MicroRNA-146a and AMD3100, two ways to control CXCR4 expression in acute myeloid leukemias

CXC chemokine receptor 4 (CXCR4) blockade in cancer treatment

CXC chemokine receptor type 4 (CXCR4) is a member of the G protein-coupled receptors (GPCRs) superfamily and is specific for CXC chemokine ligand 12 (CXCL12, also known as SDF-1), which makes CXCL12/CXCR4 axis. CXCR4 interacts with its ligand, triggering downstream signaling pathways that influence cell proliferation chemotaxis, migration, and gene expression. The interaction also regulates physiological processes, including hematopoiesis, organogenesis, and tissue repair. Multiple evidence revealed that CXCL12/CXCR4 axis is implicated in several pathways involved in carcinogenesis and plays a key role in tumor growth, survival, angiogenesis, metastasis, and therapeutic resistance. Several CXCR4-targeting compounds have been discovered and used for preclinical and clinical cancer therapy, most of which have shown promising anti-tumor activity. In this review, we summarized the physiological signaling of the CXCL12/CXCR4 axis and described the role of this axis in tumor progression, and focused on the potential therapeutic options and strategies to block CXCR4.

Aberrant regulation of CXCR4 in cancer via deviant microRNA-targeted interactions

CXCR4 is involved in many facets of cancer, including being a major player in establishing metastasis. This is in part due to the deregulation of CXCR4, which can be attributed to many genetic and epigenetic mechanisms, including aberrant microRNA-CXCR4 interaction. MicroRNAs (miRNAs) are a type of small non-coding RNA that primarily targets the 3' UTR of mRNA transcripts, which in turn suppresses mRNA and subsequent protein expression. In this review, we reported and characterized the many aberrant miRNA-CXCR4 interactions that occur throughout human cancers. In particular, we reported known target sequences located on the 3' UTR of CXCR4 transcripts that tumour suppressor miRNAs bind and therefore regulate expression by. From these aberrant interactions, we also documented affected downstream genes/pathways and whether a particular tumour suppressor miRNA was reported as a prognostic marker in its respected cancer type. In addition, a limited number of cancer-causing miRNAs coined 'oncomirs' were reported and described in relation to CXCR4 regulation. Moreover, the mechanisms underlying both tumour suppressor and oncomir deregulations concerning CXCR4 expression were also explored. Furthermore, the miR-146a-CXCR4 axis was delineated in oncoviral infected endothelial cells in the context of virus-causing cancers. Lastly, miRNA-driven therapies and CXCR4 antagonist drugs were discussed as potential future treatment options in reported cancers pertaining to deregulated miRNA-CXCR4 interactions.

MSX-122: Is an effective small molecule CXCR4 antagonist in cancer therapy?

Chemokines, a subgroup of cytokines along with their receptors, are involved in various biologic processes and regulation of a wide range of immune responses in different physiologic and pathologic states such as tissue repair, infection, and inflammation. C-X-C motif chemokine receptor 4 (CXCR4), a G-protein-coupled receptor (GPCR), has one identified natural ligand termed stromal-derived factor-1(SDF-1 or CXCL12). Evidence demonstrated that the ligation of SDF-1 to CXCR4 initiates several intracellular signaling pathways, regulating cell proliferation, survival, chemotaxis, migration, angiogenesis, adhesion, as well as bone marrow (BM)-resident cells homing and mobilization. Additionally, CXCR4 is expressed by tumor cells in blood malignancies and solid tumors. Therefore, CXCR4 is considered a potential therapeutic target in cancer therapy, and CXCR4 antagonists, including AMD3100, MSX-122, BPRCX807, WZ811, Motixafortide, TN14003, AMD3465, and AMD1170, have been employed in experimental and clinical studies to enhance cancer therapy. MSX-122 is a specific small-molecule antagonist of CXCR4/CXCL12 and the only orally available non-peptide CXCR4 antagonist with promising anti-cancer properties. Studies have shown that MSX-122 is particularly important in treating metastatic cancers and has great therapeutic potential. Accordingly, this review summarized the characteristics of MSX-122 and its effects on the CXCL12/CXCR4 axis as well as cancer therapy.

MiR-146a suppresses the expression of CXCR4 and alters survival, proliferation and migration rate in colorectal cancer cells

CXCR4 plays an important role in colorectal cancer (CRC) development and metastasis. Some previous studies have indicated CXCR4 as a therapeutic target in cancer. CXCR4 is known as a direct target of miR-146a. The present study aimed to investigate how exogenous induction of miR-146a affects CXCR4 gene and protein expression and also proliferation, apoptosis and migration of CRC cells. Transfection of Caco-2 and SW480 cells by a synthetic miR-146a mimic led to downregulation of CXCR4 expression at both gene and protein levels. It also downregulated expression of several miR-146a targets, including GSK3B, IRAK1, TRAF6, AKT2, SMAD4, EGFR and NFKB1, mostly in SW480 cells. Overexpression of miR-146a resulted in a partial cell cycle arrest in the both cell lines, while the apoptotic rate was also decreased. In regards to epithelial-mesenchymal transition factors, VIM was downregulated in the both cell lines, but SNAI1 was upregulated in Caco-2 cells. The wound closure assay showed a reduction in cell migration in SW480 cells, but an opposite effect was detected in Caco-2 cells following transfection with miR-146a mimic. Therefore, our results are indicating that overexpression of miR-146a, despite downregulation of oncogenic CXCR4, may not lead to a universal tumor suppressive effect in all CRC cells, and this is possibly due to differences in miR-146a effects on signaling pathways in each cell type. Selection of miR-146a for tumor suppression requires enough details regarding the signaling profile of cancer cells otherwise it may produce unexpected outcome.

Alterations in microRNA Expression during Hematopoietic Stem Cell Mobilization

Simple Summary

Lymphoproliferative disorders comprise a heterogeneous group of hematological malignancies characterized by abnormal lymphocyte proliferation. Autologous hematopoietic stem cell transplantation plays a very important role in the treatment of lymphoproliferative diseases. The key element in this process is the effective mobilization of hematopoietic cells from the marrow niche to the peripheral blood. Mobilization of HSC is regulated by many factors, out of which miRNAs present in the hematopoietic niche via targeting cytokines, and signaling pathways may play an important regulatory role. This study investigated the expression of selected miRNAs in patients with multiple myeloma, Hodgkin’s lymphomas, and non-Hodgkin’s lymphomas undergoing mobilization procedures. The aim of the study was to evaluate the expression of hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-126-3p, hsa-miR-146a-5p, hsa-miR-155-5p, and hsa-miR-223-3p during the mobilization procedure, and to assess their role in mobilization efficacy. The level of miRNAs was tested at two time points before the initiation of mobilization and on the day of the first apheresis. Our results suggest that the investigated miRNAs, especially hsa-miR-146a-5p, may influence the efficacy of HSC mobilization.

