Comprehensive circular RNA profiling reveals the regulatory role of the circRNA-000911/miR-449a pathway in breast carcinogenesis

miR-449a: A Promising Biomarker and Therapeutic Target in Cancer and Other Diseases

In the regulation of gene expression, epigenetic factors like non-coding RNAs (ncRNAs) play an equal role in genetics. The role of microRNAs (miRNAs), which are members of the ncRNA family, in post-transcriptional gene regulation is well-documented and has important implications for both normal and abnormal biological processes, such as angiogenesis, proliferation, survival, and apoptosis. The purpose of this study was to synthesize previous research on miR-449a by analyzing published results from various databases, as there have been a number of investigations on miR-449's potential involvement in the development of human disorders. Based on our findings, miR-449 is strongly dysregulated in a wide range of diseases, from various cancers to cardiovascular diseases, cognitive impairments, and respiratory diseases, and it may play a pivotal role in the development of these problems. In addition, miR-449a functions as a crucial regulator of the expression of several well-known genes, including E2F-3, BCL2, NOTCH1, and SOX4. This, in turn, modulates various pathways and processes related to cancer, including Notch, PI3K, and TGF-β, and contributes to the improvement of cancer drug sensitivity. Curiously, abnormalities in the expression of this miRNA may serve as diagnostic or prognostic indicators for distinguishing between healthy people and patients or to evaluate the survival rates for specific disorders. This article provides a synopsis of the current understanding of miR-449a's role in human disease development through its regulation of gene expression and the biological processes related to these genes and their linked processes. In addition, we have covered the topic of miR-449a's potential as a clinical feature (diagnosis and prognosis) indicator for a range of disorders, both neoplastic and non-neoplastic. In general, our goal was to gain a thorough comprehension of the numerous functions of miR-449a in different disorders.

CircRNA circRREB1 promotes tumorigenesis and progression of breast cancer by activating Erk1/2 signaling through interacting with GNB4

Current investigations have illuminated the essential roles played by circular RNAs (circRNAs) in driving breast cancer (BC) tumorigenesis. However, the functional implications and molecular underpinnings of most circRNAs in BC are not well characterized. Here, Circular RNA (circRNA) expression profiles were analyzed in four surgically resected BC cases along with adjacent non-cancerous tissues applying RNA microarray analysis. The levels and prognostic implications of circRREB1 in BC were subjected to quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). Experimental manipulation of circRREB1 levels in both in vivo and in vitro settings further delineated its role in BC cell growth, invasion, and metastasis. The mechanical verification of circRREB1's interaction with GNB4 was established through RNA pull-down, mass spectrometry, Western blot analysis, RNA immunoprecipitation assays (RIP), fluorescence ISH (FISH), and rescue experiments. We found that circRREB1 exhibited significant upregulation in BC tissues and cells, implicating its association with an unfavorable prognosis in BC patients. CircRREB1 knockdown elicited anti-proliferative, anti-migratory, anti-invasive, and pro-apoptotic effects in BC cells, whereas its upregulation exerted opposing influences. Follow-up mechanistic examinations suggested that circRREB1 might interact with GNB4 directly, inducing the activation of Erk1/2 signaling and driving BC progression. Our findings collectively indicate that the interplay of circRREB1 with GNB4 promotes Erk1/2 signaling, thereby fostering BC progression, and positioning circRREB1 as a candidate therapeutic target for intervention in BC.

Circular RNA-mediated miRNA sponge & RNA binding protein in biological modulation of breast cancer

Circular RNAs (circRNAs) and small non-coding RNAs of the head-to-junction circle in the construct play critical roles in gene regulation and are significantly associated with breast cancer (BC). Numerous circRNAs are potential cancer biomarkers that may be used for diagnosis and prognosis. Widespread expression of circRNAs is regarded as a feature of gene expression in highly diverged eukaryotes. Recent studies show that circRNAs have two main biological modulation models: sponging and RNA-binding. This review explained the biogenesis of circRNAs and assessed emerging findings on their sponge function and role as RNA-binding proteins (RBPs) to better understand how their interaction alters cellular function in BC. We focused on how sponges significantly affect the phenotype and progression of BC. We described how circRNAs exercise the translation functions in ribosomes. Furthermore, we reviewed recent studies on RBPs, and post-protein modifications influencing BC and provided a perspective on future research directions for treating BC.

Therapeutic and diagnostic applications of exosomal circRNAs in breast cancer

Circular RNAs (circRNAs) are regulatory elements that are involved in orchestrating gene expression and protein functions and are implicated in various biological processes including cancer. Notably, breast cancer has a significant mortality rate and is one of the most common malignancies in women. CircRNAs have been demonstrated to contribute to the pathogenesis of breast cancer including its initiation, progression, metastasis, and resistance to drugs. By acting as miRNA sponges, circRNAs can indirectly influence gene expression by disrupting miRNA regulation of their target genes, ultimately altering the course of cancer development and progression. Additionally, circRNAs can interact with proteins and modulate their functions including signaling pathways involved in the initiation and development of cancer. Recently, circRNAs can encode peptides that play a role in the pathophysiology of breast cancer and other diseases and their potential as diagnostic biomarkers and therapeutic targets for various cancers including breast cancer. CircRNAs possess biomarkers that differentiate, such as stability, specificity, and sensitivity, and can be detected in several biological specimens such as blood, saliva, and urine. Moreover, circRNAs play an important role in various cellular processes including cell proliferation, differentiation, and apoptosis, all of which are integral factors in the development and progression of cancer. This review synthesizes the functions of circRNAs in breast cancer, scrutinizing their contributions to the onset and evolution of the disease through their interactions with exosomes and cancer-related intracellular pathways. It also delves into the potential use of circRNA as a biomarker and therapeutic target against breast cancer. It discusses various databases and online tools that offer crucial circRNA information and regulatory networks. Lastly, the challenges and prospects of utilizing circRNAs in clinical settings associated with breast cancer are explored.

Identification and analysis of differentially expressed (DE) circRNA in epididymis of yak and cattleyak

Circular RNAs (circRNAs), as endogenous non-coding RNA with unique closed ring structure, is closely related to animal reproduction, and understanding the expression of circRNA in yak and cattleyak epididymal tissues is of great significance for understanding cattleyak sterility. Based on this, we screened and identified the differentially expressed circRNA in the epididymis of three yaks and two cattleyak. A total of 1,298 circRNAs were identified in the epididymis of yak and cattleyak, of which 137 differentially expressed (DE) circRNAs and the functions of some of them were elucidated in this research, as well as qPCR verification to 6 circRNAs from the 137 DE circRNAs. Gene Ontology (GO) enrichment analysis suggested that DE circRNAs were mainly related to metabolic process, development process, immune system process, reproductive process, reproduction, biological adhesion and growth. COG classification analysis showed that the DE circRNAs derived genes were mainly related to replication, recombination and repair. KEGG pathway analysis suggested that DE circRNAs were mainly involved in RNA degradation. In addition, we also screened Bta-mir-103, which is a circRNA binding miRNA related to sperm activity.

Circ_0004904 suppresses trophoblast cell proliferation, invasion and migration in preeclampsia via upregulating the expression of DNA damage inducible alpha by interacting with miR-19a-3p

Preeclampsia (PE) is the most common complication in the pregnancy of women. PE progression was found to be associated with dysregulated circular RNAs (circRNAs), and we aimed to explore the pathological mechanism with circ_0004904 in PE. The circ_0004904, microRNA-19a-3p (miR-19a-3p) and DNA damage inducible alpha (GADD45A) were quantified via reverse transcription-quantitative polymerase chain reaction assay. Trophoblast cell behaviors were examined by cell viability using Cell Counting Kit-8 assay, cell proliferation using EdU assay, cell apoptosis using flow cytometry, cell invasion using transwell assay and migration using wound healing assay. Western blot was used for protein analysis of epithelial mesenchymal transition (EMT) and GADD45A. Dual-luciferase reporter assay and RNA immunoprecipitation assay were used for target interaction analysis. The circ_0004904 upregulation was detected in placenta tissues from PE patients. Trophoblast cell proliferation, invasion, migration and EMT were repressed but cell apoptosis was promoted after overexpression of circ_0004904. Circ_0004904 acted as a miR-19a-3p sponge in trophoblast cells, and all regulatory effects of circ_0004904 on trophoblast cell behaviors were reversed by miR-19a-3p upregulation. The miR-19a-3p directly targeted GADD45A and miR-19a-3p downregulation inhibited trophoblast cell development through elevating the GADD45A level. Moreover, circ_0004904 enhanced the expression of GADD45A via sponging miR-19a-3p. Our results elucidated that circ_0004904 reduced proliferation and cell motility of trophoblast cells via the miR-19a-3p-mediated GADD45A level elevation, indicating the involvement of circ_0004904/miR-19a-3p/GADD45A in PE progression.

