Foxo3 circular RNA retards cell cycle progression via forming ternary complexes with p21 and CDK2

Engineering of a palindrome-crosslinked DNA nanoaggregate for rapid detection of circular RNA and precise identification of lung cancer

Circular RNAs (circRNAs) are endogenous covalently closed non-coding RNAs with cell-/developmental-stage-/tissue-specific expression patterns, and they can act as the miRNA sponges and gene transcription regulatory factors to influence numerous biological processes. Herein, we develop a palindrome-crosslinked DNA nanoaggregate system to rapidly detect circRNA and precisely identify lung cancer. We utilize a self-assembled palindromic DNA nanosphere (DS) as the spatial-confinement scaffold to anchor hairpin probes (HP) for the formation of the hybrid assemblies (DSH). The presence of target circSATB2 can hybridize with the hairpin probe to expose the locked palindromic sequence, initiating the cross-linking of the palindromic ends to form a self-catenated structure through intermolecular hybridization. Then the hybridized palindromic ends serve as the self-primers to initiate extension reaction and eventually assemble into the net-like crosslinked DNA nanoaggregates, resulting in the recovery of Cy5 signals. Taking advantage of the excellent antidegradation capability and superior kinetic behavior of DSH nanostructure, high amplification efficiency of Klenow Fragment polymerase (KF)-mediated extension reaction, and signal enhancement induced by the DNA nanoaggregates, this nanosystem enables mix-and-read detection of circSATB2 within 30 min under isothermal conditions (37 °C) with a limit detection of 77.56 fM. Moreover, it is capable of measuring intracellular circSATB2 with single-cell sensitivity, exploring its biological functions, and precisely identifying different stages (I/II/III) and subtypes (IA1/IA2/IA3/IB) of lung cancers, holding great potential in early screening of lung cancers.

Nuclear circGUSBP1 promotes cancer stemness via transcriptional coordination with OCT4

AIMS

Endometrial cancer (ECa) is a prevalent gynecological malignancy, with treatment often hindered by metastasis and recurrence driven by cancer stem-like cells. While circular RNAs (circRNAs) are well known for their cytoplasmic roles as microRNA sponges, their nuclear functions remain largely unexplored. This study investigates nuclear circRNAs and their roles in regulating cancer stem-like properties in ECa.

MATERIALS AND METHODS

Nuclear RNA sequencing data were analyzed to identify nuclear-enriched circRNAs. The subcellular localization of circGUSBP1 and circZNF680 was assessed via nuclear-cytoplasmic fractionation and RT-qPCR. The functional impact of circGUSBP1 was evaluated using tumorsphere formation, migration, and cisplatin sensitivity assays. Transcriptomic profiling and survival analysis were conducted using circGUSBP1-knockdown ECa cells and The Cancer Genome Atlas (TCGA) dataset.

KEY FINDINGS

CircGUSBP1 exhibited a high circular-to-linear transcript ratio and was preferentially nuclear, independent of intron retention. Its expression correlated with NANOG and OCT4 upregulation. Overexpression of circGUSBP1 enhanced tumorsphere formation, whereas circGUSBP1-knockdown (KD) reduced tumorsphere formation, impaired migration, and increased cisplatin sensitivity. Transcriptomic analysis revealed downregulation of stemness-related genes, supporting its role as a transcriptional co-activator. Notably, 230 circGUSBP1-regulated genes were co-targeted by OCT4, including SUPT16H and SUV39H2, chromatin remodelers linked to poor prognosis in ECa patients. Higher GUSBP1 expression, but not GUSB, correlated with worse survival outcomes in TCGA data.

SIGNIFICANCE

These findings identify circGUSBP1 as a nuclear regulator of cancer stemness. Through circGUSBP1/OCT4 co-regulation of chromatin modulators, circGUSBP1 promotes aggressive tumor behavior, highlighting its potential as a therapeutic target.

The role of circRNA in insulin resistance and its progression induced by adipose inflammation

CircRNAs refer to a type of closed circular non-coding RNA without a 5' cap or a 3' poly (A) structure. They are largely distributed in the cytoplasm or localized in exosomes and cannot be easily degraded by RNA exonuclease activity. Their stable expression is broadly observed across eukaryotic species. Insulin resistance (IR) refers to the inability of insulin to exert its normal biological function, as manifested by the impairment of glucose utilization in peripheral tissues (e.g., muscle and fat tissues). IR is a key factor in the pathogenesis of Type 2 diabetes (T2D) and is closely associated with obesity. Recent studies have shown that certain circRNAs play critical roles in obesity-induced diabetes by regulating IR and participating in inflammatory processes. CircRNAs, with their multiple microRNA (miRNA) binding sites, act as miRNA sponges to eliminate the inhibitory actions of miRNAs and up-regulate the expression of target genes. CircRNAs play a significant role in regulating obesity-induced diabetes through their interactions with disease-related miRNAs. In the present study, we explored the biological characteristics of circRNAs and extensively discussed the role of circRNAs in the development of inflammation and IR in adipocytes, highlighting their potential as therapeutic targets for obesity-induced diabetes. Specific circRNAs (e.g., circARF3 and circ-ZNF609) have been identified as key players in modulating IR and inflammatory responses in adipose tissue. CircRNAs are emerging as important regulators of IR and inflammation in adipocytes, with significant potential for therapeutic intervention in obesity-induced diabetes. Further research is needed to elucidate the mechanisms underlying their actions and to explore strategies for targeting circRNAs in clinical applications.

Circular RNAs in gynecological cancer: From molecular mechanisms to clinical applications (Review)

Circular RNAs (circRNAs) have emerged as promising biomarkers and therapeutic targets in gynecological cancer. The present review explored developments in circRNA research in ovarian, endometrial and cervical cancer. circRNA biogenesis, functions and roles in cancer pathogenesis have been discussed, focusing on their potential as diagnostic and prognostic markers. Furthermore, circRNAs mechanisms of action, including miRNA sponging, protein scaffolding and peptide encoding were examined, highlighting specific circRNAs implicated in each cancer type and their clinical significance. The unique properties of circRNAs, such as stability and tissue-specific expression, make them ideal candidates for biomarker development. By synthesizing the currently available literature and identifying future research directions, the present review underscored circRNAs potential to improve gynecological cancer management through novel diagnostic tools, prognostic markers and targeted therapies.

Portrayal of the complex molecular landscape of multidrug resistance in gastric cancer: Unveiling the potential targets

Gastric cancer (GC) is an aggressive malignancy among all Gastrointestinal cancer (GIC) types. Worldwide, among all cancer types, gastric cancer incidence and related mortality remain in fifth position. Multidrug resistance (MDR) in GC presents a major challenge to chemotherapy, and it significantly affects patient survival. A better understanding of the dynamic interaction of cellular factors contributing to MDR phenotype, e.g., the presence and expression of variants of MDR-related genes, including various drug-detoxifying and drug-efflux transporters, and expression of regulatory ncRNAs affecting the expression of MDR-related genes, is required to comprehend the molecular mechanisms for MDR development in GCs. This review article provides a holistic discussion of the cellular factors involved in the MDR development in GC cells, i.e., their roles and cross-talk between specific molecules that give rise to drug-sensitive and drug-resistant phenotypes. Moreover, the pharmacological perspective of drug resistance and the underlying biological processes that allow the escape of GC cells from the cytotoxic effects of drugs have also been discussed. Additionally, this review article provides an in-depth discussion on most potential candidates that can serve as MDR biomarkers in GIC cancer and the growing research interest in non-coding RNAs (ncRNAs) in GC. Notably, the miRNAs, circRNAs, and lncRNAs are not only emerging as crucial prognostic biomarkers of MDR in gastric cancers but also as potential targets for personalized medicine to combat the MDR challenge in GC patients.

