Silencing of circ_0009910 inhibits acute myeloid leukemia cell growth through increasing miR-20a-5p

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.

Circ_0035381 contributes to the progression of acute myeloid leukemia via regulating miR-186-5p/CDCA3 pathway

BACKGROUND

Circular RNAs (circRNAs) are involved in acute myeloid leukemia (AML) and may be useful for AML therapy. Herein, the project aimed to explore the functions and mechanisms of circ_0035381 in AML.

RESEARCH DESIGN AND METHODS

Circ_0035381, microRNA-186-5p (miR-186-5p), and cell division cycle associated 3 (CDCA3) expression were determined using quantitative real-time polymerase chain reaction (qRT-PCR) assay. Western blot assay was used to measure protein levels. 5'-ethynyl-2'-deoxyuridine (EdU) and flow cytometry were adopted to measure cell proliferation and apoptosis. Glucose consumption and lactate uptake were examined with commercial kits. The relationships between miR-186-5p and circ_0035381 or CDCA3 were validated using dual-luciferase reporter and RNA pull-down assays.

RESULTS

Circ_0035381 was increased in the AML subject and AML cell line. Circ_0035381 deficiency hindered the proliferation and glycolysis level and promoted apoptosis in the AML cell line. Circ_0035381 sponged miR-186-5p and miR-186-5p inhibition reversed the effect of circ_0035381 knockdown on AML cell progression. CDCA3 was the target gene of miR-186-5p. CDCA3 overexpression reversed circ_0035381 knockdown-mediated AML cell proliferation and glycolysis inhibition and apoptosis promotion.

CONCLUSIONS

Circ_0035381 promoted AML progression by elevating CDCA3 through sponging miR-186-5p, providing some clues for the diagnosis and treatment of AML.

Role of MicroRNAs in Acute Myeloid Leukemia

MicroRNA (miRNA), a significant class of regulatory non-coding RNA (ncRNA), can regulate the expression of numerous protein-coding messenger RNAs (mRNAs). miRNA plays an important part in shaping the human transcriptome. So far, in the human genome, about 2500 miRNAs have been found. Acute myeloid leukemia (AML) belongs to a malignant clonal disorder of hematopoietic stem cells and is characterized by the uncontrolled clonal proliferation of abnormal progenitor cells in the bone marrow and blood. For the past several years, significant scientific attention has been attracted to the role of miRNAs in AML, since alterations in the expression levels of miRNAs may contribute to AML development. This review describes the main functions of non-coding RNA classes and presents miRNA biogenesis. This study aims to review recent reports about altered microRNA expression and their influence on AML cell survival, cell cycle, and apoptotic potential. Additionally, it summarizes the correlations between miRNAs and their target mRNAs in AML and outlines the role of particular miRNAs in AML subtypes according to ELN recommendations.

Prognostic value of circular RNAs expression and their correlation with clinicopathological features in acute myeloid leukemia: a systematic review and meta-analysis

Acute myeloid leukemia (AML) prognosis is affected by unique factors to each individual and studies have indicated that dysregulated expression of circRNAs may serve as prognostic biomarkers for AML. Therefore, we conducted this study to assess the prognostic value of circRNAs expression and it's correlation with clinicopathological features. Comprehensive search was conducted in WOS, Scopus, PubMed, Google Scholar, ProQuest, and grey literature. The certainty of evidence was assessed using the modified GRADE approach for prognostic and clinicopathological meta-analysis. The hazard ratio (HR) was employed to assess the prognostic value of dysregulated expression of circRNAs in patient survival, while the risk ratio (RR) was utilized to analyze the correlation between circRNAs and clinicopathological features. Our results demonstrated that dysregulation of circRNAs expression was associated with poor prognosis related to overall survival (OS) indicator (HR:2.05; 95%CI: 1.75-2.40) and also related to non-OS indicators such as (EFS, LFS, RFS, and DFS) (HR:2.09, 95%CI: 1.47-2.97). Priori and post-hoc subgroup analysis was conducted to describe variables that potentially affected heterogeneity and effect size. We also evaluated the association between dysregulated expression of circRNAs and 19 clinicopathological parameters. Our results show that there is significant relationship between the dysregulated expression of circRNAs and the mentioned parameters: type M6 vs. other types (RR:1.51, 95% CI:1.12-2.03), FLT3-ITD mutation (RR:1.17, 95%CI: 1.00-1.36), and risk status (RR:1.35, 95% CI: 1.13-1.60). This systematic review and meta-analysis suggest that the investigation of circRNAs expression changes can serve as valuable biomarkers for the assessment of prognosis in AML patients.

Role of circRNAs in regulating cell death in cancer: a comprehensive review

Despite multiple diagnostic and therapeutic advances, including surgery, radiation therapy, and chemotherapy, cancer preserved its spot as a global health concern. Prompt cancer diagnosis, treatment, and prognosis depend on the discovery of new biomarkers and therapeutic strategies. Circular RNAs (circRNAs) are considered as a stable, conserved, abundant, and varied group of RNA molecules that perform multiple roles such as gene regulation. There is evidence that circRNAs interact with RNA-binding proteins, especially capturing miRNAs. An extensive amount of research has presented the substantial contribution of circRNAs in various types of cancer. To fully understand the linkage between circRNAs and cancer growth as a consequence of various cell death processes, including autophagy, ferroptosis, and apoptosis, more research is necessary. The expression of circRNAs could be controlled to limit the occurrence and growth of cancer, providing a more encouraging method of cancer treatment. Consequently, it is critical to understand how circRNAs affect various forms of cancer cell death and evaluate whether circRNAs could be used as targets to induce tumor death and increase the efficacy of chemotherapy. The current study aims to review and comprehend the effects that circular RNAs exert on cell apoptosis, autophagy, and ferroptosis in cancer to investigate potential cancer treatment targets.

Hsa_circ_0009910 knockdown in HeLa cells increases miR‑198 expression levels and decreases c‑Met expression levels and cell viability

Cervical cancer (CC) is considered a public health problem. Circular RNAs (circRNAs) serve important roles in different types of cancer, including CC. However, the mechanisms used by circRNAs to facilitate CC progression are currently unclear. The present study analyzed the effects of hsa_circ_0009910 knockdown on microRNA (miRNA/miR)-198 and mesenchymal-epithelial transition factor (c-Met) expression levels and its impact on apoptosis and the viability of HeLa cells. Differentially expressed circRNAs in CC were identified using analysis of circRNA microarray data. Bioinformatics analysis was performed to predict circRNA-microRNA (miRNA) and miRNA-mRNA interactions. The knockdown of hsa_circ_0009910 in HeLa cells was performed using small interfering RNA and the expression levels of hsa_circ_0009910, miR-198 and c-Met were assessed using reverse transcription-quantitative PCR. The viability and apoptosis of HeLa cells were evaluated using MTT, neutral red uptake and ApoLive-Glo™ multiplex assays. Hsa_circ_0009910 was significantly upregulated in HeLa cells and the knockdown of hsa_circ_0009910 increased miRNA-198 expression levels, reduced c-Met expression levels and decreased cellular viability, but not apoptosis, in HeLa cells. Overall, these results indicated that hsa_circ_0009910 could act as a molecular sponge of miRNA-198 and contribute to the upregulation of c-Met expression levels. The hsa_circ_0009910/miRNA-198/c-Met interaction network affects the viability, but not apoptosis, of HeLa cells. Based on this mechanism, the present study suggests that hsa_circ_0009910 may be a promising biomarker for CC.

