MiR-15a/16 regulates the growth of myeloma cells, angiogenesis and antitumor immunity by inhibiting Bcl-2, VEGF-A and IL-17 expression in multiple myeloma

The Multiple Myeloma Landscape: Epigenetics and Non-Coding RNAs

Simple Summary

Recent findings in multiple myeloma have led to therapies which have improved patient life quality and expectancy. However, frequent relapse and drug resistance emphasize the need for more efficient therapeutic approaches. The discovery of non-coding RNAs as key actors in multiple myeloma has broadened the molecular landscape of this disease, together with classical epigenetic factors such as methylation and acetylation. microRNAs and long non-coding RNAs comprise the majority of the described non-coding RNAs dysregulated in multiple myeloma, while circular RNAs are recently emerging as promising molecular targets. This review provides a comprehensive overview of the most recent knowledge on this topic and suggests new therapeutic strategies.

Abstract

Despite advances in available treatments, multiple myeloma (MM) remains an incurable disease and represents a challenge in oncohematology. New insights into epigenetic factors contributing to MM development and progression have improved the knowledge surrounding its molecular basis. Beyond classical epigenetic factors, including methylation and acetylation, recent genome analyses have unveiled the importance of non-coding RNAs in MM pathogenesis. Non-coding RNAs have become of interest, as their dysregulation opens the door to new therapeutic approaches. The discovery, in the past years, of molecular techniques, such as CRISPR-Cas, has led to innovative therapies with potential benefits to achieve a better outcome for MM patients. This review summarizes the current knowledge on epigenetics and non-coding RNAs in MM pathogenesis.

Non-coding RNA-based regulation of inflammation

Inflammation is a multifactorial process and various biological mechanisms and pathways participate in its development. The presence of inflammation is involved in pathogenesis of different diseases such as diabetes mellitus, cardiovascular diseases and even, cancer. Non-coding RNAs (ncRNAs) comprise large part of transcribed genome and their critical function in physiological and pathological conditions has been confirmed. The present review focuses on miRNAs, lncRNAs and circRNAs as ncRNAs and their potential functions in inflammation regulation and resolution. Pro-inflammatory and anti-inflammatory factors are regulated by miRNAs via binding to 3'-UTR or indirectly via affecting other pathways such as SIRT1 and NF-κB. LncRNAs display a similar function and they can also affect miRNAs via sponging in regulating levels of cytokines. CircRNAs mainly affect miRNAs and reduce their expression in regulating cytokine levels. Notably, exosomal ncRNAs have shown capacity in inflammation resolution. In addition to pre-clinical studies, clinical trials have examined role of ncRNAs in inflammation-mediated disease pathogenesis and cytokine regulation. The therapeutic targeting of ncRNAs using drugs and nucleic acids have been analyzed to reduce inflammation in disease therapy. Therefore, ncRNAs can serve as diagnostic, prognostic and therapeutic targets in inflammation-related diseases in pre-clinical and clinical backgrounds.

Epigenetic Modifications in Myeloma: Focused Review of Current Data and Potential Therapeutic Applications

Multiple myeloma is a common hematologic malignancy with an incidence of 1 per 100,000 population and is characterized by a nearly 100% risk of relapse, necessitating treatment with newer therapeutic agents at each instance of progression. However, use of newer agents is often precluded by cost and accessibility in a resource-constrained setting. Description of newer pathways of disease pathogenesis potentially provides opportunities for identification of therapeutic targets and a better understanding of disease biology. Identification of epigenetic changes in myeloma is an emerging premise, with several pathways contributing to pathogenesis and progression of disease. Greater understanding of epigenetic alterations provides opportunities to detect several targetable enzymes or pathways that can be of clinical use.

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.

MiR-15a Participated in the Pathogenesis of Pterygium via Targeting BCL-2：An Experimental Research