Construction of a Ligation-Controlled Single-Molecule Biosensor for Simultaneous Measurement of Multiple Cancer-Related circRNAs in Clinical Tissues

Circular RNAs (circRNAs) are noncoding RNAs with covalently closed circular structures that regulate important cellular processes, and their dysregulation is implicated in the pathogenesis and progression of various cancers. Simultaneous and specific detection of multiple circRNAs is of significant importance in the early diagnosis of cancer. Herein, we develop a ligation-controlled single-molecule biosensor for multiplexed measurement of breast cancer-associated circRNAs. This assay integrates the isothermal exponential amplification reaction (EXPAR)-induced generation of multiple DNAzymes with a Au nanoparticle (AuNP)-based spherical nucleic acid nanoprobe. The back-splice junction (BSJ) sequences of circFOXO3 and circMTO1 can serve as the templates to ligate their hairpin probes and helper probes under the catalysis of SplintR ligase, forming complete amplification templates. Afterward, the ligated amplification template can serve as both a primer and a template to initiate the EXPAR, inducing the exponential accumulation of characteristic DNAzyme sequences (i.e., DNAzymes 1 and 2). DNAzymes 1 and 2 can be paired with signal probes 1 and 2 immobilized on the AuNP surface, respectively, inducing cyclic degradation of signal probes to liberate large amounts of Cy5 and Cy3 fluorophores and achieving detection limits of 8.34 aM for circFOXO3 and 9.84 aM for circMTO1. This single-molecule biosensor has been successfully applied for simultaneous analysis of multiple circRNAs in a single cancer cell and differentiation of multiple circRNA levels between breast cancer tissues and healthy para-carcinoma tissues, offering a new paradigm for biomedical research and circRNA-related molecular diagnostics.

A Dual-Selection System for Enhanced Efficiency and Fidelity of Circular RNA Overexpression

Circular RNAs (circRNAs) are essential regulators of cellular processes, but are challenging to study using traditional methods. Overexpression approaches, such as the use of linearized plasmids and viral vectors, often result in high rates of false-positive clones, where cells retain selection markers without expressing the target circRNA. This study addresses this limitation by developing a dual-selection circRNA system designed to enhance the accuracy and reliability of circRNA overexpression. Our system integrates a fluorescent reporter gene upstream of the circRNA expression cassette, under a shared promoter, and a downstream antibiotic resistance marker, allowing for both antibiotic selection and flow cytometric cell-sorting to identify and enrich cells with genuine circRNA expression. We successfully incorporated this system into an inducible lentiviral vector for controlled overexpression in various cell types. The dual-selection circRNA system offers a significant advance for circRNA research and studies of other RNA species where accurate and reliable overexpression is essential.

Suppression of FOXO3 by BMP signaling contribute to the different primordial germ cell proliferation between layers and broilers†

Although all domestic chicken breeds originate from their wild relatives, the red junglefowl, they have been selectively bred for high yields in either egg or meat production, or both. Some breeds are highly efficient in egg production, while others perform poorly, due to long-term selection aimed for different purposes. Female primordial germ cells (PGCs) are the precursors of eggs and the population size of PGCs will ultimately determine ovarian reserve of hens. In this study, we observed that the layers exhibit greater proliferation capacity and a higher number of PGCs in the gonad compared to the broilers before meiosis. By comparing the PGC transcriptomes between layers and broilers, we identified potential genes that regulate cell proliferation. We further confirmed that FOXO3 expression is higher in broilers, where it inhibits the PGC proliferation both in vivo and in vitro. However, in layers, the upstream BMP signaling stimulate the phosphorylation of AKT and suppress FOXO3 activity. Consequently, the elevated BMP signaling and reduced FOXO3 co-operatively promote more robust PGC proliferation in layers compared to broilers and result in a greater number of PGCs in layers. Our data not only reveal molecular mechanisms underlying PGC growth in the ovary, but also provide new clues to improve the laying performance in chicken.

Role of noncoding RNA and protein interaction in pancreatic cancer

ABSTRACT

Noncoding RNAs (ncRNAs) are a class of RNA molecules with little or no protein-coding potential. Emerging evidence indicates that ncRNAs are frequently dysregulated and play pivotal roles in the pathogenesis of pancreatic cancer. Their aberrant expression can arise from chromosomal abnormalities, dysregulated transcriptional control, and epigenetic modifications. ncRNAs function as protein scaffolds or molecular decoys to modulate interactions between proteins and other biomolecules, thereby regulating gene expression and contributing to pancreatic cancer progression. In this review, we summarize the mechanisms underlying ncRNA dysregulation in pancreatic cancer, emphasize the biological significance of ncRNA-protein interactions, and highlight their clinical relevance. A deeper understanding of ncRNA-protein interactions is essential to elucidate molecular mechanisms and advance translational research in pancreatic cancer.

Circular RNA CDYL facilitates hepatocellular carcinoma stemness and PD-L1+ exosomes-mediated immunotherapy resistance via stabilizing hornerin protein by blocking synoviolin 1-mediated ubiquitination

Despite the revolutionary progress in cancer immunotherapy, only a minority of hepatocellular carcinoma (HCC) patients respond to immune checkpoint inhibitors (ICIs). In this study, we found that the oncogenic circular RNA Circ-CDYL in HCC influences the efficacy of immunotherapy and the stemness characteristics of HCC cells by interacting with the hornerin (HRNR) protein. The degraded anti-PD-L1 immunotherapy responses induced by Circ-CDYL and HRNR were confirmed by peripheral blood mononuclear cells (PBMCs) killing assays in HCC cells, patient-derived organoids, and humanized immune system mouse models. Furthermore, Circ-CDYL interference reversed the cytotoxicity and proliferation of CD8+ T cells, resulting in ameliorated immune evasion in tumor spheroids upon anti-PD-L1 treatment. Mechanistically, Circ-CDYL upregulated HRNR expression by stabilizing the HRNR protein through the prevention of its degradation by the E3 ubiquitin ligase synoviolin 1 (SYVN1), which in sequence promoted the phosphorylation of the mTORC1 and p70S6K substrate. The abnormally activated mTORC1-p70S6K signaling increases the stemness of HCC cells and upregulates PD-L1 expression, which may attenuate anti-PD-L1 therapy efficacy via PD-L1+ exosomes. Our study revealed the mechanism by which Circ-CDYL and HRNR regulate the sensitivity of HCC to anti-PD-L1 therapy, and the findings have potential implications for patient stratification and clinical decision-making in HCC immunotherapy.

Immune cell-derived exosomal non-coding RNAs in tumor microenvironment: Biological functions and potential clinical applications

The intricate interactions between immune cells and tumors exert a profound influence on cancer progression and therapeutic efficacy. Within the tumor microenvironment, exosomes have emerged as pivotal mediators of intercellular communication, with their cargo of non-coding RNAs (ncRNAs) serving as key regulatory elements. This review examines the multifaceted roles of immune cell-derived exosomal ncRNAs in tumor biology. The involvement of various immune cells, including T cells, B cells, natural killer cells, macrophages, neutrophils, and myeloid-derived suppressor cells, in utilizing exosomal ncRNAs to regulate tumor initiation and progression is explored. Additionally, the biogenesis and delivery mechanisms of these immune cell-derived exosomal ncRNAs are discussed, alongside their potential clinical applications in cancer.

The emerging functions and clinical implications of circRNAs in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a prevalent haematologic malignancy characterized by significant heterogeneity. Despite the application of aggressive therapeutic approaches, AML remains associated with poor prognosis. Circular RNAs (circRNAs) constitute a unique class of single-stranded RNAs featuring covalently closed loop structures that are ubiquitous across species. These molecules perform crucial regulatory functions in the pathogenesis of various diseases through diverse mechanisms, including acting as miRNA sponges, interacting with DNA or proteins, and encoding functional proteins/polypeptides. Recently, numerous circRNAs have been confirmed to have aberrant expression patterns in AML patients. In particular, certain circRNAs are closely associated with specific clinicopathological characteristics and thus have great potential as diagnostic/prognostic biomarkers and therapeutic targets in AML. Herein, we systematically summarize the biogenesis, degradation, and functional mechanisms of circRNAs while highlighting their clinical relevance. We also outline a series of online databases and analytical tools available to facilitate circRNA research. Finally, we discuss the current challenges and future research priorities in this evolving field.

Circular RNAs exhibit exceptional stability in the aging brain and serve as reliable age and experience indicators

Circular RNAs (circRNAs) increase in the brain with age across various animal systems. To elucidate the reasons behind this phenomenon, we profile circRNAs from fly heads at six time points throughout their lifespan. Our results reveal a linear increase in circRNA levels with age, independent of changes in mRNA levels, overall transcription, intron retention, or host gene splicing, demonstrating that the age-related accumulation is due to high stability rather than increased biogenesis. This remarkable stability suggests that circRNAs can serve as markers of environmental experience. Indeed, flies exposed to a 10-day regimen at 29°C exhibit higher levels of specific circRNAs even 6 weeks after returning to standard conditions, indicating that circRNAs can reveal past environmental stimuli. Moreover, half-life measurements show circRNA stability exceeding 20 days, with some displaying virtually no degradation. These findings underscore the remarkable stability of circRNAs in vivo and their potential as markers for stress and life experiences.

