circTADA2As suppress breast cancer progression and metastasis via targeting miR-203a-3p/SOCS3 axis

Long non-coding RNA-MIR181A1HG acts as an oncogene and contributes to invasion and metastasis in gastric cancer

Dysregulation of long non-coding RNAs (lncRNA) plays an essential role in cancer development and progression. However, their functions and mechanisms of action in gastric cancer (GC) remain largely unknown. Gene expression in GC was evaluated using quantitative real-time PCR, western blotting, immunofluorescence, immunohistochemistry, and RNA in situ hybridization. The impact of MIR181A1HG on GC cells was explored in vitro and in vivo using cell proliferation, migration, invasion assays and animal models. Biotinylated RNA pull-down, RNA immunoprecipitation, co-immunoprecipitation, chromatin immunoprecipitation, and luciferase reporter assays were performed to evaluate the molecular interactions. LncRNA-MIR181A1HG was upregulated in GC and associated with malignant progression. MIR181A1HG physically interacts with ELAVL1 to regulate epithelial-mesenchymal transition (EMT) in GC cells. MIR181A1HG intron-derived miR-181a-5p/miR-181b-5p triggers MIR181A1HG transcription through binding to and destabilizing SOCS3 messenger RNA. Specifically, SOCS3 interacts with NFATC2 and downregulated SOCS3 enhances the NFATC2-mediated transcriptional activation of the MIR181A1HG promoter. Collectively, MIR181A1HG, activated by miR-181a-5p/miR-181b-5p-SOCS3-NFATC2 positive feedback loop, contributes to GC progression through stabilizing ELAVL1. MIR181A1HG expression correlates positively with ELAVL1, miR-181a-5p, miR-181b-5p, and NFATC2 and negatively with SOCS3 in fresh GC samples. These data demonstrate that MIR181A1HG plays an important role in tumor progression by promoting invasion, metastasis, and EMT, indicating its potential as a prognostic biomarker in GC.

Deciphering the role of circular RNAs in cancer progression under hypoxic conditions

Hypoxia, characterized by reduced oxygen levels, plays a pivotal role in cancer progression, profoundly influencing tumor behavior and therapeutic responses. A hallmark of solid tumors, hypoxia drives significant metabolic adaptations in cancer cells, primarily mediated by hypoxia-inducible factor-1α (HIF-1α), a key transcription factor activated in low-oxygen conditions. This hypoxic environment promotes epithelial-mesenchymal transition (EMT), enhancing cancer cell migration, metastasis, and the development of cancer stem cell-like properties, which contribute to therapy resistance. Moreover, hypoxia modulates the expression of circular RNAs (circRNAs), leading to their accumulation in the tumor microenvironment. These hypoxia-responsive circRNAs regulate gene expression and cellular processes critical for cancer progression, making them promising candidates for diagnostic and prognostic biomarkers in various cancers. This review delves into the intricate interplay between hypoxic circRNAs, microRNAs, and RNA-binding proteins, emphasizing their role as molecular sponges that modulate gene expression and signaling pathways involved in cell proliferation, apoptosis, and metastasis. It also explores the relationship between circRNAs and the tumor microenvironment, particularly how hypoxia influences their expression and functional dynamics. Additionally, the review highlights the potential of circRNAs as diagnostic and prognostic tools, as well as their therapeutic applications in innovative cancer treatments. By consolidating current knowledge, this review underscores the critical role of circRNAs in cancer biology and paves the way for future research aimed at harnessing their unique properties for clinical advancements. Specifically, this review examines the biogenesis, expression patterns, and mechanistic actions of hypoxic circRNAs, focusing on their ability to act as molecular sponges for microRNAs and their interactions with RNA-binding proteins. These interactions impact key signaling pathways related to tumor growth, metastasis, and drug resistance, offering new insights into the complex regulatory networks governed by circRNAs under hypoxic stress.

Human and pathogen-encoded circular RNAs in viral infections: insights into functions and therapeutic opportunities

Circular RNAs (circRNAs) are emerging as important regulatory molecules in both host and viral systems, acting as microRNA sponges, protein decoys or scaffolds, and templates for protein translation. Host-derived circRNAs are increasingly recognized for their roles in immune responses, while virus-encoded circRNAs, especially those from DNA viruses, have been shown to modulate host cellular machinery to favor viral replication and immune evasion. Recently, RNA virus-encoded circRNAs were also discovered, but evidence suggests that they might be generated using a different mechanism compared to the circRNAs produced from the host and DNA viruses. This review highlights recent advances in our understanding of both host and virus-derived circRNAs, with a focus on their biological roles and contributions to pathogenesis. Furthermore, we discuss the potential of circRNAs as biomarkers and their application as therapeutic targets or scaffolds for RNA-based therapies. Understanding the roles of circRNAs in host-virus interactions offers novel insights into RNA biology and opens new avenues for therapeutic strategies against viral diseases and associated cancers.

Hsa_circ_0072088 promotes non-small cell lung cancer progression through modulating miR-1270/TOP2A axis

According to the data released by the International Agency for Research on Cancer (IARC) in 2020, lung cancer ranks second among newly diagnosed malignant tumors globally. As a special class of non-coding RNA, circRNA has become a new hotspot in the field of biomarker research. With the continuous deepening of molecular-level investigations, the underlying mechanisms of circRNA are being gradually unveiled. The more widely studied mechanism is the competitive endogenous RNA mechanism of circRNA. Studies related to circRNA expression were searched in GEO database and statistically analyzed using the "limma" package and weighted gene co-expression network analysis. The expression of circRNA, microRNA and mRNA in cells and tissues were examined via qRT-PCR. MTS assay was used to measure cell proliferation, Transwell assay was used to measure cell migration, and apoptosis assay was carried out to detect cell apoptosis. Additionally, a dual-luciferase reporter assay was further executed to explore the targeted binding relationships between circRNA-microRNA and microRNA-mRNA. It was discovered that hsa_circRNA_103809 was differentially highly expressed in non-small cell lung cancer cells, whereas miR-1270 was differentially lowly expressed. The knockdown of circ_0072088 inhibited the cell proliferation and migration, while promoting cell apoptosis. The same biological function was found with the overexpression of miR-1270. The rescue experiment further validated that circ_0072088 could regulate the biological function of cells by influencing miR-1270. Finally, the targeted binding relationship was verified by dual luciferase reporting experiment. In conclusion, circ_0072088 is differentially highly expressed in non-small cell lung cancer and can affect the progression of non-small cell lung cancer through the circ_0072088/miR-1270/TOP2A axis.

Circ_0000190 inhibits the progression of triple negative breast cancer by regulating miR-301a/MEOX2 pathway

Circular RNA (circRNA) and microRNA (miRNA) play critical roles in regulating proliferation, apoptosis, and invasion in triple-negative breast cancer (TNBC) cells. To investigate their functional significance, we employed quantitative real-time PCR (qRT-PCR) to assess the differential expression of circ_0000190, miR-301a, and mesenchyme homeobox 2 (MEOX2) between TNBC cell lines and normal breast epithelial cells. Subsequently, we established overexpression and knockdown systems for these molecules to examine their effects on TNBC cell proliferation, apoptosis, migration, invasion, and epithelial-mesenchymal transition (EMT). Additionally, we evaluated the impact of circ_0000190 overexpression on tumor growth using a mouse xenograft model, measuring tumor volume and weight. Our findings revealed that circ_0000190 and MEOX2 expression were significantly downregulated (P<0.05) in TNBC cells compared to normal breast epithelial cells, whereas miR-301a was upregulated (P<0.05). Knockdown of circ_0000190 promoted TNBC cell proliferation, migration, invasion, and EMT, while suppressing apoptosis. Mechanistically, circ_0000190 functioned as a molecular sponge for miR-301a, and its overexpression significantly inhibited miR-301a expression (P<0.001). Notably, miR-301a mimics partially reversed the suppressive effects of circ_0000190 overexpression on proliferation, migration, invasion, and EMT, as well as its pro-apoptotic effects (P<0.001). Furthermore, we identified MEOX2 as a direct target of miR-301a. MEOX2 knockdown attenuated the inhibitory effects of miR-301a silencing on proliferation, migration, invasion, and EMT, while also counteracting its pro-apoptotic function. In vivo experiments demonstrated that circ_0000190 overexpression significantly reduced tumor volume and weight (P<0.001), concomitant with elevated MEOX2 mRNA and protein levels (P<0.001) and decreased miR-301a expression (P<0.001). In conclusion, our study elucidates that circ_0000190 suppresses TNBC progression by downregulating miR-301a and upregulating MEOX2, forming a competitive endogenous RNA (ceRNA) network of circRNA-miRNA-mRNA.

circSTIL mediates pirarubicin inhibiting the malignant phenotype of triple-negative breast cancer and acts as a biomarker in plasma exosomes

In clinical practice, pirarubicin (THP) is a widely used triple-negative breast cancer (TNBC) agent. It has been found that circular RNAs (circRNAs) are involved in cancer treatment and progression. However, the biological function of circRNAs in TNBC and the relationship between THP and circRNAs remain poorly studied. circSTIL (hsa_circ_0000069) was screened and validated by bioinformatics analysis, demonstrating that it was highly expressed in TNBC cell lines and plasma exosomes, and correlated with a poor prognosis of patients. The expression level of circSTIL in patients' plasma exosomes has potential diagnostic value in distinguishing TNBC from non-TNBC. In vitro studies confirmed that overexpression of circSTIL promotes the proliferation, migration, and invasion of MDA-MB-231 cells whereas silicification of circSTIL shows the reverse effect. Also, circSTIL mediates THP inhibiting the malignant phenotype of MDA-MB-231 cells. The above results suggested that circSTIL is a possible biomarker for the diagnosis, treatment, and prognosis of TNBC.

