Circulating microRNA expression is associated with genetic subtype and survival of multiple myeloma

LNA-i-miR-221 activity in colorectal cancer: A reverse translational investigation

Colorectal cancer (CRC) is one of the most common malignancies and a relevant cause of cancer-related deaths worldwide. Dysregulation of microRNA (miRNA) expression has been associated with the development and progression of various cancers, including CRC. Among them, miR-221 emerged as an oncogenic driver, whose high expression is associated with poor patient prognosis. The present study was conceived to investigate the anti-CRC activity of miR-221 silencing based on early clinical data achieved from a first-in-human study by our group. Going back from bedside to bench, we demonstrated that LNA-i-miR-221 reduces cell viability, induces apoptosis in vitro, and impairs tumor growth in preclinical in vivo models of CRC. Importantly, we disclosed that miR-221 directly targets TP53BP2, which, together with TP53INP1, is known as a positive regulator of the TP53 apoptotic pathway. We found that (1) both these genes are overexpressed following miR-221 inhibition, (2) the strong anti-tumor activity of LNA-i-miR-221 was selectively observed on TP53 wild-type cells, and (3) this activity was reduced in the presence of the TP53-inhibitor Pifitrin-α. Our data pave the way to further investigations on TP53 functionality as a marker predictive of response to miR-221 silencing, which might be relevant for clinical applications.

An Enhanced Quantitative Reverse Transcription-PCR Approach for Measuring Circulating MicroRNAs

Short (22 nt) RNAs called microRNAs (miRNAs) bind to and inhibit target messenger RNAs in gene regulatory networks. Recent study suggests that miRNAs circulate in a stable, cell-free form and that particular miRNAs in plasma or serum may be biomarkers for cancer and other diseases. Circulating miRNAs as biomarkers provide distinct challenges including pre-analytic variance and data standardization. We describe our qRT-PCR approach for measuring circulating miRNAs as biomarkers, as well as sample preparation, experimental design, and data processing issues.

miR-26a/30d/152 are reliable reference genes for miRNA quantification in skin wound age estimation

MicroRNAs (miRNAs) are a class of small non-coding RNAs that exert their biological functions as negative regulators of gene expression. They are involved in the skin wound healing process with a dynamic expression pattern and can therefore potentially serve as biomarkers for skin wound age estimation. However, no reports have described any miRNAs as suitable reference genes (RGs) for miRNA quantification in wounded skin or samples with post-mortem changes. Here, we aimed to identify specific miRNAs as RGs for miRNA quantification to support further studies of skin wound age estimation. Overall, nine miRNAs stably expressed in mouse skin at certain posttraumatic intervals (PTIs) were preselected by next-generation sequencing as candidate RGs. These nine miRNAs and the commonly used reference genes (comRGs: U6, GAPDH, ACTB, 18S, 5S, LC-Ogdh) were quantitatively examined using quantitative real-time reverse-transcription polymerase chain reaction at different PTIs during skin wound healing in mice. The stabilities of these genes were evaluated using four independent algorithms: GeNorm, NormFinder, BestKeeper, and comparative Delta Ct. Stability was further evaluated in mice with different post-mortem intervals (PMIs). Overall, mmu-miR-26a-5p, mmu-miR-30d-5p, and mmu-miR-152-3p were identified as the most stable genes at both different PTIs and PMIs. These three miRNA RGs were additionally validated and compared with the comRGs in human samples. After assessing using one, two, or three miRNAs in combination for stability at different PTIs, PMIs, or in human samples, the set of miR-26a/30d/152 was approved as the best normalizer. In conclusion, our data suggest that the combination of miR-26a/30d/152 is recommended as the normalization strategy for miRNA qRT-PCR quantification in skin wound age estimation.

Key points

The small size of miRNAs makes them less susceptible to post-mortem autolysis or putrefaction, leading to their potential use in wound age estimation.Studying miRNAs as biological indicators of skin wound age estimation requires the selection and validation of stable reference genes because commonly used reference genes, such as U6, ACTB, GAPDH, 5S, 18S, and LC-Ogdh, are not stable.miR-26a/30d/152 are stable and reliable as reference genes and their use in combination is a recommended normalization strategy for miRNA quantitative analysis in wounded skin.

miRNAs driving diagnosis, progression, and drug resistance in multiple myeloma

Multiple myeloma (MM) is a tumor of transformed plasma cells. It's the second most common hematologic cancer after non-Hodgkin lymphoma. MM is a complex disease with many different risk factors, including ethnicity, race, and epigenetics. The microRNAs (miRNAs) are a critical epigenetic factor in multiple myeloma, influencing key aspects such as pathogenesis, prognosis, and resistance to treatment. They have the potential to assist in disease diagnosis and modulate the resistance behavior of MM towards therapeutic regimens. These characteristics could be attributed to the modulatory effects of miRNAs on some vital pathways such as NF-KB, PI3k/AKT, and P53. This review discusses the role of miRNAs in MM with a focus on their role in disease progression, diagnosis, and therapeutic resistance.

Decoding the role of miRNAs in multiple myeloma pathogenesis: A focus on signaling pathways

Multiple myeloma (MM) is a cancer of plasma cells that has been extensively studied in recent years, with researchers increasingly focusing on the role of microRNAs (miRNAs) in regulating gene expression in MM. Several non-coding RNAs have been demonstrated to regulate MM pathogenesis signaling pathways. These pathways might regulate MM development, apoptosis, progression, and therapeutic outcomes. They are Wnt/β-catenin, PI3K/Akt/mTOR, P53 and KRAS. This review highlights the impending role of miRNAs in MM signaling and their relationship with MM therapeutic interventions.

Exosomal microRNAs in cancer: Potential biomarkers and immunotherapeutic targets for immune checkpoint molecules

Exosomes are small extracellular vesicles with a lipid bilayer structure secreted from different cell types which can be found in various body fluids including blood, pleural fluid, saliva and urine. They carry different biomolecules including proteins, metabolites, and amino acids such as microRNAs which are small non-coding RNAs that regulate gene expression and promote cell-to-cell communication. One main function of the exosomal miRNAs (exomiRs) is their role in cancer pathogenesis. Alternation in exomiRs expression could indicate disease progression and can regulate cancer growth and facilitate drug response/resistance. It can also influence the tumour microenvironment by controlling important signaling that regulating immune checkpoint molecules leading to activation of T cell anti-tumour immunity. Therefore, they can be used as potential novel cancer biomarkers and innovative immunotherapeutic agents. This review highlights the use of exomiRs as potential reliable biomarkers for cancer diagnosis, treatment response and metastasis. Finally, discuses their potential as immunotherapeutic agents to regulate immune checkpoint molecules and promote T cell anti-tumour immunity.

Current perspectives on interethnic variability in multiple myeloma: Single cell technology, population pharmacogenetics and molecular signal transduction

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This review discusses the emerging single cell technologies and applications in Multiple myeloma (MM), population pharmacogenetics of MM, resistance to chemotherapy, genetic determinants of drug-induced toxicity, molecular signal transduction.

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The role(s) of epigenetics and noncoding RNAs including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) that influence the risk and severity of MM are also discussed.

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It is understood that ethnic component acts as a driver of variable response to chemotherapy in different sub-populations globally.