Circular RNAs in and out of Cells: Therapeutic Usages of Circular RNAs

RNAs are versatile molecules that are primarily involved in gene regulation and can thus be widely used to advance the fields of therapeutics and diagnostics. In particular, circular RNAs which are highly stable, have emerged as strong candidates for use on next-generation therapeutic platforms. Endogenous circular RNAs control gene regulatory networks by interacting with other biomolecules or through translation into polypeptides. Circular RNAs exhibit cell-type specific expression patterns, which can be altered in tissues and body fluids depending on pathophysiological conditions. Circular RNAs that are aberrantly expressed in diseases can function as biomarkers or therapeutic targets. Moreover, exogenous circular RNAs synthesized in vitro can be introduced into cells as therapeutic molecules to modulate gene expression networks in vivo. Depending on the purpose, synthetic circular RNA sequences can either be identical to endogenous circular RNA sequences or artificially designed. In this review, we introduce the life cycle and known functions of intracellular circular RNAs. The current stage of endogenous circular RNAs as biomarkers and therapeutic targets is also described. Finally, approaches and considerations that are important for applying the available knowledge on endogenous circular RNAs to design exogenous circular RNAs for therapeutic purposes are presented.

Circ_0000520 interacts with miR-512-5p to upregulate KIAA0100 to promote malignant behaviors in lung cancer

BACKGROUND

CircRNAs function as pivotal molecules to regulate the malignant development of lung cancer. This study was designed to research the functional role and how it acted in lung cancer progression.

METHODS

Circ_0000520, microRNA-512-5p (miR-512-5p) and Breast cancer-overexpressed gene 1 (KIAA0100) levels were measured through reverse transcription-quantitative polymerase chain reaction assay. Cell Counting Kit-8 assay and EdU assay were used to examine cell proliferation. Cell cycle and apoptosis were evaluated via flow cytometry. The protein levels were determined using western blot. Cell migration and invasion were assessed by wound healing assay and transwell assay. The circ_0000520 function in vivo was explored by tumor xenograft assay. The molecular interaction was analyzed via Dual-luciferase reporter assay.

RESULTS

Circ_0000520 was obviously upregulated in lung cancer tissues and cells. Silence of circ_0000520 inhibited proliferation, cell cycle progression, migration, invasion and angiogenesis but promoted cell apoptosis. Circ_0000520 downregulation reduced tumor growth of lung cancer in vivo. Circ_0000520 served as a miR-512-5p sponge. The oncogenic function of circ_0000520 was partly achieved by sponging miR-512-5p in lung cancer. KIAA0100 was a target of miR-512-5p and miR-512-5p inhibited the malignant behaviors of lung cancer cells via downregulating KIAA0100. Circ_0000520 targeted miR-512-5p to regulate the level of KIAA0100.

CONCLUSION

All these data demonstrated that circ_0000520 was able to drive the progression of lung cancer via the mediation of miR-512-5p/KIAA0100 axis. Circ_0000520 might be a potential biomarker for lung cancer.

Ferroptosis-associated circular RNAs: Opportunities and challenges in the diagnosis and treatment of cancer

Ferroptosis is an emerging form of non-apoptotic regulated cell death which is different from cell death mechanisms such as autophagy, apoptosis and necrosis. It is characterized by iron-dependent lipid peroxide accumulation. Circular RNA (circRNA) is a newly studied evolutionarily conserved type of non-coding RNA with a covalent closed-loop structure. It exhibits universality, conservatism, stability and particularity. At present, the functions that have been studied and found include microRNA sponge, protein scaffold, transcription regulation, translation and production of peptides, etc. CircRNA can be used as a biomarker of tumors and is a hotspot in RNA biology research. Studies have shown that ferroptosis can participate in tumor regulation through the circRNA molecular pathway and then affect cancer progression, which may become a direction of cancer diagnosis and treatment in the future. This paper reviews the molecular biological mechanism of ferroptosis and the role of circular RNA in tumors and summarizes the circRNA related to ferroptosis in tumors, which may inspire research prospects for the precise prevention and treatment of cancer in the future.

Exosomal circular RNAs: New player in breast cancer progression and therapeutic targets

Breast cancer is the most prevalent type of malignancy among women. Exosomes are extracellular vesicles of cell membrane origin that are released via exocytosis. Their cargo contains lipids, proteins, DNA, and different forms of RNA, including circular RNAs. Circular RNAs are new class of non-coding RNAs with a closed-loop shape involved in several types of cancer, including breast cancer. Exosomes contained a lot of circRNAs which are called exosomal circRNAs. By interfering with several biological pathways, exosomal circRNAs can have either a proliferative or suppressive role in cancer. The involvement of exosomal circRNAs in breast cancer has been studied with consideration to tumor development and progression as well as its effects on therapeutic resistance. However, its exact mechanism is still unclear, and there have not been available clinical implications of exo-circRNAs in breast cancer. Here, we highlight the role of exosomal circRNAs in breast cancer progression and to highlight the most recent development and potential of circRNAas therapeutic targets and diagnostics for breast cancer.

Screening for MicroRNA combination with engineered exosomes as a new tool against osteosarcoma in elderly patients

The most common primary malignant bone sarcoma is Osteogenic sarcoma (OS) which has a bimodal age distribution. Unfortunately, the treatment of OS was less effective for elderly patients than for younger ones. The study aimed to explore a new microRNA (miRNA) which can bind to combining engineered exosomes for treatment of older OS patients. Based on GSE65071 and miRNet 2.0, two up-regulated miRNAs (miR-328, miR-107) and seven down-regulated miRNAs (miR-133b, miR-206, miR-1-3p, miR-133a, miR-449a, miR-181daysay, miR-134) were selected. Next, we used FunRich software to predict the up-stream transcription factors (TFs) of differentially expressed miRNAs (DE-miRNAs). By comparing target genes predicted from DE-miRNAs with differentially expressed genes, we identified 12 down-regulated and 310 up-regulated mRNAs. For KEGG analysis, the most enriched KEGG pathway was Cell cycle, Spliceosome, and Protein digestion and absorption. By using protein-protein interactions network, topological analysis algorithm and GEPIA database, miR-449a /CCNB1 axis was identified. Experiments in vitro were conducted to confirm the results too. MiRNA-449a is down-regulated in osteosarcoma and suppresses cell proliferation by targeting CCNB1. Our findings not only reveal a novel mechanism of miR-449a /CCNB1 in OS but also had laid the groundwork for further investigation and analysis in the field of exosome engineering.

MACF1 mutations predict poor prognosis: a novel potential therapeutic target for breast cancer

OBJECTIVE

Microtubule actin cross-linking factor 1 (MACF1) mutations are known to play an important role in the progression of various cancers. However, its role in breast cancer remains to be determined. In this study, we investigated how MACF1 mutations may play a role in breast cancer development.

METHODS

The gene-expression profile data of patients with breast cancer were obtained from The Cancer Genome Atlas (TCGA)-Breast cancer cohort. We estimated the influence of MACF1 mutations on patient clinical prognosis using the Kaplan-Meier method. Further, patients with MACF1-mutant (MACF1-MT) and MACF1-wild-type (MACF1-WT) were compared to identify the differentially expressed genes (DEGs). We also performed functional enrichment analyses, constructed protein-protein interaction (PPI) and competing endogenous RNA (ceRNA) networks, and investigated the correlation between MACF1 mutations and immune-cell infiltration. To explore the prognostic value of MACF1 mutations, a nomogram was developed based on MACF1 mutations and other clinicopathological parameters.

RESULTS

Patients with MACF1-MT had a worse prognosis and higher tumor mutation burden score (P < 0.05) than patients with MACF1-WT. MACF1 mutations were demonstrated to upregulate the mTOR signaling pathway and alter energy metabolism and tumor immune microenvironment. Thus, MACF1 mutations might affect immunogenicity and result in a lower response to immunotherapy. By analyzing the Genomics of Drug Sensitivity in Cancer (GDSC), the sensitivity of breast cancer cells to 13 drugs was found to be significantly enhanced by MACF1 mutations. The prognostic model was verified in predicting the outcome of breast cancer patients.

CONCLUSION

MACF1 mutations might be a potential prognostic biomarker and a therapeutic target for breast cancer.

