Circular RNA expression profiles reveal that hsa_circ_0018289 is up-regulated in cervical cancer and promotes the tumorigenesis

A comprehensive review of the PTEN/PI3K/Akt axis in multiple myeloma: From molecular interactions to potential therapeutic targets

Phosphatase and tensin homolog (PTEN), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) signaling pathways contribute to the development of several cancers, including multiple myeloma (MM). PTEN is a tumor suppressor that influences the PI3K/Akt/mTOR pathway, which in turn impacts vital cellular processes like growth, survival, and treatment resistance. The current study aims to present the role of PTEN and PI3K/Akt/mTOR signaling in the development of MM and its response to treatment. In addition, the molecular interactions in MM that underpin the PI3K/Akt/mTOR pathway and address potential implications for the development of successful treatment plans are also discussed in detail. We investigate their relationship to both upstream and downstream regulators, highlighting new developments in combined therapies that target the PTEN/PI3K/Akt axis to overcome drug resistance, including the use of PI3K and mitogen-activated protein kinase (MAPK) inhibitors. We also emphasize that PTEN/PI3K/Akt pathway elements may be used in MM diagnosis, prognosis, and therapeutic targets.

circ_0006789 promotes cervical cancer development via the miR-615-5p/HSF1 axis

OBJECTIVE

Circular RNAs (circRNAs) are involved in the development of human cancers, including cervical cancer (CC). However, the role and mechanism of circ_0006789 (circSLC25A43) in CC are unclear. The purpose of this study was to investigate the functional role of circ_0006789 in CC.

METHODS

The expression of circ_0006789 in CC tissues and cell lines was examined by RT-qPCR. The characterization of circ_0006789 in CC cells was verified by subcellular localisation, actinomycin D assay, and RNase R assay. After circ_0006789 was knocked down in CC cell lines, the proliferation, apoptosis, migration and invasion of CC cells were assessed by CCK-8 method, flow cytometry, and Transwell assay. RIP assay, FISH assay, dual luciferase reporter gene assay and Western blot were used to investigate the regulatory mechanism between circ_0006789, miR-615-5p and heat shock factor 1 (HSF1).

RESULTS

circ_0006789 was upregulated in CC tissues and cell lines. CC cells were inhibited in their proliferation, migration, and invasion, as well as promoted to apoptosis when circ_0006789 was knocked down. It was found that circ_0006789 targeted miR-615-5p, and miR-615-5p expression was inversely correlated with circ_0006789 expression. Furthermore, HSF1 was a target gene of miR-615-5p. Furthermore, the suppressive effects on HeLa cells mediated by circ_0006789 knockdown were counter-balanced when miR-615-5p was knocked down and HSF1 was overexpressed. Mechanistically, circ_0006789 was found to promote CC development by reducing miR-615-5p and increasing HSF1 expressions.

CONCLUSION

circ_0006789 accelerates CC development via the miR-615-5p/HSF1 axis.

Circular RNA in cervical cancer: Fundamental mechanism and clinical potential

CC (CC) remains a significant global health concern, imposing a substantial health burden on women worldwide due to its high incidence and mortality rates. To address this issue, there is a need for ongoing research to uncover the underlying molecular mechanisms of CC and to discover novel diagnostic and therapeutic strategies. Recent progress in non-coding RNAs (ncRNAs) has opened new avenues for investigation, and circular RNAs (circRNAs) have emerged as molecules with diverse roles in various cellular processes. These circRNAs are distinct in structure, forming a closed loop, setting them apart from their linear counterparts. They are intricately involved in regulating different aspects of cellular functions, particularly in cell growth and development. Remarkably, circRNAs can have varying functions, either promoting or inhibiting oncogenic processes, depending on the specific cellular context. Recent studies have identified abnormal circRNAs expression patterns associated with CC, indicating their significant involvement in disease development. The differing circRNAs profiles linked to CC present promising opportunities for early detection, precise prognosis evaluation, and personalized treatment strategies. In this comprehensive review, we embark on a detailed exploration of CC-related circRNAs, elucidating their distinct roles and providing insights into the intricate molecular mechanisms governing CC's onset and progression. A growing body of evidence strongly suggests that circRNAs can serve as valuable biomarkers for early CC detection and hold potential as therapeutic targets for intervention. By delving into the complex interplay between circRNAs and CC, we are paving the way for innovative, individualized approaches to combat this serious disease, with the goal of reducing its impact on women's health globally and improving patient outcomes. As our understanding of circRNAs in the context of CC continues to deepen, the outlook for breakthroughs in diagnosis and treatment becomes increasingly promising.

The role of long non-coding RNAs and circular RNAs in cervical cancer: modulating miRNA function

Cervical cancer (CC) is a primary global health concern, ranking as the fourth leading cause of cancer-related death in women. Despite advancements in prognosis, long-term outcomes remained poor. Beyond HPV, cofactors like dietary deficiencies, immunosuppression, hormonal contraceptives, co-infections, and genetic variations are involved in CC progression. The pathogenesis of various diseases, including cancer, has brought to light the critical regulatory roles of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The aberrant expression of these miRNAs, lncRNAs, and circRNAs plays a pivotal role in the initiation and progression of CC. This review provides a comprehensive summary of the recent literature regarding the involvement of lncRNAs and circRNAs in modulating miRNA functions in cervical neoplasia and metastasis. Studies have shown that lncRNAs and circRNAs hold great potential as therapeutic agents and innovative biomarkers in CC. However, more clinical research is needed to advance our understanding of the therapeutic benefits of circRNAs and lncRNAs in CC.

Virus-Encoded Circular RNAs: Role and Significance in Viral Infections

Circular RNAs (circRNAs) have been the focus of intense scientific research to understand their biogenesis, mechanisms of action and regulatory functions. CircRNAs are single stranded, covalently closed RNA molecules lacking the 5'-terminal cap and the 3'-terminal polyadenine chain, characteristics that make them very stable and resistant. Synthesised by both cells and viruses, in the past circRNAs were considered to have no precise function. Today, increasing evidence shows that circRNAs are ubiquitous, some of them are tissue- and cell-specific, and critical in multiple regulatory processes (i.e., infections, inflammation, oncogenesis, gene expression). Moreover, circRNAs are emerging as important biomarkers of viral infection and disease progression. In this review, we provided an updated overview of current understanding of virus-encoded and cellular-encoded circRNAs and their involvement in cellular pathways during viral infection.

Non-coding RNAs in gynecologic cancer

The term "gynecologic cancer" pertains to neoplasms impacting the reproductive tissues and organs of women encompassing the endometrium, vagina, cervix, uterus, vulva, and ovaries. The progression of gynecologic cancer is linked to various molecular mechanisms. Historically, cancer research primarily focused on protein-coding genes. However, recent years have unveiled the involvement of non-coding RNAs (ncRNAs), including microRNAs, long non-coding RNAs (LncRNAs), and circular RNAs, in modulating cellular functions within gynecological cancer. Substantial evidence suggests that ncRNAs may wield a dual role in gynecological cancer, acting as either oncogenic or tumor-suppressive agents. Numerous clinical trials are presently investigating the roles of ncRNAs as biomarkers and therapeutic agents. These endeavors may introduce a fresh perspective on the diagnosis and treatment of gynecological cancer. In this overview, we highlight some of the ncRNAs associated with gynecological cancers.

