Identification of circRNA-miRNA networks for exploring an underlying prognosis strategy for breast cancer

Deciphering the Functional Status of Breast Cancers through the Analysis of Their Extracellular Vesicles

Breast cancer (BC) accounts for the highest incidence of tumor-related mortality among women worldwide, justifying the growing search for molecular tools for the early diagnosis and follow-up of BC patients under treatment. Circulating extracellular vesicles (EVs) are membranous nanocompartments produced by all human cells, including tumor cells. Since minimally invasive methods collect EVs, which represent reservoirs of signals for cell communication, these particles have attracted the interest of many researchers aiming to improve BC screening and treatment. Here, we analyzed the cargoes of BC-derived EVs, both proteins and nucleic acids, which yielded a comprehensive list of potential markers divided into four distinct categories, namely, (i) modulation of aggressiveness and growth; (ii) preparation of the pre-metastatic niche; (iii) epithelial-to-mesenchymal transition; and (iv) drug resistance phenotype, further classified according to their specificity and sensitivity as vesicular BC biomarkers. We discuss the therapeutic potential of and barriers to the clinical implementation of EV-based tests, including the heterogeneity of EVs and the available technologies for analyzing their content, to present a consistent, reproducible, and affordable set of markers for further evaluation.

A tale of exosomes and their implication in cancer

Cancer is a cause of high deaths worldwide and also a huge burden for the health system. Cancer cells have unique properties such as a high rate of proliferation, self-renewal, metastasis, and treatment resistance, therefore, the development of novel diagnoses of cancers is a tedious task. Exosomes are secreted by virtually all cell types and have the ability to carry a multitude of biomolecules crucial for intercellular communication, hence, contributing a crucial part in the onset and spread of cancer. These exosomal components can be utilized in the development of markers for diagnostic and prognostic purposes for various cancers. This review emphasized primarily the following topics: exosomes structure and functions, isolation and characterization strategies of exosomes, the role of exosomal contents in cancer with a focus in particular on noncoding RNA and protein, exosomes, and the cancer microenvironment interactions, cancer stem cells, and tumor diagnosis and prognosis based on exosomes.

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.

Non-Coding RNAs Modulating Estrogen Signaling and Response to Endocrine Therapy in Breast Cancer

The largest part of human DNA is transcribed into RNA that does not code for proteins. These non-coding RNAs (ncRNAs) are key regulators of protein-coding gene expression and have been shown to play important roles in health, disease and therapy response. Today, endocrine therapy of ERα-positive breast cancer (BC) is a successful treatment approach, but resistance to this therapy is a major clinical problem. Therefore, a deeper understanding of resistance mechanisms is important to overcome this resistance. An increasing amount of evidence demonstrate that ncRNAs affect the response to endocrine therapy. Thus, ncRNAs are considered versatile biomarkers to predict or monitor therapy response. In this review article, we intend to give a summary and update on the effects of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) on estrogen signaling in BC cells, this pathway being the target of endocrine therapy, and their role in therapy resistance. For this purpose, we reviewed articles on these topics listed in the PubMed database. Finally, we provide an assessment regarding the clinical use of these ncRNA types, particularly their circulating forms, as predictive BC biomarkers and their potential role as therapy targets to overcome endocrine resistance.

The Effects of circ_000558/miR-1225-5p/ARL4C on Regulating the Proliferation of Renal Cell Carcinoma Cells

Renal cell carcinoma (RCC) is one of the top ten tumors over the world. RCC is not sensitive to radiotherapy and chemotherapy. Therefore, it is necessary to find new targets for the treatment. CircRNAs are a special type of noncoding RNAs, which play important roles in many types of cancer. In this study, we found circ_000558 was upregulated in RCC cells, and it elevated the proliferation ability of RCC cells. The relationship between miR-1225-5p and circ_000558 or ARL4C was predicted via circBank and circular RNA interactome and confirmed by dual-luciferase reporter assay. Then, the effects of circ_000558/miR-1225-5p/ARL4C on RCC cell proliferation and apoptosis were assessed by CCK-8 assay. The results revealed that the knockdown of ARL4C significantly reduced RCC cell proliferation and overexpression of circ_000558 could significantly induce RCC cell proliferation after miR-1225-5p treatment further promoted the inhibitory ability of ARL4C knockdown. Overall, our study suggested that circ_000558/miR-1225-5p/ARL4C network was related to the RCC cell proliferation. This finding could provide new targets for the treatment and prognosis of RCC.

Expression and clinical value of circRNAs in serum extracellular vesicles for gastric cancer

Objective

At present, there are still no effective diagnosis methods for gastric cancer (GC). Increasing evidences indicate that Extracellular Vesicle circular RNAs (EV circRNAs) play a crucial role in several diseases. However, their correlations with GC are not clarified. This study aims to investigate the expression profile of serum EV circRNAs in GC and evaluate its potential clinical value.