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This review augments our understanding of genetic variability in ‘myelomagenesis’ and drug-induced toxicity, myeloma microenvironment at the molecular and cellular level, and developing precision medicine strategies to combat this malignancy.

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The emerging single cell technologies hold great promise for enhancing our understanding of MM tumor heterogeneity and clonal diversity.

Multiple myeloma (MM) is an aggressive cancer characterised by malignancy of the plasma cells and a rising global incidence. The gold standard for optimum response is aggressive chemotherapy followed by autologous stem cell transplantation (ASCT). However, majority of the patients are above 60 years and this presents the clinician with complications such as ineligibility for ASCT, frailty, drug-induced toxicity and differential/partial response to treatment. The latter is partly driven by heterogenous genotypes of the disease in different subpopulations. In this review, we discuss emerging single cell technologies and applications in MM, population pharmacogenetics of MM, resistance to chemotherapy, genetic determinants of drug-induced toxicity, molecular signal transduction, as well as the role(s) played by epigenetics and noncoding RNAs including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) that influence the risk and severity of the disease. Taken together, our discussions further our understanding of genetic variability in ‘myelomagenesis’ and drug-induced toxicity, augment our understanding of the myeloma microenvironment at the molecular and cellular level and provide a basis for developing precision medicine strategies to combat this malignancy.

Liquid biopsy: an evolving paradigm for the biological characterisation of plasma cell disorders

Liquid biopsies-a source of circulating cell-free nucleic acids, proteins and extracellular vesicles-are currently being explored for the quantitative and qualitative characterisation of the tumour genome and as a mode of non-invasive therapeutic monitoring in cancer. Emerging data suggest that liquid biopsies might offer a potentially simple, non-invasive, repeatable strategy for diagnosis, prognostication and therapeutic decision making in a genetically heterogeneous disease like multiple myeloma (MM), with particular applicability in subsets of patients where conventional markers of disease burden may be less informative. In this review, we describe the emerging utility of the evaluation of circulating tumour DNA, extracellular RNA, cell-free proteins and metabolites and extracellular vesicles in MM.

MicroRNAs as a Potential New Preventive Approach in the Transition from Asymptomatic to Symptomatic Multiple Myeloma Disease

Simple Summary

Multiple myeloma (MM) is the second most common haematologic malignancy, and it remains an incurable disease despite the advances of novel therapies. It is characterised by a multistep process that arises from a pre-malignant asymptomatic status-defined monoclonal gammopathy of undetermined significance (MGUS), evolves to a middle stage named smouldering myeloma phase (SMM), and culminates in the active disease (MM). Identification of early and non-invasive markers of the disease progression is currently an active field of investigation. In this review, we discuss the role and significance of microRNAs (miRNAs) as potential diagnostic biomarkers to predict the clinical transition from MGUS/SMM status to MM.

Abstract

Multiple myeloma (MM) is a hematological malignancy characterised by proliferation of clonal plasma cells (PCs) within the bone marrow (BM). Myelomagenesis is a multi-step process which goes from an asymptomatic phase, defined as monoclonal gammopathy of undetermined significance (MGUS), to a smouldering myeloma (SMM) stage, to a final active MM disease, characterised by hypercalcemia, renal failure, bone lesions anemia, and higher risk of infections. Overall, microRNAs (miRNAs) have shown to significantly impact on MM tumorigenesis, as a result of miRNA-dependent modulation of genes involved in pathways known to be crucial for MM pathogenesis and disease progression. We aim to revise the literature related to the role of miRNAs as potential diagnostic and prognostic biomarkers, thus highlighting their key role as novel players within the field of MM and related premalignant conditions.

Circulating miRNAs as Auxiliary Diagnostic Biomarkers for Multiple Myeloma: A Systematic Review, Meta-Analysis, and Recommendations

Multiple myeloma (MM) is a hematologic malignancy characterized by aberrant expansion of monoclonal plasma cells with high mortality and severe complications due to the lack of early diagnosis and timely treatment. Circulating miRNAs have shown potential in the diagnosis of MM with inconsistent results, which remains to be fully assessed. Here we updated a meta-analysis with relative studies and essays published in English before Jan 31, 2021. After steps of screening, 32 studies from 11 articles that included a total of 627 MM patients and 314 healthy controls were collected. All data were analyzed by REVMAN 5.3 and Stata MP 16, and the quality of included literatures was estimated by Diagnostic Accuracy Study 2 (QUADAS-2). The pooled area under the curve (AUC) shown in summary receiver operating characteristic (SROC) analyses of circulating miRNAs was 0.87 (95%CI, 0.81–0.89), and the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were 0.79, 0.86, 5, 0.27, 22, respectively. Meta-regression and subgroup analysis exhibited that “miRNA cluster”, patient “detailed stage or Ig isotype” accounted for a considerable proportion of heterogeneity, revealing the importance of study design and patient inclusion in diagnostic trials; thus standardized recommendations were proposed for further studies. In addition, the performance of the circulating miRNAs included in MM prognosis and treatment response prediction was summarized, indicating that they could serve as valuable biomarkers, which would expand their clinical application greatly.

miRNAs mediated drug resistance in hematological malignancies

Despite improvements in the therapeutic approaches for hematological malignancies in the last decades, refractory disease still occurs, and cancer drug resistance still remains a major hurdle in the clinical management of these cancer patients. The investigation of this problem has been extensive and different mechanism and molecules have been associated with drug resistance. MicroRNAs (miRNAs) have been described as having an important action in the emergence of cancer, including hematological tumors, and as being major players in their progression, aggressiveness and response to treatments. Moreover, miRNAs have been strongly associated with cancer drug resistance and with the modulation of the sensitivity of cancer cells to a wide array of anticancer drugs. Furthermore, this role has also been reported for miRNAs packaged into extracellular vesicles (EVs-miRNAs), which in turn have been described as essential for the horizontal transfer of drug resistance to sensitive cells. Several studies have been suggesting the use of miRNAs as biomarkers for drug response and clinical outcome prediction, as well as promising therapeutic tools in hematological diseases. Indeed, the combination of miRNA-based therapeutic tools with conventional drugs contributes to overcome drug resistance. This review addresses the role of miRNAs in the pathogenesis of hematological malignances, namely multiple myeloma, leukemias and lymphomas, highlighting their important action (either in their cell-free circulating form or within circulating EVs) in drug resistance and their potential clinical applications.

Interleukin-6 gene-174 G/C promoter polymorphism is not associated with multiple myeloma susceptibility: evidence from meta-analysis: A systematic review and meta-analysis

PURPOSE

Presently, whether interleukin-6 (IL-6) gene-174 G/C promoter polymorphism is correlated to the susceptibility of multiple myeloma (MM) remains controversial. For this reason, the method of meta-analysis was applied to exploring the association between IL-6 gene-174 G/C promoter polymorphism and MM.

METHOD

Two independent researchers systematically searched PubMed, EMBASE, Google academic, Cochrane Library and Chinese literature databases to screen case-control studies on IL-6 gene-174 G/C promoter polymorphism and MM susceptibility. The retrieval period was limited from the formation of the database to January 2020, and data analysis was conducted by employing Stata 11.0 software.

