Downregulation of circ_0132266 in chronic lymphocytic leukemia promoted cell viability through miR-337-3p/PML axis

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.

Recent Progress of CircRNAs in Hematological Malignancies

Circular RNAs (circRNAs) are now recognized as key regulators in the epigenetic control of genetic expression, being involved in a wide range of cellular activities such as proliferation, differentiation, and apoptosis. Their unique closed-loop structure endows them with stability and resistance to exonuclease degradation, making them not only key regulatory molecules within the cell but also promising biomarkers for disease diagnosis and prognosis, particularly in hematological malignancies. This review comprehensively explores the role of circRNAs in the pathogenesis, progression, and therapeutic resistance of common hematological malignancies. Furthermore, the review delves into the prognostic significance of circRNAs, underscoring their potential in predicting disease outcomes and treatment response. Given their extensive involvement in cancer biology, circRNAs present a frontier for novel therapeutic strategies.

Molecular significance of circRNAs in malignant lymphoproliferative disorders: pathogenesis and novel biomarkers or therapeutic targets

Recent studies have shown that circular RNAs (CircRNAs) have the novel functions and molecular mechanisms in the pathogenesis of malignant diseases. CircRNAs have been found to be associated with the occurrence and development of lymphoproliferative diseases, impacting on lymphocyte proliferation. This article provides a review of the pathogenesis of circRNAs in malignant lymphoproliferative disorders, focusing on conditions such as acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and lymphoma. Additionally, it discusses the potential value of circRNAs as novel biomarkers or therapeutic targets in these disorders.

Circular RNA as a Biomarker for Diagnosis, Prognosis and Therapeutic Target in Acute and Chronic Lymphoid Leukemia

Circular RNAs (circRNAs) are single-stranded RNAs that have received much attention in recent years. CircRNAs lack a 5' head and a 3' poly-A tail. The structure of this type of RNAs make them resistant to digestion by exonucleases. CircRNAs are expressed in different cells and have various functions. The function of circRNAs is done by sponging miRNAs, changing gene expression, and protein production. The expression of circRNAs changes in different types of cancers, which causes changes in cell growth, proliferation, differentiation, and apoptosis. Changes in the expression of circRNAs can cause the invasion and progression of tumors. Studies have shown that changes in the expression of circRNAs can be seen in acute lymphoid leukemia (ALL) and chronic lymphoid leukemia (CLL). The conducted studies aim to identify circRNAs whose expression has changed in these leukemias and their more precise function so that these circRNAs can be identified as biomarkers, prediction of patient prognosis, and treatment targets for ALL and CLL patients. In this study, we review the studies conducted on the role and function of circRNAs in ALL and CLL patients. The results of the studies show that there is a possibility of using circRNAs as biomarkers in the identification and treatment of patients in the future.

Non-Coding RNAs of Mitochondrial Origin: Roles in Cell Division and Implications in Cancer

Non-coding RNAs (ncRNAs) are a heterogeneous group, in terms of structure and sequence length, consisting of RNA molecules that do not code for proteins. These ncRNAs have a central role in the regulation of gene expression and are virtually involved in every process analyzed, ensuring cellular homeostasis. Although, over the years, much research has focused on the characterization of non-coding transcripts of nuclear origin, improved bioinformatic tools and next-generation sequencing (NGS) platforms have allowed the identification of hundreds of ncRNAs transcribed from the mitochondrial genome (mt-ncRNA), including long non-coding RNA (lncRNA), circular RNA (circRNA), and microRNA (miR). Mt-ncRNAs have been described in diverse cellular processes such as mitochondrial proteome homeostasis and retrograde signaling; however, the function of the majority of mt-ncRNAs remains unknown. This review focuses on a subgroup of human mt-ncRNAs whose dysfunction is associated with both failures in cell cycle regulation, leading to defects in cell growth, cell proliferation, and apoptosis, and the development of tumor hallmarks, such as cell migration and metastasis formation, thus contributing to carcinogenesis and tumor development. Here we provide an overview of the mt-ncRNAs/cancer relationship that could help the future development of new biomedical applications in the field of oncology.

A review on expression and regulatory mechanisms of miR-337-3p in cancer

A group of diseases generally referred to as cancer represents a serious threat to people's health all over the world and has a significant negative influence on every aspect of the lives of patients. The development of cancer is influenced by several environmental, genetic, and epigenetic factors. MicroRNAs (miRNAs), a class of non-coding RNAs, can alter the expression of genes involved in cell proliferation, migration, metastasis, and apoptosis, lead to the pathogenesis of cancer. Additionally, several effectors modify miRNAs directly, including methylation, circular RNAs, and long non-coding RNAs (lncRNAs). In this review, we have explained the role of mir-337-3p in the pathways related to the pathogenesis of different cancers. Studying the functional role of miR-337-3p is necessary for detecting novel molecules as tumor markers and discovering novel targets for cancer treatment.Communicated by Ramaswamy H. Sarma.