CircSOD2 Contributes to Tumor Progression, Immune Evasion and Anti-PD-1 Resistance in Hepatocellular Carcinoma by Targeting miR-497-5p/ANXA11 Axis

Circular RNAs (circRNAs) can function as functional molecules in hepatocellular carcinoma (HCC). Herein, circRNA superoxide dismutase 2 (circSOD2) was researched in HCC progression and immune system. The real-time polymerase chain reaction (qRT-PCR) was used for quantification of circSOD2, microRNA-497-5p (miR-497-5p) and Annexin A11 (ANXA11). Cell assays were performed by 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) and colony formation assays for proliferation, flow cytometry for apoptosis and cell cycle, wound healing assay for migration and transwell assay for migration/invasion. ANXA11 and metastatic protein levels were measured by western blot. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to analyze target binding. CD8⁺ T cell immunity was assessed by Immunohistochemistry (IHC) assay, and the effect of circSOD2 on programmed cell death 1 (PD-1) immune checkpoint inhibitors (anti-PD-1) therapy was evaluated by mice xenograft assay. CircSOD2 was upregulated in HCC tissues and cells. Knockdown of circSOD2 resulted in HCC cell growth inhibition, apoptosis promotion, cell cycle arrest and metastasis suppression. Mechanically, circSOD2 promoted HCC development by acting as a miR-497-5p sponge and miR-497-5p played a tumor-inhibitory role in HCC cells by targeting ANXA11. Moreover, circSOD2 induced upregulation of ANXA11 expression by interacting with miR-497-5p. Also, the promoting effects of circSOD2 on immune evasion and anti-PD-1 resistance were related to miR-497-5p/ANXA11 axis. This study elucidated the pivotal function of circSOD2 in HCC progression and immunosuppression by mediating miR-497-6p/ANXA11 axis. CircSOD2/miR-497-5p/ANXA11 axis was a novel view of circRNA research in HCC.

CircPDSS1 promotes the proliferation, invasion, migration, and EMT of breast cancer cell via regulating miR-320c/CKAP5 axis

Background

Breast cancer (BC) poses serious threats to women’s health. A large number of reports have proved that circular RNAs (circRNAs) exert vital functions in human cancers, including BC.

Methods

The function of circPDSS1 in BC cells was tested by CCK-8, colony formation, TUNEL, transwell-invasion, wound healing, and IF assays. RNA pull down, luciferase reporter and RIP assays were employed to verify the relationship among circPDSS1, miR-320c and CKAP5.

Results

CircPDSS1 was upregulated in BC cells, and circPDSS1 knockdown repressed BC cell malignant behaviors. Further, circPDSS1 was found to bind to miR-320c in BC cells, and miR-320c overexpression suppressed malignant processes of BC cells. MiR-320c could also bind to CKAP5. Moreover, miR-320c inhibition increased the level of CKAP5, but circPDSS1 downregulation decreased the level of CKAP5. Finally, rescue experiments indicated that CKAP5 knockdown countervailed the promoting effect of miR-320c inhibition on the malignant behaviors of circPDSS1-depleted BC cells.

Conclusions

CircPDSS1 promotes proliferation, invasion, migration as well as EMT of BC cells by modulating miR-320c/CKAP5 axis. Our finding may be useful for researchers to find new potential therapeutic or diagnostic targets for BC.

Research progress in breast cancer stem cells: characterization and future perspectives

More and more studies have proved that there are a small number of cells with self-renewal and differentiation ability in breast tumors, namely breast cancer stem cells. Such cells play a key role in the initiation, development and migration of breast tumors. The properties of breast tumor stem cells are regulated by a range of intracellular and extracellular factors, including important signaling pathways, transcription factors, non-coding RNAs, and cytokines such as Hedgehog, Wnt, Notch, microRNA93, microRNA100, and IL-6. Tumor microenvironment (such as mesenchymal stem cells, macrophages and cytokines) plays an important role in the regulation of breast tumor stem cells. Using the keywords including "breast cancer stem cells", "signal pathway", "chemotherapy tolerance", and "non-coding RNA", "triple negative breast cancer", "inhibitors", this study retrieved the original articles and reviews published before October 3, 2021, from PubMed and WEB OF SCI database and this study performed a comprehensive review of them. After treatment, there is a correlation between the metastasis-prone nature and recurrence with breast cancer stem cells. The signaling pathway of breast cancer stem cells plays a significant role in activating the function of breast cancer cells, regulating the differentiation of breast cancer cells and controlling the division of breast cancer cells. This imbalance leads to the uncontrolled growth and development of breast cancer cells. Targeted therapy that blocks the corresponding pathway may become a new perspective for breast cancer treatment. In addition, corresponding therapeutic strategies can be used according to the expression characteristics of different molecular types of breast cancer stem cells. For ER-positive breast cancer, simultaneous endocrine therapy and targeted therapy of tumor stem cells may improve the efficacy of endocrine therapy. Trastuzumab therapy significantly reduces the risk of recurrence of HER2-positive breast cancer. For drug-resistant patients, combination therapy is required due to the different phenotypes of epithelial-mesenchymal transforming tumor stem cells. This study briefly reviews the research progress of breast cancer stem cell-related signaling pathways and their inhibitors, in order to provide a reference for breast cancer patients to obtain more effective clinical treatment.

Circular RNAs Involve in Immunity of Digestive Cancers From Bench to Bedside: A Review

The immune system plays a complex role in tumor formation and development. On the one hand, immune surveillance can inhibit the growth of tumors; on the other hand, immune evasion of tumors can create conditions conducive for tumor development and growth. CircRNAs are endogenous non-coding RNAs with a covalently closed loop structure that are abundantly expressed in eukaryotic organisms. They are characterized by stable structure, rich diversity, and high evolutionary conservation. In particular, circRNAs play a vital role in the occurrence, development, and treatment of tumors through their unique functions. Recently, the incidence and mortality of digestive cancers, especially those of gastric cancer, colorectal cancer, and liver cancer, have remained high. However, the functions of circRNAs in digestive cancers immunity are less known. The relationship between circRNAs and digestive tumor immunity is systematically discussed in our paper for the first time. CircRNA can influence the immune microenvironment of gastrointestinal tumors to promote their occurrence and development by acting as a miRNA molecular sponge, interacting with proteins, and regulating selective splicing. The circRNA vaccine even provides a new idea for tumor immunotherapy. Future studies should be focused on the location, transportation, and degradation mechanisms of circRNA in living cells and the relationship between circRNA and tumor immunity. This paper provides a new idea for the diagnosis and treatment of gastrointestinal tumors.

Sevoflurane represses the progression of glioma by the regulation of circ_0037655/miR-130a-5p/RPN2 axis

Sevoflurane (SEV) is a common anesthetic to inhibit glioma progression. The previous studies have indicated the molecular mechanisms of SEV function in glioma. The objective of this study was to explore the association of circ_00037655 with SEV in glioma. Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assay. Cell proliferation was analyzed using Edu assay and colony formation assay. Flow cytometry was applied to determine cell apoptosis. Protein analysis was performed via western blot. Cell migration and invasion were assessed by transwell assay. Circ_0037655, microRNA-130a-5p (miR-130a-5p) and ribophorin II (RPN2) levels were detected using the quantitative real-time polymerase chain reaction (qRT-PCR). Dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays were used to analyze target interaction. The effect of circ_0037655 on SEV in vivo was researched by xenograft models. SEV reduced cell viability, proliferation, migration and invasion but induced apoptosis of glioma cells. Circ_0037655 expression was inhibited after SEV treatment in glioma cells. The effects of SEV on glioma cell behaviors were attenuated by upregulation of circ_0037655. Circ_0037655 interacted with miR-130a-5p and miR-130a-5p targeted RPN2. Circ_0037655 or miR-130a-5p regulated the anti-tumor function of SEV in glioma by targeting miR-130a-5p or RPN2. Circ_0037655 affected the expression of RPN2 via targeting miR-130a-5p. Circ_0037655 relieved SEV-induced glioma growth inhibition in vivo by mediating miR-130a-5p and RPN2 levels. SEV inhibited the malignant progression of glioma cells partly by regulating the circ_0037655/miR-130a-5p/RPN2 axis.

CircRNA PTPRM Promotes Non-Small Cell Lung Cancer Progression by Modulating the miR-139-5p/SETD5 Axis

Introduction: Circular RNAs (circRNAs) are important regulators in various cancers, especially hepatocellular carcinoma. However, the role of circ RNA PTPRM (circPTPRM) in the development of non-small-cell lung cancer (NSCLC) remains unclear. Methods: We collected 26 clinical specimens (corresponding to 26 normal lung tissues) of lung adenocarcinoma and the expression of mir-139-5p and circPTPRM were first detected. Cell proliferation was detected by EdU method, invasion/migration ability of cells was evaluated by transwell method. And the correlation between circPTPRM and mir-139-5p was detected by luciferase reporter gene and RNA pull-down assay. Finally, we verified our hypothesis with BALB/c nude mice. Results: Through bioinformatics software, we found that circPTPRM was negatively correlated with mir-139-5p, and then we used human adenocarcinoma tissue samples to further verify their relationship and get the same result. EdU method, transwell method, and luciferase assay, RNA pull-down assay were applied, and the results show that the knockdown of circPTPRM inhibit proliferation, migration, and invasion of cells can be reversed by mir-139-5p inhibitor. Next, we used Starbase v2.0 to identify the target site of miR-139-5p and focused on SET domain containing 5 (SETD5). We derive the hypothesis by verifying the relationship between miR-139-5p and SETD5 that circPTPRM may interact with miR-139-5p/SETD5 axis. At last, we evaluated the effects of circPTPRM, SETD5, and miR-139-5p on tumor growth in vivo using BALB/c nude mice to prove the hypothesis. Conclusion: We thus conclude that circPTPRM promotes the progression of NSCLC by regulating the miR-139-5p/SETD5 axis.