RESULT

Seven articles were ultimately included in the present study, including 594 MM patients and 681 controls. Integration analysis exhibited that compared with GC or CC genotype, GG genotype did not increase MM susceptibility (OR = 0.95, 95% CI 0.75-1.22; OR = 0.79, 95% CI 0.52-1.19, respectively). Further, in comparison with CC genotype, GC genotype also presented no effect on increasing MM susceptibility (OR = 0.79, 95% CI 0.53-1.16), while compared with GC+CC genotype, GG genotype had no significant relationship with MM susceptibility (OR = 0.94, 95% CI 0.75-1.19). In subsequent analysis, an observation was made that allele G or C was not related to MM susceptibility (OR = 0.92, 95% CI 0.76-1.12). Funnel chart and Begg test did not reveal publication bias in the included articles.

CONCLUSION

The results of the present study advocate that there is no testimony to support the relationship between IL-6 gene-174 G/C promoter polymorphism and MM susceptibility.

Liquid biopsy technologies for hematological diseases

Since the discovery of circulating tumor cells in 1869, technological advances in studying circulating biomarkers from patients' blood have made the diagnosis of nonhematologic cancers less invasive. Technological advances in the detection and analysis of biomarkers provide new opportunities for the characterization of other disease types. When compared with traditional biopsies, liquid biopsy markers, such as exfoliated bladder cancer cells, circulating cell-free DNA (cfDNA), and extracellular vesicles (EV), are considered more convenient than conventional biopsies. Liquid biopsy markers undoubtedly have the potential to influence disease management and treatment dynamics. Our main focuses of this review will be the cell-based, gene-based, and protein-based key liquid biopsy markers (including EV and cfDNA) in disease detection, and discuss the research progress of these biomarkers used in conjunction with liquid biopsy. First, we highlighted the key technologies that have been broadly adopted used in hematological diseases. Second, we introduced the latest technological developments for the specific detection of cardiovascular disease, leukemia, and coronavirus disease. Finally, we concluded with perspectives on these research areas, focusing on the role of microfluidic technology and artificial intelligence in point-of-care medical applications. We believe that the noninvasive capabilities of these technologies have great potential in the development of diagnostics and can influence treatment options, thereby advancing precision disease management.

Identification of MicroRNAs With In Vivo Efficacy in Multiple Myeloma-related Xenograft Models

BACKGROUND/AIM

Multiple myeloma is a B-cell neoplasm, which can spread within the marrow of the bones forming many small tumors. In advanced disease, multiple myeloma can spread to the blood as plasma cell leukemia. In some cases, a localized tumor known as plasmacytoma is found within a single bone. Despite the approval of several agents such as melphalan, corticosteroids, proteasome inhibitors, thalidomide-based immuno-modulatory agents, histone deacetylase inhibitors, a nuclear export inhibitor and monoclonal antibodies daratuzumab and elatuzumab, the disease presently remains uncurable.

MATERIALS AND METHODS

In order to define new targets and treatment modalities we searched the literature for microRNAs, which increase or inhibit in vivo efficacy in multiple-myeloma-related xenograft models.

RESULTS AND CONCLUSION

We identified six up-regulated and twelve down-regulated miRs, which deserve further preclinical validation.

The effect of miR-223 on cellular behaviour in non-5q myelodysplastic syndromes through targeting RPS14

Myelodysplastic syndromes (MDS) are characterised by impaired haematopoiesis and a high risk of leukaemic transformation. A decrease in RPS14 expression in non-5q MDS patients was confirmed by immunohistochemical analyses of MDS bone marrow biopsies. To determine the cause of RPS14 reduction in non-5q MDS, we analysed the 3'-UTR of RPS14 and demonstrated that miR-223 binds to the 3'-UTR of RPS14 by bioinformatics-based approach combined with the luciferase reporter assay. Using quantitative real-time polymerase chain reaction (qRT-PCR) analysis, we observed a significantly increased expression of miR-223 in CD34+ cells and SKM-1 cells derived from non-5q MDS patients in vitro and demonstrated a correlation between miR-223 levels and red blood cell counts. Exogenous miR-223 expression in SKM-1 cells could also inhibit RPS14 expression. In functional studies, overexpression of miR-223 was shown to promote cell proliferation and inhibit cell apoptosis in SKM-1 cells, and to impair erythroid differentiation in haemin-induced K562 cells. Taken together, our results revealed that the overexpression of miR-223 in MDS is closely associated with cell transformation and erythroid differentiation arrest, which is most likely mediated by targeting RPS14.

Liquid biopsies for multiple myeloma in a time of precision medicine

Multiple myeloma (MM) is a challenging, progressive, and highly heterogeneous hematological malignancy. MM is characterized by multifocal proliferation of neoplastic plasma cells in the bone marrow (BM) and sometimes in extramedullary organs. Despite the availability of novel drugs and the longer median overall survival, some patients survive more than 10 years while others die rapidly. This heterogeneity is mainly driven by biological characteristics of MM cells, including genetic abnormalities. Disease progressions are mainly due to the inability of drugs to overcome refractory disease and inevitable drug-resistant relapse. In clinical practice, a bone marrow biopsy, mostly performed in one site, is still used to access the genetics of MM. However, BM biopsy use is limited by its invasive nature and by often not accurately reflecting the mutational profile of MM. Recent insights into the genetic landscape of MM provide a valuable opportunity to implement precision medicine approaches aiming to enable better patient profiling and selection of targeted therapies. In this review, we explore the use of the emerging field of liquid biopsies in myeloma patients considering current unmet medical needs, such as assessing the dynamic mutational landscape of myeloma, early predictors of treatment response, and a less invasive response monitoring.

The power of microRNAs as diagnostic and prognostic biomarkers in liquid biopsies

In the last decades, progresses in medical oncology have ameliorated the treatment of patients and their outcome. However, further improvements are still necessary, in particular for certain types of tumors such as pancreatic, gastric, and lung cancer as well as acute myeloid leukemia where early detection and monitoring of the disease are crucial for final patient outcome. Liquid biopsy represents a great advance in the field because it is less invasive, less time-consuming, and safer compared to classical biopsies and it can be useful to monitor the evolution of the disease as well as the response of patients to therapy. Liquid biopsy allows the detection of circulating tumor cells, nucleic acids, and exosomes not only in blood but also in different biological fluids: urine, saliva, pleural effusions, cerebrospinal fluid, and stool. Among the potential biomarkers detectable in liquid biopsies, microRNAs (miRNAs) are gaining more and more attention, since they are easily detectable, quite stable in biological fluids, and show high sensitivity. Many data demonstrate that miRNAs alone or in combination with other biomarkers could improve the diagnostic and prognostic power for many different tumors. Despite this, standardization of methods, sample preparation, and analysis remain challenging and a huge effort should be made to address these issues before miRNA biomarkers can enter the clinic. This review summarizes the main findings in the field of circulating miRNAs in both solid and hematological tumors.