Advances in epigenetic alterations of chronic lymphocytic leukemia: from pathogenesis to treatment

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with alterations in genetic expression and epigenetic modifications. In recent years, the new insight into epigenetics in the pathogenesis of CLL has been developed considerably, including DNA methylation, histone modification, RNA methylation, non-coding RNAs as well as chromatin remodeling. Epigenetic modification regulates various processes such as stem cell biology, cell growth, and tumorigenesis without altering gene sequence. Growing evidence indicates that the disturbance of gene expression profiles which were regulated by epigenetic modifications exerts vital roles in the development and progress in CLL, which provides novel perspectives to explore the etiology of CLL. In addition, the integration with epigenetic therapeutic targets and the in-depth understanding of epigenetic therapy contribute to develop new therapeutic strategies for CLL. Herein, the present review discusses the advances of epigenetic alterations in the pathogenesis, diagnosis, and prognostic assessment of CLL patients and also highlights existing and emerging agents targeting epigenetic regulators.

m6A-Modified circTET2 Interacting with HNRNPC Regulates Fatty Acid Oxidation to Promote the Proliferation of Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a hematological malignancy with high metabolic heterogeneity. N6-methyladenosine (m6A) modification plays an important role in metabolism through regulating circular RNAs (circRNAs). However, the underlying mechanism is not yet fully understood in CLL. Herein, an m6A scoring system and an m6A-related circRNA prognostic signature are established, and circTET2 as a potential prognostic biomarker for CLL is identified. The level of m6A modification is found to affect the transport of circTET2 out of the nucleus. By interacting with the RNA-binding protein (RBP) heterogeneous nuclear ribonucleoprotein C (HNRNPC), circTET2 regulates the stability of CPT1A and participates in the lipid metabolism and proliferation of CLL cells through mTORC1 signaling pathway. The mTOR inhibitor dactolisib and FAO inhibitor perhexiline exert a synergistic effect on CLL cells. In addition, the biogenesis of circTET2 can be affected by the splicing process and the RBPs RBMX and YTHDC1. CP028, a splicing inhibitor, modulates the expression of circTET2 and shows pronounced inhibitory effects. In summary, circTET2 plays an important role in the modulation of lipid metabolism and cell proliferation in CLL. This study demonstrates the clinical value of circTET2 as a prognostic indicator as well as provides novel insights in targeting treatment for CLL.

PML Body Biogenesis: A Delicate Balance of Interactions

PML bodies are subnuclear protein complexes that play a crucial role in various physiological and pathological cellular processes. One of the general structural proteins of PML bodies is a member of the tripartite motif (TRIM) family-promyelocytic leukemia protein (PML). It is known that PML interacts with over a hundred partners, and the protein itself is represented by several major isoforms, differing in their variable and disordered C-terminal end due to alternative splicing. Despite nearly 30 years of research, the mechanisms underlying PML body formation and the role of PML proteins in this process remain largely unclear. In this review, we examine the literature and highlight recent progress in this field, with a particular focus on understanding the role of individual domains of the PML protein, its post-translational modifications, and polyvalent nonspecific interactions in the formation of PML bodies. Additionally, based on the available literature, we propose a new hypothetical model of PML body formation.

Novel circular RNAs of the apoptosis-related BAX and BCL2L12 genes identified in a chronic lymphocytic leukemia cell line using nanopore sequencing

Circular RNAs (circRNAs), a novel RNA type generated by back-splicing, are key regulators of gene expression, with deregulated expression and established involvement in leukemia. The products of BCL2 and its homologs, including BAX and BCL2L12, are implicated in chronic lymphocytic leukemia (CLL). However, to the best of our knowledge, nothing is known about circRNAs produced by these two genes and their role in CLL. We sought to further elucidate the contribution of BAX and BCL2L12 in CLL by unraveling the identity, localization, and potential role of their circRNAs. Therefore, total RNA from the EHEB cell line and peripheral blood mononuclear cells (PBMCs) of CLL patients and non-leukemic blood donors was extracted and reverse-transcribed using random hexamers. Next, nested PCRs with divergent primers were performed and the purified PCR products were subjected to 3rd generation nanopore sequencing. Nested PCRs were also applied to first-strand cDNAs synthesized from total RNA extracts of PBMCs from CLL patients and non-leukemic blood donors. Lastly, a single-molecule resolution fluorescent in situ hybridization method called circFISH was used to visualize the circRNA distribution in EHEB cells. We discovered several novel circRNAs produced by BAX and BCL2L12, which were characterized by great exon structure diversity. In addition, intriguing findings regarding their formation emerged. Interestingly, visualization of the most abundant circRNAs showed distinct intracellular localization. Moreover, a complex BAX and BCL2L12 circRNA expression pattern was revealed in CLL patients and non-leukemic blood donors. Our data suggest a multifaceted role of BAX and BCL2L12 circRNAs in B-cell CLL.

The Promising Role of Non-Coding RNAs as Biomarkers and Therapeutic Targets for Leukemia

Early-stage leukemia identification is crucial for effective disease management and leads to an improvement in the survival of leukemia patients. Approaches based on cutting-edge biomarkers with excellent accuracy in body liquids provide patients with the possibility of early diagnosis with high sensitivity and specificity. Non-coding RNAs have recently received a great deal of interest as possible biomarkers in leukemia due to their participation in crucial oncogenic processes such as proliferation, differentiation, invasion, apoptosis, and their availability in body fluids. Recent studies have revealed a strong correlation between leukemia and the deregulated non-coding RNAs. On this basis, these RNAs are also great therapeutic targets. Based on these advantages, we tried to review the role of non-coding RNAs in leukemia. Here, the significance of several non-coding RNA types in leukemia is highlighted, and their potential roles as diagnostic, prognostic, and therapeutic targets are covered.

Emerging roles of circRNAs in leukemia and the clinical prospects: An update

BACKGROUND

Circular RNAs (circRNAs) are a new category of endogenous non-protein coding RNAs (ncRNAs), and show the characteristics of high conservation, stability, and tissue specificity. Due to rapid advances in next-generation sequencing and transcriptome profiling technologies, circRNAs have been widely discovered in many organisms and participated in the development and progress of a variety of diseases. As a type of molecular sponge, circRNAs mainly absorb micro RNAs competitively and interplay with RNA-binding proteins to modulate the splicing as well as transcription of target genes.