Methods

High-throughput RNA sequencing (RNA-seq) was used to assess circRNA expression profiles between 4 patients with GC and 4 healthy controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were employed to determine the biological functions of differentially expressed (DE) circRNAs. A circRNA-miRNA-mRNA network was constructed using bioinformatics tools. Reverse transcription-quantitative polymerase chain reaction (RT-q)PCR was used to validate the dysregulated circRNAs. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic value of circRNAs for GC.

Results

A total of 4692 circRNAs were detected in the serum EVs of healthy controls and patients with GC, most of which were novel (98%) and intergenic (52%). 7 circRNAs were upregulated and 4 circRNAs were downregulated (|log₂Fold Change| > 2, P < 0.05). GO and KEGG pathway enrichment analyses revealed that DE circRNAs were primarily involved in glutathione metabolism, protein folding, and drug metabolism-cytochrome P450. Of these, 3 circRNAs (Chr10q11, Chr1p11, and Chr7q11) were identified to be significantly overexpressed in patients with GC compared with healthy controls using RT-qPCR. The combination of 3 EV circRNAs and carcinoembryonic antigen (CEA) produced an area under the curve (AUC) of 0.866 (95%CI: 0.803-0.915) with a sensitivity and specificity of 80.4% and 81.8%, respectively. Additionally, the expression levels of 3 EV circRNAs were significantly correlated with tumor size, lymph node metastasis, and TNM stage. The circRNA-miRNA-mRNA network showed that the 3 identified circRNAs were predicted to interact with 13 miRNAs and 91 mRNAs.

Conclusion

Our results illustrate that the panel of EV circRNAs in serum are aberrantly expressed and may act as the suitable biomarkers for gastric cancer.

Spotlight on Exosomal Non-Coding RNAs in Breast Cancer: An In Silico Analysis to Identify Potential lncRNA/circRNA-miRNA-Target Axis

Breast cancer (BC) has recently become the most common cancer type worldwide, with metastatic disease being the main reason for disease mortality. This has brought about strategies for early detection, especially the utilization of minimally invasive biomarkers found in various bodily fluids. Exosomes have been proposed as novel extracellular vesicles, readily detectable in bodily fluids, secreted from BC-cells or BC-tumor microenvironment cells, and capable of conferring cellular signals over long distances via various cargo molecules. This cargo is composed of different biomolecules, among which are the novel non-coding genome products, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and the recently discovered circular RNA (circRNA), all of which were found to be implicated in BC pathology. In this review, the diverse roles of the ncRNA cargo of BC-derived exosomes will be discussed, shedding light on their primarily oncogenic and additionally tumor suppressor roles at different levels of BC tumor progression, and drug sensitivity/resistance, along with presenting their diagnostic, prognostic, and predictive biomarker potential. Finally, benefiting from the miRNA sponging mechanism of action of lncRNAs and circRNAs, we established an experimentally validated breast cancer exosomal non-coding RNAs-regulated target gene axis from already published exosomal ncRNAs in BC. The resulting genes, pathways, gene ontology (GO) terms, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis could be a starting point to better understand BC and may pave the way for the development of novel diagnostic and prognostic biomarkers and therapeutics.

Prospect of exosomal circular RNAs in breast Cancer: presents and future

Implementing precision oncology for breast cancer (BC) is a critical method for improving patient outcomes, which relies on the use of reliable biomarkers to be effective and safe. exosomes represent a potential alternative for the diagnosis and therapy of BC, As a "liquid biopsy" and a novel source for biomarkers. Exosomes are nanoscale phospholipid bilayer vesicles released by most cells that contain a large payload of various RNA species that can alter recipient cell activity. Circular RNAs (circRNAs) were recently revealed as a looping subclass of competing endogenous noncoding RNAs (ceRNAs) capable of microRNA sponging to regulate gene expression. They provide critical regulatory functions in carcinogenesis, proliferation, invasion, metastasis, and treatment resistance, as well as cancer prognostic. However, there is still a major gap in our understanding of the role of circRNA in the advancement of BC. CircRNAs are abundant in exosomes, according to various studies, and exosomal circRNAs (exo-circRNAs) play a significant role in cancer biology. Exo-circRNAs can be picked up by nearby or distant cells, affecting many features of the target cells' pathophysiological states, thus boosting cell communication and tumor spread. In this review, we have briefly summarized the major properties and functions of exosomes. Then, we have focused on exo-circRNAs, discussing their potential roles in both driving and inhibiting BC, as well as for cancer diagnosis, prognosis, and monitoring.

