MicroRNAs: New Players in Multiple Myeloma

Serum proteomic profiling reveals MTA2 and AGO2 as potential prognostic biomarkers associated with disease activity and adverse outcomes in multiple myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy accounting for approximately 10% of hematological malignancies. Identification of reliable biomarkers for better diagnosis and prognosis remains a major challenge. This study aimed to identify potential serum prognostic biomarkers corresponding to MM disease activity and evaluate their impact on patient outcomes. Serum proteomic profiles of patients with MM and age-matched controls were performed using LC-MS/MS. In the verification and validation phases, the concentration of the candidate biomarkers was measured using an ELISA technique. In addition, the association of the proposed biomarkers with clinical outcomes was assessed. We identified 23 upregulated and 15 downregulated proteins differentially expressed in newly diagnosed and relapsed/refractory MM patients compared with MM patients who achieved at least a very good partial response to treatment (≥VGPR). The top two candidate proteins, metastasis-associated protein-2 (MTA2) and argonaute-2 (AGO2), were selected for further verification and validation studies. Both MTA2 and AGO2 showed significantly higher levels in the disease-active states than in the remission states (p < 0.001). Regardless of the patient treatment profile, high MTA2 levels were associated with shorter progression-free survival (p = 0.044; HR = 2.48; 95% CI, 1.02 to 6.02). Conversely, high AGO2 levels were associated with IgG and kappa light-chains isotypes and an occurrence of bone involvement features (p < 0.05) and were associated with prolonged time to response (p = 0.045; HR = 3.00; 95% CI, 1.03 to 8.76). Moreover, the analytic results using a publicly available NCBI GEO dataset revealed that AGO2 overexpression was associated with shorter overall survival among patients with MM (p = 0.032, HR = 1.60, 95% CI, 1.04 to 2.46). In conclusion, MTA2 and AGO2 proteins were first identified as potential biomarkers that reflect disease activity, provide prognostic values and could serve as non-invasive indicators for disease monitoring and outcome predicting among patients with MM.

Epigenetic Crosstalk between Malignant Plasma Cells and the Tumour Microenvironment in Multiple Myeloma

In multiple myeloma, cells of the bone marrow microenvironment have a relevant responsibility in promoting the growth, survival, and drug resistance of multiple myeloma plasma cells. In addition to the well-recognized role of genetic lesions, microenvironmental cells also present deregulated epigenetic systems. However, the effect of epigenetic changes in reshaping the tumour microenvironment is still not well identified. An assortment of epigenetic regulators, comprising histone methyltransferases, histone acetyltransferases, and lysine demethylases, are altered in bone marrow microenvironmental cells in multiple myeloma subjects participating in disease progression and prognosis. Aberrant epigenetics affect numerous processes correlated with the tumour microenvironment, such as angiogenesis, bone homeostasis, and extracellular matrix remodelling. This review focuses on the interplay between epigenetic alterations of the tumour milieu and neoplastic cells, trying to decipher the crosstalk between these cells. We also evaluate the possibility of intervening specifically in modified signalling or counterbalancing epigenetic mechanisms.

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.

Genome-wide identification of potential biomarkers in multiple myeloma using meta-analysis of mRNA and miRNA expression data

Multiple myeloma (MM) is a plasma cell malignancy with diverse clinical phenotypes and molecular heterogeneity not completely understood. Differentially expressed genes (DEGs) and miRNAs (DEMs) in MM may influence disease pathogenesis, clinical presentation / drug sensitivities. But these signatures overlap meagrely plausibly due to complexity of myeloma genome, diversity in primary cells studied, molecular technologies/ analytical tools utilized. This warrants further investigations since DEGs/DEMs can impact clinical outcomes and guide personalized therapy. We have conducted genome-wide meta-analysis of DEGs/DEMs in MM versus Normal Plasma Cells (NPCs) and derived unified putative signatures for MM. 100 DEMs and 1,362 DEGs were found deranged between MM and NPCs. Signatures of 37 DEMs ('Union 37') and 154 DEGs ('Union 154') were deduced that shared 17 DEMs and 22 DEGs with published prognostic signatures, respectively. Two miRs (miR-16-2-3p, 30d-2-3p) correlated with survival outcomes. PPI analysis identified 5 topmost functionally connected hub genes (UBC, ITGA4, HSP90AB1, VCAM1, VCP). Transcription factor regulatory networks were determined for five seed DEGs with ≥ 4 biomarker applications (CDKN1A, CDKN2A, MMP9, IGF1, MKI67) and three topmost up/ down regulated DEMs (miR-23b, 195, let7b/ miR-20a, 155, 92a). Further studies are warranted to establish and translate prognostic potential of these signatures for MM.