Purpose: To compare the expression levels of miR-15a between pterygium and normal conjunctiva, and further investigate the potential role of miR-15a in the progression of pterygium.Methods: 21 cases of primary pterygium were enrolled in our study. The length of the pterygium invaded into the cornea and the total thickness of the pterygium were measured with anterior segment optical coherence tomography (AS-OCT). The pterygial and adjacent normal conjunctival samples of the 21 patients were collected. Expressions of miR-15a, BCL-2, Bax in both pterygium and normal conjunctiva were measured, and correlations between miR-15a and BCL-2, miR-15a and Bax, miR-15a and clinical parameters were made. Pterygium epithelial cells (PECs) were isolated, cultured and transfected with miR-15a mimic or miR-15a inhibitor to interfere the miR-15a expression levels. The regulation of BCL-2 expression by miR-15a was examined with Real-Time PCR (RT-PCR), Western blot and immunofluorescence. The regulation of Bax expression by miR-15a was also examined with Real-Time PCR (RT-PCR) and Western blot. The cell viability of the transfected PECs was measured with the CCK-8 assay and the apoptosis in these cells was detected using the TUNEL assay.Results: The expression of miR-15a, Bax were significantly decreased while the BCL-2 was significantly increased in pterygium (p < .05). There was a negative correlation in expression between miR-15a and BCL-2 in pterygium tissues (r = -0.516, p < .05). We also found that relative miR-15a level was positively correlated with the length of pterygium invaded into the cornea (r = -0.570, p < .05). In cultured PECs, miR-15a could downregulate the expression of BCL-2 and upregulate the expression of Bax. Promotion of miR-15a could suppress cell proliferation and promote cell apoptosis in cultured PECs.Conclusions: Our study demonstrated that decreased expression of miR-15a in pterygium might be associated with the apoptosis and proliferation of abnormal cell via regulating BCL-2, which could subsequently contribute to the development of pterygium. Downregulation of miR-15a might also contribute to the pathogenesis of pterygium by other mechanisms including abnormal proliferation and neovascularization, which remain to be investigated.

miR-17-3p promotes the proliferation of multiple myeloma cells by downregulating P21 expression through LMLN inhibition

Multiple myeloma (MM), a hematological malignancy, has a poor prognosis and requires an invasive procedure. Reports have implicated miRNAs in the diagnosis, treatment and prognosis of hematological malignancies. In our study, we evaluated the expression profiles of miR-17-3p in plasma and bone marrow mononuclear cells of monoclonal gammopathy of undetermined significance (MGUS) and MM patients and healthy subjects. The results showed that the plasma and mononuclear cell expression levels of miR-17-3p in MM patients were higher than those in MGUS patients and normal controls. In addition, the expression of miR-17-3p was positively correlated with diagnostic indexes, such as marrow plasma cell abundance and serum M protein level, and positively correlated with the International Staging System stage of the disease. Receiver operating characteristic curve analysis suggested that miR-17-3p might be a diagnostic index of MM. Moreover, miR-17-3p regulated cell proliferation, apoptosis and the cell cycle through P21 in MM cell lines and promoted MM tumor growth in vivo. Furthermore, we predicted and verified LMLN as a functional downstream target gene of miR-17-3p. Negatively regulated by miR-17-3p, LMLN inhibits MM cell growth, exerting a tumor suppressive function through P21. Taken together, our data identify miR-17-3p as a promising diagnostic biomarker for MM in the clinic and unveil a new miR-17-3p-LMLN-P21 axis in MM progression.

Deficiency of miR-15a/16 upregulates NKG2D in CD8+ T cells to exacerbate dextran sulfate sodium-induced colitis

The miR-15a/16 gene cluster is located in human chromosome 13 (13q14.3) and mouse chromosome 14 (14qC3). These genes are involved in cancer development and immune regulation. Our group has previously verified the binding of the 3'-untranslated region of NKG2D gene by miR-16 through dual-luciferase reporter assay. Herein, we found that miR-16 overexpression inhibited the NKG2D expression of CD8⁺ T cells, and that CD8⁺ NKG2D⁺ T cell frequency increased in miR-15/16^-/- mice. CD8⁺ NKG2D⁺ T cells derived of miR-15/16^-/- mice displayed activatory phenotype with enhanced IFN-γ production and cytotoxicity. The transfection of lentivirus containing antago-miR-16 sequences enhanced the NKG2D expression level of CD8⁺ T cells. However, no significant differences in CD8⁺ NKG2D⁺ T cell frequencies existed between wild-type and miR-15/16-transgenic mice because NKG2D was not expressed on the rest CD8⁺ T cells. When CD8⁺ T cells of miR-15/16-transgenic mice were treated with IL-2 in vitro, the magnitude of NKG2D expression and activation of CD8⁺ T cells was lower than that of wild-type mice. miR-15/16^-/- mice showed that the exacerbation of colitis induced by dextran sulfate sodium (DSS) with more CD8⁺ T cells accumulated in inflamed colons, whereas miR-15/16-transgenic mice ameliorated DSS-induced colitis with less infiltration of CD8⁺ T cells. When NKG2D⁺ cells were depleted with NKG2D antibody in miR-15/16^-/- mice, the aggravated colitis disappeared. All these results demonstrated that NKG2D could be upregulated by decreased miR-16 in CD8⁺ T cells to mediate inflammation. Thus, gene therapy based on the overexpression of miR-16 in CD8⁺ T cells can be used for patients with inflammatory diseases.

