Circ-ATP8A2 promotes cell proliferation and invasion as a ceRNA to target EGFR by sponging miR-433 in cervical cancer

What is the role of circRNAs in the pathogenesis of cervical cancer? A systematic literature review

Cervical Cancer (CC) is one of the most prevalent neoplasms among women, considered the leading cause of gynecological death worldwide, and the fourth most common type of cancer. Regional metastasis is closely related to the low effectiveness of treatment, and validating biomarkers can optimize accuracy in diagnosis and prognosis. Among the potential biomarkers associated with disease metastasis are circular RNAs (circRNAs), whose altered expression has been linked to CC progression. In this context, this systematic review aims to compile information on the clinical-pathological significance and describe the biological function of circRNAs. Inclusion and exclusion criteria were used to include relevant literature, followed by in silico analysis. Additionally, we employed the UALCAN tools to search for host genes of circRNAs and expression data, miRTargetLink 2.0 to predict interactions of microRNA target genes and the Cytoscape software to predict possible interactions of microRNA target genes. According to the research, most circRNAs were found to be overexpressed and described as regulators of processes such as invasion, cell proliferation, apoptosis and migration. They were also implicated in clinical significance, including metastasis, TNM staging and microRNA interactions. CircRNAs may participate in critical processes in tumorigenesis; therefore, understanding the underlying molecular mechanisms of gene regulation in CC can contribute to the accuracy of diagnosis, prognosis and therapy.

Riddle of the Sphinx: Emerging role of circular RNAs in cervical cancer

Cervical cancer is a prominent cause of cancer-related mortality among women, with recent attention directed toward exploring the involvement of circular RNAs (circRNAs) in this particular cancer. CircRNAs, characterized by a covalently closed loop structure, belong to a class of single-stranded non-coding RNA (ncRNA) molecules that play crucial roles in cancer development and progression through diverse mechanisms. The abnormal expression of circRNAs in vivo is significantly associated with the development of cervical cancer. Notably, circRNAs actively interact with miRNAs in cervical cancer, leading to the regulation of diverse signaling pathways, and they can contribute to cancer hallmarks such as self-sufficiency in growth signals, insensitivity to antigrowth signals, limitless proliferation, evading apoptosis, tissue invasion and metastasis, and sustained angiogenesis. Moreover, the distinctive biomedical attributes exhibited by circRNAs, including their abundance, conservation, and stability in body fluids, position them as promising biomarkers for various cancers. In this review, we elucidate the tremendous potential of circRNAs as diagnostic markers or therapeutic targets in cervical cancer by expounding upon their biogenesis, characteristics, functions, and databases, highlighting the novel advances in the signaling pathways associated with circRNAs in cervical cancer.

Early Onset Intrahepatic Cholangiocarcinoma: Clinical Characteristics, Oncological Outcomes, and Genomic/Transcriptomic Features

INTRODUCTION

Data on clinical characteristics and disease-specific prognosis among patients with early onset intrahepatic cholangiocarcinoma (ICC) are currently limited.

METHODS

Patients undergoing hepatectomy for ICC between 2000 and 2020 were identified by using a multi-institutional database. The association of early (≤50 years) versus typical onset (>50 years) ICC with recurrence-free (RFS) and disease-specific survival (DSS) was assessed in the multi-institutional database and validated in an external cohort. The genomic and transcriptomic profiles of early versus late onset ICC were analyzed by using the Total Cancer Genome Atlas (TCGA) and Memorial Sloan Kettering Cancer Center databases.

RESULTS

Among 971 patients undergoing resection for ICC, 22.7% (n = 220) had early-onset ICC. Patients with early-onset ICC had worse 5-year RFS (24.1% vs. 29.7%, p < 0.05) and DSS (36.5% vs. 48.9%, p = 0.03) compared with patients with typical onset ICC despite having earlier T-stage tumors and lower rates of microvascular invasion. In the validation cohort, patients with early-onset ICC had worse 5-year RFS (7.4% vs. 20.5%, p = 0.002) compared with individuals with typical onset ICC. Using the TCGA cohort, 652 and 266 genes were found to be upregulated (including ATP8A2) and downregulated (including UTY and KDM5D) in early versus typical onset ICC, respectively. Genes frequently implicated as oncogenic drivers, including CDKN2A, IDH1, BRAF, and FGFR2 were infrequently mutated in the early-onset ICC patients.