Emerging role and clinical applications of circular RNAs in human diseases

Circular RNAs (circRNAs) are a large family of non-coding RNAs characterized by a single-stranded, covalently closed structure, predominantly synthesized through a back-splicing mechanism. While thousands of circRNAs have been identified, only a few have been functionally characterized. Although circRNAs are less abundant than other RNA types, they exhibit exceptional stability due to their covalently closed structure and demonstrate high cell and tissue specificity. CircRNAs play a critical role in maintaining cellular homeostasis by influencing gene transcription, translation, and post-translation processes, modulating the immune system, and interacting with mRNA, miRNA, and proteins. Abnormal circRNA expression has been associated with a wide range of human diseases and various infections. Due to their remarkable stability in body fluids and tissues, emerging research suggests that circRNAs could serve as diagnostic and therapeutic biomarkers for these diseases. This review focuses on the emerging role of circRNAs in various human diseases, exploring their biogenesis, molecular functions, and potential clinical applications as diagnostic and therapeutic biomarkers with current evidence, challenges, and future perspectives. The key theme highlights the significance of circRNAs in regulating gene expression, their involvement in diseases like cancer, neurodegenerative disorders, cardiovascular diseases, and diabetes, and their potential use in translational medicine for developing novel therapeutic strategies. We also discuss recent clinical trials involving circRNAs. Thus, this review is important for both basic researchers and clinical scientists, as it provides updated insights into the role of circRNAs in human diseases, aiding further exploration and advancements in the field.

CircRNAs: a novel potential strategy to treat breast cancer

Breast cancer is among the most prevalent malignant tumors worldwide, with triple-negative breast cancer (TNBC) being the most aggressive subtype and lacking effective treatment options. Circular RNAs (circRNAs) are noncoding RNAs that play crucial roles in the development of tumors, including breast cancer. This article examines the progress of research on circRNAs in breast cancer, focusing on four main areas: 1) breast cancer epidemiology, classification, and treatment; 2) the structure, discovery process, characteristics, formation, and functions of circRNAs; 3) the expression, mechanisms, clinical relevance, and recent advances in the study of circRNAs in breast cancer cells and the immune microenvironment, particularly in TNBC; and 4) the challenges and future prospects of the use of circRNAs in BC research.

Hsa_circ_0001492 regulates the hsa-miR-145-5p/ovarian carcinoma immunoreactive antigen domain 2 axis to promote the progression of lung adenocarcinoma

Circular RNA (circRNA) has been proven to be a key regulator in a range of tumor illnesses, such as lung adenocarcinoma (LUAD); however, the regulatory mechanisms of circRNA remain unclear. In this study, circRNA (hsa_circ_0001492) in LUAD was examined for its regulatory and functional potential. qRT-PCR was used to assess the hsa_circ_0001492 level in LUAD. The RNAse R digestion test was employed to isolate hsa_circ_0001492. The primary location of hsa_circ_0001492 enrichment in LUAD cells was identified through a nucleoplasmic separation test. LUAD cell migration, proliferation, and spherogenicity were examined using wound healing, transwell, EdU, and cell spherogenicity assays. The association between miR-145-5p and hsa_circ_0001492/ovarian carcinoma immunoreactive antigen domain 2 (OCIAD2) was validated using a dual luciferase experiment. The interaction between sh-hsa_circ_0001492 and miR-145-5p was confirmed through an RNA pull-down assay. The effects of hsa_circ_0001492, miR-145-5p, and OCIAD2 on LUAD tumor development were examined using xenograft mouse models and immunohistochemistry tests. Results showed a higher amount of hsa_circ_0001492 in LUAD. The cytoplasm of LUAD cells was observed in the area where hsa_circ_0001492 mainly accumulated; hsa_circ_0001492 enhanced LUAD cell migration, proliferation, and sphere-forming ability. MiR-145-5p and OCIAD2 were identified as targets of hsa_circ_0001492 and miR-145-5p, respectively. The level of OCIAD2 was increased by hsa_circ_0001492 through targeted binding to miR-145-5p. In nude mice, tumor growth was inhibited by silencing hsa_circ_0001492, while knockdown of miR-145-5p and overexpression of OCIAD2 promoted the growth of LUAD tumors. In conclusion, hsa_circ_0001492 regulates the hsa-miR-145-5p/OCIAD2 axis to promote the progression of LUAD, and could be a useful target for the diagnosis and treatment of LUAD.

Development of a prognostic model based on the ceRNA network in Triple-Negative Breast cancer

Background

Triple-negative breast cancer (TNBC) is an aggressive subtype with a poor prognosis. Although circular RNAs (circRNAs) have been implicated in cancer progression, their roles in TNBC remain poorly understood. In this study, we aimed to develop a prognostic model for TNBC by constructing a competing endogenous RNA (ceRNA) network. This network integrates circRNAs, long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) to identify potential biomarkers and therapeutic targets for improving clinical outcomes.

Methods

Differentially expressed circRNAs, lncRNAs, and mRNAs were identified from GEO datasets (144 samples: 94 TNBC and 50 normal tissues). A ceRNA network was constructed, and key genes were validated using The Cancer Genome Atlas (TCGA) dataset (115 TNBC and 113 para-cancer tissues). Multivariate Cox regression analysis was performed to develop a prognostic model, and Gene Set Enrichment Analysis (GSEA) was performed to identify associated pathways.

Results

Nine genes (SH3BGRL2, CA12, LRP8, NAV3, GFRA1, DCDC2, CDC7, ABAT, NPTX1) were identified as key factors in the prognostic model, which demonstrated an area under the curve (AUC) of 0.90. Patients classified as high-risk patients exhibited significantly shorter overall survival (median OS: 8.12 years vs. 9.51 years, P < 0.01). The mitogen-activated protein kinase (MAPK) signaling pathway was identified as a key regulatory pathway, with circRNAs (hsa_circ_0005455, hsa_circ_000632, hsa_circ_0001666, and hsa_circ_0000069) regulating CA12, GFRA1, and NPTX1 expression.

Conclusion

This study developed a novel prognostic model based on a ceRNA network analysis, highlighting the critical role of circRNAs and the MAPK signaling pathway in TNBC progression. These findings offer valuable insights into potential biomarkers for TNBC prognosis and reveal promising therapeutic targets for improving patient outcomes.

Research on curcumin mediating immunotherapy of colorectal cancer by regulating cancer associated fibroblasts

The objective was to investigate curcumin's (Cur) function and associated molecular mechanisms in regulating tumor immunity in colon cancer. Primary cancer-associated fibroblasts (CAFs) from mouse CT26 colon cancer tumors were isolated. Validation of primary CAFs using immunofluorescence assay was done. Cell Counting Kit-8 experiments, real-time quantitative PCR (qPCR), and enzyme linked immunosorbent assay experiments were conducted to investigate how curcumin affected the growth and cytokine secretion functions of CAFs. The effect of curcumin on regulating PD-L1 expression on CT26 cells through CAFs in vitro was explored through coculture of CAFs and tumor cells, qPCR, and western blot experiments. A mouse colon cancer cell model was established in Balb/c nude mice to explore the effect of curcumin on colon tumor cells. Changes in the tumor microenvironment were detected by flow cytometry to explore the synergistic effect of curcumin combined with anti-PD-1 monoclonal antibody in the treatment of mouse colon cancer. In vitro, curcumin prevented the growth and TGF-β secretion of CT26 cells. At the same time, curcumin inhibited the secretion of TGF-β by CAFs, thereby downregulating the PD-L1 expression of CT26 cells. In vivo, curcumin combined with anti-PD-1 antibodies can further enhance the inhibitory effect of PD-1 antibodies on tumors and increase the number of tumor-suppressing immune cells in the tumor microenvironment, such as M1 macrophages and CD8 T cells, thus inhibiting tumors. Immune M2 macrophages, regulatory T cells, and other cells were reduced. In conclusion, curcumin reduces the expression of PD-L1 in colon cancer cells and improves the tumor immune microenvironment by inhibiting the proliferation of CAFs and the secretion of TGF-β. Curcumin and anti-PD-1 treatment have synergistic inhibitory effects on colon cancer.