CircCDR1 sponges miR-1290 to regulate cell proliferation, migration, invasion, and apoptosis in esophageal squamous cell cancer

Since circCDR1 was abnormally expressed in esophageal squamous cell cancer (ESCC), the current study explored whether circCDR1 affected ESCC. Detailedly, circCDR1 expression in ESCC and linear isoform and stability of circCDR1 were detected by RT-qPCR. The location of circCDR1 was detected by fluorescence in situ hybridization (FISH). After transfection, the cell biological functions were detected by wound-healing, CCK-8, colony formation, and flow cytometry assays. The target of circCDR1 was predicted by bioinformatics, FISH, RNA pull-down, and dual-luciferase reporter assays. The correlation between circCDR1 and miR-1290 was analyzed by Pearson's correlation analysis. A subcutaneous-xenotransplant tumor model in BALB/c nude mice was established and the levels of circCDR1, miR-1290, and apoptosis/metastasis/proliferation-related factors in the cancer cells and tissues were detected by immunohistochemical analysis, western blot, or RT-qPCR. As a result, circCDR1 was low-expressed in ESCC tissues and cells, while miR-1290 was high-expressed. CircCDR1 was regulated and was negatively correlated with miR-1290. CircCDR1, located in cytoplasm, inhibited the viability, proliferation, migration, and invasion of the cancer cells and the expressions of Bcl-2, N-cadherin, and Vimentin, but enhanced cell apoptosis and the expressions of C caspase-3, Bax, E-cadherin, IGFBP4, LHX6 and NFIX. In vivo, circCDR1 promoted xenotransplanted tumor weight and volume, and the expressions of C caspase-3 and Bax yet suppressed the levels of Bcl-2, miR-1290, and Ki-67 in tumor tissues. The effects of circCDR1 on both cancer cells and tissues were opposite to and reversed by miR-1290 mimic. Collectively, circCDR1 sponged miR-1290 to regulate the progression of ESCC both in vitro and in vivo.

Role of exosomal competitive endogenous RNA (ceRNA) in diagnosis and treatment of malignant tumors

Malignant tumors are a threat to human health, thus it is critical to better understand the mechanism of tumor occurrence and development and to find key therapeutic targets. Competitive endogenous RNA (ceRNA) is a type of RNA molecule that includes mRNA of coding-protein, pseudogenes, long non-coding RNA (lncRNA), and circular RNA (circRNA) etc. It is created through a competitive combination of common small RNA (miRNA) and has an inhibitory effect on mRNA translation. ceRNA regulate the post transcriptional expression of genes by competitively binding to common microRNAs (miRNAs).Studies have shown that cernas are involved in tumor cell proliferation, invasion and migration, drug resistance, angiogenesis, as well as tumor immunity, and so on, affecting the progression of tumor development. This article reviews the reported roles of exosomal ceRNA in the diagnosis and treatment of malignant tumors and the mechanisms underlying these.

Roles and clinical application of exosomal circRNAs in the diagnosis and treatment of malignant tumors

Exosomes are microvesicles secreted by cells. They contain a variety of bioactive substances with important roles in intercellular communication. Circular RNA (circRNA), a type of nucleic acid molecule found in exosomes, forms a covalently bonded closed loop without 5′ caps or 3′ poly(A) tails. It is structurally stable, widely distributed, and tissue specific. CircRNAs mainly act as microRNA sponges and have important regulatory roles in gene expression; they are superior to other non-coding RNAs as molecular diagnostic markers and drug treatment targets. Exosomal-derived circRNAs in the body fluids of tumor patients can modulate tumor proliferation, invasion, metastasis, and drug resistance. They can be used as effective biomarkers for early non-invasive diagnosis and prognostic evaluation of tumors, and also represent ideal targets for early precision therapeutic intervention. This review provides a theoretical basis for exploring the applications of exosomal circRNAs in malignant tumor diagnosis and treatment. We describe the biological functions of exosomal circRNAs in the occurrence and development of malignant tumors, their potential utility in diagnosis and treatment, and possible mechanisms.

Circular RNAs as Potential Biomarkers in Breast Cancer

Due to the high heterogeneity and initially asymptomatic nature of breast cancer (BC), the management of this disease depends on imaging together with immunohistochemical and molecular evaluations. These tests allow early detection of BC and patient stratification as they guide clinicians in prognostication and treatment decision-making. Circular RNAs (circRNAs) represent a class of newly identified long non-coding RNAs. These molecules have been described as key regulators of breast carcinogenesis and progression. Moreover, circRNAs play a role in drug resistance and are associated with clinicopathological features in BC. Accumulating evidence reveals a clinical interest in deregulated circRNAs as diagnostic, prognostic and predictive biomarkers. Furthermore, due to their covalently closed structure, circRNAs are highly stable and easily detectable in body fluids, making them ideal candidates for use as non-invasive biomarkers. Herein, we provide an overview of the biogenesis and pleiotropic functions of circRNAs, and report on their clinical relevance in BC.

