The PU.1-Modulated MicroRNA-22 Is a Regulator of Monocyte/Macrophage Differentiation and Acute Myeloid Leukemia

SPI1+CD68+ macrophages as a biomarker for gastric cancer metastasis: a rationale for combined antiangiogenic and immunotherapy strategies

BACKGROUND

Tumor-associated macrophages (TAMs) have been demonstrated to be associated with tumor progression. However, the different subpopulations of TAMs and their roles in gastric cancer (GC) remain poorly understood. This study aims to assess the effects of Spi-1 proto-oncogene (SPI1)+CD68+ TAMs in GC.

METHODS

The distribution of SPI1+CD68+ TAMs in GC tissue was estimated by immunohistochemistry, immunofluorescence, and flow cytometry. Single-cell transcriptome analysis and multiplex fluorescence immunohistochemistry were applied to explore the role of SPI1+CD68+ TAMs in an immune contexture. SPI1 overexpression or knockdown cells were constructed to evaluate its role in macrophage polarization and angiogenesis in vitro and in vivo. Chromatin immunoprecipitation was used to verify the mechanism of SPI1 transcriptional function. The effect of combined antiangiogenic and immunotherapy was further validated using mouse peritoneal metastasis models.

RESULTS

Single-cell transcriptome analysis and immunohistochemistry demonstrated that SPI1 was expressed in macrophages, with a higher enrichment in metastatic lesions than in primary tumors. Higher SPI1+CD68+ TAMs infiltration was associated with poor overall survival. Mechanically, SPI1 promoted the M2-type macrophage polarization. SPI1 could bind to the promoter of vascular endothelial growth factor A and facilitate angiogenesis. Moreover, the level of SPI1+CD68+ TAMs infiltration was closely related to the efficacy of immunotherapy, especially when combined with antiangiogenic therapy.

CONCLUSIONS

The present study showed that SPI1+CD68+ TAMs are a promising biomarker for predicting prognosis, antiangiogenic drug sensitivity, and combination target of immunotherapy in patients with GC.

PU.1 induces tumor-associated macrophages promoting glioma progression through BTK-mediated Akt/mTOR pathway activation

Glioma, the most common primary malignant brain tumor, is characterized by infiltrating immune cells that contribute to tumor progression and therapeutic resistance. Tumor-associated macrophages (TAMs) constitute a significant proportion of these infiltrating immune cells and have been implicated in glioma progression. However, the underlying molecular mechanisms by which TAMs promote glioma progression remain elusive. In this study, we investigated the role of PU.1, a crucial transcription factor involved in myeloid cell development, in glioma-associated macrophage polarization and activation. First, bioinformatics and analysis of clinical glioma samples demonstrated a positive correlation between PU.1 expression in TAMs and disease severity. Further experiments using in vitro coculture systems revealed that the expression of PU.1 is increased in glioma cells vs. control cells. Importantly, PU.1-overexpressing macrophages exhibited a protumorigenic phenotype characterized by enhanced migration, invasion, and proliferation. Mechanistically, we found that PU.1-induced activation of the Bruton tyrosine kinase (BTK) signaling pathway led to Akt/mTOR pathway activation in macrophages, which further enhanced their protumorigenic functions. Furthermore, pharmacological inhibition of the BTK or Akt/mTOR pathway reversed the protumorigenic effects of macrophages in vitro and impaired their ability to promote glioma progression in vivo. In conclusion, our study elucidates a novel mechanism by which PU.1 induces the polarization and activation of TAMs in the glioma microenvironment. We highlight the significance of BTK-mediated Akt/mTOR pathway activation in driving the protumorigenic functions of TAMs. Targeting PU.1 and its downstream signaling pathways in TAMs may provide a promising therapeutic strategy to suppress glioma progression and improve patient outcomes.

A novel therapeutic strategy: the significance of exosomal miRNAs in acute myeloid leukemia

Acute myeloid leukemia (AML) is a fast-growing blood cancer that interferes with the normal growth of blood cells in the bone marrow and blood. It is characterized by its unpredictable outlook and high death rate. The main treatment for AML is chemotherapy, but this often results in drug resistance and the possibility of the disease returning. For this reason, new biomarkers are necessary to diagnose, predict, and treat this disease. Research has demonstrated that cells responsible for AML release exosomes that interact with the disease's microenvironment. These exosomes have significant roles in promoting leukemia growth, suppressing normal hematopoiesis, facilitating angiogenesis, and contributing to drug resistance in AML. Further investigations have shown that these exosomes contain miRNAs, which are transferred to target cells and have functional roles. Biomarkers are utilized to assess various aspects of tumor cell behavior, including proliferation, apoptosis, angiogenesis, changes in the microenvironment, transfer of drug resistance, and stability in serum and blood plasma. In this research, we showed that exosomal miRNAs and exosomes have the potential to be used as indicators for detecting various phases of AML and can aid in its medical treatment. Furthermore, they can be specifically targeted for therapeutic purposes in addressing this condition.