The role of circular RNA in immune response to tuberculosis and its potential as a biomarker and therapeutic target

Circular RNA (circRNA) is a new type of non-coding RNA that has gained significant attention in recent years, especially in tuberculosis research. Tuberculosis poses a major global public health threat. Its complex pathological mechanisms and worsening drug resistance urgently necessitate new research breakthroughs. The role of circRNA in mycobacterium tuberculosis infection is being gradually revealed, highlighting its importance in regulating gene expression, immune response, and inflammation. Additionally, researchers are interested in circRNA because of its potential for early tuberculosis diagnosis and its role as a biomarker. This article systematically analyzes existing literature to provide new insights into early tuberculosis diagnosis and personalized treatment. We also emphasize the need for future research to enhance the application of circRNA in tuberculosis prevention and control.

circEgg inhibits BmCPV infection by regulating the transition between H3K9me3 and H3K9ac

Our previous study demonstrated that the expression level of circRNA circEgg, which is encoded by histone-lysine N-methyltransferase eggless (BmEgg), is responsive to Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) infection in the silkworm. However, the precise relationship between BmCPV infection and circEgg remains unclear. In this study, we observed that the expression level of circEgg in both the midguts and cultured BmN cells significantly increased after BmCPV infection, while the expression of its host gene, BmEgg, exhibited an opposite trend. Transient expression experiments revealed that circEgg acts to inhibit BmCPV infection. Additionally, Western blot analyses indicated that BmCPV infection leads to a downregulation of histone 3 lysine 9 trimethylation (H3K9me3) and an upregulation of histone 3 lysine 9 acetylation (H3K9ac). Notably, the levels of H3K9ac and H3K9me3 were found to be positively and negatively correlated with circEgg expression, respectively, suggesting that circEgg may regulate the transition between H3K9me3 and H3K9ac. Mechanistically, we discovered that circEgg inhibits BmCPV infection by enhancing the H3K9ac level through the circEgg-bmo-miR-3391-5p-histone deacetylase Rpd3 network, while simultaneously reducing the H3K9me3 level via the circEgg-encoded protein circEgg-P122. Collectively, these findings indicate that circEgg plays a crucial role in inhibiting BmCPV infection by modulating the balance between H3K9me3 and H3K9ac.

The diagnostic and therapeutic potential of multiple myeloma-associated circular RNAs

Circular RNA (circRNA) was first discovered in viruses in 1974; they are primarily formed through back splicing, where a downstream splice donor is joined to an upstream splice acceptor, resulting in a closed circRNA transcript. Under normal conditions, most circRNAs are stably expressed; however, in pathological conditions, circRNAs can play critical roles in the disease process of multiple myeloma (MM) through mechanisms such as competing endogenous RNAs (ceRNAs), regulation of transcription and splicing, affecting protein expression and localization, and even direct encoding of peptides. In recent years, there has been increasing interest in the role of circRNAs in MM and their regulatory functions during the disease process. Numerous studies have revealed that circRNAs are involved in the pathogenesis and prognosis of MM, aiding in the identification of reliable prognostic markers and potential therapeutic targets. Therefore, this review summarizes the structural characteristics of circRNAs, and their regulatory roles in MM, and introduces the latest advancements in understanding the novel functions of circRNAs in MM.

Carotenoids Modulate FoxO-Induced Cell Cycle Awrrest in Human Cancer Cell Lines: A Scoping Review

Carotenoids, a class of antioxidants, have shown great potential for cancer management. This scoping review aimed to elucidate the anticancer mechanisms of carotenoids by using a protein interactions and pathways approach. A literature search on five databases (Web of Science, PubMed, Ovid Medline, Ovid Embase and Scopus) was carried out, and studies investigating differential protein expression in cancer cell lines treated with carotenoids published in the last 10 years were included in the analysis. Sixty-three research articles were short-listed, and 17 carotenoids were used in these studies. The most studied carotenoids were fucoxanthin, astaxanthin, and crocin. The key cancer cell lines tested in these studies included breast, gastric, and lung cancers. Analysis of the proteins identified from these studies using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) revealed the upregulation of proteins belonging to the pro-apoptotic and FoxO signaling pathways. In contrast, several proteins in the PI3k/Akt and TNF signaling pathways and cell cycle regulation were downregulated, which can explain the observed anticancer effects. The findings from this scoping review suggest that the cell cycle arrest observed in carotenoid-treated cancer cells may work through activation of the FoxO signaling pathway in these cells, highlighting their role as potential anticancer agents. Nonetheless, the lack of evidence on the pharmacology, pharmacokinetics, and physiology of carotenoids necessitates more robust and well-designed clinical trials. Similarly, further investigations into the therapeutic effects of targeting the PI3K/Akt/FoxO axis to induce cell cycle arrest and its translational potential are required to ensure the successful development of effective treatments.

Circular RNAs in neurological conditions - computational identification, functional validation, and potential clinical applications

Non-coding RNAs (ncRNAs) have gained significant attention in recent years due to advancements in biotechnology, particularly high-throughput total RNA sequencing. These developments have led to new understandings of non-coding biology, revealing that approximately 80% of non-coding regions in the genome possesses biochemical functionality. Among ncRNAs, circular RNAs (circRNAs), first identified in 1976, have emerged as a prominent research field. CircRNAs are abundant in most human cell types, evolutionary conserved, highly stable, and formed by back-splicing events which generate covalently closed ends. Notably, circRNAs exhibit high expression levels in neural tissue and perform diverse biochemical functions, including acting as molecular sponges for microRNAs, interacting with RNA-binding proteins to regulate their availability and activity, modulating transcription and splicing, and even translating into functional peptides in some cases. Recent advancements in computational and experimental methods have enhanced our ability to identify and validate circRNAs, providing valuable insights into their biological roles. This review focuses on recent developments in circRNA research as they related to neuropsychiatric and neurodegenerative conditions. We also explore their potential applications in clinical diagnostics, therapeutics, and future research directions. CircRNAs remain a relatively underexplored area of non-coding biology, particularly in the context of neurological disorders. However, emerging evidence supports their role as critical players in the etiology and molecular mechanisms of conditions such as schizophrenia, bipolar disorder, major depressive disorder, Alzheimer's disease, and Parkinson's disease. These findings suggest that circRNAs may provide a novel framework contributing to the molecular dysfunctions underpinning these complex neurological conditions.

Noncoding RNA (ncRNA)-mediated regulation of TLRs: critical regulator of inflammation in tumor microenvironment

Toll-like receptors (TLRs) are central components of the innate immune system as they recognize molecular patterns associated with pathogens and cellular damage and initiate immune responses using MyD88- and TRIF-dependent pathways. In contrast to being very useful for immune defense, dysregulated TLR signaling may be involved in diseases, such as cancer and autoimmune conditions. In cancer, TLRs create an environment that supports tumorigenesis and growth. In addition to this, a class of multifunctional noncoding RNAs (ncRNAs), including miRNAs, lncRNAs, and circRNAs, regulate gene expression without encoding proteins. MiRNAs regulate gene expression in a fine-tuned manner, while lncRNAs and circRNAs do so via diverse mechanisms. Notably, these ncRNAs interact, where lncRNAs and circRNAs function as competing endogenous RNAs and ceRNA, affecting miRNA activity. This interaction has a vital role in cancer pathology, in influencing that of various oncogenes and tumor suppressors in the tumor microenvironment; hence, modulation of ncRNAs could also be a great promising therapeutic approach. In this context, interplay between TLRs and ncRNAs is of paramount importance as they influence various parameters of the tumor microenvironment. TLR signaling works upon the expression of ncRNAs, while ncRNAs work back to regulate TLR signaling in return. An example of this includes miRNA targeting of components of the TLR; lncRNAs induced by TLR signaling possibly would favor tumor progression. Pharmacological interventions directed toward inhibiting these TLR pathways could be the model to halt malignancy by hampering pro-tumor inflammation and boosting immune responses against neoplasms. Hence, the review will highlight the complicated contrast of ncRNAs and TLRs within human cancer. By connecting the mechanisms, the researchers may study more about tumorigenesis and gather up new, innovative notions regarding therapeutic targeting.