METHODS

This review is based on a literature search using the Medline database. Search terms used were "circular RNAs and leukemia," "circRNAs and leukemia," "circRNAs and acute lymphoblastic leukemia," "circRNAs and chronic lymphoblastic leukemia," "circRNAs and acute myeloid leukemia," "circRNAs and chronic myeloid leukemia," and "circRNAs, biomarker, and hematological system."

RESULTS

CircRNAs have been proven as potential biomarkers and therapeutic targets in a variety of tumors. Recent research has found that circRNAs aberrantly exist in hematological cancers, especially leukemia, and are significantly associated with the incidence, progress, and metastasis of diseases as well as the prognosis of patients.

CONCLUSION

The current work summarizes the latest findings on circRNAs in various types of leukemia, aiming to propose prospective therapies and new drug screening methods for the treatment of leukemia.

CircRIC8B regulates the lipid metabolism of chronic lymphocytic leukemia through miR199b-5p/LPL axis

Objective

Circular RNAs (circRNAs) play a critical role in the modulation of tumor metabolism. However, the expression patterns and metabolic function of circRNAs in chronic lymphocytic leukemia (CLL) remain largely unknown. This study aimed to elucidate the role of circRNAs in the lipid metabolism of CLL.

Methods

The expression and metabolic patterns of circRNAs in a cohort of 53 patients with CLL were investigated using whole transcriptome sequencing. Cell viability, liquid chromatography with tandem mass spectrometry (LC–MS/MS) analysis, lipid analysis, Nile red staining as well as triglyceride (TG) assay were used to evaluate the biological function of circRIC8B in CLL. The regulatory mechanisms of circRIC8B/miR-199b-5p/lipoprotein lipase (LPL) axis were explored by luciferase assay, RNA immunoprecipitation (RIP), qRT-PCR, and fluorescence in situ hybridization (FISH). CCK-8 and flow cytometry were used to verify the inhibition role of cholesterol absorption inhibitor, ezetimibe, in CLL cells.

Results

Increased circRIC8B expression was positively correlated with advanced progression and poor prognosis. Knockdown of circRIC8B significantly suppressed the proliferation and lipid accumulation of CLL cells. In contrast, the upregulation of circRIC8B exerted opposite effects. Mechanistically, circRIC8B acted as a sponge of miR-199b-5p and prevented it from decreasing the level of LPL mRNA, and this promotes lipid metabolism alteration and facilitates the progression of CLL. What’s more, ezetimibe suppressed the expression of LPL mRNA and inhibited the growth of CLL cells.

Conclusions

In this study, the expressional and metabolic patterns of circRNAs in CLL was illustrated for the 1st time. Our findings revealed that circRIC8B regulates the lipid metabolism abnormalities in and development of CLL through the miR-199b-5p/LPL axis. CircRIC8B may serve as a promising prognostic marker and therapeutic target, which enhances the sensitivity to ezetimibe in CLL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-022-00302-0.

Circular RNA expression profiles and CircSnd1-miR-135b/c-foxl2 axis analysis in gonadal differentiation of protogynous hermaphroditic ricefield eel Monopterus albus

BACKGROUND

The expression and biological functions of circular RNAs (circRNAs) in reproductive organs have been extensively reported. However, it is still unclear whether circRNAs are involved in sex change. To this end, RNA sequencing (RNA-seq) was performed in gonads at 5 sexual stages (ovary, early intersexual stage gonad, middle intersexual stage gonad, late intersexual stage gonad, and testis) of ricefield eel, and the expression profiles and potential functions of circRNAs were studied.

RESULTS

Seven hundred twenty-one circRNAs were identified, and the expression levels of 10 circRNAs were verified by quantitative real-time PCR (qRT-PCR) and found to be in accordance with the RNA-seq data, suggesting that the RNA-seq data were reliable. Then, the sequence length, category, sequence composition and the relationship between the parent genes of the circRNAs were explored. A total of 147 circRNAs were differentially expressed in the sex change process, and GO and KEGG analyses revealed that some differentially expressed (such as novel_circ_0000659, novel_circ_0004005 and novel_circ_0005865) circRNAs were closely involved in sex change. Furthermore, expression pattern analysis demonstrated that both circSnd1 and foxl2 were downregulated in the process of sex change, which was contrary to mal-miR-135b. Finally, dual-luciferase reporter assay and RNA immunoprecipitation showed that circSnd1 and foxl2 can combine with mal-miR-135b and mal-miR-135c. These data revealed that circSnd1 regulates foxl2 expression in the sex change of ricefield eel by acting as a sponge of mal-miR-135b/c.

CONCLUSION

Our results are the first to demonstrate that circRNAs have potential effects on sex change in ricefield eel; and circSnd1 could regulate foxl2 expression in the sex change of ricefield eel by acting as a sponge of mal-miR-135b/c. These data will be useful for enhancing our understanding of sequential hermaphroditism and sex change in ricefield eel or other teleosts.

Bioinformatics analysis of mRNA profiles and identification of microRNA-mRNA network in CD4+ T cells in seasonal allergic rhinitis

Objective

We aimed to discover potential circulating genes and non-coding molecules (micro RNA [miRNA] and circular RNA [circRNA]) in CD4⁺ T cells in relation to seasonal allergic rhinitis (SAR).

Methods

Microarray data of GSE50223 were obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) during and outside the pollen season were analyzed using R software and by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway analyses. The protein–protein interactions, modules, miRNAs targeting DEGs, merged miRNA–DEG networks, and circRNAs targeted with miRNAs were further analyzed.

Results

We identified 211 DEGs during the pollen season and eight DEGs outside the season, of which only MMP12, NR4A2, and CD69 were differentially expressed both during and outside the pollen season. DEGs during the pollen season were enriched in the GO categories ‘neutrophil degranulation’, ‘neutrophil activation involved in immune response’, ‘neutrophil mediated immunity’, and ‘neutrophil activation’. A significant module was identified with key nodes of CDK6 and hsa-miR-29b-3p. Six significant circRNAs were also identified.

