CircRNA hsa_circRNA_0001776 inhibits proliferation and promotes apoptosis in endometrial cancer via downregulating LRIG2 by sponging miR-182

circRNAs in Endometrial Cancer-A Promising Biomarker: State of the Art

Endometrial cancer (EC) is one of the most common malignant tumors among women in the 21st century, whose mortality rate is increasing every year. Currently, the diagnosis of EC is possible only after a biopsy. However, it is necessary to find a new biomarker that will help in both the diagnosis and treatment of EC in a non-invasive way. Circular RNAs (circRNAs) are small, covalently closed spherical and stable long non-coding RNAs (lncRNAs) molecules, which are abundant in both body fluids and human tissues and are expressed in various ways. Considering the new molecular classification of EC, many studies have appeared, describing new insights into the functions and mechanisms of circRNAs in EC. In this review article, we focused on the problem of EC and the molecular aspects of its division, as well as the biogenesis, functions, and diagnostic and clinical significance of circRNAs in EC.

MicroRNA-495: a therapeutic and diagnostic tumor marker

Therapeutic and diagnostic progresses have significantly reduced the mortality rate among cancer patients during the last decade. However, there is still a high rate of mortality among cancer patients. One of the important reasons involved in the high mortality rate is the late diagnosis in advanced tumor stages that causes the failure of therapeutic strategies in these patients. Therefore, investigating the molecular mechanisms involved in tumor progression has an important role in introducing the efficient early detection markers. MicroRNAs (miRNAs) as stable factors in body fluids are always considered as non-invasive diagnostic and prognostic markers. In the present review, we investigated the role of miR-495 in tumor progression. It has been reported that miR-495 has mainly a tumor suppressor function through the regulation of transcription factors and tyrosine kinases as well as cellular processes such as multidrug resistance, chromatin remodeling, and signaling pathways. This review can be an effective step towards introducing the miR-495 as a non-invasive diagnostic/prognostic marker as well as a suitable target in tumor therapy.

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.

CircCCL22 Regulates CDC25A via Sponging miR-543 and Promotes Proliferation and Metastasis in Endometrial Cancer

Endometrial cancer (EC) is the most common gynecological tumor. Circular RNAs are a novel type of non-coding RNA that have important regulatory functions, particularly in the pathogenic progression of cancer. In this study, we investigated the function of circCCL22, and elucidated its molecular mechanism in EC progresssion. The expression of circCCL22, miR-543 and CDC25A in EC tissues and cells were determined by qRT-PCR and western blot. Cell counting kit-8, 5-ethynyl-2'-deoxyuridine, wound healing and transwell assays were executed to assess the cell viability, proliferation, migration and invasion. Dual-luciferase report assay was utilized to investigate the interaction of miR-543 with circCCL22 and CDC25A. The role of circCCL22 in EC in vivo was investigated by xenograft assay. CircCCL22 was notably upregulated in EC tissues and cells. Functionally, circCCL22 knockdown suppressed EC cell proliferation, migration and invasion in vitro, and inhibited tumor growth in vivo. Mechanistically, circCCL22 acted as "miR-543 sponges" to regulate its targeted gene CDC25A expression in EC cells. The inhibiting effect induced by circCCL22 knockdown on EC cell proliferation, migration and invasion was greatly reversed by miR-543 inhibition or CDC25A overexpression. Our results revealed that circCCL22 regulated EC progression through targeting miR-543/CDC25A axis, and it could be a novel therapeutic target of EC.

The miR-183 Cluster: Biogenesis, Functions, and Cell Communication via Exosomes in Cancer

Cancer is one of the leading causes of human death. MicroRNAs have been found to be closely associated with cancer. The miR-183 cluster, comprising miR-183, miR-96, and miR-182, is transcribed as a polycistronic miRNA cluster. Importantly, in most cases, these clusters promote cancer development through different pathways. Exosomes, as extracellular vesicles, play an important role in cellular communication and the regulation of the tissue microenvironment. Interestingly, the miR-183 cluster can be detected in exosomes and plays a functional regulatory role in tumor development. Here, the biogenesis and functions of the miR-183 cluster in highly prevalent cancers and their relationship with other non-coding RNAs are summarized. In addition, the miR-183 cluster in exosomes has also been discussed. Finally, we discuss the miR-183 cluster as a promising target for cancer therapy. This review is expected to provide a new direction for cancer treatment.