The Crosstalk Between Regulatory Non-Coding RNAs and Nuclear Factor Kappa B in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal type of malignancies that possesses great loss of life safety to human beings worldwide. However, few effective means of curing HCC exist and its specific molecular basis is still far from being fully elucidated. Activation of nuclear factor kappa B (NF-κB), which is often observed in HCC, is considered to play a significant part in hepatocarcinogenesis and development. The emergence of regulatory non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), is a defining advance in cancer biology, and related research in this branch has yielded many diagnostic and therapeutic opportunities. Recent studies have suggested that regulatory ncRNAs act as inhibitors or activators in the initiation and progression of HCC by targeting components of NF-κB signaling or regulating NF-κB activity. In this review, we attach importance to the role and function of regulatory ncRNAs in NF-κB signaling of HCC and NF-κB-associated chemoresistance in HCC, then propose future research directions and challenges of regulatory ncRNAs mediated-regulation of NF-κB pathway in HCC.

[Research Progress in CircRNA and Radiotherapy Resistance of Non-small Cell Lung Cancer]

As the main type of lung cancer, non-small cell lung cancer (NSCLC) is a common cancer which is characterized by low 5-year survival rate and worse prognosis. Nowadays, some studies show that the low survival rate and worse prognosis are due to the resistance to radiotherapy caused by circRNA. Therefore, to find out the relationship between circRNA and radiotherapy resistance of NSCLC was imoprtant. According to research the relevant literatures, the relationship between circRNA and radiotherapy resistance of NSCLC was explored. CircRNA plays an important role in the invasion, metastasis, proliferation and treatment resistance of NSCLC. The radiation resistance of tumor cells induced by circRNA has become a crucial problem in radiotherapy. CircRNA plays an important role in the radiotherapy resistance of NSCLC.
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Circular RNA hsa_circ_0001598 promotes programmed death-ligand-1-mediated immune escape and trastuzumab resistance via sponging miR-1184 in breast cancer cells

Approximately 25% of breast cancer (BC) patients are HER2-positive. Trastuzumab is used as a targeted therapy drug to treat HER2-positive BC patients; however, the drug resistance remains a big challenge. Circular RNAs (circRNAs) are reported to be involved in drug resistance, but the role of circ_0001598 has never been studied in BC. First, we identified the expression of circ_0001598 by RT-qPCR in BC. The gain-of-function and loss-of-function studies were applied to study the functional roles of circ_0001598 and its target gene. We observed upregulation of circ_0001598 in BC tissues, especially in trastuzumab-resistant BC samples. We further identified that miR-1184 is a functional target of circ_0001598. Moreover, it was found that programmed death-ligand 1 (PD-L1) was a direct target of miR-1184. The oncogenic effects of circ_0001598 in promoting BC cell growth, trastuzumab-resistance, PD-L1 expression, and escaping of CD8 T cell killing were abolished after the restoration of miR-1184. In conclusion, we demonstrate that circ_0001598/miR-1184/PD-L1 signaling plays a crucial role in the regulation of BC progression and trastuzumab-resistance phonotypes, which suggests that circ_0001598 may be a molecular target to treat HER2-positive BC patients.

Recent Advances in Diagnostic and Therapeutic Approaches for Breast Cancer: A Comprehensive Review

A silent monster, breast cancer, is a challenging medical task for researchers. Breast cancer is a leading cause of death in women with respect to other cancers. A case of breast cancer is diagnosed among women every 19 seconds, and every 74 seconds, a woman dies of breast cancer somewhere in the world. Several risk factors, such as genetic and environmental factors, favor breast cancer development. This review tends to provide deep insights regarding the genetics of breast cancer along with multiple diagnostic and therapeutic approaches as problem-solving negotiators to prevent the progression of breast cancer. This assembled data mainly aims to discuss omics-based approaches to provide enthralling diagnostic biomarkers and emerging novel therapies to combat breast cancer. This review article intends to pave a new path for the discovery of effective treatment options.

circ_0005379 inhibits the progression of oral squamous cell carcinoma by regulating the miR-17-5p/acyl-CoA oxidase 1 axis

OBJECTIVES

To investigate the effects of circ_0005379 on the proliferation, apoptosis, migration, and invasion of oral squamous cell carcinoma (OSCC) cells and its mechanism.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression levels of circ_0005379 and miR-17-5p in OSCC tissues and SCC15 cell lines. Western blot was used to detect the expression levels of acyl-CoA oxidase 1 (ACOX1). The circ_0005379 overexpression vector was transfected into SCC15 cells. Methyl thiazolyl tetrazolium blue staining, flow cytometry, Transwell, and Western blot were used to detect the effects of circ_0005379 overexpression on the proliferation, apoptosis, migration, and invasion of SCC15 cells and the expression of E-cadherin, β-catenin, and Snail proteins. Dual luciferase reporter assay and RNA immunoprecipitation were used to examine the regulation of circ_0005379, miR-17-5p, miR-17-5p, and ACOX1 in SCC15 cells. A nude mouse xenograft model of SCC15 cells stably overexpressing circ_0005379 was established, and the effect of circ_0005379 overexpression on the growth of xenografts in nude mice was observed.

RESULTS

Compared with adjacent cancer tissues, the expression levels of circ_0005379 and ACOX1 proteins in OSCC tissues were decreased (P<0.05), and the expression level of miR-17-5p was increased (P<0.05). Compared with HOK-16A cells, the expression levels of circ_0005379 and ACOX1 proteins in SCC15 cell lines were decreased (P<0.05), and the expression level of miR-17-5p was increased (P<0.05). After overexpressing circ_0005379, the activity and number of migrating and invading SCC15 cells and the expression levels of β-catenin and Snail proteins were decreased (P<0.05); however, the apoptosis rate and expression level of E-cadherin protein were increased (P<0.05). In SCC15 cells, circ_0005379 targeted the negative regulation of miR-17-5p expression, and miR-17-5p targeted the negative regulation of ACOX1 expression. Overexpressing miR-17-5p or silencing ACOX1 could reverse the effects of circ_0005379 overexpression on the proliferation, apoptosis, migration, and invasion of OSCC cell lines. The tumor volume and weight of nude mice overexpressing circ_0005379 were decreased (P<0.05), the expression levels of circ_0005379 and ACOX1 protein in tumor tissues were increased (P<0.05), and the expression level of miR-17-5p was decreased (P<0.05).

CONCLUSIONS

circ_0005379 may inhibit the proliferation, migration, and invasion of OSCC cells by downregulating the expression of miR-17-5p and upregulating ACOX1, which promote apoptosis and inhibit tumor growth in vivo. circ_0005379 may be a potential target for OSCC treatment.

CircRNA circFOXK2 facilitates oncogenesis in breast cancer via IGF2BP3/miR-370 axis

Metastasis is the leading cause of breast cancer (BC)-related deaths. Circular RNAs (circRNAs) have emerged as essential regulators for cancer progression and metastasis. Therefore, the objective of this study was to investigate the role of circRNAs in BC metastasis and related mechanism. In this study, we established the BC cell line with high or low potential of metastasis. RNA sequencing, migration and invasion assay, Fluorescence in situ hybridization, luciferase report assay, circRNA pulldown, and transmission electron microscopy were performed to elucidate the molecular mechanism. The results showed that circRNA circFOXK2 was significantly increased in BC cells with high metastatic ability, and the upregulation of circFOXK2 was correlated with poor clinicopathological characteristics. Functional experiments demonstrated that overexpression of circFOXK2 promoted migration and invasion of BC cells. Also. circFOXK2 could act with IGF2BP3, an RNA-binding protein, and miR-370 to synergistically promote BC metastasis. Moreover, miR-370 could be transferred through exosomes to enhance the metastatic ability of recipient cells. In conclusion, circFOXK2 functions as a key regulator in BC metastasis, and the role of circFOXK2 on BC metastasis is tightly associated with the involvement of IGF2BP3 and miR-370. CircFOXK2 might serve as a potential biomarker for the diagnosis and treatment of BC.

Circular RNAs Interaction with MiRNAs: Emerging Roles in Breast Cancer

Despite significant advances in cancer therapy strategies, breast cancer is one of the most common and lethal malignancies worldwide. Characterization of a new class of RNAs using next-generation sequencing opened new doors toward uncovering etiopathogenesis mechanisms of breast cancer as well as prognostic and diagnostic biomarkers. Circular RNAs (circRNAs) are a novel class of RNA with covalently closed and highly stable structures generated primarily from the back-splicing of precursor mRNAs. Although circRNAs exert their function through various mechanisms, acting as a sponge for miRNAs is their primary mechanism of function. Furthermore, growing evidence has shown that aberrant expression of circRNAs is involved in the various hallmarks of cancers. This paper reviews the biogenesis, characteristics, and mechanism of functions of circRNAs and their deregulation in various cancers. Finally, we focused on the circRNAs roles as a sponge for miRNAs in the development, metastasis, angiogenesis, drug resistance, apoptosis, and immune responses of breast cancer.