Conclusions

Some genes, miRNAs, and circRNAs in CD4⁺ T may play vital roles in SAR and may thus be potential targets for the prevention and treatment of SAR.

Roles of circRNAs in hematological malignancies

As one of the leading causes of death, hematologic malignancies are associated with an ever-increasing incidence, and drug resistance and relapse of patients after treatment represent clinical challenges. Therefore, there are pressing demands to uncover biomarkers to indicate the development, progression, and therapeutic targets for hematologic malignancies. Circular RNAs (circRNAs) are covalently closed circular-single-stranded RNAs whose biosynthesis is regulated by various factors and is widely-expressed and evolutionarily conserved in many organisms and expressed in a tissue−/cell-specific manner. Recent reports have indicated that circRNAs plays an essential role in the progression of hematological malignancies. However, circRNAs are difficult to detect with low abundance using conventional techniques. We need to learn more information about their features to develop new detection methods. Herein, we sought to retrospect the current knowledge about the characteristics of circRNAs and summarized research on circRNAs in hematological malignancies to explore a potential direction.

Nucleic Acid Biomarkers in Waldenström Macroglobulinemia and IgM-MGUS: Current Insights and Clinical Relevance

Waldenström Macroglobulinemia (WM) is an indolent lymphoplasmacytic lymphoma, characterized by the production of excess immunoglobulin M monoclonal protein. WM belongs to the spectrum of IgM gammopathies, ranging from asymptomatic IgM monoclonal gammopathy of undetermined significance (IgM-MGUS), through IgM-related disorders and asymptomatic WM to symptomatic WM. In recent years, its complex genomic and transcriptomic landscape has been extensively explored, hereby elucidating the biological mechanisms underlying disease onset, progression and therapy response. An increasing number of mutations, cytogenetic abnormalities, and molecular signatures have been described that have diagnostic, phenotype defining or prognostic implications. Moreover, cell-free nucleic acid biomarkers are increasingly being investigated, benefiting the patient in a minimally invasive way. This review aims to provide an extensive overview of molecular biomarkers in WM and IgM-MGUS, considering current shortcomings, as well as potential future applications in a precision medicine approach.

The emerging role non-coding RNAs in B cell-related disorders

Long non-coding RNAs and microRNAs have recently attained much attention regarding their role in the development of B cell lineage as well as participation in the lymphomagenesis. These transcripts have a highly cell type specific signature which endows them the potential to be used as biomarkers for clinical situations. Aberrant expression of several non-coding RNAs has been linked with B cell malignancies and immune related disorders such as rheumatoid arthritis, systemic lupus erythematous, asthma and graft-versus-host disease. Moreover, these transcripts can alter response of immune system to infectious conditions. miR-7, miR-16-1, miR-15a, miR-150, miR-146a, miR-155, miR-212 and miR-132 are among microRNAs whose role in the development of B cell-associated disorders has been investigated. Similarly, SNHG14, MALAT1, CRNDE, AL133346.1, NEAT1, SMAD5-AS1, OR3A4 and some other long non-coding RNAs participate in this process. In the current review, we describe the role of non-coding RNAs in B cell malignancies.

circFAT1(e2) Inhibits Cell Apoptosis and Facilitates Progression in Vascular Smooth Muscle Cells through miR-298/MYB Axis

Presently, as one of the three types of muscles in the human body, smooth muscle carries out many biological activities. Meanwhile, its abnormal development also leads to many diseases. Circular RNA, belonging to the noncoding RNA family, is demonstrated to function importantly in various diseases including smooth muscle. Here, we assumed circFAT1(e2) probably exhibited a primary role in vascular smooth muscle. Therefore, we conducted cell viability and cell apoptosis assay to validate the effects of circFAT1(e2) on vascular smooth muscle progression. Then, we supposed miR-298 was one target of circFAT1(e2) and executed corresponding experiments to test this hypothesis. Dual-luciferase reporter assay indicated miR-298 could bind to circFAT1(e2) and then modulated MYB level, thus regulating smooth muscle progression. Subsequently, based on the GSE41177 dataset, we identified 1982 differentially expressed genes (DEGs) in atrial fibrillation, and all DEGs were upregulated, including MYB. Finally, enrichment analysis of upregulated genes indicated that they were related to endodermal cell differentiation. The protein-protein interaction network revealed that EGFR, GNG2, and FPR2 were related to atrial fibrillation. In conclusion, our data find that circFAT1(e2) sponges miR-298 and then regulates MYB expression, thus affecting atrial fibrillation progression. Our findings provide a newly produced indicator and target for vascular smooth muscle diagnosis and treatment.

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.

Circular RNAs and their role in renal cell carcinoma: a current perspective

Circular RNAs (circRNAs) are a new class of long non-coding RNAs, that results from a special type of alternative splicing referred to as back-splicing. They are widely distributed in eukaryotic cells and demonstrate tissue-specific expression patterns in humans. CircRNAs actively participate in various important biological activities like gene transcription, pre-mRNA splicing, translation, sponging miRNA and proteins, etc. With such diverse biological functions, circRNAs not only play a crucial role in normal human physiology, as well as in multiple diseases, including cancer. In this review, we summarized our current understanding of circRNAs and their role in renal cell carcinoma (RCC), the most common cancer of kidneys. Studies have shown that the expression level of several circRNAs are considerably varied in RCC samples and RCC cell lines suggesting the potential role of these circRNAs in RCC progression. Several circRNAs promote RCC development and progression mostly via the miRNA/target gene axis making them ideal candidates for novel anti-cancer therapy. Apart from these, there are a few circRNAs that are significantly downregulated in RCC and overexpression of these circRNAs leads to suppression of RCC growth. Differential expression patterns and novel functions of circRNAs in RCC suggest that circRNAs can be utilized as potential biomarkers and therapeutic targets for RCC therapy. However, our current understanding of the role of circRNA in RCC is still in its infancy and much comprehensive research is needed to achieve clinical translation of circRNAs as biomarkers and therapeutic targets in developing effective treatment options for RCC.

