament (OPLL) of the spine is a common pathological condition that causes intractable myelopathy and radiculopathy, mainly the result of an endochondral ossification-like process. Our previous genome-wide association study identified six susceptibility loci for OPLL, including the cell division cycle 5-like (CDC5L) gene region. Here, we found CDC5L to be expressed in type II collagen-producing chondrocyte-like fibroblasts in human OPLL specimens, as well as in differentiating ATDC5 chondrocytes. Cdc5l siRNA transfection in murine chondrocytes decreased the expression of the early chondrogenic genes Sox9 and Col2a1, diminished the cartilage matrix production, and enhanced the expression of parathyroid-hormone-related protein (a resting chondrocyte marker). We also showed that Cdc5l shRNA suppressed the growth of cultured murine embryonal metatarsal cartilage rudiments and that Cdc5l knockdown suppressed the growth of ATDC5 cells. Fluorescence-activated cell sorting analysis revealed that the G2/M cell cycle transition was blocked; our data showed that Cdc5l siRNA transfection enhanced expression of Wee1, an inhibitor of the G2/M transition. Cdc5l siRNA also decreased the pre-mRNA splicing efficiency of Sox9 and Col2a1 genes in both ATDC5 cells and primary chondrocytes; conversely, loss of Cdc5l resulted in enhanced splicing of Wee1 pre-mRNA. Finally, an RNA-binding protein immunoprecipitation assay revealed that Cdc5l bound directly to these target gene transcripts. Overall, we conclude that Cdc5l promotes both early chondrogenesis and cartilage growth and may play a role in the etiology of OPLL, at least in part by fine-tuning the pre-mRNA splicing of chondrogenic genes and Wee1, thus initiating the endochondral ossification process.

CircASXL1 Knockdown Restrains Hypoxia-Induced DDP Resistance and NSCLC Progression by Sponging miR-206

Background

Non-small cell lung carcinoma (NSCLC) is a primary prevalent type of cancer in people worldwide. Cisplatin (DDP) has been widely used to treat NSCLC; however, its curative effect was restrained under hypoxia. In this study, the effects of hypoxia treatment on DDP resistance and NSCLC progression and underneath mechanism were revealed.

Methods

The expression of circular RNA ASXL1 (circASXL1) and microRNA-206 (miR-206) in NSCLC tissues, cells and hypoxia-mediated NSCLC cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of proliferation, metastasis and apoptosis-related proteins, drug resistance-related protein and hypoxia-inducible factor-1alpha (HIF-1α) protein was detected by Western blot. The effects of circASXL1 knockdown on hypoxia-induced DDP resistance and NSCLC progression were revealed by cell counting kit-8 proliferation (CCK-8), cell colony formation, transwell and flow apoptosis assays. RNA immunoprecipitation (RIP) assay was performed to determine whether circASXL1 could form silence-inducing complexes with miRNA. The associated relationship between circASXL1 and miR-206 was predicted by circBank online database, and identified by RNA pull-down and dual-luciferase reporter assays. The effects between circASXL1 knockdown and miR-206 downregulation on tumor growth in vivo were investigated by in vivo tumor formation assay.

Results

CircASXL1 expression was dramatically upregulated, whereas miR-206 was significantly down-regulated in NSCLC tissues, cells and hypoxia-mediated NSCLC cells as compared to control groups. CircASXL1 knockdown reversed hypoxia-mediated promotion effects on DDP resistance, cell proliferation, migration, and invasion, and inhibition impact on cell apoptosis, whereas these effects were restored by miR-206 inhibitor. Additionally, circASXL1 was found to form silence-inducing complexes with miRNA and act as a sponge of miR-206. CircASXL1 silencing downregulated HIF-1α expression by controlling miR-206 expression. Furthermore, circASXL1 silencing repressed tumor growth in vivo by sponging miR-206.