Quantitative polymerase Chain reaction profiling of microRNAs in peripheral lymph-monocytes from MGUS subjects

Monoclonal gammopathy of undetermined significance (MGUS) is a pre-malignant abnormality of plasma cells, with increased serum levels of immunoglobulins. Patients with MGUS may evolve to multiple myeloma through a multistep process including deregulated gene expression. microRNAs are small non-coding RNA molecules involved in post-transcriptional regulation of crucial biological processes, such as morphogenesis, cell differentiation, apoptosis, and cancer. This study aimed to evaluate microRNA expression on peripheral lymph-monocytes from MGUS subjects compared with healthy controls using qPCR arrays. Blood samples were collected by venipuncture from fifteen, newly diagnosed MGUS patients and fifteen healthy subjects. A further group (validation group) of six newly diagnosed MGUS patients and five healthy control were enrolled for the validation of miRNAs and their mRNAs target. The study was conducted performing miProfile miRNA qPCR arrays, followed by validation of miRNAs and related mRNA targets through RT-qPCR. The functional interaction between microRNAs and target gene were obtained by Ingenuity Pathways Analysis (IPA). IPA network analysis identified only molecules and relationships experimentally observed in peripheral lymphomonocytes. The following miRNAs :133a-3p, 16-5p, 291-3p, 23a-3p, 205-5p, 17-5p, 7a-5p, 221-3p, 30c-5p, 126a-3p,155-5p, let-7a-5p and 26a-5p, involved in the regulation of genes with a role in lymphocyte homeostasis, cell proliferation, apoptosis, and multiple myeloma (MM) progression, were differently expressed in MGUS with respect to healthy subjects. This miRNA signature and its relative targets could be considered for the formulation of new therapeutic strategies in the prophylaxis or treatment of monoclonal gammopathies.

microRNAs in Autism Spectrum Disorders

BACKGROUND

Efforts to unravel the extensive impact of the non-coding elements of the human genome on cell homeostasis and pathological processes have gained momentum over the last couple of decades. miRNAs refer to short, often 18-25 nucleotides long, non-coding RNA molecules which can regulate gene expression. Each miRNA can regulate several mRNAs.

METHODS

This article reviews the literature on the roles of miRNAs in autism.

RESULTS

Considering the fact that ~ 1% of the human DNA encodes different families of miRNAs, their overall impact as critical regulators of gene expression in the mammalian brain should be immense. Though the autism spectrum disorders (ASDs) are predominantly genetic in nature and several candidate genes are already identified, the highly heterogeneous and multifactorial nature of the disorder makes it difficult to identify common genetic risk factors. Several studies have suggested that the environmental factors may interact with the genetic factors to increase the risk. miRNAs could possibly be one of those factors which explain this link between genetics and the environment.

CONCLUSION

In the present review, we have summarized our current knowledge on miRNAs and their complex roles in ASD, and also on their therapeutic applications.

Multiple Myeloma: Available Therapies and Causes of Drug Resistance

Multiple myeloma (MM) is the second most common blood cancer. Treatments for MM include corticosteroids, alkylating agents, anthracyclines, proteasome inhibitors, immunomodulatory drugs, histone deacetylase inhibitors and monoclonal antibodies. Survival outcomes have improved substantially due to the introduction of many of these drugs allied with their rational use. Nonetheless, MM patients successively relapse after one or more treatment regimens or become refractory, mostly due to drug resistance. This review focuses on the main drugs used in MM treatment and on causes of drug resistance, including cytogenetic, genetic and epigenetic alterations, abnormal drug transport and metabolism, dysregulation of apoptosis, autophagy activation and other intracellular signaling pathways, the presence of cancer stem cells, and the tumor microenvironment. Furthermore, we highlight the areas that need to be further clarified in an attempt to identify novel therapeutic targets to counteract drug resistance in MM patients.

Transcriptome analysis identifies key regulators and networks in Acute myeloid leukemia

OBJECTIVES

Acute myeloid leukemia (AML) is a heterogeneous and highly recurrent hematological malignancy. Studies have shown an association between microRNAs and drive genes in AMLs. However, the regulatory roles of miRNAs in AML and how they act on downstream targets and the signaling pathway has been little studied.

METHODS

As to understand the mechanism of mRNA-miRNA interaction in the blood malignancy from a large scale of transcriptomic sequencing studies, we applied a comprehensive miRNA-mRNA association, co-expression gene network and ingenuity pathway analysis using TCGA AML datasets.

RESULTS

Our results showed that his-mir-335 was a critical regulatory of homeobox A gene family. PBX3, KAT6A, MEIS1, and COMMD3-BMI1 were predicted as top transcription regulators in the regulatory network of the HOXA family. The most significantly enriched functions were cell growth, proliferation, and survival in the mRNA-miRNA network.