ALKBH5 promotes T-cell acute lymphoblastic leukemia growth via m6A-guided epigenetic inhibition of miR-20a-5p

This study investigates the role of ALKBH5-mediated m6A demethylation in T-cell acute lymphoblastic leukemia (T-ALL). T-ALL cell lines (HPB-ALL, MOLT4, Jurkat, CCRF-CEM) and human T cells were analyzed. CCRF-CEM and Jurkat cells were transfected with si-ALKBH5, miR-20a-5p-inhibitor, and pcDNA3.1-DDX5. The expression levels of ALKBH5, miR-20a-5p, and DDX5 in these cells were determined using qRT-PCR and Western blotting. Cell viability, proliferation, colony formation, and apoptosis were assessed using CCK-8, EdU staining, colony formation assay, and flow cytometry. mRNA m6A levels were quantified with an m6A RNA methylation detection reagent, and RNA immunoprecipitation was employed to measure the enrichment of DGCR8 and m6A on the primary transcript pri-miR-20a of miR-20a-5p. Dual-luciferase assay confirmed the binding relationship between miR-20a-5p and DDX5. Results showed that ALKBH5 and DDX5 were upregulated in T-ALL tissues and cells, whereas miR-20a-5p was downregulated. Silencing ALKBH5 inhibited T-ALL cell viability, colony formation, and proliferation, while promoting apoptosis. These effects were reversed by miR-20a-5p inhibition or DDX5 overexpression. ALKBH5 reduced the relative m6A level in T-ALL cells and decreased miR-20a-5p expression by reducing DGCR8 binding to pri-miR-20a-5p. miR-20a-5p suppressed DDX5 transcription. In conclusion, ALKBH5-mediated m6A demethylation decreases DGCR8 binding to pri-miR-20a, thereby repressing miR-20a-5p expression and enhancing DDX5 expression, ultimately inhibiting T-ALL cell apoptosis and promoting proliferation.

The increase in the expression of circRNAs may contributes to a poor prognosis in acute myeloid leukemia: A systematic review and meta-analysis

OBJECTIVE

The primary methods for defining the prognostic risk of AML patients are cytogenetic and molecular analysis at the time of diagnosis. However, the prognosis of intermediate-risk patients is still not well assessed for biomarkers. The main objective of this meta-analysis is to evaluate the relationship between circRNAs and AML prognosis, to provide a theoretical basis for finding effective prognostic indicators in intermediate-risk patients, and to provide an important scientific basis for the development or revision of WHO practice guidelines and ELN risk classification, and to highlight the importance of continuing to focus on and evaluate the prognostic impact of circRNAs on AML in future studies.

METHODS

We performed a comprehensive literature search across PubMed, the Cochrane Library, and Web of Science databases for studies published up to September 15, 2024. Articles were selected based on inclusion criteria. The Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of studies. The outcome measure of overall survival (OS) was used, and hazard ratios (HR) and 95 % confidence intervals (CI) were pooled to estimate the relationship between circRNA expression and prognosis in AML using STATA 17.0 software.

RESULTS

A total of 13 studies involving 1401 AML patients were included. The studies showed a significantly increased hazard ratio (HR) of upregulated CircRNA expression for OS (HR=1.87, 95 % CI=1.51-2.32, P < 0.001). The results of subgroups analysis showed a significant increase in the hazard ratio (HR) for upregulation of CircRNA expression in EFS and circ_0012152（HR= 1.66, 95 % CI= 1.19-2.32, P < 0.005 and HR= 2.26,95 % CI= 1.27-4.00, P < 0.005), respectively. No significant heterogeneity or publication bias was detected.

CONCLUSION

Upregulated circRNA expression is significantly associated with poor prognosis in AML patients and may serve as a prognostic marker for AML.

Immune checkpoints and ncRNAs: pioneering immunotherapy approaches for hematological malignancies

Hematological malignancies are typically treated with chemotherapy and radiotherapy as the first-line conventional therapies. However, non-coding RNAs (ncRNAs) are a rapidly expanding field of study in cancer biology that influences the growth, differentiation, and proliferation of tumors by targeting immunological checkpoints. This study reviews the results of studies (from 2012 to 2024) that consider the immune checkpoints and ncRNAs in relation to hematological malignancies receiving immunotherapy. This article provides a summary of the latest advancements in immunotherapy for treating hematological malignancies, focusing on the role of immune checkpoints and ncRNAs in the immune response and their capacity for innovative strategies. The paper also discusses the function of immune checkpoints in maintaining immune homeostasis and how their dysregulation can contribute to developing leukemia and lymphoma. Finally, this research concludes with a discussion on the obstacles and future directions in this rapidly evolving field, emphasizing the need for continued research to fully harness the capacity of immune checkpoints and ncRNAs in immunotherapy for hematological malignancies.

Circular RNA as Diagnostic and Prognostic Biomarkers in Hematological Malignancies:Systematic Review

Objectives: While various serum and tissue biomarkers have been explored for tumor diagnosis, the sensitivity and specificity have not yield optimal results. Circular RNAs (circRNAs) are more stable, conserved, and tissue-specific than linear RNA. Recent reports indicate that circRNAs could serve as potential biomarkers in the diagnosis or/and prognosis of tumors. In this study, we systematically examined the relationship between circRNA expression and diagnostic and prognostic outcomes in patients with hematological tumors. Methods: We searched several databases, including Google Scholar, MEDLINE, Scopus, PubMed, Embase, ScienceDirect, Ovid-Medline, Chinese National Knowledge Infrastructure, WanFang and SinoMed, with a cutoff date of June 12, 2024. The study protocol was PROSPERO (CRD42020188627). Result: A total of 73 studies were included in our review, comprising 39 diagnostic studies and 65 prognostic studies. Clinical parameters were assessed based on pooled adds ratios and 95% confidence intervals (CIs). Overall survival (OS) was evaluated using hazard ratios (HRs) and 95% CIs. The pooled area under the curve was 0.86, indicating the potential to identify hematological tumor patients, with sensitivity and specificity of 79% each. The diagnostic score for circRNAs related to hematological malignancies was 2.12. Notably, different hematological malignancies subgroups displayed varying prognoses. Specifically, lymphoid leukemia circRNA showed a negative impacct on prognosis (HR = 1.25, 95% CI: 1.10-1.43, P < 0.001). Conclusion: Our findings provide compelling evidence that circRNA may be serve as a promising alternative for the diagnosis and prognosis of hematological tumors.

Circ_0058058 Knockdown Inhibits Acute Myeloid Leukemia Progression by Sponging miR-4319 to Regulate EIF5A2 Expression

Background: Acute myeloid leukemia (AML) is the most common acute leukemia in adults. Circular RNAs (circRNAs) participate in the deterioration of many hominine cancers, including AML. In this study, the authors investigated the role and potential mechanism of circ_0058058 in AML progression. Methods: The expression of circ_0058058, microRNA-4319 (miR-4319), and eukaryotic initiation factor 5A2 (EIF5A2) was determined by quantitative real-time polymerase chain reaction. Cell proliferation, apoptosis, migration, and invasion were evaluated by cell counting kit-8 (CCK-8), cell colony formation, flow cytometry, and transwell assay, respectively. Levels of the relative proteins were detected by Western blot. The connection among circ_0058058, miR-4319, and EIF5A2 was verified by dual-luciferase reporter assay. Results: Circ_0058058 and EIF5A2 were enhanced, whereas miR-4319 was declined in AML. Circ_0058058 knockdown inhibited cell proliferation, migration, and invasion, and facilitated cell apoptosis by targeting miR-4319 in AML cells. Moreover, as a target of miR-4319, EIF5A2 overexpression overturned the inhibitory effects of miR-4319 upregulation on AML progression. Besides, circ_0058058 sponged miR-4319 to upregulate EIF5A2 expression in AML cells. Conclusion: Circ_0058058 knockdown inhibited cell proliferation, migration, and invasion, but accelerated cell apoptosis by reducing EIF5A2 expression by targeting miR-4319, suggesting that circ_0058058 could be a therapeutic target for the treatment of AML.

CircRNA: a rising star in leukemia

Non-coding RNA are a class of RNA that lack the potential to encode proteins. CircRNAs, generated by a post-splicing mechanism, are a newly discovered type of non-coding RNA with multi-functional covalent loop structures. CircRNAs may play an important role in the occurrence and progression of tumors. Research has shown that circRNAs are aberrantly expressed in various types of human cancers, including leukemia. In this review, we summarize the expression and function of circRNAs and their impact on different types of leukemia. We also illustrate the function of circRNAs on immune modulation and chemoresistance in leukemia and their impact on its diagnosis and prognosis. Herein, we provide an understanding of recent advances in research that highlight the importance of circRNAs in proliferation, apoptosis, migration, and autophagy in different types of leukemia. Furthermore, circRNAs make an indispensable difference in the modulation of the immunity and chemoresistance of leukemia. Increasing evidence suggests that circRNAs may play a vital role in the diagnostic and prognostic markers of leukemia because of their prominent properties. More detailed preclinical studies on circRNAs are needed to explore effective ways in which they can serve as biomarkers for the diagnosis and prognosis of leukemia in vivo.