The Regulation Network and Clinical Significance of Circular RNAs in Breast Cancer

Breast cancer is one of the most common malignant tumors in women worldwide. Circular RNA (circRNA) is a class of structurally stable non-coding RNA with a covalently closed circular structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been discovered and have proven to be clinically significant in the development and progression of breast cancer. Importantly, several regulators of circRNA biogenesis have been discovered. Here, we systematically summarize recent progress regarding the network of regulation governing the biogenesis, degradation, and distribution of circRNAs, and we comprehensively analyze the functions, mechanisms, and clinical significance of circRNA in breast cancer.

Downregulating circRNA_0044516 Inhibits Cell Proliferation in Gastric Cancer Through miR-149/Wnt1/β-catenin Pathway

BACKGROUND

Circular RNAs (circRNAs) play important roles in the progression of gastric cancer (GC). The Wnt1/β-catenin pathway can promote the proliferation of GC cells. This study aimed to explore whether circRNA_0044516 can regulate the proliferation of GC cells by modulating the Wnt1/β-catenin pathway.

METHODS

The expression of circRNA_0044516, miR-149, Wnt1, and β-catenin in GC tissues or cells was detected by qRT-PCR and western blot. Cell viability and apoptosis were measured by CCK-8 and flow cytometry assays, respectively. The interaction between circRNA_0044516 and miR-149 was determined by luciferase reporter and RNA pull-down assays.

RESULTS

Upregulated circRNA_0044516 was found in GC tissues and cell lines. Downregulating circRNA_0044516 inhibited the viability and promoted apoptosis of GC cells. CircRNA_0044516 targeted miR-149, and its downregulation elevated miR-149 level in GC cells. Mechanistically, silencing circRNA_0044516 reduced the protein level of Wnt1 and β-catenin through miR-149, and finally suppressed viability and contributed to apoptosis of GC cells. Moreover, circRNA_0044516 knockdown inhibited the tumor growth of HGC-27 cells in nude mice.

CONCLUSIONS

Our results indicated an important role of circRNA_0044516 in GC and elucidated that downregulation of circRNA_0044516 inhibits the proliferation of GC cells through miR-149/Wnt1/β-catenin.

Silencing of circTASP1 inhibits proliferation and induces apoptosis of acute myeloid leukaemia cells through modulating miR-515-5p/HMGA2 axis

Acute myeloid leukaemia (AML) is a common hematopoietic disease that is harmful to the lives of children and adults. CircRNAs are aberrantly expressed in the haematologic malignancy cells. However, the expression of circTASP1 and its function in AML remain unclear. In this study, we showed that circTASP1 was significantly up‐regulated in AML peripheral blood samples and cells. Knockdown of circTASP1 inhibited proliferation and promoted apoptosis of HL60 and THP‐1 cells in vitro. Bioinformatics prediction and luciferase reporter assay proved that circTASP1 sponged miR‐515‐5p and negatively regulated miR‐515‐5p expression in HL60 and THP‐1 cells. High mobility group A2 (HMGA2) was proved to be a downstream target of miR‐515‐5p. The rescue experiments confirmed that knockdown of circTASP1 inhibited proliferation and induced apoptosis by modulating miR‐515‐5p/HMGA2 pathway. Moreover, the in vivo experiment indicated that knockdown of circTASP1 suppressed tumour growth. In conclusion, circTASP1 acts as a sponge for miR‐515‐5p to regulate HMGA2, thereby promoting proliferation and inhibiting apoptosis during AML progression. Thus, circTASP1 has the potential to be explored as a therapeutic target for AML treatment.

Circular RNAs regulate cancer-related signaling pathways and serve as potential diagnostic biomarkers for human cancers

Circular RNAs (circRNAs) are RNAs that have an important role in various pathological processes, including cancer. After the usage of high-throughput RNA sequencing, many circRNAs were found to be differentially expressed in various cancer cell lines and regulate cell signaling pathways by modulating particular gene expressions. Understanding their role in these pathways and what cancers they are found in can set the stage for identifying diagnostic and prognostic biomarkers and therapeutic targets of cancer. This paper will discuss which circRNAs are found in different cancers and what mechanisms they use to upregulate or downregulate certain cellular components.

Exosomal circRNA as a novel potential therapeutic target for multiple myeloma-related myocardial damage

Introduction

Myocardial damage is a mostly incurable complication of multiple myeloma (MM) that seriously affects the treatment outcome and quality of life of patients. Exosomal circular RNAs (exo-circRNAs) play an important role in tumor occurrence and development and are considered key factors in MM pathogenesis. However, the role and mechanism of action of exo-circRNAs in MM-related myocardial damage are still unclear. This study aimed to investigate correlations between exo-circRNAs and MM and to preliminarily explore the role of exo-circRNAs in MM-related myocardial damage.

Methods

Six MM patients and five healthy controls (HCs) were included in the study. High-throughput sequencing and qRT-PCR verification were used to obtain a profile of abnormally expressed exo-circRNAs. GO, KEGG, miRanda, TargetScan and Metascape were used for bioinformatics analyses. H9C2 cells treated with exosomes from U266 cells were used in cell experiments. CCK-8, PCR, immunofluorescence and western blotting assays were used to detect cell proliferation and expression of autophagy-related indicators. Electron microscopy was used to observe the number of autophagic vesicles.

Results

Bioinformatics analysis showed that circRNAs with upregulated expression had the potential to promote MM-related myocardial damage. In addition, PCR results confirmed that circ-G042080 was abundantly expressed in the serum exosomes of 20 MM patients. Correlation analysis showed that the expression level of circ-G042080 was positively correlated with the clinical level of MM and MM-related myocardial damage and that circ-G042080 might interfere with MM-related myocardial damage through a downstream miRNA/TLR4 axis. Cell experiments demonstrated that the circ-G042080/hsa-miR-4268/TLR4 axis might exist in H9C2 cells incubated with exosomes and cause abnormal autophagy.

Conclusion

Abnormal expression of serum exo-circRNAs was found to be associated with MM-related myocardial damage, suggesting that exo-circRNAs might become a new diagnostic marker of MM-related myocardial damage and a therapeutic target.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02011-w.

The biogenesis, function and clinical significance of circular RNAs in breast cancer

Circular RNAs (circRNAs) are noncoding RNAs that form covalently closed loop structures. CircRNAs are dysregulated in cancer and play key roles in tumorigenesis, diagnosis, and tumor therapy. CircRNAs function as competing endogenous RNAs or microRNA sponges that regulate transcription and splicing, binding to proteins, and translation. CircRNAs may serve as novel biomarkers for cancer diagnosis, and they show potential as therapeutic targets in cancers including breast cancer (BC). In women, BC is the most common malignant tumor worldwide and the second leading cause of cancer death. Although evidence indicates that circRNAs play a critical role in BC, the mechanisms regulating the function of circRNAs in BC remain poorly understood. Here, we provide literature review aiming to clarify the role of circRNAs in BC and summarize the latest research. We provide a systematic overview of the biogenesis and biological functions of circRNAs, elaborate on the functional roles of circRNAs in BC, and highlight the value of circRNAs as diagnostic and therapeutic targets in BC.

Current research on circular RNAs and their potential clinical implications in breast cancer

Breast cancer (BC) is one of the most common cancers and the leading causes of death among women worldwide, and its morbidity rate is growing. Discovery of novel biomarkers is necessary for early BC detection, treatment, and prognostication. Circular RNAs (circRNAs), a novel type of endogenous non-coding RNAs with covalently closed continuous loops, have been found to have a crucial role in tumorigenesis. Studies have demonstrated that circRNAs are aberrantly expressed in the tumor tissues and plasma of patients with BC, and they modulate gene expression affecting the proliferation, metastasis, and chemoresistance of BC by specifically binding and regulating the expression of microRNAs (miRNAs). Therefore, circRNAs can be used as novel potential diagnostic and prognostic markers, and therapeutic targets for BC. This article summarizes the properties, functions, and regulatory mechanisms of circRNAs, particularly current research on their association with BC proliferation, metastasis, and chemoresistance.

CircRNAs: role in human diseases and potential use as biomarkers

Circular RNAs (circRNAs) are a class of endogenous RNAs characterized by a covalent loop structure. In comparison to other types of RNAs, the abundance of circRNAs is relatively low but due to the circular configuration, their stability is very high. In addition, circRNAs display high degree of tissue specificity. The sponging activity of circRNAs toward microRNAs is the best-described mode of action of circRNAs. However, the ability of circRNAs to bind with specific proteins, as well as to encode short proteins, propose alternative functions. This review introduces the biogenesis of circRNAs and summarizes the roles played by circRNAs in human diseases. These include examples of their functional roles in several organ-specific cancers, such as head and neck and breast and lung cancers. In addition, we review potential functions of circRNAs in diabetes, cardiovascular, and neurodegenerative diseases. Recently, a growing number of studies have demonstrated involvement of circRNAs in a wide spectrum of signaling molecular pathways, but at the same time many different and controversial views on circRNAs role and function are emerging. We conclude by offering cellular homeostasis generated by networks comprising circular RNAs, other non-coding RNAs and RNA-binding proteins. Accordingly, it is predictable that circRNAs, due to their highly stable nature and remarkable tissue specificity, will emerge as reliable biomarkers of disease course and treatment efficacy.