CONCLUSION

Our work revealed that regulation of the HOXA gene family and its regulation played an important role in the development of AML.

MicroRNAs as New Biomarkers for Diagnosis and Prognosis, and as Potential Therapeutic Targets in Acute Myeloid Leukemia

Acute myeloid leukemias (AML) are clonal disorders of hematopoietic progenitor cells which are characterized by relevant heterogeneity in terms of phenotypic, genotypic, and clinical features. Among the genetic aberrations that control disease development there are microRNAs (miRNAs). miRNAs are small non-coding RNAs that regulate, at post-transcriptional level, translation and stability of mRNAs. It is now established that deregulated miRNA expression is a prominent feature in AML. Functional studies have shown that miRNAs play an important role in AML pathogenesis and miRNA expression signatures are associated with chemotherapy response and clinical outcome. In this review we summarized miRNA signature in AML with different cytogenetic, molecular and clinical characteristics. Moreover, we reviewed the miRNA regulatory network in AML pathogenesis and we discussed the potential use of cellular and circulating miRNAs as biomarkers for diagnosis and prognosis and as therapeutic targets.

Epigenetics in multiple myeloma: From mechanisms to therapy

Multiple myeloma (MM) is a tumor of antibody producing plasmablasts/plasma cells that resides within the bone marrow (BM). In addition to the well-established role of genetic lesions and tumor-microenvironment interactions in the development of MM, deregulated epigenetic mechanisms are emerging as important in MM pathogenesis. Recently, MM sequencing and expression projects have revealed that mutations and copy number variations as well as deregulation in the expression of epigenetic modifiers are characteristic features of MM. In the past decade, several studies have suggested epigenetic mechanisms via DNA methylation, histone modifications and non-coding RNAs as important contributing factors in MM with impacts on disease initiation, progression, clonal heterogeneity and response to treatment. Herein we review the present view and knowledge that has accumulated over the past decades on the role of epigenetics in MM, with focus on the interplay between epigenetic mechanisms and the potential use of epigenetic inhibitors as future treatment modalities for MM.

Global miRNA expression analysis identifies novel key regulators of plasma cell differentiation and malignant plasma cell

MicroRNAs (miRNAs) are small noncoding RNAs that attenuate expression of their mRNA targets. Here, we developed a new method and an R package, to easily infer candidate miRNA–mRNA target interactions that could be functional during a given biological process. Using this method, we described, for the first time, a comprehensive integrated analysis of miRNAs and mRNAs during human normal plasma cell differentiation (PCD). Our results reveal 63 miRNAs with significant temporal changes in their expression during normal PCD. We derived a high-confidence network of 295 target relationships comprising 47 miRNAs and 141 targets. These relationships include new examples of miRNAs that appear to coordinately regulate multiple members of critical pathways associated with PCD. Consistent with this, we have experimentally validated a role for the miRNA-30b/c/d-mediated regulation of key PCD factors (IRF4, PRDM1, ELL2 and ARID3A). Furthermore, we found that 24 PCD stage-specific miRNAs are aberrantly overexpressed in multiple myeloma (MM) tumor plasma cells compared to their normal counterpart, suggesting that MM cells frequently acquired expression changes in miRNAs already undergoing dynamic expression modulation during normal PCD. Altogether, our analysis identifies candidate novel key miRNAs regulating networks of significance for normal PCD and malignant plasma cell biology.

Epigenetic repression of miR-375 is the dominant mechanism for constitutive activation of the PDPK1/RPS6KA3 signalling axis in multiple myeloma

Cytogenetic/molecular heterogeneity is the hallmark of multiple myeloma (MM). However, we recently showed that the serine/threonine kinase PDPK1 and its substrate RPS6KA3 (also termed RSK2) are universally active in MM, and play pivotal roles in myeloma pathophysiology. In this study, we assessed involvement of aberrant miR-375 repression in PDPK1 overexpression in MM. An analysis of plasma cells from 30 pre-malignant monoclonal gammopathies of undetermined significance and 73 MM patients showed a significant decrease in miR-375 expression in patient-derived plasma cells regardless of the clinical stage, compared to normal plasma cells. Introduction of miR-375 reduced PDPK1 expression in human myeloma cell lines (HMCLs), indicating that miR-375 is the dominant regulator of PDPK1 expression. In addition, miR-375 introduction also downregulated IGF1R and JAK2 in HMCLs. CpG islands in the MIR375 promoter were pathologically hypermethylated in all 8 HMCLs examined and in most of 58 patient-derived myeloma cells. Treatment with SGI-110, a hypomethylating agent, and/or trichostatin A, a histone deacetylase inhibitor, increased miR-375 expression, but repressed PDPK1, IGF1R and JAK2 in HMCLs. Collectively, these results show the universal involvement of overlapping epigenetic dysregulation for abnormal miR-375 repression in MM, which is likely to contribute to myelomagenesis and to subsequent myeloma progression by activating oncogenic signalling pathways.