CONCLUSIONS

Early-onset ICC has distinct clinical and genomic/transcriptomic features. Morphologic and clinicopathologic characteristics were unable to fully explain differences in outcomes among early versus typical onset ICC patients. The current study offers a preliminary landscape of the molecular features of early-onset ICC.

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.

Circular RNAs and cervical cancer: friends or foes? A landscape on circRNA-mediated regulation of key signaling pathways involved in the onset and progression of HPV-related cervical neoplasms

Cervical cancer (CC) is a common gynecologic malignancy, accounting for a significant proportion of women death worldwide. Human papillomavirus (HPV) infection is one of the major etiological causes leading to CC onset; however, genetic, and epigenetic factors are also responsible for disease expansion. Circular RNAs (circRNAs), which are known as a particular subset of non-coding RNA (ncRNA) superfamily, with covalently closed loop structures, have been reported to be involved in the progression of diverse diseases, especially neoplasms. In this framework, abnormally expressed circRNAs are in strong correlation with CC pathogenesis through regulating substantial signaling pathways. Also, these RNA molecules can be considered as promising biomarkers and therapeutic targets for CC diagnosis/prognosis and treatment, respectively. Herein, we first review key molecular mechanisms, including Wnt/β-catenin, MAPK, and PI3K/Akt/mTOR signaling pathways, as well as angiogenesis and metastasis, by which circRNAs interfere with CC development. Then, diagnostic, prognostic, and therapeutic potentials of these ncRNA molecules will be highlighted in depth.

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.

Circ_0057452 sponges miR-7-5p to promote keloid progression through upregulating GAB1

Increasing evidence has shown that circular RNAs (circRNAs) play critical roles in various diseases, including keloid. The purpose of this study was to investigate the role of circ_0057452 and related action mechanisms during the development of keloid. The expression levels of circ_0057452, microRNA-7-5p (miR-7-5p) and GRB2 associated binding protein 1 (GAB1) mRNA were determined by quantitative real-time PCR (qRT-PCR). Cell proliferation was evaluated using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and 5-Ethynyl-2'-deoxyuridine (Edu) assays. Flow cytometry analysis was utilized to determine cell cycle distribution and cell apoptosis. Western blot assay was used to measure apoptosis-related, collagen synthesis-related, and GAB1 protein levels. Cell migration and invasion were detected by wound healing assay and transwell assay. The interaction between miR-7-5p and circ_0057452 or GAB1 was confirmed by dual-luciferase reporter, RNA pull-down, and RNA Immunoprecipitation (RIP) assays. Circ_0057452 and GAB1 were upregulated in keloid tissues and keloid fibroblasts (KFs), while miR-7-5p was downregulated. Circ_0057452 knockdown or miR-7-5p overexpression inhibited the proliferation, migration, invasion, and collagen synthesis and induced cell cycle arrest and apoptosis of KFs. MiR-7-5p was targeted by circ_0057452, and its inhibition overturned the effects of circ_0057452 knockdown. In addition, GAB1 was a target of miR-7-5p, and GAB1 upregulation abolished the role of miR-7-5p overexpression and circ_0057452 knockdown in KFs. Circ_0057452 regulated the expression of GAB1 by adsorbing miR-7-5p in KFs. Circ_0057452 knockdown suppressed keloid development by regulating miR-7-5p/GAB1 axis, which might provide a promising therapeutic target for keloid.

The role of MiRNA ‐433 in malignant tumors of digestive tract as tumor suppressor

Background

MicroRNAs (miRNAs) are a class of short non‐coding RNAs with a length of approximate 22 nuclei acids that can be expressed both as an oncogene and tumor suppressor gene in human cancers. MiRNAs can participate in the post‐ transcriptional regulation of gene expression, and regulate the several cancer‐related processes, including proliferation, apoptosis, metastasis, etc.