Circulating microRNAs and Their Role in Multiple Myeloma

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by bone marrow infiltration of clonal plasma cells. The recent literature has clearly demonstrated clonal heterogeneity in terms of both the genomic and transcriptomic signature of the tumor. Of note, novel studies have also highlighted the importance of the functional cross-talk between the tumor clone and the surrounding bone marrow milieu, as a relevant player of MM pathogenesis. These findings have certainly enhanced our understanding of the underlying mechanisms supporting MM pathogenesis and disease progression. Within the specific field of small non-coding RNA-research, recent studies have provided evidence for considering microRNAs as a crucial regulator of MM biology and, in this context, circulating microRNAs have been shown to potentially contribute to prognostic stratification of MM patients. The present review will summarize the most recent studies within the specific topic of microRNAs and circulating microRNAs in MM.

Identifying the optimal target genes associated with multiple myeloma by a novel bioinformatical analysis

Multiple myeloma (MM) is one of the most frequent malignant hematopoietic diseases, the pathogenesis of which remains unclear. It is well known that miRNAs are aberrantly expressed in many tumors, thus, investigating the target genes of miRNAs contributes to understanding the functional effect of miRNAs on MM. In this study, plasma samples of 147 patients with MM and 15 normal donors were collected. Using high-throughout microarray and limma package to screen the differentially expressed genes. Furthermore, to accurately predict the optimal target genes of MM, the logFC, targetScanCS and targetScanPCT values of known genes in four miRNAs (i.e. has-miR-21, has-miR-20a, has-miR-148a and has-miR-99b) were used to compute the targetScore values. As a result, 171 genes with larger difference were screened out using t-test, F-test and eBayes statistics analysis. Furthermore, 34 potential target genes associated with MM were selected by integrating the differentially expressed genes (DEGs) and the genes obtained by targetScore algorithm. Additionally, combining with the mutated genes in MM and the obtained DEGs, 41 consistently expressed genes were obtained. Finally, 5 optimal target genes, including SYK, LCP1, HIF1A, ALDH1A1 and MAFB, were screened out by the intersection of 34 DEGs and 41 mutated genes. In a word, this novel target gene prediction algorithm may contribute to improve our understanding on the pathogenesis of miRNAs in MM, which open up a new approach for future study.

Expanding the repertoire of miRNAs and miRNA-offset RNAs expressed in multiple myeloma by small RNA deep sequencing

Microarray analysis of the multiple myeloma (MM) miRNome has unraveled the differential expression of miRNAs in cytogenetic subgroups, their involvement in the tumor biology and their effectiveness in prognostic models. Herein, the small RNA transcriptional landscape in MM has been investigated exploiting the possibilities offered by small RNA-seq, including accurate quantification of known mature species, discovery and characterization of isomiRs, and miRNA-offset RNAs (moRNAs). Matched small RNA-seq and miRNA GeneChip^® microarray expression profiles were obtained in a representative panel of 30 primary MM tumors, fully characterized for genomic aberrations and mutations. RNA-seq and microarray gave concordant estimations of known species. Enhanced analysis of RNA-seq data with the miR&moRe pipeline led to the characterization of 655 known and 17 new mature miRNAs and of 74 moRNAs expressed in the considered cohort, 5 of which (moR-150-3p, moR-24-2-5p, moR-421-5p, moR-21-5p, and moR-6724-5p) at high level. Ectopic expression of miR-135a-3p in t(4;14) patients, upregulation of moR-150-3p and moR-21-5p in t(14;16)/t(14;20) samples, and of moR-6724-1-5p in patients overexpressing CCND1 were uncovered and validated by qRT-PCR. Overall, RNA-seq offered a more complete overview of small non-coding RNA in MM tumors, indicating specific moRNAs that demand further investigations to explore their role in MM biology.

SUN2: A potential therapeutic target in cancer

The incidence of cancer is increasing at an alarming rate despite recent advances in prevention strategies, diagnostics and therapeutics for various types of cancer. The identification of novel biomarkers to aid in prognosis and treatment for cancer is urgently required. Uncontrolled proliferation and dysregulated apoptosis are characteristics exhibited by cancer cells in the initiation of various types of cancer. Notably, aberrant expression of crucial oncogenes or cancer suppressors is a defining event in cancer occurrence. Research has demonstrated that SAD1/UNC84 domain protein-2 (SUN2) serves a suppressive role in breast cancer, atypical teratoid/rhabdoid tumors and lung cancer progression. Furthermore, SUN2 inhibits cancer cell proliferation, migration and promotes apoptosis. Recent reports have also shown that SUN2 serves prominent roles in resistance to the excessive DNA damage that destabilizes the genome and promotes cancer development, and these functions of SUN2 are critical for evading initiation of cancer. Additionally, increasing evidence has demonstrated that SUN2 is involved in maintaining cell nuclear structure and appears to be a central component for organizing the natural nuclear architecture in cancer cells. The focus of the present review is to provide an overview on the pharmacological functions of SUN2 in cancers. These findings suggest that SUN2 may serve as a promising therapeutic target and novel predictive marker in various types of cancer.

NRF2 Is One of the Players Involved in Bone Marrow Mediated Drug Resistance in Multiple Myeloma

Multiple myeloma with clonal plasma expansion in bone marrow is the second most common hematologic malignancy in the world. Though the improvement of outcomes from the achievement of novel agents in recent decades, the disease progresses and leads to death eventually due to the elusive nature of myeloma cells and resistance mechanisms to therapeutic agents. In addition to the molecular and genetic basis of resistance pathomechanisms, the bone marrow microenvironment also contributes to disease progression and confers drug resistance in myeloma cells. In this review, we focus on the current state of the literature in terms of critical bone marrow microenvironment components, including soluble factors, cell adhesion mechanisms, and other cellular components. Transcriptional factor nuclear factor erythroid-derived-2-like 2 (NRF2), a central regulator for anti-oxidative stresses and detoxification, is implicated in chemoresistance in several cancers. The functional roles of NRF2 in myeloid-derived suppressor cells and multiple myeloma cells, and the potential of targeting NRF2 for overcoming microenvironment-mediated drug resistance in multiple myeloma are also discussed.

The potential function of microRNAs as biomarkers and therapeutic targets in multiple myeloma

Multiple myeloma (MM), accounting for ~1% of all types of human cancer and 13% of all hematological malignancies, is characterized by the malignant proliferation of monoclonal plasma cells (PCs) in the bone marrow. MM leads to end stage organ impairment, including bone lesions, renal dysfunction, hypercalcemia and anemia. So far, the specific pathogenesis of MM remains unclear and no early-stage sensitive biomarker of MM has been well characterized. Furthermore, treating MM is difficult, as the majority of patients eventually relapse or become refractory following treatment using presently available methods. To date, a number of studies have demonstrated that microRNAs (miRNAs) may serve crucial functions in the progression of numerous cancers, including MM. During the tumorigenesis and pathogenesis of MM, there are multiple carcinogenic events that involve the pernicious transformation from normal to malignant PCs. miRNAs, as oncogenes or tumor suppressors, regulate MM progression-related signaling pathways. In the present review, the up-to-date preliminary basic studies and associated clinical works on the underlying mechanisms of aberrant miRNA profiling in MM have been summarized, including an evaluation of its value as a potential biomarker and a novel therapeutic strategy for MM.