Multiple myeloma and persistence of drug resistance in the age of novel drugs (Review)

Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease. Specifically, the emergence of multidrug resistance (MDR) during the course of treatment contributes significantly to treatment failure. The introduction of the immunomodulatory agents and proteasome inhibitors has seen an increase in overall patient survival, however, for the majority of patients, relapse remains inevitable with evidence that these agents, like the conventional chemotherapeutics are also subject to the development of MDR. Clinical management of patients with MM is currently compromised by lack of a suitable procedure to monitor the development of clinical drug resistance in individual patients. The current MM prognostic measures fail to pick the clonotypic tumor cells overexpressing drug efflux pumps, and invasive biopsy is insufficient in detecting sporadic tumors in the skeletal system. This review summarizes the challenges associated with treating the complex disease spectrum of myeloma, with an emphasis on the role of deleterious multidrug resistant clones orchestrating relapse.

Epigenetics in Multiple Myeloma

Multiple myeloma is characterized by clonal proliferation of plasma cells within the bone marrow resulting in anemia, lytic bone lesions, hypercalcemia, and renal impairment. Despite advanced in our understanding of this complex disease in recent years, it is still considered an incurable malignancy. This is, in part, due to the highly heterogenous genomic and phenotypic nature of the disease, which is to date incompletely understood. It is clear that a deeper level of knowledge of the biological events underlying the development of these diseases is needed to identify new targets and generate effective novel therapies. MicroRNAs (miRNAs), which are single strand, 20-nucleotide, noncoding RNA's, are key regulators of gene expression and have been reported to exert transcriptional control in multiple myeloma. miRNAs are now recognized to play a role in many key areas such as cellular proliferation, differentiation, apoptosis and stress response. Substantial advances have been made in recent years in terms of our understanding of the biological role of miRNAs in a diverse range of hematological and solid malignancues, In multiple myeloma these advances have yielded new information of prognostic and diagnostic relevance which have helped to shed light on epigenetic regulation in this disease.

Systematic analysis of berberine-induced signaling pathway between miRNA clusters and mRNAs and identification of mir-99a ∼ 125b cluster function by seed-targeting inhibitors in multiple myeloma cells

BACKGROUND

Berberine (BBR) is a natural alkaloid derived from a traditional Chinese herbal medicine. However, the exact mechanisms underlying the different effects of berberine on MM cells have not been fully elucidated.

METHODS

A systematic analysis assay integrated common signaling pathways modulated by the 3 miRNA clusters and mRNAs in MM cells after BBR treatment. The role of the mir-99a ∼ 125b cluster, an important oncomir in MM, was identified by comparing the effects of t-anti-mirs with complete complementary antisense locked nucleic acids (LNAs) against mature mir-125b (anti-mir-125b).

RESULTS

Three miRNAs clusters (miR-99a ∼ 125b, miR-17 ∼ 92 and miR-106 ∼ 25) were significantly down-regulated in BBR-treated MM cells and are involved in multiple cancer-related signaling pathways. Furthermore, the top 5 differentially regulated genes, RAC1, NFκB1, MYC, JUN and CCND1 might play key roles in the progression of MM. Systematic integration revealed that 3 common signaling pathways (TP53, Erb and MAPK) link the 3 miRNA clusters and the 5 key mRNAs. Meanwhile, both BBR and seed-targeting t-anti-mir-99a ∼ 125b cluster LNAs significantly induced apoptosis, G2-phase cell cycle arrest and colony inhibition.

CONCLUSIONS

our results suggest that BBR suppresses multiple myeloma cells, partly by down-regulating the 3 miRNA clusters and many mRNAs, possibly through TP53, Erb and MAPK signaling pathways. The mir-99a ∼ 125b cluster might be a novel target for MM treatment. These findings provide new mechanistic insight into the anticancer effects of certain traditional Chinese herbal medicine compounds.