Exosome-delivered circRNA circSYT15 contributes to cisplatin resistance in cervical cancer cells through the miR-503-5p/RSF1 axis

The development of chemotherapy resistance is a major obstacle for cervical cancer (CC) patients. Exosome-mediated transfer of circular RNAs (circRNAs) was found to have relevance to the CC. This study is designed to explore the role and mechanism of exosomal circRNA synaptotagmin 15 (circSYT15) on cisplatin (DDP) resistance in CC. Cell proliferation ability and apoptosis rate were detected by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), colony formation, and flow cytometry assays. CircSYT15, microRNA-503-5p (miR-503-5p), Remodeling spacing factor 1 (RSF1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Exosomes were analyzed by a transmission electron microscope and nanoparticle tracking analysis. CD63, CD81, TSC101, Bcl-2, Bax, C-caspase 3, and RSF1 protein levels were examined by western blot assay. The binding between miR-503-5p and circSYT15 or RSF1 was predicted by circBank or Starbase and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP). The biological role of exosomal circSYT15 in DDP resistance of CC in vivo. CircSYT15 was upregulated in the DDP-resistant CC cells and exosomes isolated from DDP-resistant CC cells. CircSYT15 knockdown repressed the proliferation and drug resistance of CC and induced apoptosis in CC cells. Exosomes shuttled circSYT15 act as a sponge to affect RSF1 expression, thereby promoting proliferation and drug resistance and repressing apoptosis of sensitive CC cells. Exosomal circSYT15 boost DDP resistance of cervical cancer in vivo. Exosome-mediated transfer of circSYT15 enhanced DDP resistance in CC partly by targeting the miR-503-5p/RSF1 axis, providing a foundation for future clinical applications of CC drug resistance.

Circ_0042986 Presence Restrains Cervical Cancer Development via Upregulating PEG3 by Directly Targeting miR-582-3p

The participation of circular RNAs (circRNAs) in carcinogenesis is widely established. Numerous circRNAs with aberrant expression in cervical cancer (CC) are identified by RNA sequencing, whereas the function of these circRNAs remains unclear. We thus aimed to unveil the effects and mechanisms of circ_0042986 in CC. Circ_0042986 with aberrant downregulation in CC was obtained from GSE10286 dataset. qPCR and western blotting were employed for the detection of circ_0042986, miR-582-3p, and paternally expressed 3 (PEG3) expressions. EdU assay, colony formation assay, wound healing assay, transwell assay, tube formation assay, and flow cytometry assay were applied for functional analyses. The potential binding site was ensured by dual-luciferase reporter analysis, and their binding relationship was verified by pull-down assay. The transplanted tumor models were constructed for in vivo function verification of circ_0042986. Our findings exposed that the downregulation of circ_0042986 was verified in clinical CC samples. Circ_0042986 overexpression largely attenuated CC cell growth, invasiveness, angiogenesis, and survival. MiR-582-3p was targeted by circ_0042986, and the inhibitory roles of circ_0042986 presence were partly abolished by miR-582-3p enrichment. MiR-582-3p combined with PEG3, and circ_0042986 increased PEG3 expression via decoying miR-582-3p. The interaction between miR-582-3p and PEG3 on CC cell functions was confirmed, evidenced by the reversal effects of PEG3 knockdown on miR-582-3p deficiency-inhibited cancer cell malignant behaviors. Circ_0042986 overexpression also limited tumorigenesis of CC in animal models. In summary, circ_0042986 overexpression decoyed miR-582-3p to increase PEG3 expression, thereby blocking the malignant progression of CC.

Competing Endogenous RNA (ceRNA) Networks and Splicing Switches in Cervical Cancer: HPV Oncogenesis, Clinical Significance and Therapeutic Opportunities

Cervical cancer (CC) is the primary cause of female cancer fatalities in low-middle-income countries (LMICs). Persistent infections from the human papillomavirus (HPV) can result in cervical cancer. However, numerous different factors influence the development and progression of cervical cancer. Transcriptomic knowledge of the mechanisms with which HPV causes cervical cancer pathogenesis is growing. Nonetheless, there is an existing gap hindering the development of therapeutic approaches and the improvement of patient outcomes. Alternative splicing allows for the production of numerous RNA transcripts and protein isoforms from a single gene, increasing the transcriptome and protein diversity in eukaryotes. Cancer cells exhibit astounding transcriptome modifications by expressing cancer-specific splicing isoforms. High-risk HPV uses cellular alternative splicing events to produce viral and host splice variants and proteins that drive cancer progression or contribute to distinct cancer hallmarks. Understanding how viruses utilize alternative splicing to drive pathogenesis and tumorigenesis is essential. Although research into the role of miRNAs in tumorigenesis is advancing, the function of other non-coding RNAs, including lncRNA and circRNA, has been understudied. Through their interaction with mRNA, non-coding RNAs form a network of competing endogenous RNAs (ceRNAs), which regulate gene expression and promote cervical cancer development and advancement. The dysregulated expression of non-coding RNAs is an understudied and tangled process that promotes cervical cancer development. This review will present the role of aberrant alternative splicing and immunosuppression events in HPV-mediated cervical tumorigenesis, and ceRNA network regulation in cervical cancer pathogenesis will also be discussed. Furthermore, the therapeutic potential of splicing disruptor drugs in cervical cancer will be deliberated.

Novel Insight of CircRNAs in Cervical Cancer: Potential Biomarkers and Therapeutic Target

Cervical cancer (CC) is a prominent cancer around the globe, with a high incidence, and fatality rate. Numerous recent investigations have shown that various non-coding RNAs are associated with the progression of CC. Circular RNAs, a novel class of non-coding RNAs, have a single chain covalent closed-loop structure and are involved in cell growth and other physiological processes. These dysregulated circRNAs seem to have environment-specific functions. They have been demonstrated in certain studies to have a dual involvement in oncogene production and tumor inhibition in different cell settings. Simultaneously, some evidence indicates that circRNAs are abnormally expressed in CC and contributes to its progression. Thus, the distinctive expression profile of circRNAs is associated with the diagnosis, prognosis, and treatment outcomes of CC. We summarized numerous CC-specific circles and their function in revealing the molecular processes of carcinogenesis and progression in CC in this review. Taken together, these data suggest that circRNA may be used as an early detection biomarker and potential therapeutic target in patients with CC.

The Emerging Roles of Circ-ABCB10 in Cancer

Circular RNAs (circRNAs) are non-coding RNAs (ncRNAs) without 5′ caps and 3′ tails, which are formed from precursor mRNAs (pre-mRNAs) that are inversely back-spliced by exons. CircRNAs are characterized by a covalently closed circular structure and are abundantly expressed in eukaryotic cells. With the development of RNA-sequencing, it was discovered that circRNAs play important roles in the regulation of numerous human genes and are related to the occurrence, development, and prognosis of diseases. Studies in various cancers have revealed that circRNAs have both positive and negative effects on the occurrence and development of tumors. Circ-ABCB10, a circular RNA originating from exons of ABCB10 located on chromosome 1q42, has been proven to play an important role in different types of cancers. Here, we report the primary findings of recent research studies by many contributors about the roles of circ-ABCB10 in cancer and clearly formulate its influence and functions in different aspects of cancer biology, which gives us a broad picture of circ-ABCB10. Thus, this study aimed to generalize the roles of circ-ABCB10 in the diagnosis and treatment of different types of tumors and its related miRNA genes. In this way, we wish to provide a sufficient understanding and assess the future development direction of the research on circ-ABCB10.

Circular RNAs as emerging players in cervical cancer tumorigenesis; A review to roles and biomarker potentials

Cervical cancer is the most lethal gynecological cancer among women worldwide. Most of the patients are diagnosed at the advanced stages due to late diagnosis and lack of accessible and valuable approaches for early detection of the disease. Circular RNAs (circRNAs) are a distinguishable class of non-coding RNAs with characteristic loop structures. Although their function has not been completely elucidated; however, recent evidence has suggested regulatory functions for circRNAs on gene expression controlling various biological functions like cell growth and apoptosis, development, embryogenesis, and pathogenesis of human diseases particularly cancers. Studies show the role of dysregulated circRNAs in biological processes including cell proliferation, migration, invasion, apoptosis, angiogenesis, and chemoresistance contributing to affect tumorigenesis in ovarian cancer cells, animal, and clinical studies. These effects can be defined as consistent with several tumorigenesis characteristics, which are defined as "hallmarks of cancer". Additionally, dysregulated circRNAs exhibit prognostic, and diagnostic potentials both in the prediction of prognosis in ovarian cancer patients, and also their discrimination from healthy individuals. Furthermore, targeting circRNAs has shown positive results in the suppression of malignant features of cancer cells, and also in overcoming chemoresistance. In this review, I have gathered the majority of studies evaluating the role of circRNAs in the development, and progression of cervical cancer, and also have discussed prognostic, diagnostic, and therapeutic potentials of circRNAs for clinical applications in cervical cancer patients.

