CircMTO1: A circular RNA with roles in the carcinogenesis

Invention of circRNA promoting RNA to specifically promote circRNA production

CircRNA, an essential RNA molecule involved in various biological functions and diseases, often exhibits decreased expression in tumor tissues, playing a role as a tumor suppressor, and suggesting therapeutic potential for cancer. However, current methods for promoting circRNA production are limited. This study introduces a novel approach for enhancing circRNA biogenesis, termed circRNA promoting RNA (cpRNA). CpRNA is designed to complement the flanking sequences of reverse complementary matches (RCMs) within pre-mRNA, thereby facilitating circRNA formation through improved exon circularization. Using a split-GFP reporter system, we demonstrated that cpRNA significantly enhance circGFP production. Optimization identified the best conditions for cpRNA to promote circRNA biogenesis, and these cpRNAs were then used to augment the production of endogenous circRNAs. These results indicate that cpRNAs can specifically increase the production of endogenous circRNAs with RCMs, such as circZKSCAN1 and circSMARCA5 in cancer cells, thereby inhibiting cell proliferation and migration by modulating circRNA-related pathways, showcasing the therapeutic potential of cpRNAs. Mechanistic studies have also shown that cpRNA promotes circRNA biogenesis, in part, by antagonizing the unwinding function of DHX9. Overall, these findings suggest that cpRNA represents a promising strategy for circRNA overexpression, offering a potential treatment for diseases marked by low circRNA levels.

Noncoding RNAs in atherosclerosis: regulation and therapeutic potential

Atherosclerosis, a chronic disease of arteries, results in high mortality worldwide as the leading cause of cardiovascular disease. The development of clinically relevant atherosclerosis involves the dysfunction of endothelial cells and vascular smooth muscle cells. A large amount of evidence indicates that noncoding RNAs, such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), are involved in various physiological and pathological processes. Recently, noncoding RNAs were identified as key regulators in the development of atherosclerosis, including the dysfunction of endothelial cells, and vascular smooth muscle cells and it is pertinent to understand the potential function of noncoding RNAs in atherosclerosis development. In this review, the latest available research relates to the regulatory role of noncoding RNAs in the progression of atherosclerosis and the therapeutic potential for atherosclerosis is summarized. This review aims to provide a comprehensive overview of the regulatory and interventional roles of ncRNAs in atherosclerosis and to inspire new insights for the prevention and treatment of this disease.

Deciphering the impact of circRNA-mediated autophagy on tumor therapeutic resistance: a novel perspective

Cancer therapeutic resistance remains a significant challenge in the pursuit of effective treatment strategies. Circular RNAs (circRNAs), a class of non-coding RNAs, have recently emerged as key regulators of various biological processes, including cancer progression and drug resistance. This review highlights the emerging role of circRNAs-mediated autophagy in cancer therapeutic resistance, a cellular process that plays a dual role in cancer by promoting both cell survival and death. Increasing evidence suggests that circRNAs can modulate autophagy pathways, thereby influencing the response of cancer cells to therapeutic agents. In this context, the intricate interplay between circRNAs, autophagy, and therapeutic resistance is explored. Various mechanisms are discussed through which circRNAs can impact autophagy, including direct interactions with autophagy-related genes, modulation of signaling pathways, and cross-talk with other non-coding RNAs. Furthermore, the review delves into specific examples of how circRNA-mediated autophagy regulation can contribute to resistance against chemotherapy and radiotherapy. Understanding these intricate molecular interactions provides valuable insights into potential strategies for overcoming therapeutic resistance in cancer. Exploiting circRNAs as therapeutic targets or utilizing them as diagnostic and predictive biomarkers opens new avenues for developing personalized treatment approaches. In summary, this review underscores the importance of circRNA-mediated autophagy in cancer therapeutic resistance and proposes future directions for research in this exciting and rapidly evolving field.