Hsa_circ_0002346 inhibits proliferation, invasion, and migration of breast cancer cells and promotes apoptosis: A novel potential biomarker for breast cancer

BackgroundCircular RNA hsa_circ_0002346 has been implicated in the progression of various tumors, yet the functional role in breast cancer remains poorly understood. This study aimed to investigate the significance of hsa_circ_0002346 in breast cancer (BC).MethodsQuantitative reverse transcriptase polymerase chain reaction assays were performed to detect hsa_circ_0002346 expression in BC cell lins and 27 patients with BC. Then, siRNAs were used to knock down hsa_circ_0002346. And detecting function of downregulated hsa_circ_0002346 by proliferation colony formation, apoptosis assays, wound-healing assays and Transwell assays. Finally, we assess the levels of the EMT-associated proteins.ResultsOur findings suggest that hsa_circ_0002346 levels were significantly downregulated in breast cancer and may play a crucial role in regulating key cellular processes associated with cancer progression. The expression level of hsa_circ_0002346 was correlated with lymph node metastasis. The knockdown of hsa_circ_0002346 resulted in increased tumor cell proliferation, invasion, migration and decreased apoptosis. Additionally, alterations in the expression of EMT-associated proteins further support the hypothesis that hsa_circ_0002346 is implicated in the metastatic processes of breast cancer.Conclusionhsa_circ_0002346 emerges as a promising biomarker for breast cancer and a potential therapeutic target for future treatment strategies.

In silico analysis and comprehensive review of circular-RNA regulatory roles in breast diseases; a step-toward non-coding RNA precision

In the current comprehensive review, we first highlighted circRNAs, which are key ncRNAs. Next, we discussed the relationships among circRNAs and breast cancer subtypes via in silico databases analysis and extensive literature search. CircRNAs, that sponge miRNA axes or act as silencers of oncogenic mRNAs, have been extensively addressed in the context of this review. During BC pathogenesis, the circRNA/microRNA/messenger RNA (mRNA) axis plays a major role in disease growth, progression, and survival/resistance and could be targeted for improved treatment options. This review also aimed to address oncogenic and tumor suppressor mRNAs, which are regulated by various circRNAs in BC. Moreover, we mentioned the relation of different circRNAs with cancer hallmarks, patient survival together with drug resistance. Additionally, we discussed circRNAs as vaccines and biomarkers in BC. Finally, we studied exosomal circRNAs as a hot interesting area in the research. REVIEW SIGNIFICANCE: Via using in silico databases, bioinformatics analysis, and a thorough literature search to first highlight circRNA as a crucial ncRNA and its biogenesis, and then we explored the connection between circRNA and breast illnesses. In the framework of the review, circRNA sponged-miRNAs axis or as silencers to oncogenic mRNAs were extensively discussed. In the pathophysiology of BC, the circular RNA/microRNA/messenger RNA axis is crucial for the propagation of the disease and resistance that may be targeted for more effective treatment options, in order to confront tumor suppressor and oncogenic mRNAs that are presently regulated by circRNAs in BC. For better patient results, we advised further mechanistic research to elucidate additional ncRNA axis that may be targeted for the therapy of BC and for prognosis/ or early diagnosis.

CircCOCH plays a critical role in Hepatocellular carcinoma through modulating miR-450a and activating PI3K/mTOR pathway

Hepatocellular carcinoma (HCC) is a primary liver cancer with high pathogenicity and extremely poor prognosis. The role of circular RNAs (circRNAs) in HCC carcinogenesis and progression remains to be determined. Based on the analysis of HCC-related databases, as well as the expression analysis and identification of 25 HCC patient tissues and HCC cell lines, we found that the hsa_circ_0031431 (circCOCH) is significantly highly expressed in HCC tissues and cell lines. High circCOCH expression is associated with enhanced tumor proliferation and metastasis, and knocking down circCOCH can inhibit the growth of HCC in vivo and in vitro. Mechanistic studies show that circCOCH upregulates the expression of epidermal growth factor receptor (EGFR) through sponge miR-450a, thereby activating the Phosphoinositide 3-kinases (PI3Ks) cell pathway to promote HCC proliferation and metastasis. Futhermore, we found that IGF2BP3 mediates the biogenesis of circCOCH. The present study provides innovative insights into the role of circRNAs in the etiology of HCC carcinogenesis and might serve as a new promising therapeutic target for HCC.

Circular RNAs as a novel molecular mechanism in diagnosis, prognosis, therapeutic target, and inhibiting chemoresistance in breast cancer

Breast cancer (BC) is the most common cancer among women, characterized by significant heterogeneity. Diagnosis of the disease in the early stages and appropriate treatment plays a crucial role for these patients. Despite the available treatments, many patients due to drug resistance do not receive proper treatments. Recently, circular RNAs (circRNAs), a type of non-coding RNAs (ncRNAs), have been discovered to be involved in the progression and resistance to drugs in BC. CircRNAs can promote or inhibit malignant cells by their function. Numerous circRNAs have been discovered to be involved in the proliferation, invasion, and migration of tumor cells, as well as the progression, pathogenesis, tumor metastasis, and drug resistance of BC. Circular RNAs can also serve as a biomarker for diagnosing, predicting prognosis, and targeting therapy. In this review, we present an outline of the variations in circRNAs expression in various BCs, the functional pathways, their impact on the condition, and their uses in clinical applications.

Plasma Exosome miR-203a-3p is a Potential Liquid Biopsy Marker for Assessing Tumor Progression in Breast Cancer Patients

Background

Timely detection of tumor progression in breast cancer (BC) patients is critical for therapeutic management and prognosis. Plasma exosomal miRNAs are potential liquid biopsy markers for monitoring tumor progression, but their roles in BC remain unclear.

Methods

In the TCGA database, we first screened for miRNAs significantly associated with BC progression by comparing miRNA expression in para-carcinoma tissues, stage I BC tissues, and stage II-III BC tissues (n = 1026). Cox regression analyses and survival analyses were performed on candidate miRNAs to explore their prognostic value (n = 848). KEGG, GO, and PPI analyses were used to identify enriched pathways associated with cancer. Finally, the potential of candidate miRNAs as liquid biopsy markers was evaluated by sequencing and analyzing plasma exosomal miRNAs from our collection of 45 BC patients (14 in stage I, 31 in stage II-III) and 5 healthy controls, combined with qRT-PCR analysis to assess the correlation of candidate gene expression in plasma exosomes and BC tissues.

Results

We found that only miR-203a-3p was progressively elevated with BC progression and was associated with poor prognosis in the TCGA dataset. Its potential target genes were enriched in pathways related to tumor progression, and the downregulation of 48 of these genes was associated with poor prognosis. More importantly, plasma exosomal miR-203a-3p was also found to gradually increase with BC progression, and its expression was positively correlated with miR-203a-3p in BC tissues. This result suggests that plasma exosomal miR-203a-3p may reflect the expression of miR-203a-3p in tumor tissues and serve as a potential liquid biopsy marker for monitoring BC progressions.

Conclusion

We found for the first time that elevated miR-203a-3p was associated with BC progression and poor prognosis. Our findings suggested that plasma exosomal miR-203a-3p could hold potential as a liquid biopsy marker for evaluating BC progression in patients.

