Epigenetic silencing of tumor suppressor long non-coding RNA BM742401 in chronic lymphocytic leukemia

Multiple omics levels of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a lymphoproliferative malignancy characterized by the proliferation of functionally mature but incompetent B cells. It is the most prevalent type of leukemia in Western populations, accounting for approximately 25% of new leukemia cases. While recent advances, such as ibrutinib and venetoclax treatment have improved patient outlook, aggressive forms of CLL such as Richter transformation still pose a significant challenge. This discrepancy may be due to the heterogeneity of factors contributing to CLL development at multiple -omics levels. However, information on the omics of CLL is fragmented, hindering multi-omics-based research into potential treatment options. To address this, we aggregated and presented a selection of important aspects of various omics levels of the disease in this review. The purpose of the present literature analysis is to portray examples of CLL studies from different omics levels, including genomics, epigenomics, transcriptomics, epitranscriptomics, proteomics, epiproteomics, metabolomics, glycomics and lipidomics, as well as those identified by multi-omics approaches. The review includes the list of 102 CLL-associated genes with relevant genomics information. While single-omics studies yield substantial and useful data, they omit a significant level of complex biological interplay present in the disease. As multi-omics studies integrate several different layers of data, they may be better suited for complex diseases such as CLL and have thus far yielded promising results. Future multi-omics studies may assist clinicians in improved treatment choices based on CLL subtypes as well as allow the identification of novel biomarkers and targets for treatments.

The Role of Methylation in Chronic Lymphocytic Leukemia and Its Prognostic and Therapeutic Impacts in the Disease: A Systematic Review

Epigenetic regulation has been thoroughly investigated in recent years and has emerged as an important aspect of chronic lymphocytic leukemia (CLL) biology. Characteristic aberrant features such as methylation patterns and global DNA hypomethylation were the early findings of the research during the last decades. The investigation in this field led to the identification of a large number of genes where methylation features correlated with important clinical and laboratory parameters. Gene-specific analyses investigated methylation in the gene body enhancer regions as well as promoter regions. The findings included genes and proteins involved in key pathways that play central roles in the pathophysiology of the disease. Τhe application of these findings beyond the theoretical understanding can not only lead to the creation of prognostic and predictive models and scores but also to the design of novel therapeutic agents. The following is a review focusing on the present knowledge about single gene/gene promoter methylation or mRNA expression in CLL cases as well as records of older data that have been published in past papers.

The Role of Long Noncoding RNAs in Progression of Leukemia: Based on Chromosomal Location

Long non-coding RNA [LncRNA] dysregulation has been seen in many human cancers, including several kinds of leukemia, which is still a fatal disease with a poor prognosis. LncRNAs have been demonstrated to function as tumor suppressors or oncogenes in leukemia. This study covers current research findings on the role of lncRNAs in the prognosis and diagnosis of leukemia. Based on recent results, several lncRNAs are emerging as biomarkers for the prognosis, diagnosis, and even treatment outcome prediction of leukemia and have been shown to play critical roles in controlling leukemia cell activities, such as proliferation, cell death, metastasis, and drug resistance. As a result, lncRNA profiles may have superior predictive and diagnostic potential in leukemia. Accordingly, this review concentrates on the significance of lncRNAs in leukemia progression based on their chromosomal position.

Long Non-Coding RNA Signatures in Lymphopoiesis and Lymphoid Malignancies

Lymphoid cells play a critical role in the immune system, which includes three subgroups of T, B, and NK cells. Recognition of the complexity of the human genetics transcriptome in lymphopoiesis has revolutionized our understanding of the regulatory potential of RNA in normal lymphopoiesis and lymphoid malignancies. Long non-coding RNAs (lncRNAs) are a class of RNA molecules greater than 200 nucleotides in length. LncRNAs have recently attracted much attention due to their critical roles in various biological processes, including gene regulation, chromatin organization, and cell cycle control. LncRNAs can also be used for cell differentiation and cell fate, as their expression patterns are often specific to particular cell types or developmental stages. Additionally, lncRNAs have been implicated in lymphoid differentiation, such as regulating T-cell and B-cell development, and their expression has been linked to immune-associated diseases such as leukemia and lymphoma. In addition, lncRNAs have been investigated as potential biomarkers for diagnosis, prognosis, and therapeutic response to disease management. In this review, we provide an overview of the current knowledge about the regulatory role of lncRNAs in physiopathology processes during normal lymphopoiesis and lymphoid leukemia.