Estrogen-induced circFAM171A1 regulates sheep myoblast proliferation through the oar-miR-485-5p/MAPK15/MAPK pathway

Estrogen is an important hormone that affects muscle development in female animals. Previous studies have shown that estrogen can protect muscle cells from apoptosis by inhibiting the MAPK signaling pathway. However, the molecular mechanisms by which estrogen-induced MAPK signaling regulates myoblast growth and development remain unclear. In this study, RNA-seq was performed on ovariectomized small-tailed Han (OR-STH) sheep and sham surgery small-tailed Han (STH) sheep to analyze the effects of estrogen on muscle growth and development in female animals. There were 8721 differentially expressed circRNAs (DECs), 143 differentially expressed miRNAs (DEMs) and 2238 differentially expressed mRNAs (DEGs) in the longissimus dorsi between the OR-STH and STH groups. Bioinformatics analysis revealed that the differentially expressed gene MAPK15 was significantly enriched in the MAPK signaling pathway, which is important for muscle development. Therefore, we constructed the ceRNA network circFAM171A1/oar-miR-485-5p/MAPK15 and explored its effect on muscle growth and development. The results of the molecular mechanism experiments indicated that circFAM171A1 can sponge oar-miR-485-5p to regulate MAPK15. The addition of the exogenous hormone estradiol (E2) to sheep myoblasts could induce circFAM171A1, regulate the expression of oar-miR-485-5p and MAPK15, and promote the proliferation of sheep myoblasts. The results showed that MAPK15 and circFAM171A1 significantly promoted the proliferation of myoblasts and inhibited the apoptosis of myoblasts in sheep, whereas oar-miR-485-5p inhibited the expression of MAPK15 and circFAM171A1, inhibited myoblast proliferation and promoted apoptosis. Furthermore, circFAM171A1 attenuated the inhibitory effect of oar-miR-485-5p on myoblasts. In summary, estrogen induced the expression of circFAM171A1 in sheep myoblasts, and circFAM171A1 can act as a sponge for oar-miR-485-5p to promote the expression of the target gene MAPK15 and ultimately regulate the proliferation of sheep myoblasts. This study provides new insights into the molecular mechanism of estrogen regulation of muscle growth and development in female animals.

o8G-modified circPLCE1 inhibits lung cancer progression via chaperone-mediated autophagy

BACKGROUND

Lung cancer poses a serious threat to human health, but its molecular mechanisms remain unclear. Circular RNAs (circRNAs) are closely associated with tumour progression, and the important role of 8-oxoguanine (o8G) modification in regulating the fate of RNA has been gradually revealed. However, o8G modification of circRNAs has not been reported. We identified circPLCE1, which is significantly downregulated in lung cancer, and further investigated the o8G modification of circPLCE1 and the related mechanism in lung cancer progression.

METHODS

We identified differentially expressed circRNAs by RNA high-throughput sequencing and then conducted methylated RNA immunoprecipitation (MeRIP), immunofluorescence (IF) analysis, crosslinking immunoprecipitation (CLIP) and actinomycin D (ActD) assays to explore circPLCE1 o8G modification. The biological functions of circPLCE1 in vivo and in vitro were clarified via establishing a circPLCE1 silencing/overexpression system. Tagged RNA affinity purification (TRAP), RNA Immunoprecipitation (RIP) and coimmunoprecipitation (Co-IP) assays, and pSIN-PAmCherry-KFERQ-NE reporter gene were used to elucidate the molecular mechanism by which circPLCE1 inhibits lung cancer progression.

RESULTS

This study revealed that reactive oxygen species (ROS) can induce circPLCE1 o8G modification and that AUF1 can mediate a decrease in circPLCE1 stability. We found that circPLCE1 significantly inhibited lung cancer progression in vitro and in vivo and that its expression was associated with tumour stage and prognosis. The molecular mechanism was elucidated: circPLCE1 targets the HSC70 protein, increases its ubiquitination level, regulates ATG5-dependent macroautophagy via the chaperone-mediated autophagy (CMA) pathway, and ultimately inhibits lung cancer progression.

CONCLUSION

o8G-modified circPLCE1 inhibits lung cancer progression through CMA to inhibit macroautophagy and alter cell fate. This study provides not only a new theoretical basis for elucidating the molecular mechanism of lung cancer progression but also potential targets for lung cancer treatment.

Roles of circRNAs in viral pathogenesis

Circular RNAs (circRNAs) are a class of non-coding RNAs with a covalently closed circular structure, lacking 5'-caps or 3'-poly(A) tails. They are relatively conserved, highly stable, and often exhibit tissue- or cell-specific production in eukaryotic cells. Based on the advances in sequencing technologies and bioinformatics, multiple reports have suggested that viruses and other microorganisms may encode circRNA-like molecules, providing new insights into the physiological and pathological roles of circRNAs. The innate immune system functions as the body's primary defense mechanism against viral infections. It detects pathogen-associated molecular patterns (PAMPs) and activates signaling pathways to suppress viral replication and limit their spread. CircRNAs are involved in regulation of the host innate immune signaling pathways and play essential roles in viral pathogenesis. It has been shown that circRNAs can regulate gene expression by acting as miRNA sponges or protein sponges, or encoding small proteins in specific cases. For example, previous studies have revealed that circRNAs participate in the host antiviral immune response through the competitive endogenous RNA (ceRNA) network by acting as miRNA sponges. This review highlights research progress in the regulation and functions of host- and virus-encoded circRNAs in host-virus interactions, as well as their potential as diagnostic biomarkers and therapeutic targets in clinical applications.

Circular RNA circCLASP2 promotes nasopharyngeal carcinoma progression through binding to DHX9 to enhance PCMT1 translation

BACKGROUND

Circular RNAs (circRNAs), characterized by their covalently closed-loop structures, constitute a distinct class of non-coding RNAs. They play pivotal regulatory roles within cells and are intricately associated with the progression of malignant tumors. However, their roles and the underlying mechanisms in nasopharyngeal carcinoma (NPC) progression have yet to be fully uncovered and comprehensively understood.

METHODS

Employing RNA sequencing technology, high-abundance circular RNAs in NPC were identified. Expression analysis of circCLASP2 in NPC tissues was conducted using quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization experiments. Through in vitro and in vivo functional assays, the influence of circCLASP2 on the proliferation and metastasis of NPC was investigated. LC-MS/MS technology analyzed the binding partners of circCLASP2, its differentially regulated targets, and the associated proteins of PCMT1. Interactions among circCLASP2, DHX9 protein, and PCMT1 mRNA were elucidated through RNA immunoprecipitation and RNA pull-down techniques. The effects of circCLASP2 and DHX9 on RNA G-quadruplex (rG4) structures and PCMT1 mRNA translation were explored through immunofluorescence (IF), ribosomal gradient separation, and dual-luciferase reporter assays. Immunoprecipitation (IP) revealed the downstream effector of the circCLASP2-DHX9-PCMT1 regulatory axis and Phalloidin staining confirmed its ultimate effect on the cytoskeleton. PDS treatment was applied for interventions in NPC, demonstrating potential therapeutic avenues.

RESULTS

Our research revealed that circCLASP2, a novel circRNA that has not been reported in tumors, is upregulated in NPC and fosters cell proliferation and metastasis both in vitro and in vivo. Mechanistically, circCLASP2 acts as a molecular scaffold, facilitating the approximation of DHX9 to PCMT1 mRNA. DHX9 unwinds the inhibitory rG4 structure near the translation initiation site on PCMT1 mRNA, increasing PCMT1 expression. PCMT1 binds to and upregulates cytoskeleton-associated proteins, modulating cytoskeleton strength and dynamics and ultimately driving NPC cell proliferation and metastasis. In both in vitro and in vivo experiments, PDS significantly inhibits NPC growth and metastasis, showcasing promising therapeutic potential.

CONCLUSIONS

Our investigation pinpointed a circular RNA, circCLASP2, which is upregulated in NPC and augments cytoskeletal functions via the DHX9-PCMT1 axis, contributing to the malignancy progression of NPC. This pathway holds promise as a potential therapeutic target for NPC. Furthermore, these molecules could also serve as biomarkers for adjunct diagnosis and prognosis assessment in NPC.