Circular RNA-associated ceRNA network involved in HIF-1 signalling in triple-negative breast cancer: circ_0047303 as a potential key regulator

The aggressive and highly metastatic nature of triple‐negative breast cancer (TNBC) causes patients to suffer from the poor outcome. HIF‐1 signalling pathway is a prominent pathway that contributes to angiogenesis and metastasis progression in tumours. On the contrary, the undeniable importance of circular RNAs (circRNAs) as multifunctional non‐coding RNAs (ncRNAs) has been identified in breast cancer. These ncRNAs owing to their high stability and specificity have been becoming a hotspot in cancer researches. circRNAs act as competing endogenous RNAs (ceRNAs) and compete with mRNAs for shared miRNAs, thus modulate gene expression. Since the most dysregulated biological functions in TNBC are associated with cellular invasion, understanding the molecular pathogenesis of these processes is a crucial step towards the development of new treatment approaches. The purpose of this study is to undermine the circRNA‐associated ceRNA network involved in HIF‐1 signalling in TNBC using an integrative bioinformatics approach. In the next step, the novel circ_0047303‐mediated ceRNA regulatory axes have been extracted and validated across TNBC samples. We show that circ_0047303 has the highest degree in the circRNA‐associated ceRNA network and shows a significant up‐expression in TNBC. Moreover, our results suggest that circ_0047303 could mediate the upregulation of key angiogenesis‐related genes, including HIF‐1, EIF4E2 and VEGFA in TNBC through sponging the tumour‐suppressive miRNAs. The circ_0047303 could be a promising molecular biomarker and/or therapeutic target for TNBC.

Tumor-Derived Exosomal Non-Coding RNAs: The Emerging Mechanisms and Potential Clinical Applications in Breast Cancer

Breast cancer (BC) is the most frequent malignancy and is ranking the leading cause of cancer-related death among women worldwide. At present, BC is still an intricate challenge confronted with high invasion, metastasis, drug resistance, and recurrence rate. Exosomes are membrane-enclosed extracellular vesicles with the lipid bilayer and recently have been confirmed as significant mediators of tumor cells to communicate with surrounding cells in the tumor microenvironment. As very important orchestrators, non-coding RNAs (ncRNAs) are aberrantly expressed and participate in regulating gene expression in multiple human cancers, while the most reported ncRNAs within exosomes in BC are microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Notably, ncRNAs containing exosomes are novel frontiers to shape malignant behaviors in recipient BC cells such as angiogenesis, immunoregulation, proliferation, and migration. It means that tumor-derived ncRNAs-containing exosomes are pluripotent carriers with intriguing and elaborate roles in BC progression via complex mechanisms. The ncRNAs in exosomes are usually excavated based on specific de-regulated expression verified by RNA sequencing, bioinformatic analyses, and PCR experiments. Here, this article will elucidate the recent existing research on the functions and mechanisms of tumor-derived exosomal miRNA, lncRNA, circRNA in BC, especially in BC cell proliferation, metastasis, immunoregulation, and drug resistance. Moreover, these tumor-derived exosomal ncRNAs that existed in blood samples are proved to be excellent diagnostic biomarkers for improving diagnosis and prognosis. The in-depth understanding of tumor-derived exosomal ncRNAs in BC will provide further insights for elucidating the BC oncogenesis and progress and exploring novel therapeutic strategies for combating BC.

Circular RNA Foxo3 enhances progression of ovarian carcinoma cells

Background: Ovarian carcinoma (OC) is the deadliest gynecologic malignancy in females worldwide. Circular RNA Foxo3 (Foxo3) plays essential roles in various cancers. However, the detailed function of Foxo3 in OC remains unclear. This study aimed to investigate the role of Foxo3 in OC and the underlying molecular mechanism.

Methods: The abundance of Foxo3 was detected in OC cell lines by qPCR. Lentivirus transduction, CCK-8, wound healing assays, transwell migration and invasion assays, luciferase reporter assay, western blotting, fluorescence in situ hybridization (FISH), transmission electron microscopy, nanoparticle tracking analysis, and bioinformatics analysis were performed to investigate the underlying mechanism.