Conclusion

CircASXL1 knockdown inhibited DDP resistance, cell proliferation, migration and invasion, whereas induced cell apoptosis under hypoxia by associating with miR-206 in NSCLC. This study provides a new sight in treating NSCLC with DDP under hypoxia.

Circular RNAs: Emerging Regulators of the Major Signaling Pathways Involved in Cancer Progression

Signal transduction is an essential process that regulates and coordinates fundamental cellular processes, such as development, immunity, energy metabolism, and apoptosis. Through signaling, cells are capable of perceiving their environment and adjusting to changes, and most signaling cascades ultimately lead to alterations in gene expression. Circular RNAs (circRNAs) constitute an emerging type of endogenous transcripts with regulatory roles and unique properties. They are stable and expressed in a tissue-, cell-, and developmental stage-specific manner, while they are involved in the pathogenesis of several diseases, including cancer. Aberrantly expressed circRNAs can mediate cancer progression through regulation of the activity of major signaling cascades, such as the VEGF, WNT/β-catenin, MAPK, PI3K/AKT, and Notch signaling pathways, as well as by interfering with signaling crosstalk. Deregulated signaling can then function to induce angiogenesis, promote invasion, migration, and metastasis, and, generally, modulate the hallmarks of cancer. In this review article, we summarize the most recently described and intriguing cases of circRNA-mediated signaling regulation that are involved in cancer progression, and discuss the biomarker potential of circRNAs, as well as future therapeutic applications.

The Short Non-Coding RNA 1251-5p Regulates Stemness Transformation and Inhibits Aggression of Lung Malignant Tumor Cells

Our study investigated the effect of short-chain non-coding RNA 1251-5p on the movement and permeation of pulmonary carcinoma stem cells. LCSC in pulmonary carcinoma cells was determined and isolated by flow cytometry. After cell transfection, qRT-PCR and immunoblotting measured the level of MiR-1251-5p, MiR-650, SLC34A2, Oct4 and CD133. Spherometric mensuration was used to assess sphericity formation situation. Transwell analyzed the movement and permeation of cells, detected the relationship among MiR-1251-5p, MiR-650 and SLC34A2 by fluorescein enzyme report gene, and the results were verified by RIP and RNA pull-down detection methods. Knock-down of MiR-1251-5p can enhance the stem cell-like characteristics of LCC, promote cell migration and invasion, upregulate the level of MiR-650, Oct4 and CD133, and downregulate the level of SLC34A2, while MiR-650 inhibitor can restore the effect of the knock-down on the hyperplasia, movement and permeation of LCSC cells. Si-Mir-1251-5p promoted stem cell like characteristics of pulmonary carcinoma cell lineage H1299 and downregulated the expression of Oct4 and CD133, and upregulated the level of SLC34A2. SLC34A2 expression was negatively correlated with MiR-650 expression and positively correlated with MiR-1251-5p in LCSC cellular tissues. MiR-1251-5p regulates LCC stem cell-like state, and inhibits the movement and permeation of pulmonary carcinoma cells via MiR-650/SLC34A2 axis.

Schisandrin B Inhibits Cell Viability and Migration, and Induces Cell Apoptosis by circ_0009112/miR-708-5p Axis Through PI3K/AKT Pathway in Osteosarcoma

Osteosarcoma is a primary tumor of bone and its incidence is increasing. Schisandrin B (Sch B), a generally used lignan in Chinese medicine, has been found to repress cancer progression. This study aims to reveal the effects and regulatory mechanism of Sch B in the viability, apoptosis and migration of osteosarcoma cells. In this study, we found circ_0009112 expression was higher and miR-708-5p expression was lower in SaOS2 and U2OS cells than in hFOB1.19 cells. Circ_0009112 expression was downregulated, but miR-708-5p was upregulated by Sch B treatment in a dose-dependent manner in SaOS2 and U2OS cells. Sch B exposure inhibited osteosarcoma development in vitro and in vivo; however, these effects were restored by circ_0009112. Furthermore, circ_0009112 acted as a sponge of miR-708-5p. Circ_0009112 regulated PI3K/AKT pathway after Sch B treatment by associating with miR-708-5p. Sch B exposure inhibited cell viability and migration, whereas promoted cell apoptosis by regulating circ_0009112/miR-708-5p axis through PI3K/AKT pathway in osteosarcoma cells. This study provided a theoretical basis for further studying osteosarcoma therapy with Sch B.