The emerging role of microRNA-22 in the Leukemia: experimental and clinical implications

MicroRNAs (miRNAs) are short noncoding RNAs, approximately 20-24 nucleotides long that negatively regulate gene expression by either inhibiting translation or cleaving complementary mRNA to participate in various biological processes. Accumulating evidence has indicated that miRNAs are widely present in hematological cancers, particularly leukemia, exhibiting either upregulation or downregulation in leukemia patients compared with healthy controls. These miRNAs have a pivotal role in the development, progression and metastasis of leukemia, as well as in the prognosis and/or relapse of patients. miR-22 is one of the abnormally expressed miRNAs in a variety of leukemia diseases, and is considered to be one of the few cancer suppressors. Recent research has demonstrated that miR-22 is involved in the regulation of leukemia cell proliferation, differentiation and apoptosis, and could be a promising biomarker and prognostic indicator for leukemia. Here, we summarize all relevant findings that carry out experimental investigation and clinical analyses, aiming to elucidate the comprehensive implications of miR-22 in various types of leukemia for the development of new therapeutic and prognostic strategies and new drug targets for the treatment of leukemia.

Insight into microRNAs' involvement in hematopoiesis: current standing point of findings

Hematopoiesis is a complex process in which hematopoietic stem cells are differentiated into all mature blood cells (red blood cells, white blood cells, and platelets). Different microRNAs (miRNAs) involve in several steps of this process. Indeed, miRNAs are small single-stranded non-coding RNA molecules, which control gene expression by translational inhibition and mRNA destabilization. Previous studies have revealed that increased or decreased expression of some of these miRNAs by targeting several proto-oncogenes could inhibit or stimulate the myeloid and erythroid lineage commitment, proliferation, and differentiation. During the last decades, the development of molecular and bioinformatics techniques has led to a comprehensive understanding of the role of various miRNAs in hematopoiesis. The critical roles of miRNAs in cell processes such as the cell cycle, apoptosis, and differentiation have been confirmed as well. However, the main contribution of some miRNAs is still unclear. Therefore, it seems undeniable that future studies are required to focus on miRNA activities during various hematopoietic stages and hematological malignancy.

Role of the pioneer transcription factor GATA2 in health and disease

The transcription factor GATA2 is involved in human diseases ranging from hematopoietic disorders, to cancer, to infectious diseases. GATA2 is one of six GATA-family transcription factors that act as pioneering transcription factors which facilitate the opening of heterochromatin and the subsequent binding of other transcription factors to induce gene expression from previously inaccessible regions of the genome. Although GATA2 is essential for hematopoiesis and lymphangiogenesis, it is also expressed in other tissues such as the lung, prostate gland, gastrointestinal tract, central nervous system, placenta, fetal liver, and fetal heart. Gene or transcriptional abnormalities of GATA2 causes or predisposes patients to several diseases including the hematological cancers acute myeloid leukemia and acute lymphoblastic leukemia, the primary immunodeficiency MonoMAC syndrome, and to cancers of the lung, prostate, uterus, kidney, breast, gastric tract, and ovaries. Recent data has also linked GATA2 expression and mutations to responses to infectious diseases including SARS-CoV-2 and Pneumocystis carinii pneumonia, and to inflammatory disorders such as atherosclerosis. In this article we review the role of GATA2 in the etiology and progression of these various diseases.