EZH2 inhibition in multiple myeloma downregulates myeloma associated oncogenes and upregulates microRNAs with potential tumor suppressor functions

Multiple Myeloma (MM) is a plasma cell tumor localized to the bone marrow (BM). Despite the fact that current treatment strategies have improved patients' median survival time, MM remains incurable. Epigenetic aberrations are emerging as important players in tumorigenesis making them attractive targets for therapy in cancer including MM. Recently, we suggested the polycomb repressive complex 2 (PRC2) as a common denominator of gene silencing in MM and presented the PRC2 enzymatic subunit enhancer of zeste homolog 2 (EZH2) as a potential therapeutic target in MM. Here we further dissect the anti-myeloma mechanisms mediated by EZH2 inhibition and show that pharmacological inhibition of EZH2 reduces the expression of MM-associated oncogenes; IRF-4, XBP-1, PRDM1/BLIMP-1 and c-MYC. We show that EZH2 inhibition reactivates the expression of microRNAs with tumor suppressor functions predicted to target MM-associated oncogenes; primarily miR-125a-3p and miR-320c. ChIP analysis reveals that miR-125a-3p and miR-320c are targets of EZH2 and H3K27me3 in MM cell lines and primary cells. Our results further highlight that polycomb-mediated silencing in MM includes microRNAs with tumor suppressor activity. This novel role strengthens the oncogenic features of EZH2 and its potential as a therapeutic target in MM.

Expression of the miR-148/152 Family in Acute Myeloid Leukemia and its Clinical Significance

Background

MicroRNAs (miRNAs) play an important role in the development and progression of acute myeloid leukemia (AML). The miR-148/152 family has been reported to be express differently in various kinds of tumors. We investigated the expression level of the miR-148/152 family in AML patients and their clinical significance.

Material/Methods

Expression levels of the miR-148/152 family in 80 patients with newly diagnosed AML and 20 healthy participants were analyzed by qRT-PCR. We also evaluated the relationship between the expression levels of the miR-148/152 family and clinicopathological features of AML patients.

Results

Compared with healthy controls, we found a significant lower expression of downregulated miR-148/152 in AML patients (p<0.0001). The expression of miR148/152 family was associated with various AML clinicopathological risk parameters including FAB classifications, cytogenetics, and gene mutations. The number of patients with high expression levels of miR-148a/b was significantly increased in the low-risk group and significantly decreased in the high-risk group. (p=0.025, p=0.000, respectively). Patients with higher expression of miR-148b showed a higher complete remission (CR) rate (p=0.043). Importantly, higher expression of miR-148a/b was correlated with lower relapse rate (p=0.035, p=0.027, respectively) and showed a longer relapse-free survival (RFS) (p=0.0321, p=0.002, respectively). In the subgroup analysis, RFS was significantly affected by the expression of miR-148a/b in patients the high and the intermediate-risk groups (p=0.0499, p=0.0114, respectively).

Conclusions

The expression levels of the miR-148/152 family were lower in patients with AML compared to healthy controls, and were associated with various AML clinicopathological parameters and therapeutic effect. The miR-148/152 family may prove to be a new biomarker for AML.

Evaluating the prognostic value of miR-148/152 family in cancers: based on a systemic review of observational studies

Background

The prognostic significance of MicroRNA-148/152 (miR-148/152) family expression in various cancers has been investigated by many studies with inconsistent results. To address this issue, we performed a meta-analysis to clarify this relationship.

Materials and Methods

Eligible studies were recruited by a systematic literature search and assessed the quality of included studies based on Quality In Prognosis Studies (QUIPS) and Newcastle-Ottawa Scale (NOS). Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for overall survival (OS) and disease free survival/progressive free survival/recurrence free survival (DFS/PFS/RFS) were calculated to estimate the effects of miR-148/152 family expression on prognosis.

Results

A final total of 23 articles (26 studies) were considered in evidence synthesis. A significant association was observed between low miR-148a level and poor OS in patients (HR = 1.59, 95% CI: 1.14 – 2.20, P = 0.00), especially with digestive tract cancer (DTC) (HR = 1.29, 95% CI: 1.03–1.63, P = 0.03), and another significant association was observed between low miR-148b level and poor OS in patients (HR=2.09, 95% CI: 1.70–2.56, P = 0.00), especially with (hepatocellular carcinoma) HCC (HR = 1.97, 95% Cl: 1.52–2.56, P = 0.00) and non-small cell lung cancer (NSCLC) (HR = 2.29, 95% Cl: 1.64–3.18, P = 0.00). The significant correlation between miR-152 and DFS/RFS was found in our research (HR = 3.49, 95% Cl: 1.13–10.08, P = 0.03).

Conclusions

Our findings suggest that low miR-148/152 family expression is significantly associated with poor prognosis and may be a feasible prognostic biomarker in some cancers, especially in HCC and NSCLC.

Oncogenic role of microRNA-20a in human multiple myeloma

microRNAs are important in cancer biogenesis and development. However, their underlying mechanisms in multiple myeloma (MM) are barely characterized. microRNA-20a (miR-20a) is a member of the microRNA-17-92 cluster. It has been implicated in various cancers, regulating the proliferation and invasion of cancer cells in vitro. Compared with healthy donors, it also has been reported to be elevated in plasma of MM patients. Here, we investigated the function of miR-20a. Our results showed that it promotes proliferation and inhibits apoptosis of MM cells in vitro by inhibiting early growth response protein 2. The effects of miR-20a were also evaluated in MM xenograft models of SCID/NOD mice. Apparent antitumor activity was achieved in xenograft mice injected with miR-20a inhibitor, while mimics of miR-20a significantly promoted tumor growth. These data indicate that miR-20a plays a crucial role in the biology of MM and represents a potential target for novel therapies for MM patients.

Role of epigenetics-microRNA axis in drug resistance of multiple myeloma

Despite administration of novel therapies, multiple myeloma (MM) remains incurable with resistance to drugs leading to relapse in most patients. Thus, it is critical to understand the detailed mechanisms underlying the drug resistance of MM and develop more effective therapeutic strategies. Genetic abnormalities are well known to play a central role in MM pathogenesis and therapy resistance; however, epigenetic aberrations mainly affecting the patterns of DNA methylation/histone modifications of genes (especially tumor suppressors) and miRNAs have also been shown to be involved. Importantly, while epigenetic silencing of miRNAs in MM is well documented, some epigenetic markers are known to be direct targets of miRNAs particularly the recently described "epimiRNAs". Drugs targeting epigenetic modifiers (e.g., HDACs, EZH2) can sensitize MM-resistant cells to anti-myeloma drugs and reversibility of epigenetic changes makes these drugs promising therapeutic agents. Therefore, combination of miRNA mimics with inhibitors of epigenetic modifiers would be a more potent therapeutic strategy in MM patients in relapse or refractory to treatments. In this review, we will discuss the findings of recent investigations on epigenetics/miRNA regulatory axis in development of drug resistance in MM and highlight possible approaches for therapeutic applications of such interaction.

Identification of a novel microRNA, miR-4449, as a potential blood based marker in multiple myeloma

BACKGROUND

miRNAs act in diverse biological processes including development, cell growth, apoptosis, and hematopoiesis, suggesting their role in cancer.

METHODS

We examined the miRNAs perturbed in CD138+ primary multiple myeloma (MM) cells, using microarray analysis and real-time quantitative PCR (RT-qPCR). Serum miR-4449 expression levels were detected from 71 primary MM patients and 46 healthy controls by RT-qPCR.