Abstract

microRNAs play an important role in the regulation of gene expression, cell fate, hematopoiesis, and may influence the efficacy of CD34+ cell mobilization. The present study examines the role of hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-126-3p, hsa-miR-146a-5p, hsa-miR-155-5p, and hsa-miR-223-3p in the course of hematopoietic stem cell mobilization. The numbers of CD34+ cells collected in patients with hematological malignancies (39 multiple myelomas, 11 lymphomas) were determined during mobilization for an autologous hematopoietic stem cell transplantation. The miRNA level was evaluated by RT-PCR. Compared to baseline, a significant decline in hsa-miR-15a-5p, hsa-miR-16-5p, hsa-miR-126-3p, hsa-miR-146a-5p, and hsa-miR-155-5p was observed on the day of the first apheresis (day A). An increase was observed only in the expression of hsa-miR-34a-5p. On day A, a negative correlation was found between hsa-miR-15a-5p and hsa-miR-146a-5p levels and the number of CD34+ cells in peripheral blood. A negative correlation was observed between hsa-miR-146a-5p and the number of collected CD34+ cells after the first apheresis. Good mobilizers, defined according to GITMO criteria, demonstrated a lower hsa-miR-146a-5p level on day A than poor mobilizers. Patients from the hsa-miR-146a-5p “low expressors” collected more CD34+ cells than “high expressors”. Our results suggest that the investigated miRNAs, especially hsa-miR-146a-5p, may influence the efficacy of HSC mobilization.

Atorvastatin Pretreatment Ameliorates Mesenchymal Stem Cell Migration through miR-146a/CXCR4 Signaling

BACKGROUND

We previously found that atorvastatin (ATV) enhanced mesenchymal stem cells (MSCs) migration, by a yet unknown mechanism. CXC chemokine receptor 4 (CXCR4) is critical to cell migration and regulated by microRNA-146a (miR-146a). Therefore, this study aimed to assess whether ATV ameliorates MSCs migration through miR-146a/CXCR4 signaling.

METHODS

Expression of CXCR4 was evaluated by flow cytometry. Expression of miR-146a was examined by reverse transcription-quantitative polymerase chain reaction. A transwell system was used to assess the migration ability of MSCs. Recruitment of systematically delivered MSCs to the infarcted heart was evaluated in Sprague-Dawley rats with acute myocardial infarction (AMI). Mimics of miR-146a were used in vitro, and miR-146a overexpression lentivirus was used in vivo, to assess the role of miR-146a in the migration ability of MSCs.

RESULTS

The results showed that ATV pretreatment in vitro upregulated CXCR4 and induced MSCs migration. In addition, flow cytometry demonstrated that miR-146a mimics suppressed CXCR4, and ATV pretreatment no longer ameliorated MSCs migration because of decreased CXCR4. In the AMI model, miR-146a-overexpressing MSCs increased infarct size and fibrosis.

CONCLUSION

The miR-146a/CXCR4 signaling pathway contributes to MSCs migration and homing induced by ATV pretreatment. miR-146a may be a novel therapeutic target for stimulating MSCs migration to the ischemic tissue for improved repair.

Role of CXCR4 in the progression and therapy of acute leukaemia

CXCR4 is expressed on leukaemia cells and haematopoietic stem cells (HSCs), and its ligand stromal-derived factor 1 (SDF-1) is produced abundantly by stromal cells in the bone marrow (BM). The SDF-1/CXCR4 axis plays important roles in homing to and retention in the protective BM microenvironment of malignant leukaemia cells and normal HSCs. CXCR4 expression is regulated by multiple mechanisms and the level of CXCR4 expression on leukaemia cells has prognostic indications in patients with acute leukaemia. CXCR4 antagonists can mobilize leukaemia cells from BM to circulation, which render them effectively eradicated by chemotherapeutic agents, small molecular inhibitors or hypomethylating agents. Therefore, such combinational therapies have been tested in clinical trials. However, new evidence emerged that drug-resistant leukaemia cells were not affected by CXCR4 antagonists, and the migration of certain leukaemia cells to the leukaemia niche was independent of SDF-1/CXCR4 axis. In this review, we summarize the role of CXCR4 in progression and treatment of acute leukaemia, with a focus on the potential of CXCR4 as a therapeutic target for acute leukaemia. We also discuss the potential value of using CXCR4 antagonists as chemosensitizer for conditioning regimens and immunosensitizer for graft-vs-leukaemia effects of allogeneic haematopoietic stem cell transplantation.

Exosomes derived from chronic lymphocytic leukaemia cells transfer miR-146a to induce the transition of mesenchymal stromal cells into cancer-associated fibroblasts

Chronic lymphocytic leukaemia (CLL) is the most prevalent leukaemia and remains incurable. Mesenchymal stem cells (MSCs) can promote tumour progression by differentiating into cancer-associated fibroblasts (CAFs). However, the mechanisms by which tumour cells induce the transition of MSCs to CAFs are still largely undefined. Exosomes can regulate recipient cellular function by mediating intracellular communication. This study aimed to investigate whether CLL cells regulate the transition of bone marrow-derived MSCs (BM-MSCs) to CAFs via exosomal miR-146a delivery. The exosomes were isolated from CLL cell line MEC-1 (CLL-Exo) and then co-cultured with BM-MSCs. The expression of α-smooth muscle actin (α-SMA) and fibroblast-activated protein (FAP) were determined by immunofluorescence, quantitative real-time polymerase chain reaction and western blot. A luciferase reporter assay was performed to verify whether ubiquitin-specific peptidase 16 (USP16) was a target of miR-146a. CLL-Exo treatment up-regulated miR-146a and down-regulated expression of CAF markers (α-SMA and FAP) and USP16. The inducing effect of CLL-Exo on CAF marker expression was compromised when miR-146a expression was inhibited in CLL-Exo. USP16 was confirmed as a direct target of miR-146a and USP16 overexpression in BM-MSCs abrogated the CLL-Exo-mediated up-regulation of CAF markers. Collectively, CLL-Exo delivered miR-146a into BM-MSCs where miR-146a mediated transition of BM-MSCs into CAFs by targeting USP16.

MicroRNAs Associated With a Good Prognosis of Acute Myeloid Leukemia and Their Effect on Macrophage Polarization

Acute myeloid leukemia (AML) is an aggressive myeloid malignancy with poor outcomes despite very intensive therapeutic approaches. For the majority of patients which are unfit and treated less intensively, the prognosis is even worse. There has been unspectacular progress in outcome improvement over the last decades and the development of new approaches is of tremendous interest. The tumor microenvironment is credited with an important role in supporting cancer growth, including leukemogenesis. Macrophages are part of the tumor microenvironment and their contribution in this setting is increasingly being deciphered, these cells being credited with a tumor supporting role. Data on macrophage role and polarization in leukemia is scarce. MicroRNAs (miRNAs) have a role in the post-transcriptional regulation of gene expression, by impending translation and promoting degradation of messenger RNAs. They are important modulators of cellular pathways, playing major roles in normal hematopoietic differentiation. miRNA expression is significantly correlated with the prognosis of hematopoietic malignancies, including AML. Oncogenic miRNAs correlate with poor prognosis, while tumor suppressor miRNAs, which inhibit the expression of proto-oncogenes, are correlated with a favorable prognosis. miRNAs are proposed as biomarkers for diagnosis and prognosis and are regarded as therapeutic approaches in many cancers, including AML. miRNAs with epigenetic or modulatory activity, as well as with synergistic activity with chemotherapeutic agents, proved to be promising therapeutic targets in experimental, pre-clinical approaches. The clinical availability of emerging compounds with mimicking or suppressor activity provides the opportunity for future therapeutic targeting of miRNAs. The present paper is focusing on miRNAs which, according to current knowledge, favorably impact on AML outcomes, being regarded as tumor suppressors, and reviews their role in macrophage polarization. We are focusing on miRNA expression in the setting of AML, but data on correlations between miRNA expression and macrophage polarization is mostly coming from studies involving normal tissue.

