Circular RNA hsa_circ_0000282 contributes to osteosarcoma cell proliferation by regulating miR-192/XIAP axis

Osteosarcoma in a ceRNET perspective

Osteosarcoma (OS) is the most prevalent and fatal type of bone tumor. It is characterized by great heterogeneity of genomic aberrations, mutated genes, and cell types contribution, making therapy and patients management particularly challenging. A unifying picture of molecular mechanisms underlying the disease could help to transform those challenges into opportunities.This review deeply explores the occurrence in OS of large-scale RNA regulatory networks, denominated "competing endogenous RNA network" (ceRNET), wherein different RNA biotypes, such as long non-coding RNAs, circular RNAs and mRNAs can functionally interact each other by competitively binding to shared microRNAs. Here, we discuss how the unbalancing of any network component can derail the entire circuit, driving OS onset and progression by impacting on cell proliferation, migration, invasion, tumor growth and metastasis, and even chemotherapeutic resistance, as distilled from many studies. Intriguingly, the aberrant expression of the networks components in OS cells can be triggered also by the surroundings, through cytokines and vesicles, with their bioactive cargo of proteins and non-coding RNAs, highlighting the relevance of tumor microenvironment. A comprehensive picture of RNA regulatory networks underlying OS could pave the way for the development of innovative RNA-targeted and RNA-based therapies and new diagnostic tools, also in the perspective of precision oncology.

Synergistic Immunoregulation: harnessing CircRNAs and PiRNAs to Amplify PD-1/PD-L1 Inhibition Therapy

The utilization of PD-1/PD-L1 inhibitors marks a significant advancement in cancer therapy. However, the efficacy of monotherapy is still disappointing in a substantial subset of patients, necessitating the exploration of combinational strategies. Emerging from the promising results of the KEYNOTE-942 trial, RNA-based therapies, particularly circRNAs and piRNAs, have distinguished themselves as innovative sensitizers to immune checkpoint inhibitors (ICIs). These non-coding RNAs, notable for their stability and specificity, were once underrecognized but are now known for their crucial roles in regulating PD-L1 expression and bolstering anti-cancer immunity. Our manuscript offers a comprehensive analysis of selected circRNAs and piRNAs, elucidating their immunomodulatory effects and mechanisms, thus underscoring their potential as ICIs enhancers. In conjunction with the recent Nobel Prize-awarded advancements in mRNA vaccine technology, our review highlights the transformative implications of these findings for cancer treatment. We also discuss the prospects of circRNAs and piRNAs in future therapeutic applications and research. This study pioneers the synergistic application of circRNAs and piRNAs as novel sensitizers to augment PD-1/PD-L1 inhibition therapy, demonstrating their unique roles in regulating PD-L1 expression and modulating immune responses. Our findings offer a groundbreaking approach for enhancing the efficacy of cancer immunotherapy, opening new avenues for treatment strategies. This abstract aims to encapsulate the essence of our research and the burgeoning role of these non-coding RNAs in enhancing PD-1/PD-L1 inhibition therapy, encouraging further investigation into this promising field.

Alteration in the Expression of Circular Rnas and its association with the Development and Progression of Osteosarcoma, an Integrative Review with High Sensitivity Research

BACKGROUND

Osteosarcoma is the most common primary malignant bone tumor, mainly affecting children, young adults, and the elderly. It is an aggressive cancer with a poor prognosis, exhibiting low survival rates even with standard treatment. Recently, circular RNA molecules capable of influencing gene expression through various functions, with their main role being acting as microRNA sponges and reducing their intracellular expression, have been identified. Recent studies have linked circular RNAs to osteosarcoma development and progression. Therefore, the present study aimed to investigate the alteration in circular RNA expression during osteosarcoma development and progression.

METHODS

An integrative literature review was conducted from September 10th to November 12th, 2021, using the following databases: PubMed/MEDLINE, SCOPUS, Web of Science, OVID, and EMBASE. 129 full articles were included in the review. The obtained data were organized using a standardized data collection instrument, which included the following information: altered expression profile of circular RNAs, associated cancer hallmarks, clinical-pathological relationships of circular RNAs, and perspectives on the studied circular RNAs.

RESULTS

A total of 94 distinct circular RNAs were identified, predominantly showing an increased expression pattern. Approximately 91% of the studies that aimed to identify the mechanisms of action of circular RNAs highlighted the function of circular RNAs as microRNA sponges. The most associated cancer hallmarks with the identified circular RNAs were proliferative signaling induction, invasion and metastasis, and resistance to cell death. The altered expression of these circular RNAs generally correlated with a worse prognosis for patients, as evidenced by clinical features such as shorter survival, advanced Enneking and/or TNM stage, higher incidence of metastasis, larger tumor size, and increased chemoresistance.