Non-Coding RNAs in Normal B-Cell Development and in Mantle Cell Lymphoma: From Molecular Mechanism to Biomarker and Therapeutic Agent Potential

B-lymphocytes are essential for an efficient immune response against a variety of pathogens. A large fraction of hematologic malignancies are of B-cell origin, suggesting that the development and activation of B cells must be tightly regulated. In recent years, differentially expressed non-coding RNAs have been identified in mantle cell lymphoma (MCL) tumor samples as opposed to their naive, normal B-cell compartment. These aberrantly expressed molecules, specifically microRNAs (miRNAs), circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs), have a role in cellular growth and survival pathways in various biological models. Here, we provide an overview of current knowledge on the role of non-coding RNAs and their relevant targets in B-cell development, activation and malignant transformation, summarizing the current understanding of the role of aberrant expression of non-coding RNAs in MCL pathobiology with perspectives for clinical use.

Dysregulation of miRNA in Leukemia: Exploiting miRNA Expression Profiles as Biomarkers

Micro RNAs (miRNAs) are a class of small non-coding RNAs that have a crucial role in cellular processes such as differentiation, proliferation, migration, and apoptosis. miRNAs may act as oncogenes or tumor suppressors; therefore, they prevent or promote tumorigenesis, and abnormal expression has been reported in many malignancies. The role of miRNA in leukemia pathogenesis is still emerging, but several studies have suggested using miRNA expression profiles as biomarkers for diagnosis, prognosis, and response to therapy in leukemia. In this review, the role of miRNAs most frequently involved in leukemia pathogenesis is discussed, focusing on the class of circulating miRNAs, consisting of cell-free RNA molecules detected in several body fluids. Circulating miRNAs could represent new potential non-invasive diagnostic and prognostic biomarkers of leukemia that are easy to isolate and characterize. The dysregulation of some miRNAs involved in both myeloid and lymphoid leukemia, such as miR-155, miR-29, let-7, and miR-15a/miR-16-1 clusters is discussed, showing their possible employment as therapeutic targets.

lncRNA MIR210HG promotes the progression of endometrial cancer by sponging miR-337-3p/137 via the HMGA2-TGF-β/Wnt pathway

Epithelial-mesenchymal transition (EMT) promotes tumorigenesis and metastasis and increases tumor tolerance to treatment intervention. Abnormal activation of transforming growth factor β (TGF-β) and Wnt pathway induces EMT. Long non-coding RNAs (lncRNAs) significantly influence EMT regulation. Herein, we show that MIR210HG is overexpressed in endometrial cancer tissues, which is associated with poor prognosis. MIR210HG silencing significantly inhibited proliferation, migration, invasion, and EMT phenotype formation in vitro as well as tumorigenesis in vivo. Mechanistically, bioinformatics analyses, RNA binding protein immunoprecipitation (RIP) assays, and luciferase assays showed that MIR210HG acts as a molecular sponge of miR-337-3p and miR-137 to regulate the expression of HMGA2. Additionally, MIR210HG overexpression significantly enriched the Wnt/β-catenin and TGF-β/Smad3 signaling pathway genes, while MIR210HG or HMGA2 knockdown suppressed the Wnt/β-catenin and TGF-β/Smad3 signaling pathway. Our findings on the MIR210HG-miR-337-3p/137-HMGA2 axis illustrate its potential as a target for endometrial cancer therapeutic development.

Circ_0000527 promotes osteosarcoma cell progression through modulating miR-646/ARL2 axis

Accumulating evidence shows that circRNAs play critical roles in the development of human tumors. We observed that circ_0000527 was overexpressed in osteosarcoma cells (SAOS-2, HOS, MG-63 and U2OS) compared in hFOB1.19 cells. We demonstrated that the circ_0000527 level was higher in osteosarcoma specimens than in non-tumor specimens. The ectopic expression of circ_0000527 was shown to induce cell growth, cell cycle progression and the secretion of inflammatory mediators, including IL-1β, IL-6, IL-8 and TNF-α. We demonstrated that circ_0000527 sponges miR-646 in osteosarcoma cells and that ARL2 is a target gene of miR-646. MiR-646 expression was decreased and ARL2 was overexpressed in osteosarcoma cells (SAOS-2, HOS, MG-63 and U2OS) compared to hFOB1.19 cells. Overexpression of circ_0000527 was demonstrated to induce ARL2 expression in MG-63 cells. We showed that miR-646 was downregulated in osteosarcoma specimens compared to that of non-tumor specimens and that the level of circ_0000527 was negatively correlated with miR-646 expression in osteosarcoma specimens. The elevated expression of circ_0000527 was shown to promote cell growth and cell cycle progression by modulating miR-646 expression. The ectopic expression of circ_0000527 was shown to promote cell growth, cell cycle progression and the secretion of inflammatory mediators by modulating ARL2. The present study suggested that the circ_0000527/miR-646/ARL2 axis may be a potential treatment target for osteosarcoma.