Recent findings

Expression of miRNA‐433 has been reported to vary in different tumors and affected by various factors. We have summarized the different previous studies and found that miRNA‐433 can significantly inhibit the growth of the cancer cells not only in malignant tumors of the digestive tract, but also in lung cancer, breast cancer, cervical cancer, ovarian cancer, bladder cancer, renal carcinoma, glioma, retinoblastoma and osteosarcoma.

Conclusion

When the expression of miRNA‐433 was up‐regulated, the proliferation, metastasis and invasion abilities of the malignant tumor cells were significantly inhibited. At the same time, the potential mechanisms through which miRNA‐433 can suppress the growth and metastasis of the cancer cells were found to be basically the same, and involved modulation of the specific signaling pathways or target genes in the malignant tumors. Overall, it can be concluded that miRNA‐433 can serve as potential and valuable therapeutic target.

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.

Down-regulated Circ_0000190 promotes cervical cancer by facilitating the activity of proto-oncogene protein EIF4E

Circular RNAs (circRNAs), a new class of non-coding RNAs, have been recently confirmed to regulate cell development, functions and certain types of pathological responses. In addition, it has been proved that circ_0000190 can serve as a tumor suppressor in several cancers. However, the underlying mechanism and biological functions of it in cervical cancer (CC) remain to be revealed. In our study, relative expression of indicated molecules was detected by RT-qPCR analysis. Loss-of-function and gain-of-function experiments were conducted to detect cell functions. Mechanism experiments including RIP assay, luciferase reporter assay and pull down assay were applied to verify the interaction among the indicated molecules. Overexpressed circ_0000190 attenuated CC progression in vitro and in vivo. Circ_0000190 functioned through the modulation of miR-1252-5p/EIF4EBP2 axis. Rescue experiments found that miR-1252-5p overexpression or EIF4EBP2 knockdown could reverse the influence on CC cells caused by circ_0000190 overexpression. Interestingly, it was found that EIF4EBP2 could bind to proto-oncogene eIF4E and prevent eIF4E from forming into complex and functioning. Circ_0000190 served as a tumor suppressor in CC and down-regulated circ_0000190 expression could weaken the binding ability of EIF4EBP2 to eIF4E thus leading to CC tumorigenesis. In our investigation, a novel tumor suppressive gene circ_0000190 was recognized, which could be treated as a promising biomarker for the diagnosis of CC.

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.

Functions of non-coding RNAs in regulating cancer drug targets

With the development of precision medicine, the efficiency of tumor treatment has been significantly improved. More attention has been paid to targeted therapy and immunotherapy as the key to precision treatment of cancer. Targeting epidermal growth factor receptor (EGFR) has become one of the most important targeted treatments for various cancers. Comparing with traditional chemotherapy drugs, targeting EGFR is highly selective in killing tumor cells with better safety, tolerability and less side effect. In addition, tumor immunotherapy has become the fourth largest tumor therapy after surgery, radiotherapy and chemotherapy, especially immune checkpoint inhibitors. However, these treatments still produce a certain degree of drug resistance. Non-coding RNAs (ncRNAs) were found to play a key role in carcinogenesis, treatment and regulation of the efficacy of anticancer drugs in the past few years. Therefore, in this review, we aim to summarize the targeted treatment of cancers and the functions of ncRNAs in cancer treatment.

CircCDK17 knockdown inhibits tumor progression and cell glycolysis by downregulaing YWHAZ expression through sponging miR-1294 in cervical cancer

BACKGROUND

Cervical cancer (CC) is the fourth aggressive tumor affecting women worldwide. Circular RNA (circRNA) is enrolled in CC process. This study aims to unveil the profiles of circ_101119 (circCDK17) in cell proliferation, migration, invasion, apoptosis and glycolysis in CC.

METHODS

The expression levels of circCDK17, microRNA-1294 (miR-1294) and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ) mRNA were detected by quantitative real time polymerase chain reaction (qRT-PCR). The protein expression levels of YWHAZ, recombinant glucose transporter 1 (GLUT1) and hexokinase 2 (HK2) were determined by western blot. Cell proliferation, migratory and invasive abilities and apoptosis were illustrated by cell counting kit-8 (CCK-8) assay, transwell assay and flow cytometry analysis, respectively. Cell lactate production, glucose uptake and adenosine 5'-triphosphate (ATP) level were severally elucidated by lactate assay kit, glucose assay kit and ATP detection kit.