CONSLUSION

These findings indicate the significance of circular RNA molecules in osteosarcoma carcinogenesis, suggesting their potential as new prognostic and/or diagnostic biomarkers, as well as alternative therapeutic targets in the fight against osteosarcoma.

CircMETTL15 induces TMTC3 production by absorbing miR-944 to promote hepatocellular carcinoma cell malignancy

Previous data have suggested the involvement of circular RNA (circRNA) in hepatocellular carcinoma (HCC) progression. Up to now, the effect of circMETTL15 on HCC development remains unknown. This study aims to analyze the function of circMETTL15 in HCC development and the underlying mechanism. RNA expression of circMETTL15, miR-944, and transmembrane O-mannosyltransferase targeting cadherins 3 (TMTC3) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was evaluated by Western blot analysis assay or immunohistochemistry assay. Cell proliferation was investigated by cell counting kit-8 assay, 5-Ethynyl-29-deoxyuridine (EdU) assay, and cell colony formation assay. Cell migration and invasion were assessed by wound-healing assay and transwell assay, respectively. Angiogenic capacity was analyzed by tube formation assay. Dual-luciferase reporter assay and RNA immunoprecipitation assay were conducted to identify the interplay between miR-944 and circMETTL15 or TMTC3. Xenograft mouse model assay was conducted to reveal the effect of circMETTL15 on tumor formation in vivo. CircMETTL15 and TMTC3 expression were significantly upregulated, while miR-944 expression was downregulated in HCC tissues and cells. CircMETTL15 knockdown led to decreased cell proliferation, migration, invasion, and tube formation. Besides, the inhibitors of miR-944, a target miRNA of circMETTL15, partially restored circMETTL15 silencing-mediated effects on the proliferation, migration, invasion, and tube formation of HCC cells. MiR-944 overexpression also inhibited HCC cell malignancy by targeting TMTC3. Furthermore, circMETTL15 absence inhibited tumor formation by regulating miR-944 and TMTC3 in vivo. In conclusion, circMETTL15 induced HCC development through the miR-944/TMTC3 pathway, raising the potential of circMETTL15 as a target for HCC therapy.

Tissue-Specific Expression of Circ_015343 and Its Inhibitory Effect on Mammary Epithelial Cells in Sheep

Circular RNAs (circRNAs) are a kind of non-coding RNA that have an important molecular function in mammary gland development and lactation of mammals. In our previous study, circ_015343 was found to be highly expressed in the ovine mammary gland tissue at the peak-lactation period by using RNA sequencing (RNA-seq). In the present study, the authenticity of circ_015343 was confirmed by using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and Sanger sequencing. The circ_015343 was derived from the complete 10 exons of aminoadipic semialdehyde synthase (AASS), ranging from exon 2 to exon 11 and mainly located in cytoplasm of ovine mammary epithelial cells. The circRNA was found to be expressed in eight ovine tissues, with the highest expression level in the mammary gland and the least expression in Longissimus dorsi muscle. The circ_015343 had a lower level of expression in a sheep breed with higher milk yield and milk fat content. The disturbed circ_015343 increased the viability and proliferation of the ovine mammary epithelial cells. The inhibition of circ_015343 also increased the expression levels of three milk fat synthesis marker genes: acetyl-coenzyme A carboxylase alpha (ACACA), fatty acid-binding protein 4 (FABP4), and sterol regulatory element-binding protein 1 (SREBP1), as well as three proliferation-related genes: cyclin dependent kinase 2 (CDK2), cyclin dependent kinase 4 (CDK4) and proliferating cell nuclear antigen (PCNA), but decreased the expression level of its parent gene AASS. A circRNA-miRNA-mRNA interaction network showed that circ_015343 would bind some microRNAs (miRNAs) to regulate the expression of functional genes related to the development of mammary gland and lactation. This study contributes to a better understanding of the roles of circ_015343 in the mammary gland of sheep.

CircDOCK1 promotes the tumorigenesis and cisplatin resistance of osteogenic sarcoma via the miR-339-3p/IGF1R axis

Background

Circular RNAs (circRNAs), a class of noncoding RNAs (ncRNAs), may modulate gene expression by binding to miRNAs. Additionally, recent studies show that circRNAs participate in some pathological processes. However, there is a large gap in the knowledge about circDOCK1 expression and its biological functions in osteogenic sarcoma (OS).