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.

Exosomes from Bone Marrow Microenvironment-Derived Mesenchymal Stem Cells Affect CML Cells Growth and Promote Drug Resistance to Tyrosine Kinase Inhibitors

Although major advances have been achieved in the treatment of chronic myeloid leukemia (CML) by using tyrosine kinase inhibitors, patients relapse after withdrawal and need long-term medication. This reflects the CML clones have not been eliminated completely. The precise mechanisms for the maintenance of CML cells are not yet fully understood. The bone marrow microenvironment constitutes the sanctuary for leukemic cells. Mesenchymal stem cells (MSC) are an important component of the bone marrow microenvironment (BM). It plays an important role in the development and drug resistance of CML. Accumulating evidence indicates that exosomes play a vital role in cell-to-cell communication. We successfully isolated and purified exosomes from human bone marrow microenvironment-derived mesenchymal stem cells (hBMMSC-Exo) by serial centrifugation. In the present study, we investigated the effect of hBMMSC-Exo on the proliferation, apoptosis, and drug resistance of CML cells. The results demonstrated that hBMMSC-Exo had the ability to inhibit the proliferation of CML cells in vitro via miR-15a and arrest cell cycle in the G0/G1 phase. However, the results obtained from BALB/c nu/nu mice studies apparently contradicted the in vitro results. In fact, hBMMSC-Exo increased tumor incidence and promoted tumor growth in vivo. Further study showed the antiapoptotic protein Bcl-2 expression increased, whereas the Caspase3 expression decreased. Moreover, the in vivo study in the xenograft tumor model showed that hBMMSC-Exo promoted the proliferation and decreased the sensitivity of CML cells to tyrosine kinase inhibitors, resulting in drug resistance. These results demonstrated that hBMMSC-Exo supported the maintenance of CML cells and drug resistance in BM by cell-extrinsic protective mechanisms. They also suggested that hBMMSC-Exo might be a potential target to overcome the microenvironment-mediated drug resistance.

The Interplay among miRNAs, Major Cytokines, and Cancer-Related Inflammation

Inflammation is closely related with the progression of cancer and is an indispensable component that orchestrates the tumor microenvironment. Studies suggest that different mediator and cellular effectors, including cytokines (interleukins, tumor necrosis factor-α [TNF-α], transforming growth factor-β [TGF-β], and granulocyte macrophage colony-stimulating factor [GM-CSF]), chemokines, as well as some transcription factors (nuclear factor κB [NF-κB], signal transducer and activator of transcription 3 [STAT3], hypoxia-inducible factor-1α [HIF1α]), play a crucial role during cancer-related inflammation (CRI). MicroRNAs (miRNAs) are the key components of cellular physiology. They play notable roles during posttranscriptional gene regulation and, thus, might have a potential role in controlling the inflammatory cascade during cancer progression. Taking into consideration the role identified for miRNAs in relation to inflammatory cytokines, we have tried to review their participation in neoplastic progression. Additionally, the involvement of miRNAs with some important transcription factors (NF-κB, STAT3, HIF1α) and proteins (cyclooxygenase-2 [COX-2], inducible nitric oxide synthase [iNOS]) closely associated with inflammation during cancer has also been discussed. A clear insight into the responsibility of miRNAs in cytokine signaling and inflammation related to CRI could project them as new therapeutic molecules, which could lead to improved treatment of CRI in the near future.

Roles of noncoding RNAs in drug resistance in multiple myeloma

Despite the administration of new effective drugs in recent years, relapse and drug resistance are still the main obstacles in multiple myeloma (MM) treatment, making MM an incurable disease. To overcome drug resistance in MM, it is critical to understand the underlying mechanisms of malfunctioning gene expression and develop novel targeted therapies. During the past few decades, with the discovery and characterization of noncoding RNAs (ncRNAs), the landscape of dysregulated ncRNAs of cancers as well as their biological and pathobiological functions in tumorigenesis and drug resistance have been recognized. Studies about ncRNAs improved the understanding of variations of drug response among individuals at a level distinguished from genetic polymorphism, and provided with new orientations for targeted therapies. In this review, we will summarize the emerging impact and underlying molecular mechanisms of the most relevant classes of ncRNAs in drug resistance of MM, and discuss the potential as well as strategies of treating ncRNAs as therapeutic targets.