RESULTS

CircCDK17 expression and the mRNA and protein expression levels of YWHAZ were dramatically upregulated, while miR-1294 expression was obviously downregulated in CC tissues or cells compared with control groups. CircCDK17 silencing suppressed cell proliferation, migration, invasion and glycolysis, and induced cell apoptosis in CC; however, miR-1294 inhibitor restrained these effects. Additionally, circCDK17 was a sponge of miR-1294 and miR-1294 bound to YWHAZ. Furthermore, circCDK17 knockdown inhibited tumor formation in vivo.

CONCLUSION

CircCDK17 knockdown repressed cell proliferation, migration, invasion and glycolysis, and promoted cell apoptosis via miR-1294/YWHAZ axis in CC. This finding provides a theoretical basis in studying circRNA-mediated therapy in CC.

Circular RNA ZNF609 functions as a competing endogenous RNA in regulating E2F transcription factor 6 through competitively binding to microRNA-197-3p to promote the progression of cervical cancer progression

Countless studies have demonstrated that Circular RNAs (circRNAs) exert vital effects in regulating tumorigenesis of various cancers. CircRNA ZNF609 (circ-ZNF609) has been reported as an oncogene in various human cancers. Nevertheless, its regulating effect in cervical cancer (CC) remains to be further explored. RT-qPCR was adopted to measure circ-ZNF609, miR-197-3p and E2F6 levels. CC cell proliferation, migration and invasion were analyzed via CCK-8 and transwell assays. Dual-luciferase reporter assay was adopted to confirm the interaction between miR-197-3p and circ-ZNF609 or E2F6. In the present study, it was found that circ-ZNF609 was elevated in CC tissues and cell lines, and circ-ZNF609 deletion repressed cell viability, migration and invasion in CC. Moreover, circ-ZNF609 was identified to negatively regulate miR-197-3p expression in CC cells. The inhibition of miR-197-3p abrogated the inhibitory effect on CC cell proliferation, migration and invasion induced by circ-ZNF609 knockdown. Additionally, we further demonstrated that circ-ZNF609 upregulated E2F6 by interacting with miR-197-3p. Finally, rescue assays indicated that E2F6 overexpression upended the suppression of CC progression induced by circ-ZNF609 deletion. In conclusion, circ-ZNF609 promoted CC progression through modulating the miR-197-3p/E2F6 axis as an oncogene. This finding offers a unique insight into CC molecular mechanism and suggests a potential target for CC therapy.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The functions and potential roles of extracellular vesicle noncoding RNAs in gynecological malignancies

Extracellular vesicles (EVs) are small membranous vesicles secreted by multiple kinds of cells and are widely present in human body fluids. EVs containing various constituents can transfer functional molecules from donor cells to recipient cells, thereby mediating intercellular communication. Noncoding RNAs (ncRNAs) are a type of RNA transcript with limited protein-coding capacity, that have been confirmed to be enriched in EVs in recent years. EV ncRNAs have become a hot topic because of their crucial regulating effect in disease progression, especially in cancer development. In this review, we summarized the biological functions of EV ncRNAs in the occurrence and progression of gynecological malignancies. In addition, we reviewed their potential applications in the diagnosis and treatment of gynecological malignancies.

Exosome-derived microRNA-433 inhibits tumorigenesis through incremental infiltration of CD4 and CD8 cells in non-small cell lung cancer