Results: The results demonstrated that Foxo3 was significantly upregulated in OC cell lines. Overexpression and knockdown of Foxo3 promoted and inhibited the proliferation, migration, and invasion of OC cells, respectively. Foxo3 could bind to miR-422a to negatively regulate miR-422a expression. Also, proteolipid protein 2 (PLP2) was a targeting gene of miR-422a. Additionally, Foxo3 was highly expressed in exosomes derived from OC cells. Furthermore, Foxo3 could be shuttled to OC cells by exosomes and promoted OC progression.

Conclusions: Foxo3 promoted OC progression through exosome-mediated intercellular interaction to target miR-422a/PLP2 axis. Foxo3 may serve as a potential biomarker for OC.

EIF4A3-mediated hsa_circ_0088088 promotes the carcinogenesis of breast cancer by sponging miR-135-5p

Circular RNAs have participated in oncology progress. Nevertheless, the potential mechanisms are not completely understood. We intended to inspect the functions of hsa_circ_0088088 on breast malignancy, together with the possible mechanism(s). hsa_circ_0088088 expression in breast malignancy was studied using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). The overall survival was studied by the Kaplan-Meier curve. The biological functions of hsa_circ_0088088 aberrant expression on cell growth and metastasis were evaluated in MDA-MB-231 cells. Bioinformatics analysis, RNA immunoprecipitation (RIP), and qRT-PCR were accomplished to confirm the possible regulatory effects of eukaryotic initiation factor 4A3 (EIF4A3) on the biogenesis of hsa_circ_0088088. Furthermore, a dual-luciferase reporter assay, qRT-PCR, and RNA pull-down assay were used to confirm the association between the hsa_circ_0088088 and miR-135-5p in MDA-MB-231 cells. hsa_circ_0088088 was upregulated in the tumor tissues and cells, and higher expression presented an unfavorable prognosis. hsa_circ_0088088 overexpression promoted cell growth and metastasis in MDA-MB-231 cells. EIF4A3 was found to positively regulate hsa_circ_0088088. Furthermore, we confirmed that hsa_circ_0088088 sponges miR-135-5p and directly targets miR-135-5p with respect to the cell growth and metastasis in MDA-MB-231 cells. Our data suggest that EIF4A3-induced hsa_circ_0088088 stimulates the carcinogenic effects of breast tumors by sponging miR-135-5p.

Emerging important roles of circRNAs in human cancer and other diseases

CircRNAs are a large class of endogenous single-stranded RNA that is different from other linear RNA, which are produced by back-splicing and fusion of either exons, introns, or both exon-intron into covalently closed loops. CircRNAs are found in almost all living organisms and have emerged as potentially important players effecting on all life activities. It was characterized by stable structure, resistant to RNA degradation, highly abundance and conservation and tissue-specific expression. Early circRNAs were ignored as a by-product of meaningless abnormally cut RNA and had little biological function. Currently, circRNAs have become a research hotspot due to its special characteristics. CircRNAs could function as miRNA sponges, interfere with splicing and bind to protein to regulate the expression of parental genes and so on. In recent years, an increasing number of studies have revealed that circRNAs are closely related to a series of physiological and pathological processes. Additionally, circRNAs play an important role in the occurrence and development of a variety of diseases, suggesting circRNAs may be as novel indicators or biomarkers for cancer and other diseases with which they are associated. In this article, we review the biogenesis, biological functions of circRNAs and recent advances in circRNAs research in human diseases. Results will provide new insights on the roles and new ideas of circRNAs for the diagnosis and treatment of diseases and possible directions and approach for future circRNA applications.

Tumor-derived exosomal components: the multifaceted roles and mechanisms in breast cancer metastasis

Breast cancer (BC) is the most frequently invasive malignancy and the leading cause of tumor-related mortality among women worldwide. Cancer metastasis is a complex, multistage process, which eventually causes tumor cells to colonize and grow at the metastatic site. Distant organ metastases are the major obstacles to the management of advanced BC patients. Notably, exosomes are defined as specialized membrane-enclosed extracellular vesicles with specific biomarkers, which are found in a wide variety of body fluids. Recent studies have demonstrated that exosomes are essential mediators in shaping the tumor microenvironment and BC metastasis. The transferred tumor-derived exosomes modify the capability of invasive behavior and organ-specific metastasis in recipient cells. BC exosomal components, mainly including noncoding RNAs (ncRNAs), proteins, lipids, are the most investigated components in BC metastasis. In this review, we have emphasized the multifaceted roles and mechanisms of tumor-derived exosomes in BC metastasis based on these important components. The underlying mechanisms mainly include the invasion behavior change, tumor vascularization, the disruption of the vascular barrier, and the colonization of the targeted organ. Understanding the significance of tumor-derived exosomal components in BC metastasis is critical for yielding novel routes of BC intervention.