Metabolic reprogramming and interventions in endometrial carcinoma

Cancer cells are usually featured by metabolic adaptations that facilitate their growth, invasion, and metastasis. Thus, reprogramming of intracellular energy metabolism is currently one of the hotspots in the field of cancer research. Whereas aerobic glycolysis (known as the Warburg effect) has long been considered a dominant form of energy metabolism in cancer cells, emerging evidence indicates that other metabolic forms, especially oxidative phosphorylation (OXPHOS), may play a critical role at least in some types of cancer. Of note, women with metabolic syndromes (MetS), including obesity, hyperglycemia, dyslipidemia, and hypertension, have an increased risk of developing endometrial carcinoma (EC), suggesting a close link between metabolism and EC. Interestingly, the metabolic preferences vary among EC cell types, particularly cancer stem cells and chemotherapy-resistant cells. Currently, it is commonly accepted that glycolysis is the main energy provider in EC cells, while OXPHOS is reduced or impaired. Moreover, agents specifically targeting the glycolysis and/or OXPHOS pathways can inhibit tumor cell growth and promote chemosensitization. For example, metformin and weight control not only reduce the incidence of EC but also improve the prognosis of EC patients. In this review, we comprehensively overview the current in-depth understanding of the relationship between metabolism and EC and provide up-to-date insights into the development of novel therapies targeting energy metabolism for auxiliary treatment in combination with chemotherapy for EC, especially those resistant to conventional chemotherapy.

Role of circular RNA and its delivery strategies to cancer - An overview

With the passage of years and the progress of research on ribonucleic acids, the range of forms in which these molecules have been observed grows. One of them, discovered relatively recently, is circular RNA - covalently closed circles (circRNA). In recent years, there has been a huge increase in the interest of researchers in this group of molecules. It entailed a significant increase in the state of knowledge about them, which in turn caused a dramatic change in their perception. Rather than seeing circular RNAs as curiosities that represent a minor information noise in a cell or a result of RNA misprocessing, they came to be regarded as a common, essential, and potentially extremely useful group of molecules. Nevertheless, the current state of the art of circRNA is full of white cards. A lot of valuable information has been obtained from high-throughput methods to study whole transcriptomes, but many issues related to circular RNAs still need to be clarified. Presumably, each answer obtained will raise several new questions. However, circRNAs have a wealth of potential applications, including therapeutic applications.

CircSMAD2 accelerates endometrial cancer cell proliferation and metastasis by regulating the miR-1277-5p/MFGE8 axis

OBJECTIVE

Endometrial cancer (EC) is a common gynecological malignant tumor. CircRNAs play crucial roles in cancer progression and metastasis. However, the biological functions of circRNAs in EC remain largely unknown.

METHODS

CircSMAD2, miR-1277-5p, MFGE8 and relative maker protein expression in EC tissues or cell lines were analyzed by quantitative real-time polymerase chain reaction and Western blot. In vitro and in vivo functional assays, including EDU, CCK8, colony formation, transwell, tube formation and tumor xenograft assays, were conduct to explore the effects of circSMAD2 on EC. Mechanism assays were conducted to confirm the binding between miR-1277-5p and circSMAD2 or MFGE8 expression.

RESULTS

Upregulation of circSMAD2 was uncovered in both EC tissues and cell lines. Functionally, silencing of circSMAD2 apparently inhibited the proliferation, migration, invasion and angiogenesis of EC cell lines in vitro. Mechanistically, circSMAD2 sponged miR-1277-5p to upregulate MFGE8 expression. The decrease of miR-1277-5p and increase of MFGE8 were observed both in EC tissues and cell lines. Then MFGE8 knockdown or miR-1277-5p upregulation suppressed EC cell oncogenic biological behavior. Rescue experiments showed that miR-1277-5p mimics countervailed the anticancer effects of circSMAD2 silencing on EC. Besides that, MFGE8 overexpression also attenuated the inhibitory action of miR-1277-5p mimic in EC. Moreover, knockdown of circSMAD2 inhibited EC growth in vivo.

CONCLUSION

CircSMAD2 functions as an oncogene in promoting the progression of EC through miR-1277-5p/MFGE8 axis.