Tumor-derived exosomal microRNAs (miRNAs/miRs) serve a vital biological role in tumorigenesis and development, but the effects and underlying mechanisms remain unclear. To explore the impact of exosomal miR-433 in non-small cell lung cancer (NSCLC) and understand its mechanism of action in NSCLC progression, the present study isolated the exosomes from the plasma of patients with NSCLC after chemotherapy and found that miR-433 expression was lower in plasma of patients with resistant NSCLC compared with in plasma of patients with sensitive NSCLC and in normal serum. Additionally, miR-433 expression was markedly negatively associated with a large tumor size, distant metastasis, advanced TNM stage and a poor prognosis in patients with NSCLC. miR-433 inhibited tumor growth by blocking the cell cycle in vitro and in vivo, as well as by promoting apoptosis and T-cell infiltration in the tumor microenvironment. Additionally, miR-433 inhibited chemoresistance to cisplatin by regulating DNA damage. Moreover, miR-433 inactivated the WNT/β-catenin signaling pathway by targeting transmembrane p24 trafficking protein 5 in NSCLC. Overall, the current findings may provide a potential prognostic biomarker and therapeutic target for patients with NSCLC.

CircMYBL2 regulates the resistance of cervical cancer cells to paclitaxel via miR-665-dependent regulation of EGFR

Circular RNAs are considered to be associated with cancer resistance. This study aims to investigate the function and mechanism of circMYBL2 in paclitaxel (PTX) resistance of cervical cancer (CC). The expression of circMYBL2, miR-665 and epidermal growth factor receptor (EGFR) was investigated using quantitative real-time polymerase chain reaction assay. Cell viability, cell colony number, cell proliferation, apoptosis and lactate dehydrogenase (LDH) were detected by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, colony formation, 5-ethynyl-2'-deoxyuridine incorporation, flow cytometry and LDH release assays, respectively. The interaction between miR-665 and circMYBL2 or EGFR was confirmed by dual-luciferase reporter assay. The protein expression levels were quantified by western blot or immunohistochemistry assay. Mice xenograft models were constructed to investigate the effect of circMYBL2 on CC tumor growth. CircMYBL2 was upregulated in CC tissues and cells, especially in PTX-resistant CC tissues and cells, and it was a stable circRNA mainly distributed in the cytoplasm. CircMYBL2 could enhance the PTX resistance of CC cells in vitro and promote CC tumor growth in vivo. Mechanistically, circMYBL2 could inhibit the PTX sensitivity and promote cell malignant behaviors in PTX-sensitive and PTX-resistant CC cells via upregulating EGFR mediated by miR-665. CircMYBL2 played a positive role in the PTX resistance and malignant activities of PTX-sensitive and PTX-resistant CC cells by regulating the miR-665/EGFR network, providing a novel therapeutic strategy for the treatment of CC patients resistant to PTX.

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.

A Systematic Review of MicroRNAs Involved in Cervical Cancer Progression

To obtain a better understanding on the role of microRNAs in the progression of cervical cancer, a systematic review was performed to analyze cervical cancer microRNA studies. We provide an overview of the studies investigating microRNA expression in relation to cervical cancer (CC) progression, highlighting their common outcomes and target gene interactions according to the regulatory pathways. To achieve this, we systematically searched through PubMed MEDLINE, EMBASE, and Google Scholar for all articles between April 2010 and April 2020, in accordance with the PICO acronym (participants, interventions, comparisons, outcomes). From 27 published reports, totaling 1721 cases and 1361 noncancerous control tissue samples, 26 differentially expressed microRNAs (DEmiRNAs) were identified in different International Federation of Gynecology and Obstetrics (FIGO) stages of cervical cancer development. It was identified that some of the dysregulated microRNAs were associated with specific stages of cervical cancer development. The results indicated that DEmiRNAs in different stages of cervical cancer were functionally involved in several key hallmarks of cancer, such as evading growth suppressors, enabling replicative immortality, activation of invasion and metastasis, resisting cell death, and sustained proliferative signaling. These dysregulated microRNAs could play an important role in cervical cancer's development. Some of the stage-specific microRNAs can also be used as biomarkers for cancer classification and monitoring the progression of cervical cancer.