circPGAM1 enhances autophagy signaling during laryngocarcinoma drug resistance by regulating miR-376a

circRNAs have been shown to be involved in cancer progression. It is unclear whether circPGAM1 exerts its effect on laryngocarcinoma drug resistance. In this study, we employed colony formation and MTT assay to determine colony number and cell viability under cisplatin treatment. TUNEL experiment was used to evaluate apoptosis of laryngocarcinoma cells in the presence of cisplatin. Xenograft tumor experiment was performed to assess in vivo tumor growth of SNU46 cells. We found that circPGAM1 enhanced colony formation and viability of SNU46 and M4E cells. In contrast, circPGAM1 caused attenuated cell apoptosis. Furthermore, we also confirmed that circPGAM1 played a key role in tumor growth in animal model and clinical patients. miR-376a was identified and proved to act as key effector for circPGAM1-mediated drug resistance. Finally, autophagy-related gene ATG2A was shown to rescue miR-376a-modulated drug resistance of laryngocarcinoma cells. Herein, we illuminate the role of circPGAM1 in laryngocarcinoma drug resistance, thereby facilitating development of targeted therapy for treating laryngocarcinoma.

Long Noncoding RNA LINC00963 Promotes CDC5L-Mediated Malignant Progression in Gastric Cancer

Background

Gastric cancer (GC) is a common cancer with high incidence and mortality worldwide. In recent years, accumulating evidence has shown that long noncoding RNAs (lncRNAs) exert critical roles in the development and progression of cancer by acting as a tumor initiator or suppressor. LINC00963 is a newly reported lncRNA related to cancer, and its role in GC remains unclear.

Materials and Methods

The expression levels of LINC00963, miR-612, and cell division cycle 5-like protein (CDC5L) were measured using quantitative real-time PCR or Western blot. The biological functions of LINC00963, miR-612, and CDC5L in GC cells were analyzed by transwell and proliferation experiments. The expression of CDC5L in patients with GC was evaluated using the Oncomine database. Bone marrow-derived dendritic cells (DCs) were derived from C57BL/6 mice.

Results

LINC00963 expression was higher in GC tissues than in adjacent normal tissues. Similar results were found in GC cell lines and normal human gastric epithelial cells. Upregulation of LINC00963 was related to the poor prognosis of patients with GC. Knockdown of LINC00963 inhibited the proliferation, invasion, and metastasis but promoted the apoptosis of GC cells. Furthermore, silencing of LINC00963 in GC cells significantly suppressed the tumor growth of GC. Bioinformatics analysis indicated that LINC00963 could target miR-612 by functioning as a competing endogenous RNA. The expression of miR-612 decreased in GC tissues and cell lines. Meanwhile, LINC00963 expression was negatively associated with miR-612. CDC5L was a direct target of miR-612. miR-612 suppressed the expression of CDC5L in GC tissues and cells. Moreover, LINC00963 inhibited the differentiation and maturation of DCs by regulating miR-612 expression in DCs.

Conclusion

LINC00963 promoted the progression of GC by competitively binding to miR-612 to regulate the expression of CDC5L and mediated DC-related anti-tumor immune response. Thus, targeting LINC00963 may be a promising therapeutic strategy for GC.

The novel circ_0028171/miR-218-5p/IKBKB axis promotes osteosarcoma cancer progression

Background

Recently, it has been demonstrated that circular RNA (circRNA) contributes to the production and progression in human cancer. However, the specific function and underlying mechanism of circ_0028171 in osteosarcoma (OS) still remain largely unclear and require to be investigated.