Identification of subtype specific miRNA-mRNA functional regulatory modules in matched miRNA-mRNA expression data: multiple myeloma as a case

Identification of miRNA-mRNA modules is an important step to elucidate their combinatorial effect on the pathogenesis and mechanisms underlying complex diseases. Current identification methods primarily are based upon miRNA-target information and matched miRNA and mRNA expression profiles. However, for heterogeneous diseases, the miRNA-mRNA regulatory mechanisms may differ between subtypes, leading to differences in clinical behavior. In order to explore the pathogenesis of each subtype, it is important to identify subtype specific miRNA-mRNA modules. In this study, we integrated the Ping-Pong algorithm and multiobjective genetic algorithm to identify subtype specific miRNA-mRNA functional regulatory modules (MFRMs) through integrative analysis of three biological data sets: GO biological processes, miRNA target information, and matched miRNA and mRNA expression data. We applied our method on a heterogeneous disease, multiple myeloma (MM), to identify MM subtype specific MFRMs. The constructed miRNA-mRNA regulatory networks provide modular outlook at subtype specific miRNA-mRNA interactions. Furthermore, clustering analysis demonstrated that heterogeneous MFRMs were able to separate corresponding MM subtypes. These subtype specific MFRMs may aid in the further elucidation of the pathogenesis of each subtype and may serve to guide MM subtype diagnosis and treatment.

MicroRNAs in B-cells: from normal differentiation to treatment of malignancies

MicroRNAs (miRNAs) are small non-coding RNAs that play important post-transcriptional regulatory roles in a wide range of biological processes. They are fundamental to the normal development of cells, and evidence suggests that the deregulation of specific miRNAs is involved in malignant transformation due to their function as oncogenes or tumor suppressors. We know that miRNAs are involved in the development of normal B-cells and that different B-cell subsets express specific miRNA profiles according to their degree of differentiation. B-cell-derived malignancies contain transcription signatures reminiscent of their cell of origin. Therefore, we believe that normal and malignant B-cells share features of regulatory networks controlling differentiation and the ability to respond to treatment. The involvement of miRNAs in these processes makes them good biomarker candidates. B-cell malignancies are highly prevalent, and the poor overall survival of patients with these malignancies demands an improvement in stratification according to prognosis and therapy response, wherein we believe miRNAs may be of great importance. We have critically reviewed the literature, and here we sum up the findings of miRNA studies in hematological cancers, from the development and progression of the disease to the response to treatment, with a particular emphasis on B-cell malignancies.

Identifying microRNAs involved in aging of the lateral wall of the cochlear duct

Age-related hearing loss is a progressive sensorineural hearing loss that occurs during aging. Degeneration of the organ of Corti and atrophy of the lateral wall of the cochlear duct (or scala media) in the inner ear are the two primary causes. MicroRNAs (miRNAs), a class of short non-coding RNAs that regulate the expression of mRNA/protein targets, are important regulators of cellular senescence and aging. We examined miRNA gene expression profiles in the lateral wall of two mouse strains, along with exploration of the potential targets of those miRNAs that showed dynamic expression during aging. We show that 95 and 60 miRNAs exhibited differential expression in C57 and CBA mice during aging, respectively. A majority of downregulated miRNAs are known to regulate pathways of cell proliferation and differentiation, while all upregulated miRNAs are known regulators in the pro-apoptotic pathways. By using apoptosis-related gene array and bioinformatic approaches to predict miRNA targets, we identify candidate miRNA-regulated genes that regulate apoptosis pathways in the lateral wall of C57 and CBA mice during aging.

Drug resistance in multiple myeloma: latest findings and new concepts on molecular mechanisms

In the era of new and mostly effective therapeutic protocols, multiple myeloma still tends to be a hard-to-treat hematologic cancer. This hallmark of the disease is in fact a sequel to drug resistant phenotypes persisting initially or emerging in the course of treatment. Furthermore, the heterogeneous nature of multiple myeloma makes treating patients with the same drug challenging because finding a drugable oncogenic process common to all patients is not yet feasible, while our current knowledge of genetic/epigenetic basis of multiple myeloma pathogenesis is outstanding. Nonetheless, bone marrow microenvironment components are well known as playing critical roles in myeloma tumor cell survival and environment-mediated drug resistance happening most possibly in all myeloma patients. Generally speaking, however; real mechanisms underlying drug resistance in multiple myeloma are not completely understood. The present review will discuss the latest findings and concepts in this regard. It reviews the association of important chromosomal translocations, oncogenes (e.g. TP53) mutations and deranged signaling pathways (e.g. NFκB) with drug response in clinical and experimental investigations. It will also highlight how bone marrow microenvironment signals (Wnt, Notch) and myeloma cancer stem cells could contribute to drug resistance in multiple myeloma.