Mechanism of Action of circRNA/miRNA Network in DLBCL

Circular RNAs (circRNAs) make up approximately 10% of the human transcriptome. CircRNAs belong to the broad group of non-coding RNAs and characteristically are formed by backsplicing into a stable circular loop. Their main role is to regulate transcription through the inhibition of miRNAs' expression, termed miRNA sponging. CircRNAs promote tumorigenesis/lymphomagenesis by competitively binding to miRNAs at miRNA binding sites. In diffuse large B-cell lymphoma (DLBCL), several circRNAs have been identified and their expression is related to both progression and response to therapy. DLBCL is the most prevalent and aggressive subtype of B-cell lymphomas and accounts for about 25% to 30% of all non-Hodgkin lymphomas. DLBCL displays great heterogeneity concerning histopathology, biology, and genetics. Patients who have relapsed or have refractory disease after first-line therapy have a very poor prognosis, demonstrating an important unmet need for new treatment options. As more circRNAs are identified in the future, we will better understand their biological roles and potential use in treating cancer, including DLBCL. For example, circAmotl1 promotes nuclear translocation of MYC and upregulation of translational targets of MYC, thus enhancing lymphomagenesis. Another example is circAPC, which is significantly downregulated in DLBCL and correlates with disease aggressiveness and poor prognosis. CircAPC increases expression of the host gene adenomatous polyposis coli (APC), and in doing so inactivates the canonical Wnt/β-catenin signaling and restrains DLBCL growth. MiRNAs belong to the non-coding regulatory molecules that significantly contribute to lymphomagenesis through their target mRNAs. In DLBCL, among the highly expressed miRNAs, are miR-155-5p and miR-21-5p, which regulate NF-ĸB and PI3K/AKT signaling pathways. The aim of this review is to describe the function and mechanism of regulation of circRNAs on miRNAs' expression in DLBCL. This will help us to better understand the regulatory network of circRNA/miRNA/mRNA, and to propose novel therapeutic targets to treat DLBCL.

Circular RNAs as key regulators in cancer hallmarks: New progress and therapeutic opportunities

Circular RNAs (circRNAs) have emerged as critical regulators in cancer biology, contributing to various cancer hallmarks, including cell proliferation, apoptosis, metastasis, and drug resistance. Defined by their covalently closed loop structure, circRNAs possess unique characteristics like high stability, abundance, and tissue-specific expression. These non-coding RNAs function through mechanisms such as miRNA sponging, interactions with RNA-binding proteins (RBPs), and modulating transcription and splicing. Advances in RNA sequencing and bioinformatics tools have enabled the identification and functional annotation of circRNAs across different cancer types. Clinically, circRNAs demonstrate high specificity and sensitivity in samples, offering potential as diagnostic and prognostic biomarkers. Additionally, therapeutic strategies involving circRNA mimics, inhibitors, and delivery systems are under investigation. However, their precise mechanisms remain unclear, and more clinical evidence is needed regarding their roles in cancer hallmarks. Understanding circRNAs will pave the way for novel diagnostic and therapeutic approaches, potentially improving patient outcomes.

Research progress of circular RNA FOXO3 in diseases (review)

Circular RNAs (circRNAs) are a newly discovered class of endogenous non-coding RNAs with a closed-loop structures, and they exert crucial regulatory functions in diverse biological processes and disease development through the modulation of linear RNA transcription, downstream gene expression, and protein translation, among others. Circular RNA FOXO3(circFOXO3, Hsa_circ_0006404) originates from exon 2 of the FOXO3 gene and exhibits widespread cytoplasmic expression in eukaryotic cells. It shows specific expression in different tissues or cells. Recent research has associated circFOXO3 with various diseases such as cancer, cardiovascular diseases, neurological disorders, senescence, and inflammation. However, a comprehensive review of the research progress of circFOXO3 in human diseases has not been conducted. In this paper, we provide a systematic review of the latest advances in circFOXO3 research in diseases, elucidate its biological functions and potential molecular mechanisms, and discuss the future directions and challenges in circRNAs research to provide valuable references and inspiration for research in this field.

Circular RNAs in cancer stem cells: Insights into their roles and mechanisms (Review)

Cancer stem cells (CSCs) represent a small, yet pivotal subpopulation of tumor cells that play significant roles in tumor initiation, progression and therapeutic resistance. Circular RNAs (circRNAs) are a distinct class of RNAs characterized by their closed‑loop structures, lacking 5' to 3'ends. There is growing evidence that circRNAs are integral to the development and regulation of CSCs. Aberrant expression of circRNAs in CSCs can contribute to oncogenic properties and drug resistance. Specifically, oncogenic circRNAs modulate CSC behavior via key signaling pathways, thereby promoting CSC self‑renewal and maintenance, as well as tumor progression. This review summarizes the latest research on the functional roles and regulatory mechanisms of circRNAs in CSC behavior and discusses potential applications and challenges of targeting circRNAs in CSCs. Understanding the intricate interactions between circRNAs and CSCs may lead to novel therapeutic strategies that effectively combat treatment resistance and improve patient outcomes.

5-Methylcytosine-modified circRNA-CCNL2 regulates vascular remdeling in hypoxic pulmonary hypertension through binding to FXR2

Pulmonary hypertension (PH) is a malignant cardiovascular disease with a complex etiology. 5-Methylcytosine (m5C) is a post-transcriptional RNA modification identified in both stable and highly abundant RNAs, with a lower frequency of occurrence in circular RNAs (circRNAs). Nevertheless, the function of m5C-modified circRNAs in the pathogenesis of PH remains uncertain. The objective of this study was to investigate the biological role and molecular mechanisms of m5C-modified circRNA-CCNL2 in hypoxic PH pulmonary vascular remodeling. Our findings revealed that hypoxia downregulates circCCNL2 expression, and overexpression of circCCNL2 attenuates PH progression and inhibits the proliferation of pulmonary artery smooth muscle cell (PASMCs). Bioinformatics predictions indicated the presence of m5C modification sites in circCCNL2, which NSUN2 mediated. The downregulation of NSUN2 resulted in a reduction in m5C modification of circCCNL2. It was also observed that the stability of circRNAs was associated with the proliferation of PASMCs. From a mechanistic standpoint, low expression of circCCNL2 resulted in reduced binding of FXR2, while increased association of free FXR2 with CDKL3 led to enhanced proliferation of PASMCs. Notably, circCCNL2 expression was found to be regulated by alternative splicing involving SRSF2, with reduced pre-CCNL2 splicing resulting from low SRSF2 expression, ultimately leading to decreased circCCNL2 expression. This is the first demonstration that m5C-modified circCCNL2 can slow the development of PH and inhibit the proliferation of PASMCs by binding to FXR2. These findings offer new insights into the regulation of circRNAs through m5C modifications and the role of epigenetic reprogramming in PH.

CircNIPBLL modulates the inflammatory response against Eimeria tenella infection via sponging gga-miR-2954

Coccidiosis, a parasitic disease caused by Eimeria protozoa that parasitizes intestinal tissues of chicken, poses a challenge to the development of the poultry industry. circRNAs are a class of circular RNA macromolecules crucial in the immune response to pathogens. Previous studies have shown that gga-miR-2954 inhibits the inflammatory response to Eimeria tenella (E. tenella) infection. In this study, we screened the key circRNA (circNIPBLL) regulating gga-miR-2954 using a co-expression network. The RNase R and Actinomycin D assays showed that the circular structure of the circNIPBLL was stable. Besides, the circNIPBLL expression was mainly distributed in the cytoplasm but did not have coding capacity. Overexpression of circNIPBLL significantly promoted the production of the IL-6, IL-1β, TNF-α, and IL-8 in sporozoite-stimulated DF-1 cells, whereas circNIPBLL knockdown significantly inhibited these effects. Moreover, circNIPBLL induced apoptosis of DF-1 cells stimulated by sporozoites. Mechanistically, circNIPBLL functioned as a sponge for gga-miR-2954, and overexpression of circNIPBLL rescued the effect of gga-miR-2954 mimic on the inflammatory response of DF-1 cells stimulated with sporozoites. Taken together, this study suggested that circNIPBLL modulated the inflammatory response against E. tenella infection by sponging gga-miR-2954, which may provide novel insights into the immune mechanisms of chicken resistance to E. tenella.

circTUBD1-hnRNPK Regulates the Proliferation and Migration of LSCC by Targeting CCAR1

BACKGROUND

Laryngeal squamous cell carcinoma (LSCC) is one of the most prevalent malignancies of the head and neck region. Circular RNAs (circRNAs) have been found to exhibit abnormal expression patterns in various tumors and play pivotal roles in tumorigenesis and tumor progression.

METHODS

Functional assays assessed proliferation, migration, and invasion. Mechanistic studies were performed to explore the interaction between circTUBD1 and heterogeneous nuclear ribonucleoprotein K (hnRNPK), as well as its regulation of Cell Cycle and Apoptosis Regulator 1 (CCAR1). In vivo experiments confirmed circTUBD1's role in tumor growth and metastasis.

RESULTS

We discovered that circTUBD1 is significantly upregulated in LSCC and promotes the proliferation, invasion, and migration of LSCC cells. circTUBD1 forms a circRNA-protein complex with hnRNPK and facilitates LSCC progression by regulating CCAR1. Furthermore, in vivo experiments in mice demonstrated that silencing circTUBD1 inhibits the proliferation and metastasis of LSCC.