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Exploring the impact of circRNAs on cancer glycolysis: Insights into tumor progression and therapeutic strategies

Cancer cells exhibit altered metabolic pathways, prominently featuring enhanced glycolytic activity to sustain their rapid growth and proliferation. Dysregulation of glycolysis is a well-established hallmark of cancer and contributes to tumor progression and resistance to therapy. Increased glycolysis supplies the energy necessary for increased proliferation and creates an acidic milieu, which in turn encourages tumor cells' infiltration, metastasis, and chemoresistance. Circular RNAs (circRNAs) have emerged as pivotal players in diverse biological processes, including cancer development and metabolic reprogramming. The interplay between circRNAs and glycolysis is explored, illuminating how circRNAs regulate key glycolysis-associated genes and enzymes, thereby influencing tumor metabolic profiles. In this overview, we highlight the mechanisms by which circRNAs regulate glycolytic enzymes and modulate glycolysis. In addition, we discuss the clinical implications of dysregulated circRNAs in cancer glycolysis, including their potential use as diagnostic and prognostic biomarkers. All in all, in this overview, we provide the most recent findings on how circRNAs operate at the molecular level to control glycolysis in various types of cancer, including hepatocellular carcinoma (HCC), prostate cancer (PCa), colorectal cancer (CRC), cervical cancer (CC), glioma, non-small cell lung cancer (NSCLC), breast cancer, and gastric cancer (GC). In conclusion, this review provides a comprehensive overview of the significance of circRNAs in cancer glycolysis, shedding light on their intricate roles in tumor development and presenting innovative therapeutic avenues.

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

Advanced Insights into Competitive Endogenous RNAs (ceRNAs) Regulated Pathogenic Mechanisms in Metastatic Triple-Negative Breast Cancer (mTNBC)

Triple-negative breast cancer is aggressive and challenging to treat because of a lack of targets and heterogeneity among tumors. A paramount factor in the mortality from breast cancer is metastasis, which is driven by genetic and phenotypic alterations that drive epithelial-mesenchymal transition, stemness, survival, migration and invasion. Many genetic and epigenetic mechanisms have been identified in triple-negative breast cancer that drive these metastatic phenotypes; however, this knowledge has not yet led to the development of effective drugs for metastatic triple-negative breast cancer (mTNBC). One that may not have received enough attention in the literature is post-translational regulation of broad sets of cancer-related genes through inhibitory microRNAs and the complex competitive endogenous RNA (ceRNA) regulatory networks they are influenced by. This field of study and the resulting knowledge regarding alterations in these networks is coming of age, enabling translation into clinical benefit for patients. Herein, we review metastatic triple-negative breast cancer (mTNBC), the role of ceRNA network regulation in metastasis (and therefore clinical outcomes), potential approaches for therapeutic exploitation of these alterations, knowledge gaps and future directions in the field.

Therapeutic SHPRH-146aa encoded by circ-SHPRH dynamically upregulates P21 to inhibit CDKs in neuroblastoma

Recent research has underscored the significance of circular RNAs (circRNAs) in various cancers, including neuroblastoma (NB). Specifically, circ-SHPRH, a unique circRNA, has been revealed to inhibit tumor growth by sequestering miRNAs or producing the SHPRH-146aa protein. To explore circ-SHPRH's involvement in NB and its potential application in gene therapy, this study examined circ-SHPRH expression in 94 NB tissues and cell lines (SK-N-BE(2), SH-SY5Y) using real-time PCR and fluorescence in situ hybridization (FISH). Functional assays encompassing both overexpression and knockdown experiments in NB cell lines, as well as in vivo investigations, were conducted. RNA-seq analysis revealed a correlation between circ-SHPRH and the pathway of P21 (CDKN1A), a pivotal cell cycle regulator. Validation through PCR and other techniques confirmed that circ-SHPRH upregulated P21 expression. Furthermore, the regulatory role of circ-SHPRH in the P21-CDK pathway was corroborated through SHPRH-146aa expression analysis. Notably, adenovirus-mediated circ-SHPRH overexpression effectively curbed NB tumor growth in NSG mice, while combining circ-SHPRH with everolimus exhibited potential for NB treatment. This study elucidates the remarkable significance of circ-SHPRH in NB and its prospective utility in gene therapy, thereby paving the way for innovative therapeutic approaches.

Engineering circular RNA for molecular and metabolic reprogramming

The role of messenger RNA (mRNA) in biological systems is extremely versatile. However, it's extremely short half-life poses a fundamental restriction on its application. Moreover, the translation efficiency of mRNA is also limited. On the contrary, circular RNAs, also known as circRNAs, are a common and stable form of RNA found in eukaryotic cells. These molecules are synthesized via back-splicing. Both synthetic circRNAs and certain endogenous circRNAs have the potential to encode proteins, hence suggesting the potential of circRNA as a gene expression machinery. Herein, we aim to summarize all engineering aspects that allow exogenous circular RNA (circRNA) to prolong the time that proteins are expressed from full-length RNA signals. This review presents a systematic engineering approach that have been devised to efficiently assemble circRNAs and evaluate several aspects that have an impact on protein production derived from. We have also reviewed how optimization of the key components of circRNAs, including the topology of vector, 5' and 3' untranslated sections, entrance site of the internal ribosome, and engineered aptamers could be efficiently impacting the translation machinery for molecular and metabolic reprogramming. Collectively, molecular and metabolic reprogramming present a novel way of regulating distinctive cellular features, for instance growth traits to neoplastic cells, and offer new possibilities for therapeutic inventions.

Optimal design of synthetic circular RNAs

Circular RNAs are an unusual class of single-stranded RNAs whose ends are covalently linked via back-splicing. Due to their versatility, the need to express circular RNAs in vivo and in vitro has increased. Efforts have been made to efficiently and precisely synthesize circular RNAs. However, a review on the optimization of the processes of circular RNA design, synthesis, and delivery is lacking. Our review highlights the multifaceted aspects considered when producing optimal circular RNAs and summarizes the available options for each step of exogenous circular RNA design and synthesis, including circularization strategies. Additionally, this review describes several potential applications of circular RNAs.

MicroRNAs as promising biomarkers and potential therapeutic agents in breast cancer management: a comprehensive review

Breast cancer (BC), a complex and varied ailment, poses a significant global health burden. MicroRNAs (miRNAs) have emerged as vital regulators in BC progression, with potential implications for diagnosis and treatment. This review aims to synthesize current insights into miRNA dysregulation in BC. MiRNAs, small RNA molecules, govern gene expression post-transcriptionally and are implicated in BC initiation, metastasis, and therapy resistance. Differential expression of specific miRNAs in BC tissues versus normal breast tissue sheds light on underlying molecular mechanisms. MiRNAs also offer promise as diagnostic biomarkers due to their stable nature, accessibility in bodily fluids, and altered expression patterns in early-stage disease, augmenting conventional diagnostic methods. Beyond diagnosis, miRNAs also hold promise as therapeutic targets in BC. By modulating the expression of specific dysregulated miRNAs, it may be possible to restore normal cellular functions and overcome treatment resistance. However, several challenges need to be addressed before miRNA-based therapies can be translated into clinical practice, including the development of efficient delivery systems and rigorous evaluation through preclinical and clinical trials. MiRNAs represent a promising avenue in BC research, offering potential applications in diagnosis, prognosis, and therapeutic interventions. As our understanding of miRNA biology deepens and technology advances, further research and collaborative efforts are needed to fully exploit the diagnostic and therapeutic potential of miRNAs in BC management. Ultimately, the integration of miRNA-based approaches into clinical practice may lead to more personalized and effective strategies for combating this devastating disease.

Hsa_circ_0003356 suppresses gastric cancer progression via miR-556-5p/FKBP5 axis

BACKGROUND

CircRNAs are implicated in the tumorigenesis of various human cancers. This study aims to explore how circ_0003356 contributes to the development of gastric cancer (GC).

METHODS

Circ_0003356 expression was analyzed in GSE184882 dataset and validated in our cohort of GC patients and human GC cell lines. The correlations between circ_0003356 levels and prognostic parameters were analyzed. The contribution of circ_0003356 in GC cell malignant behaviors such as cell survival, apoptosis and invasion were investigated by circ_0003356 overexpression in GC cell lines. The downstream targets of circ_0003356 were predicted and verified in vitro and in vivo. The in vivo function of circ_0003356 was studied as well in a xenograft mouse model.

RESULTS

Circ_0003356 expressed at a low level in human GC tissues and cells, which was closely associated with poor outcome of GC patients. Circ_0003356 overexpression induced GC cell apoptosis while depressed the growing, migration and invasive abilities through miR-556-5p/FKBP5 axis. In vivo model showed retarded tumor growth when circ_0003356-overexpressed cells were inoculated.

CONCLUSION

Circ_0003356 is identified as a potential biomarker of the prognosis of human gastric cancer, and circ_0003356/miR-556-5p/FKBP5 axis could be a promising target in gastric cancer treatment.