Mutual interaction of lncRNAs and epigenetics: focusing on cancer

Long noncoding RNAs are characterized as noncoding transcripts longer than 200 nucleotides in response to a variety of functions within the cells. They are involved in almost all cellular mechanisms so as epigenetics. Given that epigenetics is an important phenomenon, which participates in the biology of complex diseases, many valuable studies have been performed to demonstrate the control status of lncRNAs and epigenetics. DNA methylation and histone modifications as epigenetic mechanisms can regulate the expression of lncRNAs by affecting their coding genes. Reciprocally, the three-dimensional structure of lncRNAs could mechanistically control the activity of epigenetic-related enzymes. Dysregulation in the mutual interaction between epigenetics and lncRNAs is one of the hallmarks of cancer. These mechanisms are either directly or indirectly involved in various cancer properties such as proliferation, apoptosis, invasion, and metastasis. For instance, lncRNA HOTAIR plays a role in regulating the expression of many genes by interacting with epigenetic factors such as DNA methyltransferases and EZH2, and thus plays a role in the initiation and progression of various cancers. Conversely, the expression of this lncRNA is also controlled by epigenetic factors. Therefore, focusing on this reciprocated interaction can apply to cancer management and the identification of prognostic, diagnostic, and druggable targets. In the current review, we discuss the reciprocal relationship between lncRNAs and epigenetic mechanisms to promote or prevent cancer progression and find new potent biomarkers and targets for cancer diagnosis and therapy.

Diagnostic and Therapeutic Implications of Long Non-Coding RNAs in Leukemia

Leukemia is a heterogenous group of hematological malignancies categorized in four main types (acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL). Several cytogenetic and molecular markers have become a part of routine analysis for leukemia patients. These markers have been used in diagnosis, risk-stratification and targeted therapy application. Recent studies have indicated that numerous regulatory RNAs, such as long non-coding RNAs (lncRNAs), have a role in tumor initiation and progression. When it comes to leukemia, data for lncRNA involvement in its etiology, progression, diagnosis, treatment and prognosis is limited. The aim of this review is to summarize research data on lncRNAs in different types of leukemia, on their expression pattern, their role in leukemic transformation and disease progression. The usefulness of this information in the clinical setting, i.e., for diagnostic and prognostic purposes, will be emphasized. Finally, how particular lncRNAs could be used as potential targets for the application of targeted therapy will be considered.

The emerging role of non-coding RNAs in the epigenetic regulation of pediatric cancers

Epigenetics is a process that involves the regulation of gene expression without altering the sequence of DNA. Numerous studies have documented that epigenetic mechanisms play a critical role in cell growth, differentiation, and cancer over the past decade. The well-known epigenetic modifications are either on DNA or at the histone proteins. Although several studies have focused on regulating gene expression by non-coding RNAs, the current understanding of their biological functions in various human diseases, particularly in cancers, is inadequate. Only about two percent of DNA is involved in coding the protein-coding genes, and leaving the rest 98 percent is non-coding and the scientific community regarded as junk or noise with no known purpose. Most non-coding RNAs are derived from such junk DNA and are known to be involved in various signaling pathways involving cancer initiation, progression, and the development of therapy resistance in many human cancer types. Recent studies have suggested that non-coding RNAs, especially microRNAs, piwi-interactingRNAs, and long non-coding RNAs, play a significant role in controlling epigenetic mechanism(s), indicating the potential effect of epigenetic modulation of non-coding RNAs on cancer progression. In this review article, we briefly presented epigenetic marks' characteristics, crosstalk between epigenetic modifications and microRNAs, piwi-interactingRNAs, and long non-coding RNAs to uncover the effect on the phenotype of pediatric cancers. Further, current knowledge on understanding the RNA epigenetics will help design novel therapeutics that target epigenetic regulatory networks to benefit cancer patients in the clinic.