The non-coding competing endogenous RNAs in acute myeloid leukemia: biological and clinical implications

Acute myeloid leukemia (AML) is a hematologic carcinoma that has seen a considerable improvement in patient prognosis because of genetic diagnostics and molecularly-targeted therapies. Nevertheless, recurrence and drug resistance remain significant obstacles to leukemia treatment. It is critical to investigate the underlying molecular mechanisms and find solutions. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), circular RNAs, long non-coding RNAs, and pseudogenes, have been found to be crucial components in driving cancer. The competing endogenous RNA (ceRNA) mechanism has expanded the complexity of miRNA-mediated gene regulation. A great deal of literature has shown that ncRNAs are essential to the biological functions of the ceRNA network (ceRNET). NcRNAs can compete for the same miRNA response elements to influence miRNA-target RNA interactions. Recent evidence suggests that ceRNA might be a potential biomarker and therapeutic strategy. So far, however, there have been no comprehensive studies on ceRNET about AML. What is not yet clear is the clinical application of ceRNA in AML. This study attempts to summarize the development of research on the related ceRNAs in AML and the roles of ncRNAs in ceRNET. We also briefly describe the mechanisms of ceRNA and ceRNET. What's more significant is that we explore the clinical value of ceRNAs to provide accurate diagnostic and prognostic biomarkers as well as therapeutic targets. Finally, limitations and prospects are considered.

Preleukemic Fusion Genes Induced via Ionizing Radiation

Although the prevalence of leukemia is increasing, the agents responsible for this increase are not definitely known. While ionizing radiation (IR) was classified as a group one carcinogen by the IARC, the IR-induced cancers, including leukemia, are indistinguishable from those that are caused by other factors, so the risk estimation relies on epidemiological data. Several epidemiological studies on atomic bomb survivors and persons undergoing IR exposure during medical investigations or radiotherapy showed an association between radiation and leukemia. IR is also known to induce chromosomal translocations. Specific chromosomal translocations resulting in preleukemic fusion genes (PFGs) are generally accepted to be the first hit in the onset of many leukemias. Several studies indicated that incidence of PFGs in healthy newborns is up to 100-times higher than childhood leukemia with the same chromosomal aberrations. Because of this fact, it has been suggested that PFGs are not able to induce leukemia alone, but secondary mutations are necessary. PFGs also have to occur in specific cell populations of hematopoetic stem cells with higher leukemogenic potential. In this review, we describe the connection between IR, PFGs, and cancer, focusing on recurrent PFGs where an association with IR has been established.

Impact of U2AF1 mutations on circular RNA expression in myelodysplastic neoplasms

Mutations in U2AF1 are relatively common in myelodysplastic neoplasms (MDS) and are associated with an inferior prognosis, but the molecular mechanisms underlying this are not fully elucidated. Circular RNAs (circRNAs) have been implicated in cancer, but it is unknown how mutations in splicing factors may impact on circRNA biogenesis. Here, we used RNA-sequencing to investigate the effects of U2AF1 mutations on circRNA expression in K562 cells with a doxycycline-inducible U2AF1^S34 mutation, in a mouse model with a doxycycline-inducible U2AF1^S34 mutation, and in FACS-sorted CD34+ bone marrow cells from MDS patients with either U2AF1^S34 or U2AF1^Q157 mutations. In all contexts, we found an increase in global circRNA levels in the U2AF1-mutated setting, which was independent of expression changes in the cognate linear host genes. In patients, the U2AF1^S34 and U2AF1^Q157 mutations were both associated with an overall increased expression of circRNAs. circRNAs generated by a non-Alu-mediated mechanism generally showed the largest increase in expression levels. Several well-described cancer-associated circRNAs, including circZNF609 and circCSNK1G3, were upregulated in MDS patients with U2AF1 mutations compared to U2AF1-wildtype MDS controls. In conclusion, high circRNA expression is observed in association with U2AF1 mutations in three biological systems, presenting an interesting possibility for biomarker and therapeutic investigation.

Circular RNAs and Untranslated Regions in Acute Myeloid Leukemia

Before the advent of next-generation sequencing, research on acute myeloid leukemia (AML) mostly centered on protein-coding genes. In recent years, breakthroughs in RNA sequencing technologies and whole transcriptome analysis have led to the discovery that approximately 97.5% of the human genome is transcribed into non-coding RNAs (ncRNAs). This paradigm shift has led to an explosion of research interest in different classes of non-coding RNAs, such as circular RNAs (circRNAs) as well as non-coding untranslated regions (UTRs) of protein-coding messenger RNAs. The critical roles of circRNAs and UTRs in AML pathogenesis have become increasingly apparent. In this review, we discuss the cellular mechanisms of circRNAs and summarize recent studies that reveal their biological roles in AML. Furthermore, we also review the contribution of 3'UTRs to disease progression. Finally, we discuss the potential of circRNAs and 3'UTRs as new biomarkers for disease stratification and/or the prediction of treatment response and targets for the development of RNA-directed therapeutic applications.

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

CircPTK2 promotes cell viability, cell cycle process, and glycolysis and inhibits cell apoptosis in acute myeloid leukemia by regulating miR-582-3p/ALG3 axis

BACKGROUND

Circular RNA (circRNA) regulates the pathogenesis of acute myeloid leukemia (AML). However, the mechanism of circRNA protein tyrosine kinase 2 (circPTK2) in AML remains unclear.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) assay was adopted for circPTK2, miR-582-3p and alpha-1,3-mannosyltransferase (ALG3) mRNA levels. 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and 5'-ethynyl-2'-deoxyuridine (EdU) assay were conducted for cell proliferation. Flow cytometry analysis was employed for cell apoptosis and cell cycle process. The glycolysis level was estimated by specific commercial kits. Western blot assay was utilized for protein levels. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the interaction between miR-582-3p and circPTK2 or ALG3.

RESULTS

CircPTK2 level was enhanced in AML peripheral blood samples and cells. CircPTK2 knockdown restrained AML cell proliferation and glycolysis and promoted cell apoptosis and cell cycle arrest. Mechanically, circPTK2 functioned as the sponge for miR-582-3p to positively ALG3 expression in AML cells. Moreover, miR-582-3p inhibition ameliorated the impacts of circPTK2 knockdown on AML cell processes. MiR-582-3p overexpression regulated cell phenotypes by targeting ALG3.

CONCLUSION

CircPTK2 contributed to AML cell malignant behaviors by modulation of miR-582-3p/ALG3 axis, which might provide a potential target for AML therapy.

Functions and clinical significance of circular RNAs in acute myeloid leukemia

Circular RNAs (circRNAs) are a class of covalently closed single-stranded RNA molecules. Four types of circRNAs have been reported in animal cells, and they have typical characteristics in their biogenesis, nuclear export and degradation. Advances in our understanding of the molecular functions of circRNAs in sponging microRNAs, modulating transcription, regulating RNA-binding proteins, as well as encoding proteins have been made very recently. Dysregulated circRNAs are associated with human diseases such as acute myeloid leukemia (AML). In this review, we focus on the recently described mechanisms, role and clinical significance of circRNAs in AML. Although great progress of circRNAs in AML has been achieved, substantial efforts are still required to explore whether circRNAs exert their biological function by other mechanisms such as regulation of gene transcription or serving as translation template in AML. It is also urgent that researchers study the machineries regulating circRNAs fate, the downstream effectors of circRNAs modulatory networks, and the clinical application of circRNAs in AML.