The therapeutic potential of circular RNA in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is among the most aggressive subtypes of the disease that does not express estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Circular RNAs (circRNAs) are a type of non-coding RNA with a circular shape formed by non-standard splicing or reverse splicing. Numerous circRNAs exhibit abnormal expression in various malignancies, showing their critical role in the emergence and growth of tumors. Recent studies have shown evidence supporting the idea that certain circRNAs regulate the proliferation and metastasis of TNBC. In addition, circRNAs alter metabolism and the immune microenvironment to promote or inhibit the development of TNBC. Notably, circRNAs may affect the efficacy of clinical drug therapy, serve as therapeutic targets, and be used as molecular biomarkers in the future. Herein, we will first summarize the biogenesis and function of circRNAs. Then, we will explain current research on circRNAs related to TNBC and their potential to serve as therapeutic targets or biomarkers for future drug development, providing a new direction and idea for TNBC therapy.

Bioinformatics analysis of the potentially functional circRNA-miRNA-mRNA network in breast cancer

Breast cancer (BC) is the most common cancer among women with high morbidity and mortality. Therefore, new research is still needed for biomarker detection. GSE101124 and GSE182471 datasets were obtained from the Gene Expression Omnibus (GEO) database to evaluate differentially expressed circular RNAs (circRNAs). The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) databases were used to identify the significantly dysregulated microRNAs (miRNAs) and genes considering the Prediction Analysis of Microarray classification (PAM50). The circRNA-miRNA-mRNA relationship was investigated using the Cancer-Specific CircRNA, miRDB, miRTarBase, and miRWalk databases. The circRNA-miRNA-mRNA regulatory network was annotated using Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database. The protein-protein interaction network was constructed by the STRING database and visualized by the Cytoscape tool. Then, raw miRNA data and genes were filtered using some selection criteria according to a specific expression level in PAM50 subgroups. A bottleneck method was utilized to obtain highly interacted hub genes using cytoHubba Cytoscape plugin. The Disease-Free Survival and Overall Survival analysis were performed for these hub genes, which are detected within the miRNA and circRNA axis in our study. We identified three circRNAs, three miRNAs, and eighteen candidate target genes that may play an important role in BC. In addition, it has been determined that these molecules can be useful in the classification of BC, especially in determining the basal-like breast cancer (BLBC) subtype. We conclude that hsa_circ_0000515/miR-486-5p/SDC1 axis may be an important biomarker candidate in distinguishing patients in the BLBC subgroup of BC.

circTADA2A inhibited SLC38A1 expression and suppresses melanoma progression through the prevention of CNBP trans-activation

BACKGROUND

CircTADA2A has been demonstrated to play critical roles in the occurrence and development of human cancer. However, the expression pattern and biological mechanisms of circTADA2A in melanoma remains largely unknown.

METHODS

CircTADA2A were detected by quantitative real-time RT-PCR (qRT-PCR) and validated by Sanger sequencing. Function of circTADA2A and its protein partner in melanoma cells was investigated using RNA interference and overexpression assays. Interaction of circTADA2A, CCHC-type zinc finger nucleic acid binding protein (CNBP) and solute carrier family 38 member 1 (SLC38A1) was confirmed by RNA immunoprecipitation, RNA pull-down, and dual-luciferase reporter assay. The expression of genes and proteins were detected by qRT-PCR and western blot assays.

RESULTS

Data from the investigation showed that a novel circRNA (circTADA2A, hsa_circ_0043278) was markedly downregulated in melanoma cells. Functionally, circTADA2A repressed cell proliferation, migration, invasion in melanoma cells. Mechanistically, circTADA2A interacted with CNBP, acting to suppress the binding of CNBP to the SLC38A1 promoter and subsequently restrained SLC38A1 transcription, which resulting in repression of melanoma progression.

CONCLUSIONS

CircTADA2A suppresses melanoma progression by regulating CNBP/SLC38A1 axis, indicating a potential therapeutic target in melanoma.

Circular ZDHHC11 supports Burkitt lymphoma growth independent of its miR-150 binding capacity

We previously showed that MYC promoted Burkitt lymphoma (BL) growth by inhibiting the tumor suppressor miR-150, resulting in release of miR-150 targets MYB and ZDHHC11. The ZDHHC11 gene encodes three different transcripts including a mRNA (pcZDHHC11), a linear long non-coding RNA (lncZDHHC11) and a circular RNA (circZDHHC11). All transcripts contain the same region with 18 miR-150 binding sites. Here we studied the relevance of circZDHHC11, including this miR-150 binding site region, for growth of BL cells. CircZDHHC11 was mainly present in the cytoplasmic fraction in BL cells and its localization was not altered upon miR-150 overexpression. Knockdown of circZDHHC11 caused a strong inhibition of BL growth without affecting the expression levels of MYC, MYB, miR-150 and other genes. Overexpression of circZDHHC11 neither affected cell growth, nor rescued the phenotype induced by miR-150 overexpression. Genomic deletion of the miR-150 binding site region did not affect growth, nor did it change the effect of circZDHHC11 knockdown. This indicated that the miR-150 binding site region is dispensable for the growth promoting role of circZDHHC11. To conclude, our results show that circZDHHC11 is a crucial factor supporting BL cell growth independent of its ability to sponge miR-150.

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.

Hsa_circ_0001707 regulates endothelial-mesenchymal transition in esophageal squamous cell carcinoma via miR-203a-3p/Snail2 pathway

Esophageal squamous cell carcinoma (ESCC) is a malignant tumor with high mortality and poor prognosis. Despite intensive research focused on tumor suppression, the 5-year survival rate of ESCC is lower than 15%. Therefore, investigate fundamental mechanisms involved in ESCC is on-demand crucial for diagnostics and developing targeted therapeutic drugs. Circular RNAs (circRNAs), as an emerging class of non-coding RNA, have been elucidated that circRNAs participated in regulating a variety of pathological processes and tumorigenesis. Nevertheless, the functional role of circRNAs in the occurrence and development of ESCC remains unclear. We identify a novel circRNA (hsa_circ_0001707), which was highly expressed in ESCC patients' tissues and cell lines. Furthermore, gain- and loss-of-function assays were performed and found that overexpression of hsa_circ_0001707 significantly promote tumor proliferation, metastasis, and invasion. By functioning as a competing endogenous RNA (ceRNA), the dual-luciferase activity assay verified that hsa_circ_0001707 can endogenously bind with miR-203a-3p and regulate its downstream gene Snail2. Rescue assay further confirms that hsa_circ_0001707 downregulation could partially attenuate the facilitation effect of miR-203a-3p, thereby inhibiting the endothelial-mesenchymal transition (EMT) process of ESCC. Our results suggested that hsa_circ_0001707 play an oncogenic role in the pathogenesis of ESCC, which might be a potential biomarker for diagnostics and targeting therapy.

DNMTs-mediated SOCS3 methylation promotes the occurrence and development of AML

OBJECTIVES

As a tumor suppressor gene, SOCS3 inhibits the growth of tumor cells by regulating JAK/STAT signaling pathway through negative feedback. This study aimed to investigate the biological function and mechanism of SOCS3 methylation mediated by DNMTs in the development of AML.

METHODS

Bone marrow samples were collected from 70 AML patients and 20 healthy volunteers. The expression and methylation status of each gene were detected by RT-qPCR, western blot and MS-PCR, and the growth and apoptosis rate of leukemia cell lines were detected by CCK-8 and flow cytometry. The effects of changes in SOCS3 gene expression and methylation status of AML cell lines were observed by gene transfection and gene knockdown.

RESULTS

The methylation rate of SOCS3 in AML initial treatment group was significantly higher than that in the remission group and the normal control group (60% vs. 0%, 0%). The expression of SOCS3 in the SOCS3 methylation group was significantly lower than that in the non-methylated group and control group, while the expression of DNMT1, DNMT3a, p-JAK2, p-STAT3 and p-STAT5 were significantly higher than those in the non-methylated group and control group. Demethylation treatment, SOCS3 transfection and DNMT3a knockdown could up-regulate the expression of SOCS3, which decreased the proliferation and increased the apoptosis of leukemia cell lines.

CONCLUSION

SOCS3 methylation mediated by DNMTs promotes the occurrence and development of AML and can be used as a potential biomarker for the diagnosis and efficacy evaluation of AML.

miR-203a-A multifaceted regulator modulating cancer hallmarks and therapy response

MicroRNAs (miRNAs) are a class of noncoding RNAs of about 19-25 nucleotides, which serve as critical modulators of various cellular and biological processes by target gene regulation. Dysregulated expression of miRNAs modulates the pathophysiology of various human diseases, including cancer. Among miRNAs, miR-203a is one of the most extensively researched dysregulated miRNAs in different cancers. Our review investigated the roles of miR-203a in the hallmarks of cancer modulating different pathways through target gene regulations, chemoresistance, its crosstalk with other ncRNAs or genes in terms of ceRNAs impacting oncogenesis, and its potential applications in the diagnosis, prognosis, and chemotherapeutic responses in different cancer types. miR-203a impacts cancer cell behavior by regulating these exclusive hallmarks- sustaining proliferation, cell growth, invasion and metastasis, cell death, and angiogenesis. Besides, miR-203a is found in human circulating biofluids like plasma or serum of colorectal cancer, cervical cancer, and hepatocellular carcinoma, hinting at its potential as a biomarker. Further, miR-203a is involved in enhancing the chemosensitivity of cisplatin, docetaxel, paclitaxel, doxorubicin, and 5-fluorouracil in a variety of malignancies through their cognate target genes. These results suggest that miR-203a is a crucial multifaceted miRNA that controls cancer cell proliferation, metastasis, and chemotherapy response, shedding new light on its possible application.