The Landscape of lncRNAs in Multiple Myeloma: Implications in the "Hallmarks of Cancer", Clinical Perspectives and Therapeutic Opportunities

Simple Summary

Multiple myeloma (MM) is an aggressive hematological neoplasia caused by the uncontrolled proliferation of aberrant plasmacells. Neoplastic transformation and progression are driven by a number of biological processes, called ‘hallmarks of cancer’, which are regulated by different molecules, including long non-coding RNAs. A deeper understanding of the mechanisms that regulate MM development and progression will help to improve patients stratification and management, and promote the identification of new therapeutic targets.

Abstract

Long non-coding RNAs (lncRNAs) are transcripts longer than 200 nucleotides that are not translated into proteins. Nowadays, lncRNAs are gaining importance as key regulators of gene expression and, consequently, of several biological functions in physiological and pathological conditions, including cancer. Here, we point out the role of lncRNAs in the pathogenesis of multiple myeloma (MM). We focus on their ability to regulate the biological processes identified as “hallmarks of cancer” that enable malignant cell transformation, early tumor onset and progression. The aberrant expression of lncRNAs in MM suggests their potential use as clinical biomarkers for diagnosis, patient stratification, and clinical management. Moreover, they represent ideal candidates for therapeutic targeting.

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.

Emerging role of long non-coding RNAs in endothelial dysfunction and their molecular mechanisms

Long non-coding RNAs (lncRNAs) are the novel class of transcripts involved in transcriptional, post-transcriptional, translational, and post-translational regulation of physiology and the pathology of diseases. Studies have evidenced that the impairment of endothelium is a critical event in the pathogenesis of atherosclerosis and its complications. Endothelial dysfunction is characterized by an imbalance in vasodilation and vasoconstriction, oxidative stress, proinflammatory factors, and nitric oxide bioavailability. Disruption of the endothelial barrier permeability, the first step in developing atherosclerotic lesions is a consequence of endothelial dysfunction. Though several factors interfere with the normal functioning of the endothelium, intrinsic epigenetic mechanisms governing endothelial function are regulated by lncRNAs and perturbations contribute to the pathogenesis of the disease. This review comprehensively addresses the biogenesis of lncRNA and molecular mechanisms underlying and regulation in endothelial function. An insight correlating lncRNAs and endothelial dysfunction-associated diseases can positively impact the development of novel biomarkers and therapeutic targets in endothelial dysfunction-associated diseases and treatment strategies.

An immunotherapeutic approach to decipher the role of long non-coding RNAs in cancer progression, resistance and epigenetic regulation of immune cells

Immunotherapeutic treatments are gaining attention due to their effective anti-tumor response. Particularly, the revolution of immune checkpoint inhibitors (ICIs) produces promising outcomes for various cancer types. However, the usage of immunotherapy is limited due to its low response rate, suggesting that tumor cells escape the immune surveillance. Rapid advances in transcriptomic profiling have led to recognize immune-related long non-coding RNAs (LncRNAs), as regulators of immune cell-specific gene expression that mediates immune stimulatory as well as suppression of immune response, indicating LncRNAs as targets to improve the efficacy of immunotherapy against tumours. Moreover, the immune-related LncRNAs acting as epigenetic modifiers are also under deep investigation. Thus, herein, is a summarised knowledge of LncRNAs and their regulation in the adaptive and innate immune system, considering their importance in autophagy and predicting putative immunotherapeutic responses.

Long non-coding RNA CRNDE suppressing cell proliferation is regulated by DNA methylation in chronic lymphocytic leukemia

Long non-coding RNA CRNDE and DNA methylation play a vital role in the occurrence and development of chronic lymphocytic leukemia (CLL). This study attempted to investigate the biological role of CRNDE methylation in CLL. The expression and methylation levels of CRNDE in CLL cell lines (MEC-1 and HG3) before or after methylation inhibitor (5-Aza-2'-deoxycytidine, 5-Aza-CdR) treatment was detected by quantitative real-time PCR or methylation-Specific PCR. The relationship among CRNDE, miR-28 and NDRG2 was verified by luciferase reporter assay. The effect of CRNDE overexpression and 5-Aza-CdR treatment on cell proliferation and apoptosis of MEC-1 and HG3 cells were assessed by CCK8 and flow cytomery. Compared with normal B lymphocytes, CRNDE was down-regulated and the methylation level of CRNDE was increased in MEC-1 and HG3 cells. Then, 5-Aza-CdR treatment caused an increase of CRNDE expression in MEC-1 and HG3 cells by demethylation. The overexpression or demethylation of CRNDE inhibited cell proliferation and promoted apoptosis in MEC-1 and HG3 cells by up-regulating CRNDE expression. Moreover, CRNDE functioned as a competing endogenous RNA to repress miR-28, which controlled its down-stream target NDRG2. CRNDE overexpression inhibited cell proliferation and promoted apoptosis via miR-28/NDRG2 axis in CLL. In conclusion, our data elaborated that CRNDE expression was regulated by DNA methylation, and the protective effect of CRNDE on CLL was attributed to the inhibition of proliferation in CLL via miR-28/NDRG2 axis. Thus, this work highlights a novel competing endogenous RNA circuitry involving key regulators of CLL.