Integrative analysis of differential miRNA and functional study of miR-21 by seed-targeting inhibition in multiple myeloma cells in response to berberine

Background

Berberine is a natural alkaloid derived from a traditional Chinese herbal medicine. It is known to modulate microRNA (miRNA) levels, although the mechanism for this action is unknown. Here, we previously demonstrate that the expression of 87 miRNAs is differentially affected by berberine in multiple myeloma cells. Among 49 miRNAs that are down-regulated, nine act as oncomirs, including miR-21. Integrative analysis showed that 28 of the down-regulated miRNAs participate in tumor protein p53 (TP53) signaling and other cancer pathways. miR-21 is involved in all these pathways, and is one of the most important oncomirs to be affected by berberine in multiple myeloma cells.

Results

We confirmed that berberine down-regulated miRNA-21 expression and significantly up-regulated the expression of programmed cell death 4 (PDCD4), a predicted miR-21 target. Luciferase reporter assays confirmed that PDCD4 was directly regulated by miR-21. Bioinformatic analysis revealed that the miR-21 promoter can be targeted by signal transducer and activator of transcription 3 (STAT3). Down-regulation of interleukin 6 (IL6) by berberine might lead to inhibition of miR-21 transcription through STAT3 down-regulation in multiple myeloma. Furthermore, both berberine and seed-targeting anti-miR-21 oligonucleotide induced apoptosis, G2-phase cell cycle arrest and colony inhibition in multiple myeloma cell lines. Depletion of PDCD4 by short interfering RNA could rescue berberine-induced cytotoxicity in multiple myeloma cells.

Conclusions

Our results suggest that berberine suppresses multiple myeloma cell growth, at least in part, by down-regulating miR-21 levels possibly through IL6/STAT3. This led to increased PDCD4 expression, which is likely to result in suppression of the p53 signaling pathway. These findings may also provide new mechanistic insight into the anti-cancer effects of certain compounds in traditional Chinese herbal medicines.

p53 abnormalities and potential therapeutic targeting in multiple myeloma

p53 abnormalities are regarded as an independent prognostic marker in multiple myeloma. Patients harbouring this genetic anomaly are commonly resistant to standard therapy. Thus, various p53 reactivating agents have been developed in order to restore its tumour suppressive abilities. Small molecular compounds, especially, have gained popularity in its efficacy against myeloma cells. For instance, promising preclinical results have steered both nutlin-3 and PRIMA-1 into phase I/II clinical trials. This review summarizes different modes of p53 inactivation in myeloma and highlights the current p53-based therapies that are being utilized in the clinic. Finally, we discuss the potential and promise that the novel small molecules possess for clinical application in improving the treatment outcome of myeloma.

Association of Chromosomal Translocation and MiRNA Expression with The Pathogenesis of Multiple Myeloma

Multiple myeloma (MM), is the second most common blood cancer after non-Hodgkin's lymphoma. Genetic changes, structural and numerical chromosome anomalies, are involved in pathogenesis of MM, and are among the most important prognostic factors of disease-associated patient survival. MicroRNAs (miRNAs) are small 19-22 nucleotide single-stranded RNAs involved in important cellular processes. Cytogenetic changes in plasma cells alter miRNA expression and function. MiRNAs act as tumor suppressors and oncogenes by affecting intracellular signaling pathways. MiRNA expression is associated with a specific genetic change and may assist with diagnosis and disease prognosis. This study aims to evaluate recent findings in MM-associated cytogenetic changes and their relationship with changes in the expression of miRNAs. We have determined that MM-associated cytogenetic changes are related to changes in the expression of miRNAs and CD markers (cluster of differentiation) are associated with disease survival. Information about these changes can be used for therapeutic purposes and disease prognosis.

The Role of miRNA in Haematological Malignancy

Currently, there are over 1,800 annotated human miRNAs, many of which have tissue-specific expression. Numerous studies have highlighted their role in haematopoietic differentiation and proliferation, acting as master regulators of haematopoietic stem cell function. Aberrant expression of miRNAs has been observed in haematological cancers, exhibiting unique expression signatures in comparison to normal counterparts. Functional and target analyses as well as animal models have attempted to annotate how different miRNA may contribute to the pathophysiology of these malignancies from modulating cancer associated genes, functioning directly as oncogenes or tumour suppressor genes or acting as bystanders or regulators of the epigenetic mechanisms in cancer. miRNAs have also been shown to play a role in modulating drug resistance and determining prognosis between the various subtypes of blood cancers. This review discusses the important role that miRNAs play in haematological malignancies by exploring associations that exist between the two and trying to examine evidence of causality to support the tantalising possibility that miRNAs might serve as therapeutic targets in blood cancers.