Endothelium-Targeted Deletion of microRNA-15a/16-1 Promotes Poststroke Angiogenesis and Improves Long-Term Neurological Recovery

RATIONALE

Angiogenesis promotes neurological recovery after stroke and is associated with longer survival of stroke patients. Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. However, the function of the miR-15a/16-1 cluster in endothelium on postischemic cerebral angiogenesis is not known.

OBJECTIVE

To investigate the functional significance and molecular mechanism of endothelial miR-15a/16-1 cluster on angiogenesis in the ischemic brain.

METHODS AND RESULTS

Endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice and wild-type littermate controls were subjected to 1 hour middle cerebral artery occlusion followed by 28-day reperfusion. Deletion of miR-15a/16-1 cluster in endothelium attenuates post-stroke brain infarction and atrophy and improves the long-term sensorimotor and cognitive recovery against ischemic stroke. Endothelium-targeted deletion of the miR-15a/16-1 cluster also enhances post-stroke angiogenesis by promoting vascular remodeling and stimulating the generation of newly formed functional vessels, and increases the ipsilateral cerebral blood flow. Endothelial cell-selective deletion of the miR-15a/16-1 cluster up-regulated the protein expression of pro-angiogenic factors VEGFA (vascular endothelial growth factor), FGF2 (fibroblast growth factor 2), and their receptors VEGFR2 (vascular endothelial growth factor receptor 2) and FGFR1 (fibroblast growth factor receptor 1) after ischemic stroke. Consistently, lentiviral knockdown of the miR-15a/16-1 cluster in primary mouse or human brain microvascular endothelial cell cultures enhanced in vitro angiogenesis and up-regulated pro-angiogenic proteins expression after oxygen-glucose deprivation, whereas lentiviral overexpression of the miR-15a/16-1 cluster suppressed in vitro angiogenesis and down-regulated pro-angiogenic proteins expression. Mechanistically, miR-15a/16-1 translationally represses pro-angiogenic factors VEGFA, FGF2, and their receptors VEGFR2 and FGFR1, respectively, by directly binding to the complementary sequences within 3'-untranslated regions of those messenger RNAs.

CONCLUSIONS

Endothelial miR-15a/16-1 cluster is a negative regulator for postischemic cerebral angiogenesis and long-term neurological recovery. Inhibition of miR-15a/16-1 function in cerebrovascular endothelium may be a legitimate therapeutic approach for stroke recovery.

Circulating miRNAs as diagnostic biomarkers for multiple myeloma and monoclonal gammopathy of undetermined significance

Background

Multiple myeloma (MM) is still an incurable hematological malignancy evolved from asymptomatic monoclonal gammopathy of undetermined significance (MGUS). New evidence suggests that circulating microRNAs (miRNAs) can serve as stable diagnostic biomarkers for MM and MUGS.

Methods

Serum miRNAs in MM patients, MUGS patients, and healthy controls (HC) were performed by Agilent Bioanalyzer 2100. MicroRNAs in MM detected as promising biomarkers were validated by using quantitative real‐time PCR (qRT‐PCR). Receiver operator characteristic (ROC) curve and multivariate logistic analysis were used to evaluate the diagnostic value of miRNAs for MM and MUGS.

Results

In microarray analysis, the top ten differential expressed miRNAs in MM included miR‐134‐5p, miR‐107, miR‐15a‐5p, miR‐5159‐3p, miR‐1914‐3p, miR‐4723‐3p, miR‐5588‐3p, miR‐6893‐3p, miR‐7106‐3p, and miR‐6722‐5p. Three up‐regulated miRNAs (miR‐134‐5p, miR‐107, and miR‐15a‐5p) were further validated. The elevated expression levels of miR‐134‐5p, miR‐107, and miR‐15a‐5p in qRT‐PCR were increased consistent with microarray analysis. These miRNAs distinguished MM and MUGS from HC significantly. Multivariate logistic analysis showed combination miR‐107, miR‐15a‐5p with Hb, the AUC was 0.954 (95% CI: 0.890‐1.000), sensitivity of 91.3%, and specificity of 93.7% for distinguishing MM from MUGS.

Conclusions

These data demonstrate that miR‐134‐5p, miR‐107, and miR‐15a‐5p are potential diagnostic biomarkers in MM and MUGS. Moreover, the combination miR‐107 and miR‐15a‐5p with Hb can distinguish MM from MUGS.