Bioinformatic analysis of differentially expressed profiles of lncRNAs and miRNAs with their related ceRNA network in endometrial cancer

Increasing evidence suggests that long non-coding riboneucleic acids (lncRNAs), as competing endogenous RNA (ceRNA), play a key role in the initiation, invasion, and metastasis of cancer. As a new hypothesis, the lncRNA-micro RNA (miRNA)-messenger RNA (mRNA), ceRNA regulatory network has been successfully constructed in a variety of cancers. However, lncRNA, which plays a ceRNA function in endometrial cancer (EC), is still poorly understood. In this study, we downloaded EC expression profiling from The Cancer Genome Atlas database and used the R software "edgeR" package to analyze the differentially expressed genes between EC and normal endometrium samples. Then, differentially expressed (DE) lncRNAs, miRNAs and mRNAs were selected to construct a lncRNA-miRNA-mRNA prognosis-related regulatory network based on interaction information. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed on the genes in the network to predict the potential underlying mechanisms and functions of lncRNAs in EC. Kaplan-Meier method and the log-rank test were used for survival analysis. Based on the "ceRNA hypothesis," we constructed a co-expression network of mRNA and lncRNA genes mediated by miRNA in the process of tumor genesis. Furthermore, we successfully constructed a dysregulated lncRNA-associated ceRNA network containing 96 DElncRNAs, 27 DEmiRNAs, and 74 DEmRNAs. Through Kaplan-Meier curve analysis, we found that 9 lncRNAs, 3 miRNAs, and 12 mRNAs were significantly correlated with the overall survival rate of patients among all lncRNAs, miRNAs, and mRNAs involved in ceRNA (P < .05). Our research provides a new perspective for the interaction among lncRNAs, miRNAs, and mRNA and lays the foundation for further research on the mechanism of lncRNAs in the occurrence of EC.

Circ_0075960 targets the miR-202-5p/CTNND1 axis to promote the growth and migration of endometrial carcinoma cells via regulating Wnt/β-catenin signaling activity

BACKGROUND

Endometrial carcinoma (EC) is one of the most common malignant tumors of the female reproductive tract, involving multiple molecular alterations. Circular RNA (circRNA) dysregulation is frequently observed in EC tissues, suggesting the involvement of circRNA in EC development. We aimed to investigate the role of circ_0075960 in EC.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot assays were applied for expression analysis. CCK-8, EdU, colony formation, flow cytometry and wound healing assays were employed for functional analysis. The predicted binding relationship between miR-202-5p and circ_0075960 or CTNND1 was validated by dual-luciferase reporter experiment. In vivo animal models were constructed in nude mice to verify the role of circ_0075960 in tumor growth.

RESULTS

Circ_0075960 and CTNND1 were upregulated, while miR-202-5p was downregulated in EC. Knockdown of circ_0075960 induced EC cell apoptosis, suppressed cell proliferation and migration, and repressed tumor growth in animal models. MiR-202-5p was targeted by circ_0075960 and it directly bound to CTNND1 3'UTR. The inhibition of circ_0075960 knockdown or miR-202-5p enrichment on EC cell proliferation and migration was reversed by miR-202-5p depletion or CTNND1 overexpression, respectively. Circ_0075960 targeted miR-202-5p to positively regulate CTNND1 expression. Moreover, circ_0075960 knockdown weakened the activity of Wnt/β-catenin signaling via targeting the miR-202-5p/CTNND1 axis.

CONCLUSION

Circ_0075960 targets the miR-202-5p/CTNND1 axis to modulate Wnt/β-catenin signaling activity, thus contributing to the malignant development of EC.

CircWDR26 regulates endometrial carcinoma progression via miR-212-3p-mediated typing genes MSH2

Background

Circular RNAs (circRNA) are important in mediating tumor progression, but their roles in endometrial carcinoma (EC) are not fully understood yet. Many circRNAs are dysregulated and may contribute to EC progression. The functions of circWDR26 in EC remain unknown.

Methods

The expression of circWDR26 in EC and adjacent normal tissues, and cell lines was determined by qPCR. The proliferation, apoptosis, migration, and invasion of EC cells was examined by CCK-8 assay, flow cytometry, wound healing assay and Transwell assay. The interaction between circWDR26, MSH2 and miR-212-3p was determined by luciferase assay. EC cells were inoculated into nude mice and tumor burden was determined by measuring tumor dimensions, size, and weight. The proliferative marker Ki67 in EC tissue was determined by immunohistochemistry.