Helicobacter pylori upregulates circPGD and promotes development of gastric cancer

PURPOSE

Helicobacter pylori (H. pylori) has unique biochemical traits and pathogenic mechanisms, which make it a substantial cause of gastrointestinal cancers. Circular RNAs (circRNAs) have concurrently been identified as an important participating factor in the pathophysiology of several different cancers. However, the underlying processes and putative interactions between H. pylori and circRNAs have received very little attention. To address this issue, we explored the interaction between H. pylori and circRNAs to investigate how they might jointly contribute to the occurrence and development of gastric cancer.

METHODS

Changes in circPGD expression in H. pylori were detected using qRT-PCR. Cell proliferation and migration changes were assayed by colony formation, the CCK-8 assay and the transwell assay. Apoptosis was measured by flow cytometry. Western blot was conducted to detect changes in cell migration, apoptosis, proliferation and inflammation-associated proteins. QRT-PCR was used to measure changes in circPGD and inflammation-associated factors.

RESULTS

We found that H. pylori induced increased circPGD expression in infected human cells and facilitated gastric cancer progression in three ways by promoting cell proliferation and migration, enhancing the inflammatory response, and inhibiting apoptosis.

CONCLUSIONS

CircPGD appears to play a role in H. pylori-related gastric cancer and may thus be a viable, novel target for therapeutic intervention.

Emerging functions and significance of circCDYL in human disorders

Circular RNAs (circRNAs) are a group of non-coding transcripts in which a loop structure is shaped via a back splicing procedure. They have central roles in the regulation of gene expression. hsa_circ_0008285, alternatively named as circCDYL, is a circular RNA originated from the exon 4 of CDYL gene. It is produced by a back-splice incident and is mainly located in the cytoplasm. It has no internal ribosome entry site, open reading frame and intronic sequences. CircCDYL dysregulation has been reported in the malignant conditions including multiple myeloma, mantle cell lymphoma, breast cancer, non-small cell lung cancer, Wilms tumor, bladder cancer, colon cancer, and hepatocellular carcinoma. It also has an emerging role in the pathophysiology of non-malignant conditions including myocardial infarction, gestational diabetes mellitus, membranous nephropathy, and abdominal aortic aneurysm. In the current study, we summarize the emerging roles of circCDYL in malignant and non-malignant conditions.

Circular RNAs and inflammation: Epigenetic regulators with diagnostic role

Circular RNAs (circRNAs) are a group of transcripts generally known to be non-coding transcripts, but occasionally producing short peptides. Circ_Ttc3/miR-148a, circ_TLK1/miR-106a-5p, circ_VMA21/miR-9-3p, circ_0068,888/miR-21-5p, circ_VMA21/miR-199a-5p, circ_AFF2/miR-375, circ_0008360/miR-135b-5p and circ-FBXW7/miR-216a-3p are examples of circRNA/miRNA pairs that contribute in the pathogenesis of immune-related conditions. CircRNAs have been found to regulate function of immune system and participate in the pathophysiology of immune-related disorders. In the current study, we searched PubMed and Google Scholar databases until July 2022 with the key words "circRNA" OR "circular RNA" AND "inflammation". Then, we assessed the abstract of retrieved articles to include original articles that assessed contribution of circRNAs in the pathoetiology of inflammation and related disorders. Finally, we went through the main texts of the articles and tabulated the available information. Therefore, the current study summarizes the role of circRNAs in the pathoetiology of sepsis, atherosclerosis, rheumatoid arthritis and osteoarthritis, immune-related cardiovascular, pulmonary, gastrointestinal and nervous system disorders.

Triple Amplification Strategy of CHA-PER-DNAzyme for Ultrasensitive Detection of circRNA Associated with Hepatocellular Carcinoma