The Chemokine Receptor CXCR4 in Cell Proliferation and Tissue Regeneration

The CXCR4 receptor upon binding its ligands triggers multiple signaling pathways that orchestrate cell migration, hematopoiesis and cell homing, and retention in the bone marrow. However, CXCR4 also directly controls cell proliferation of non-hematopoietic cells. This review focuses on recent reports pointing to its pivotal role in tissue regeneration and stem cell activation, and discusses the connection to the known role of CXCR4 in promoting tumor growth. The mechanisms may be similar in all cases, since regeneration often recapitulates developmental processes, and cancer often exploits developmental pathways. Moreover, cell migration and cell proliferation appear to be downstream of the same signaling pathways. A deeper understanding of the complex signaling originating from CXCR4 is needed to exploit the opportunities to repair damaged organs safely and effectively.

Microarray analysis of differentially expressed microRNAs in myelodysplastic syndromes

BACKGROUND

Our study aimed to analyze differential microRNA expression between myelodysplastic syndromes (MDS) and normal bone marrow, and to identify novel microRNAs relevant to MDS pathogenesis.

METHODS

MiRNA microarray analysis was used to profile microRNA expression levels in MDS and normal bone marrow. Quantitative real-time polymerase chain reaction was employed to verify differentially expressed microRNAs.

RESULTS

MiRNA microarray analysis showed 96 significantly upregulated (eg, miR-146a-5p, miR-151a-3p, miR-125b-5p) and 198 significantly downregulated (eg, miR-181a-2-3p, miR-124-3p, miR-550a-3p) microRNAs in MDS compared with normal bone marrow. The quantitative real-time polymerase chain reaction confirmed the microarray analysis: expression of six microRNAs (miR-155-5p, miR-146a-5p, miR-151a-3p, miR-221-3p, miR-125b-5p, and miR-10a-5p) was significantly higher in MDS, while 3 microRNAs (miR-181a-2-3p, miR-124-3p, and miR-550a-3p) were significantly downregulated in MDS. Bioinformatics analysis demonstrated that differentially expressed microRNAs might participate in MDS pathogenesis by regulating hematopoiesis, leukocyte migration, leukocyte apoptotic process, and hematopoietic cell lineage.

CONCLUSIONS

Our study indicates that differentially expressed microRNAs might play a key role in MDS pathogenesis by regulating potential relevant functional and signaling pathways. Targeting these microRNAs may provide new treatment modalities for MDS.

Dual CXCR4 and E-Selectin Inhibitor, GMI-1359, Shows Anti-Bone Metastatic Effects and Synergizes with Docetaxel in Prostate Cancer Cell Intraosseous Growth

Metastatic castration resistant prostate cancer (mCRPC) relapses due to acquired resistance to docetaxel-based chemotherapy and remains a major threat to patient survival. In this report, we tested the effectiveness of a dual CXCR4/E-selectin antagonist, GM-I1359, in vitro and in vivo, as a single agent or in combination with docetaxel (DTX). This agent was compared to the single CXCR4 antagonist, CTCE-9908, and E-selectin antagonist, GMI-1271. Here we demonstrate that CXCR4 antagonism reduced growth and enhanced DTX treatment in PCa cell lines as well as restored DTX effectiveness in DTX-resistant cell models. The efficacy of dual antagonist was higher respect to those observed for single CXCR4 antagonism. GM1359 impacted bone marrow colonization and growth in intraventricular and intratibial cell injection models. The anti-proliferative effects of GMI-1359 and DTX correlated with decreased size, osteolysis and serum levels of both mTRAP and type I collagen fragment (CTX) in intra-osseous tumours suggesting that the dual CXCR4/E-selectin antagonist was a docetaxel-sensitizing agent for bone metastatic growth. Single agent CXCR4 (CTCE-9908) and E-selectin (GMI-1271) antagonists resulted in lower sensitizing effects compared to GMI-1359. These data provide a biologic rationale for the use of a dual E-selectin/CXCR4 inhibitor as an adjuvant to taxane-based chemotherapy in men with mCRPC to prevent and reduce bone metastases.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

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.

MiR-9 functions as a tumor suppressor in acute myeloid leukemia by targeting CX chemokine receptor 4

MicroRNAs (miRNAs) play key roles in the pathogenesis of many cancers, including acute myeloid leukemia (AML). Although miRNA-9 (miR-9) is involved in the leukemogenesis of AML, the underlying mechanisms remain to be elucidated. In this study, we found that miR-9 and C-X-C chemokine receptor 4 (CXCR4) were differentially expressed in myeloid leukemia, particularly in AML. The inverse correlation between miR-9 and CXCR4 was identified in AML samples and cell lines. The AML patients simultaneously with high levels of CXCR4 and low expression of miR-9 possessed poor prognosis. In vitro, miR-9 inhibited the proliferation, apoptosis resistance, migration, and invasion of AML cells. Dual luciferase assays verified CXCR4 as a direct target of miR-9. The suppressive effects of miR-9 on AML cells were counteracted or mimicked by CXCR4 overexpression or depletion, respectively. Overall, this study reveals that miR-9 retards the aggressive behaviors of AML cells by repressing CXCR4. Thus, miR-9/CXCR4 axis may represent a potential therapeutic target for AML.

miR‑146a‑5p expression is upregulated by the CXCR4 antagonist TN14003 and attenuates SDF‑1‑induced cartilage degradation

Osteoarthritis (OA) is an aseptic inflammatory disease which is associated with the stromal cell-derived factor 1/C-X-C chemokine receptor type 4 (SDF-1/CXCR4) axis. Accumulating studies have identified numbers of microRNAs (miRNAs) that serve important roles in the pathogenesis of OA. However, whether and how the inhibition of the SDF-1/CXCR4 axis induces alterations in miRNA expression remains largely unclear. miRNA profiling was performed in OA chondrocytes stimulated with SDF-1 alone, or SDF-1 with the CXCR4 antagonist TN14003 by miRNA microarray. Candidate miRNAs were verified by reverse transcription quantitative polymerase chain reaction. Bioinformatic analyses including target prediction, gene ontology (GO) and pathway analysis were performed to explore the potential functions of candidate miRNAs. Notably, 7 miRNAs (miR-146a-5p, miR-221-3p, miR-126-3p, miR-185-5p, miR-155-5p, miR-124-3p and miR-130a-3p) were significantly differentially expressed. GO analysis indicated that miR-146a-5p and its associated genes were enriched in receptor regulatory activity, nuclear factor-kappa-light-chain-enhancer of activated B cells (NF-κB)-inducing kinase activity, cellular response to interleukin-1, cytokine-cytokine receptor interaction, NF-κB signaling pathway and osteoclast differentiation pathways. CXCR4 was predicted to be a target of miR-146a-5p with high importance. The mRNA and protein levels of key factors involved in cartilage degeneration were measured following manipulation of the expression levels of miR-146a-5p in OA chondrocytes. CXCR4 and MMP-3 levels were negatively associated with miR-146a-5p expression, while the levels of type II collagen and aggrecan were positively associated. These data reveal that TN14003 upregulates miR-146a-5p expression, and also pinpoints a novel role of miR-146a-5p in inhibiting cartilage degeneration by directly targeting the SDF-1/CXCR4 axis.