RESULTS

Our analysis revealed up-regulation of 54 and down-regulation of 28 miRNAs in MM subjects compared to healthy controls. miR-4449 has not been reported in MM. It was found that the relative expression of bone marrow miR-4449 in MM patients (2.14±1.42) was higher than that in healthy controls (0.815±0.165) (U=8, p=0.0093). The relative expression of serum miR-4449 in MM patients (2.11±2.10) was significantly higher than that in healthy controls (0.357±0.235) (U=374, p<0.0001) and was significantly correlated with β2M, λ light and κ light chain concentration (r=0.480, p=0.0003; r=0.560, p<0.0001; r=0.560, p<0.0001), but not correlated with the lactate dehydrogenase (LDH) concentration (r=0.247, p=0.0611). The area under the curve (AUC) of the receiver-operating characteristics (ROC) curve of serum miR-4449 was 0.885 (95% CI, 0.826-0.945), which is higher than for other markers. Combining miR-4449, λ light chain, and β2M together, the sensitivity was highest compared with λ light chain or β2M alone, or combined.

CONCLUSIONS

The expression levels of serum miR-4449 in MM patients were significantly higher than in healthy controls, suggesting that it may prove to be useful in the auxiliary diagnosis of MM.

Potential Value of miR-221/222 as Diagnostic, Prognostic, and Therapeutic Biomarkers for Diseases

microRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by base pairing with their target messenger RNAs. Dysregulation of miRNAs is involved in the pathological initiation and progression of many human diseases. miR-221 and miR-222 (miR-221/222) are two highly homologous miRNAs, and they are significantly overexpressed in several types of human diseases. Silencing miR-221/222 could represent a promising approach for therapeutic studies. In the present review, we will describe the potential value of miR-221/222 as diagnostic, prognostic, and therapeutic biomarkers in various diseases including cancer and inflammatory diseases.

MicroRNA expression patterns and target prediction in multiple myeloma development and malignancy

Epigenetic changes have emerged as key causes in the development and progression of multiple myeloma (MM). In this study, global microRNA (miRNA) expression profiling were performed for 27 MM (19 specimens and 8 cell lines) and 3 normal controls by microarray. miRNA-targets were identified by integrating the miRNA expression profiles with mRNA expression profiles of the matched samples (unpublished data). Two miRNAs were selected for verification by RT-qPCR (miR-150-5p and miR-4430). A total of 1791 and 8 miRNAs were over-expressed and under-expressed, respectively in MM compared to the controls (fold change ≥2.0; p < 0.05). The miRNA-mRNA integrative analysis revealed inverse correlation between 5 putative target genes (RAD54L, CCNA2, CYSLTR2, RASGRF2 and HKDC1) and 15 miRNAs (p < 0.05). Most of the differentially expressed miRNAs are involved in survival, proliferation, migration, invasion and drug resistance in MM. Some have never been described in association with MM (miR-33a, miR-9 and miR-211). Interestingly, our results revealed 2 miRNAs, which are closely related to B cell differentiation (miR-150 and miR-125b). For the first time, we suggest that miR-150 might be potential negative regulator for two critical cell cycle control genes, RAD54L and CCNA2, whereas miR-125b potentially target RAS and CysLT signaling proteins, namely RASGRF2 and CYSLTR2, respectively. This study has enhanced our understanding on the pathobiology of MM and opens up new avenues for future research in myelomagenesis.

Epigenetics in cancer: Fundamentals and Beyond

Activation of oncogenes or the deactivation of tumor suppressor genes has long been established as the fundamental mechanism leading towards carcinogenesis. Although this age old axiom is vastly accurate, thorough study over the last 15years has given us unprecedented information on the involvement of epigenetic in cancer. Various biochemical pathways that are essential towards tumorigenesis are regulated by the epigenetic phenomenons like remodeling of nucleosome by histone modifications, DNA methylation and miRNA mediated targeting of various genes. Moreover the presence of mutations in the genes controlling the epigenetic players has further strengthened the association of epigenetics in cancer. This merger has opened up newer avenues for targeted anti-cancer drug therapy with numerous pharmaceutical industries focusing on expanding their research and development pipeline with epigenetic drugs. The information provided here elaborates the elementary phenomena of the various epigenetic regulators and discusses their alteration associated with the development of cancer. We also highlight the recent developments in epigenetic drugs combining preclinical and clinical data to signify this evolving field in cancer research.

Identification of four potential predicting miRNA biomarkers for multiple myeloma from published datasets

Background

Multiple myeloma is a cancer which has a high occurrence rate and causes great injury to people worldwide. In recent years, many studies reported the effects of miRNA on the appearance of multiple myeloma. However, due to the differences of samples and sequencing platforms, a large number of inconsistent results have been generated among these studies, which limited the cure of multiple myeloma at the miRNA level.

Methods

We performed meta-analyses to identify the key miRNA biomarkers which could be applied on the treatment of multiple myeloma. The key miRNAs were determined by overlap comparisons of seven datasets in multiple myeloma. Then, the target genes for key miRNAs were predicted by the software TargetScan. Additionally, functional enrichments and binding TFs were investigated by DAVID database and Tfacts database, respectively.

Results

Firstly, comparing the normal tissues, 13 miRNAs were differently expressed miRNAs (DEMs) for at least three datasets. They were considered as key miRNAs, with 12 up-regulated (hsa-miR-106b, hsa-miR-125b, hsa-miR-130b, hsa-miR-138, hsa-miR-15b, hsa-miR-181a, hsa-miR-183, hsa-miR-191, hsa-miR-19a, hsa-miR-20a, hsa-miR-221 and hsa-miR-25) and one down-regulated (hsa-miR-223). Secondly, functional enrichment analyses indicated that target genes of the upregulated miRNAs were mainly transcript factors and enriched in transcription regulation. Besides, these genes were enriched in multiple pathways: the cancer signal pathway, insulin signal metabolic pathway, cell binding molecules, melanin generation, long-term regression and P53 signaling pathway. However, no significant enrichment was found for target genes of the down-regulated genes. Due to the distinct regulation function, four miRNAs (hsa-miR-19a has-miR-221 has-miR25 and has-miR223) were ascertained as the potential prognostic and diagnostic markers in MM. Thirdly, transcript factors analysis unveiled that there were 148 TFs and 60 TFs which bind target genes of the up-regulated miRNAs and target genes of the down-regulated miRNAs, respectively. They respectively generated 652 and 139 reactions of TFs and target genes. Additionally, 50 (31.6%) TFs were shared, while higher specificity was found in TFs of target genes for the upregulated miRNAs.

Discussions

Together, our findings provided the key miRNAs which affected occurrence of multiple myeloma and regulation function of these miRNAs. It is valuable for the prognosis and diagnosis of multiple myeloma.

MicroRNA-20a in human faeces as a non-invasive biomarker for colorectal cancer

Objective

Detection of microRNA (miRNA) aberrations in human faeces is a new approach for colorectal cancer (CRC) screening. The aim of this study was to characterise miR-20a in faeces as a non-invasive biomarker for diagnosis of CRC.