Biological and clinical studies have indicated that aberrant expression of circMTO1 served as a crucial biomarker for the diagnosis and prognosis of hepatocellular carcinoma (HCC) patients as well as a potential therapeutic target. However, the detection of circRNAs currently faces challenges such as homologous linear RNA interference and low-expression abundance of certain circRNAs. Therefore, we developed a triple amplification method based on catalytic hairpin assembly (CHA) activation by back-splice junction (BSJ), resulting in CHA products that triggered primer exchange reaction to generate DNAzyme. Subsequently, DNAzyme cleaved the fluorescent reporter chain, enabling ultrasensitive detection of hepatocellular carcinoma-associated circMTO1 through the output fluorescence signal. The catalytic hairpin opening sequence within CHA specifically targeted the BSJ sequence in circRNA, thereby avoiding false positive signals observed in circRNA assays due to the recognition of homologous linear RNA molecules. Moreover, this triple amplification method facilitated sensitive detection of circRNA and addressed the issue of low-abundance expression levels associated with circMTO1 in HCC samples. Notably, our newly designed assay for detecting circRNA exhibited a linear range from 1 fM to 100 nM with a detection limit of 0.265 fM. Furthermore, it demonstrated excellent and consistent performance even within complex systems. Our proposed method enabled the specific and sensitive detection of circMTO1 in various cancer cells and blood samples from HCC patients, providing an innovative approach for investigating the role of circRNA in tumorigenesis and development while promoting its clinical application.

circGFRA1: A circular RNA with important roles in human carcinogenesis

Circular RNAs (circRNAs) are a type of covalently closed RNA molecules, which are mainly formed by back splicing of a precursor mRNA upstream exon into a downstream exon. Abnormally expressed circRNAs can modulate gene transcription by indirectly interacting with microRNAs (miRNAs). According to the current studies, circGFRA1 has been suggested to be upregulated in various cancers. circGFRA1 (hsa_circ_005239) is a type of cancer-related circRNA, which is predicted to be originated from the GFRA1 on chromosome 10. circGFRA1 can act as a sponge for several miRNAs, including miR-34a, miR-1228, miR-361-5p, miR-149, miR-498, miR-188-3p, miR-3064-5p, miR-449a. Additionally, it can regulate signaling pathways such as TGF-β and PI3K/ AKT. circGFRA1 upregulation has been correlated with patients' poor overall survival in diverse cancers. In the present review, we have summarized the oncogenic effect of circGFRA1 in various cancers according to the adopted criteria from in vitro, in vivo, and clinical research. Moreover, functional enrichment analysis was performed on the circGFRA1 host gene and its protein interaction network to detect gene ontology and related pathways.

A spotlight on the interplay between Wnt/β-catenin signaling and circular RNAs in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the deadliest cancers due to multifocal development and distant metastasis resulting from late diagnosis. Consequently, new approaches to HCC diagnosis and treatment are required to reduce mortality rates. A large body of evidence suggests that non-coding RNAs (ncRNAs) are important in cancer initiation and progression. Cancer cells release many of these ncRNAs into the blood or urine, enabling their use as a diagnostic tool. Circular RNAs (CircRNAs) are as a members of the ncRNAs that regulate cancer cell expansion, migration, metastasis, and chemoresistance through different mechanisms such as the Wnt/β-catenin Signaling pathway. The Wnt/β-catenin pathway plays prominent roles in several biological processes including organogenesis, stem cell regeneration, and cell survival. Aberrant signaling of both pathways mentioned above could affect the progression and metastasis of many cancers, including HCC. Based on several studies investigated in the current review, circRNAs have an effect on HCC formation and progression by sponging miRNAs and RNA-binding proteins (RBPs) and regulating the Wnt/β-catenin signaling pathway. Therefore, circRNAs/miRNAs or RBPs/Wnt/β-catenin signaling pathway could be considered promising prognostic and therapeutic targets in HCC.

Circular RNA circSLC7A11 contributes to progression and stemness of laryngeal squamous cell carcinoma via sponging miR-877-5p from LASP1

Background

Laryngeal squamous cell carcinoma (LSCC) belongs to tumors of head and neck. Circular RNA circSLC7A11 functions as oncogenes in various tumors. However, the role of circSLC7A11 in LSCC remains largely unknown. Here, we aimed to clarify the circSLC7A11 function in LSCC.

Methods

Relevance between circSLC7A11 expressions and LSCC clinicopathological was checked using chi-square. Relevance between circSLC7A11 expressions and LSCC patients' survival time was validated using Kaplan-Meier analysis. CircSLC7A11 expressions in LSCC tissues and cells were determined using quantitative real-time PCR. CircSLC7A11 functions in LSCC were examined by Cell Counting Kit-8, EdU analysis, Western blot, flow cytometry, sphere formation assay, and Transwell analysis. Meanwhile, circSLC7A11 mechanism in LSCC was determined using dual-luciferase reporter analysis, RNA pull-down, RNA Immunoprecipitation.