Genomic Alterations Affecting Competitive Endogenous RNAs (ceRNAs) and Regulatory Networks (ceRNETs) with Clinical Implications in Triple-Negative Breast Cancer (TNBC)

The concept of competitive endogenous RNA regulation has brought on a change in the way we think about transcriptional regulation by miRNA-mRNA interactions. Rather than the relatively simple idea of miRNAs negatively regulating mRNA transcripts, mRNAs and other non-coding RNAs can regulate miRNAs and, therefore, broad networks of gene products through competitive interactions. While this concept is not new, its significant roles in and implications on cancer have just recently come to light. The field is now ripe for the extrapolation of technologies with a substantial clinical impact on cancer. With the majority of the genome consisting of non-coding regions encoding regulatory RNAs, genomic alterations in cancer have considerable effects on these networks that have been previously unappreciated. Triple-negative breast cancer (TNBC) is characterized by high mutational burden, genomic instability and heterogeneity, making this aggressive breast cancer subtype particularly relevant to these changes. In the past few years, much has been learned about the roles of competitive endogenous RNA network regulation in tumorigenesis, disease progression and drug response in triple-negative breast cancer. In this review, we present a comprehensive view of the new knowledge and future perspectives on competitive endogenous RNA networks affected by genomic alterations in triple-negative breast cancer. An overview of the competitive endogenous RNA (ceRNA) hypothesis and its bearing on cellular function and disease is provided, followed by a thorough review of the literature surrounding key competitive endogenous RNAs in triple-negative breast cancer, the genomic alterations affecting them, key disease-relevant molecular and functional pathways regulated by them and the clinical implications and significance of their dysregulation. New knowledge of the roles of these regulatory mechanisms and the current acceleration of research in the field promises to generate insights into the diagnosis, classification and treatment of triple-negative breast cancer through the elucidation of new molecular mechanisms, therapeutic targets and biomarkers.

cirCodAn: A GHMM-based tool for accurate prediction of coding regions in circRNA

Studies focusing on characterizing circRNAs with the potential to translate into peptides are quickly advancing. It is helping to elucidate the roles played by circRNAs in several biological processes, especially in the emergence and development of diseases. While various tools are accessible for predicting coding regions within linear sequences, none have demonstrated accurate open reading frame detection in circular sequences, such as circRNAs. Here, we present cirCodAn, a novel tool designed to predict coding regions in circRNAs. We evaluated the performance of cirCodAn using datasets of circRNAs with strong translation evidence and showed that cirCodAn outperformed the other tools available to perform a similar task. Our findings demonstrate the applicability of cirCodAn to identify coding regions in circRNAs, which reveals the potential of use of cirCodAn in future research focusing on elucidating the biological roles of circRNAs and their encoded proteins. cirCodAn is freely available at https://github.com/denilsonfbar/cirCodAn.

circNFIB decreases synthesis of arachidonic acid and inhibits breast tumor growth and metastasis

We identified circNFIB (hsa_circ_0086376) as a down-regulated circRNA in breast cancer but its effect is unclear. We aimed to explore the roles of circNFIB in breast cancer. The expression levels of circNFIB in breast cancer tissues and cells were detected. Both in vitro and in vivo experiments were used to assess the effects and mechanisms of circNFIB. circNFIB was down-regulated in 29 breast cancer tissues compared to adjacent normal tissues. circNFIB is a highly conserved circRNA and mainly located in cytoplasm of breast cancer cells. In vitro experiments showed that overexpression of circNFIB inhibited proliferation and invasion of breast cancer cells, whereas knockdown of circNFIB induced proliferation and invasion. Animal experiments indicated that circNFIB inhibited tumor growth and metastasis in vivo. Bioinformatics analysis showed that circNFIB contained an open reading frame (ORF) spanning its spliced junction, an internal ribosome entry site (IRES) and a N6-methyladenosine (m6A) site, suggesting circNFIB had the potential to encode a 56 amino acid (aa) protein, which was then confirmed by experiments. Metabonomics analysis results indicated that circNFIB may inhibit synthesis of arachidonic acid (AA) by regulating phospholipase. EIF4A3 and U2AF65 may regulate circNFIB expression by binding to the flanking sequence of circNFIB. In conclusion, circNFIB is a down-regulated circRNA in breast cancer tissues and encodes a 56 aa protein. circNFIB down-regulates AA in breast cancer cells, thus decreasing AA metabolites. Based on reported evidences of AA metabolites on cancer, we speculated that circNFIB may inhibit breast tumor growth and metastasis partly by inhibiting AA.

CircSETD2 inhibits YAP1 by interaction with HuR during breast cancer progression

CircRNAs have been proven to play a pivotal role in cancer progression. The present study aims to explore the roles and related mechanisms of circSETD2 in breast cancer proliferation, migration and invasion. The expression of circSETD2 in BC was assessed by the GEO database and qRT‒PCR. The biological function and underlying molecular mechanism of circSETD2 in BC were explored using in vitro and in vivo experiments, including CCK8, transwell, RIP, western blot, and xenograft mouse models. The expression of circSETD2 was downregulated in BC tumors, in accordance with the GEO database. Overexpression of circSETD2 significantly suppressed cell growth, cell migration and invasion. Mechanistically, circSETD2 reduced the stabilization of YAP1 by competitively binding with HuR, resulting in inactivation of downstream targets such as CTGF, myc and Slug. Our work suggests that the novel signaling axis circSETD2/HuR/YAP1 plays an important role in BC progression. The molecular mechanism underlying this signaling axis may provide a potential therapeutic target for BC treatment.

Exosomal circRNA RHOT1 promotes breast cancer progression by targeting miR-204-5p/ PRMT5 axis

BACKGROUND

Circular RNA RHOT1 (circRHOT1) plays crucial roles in tumorigenesis by competing with microRNAs. It is largely abundant in tumor cell-derived exosomes. Meanwhile, cancer-derived exosomes participate in diverse biological processes. However, the expression patterns and functions of exosomal circRHOT1 in breast cancer remain unknown. This study is aimed to investigate and elucidate the exosomal circRHOT1/miR-204-5p/PRMT5 axis in breast cancer.

METHODS

The exosomes derived from serum samples of breast cancer patients and breast cancer cell lines were characterized using transmission electron microscopy and Western blot. MTT, colony formation, wound healing, and transwell assays were utilized to analyze cell proliferation, migration, and invasion of breast cancer cells. Flow cytometry was used for apoptosis analysis. The bioinformatics method was employed to screen differentially expressed novel circRNAs and predict the microRNA targets of circRHOT1. Dual-luciferase reporter gene assays were performed to verify their direct interaction. Finally, Xenograft experiments were used to investigate the effect of exosomal circRHOT1 on tumor growth in vivo.

RESULTS

CircRHOT1 exhibited significantly high expression in exosomes derived from the serum of breast cancer patients and breast cancer cell lines, which suggested its potential diagnostic value. Breast cancer-derived exosomes promoted the cell proliferation, migration, invasion, and epithelial-mesenchymal transition of breast cancer cells while inhibiting apoptosis. However, exosomes with downregulated circRHOT1 inhibited the growth of co-cultured cells. Mechanistically, circRHOT1 acted as a sponge of miR-204-5p and promoted protein arginine methyltransferase 5 (PRMT5) expression. Moreover, miR-204-5p inhibitor and pcPRMT5 could reverse the tumor suppressive effects mediated by circRHOT1-knockdown. Furthermore, treatment with exosomes derived from breast cancer cells with circRHOT1 knockdown attenuated tumor growth in tumor-bearing nude mice, which was accompanied by a reduction in PRMT5 expression and an enhancement of miR-204-5p expression.

CONCLUSION

The exosomal circRHOT1 may promote breast cancer progression by regulating the miR-204-5p/PRMT5 axis. The current study strengthens the role of circRHOT1, miR-204-5p, and PRMT5 in breast cancer development and provides a potential treatment strategy for breast cancer.