Non-coding RNAs (miRNAs and lncRNAs) and their roles in lymphogenesis in all types of lymphomas and lymphoid malignancies

Contemporary developments in molecular biology have been combined with discoveries on the analysis of the role of all non-coding RNAs (ncRNAs) in human diseases, particularly in cancer, by examining their roles in cells. Currently, included among these common types of cancer, are all the lymphomas and lymphoid malignancies, which represent a diverse group of neoplasms and malignant disorders. Initial data suggest that non-coding RNAs, particularly long ncRNAs (lncRNAs), play key roles in oncogenesis and that lncRNA-mediated biology is an important key pathway to cancer progression. Other non-coding RNAs, termed microRNAs (miRNAs or miRs), are very promising cancer molecular biomarkers. They can be detected in tissues, cell lines, biopsy material and all biological fluids, such as blood. With the number of well-characterized cancer-related lncRNAs and miRNAs increasing, the study of the roles of non-coding RNAs in cancer is bringing forth new hypotheses of the biology of cancerous cells. For the first time, to the best of our knowledge, the present review provides an up-to-date summary of the recent literature referring to all diagnosed ncRNAs that mediate the pathogenesis of all types of lymphomas and lymphoid malignancies.

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.

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.

Epigenetic silencing of long non-coding RNA BM742401 in multiple myeloma: impact on prognosis and myeloma dissemination

Background

Long non-coding RNA (lncRNA) BM742401 is a tumor suppressor in gastric cancer and chronic lymphocytic leukemia. As the promoter and coding region of BM742401 are fully embedded in a CpG island, we hypothesized that BM742401 is a tumor suppressor lncRNA epigenetically silenced by promoter DNA methylation in multiple myeloma.

Methods

Methylation-specific PCR and quantitative bisulfite pyrosequencing were performed to detect the methylation of BM742401 in normal plasma cells, myeloma cell lines and primary myeloma samples. The expression of BM742401 was measured by qRT-PCR. The function of BM742401 in multiple myeloma cells was analyzed by lentivirus transduction followed by migration assay.

Results

BM742401 methylation was detected in 10 (66.7%) myeloma cell lines but not normal plasma cells, and inversely correlated with expression of BM742401. In primary samples, BM742401 methylation was detected in 3 (12.5%) monoclonal gammopathy of undetermined significance, 9 (15.8%) myeloma at diagnosis and 8 (17.0%) myeloma at relapse/progression. Moreover, BM742401 methylation at diagnosis was associated with inferior overall survival (median OS: 25 vs. 39 months; P = 0.0496). In myeloma cell line JJN-3, stable overexpression of BM742401 by lentivirus transduction resulted in reduced cell migration (P = 0.0001) but not impacting cell death or proliferation.

Conclusions

This is the first report of tumor-specific methylation-mediated silencing of BM742401 in myeloma, which is likely an early event in myelomagenesis with adverse impact on overall survival. Moreover, BM742401 is a tumor suppressor lncRNA by inhibiting myeloma cell migration, hence implicated in myeloma plasma cell homing, metastasis and disease progression.

The role of long non-coding RNAs and downstream signaling pathways in leukemia progression

The study of long non-coding RNAs (lncRNA) is a newly established field and our knowledge about them is rapidly growing. These kinds of RNAs are unchanged parts of the genome throughout evolution, that modulate cell growth, differentiation, and apoptosis during diverse physiological and pathological processes including leukemia development. They have the capability to be useful biomarkers for the diagnosis, clinical typing, prognosis, as well as potential therapeutic targets. In this study, we summarized the role of lncRNAs in the expression and function of white blood cells and oncogenic transformation into four main types of leukemia.