miR-146 and miR-155: Two Key Modulators of Immune Response and Tumor Development

MicroRNAs (miRNAs or miRs) are a class of evolutionarily-conserved small, regulatory non-coding RNAs, 19–3 nucleotides in length, that negatively regulate protein coding gene transcripts’ expression. miR-146 (146a and 146b) and miR-155 are among the first and most studied miRs for their multiple roles in the control of the innate and adaptive immune processes and for their deregulation and oncogenic role in some tumors. In the present review, we have focused on the recent acquisitions about the key role played by miR-146a, miR-146b and miR-155 in the control of the immune system and in myeloid tumorigenesis. Growing experimental evidence indicates an opposite role of miR-146a with respect to miR-155 in the fine regulation of many steps of the immune response, acting at the level of the various cell types involved in innate and adaptive immune mechanisms. The demonstration that miR-155 overexpression plays a key pathogenic role in some lymphomas and acute myeloid leukemias has led to the development of an antagomir-based approach as a new promising therapeutic strategy.

Phosphatidylcholine-specific phospholipase C inhibition down- regulates CXCR4 expression and interferes with proliferation, invasion and glycolysis in glioma cells

Background

The chemokine receptor CXCR4 plays a crucial role in tumors, including glioblastoma multiforme (GBM), the most aggressive glioma.

Phosphatidylcholine-specific phospholipase C (PC-PLC), a catabolic enzyme of PC metabolism, is involved in several aspects of cancer biology and its inhibition down-modulates the expression of growth factor membrane receptors interfering with their signaling pathways.

In the present work we investigated the possible interplay between CXCR4 and PC-PLC in GBM cells.

Methods

Confocal microscopy, immunoprecipitation, western blot analyses, and the evaluation of migration and invasion potential were performed on U87MG cells after PC-PLC inhibition with the xanthate D609. The intracellular metabolome was investigated by magnetic resonance spectroscopy; lactate levels and lactate dehydrogenase (LDH) activity were analyzed by colorimetric assay.

Results

Our studies demonstrated that CXCR4 and PC-PLC co-localize and are associated on U87MG cell membrane. D609 reduced CXCR4 expression, cell proliferation and invasion, interfering with AKT and EGFR activation and expression. Metabolic analyses showed a decrease in intracellular lactate concentration together with a decrement in LDH activity.

Conclusions

Our data suggest that inhibition of PC-PLC could represent a new molecular approach in glioma biology not only for its ability in modulating cell metabolism, glioma growth and motility, but also for its inhibitory effect on crucial molecules involved in cancer progression.

Mesenchymal Stem Cells Support Survival and Proliferation of Primary Human Acute Myeloid Leukemia Cells through Heterogeneous Molecular Mechanisms

Acute myeloid leukemia (AML) is a bone marrow malignancy, and various bone marrow stromal cells seem to support leukemogenesis, including osteoblasts and endothelial cells. We have investigated how normal bone marrow mesenchymal stem cells (MSCs) support the in vitro proliferation of primary human AML cells. Both MSCs and primary AML cells show constitutive release of several soluble mediators, and the mediator repertoires of the two cell types are partly overlapping. The two cell populations were cocultured on transwell plates, and MSC effects on AML cells mediated through the local cytokine/soluble mediator network could thus be evaluated. The presence of normal MSCs had an antiapoptotic and growth-enhancing effect on primary human AML cells when investigating a group of 51 unselected AML patients; this was associated with increased phosphorylation of mTOR and its downstream targets, and the effect was independent of cytogenetic or molecular-genetic abnormalities. The MSCs also supported the long-term proliferation of the AML cells. A subset of the patients also showed an altered cytokine network with supra-additive levels for several cytokines. The presence of cytokine-neutralizing antibodies or receptor inhibitors demonstrated that AML cells derived from different patients were heterogeneous with regard to effects of various cytokines on AML cell proliferation or regulation of apoptosis. We conclude that even though the effects of single cytokines derived from bone marrow MSCs on human AML cells differ among patients, the final cytokine-mediated effects of the MSCs during coculture is growth enhancement and inhibition of apoptosis.

Hypoxia and hyperoxia differentially control proliferation of rat neural crest stem cells via distinct regulatory pathways of the HIF1α-CXCR4 and TP53-TPM1 proteins

BACKGROUND

Neural crest stem cells (NCSCs) are a population of adult multipotent stem cells. We are interested in studying whether oxygen tensions affect the capability of NCSCs to self-renew and repair damaged tissues. NCSCs extracted from the hair follicle bulge region of the rat whisker pad were cultured in vitro under different oxygen tensions.

RESULTS

We found significantly increased and decreased rates of cell proliferation in rat NCSCs (rNCSCs) cultured, respectively, at 0.5% and 80% oxygen levels. At 0.5% oxygen, the expression of both hypoxia-inducible factor (HIF) 1α and CXCR4 was greatly enhanced in the rNCSC nuclei and was suppressed by incubation with the CXCR4-specific antagonist AMD3100. In addition, the rate of cell apoptosis in the rNCSCs cultured at 80% oxygen was dramatically increased, associated with increased nuclear expression of TP53, decreased cytoplasmic expression of TPM1 (tropomyosin-1), and increased nuclear-to-cytoplasmic translocation of S100A2. Incubation of rNCSCs with the antioxidant N-acetylcysteine (NAC) overcame the inhibitory effect of 80% oxygen on proliferation and survival of rNCSCs.

CONCLUSIONS

Our results show for the first time that extreme oxygen tensions directly control NCSC proliferation differentially via distinct regulatory pathways of proteins, with hypoxia via the HIF1α-CXCR4 pathway and hyperoxia via the TP53-TPM1 pathway. Developmental Dynamics 246:162-185, 2017. © 2016 Wiley Periodicals, Inc.

MicroRNA-146a rs2910164 is associated with severe preeclampsia in Black South African women on HAART

BACKGROUND

South African (SA) Black women have a high prevalence of preeclampsia and HIV, both conditions associated with increased inflammation. miR-146a is an inflammatory-associated miR and a common single nucleotide polymorphism (rs2910164) has been associated with several disease conditions. To date, this SNP has not been investigated in SA Black women. We therefore aimed to investigate the miR-146a G > C SNP in SA Blacks with preeclampsia, and further examine possible association among preeclamptic (PE) women with HIV infection on HAART.