Results

CircSLC7A11 was highly expressed in LSCC, and high circSLC7A11 expressions were interrelated to the TNM stage. Also, LSCC patients with high circSLC7A11 owned shorter overall survival. Functional studies revealed that circSLC7A11 knockdown reduced LSCC cell proliferation, migration, invasion, stemness characteristics, and enhanced cell apoptosis. Mechanistic study data corroborated that circSLC7A11 targeted miR-877-5p, miR-877-5p targeted LASP1. LASP1 was negatively interrelated to miR-877-5p and was positively interrelated to circSLC7A11 in LSCC tissues. Also, circSLC7A11 knockdown reduced the LASP1 levels, and miR-877-5p inhibitor co-transfection reversed this reduction. Rescue assays further demonstrated that circSLC7A11 accelerated LSCC through miR-877-5p/LASP1.

Conclusion

CircSLC7A11 exerted oncogenic functions in LSCC by miR-877-5p/LASP1, hinting that circSLC7A11 was a novel biomarker for LSCC.

Exosomal ERBB2IP contributes to tumor growth via elevating PSAT1 expression in non-small cell lung carcinoma

BACKGROUND

Both exosomes and circular RNAs (circRNAs) are involved in tumor growth. Hsa_circ_0001492 (circERBB2IP) has been reported to be overexpressed in plasma exosomes from patients with lung adenocarcinoma, but the biological role of exosomal circERBB2IP in non-small cell lung carcinoma (NSCLC) is indistinct.

METHODS

Exosomes isolated from serums and medium samples were validated by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting. Relative expression of circERBB2IP was detected by RT-qPCR. Loss-of-function was done to determine the effect of circERBB2IP on NSCLC cell proliferation and migration. Molecular mechanisms associated with circERBB2IP were predicted by bioinformatic analysis and validated by dual-luciferase reporter, RIP, and RNA pulldown assays. In vivo experiments were performed to identify the function of circERBB2IP in NSCLC.

RESULTS

We discovered that circERBB2IP expression was correlated with TNM grade, lymph node metastasis and tumor size of NSCLC patients. Upregulation of circERBB2IP was observed in exosomes derived from NSCLC patient's serum and circERBB2IP might be a potential diagnostic biomarker for NSCLC. CircERBB2IP was transmitted between carcinoma cells through exosomes. Knockdown of circERBB2IP lowered cell growth in mouse models and restrained NSCLC cell proliferation and migration. CircERBB2IP could mediate PSAT1 expression via sponging miR-5195-3p.

CONCLUSION

In conclusion, circERBB2IP may drive NSCLC growth by the miR-5195-3p/PSAT1 axis in NSCLC, shedding light on a diagnostic biomarker and therapeutic target for NSCLC.

Contribution of CRNDE lncRNA in the development of cancer and the underlying mechanisms

Colorectal Neoplasia Differentially Expressed (CRNDE) is an lncRNA with crucial roles in cancer development. It is located on chromosome 16 on the opposite strand to the adjacent IRX5 gene, implying the presence of a shared bidirectional promoter for these two genes. Expression of CRNDE has been assessed in a diverse array of hematological malignancies and solid tumors, representing its potential as a therapeutic target in these conditions. This lncRNA has a regulatory effect on activity of several pathways and axes that are involved in the regulation of cell apoptosis, immune responses and tumorigenesis. The current review is an updated review about the role of CRNDE in the development of cancers.

Investigation of the clinicopathological and prognostic role of circMTO1 in multiple cancers

OBJECTIVE

To observe the prognostic value of circular RNA mitochondrial tRNA translation optimization 1 (circMTO1) in human tumors.

METHODS

We searched multiple databases for related reports published before November 01, 2021. The OR/HR and 95% CI were extracted to explore the correlation between circMTO1 expression and clinicopathological features in various cancers. The stability of the results from meta-analysis was estimated via sensitivity analysis. We adopted Begg's funnel plots and Egger's test to appraise the potential bias of publication. Subgroup analysis for overall survival (OS) were also performed.