Results

The expression of circWDR26 in EC tissues or cell lines was higher than in the normal tissue or endometrial epithelial cells. Downregulation of circWDR26 resulted in attenuated proliferation, increased apoptosis, reduced migration and invasion of EC cells. Mechanistically, circWDR26 targeted and suppressed the expression of miR-212-3p. We further found that MSH2 was the novel target of miR-212-3p and was upregulated by circWDR26 via inhibiting miR-212-3p. In vivo experiment demonstrated that circWDR26 was essential for EC tumor growth.

Conclusion

circWDR26 promoted EC progression by regulating miR-212-3p/MSH2 axis and provided novel insights into anti-cancer treatment.

STAT3-EMT axis in tumors: modulation of cancer metastasis, stemness and therapy response

Epithelial-to-mesenchymal transition (EMT) mechanism is responsible for metastasis of tumor cells and their spread to various organs and tissues of body, providing undesirable prognosis. In addition to migration, EMT increases stemness and mediates therapy resistance. Hence, pathways involved in EMT regulation should be highlighted. STAT3 is an oncogenic pathway that can elevate growth rate and migratory ability of cancer cells and induce drug resistance. The inhibition of STAT3 signaling impairs cancer progression and promotes chemotherapy-mediated cell death. Present review focuses on STAT3 and EMT interaction in modulating cancer migration. First of all, STAT3 is an upstream mediator of EMT and is able to induce EMT-mediated metastasis in brain tumors, thoracic cancers and gastrointestinal cancers. Therefore, STAT3 inhibition significantly suppresses cancer metastasis and improves prognosis of patients. EMT regulators such as ZEB1/2 proteins, TGF-β, Twist, Snail and Slug are affected by STAT3 signaling to stimulate cancer migration and invasion. Different molecular pathways such as miRNAs, lncRNAs and circRNAs modulate STAT3/EMT axis. Furthermore, we discuss how STAT3 and EMT interaction affects therapy response of cancer cells. Finally, we demonstrate targeting STAT3/EMT axis by anti-tumor agents and clinical application of this axis for improving patient prognosis.

Circular RNA circ_0006948 Promotes Esophageal Squamous Cell Carcinoma Progression by Regulating microRNA-3612/LASP1 Axis

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is the most prevalent malignancy worldwide. Circular RNAs (circRNAs) circ_0006948 is reported to be upregulated in ESCC cells.

AIMS

This study is designed to explore the role and mechanism of circ_0006948 in ESCC progression.

METHODS

Circ_0006948, linear FNDC3B, microRNA-3612 (miR-3612), and LIM and SH3 protein 1 (LASP1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, colony number, migration, invasion, and apoptosis were examined by Cell Counting Kit-8 (CCK-8), colony formation, transwell, and flow cytometry assays, severally. Glucose consumption, lactate production, and ATP level were measured by the corresponding kits. Protein levels of hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA), and LASP1 were assessed by western blot assay. The cytoplasmic localization of circ_0006948 was identified by the subcellular fractionation assay. The binding relationship between miR-3612 and circ_0006948 or LASP1 was predicted by starBase or TargetScan and then verified by a dual-luciferase reporter assay. The biological role of circ_0006948 on ESCC tumor growth was examined by the xenograft tumor model in vivo.

RESULTS

Circ_0006948 and LASP1 were increased, and miR-3612 was decreased in ESCC tissues and cells. Furthermore, circ_0006948 knockdown could suppress cell viability, colony number, migration, invasion, glycolysis, and boost apoptosis in ESCC cells. Mechanically, circ_0006948 could act as a sponge of miR-3612 to regulate LASP1 expression. In addition, circ_0006948 silencing inhibited ESCC tumor growth in vivo.

CONCLUSION

Circ_0006948 boosted ESCC progression partly by regulating the miR-3612/LASP1 axis, providing an underlying therapeutic target for the ESCC treatment.

Circular RNAs profiles of osteoarthritic synovium

Purposes: To identify the Circular RNAs (circRNAs) expression profile in the synovium of patients with Osteoarthritis (OA) and explore their potential regulatory mechanism. Methods: Transcriptome high-throughput sequencing was used to...