CONCLUSIONS

This study provides evidence that circTUBD1 is a potential tumor marker for LSCC and underscores the therapeutic potential of targeting circTUBD1 in this cancer type.

Biological roles and molecular mechanism of circular RNAs in epithelial-mesenchymal transition of gastrointestinal malignancies

Circular RNAs (circRNAs) are formed by splicing of precursor RNAs and covalently linked at the 5' and 3' ends. Dysregulated circRNAs are closely related to the epithelial-mesenchymal transition (EMT) of gastrointestinal malignancies. CircRNAs, including circRNA_0008717, circGOT1, circ-DOCK5, circVPS33B, circPVT1, circMET, circ-OXCT1, circ_67835, circRTN4, circ_0087502, circFNDC38, circ_PTEN1, circPGPEP1, and circ-E-Cad are involved in the EMT process of gastrointestinal malignancies through a variety of mechanisms, such as regulating EMT-inducing transcription factors, signaling pathways, and tumor microenvironments. Gastrointestinal (GI) malignancies are common malignant tumors worldwide, and the heterogeneity and easy metastasis of gastrointestinal malignancies limit the effectiveness of medical treatments. Therefore, investigating the molecular mechanisms involved in the pathogenesis of gastrointestinal malignancies is essential for clinical treatment. This article summarizes the biological roles and molecular mechanism of circRNAs in EMT of gastrointestinal malignancies, providing a theoretical basis for applying EMT-related circRNAs in targeted therapy.

Microglial circDlg1 modulates neuroinflammation by blocking PDE4B ubiquitination-dependent degradation associated with Alzheimer's disease

Background: Abnormal activation of microglia occurs in the early stage of Alzheimer's disease (AD) and leads to subsequent neuroinflammation and major AD pathologies. Circular RNAs (circRNAs) are emerging as great potential therapeutic targets in AD. However, the extent of circRNAs entwined and the underlying mechanism in microglia-driven neuroinflammation in AD remain elusive. Methods: The circular RNA Dlg1 (circDlg1) was identified using circRNA microarray screening in magnetic-isolated microglia of APP/PS1 mice. CircDlg1 expression in microglia of APP/PS1 mice and AD patients was validated by FISH. Flow cytometry and immunostaining were conducted to explore the roles of circDlg1 in microglia. Adeno-associated virus 9 preparations for interfering with microglial circDlg1 were microinjected into mouse lateral ventricle to explore influences on microglial response, neuroinflammation and AD pathologies. Y-maze, novel object recognition and Morris water maze tasks were performed to assess cognitive performance. RNA pulldown assays, mass spectrometry analysis, RNA immunoprecipitation, and co-immunoprecipitation were performed to validate the underlying regulatory mechanisms of circDlg1. Results: A novel circular RNA circDlg1 was observed elevated using circRNA microarray screening in microglia isolated from APP/PS1 mice and validated increased in intracerebral microglia of AD patients. Microglia-specific knockdown of circDlg1 remarkably ameliorated microglial recruitment and envelopment of amyloid-β (Aβ), mitigated neuroinflammation, and prevented cognitive decline in APP/PS1 mice. Mechanistically, circDlg1 interfered with the interaction between phosphodiesterase 4b (PDE4B) and Smurf2, an E3 ubiquitin ligase of PDE4B. The formed ternary complex protected PDE4B from ubiquitination-dependent degradation via unique N-terminal targeting domain, thus consequently decreasing cAMP levels. We further confirmed that microglial circDlg1 downregulation significantly activated PKA/CREB anti-inflammatory pathway by decreasing PDE4B protein levels in APP/PS1 mice. Conclusion: The novel microglia-upregulated circDlg1 tightly involves in neuroinflammation in APP/PS1 mice via determining the protein fate of PDE4B. Microglial loss of circDlg1 promotes microglial protective response to Aβ deposition and relieves neuroinflammation, thus suggesting a potential therapeutic strategy that specifically targets the microglial response in AD.

A Preliminary Study of CircRNA Expression Characteristics in the Progression of Colorectal Cancer

Colorectal cancer (CRC) progression involves complex genetic changes. This study examines circRNA expression in CRC to identify biomarkers for improved diagnosis and staging. The objective of this study is to explore the role of circular RNA (circRNA) in CRC progression and identify specific circRNA biomarkers. Using high-throughput circRNA chip technology, cancerous and adjacent tissues from three CRC patients (staged as T1-3N0M0) were analyzed to identify differentially expressed circRNAs. Bioinformatics analyses, including co-expression network construction, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, were performed to evaluate circRNA function and pathways. A total of 404 differentially expressed circRNAs were identified, with significant variations between cancerous and adjacent tissues. Trend analysis revealed that circRNA expression decreased progressively with CRC advancement. Co-expression network analysis highlighted eight key circRNAs, including hsa_circ_0000007, associated with CRC progression. GO and KEGG analyses indicated these circRNAs are involved in ribosome biogenesis, metabolism, and the regulation of G1-S phase transcription through the RB1 gene. The expression of hsa_circ_0000007, hsa_circ_0023608, hsa_circ_0026694, and hsa_circ_0029903 decreased as CRC progressed, suggesting their potential as biomarkers for CRC diagnosis and staging. These findings offer insights into the molecular mechanisms underlying CRC progression.

Identifying insulin-responsive circRNAs in chicken pectoralis

BACKGROUND

Circular RNAs (circRNAs) are stable, covalently closed non-coding RNAs formed by reverse splicing of precursor mRNA. They play critical roles in various biological processes, including insulin secretion and metabolism. However, their function in avian skeletal muscle's response to insulin remains poorly understood. This study aimed to comprehensively identify insulin-responsive circRNAs and explore their temporal and breed-specific regulation in poultry.

RESULTS

Using strand-specific RNA sequencing (ssRNA-Seq) on the pectoralis muscles of both Arbor Acres (AA) broilers and Silky fowls following insulin administration (5 IU/kg.BW, PBS as control). We identified 2,027 muscle circRNAs. Insulin-responsive circRNAs were detected in Silky fowls (29) and broilers (45) at 120 min, and in broilers (20) at 15 min post-injection. These circRNAs are enriched in processes such as exocrine pancreas development, response to exogenous stimuli, and regulation of intracellular signal transduction, likely mediated through a circRNA-miRNA network. Fewer insulin-responsive circRNAs were shared between time points in broilers (1) or between breeds (3) at 120 min. We further characterized a conserved insulin-responsive circRNA (circINSR), formed by exon 2 of the Insulin Receptor (INSR). The circINSR showed a similar spatiotemporal expression pattern to INSR, but exhibited distinct changes post-insulin administration. In broilers, INSR expression was dynamically modulated, while circINSR was downregulated only at 15 min (P < 0.01). Conversely, glucose did not change muscle circINSR but increased INSR at 10 min (P < 0.01). Energy restriction significantly downregulated circINSR (P < 0.01) without affecting INSR levels, and pyruvate had no effect on either circINSR or INSR levels.

CONCLUSION

This study reveals the dynamic and breed-specific roles of circRNAs, particularly circINSR, in avian skeletal muscle's response to insulin. The distinct regulation of circINSR and INSR under various metabolic conditions suggests a complex regulatory mechanism. These findings provide novel insights into the molecular basis of insulin signaling in avian species and highlight the potential of circRNAs as biomarkers for metabolic regulation.

The Role of the Fox Gene in Breast Cancer Progression

Forkhead box (FOX) genes are a family of transcription factors that participate in many biological activities, from early embryogenesis to the formation of organs, and from regulation of glucose metabolism to regulation of longevity. Given the extensive influence in the multicellular process, FOX family proteins are responsible for the progression of many types of cancers, especially lung cancer, breast cancer, prostate cancer, and other cancers. Breast cancer is the most common cancer among women, and 2.3 million women were diagnosed in 2020. So, various drugs targeting the FOX signaling pathway have been developed to inhibit breast cancer progression. While the role of the FOX family gene in cancer development has not received enough attention, discovering more potential drugs targeting the FOX signaling pathway is urgently demanded. Here, we review the main members in the FOX gene family and summarize their signaling pathway, including the regulation of the FOX genes and their effects on breast cancer progression. We hope this review will emphasize the understanding of the role of the FOX gene in breast cancer and inspire the discovery of effective anti-breast cancer medicines targeting the FOX gene in the future.