Circ_0000511 accelerates the proliferation, migration and invasion, and restrains the apoptosis of breast cancer cells through the miR‑326/TAZ axis

Circular RNA 0000511 (circ_0000511) has been observed to be dysregulated in breast cancer (BC). However, the functions of circ_0000511 in breast cancer remain unknown. The expression levels of circ_0000511, ribonuclease P RNA component H1, microRNA-326 (miR-326) and transcriptional co-activator with PDZ-binding motif (TAZ) were examined by reverse transcription-quantitative PCR. Colony formation and MTT assays were conducted to analyze the cellular proliferative ability. The apoptotic rate was assessed by flow cytometry. Western blot analysis was used to evaluate the expression levels of B cell leukemia/lymphoma 2 (Bcl-2), Bcl-2 associated X apoptosis regulator, cleaved caspase-3 and TAZ. Transwell assays were performed to evaluate the migration and invasion of BC cells. The target interaction between miR-326 and circ_0000511 or TAZ was confirmed by dual-luciferase reporter assay. Xenograft assay was used to identify the function of circ_0000511 in vivo. Circ_0000511 abundance was abnormally elevated in BC tissue samples and cell lines compared with in matched normal cases. Circ_0000511 interference suppressed the proliferation, migration and invasion, and induced apoptosis of BC cells. miR-326 was a direct target of circ_0000511, and circ_0000511 silencing-mediated effects in BC cells were largely reversed by the knockdown of miR-326. miR-326 directly bound to TAZ mRNA, and TAZ accumulation largely attenuated miR-326 overexpression-induced effects in BC cells. Circ_0000511 upregulated the expression levels of TAZ partly via targeting miR-326 in BC cells. Circ_0000511 silencing restrained tumor growth in vivo. Circ_0000511 accelerated the proliferation, migration and invasion, while inhibiting the apoptosis of BC cells through upregulating TAZ expression via sponging miR-326. The circ_0000511/miR-326/TAZ axis may be a novel therapeutic target for BC treatment.

Gynecologic cancers and non-coding RNAs: Epigenetic regulators with emerging roles

Gynecologic cancers involve the female genital organs, such as the vulva, vagina, cervix, endometrium, ovaries, and fallopian tubes. The occurrence and frequency of gynecologic cancer depends on personal lifestyle, history of exposure to viruses or carcinogens, genetics, body shape, and geographical habitat. For a long time, research into the molecular biology of cancer was broadly restricted to protein-coding genes. Recently it has been realized that non-coding RNAs (ncRNA), including long noncoding RNAs (LncRNAs), microRNAs, circular RNAs and piRNAs (PIWI-interacting RNAs), can all play a role in the regulation of cellular function within gynecological cancer. It is now known that ncRNAs are able to play dual roles, i.e. can exert both oncogenic or tumor suppressive functions in gynecological cancer. Moreover, several clinical trials are underway looking at the biomarker and therapeutic roles of ncRNAs. These efforts may provide a new horizon for the diagnosis and treatment of gynecological cancer. Herein, we summarize some of the ncRNAs that have been shown to be important in gynecological cancers.

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.

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 RNA DGKB Promotes the Progression of Neuroblastoma by Targeting miR-873/GLI1 Axis

Accumulated evidences suggested that circular RNAs (circRNA) played critical roles in tumorigenesis and progression. To our knowledge, no study reported the function of circular RNA DGKB (circDGKB, circRNA ID: hsa_circ_0133622) on progression of neuroblastoma (NB). Here, we showed that circDGKB was upregulated in NB tissues compared to the normal dorsal root ganglia. Moreover, the expression level of circDGKB was negatively correlated with the survival rate of NB patients. Mechanically, overexpression of circDGKB promoted the proliferation, migration, invasion, and tumorigenesis of NB cells and reduced cell apoptosis, and vice versa. In addition, qRT-PCR and/or Western blot results showed that circDGKB overexpression inhibited the expression level of miR-873 and enhanced GLI1 expression. Moreover, miR-873 functioned an opposite role to circDGKB and significantly weakened circDGKB role in promoting NB progression. Furthermore, GLI1 upregulation also rescued the miR-873 role in inhibiting NB progression. In conclusion, our work proved that circDGKB promoted NB progression via targeting miR-873/GLI1 axis in vitro and in vivo. Our study provided a new target for NB treatment and indicated that circDGKB could act as a novel diagnostic marker for NB.