METHODS

This hospital-based, case-control study included 95 normotensive and 98 PE Black SA women (aged 16-46 years old). Patients and controls were genotyped by PCR-RFLP. Using a Cytometric Bead Array assay, serum cytokine levels (including Th1- and Th2-related cytokines) were determined in 4 groups of pregnant women, viz: normotensive, HIV infected, PE + HIV infected, and PE women.

RESULTS

There was no significant association between the miR-146a polymorphism and PE susceptibility in our data. However, in the subgroup analyses, the variant genotypes (GC/CC) were significantly associated with lower severe PE risk (p = 0.0497), more especially in the presence of HIV and HAART (p = 0.017). In the normotensive group, the variant genotypes were associated with lower IL-2 in both the total normotensive group (269 ± 1.26 (36) vs 273 ± 1.31 (23); p = 0.035) and the PE HIV+ sub-group 265 ± 1.54 (19) vs 271 ± 1.38 (11); p = 0.008).

CONCLUSIONS

Our study suggests that miR-146a rs2910164 polymorphism might not be associated with PE susceptibility, cytokines or related features. However, the miR-146a GC/CC genotype might reduce susceptibility to severe PE, which might be further influenced by the presence of co-morbid HIV infection among pregnant women on HAART. This variant genotype may also be associated with reduced circulating IL-2 levels and thus reduced pro-inflammatory response in normotensive women, which may be further influenced by the presence of HIV infection and HAART.

The effect of miR-146a on STAT1 expression and apoptosis in acute lymphoblastic leukemia Jurkat cells

The effect of miR-146a-dependent regulation of STAT1 on apoptosis in acute lymphoblastic leukemia (ALL) Jurkat cells was investigated. The miR-146a mimic and miR-146a inhibitor vectors were constructed in vitro, and experimental grouping was as follows: Control group (untreated Jurkat cells), empty vector group (Jurkat cells transfected with empty vector), agonist group (Jurkat cells transfected with miR-146a mimic) and the inhibitor group (Jurkat cells transfected with miR-146a inhibitor). Western blot analysis was used to observe the expression, respectively, of STAT1, p-STAT1 and Bcl-xL, and flow cytometry was used to test apoptosis in Jurkat cells. STAT1 and p-STAT1 expression in the agonist group was higher than that in the control and empty vector groups, but lower in the inhibitor group, and differences were statistically significant (P<0.05). The rate of apoptosis in the agonist group was significantly higher than that of the control group and blank vector group, and it was significantly lower in the inhibitor group (P<0.05). As a tumor suppressor, miR-146a can regulate expression of apoptosis-promoting factor STAT1, and anti-apoptosis factor Bcl-xL, and is able to promote apoptosis of ALL Jurkat cells.

Onco-GPCR signaling and dysregulated expression of microRNAs in human cancer

The G-protein-coupled receptor (GPCR) family is the largest family of cell-surface receptors involved in signal transduction. Aberrant expression of GPCRs and G proteins are frequently associated with prevalent human diseases, including cancer. In fact, GPCRs represent the therapeutic targets of more than a quarter of the clinical drugs currently on the market. MiRNAs (miRNAs) are also aberrantly expressed in many human cancers, and they have significant roles in the initiation, development and metastasis of human malignancies. Recent studies have revealed that dysregulation of miRNAs and their target genes expression are associated with cancer progression. The emerging information suggests that miRNAs play an important role in the fine tuning of many signaling pathways, including GPCR signaling. We summarize our current knowledge of the individual functions of miRNAs regulated by GPCRs and GPCR signaling-associated molecules, and miRNAs that regulate the expression and activity of GPCRs, their endogenous ligands and their coupled heterotrimeric G proteins in human cancer.

Panobinostat for the treatment of acute myelogenous leukemia

INTRODUCTION

Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi).

AREAS COVERED

The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML.

EXPERT OPINION

Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.

Identification of β-Dystrobrevin as a Direct Target of miR-143: Involvement in Early Stages of Neural Differentiation

Duchenne Muscular Dystrophy, a genetic disorder that results in a gradual breakdown of muscle, is associated to mild to severe cognitive impairment in about one-third of dystrophic patients. The brain dysfunction is independent of the muscular pathology, occurs early, and is most likely due to defects in the assembly of the Dystrophin-associated Protein Complex (DPC) during embryogenesis. We have recently described the interaction of the DPC component β-dystrobrevin with members of complexes that regulate chromatin dynamics, and suggested that β-dystrobrevin may play a role in the initiation of neuronal differentiation. Since oxygen concentrations and miRNAs appear as well to be involved in the cellular processes related to neuronal development, we have studied how these factors act on β-dystrobrevin and investigated the possibility of their functional interplay using the NTera-2 cell line, a well-established model for studying neurogenesis. We followed the pattern of expression and regulation of β-dystrobrevin during the early stages of neuronal differentiation induced by exposure to retinoic acid (RA) under hypoxia as compared with normoxia, and found that β-dystrobrevin expression is regulated during RA-induced differentiation of NTera-2 cells. We also found that β-dystrobrevin pattern is delayed under hypoxic conditions, together with a delay in the differentiation and an increase in the proliferation rate of cells. We identified miRNA-143 as a direct regulator of β-dystrobrevin expression, demonstrated that β-dystrobrevin is expressed in the nucleus and showed that, in line with our previous in vitro results, β-dystrobrevin is a repressor of synapsin I in live cells. Altogether the newly identified regulatory pathway miR-143/β-dystrobrevin/synapsin I provides novel insights into the functions of β-dystrobrevin and opens up new perspectives for elucidating the molecular mechanisms underlying the neuronal involvement in muscular dystrophy.

Granulocyte colony-stimulating factor inhibits CXCR4/SDF-1α signaling and overcomes stromal-mediated drug resistance in the HL-60 cell line

Combining cytarabine, aclarubicin and granulocyte colony-stimulating factor (G-CSF) has demonstrated marked efficacy in the treatment of elderly and relapsed/refractory patients with acute myeloid leukemia (AML); however, the role of G-CSF remains poorly understood. The present study aimed to investigate the ability of G-CSF to overcome stromal-mediated drug resistance and the underlying molecular mechanism. Two types of co-culture models were established in the HS-5 human bone marrow/stromal and HL-60 human promyelocytic leukemia cell lines, in order to imitate the interactions between stromal and leukemia cells in vitro, which is mediated by the stromal cell-derived factor (SDF)-1α signaling axis. In the present study, HL-60 cells were attracted and adhered to HS-5 cells using migration assay and flow cytometry, respectively; however, these interactions were inhibited by treatment with G-CSF and/or the C-X-C chemokine receptor type 4 (CXCR4) antagonist, AMD3100. Co-culture with HS-5 cells, including direct and indirect contact, protected HL-60 cells against spontaneous apoptosis or drug-induced apoptosis; however, these protective effects were disrupted by treatment with G-CSF and/or AMD3100. Notably, G-CSF and/or AMD3100 did not alter cell viability or apoptosis when HL-60 cells were cultured with medium alone. In addition, G-CSF significantly reduced the expression levels of surface CXCR4 protein, total CXCR4 protein and CXCR4 mRNA, and significantly upregulated the expression of microRNA (miR)-146a. Conversely, AMD3100 significantly reduced surface CXCR4 expression levels, but not the total CXCR4, CXCR4 mRNA or miR-146a expression levels. The results of the present study suggested that interfering with the CXCR4/SDF-1α signaling axis via G-CSF inhibited the migration and adhesion of HL-60 cells to HS-5 cells and eliminated HS5 cell-mediated protective effects. Furthermore, G-CSF administration reduced CXCR4 expression levels by upregulating the expression of miR-146a, whereas AMD3100 appeared to be predominantly dependent on receptor internalization. Therefore, a G-CSF/miR-146a/CXCR4 pathway may explain how G-CSF inhibits CXCR4/SDF-1α signaling and overcomes stromal cell-mediated drug resistance in acute myeloid leukemia.