Methods

Differentially expressed circRNAs in OS cell lines and tissues were identified by circRNA microarray analysis and quantitative real-time PCR (qRT–PCR). To explore the actions of circDOCK1 in vivo and in vitro, circDOCK1 was knocked down or overexpressed. To assess the binding and regulatory associations among miR-339-3p, circDOCK1 and IGF1R, we performed rescue experiments, RNA immunoprecipitation (RIP), RNA pulldown assays and dual-luciferase assays. Moreover, we performed apoptosis assays to reveal the regulatory effects of the circDOCK1/miR-339-3p/IGF1R axis on cisplatin sensitivity.

Results

CircDOCK1 expression remained stable in the cytoplasm and was higher in OS tissues and cells than in the corresponding controls. Overexpression of circDOCK1 increased oncogenicity in vivo and malignant transformation in vitro. In the U2OS and MG63 cell lines, circDOCK1 modulated tumor progression by regulating IGF1R through sponging of miR-339-3p. Additionally, in the U2OS/DDP and MG63/DDP cell lines, cisplatin sensitivity was regulated by circDOCK1 via the miR-339-3p/IGF1R axis.

Conclusions

CircDOCK1 can promote progression and regulate cisplatin sensitivity in OS via the miR-339-3p/IGF1R axis. Thus, the circDOCK1/miR-339-3p/IGF1R axis may be a key mechanism and therapeutic target in OS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01453-0.

The Circ_0001367/miR-545-3p/LUZP1 Axis Regulates Cell Proliferation, Migration and Invasion in Glioma Cells

Glioma is the most common primary intracranial malignant tumour in adults. It has a high incidence and poses a serious threat to human health. Circular RNA is a hotspot of cancer research. In this study, we aimed to explore the role of circ_0001367 in gliomagenesis and the underlying mechanism. First, qRT-PCR was conducted, which showed that circ_0001367 level was downregulated in glioma tissues and cells. Next, gain-of-function and loss-of-function assays were performed, which indicated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells. Subsequent bioinformatics analysis, dual-luciferase reporter assays, RNA immunoprecipitation assays and cell function assays demonstrated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells by absorbing miR-545-3p and thereby regulating the expression of leucine zipper protein (LUZP1). Finally, an in vivo experiment was conducted, which demonstrated that circ_0001367 inhibited glioma growth in vivo by modulating miR-545-3p and LUZP1. Taken together, the results of this study demonstrate that the circ_0001367/miR-545-3p/LUZP1 axis may be a novel target for glioma therapy.

Circ-METTL15 contributes to the proliferation, metastasis, immune escape and restrains apoptosis in lung cancer by regulating miR-1299/PDL1 axis

BACKGROUND

Circular RNAs (circRNAs) are important regulators in the pathogenesis of lung cancer. The study aims to explore the function and mechanism of circRNA methyltransferase-like 15 (circ-METTL15) in lung cancer development.

METHODS

The expression of circ-METTL15, miR-1299 and programmed death-ligand 1 (PDL1) were investigated by qRT-PCR assay. Cell viability, colony formation, cell proliferation and invasion were determined by MTT, colony formation, EDU incorporation and transwell assays, respectively. Cell apoptosis was attested by flow cytometry and TUNEL assays. Interferon-γ (IFN-γ) and Tumour Necrosis Factor-α (TNF-α) production were tested by enzyme-linked immunosorbent assay (ELISA), and the survival rate of cancer cells was assessed by cytotoxicity analysis. The protein expression was examined by western blot or immunohistochemistry (IHC) assay. The interaction between miR-1299 and circ-METTL15 or PDL1 was confirmed via dual-luciferase reporter assay. Xenograft models were established in mice to explore the role of circ-METTL15 in tumour growth in vivo.

RESULTS

Circ-METTL15 was upregulated in lung cancer tissues and cells. Circ-METTL15 silencing suppressed cell proliferation, colony formation, invasion, immune escape and promoted cell apoptosis in lung cancer cells. Circ-METTL15 was a sponge of miR-1299, and it could exert regulatory function in lung cancer via miR-1299. Furthermore, PDL1 was a functional target of miR-1299, and miR-1299 inhibited lung cancer cell development via decreasing PDL1 expression. Moreover, circ-METTL15 controlled PDL1 expression by acting as a sponge of miR-1299. Besides, circ-METTL15 downregulation blocked lung cancer tumour growth in vivo by regulating the miR-1299/PDL1 axis.

CONCLUSION

Circ-METTL15 promoted lung cancer malignant progression at least partly through modulating PDL1 by sponging miR-1299.