Circular RNA hsa_circ_0004543 Aggravates Cervical Cancer Development by Sponging MicroRNA hsa-miR-217 to Upregulate Hypoxia-Inducible Factor

Cervical cancer (CC) is the 4^th principal source of cancer death in females with 604,000 new patients and 342,000 deaths in 2020 worldwide. It has been extensively shown that circRNAs are involved in regulating CC development. Nevertheless, the function and mechanisms of hsa_circ_0004543 in regulating CC need to be clearly elucidated. Herein, hsa_circ_0004543 expressions were compared between 40 paired paracancerous and cancerous specimens from CC patients and between 6 CC cell lines and a normal human cervical epithelial cell line based on qRT-PCR. Potential complementary binding sites between hsa-miR-217 and hsa_circ_0004543 were predicted using the interactome, while binding sites for the hypoxia-inducible factor-1a (HIF-1a) were predicted by TargetScan. The function and mechanism of hsa_circ_0004543 in the development of CC were estimated by silencing hsa_circ_0004543 with/without hsa-miR-217 or HIF-1a overexpression. The association between gene expressions was evaluated with Pearson's correlation analysis. Molecular mechanisms were explored by ribonucleic acid (RNA) pulldown, dual-luciferase activity, and rescue experimental assays. Our results revealed that the hsa_circ_0004543 expression was considerably increased in CC tissues and cells. Its silencing repressed proliferation and metastasis, while it increased apoptosis of CC cells. The investigation of the mechanism showed that hsa-miR-217 silencing or HIF-1a overexpression rescued hsa_circ_0004543, and silencing inhibited malignant phenotypes of CC cells. hsa_circ_0004543 upregulated the HIF-1α expression by sponging hsa-miR-217 in CC development. Therefore, the hsa_circ_0004543 functioned as a competing endogenous RNA (ceRNA) of hsa-miR-217 to increase CC oncogenesis and metastasis by the upregulation of the HIF-1α expression. Consequently, targeting the hsa_circ_0004543/hsa-miR-217/HIF-1α axis might be a potential treatment approach for CC.

circEPS15 Overexpression in Hepatocellular Carcinoma Modulates Tumor Invasion and Migration

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. Recent evidence has shown that circular RNAs (circRNAs) play important roles in tissue development, gene transcription, signal regulation and tumorigenesis. However, whether circRNAs are involved in HCC progression and encode functional proteins remains largely unknown. In the present study, we aimed to explore the function and molecular mechanism of circRNAs in HCC. First, many circRNAs were found to be differentially expressed in HCC samples and paired adjacent normal liver tissues. The validation of dysregulated circRNAs by qRT-PCR revealed that circEPS15 expression was downregulated in HCC tissues, and the survival curves showed that low circEPS15 levels were associated with poor overall survival in HCC patients. Then, the overexpression of circEPS15 suppressed tumor cell invasion and migration by inhibiting the TJP1/CDH2/VIM signaling pathway and retarded cell cycle progression, which was confirmed by the Transwell culture system, wound healing assays, flow cytometry and western blot assays. After that, the spanning junction open reading frame in circEPS15 driven by IRES was shown to encode a novel protein, which was verified by western blotting with full-length, mutated, and truncated sequences of circEPS15 with a FLAG tag. Moreover, ceRNA analysis and qRT-PCR results suggest a possible circRNA (circEPS15)-miRNA-mRNA network in HCC. Collectively, our study reveals that endogenous circEPS15 plays a novel role in repressing HCC through the ceRNA network and encodes a functional protein.

Molecular Markers to Predict Prognosis and Treatment Response in Uterine Cervical Cancer

Uterine cervical cancer is one of the leading causes of cancer-related mortality in women worldwide. Each year, over half a million new cases are estimated, resulting in more than 300,000 deaths. While less-invasive, fertility-preserving surgical procedures can be offered to women in early stages, treatment for locally advanced disease may include radical hysterectomy, primary chemoradiotherapy (CRT) or a combination of these modalities. Concurrent platinum-based chemoradiotherapy regimens remain the first-line treatments for locally advanced cervical cancer. Despite achievements such as the introduction of angiogenesis inhibitors, and more recently immunotherapies, the overall survival of women with persistent, recurrent or metastatic disease has not been extended significantly in the last decades. Furthermore, a broad spectrum of molecular markers to predict therapy response and survival and to identify patients with high- and low-risk constellations is missing. Implementation of these markers, however, may help to further improve treatment and to develop new targeted therapies. This review aims to provide comprehensive insights into the complex mechanisms of cervical cancer pathogenesis within the context of molecular markers for predicting treatment response and prognosis.

Prognostic Nomogram Based on Circular RNA-Associated Competing Endogenous RNA Network for Patients with Lung Adenocarcinoma

Evidence is increasingly indicating that circular RNAs (circRNAs) are closely involved in tumorigenesis and cancer progression. However, the function and application of circRNAs in lung adenocarcinoma (LUAD) are still unknown. In this study, we constructed a circRNA-associated competitive endogenous RNA (ceRNA) network to investigate the regulatory mechanism of LUAD procession and further constructed a prognostic signature to predict overall survival for LUAD patients. Differentially expressed circRNAs (DEcircRNAs), differentially expressed miRNAs (DEmiRNAs), and differentially expressed mRNAs (DEmRNAs) were selected to construct the ceRNA network. Based on the TargetScan prediction tool and Pearson correlation coefficient, we constructed a circRNA-associated ceRNA network including 11 DEcircRNAs, 8 DEmiRNAs, and 49 DEmRNAs. GO and KEGG enrichment indicated that the ceRNA network might be involved in the regulation of GTPase activity and endothelial cell differentiation. After removing the discrete points, a PPI network containing 12 DEmRNAs was constructed. Univariate Cox regression analysis showed that three DEmRNAs were significantly associated with overall survival. Therefore, we constructed a three-gene prognostic signature for LUAD patients using the LASSO method in the TCGA-LUAD training cohort. By applying the signature, patients could be categorized into the high-risk or low-risk subgroups with significant survival differences (HR: 1.62, 95% CI: 1.12-2.35, log-rank p = 0.009). The prognostic performance was confirmed in an independent GEO cohort (GSE42127, HR: 2.59, 95% CI: 1.32-5.10, log-rank p = 0.004). Multivariate Cox regression analysis proved that the three-gene signature was an independent prognostic factor. Combining the three-gene signature with clinical characters, a nomogram was constructed. The primary and external verification C-indexes were 0.717 and 0.716, respectively. The calibration curves for the probability of 3- and 5-year OS showed significant agreement between nomogram predictions and actual observations. Our findings provided a deeper understanding of the circRNA-associated ceRNA regulatory mechanism in LUAD pathogenesis and further constructed a useful prognostic signature to guide personalized treatment of LUAD patients.

Identification of a novel circ_0018289/miR-183-5p/TMED5 regulatory network in cervical cancer development

Background

Circular RNAs (circRNAs) are increasingly implicated in regulating human carcinogenesis. Previous work showed the oncogenic activity of circ_0018289 in cervical cancer. However, the molecular basis underlying the modulation of circ_0018289 in cervical carcinogenesis is still not fully understood.