Aberrant LncRNA Expression in Leukemia

Leukemia is a common malignant cancer of the hematopoietic system, whose pathogenesis has not been fully elucidated. Long noncoding RNAs (lncRNAs) are transcripts longer than 200 nucleotides without protein-coding function. Recent studies report their role in cellular processes such as the regulation of gene expression, as well as in the carcinogenesis, occurrence, development, and prognosis of various tumors. Evidence indicating relationships between a variety of lncRNAs and leukemia pathophysiology has increased dramatically in the previous decade, with specific lncRNAs expected to serve as diagnostic biomarkers, novel therapeutic targets, and predictors of clinical outcomes. Furthermore, these lncRNAs might offer insight into disease pathogenesis and novel treatment options. This review summarizes progress in studies on the role(s) of lncRNAs in leukemia.

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).

Advances in Epigenetics and Epigenomics in Chronic Lymphocytic Leukemia

Purpose of Review

The development and progression of chronic lymphocytic leukemia (CLL), a highly heterogenous B cell malignancy, are influenced by both genetic and environmental factors. Environmental factors, including pharmacological interventions, can affect the epigenetic landscape of CLL and thereby determine the CLL phenotype, clonal evolution, and clinical outcome. In this review, we critically present the latest advances in the field of CLL epigenomics/epigenetics in order to provide a systematic overview of to-date achievements and highlight the potential of epigenomics approaches in light of novel treatment therapies.

Recent Findings

Recent technological advances have enabled broad and precise mapping of the CLL epigenome. The identification of CLL-specific DNA methylation patterns has allowed for accurate CLL subtype definition, a better understanding of clonal origin and evolution, and the discovery of reliable biomarkers. More recently, studies have started to unravel the prognostic, predictive, and therapeutic potential of mapping chromatin dynamics and histone modifications in CLL. Finally, analysis of non-coding RNA expression has indicated their contribution to disease pathogenesis and helped to define prognostic subsets in CLL.

Summary

Overall, the potential of CLL epigenomics for predicting treatment response and resistance is mounting, especially with the advent of novel targeted CLL therapies.

SFTA1P, LINC00968, GATA6-AS1, TBX5-AS1, and FEZF1-AS1 are crucial long non-coding RNAs associated with the prognosis of lung squamous cell carcinoma

Lung cancer has high incidence and mortality rates, and lung squamous cell carcinoma (LUSC) is a common form of non-small-cell lung carcinoma (NSCLC). The aim of our study was to discover long non-coding RNAs (lncRNAs) associated with LUSC prognosis. RNA-sequencing data obtained from LUSC samples were extracted from The Cancer Genome Atlas database. Using the limma package, differentially expressed genes (DEGs; including differentially expressed lncRNA genes (DELs), coding genes (DECs), and other genes (DEOs)) between LUSC and control samples were analyzed. Using Kaplan-Meier survival analysis, prognosis-associated lncRNAs were further selected. Following the calculation of Pearson's correlation coefficients between DELs and other DEGs, the DEL-DEG co-expression network was visualized using Cytoscape software. Using the clusterProfiler package, potential functions for DECs co-expressed with DELs were predicted. There were 1,305 DEGs in LUSC samples, including 153 DELs, 1,109 DECs, and 43 DEOs. Based on survival analysis, 22 prognosis-associated lncRNAs (including surfactant associated 1, pseudogene (SFTA1P), long intergenic non-protein coding RNA 968 (LINC00968), GATA6 antisense RNA 1, (GATA6-AS1) TBX5 antisense RNA 1 (TBX5-AS1) and FEZF1 antisense RNA 1 (FEZF1-AS1)) in LUSC were selected from these DELs, and the associated abnormal expression levels were also verified in LUSC clinical samples. A DEL-DEG co-expression network was constructed, which involved 93 DELs. Co-expressed DECs were enriched for only 8 prognosis-associated DELs, including LINC00968, SFTA1P, and TBX5-AS1. Specifically, mitogen-activated protein kinase (MAPK) signaling pathway-associated genes were enriched in DECs co-expressed with LINC00968, SFTA1P, GATA6-AS1, TBX5-AS1 and FEZF1-AS1, which may be prognosis-associated lncRNAs in LUSC. In addition, LINC00968 may affect the outcome of patients with LUSC via the MAPK signaling pathway.