Rapamycin inhibits the progression of human acute myeloid leukemia by regulating circ_0094100/miR-217/ATP1B1 axis

Rapamycin has been reported to inhibit the progression of diverse tumor cells. However, the functions of rapamycin in acute myeloid leukemia (AML) are little known. Cell Counting Kit-8 (CCK-8) assay was conducted to evaluate cell viability. Flow cytometry analysis was employed to analyze cell apoptosis and cell cycle process. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was performed to determine the levels of circRNA_0094100 (circ_0094100) and microRNA-217 (miR-217). Western blot assay was carried out to measure the protein levels of proliferating cell nuclear antigen (PCNA), cyclin D1, B-cell lymphoma-2 (Bcl-2) and ATPase Na+/K+ transporting subunit beta 1 (ATP1B1). Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to verify the relationship between miR-217 and circ_0094100 or ATP1B1. Rapamycin treatment suppressed AML cell viability and promoted apoptosis in a dose-dependent way. Circ_0094100 was elevated in AML tissues and cells. Moreover, the circ_0094100 level was reduced in AML cells treated with rapamycin. Circ_0094100 knockdown further inhibited rapamycin-mediated AML cell viability, and cell cycle, and promoted cell apoptosis. Circ_0094100 silencing reduced the protein levels of PCNA, cyclin D1, and Bcl-2 in rapamycin-treated AML cells. For mechanism analysis, circ_0094100 acted as the sponge for miR-217 and miR-217 inhibition reversed circ_0094100 knockdown-mediated malignant behaviors of rapamycin-treated AML cells. Furthermore, miR-217 overexpression suppressed cell viability and cell cycle and facilitated apoptosis in rapamycin-exposed AML cells, which were abolished by increasing ATP1B1. Rapamycin inhibited AML cell viability and cell cycle process and induced apoptosis through regulating circ_0094100/miR-217/ATP1B1 axis.

Circular RNAs Activity in the Leukemic Bone Marrow Microenvironment

Acute myeloid leukemia (AML) is a hematological malignancy originating from defective hematopoietic stem cells in the bone marrow. In spite of the recent approval of several molecular targeted therapies for AML treatment, disease recurrence remains an issue. Interestingly, increasing evidence has pointed out the relevance of bone marrow (BM) niche remodeling during leukemia onset and progression. Complex crosstalk between AML cells and microenvironment components shapes the leukemic BM niche, consequently affecting therapy responsiveness. Notably, circular RNAs are a new class of RNAs found to be relevant in AML progression and chemoresistance. In this review, we provided an overview of AML-driven niche remodeling. In particular, we analyzed the role of circRNAs and their possible contribution to cell-cell communication within the leukemic BM microenvironment. Understanding these mechanisms will help develop a more effective treatment for AML.

Advances in the Study of circRNAs in Hematological Malignancies

Circular RNAs (circRNAs) are non–protein-coding RNAs that have a circular structure and do not possess a 5` cap or 3` poly-A tail. Their structure is more stable than that of linear RNAs, and they are difficult to deform via hydrolysis. Advancements in measurement technology such as RNA sequencing have enabled the detection of circRNAs in various eukaryotes in both in vitro and in vivo studies. The main function of circRNAs involves sponging of microRNAs (MiRNAs) and interaction with proteins associated with physiological and pathological processes, while some circRNAs are involved in translation. circRNAs act as tumor suppressors or oncogenes during the development of many tumors and are emerging as new diagnostic and prognostic biomarkers. They also affect resistance to certain chemotherapy drugs such as imatinib. The objective of this review is to investigate the expression and clinical significance of circRNAs in hematological malignancies. We will also explore the effect of circRNAs on proliferation and apoptosis in hematological malignancy cells and their possible use as biomarkers or targets to determine prognoses. The current literature indicates that circRNAs may provide new therapeutic strategies for patients with hematologic malignancies.

CircATIC Contributes to Multiple Myeloma Progression via miR-324-5p-Dependent Regulation of HGF

Circular RNA (circRNA) 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (circATIC; hsa_circ_0058058) was observed to be upregulated in multiple myeloma (MM) by former article. However, the function and exact mechanism of circATIC in MM development remain barely known. CircRNA-microRNA (miRNA)-messenger RNA (mRNA) axis was established through using bioinformatic databases (starbase, Circinteractome, and microT-CDS). Dual-luciferase reporter assay, RNA immunoprecipitation assay, and RNA-pull down assay were utilized to verify the target relationship between microRNA-324-5p (miR-324-5p) and circATIC or hepatocyte growth factor (HGF). CircATIC expression was upregulated in MM patients and cell lines. CircATIC interference notably hampered cell proliferation, migration, invasion, and glycolysis and induced cell apoptosis of MM cells. MiR-324-5p was a target of circATIC. CircATIC silencing-mediated effects in MM cells were largely overturned by the knockdown of miR-324-5p. HGF was a target of miR-324-5p, and circATIC upregulated the expression of HGF partly through sponging miR-324-5p in MM cells. MiR-324-5p suppressed the malignant behaviors of MM cells, which were largely counteracted by the overexpression of HGF in MM cells. CircATIC accelerated the proliferation, migration, invasion, and glycolysis and suppressed the apoptosis of MM cells through mediating miR-324-5p/HGF signaling.

Regulatory mechanism of miR-20a-5p expression in Cancer

MicroRNAs(miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes with a length of about 22 nucleotides. The dysregulation of miRNAs has been proven to be one of the vital causes of cancer, which makes them a biomarker for cancer diagnosis and prognosis. Compared with surgery and chemotherapy, nucleic acid therapy targeting specific miRNAs is a promising candidate for cancer treatment. miR-20a-5p plays an anticancer role in high-incidence human cancers such as cervical cancer, breast cancer and leukemia, which is of great importance in the diagnosis of cancers. The up-regulation and down-regulation of miR-20a-5p offers a possible breakthrough for the treatment of cancers. In this paper, we aim to investigate the functional significance of miR-20a-5p in different cancers, reviewing the expression differences of miR-20a-5p in cancer, while systematically summarizing the changes of circRNA-miR-20a-5p networks, and probe how it promotes messenger RNA (mRNA) degradation or inhibits mRNA translation to regulate downstream gene expression. We've also summarized the biogenesis mechanism of miRNAs, and emphasized its role in cell proliferation, cell apoptosis and cell migration. On this basis, we believe that miR-20a-5p is a promising and effective marker for cancer diagnosis, prognosis and treatment.

The emerging landscape of exosomal CircRNAs in solid cancers and hematological malignancies

Circular RNAs (circRNAs) are a type of recently discovered noncoding RNA. They exert their biological functions by competitively binding to microRNAs (miRNAs) as miRNA sponges, promoting gene transcription and participating in the regulation of selective splicing, interacting with proteins and being translated into proteins. Exosomes are derived from intracavitary vesicles (ILVs), which are formed by the inward budding of multivesicular bodies (MVBs), and exosome release plays a pivotal role in intercellular communication. Accumulating evidence indicates that circRNAs in exosomes are associated with solid tumor invasion and metastasis. Additionally, emerging studies in the last 1 ~ 2 years have revealed that exosomal circRNA also have effect on hematological malignancies. In this review, we outline the properties and biological functions of circRNAs and exosomes. In particular, we summarize in detail the mechanism and roles of exosomal circRNAs and highlight their application as novel biomarkers in malignant tumors.

Recent progress of circular RNAs in different types of human cancer: Technological landscape, clinical opportunities and challenges (Review)

Circular RNAs (circRNAs) are a novel class of endogenous non‑coding RNAs that have been recently regarded as functionally active. CircRNAs are remarkably stable and known to possess several biological functions such as microRNA sponging, regulating transcription and splicing and occasionally acting as polypeptide‑producing templates. CircRNAs show tissue‑specific expression and have been reported to be associated with the progression of several types of malignancies. Given the recent progress in genome sequencing and bioinformatics techniques, a rapid increment in the biological role of circRNAs has been observed. Concurrently, the patent search from different patent databases shows that the patent number of circRNA is increasing very quickly. These phenomena reveal a rapid development of the technological landscape. In the present review, the recent progress on circRNAs in various kinds of cancer has been investigated and their function as biomarkers or therapeutic targets and their technological landscape have been appreciated. A new insight into circRNAs structure and functional capabilities in cancer has been reviewed. Continually increasing knowledge on their critical role during cancer progression is projecting them as biomarkers or therapeutic targets for various kinds of cancer. Thus, recent updates on the functional role of circRNAs in terms of the technological landscape, clinical opportunities (biomarkers and therapeutic targets), and challenges in cancer have been illustrated.

Circ_0000745 promotes acute lymphoblastic leukemia progression through mediating miR-494-3p/NET1 axis

BACKGROUND

Circular RNAs (circRNAs) have shown important regulatory roles in tumorigenesis. However, the role and working mechanism of circ_0000745 in acute lymphoblastic leukemia (ALL) development remain largely unclear.