ATF2 orchestrates macrophage differentiation and activation to promote antibacterial responses

The differentiation and activation of macrophages are critical regulatory programs that are central to host inflammation and pathogen defense. However, the transcriptional regulatory pathways involved in these programs are not well understood. Herein, we demonstrate that the activity and expression of the transcription factor ATF2 is precisely regulated during primary human monocyte-to-macrophage differentiation and that its activation is linked to M1 polarization and antibacterial responses. Genetic perturbation experiments demonstrated that deletion of ATF2 (THP-ΔATF2) resulted in irregular and abnormal macrophage morphology, whereas macrophages overexpressing ATF2 (THP-ATF2) developed round and pancake-like morphology, resembling classically activated (M1) macrophages. Mechanistically, we show that ATF2 binds to the core promoter of PPM1A, a phosphatase that regulates monocyte-to-macrophage differentiation, to regulate its expression. Functionally, overexpression of ATF2 sensitized macrophages to M1 polarization, resulting in increased production of major histocompatibility complex class II, IL-1β, and IP-10; improved phagocytic capacity; and enhanced control of the intracellular pathogen Mycobacterium tuberculosis. Gene expression profiling revealed that overexpression of ATF2 reprogramed macrophages to promote antibacterial pathways enriched in chemokine signaling, metabolism, and antigen presentation. Consistent with pathways analysis, metabolic profiling revealed that genetic overexpression or stimuli-induced activation of ATF2 alters the metabolic capacity of macrophages and primes these cells for glycolytic metabolism during M1 polarization or bacterial infection. Our findings reveal that ATF2 plays a central role during macrophage differentiation and M1 polarization to enhance the functional capacities of macrophages.

Clinical Significance of microRNAs in Hematologic Malignancies and Hematopoietic Stem Cell Transplantation

Hematologic malignancies are a group of neoplastic conditions that can develop from any stage of the hematopoiesis cascade. Small non-coding microRNAs (miRNAs) play a crucial role in the post-transcriptional regulation of gene expression. Mounting evidence highlights the role of miRNAs in malignant hematopoiesis via the regulation of oncogenes and tumor suppressors involved in proliferation, differentiation, and cell death. In this review, we provide current knowledge about dysregulated miRNA expression in the pathogenesis of hematological malignancies. We summarize data about the clinical utility of aberrant miRNA expression profiles in hematologic cancer patients and their associations with diagnosis, prognosis, and the monitoring of treatment response. Moreover, we will discuss the emerging role of miRNAs in hematopoietic stem cell transplantation (HSCT), and severe post-HSCT complications, such as graft-versus-host disease (GvHD). The therapeutical potential of the miRNA-based approach in hemato-oncology will be outlined, including studies with specific antagomiRs, mimetics, and circular RNAs (circRNAs). Since hematologic malignancies represent a full spectrum of disorders with different treatment paradigms and prognoses, the potential use of miRNAs as novel diagnostic and prognostic biomarkers might lead to improvements, resulting in a more accurate diagnosis and better patient outcomes.

Epigenetic regulation in hematopoiesis and its implications in the targeted therapy of hematologic malignancies

Hematologic malignancies are one of the most common cancers, and the incidence has been rising in recent decades. The clinical and molecular features of hematologic malignancies are highly heterogenous, and some hematologic malignancies are incurable, challenging the treatment, and prognosis of the patients. However, hematopoiesis and oncogenesis of hematologic malignancies are profoundly affected by epigenetic regulation. Studies have found that methylation-related mutations, abnormal methylation profiles of DNA, and abnormal histone deacetylase expression are recurrent in leukemia and lymphoma. Furthermore, the hypomethylating agents and histone deacetylase inhibitors are effective to treat acute myeloid leukemia and T-cell lymphomas, indicating that epigenetic regulation is indispensable to hematologic oncogenesis. Epigenetic regulation mainly includes DNA modifications, histone modifications, and noncoding RNA-mediated targeting, and regulates various DNA-based processes. This review presents the role of writers, readers, and erasers of DNA methylation and histone methylation, and acetylation in hematologic malignancies. In addition, this review provides the influence of microRNAs and long noncoding RNAs on hematologic malignancies. Furthermore, the implication of epigenetic regulation in targeted treatment is discussed. This review comprehensively presents the change and function of each epigenetic regulator in normal and oncogenic hematopoiesis and provides innovative epigenetic-targeted treatment in clinical practice.