Methods

The levels of circ_0018289, microRNA (miR)-183-5p, and transmembrane p24 trafficking protein 5 (TMED5) were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot assay. Ribonuclease (RNase) R and subcellular localization assays were used to characterize circ_0018289. Cell proliferation was detected by the Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2′-deoxyuridine (Edu) assays. Cell apoptosis and tube formation were assessed by flow cytometry and tube formation assays, respectively. A dual-luciferase reporter assay was performed to confirm the direct relationship between miR-183-5p and circ_0018289 or TMED5. The role of circ_0018289 in tumor growth was gauged by mouse xenograft experiments.

Results

Circ_0018289 was overexpressed in cervical cancer tissues and cells. Circ_0018289 silencing impeded cell proliferation, enhanced cell apoptosis, and suppressed angiogenesis in vitro, as well as diminished tumor growth in vivo. Mechanistically, circ_0018289 targeted and regulated miR-183-5p by binding to miR-183-5p, and circ_0018289 regulated cervical cancer development and angiogenesis partially through miR-183-5p. Moreover, TMED5 was directly targeted and inhibited by miR-183-5p through the perfect complementary sites in TMED5 3′UTR, and TMED5 knockdown phenocopied miR-183-5p overexpression in suppressing cervical cancer development and angiogenesis. Furthermore, circ_0018289 induced TMED5 expression by competitively binding to shared miR-183-5p.

Conclusion

Our observations identified the circ_0018289/miR-183-5p/TMED5 regulatory network as a novel molecular basis underlying the modulation of cervical carcinogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02350-y.

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

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

Profiling of circular RNAs and circTPCN/miR-634/mTOR regulatory pathway in cervical cancer

Circular RNAs (circRNAs) are highly stable forms of endogenous non-coding RNA molecules with diverse biological functions. Some of them have been demonstrated to play crucial roles in the initiation or development of cancers through regulation of gene expression. However, the profiles and the roles of circRNAs in tumorigenesis of cervical cancer remain largely unknown. In the current study, we investigated the expression profiles of circRNAs and their potential oncogenic mechanisms in cervical cancer. The expression patterns, obtained using a microarray assay, revealed a total of 192 differentially expressed circRNAs, of which 106 were upregulated and 86 were downregulated, in cervical cancer samples compared with normal cervical samples. The differential expression of circRNAs was validated using quantitative real-time polymerase chain reaction. Two circRNAs (circTPCN and circFAM185A) were confirmed to be significantly upregulated in cervical cancer samples, indicating that they represent potential biomarkers of cervical cancer. The role and the potential molecular mechanism of circTPCN in cervical cancer tumorigenesis were further investigated. Knockdown of circTPCN significantly suppressed proliferation, migration, and invasion and increased apoptosis of cervical cancer cells in vitro. Molecular analysis revealed that circTPCN acted as a sponge of miR-634 to enhance mTOR expression. Thus, the circTPCN/miR-634/mTOR regulatory pathway might be involved in cervical cancer tumorigenesis, and circTPCN is a potential therapeutic target in cervical cancer.

Investigating the Underlying Mechanisms of Circular RNAs and Their Application in Clinical Research of Cervical Cancer

Circular RNAs (circRNAs) are non-coding RNA molecules, and these are differentially expressed in various diseases, including cancer, suggesting that circRNAs can regulate certain diseases. CircRNAs can act as miRNAs sponges, RNA-binding protein (RBP) sponges, and translation regulators, and they can become an important part of the regulation of gene expression. Furthermore, because of their biomedical features in body fluids, such as high abundance, conservation, and stability, circRNAs are seen as potential biomarkers for various cancers. Cervical cancer (CC) is one of the main causes of cancer-related death in women, and there have been a large number of studies that analyze circRNAs as a new object to be evaluated in CC. Therefore, this review, by understanding the role of circRNAs in CC, may create innovative strategies in the future clinical diagnosis, treatment, and prognosis of CC and promote the development of personalized and highly accurate cancer therapy.

Silencing of circular RNA_0000326 inhibits cervical cancer cell proliferation, migration and invasion by boosting microRNA-338-3p-dependent down-regulation of CDK4

Cervical cancer is one of the leading causes of cancer-related death among women, which is attributed partly by limited treatment options. Recent studies have provided in-depth explanations regarding the role of circular RNA in cancers. We aimed to investigate the role of circular RNA_0000326 in cervical cancer. Bioinformatics analysis revealed a high circ_0000326 expression in cervical cancer. Cervical cancer cells and tissues were also observed to have elevated levels of circ_0000326 and the upregulation of circ_0000326 depended on the stage of cancer. Transfection with siRNA of circ_0000326 resulted in the inhibition of proliferation, migration and cell cycle of cancer cells. Interestingly, we confirmed that circ_0000326 served as a sponge for microRNA-338-3p and that the miRNA bound to Cyclin-dependent kinase 4. In the presence of microRNA-338-3p mimic or silencing of circ_0000326, Cyclin-dependent kinase 4 expression was decreased. Transfection with microRNA-338-3p mimic inhibited cell clone formation and proliferation. Moreover, in vivo experiment revealed that the injection of shRNA-circ_0000326 lentivirus suppressed tumor growth and decreased Cyclin-dependent kinase 4 expression. Taken altogether, our results showed that circ_0000326 exerted oncogenic effects on cervical cancer by upregulating Cyclin-dependent kinase 4 via sponging microRNA-338-3p. This systematic investigation on circ_0000326 could provide further insight into cervical cancer.

The Role of circRNAs in Human Papillomavirus (HPV)-Associated Cancers

Circular RNAs (circRNAs) are a new class of "non-coding RNAs" that originate from non-sequential back-splicing of exons and/or introns of precursor messenger RNAs (pre-mRNAs). These molecules are generally produced at low levels in a cell-type-specific manner in mammalian tissues, but due to their circular conformation they are unaffected by the cell mRNA decay machinery. circRNAs can sponge multiple microRNAs or RNA-binding proteins and play a crucial role in the regulation of gene expression and protein translation. Many circRNAs have been shown to be aberrantly expressed in several cancer types, and to sustain specific oncogenic processes. Particularly, in virus-associated malignancies such as human papillomavirus (HPV)-associated anogenital carcinoma and oropharyngeal and oral cancers, circRNAs have been shown to be involved in tumorigenesis and cancer progression, as well as in drug resistance, and some are useful diagnostic and prognostic markers. HPV-derived circRNAs, encompassing the HPV E7 oncogene, have been shown to be expressed and to serve as transcript for synthesis of the E7 oncoprotein, thus reinforcing the virus oncogenic activity in HPV-associated cancers. In this review, we summarize research advances in the biogenesis of cell and viral circRNAs, their features and functions in the pathophysiology of HPV-associated tumors, and their importance as diagnostic, prognostic, and therapeutic targets in anogenital and oropharyngeal and oral cancers.

Circular RNAs: A Promising Biomarker for Endometrial Cancer

Endometrial cancer (EC) is one of the most common malignant tumors of the female reproductive tract. EC patients have high morbidity and mortality rates and remain an important cause of cancer-related morbidity and mortality worldwide. More and more studies have shown that a large number of non-coding RNAs (such as microRNAs and long non-coding RNAs) are associated with the occurrence of diseases. Circular RNAs (circRNAs) is an endogenous non-coding RNA. It has a unique covalent structure. Many studies in recent years have found circRNAs differential expression in a variety of tumor tissues compared to matched normal tissues. In endometrial carcinoma, there also are multiple circRNAs differentially expressed and therefore circRNAs perhaps can be used as a diagnostic and prognosis biomarkers of EC. In this review, we described the biogenesis, function and characteristics of circRNAs, and the circRNAs with potential influence and clinical significance on the development of EC were summarized. Adenocarcinoma is the most common form of EC, so this review focuses on endometrioid adenocarcinoma.