Inhibitory role of circRNA_100395 in the proliferation and metastasis of prostate cancer cells

OBJECTIVE

Circular RNAs (circRNAs) are non-coding RNAs with high cancer-specific expression and the potential for regulating tumorigenesis. CircRNA_100395 is expressed at low levels in many cancers and is involved in the regulation of tumor cell proliferation and metastasis. However, its expression and function in prostate cancer remain unclear.

METHODS

Endogenous expression levels of circRNA_100395 and microRNA-1228 (miR-1228) in prostate cancer tissue samples and cell lines were detected by quantitative reverse transcription-polymerase chain reaction. Cell proliferation, invasion, and migration, cell cycle distribution, and epithelial-mesenchymal transition (EMT) were analyzed in circRNA_100395-overexpressing prostate cancer cells by Cell Counting Kit-8, flow cytometry, Transwell assay, and western blotting, respectively.

RESULTS

CircRNA_100395 expression was downregulated in cancerous prostate tissues relative to adjacent normal tissues. CircRNA_100395 expression was negatively correlated with tumor size, Gleason score, tumor stage, and lymph node metastasis. Moreover, circRNA_100395 overexpression inhibited cell proliferation, altered cell cycle distribution, reduced cell migration and invasion abilities, and suppressed EMT in prostate cancer cells. Moreover, miR-1228 was a direct downstream target of circRNA_100395, and the anti-tumor ability of circRNA_100395 was significantly reversed by miR-1228.

CONCLUSION

This study identified circRNA_100395 as an anti-tumor circRNA and a potential therapeutic target for prostate cancer.

Circular RNAs: Their Role in the Pathogenesis and Orchestration of Breast Cancer

As one of the most frequently occurring malignancies in women, breast cancer (BC) is still an enormous threat to women all over the world. The high mortality rates in BC patients are associated with BC recurrence, metastatic progression to distant organs, and therapeutic resistance. Circular RNAs (circRNAs), belonging to the non-coding RNAs (ncRNAs), are connected end to end to form covalently closed single-chain circular molecules. CircRNAs are widely found in different species and a variety of human cells, with the features of diversity, evolutionary conservation, stability, and specificity. CircRNAs are emerging important participators in multiple diseases, including cardiovascular disease, inflammation, and cancer. Recent studies have shown that circRNAs are involved in BC progress by regulating gene expression at the transcriptional or post-transcriptional level via binding to miRNAs then inhibiting their function, suggesting that circRNAs may be potential targets for early diagnosis, treatment, and prognosis of BC. Herein, in this article, we have reviewed and summarized the current studies about the biogenesis, features, and functions of circRNAs. More importantly, we emphatically elucidate the pivotal functions and mechanisms of circRNAs in BC growth, metastasis, diagnosis, and drug resistance. Deciphering the complex networks, especially the circRNA-miRNA target gene axis, will endow huge potentials in developing therapeutic strategies for combating BC.

The Role of Exosomes in the Female Reproductive System and Breast Cancers

Exosomes are nanoscale extracellular vesicles released by nearly all cell types. Exosomes were originally considered as waste receptacles for discarding unwanted cellular products; however, these organelles are now considered to be important for cell communication by delivering biologically active molecules such as proteins, DNA, non-coding RNA and mRNA. Studies have revealed that exosomes are closely related to several diseases, especially cancers. Exosomes are indispensable for the emergence and progression of tumor. Here, we review the status of research on exosomes in the female reproductive system cancers and breast cancer, focusing on their biological roles in chemical resistance and immune responses, as well as their underlying applications in drug delivery and nanotherapy and as biological markers for tumor diagnosis.

Research on the circular RNA bioinformatics in patients with acute myocardial infarction

OBJECTIVE

Through the detection of circular RNA (circRNA) using expression profiling chips, we searched for circRNAs related to acute myocardial infarction (AMI) and explored their relationship and possible mechanisms with AMI.

METHOD

The study subjects included 3 AMI patients and 3 controls, and circRNA expression profiling analysis was performed using a microarray gene chip to identify circRNAs with large differences in expression between groups and to construct a circRNA-miRNA network.