Methods

In our study, we confirmed differentially expressed circRNAs by microarray analysis in normal bone cells vs. OS cell lines. The expression of circ-0028171 in OS was measured by qRT-PCR. Nuclear-cytoplasmic fractionation was employed to identify the localization of circ-0028171, and RNase R and actinomycin D treatment were used to prove its circular characteristic. In vitro experiments, such as CCK-8 method, cell count, cell colony formation, transwell migration and invasion assays, and in vivo tumor models were adopted to evaluate the effect of circ_0028171. Further, luciferase reporter, RIP and RNA pull-down assays were conducted to confirm the binding sites of circ_0028171 with miR-218-5p.

Results

We found that circ_0028171 displayed a remarkably higher expression in both OS tissues and cell lines. Circ_0028171 mainly located in the cytoplasm as a stable cyclic transcript. Knockdown of circ_0028171 suppressed OS tumor growth in vitro and in vivo, while up-regulated circ_0028171 remarkably enhanced cell proliferation, migration and invasion abilities in OS. Several mechanistic experiments revealed that circ_0028171 served as a sponge of miR-218-5p to increase IKBKB expression.

Conclusions

our research reveals that circ_0028171 might promote the malignant behavior of OS tissues through miR-218-5p/IKBKB axis, which could be a potential novel marker for early diagnosis of OS.

Circ-PGAM1 promotes malignant progression of epithelial ovarian cancer through regulation of the miR-542-3p/CDC5L/PEAK1 pathway

Background

Epithelial ovarian cancer (EOC) is the most common ovarian malignant cancer. Circular RNA is a type of endogenous noncoding RNA and is considered as a novel regulatory molecule in the development and progression of tumors. This study investigated the expression and functions of a circular RNA, circular‐phosphoglycerate mutase 1 (circ‐PGAM1), in EOC tissues and cells.

Methods

The expression of circ‐PGAM1 and miR‐542‐3p in EOC was analyzed using quantitative RT‐PCR. Immunohistochemistry and western blot were performed to confirm the localization and expression of cell division cycle 5‐like (CDC5L) and pseudopodium enriched atypical kinase 1 (PEAK1) in EOC tissues. Cell lines (CAOV3 and OVCAR3) overexpressing or silencingcirc‐PGAM1 and miR‐542‐3p were established to explore the functions of circ‐PGAM1 and miR‐542‐3p in ovarian cancer cells. Furthermore, dual‐luciferase reporter assay was performed to study the interactions between circ‐PGAM1 and miR‐542‐3p and between miR‐542‐3p and CDC5L. CCK‐8, transwell, and flow cytometry were used to study the effect of circ‐PGAM1 and miR‐542‐3p on cell biological behaviors including proliferation, migration, invasion, and apoptosis. The interaction between CDC5L and the PEAK1 gene promoter was confirmed using chromatin immunoprecipitation (ChIP).

Results

Circ‐PGAM1 was upregulated in EOC tissues, whereas linear PGAM1 was not deregulated in EOC tissues. Silencing of circ‐PAGM1 inhibited proliferation, migration, and invasion of ovarian cancer cells and promoted cell apoptosis. MiR‐542‐3p was downregulated in EOC tissues, and miR‐542‐3p overexpression inhibited malignant progression of ovarian cancer cells. Circ‐PGAM1 directly interacted with miR‐542‐3p, with mutual negative feedback between them. CDC5L was a direct target of miR‐542‐3p and played an oncogenic role in ovarian cancer cells. Furthermore, the CDC5L protein binds directly to the PEAK1 promoter to promote its transcription. PEAK1 overexpression activated ERK1/2 and JAK2 signaling pathways and promoted malignant biological behaviors of ovarian cancer cells. Circ‐PAGM1 silencing combined with miR‐542‐3p overexpression played the greatest anticancer role in vivo.

Conclusion

The circ‐PGAM1/miR‐542‐3p/CDC5L/PEAK1 pathway played an important role in the progression of ovarian cancer and might be a novel therapeutic target for ovarian cancer.