Circ-CCDC66 upregulates REXO1 expression to aggravate cervical cancer progression via restraining miR-452-5p

Background

Cervical cancer is one most common cancer types among females over the world. While its underlying mechanisms remain unclear. Circ-CCDC66 has been revealed to participate in multiple biological functions, and contribute to various diseases’ progression. In the current study, we aimed to demonstrate the role of circ-CCDC66 in cervical cancer progression.

Methods

Real-time quantitative PCR (RT-qPCR) was conducted to measure the expression of circ-CCDC66, miR-452-5p, and REXO1 mRNA. Cell fractionation assay and RNA fluorescence in situ hybridization (FISH) were performed to locate circ-CCDC66 in cells. Cell account kit 8 (CCK-8) was used to detect cell proliferation ability. Transwell assay was applied to evaluate cell migration or invasion ability. Bioinformatics analysis, biotinylated RNA pull-down, RNA immunoprecipitation, and dual-luciferase reporter assays were conducted to assess the association between miR-452 and circ-CCDC66 or REXO1. Western blot was applied to measure the protein expression of REXO1. The animal tumor model was used to assess the effect of circ-CCDC66 in vivo.

Results

The expression of circ-CCDC66 was upregulated in cervical cancer tumor tissues in comparison with normal tissues, and correlated with later tumor stage and larger tumor size. Downregulated circ-CCDC66 inhibited cervical cancer cell proliferation, migration, and invasion. Circ-CCDC66 was an efficient molecular sponge for miR-452-5p, and negatively regulated miR-452-5p expression. MiR-452-5p directly targeted to REXO1. Circ-CCDC66 regulated REXO1 expression to modulate cervical cancer progression via miR-452-5p. Moreover, downregulated circ-CCDC66 was found to suppress tumor growth in vivo.

Conclusion

Our results demonstrated the role of circ-CCDC66/miR-452-5p/REXO1 axis in cervical cancer progression, we might provide novel therapeutic targets for cervical cancer clinical intervention.

Hsa_circ_0102171 aggravates the progression of cervical cancer through targeting miR-4465/CREBRF axis

Cervical cancer (CC) has caused numerous cancer-related deaths in women. Recent years, circular RNAs have been reported as vital factors in CC tumorigenesis. Our current study focused on the role of hsa_circ_0102171 (called circ_0102171 subsequently) in CC. At first, we applied reverse transcription polymerase chain reaction to detect the expression of circ_0102171 in CC tissues and cells. Subsequently, we silenced circ_0102171 to conduct loss-of-function assays, including cell counting kit-8 assay, 5-ethynyl-2'-deoxyuridine staining, Transwell assay, and flow cytometry analysis. Interestingly, we discovered that circ_0102171 expressed at a high level in CC tissues and cells. Functionally, silencing circ_0102171 prohibited cell proliferation, migration and invasion, and strengthened cell apoptosis in CC in vitro. Mechanistic investigations revealed that circ_0102171 could act as a sponge for miR-4465. Gain-of-function assays demonstrated that miR-4465 hindered the growth and migration of CC cells. Moreover, circ_0102171 enhanced the level of CREB3 regulatory factor (CREBRF) which was the downstream target of miR-4465. Rescue assays suggested that CREBRF and miR-4465 could involve in circ_0102171-mediated CC progression. Finally, in vivo data supported that silencing circ_0102171 hindered CC cell growth. In conclusion, circ_0102171 aggravates CC progression via targeting miR-4465/CREBRF axis.

Regulation of microRNA-497 expression in human cancer

MicroRNAs (miRNAs/miRs) are a type of non-coding single-stranded RNA, with a length of ~22 nt, which are encoded by endogenous genes and are involved in the post-transcriptional regulation of gene expression in animals and plants. Studies have demonstrated that miRNAs play an important role in the occurrence, development, metastasis, diagnosis and treatment of cancer. In recent years, miR-497 has been identified as one of the key miRNAs in a variety of cancer types and has been shown to be downregulated in a variety of solid tumors. However, the regulation of miR-497 expression involves a complex network, which is affected by several factors. The aim of the present review was to summarize the mechanism of regulation of miR-497 expression at the pre-transcriptional and transcriptional levels in cancer, as well as the role of miR-497 expression imbalance in cancer diagnosis, treatment and prognosis. The regulatory mechanisms of miR-497 expression may aid in our understanding of the causes of miR-497 expression imbalance and provide a reference value for further research on the diagnosis and treatment of cancer.

Circular RNAs: Novel biomarkers for cervical, ovarian and endometrial cancer (Review)

Cervical, ovarian and endometrial cancer are the three most common types of malignant tumor and the leading causes of cancer‑associated death in women. Tumor debulking surgery followed by platinum and paclitaxel chemotherapy is the current treatment regime of choice. However, as a result of late diagnosis and chemoresistance, the survival rates of patients with advanced gynecological cancers remains unsatisfactory. Circular RNAs (circRNAs) are stable noncoding RNAs that are present in a wide variety of tissue and cell types. With the enhancement of RNA sequencing methods, increasing numbers of circRNAs have been identified, and their functions are gradually being revealed. In recent years, circRNAs have received increasing attention for their regulatory roles in cervical, ovarian and endometrial cancer. The aim of the present review was to summarize the possible mechanisms of recently identified circRNAs; we hypothesize that a novel diagnostic and therapeutic biomarker may be identified to prolong the survival time of patients with gynecological malignancies.

Circular RNA hsa_circ_0003204 promotes cervical cancer cell proliferation, migration, and invasion by regulating MAPK pathway

Cervical cancer (CC) is the second most common malignancy in women worldwide. The mechanism underlying CC development remains unclear. Recently, Circular RNAs (circRNAs)have attracted attention because of its role in tumorigenesis. To investigate circRNAsin CC, RNA sequencing was employed to characterize circRNA expression profile between CC tissues and matched adjacent normal tissues. The expression of hsa_circ_0003204 was examined in CC tissues and cell lines by real-time PCR. Migration assay and invasion assay were used to verify the effect of hsa_circ_0003204 on migration and invasion ability in CC cell lines. Tumor formation assay in nude mice was used to analyze the effect of hsa_circ_0003204 on the tumorigenicity of CC cell lines in vitro. Western blotting analyzes were performed to investigate the role of hsa_circ_0003204 in the regulation of MAPK signaling activation. We found that circRNA hsa_circ_0003204 was significantly upregulated in CC tissues. The function and potential molecular mechanisms of hsa_circ_0003204 were also investigated in vitro and in vivo. Hsa_circ_0003204 knockdown reduced cell growth, migration, and invasion but promoted cells apoptosis. However, the over-expression of hsa_circ_0003204 had the opposite effect. The MAPK pathway was different in hsa_circ_0003204 over-expression or down-expression cells, compared to parental cells. In addition, over-expression of hsa_circ_0003204 significantly increased tumor volume and tumor weight in vivo.Taken together, results indicated hsa_circ_0003204 may serve as a potential therapeutic target for patients with CC.

Circ_0084927 Facilitates Cervical Cancer Development via Sponging miR-142-3p and Upregulating ARL2

Background

Cervical cancer is a fatal burden for women. Circular RNAs (circRNAs) are important regulators in cancer development. Our study aimed to investigate the function and action mechanism of a novel circRNA, circ_0084927, in cervical cancer.