An Immunocompetent Environment Unravels the Proto-Oncogenic Role of miR-22

MiR-22 was first identified as a proto-oncogenic microRNA (miRNA) due to its ability to post-transcriptionally suppress the expression of the potent PTEN (Phosphatase And Tensin Homolog) tumor suppressor gene. miR-22 tumorigenic role in cancer was subsequently supported by its ability to positively trigger lipogenesis, anabolic metabolism, and epithelial-mesenchymal transition (EMT) towards the metastatic spread. However, during the following years, the picture was complicated by the identification of targets that support a tumor-suppressive role in certain tissues or cell types. Indeed, many papers have been published where in vitro cellular assays and in vivo immunodeficient or immunosuppressed xenograft models are used. However, here we show that all the studies performed in vivo, in immunocompetent transgenic and knock-out animal models, unanimously support a proto-oncogenic role for miR-22. Since miR-22 is actively secreted from and readily exchanged between normal and tumoral cells, a functional immune dimension at play could well represent the divider that allows reconciling these contradictory findings. In addition to a critical review of this vast literature, here we provide further proof of the oncogenic role of miR-22 through the analysis of its genomic locus vis a vis the genetic landscape of human cancer.

The Monocyte, a Maestro in the Tumor Microenvironment (TME) of Breast Cancer

Simple Summary

Breast cancer is one of the most prevalent cancers worldwide, surpassing lung cancer as the leading cause of overall cancer incidence. Available possible treatments nowadays include chemotherapy, hormonal therapy, and HER2-targeted therapy. Chemotherapy is notorious for its severe adverse effects. On the other hand, hormonal and HER2-targeted therapies only cover a narrow range of breast cancer subtypes. Accordingly, it is important to shed light on other therapy options. For this reason, immunotherapy nowadays is one of the most important research topics. It can be accomplished either by enhancing the pro-inflammatory immunity or suppressing the anti-inflammatory immunity. This review article aims to shed light on the importance of monocytes in the TME of breast cancer. The review also aims to highlight the behavior of the monocyte-derived populations, especially the anti-inflammatory populations. Thus, suppressing this anti-inflammatory activity might have a remarkable impact on future immunotherapy research.

Abstract

Breast cancer (BC) is well-known for being a leading cause of death worldwide. It is classified molecularly into luminal A, luminal B HER2−, luminal B HER2+, HER2+, and triple-negative breast cancer (TNBC). These subtypes differ in their prognosis; thus, understanding the tumor microenvironment (TME) makes new treatment strategies possible. The TME contains populations that exhibit anti-tumorigenic actions such as tumor-associated eosinophils. Moreover, it contains pro-tumorigenic populations such as tumor-associated neutrophils (TANs), or monocyte-derived populations. The monocyte-derived populations are tumor-associated macrophages (TAMs) and MDSCs. Thus, a monocyte can be considered a maestro within the TME. Moreover, the expansion of monocytes in the TME depends on many factors such as the BC stage, the presence of macrophage colony-stimulating factor (M-CSF), and the presence of some chemoattractants. After expansion, monocytes can differentiate into pro-inflammatory populations such as M1 macrophages or anti-inflammatory populations such as M2 macrophages according to the nature of cytokines present in the TME. Differentiation to TAMs depends on various factors such as the BC subtype, the presence of anti-inflammatory cytokines, and epigenetic factors. Furthermore, TAMs and MDSCs not only have a role in tumor progression but also are key players in metastasis. Thus, understanding the monocytes further can introduce new target therapies.

MiR-22 Deficiency Fosters Hepatocellular Carcinoma Development in Fatty Liver

MiR-22 is mostly considered as a hepatic tumor-suppressor microRNA based on in vitro analyses. Yet, whether miR-22 exerts a tumor-suppressive function in the liver has not been investigated in vivo. Herein, in silico analyses of miR-22 expression were performed in hepatocellular carcinomas from human patient cohorts and different mouse models. Diethylnitrosamine-induced hepatocellular carcinomas were then investigated in lean and diet-induced obese miR-22-deficient mice. The proteome of liver tissues from miR-22-deficient mice prior to hepatocellular carcinoma development was further analyzed to uncover miR-22 regulated factors that impact hepatocarcinogenesis with miR-22 deficiency. MiR-22 downregulation was consistently observed in hepatocellular carcinomas from all human cohorts and mouse models investigated. The time of appearance of the first tumors was decreased and the number of tumoral foci induced by diethylnitrosamine was significantly increased by miR-22-deficiency in vivo, two features which were further drastically exacerbated with diet-induced obesity. At the molecular level, we provide evidence that the loss of miR-22 significantly affects the energetic metabolism and mitochondrial functions of hepatocytes, and the expression of tumor-promoting factors such as thrombospondin-1. Our study demonstrates that miR-22 acts as a hepatic tumor suppressor in vivo by restraining pro-carcinogenic metabolic deregulations through pleiotropic mechanisms and the overexpression of relevant oncogenes.