MicroRNA theragnostics for the clinical management of multiple myeloma

Theragnostics represent cutting-edge, multi-disciplinary strategies that combine diagnostics with therapeutics in order to generate personalized therapies that improve patient outcome. In oncology, the approach is aimed at more accurate diagnosis of cancer, optimization of patient selection to identify those most likely to benefit from a specific therapy and to generate effective therapeutics that enhance patient survival. MicroRNAs (miRNAs) are master regulators of the human genome that orchestrate myriad cellular pathways to control growth during physiologic and pathologic conditions. Compelling evidence shows that miRNA deregulation promotes events linked to tumor initiation, metastasis and drug resistance as seen in multiple myeloma (MM), an invariably fatal hematologic malignancy. miRNAs are readily detected in body fluids, for example, serum, plasma, urine, as well as circulating tumor cells to demonstrate their potential as readily accessible, non-invasive diagnostic and prognostic biomarkers and potential therapeutics. Specific miRNAs are aberrantly expressed early in myelomagenesis and may more readily detect high-risk disease than current methods. Although only recently discovered miRNAs have rapidly advanced from preclinical studies to evaluation in human clinical trials. The development of miRNA theragnostics should provide widely applicable tools for the targeted delivery of personalized medicines to improve the outcome of patients with MM.

Small-molecule multi-targeted kinase inhibitor RGB-286638 triggers P53-dependent and -independent anti-multiple myeloma activity through inhibition of transcriptional CDKs

Small molecule multi-targeted CDK inhibitors (CDKIs) are of particular interest due to their potent antitumor activity independent of p53 gene alterations. P53 deletion is associated with a very poor prognosis in multiple myeloma (MM). In this regard, we tested the anti-MM activity of RGB-286638, an indenopyrazole-derived CDKI with Ki-nanomolar activity against transcriptional CDKs. We examined RGB-286638’s mode-of-action in MM cell lines with wild type (wt)-p53 and those expressing mutant p53. RGB-286638 treatment resulted in MM cytotoxicity in vitro associated with inhibition of MM tumor growth and prolonged survival in vivo. RGB-286638 displayed caspase-dependent apoptosis in both wt-p53 and mutant-p53 cells that was closely associated with the downregulation of RNA polymerase II phosphorylation and inhibition of transcription. RGB-286638-triggered p53 accumulation via nucleolar stress and loss of Mdm2, accompanied by induction of p53 DNA binding activity. Additionally, RGB-286638 mediated p53-independent activity, which was confirmed by cytotoxicity in p53-knockdown and p53-mutant cells. We also demonstrated downregulation of oncogenic miR-19, miR-92a-1, and miR-21. Our data provide the rationale for the development of transcriptional CDK inhibitors as therapeutic agents, which activate p53 in competent cells, while circumventing p53 deficiency through alternative p53-independent cell death mechanisms in p53-mutant/deleted cells.

Molecular profiling of multiple myeloma: from gene expression analysis to next-generation sequencing

INTRODUCTION

Multiple myeloma is a fatal malignant proliferation of clonal bone marrow Ig-secreting plasma cells, characterized by wide clinical, biological, and molecular heterogeneity.

AREAS COVERED

Herein, global gene and microRNA expression, genome-wide DNA profilings, and next-generation sequencing technology used to investigate the genomic alterations underlying the bio-clinical heterogeneity in multiple myeloma are discussed.

EXPERT OPINION

High-throughput technologies have undoubtedly allowed a better comprehension of the molecular basis of the disease, a fine stratification, and early identification of high-risk patients, and have provided insights toward targeted therapy studies. However, such technologies are at risk of being affected by laboratory- or cohort-specific biases, and are moreover influenced by high number of expected false positives. This aspect has a major weight in myeloma, which is characterized by large molecular heterogeneity. Therefore, meta-analysis as well as multiple approaches are desirable if not mandatory to validate the results obtained, in line with commonly accepted recommendation for tumor diagnostic/prognostic biomarker studies.

Promises and challenges of MicroRNA-based treatment of multiple myeloma

MicroRNAs (miRNAs) recently emerged with a key role in multiple myeloma (MM) pathophysiology and are considered important regulators of MM cell growth and survival. Since miRNAs can act either as oncogenes or tumour suppressors, the potential of targeting the miRNA network arises as a novel therapeutic approach for human cancer. Potential strategies based on miRNA therapeutics basically rely on miRNA inhibition or miRNA replacement approaches and take benefit respectively from the use of antagomirs or synthetic miRNAs as well as from lipid-based nanoparticles which allow an efficient miRNA-delivery. The availability of experimental in vivo platforms which recapitulate the growth of MM cells within the specific human bone marrow microenvironment in immunocompromised mice (SCID-hu and SCID-synth-hu) provides powerful systems for development of miRNA-based therapeutics in MM. Preliminary findings on the anti-MM activity of synthetic miRNAs in such experimental models offer a proof-of-principle that miRNA therapeutics is a promising opportunity for this still incurable disease representing the rationale for a new venue of investigation in this specific field.