Tumor-derived exosomal circPSMA1 facilitates the tumorigenesis, metastasis, and migration in triple-negative breast cancer (TNBC) through miR-637/Akt1/β-catenin (cyclin D1) axis

Circular RNAs (circRNAs) are increasingly gaining importance and attention due to their diverse potential functions and their value as diagnostic biomarkers (disease specific). This study aims to explore the novel mechanisms by which exosome-contained circRNAs promote tumor development and metastasis in TNBC. We identified increased circRNA circPSMA1 in TNBC cells, their exosomes, and serum exosomes samples from TNBC patients. The overexpression of circPSMA1 promoted TNBC cell proliferation, migration, and metastasis both in vitro and in vivo. Moreover, we investigated the tumor-infiltrating immune cells (TICs) or stromal components in immune microenvironment (IME), and identified the significant differences in the immune cells between TNBC and non-TNBC samples. Mechanistically, circPSMA1 acted as a "miRNAs sponge" to absorb miR-637; miR-637 inhibited TNBC cell migration and metastasis by directly targeted Akt1, which recognized as a key immune-related gene and affected downstream genes β-catenin and cyclin D1. Subsequent co-culture experiments also demonstrated that exosomes from TNBC carrying large amounts of circPSMA1 could transmit migration and proliferation capacity to recipient cells. Kaplan-Meier plots showed that high expression of Akt1 and low expression of mir-637 are highly correlated with poor prognosis in patients with lymph node metastasis of TNBC. Collectively, all these results reveal that circPSMA1 functions as a tumor promoter through the circPSMA1/miR-637/Akt1-β-catenin (cyclin D1) regulatory axis, which can facilitate the tumorigenesis, metastasis, and immunosuppression of TNBC. Our research proposes a fresh perspective on novel potential biomarkers and immune treatment strategies for TNBC.

circSnx12 Is Involved in Ferroptosis During Heart Failure by Targeting miR-224-5p

Circular RNA (circRNA) is a subclass of non-coding RNAs that enables the circular transcripts resistant to the exonuclease digestion. Iron homeostasis is essential for the body to maintain normal physiological functions. At present, the relationship among circRNA, iron metabolism and heart failure remains largely unknown. This study aimed to explore the regulatory mechanism of circRNA and iron metabolism in heart failure. We obtained circRNA, miRNA and mRNA data from public databases and built a ceRNA network. The prediction results were verified in the myocardial tissues of pressure overload-induced heart failure mice through the use of histopathological staining methods, iron and malondialdehyde (MDA) measurement tests, quantitative real-time PCR (qRT-PCR), Western blot analysis and luciferase reporter assay. A total of 4 genes related to iron metabolism and oxidative stress were identified, and a ceRNA network involving 7 circRNAs, 7 miRNAs, and 4 mRNAs was constructed using bioinformatics tools. The results of qRT-PCR and Western blot analyses indicated that the expression level of FTH1 was similar with that predicted by bioinformatics analysis. Echocardiographic measurement showed that heart failure mice have lower fractional shortening and ejection fraction. Moreover, the myocardium of heart failure mice displayed obvious fibrosis as well as increased levels of iron and MDA compared to control mice. Besides, circSnx12 could act as an endogenous sponge to bind with miR-224-5p, and the 3'UTR region of FTH1 also had miRNA binding sites. A circRNA-miRNA-mRNA regulatory network was successfully constructed by identifying differentially expressed genes related to iron metabolism. This new approach reveals potential circRNA targets for the treatment of heart failure.

CircRNA_OTUD7A upregulates FOXP1 expression to facilitate the progression of diffuse large B-cell lymphoma via acting as a sponge of miR-431-5p

BACKGROUND

A growing number of studies have shown that circular RNA (circRNA) is an important regulator molecule in cancer progression, but it has been poorly studied in diffuse large b-cell lymphoma (DLBCL).

OBJECTIVE

This study aimed to explore the role of circ_OTUD7A in DLBCL.

METHODS

Relative expression levels of circ_OTUD7A, microRNA (miR)-431-5p and forkhead box P1 (FOXP1) were determined by quantitative real-time PCR (qRT-PCR). The proliferation of cells was elevated by colony formation assay and MTT assay. Western blot (WB) analysis was employed to measure the protein levels of proliferation marker, epithelial-mesenchymal transition (EMT) markers, cyclin marker, apoptosis markers and FOXP1. Moreover, the apoptosis, cell cycle process, migration and invasion of cells were detected using flow cytometry and transwell assay, respectively. In addition, the interaction between miR-431-5p and circ_OTUD7A or FOXP1 was confirmed by dual-luciferase reporter assay.

RESULTS

Circ_OTUD7A was highly expressed in DLBCL, and its knockdown could inhibit DLBCL cell proliferation and metastasis, while promote cell cycle arrest and apoptosis. Similarly, FOXP1 also was upregulated in DLBCL, and its silencing could restrain the progression of DLBCL cells. Further experiments revealed that circ_OTUD7A could sponge miR-431-5p and miR-431-5p could target FOXP1. MiR-431-5p inhibitor could reverse the suppressive effect of circ_OTUD7A silencing on DLBCL progression, and FOXP1 overexpression also could reverse the inhibitory effect of miR-431-5p mimic on DLBCL progression.

CONCLUSION

Circ_OTUD7A promoted the progression of DLBCL by regulating the miR-431-5p/FOXP1 axis, which suggested that circ_OTUD7A might function as an oncogene in DLBCL.

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.

Increased Expression of hsa_circ_0002111 and Its Clinical Significance in Papillary Thyroid Cancer

Circular RNA (circRNA) is a newly discovered non-coding RNA. Recent reports suggest that circRNAs are key regulators of tumorigenesis because of their special structure. In order to investigate the role of hsa_circ_0002111 in papillary thyroid cancer (PTC), we use quantitative real-time polymerase chain reaction (qRT-PCR) to determine the expression pattern of hsa_circ_0002111 in 82 paired PTC and adjacent non-cancerous thyroid tissues. Cell counting kit-8, colony formation, and transwell assays were conducted to assess the effect of hsa_circ_0002111 on PTC cell proliferation, migration, and invasion. We found that the expression of hsa_circ_0002111 was significantly up-regulated in PTC tissues compared with adjacent non-cancerous tissues (P < 0.0001). Expression of hsa_circ_0002111 was also associated with advanced TNM stage and lymph-node metastasis of patients with PTC. The area under the receiver operating characteristic curve was 0.833. Further, cell function assays showed that hsa_circ_0002111 inhibition significantly suppressed the proliferation and invasion abilities of PTC cells in vitro. In conclusions, the study findings show that the over-expression of hsa_circ_0002111 promotes PTC, and thus hsa_circ_0002111 may be a potential diagnostic biomarker and therapeutic target for PTC.

Construction of Circular RNA-MicroRNA-Messenger RNA Regulatory Network of Recurrent Implantation Failure to Explore Its Potential Pathogenesis

Background: Many studies on circular RNAs (circRNAs) have recently been published. However, the function of circRNAs in recurrent implantation failure (RIF) is unknown and remains to be explored. This study aims to determine the regulatory mechanisms of circRNAs in RIF.

Methods: Microarray data of RIF circRNA (GSE147442), microRNA (miRNA; GSE71332), and messenger RNA (mRNA; GSE103465) were downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed circRNA, miRNA, and mRNA. The circRNA–miRNA–mRNA network was constructed by Cytoscape 3.8.0 software, then the protein–protein interaction (PPI) network was constructed by STRING database, and the hub genes were identified by cytoHubba plug-in. The circRNA–miRNA–hub gene regulatory subnetwork was formed to understand the regulatory axis of hub genes in RIF. Finally, the Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the hub genes were performed by clusterProfiler package of Rstudio software, and Reactome Functional Interaction (FI) plug-in was used for reactome analysis to comprehensively analyze the mechanism of hub genes in RIF.

Results: A total of eight upregulated differentially expressed circRNAs (DECs), five downregulated DECs, 56 downregulated differentially expressed miRNAs (DEmiRs), 104 upregulated DEmiRs, 429 upregulated differentially expressed genes (DEGs), and 1,067 downregulated DEGs were identified regarding RIF. The miRNA response elements of 13 DECs were then predicted. Seven overlapping miRNAs were obtained by intersecting the predicted miRNA and DEmiRs. Then, 56 overlapping mRNAs were obtained by intersecting the predicted target mRNAs of seven miRNAs with 1,496 DEGs. The circRNA–miRNA–mRNA network and PPI network were constructed through six circRNAs, seven miRNAs, and 56 mRNAs; and four hub genes (YWHAZ, JAK2, MYH9, and RAP2C) were identified. The circRNA–miRNA–hub gene regulatory subnetwork with nine regulatory axes was formed in RIF. Functional enrichment analysis and reactome analysis showed that these four hub genes were closely related to the biological functions and pathways of RIF.