Dicer deficiency impairs proliferation but potentiates anti-tumoral effect of macrophages in glioblastoma

Glioblastoma is a lethal primary brain tumor with abundant immune-suppressive glioblastoma-associated macrophage (GAM) infiltration. Skewing immune suppressive GAMs towards an immune-activating phenotype represents a promising immunotherapeutic strategy against glioblastoma. Herein, we reported that genetic deletion of miRNA-processing enzyme Dicer in macrophages inhibited the growth of GL261 murine glioblastoma xenografts and prolonged survival of tumor-bearing mice. Single cell RNA sequencing (scRNA-seq) of the tumor-infiltrating immune cells revealed that Dicer deletion in macrophages reduced the proportion of cell-cycling GAM cluster and reprogramed the remaining GAMs towards a proinflammatory activation state (enhanced phagocytotic and IFN-producing signature). Dicer-deficient GAMs showed reduced level of cyclin-dependent kinases (CDK1 and CDK2) and increased expression of CDK inhibitor p27 Kip1, thus manifesting impaired proliferation. Dicer knockout enhanced phagocytotic activity of GAMs to eliminate GL261 tumor cells. Increased proinflammatory GAM clusters in macrophage Dicer-deficient mice actively interacted with tumor-infiltrating T cells and NK cells through TNF paracrine signaling to create a pro-inflammatory immune microenvironment for tumor cell elimination. Our work identifies the role of Dicer deletion in macrophages in generating an immune-activating microenvironment, which could be further developed as a potential immunotherapeutic strategy against glioblastoma.

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

MicroRNA-22 represses glioma development via activation of macrophage-mediated innate and adaptive immune responses

Macrophage-mediated tumor cell phagocytosis and subsequent neoantigen presentation are critical for generating anti-tumor immunity. This study aimed to uncover the potential clinical value and molecular mechanisms of miRNA-22 (miR-22) in tumor cell phagocytosis via macrophages and more efficient T cell priming. We found that miR-22 expression was markedly downregulated in primary macrophages from glioma tissue samples compared to adjacent tissues. miR-22-overexpressing macrophages inhibited glioma cell proliferation and migration, respectively. miR-22 upregulation stimulated the phagocytic ability of macrophages, enhanced tumor cell phagocytosis, antigen presentation, and efficient T cell priming. Additionally, our data revealed that miR-22-overexpressing macrophages inhibited glioma formation in vivo, HDAC6 was a target, and NF-κB signaling was a pathway closely associated with miR-22 in tumor-associated macrophages (TAMs) of glioma. Our findings revealed the essential roles of miR-22 in tumor cell phagocytosis by macrophages and more efficient T cell priming, facilitating further research on phagocytic regulation to enhance the response to tumor immunotherapy.

miR-181c regulates MCL1 and cell survival in GATA2 deficient cells

GATA2 is a transcription factor critical for hematopoiesis. Germline mutations in GATA binding protein 2 (GATA2) led to haploinsufficiency, severe cytopenias of multiple cell lineages, susceptibility to infections and strong propensity to develop myelodysplastic syndrome, and acute myeloid leukemia. Mechanisms of progressive cytopenias remain unclear. MicroRNA (miRNA) represents a unique mechanism of post-transcriptional gene regulation. In this study, miRNA profiles were evaluated and eight miRNAs were found to be differentially expressed (≥2-fold, P ≤ 0.05) in patient-derived cell lines (N = 13) in comparison to controls (N = 10). miR-9, miR-181a-2-3p, miR-181c, miR-181c-3p, miR-486-3p, and miR-582 showed increased expression, whereas miR-223 and miR-424-3p showed decreased expression. Cell death assays indicated that miR-181c potently induces cell death in lymphoid (Ly-8 and SP-53) and myeloid (HL-60) cell lines. miR-181c was predicted to target myeloid cell leukemia (MCL)1, which was confirmed by transfection assays, resulting in significantly reduced MCL1 mRNA and decreased live cell numbers. Bone marrow analysis of 34 GATA2 patients showed significantly decreased cellularity, CD34-positive cells, monocytes, dendritic cells, NK cells, B cells, and B cell precursors in comparison to healthy controls (N = 29; P < 0.001 for each), which was accompanied by decreased levels of MCL1 (P < 0.05). GATA2 expression led to significant repression of miR-181c expression in transfection experiments. Conversely, knockdown of GATA2 led to increased miR-181c expression. These findings indicate that miR-181c expression is increased and MCL1 levels decreased in GATA2 deficiency cells, and that GATA2 represses miR-181c transcription. Increased miR-181c may contribute to elevated cell death and cytopenia in GATA2 deficiency potentially through down-regulation of MCL1.