The expression pattern of small nucleolar and small Cajal body-specific RNAs characterizes distinct molecular subtypes of multiple myeloma

Small nucleolar RNAs (snoRNAs) and small Cajal body-specific RNAs (scaRNAs) are non-coding RNAs involved in the maturation of other RNA molecules and generally located in the introns of host genes. It is now emerging that altered sno/scaRNAs expression may have a pathological role in cancer. This study elucidates the patterns of sno/scaRNAs expression in multiple myeloma (MM) by profiling purified malignant plasma cells from 55 MMs, 8 secondary plasma cell leukemias (sPCLs) and 4 normal controls. Overall, a global sno/scaRNAs downregulation was found in MMs and, even more, in sPCLs compared with normal plasma cells. Whereas SCARNA22 resulted the only sno/scaRNA characterizing the translocation/cyclin D4 (TC4) MM, TC2 group displayed a distinct sno/scaRNA signature overexpressing members of SNORD115 and SNORD116 families located in a region finely regulated by an imprinting center at 15q11, which, however, resulted overall hypomethylated in MMs independently of the SNORD115 and SNORD116 expression levels. Finally, integrative analyses with available gene expression and genome-wide data revealed the occurrence of significant sno/scaRNAs/host genes co-expression and the putative influence of allelic imbalances on specific snoRNAs expression. Our data extend the current view of sno/scaRNAs deregulation in cancer and add novel information to the bio-molecular complexity of plasma cell dyscrasias.

Downregulation of specific miRNAs in hyperdiploid multiple myeloma mimics the oncogenic effect of IgH translocations occurring in the non-hyperdiploid subtype

Currently, multiple myeloma (MM) patients are broadly grouped into a non-hyperdiploid (nh-MM) group, highly enriched for IgH translocations, or into a hyperdiploid (h-MM) group, which is typically characterized by trisomies of some odd-numbered chromosomes. We compared the micro RNA (miRNA) expression profiles of these two groups and we identified 16 miRNAs that were downregulated in the h-MM group, relative to the nh-MM group. We found that target genes of the most differentially expressed miRNAs are directly involved in the pathogenesis of MM; specifically, the inhibition of hsa-miR-425, hsa-miR-152 and hsa-miR-24, which are all downregulated in h-MM, leads to the overexpression of CCND1, TACC3, MAFB, FGFR3 and MYC, which are the also the oncogenes upregulated by the most frequent IgH chromosomal translocations occurring in nh-MM. Importantly, we showed that the downregulation of these specific miRNAs and the upregulation of their targets also occur simultaneously in primary cases of h-MM. These data provide further evidence on the unifying role of cyclin D pathways deregulation as the key mechanism involved in the development of both groups of MM. Finally, they establish the importance of miRNA deregulation in the context of MM, thereby opening up the potential for future therapeutic approaches based on this molecular mechanism.

Synthetic miR-34a mimics as a novel therapeutic agent for multiple myeloma: in vitro and in vivo evidence

PURPOSE

Deregulated expression of miRNAs has been shown in multiple myeloma (MM). A promising strategy to achieve a therapeutic effect by targeting the miRNA regulatory network is to enforce the expression of miRNAs that act as tumor suppressor genes, such as miR-34a.

EXPERIMENTAL DESIGN

Here, we investigated the therapeutic potential of synthetic miR-34a against human MM cells in vitro and in vivo.

RESULTS

Either transient expression of miR-34a synthetic mimics or lentivirus-based miR-34a-stable enforced expression triggered growth inhibition and apoptosis in MM cells in vitro. Synthetic miR-34a downregulated canonic targets BCL2, CDK6, and NOTCH1 at both the mRNA and protein level. Lentiviral vector-transduced MM xenografts with constitutive miR-34a expression showed high growth inhibition in severe combined immunodeficient (SCID) mice. The anti-MM activity of lipidic-formulated miR-34a was further shown in vivo in two different experimental settings: (i) SCID mice bearing nontransduced MM xenografts; and (ii) SCID-synth-hu mice implanted with synthetic 3-dimensional scaffolds reconstituted with human bone marrow stromal cells and then engrafted with human MM cells. Relevant tumor growth inhibition and survival improvement were observed in mice bearing TP53-mutated MM xenografts treated with miR-34a mimics in the absence of systemic toxicity.

CONCLUSIONS

Our findings provide a proof-of-principle that formulated synthetic miR-34a has therapeutic activity in preclinical models and support a framework for development of miR-34a-based treatment strategies in MM patients.