Hsa_circRNA_102051 regulates colorectal cancer proliferation and metastasis by mediating Notch pathway

BACKGROUND

The purpose of this study was to investigate the role of hsa_circRNA_102051 in colorectal cancer (CRC) and its effect on the stemness of tumor cells.

METHODS

CircRNA microarray was under analysis to screen differentially expressed novel circRNAs in the pathology of CRC. Quantitative real-time PCR was used to detect the relative RNA expression in CRC cells and samples. The effects of hsa_circRNA_102051 on biological functions in CRC cells were accessed both in vitro and in vivo. FISH, RIP and luciferase reporter assay were conducted to confirm the regulatory correlations between hsa_circRNA_102051 and miR-203a, as well as miR-203a and BPTF. Xenograft models were applied to further verify the impacts and fluctuations of hsa_circRNA_102051/miR-203a/BPTF. Moreover, the mechanism how hsa_circRNA_102051 affected the Notch signals was also elucidated.

RESULTS

Hsa_circRNA_102051 was up-regulated in CRC tissues and cell lines, capable to promote the growth and invasion of CRC. In addition, hsa_circRNA_102051 could enhance stemness of CRC cells. BPTF was identified as downstream factors of hsa_circRNA_102051, and miR-203a was determined directly targeting both hsa_circRNA_102051 and BPTF as an intermediate regulator. Hsa_circRNA_102051 in CRC could block miR-203a expression, and subsequently activated BPTF. Hsa_circRNA_102051/miR-203a/BPTF axis modulated stemness of CRC cells by affecting Notch pathway.

CONCLUSIONS

Our findings provided new clues that hsa_circRNA_102051 might be a potential predictive or prognostic factor in CRC, which induced the fluctuation of downstream miR-203a/BPTF, and subsequently influenced tumor growth, activities and stemness. Thereinto, the Notch signals were also involved. Hence, the hsa_circRNA_102051/miR-203a/BPTF axis could be further explored as a therapeutic target for anti-metastatic therapy in CRC patients.

The emerging regulatory roles of non-coding RNAs associated with glucose metabolism in breast cancer

Altered energy metabolism is one of the hallmarks of tumorigenesis and essential for fulfilling the high demand for metabolic energy in a tumor through accelerating glycolysis and reprogramming the glycolysis metabolism through the Warburg effect. The dysregulated glucose metabolic pathways are coordinated not only by proteins coding genes but also by non-coding RNAs (ncRNAs) during the initiation and cancer progression. The ncRNAs are responsible for regulating numerous cellular processes under developmental and pathological conditions. Recent studies have shown that various ncRNAs such as microRNAs, circular RNAs, and long noncoding RNAs are extensively involved in rewriting glucose metabolism in human cancers. In this review, we demonstrated the role of ncRNAs in the progression of breast cancer with a focus on outlining the aberrant expression of glucose metabolic pathways. Moreover, we have discussed the existing and probable future applications of ncRNAs to regulate energy pathways along with their importance in the prognosis, diagnosis, and future therapeutics for human breast carcinoma.

MicroRNAs Present in Malignant Pleural Fluid Increase the Migration of Normal Mesothelial Cells In Vitro and May Help Discriminate between Benign and Malignant Effusions

The sensitivity of pleural fluid (PF) analyses for the diagnosis of malignant pleural effusions (MPEs) is low to moderate. Knowledge about the pathobiology and molecular characteristics of this condition is limited. In this study, the crosstalk between stromal cells and tumor cells was investigated in vitro in order to reveal factors that are present in PF which can mediate MPE formation and aid in discriminating between benign and malignant etiologies. Eighteen PF samples, in different proportions, were exposed in vitro to mesothelial MeT-5A cells to determine the biological effects on these cells. Treatment of normal mesothelial MeT-5A cells with malignant PF increased cell viability, proliferation, and migration, and activated different survival-related signaling pathways. We identified differentially expressed miRNAs in PF samples that could be responsible for these changes. Consistently, bioinformatics analysis revealed an enrichment of the discovered miRNAs in migration-related processes. Notably, the abundance of three miRNAs (miR-141-3p, miR-203a-3, and miR-200c-3p) correctly classified MPEs with false-negative cytological examination results, indicating the potential of these molecules for improving diagnosis. Malignant PF produces phenotypic and functional changes in normal mesothelial cells. These changes are partly mediated by certain miRNAs, which, in turn, could serve to differentiate malignant from benign effusions.

circWHSC1: A circular RNA piece in the human cancer puzzle

Circular RNAs (circRNAs) are a group of non-coding RNAs with a closed loop shape, which are transcribed via non-canonical splicing. They are mainly formed by reverse splicing of a precursor mRNA. circWHSC1 (Hsa_circ_0001387), is a cancer-related circRNA that originated from the Wolf-Hirschhorn syndrome candidate 1 (WHSC1) gene on chromosome 4. circWHSC1 has been found to be overexpressed in different neoplastic conditions. circWHSC1 acts as a sponge for many different miRNAs, including miR-195-5p, miR-532-3p, miR-646, miR-142-3p, miR-7, miR-296-3p, miR-145, miR-1182, miR-212-5p, etc. It can also moderate several signaling pathways, including FASN/AMPK/mTOR, LTBP2, NPM1, HOXA1, TAB2, AKT3, hTERT, and MUC1. Studies have shown that circWHSC1 may leads to an increase in cell growth, tumor size, cell migration, invasion, and metastasis, but a reduction in apoptosis rates. Moreover, upregulation of CircWHSC1 has been associated with reduced patient's survival in different cancers, representing the function of this circRNA as a novel prognostic marker. Nevertheless, there are no reviews focusing on the relationship between circWHSC1 and cancers. Therefore, in the current review, we will first describe the oncogenic effect of circWHSC1 in various tissues according to the evidence from in vitro, in vivo, and human studies.

Exploiting Long Non-Coding RNAs and Circular RNAs as Pharmacological Targets in Triple-Negative Breast Cancer Treatment

Breast cancer is one of the most frequent causes of cancer death among women worldwide. In particular, triple-negative breast cancer (TNBC) represents the most aggressive breast cancer subtype because it is characterized by the absence of molecular targets, thus making it an orphan type of malignancy. The discovery of new molecular druggable targets is mandatory to improve treatment success. In that context, non-coding RNAs represent an opportunity for modulation of cancer. They are RNA molecules with apparently no protein coding potential, which have been already demonstrated to play pivotal roles within cells, being involved in different processes, such as proliferation, cell cycle regulation, apoptosis, migration, and diseases, including cancer. Accordingly, they could be used as targets for future TNBC personalized therapy. Moreover, the peculiar characteristics of non-coding RNAs make them reliable biomarkers to monitor cancer treatment, thus, to monitor recurrence or chemoresistance, which are the most challenging aspects in TNBC. In the present review, we focused on the oncogenic or oncosuppressor role of long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) mostly involved in TNBC, highlighting their mode of action and depicting their potential role as a biomarker and/or as targets of new non-coding RNA-based therapeutics.

Circular RNA ATP2C1 (has_circ_0005797) sponges miR-432/miR-335 to promote breast cancer progression through regulating CCND1 expression

Breast cancer (BC) is the most frequently diagnosed malignancy in the world. Accumulating evidence has indicated that circular RNAs (circRNAs) play essential roles in BC. Here we investigated the biological functions of circATP2C as a competing endogenous RNA (ceRNA) in BC development. We found that circATP2C1 expression was upregulated in BC cells and tissues and was significantly associated with the poor overall survival in BC patients. CircATP2C1 is more resistant to RNase R exonuclease and Actinomycin D than is the linear mRNA of ATP2C1. CircATP2C1-knockdown inhibited the viability, colony proliferation and invasion abilities, while increasing the apoptosis rates of BC cells in vitro, as well as inhibiting tumor mass, size and weight in vivo. Upregulation of miR-432 and miR-335 inhibited CCND1 expression in BC cells. Both miR-432/miR-335 specifically bind to the 3'-UTR of circATP2C1 and CCND1 (CyclinD1). The inhibition of the aggression of BC cells by circATP2C1-knockdown was rescued by co-transfection of miR-432/miR-335 inhibitors. In conclusion, circATP2C1 promotes BC oncogenesis and metastasis by sponging miR-432/miR-335 to abolish the inhibition of the target gene, CCND1. This study suggests that circATP2C1 has implications for BC diagnosis and treatment.