The Non-Coding RNA Landscape of Plasma Cell Dyscrasias

Despite substantial advancements have been done in the understanding of the pathogenesis of plasma cell (PC) disorders, these malignancies remain hard-to-treat. The discovery and subsequent characterization of non-coding transcripts, which include several members with diverse length and mode of action, has unraveled novel mechanisms of gene expression regulation often malfunctioning in cancer. Increasing evidence indicates that such non-coding molecules also feature in the pathobiology of PC dyscrasias, where they are endowed with strong therapeutic and/or prognostic potential. In this review, we aim to summarize the most relevant findings on the biological and clinical features of the non-coding RNA landscape of malignant PCs, with major focus on multiple myeloma. The most relevant classes of non-coding RNAs will be examined, along with the mechanisms accounting for their dysregulation and the recent strategies used for their targeting in PC dyscrasias. It is hoped these insights may lead to clinical applications of non-coding RNA molecules as biomarkers or therapeutic targets/agents in the near future.

Therapeutic effects of oligo-single-stranded DNA mimicking of hsa-miR-15a-5p on multiple myeloma

Despite the fact that a few novel agents improve the outcome of patients, MM remains incurable. Hence, developing a novel treatment strategy may prove to be promising for the clinical management of MM. Noncoding small RNAs, a cluster of RNAs that do not encode functional proteins, have been underlined that play a pivotal role in the pathogenesis of MM. Our previous study indicated that miR-15a acted as a tumor suppressor, which inhibited the cell proliferation and promoted the apoptosis of MM cells. The level of miR-15a was downregulated in MM cells and correlated with inferior outcome of MM patients. In the present study, we first developed an oligo-single-stranded DNA mimicking the sequence of hsa-miR-15a-5p (OMM-15a) and modified with locked nucleic acid (LNA-15a) to evaluate its anti-MM effects. Our results indicated that the LNA-15a presented an exciting anti-MM effect that showed notable cell growth suppression and apoptosis promotion in MM and other cancer cell lines through downregulating the expression level of target genes BCL-2, VEGF-A, and PHF19. Moreover, LNA-15a treatment significantly improved the anti-MM activity of bortezomib with the synergism effect in OCI-My5 MM cells. In our in vivo study, LNA-15a treatment significantly suppressed the tumor growth, and prolonged the survival of mice compared with the control group. However, our results indicated that the native form of oligo-single-stranded DNA mimic of hsa-miR-15a-5p (OMM-15a) without any modification had no effective inhibition on cell growth, even after increasing the dosage of OMM-15a in the treatment. Altogether, our finding provides the preclinical rationale to support the oligo-single-stranded DNA mimic of hsa-miR-15a with LNA modification, which is a promising tool for the therapy of both MM and other tumors with miR-15a downregulation.

Factors Regulating microRNA Expression and Function in Multiple Myeloma

Intensive research has been undertaken during the last decade to identify the implication of microRNAs (miRNAs) in the pathogenesis of multiple myeloma (MM). The expression profiling of miRNAs in MM has provided relevant information, demonstrating different patterns of miRNA expression depending on the genetic abnormalities of MM and a key role of some miRNAs regulating critical genes associated with MM pathogenesis. However, the underlying causes of abnormal expression of miRNAs in myeloma cells remain mainly elusive. The final expression of the mature miRNAs is subject to multiple regulation mechanisms, such as copy number alterations, CpG methylation or transcription factors, together with impairment in miRNA biogenesis and differences in availability of the mRNA target sequence. In this review, we summarize the available knowledge about the factors involved in the regulation of miRNA expression and functionality in MM.

Abnormal microRNA expression in the course of hematological malignancies

Research on the carcinogenesis process is currently focused primarily on understanding its genetic basis and molecular abnormalities that may be predictive factors and therapeutic targets. It was clearly confirmed recently that microRNAs are involved in the mechanisms of leukocyte development, differentiation, and apoptosis, as well as in the pathogenesis of proliferative diseases of the hematopoietic system. Currently, research strategies allow determination of the deregulation of microRNA profiles in relation to other cytogenetic aberrations, as well as prognostic factors and primary end points. The problem of the possibility of their use as therapeutic targets is also increasingly discussed. In this article, we analyze literature data on abnormalities in microRNA expression in proliferative diseases of the hematopoietic system in the context of classic cytogenetic and molecular aberrations.