METHODS

The expression of circ_0000745, sperm antigen with calponin homology and coiled-coil domains 1 (SPECC1), microRNA-494-3p (miR-494-3p), and neuroepithelial cell transforming 1 (NET1) messenger RNA (mRNA) and protein was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot assay. Flow cytometry was performed to assess cell apoptosis and cell cycle progression. Extracellular acidification rate (ECAR) was assessed to analyze cell glycolysis. Cell viability was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. Ferroptosis was assessed through measuring the intracellular levels of iron and lipid reactive oxygen species (ROS). Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to validate the interaction between miR-494-3p and circ_0000745 or NET1.

RESULTS

Circ_0000745 expression was elevated in ALL patients and cell lines. Circ_0000745 knockdown restrained cell cycle progression and glycolysis and triggered cell apoptosis and ferroptosis. Circ_0000745 acted as a molecular sponge for miR-494-3p in ALL cells. miR-494-3p silencing partly diminished circ_0000745 knockdown-induced anti-tumor effects in ALL cells. NET1 was a target of miR-494-3p, and miR-494-3p overexpression-induced anti-tumor influences were partly counteracted by the accumulation of NET1 in ALL cells. Circ_0000745 can positively regulate NET1 expression by sponging miR-494-3p in ALL cells.

CONCLUSION

Circ_0000745 contributed to ALL development partly by binding to miR-494-3p to induce NET1 expression.0020.

Epigenetic modifications in acute myeloid leukemia: The emerging role of circular RNAs (Review)

Canonical epigenetic modifications, which include histone modification, chromatin remodeling and DNA methylation, play key roles in numerous cellular processes. Epigenetics underlies how cells that posses DNA with similar sequences develop into different cell types with different functions in an organism. Earlier epigenetic research has primarily been focused at the chromatin level. However, the number of studies on epigenetic modifications of RNA, such as N1‑methyladenosine, 2'‑O‑ribosemethylation, inosine, 5‑methylcytidine, N6‑methyladenosine (m6A) and pseudouridine, has seen an increase. Circular RNAs (circRNAs), a type of RNA species that lacks a 5' cap or 3' poly(A) tail, are abundantly expressed in acute myeloid leukemia (AML) and may regulate disease progression. circRNAs possess various functions, including microRNA sponging, gene transcription regulation and RNA‑binding protein interaction. Furthermore, circRNAs are m6A methylated in other types of cancer, such as colorectal and hypopharyngeal squamous cell cancers. Therefore, the critical roles of circRNA epigenetic modifications, particularly m6A, and their possible involvement in AML are discussed in the present review. Epigenetic modification of circRNAs may become a diagnostic and therapeutic target for AML in the future.

Circular RNAs in acute myeloid leukemia

Although mechanistic studies clarifying the molecular underpinnings of AML have facilitated the development of several novel targeted therapeutics, most AML patients still relapse. Thus, overcoming the inherent and acquired resistance to current therapies remains an unsolved clinical problem. While current diagnostic modalities are primarily defined by gross morphology, cytogenetics, and to an extent, by deep targeted gene sequencing, there is an ongoing demand to identify newer diagnostic, therapeutic and prognostic biomarkers for AML. Recent interest in exploring the role of circular RNA (circRNA) in elucidating AML biology and therapy resistance has been promising. This review discerns the circular RNAs’ evolving role on the same scientific premise and attempts to identify its potential in managing AML.

From circRNAs to fusion circRNAs in hematological malignancies

Circular RNAs (circRNAs) represent a type of endogenous noncoding RNA generated by back-splicing events. Unlike the majority of RNAs, circRNAs are covalently closed, without a 5' end or a 3' poly(A) tail. A few circRNAs can be associated with polysomes, suggesting a protein-coding potential. CircRNAs are not degraded by RNA exonucleases or ribonuclease R and are enriched in exosomes. Recent developments in experimental methods coupled with evolving bioinformatic approaches have accelerated functional investigation of circRNAs, which exhibit a stable structure, a long half-life, and tumor specificity and can be extracted from body fluids and used as potential biological markers for tumors. Moreover, circRNAs may regulate the occurrence and development of cancers and contribute to drug resistance through a variety of molecular mechanisms. Despite the identification of a growing number of circRNAs, their effects in hematological cancers remain largely unknown. Recent studies indicate that circRNAs could also originate from fusion genes (fusion circRNAs, f-circRNAs) next to chromosomal translocations, which are considered the primary cause of various cancers, notably hematological malignancies. This Review will focus on circRNAs and f-circRNAs in hematological cancers.

Circ_0009910 sponges miR-491-5p to promote acute myeloid leukemia progression through modulating B4GALT5 expression and PI3K/AKT signaling pathway

BACKGROUND

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias with an overall poor prognosis. Circular RNAs (circRNAs) have been verified to play important regulatory roles in AML progression. However, the role and molecular mechanism of circ_0009910 in AML development have not be completely clarified.

METHODS

The expression levels of circ_0009910, microRNA-491-5p (miR-491-5p), and β-1, 4-galactosyltransferase 5 (B4GALT5) were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. Cell proliferation and self-renewal ability were assessed via Cell Counting Kit-8 (CCK-8) and sphere formation assay. Cell cycle distribution and cell apoptosis were evaluated by flow cytometry. Caspase-3 activity was tested by Caspase-3 Activity Assay Kit. Western blot was used to examine the protein levels of autophagy-related markers and PI3K/AKT pathway-related markers. The interaction between miR-491-5p and circ_0009910 or B4GALT5 was confirmed by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, or RNA pull-down assay.

RESULTS

Circ_0009910 was highly expressed in AML tissues and cells. Silenced circ_0009910 could significantly inhibit the proliferation, sphere formation, and autophagy and promoted the apoptosis of AML cells. Circ_0009910 bound to miR-491-5p in AML cells, and circ_0009910 promoted AML progression partly through sponging miR-491-5p in vitro. B4GALT5 was a target of miR-491-5p, and miR-491-5p overexpression-mediated influences in AML cells were effectually overturned by the addition of B4GALT5 overexpression plasmid. Furthermore, circ_0009910 could regulate the expression of B4GALT5 by downregulating miR-491-5p in AML cells. Additionally, circ_0009910 could activate the PI3K/AKT signaling pathway by sponging miR-491-5p.

CONCLUSION

Circ_0009910 could suppress the proliferation, sphere formation, and autophagy and accelerated apoptosis by modulating B4GALT5 expression and activating the PI3K/AKT signaling pathway via sponging miR-491-5p in AML cells, suggesting that circ_0009910 might be a potential biomarker for the treatment of AML.

CircRNF220, not its linear cognate gene RNF220, regulates cell growth and is associated with relapse in pediatric acute myeloid leukemia

Background

Circular RNAs (circRNAs) constitute a family of transcripts with unique structures and have been confirmed to be critical in tumorigenesis and to be potential biomarkers or therapeutic targets. However, only a few circRNAs have been functionally characterized in pediatric acute myeloid leukemia (AML).

Methods

Here, we investigated the expression pattern of circRNAs in pediatric AML using a circRNA microarray. The characteristics, potential diagnostic value, and prognostic significance of circRNF220 were evaluated. A series of functional experiments were performed to investigate the role of circRNF220 in primary pediatric AML cells. Then we investigated the aberrant transcriptional networks regulated by circRNF220 in primary AML cells by RNA-seq. Furthermore, biotin RNA pulldown assays were implemented to verify the relationship between circRNF220 and miR-30a.

Results

We identified a circRNA, circRNF220, which was specifically abundant in and accumulated in the peripheral blood and bone marrow of pediatric patients with AML. It could distinguish AML from ALL and other hematological malignancies with high sensitivity and specificity. Significantly, circRNF220 expression independently predicted prognosis, while high expression of circRNF220 was an unfavorable prognostic marker for relapse. Furthermore, we characterized the function of circRNF220 and found that circRNF220 knockdown specifically inhibited proliferation and promoted apoptosis in AML cell lines and primary cells. Mechanistically, circRNF220 may act as an endogenous sponge of miR-30a to sequester miR-30a and inhibit its activity, which increases the expression of its targets MYSM1 and IER2 and implicated in AML relapse.

Conclusions

Collectively, these findings demonstrated that circRNF220 could be highly efficient and specific for the accurate diagnosis of pediatric AML, with implications for relapse prediction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01395-7.