CircPTK2 as a Valuable Biomarker and Treatment Target in Cancer

Circular RNA (CircRNA)s, a newly discovered type of noncoding RNAs, have been found to play a role in controlling the development and aggressiveness of tumors. Abnormal control of circRNA has been observed in various types of human cancers, including bladder cancer, hepatocellular carcinoma (HCC), breast cancer, and gastric cancer (GC). CircRNAs possess binding sites for microRNAs (miRNAs) and function as miRNA sponges in posttranscriptional regulation. This mechanism has been documented to influence the course of cancer. Significantly, among these putative circRNAs, circular RNA protein tyrosine kinase 2 (circPTK2) exhibited increased expression and displayed a substantial association with adverse clinical characteristics and a negative prognosis. The production of these transcripts occurs via a back-splicing mechanism. The enclosed conformation of circRNAs shields them from destruction and enhances their potential as biomarkers. Gaining insight into the molecular mechanisms involved in these processes would aid in the development of treatment approaches and the discovery of new tumor markers. This article provides a comprehensive assessment of the latest research on the biosynthesis and features of circRNAs. It examines the role of circPTK2 in the diagnosis, treatment, and prognosis evaluation of cancer.

Breaking new ground: Unraveling the USP1/ID3/E12/P21 axis in vascular calcification

Vascular calcification (VC) poses significant challenges in cardiovascular health. This study employs single-cell transcriptome sequencing to dissect cellular dynamics in this process. We identify distinct cell subgroups, notably in vascular smooth muscle cells (VSMCs), and observe differences between calcified atherosclerotic cores and adjacent regions. Further exploration reveals ID3 as a key gene regulating VSMC function. In vitro experiments demonstrate ID3's interaction with USP1 and E12, modulating cell proliferation and osteogenic differentiation. Animal models confirm the critical role of the USP1/ID3/E12/P21 axis in VC. This study sheds light on a novel regulatory mechanism, offering potential therapeutic targets.

MicroRNA-specific targets for neuronal plasticity, neurotransmitters, neurotrophic factors, and gut microbes in the pathogenesis and therapeutics of depression

Depression is of great concern because of the huge burden, and it is impacted by various epigenetic modifications, e.g., histone modification, covalent modifications in DNA, and silencing mechanisms of non-coding protein genes, e.g., microRNAs (miRNAs). MiRNAs are a class of endogenous non-coding RNAs. Alternations in specific miRNAs have been observed both in depressive patients and experimental animals. Also, miRNAs are highly expressed in the central nervous system and can be delivered to different tissues via tissue-specific exosomes. However, the mechanism of miRNAs' involvement in the pathological process of depression is not well understood. Therefore, we summarized and discussed the role of miRNAs in depression. Conclusively, miRNAs are involved in the pathology of depression by causing structural and functional changes in synapses, mediating neuronal regeneration, differentiation, and apoptosis, regulating the gut microbes and the expression of various neurotransmitters and BDNF, and mediating inflammatory and immune responses. Moreover, miRNAs can predict the efficacy of antidepressant medications and explain the mechanism of action of antidepressant drugs and aerobic exercise to prevent and assist in treating depression.

Translation of circular RNAs

Circular RNAs (circRNAs) are covalently closed RNAs that are present in all eukaryotes tested. Recent RNA sequencing (RNA-seq) analyses indicate that although generally less abundant than messenger RNAs (mRNAs), over 1.8 million circRNA isoforms exist in humans, much more than the number of currently known mRNA isoforms. Most circRNAs are generated through backsplicing that depends on pre-mRNA structures, which are influenced by intronic elements, for example, primate-specific Alu elements, leading to species-specific circRNAs. CircRNAs are mostly cytosolic, stable and some were shown to influence cells by sequestering miRNAs and RNA-binding proteins. We review the increasing evidence that circRNAs are translated into proteins using several cap-independent translational mechanisms, that include internal ribosomal entry sites, N6-methyladenosine RNA modification, adenosine to inosine RNA editing and interaction with the eIF4A3 component of the exon junction complex. CircRNAs are translated under conditions that favor cap-independent translation, notably in cancer and generate proteins that are shorter than mRNA-encoded proteins, which can acquire new functions relevant in diseases.

Fateful Decisions of Where to Cut the Line: Pathology Associated with Aberrant 3' End Processing and Transcription Termination

Aberrant gene expression lies at the heart of many pathologies. This review will point out how 3' end processing, the final mRNA-maturation step in the transcription cycle, is surprisingly prone to regulated as well as stochastic variations with a wide range of consequences. Whereas smaller variations contribute to the plasticity of gene expression, larger alternations to 3' end processing and coupled transcription termination can lead to pathological consequences. These can be caused by the local mutation of one gene or affect larger numbers of genes systematically, if aspects of the mechanisms of 3' end processing and transcription termination are altered.

Circular RNA regulatory role in pathological cardiac remodelling

Cardiac remodelling involves structural, cellular and molecular alterations in the heart after injury, resulting in progressive loss of heart function and ultimately leading to heart failure. Circular RNAs (circRNAs) are a recently rediscovered class of non-coding RNAs that play regulatory roles in the pathogenesis of cardiovascular diseases, including heart failure. Thus, a more comprehensive understanding of the role of circRNAs in the processes governing cardiac remodelling may set the ground for the development of circRNA-based diagnostic and therapeutic strategies. In this review, the current knowledge about circRNA origin, conservation, characteristics and function is summarized. Bioinformatics and wet-lab methods used in circRNA research are discussed. The regulatory function of circRNAs in cardiac remodelling mechanisms such as cell death, cardiomyocyte hypertrophy, inflammation, fibrosis and metabolism is highlighted. Finally, key challenges and opportunities in circRNA research are discussed, and orientations for future work to address the pharmacological potential of circRNAs in heart failure are proposed. LINKED ARTICLES: This article is part of a themed issue Non-coding RNA Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.2/issuetoc.

Knockdown of hsa_circ_0102231 Impedes the Progression of Liver Cancer through the miR-873-SOX4 Axis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most intractable tumors in the world due to its high rate of recurrence and heterogeneity.

AIMS

The objective of this study was to investigate the role of circular RNA 0102231 (hsa_circ_ 0102231) in the progression of liver cancer.

METHODS

In this study, quantitative polymerase chain reaction experiments were performed to quantify the hsa_circ_0102231 level in different liver cancer cell lines. Bioinformatics analysis, as well as a dual-luciferase reporter and RNA pull-down assay, were used to identify putative hsa_circ_ 0102231 downstream targets. Colony formation and CCK8 assays were utilized to examine cell proliferation, whereas Transwell assays were employed to monitor cell migration. Lastly, the role of hsa_circ_0102231 in liver cancer was assessed in a subcutaneous xenograft model.

RESULTS

The expression of hsa_circ_0102231 increased significantly in HepG2 and Huh-7 cells compared with controls, and hsa_circ_0102231 knockdown inhibited cell proliferation and migration in vitro and in vivo. Bioinformatics analysis, as well as a dual-luciferase reporter and RNA pulldown assay, revealed that miR-873 and SOX4 were hsa_circ_0102231 downstream targets. miR-873 inhibition or SOX4 overexpression rescued the proliferation and migration of HepG2 and Huh-7 cells after hsa_circ_0102231 knockdown. Furthermore, SOX4 overexpression reversed the miR-873-induced inhibition of cell migration and proliferation in vitro.

CONCLUSION

These results show that hsa_circ_0102231 knockdown impedes the progression of liver cancer by regulating the miR-873/SOX4 axis. However, further studies are needed to determine whether hsa_circ_0102231 may be a therapeutic target in liver cancer.

Circular RNAs as a novel class of potential therapeutic and diagnostic biomarkers in reproductive biology/diseases

Infertility is a prevalent problem among 10% of people within their reproductive years. Sometimes, even advanced treatment options like assisted reproduction technology have the potential to result in failed implantation. Because of the expected changes in gene expression during both in vitro and in vivo fertilization processes, these methods of assisting fertility have also been associated with undesirable pregnancy outcomes related to infertility. In this aspect, Circular RNAs (circRNAs) play a crucial role as epigenetic modifiers in a wide range of biological and pathological activities, including problems with fertility. CircRNAs are integral pieces in multiple cellular functions, including moving substances within the nucleus, silencing one X chromosome, cell death, the ability of stem cells to differentiate into different cell types, and the process of gene expression inherited from parental genes. Due to the progress made in high-speed gene sequencing, a large amount of circRNA molecules have been detected, revealing their significant functions in diverse biological functions like enhancing testicular development, preserving the differentiation and renewal of spermatogonial cells, and controlling spermatocyte meiosis. Moreover, these non-coding RNAs contribute in different aspects of female reproductive system including pregnancy-related diseases, gynecologic cancers, and endometriosis. In conclusion, there is no denying that circRNAs have immense potential to be used as biomarkers and treatments for reproductive disorders in males and females. In this research, we provide a comprehensive analysis of the multiple circRNAs associated with women's infertility.