The Role of miRNA in Regulating the Fate of Monocytes in Health and Cancer

Monocytes represent a heterogeneous population of blood cells that provide a link between innate and adaptive immunity. The unique potential of monocytes as both precursors (e.g., of macrophages) and effector cells (as phagocytes or cytotoxic cells) makes them an interesting research and therapeutic target. At the site of a tumor, monocytes/macrophages constitute a major population of infiltrating leukocytes and, depending on the type of tumor, may play a dual role as either a bad or good indicator for cancer recovery. The functional activity of monocytes and macrophages derived from them is tightly regulated at the transcriptional and post-transcriptional level. This review summarizes the current understanding of the role of small regulatory miRNA in monocyte formation, maturation and function in health and cancer development. Additionally, signatures of miRNA-based monocyte subsets and the influence of exogenous miRNA generated in the tumor environment on the function of monocytes are discussed.

Epigenetic regulation of immunosuppressive tumor-associated macrophages through dysregulated microRNAs

Macrophages are immune cells that play different roles under different physiological conditions. They are present in all tissues where they primarily protect from bacteria and pathogens in addition to assisting in tissue repair. During tumor progression, macrophages can exert contrasting effects based on the M1 vs. M2 polarization. The M2 macrophages support tumor growth through mechanisms that help suppress immune responses and/or circumvent immune-surveillance. A number of such mechanisms such as production of IL-10 and arginase, and expression of PD-L1, V-domain Ig suppressor of T cell activation and B7 family molecule B7-H4 are now believed central to the immunosuppressive effects of tumor-associated macrophages (TAMs). Emerging data has identified epigenetic regulation of these immunosuppressive mechanisms by small non-coding RNAs, the microRNAs (miRNAs). This review discusses the available literature on the subject, including the exosomes mediated transfer of miRNAs between cancer cells and the macrophages within the tumor microenvironment. A number of miRNAs are now believed to be involved in TAMs' production of IL-10 and expression of PD-L1 while the information on such regulation of other immunosuppressive mechanisms is slowly emerging. A better understanding of epigenetic regulation of macrophages-mediated immunosuppressive effect can help identify novel targets for therapy and aid the design of future studies aimed at sensitizing tumors to immune responses.

Loss of Mir146b with aging contributes to inflammation and mitochondrial dysfunction in thioglycollate-elicited peritoneal macrophages

Macrophages undergo programmatic changes with age, leading to altered cytokine polarization and immune dysfunction, shifting these critical immune cells from protective sentinels to disease promoters. The molecular mechanisms underlying macrophage inflammaging are poorly understood. Using an unbiased RNA sequencing (RNA-seq) approach, we identified Mir146b as a microRNA whose expression progressively and unidirectionally declined with age in thioglycollate-elicited murine macrophages. Mir146b deficiency led to altered macrophage cytokine expression and reduced mitochondrial metabolic activity, two hallmarks of cellular aging. Single-cell RNA-seq identified patterns of altered inflammation and interferon gamma signaling in Mir146b-deficient macrophages. Identification of Mir146b as a potential regulator of macrophage aging provides novel insights into immune dysfunction associated with aging.

Pediatric Neoplasms Presenting with Monocytosis

PURPOSE OF REVIEW

Juvenile myelomonocytic leukemia (JMML) is a rare but severe pediatric neoplasm with hematopoietic stem cell transplant as its only established curative option. The development of targeted therapeutics for JMML is being guided by an understanding of the pathobiology of this condition. Here, we review JMML with an emphasis on genetics in order to (i) demonstrate the relationship between JMML genotype and clinical phenotype and (ii) explore potential genetic targets of novel JMML therapies.

RECENT FINDINGS

DNA hypermethylation studies have demonstrated consistently that methylation is related to disease severity. Increasing understanding of methylation in JMML may open the door to novel therapies, such as DNA methyltransferase inhibitors. The PI3K/AKT/MTOR, JAK/STAT, and RAF/MEK/ERK pathways are being investigated as therapeutic targets for JMML. Future therapy for JMML will be driven by an increased understanding of pathobiology. Targeted therapeutic approaches hold potential for improving outcomes in patients with JMML.