RESULTS

Compared with the control group, there were 650 differentially expressed circRNAs found in AMI patients (P < .05, fold change > 2), including 535 up-regulated circRNAs, such as hsa_circ_0050908, hsa_circRNA4010-22, hsa_circ_0081241, hsa_circ_0010551, hsa_circRNA4010-20, hsa_circRNA14702, hsa_circ_0115392, has_circRNA1825-44, has_circRNA8493-7, and hsa_circ_0025097. Furthermore, there were 115 down-regulated circRNAs, such as hsa_circ_0066439, hsa_circ_0054211, hsa_circ_0095920, hsa_circ_0122984, hsa_circ_0113067, hsa_circ_0039155, hsa_circRNA4014-45, hsa_circ_0122979, hsa_circ_0059665, and hsa_circ_0009319. The circRNAs hsa_circ_0066439, hsa_circ_0081241, and hsa_circ_0122984 can regulate multiple signal pathways to participate in the AMI process through hsa-miR-1254, hsa-miR-328-5p, and other miRNAs. In addition, the expression of circRNA-miRNA in peripheral blood is related to the network. Differentially expressed circRNAs are involved in chromatin organization, chromatin-modifying enzymes, signal transduction, lysine degradation, the mitogen-activated protein kinase (MAPK) signaling pathway, focal adhesion, and a variety of other pathways, such as myocardial infarction, coronary heart disease, hypertension, and other diseases. The gene ontology analysis results show that molecular function mainly involves binding and molecular structural activity, whereas the biological process mainly involves a single biological process, a cellular component for organization, and a cellular process, and the cellular component mainly involves a protein complex, an extracellular matrix, and a membrane.

CONCLUSION

circRNA and microRNA interact to participate in the development of AMI. circRNA may be involved in the pathogenesis of AMI.

ceRNA network development and tumour-infiltrating immune cell analysis of metastatic breast cancer to bone

PURPOSE

Advanced breast cancer commonly metastasises to bone; however, the molecular mechanisms underlying the affinity for breast cancer cells to bone remains unclear. Thus, we developed nomograms based on a competing endogenous RNA (ceRNA) network and analysed tumour-infiltrating immune cells to elucidate the molecular pathways that may predict prognosis in patients with breast cancer.

METHODS

We obtained the RNA expression profile of 1091 primary breast cancer samples included in The Cancer Genome Atlas database, 58 of which were from patients with bone metastasis. We analysed the differential RNA expression patterns between breast cancer with and without bone metastasis and developed a ceRNA network. Cibersort was employed to differentiate between immune cell types based on tumour transcripts. Nomograms were then established based on the ceRNA network and immune cell analysis. The value of prognostic factors was evaluated by Kaplan-Meier survival analysis and a Cox proportional risk model.

RESULTS

We found significant differences in long non-coding RNAs (lncRNAs), 18 microRNAs (miRNAs), and 20 messenger RNAs (mRNAs) between breast cancer with and without bone metastasis, which were used to construct a ceRNA network. We found that the protein-coding genes GJB3, CAMMV, PTPRZ1, and FBN3 were significantly differentially expressed by Kaplan-Meier analysis. We also observed significant differences in the abundance of plasma cell and follicular helper T cell populations between the two groups. In addition, the proportion of mast cells, gamma delta T cells, and plasma cells differed depending on disease location and stage. Our analysis showed that a high proportion of follicular helper T cells and a low proportion of eosinophils promoted survival and that DLX6-AS1, Wnt6, and GABBR2 expression may be associated with bone metastasis in breast cancer.

CONCLUSIONS

We developed a bioinformatic tool for exploring the molecular mechanisms of bone metastasis in patients with breast cancer and identified factors that may predict the occurrence of bone metastasis.

Exosome-Shuttled circSHOC2 from IPASs Regulates Neuronal Autophagy and Ameliorates Ischemic Brain Injury via the miR-7670-3p/SIRT1 Axis

The aim of the present study was to investigate the neuroprotective roles and mechanisms of the circular RNA circSHOC2 in ischemic-preconditioned astrocyte-derived exosomes (IPAS-EXOs) against ischemic stroke. We established an ischemia model based on oxygen glucose deprivation (OGD) in vitro and isolated resultant exosomes from astrocytes. Neuronal viability and apoptosis were determined by Cell Counting Kit-8 (CCK-8) assays and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) staining, respectively. Autophagy-related proteins were analyzed by western blotting. We found that exosomes derived from IPAS-preconditioned medium (IPAS-CM) exerted neuroprotection. Furthermore, circSHOC2 expression was significantly upregulated in exosomes released from IPAS-CM. Overexpression of circSHOC2 in neurons yielded the same protective effects as those from IPAS-EXOs in vitro, and similar results were also observed in the middle cerebral artery occlusion (MCAO) mouse model. Mechanistically, circSHOC2 reduced neuronal apoptosis via regulating autophagy. Furthermore, circSHOC2 was found to sponge miR-7670-3p, which regulated SIRT1 expression. Transfection with an miR-7670-3p small interfering RNA (siRNA) (siRNA-7670-3p) and incubation with circSHOC2 extracellular vesicles attenuated ischemia-induced neuronal apoptosis in vivo and in vitro, while silencing of SIRT1 reversed the protective effects of exosomal circSHOC2 on hypoxic cerebral neurons. Taken together, our findings indicate that circSHOC2 in IPAS-EXOs suppressed neuronal apoptosis and ameliorated neuronal damage by regulating autophagy and acting on the miR-7670-3p/SIRT1 axis, which might contribute to a therapeutic strategy for ischemic stroke treatment.