The miR-15a/16 gene cluster in human cancer: A systematic review

MicroRNAs (miRNAs) are an important class of endogenous small noncoding single-stranded RNAs that suppress the expression of their target genes through messenger RNA (mRNA) degradation to inhibit transcription and translation. MiRNAs play a crucial regulatory role in many biological processes including proliferation, metabolism, and cellular malignancy. miR-15a/16 is an important tumor suppressor gene cluster with a variety of factors that regulate its transcriptional activity. It has been discovered that a relative reduction of miR-15a/16 expression in various cancers is closely related to the occurrence and progression of tumors. miR-15a/16 takes part in a wide array of biological processes including tumor cell proliferation, apoptosis, invasion, and chemoresistance by binding to the 3'-untranslated region of its target gene's mRNA. In this review, we will examine the complex regulatory network of miR-15a/16 gene expression and its biological functions in human cancers to further elucidate the molecular mechanisms of its antitumor effects.

Overexpression of miR‑21 is involved in acute monocytic leukemia‑associated angiogenesis by targeting IL‑12

Angiogenesis is important in pathophysiological processes, including the pathogenesis of acute monocytic leukemia (AML). MicroRNA‑21 (miR‑21) is overexpressed and exhibits oncogenic activity in cancer. However, the biological mechanism underlying the effect of miR‑21 in AML remains to be fully elucidated. In the present study, the expression levels of miR‑21 and vascular endothelial growth factor (VEGF) were determined in 26 patients with AML and 28 healthy individuals. The secretion of VEGF was also measured following the transfection of THP‑1 cells with miR‑21 mimic or inhibitor. The supernatants of the THP‑1 cells, which were transfected with miR‑21 mimic, inhibitor or small interfering RNA (si)VEGF, respectively, were used to incubate human umbilical vein endothelial cells (HUVECs), following which tube formation of the HUVECs was measured. miR‑21 targets were predicted using a biological target prediction website and confirmed using a luciferase assay. The effects of interleukin (IL)‑12 were investigated by examining the tube formation of HUVECs and the secretion of VEGF following recombinant human (rh) IL‑12 pretreatment. The results revealed that miR‑21 and VEGF expression was significantly increased in the peripheral blood monocytes of the patients, compared with the healthy controls. There was negative correlation between the expression of IL‑12 and miR‑21 in the serum of patients with AML. Furthermore, supernatant VEGF levels from the miR‑21 mimic‑transfected THP‑1 cells were increased, whereas a decreasing trend was observed in the miR‑21 inhibitor group. The angiogenic ability of the HUVECs pretreated with supernatant from the THP‑1 cells transfected with miR‑21 mimic was higher, and was lower in THP‑1 cells co‑transfected with miR‑21 mimic and siVEGF, compared with the miR‑21 mimic only group. A luciferase assay demonstrated that IL‑12 was the direct target of miR‑21, and the level of IL‑12 in the supernatant of THP‑1 cells transfected with miR‑21 mimic was increased. IL‑12 pretreatment increased VEGF expression and angiogenic ability in HUVECs. The inactivation of miR‑21 or activation of its target gene may be a potential therapeutic strategy in human AML.

The expression and role of miR-181a in multiple myeloma

This study aims to investigate the role of miR-181a in multiple myeloma (MM). Fresh peripheral blood and bone marrows were collected. Expression of miR-181a, BCL-2 mRNA, and NOVA1 mRNA was detected by RT-qPCR. The correlation between miR-181a and clinical features of MM was further analyzed. miR-181a in serum and bone marrow mononuclear cells of MM patients were significantly higher. And, miR-181a level was significantly higher in MM Durie-Salmon stage III than that in stage I+II. miR-181a was positively correlated to Durie-Salmon staging, age, kidney injury, bone injury, β2-MG whereas negatively related to red blood cell, hemoglobin, and albumin. Additionally, BCL-2 and NOVA1 were predicted to be downstream targets of miR-181a. BCL-2 mRNA was significantly higher in the bone marrow mononuclear cells from MM patients. To sum up, the miR-181a expression is increased in peripheral blood and bone marrow of MM patients and is closely related to the clinical pathological indicators of MM.