Non-Coding RNAs: The "Dark Side Matter" of the CLL Universe

For many years in the field of onco-hematology much attention has been given to mutations in protein-coding genes or to genetic alterations, including large chromosomal losses or rearrangements. Despite this, biological and clinical needs in this sector remain unmet. Therefore, it is not surprising that recent studies have shifted from coded to non-coded matter. The discovery of non-coding RNAs (ncRNAs) has influenced several aspects related to the treatment of cancer. In particular, in chronic lymphocytic leukemia (CLL) the knowledge of ncRNAs and their contextualization have led to the identification of new biomarkers used to follow the course of the disease, to the anticipation of mechanisms that support resistance and relapse, and to the selection of novel targeted treatment regimens. In this review, we will summarize the main ncRNAs discovered in CLL and the molecular mechanisms by which they are affected and how they influence the development and the progression of the disease.

MicroRNAs: Tiny Regulators of Gene Expression with Pivotal Roles in Normal B-Cell Development and B-Cell Chronic Lymphocytic Leukemia

Simple Summary

The involvement of miRNAs in physiological cellular processes has been well documented. The development of B cells, which is dictated by a miRNA-transcription factor regulatory network, suggests a typical process partly orchestrated by miRNAs. Besides their contribution in normal hematopoiesis, miRNAs have been severally reported to be implicated in hematological malignancies, a typical example of which is B-cell chronic lymphocytic leukemia (B-CLL). Numerous studies have attempted to highlight the regulatory role of miRNAs in B-CLL or establish some of them as molecular biomarkers or therapeutic targets. Thus, a critical review summarizing the current knowledge concerning the multifaceted role of miRNAs in normal B-cell development and B-CLL progression, prognosis, and therapy, is urgent. Moreover, this review aims to highlight important miRNAs in both normal B-cell development and B-CLL and discuss future perspectives concerning their regulatory potential and establishment in clinical practice.

Abstract

MicroRNAs (miRNAs) represent a class of small non-coding RNAs bearing regulatory potency. The implication of miRNAs in physiological cellular processes has been well documented so far. A typical process orchestrated by miRNAs is the normal B-cell development. A stage-specific expression pattern of miRNAs has been reported in the developmental procedure, as well as interactions with transcription factors that dictate B-cell development. Besides their involvement in normal hematopoiesis, miRNAs are severally implicated in hematological malignancies, a typical paradigm of which is B-cell chronic lymphocytic leukemia (B-CLL). B-CLL is a highly heterogeneous disease characterized by the accumulation of abnormal B cells in blood, bone marrow, lymph nodes, and spleen. Therefore, timely, specific, and sensitive assessment of the malignancy is vital. Several studies have attempted to highlight the remarkable significance of miRNAs as regulators of gene expression, biomarkers for diagnosis, prognosis, progression, and therapy response prediction, as well as molecules with potential therapeutic utility. This review seeks to outline the linkage between miRNA function in normal and malignant hematopoiesis by demonstrating the main benchmarks of the implication of miRNAs in the regulation of normal B-cell development, and to summarize the key findings about their value as regulators, biomarkers, or therapeutic targets in B-CLL.

Review on circular RNAs and new insights into their roles in cancer

Circular RNAs (circRNAs) are a very interesting class of conserved single-stranded RNA molecules derived from exonic or intronic sequences by precursor mRNA back-splicing. Unlike canonical linear RNAs, circRNAs form covalently closed, continuous stable loops without a 5'end cap and 3'end poly(A) tail, and therefore are resistant to exonuclease digestion. The majority of circRNAs are highly abundant, and conserved across different species with a tissue or developmental-stage-specific expression. circRNAs have been shown to play important roles as microRNA sponges, regulators of gene splicing and transcription, RNA-binding protein sponges and protein/peptide translators. Emerging evidence reveals that circRNAs function in various human diseases, particularly cancers, and may function as better predictive biomarkers and therapeutic targets for cancer treatment. In consideration of their potential clinical relevance, circRNAs have become a new research hotspot in the field of tumor pathology. In the present study, the current understanding of the biogenesis, characteristics, databases, research methods, biological functions subcellular distribution, epigenetic regulation, extracellular transport and degradation of circRNAs was discussed. In particular, the multiple databases and methods involved in circRNA research were first summarized, and the recent advances in determining the potential roles of circRNAs in tumor growth, migration and invasion, which render circRNAs better predictive biomarkers, were described. Furthermore, future perspectives for the clinical application of circRNAs in the management of patients with cancer were proposed, which could provide new insights into circRNAs in the future.

miRNA biomarkers for predicting overall survival outcomes for head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a malignant tumor of the upper aerodigestive tract. The loss and gain of miRNA function promote cancer development through various mechanisms. RNA sequencing (RNA-seq) and miRNAs sequencing data from the Cancer Genome Atlas (TCGA) was used to show the dysfunctional miRNAs microenvironment and to provide useful biomarkers for miRNAs therapy. Seven miRNAs were found to be independent prognostic factors of HNSCC patients in the training cohort. A total of 60 target genes for these miRNAs were predicted. Nine target genes (CDCA4, CXCL14, FLNC, KLF7, NBEAL2, P4HA1, PFKM, PFN2 and SEPPINE1) were correlated with patient's overall survival (OS) outcomes. We identified novel miRNAs markers for the prognosis of head and neck squamous cell carcinoma.

The functions and clinical significance of circRNAs in hematological malignancies

With covalently closed circular structures, circular RNAs (circRNAs) were once misinterpreted as by-products of mRNA splicing. Being abundant, stable, highly conserved, and tissue-specific, circRNAs are recently identified as a type of regulatory RNAs. CircRNAs bind to certain miRNAs or proteins to participate in gene transcription and translation. Emerging evidence has indicated that the dysregulation of circRNAs is closely linked to the tumorigenesis and treatment response of hematological malignancies. CircRNAs play critical roles in various biological processes, including tumorigenesis, drug resistance, tumor metabolism, autophagy, pyroptosis, and ferroptosis. The N6-methyladenosine modification of circRNAs and discovery of fusion-circRNAs provide novel insights into the functions of circRNAs. Targeting circRNAs in hematological malignancies will be an attractive treatment strategy. In this review, we systematically summarize recent advances toward the novel functions and molecular mechanisms of circRNAs in hematological malignancies, and highlight the potential clinical applications of circRNAs as novel biomarkers and therapeutic targets for future exploration.