Hsa_circ_0000437 Inhibits the Development of Endometrial Carcinoma through miR-626/CDKN1B Axis

BACKGROUND

Circular RNAs (circRNAs) are pivotal in cancer biology. Nevertheless, the biological functions of circular RNA hsa_circ_0000437 (circ_0000437) have not yet been elucidated. In the present study, we studied the expression characteristics of circ_0000437 in endometrial carcinoma (EC) and explored the roles and potential mechanisms of circ_0000437 in EC progression.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was adopted to detect the expressions of circ_0000437, microRNA-626 (miR-626) and cyclin-dependent kinase inhibitor 1B (CDKN1B) in EC tissues and cells. 5-Ethynyl-2'-deoxyuridine (EdU), cell counting kit-8 (CCK-8) and Transwell assays were performed to evaluate EC cell proliferation and invasion. The expressions of CDKN1B and epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin and N-cadherin) were detected by Western blot. Moreover, the targeted relationship between miR- 626 and circ_0000437 or CDKN1B was determined by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

RESULTS

Circ_0000437 expression was reduced in EC tissues, and the low expression of circ_0000437 was positively correlated with the lymph node metastasis and high TNM stage of EC patients. Knocking down circ_0000437 promoted the proliferation, invasion and EMT of EC cells. Circ_0000437 directly targeted miR-626 and negatively modulated miR-626 expression in EC cells. CDKN1B was identified as the downstream target of miR-626 in EC cells. Besides, CDKN1B overexpression of miR-626 knockdown reversed the effects of knocking down circ_0000437 on EC cells.

CONCLUSION

Circ_0000437 regulates the miR-626/CDKN1B pathway to suppress the proliferation, invasion and EMT of EC cells. This indicates that circ_0000437 may be a promising biomarker and therapy target for EC.

A Novel Age-Related Circular RNA Circ-ATXN2 Inhibits Proliferation, Promotes Cell Death and Adipogenesis in Rat Adipose Tissue-Derived Stromal Cells

Adipose tissue-derived stromal cells are promising candidates investigating the stem cell-related treatment. However, their proportion and utility in the human body decline with time, rendering stem cells incompetent to complete repair processes in vivo. The involvement of circRNAs in the aging process is poorly understood. Rat subcutaneous adipose tissue from 10-week-old and 27-month-old rats were used for hematoxylin and eosin (H and E) staining, TUNEL staining, and circRNA sequencing. Rat adipose tissue-derived stromal cells were cultured and overexpressed with circ-ATXN2. Proliferation was examined using xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Apoptosis was induced by CoCl2 and examined using flow cytometry. RT-PCR assay and Oil Red O staining were used to measure adipogenesis at 48 h and 14 days, respectively. H and E staining showed that the diameter of adipocytes increased; however, the number of cells decreased in old rats. TUNEL staining showed that the proportion of apoptotic cells was increased in old rats. A total of 4,860 and 4,952 circRNAs was detected in young and old rats, respectively. Among them, 67 circRNAs exhibited divergent expression between the two groups (fold change ≥2, p ≤ 0.05), of which 33 were upregulated (49.3%) and 34 were downregulated (50.7%). The proliferation of circ-ATXN2-overexpressing cells decreased significantly in vitro, which was further validated by xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Overexpression of circ-ATXN2 significantly increased the total apoptotic rate from 5.78 ± 0.46% to 11.97 ± 1.61%, early apoptotic rate from 1.76 ± 0.22% to 5.50 ± 0.66%, and late apoptosis rate from 4.02 ± 0.25% to 6.47 ± 1.06% in adipose tissue-derived stromal cells. Furthermore, in circ-ATXN2-overexpressing cells, RT-PCR assay revealed that the expression levels of adipose differentiation-related genes PPARγ and CEBP/α were increased and the Oil Red O staining assay showed more lipid droplets. Our study revealed the expression profile of circRNAs in the adipose tissue of old rats. We found a novel age-related circular RNA—circ-ATXN2—that inhibits proliferation and promotes cell death and adipogenesis in rat adipose tissue-derived stromal cells.

Downregulated circular RNA hsa_circ_0005797 inhibits endometrial cancer by modulating microRNA-298/Catenin delta 1 signaling

Abnormal expression of circular RNA (circRNA) expression has been implicated in endometrial cancer (EC) progression. Thus, investigation of the mechanism of hsa_circ_0005797 during EC etiology may provide new insight into the treatment of EC. In the present study, we found that hsa_circ_0005797 expression was significantly increased in EC biological samples and cell lines, whereas its downregulation inhibited in vitro tumor cells proliferation and invasion phenotypes and suppressed tumor formation in nude mice. In mechanism, we characterized hsa_circ_0005797 as an miR-298 sponge, with CTNND1 identified as a target of miR-298. Our rescue assay data further revealed that hsa_circ_0005797 silencing inhibited EC cells proliferation and invasion via miR-298/CTNND1 signaling. In conclusion, our study confirmed hsa_circ_0005797 is a poor prognostic factor for EC and modulates EC phenotypes by regulating the hsa_circ_000579/miR-298/CTNND1 signaling, which provides potential treatment targets for EC

Circular RNA-Is the Circle Perfect?