Long non-coding RNAs in hematological malignancies: translating basic techniques into diagnostic and therapeutic strategies

Recent studies have revealed that non-coding regions comprise the vast majority of the human genome and long non-coding RNAs (lncRNAs) are a diverse class of non-coding RNAs that has been implicated in a variety of biological processes. Abnormal expression of lncRNAs has also been linked to different human diseases including cancers, yet the regulatory mechanisms and functional effects of lncRNAs are still ambiguous, and the molecular details also need to be confirmed. Unlike protein-coding gene, it is much more challenging to unravel the roles of lncRNAs owing to their unique and complex features such as functional diversity and low conservation among species, which greatly hamper their experimental characterization. In this review, we summarize and discuss both conventional and advanced approaches for the identification and functional characterization of lncRNAs related to hematological malignancies. In particular, the utility and advancement of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system as gene-editing tools are envisioned to facilitate the molecular dissection of lncRNAs via different knock-in/out strategies. Besides experimental considerations specific to lncRNAs, the roles of lncRNAs in the pathogenesis and progression of leukemia are also highlighted in the review. We expect that these insights may ultimately lead to clinical applications including development of biomarkers and novel therapeutic approaches targeting lncRNAs.

Integrative analysis identified mediation effects of lncRNAs on the correlations between methylation and mRNA

The aim of this study was to construct DNA methylation-lncRNA-mRNA interaction trios in peripheral blood mononuclear cells. We first conducted eQTL analyses using genome-wide methylation, lncRNA and mRNA expression data from 43 Chinese females. Next, causal inference test (CIT) was used to detect the lncRNA mediation effects on methylation and mRNA. Methylation-lncRNA cis-eQTL analysis identified 11 significant cis-methylation-lncRNA pairs. Combined with the results from the next lncRNA-mRNA eQTL and methylation-mRNA eQTL analyses, the 11 significant pairs and their corresponding 11,204 target e-mRNAs formed 12,245 trios. Further CIT identified six lncRNAs as mediators in regulating the corresponding pairs between methylation and mRNA. This study detected lncRNAs with mediation effects on the correlations between DNA methylations and a large number of mRNAs.

Long Non-Coding RNAs Guide the Fine-Tuning of Gene Regulation in B-Cell Development and Malignancy

With the introduction of next generation sequencing methods, such as RNA sequencing, it has become apparent that alterations in the non-coding regions of our genome are important in the development of cancer. Particularly interesting is the class of long non-coding RNAs (lncRNAs), including the recently described subclass of circular RNAs (circRNAs), which display tissue- and cell-type specific expression patterns and exert diverse regulatory functions in the cells. B-cells undergo complex and tightly regulated processes in order to develop from antigen naïve cells residing in the bone marrow to the highly diverse and competent effector cells circulating in peripheral blood. These processes include V(D)J recombination, rapid proliferation, somatic hypermutation and clonal selection, posing a risk of malignant transformation at each step. The aim of this review is to provide insight into how lncRNAs including circRNAs, participate in normal B-cell differentiation, and how deregulation of these molecules is involved in the development of B-cell malignancies. We describe the prognostic value and functional significance of specific deregulated lncRNAs in diseases such as acute lymphoblastic leukemia, chronic lymphocytic leukemia, mantle cell lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, Burkitt lymphoma and multiple myeloma, and we provide an overview of the current knowledge on the role of circRNAs in these diseases.

Epigenetic silencing of LPP/miR-28 in multiple myeloma

Aims

miR-28-5- is a tumour suppressor microRNA implicated in cancers. As a CpG island is absent in miR-28-5- but present in its host gene, LPP (LIM domain containing preferred translocation partner in lipoma), we hypothesized that miR-28-5p is epigenetically silenced by promoter DNA methylation of its host gene in multiple myeloma.