Interaction of drugs of abuse and microRNA with HIV: a brief review

MicroRNAs (miRNAs), the post-transcriptional regulators of gene expression, play key roles in modulating many cellular processes. The changes in the expression profiles of several specific miRNAs affect the interactions between miRNA and their targets in various illnesses, including addiction, HIV, cancer etc. The presence of anti-HIV-1 microRNAs (which regulate the level of infectivity of HIV-1) have been validated in the cells which are the primary targets of HIV infection. Drugs of abuse impair the intracellular innate anti-HIV mechanism(s) in monocytes, contributing to cell susceptibility to HIV infection. Emerging evidence has implicated miRNAs are differentially expressed in response to chronic morphine treatment. Activation of mu opioid receptors (MOR) by morphine is shown to down regulate the expression of anti-HIV miRNAs. In this review, we summarize the results which demonstrate that several drugs of abuse related miRNAs have roles in the mechanisms that define addiction, and how they interact with HIV.

MicroRNAs; easy and potent targets in optimizing therapeutic methods in reparative angiogenesis

The age‐related senescence of adult tissues is associated with the decreased level of angiogenic capability and with the development of a degenerative disease such as atherosclerosis which thereafter result in the deteriorating function of multiple systems. Findings indicate that tissue senescence not only diminishes repair processes but also promotes atherogenesis, serving as a double‐edged sword in the development and prognosis of ischaemia‐associated diseases. Evidence evokes microRNAs (miRNAs) as molecular switchers that underlie cellular events in different tissues. Here, miRNAs would promote new potential targets for optimizing therapeutic methods in blood flow recovery to the ischaemic area. Effectively beginning an ischaemia therapy, a more characteristic of miRNA changes in adult tissues is prerequisite and in the forefront. It may also be a preliminary phase in treatment strategies by stem cell‐based therapy.

Serum Exosome MicroRNA as a Minimally-Invasive Early Biomarker of AML

Relapse remains the major cause of mortality for patients with Acute Myeloid Leukemia (AML). Improved tracking of minimal residual disease (MRD) holds the promise of timely treatment adjustments to preempt relapse. Current surveillance techniques detect circulating blasts that coincide with advanced disease and poorly reflect MRD during early relapse. Here, we investigate exosomes as a minimally invasive platform for a microRNA (miRNA) biomarker. We identify a set of miRNA enriched in AML exosomes and track levels of circulating exosome miRNA that distinguish leukemic xenografts from both non-engrafted and human CD34+ controls. We develop biostatistical models that reveal circulating exosomal miRNA at low marrow tumor burden and before circulating blasts can be detected. Remarkably, both leukemic blasts and marrow stroma contribute to serum exosome miRNA. We propose development of serum exosome miRNA as a platform for a novel, sensitive compartment biomarker for prospective tracking and early detection of AML recurrence.

CXCR4 3'UTR functions as a ceRNA in promoting metastasis, proliferation and survival of MCF-7 cells by regulating miR-146a activity

CXCR4 is the most common chemokine receptor expressed on tumor cells, and it is closely correlated with cancer cell stemness. This study was carried out to explore whether CXCR4 could function as a competitive endogenous RNA to promote metastasis, proliferation and survival in MCF-7 breast cancer cells. We validated that CXCR4, together with TRAF6 and EGFR, was directly targeted by miR-146a in MCF-7 cells. Overexpression of CXCR4 3'UTR inhibited the activity of miR-146a, thus elevating the expression of CXCR4, TRAF6 and EGFR. These oncoproteins further activated NF-κB pathway and promoted the proliferation, migration, invasion and anti-apoptotic activity of MCF-7 cells. Collectively, our study provided new insights into the function of CXCR4 in breast cancer: it promotes tumor progression as both a protein-coding gene and a non-coding RNA, complicating the mechanism by which oncogenes promote tumor progression.

Differential hypoxic regulation of the microRNA-146a/CXCR4 pathway in normal and leukemic monocytic cells: impact on response to chemotherapy

High expression of the chemokine receptor 4, CXCR4, associated with a negative prognosis in acute myeloid leukemia, is related to hypoxia. Because CXCR4 expression is under the post-transcriptional control of microRNA-146a in normal and leukemic monocytic cells, we first investigated the impact of hypoxia on microRNA-146a and CXCR4 expression during monocytopoiesis and in acute monocytic leukemia. We then analyzed the effects of hypoxia on drug sensitivity of CXCR4-expressing leukemic cells. We found that microRNA-146a is a target of hypoxia-inducible factor-1α or -2α in relation to the stage of monocytopoiesis and the level of hypoxia, and demonstrated the regulation of the microRNA-146a/CXCR4 pathway by hypoxia in monocytes derived from CD34(+) cells. Thus, in myeloid leukemic cell lines, hypoxia-mediated control of the microRNA-146a/CXCR4 pathway depends only on the capacity of hypoxia-inducible factor-1α to up-regulate microRNA-146a, which in turn decreases CXCR4 expression. However, at variance with normal monocytic cells and leukemic cell lines, in acute monocytic leukemia overexpressing CXCR4, hypoxia up-modulates microRNA-146a but fails to down-modulate CXCR4 expression. We then investigated the effect of hypoxia on the response of leukemic cells to chemotherapy alone or in combination with stromal-derived factor-1α. We found that hypoxia increases stromal-derived factor-1α-induced survival of leukemic cells by decreasing their sensitivity to anti-leukemic drugs. Altogether, our results demonstrate that hypoxia-mediated regulation of microRNA-146a, which controls CXCR4 expression in monocytic cells, is lost in acute monocytic leukemia, thus contributing to maintaining CXCR4 overexpression and protecting the cells from anti-leukemic drugs in the hypoxic bone marrow microenvironment.

Human TM9SF4 Is a New Gene Down-Regulated by Hypoxia and Involved in Cell Adhesion of Leukemic Cells

Background

The transmembrane 9 superfamily protein member 4, TM9SF4, belongs to the TM9SF family of proteins highly conserved through evolution. TM9SF4 homologs, previously identified in many different species, were mainly involved in cellular adhesion, innate immunity and phagocytosis. In human, the function and biological significance of TM9SF4 are currently under investigation. However, TM9SF4 was found overexpressed in human metastatic melanoma and in a small subset of acute myeloid leukemia (AMLs) and myelodysplastic syndromes, consistent with an oncogenic function of this gene.