Circular RNA circPRKCI contributes to malignant progression of T-cell acute lymphoblastic leukemia by modulating miR-20a-5p/SOX4 axis

Circular RNAs (circRNAs) have demonstrated critical roles in the development of cancers. This study aimed to explore the function of circular RNA circPRKCI/miR-20a-5p/SOX4 axis in acute lymphoblastic leukemia (ALL). Our data showed that the expression of circPRKCI and SOX4 was enhanced while the expression of miR-20a-5p was reduced in the clinical T-ALL samples. The expression of miR-20a-5p was negatively associated with circPRKCI and SOX4 in the T-ALL patients and the expression of circPRKCI was positive correlated with SOX4 in the T-ALL patients. Functionally, the silencing of circPRKCI suppressed the viability of T-ALL cells. Conversely, the knockdown of circPRKCI promoted the apoptosis of T-ALL cells. The levels of cleaved PARP and cleaved caspase3 were induced by the depletion of circPRKCI in T-ALL cells. Mechanically, the luciferase activity of circPRKCI was significantly decreased in T-ALL cells after the treatment of miR-20a-5p mimic. Meanwhile, the silencing of circPRKCI promoted the expression of miR-20a-5p in T-ALL cells, implying that circPRKCI serves as a competitive endogenous RNAs (ceRNA) of miR-20a-5p. We validated that the treatment of miR-20a-5p mimic inhibited the viability of T-ALL cells. MiR-20a-5p mimic enhanced the apoptosis of T-ALL cells. The expression of cleaved PARP and cleaved caspase3 was increased by miR-20a-5p mimic in the cells. In summarization, we concluded that circular RNA circPRKCI contributed to malignant progression of T-cell acute lymphoblastic leukemia by modulating miR-20a-5p/SOX4 axis. Targeting circPRKCI may serve as a promising therapeutic strategy of T-ALL.

Curcumin attenuates Adriamycin-resistance of acute myeloid leukemia by inhibiting the lncRNA HOTAIR/miR-20a-5p/WT1 axis

Acute myeloid leukemia (AML) is a common subtype of leukemia, and a large proportion of patients with AML eventually develop drug resistance. Curcumin exerts cancer suppressive effects and increases sensitivity to chemotherapy in several diseases. This study aimed to investigate the mechanism by which curcumin affects the resistance of AML to Adriamycin by regulating HOX transcript antisense RNA (HOTAIR) expression. Cell viability, colony-formation, flow cytometry, and Transwell assays were used to assess cell proliferation, apoptosis, and migration. A dual-luciferase reporter assay was used to verify the interaction between microRNA (miR)-20a-5p and HOTAIR or Wilms' tumor 1 (WT1). RT-qPCR and Western blotting assays were performed to detect gene and protein expression. The results showed that curcumin suppressed the resistance to Adriamycin, inhibited the expression of HOTAIR and WT1, and promoted the expression of miR-20a-5p in human acute leukemia cells (HL-60) or Adriamycin-resistant HL-60 cells (HL-60/ADR). Furthermore, curcumin suppressed proliferation and promoted apoptosis of HL-60/ADR cells. Overexpression of HOTAIR reversed the regulatory effect of curcumin on apoptosis and migration and restored the effect of curcumin on inducing the expression of cleaved caspase3, Bax, and P27. In addition, HOTAIR upregulated WT1 expression by targeting miR-20a-5p, and inhibition of miR-20a-5p reversed the regulation of Adriamycin resistance by curcumin in AML cells. Finally, curcumin inhibited Adriamycin resistance by suppressing the HOTAIR/miR-20a-5p/WT1 pathway in vivo. In short, curcumin suppressed the proliferation and migration, blocked the cell cycle progression of AML cells, and sensitized AML cells to Adriamycin by regulating the HOTAIR/miR-20a-5p/WT1 axis. These findings suggest a potential role of curcumin and HOTAIR in AML treatment.

MiR-20a-5p functions as a potent tumor suppressor by targeting PPP6C in acute myeloid leukemia

Acute myeloid leukemia (AML) is as a highly aggressive and heterogeneous hematological malignancy. MiR-20a-5p has been reported to function as an oncogene or tumor suppressor in several tumors, but the clinical significance and regulatory mechanisms of miR-20a-5p in AML cells have not been fully understood. In this study, we found miR-20a-5p was significantly decreased in bone marrow from AML patients, compared with that in healthy controls. Moreover, decreased miR-20a-5p expression was correlated with risk status and poor survival prognosis in AML patients. Overexpression of miR-20a-5p suppressed cell proliferation, induced cell cycle G0/G1 phase arrest and apoptosis in two AML cell lines (THP-1 and U937) using CCK-8 assay and flow cytometry analysis. Moreover, miR-20a-5p overexpression attenuated tumor growth in vivo by performing tumor xenograft experiments. Luciferase reporter assay and western blot demonstrated that protein phosphatase 6 catalytic subunit (PPP6C) as a target gene of miR-20a-5p was negatively regulated by miR-20a-5p in AML cells. Furthermore, PPP6C knockdown imitated, while overexpression reversed the effects of miR-20a-5p overexpression on AML cell proliferation, cell cycle G1/S transition and apoptosis. Taken together, our findings demonstrate that miR-20a-5p/PPP6C represent a new therapeutic target for AML and a potential diagnostic marker for AML therapy.

Importance of Circ0009910 in colorectal cancer pathogenesis as a possible regulator of miR-145 and PEAK1

Introduction

Colorectal cancer (CRC) is one of the most frequent neoplasms in the world. Based on the emerging role of noncoding RNAs, particularly circular RNAs in pathogenesis of cancers, we designed this study to inspect the expression levels of a circ0009910-mediated regulatory pathway in colorectal cancer.

Methods

After bioinformatics analyses and construction of putative circ0009910/ miR-145-5p/PEAK1 pathway, the expression levels of these components were evaluated in 50 CRC tissues and adjacent specimens by quantitative real-time PCR. Moreover, we appraised the correlation coefficients between these transcripts and calculated the correlation between circ0009910 expression levels with clinicopathological features of patients.

Results

Circ0009910 and PEAK1 were significantly upregulated, while miR-145-5p was decreased in CRC samples compared with adjacent tissues (p < 0.05). Moreover, statistically significant correlations were observed between expression levels of circ0009910, miR-145-5p, and PEAK1. We also reported considerable correlations between circ0009910 expression and clinicopathological parameters including sex and perineural invasion. Finally, ROC curve analysis showed circ0009910 level as a discriminative biomarker for CRC.

Conclusion

For the first time, we could introduce circ0009910 as an important biomarker in CRC. Collectively, this investigation helped us to identify a newly diagnosed pathway in CRC that can be a potential axis for designing effective drugs for treatment of CRC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02378-0.

CircKDM4C upregulates P53 by sponging hsa-let-7b-5p to induce ferroptosis in acute myeloid leukemia

To investigate the role of circKDM4C in acute myeloid leukemia (AML), the expression of circKDM4C, hsa-let-7b-5p, and P53 was measured by qRT-RCR. AML cell lines(K-562 and HL-60) were transfected correspondingly and investigated for cell proliferation, migration, and invasion abilities by CCK-8, colony formation, transwell, and wound healing assays, respectively. The levels of P53, ACSL4, PTGS2, GPX4, and FTH1 in the K-562, and HL-60 cells were measured by western blotting. Also, circKDM4C mediated regulation of ferroptosis was studied. The Phen Green SK probe and confocal laser scanning microscope were used to assess the cellular iron levels. The reactive oxygen species levels were analyzed by fluorescence-activated cell sorting using the C11-BODIPY probe. Bioinformatics analysis predicted the putative binding sites among circKDM4C, hsa-let-7b-5p, and P53. These were verified using the dual-luciferase reporter assay, RNA pull-down, and RNA immunoprecipitation assays. Finally, in vitro findings were also verified in vivo using the nude mice. CircKDM4C was significantly down-regulated in AML patients. The overexpression of circKDM4C in AML cell lines inhibited the cell proliferation, migration, invasion, and promoted ferroptosis. We found that circKDM4C acts as a sponge of hsa-let-7b-5p and thereby regulates p53 which is a target gene of hsa-let-7b-5p. Also, the expression of circKDM4C and hsa-let-7b-5p are negatively correlated, while circKDM4C and p53 are positively correlated to AML patients. Moreover, we found that circKDM4C induces ferroptosis by sponging hsa-let-7b-5p which upregulates the expression of P53. This work emphasizes the role of circKDM4C in AML patients, which could be explored for the therapeutic role.