Circle RNA circABCB10 Modulates PFN2 to Promote Breast Cancer Progression, as Well as Aggravate Radioresistance Through Facilitating Glycolytic Metabolism Via miR-223-3p

Background: Breast cancer (BC) is a common tumor in women worldwide, and irradiation (IR) resistance is a major obstacle for BC therapy. Circle RNAs (circRNAs) were identified as implicated in the progression of cancer and IR resistance. However, the role of circABCB10 in BC progression and IR resistance is not well defined. Materials and Methods: The levels of circABCB10, miR-223-3p, and profilin-2 (PFN2) were detected by quantitative real-time polymerase chain reaction. The cell viability and survival rate were monitored by MTT assay. The glucose consumption, lactic acid production, LDH-A activity, and ATP production were evaluated to measure glycolysis. The protein levels of hypoxia inducible factor-1α (HIF-1α), hexokinase 2 (HK2), lactate dehydrogenase A chain (LDH-A), and PFN2 were estimated by Western blot assay. The colony formation rate was tested by colony formation assay. Dual-luciferase reporter assay was constructed to validate the interaction between miR-223-3p and circABCB10 or PFN2. The mice xenograft assay was performed to further verify the effects of circABCB10 on BC progression in vivo. Results: CircABCB10 and PFN2 were elevated, while miR-223-3p was reduced in BC tissues and cells. CircABCB10 sponged miR-223-3p, and PFN2 was a target of miR-223-3p in BC cells. CircABCB10 silencing inhibited cell proliferation, glycolysis, colony formation, and decreased IR resistance in BC cells by modulating miR-223-3p. Meanwhile, circABCB10 depletion restrained xenograft tumor growth in vivo. Also, miR-223-3p overexpression refrained cell proliferation, glycolysis, and colony formation while improving IR sensitivity in BC cells by regulating PFN2. Besides, circABCB10 knockdown declined PFN2 in BC cells via miR-223-3p. The glycolysis inhibitor 2-deoxy-D-glucose enhanced IR sensitivity in BC cells via circABCB10. Conclusion: CircABCB10 knockdown contributed to irradiation sensitivity by negatively regulating glycolysis via the miR-223-3p/PFN axis in breast cancer.

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.

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 RNAs and their emerging roles as diagnostic and prognostic biomarkers in ovarian cancer

Ovarian cancer (OC), one of the gynecologic malignancies with high invasive and metastatic potential, has a low survival rate in females. Although cytoreductive surgery combined with chemotherapy is the principal treatment for OC, the prognosis remains poor, and the recurrence rate of OC remains high. It is urgent to explore novel biomarkers for the diagnosis and prognosis of OC, as well as therapeutic targets. Circular RNAs (circRNAs) are a class of highly conserved, stable and abundant noncoding RNAs (ncRNAs). Recent studies have shown that circRNAs participate in OC progression by regulating various processes, including cell proliferation, migration, invasion and apoptosis. In addition, circRNAs are potential biomarkers for OC diagnosis and prognosis. This review provides an overview of recent findings on circRNAs in OC, including their functions and molecular mechanisms, and discusses their potential roles as diagnostic and prognostic biomarkers, as well as therapeutic targets for OC.

Circular RNAs: A novel biomarker for cervical cancer

Besides messenger RNAs, recent RNA-Seq and biochemical analysis showed another type of RNAs as a product of splicing which is named circular RNA (circRNA). Evidence demonstrated that circRNAs are abundant in the cells and are able to show cell/tissue-specific expression or tissue developmental stage which suggest that circRNAs may have regulatory potentials. In recent years, researchers have focused attention on circRNAs because of their key functions in various cellular mechanisms. CircRNAs also have the potential to be as promising biomarkers for diagnosis of various diseases such as cancer. Growing up evidence has shown the various roles of circRNAs in multiple cancers. In recent years, cervical cancer as one of the main causes of cancer death in women has been interesting for molecular research. CircRNAs are one of the novel objects which have recently been evaluated in this cancer. The improvement in our knowledge of the roles of circRNAs in cervical cancer may lead to new transcription therapeutic approaches to cervical cancer inhibition. Therefore, the purpose of this review is to review many studies which examined the role of circRNAs in cervical cancer carcinogenesis and progression up till date and to summarize possible mechanisms of action of circRNAs in cervical neoplasm.