The ceramide pathway is involved in the survival, apoptosis and exosome functions of human multiple myeloma cells in vitro

Multiple myeloma (MM) is characterized by the clonal proliferation of malignant plasma cells and refractoriness to traditional therapies. It has been shown that exosomes are involved in modulating the progression and the metastasis of cancers through microRNAs (miRs). Ceramide is a type of sphingolipid; the ceramide pathway of exosomal secretion has been shown to affect the apoptosis of cancer cells. But the role of this pathway in MM cell function, exosome function and miR regulation remains unknown. In this study, we showed that C6 ceramide (an exogenous ceramide supplement, 1.25-40 μmol/L) dose-dependently inhibited the proliferation and promoted the apoptosis in human MM OPM2 cell line, which were associated with elevated caspase 3/9 and PARP cleavage. We also found that C6 ceramide (5-20 μmol/L) dose-dependently stimulated exosome secretion and increased exosomal levels of tumor-suppressive miRs (miR 202, miR 16, miR 29b and miR 15a). Of note, exosomes from C6 ceramide-treated OPM2 cells could influence the proliferation and apoptosis of the recipient OPM2 cells, which correlated with increased tumor-suppressive exosomal miRs. In contrast, GW4869 (a ceramide inhibitor, 5-20 μmol/L) exerted the opposite effects on the regulation of MM function, exosome secretion and miR levels in MM exosomes. However, exosomes from GW4869-treated OPM2 cells had no effect on these miRs and the survival of targeted OPM2 cells. Taken together, our findings reveal that the ceramide pathway modulates MM survival, probably directly via the caspase pathway and indirectly via exosomal miR mechanisms.

The mechanism study of miR-125b in occurrence and progression of multiple myeloma

Although many efforts have contributed to improve our knowledge of molecular pathogenesis about multiple myeloma (MM), the role and significance of microRNAs and long noncoding RNAs in MM cells, along with the core mechanism remains virtually absent. The mRNA levels of miR-125b and MALAT1 in MM cell lines were detected by qRT-PCR. The influence of Lenti-Sh-miR-125b on cell viability and the Notch-1 pathway-related proteins were assessed by MTT method and western blot, respectively. We also investigated the regulation effect between MALAT1 and Notch1 pathway. Moreover, the connection between Notch1 signaling and MM cell growth was discussed in-depth. The reverse effect of pcDNA-Notch1 on the cell viability and Notch-1 pathway proteins induced by Si-MALAT1 was also studied. Furthermore, miR-125b overexpressing MM cell lines were injected subcutaneously into nude mice. MiR-125b and MALAT1 were inversely expressed in MM cell lines. Lenti-Sh-miR-125b inhibited the expression of MALAT1 and Notch-1 protein. Binding sites were confirmed between miR-125b and MALAT1, and silencing MALAT1 did not alter the expression of Notch-1. The apoptosis rate was increased and the survival rate was decreased obviously in GSI XII (targeted cleavage of Notch-1 receptor) group, along with the inhibited Notch1 and HES1 proteins. Moreover, the decreased cell viability and Notch-1 pathway proteins induced by Si-MALAT1 could be reversed by pcDNA-Notch1. Lenti-Sh-miR-125b promoted survival and decreased Notch1 and HES1 proteins levels, while this effect was reversed by si -MALAT1. MiR-125b regulated MALAT1 expression via Notch1 signaling pathway to regulate cell growth, thus participating in the occurrence and progression of MM, which functioned as a therapeutic target for tracking MM.

Inflammatory and Anti-Inflammatory Equilibrium, Proliferative and Antiproliferative Balance: The Role of Cytokines in Multiple Myeloma

Multiple myeloma (MM) is typically exemplified by a desynchronized cytokine system with increased levels of inflammatory cytokines. We focused on the contrast between inflammatory and anti-inflammatory systems by assessing the role of cytokines and their influence on MM. The aim of this review is to summarize the available information to date concerning this equilibrium to provide an overview of the research exploring the roles of serum cytokines in MM. However, the association between MM and inflammatory cytokines appears to be inadequate, and other functions, such as pro-proliferative or antiproliferative effects, can assume the role of cytokines in the genesis and progression of MM. It is possible that inflammation, when guided by cancer-specific Th1 cells, may inhibit tumour onset and progression. In a Th1 microenvironment, proinflammatory cytokines (e.g., IL-6 and IL-1) may contribute to tumour eradication by attracting leucocytes from the circulation and by increasing CD4 ⁺ T cell activity. Hence, caution should be used when considering therapies that target factors with pro- or anti-inflammatory activity. Drugs that may reduce the tumour-suppressive Th1-driven inflammatory immune response should be avoided. A better understanding of the relationship between inflammation and myeloma will ensure more effective therapeutic interventions.