Results

miR-20a expression was significantly higher in the 40 CRC tumours compared to their respective adjacent normal tissues (P = 0.0065). Levels of miR-20a were also significantly higher in faecal samples from CRC patients (P < 0.0001). The area under receiver operating characteristic (AUROC) curve for miR-20a was 0.73, with a sensitivity of 55% and specificity of 82% for CRC patients compared with controls. No significant difference in the level of miR-20a was found between patients with proximal, distal, and rectal cancer. The use of antibiotics did not influence faecal miR-20a levels.

Patients and Methods

miR-20a was selected from an expression microarray containing 667 miRNAs. Further verification of miR-20a was performed in 40 pairs of primary CRC tissues, as well as 595 faecal samples (198 CRCs, 199 adenomas, and 198 healthy controls) using TaqMan probe based quantitative Real-Time PCR (qRT-PCR).

Conclusions

Faecal-based miR-20a can be utilised as a potential non-invasive biomarker for CRC screening.

Identification of Long Non-Coding RNAs Deregulated in Multiple Myeloma Cells Resistant to Proteasome Inhibitors

While the clinical benefit of proteasome inhibitors (PIs) for multiple myeloma (MM) treatment remains unchallenged, dose-limiting toxicities and the inevitable emergence of drug resistance limit their long-term utility. Disease eradication is compromised by drug resistance that is either present de novo or therapy-induced, which accounts for the majority of tumor relapses and MM-related deaths. Non-coding RNAs (ncRNAs) are a broad class of RNA molecules, including long non-coding RNAs (lncRNAs), that do not encode proteins but play a major role in regulating the fundamental cellular processes that control cancer initiation, metastasis, and therapeutic resistance. While lncRNAs have recently attracted significant attention as therapeutic targets to potentially improve cancer treatment, identification of lncRNAs that are deregulated in cells resistant to PIs has not been previously addressed. We have modeled drug resistance by generating three MM cell lines with acquired resistance to either bortezomib, carfilzomib, or ixazomib. Genome-wide profiling identified lncRNAs that were significantly deregulated in all three PI-resistant cell lines relative to the drug-sensitive parental cell line. Strikingly, certain lncRNAs deregulated in the three PI-resistant cell lines were also deregulated in MM plasma cells isolated from newly diagnosed patients compared to healthy plasma cells. Taken together, these preliminary studies strongly suggest that lncRNAs represent potential therapeutic targets to prevent or overcome drug resistance. More investigations are ongoing to expand these initial studies in a greater number of MM patients to better define lncRNAs signatures that contribute to PI resistance in MM.

Tissue specific expression of extracellular microRNA in human breast cancers and normal human breast tissue in vivo

Extracellular circulating microRNAs (miRNAs) have been suggested to be biomarkers for disease monitoring but data are inconsistent, one reason being that blood miRNA is of heterogeneous origin. Here, we sampled extracellular microRNAs locally in situ using microdialysis. Three different cohorts of women were included; postmenopausal women with ongoing breast cancer investigated within the cancer and in normal adjacent breast tissue, postmenopausal women investigated in their normal healthy breast and subcutaneous fat before and after six weeks of tamoxifen therapy, premenopausal women during the menstrual cycle. Samples were initially screened using TaqMan array cards with subsequently absolute quantification. 124 miRNA were expressed in microdialysates. After absolute quantifications extracellular miRNA-21 was found to be significantly increased in breast cancer. In addition, the levels were significantly higher in pre-menopausal breast tissue compared with postmenopausal. In breast tissue of pre-menopausal women miRNA-21 exhibited a cyclic variation during the menstrual cycle and in postmenopausal women six weeks of tamoxifen treatment decreased miRNA-21 suggesting that this miRNA may be important for breast carcinogenesis. None of these changes were found in plasma or microdialysates from subcutaneous fat. Our data revealed tissue specific changes of extracellular circulating miRNAs that would be otherwise unraveled using blood samples.

Liquid biopsies for liquid tumors: emerging potential of circulating free nucleic acid evaluation for the management of hematologic malignancies

Circulating free nucleic acids; cell free DNA and circulating micro-RNA, are found in the plasma of patients with hematologic and solid malignancies at levels higher than that of healthy individuals. In patients with hematologic malignancy cell free DNA reflects the underlying tumor mutational profile, whilst micro-RNAs reflect genetic interference mechanisms within a tumor and potentially the surrounding microenvironment and immune effector cells. These circulating nucleic acids offer a potentially simple, non-invasive, repeatable analysis that can aid in diagnosis, prognosis and therapeutic decisions in cancer treatment.

MicroRNA 152 regulates hepatic glycogenesis by targeting PTEN

Hepatic insulin resistance, defined as a diminished ability of hepatocytes to respond to the action of insulin, plays an important role in the development of type 2 diabetes and metabolic syndrome. Aberrant expression of mmu-miR-152-3p (miR-152) is related to the pathogenesis of tumors such as hepatitis B virus related hepatocellular carcinoma. However, the role of miR-152 in hepatic insulin resistance remains unknown. In the present study, we identified the potential role of miR-152 in regulating hepatic glycogenesis. The expression of miR-152 and the level of glycogen were significantly downregulated in the liver of db/db mice and mice fed a high fat diet. In vivo and in vitro results suggest that inhibition of miR-152 expression induced impaired glycogenesis in hepatocytes. Interestingly, miR-152 expression, glycogen synthesis and protein kinase B/glycogen synthase kinase (AKT/GSK) pathway activation were significantly decreased in the liver of mice injected with 16 μg·mL(-1) interleukin 6 (IL-6) by pumps for 7 days and in NCTC 1469 cells treated with 10 ng·mL(-1) IL-6 for 24 h. Moreover, hepatic overexpression of miR-152 rescued IL-6-induced impaired glycogenesis. Finally, phosphatase and tensin homolog (PTEN) was identified as a direct target of miR-152 to mediate hepatic glycogen synthesis. Our findings provide mechanistic insight into the effects of miR-152 on the regulation of the AKT/GSK pathway and the synthesis of glycogen in hepatocytes. Downregulated miR-152 induced impaired hepatic glycogenesis by targeting PTEN. PTEN participated in miR-152-mediated glycogenesis in hepatocytes via regulation of the AKT/GSK pathway.

Mir-221/222 are promising targets for innovative anticancer therapy

INTRODUCTION

MicroRNAs (miRNAs) are key non-coding RNA post-transcriptional regulators of messenger RNAs (mRNAs), and are deeply dysregulated in human cancer. A rising body of evidence indicates that miRNAs represent valuable therapeutic targets. In this light, the cluster miR-221/222 are of particular relevance, given that they are strongly upregulated in a variety of solid and hematologic malignancies.

AREA COVERED

This review summarizes recent findings on the roles played by miR-221/222 in human cancer and their potential clinical value as promising targets for therapeutic studies.

EXPERT OPINION

The rising body of advanced preclinical evidence on the biological significance of miR-221/222 in a variety of malignancies indicates that they will play a crucial role in the future of innovative therapeutic strategies, both as validated biomarkers and targets.