Non-Coding RNAs as Cancer Hallmarks in Chronic Lymphocytic Leukemia

The discovery of non-coding RNAs (ncRNAs) and their role in tumor onset and progression has revolutionized the way scientists and clinicians study cancers. This discovery opened new layers of complexity in understanding the fine-tuned regulation of cellular processes leading to cancer. NcRNAs represent a heterogeneous group of transcripts, ranging from a few base pairs to several kilobases, that are able to regulate gene networks and intracellular pathways by interacting with DNA, transcripts or proteins. Deregulation of ncRNAs impinge on several cellular responses and can play a major role in each single hallmark of cancer. This review will focus on the most important short and long non-coding RNAs in chronic lymphocytic leukemia (CLL), highlighting their implications as potential biomarkers and therapeutic targets as they relate to the well-established hallmarks of cancer. The key molecular events in the onset of CLL will be contextualized, taking into account the role of the "dark matter" of the genome.

Profiling of circular RNAs in age-related cataract reveals circZNF292 as an antioxidant by sponging miR-23b-3p

Age-related cataract (ARC) is one of the major causes of visual impairment and reversible blindness worldwide. Accumulating evidence has revealed that circular RNAs (circRNAs) are involved in multiple regulatory processes in various ocular diseases. However, the expression profile, regulatory roles, and underlying mechanisms of circRNAs in ARC remain largely unknown. Herein we deep-sequenced circRNAs of anterior lens capsules from normal and ARC lenses, and detected 23,787 candidate circRNAs. Of these, 466 were significantly differentially expressed, and a higher correlation in down-regulated circRNAs between ARC and diabetic cataract was observed compared with up-regulated ones. Subsequent bioinformatics analysis disclosed that certain differentially expressed circRNAs participated in oxidative stress and apoptosis-related signaling pathways in ARC. Notably, the level of circZNF292 was significantly decreased, while miR-23b-3p was significantly increased in ARC. The target region prediction and dual-luciferase reporter assays proved that circZNF292 acted as a competitive endogenous RNA to regulate the expression of anti-oxidative genes through competing with miR-23b-3p. Our results indicate that circZNF292, a down-regulated circRNA in the anterior lens capsule of ARC patients, may be involved in resistance to oxidative damage and apoptosis of lens epithelial cells by sponging miR-23b-3p, providing a potential target for prevention and treatment of ARC.

Recent progress in study of circRNAs and its role in leukemia

Circular RNAs (circRNAs) are a class of newly identified noncoding RNA and are considered as a new feature of eukaryotic gene expression. Hundreds of thousands of endogenous circRNAs have been found in mammalian cells, which we knew little before. CircRNAs are covalently closed, circular RNA molecules that typically comprise exonic sequences and are spliced at canonical splice sites. Researchers with RNA-Seq technology have identified that the expression of circRNAs is developmentally regulated, tissue- and cell-type specific. Like long noncoding RNAs (lncRNAs), circRNAs are becoming a new research hotspot in the RNA field, and aberrant expression of circRNAs could contribute to carcinogenesis. Recent studies have demonstrated that circRNAs play important roles in the development, maintenance, and progression of leukemia. Herein, we describe the biologic characteristics and functions of circRNAs, with a focus on circRNAs that play essential roles in leukemia.

Circular RNAs in leukemia

In pace with the development of gene sequencing technology and transcriptome research, it has been found that 70 to 90% of the human genome is transcribed into RNAs, while only 2% of RNAs encode proteins. This implies that non-coding RNAs (ncRNAs) may exert vital biological functions and a full analysis of non-coding transcriptomes is needed. Over the past decade, the advance in high-throughput sequencing and transcriptome profiling has enabled the identification of circular RNAs (circRNAs) involved in many biological processes and the occurrence and development of diseases. Accumulating evidence has revealed that circRNAs may serve as new biomarkers for diagnosis as well as provide promising therapeutic approaches and novel drug screening strategies for leukemia. A comprehensive understanding of circRNAs in leukemia is a prerequisite for the development of clinical translational research. In this review, we will discuss the general information of circRNAs and focus on the current advances in understanding the association between dysregulated circRNAs and leukemia.

Circular RNAs in Blood Malignancies

Circular (circ)RNAs influence a wide range of biological processes at least in part by interacting with proteins and microRNAs. CircRNAs expressed in the hematopoietic compartment have been increasingly recognized as modulators of physiological and pathological features of hematopoetic stem cell (HSC)-derived populations. In particular, several circRNAs were found to enhance or suppress tumor progression in blood malignancies such as leukemias and lymphomas. Moreover, numerous circRNAs have been proposed to help confer resistance to the conventional treatments used in hematopoietic cancers. Here, we review the most important circRNAs described thus far in acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), lymphomas, and multiple myeloma (MM). We discuss the usefulness of circRNAs as diagnostic and prognostic markers and their potential value as therapeutic targets.