Methods

Methylation-specific PCR, verified by quantitative bisulfite pyrosequencing, was employed to study methylation of LPP/miR-28 in healthy controls (n=10), human myeloma cell lines (HMCLs) (n=15), and primary myeloma marrow samples at diagnosis (n=49) and at relapse (n=18). Quantitative reverse transcription PCR was used to investigate expression of miR-28-5p, LPP and CCND1.

Results

LPP/miR-28 was completely unmethylated in all healthy controls and 12 (80%) HMCLs, but partially methylated in three (20%) HMCLs. Methylation of LPP/miR-28 correlated with low expression of miR-285p (p=0.012) and LPP (p=0.037) in HMCLs. In RPMI-8226R cells, in which LPP/miR-28 was partially methylated, 5-AzadC treatment led to demethylation of LPP/miR-28 and re-expression of both miR-28-5p (p=0.0007) and LPP (p=0.0007), whereas continuous culture without 5-AzadC restored LPP/miR-28 methylation and reduced expression of both miR-28-5p (p=0.0013) and LPP (p=0.0025). Moreover, a known miR-28-5p target, CCND1, was expressed at higher levels in HMCLs with LPP/miR-28 methylation than those without, consistent with a tumour suppressor role of miR-28-5p in myeloma. However, in primary samples, LPP/miR-28 was methylated in two (4.1%) at diagnosis, whereas none at relapse.

Conclusions

This is the first report of epigenetic regulation of the intronic miR-28-5p expression by promoter DNA methylation of its host gene, hence warrants further study in different cancers.

Effects of long non-coding RNA H19 and microRNA let7a expression on thyroid cancer prognosis

This study aims to explore the effects of long non-coding RNA H19 (lncRNA H19) and microRNA let7a (miRNA let7a) expression on the prognosis of thyroid cancer (TC). This may aid in the discovery of more effective treatment and prognosis approaches for TC. Between January 2008 and January 2011, 131 TC tissues and adjacent tissues were obtained from TC patients. An additional 122 normal thyroid tissues were also collected as normal controls from patients with benign thyroid lesions. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect lncRNA H19 and miRNA let7a mRNA expression. Five-year follow-ups were conducted. A Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic values of lncRNA H19 and miRNA let7a in TC. The Kaplan-Meier method was applied to analyze the 5-year survival rate of TC patients. Univariate and multivariate factor analyses were employed to analyze the prognostic factors of TC. The lncRNA H19 mRNA expression was higher while the miRNA let7a mRNA expression was lower in TC tissues than, in the normal thyroid tissues and adjacent tissues. The area under the ROC curve (AUC) of lncRNA H19 and miRNA let7a were 0.801 and 0.116, with sensitivity at 72.5% and 84%, as well as specificity 75.4% and 77%, respectively. In TC patients with tumor diameters≥1.0cm, lncRNA H19 mRNA expression was elevated, but miRNA let7a mRNA expression was reduced. This was also evident in TC patients with TNM stages III+IV and those with lymph node metastasis. TC patients with a lower 5-year survival rate showed upregulated levels of lncRNA H19 expression and, downregulated levels of miRNA let7a expression. LncRNA H19 and miRNA let7a expression, tumor diameter, TNM stage and lymph node metastasis were independent prognostic factors of TC. This study demonstrated that increased lncRNA H19 and decreased miRNA let7a expression levels are associated with poor prognosis in TC patients. An inverse relationship between lncRNA H19 and miRNA let7a expression levels was exhibited.

Long non-coding RNAs in B-cell malignancies: a comprehensive overview

B-cell malignancies constitute a large part of hematological neoplasias. They represent a heterogeneous group of diseases, including Hodgkin's lymphoma, most non-Hodgkin's lymphomas (NHL), some leukemias and myelomas. B-cell malignancies reflect defined stages of normal B-cell differentiation and this represents the major basis for their classification. Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts longer than 200 nucleotides, for which many recent studies have demonstrated a function in regulating gene expression, cell biology and carcinogenesis. Deregulated expression levels of lncRNAs have been observed in various types of cancers including hematological malignancies. The involvement of lncRNAs in cancer initiation and progression and their attractive features both as biomarker and for therapeutic research are becoming increasingly evident. In this review, we summarize the recent literature to highlight the status of the knowledge of lncRNAs role in normal B-cell development and in the pathogenesis of B-cell tumors.