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 tissue specific regulation of miR22 expression in the lung and brain by ribosomal protein L29

Endogenous miR22 is associated with a diverse range of biological processes through post-translational modification of gene expression and its deregulation results in various diseases including cancer. Its expression is usually tissue or cell-specific, however, the reasons behind this tissue or cell specificity are not clearly outlined till-date. Therefore, our keen interest was to investigate the mechanisms of tissue or cell-specific expression of miR22. In the current study, miR22 expression showed a tissues-specific difference in the poly(I:C) induced inflammatory mouse lung and brain tissues. The cell-specific different expression of miR22 was also observed in inflammatory glial cells and endothelial cells. The pattern of RPL29 expression was also similar to miR22 in these tissues and cells under the same treatment. Interestingly, the knockdown of RPL29 exerted an inhibitory effect on miR22 and its known transcription factors including Fos-B and c-Fos. Fos-B and c-Fos were also differentially expressed in the two cell lines transfected with poly(I:C). The knockdown of c-Fos also exerted its negative effects on miR22 expression in both cells. These findings suggest that RPL29 might have regulatory roles on tissue or cell-specific expression of miR22 through the transcription activities of c-Fos and also possibly through Fos-B.

The Transcriptional Network That Controls Growth Arrest and Macrophage Differentiation in the Human Myeloid Leukemia Cell Line THP-1

The response of the human acute myeloid leukemia cell line THP-1 to phorbol esters has been widely studied to test candidate leukemia therapies and as a model of cell cycle arrest and monocyte-macrophage differentiation. Here we have employed Cap Analysis of Gene Expression (CAGE) to analyze a dense time course of transcriptional regulation in THP-1 cells treated with phorbol myristate acetate (PMA) over 96 h. PMA treatment greatly reduced the numbers of cells entering S phase and also blocked cells exiting G2/M. The PMA-treated cells became adherent and expression of mature macrophage-specific genes increased progressively over the duration of the time course. Within 1–2 h PMA induced known targets of tumor protein p53 (TP53), notably CDKN1A, followed by gradual down-regulation of cell-cycle associated genes. Also within the first 2 h, PMA induced immediate early genes including transcription factor genes encoding proteins implicated in macrophage differentiation (EGR2, JUN, MAFB) and down-regulated genes for transcription factors involved in immature myeloid cell proliferation (MYB, IRF8, GFI1). The dense time course revealed that the response to PMA was not linear and progressive. Rather, network-based clustering of the time course data highlighted a sequential cascade of transient up- and down-regulated expression of genes encoding feedback regulators, as well as transcription factors associated with macrophage differentiation and their inferred target genes. CAGE also identified known and candidate novel enhancers expressed in THP-1 cells and many novel inducible genes that currently lack functional annotation and/or had no previously known function in macrophages. The time course is available on the ZENBU platform allowing comparison to FANTOM4 and FANTOM5 data.

Lnc-M2 controls M2 macrophage differentiation via the PKA/CREB pathway

Long noncoding RNAs (lncRNAs) play an indispensable role in the process of M1 macrophage via regulating the development of macrophages and their responses to bacterial pathogens and viral infections. However, there are few studies on the lncRNA-mediated functions and regulatory mechanisms of M2 macrophage polarization. In this study, we found a number of differentially expressed lncRNAs between human monocyte derived M0 and M2 macrophages according to array analysis and quantitative polymerase chain reaction (qPCR) validation. The lncRNA RP11-389C8.2 (we named lnc-M2 in this study) was observed to be highly expressed in M2 macrophages. In Situ Localization and Quantification Analysis showed that lnc-M2 was expressed in the nucleus and cytosolic compartments of M2 macrophages. Notably, lnc-M2 knockdown enhanced the phagocytic ability of M2 macrophages. Ulteriorly, the results of RNA-Protein interaction experiments indicated that protein kinase A (PKA) was a lnc-M2 associated RNA-binding protein (RBP). Western blot showed that phosphorylated cAMP response element binding protein (p-CREB), a well-known key downstream transcription factor of PKA, was lowly phosphorylated in lnc-M2-silencing M2 macrophages. Furthermore, we found that transcriptional factor Signal Transducer And Activator Of Transcription 3 (STAT3) promoted lnc-M2 transcription along with the up-regulation of epigenetic histone modification markers at the lnc-M2 promoter locus, indicating that STAT3 activated lnc-M2 and eventually facilitated the process of M2 macrophage differentiation via the PKA/CREB pathway. Collectively, our date provide evidence that the transcription factor STAT3 can promote the transcription of lnc-M2 and facilitated the process of M2 macrophage differentiation via the PKA/CREB pathway. This study highlights a novel mechanism underlying the M2 macrophage differentiation.