MicroRNAs: Novel Crossroads between Myeloma Cells and the Bone Marrow Microenvironment

Multiple myeloma (MM) is a hematologic malignancy of differentiated plasma cells that accumulate in the bone marrow, where a complex microenvironment made by different cell types supports proliferation, survival, and drug resistance of tumor cells. MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression at posttranscriptional level. Emerging evidence indicates that miRNAs are aberrantly expressed or functionally deregulated in MM cells as the result of multiple genetic or epigenetic mechanisms and that also the tumor microenvironment regulates MM cell functions by miRNAs. Consistently, modulation of miRNA levels in MM cells has been demonstrated to impair their functional interaction with the bone marrow microenvironment and to produce significant antitumor activity even able to overcome the protective bone marrow milieu. This review will describe the most recent findings on miRNA function in the context of MM bone marrow microenvironment, focusing on the therapeutic potential of miRNA-based approaches.

The impact of standard chemotherapy on miRNA signature in plasma in AML patients

AIM

In our pilot study, we used plasma samples as liquid biopsy to search for miRNA signatures in patients with acute myeloid leukemia (AML) at diagnosis and in remission achieved after standard chemotherapy before planned transplantation.

MATERIAL AND METHODS

We examined 10 plasma samples from healthy volunteers and 8 paired samples from patients with AML at diagnosis and in remission using TaqMan MicroRNA Arrays. The results were validated using single-target qPCR reactions run in triplicates.

RESULTS

We selected 6 miRNAs with expressions significantly sensitive to therapy: miR-199b-5p, miR-301b, miR-326, miR-361-5p, miR-625 and miR-655. All selected miRNAs were not or very weakly expressed in healthy individuals. They were abundant in plasma in patients at diagnosis but their levels decreased after chemotherapy.

CONCLUSION

We detected a therapy sensitive miRNA signature in plasma of patients with AML.

A serum microRNA signature associated with complete remission and progression after autologous stem-cell transplantation in patients with multiple myeloma

We have examined serum microRNA expression in multiple myeloma (MM) patients at diagnosis and at complete response (CR) after autologous stem-cell transplantation (ASCT), in patients with stable monoclonal gammopathy of undetermined significance, and in healthy controls. MicroRNAs were first profiled using TaqMan Human MicroRNA Arrays. Differentially expressed microRNAs were then validated by individual TaqMan MicroRNA assays and correlated with CR and progression-free survival (PFS) after ASCT. Supervised analysis identified a differentially expressed 14-microRNA signature. The differential expression of miR-16 (P = 0.028), miR-17 (P = 0.016), miR-19b (P = 0.009), miR-20a (P = 0.017) and miR-660 (P = 0.048) at diagnosis and CR was then confirmed by individual assays. In addition, high levels of miR-25 were related to the presence of oligoclonal bands (P = 0.002). Longer PFS after ASCT was observed in patients with high levels of miR-19b (6 vs. 1.8 years; P < 0.001) or miR-331 (8.6 vs. 2.9 years; P = 0.001). Low expression of both miR-19b and miR-331 in combination was a marker of shorter PFS (HR 5.3; P = 0.033). We have identified a serum microRNA signature with potential as a diagnostic and prognostic tool in MM.

The role of circulating miRNAs in multiple myeloma

Multiple myeloma (MM) is a common malignant hematological disease. Dysregulation of microRNAs (miRNAs) in MM cells and bone marrow microenviroment has important impacts on the initiation and progression of MM and drug resistance in MM cells. Recently, it was reported that MM patient serum and plasma contained sufficiently stable miRNA signatures, and circulating miRNAs could be identified and measured accurately from body fluid. Compared to conventional diagnostic parameters, the circulating miRNA profile is appropriate for the diagnosis of MM and estimates patient progression and therapeutic outcome with higher specificity and sensitivity. In this review, we mainly focus on the potential of circulating miRNAs as diagnostic, prognostic, and predictive biomarkers for MM and summarize the general strategies and methodologies for identification and measurement of circulating miRNAs in various cancers. Furthermore, we discuss the correlation between circulating miRNAs and the cytogenetic abnormalities and biochemical parameters assessed in multiple myeloma.

The role of microRNAs in osteoclasts and osteoporosis

Osteoclasts are the exclusive cells of bone resorption. Abnormally activating osteoclasts can lead to low bone mineral density, which will cause osteopenia, osteoporosis, and other bone disorders. To date, the mechanism of how osteoclast precursors differentiate into mature osteoclasts remains elusive. MicroRNAs (miRNAs) are novel regulatory factors that play an important role in numerous cellular processes, including cell differentiation and apoptosis, by post-transcriptional regulation of genes. Recently, a number of studies have revealed that miRNAs participate in bone homeostasis, including osteoclastic bone resorption, which sheds light on the mechanisms underlying osteoclast differentiation. In this review, we highlight the miRNAs involved in regulating osteoclast differentiation and bone resorption, and their roles in osteoporosis.

Transcriptional repression by the HDAC4-RelB-p52 complex regulates multiple myeloma survival and growth

Although transcriptional activation by NF-κB is well appreciated, physiological importance of transcriptional repression by NF-κB in cancer has remained elusive. Here we show that an HDAC4-RelB-p52 complex maintains repressive chromatin around proapoptotic genes Bim and BMF and regulates multiple myeloma (MM) survival and growth. Disruption of RelB-HDAC4 complex by a HDAC4-mimetic polypeptide blocks MM growth. RelB-p52 also represses BMF translation by regulating miR-221 expression. While the NIK-dependent activation of RelB-p52 in MM has been reported, we show that regardless of the activation status of NIK and the oncogenic events that cause plasma cell malignancy, several genetically diverse MM cells including Bortezomib-resistant MM cells are addicted to RelB-p52 for survival. Importantly, RelB is constitutively phosphorylated in MM and ERK1 is a RelB kinase. Phospho-RelB remains largely nuclear and is essential for Bim repression. Thus, ERK1-dependent regulation of nuclear RelB is critical for MM survival and explains the NIK-independent role of RelB in MM.

Aberrant Levels of miRNAs in Bone Marrow Microenvironment and Peripheral Blood of Myeloma Patients and Disease Progression

The bone marrow (BM) microenvironment of multiple myeloma (MM) is reported to play a role in the biology of disease. In this study, we found that the extracellular BM microenvironment in MM contains a unique miRNA signature detectable by miRNA microarray and quantitative real-time PCR, which is partially represented in the peripheral blood. Eleven miRNAs were significantly decreased in both BM and serum of MM patients in comparison with controls. Evaluation of these miRNAs in plasma of a separate cohort of MM patients and controls confirmed significantly aberrant levels of let-7a, let-7b, let-7i, miR-15b, miR-16, and miR-20a in both serum and plasma. We then studied the myeloma precursor diseases and found that a subset of the MM miRNAs exhibited aberrant expression in monoclonal gammopathy of undetermined significance and smoldering myeloma. miRNA analysis of enriched CD138(+) plasma cells from MM and monoclonal gammopathy of undetermined significance found that most of the validated MM BM signature miRNAs were significantly decreased in MM plasma cells. Gene expression profiling indicated that multiple targets of the decreased miRNAs found increased expression in MM plasma cells, including ATF2, HRAS, HDAC4, TGFB1, TGFBR1, and mitogen-activated protein kinases. The findings suggest that these miRNAs are detectable in aberrant levels in the peripheral blood of patients with plasma cell proliferation and may play a role in aberrant plasma cell proliferation and disease progression.