The Roles of circMTO1 in Cancer

CircWHSC1 (CircNSD2): A Novel Circular RNA in Multiple Cancers

Circular RNAs (circRNAs) are a type of non-coding RNA (ncRNA) that possesses a unique single-stranded circular structure. They are primarily formed through alternative splicing of pre-mRNA (messenger RNA). The primary biological function of circRNAs is to regulate gene expression at both the transcriptional and post-transcriptional levels. Recent studies have increasingly demonstrated a close association between the dysregulation of circRNAs and the progression of diverse cancers, where they can function as either tumor suppressors or oncogenes. circWHSC1 (circNSD2) is a circular ncRNA that originates from the first 2 exons of the Wolf-Hirschhorn syndrome candidate gene (WHSC1). As Chen 2019 discovery that circWHSC1 (circNSD2) functions as a sponge for miRNAs and promotes cancer, this circRNA has garnered significant interest among researchers. circWHSC1 (circNSD2) has been found to be up-regulated in various malignant tumors, including nasopharyngeal carcinoma, lung cancer, breast cancer, liver cancer, colorectal cancer, ovarian cancer, cervical cancer, and endometrial cancer. It exerts its effects on cancer by either inhibiting or promoting the expression of related genes through direct or indirect pathways, ultimately affecting cancer proliferation, invasion, and prognosis. This article provides a comprehensive review and discussion of the biological roles of circWHSC1 (circNSD2) and its target genes in various cancers, as well as the latest research progress on related molecular biological regulatory mechanisms. Furthermore, the potential significance of circWHSC1 (circNSD2) in future clinical applications and transformations is thoroughly analyzed and discussed.

Circular RNA circ_0058123 Targets the miR-939-5p/RAC1 Pathway to Promote the Development of Colorectal Cancer

Circular RNA (circRNA) can be used as a potential target for cancer treatment. However, the biological function and potential molecular mechanism of circ_0058123 in the development of colorectal cancer (CRC) are still unclear. The expression levels of circ_0058123, microRNA-939-5p (miR-939-5p) and Rac family small GTPase 1 (RAC1) were measured by quantitative real-time polymerase chain reaction or western blot assay. 5-Ethynyl-2'-deoxyuridine (EdU) incorporation assay, transwell assay, tube formation assay and flow cytometry apoptosis assay were conducted to assess CRC cell functions. In addition, protein expression was measured with western blot assay. Dual-luciferase reporter assays and RNA immunoprecipitation assay were conducted to confirm the relationships between miR-939-5p and circ_0058123, and miR-939-5p and RAC1. In vivo CRC tumor growth experiment also were carried out to determine circ_0058123-mediatede effects on tumor formation. Our data showed that circ_0058123 and RAC1 expression were increased, but miR-939-5p was decreased in both of CRC tissues and cell lines. Circ_0058123 depletion repressed CRC cell proliferation, migration, invasion and tube formation but promoted cell apoptosis. Down-regulation of circ_0058123 could significantly suppress the CRC progression, while the addition of miR-939-5p inhibitor could reverse this effect. Circ_0058123 directly targeted miR-939-5p, and RAC1 was a target of miR-939-5p. Furthermore, RAC1 overexpression could rescue the effect of miR-939-5p on CRC development. Lastly, silence of circ_0058123 inhibited CRC tumor growth in vivo. In conclusion, circ_0058123 could promote CRC progression through regulating the miR-939-5p/RAC1 axis and may be a valuable biomarker for early diagnosis and prognosis of CRC.

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.

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.

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.

Circular RNAs in Diabetic Nephropathy: Updates and Perspectives

Circular RNAs (circRNAs) are widespread endogenous transcripts lacking 5′-caps and 3′-polyadenylation tails. Their closed-loop structure confers exonuclease resistance and extreme stability. CircRNAs play essential roles in various diseases, including diabetes. Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease and is one of the most common complications of diabetes. CircRNAs are key in DN and therefore important for understanding DN pathophysiology and developing new therapeutic strategies. In the present review, we briefly introduce the characteristics and functions of circRNAs and summarize recent discoveries on how circRNAs participate in DN. Based on these advances, we suggest future perspectives for studying circRNAs in DN to improve DN treatment and management.

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.

A Concise Review on the Role of CircPVT1 in Tumorigenesis, Drug Sensitivity, and Cancer Prognosis

CircPVT1 (hsa_circ_0001821) is a cancer-related circular RNA (circRNA) that originated from a genomic locus on chromosome 8q24. This locus has been previously found to encode the oncogenic long non-coding RNA PVT1. Expression of this circRNA has been found to be upregulated in diverse neoplastic conditions. CircPVT1 acts as a sponge for miR-125a, miR-125b, miR-124-3p, miR-30a-5p, miR-205-5p, miR-423-5p, miR-526b, miR-137, miR-145-5p, miR-497, miR-30d/e, miR-455-5p, miR-29a-3p, miR-204-5p, miR-149, miR-106a-5p, miR-377, miR-3666, miR-203, and miR-199a-5p. Moreover, it can regulate the activities of PI3K/AKT, Wnt5a/Ror2, E2F2, and HIF-1α. Upregulation of circPVT1 has been correlated with decreased survival of patients with different cancer types. In the current review, we explain the oncogenic impact of circPVT1 in different tissues based on evidence from in vitro, in vivo, and clinical investigations.