Cancer Hallmarks and MicroRNAs: The Therapeutic Connection

Human cancers are characterized by a number of hallmarks, including sustained proliferative signaling, evasion of growth suppressors, activated invasion and metastasis, replicative immortality, angiogenesis, resistance to cell death, and evasion of immune destruction. As microRNAs (miRNAs) are deregulated in virtually all human cancers, they show involvement in each of the cancer hallmarks as well. In this chapter, we describe the involvement of miRNAs in cancer from a cancer hallmarks and targeted therapeutics point of view. As no miRNA-based cancer therapeutics are available to date, and the only clinical trial on miRNA-based cancer therapeutics (MRX34) was terminated prematurely due to serious adverse events, we are focusing on protein-coding miRNA targets for which targeted therapeutics in oncology are already approved by the FDA. For each of the cancer hallmarks, we selected major protein-coding players and describe the miRNAs that target them.

LncRNA OIP5-AS1 loss-induced microRNA-410 accumulation regulates cell proliferation and apoptosis by targeting KLF10 via activating PTEN/PI3K/AKT pathway in multiple myeloma

Numerous studies confirmed that aberrant miRNAs expression contributes to multiple myeloma (MM) development and progression. However, the roles of specific miRNAs in MM remain to be investigated. In present study, we demonstrated that miR-410 expression was increased in MM newly diagnosed and relapsed tissues and cell lines. Clinical analysis revealed that miR-410 was positively correlated with advanced ISS stage. Moreover, high miR-410 expression in MM patients showed an obvious shorter overall survival and progression-free survival. Gain- and loss-of function experiments indicated that miR-410 promoted cell proliferation, cell cycle progression and apoptosis inhibition both in vitro and in vivo. Moreover, KLF10 was identified as a direct downstream target of miR-410 in MM cells, and mediated the functional influence of miR-410 in MM, resulting in PTEN/AKT activation. In clinical samples of MM, miR-410 inversely correlated with KLF10. Alteration of KLF10 expression or AKT inhibitor at least partially abolished the biological effects of miR-410 on MM cells. Furthermore, downregulated expression of lncRNA OIP5-AS1 was inversely correlated with miR-410 expression in MM tissues. LncRNA OIP5-AS1 could modulate the miR-410 expression and regulate its target KLF10/PTEN/AKT-mediated cellular behaviors. Taken together, this research supports the first evidence that lncRNA OIP5-AS1 loss-induced miR-410 accumulation facilitates cell proliferation, cycle progression and apoptosis inhibition by targeting KLF10 via activating PTEN/PI3K/AKT pathway in MM.

Gestational Exposure to Sidestream (Secondhand) Cigarette Smoke Promotes Transgenerational Epigenetic Transmission of Exacerbated Allergic Asthma and Bronchopulmonary Dysplasia

Embryonic development is highly sensitive to xenobiotic toxicity and in utero exposure to environmental toxins affects physiological responses of the progeny. In the United States, the prevalence of allergic asthma (AA) is inexplicably rising and in utero exposure to cigarette smoke increases the risk of AA and bronchopulmonary dysplasia (BPD) in children and animal models. We reported that gestational exposure to sidestream cigarette smoke (SS), or secondhand smoke, promoted nicotinic acetylcholine receptor-dependent exacerbation of AA and BPD in mice. Recently, perinatal nicotine injections in rats were reported to induce peroxisome proliferator-activated receptor γ-dependent transgenerational transmission of asthma. Herein, we show that first generation and second generation progeny from gestationally SS-exposed mice exhibit exacerbated AA and BPD that is not dependent on the decrease in peroxisome proliferator-activated receptor γ levels. Lungs from these mice show strong eosinophilic infiltration, excessive Th2 polarization, marked airway hyperresponsiveness, alveolar simplification, decreased lung compliance, and decreased lung angiogenesis. At the molecular level, these changes are associated with increased RUNX3 expression, alveolar cell apoptosis, and the antiangiogenic factor GAX, and decreased expression of HIF-1α and proangiogenic factors NF-κB and VEGFR2 in the 7-d first generation and second generation lungs. Moreover, the lungs from these mice exhibit lower levels of microRNA (miR)-130a and increased levels of miR-16 and miR-221. These miRs regulate HIF-1α-regulated apoptotic, angiogenic, and immune pathways. Thus the intergenerational effects of gestational SS involve epigenetic regulation of HIF-1α through specific miRs contributing to increased incidence of AA and BPD in the progenies.