Methods

The expression of circ_0084927, miR-142-3p and ADP-ribosylation factor-like protein 2 (ARL2) mRNA was measured by quantitative real-time polymerase chain reaction (qRT-PCR). For functional analyses, cell proliferation was assessed using cell counting kit-8 (CCK-8) assay. Cell cycle distribution was monitored by flow cytometry assay. Cell migration and cell invasion were evaluated by transwell assay. The interaction between miR-142-3p and circ_0084927 or ARL2 was predicted by the bioinformatics analysis and validated by dual-luciferase reporter assay and RNA immunoprecipitation assay (RIP) assay. The expression of ARL2 at the protein level was detected by Western blot. Animal tumor formation assay was performed to monitor the tumorigenicity of circ_0084927 in vivo.

Results

The expression of circ_0084927 and ARL2 was enhanced in cervical cancer tissues and cells, while the expression of miR-142-3p was opposite to them. Circ_0084927 knockdown significantly blocked cervical cancer cell proliferation, migration and invasion and induced cell cycle arrest. MiR-142-3p was targeted by circ_0084927, and miR-142-3p inhibition reversed the effects of circ_0084927 knockdown. Besides, miR-142-3p bound to ARL2, and the inhibitory effects of miR-142-3p restoration on cell proliferation, cycle, migration and invasion were counteracted by ARL2 overexpression. More importantly, circ_0084927 upregulated ARL2 expression by sponging miR-142-3p. Circ_0084927 knockdown retarded tumor growth in vivo by regulating miR-142-3p and ARL2.

Conclusion

Circ_0084927 accelerated the progression of cervical cancer partly by mediating the miR-142-3p/ARL2 axis.

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

BACKGROUND

Increasing evidence has indicated that circular RNAs (circRNAs) play vital roles in modulating tumor progression. However, regulatory roles and underlying mechanisms of circRNA circ_0072995 in epithelial ovarian cancer (EOC) are not well characterized.

RESULTS

Circ_0072995 was up regulated in EOC afflicted tissues and cell lines (HO8910 and A2780), and was mainly located in the cytoplasm. The expression of circ_0072995 was associated with the pathological grade of EOC for respective patients. Functional experiments revealed that circ_0072995 promoted EOC cell proliferation, migration, induced apoptosis, as well as enhanced tumorigenesis in vivo. Mechanistic analyses indicated that circ_0072995 may have acted as a sponge of miR-147a such as to relieve repressive effects of miR-147a upon its target CDK6.

CONCLUSIONS

Our results revealed that circ_0072995 promoted EOC progression through the circ_0072995/miR-147a/CDK6 axis and may represent a strategy for treatment of EOC afflicted patients.

METHODS

Expression of circ_0072995 was evaluated in 40 EOC tissue samples and cell lines by qRT-PCR. The location of circ_0072995 was determined via nuclear-cytoplasmic fractionation. A series of functional experiments facilitated determinations of effects of circ_0072995 on EOC progression in vitro, and in vivo. Underlying mechanisms and influence of circ_0072995 on EOC were confirmed by bioinformatic analyses, luciferase reporter assays, qRT-PCR, and Western blotting.

Involvement of a novel circularRNA, hsa_circ_0000520, attenuates tumorigenesis of cervical cancer cell through competitively binding with miR-146b-3p

The implication of circular RNAs (circRNAs) in the pathogenesis of human cervical cancer (CC) has been demonstrated by numerous of researches, nevertheless, the whole regulatory network of circRNAs in CC remains unclear. In the present study, two GSE data sets (GSE113696 and GSE102686) were enrolled to analysed different expressed circRNA. We found that hsa_circ_0000520(circ_0000520) was decreased in CC tissues and cell lines. Functional studies indicated circ_0000520 overexpression in vitro repressed CC cell proliferation, invasion and migration, while promoted CC cell apoptosis. Moreover, circ_0000520 overexpression in vivo repressed CC tumour growth. Mechanismly, circ_0000520 and PAX5 were revealed to directly bind to miR-146b-3p, and circ_0000520 could indirectly regulate PAX5 by sponging miR-146b-3p. In conclusion, circ_0000520 repressed CC progression in vitro and in vivo by sponging miR-146b-3p to release PAX5.

Circular RNAs: New Epigenetic Signatures in Viral Infections

Covalent closed circular RNAs (circRNAs) can act as a bridge between non-coding RNAs and coding messenger RNAs. CircRNAs are generated by a back-splicing mechanism during post-transcriptional processing and are abundantly expressed in eukaryotic cells. CircRNAs can act via the modulation of RNA transcription and protein production, and by the sponging of microRNAs (miRNAs). CircRNAs are now thought to be involved in many different biological and pathological processes. Some studies have suggested that the expression of host circRNAs is dysregulated in several types of virus-infected cells, compared to control cells. It is highly likely that viruses can use these molecules for their own purposes. In addition, some viral genes are able to produce viral circRNAs (VcircRNA) by a back-splicing mechanism. However, the viral genes that encode VcircRNAs, and their functions, are poorly studied. In this review, we highlight some new findings about the interaction of host circRNAs and viral infection. Moreover, the potential of VcircRNAs derived from the virus itself, to act as biomarkers and therapeutic targets is summarized.

Circular RNA UBAP2 contributes to tumor growth and metastasis of cervical cancer via modulating miR-361-3p/SOX4 axis

Background

Increasing researches have reported that circular RNA UBAP2 (circUBAP2) may be a potential prognosis biomarker and participate in the development of several cancers; however, the role of circUBAP2 in cervical cancer (CC) remains largely unclear.

Methods

We applied qRT-PCR and Western blot to examine expression levels of circUBAP2, miR-361-3p, SOX4, Bax, Bcl-2, Cleaved caspase 3, N-cadherin, Vimentin and E-cadherin. Cell proliferation, apoptosis, invasion and migration were analyzed by MTT assay, Flow cytometry, and Transwell assay, respectively. The interaction between miR-361-3p and circUBAP2 or SOX4 was confirmed by luciferase reporter assay and pull-down assay. Murine xenograft model was established by injecting SiHa cells which stably transfected sh-circUBAP2.

Results

CircUBAP2 was up-regulated in CC tissues and cell lines and high circUBAP2 expression predicated poor outcome. Knockdown of circUBAP2 suppressed cell proliferation, migration, invasion and EMT, while induced apoptosis in CC in vitro, and inhibited tumor growth and metastasis in vivo. MiR-361-3p directly bound to circUBAP2 or SOX4, and circUBAP2 could regulate SOX4 expression by sponging miR-361-3p in CC cells. Furthermore, rescue assay results demonstrated that the inhibitory effects of circUBAP2 knockdown on cell growth and metastasis were partially reversed by miR-361-3p down-regulation or SOX4 up-regulation in CC.

Conclusion

CircUBAP2 represents a prognostic marker and contributes to tumor growth and metastasis via modulating miR-361-3p/SOX4 axis in CC, which indicates a potential therapeutic target for CC treatment.

Circular RNA-ABCB10 promotes angiogenesis induced by conditioned medium from human amnion-derived mesenchymal stem cells via the microRNA-29b-3p/vascular endothelial growth factor A axis

The powerful ability of human amnion-derived mesenchymal stem cells (hAMSCs) to promote angiogenesis suggests that they may facilitate angiogenesis-associated therapeutic strategies. However, the molecular mechanisms underlying hAMSC-induced angiogenesis remain largely unknown. The present study results suggested that enhanced migration and tube formation in human umbilical vein endothelial cells (HUVECs) was induced by conditioned medium from hAMSCs (hAMSC-CM). In addition, culture with this conditioned medium resulted in the increased expression of circular RNA ATP binding cassette subfamily B member 10 (circ-ABCB10) and vascular endothelial growth factor A (VEGFA). In the present study genes related to thecirc-ABCB10/microRNA (miR)-29b-3p/VEGFA pathway were predicted using bioinformatics software, and further investigated using in vitro luciferase reporter assays. Loss-of-function assays were performed using small interfering RNAs (siRNAs). The results suggested that siRNA-silencing of circ-ABCB10 in HUVECs weakened migration and tube formation of HUVECs following hAMSC-CM treatment and reduced the levels of VEGFA expression. Treatment with an miR-29b-3p inhibitor could largely rescue these effects in HUVECs, following circ-ABCB10 silencing. The present study results suggest that the circ-ABCB10/miR-29b-3p/VEGFA pathway may be involved in the pro-angiogenic role of hAMSC-CM in HUVECs.