Competing endogenous RNA regulation in hematologic malignancies

The clinical application of cytogenetic analysis and molecular-targeted drugs has dramatically improved the prognosis for many patients with hematologic malignancy, especially for those with chronic myeloid leukemia (CML) and acute promyelocytic leukemia (APL). Nevertheless, the treatment of hematologic malignancies is still faced with problems, such as disease recurrence and drug resistance, so further exploring the underlying molecular mechanism is urgent. With the discovery of different RNA species, the mechanism of RNA-RNA interaction has caught more and more attention. "Competing endogenous RNA (ceRNA) hypothesis" is one of the fascinating products of recent researches. CeRNAs are endogenous RNA transcripts that share mutual microRNA response elements (MREs) and regulate expression of each other by competing for the same microRNAs pools. The hypothesis links different RNA species together and enriches our understanding of the human genome. Here, we introduce the hypothesis critically, summary the research progress in the field of hematologic malignancies and the current investigation methods, and address its promising clinical value in offering new predictive, prognostic biomarkers and therapeutic targets.

Mitochondrial Genome-Derived circRNA mc-COX2 Functions as an Oncogene in Chronic Lymphocytic Leukemia

Circular RNAs (circRNAs), a novel family of non-coding RNAs, play crucial roles in cancer progression. While the existing research focuses on nuclear genome-derived (nu)-circRNAs, the biological and clinical characteristics of mitochondrial genome-derived (mt)-circRNAs remain largely unknown, especially in chronic lymphocytic leukemia (CLL). In this study, we attempted to identify the novel characteristics of mc-COX2 (mitochondrial genome-derived circRNAs [mc]), one of the mt-circRNAs that can be involved in CLL progression. mt-circRNAs were found to be highly expressed in the plasma exosomes of CLL patients. The endogenous reduction of mc-COX2 can affect mitochondrial functions, suppress cell proliferation, and induce cell apoptosis. The upregulation of mc-COX2 was positively associated with leukemogenesis and worsening survival of CLL patients. Notably, functional analysis revealed that mc-COX2, as differing from conventional nu-circRNAs, was less stable and may function through novel mechanisms other than acting as the competing endogenous RNA. We also screened and tested several chemical compounds and small-molecule inhibitors that can decrease the generation of mc-COX2. It was found that the silencing of mc-COX2 in CLL cells strengthened the anti-tumor effects of drugs used in coordination. Our findings prove that mc-COX2, a critical mt-circRNA highly expressed in plasma, derived from CLL cells and delivered by exosomes, is associated with the progression and prognosis of CLL.

Role of non-coding RNA networks in leukemia progression, metastasis and drug resistance

Early-stage detection of leukemia is a critical determinant for successful treatment of the disease and can increase the survival rate of leukemia patients. The factors limiting the current screening approaches to leukemia include low sensitivity and specificity, high costs, and a low participation rate. An approach based on novel and innovative biomarkers with high accuracy from peripheral blood offers a comfortable and appealing alternative to patients, potentially leading to a higher participation rate.

Recently, non-coding RNAs due to their involvement in vital oncogenic processes such as differentiation, proliferation, migration, angiogenesis and apoptosis have attracted much attention as potential diagnostic and prognostic biomarkers in leukemia. Emerging lines of evidence have shown that the mutational spectrum and dysregulated expression of non-coding RNA genes are closely associated with the development and progression of various cancers, including leukemia. In this review, we highlight the expression and functional roles of different types of non-coding RNAs in leukemia and discuss their potential clinical applications as diagnostic or prognostic biomarkers and therapeutic targets.

Tumor Suppressors in Chronic Lymphocytic Leukemia: From Lost Partners to Active Targets

Tumor suppressors play an important role in cancer pathogenesis and in the modulation of resistance to treatments. Loss of function of the proteins encoded by tumor suppressors, through genomic inactivation of the gene, disable all the controls that balance growth, survival, and apoptosis, promoting cancer transformation. Parallel to genetic impairments, tumor suppressor products may also be functionally inactivated in the absence of mutations/deletions upon post-transcriptional and post-translational modifications. Because restoring tumor suppressor functions remains the most effective and selective approach to induce apoptosis in cancer, the dissection of mechanisms of tumor suppressor inactivation is advisable in order to further augment targeted strategies. This review will summarize the role of tumor suppressors in chronic lymphocytic leukemia and attempt to describe how tumor suppressors can represent new hopes in our arsenal against chronic lymphocytic leukemia (CLL).

Tip of the iceberg: roles of circRNAs in hematological malignancies

Circular RNAs (circRNAs) are a new class of covalently closed RNA molecules whose 3'- and 5'-ends are linked by a back-splicing event. Emerging evidence has shown that circRNAs play a vital role in the occurrence and development of many diseases and are promising biomarkers and therapeutic targets. However, knowledge of circRNAs in hematological malignancies is limited. In this review, the biogenesis, categories, characteristics, and functions of circRNAs are summarized, especially the roles of circRNAs in hematopoiesis and hematological malignancies.

CircRNA Cdr1as functions as a competitive endogenous RNA to promote hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Recent years, circular RNA (circRNA) have been shown to exert vital functions in the pathological progressions of many diseases. A growing number of evidences have identified the representative function of exosomal circRNAs in the physiological state of donor cells, which further induces cellular responses after captured by recipient cells. However, the contributions of circRNAs to HCC remain largely unknown. In vitro and in vivo regulatory roles of circRNA Cdr1as in proliferative and migratory abilities of HCC were evaluated by CCK8, EdU, Transwell and tumourigenicity assays, respectively. Results showed circRNA Cdr1as was highly expressed in HCC cell lines and tissues. Overexpression of circRNA Cdr1as greatly accelerated HCC cells to proliferate and migrate. Mechanistically, we found that Cdr1as could promote the expression of AFP, a well-known biomarker for HCC, by sponging miR-1270. Further studies showed exosomes extracted from HCC cells overexpressing circRNA Cdr1as accelerated the proliferative and migratory abilities of surrounding normal cells. In all, circRNA Cdr1as serves as a ceRNA to promote the progression of HCC. Meanwhile, it is directly transferred from HCC cells to surrounding normal cells via exosomes to further mediate the biological functions of surrounding cells.