Circular RNA (circRNA) is a distinct class of non-coding RNA produced, in principle, using a back-splicing mechanism, conserved during evolution, with increased stability and a tissue-dependent expression. Circular RNA represents a functional molecule with roles in the regulation of transcription and splicing, microRNA sponge, and the modulation of protein–protein interaction. CircRNAs are involved in essential processes of life such as apoptosis, cell cycle, and proliferation. Due to the regulatory role (upregulation/downregulation) in pathogenic mechanisms of some diseases (including cancer), its potential roles as a biomarker or therapeutic target in these diseases were studied. This review focuses on the importance of circular RNA in cancer.

Circular RNA intraflagellar transport 80 facilitates endometrial cancer progression through modulating miR-545-3p/FAM98A signaling

Objective

Endometrial cancer (ECa) is a common gynecological malignancy. Circular RNAs (circRNAs) have been identified as key regulators of human tumorigenesis and development. Herein, we explored the role and mechanism of circular RNA intraflagellar transport 80 (circ-IFT80, also called circ_0067835) in ECa.

Methods

Circ-IFT80, microRNA-545-3p (miR-545-3p), and family with sequence similarity 98 member A (FAM98A) were quantified by quantitative real-time polymerase chain reaction or Western blot. The biological characteristics of ECa cells were evaluated via Cell Counting Kit-8, 5-ethynyl-2′-deoxyuridine, transwell, tube formation and flow cytometry assays. Dual-luciferase reporter assay or RNA pull-down assay was employed to verify the binding relationship between miR-545-3p and circ-IFT80 or FAM98A. Xenograft assays were conducted to analyze the effect of circ-IFT80 in vivo.

Results

Circ-IFT80 and FAM98A were up-regulated, and miR-545-3p was down-regulated in ECa tissues and cells. Knockdown of circ-IFT80 blocked proliferation, migration, invasion and angiogenesis and promoted apoptosis in ECa cells. Moreover, circ-IFT80 harbored a binding site for miR-545-3p, and the effects of circ-IFT80 were mediated by miR-545-3p. FAM98A was a direct target of miR-545-3p, and miR-545-3p hindered ECa cell progression via targeting FAM98A. Circ-IFT80 induced FAM98A expression through miR-545-3p. Furthermore, silence of circ-IFT80 suppressed tumor growth in vivo.

Conclusion

Circ-IFT80 may promote the malignant progression of ECa cells at least in part by modulating miR-545-3p/FAM98A axis, providing a potential therapeutic target for ECa.

We further investigated the potential role of circ-IFT80 in endometrial cancer (ECa) and unveiled that circ-IFT80 accelerated the malignant progression of ECa via decoying miR-545-3p and consequently enhancing FAM98A. Our findings provided novel insights into the pathogenesis of ECa and revealed promising therapeutic targets.

circ-ACACA promotes proliferation, invasion, migration and glycolysis of cervical cancer cells by targeting the miR-582-5p/ERO1A signaling axis

Circular RNAs (circ) have been reported to serve crucial roles in the regulation of cancer occurrence and development. The present study aimed to investigate the role of circ-acetyl-CoA carboxylase α (ACACA) in the progression of cervical cancer (CC). The expression levels of circ-ACACA in several CC cell lines were first determined using reverse transcription-quantitative PCR. circ-ACACA expression was subsequently knocked down to evaluate its effects on the viability, proliferation, apoptosis, invasion and migration of CC cells using MTT, colony formation, TUNEL, transwell and wound healing assays, respectively. ¹³C-labeling of intracellular metabolites and analysis of glucose consumption and lactate production were performed to determine the levels of glycolysis. In addition, the expression levels of endoplasmic reticulum oxidoreductase 1α (ERO1α; ERO1A) and glycolysis-related proteins were analyzed using western blotting. The binding interactions among circ-ACACA, microRNA (miR)-582-5p and ERO1A were validated using dual-luciferase reporter assays. Subsequently, rescue experiments were performed to determine the potential underlying mechanism by which circ-ACACA affected CC cell functions. The results revealed that circ-ACACA expression was significantly upregulated in CC cells and silencing of circ-ACACA significantly reduced the proliferation, invasion and migration, and promoted the apoptosis of CC cells. Knockdown of circ-ACACA markedly inhibited glycolysis in CC cells. However, the effects of silencing of circ-ACACA on CC cells were reversed following transfection with the miR-582-5p inhibitor or pcDNA3.1-ERO1A overexpression plasmid. In conclusion, to the best of our knowledge, the present study was the first to investigate the role of circ-ACACA in CC progression. The results suggested that circ-ACACA may promote CC tumorigenesis and glycolysis by targeting the miR-582-5p/ERO1A signaling axis. Therefore, circ-ACACA may be a promising biomarker for CC diagnosis and treatment.