RESULTS

11 studies containing 1383 patients and 4 articles including 536 patients were enrolled. We found that low expression status of circMTO1 was significantly related to big tumor size (OR=2.11, 95% CI: 1.26-3.56, P<0.05), poor differentiation tumors (OR=2.09, 95% CI: 1.46-2.98, P<0.05), OS (HR=2.02, 95% CI: 1.63-2.50, P<0.05), disease-free survival (DFS) (HR=1.83, 95% CI: 1.27-2.56, P<0.05) of cancers. Subgroup analysis indicated that low expression status of circMTO1 was correlated with OS, regardless of analysis method, cut-off value, case number and NOS score.

CONCLUSIONS

The low expression of circMTO1 may predict big tumor size, poor differentiation and worse outcome of cancer, presenting that circMTO1 may be a useful biomarker for prognosis of tumors.

High Expression of Circular RNA-Mitochondrial tRNA Translation Optimization 1 Assists the Diagnosis of High-Risk Human Papillomavirus Infection in Cervical Cancer

OBJECTIVE

Persistence of high-risk human papillomavirus (HR-HPV) infection is a paramount determinant in cervical cancer (CC) development. Circular RNAs have the potential to be promising biomarkers for various cancers. This study explored circular RNA-mitochondrial tRNA translation optimization 1 (circMTO1) expression in the serum of CC patients and its clinical value in diagnosing CC and predicting HR-HPV infection.

MATERIALS AND METHODS

In total, 125 CC patients (including 78 cases with HR-HPV) were enrolled, with another 76 healthy people as controls. Serum circMTO1 and miR-199a expressions were detected by reverse transcription-quantitative polymerase chain reaction, and the diagnostic efficacy of circMTO1 for CC and HR-HPV infection was analyzed by the receiver operating characteristic curve. According to the median of serum circMTO1 expression, CC patients were assigned into circMTO1 low/high expression groups to analyze the correlation between circMTO1 and clinical parameters using the Fisher and χ 2 tests. Independent association of circMTO1 with HR-HPV infection in CC was evaluated via logistics multivariate regression analysis. Targeted relationship between miR-199a and circMTO1 was predicted by Starbase Web site and validated via dual-luciferase assay, with their correlation further assessed by Pearson analysis.

RESULTS

Serum circMTO1 was increased in CC patients and prominently elevated in HR-HPV-positive CC patients, with a level greater than 1.485 assisting CC diagnosis and a level greater than 2.480 assisting HR-HPV-positive diagnosis. The circMTO1 was interrelated to clinical stage, tumor differentiation, lymph node metastasis, invasion depth, and independently linked with HR-HPV infection in CC. Serum miR-199a was downregulated in HR-HPV-positive CC patients and inversely correlated with circMTO1.

CONCLUSIONS

Serum circMTO1 is upregulated in HR-HPV-positive CC patients and has a diagnostic value for HR-HPV infection in CC.

Long non-coding RNA NRAV enhances proliferation and invasion of hepatocellular carcinoma cells by modulating the Wnt/β-catenin signaling pathway