Purpose and Results

In this study, we first analyzed the expression and regulation of TM9SF4 in normal and leukemic cells and identified TM9SF4 as a gene highly expressed in human quiescent CD34⁺ hematopoietic progenitor cells (HPCs), regulated during monocytic and granulocytic differentiation of HPCs, both lineages giving rise to mature myeloid cells involved in adhesion, phagocytosis and immunity. Then, we found that TM9SF4 is markedly overexpressed in leukemic cells and in AMLs, particularly in M2, M3 and M4 AMLs (i.e., in AMLs characterized by the presence of a more or less differentiated granulocytic progeny), as compared to normal CD34⁺ HPCs. Proliferation and differentiation of HPCs occurs in hypoxia, a physiological condition in bone marrow, but also a crucial component of cancer microenvironment. Here, we investigated the impact of hypoxia on TM9SF4 expression in leukemic cells and identified TM9SF4 as a direct target of HIF-1α, downregulated in these cells by hypoxia. Then, we found that the hypoxia-mediated downregulation of TM9SF4 expression is associated with a decrease of cell adhesion of leukemic cells to fibronectin, thus demonstrating that human TM9SF4 is a new molecule involved in leukemic cell adhesion.

Conclusions

Altogether, our study reports for the first time the expression of TM9SF4 at the level of normal and leukemic hematopoietic cells and its marked expression at the level of AMLs displaying granulocytic differentiation.

miR-146a controls CXCR4 expression in a pathway that involves PLZF and can be used to inhibit HIV-1 infection of CD4(+) T lymphocytes

MicroRNA miR-146a and PLZF are reported as major players in the control of hematopoiesis, immune function and cancer. PLZF is described as a miR-146a repressor, whereas CXCR4 and TRAF6 were identified as miR-146a direct targets in different cell types. CXCR4 is a co-receptor of CD4 molecule that facilitates HIV-1 entry into T lymphocytes and myeloid cells, whereas TRAF6 is involved in immune response. Thus, the role of miR-146a in HIV-1 infection is currently being thoroughly investigated. In this study, we found that PLZF mediates suppression of miR-146a to control increases of CXCR4 and TRAF6 protein levels in human primary CD4(+) T lymphocytes. We show that miR-146a upregulation by AMD3100 treatment or PLZF silencing, decreases CXCR4 protein expression and prevents HIV-1 infection of leukemic monocytic cell line and CD4(+) T lymphocytes. Our findings improve the prospects of developing new therapeutic strategies to prevent HIV-1 entry via CXCR4 by using the PLZF/miR-146a axis.

Conditioned medium from mesenchymal stem cells enhances the migration of hepatoma cells through CXCR4 up-regulation and F-actin remodeling

Interactions between tumors and mesenchymal stem cells (MSCs) can regulate cancer cell behavior and cancer progression. Rat bone marrow-derived MSCs (rMSCs) were isolated and purified by Percoll density gradient centrifugation. Conditioned media from rMSCs (MSC-CM) was prepared, and its role in cancer cell migration and the underlying molecular mechanism were investigated. MSC-CM increased the migration and up-regulated the expression of CXC chemokine receptor 4 (CXCR4) in rat hepatoma cells (CBRH-7919). F-actin remodeling was observed, and the Young's modulus was decreased in CBRH-7919 cells. A CXCR4 inhibitor suppressed the MSC-CM-induced CXCR4 expression and migration, restored the decrease in the Young's modulus and disrupted the formation of F-actin. MSC-CM thus promotes CBRH-7919 cell migration by lessening cell stiffness and increasing F-actin formation through up-regulation of CXCR4 expression. MSC-CM may therefore have a positive impact on cancer metastases and underlines a potential safety issue associated with clinical applications of MSCs.

NRF2-driven miR-125B1 and miR-29B1 transcriptional regulation controls a novel anti-apoptotic miRNA regulatory network for AML survival

Transcription factor NRF2 is an important regulator of oxidative stress. It is involved in cancer progression, and has abnormal constitutive expression in acute myeloid leukaemia (AML). Posttranscriptional regulation by microRNAs (miRNAs) can affect the malignant phenotype of AML cells. In this study, we identified and characterised NRF2-regulated miRNAs in AML. An miRNA array identified miRNA expression level changes in response to NRF2 knockdown in AML cells. Further analysis of miRNAs concomitantly regulated by knockdown of the NRF2 inhibitor KEAP1 revealed the major candidate NRF2-mediated miRNAs in AML. We identified miR-125B to be upregulated and miR-29B to be downregulated by NRF2 in AML. Subsequent bioinformatic analysis identified putative NRF2 binding sites upstream of the miR-125B1 coding region and downstream of the mir-29B1 coding region. Chromatin immunoprecipitation analyses showed that NRF2 binds to these antioxidant response elements (AREs) located in the 5' untranslated regions of miR-125B and miR-29B. Finally, primary AML samples transfected with anti-miR-125B antagomiR or miR-29B mimic showed increased cell death responsiveness either alone or co-treated with standard AML chemotherapy. In summary, we find that NRF2 regulation of miR-125B and miR-29B acts to promote leukaemic cell survival, and their manipulation enhances AML responsiveness towards cytotoxic chemotherapeutics.

MicroRNAs differentially present in the plasma of HIV elite controllers reduce HIV infection in vitro

Elite controllers maintain HIV-1 viral loads below the limit of detection. The mechanisms responsible for this phenomenon are poorly understood. As microRNAs (miRNAs) are regulators of gene expression and some of them modulate HIV infection, we have studied the miRNA profile in plasma from HIV elite controllers and chronically infected individuals and compared against healthy donors. Several miRNAs correlate with CD4+ T cell count or with the known time of infection. No significant differences were observed between elite controllers and healthy donors; however, 16 miRNAs were different in the plasma of chronic infected versus healthy donors. In addition, levels of hsa-miR-29b-3p, hsa-miR-33a-5p and hsa-miR-146a-5p were higher in plasma from elite controllers than chronic infected and hsa-miR-29b-3p and hsa-miR-33a-5p overexpression significantly reduced the viral production in MT2 and primary T CD4+ cells. Therefore, levels of circulating miRNAs might be of diagnostic and/or prognostic value for HIV infection, and hsa-miR-29b-3p and miR-33a-5p may contribute to the design of new anti-HIV drugs.