Silencing circ‑BIRC6 inhibits the proliferation, invasion, migration and epithelial‑mesenchymal transition of bladder cancer cells by targeting the miR‑495‑3p/XBP1 signaling axis

Circular RNAs (circRNAs) regulate gene expression by acting as a 'sponge' for microRNAs (miRs) and play crucial roles in tumorigenesis, including in bladder cancer (BC). circRNA‑baculoviral IAP repeat‑containing 6 (circ‑BIRC6) has been reported to participate in the pathogenesis of several cancer types. The present study aimed to elucidate the roles and potential mechanisms of circ‑BIRC6 in the progression of BC. circ‑BIRC6 expression levels in BC cell lines were determined using reverse transcription‑quantitative PCR. Following circ‑BIRC6 knockdown, cell proliferation, invasion and migration were detected using Cell Counting Kit‑8, colony formation, Transwell and wound healing assays, respectively. Western blotting was also conducted to evaluate the expression levels of X‑box binding protein 1 (XBP1) and epithelial‑mesenchymal transition (EMT)‑associated proteins. In addition, rescue experiments were performed using by transfecting a miR‑495‑3p inhibitor into T24 cells following circ‑BIRC6 knockdown. The interactions between circ‑BIRC6, miR‑495‑3p and XBP1 was verified using dual luciferase reporter assays. Moreover, T24 cells with circ‑BIRC6 knockdown and miR‑495‑3p inhibitor transfection were used for the tumor‑bearing experiment. Tumor growth was observed and Ki‑67 expression was determined using immunohistochemistry. The results demonstrated that circ‑BIRC6 expression was upregulated in BC cell lines. Moreover, circ‑BIRC6 knockdown notably attenuated the proliferation, invasion, migration and EMT of BC cells, which was blocked by the miR‑495‑3p inhibitor. It was also identified that circ‑BIRC6 sponged miR‑495‑3p to regulate XBP1 expression. In addition, results from the xenograft experiments indicated that the knockdown of circ‑BIRC6 and miR‑495‑3p expression significantly inhibited tumor growth. It was also found that the expression levels of XBP1, Ki‑67 and EMT‑associated proteins in tumor tissues of the co‑transfection group were markedly restored compared with the circ‑BIRC6 knockdown group. In conclusion, these findings demonstrated that circ‑BIRC6 knockdown suppressed BC tumorigenesis and progression via regulation of the miR‑495‑3p/XBP1 signaling axis, offering a promising therapeutic target for the treatment of BC.

Circular RNAs Regulate Glucose Metabolism in Cancer Cells

Circular RNAs (circRNAs) were originally thought to result from RNA splicing errors. However, it has been shown that circRNAs can regulate cancer onset and progression in various ways. They can regulate cancer cell proliferation, differentiation, invasion, and metastasis. Moreover, they modulate glucose metabolism in cancer cells through different mechanisms such as directly regulating glycolytic enzymes and glucose transporter (GLUT) or indirectly regulating signal transduction pathways. In this review, we elucidate on the role of circRNAs in regulating glucose metabolism in cancer cells, which partly explains the pathogenesis of malignant tumors, and provides new therapeutic targets or new diagnostic and prognostic markers for human cancers.