Many dysregulated lncRNAs have been reported to perform an integral function in hepatocellular carcinoma (HCC). However, the role of long non-coding RNA (lncRNA) NRAV in HCC has not been elucidated. To address this issue, we investigated the function of NRAV in HCC in this research. Through bioinformatics prediction and real-time quantitative polymerase chain reaction validation, we found that NRAV plays an upmodulating role in HCC cells and tissues, and patients with high NRAV expression showed a poor prognosis. Cell viability was examined by conducting a Cell Counting Kit-8 analysis. Subsequently, the proliferation capacity of the cells was analyzed utilizing cell colony formation assay, and transwell invasion experiments were conducted to identify the cell invasion ability. To determine the association between NRAV and miR-199a-3p, and CDGSH iron-sulfur domain-containing protein 2 (CISD2), we conducted a dual luciferase assay. The protein and gene expressions were estimated utilizing Western blot. Findings illustrated that the overexpression of NRAV enhanced the HCC cell viability, proliferation and invasion, whereas they were inhibited significantly by down expression of NRAV. The dual-luciferase assay showed that miR-199a-3p is not only a target for NRAV but also interacts with the 3' UTR of CISD2 in HCC cells. MiR-199a-3p/CISD2 axis performs a function in NRAV-mediated cell behavior regulation. NRAV may trigger the Wnt/β-catenin signaling via the modulation of the miR-199a-3p/CISD2 axis in HCC. The findings of this work can provide novel insights into clinical diagnosis and the treatment of HCC in the future.Abbreviations: HCC, hepatocellular carcinoma; LncRNA, long non-coding RNA; CISD2, CDGSH iron-sulfur domain-containing protein 2; CCK-8, Cell Counting Kit-8; cDNA, single-stranded complementary DNA; RT-qPCR, real-time quantitative polymerase chain reaction; BCA, bicinchoninic acid; ceRNA, competing endogenous RNAs.

CircRNA circ_0006156 inhibits the metastasis of prostate cancer by blocking the ubiquitination of S100A9

Circular RNAs (circRNAs) have been demonstrated to play vital roles in cancer development and progression. However, studies on the association between circRNAs and prostate cancer (PCa) are still lacking. CircRNA sequencing of two pairs of PCa tissues and adjacent normal tissues was conducted in the present study, and qRT-PCR was performed to verify the results. Functional experiments were performed to investigate cellular functions after specific changes. Mass spectrometry analysis after RNA pull-down experiments and Co-IP assays were further conducted. Downstream target proteins were predicted via online databases and detected in vitro by Western blot analysis and in vivo by immunohistochemistry. Hsa_circ_0006156 (subsequently named circ_0006156) expresses at low levels in both PCa tissues and cells, and it significantly inhibits the migration and invasion of PCa cells. Circ_0006156 binds to and blocks the ubiquitination of S100A9. Moreover, functional assays revealed that circ_0006156 represses the malignant progression of PCa by binding to S100A9. Finally, in vivo experiments showed that circ_0006156 suppresses PCa migration and invasion by increasing S100A9, revealing circ_0006156 as a potential novel effective target for PCa treatment.

CircMTO1 suppresses hepatocellular carcinoma progression via the miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling pathway and epithelial-to-mesenchymal transition

CircRNA mitochondrial tRNA translation optimization 1 (circMTO1) functions as a tumor suppressor usually and is related to the progression of many tumors, including hepatocellular carcinoma (HCC). CircMTO1 is downregulated in HCC as compared to adjacent nontumor tissue, which may suppress the HCC progression by certain signal pathways. However, the underlying signal pathway remains largely unknown. The interactions between circMTO1 and miR-541-5p were predicted through bioinformatics analysis and verified using pull-down and dual-luciferase reporter assays. CCK-8, transwell, and apoptosis assays were performed to determine the effect of miR-541-5p on HCC progression. Using bioinformatic analysis, dual-luciferase reporter assay, RT-qPCR, and western blot, ZIC1 was found to be the downstream target gene of miR-541-5p. The regulatory mechanisms of circMTO1, miR-541-5p, and ZIC1 were investigated using in vitro and in vivo rescue experiments. The results depicted that silencing circMTO1 or upregulating miR-541-5p expression facilitated HCC cell proliferation, migration, and invasion and inhibited apoptosis. CircMTO1 silencing upregulated the expression of downstream ZIC1 regulators of the Wnt/β-catenin pathway markers, β-catenin, cyclin D1, c-myc, and the mesenchymal markers N-cadherin, Vimentin, and MMP2, while the epithelial marker E-cadherin was downregulated. MiR-541-5p knockdown had the opposite effect and reversed the effect of circMTO1 silencing on the regulation of downstream ZIC1 regulators. Intratumoral injection of miR-541-5p inhibitor suppressed tumor growth and reversed the effect of circMTO1 silencing on the promotion of tumor growth in HCC. These findings indicated that circMTO1 suppressed HCC progression via the circMTO1/ miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling and epithelial-to-mesenchymal transition, making it a novel therapeutic target.