The emerging roles of exosomal circRNAs in diseases

Exosomes, the nanoscale phospholipid bilayer vesicles, enriched in selected proteins, nucleic acids and lipids, which they participated in a variety of biological processes in the body, including physiology and pathology. CircRNAs (circular RNAs) are a class of single-stranded closed molecules with tissue development specific expression patterns that have crucial regulatory functions in various diseases. Non-coding RNAs (such as microRNAs and long non‑coding RNAs) in exosomes have also been shown to play an important regulatory role in humans. However, little research has focused on exosomal circRNAs. Recently, CircRNAs have been identified to be enriched and stably expressed in exosomes. In this review, we summarize the biogenesis and biological functions of exosomes and circRNA, and further revealed the potential role of exosome-derived circRNA in different diseases. Besides, we propose its use as a diagnostic marker and therapeutic punctuation for diseases, especially in cancer.

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.

Blocking circ_0000520 Suppressed Breast Cancer Cell Growth, Migration and Invasion Partially via miR-1296/SP1 Axis Both in vitro and in vivo

Background

Breast cancer (BCa) is an overwhelming malignant tumor mainly in women globally. Circular RNAs (circRNAs) are a special type of noncoding RNAs involved in competing endogenous RNA (ceRNA) network, a classic molecular mechanism of the tumorigenesis of human cancers, including BCa. Here, we intended to explore the role and mechanism of hsa_circ_0000520 (circ_0000520) in BCa cells.

Methods

Expression of circ_0000520, miRNA-1296-5p (miR-1296) and specificity protein 1 (SP1) was measured by real time-quantitative PCR and Western blotting. Cell growth was measured by cell counting kit-8, colony formation assay and flow cytometry method. Cell migration and invasion were assessed by transwell assays and Western blotting. Tumor growth was determined by xenograft models. The direct interaction among circ_0000520, miR-1296 and SP1 was confirmed by dual-luciferase reporter assay and RNA pull-down assay.

Results

circ_0000520 was upregulated in BCa tumors and cell lines (T47D, MCF7, MDA-MB-231, BT549, and SKBR3), and circ_0000520 high expression was associated with poor overall survival. Blocking circ_0000520 suppressed cell viability, colony formation, migration and invasion, but promoted cell cycle arrest and apoptosis rate in MDA-MB-231 and MCF7 cells. circ_0000520 could directly regulate miR-1296 expression, and SP1 was a novel target for miR-1296. Moreover, the anti-tumor role of circ_0000520 silencing was abrogated by miR-1296 downregulation or SP1 restoration. Notably, tumor growth of MDA-MB-231 cells in mice was restrained by circ_0000520 deletion.

Conclusion

circ_0000520 knockdown could suppress cell growth, migration and invasion both in vitro and in vivo through regulating miR-1296/SP1 pathway.

[Circular RNA expression pattern and competing endogenous RNA network involved in rotator cuff tendinopathy]

Objective

To detect the differentially expressed circular RNA (circRNA) in rotator cuff tendinopathy and analyze the potential molecular mechanism of these parental genes.

Methods

Ten supraspinatus tendons donated from patients who underwent tendon repair surgery between June 2018 and June 2019 were used for RNA-sequence. All rotator cuff tendinopathy and normal tendon samples were confirmed by MRI, histological staining, and observation by arthroscopy. All pathological tendons were matched with tendon samples for patients' age, gender, body mass index, and Bonar score. The bioinformatic analysis was performed based on the differentially expressed circRNA and their parental genes, including gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and competing endogenous RNA (ceRNA) network construction.

Results

There were 94 differentially expressed circRNAs, including 31 up-regulated and 63 down-regulated, detected between the rotator cuff tendinopathy and normal tendon samples with |log2 fold change (FC)| >2, P<0.05. GO analysis showed that the genes were mostly enriched in response to cyclic adenosine monophosphate (cAMP). KEGG pathway analysis showed that the most genes were enriched in extracellular matrix-receptor interaction, protein digestion and absorption, cell cycle, and nuclear factor κB signaling pathway. ceRNA networks showed the interactions among circRNAs, mRNAs, and miRNAs. And circRNA.8951-has-miR-6089-DNMT3B was the most sum max energy.

Conclusion

This bioinformatic study reveals several potential therapeutic targets for rotator cuff tendinopathy, which paves the way to better treatment and prevention of this disorder.