Silencing of circTASP1 inhibits proliferation and induces apoptosis of acute myeloid leukaemia cells through modulating miR-515-5p/HMGA2 axis

Acute myeloid leukaemia (AML) is a common hematopoietic disease that is harmful to the lives of children and adults. CircRNAs are aberrantly expressed in the haematologic malignancy cells. However, the expression of circTASP1 and its function in AML remain unclear. In this study, we showed that circTASP1 was significantly up‐regulated in AML peripheral blood samples and cells. Knockdown of circTASP1 inhibited proliferation and promoted apoptosis of HL60 and THP‐1 cells in vitro. Bioinformatics prediction and luciferase reporter assay proved that circTASP1 sponged miR‐515‐5p and negatively regulated miR‐515‐5p expression in HL60 and THP‐1 cells. High mobility group A2 (HMGA2) was proved to be a downstream target of miR‐515‐5p. The rescue experiments confirmed that knockdown of circTASP1 inhibited proliferation and induced apoptosis by modulating miR‐515‐5p/HMGA2 pathway. Moreover, the in vivo experiment indicated that knockdown of circTASP1 suppressed tumour growth. In conclusion, circTASP1 acts as a sponge for miR‐515‐5p to regulate HMGA2, thereby promoting proliferation and inhibiting apoptosis during AML progression. Thus, circTASP1 has the potential to be explored as a therapeutic target for AML treatment.

Predicting circRNA-Disease Associations Based on Deep Matrix Factorization with Multi-source Fusion

Recently, circRNAs with covalently closed loops have been discovered to play important parts in the progression of diseases. Nevertheless, the study of circRNA-disease associations is highly dependent on biological experiments, which are time-consuming and expensive. Hence, a computational approach to predict circRNA-disease associations is urgently needed. In this paper, we presented an approach that is based on deep matrix factorization with multi-source fusion (DMFMSF). In DMFMSF, several useful circRNA and disease similarities were selected and then combined by similarity kernel fusion. Then, linear and non-linear characteristics were mined using singular value decomposition (SVD) and deep matrix factorization to infer potential circRNA-disease associations. Performance of the proposed DMFMSF on two benchmark datasets are rigorously validated by leave-one-out cross-validation(LOOCV) and fivefold cross-validation (5-fold CV). The experimental results showed that DMFMSF is superior over several existing computational approaches. In addition, five important diseases, hepatocellular carcinoma, breast cancer, acute myeloid leukemia, colorectal cancer, and coronary artery disease were applied in case studies. The results suggest that DMFMSF can be used as an accurate and efficient computational tool for predicting circRNA-disease associations.

Circular RNA Circ_0008035 Participates in the Progression of Multiple Myeloma by Regulating miRNA-1256

Anomalous expression of micro RNAs (miRNAs) and circular RNAs (circRNAs) were strongly correlated to the progression of multiple cancers, including multiple myeloma (MM). This study aimed to investigate whether circ_0008035 exerts its roles on MM cells by targetingmiRNA-1256. To analyze the levels of circ_0008035 and miRNA-1256 in MM samples and healthy bone marrow samples, a real time quantitative PCR (RT-qPCR) assay was executed. Cell proliferation and apoptosis were detected with a cell counting kit (CCK-8) and flow cytometry assay, respectively. The cell invasive and migration ability were assessed using a transwell assay. Dual-luciferase reporter assay and RTqPCR were applied to analyze and compare the targeting effect of circ_0008035 and miRNA-1256. Circ_0008035 was overexpressed, while miRNA-1256 expression declined in MM bone marrow tissues. RPMI8226 cells transfected with si-circ_0008035 or miRNA-1256 mimic exhibited lower proliferation and migration capabilities, while cell apoptosis was remarkably elevated. Circ_0008035 acts as a miRNA-1256sponge and negatively controls miRNA-1256 expression. Transfection of anti-miRNA-1256 reversed proliferation and migration inhibition and promoted cell apoptosis, which was motivated by si-circ_0008035 transfection. Circ_0008035 negatively regulated miRNA-1256, and the circ_0008035/miRNA-1256 axis regulates the progression of MM, thus providing a potential target for MM therapy.

Circ_0009910 shuttled by exosomes regulates proliferation, cell cycle and apoptosis of acute myeloid leukemia cells by regulating miR-5195-3p/GRB10 axis

The exosomes are involved in intercellular communication via RNA trafficking in human diseases. Hsa_circ_0009910 (circ_0009910) is a novel leukemia-related circular RNA. However, the mechanism of circ_0009910 in acute myeloid leukemia (AML) cell-to-cell communication remained obscure. Expression of circ_0009910, miRNA (miR)-5195-3p and growth factor receptor-bound protein 10 (GRB10) was detected by quantitative real-time polymerase chain reaction and Western blotting. A stable cell coculture model was established and functional experiment was performed using Cell Counting Kit-8 assay, flow cytometry, and Western blotting. The interaction among circ_0009910, miR-5195-3p and GRB10 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation. As a result, circ_0009910 was upregulated in AML bone marrows and cells (HL-60 and MOLM-13), even higher in AML cells-derived exosomes. Functionally, blocking circ_0009910 via small interfering RNA (siRNA) suppressed cell proliferation and cell cycle progression, but facilitated apoptosis rate of HL-60 and MOLM-13 cells, accompanied with lower B-cell lymphoma 2 (Bcl-2) level and higher Bcl-2-associated X protein (Bax) level. circ_0009910 shuttled via exosomes negatively regulated miR-5195-3p expression by target binding. Furthermore, circ_0009910 knockdown via exosomes and miR-5195-3p overexpression via mimic resulted in similar results of circ_0009910 siRNA in proliferation, apoptosis and cell cycle progression of AML cells. Meanwhile, the role of circ_0009910 knockdown in AML cells was partially reversed by miR-5195-3p deletion, and restoring GRB10 could abrogate miR-5195-3p effect as well. Notably, GRB10 was a downstream target of miR-5195-3p. circ_0009910-containing exosomes mediated proliferation, apoptosis and cell cycle progression of AML cells partially through miR-5195-3p/GRB10 axis.

Trace the profile and function of circular RNAs in Sertoli cell only syndrome

Studies increasingly show the involvement of circular RNAs (circRNAs) in several diseases. This study aims to explore the circRNA expression pattern in the testicular tissues of patients with Sertoli only cell syndrome (SCOS) and their potential functions. High throughput circRNA microarray analysis indicated that 399 circRNAs were upregulated and 1195 were down-regulated (fold change >2, P < 0.05) in SCOS relative to obstructive azoospermia (OA). The hsa_circRNA_101222, hsa_circRNA_001387, hsa_circRNA_001153, hsa_circRNA_101373 and hsa_circRNA_103864 were validated by qRT-PCR. Furthermore, the hosting genes of the differentially expressed circRNAs (DEcircRNAs) were enriched in biological processes related to cell cycle and intercellular communication. Also, the overlapping genes between the hosting genes of SCOS-related DEcircRNAs and those highly expressed in Sertoli cells of non-obstructive azoospermia (NOA) were enriched in immune cell development and cell communication. Taken together, aberrantly expressed circRNAs likely mediate SCOS development by regulating the function of Sertoli cells and the spermatogenic microenvironment.

The characteristics of circRNA as competing endogenous RNA in pathogenesis of acute myeloid leukemia

Background

As one of the novel molecules, circRNA has been identified closely involved in the pathogenesis of many diseases. However, the function of circRNA in acute myeloid leukemia (AML) still remains unknown.

Methods

In the current study, the RNA expression profiles were obtained from Gene Expression Omnibus (GEO) datasets. The differentially expressed RNAs were identified using R software and the competing endogenous RNA (ceRNA) network was constructed using Cytoscape. Functional and pathway enrichment analyses were performed to identify the candidate circRNA-mediated aberrant signaling pathways. The hub genes were identified by MCODE and CytoHubba plugins of Cytoscape, and then a subnetwork regulatory module was established.

Results

A total of 27 circRNA-miRNA pairs and 208 miRNA-mRNA pairs, including 12 circRNAs, 24 miRNAs and 112 mRNAs were included in the ceRNA network. Subsequently, a subnetwork, including 4 circRNAs, 5 miRNAs and 6 mRNAs, was established based on related circRNA-miRNA-mRNA regulatory modules.