Dissecting the Role of Circular RNAs in Sarcomas with Emphasis on Osteosarcomas

Circular RNAs (circRNAs) are single-stranded RNAs generated from exons back-splicing from a single pre-mRNA, forming covalently closed loop structures which lack 5'-3'-polarity or polyadenylated tail. Ongoing research depicts that circRNAs play a pivotal role in tumorigenesis, tumor progression, metastatic potential and chemoresistance by regulating transcription, microRNA (miRNA) sponging, RNA-binding protein interactions, alternative splicing and to a lesser degree, protein coding. Sarcomas are rare malignant tumors stemming from mesenchymal cells. Due to their clinically insidious onset, they often present at advanced stage and their treatment may require aggressive chemotherapeutic or surgical options. This review is mainly focused on the regulatory functions of circRNAs on osteosarcoma progression and their potential role as biomarkers, an area which has prompted lately extensive research. The attributed oncogenic role of circRNAs on other mesenchymal tumors such as Kaposi Sarcoma (KS), Rhabdomyosarcoma (RMS) or Gastrointestinal Stromal Tumors (GISTs) is also described. The involvement of circRNAs on sarcoma oncogenesis and relevant emerging diagnostic, prognostic and therapeutic applications are expected to gain more research interest in the future.

The emerging role of circular RNAs in common solid malignant tumors in children

Malignant tumors are one of the fatal diseases that threaten children’s physical and mental health and affect their development. Research has shown that the occurrence and development of malignant tumors are associated with the abnormal expression and regulation of genes. Circular RNAs (circRNAs) are noncoding RNAs that have a closed circular structure, with a relatively stable expression, and do not undergo exonuclease-mediated degradation readily. Recent studies have shown that circRNA plays an important role in the occurrence, metastasis, and invasion of solid malignant tumors (SMTs) in children. Thus, circRNA is being considered as a breakthrough in the treatment of SMTs in children. In this review, we describe the functions and mechanisms of circRNAs involved in SMTs in children oncogenesis, and summarize the roles of circRNAs in regulating cell proliferation, cell apoptotic death, the cell cycle, cell migrative and invasive ability, epithelial-mesenchymal transition (EMT), cancer stem cells and drug resistance in SMTs in children. In addition, we also discuss the role of circRNAs in the early diagnosis, pathological grading, targeted therapy, and prognosis evaluation of common SMTs in children. CircRNAs are likely to provide a novel direction in therapy in SMTs of children.

Diagnostic and Prognostic Role of miR-192 in Different Cancers: A Systematic Review and Meta-Analysis

Introduction

It has been shown that miR-192 is abnormally expressed in a variety of cancer types and participates in different kinds of signaling pathways. The role of miR-192 in the diagnosis and prognosis of cancer has not been verified. This article is aimed at exploring the diagnostic and prognostic value of miR-192 through a systematic review and meta-analysis.

Methods

A systematic search was performed through PubMed, Embase, Web of Science, and Cochrane Library databases up to June 16, 2020. A total of 16 studies were enrolled in the meta-analyses, of which 11 articles were used for diagnostic meta-analysis and 5 articles were used for prognostic meta-analysis. The values of sensitivity and specificity using miR-192 expression as a diagnostic tool were pooled in the diagnostic meta-analysis. The hazard ratios (HRs) of overall survival (OS) with 95 confidence intervals (CIs) were extracted from the studies, and pooled HRs were evaluated in the prognostic meta-analysis. Eleven studies including 667 cancer patients and 514 controls met the eligibility criteria for the diagnostic meta-analysis. Five studies including 166 patients with high miR-192 expression and 236 patients with low miR-192 expression met the eligibility criteria for the prognostic meta-analysis.

Results

The overall diagnostic accuracy was as follows: sensitivity 0.79 (95%CI = 0.75-0.82), specificity 0.74 (95%CI = 0.64-0.82), positive likelihood ratio 3.03 (95%CI = 2.11-4.34), negative likelihood ratio 0.29 (95%CI = 0.23-0.37), diagnostic odds ratio 10.50 (95%CI = 5.89-18.73), and area under the curve ratio (AUC) 0.82 (95%CI = 0.78-0.85). The overall prognostic analysis showed that high expression of miR-192 in patients was associated with positive survival (HR = 0.62, 95%CI : 0.41-0.93, p = 0.020).

Conclusion

Our results revealed that miR-192 was a potential biomarker with good sensitivity and specificity in cancers. Moreover, highly expressed miR-192 predicted a good prognosis for patients.