Circ_0091702 relieves lipopolysaccharide (LPS)-induced cell injury by regulating the miR-182/PDE7A axis in sepsis

Circular RNA (circRNA) plays an important role in the progression of sepsis. Circ_0091702 has been found to be an important regulator of sepsis progression, so its role and mechanism in sepsis progression deserve to be further explored. LPS could suppress cell viability, while enhance cell apoptosis and inflammation to induce cell injury. Circ_0091702 was downregulated in LPS-induced HK2 cells, and its overexpression alleviated LPS-induced cell injury. MiR-182 could be sponged by circ_0091702. Moreover, miR-182 inhibitor could relieve LPS-induced cell injury, and its overexpression also reversed the inhibition of circ_0091702 on LPS-induced cell injury. PDE7A was a target of miR-182, and its expression was reduced in LPS-induced HK2 cells. Additionally, silencing of PDE7A reversed the suppressive effect of circ_0091702 on LPS-induced cell injury. Our data suggested that circ_0091702 sponged miR-182 to regulate PDE7A, thereby alleviating LPS-induced cell injury in sepsis.

hsa_circ_0001610 knockdown modulates miR-646-STAT3 axis to suppress endometrial carcinoma progression

BACKGROUND

Endometrial carcinoma (EC) development is associated with dysregulated circular RNA profiles. The purpose of the current research is to study the role and mechanism of hsa_circ_0001610 (circ_0001610) in EC progression.

METHODS

circ_0001610, microRNA (miR)-646, and signal transducer and activator of transcription 3 (STAT3) expression levels were measured in EC. Functional analyses were performed using Cell Counting Kit-8, colony formation, transwell, wound healing, flow cytometry, glycolysis, and xenograft analyses. Binding association was evaluated with dual-luciferase reporter assay.

RESULTS

circ_0001610 levels were upregulated in EC samples (n = 30) and cells. circ_0001610 interference restrained cell proliferation, migration, and invasion, and promoted apoptosis. circ_0001610 downregulation constrained glycolysis through reducing glucose consumption, lactate production, and levels of adenosine triphosphate, extracellular acidification, hexokinase 2, and lactate dehydrogenase A, and increasing oxygen consumption rate. miR-646 is targeted by circ_0001610, and miR-646 inhibition attenuated interference of circ_0001610-mediated suppression of EC development. STAT3 was modulated by miR-646, and miR-646 upregulation restrained EC progression by decreasing STAT3. circ_0001610 silencing reduced STAT3 levels by sponging miR-646 and reduced the growth of xenograft tumor established by EC cells.

CONCLUSION

circ_0001610 knockdown represses EC progression through modulating the miR-646-STAT3 axis.

MicroRNA as Epigenetic Modifiers in Endometrial Cancer: A Systematic Review

Simple Summary

Endometrial cancer (EC) is the 2nd most common gynecologic cancer worldwide. MicroRNAs (miRNAs) are small noncoding RNAs that contribute to epigenetic regulation. The objective of this systematic review is to summarize our current knowledge on the role of miRNAs in the epigenetic deregulation of tumor-related genes in EC. It includes all miRNAs reported to be involved in EC including their roles in DNA methylation and RNA-associated silencing. This systematic review should be useful for development of novel strategies to improve diagnosis and risk assessment as well as for new treatments aimed at miRNAs, their target genes or DNA methylation.

Abstract

The objective of this systematic review is to summarize our current knowledge on the influence of miRNAs in the epigenetic deregulation of tumor-related genes in endometrial cancer (EC). We conducted a literature search on the role of miRNAs in the epigenetic regulation of EC applying the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The following terms were used: microRNA, miRNA, miR, endometrial cancer, endometrium, epigenetic, epimutation, hypermethylation, lynch, deacetylase, DICER, novel biomarker, histone, chromatin. The miRNAs were classified and are presented according to their function (tumor suppressor or onco-miRNA), their targets (when known), their expression levels in EC tissue vs the normal surrounding tissue, and the degree of DNA methylation in miRNA loci and CpG sites. Data were collected from 201 articles, including 190 original articles, published between November 1, 2008 and September 30, 2020 identifying 313 different miRNAs implicated in epigenetic regulation of EC. Overall, we identified a total of 148 miRNAs with decreased expression in EC, 140 miRNAs with increased expression in EC, and 22 miRNAs with discordant expression levels. The literature implicated different epigenetic phenomena including altered miRNA expression levels (miR-182, -230), changes in the methylation of miRNA loci (miR-34b, -129-2, -130a/b, -152, -200b, -625) and increased/decreased methylation of target genes (miR-30d,-191). This work provides an overview of all miRNAs reported to be involved in epigenetic regulation in EC including DNA methylation and RNA-associated silencing. These findings may contribute to novel strategies in diagnosis, risk assessment, and treatments aimed at miRNAs, their target genes or DNA methylation.

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.