Conclusions

In summary, this work analyzes the characteristics of circRNA as competing endogenous RNA in AML pathogenesis, which would provide hints for developing novel prognostic, diagnostic and therapeutic strategy for AML.

Exosomal microRNA panels as biomarkers for hematological malignancies

Hematological malignancies are classified as a heterogeneous category of cancers with various degrees of incidence and prognosis and different etiologies. Due to their aggressive essence they should be diagnosed as early as possible to improve prognosis, treatment outcome and survival. Bases on the limitations of previously identified biomarkers in terms of sensitivity, specificity and predictability, it is necessary to develop new diagnostic tools and biomarkers for the early diagnosis of hematological malignancies. Exosomes are nanovesicles secreted by almost all cell types in both physiological and pathological conditions. They play major roles in intercellular communication and are recently being considered as disease biomarkers. These nanovesicles carry proteins, lipids and nucleic acids like microRNAs (miRNAs). miRNAs are small noncoding RNAs, which act as translational suppressors via regulating protein-coding genes. The aberrant expression of miRNAs has been shown in various conditions including hematological malignancies. Moreover, it is now known that tumor cells secrete higher amounts of exosomes compared to normal cells. The idea of using exosomal miRNAs in serum as biomarkers is based on their surprisingly high stability and specificity. In the present paper, we reviewed and recommended exosomal miRNA panels including (miR-150, miR-155 and miR-1246), (miR-17-5p, miR-20a-5p, miR-16-5p and miR-5a-5p), (miR-18a, Let-7b) and (miR192-5p, miR21-5p, miR320b and Let-7d), for their potential to be used as non-invasive biomarkers in different hematological malignancies such as multiple myeloma, leukemia, and lymphoma.

Development and validation of a novel circular RNA as an independent prognostic factor in acute myeloid leukemia

BACKGROUND

Although there are many clinical and molecular biomarkers in acute myeloid leukemia (AML), the novel and reliable biomarkers are still required to predict the overall survival at the time of disease diagnosis.

METHODS

In order to identify independent predictors, we firstly selected 60 cytogenetically normal AML (CN-AML) patients using the propensity score analysis to balance the confounders and performed circular RNA (circRNA) sequencing. Next, one outcome related to circRNA was selected and validated in the independent cohort of 218 CN-AML patients. We then constructed circRNA-miRNA-mRNA regulated network and performed cellular metabolomic analysis to decipher the underlying biological insights.

RESULTS

We identified 308 circRNAs as independent candidate predictors of overall survival. Hsa_circ_0075451 expression was validated as an independent predictor with a weak predictive ability for overall survival. The regulated network of this circular RNA indicated 84 hub genes that appear to be regulated by 10 miRNAs sponged by hsa_circ_0075451. The regulatory axis of hsa_circ_0075451 -| miR-330-5p/miR-326 -| PRDM16 was validated by the dual luciferase report assay, fluorescence in situ hybridization, and ShRNA interference assay.

CONCLUSIONS

Our data demonstrates that hsa_circ_0075451 expression may independently contribute to the poor prognosis of AML and present a novel therapeutic target.

Hsa_circ_0002483 regulates miR-758-3p/MYC axis to promote acute myeloid leukemia progression

Circular RNAs are relevant to progression of acute myeloid leukemia (AML). Nevertheless, how and whether hsa_circ_0002483 (circ_0002483) participates in AML progression are largely uncertain. The bone marrow samples were harvested from 31 AML patients or 31 normal subjects. Circ_0002483, microRNA (miR)-758-3p and myelocytomatosis oncogene (MYC) abundances were examined via quantitative reverse transcription polymerase chain reaction and Western blot. Cell proliferation, cycle process and apoptosis were analyzed via Cell Counting Kit-8, flow cytometry, caspase 3 activity and related protein levels. Target relationship was investigated by dual-luciferase reporter assay and RNA immunoprecipitation. Circ_0002483 expression was elevated in AML patients and cells. Circ_0002483 silence constrained AML cell proliferation and facilitated cell cycle arrest and apoptosis. miR-758-3p was reduced in AML and decreased via circ_0002483. miR-758-3p down-regulation mitigated the inhibitive influence of circ_0002483 interference on AML progression. MYC was decreased by miR-758-3p, and circ_0002483 could regulate MYC expression by miR-758-3p. miR-758-3p overexpression restrained cell proliferation and promoted cycle arrest and apoptosis via decreasing MYC. Circ_0002483 knockdown repressed AML cell proliferation and promoted cycle arrest and apoptosis via controlling miR-758-3p/MYC axis.

Effect of total flavones of Selaginella uncinata (Desv.) spring on proliferation, apoptosis, and glycolysis in gastric cancer cells

BACKGROUND

Plant extracts have anti-gastric cancer effects, but the specific mechanisms of action have not yet been elucidated. Total flavones of Selaginella uncinata (Desv.) spring (TFS) have anti-inflammatory, antioxidant, and anti-tumor effects, but their effect on the biological behavior of gastric cancer cells and the underlying mechanism have not been elucidated.

AIM

To explore the effect of TFS on the proliferation, apoptosis, and glycolysis in gastric cancer cells and its regulatory effect on circ_0009910.

METHODS

Human gastric cancer cell line AGS was cultured in vitro, and the cells were treated with different concentrations of TFS. pcDNA and pcDNA-circ_0009910 were transfected into AGS cells, respectively, and the cells were then treated with TFS Cell proliferation was detected by MTT method and plate clone formation assay. Flow cytometry was used to detect the apoptosis rate. The lactate dehydrogenase colorimetric method was used to detect lactic acid content and glucose consumption. The expression of circ_0009910 was detected by qRT-PCR method. Western blot method was used to detect the expression of Bax and Bcl-2 proteins.

RESULTS

TFS treatment significantly reduced cell viability, the protein level of Bcl-2, glucose consumption, the level of lactate (P < 0.05), and the number of formed clones (P < 0.05), and increased the apoptosis rate and the protein level of Bax (P < 0.05). The expression level of circ_0009910 was decreased (P < 0.05) in a dose-dependent manner. Compared with the TFS-H + pcDNA group, cell viability, the protein level of Bcl-2, glucose consumption, the lactate level, and the number of formed clones in the TFS-H + pcDNA-circ_0009910 group were increased significantly (P < 0.05), and the apoptosis rate and the protein level of Bax were significantly reduced (P < 0.05).

CONCLUSION

TFS can promote apoptosis, inhibit proliferation, and reduce glycolysis by down-regulating the expression of circ_0009910 in gastric cancer cells.

CircRAD18 Accelerates the Progression of Acute Myeloid Leukemia by Modulation of miR-206/PRKACB Axis

Background

Circular RNAs (circRNAs) play a crucial role in tumorigenesis. However, the effects of circRNAs on acute myeloid leukemia (AML) remain largely unexplored. We explored the function of circRAD18 in AML development.

Methods

QRT-PCR was performed for the levels of circRAD18, RAD18, microRNA-206 (miR-206) and protein kinase CAMP-activated catalytic subunit beta (PRKACB). Cell Counting Kit-8 (CCK-8) assay and colony formation assay were utilized for cell proliferation. Flow cytometry analysis was carried out to analyze cell apoptosis and cell cycle process. Transwell assay was manipulated for cell migration and invasion. Western blot assay was conducted for protein levels. Dual-luciferase reporter assay was adopted to verify the interaction between miR-206 and circRAD18 or PRKACB.

Results

CircRAD18 level was increased in AML patients’ blood specimens and AML cell lines compared to normal controls. CircRAD18 knockdown impeded the proliferation, migration and invasion and facilitated the apoptosis and cell cycle arrest in AML cells. Moreover, circRAD18 was identified as a sponge for miR-206, and circRAD18 knockdown-mediated effect on AML cell progression was reversed by miR-206 suppression. Additionally, PRKACB was the target gene of miR-206. MiR-206 overexpression suppressed the malignant behaviors of AML cells, while PRKACB elevation restored the effects.

Conclusion

CircRAD18 aggravated the malignancy of AML cells through reducing miR-206 expression and elevating PRKACB expression, indicating circRAD18 might be a therapeutic target for AML.