Conclusion: The results of this study provide further understanding of the potential pathogenesis from the perspective of circRNA-related competitive endogenous RNA network in RIF.

Baicalein Represses Cervical Cancer Cell Growth, Cell Cycle Progression and Promotes Apoptosis via Blocking AKT/mTOR Pathway by the Regulation of circHIAT1/miR-19a-3p Axis

Background

Baicalein has a significant anti-cancerous function in the treatment of cervical cancer (CC). Its functional mechanism regarding circular RNA (circRNA) hippocampus abundant transcript 1 (circHIAT1) and microRNA-19a-3p (miR-19a-3p) was explored in this research.

Methods

CC cell viability and colony formation were determined using Cell Counting Kit-8 (CCK-8) and colony formation assay. Cell cycle progression and apoptosis were analyzed via flow cytometry. Protein markers of cell cycle, apoptosis and protein kinase B/mammalian target of rapamycin (AKT/mTOR) pathway were detected by Western blot. CircHIAT1 and miR-19a-3p levels were assayed through the quantitative real-time polymerase chain reaction (qRT-PCR). The interaction between circHIAT1 and miR-19a-3p was validated by dual-luciferase reporter and RNA pull-down assays. In vivo experiment was performed by xenograft model.

Results

CC cell growth and cell cycle progression were repressed while apoptosis was enhanced by baicalein. MiR-19a-3p was downregulated in baicalein-treated CC cells and miR-19a-3p overexpression lightened the baicalein-induced CC progression inhibition. Moreover, circHIAT1 was found to be a sponge of miR-19a-3p in CC cells. Baicalein-induced cell growth inhibition, cell cycle arrest and apoptosis promotion were neutralized by knockdown of circHIAT1 via targeting miR-19a-3p. Baicalein acted on the circHIAT1/miR-19a-3p to inactivate AKT/mTOR pathway. Baicalein also reduced CC tumor growth in vivo via regulating the levels of circHIAT1 and miR-19a-3p.

Conclusion

These findings demonstrated that the inhibitory function of baicalein in CC progression was dependent on the repression of AKT/mTOR pathway by upregulating circHIAT1 to sponge miR-19a-3p, showing a specific mechanism for baicalein in CC.

circRNA_141539 can serve as an oncogenic factor in esophageal squamous cell carcinoma by sponging miR-4469 and activating CDK3 gene

The abnormal expression and regulation of circular RNA (circRNA) is involved in the occurrence and development of a variety of tumors. The current study aimed to determine the role of circRNA_141539 in esophageal squamous cell carcinoma (ESCC). CircRNA_141539 expression in ESCC was detected via circRNA chip analysis and verified via reverse transcription-quantitative PCR. Associations between circRNA_141539, patient clinicopathological characteristics and prognosis were also statistically analyzed. Additionally, the effects of circRNA_141539 on ESCC cell proliferation and invasion were assessed. A dual-luciferase assay was performed to analyze the interaction between circRNAs, microRNAs (miRs) and mRNAs. The results revealed that circRNA_141539 was significantly up-regulated in patients with ESCC. Furthermore, high circRNA_141539 expressions were significantly associated with TNM stage, differentiation and poor prognosis, revealing high diagnostic value (P<0.05). Furthermore, circRNA_141539 overexpression promoted cell proliferation and invasion, while circRNA_141539 silencing inhibited cell proliferation and invasion (P<0.05). The dual-luciferase reporter assay identified that circRNA_141539 directly binds to miR-4469 and also revealed that cyclin-dependent kinase-3 (CDK3) was negatively regulated by miR-4469. The results indicated that circRNA_141539 served as an oncogenic factor in ESCC by sponging miR-4469 and activating CDK3 expression. circRNA_141539 may present as a novel diagnostic and prognostic biomarker and a therapeutic target for patients with ESCC.

Recent Discoveries of Macromolecule- and Cell-Based Biomarkers and Therapeutic Implications in Breast Cancer

Breast cancer is the most commonly diagnosed cancer type and the leading cause of cancer-related mortality in women worldwide. Breast cancer is fairly heterogeneous and reveals six molecular subtypes: luminal A, luminal B, HER2+, basal-like subtype (ER−, PR−, and HER2−), normal breast-like, and claudin-low. Breast cancer screening and early diagnosis play critical roles in improving therapeutic outcomes and prognosis. Mammography is currently the main commercially available detection method for breast cancer; however, it has numerous limitations. Therefore, reliable noninvasive diagnostic and prognostic biomarkers are required. Biomarkers used in cancer range from macromolecules, such as DNA, RNA, and proteins, to whole cells. Biomarkers for cancer risk, diagnosis, proliferation, metastasis, drug resistance, and prognosis have been identified in breast cancer. In addition, there is currently a greater demand for personalized or precise treatments; moreover, the identification of novel biomarkers to further the development of new drugs is urgently needed. In this review, we summarize and focus on the recent discoveries of promising macromolecules and cell-based biomarkers for the diagnosis and prognosis of breast cancer and provide implications for therapeutic strategies.

CircASH2L Promotes Ovarian Cancer Tumorigenesis, Angiogenesis, and Lymphangiogenesis by Regulating the miR-665/VEGFA Axis as a Competing Endogenous RNA

Ovarian cancer is the leading cause of gynecologic cancer-related deaths. Emerging research has revealed a close relationship between circular RNAs (circRNAs) and ovarian cancer development, metastasis, and prognosis. The objective of our research was to further explore the relationship between circASH2L and ovarian cancer. Quantitative real-time polymerase chain reaction was used to detect the differential expression of circRNAs between normal ovaries and ovarian cancer tissues. The impact of circASH2L on the proliferation, invasion, and tumorigenicity of ovarian cancer cells was evaluated using gain- and loss-of-function experiments. The molecular mechanisms of circASH2L function were investigated using bioinformatics analysis, RNA fluorescence in situ hybridization, western blots, and dual-luciferase reporter assays. The results showed that circASH2L was remarkably upregulated in ovarian cancer. The invasion and growth of ovarian cancer cells were suppressed by circASH2L knockdown in vitro, and downregulation of circASH2L restrained both angiogenesis and lymphangiogenesis of tumor xenografts in vivo. Furthermore, circASH2L was mostly distributed in the cytoplasm, where it competes with vascular endothelial growth factor A (VEGFA) for binding to miR-665. These findings indicate that circASH2L has an oncogenic function in ovarian cancer. In conclusion, circASH2L plays a critical role in regulating ovarian cancer cell tumorigenesis, angiogenesis, and lymphangiogenesis through the miR-665/VEGFA axis and, therefore, is a possible candidate target for ovarian cancer treatment.

Circ_0061825 Acts as a miR-593-3p Sponge to Promote Breast Cancer Progression by Regulating FGFR3 Expression

Background

Breast cancer (BC) remains the most common malignancy among women. Circular RNAs (circRNAs) have been demonstrated to play important roles in human cancers, including BC. In this study, we sought to identify the precise parts of circ_0061825 (circRNA trefoil factor 1, circ_TFF1) in BC pathogenesis.

Methods

The expression levels of circ_0061825, miR-593-3p and fibroblast growth factor receptor 3 (FGFR3) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. Circ_0061825 was characterized using ribonuclease (RNase) R digestion, actinomycin D and subcellular fractionation assays. Cell viability, colony formation, migration, invasion, cell cycle progression and apoptosis were evaluated using Cell Counting Kit-8 (CCK-8), colony formation, wound-healing, transwell and flow cytometry assays, respectively. Targeted relationships among circ_0061825, miR-593-3p and FGFR3 were determined by a dual-luciferase reporter assay. Animal studies were used to assess the impact of circ_0061825 in tumor growth in vivo.

Results

Our data indicated that circ_0061825 was overexpressed in BC tissues and cells, and it was mainly localized in the cytoplasm of BC cells. Circ_0061825 knockdown hampered BC cell viability, colony formation, migration, invasion, cell cycle progression and enhanced cell apoptosis in vitro and weakened tumor growth in vivo. Mechanistically, circ_0061825 functioned as a molecular sponge of miR-593-3p, and circ_0061825 knockdown repressed BC cell malignant progression in vitro by miR-593-3p. FGFR3 was a direct target of miR-593-3p, and circ_0061825 modulated FGFR3 expression through sponging miR-593-3p. Moreover, miR-593-3p overexpression hindered BC cell malignant progression in vitro by down-regulating FGFR3.

Conclusion

Our current work provided evidence that circ_0061825, an up-regulated circRNA in BC, regulated BC malignant progression at least in part through targeting the miR-593-3p/FGFR3 axis, illuminating a novel therapeutic target for BC management.