CircCRIM1 suppresses osteosarcoma progression via sponging miR146a-5p and targeting NUMB

CircCRIM1 (hsa_circ_0002346) is a circular RNA derived from gene CRIM1 (the cysteine rich transmembrane BMP regulator 1 circRNAs) by back-splicing. Recent studies have suggested the diverse function of CircCRIM1 in the tumorigenesis of multiple malignancies, including osteosarcoma (OS). Here, we investigated the role and mechanism of circCRIM1 during OS progression. Differentially expressed circRNAs (including circCRIM1) in OS and human osteoblast (hFOB1.19) cell lines were selected by searching the circRNA expression microarray dataset of GSE96964. The expression levels of circCRIM1 and its sponging miRNAs and target genes were examined by RT-qPCR. The effects of circCRIM1 on the proliferation, migration, and invasion of OS cells were investigated by in vitro gain of function experiments. The in vivo function of circCRIM1 on OS was evaluated by measuring the subcutaneous and in situ tumor growth in nude mice. In addition, dual-luciferase reporter assay and in situ hybridization (FISH) were performed to explore the underlying mechanisms of circCRIM1 and its sponging miRNAs and target genes in OS. CircCRIM1 is downregulated in human OS cell lines and predominantly presents in the cytoplasm as demonstrated by RT-qPCR and FISH assays. Overexpression of circCRIM1 suppressed the migration, invasion, proliferation of OS cells in vitro and OS tumor growth in vivo. Mechanistically, we identified miR146a-5p as a sponge miRNA of circCRIM1 through bioinformatic prediction and confirmed their interaction and colocalization via reporter gene assay and FISH analysis. This interaction leads to increase expression of the downstream target gene NUMB, which will cause inhibition of the Notch signal pathway. We further demonstrated that miR146a-5p overexpression could reverse the antitumor effect induced by circCRIM1 in OS cells. Our results support that circCRIM1 acts as a tumor suppressor in OS by sponging miR146a-5p and its downstream target NUMB.

The recent advancements in circRNA research: From biogenesis to therapeutic interventions

Circular RNAs (circRNAs) belong to the genre of long non-coding RNAs that are formed by special back-splicing events and are currently the molecule of interest for studies globally due their involvement in various ailments like diabetes, neurodegenerative disorders, cardio-vascular diseases and cancers. These class of highly stable RNAs participate in diverse cellular functionalities including microRNA (miRNA) sponging, ceRNA (competing endogenous RNA) activity or via exhibiting RNA binding protein (RBP) interactions. They are also known to regulate cancer progression both positively and negatively through various biological pathways such as, modulating the cell cycle and apoptotic pathways, epigenetic regulation, and translational and/or transcriptional regulations etc. Given its significance, a variety of computational tools and dedicated databases have been created for the identification, quantification, and differential expression of such RNAs in combination with sequencing approaches. In this review, we provide a comprehensive analysis of the numerous computational tools, pipelines, and online resources developed in recent years for the detection and annotation of circRNAs. We also summarise the most recent findings regarding the characteristics, functions, biological processes, and involvement of circRNAs in diseases. The review emphasises the significance of circRNAs as potential disease biomarkers and new treatment targets.

A novel polypeptide CAPG-171aa encoded by circCAPG plays a critical role in triple-negative breast cancer

BACKGROUND

The treatment of Triple-negative breast cancer (TNBC) has always been challenging due to its heterogeneity and the absence of well-defined molecular targets. The present study aims to elucidate the role of protein-coding circRNAs in the etiology and carcinogenesis of TNBC.

METHODS

CircRNA expression data in TNBC (GEO: GSE113230, GSE101123) were reanalyzed and then circCAPG was selected for further study. To identify the polypeptide-coding function of circCAPG, a series of experiments, such as Mass spectrometry and dual-luciferase reporter assays were conducted. Cell proliferation, apoptosis and metastasis parameters were determined to investigate the cancerous functions CAPG-171aa plays in both TNBC organoids and nude mice. Mechanistically, the relation between CAPG-171aa and STK38 in TNBC was verified by immunoprecipitation analyses and mass spectrometry. The interactions between SLU7 and its binding site on circCAPG were validated by RIP-qPCR experiments.

RESULTS

In both TNBC clinical samples and cell lines, the expression level of circCAPG was identified to be higher compared with normal ones and positively correlated with the overall survival (n = 132) in a 10-year follow-up study, in which the area under the curve of receiver operating characteristic was 0.8723 with 100% specificity and 80% sensitivity. In addition, we found that circCAPG knockdown (KD) significantly inhibited the growth of TNBC organoids. Intriguingly, circCAPG can be translated into a polypeptide named CAPG-171aa which promotes tumor growh by disrupting the binding of serine/threonine kinase 38 (STK38) to SMAD-specific E3 ubiquitin protein ligase 1 (SMURF1) and thereby preventing MEKK2 ubiquitination and proteasomal degradation. Furthermore, we found that SLU7 Homolog- Splicing Factor (SLU7) can regulate the bio-generation of circCAPG through binding to the flanking Alu sequences of circRNA transcripts.

CONCLUSIONS

circCAPG significantly enhances the proliferation and metastasis of TNBC cells by encoding a novel polypeptide CAPG-171aa and afterwards activates MEKK2-MEK1/2-ERK1/2 pathway. Additionally, the formation of circCAPG is found to be mediated by SLU7. The present study provides innovative insight into the role of protein-coding circRNAs CAPG-171aa in TNBC, and its capacity to serve as a promising prognostic biomarker and potential therapeutic target in TNBC.

A Unique Circular RNA Expression Pattern in the Peripheral Blood of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease with obscure aetiology. The underdiagnosis rate of ME/CFS is high due to the lack of diagnostic criteria based on objective markers. In recent years, circRNAs have emerged as potential genetic biomarkers for neurological diseases, including Parkinson's disease and Alzheimer's disease, making them likely to have the same prospect of being biomarkers in ME/CFS. However, despite the extensive amount of research that has been performed on the transcriptomes of ME/CFS patients, all of them are solely focused on linear RNAs, and the profiling of circRNAs in ME/CFS has been completely omitted. In this study, we investigated the expression profiles of circRNAs, comparing ME/CFS patients and controls before and after two sessions of cardiopulmonary exercise longitudinally. In patients with ME/CFS, the number of detected circRNAs was higher compared to healthy controls, indicating potential differences in circRNA expression associated with the disease. Additionally, healthy controls showed an increase in the number of circRNAs following exercise testing, while no similar pattern was evident in ME/CFS patients, further highlighting physiological differences between the two groups. A lack of correlation was observed between differentially expressed circRNAs and their corresponding coding genes in terms of expression and function, suggesting the potential of circRNAs as independent biomarkers in ME/CFS. Specifically, 14 circRNAs were highly expressed in ME/CFS patients but absent in controls throughout the exercise study, indicating a unique molecular signature specific to ME/CFS patients and providing potential diagnostic biomarkers for the disease. Significant enrichment of protein and gene regulative pathways were detected in relation to five of these 14 circRNAs based on their predicted miRNA target genes. Overall, this is the first study to describe the circRNA expression profile in peripheral blood of ME/CFS patients, providing valuable insights into the molecular mechanisms underlying the disease.

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.

Hsa_circ_0060467 promotes breast cancer liver metastasis by complexing with eIF4A3 and sponging miR-1205

Breast cancer (BC) is the most common cancer and the top cause of female mortality worldwide. The prognosis for patients with breast cancer liver metastasis (BCLM) remains poor. Emerging studies suggest that circular RNAs (circRNAs) are associated with the progression of BC. Exploration of circRNAs presents a promising avenue for identifying metastasis-targeting agents and improving the prognosis of patients with BCLM. Microarray and bioinformatic analyses were used to analyze differentially expressed circRNAs between three pairs of BCLM and primary BC. The roles of hsa_circ_0060467 (circMYBL2) and its target gene E2F1 in BC cells were explored by multiple functional experiments. And xenograft mouse models and hepatic metastases of BC hemi-spleen models were used to illustrate the function of circMYBL2 in vivo. The intrinsic molecular mechanism involving circMYBL2 was confirmed by bioinformatics analyses, RIP assays, CHIRP assays, luciferase reporter assays, and rescue experiments. CircMYBL2 was overexpressed in BCLM tissues and BC cells. Functionally, circMYBL2 can facilitate the proliferation and liver metastasis of BC. Mechanistically, circMYBL2 upregulated the transcription factor E2F1 by sponging miR-1205 and complexing with eukaryotic translation initiation factor 4A3 (eIF4A3) and then facilitated the epithelial-mesenchymal transition (EMT) process in BC cells. Our findings showed that circMYBL2 promoted the tumorigenesis and aggressiveness of BC through the circMYBL2/miR-1205/E2F1 and circMYBL2/eIF4A3/E2F1 axes, which may provide a novel targeted therapy for patients with BCLM.