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

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

Recent advances in the contribution of noncoding RNAs to cisplatin resistance in cervical cancer

Cervical cancer (CC) remains a major disease burden on the female population worldwide. Chemotherapy with cisplatin (cis-diamminedichloroplatinum (II); CDDP) and related drugs are the main treatment option for CC; however, their efficacy is limited by the development of drug resistance. Noncoding RNAs (ncRNAs) have been found to play critical roles in numerous physiological and pathological cellular processes, including drug resistance of cancer cells. In this review, we describe some of the ncRNAs, including miRNAs, lncRNAs and circRNAs, that are involved in the sensitivity/resistance of CC to CDDP-based chemotherapy and discuss their mechanisms of action. We also describe some ncRNAs that could be therapeutic targets to improve the sensitivity of CC to CDDP-based chemotherapy.

Beyond MicroRNAs: Emerging Role of Other Non-Coding RNAs in HPV-Driven Cancers

Persistent infection with high-risk Human Papilloma Virus (HPV) leads to the development of several tumors, including cervical, oropharyngeal, and anogenital squamous cell carcinoma. In the last years, the use of high-throughput sequencing technologies has revealed a number of non-coding RNA (ncRNAs), distinct from micro RNAs (miRNAs), that are deregulated in HPV-driven cancers, thus suggesting that HPV infection may affect their expression. However, since the knowledge of ncRNAs is still limited, a better understanding of ncRNAs biology, biogenesis, and function may be challenging for improving the diagnosis of HPV infection or progression, and for monitoring the response to therapy of patients affected by HPV-driven tumors. In addition, to establish a ncRNAs expression profile may be instrumental for developing more effective therapeutic strategies for the treatment of HPV-associated lesions and cancers. Therefore, this review will address novel classes of ncRNAs that have recently started to draw increasing attention in HPV-driven tumors, with a particular focus on ncRNAs that have been identified as a direct target of HPV oncoproteins.

A potential disease monitoring and prognostic biomarker in cervical cancer patients: The clinical application of circular RNA_0018289

OBJECTIVE

This study aimed to investigate the tumor circular RNA_0018289 (circ_0018289) expression and its correlation with clinical characteristics as well as survival profiles in cervical cancer patients.

METHODS

A hundred and ninety-two cervical cancer patients who received surgical resection were recruited in this prospective study. Tumor tissue and paired adjacent tissue were obtained during the surgery, in which circ_0018289 expression was detected by reverse transcription quantitative polymerase chain reaction. Disease-free survival (DFS) and overall survival (OS) were recorded.

RESULTS

Circ_0018289 expression was upregulated in tumor tissue compared with paired adjacent tissue (P < .001), and receiver operative characteristic curve disclosed its good value for separating tumor tissue from adjacent tissue with an area under curve of 0.907 (95% CI: 0.879-0.935). Additionally, tumor circ_0018289 expression was positively associated with tumor size (P = .009), lymph node metastasis (P = .005) and Federation International of Gynecology and Obstetrics stage (P = .005). The DFS (P = .005) and OS (P = .015) were both worse in patients with circ_0018289 high expression compared to patients with circ_0018289 low expression. Meanwhile, in patients with circ_0018289 high expression, DFS and OS were the longest in patients with high+ expression followed by patients with high++ expression, and the shortest in patients with high+++ expression. Moreover, circ_0018289 high expression could independently predict worse DFS in the total cervical cancer patients (P = .042).

CONCLUSION

Circ_0018289 could serve as a potential disease monitoring and prognostic biomarker in cervical cancer patients.

Serum Circular FoxO3a Serves as a Novel Prognostic Biomarker in Squamous Cervical Cancer

Purpose

Circular RNAs (circRNAs) are novel type of noncoding RNAs that play important roles and serve as noninvasive biomarkers in various cancers. In the present study, we focused on circFoxO3a and aimed to investigate its prognostic value as a novel serum biomarker for squamous cervical cancer (SCC).

Patients and Methods

Our study included 103 SCC patients from Obstetrics and Gynecology Hospital of Fudan University. Expression levels of circFoxO3a in the serum of patients with SCC were examined by reverse transcription‑quantitative PCR (RT‑qPCR). The correlation between serum circFoxO3a expression and clinicopathologic factors was analyzed. The Kaplan–Meier method and multivariate Cox regression analysis were applied to evaluate the independent prognostic factors for SCC. A prognostic predictive nomogram was constructed using R software.

Results

Levels of serum circFoxO3a were decreased in SCC patients compared with controls. Low expression of circFoxO3a was correlated with deeper stromal invasion and positive lymph node metastasis. Moreover, SCC patients with lower expression of serum circFoxO3a showed poorer prognosis, including both overall survival (OS) and recurrence-free survival (RFS). Multivariate Cox analysis indicated low serum circFoxO3a levels to be an unfavorable prognostic factor for both OS and RFS, independent of positive lymph node metastasis. Notably, the predictive nomogram we established further confirmed that serum circFoxO3a is a useful tool for predicting survival in SCC.

Conclusion

Altogether, our findings demonstrated that serum circFoxO3a could serve as a potential novel noninvasive predictive prognostic biomarker and therapeutic target for SCC.

Diagnostic value of circular RNAs in female reproductive system diseases: A PRISMA-compliant meta-analysis

Circular RNAs (circRNAs) are novel non-coding RNAs that have been reported to be involved in the progression of numerous diseases. However, the clinical diagnostic value of circRNAs in female reproductive system diseases remains unknown. The present study is a systemic review and meta-analysis of the available literature on circRNAs as novel biomarkers for female reproductive system diseases. Relevant studies were systematically searched using the PubMed, Embase, Web of Science and Cochrane Library databases. The data obtained from the included studies were analyzed by RevMan5.3 and STATA 14.2. A total of six studies involving 613 individuals across three types of disease examined the diagnostic capabilities of circRNAs. Within these publications, the pooled sensitivity of circRNAs was 0.70 (95% CI, 0.64-0.76), and the pooled specificity was 0.70 (95% CI, 0.64-0.75). The pooled positive likelihood ratio and negative likelihood ratio were 2.33 and 0.42, respectively. The diagnostic score was 1.70 and the pooled diagnostic odds ratio was 5.48. The area under the summary receiver operator characteristic curve was 0.76 (95% CI, 0.72-0.79), indicating that circRNAs exhibited a moderate diagnostic value for female reproductive system diseases and may function as potential diagnostic biomarkers. However, further studies are required to verify the clinical applications of circRNAs.

A New World of Biomarkers and Therapeutics for Female Reproductive System and Breast Cancers: Circular RNAs

As one of the most recently (re)discovered types of non-coding RNAs (ncRNA), circular RNAs (circRNAs) differentiate from other ncRNAs by a specific biogenesis, high stability, and distinct functions. The biogenesis of circRNAs can be categorized into three mechanisms that permit the back-splicing reaction: exon-skipping, pairing of neighboring introns, and dimerization of RNA-binding proteins. Regarding their stability, circRNAs have no free ends, specific to linear RNA molecules, prompting a longer half-life and resistance to exonuclease-mediated activity by RNase R, bypassing the common RNA turnover process. Regarding their functions, circular transcripts can be categorized into four broad roles: miRNA sponging, protein binding, regulation of transcription, and coding for proteins and peptides. Female reproductive system (including mainly ovarian, corpus, and cervix uteri cancers) and breast cancers are the primary causes of death in women worldwide, accounting for over 1,212,772 deaths in 2018. We consider that a better understanding of the molecular pathophysiology through the study of coding and non-coding RNA regulators could improve the diagnosis and therapeutics of these cancers. Developments in the field of circRNA in regard to breast or gynecological cancers are recent, with most circRNA-related discoveries having been made in the last 2 years. Therefore, in this review we summarize the newly detected roles of circRNAs in female reproductive system (cervical cancer, ovarian cancer, and endometrial cancer) and breast cancers. We argue that circRNAs can become essential elements of the diagnostic and therapeutic tools for female reproductive system cancers in the future.