MSC-derived exosomal circMYO9B accelerates diabetic wound healing by promoting angiogenesis through the hnRNPU/CBL/KDM1A/VEGFA axis

Diabetic foot ulcer (DFU) is a common but devastating complication of diabetes mellitus and might ultimately lead to amputation. Elucidating the regulatory mechanism of wound healing in DFU is quite important for developing DFU management strategies. Here, we show, mecenchymal stem cell (MSC)-derived exosomes promoted the proliferation, migration and angiogenesis of high glucose-treated endothelial cells and reduced cell apoptosis. These effects were further enhanced by MSC-derived exosomes carrying circMYO9B overexpression. Mechanistically, circMYO9B promoted the translocation of hnRNPU from nucleus to cytoplasm and consequently destabilized CBL, thereby reducing the ubiquitination and degradation of KDM1A to promote VEGFA expression in endothelial cells. MSC-derived exosomes carrying circMYO9B promotes angiogenesis and thus accelerates diabetic wound healing through regulating the hnRNPU/CBL/KDM1A/VEGFA axis, indicating potential therapeutic targets and strategies for DFU treatment.

CircMIB1 inhibits glioma development and progression through a competing endogenous RNA interaction network

Introduction

The critical role of circular RNAs as non-coding RNAs in glioma has been extensively investigated. Therefore, we aimed to explore the role and potential molecular mechanisms of circRNA-mind bomb homolog 1 (circMIB1) in gliomas.

Methods

RNA sequencing was used to analyze the expression profiles of circRNAs in glioma tissues and normal brain tissues. Quantitative real-time polymerase chain reaction was implemented to examine the levels of circMIB1 in glioma cells and tissues. The circMIB1 was identified as a cyclic RNA molecule by DNA nucleic acid electrophoresis and ribonuclease R assay. The relationship between circMIB1 expression and the prognosis of glioma patients and its potential as a biomarker were analysed using Kaplan-Meier, Receiver operating characteristic curves, and Principal component analysis. Bioinformatics analysis predicted the miRNAs that bind to circMIB1 and their downstream targets, and analysed the functions of these genes.

Results

Firstly, a novel circRNA molecule termed circMIB1 was identified and validated by RNA sequencing. The expression of circMIB1 was significantly downregulated in glioma cells and tissues, and was closely associated with the tumor grade and survival prognosis of patients with glioma. Hence, it may be useful as a biomarker for glioma. Secondly, it was predicted that circMIB1 binds to hsa-miR-1290 based on bioinformatics analysis, which was significantly upregulated in glioma cells and tissues, and correlated with the tumor grade and overall survival of patients. Thirdly, through a series of bioinformatics analyses identified six genes downstream of hsa-miR-1290 that were significantly associated with glioma expression and prognosis, these genes are associated with cell cycle, cell necrosis and cell circadian rhythms.

Discussion

CircMIB1 may play a role in inhibiting glioma development through the hsa-miR-1290 competitive endogenous RNA interaction network, these findings provide new ideas and directions for the diagnosis and treatment of glioma.

The emerging role of circular RNAs in cisplatin resistance in ovarian cancer: From molecular mechanism to future potential

Ovarian cancer (OC) is the most common cause of death in female cancers. The prognosis of OC is very poor due to delayed diagnosis and identification of most patients in advanced stages, metastasis, recurrence, and resistance to chemotherapy. As chemotherapy with platinum-based drugs such as cisplatin (DDP) is the main treatment in most OC cases, resistance to DDP is an important obstacle to achieving satisfactory therapeutic efficacy. Consequently, knowing the different molecular mechanisms involved in resistance to DDP is necessary to achieve new therapeutic approaches. According to numerous recent studies, non-coding RNAs (ncRNAs) could regulate proliferation, differentiation, apoptosis, and chemoresistance in many cancers, including OC. Most of these ncRNAs are released by tumor cells into human fluid, allowing them to be used as tools for diagnosis. CircRNAs are ncRNA family members that have a role in the initiation, progression, and chemoresistance regulation of various cancers. In the current study, we investigated the roles of several circRNAs and their signaling pathways on OC progression and also on DDP resistance during chemotherapy.

Crosstalk between circular RNAs and the STAT3 signaling pathway in human cancer

Circular RNAs (circRNAs) are endogenous covalently closed single-stranded RNAs produced by reverse splicing of pre-mRNA. Emerging evidence suggests that circRNAs contribute to cancer progression by modulating the oncogenic STAT3 signaling pathway, which plays key roles in human malignancies. STAT3 signaling-related circRNAs expression appears to be extensively dysregulated in diverse cancer types, where they function either as tumor suppressors or oncogenes. However, the biological effects of STAT3 signaling-related circRNAs and their associations with cancer have not been systematically studied before. Given this, shedding light on the interaction between circRNAs and STAT3 signaling pathway in human malignancies may provide several novel insights into cancer therapy. In this review, we provide a comprehensive introduction to the molecular mechanisms by which circRNAs regulate STAT3 signaling in cancer progression, and the crosstalk between STAT3 signaling-related circRNAs and other signaling pathways. We also further discuss the role of the circRNA/STAT3 axis in cancer chemotherapy sensitivity.

A previously unidentified circRNA inhibits virus replication by regulating the miR-24-3p/KEAP1 axis

Circular RNAs (circRNAs) exert diverse biological functions in different processes. However, the role of circRNAs during virus infection is mostly unknown. Herein, we explored the characteristics of host circRNAs using alphaherpesvirus pseudorabies virus (PRV) as a model. PRV infection upregulated the expression of circRNA circ29164, which does not encode a protein. RNA pulldown assays identified that circ29164 interacts with the microRNA ssc-miRNA-24-3p. Further analysis indicated that ssc-miR-24-3p targets the mRNA encoding kelch-like ECH-associated protein 1 (KEAP1), and circ29164 competitively binds to ssc-miR-24-3p to prevent it binding to Keap1. Apoptosis detection demonstrated that circ29164 or Keap1 overexpression, but not knockdown, induced caspase 3 activity and the release of cytochrome C from mitochondria, and inhibited PRV replication. Taken together, these data identified a previously undiscovered circRNA, circ29164, which inhibits PRV replication by competitively binding to ssc-24-3p to maintain KEAP1 levels.

Circular RNAs as multifaceted molecular regulators of vital activity and potential biomarkers of aging

Aging presents a significant challenge to health and social care systems due to the increasing proportion of the elderly population. The identification of reliable biomarkers to assess the progression of aging remains an unresolved question. Circular RNAs (circRNAs) are single-stranded covalently closed RNAs. They have been found to regulate various biological processes. CircRNAs are present in human biological fluids, are relatively stable, and accumulate with age, making them promising as biomarkers of aging. Current information on the expression of circRNAs in aging was analyzed using scientific databases. In this review, we have identified key stages in the study of circRNAs during aging and summarized the current understanding of their biogenesis. By focusing on the role of circRNAs in processes that contribute to aging - such as genomic stability, metabolism, cell death, and signaling pathways - we hypothesize that circRNAs may drive the aging process through their age-related accumulation and resultant deregulation. Examples of age-related differential expression of circRNAs in various species, including humans, are provided. This review highlights the importance of finding novel epigenetic biomarkers of aging, beyond the already identified molecules (circFOXO3, circRNA100783, circPVT1), and highlights circRNAs as a potential therapeutic target for the treatment of age-associated diseases.

The landscape of circRNAs in gliomas temozolomide resistance: Insights into molecular pathways

As the deadliest type of primary brain tumor, gliomas represent a significant worldwide health concern. Circular RNA (circRNA), a unique non-coding RNA molecule, seems to be one of the most alluring target molecules involved in the pathophysiology of many kinds of cancers. CircRNAs have been identified as prospective targets and biomarkers for the diagnosis and treatment of numerous disorders, particularly malignancies. Recent research has established a clinical link between temozolomide (TMZ) resistance and certain circRNA dysregulations in glioma tumors. CircRNAs may play a therapeutic role in controlling or overcoming TMZ resistance in gliomas and may provide guidance for a novel kind of individualized glioma therapy. To address the biological characteristics of circRNAs and their potential to induce resistance to TMZ, this review has highlighted and summarized the possible roles that circRNAs may play in molecular pathways of drug resistance, including the Ras/Raf/ERK PI3K/Akt signaling pathway and metabolic processes in gliomas.