Premalignant PTEN-deficient thymocytes activate microRNAs miR-146a and miR-146b as a cellular defense against malignant transformation

Cancer develops by a multistep process during which cells acquire characteristics that allow them to evade apoptosis and proliferate unchecked. Sequential acquisition of genetic alterations drives this process but also causes cellular stress, frequently prompting cells to enter a premalignant period during which they mount a defense against transformation. T cell-specific deletion of the tumor suppressor PTEN in mice induces premalignancy in the thymus and development of CD4(+) T-cell lymphomas in the periphery. Here we sought to identify factors mediating the cellular defense against transformation during the premalignant period. We identified several microRNAs upregulated specifically in premalignant thymocytes, including miR-146a, miR-146b, and the miR-183/96/182 cluster. CD4-driven T cell-specific transgenic overexpression of mir-146a and mir-146b significantly delayed PTEN-deficient lymphomagenesis and delayed c-myc oncogene induction, a key driver of transformation in PTEN-deficient T-cell malignancies. We found that miR-146a and miR-146b targeting of Traf6 attenuates TCR signaling in the thymus and inhibits downstream NF-κB-dependent induction of c-myc. Additionally, c-myc repression in mature CD4 T cells by miR-146b impaired TCR-mediated proliferation. Hence, we have identified 2 miRNAs that are upregulated as part of the cellular response against transformation that, when overrepresented, can effectively inhibit progression to malignancy in the context of PTEN deficiency.

ApoptomiRs expression modulated by BCR-ABL is linked to CML progression and imatinib resistance

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative disease characterized by the presence of Philadelphia chromosome (Ph) leading to expression of a BCR-ABL1 fusion oncogene. The BCR-ABL protein has a constitutive tyrosine kinase activity which is responsible for CML pathogenesis by promoting cell apoptosis resistance; however, the cellular and molecular mechanisms associated with BCR-ABL expression and apoptosis impairment in CML leukemic cells have not been fully elucidated.

METHODS

This study evaluated apoptomiRs and their predicted apoptotic genes in BCR-ABL(+) cells from patients in different phases of CML treated with tyrosine kinase inhibitor (TKI) according to their imatinib (IM) response by qPCR. Phosphotyrosine and c-ABL expressions in HL-60.BCR-ABL cells treated with TKI were done by Western blot.

RESULTS

We found that dasatinib (DAS) modulated miR-let-7d, miR-let-7e, miR-15a, miR-16, miR-21, miR-130a and miR-142-3p expressions while IM modulated miR-15a and miR-130a levels. miR-16, miR-130a and miR-145 expressions were modulated by nilotinib (NIL). We observed higher miR-15a, miR-130b and miR-145; and lower miR-16, miR-26a and miR-146a expressions in CML-CP in comparison with controls. CML-AP patients showed low miR-let-7d, miR-15a, miR-16, miR-29c, miR-142-3p, miR-145, and miR-146a levels in comparison with CML-CP. We noted that the miR-26a, miR-29c, miR-130b and miR-146a expressions were downregulated in IM resistant patients in comparison with IM responsive patients.

CONCLUSIONS

This study showed the modulation of apoptomiRs by BCR-ABL kinase activity and the deregulation of apoptomiRs and their predicted apoptotic target genes in different CML phases and after treatment with TK inhibitors. ApoptomiRs may be involved in the BCR-ABL(+) cell apoptosis regulation.

Association of miR-146a gene polymorphism with risk of nasopharyngeal carcinoma in the central-southern Chinese population

This case-control study focused on estimating the association between miR-146a polymorphism and risk of nasopharyngeal carcinoma (NPC) in central-south China. In total, 160 patients with NPC and 200 healthy controls in central-south China were genotyped using polymerase chain reaction-restriction fragment length polymorphism assay. Chi-square test was used to assess the different distribution of miR-146a polymorphism between NPC patients and controls; and logistic regression analysis was applied to analyze the associations between miR-146a polymorphism with cancer risk in different contrast models. Significant differences between NPC patients and controls were found in genotype (P=0.033 for GG versus CG versus CC; and odds ratio (OR)=0.568, 95% confidence interval (CI)=0.354-0.912, P=0.019 for CG versus CC; and OR=0.503, 95% CI=0.261-0.971, P=0.041 for CG versus CC; and OR=0.564, 95% CI=0.360-0.884, P=0.012 for GG+CG versus CC, respectively) and allelic analysis (P=0.025 for G versus C). Our findings suggested that polymorphism of mir-146a was associated with NPC in the central-southern Chinese population.

CXCR4 chemokine receptor signaling induces apoptosis in acute myeloid leukemia cells via regulation of the Bcl-2 family members Bcl-XL, Noxa, and Bak

The CXCR4 chemokine receptor promotes survival of many different cell types. Here, we describe a previously unsuspected role for CXCR4 as a potent inducer of apoptosis in acute myeloid leukemia (AML) cell lines and a subset of clinical AML samples. We show that SDF-1, the sole ligand for CXCR4, induces the expected migration and ERK activation in the KG1a AML cell line transiently overexpressing CXCR4, but ERK activation did not lead to survival. Instead, SDF-1 treatment led via a CXCR4-dependent mechanism to apoptosis, as evidenced by increased annexin V staining, condensation of chromatin, and cleavage of both procaspase-3 and PARP. This SDF-1-induced death pathway was partially inhibited by hypoxia, which is often found in the bone marrow of AML patients. SDF-1-induced apoptosis was inhibited by dominant negative procaspase-9 but not by inhibition of caspase-8 activation, implicating the intrinsic apoptotic pathway. Further analysis showed that this pathway was activated by multiple mechanisms, including up-regulation of Bak at the level of mRNA and protein, stabilization of the Bak activator Noxa, and down-regulation of antiapoptotic Bcl-XL. Furthermore, adjusting expression levels of Bak, Bcl-XL, or Noxa individually altered the level of apoptosis in AML cells, suggesting that the combined modulation of these family members by SDF-1 coordinates their interplay to produce apoptosis. Thus, rather than mediating survival, SDF-1 may be a means to induce apoptosis of CXCR4-expressing AML cells directly in the SDF-1-rich bone marrow microenvironment if the survival cues of the bone marrow are disrupted.

The emerging role of MIR-146A in the control of hematopoiesis, immune function and cancer

MicroRNA (miRs) represent a class of small non-coding regulatory RNAs playing a major role in the control of gene expression by repressing protein synthesis at the post-transcriptional level. Studies carried out during the last years have shown that some miRNAs plays a key role in the control of normal and malignant hgematopoiesis. In this review we focus on recent progress in analyzing the functional role of miR-146a in the control of normal and malignant hematopoiesis. On the other hand, this miRNA has shown to impact in the control of innate immune responses. Finally, many recent studies indicate a deregulation of miR-146 in many solid tumors and gene knockout studies indicate a role for this miRNA as a tumor suppressor.

The emerging role of MIR-146A in the control of hematopoiesis, immune function and cancer

MicroRNA (miRs) represent a class of small non-coding regulatory RNAs playing a major role in the control of gene expression by repressing protein synthesis at the post-transcriptional level. Studies carried out during the last years have shown that some miRNAs plays a key role in the control of normal and malignant hgematopoiesis. In this review we focus on recent progress in analyzing the functional role of miR-146a in the control of normal and malignant hematopoiesis. On the other hand, this miRNA has shown to impact in the control of innate immune responses. Finally, many recent studies indicate a deregulation of miR-146 in many solid tumors and gene knockout studies indicate a role for this miRNA as a tumor suppressor.