CircDDX42 Accelerates the Development of Pancreatic Cancer via miR-613/ID4/PI3K/AKT Axis

Background

Pancreatic cancer (PC) is one of the fatal cancers globally. CircDEAD-box helicase 42 (circDDX42) has been reported to play an oncogenic role in many cancers. The purpose of our study was to explore the relationship between circDDX42 and PC development and the potential mechanism by which circDDX42 modulating the progression of PC.

Methods

The enrichment of circDDX42, miR-613 and inhibitor of DNA binding 4 (ID4) was determined by quantitative real-time polymerase chain reaction (qRT-PCR) in PC tissues and cells. The proliferation, apoptosis and metastasis of PC cells were examined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Western blot, flow cytometry and transwell migration and invasion assays, respectively. The binding sites between miR-613 and circDDX42 or ID4 were predicted by Starbase bioinformatic software, and dual-luciferase reporter assay was conducted to verify the combination between miR-613 and circDDX42 or ID4. Western blot was carried out to detect the abundance of ID4, p-phosphatidylinositol 3-kinase (p-PI3K), PI3K, p-AKT serine/threonine kinase (p-AKT) and AKT in PC cells. The in vivo role of circDDX42 was verified through using murine xenograft model.

Results

The level of circDDX42 was enhanced in PC tissues and cells compared with that in matching normal tissues and HPDE cells. CircDDX42 promoted the proliferation and metastasis and suppressed the apoptosis of PC cells. CircDDX42 could sponge miR-613, and miR-613 was negatively regulated by circDDX42 in PC cells. MiR-613 suppressed the progression of PC. ID4 was a direct target of miR-613. ID4 was inversely modulated by miR-613 and positively regulated by circDDX42 in PC cells. ID4 played an oncogenic role in the tumorigenesis of PC. CircDDX42/miR-613/ID4 axis regulated the activation of PI3K/AKT pathway in PC cells. ID4 facilitated the progression of PC via activating PI3K/AKT signal pathway. CircDDX42 promoted the tumor growth of PC in vivo.

Conclusion

CircDDX42 accelerated the proliferation and metastasis while impeded the apoptosis of PC cells via circDDX42/miR-613/ID4/PI3K/AKT axis. This axis might be a promising target for PC therapy.

The emerging prospects of circular RNA in tumor immunity

Circular RNA (circRNA), as a cluster of endogenous non-coding RNA (ncRNA) with tissue-specific expression in various eukaryotic species, may be involved in a variety of human physiological and pathological processes. With the continuous development of high-throughput sequencing in recent years, circRNA has been increasingly widely studied and become a hot spot in the field of tumor research. The immune system plays a crucial and complex role in tumor development. It is not only capable of inhibiting tumor progression, but it can also create conditions suitable for tumor development, thereby promoting tumor progression. Moreover, through ncRNA, tumor immunotherapy, as an essential means of tumor therapy, may regulate tumor immunity to achieve the purpose of treatment. This article reviews the role of circRNA in tumor immunity to supply a sufficient theoretical basis for tumor immunotherapy.

Circular RNA hsa_circ_0001785 inhibits the proliferation, migration and invasion of breast cancer cells in vitro and in vivo by sponging miR-942 to upregulate SOCS3

Circular RNAs (circRNAs) are a class of widely expressed noncoding RNA with significant regulatory potential discovered in recent years. The purpose of this study was to investigate the effects of hsa_circ_0001785 on the proliferation, migration and invasion of breast cancer (BC) cells in vivo and in vitro and the potential underlying molecular mechanism. In the present study, the expressions of hsa_circ_0001785 in five BC cells (T47D, MCF-7, MDA-MB-453, MDA-MB-231 and BT-549) and one normal breast cell (MCF-10A) were the first to examined by qRT-PCR. Then, we studied the biological function of hsa_circ_0001785 in BC by in vivo and in vitro experiments. CCK-8, clone formation, wound-healing and Transwell assays were performed to analyze the cellular proliferation, migration and invasion in vitro. The subcutaneous tumor model of nude mice was used for in vivo experiment. In addition, we determined that hsa_circ_0001785 acted as competing endogenous RNAs (ceRNAs) in BC by RNA immunoprecipitation (RIP) and dual-luciferase reporter assays. Results showed that the expressions of hsa_circ_0001785 were decreased in BC cells. Hsa_circ_0001785 overexpression inhibited the proliferation, migration, invasion of BC cells and tumor growth in nude mice. RIP and dual-luciferase reporter assay demonstrated that hsa_circ_0001785 could regulate the SOCS3 by sponging miR-942. In general, circular RNA hsa_circ_0001785 inhibits the proliferation, migration and invasion of BC cells by modulating the miR-942/SOCS3 signaling axis.

QIMCMDA: MiRNA-Disease Association Prediction by q-Kernel Information and Matrix Completion

Studies have shown that microRNAs (miRNAs) are closely associated with many human diseases, but we have not yet fully understand the role and potential molecular mechanisms of miRNAs in the process of disease development. However, ordinary biological experiments often require higher costs, and computational methods can be used to quickly and effectively predict the potential miRNA-disease association effect at a lower cost, and can be used as a useful reference for experimental methods. For miRNA-disease association prediction, we have proposed a new method called Matrix completion algorithm based on q-kernel information (QIMCMDA). We use fivefold cross-validation and leave-one-out cross-validation to prove the effectiveness of QIMCMDA. LOOCV shows that AUC can reach 0.9235, and its performance is significantly better than other commonly used technologies. In addition, we applied QIMCMDA to case studies of three human diseases, and the results show that our method performs well in inferring potential interaction between miRNAs and diseases. It is expected that QIMCMDA will become an excellent supplement in the field of biomedical research in the future.

Oncolytic Vaccinia Virus-Mediated Antitumor Effect and Cell Proliferation Were Promoted in PTC by Regulating circRNA_103598/miR-23a-3p/IL-6 Axis

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of thyroid malignancy, and cases have been rising steadily worldwide in the past few decades. Despite great progress having been made in surgery and chemotherapy for PTC, the survival rate of PTC patients has not increased significantly. Therefore, there is an urgent need to explore novel treatment strategies.

MATERIALS AND METHODS

The levels of circRNA_103598, miR-23a-3p and IL-6 mRNA in PTC tissues and cells were examined by qRT-PCR assay. Cell proliferation and IC50 values of oncolytic vaccinia virus (OVV) were detected by CCK-8 assay. A dual-luciferase reporter assay was performed to detect the relationships among circRNA_103598, miR-23a-3p and IL-6. ELISA was carried out to detect the expression of IL-6.

RESULTS

We found that circRNA_103598 was increased in PTC tissues and cell lines and acted as a sponge for miR-23a-3p. Moreover, knockdown of miR-23a-3p suppressed the OVV-mediated antitumor effect and cell proliferation in PTC. In addition, we revealed that circRNA_103598 bound to miR-23a-3p as a sponge to promote IL-6 expression.

CONCLUSION

Our study first revealed the high expression and oncogenic function of circRNA_103598 in PTC cells. Then, circRNA_103598 sponged miR-23a-3p to upregulate IL-6 expression, with the resulted that cell proliferation was promoted and the OVV-mediated antitumor effect was enhanced by strengthening the viral replication, providing new insights into future therapy for PTC.

Hsa_circRNA_0000518 facilitates breast cancer development via regulation of the miR-326/FGFR1 axis

Background

Breast cancer (BC) is a heterogeneous malignant tumor that threatens the health of women worldwide. Hsa_circRNA_0000518 (circ_0000518) has been revealed to be upregulated in BC tissues. However, the role and mechanism of circ_0000518 in BC are indistinct.

Methods

Quantitative real‐time polymerase chain reaction (qRT‐PCR) was implemented to detect the levels of circ_0000518, microRNA (miR)‐326, and fibroblast growth factor receptor 1 (FGFR1) mRNA in BC tissues and cells. Cell counting kit‐8 (CCK‐8), colony formation, flow cytometry, and transwell assays were executed to estimate BC cell proliferation, cell cycle progression, apoptosis, migration, and invasion. The relationship between circ_0000518 or FGFR1 and miR‐326 was verified by dual‐luciferase reporter and/or RNA immunoprecipitation (RIP) assays. The role of circ_0000518 in vivo was confirmed by xenograft assay.

Results

Circ_0000518 and FGFR1 were upregulated while miR‐326 was downregulated in BC tissues and cells. Circ_0000518 silencing impeded tumor growth in vivo and induced cell cycle arrest, apoptosis, cured proliferation, colony formation, migration, and invasion of BC cells in vitro. Circ_0000518 regulated FGFR1 expression via competitively binding to miR‐326 in BC cells. MiR‐326 inhibitor reversed the inhibitory influence of circ_0000518 knockdown on the malignant behaviors of BC cells. FGFR1 overexpression abolished miR‐326 mimic‐mediated influence on the malignant behaviors of BC cells.

Conclusions

Circ_0000518 facilitated BC development via regulation of the miR‐326/FGFR1 axis, suggesting that circ_0000518 might be a promising target for BC treatment.