The Role of microRNAs, Long Non-coding RNAs, and Circular RNAs in Cervical Cancer

Prolonged infection of uterine cervix epithelium with human papillomavirus (HPV) and constitutive expression of viral oncogenes have been recognized as the main cause of the complex molecular changes leading to transformation of cervical epithelial cells. Deregulated expression of microRNAs (miRNA), long non-coding RNAs (lncRNA), and circular RNAs (circRNA) is involved in the initiation and promotion processes of cervical cancer development. Expression profiling of small RNAs in cervical neoplasia revealed up-regulated “oncogenic” miRNAs, such as miR-10a, miR-21, miR-19, and miR-146a, and down regulated “tumor suppressive” miRNAs, including miR-29a, miR-372, miR-214, and miR-218, associated with cell growth, malignant transformation, cell migration, and invasion. Also several lncRNAs, comprising among others HOTAIR, MALAT1, GAS5, and MEG3, have shown to be associated with various pathogenic processes such as tumor progression, invasion as well as therapeutic resistance and emerged as new diagnostic and prognostic biomarkers in cervical cancer. Moreover, human genes encoded circular RNAs, such as has_circ-0018289, have shown to sponge specific miRNAs and to concur to the deregulation of target genes. Viral encoded circE7 has also demonstrated to overexpress E7 oncoprotein thus contributing to cell transformation. In this review, we summarize current literature on the complex interplay between miRNAs, lncRNAs, and circRNAs and their role in cervical neoplasia.

Circular RNA HIPK3 Promotes EMT of Cervical Cancer Through Sponging miR-338-3p to Up-Regulate HIF-1α

Background

Cervical cancer (CC) is the 4th most common malignancy and cancer-related fatality in women worldwide. Circular RNA is a newly recognized noncoding RNA form. More reports have confirmed their important regulatory functions in diverse physiological and cancer processes. However, the function and mechanisms of circ-HIPK3 in CC remain unknown.

Methods

circ-HIPK3 expression status was verified between 45 paired CC and normal adjacent tissues from 45 CC patients, also the 6 CC cell lines and a normal human cervical epithelial End1/E6E7 cell line by qRT-PCR. Effects of circ-HIPK3 silence on CC cell phenotypes were estimated. Circular RNA interactome was applied to forecast binding site between circ-HIPK3 and miRNAs. Pearson correlation analysis was used to confirm the relationship between genes. Point mutation, RNA pull-down, luciferase assay and rescue experiments were applied for molecular mechanism exploration.

Results

circ-HIPK3 expression was significantly elevated in CC cells and tissues. circ-HIPK3 silence repressed growth and metastasis, while induced apoptosis in CC cells. circ-HIPK3 sponged miRNA-338-3p (miR-338-3p); miR-338-3p to up-regulate hypoxia-inducible factor-1α (HIF-1α) and CC progress. MiR-338-3p silence or HIF-1α over-expression rescued circ-HIPK3 knockdown caused inhibition of CC malignant characteristics.

Conclusion

circ-HIPK3 acts as a competing endogenous RNA of miR-338-3p to promote cell growth and metastasis in CC, via regulating HIF-1α mediated EMT. Therefore, targeting circ-HIPK3/miR-338-3p/HIF-1α axis may be a novel therapeutic strategy for CC.

Hsa_circ_CSPP1/MiR-361-5p/ITGB1 Regulates Proliferation and Migration of Cervical Cancer (CC) by Modulating the PI3K-Akt Signaling Pathway

This study aimed to investigate the regulatory mechanism of circular RNA CSPP1 (hsa_circ_CSPP1) in cervical cancer. Based on GEO database, differentially expressed circRNAs and mRNAs related to cervical cancer were screened out by R software. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and Gene Ontology (GO) term analysis were performed to analyze the functional and pathway enrichment of identified DEGs. In addition, Cytoscape software was used to build interaction network of DEGs. The mRNA expressions were examined by qRT-PCR. Western blot was conducted to view the expression of proteins. Cell proliferation and apoptosis were respectively evaluated using CCK-8 assay and flow cytometry, whereas cell migration abilities were detected by Transwell assay. The relationship among factors was validated by dual-luciferase reporter gene assay. The influence in cervical tumor growth was further verified through nude mouse model in vivo. Hsa_circ_CSPP1 and ITGB1 were high-expressed in cervical cancer, while miR-361-5p was low-expressed. Hsa_circ_CSPP1 knockdown or miR-361-5p overexpression could suppress cervical cancer cell proliferation and migration, whereas promoted cell apoptosis. In addition, further experiments demonstrated that both hsa_circ_CSPP1 and ITGB1 mRNA were targets of miR-361-5p. Repressing hsa_circ_CSPP1 restrained cell viability and mobility and induced apoptosis through sponging miR-361-5p. Meanwhile, miR-361-5p also inhibited cervical cancer tumorigenesis via downregulation of ITGB1. Knockdown of hsa_circ_CSPP1 impeded tumor growth through suppressing the expression of downstream gene ITGB1, PI3K, and Akt. Circular RNA hsa_circ_CSPP1 regulates cell migration and proliferation in cervical cancer through miR-361-5p/ITGB1 in PI3K-Akt signaling pathway.

Circular RNAs: The star molecules in cancer

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs with a closed loop structure. These RNAs are produced by pre-mRNA through variable shear processing and are highly conserved. Such highly conserved molecules play an important role in biology, especially in cancer biology. With the development of experimental techniques such as circRNA microarray screening and high-throughput sequencing technologies, the mystery of circRNAs has gradually been unveiled and the values of function and application have gradually emerged. Among them, cancer-related circRNAs are the most eye-catching. Numerous studies have shown that some circRNAs were involved in the pathogenesis of cancer. This review systematically introduced the cancer-related circRNAs and their origin, formation mechanisms, functions, and applications in the diagnosis and treatment of sixteen kinds of tumors.

Upregulated circ_0005576 facilitates cervical cancer progression via the miR-153/KIF20A axis

Circular RNAs (circRNAs) are a novel group of noncoding RNAs characterized by a covalently closed loop. An increasing evidence suggests that deregulated circRNAs exert their essential regulatory roles in oncogenesis. However, little is explored on the biological role of novel circRNAs in cervical cancer (CC) progression. In the present study, we analyzed two GSE microarrays to screen for CC-specific circRNAs and found two circRNAs both expressed in CC cells and tissues. Among them, circ_0005576 was significantly overexpressed in both CC tissues and cell lines. Furthermore, upregulated circ_0005576 was positively associated with advanced FIGO stage, lymph node metastasis, but was negatively related with overall survival of CC patients. Additionally, circ_0005576 knockdown induced a suppressed cell growth, colony formation and metastasis of HeLa and SiHa cells. Mechanistically, circ 0005576 was mainly located in the cytoplasm and served as a sponge of miR-153-3p to increase kinesin family member 20A (KIF20A) expression. Rescue assays further validated the effects of circ_0005576/miR-153-3p/KIF20A axis on CC proliferation, migration and invasion. In conclusion, our research reveals a novel circ_0005576/miR-153-3p/KIF20A axis promoting CC progression, which may suggest a new insight into the pathogenesis of CC.