Serum miR-22 is a novel prognostic marker for acute myeloid leukemia

Background

It has been demonstrated that aberrant expression of serum microRNAs is potential markers for the prognostic prediction of acute myeloid leukemia (AML). However, the clinical significance of serum miR‐22 remained uncovered. In this study, we aimed to explore the potential prognostic value of serum miR‐22 for AML.

Methods

Blood samples were collected from 124 patients with AML and 60 healthy individuals. Serum miR‐22 level was detected by quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR), and its potential clinical value was investigated.

Results

Our results showed that serum miR‐22 expression was significantly downregulated in AML subjects compared to healthy controls. Serum miR‐22 levels were lowest in AML patients with M4/M5 subtypes, and low serum miR‐22 expression occurred more frequently in AML patients with higher white blood cell counts or poor cytogenetic risk. Receiver operating characteristic (ROC) analysis revealed that serum miR‐22 well differentiated AML cases from healthy controls. In addition, serum miR‐22 downregulation was closely associated with worse clinical features and shorter survival. Low serum miR‐22 expression was confirmed to be an independent predictor for overall survival and relapse‐free survival in AML patients. Moreover, the expression level of serum miR‐22 was dramatically increased following treatment. In addition, serum miR‐22 levels were significantly higher in AML patients achieving complete remission (CR) than those without CR.

Conclusion

Collectively, serum miR‐22 might serve as a novel and promising prognostic biomarker for AML.

Transcriptional, Epigenetic and Metabolic Programming of Tumor-Associated Macrophages

Macrophages are key innate immune cells in the tumor microenvironment (TME) that regulate primary tumor growth, vascularization, metastatic spread and tumor response to various types of therapies. The present review highlights the mechanisms of macrophage programming in tumor microenvironments that act on the transcriptional, epigenetic and metabolic levels. We summarize the latest knowledge on the types of transcriptional factors and epigenetic enzymes that control the direction of macrophage functional polarization and their pro- and anti-tumor activities. We also focus on the major types of metabolic programs of macrophages (glycolysis and fatty acid oxidation), and their interaction with cancer cells and complex TME. We have discussed how the regulation of macrophage polarization on the transcriptional, epigenetic and metabolic levels can be used for the efficient therapeutic manipulation of macrophage functions in cancer.

Landscape of Tumor Suppressor Mutations in Acute Myeloid Leukemia

Acute myeloid leukemia is mainly characterized by a complex and dynamic genomic instability. Next-generation sequencing has significantly improved the ability of diagnostic research to molecularly characterize and stratify patients. This detailed outcome allowed the discovery of new therapeutic targets and predictive biomarkers, which led to develop novel compounds (e.g., IDH 1 and 2 inhibitors), nowadays commonly used for the treatment of adult relapsed or refractory AML. In this review we summarize the most relevant mutations affecting tumor suppressor genes that contribute to the onset and progression of AML pathology. Epigenetic modifications (TET2, IDH1 and IDH2, DNMT3A, ASXL1, WT1, EZH2), DNA repair dysregulation (TP53, NPM1), cell cycle inhibition and deficiency in differentiation (NPM1, CEBPA, TP53 and GATA2) as a consequence of somatic mutations come out as key elements in acute myeloid leukemia and may contribute to relapse and resistance to therapies. Moreover, spliceosomal machinery mutations identified in the last years, even if in a small cohort of acute myeloid leukemia patients, suggested a new opportunity to exploit therapeutically. Targeting these cellular markers will be the main challenge in the near future in an attempt to eradicate leukemia stem cells.

After 95 years, it's time to eRASe JMML

Juvenile myelomonocytic leukaemia (JMML) is a rare clonal disorder of early childhood. Constitutive activation of the RAS pathway is the initial event in JMML. Around 90% of patients diagnosed with JMML carry a mutation in the PTPN11, NRAS, KRAS, NF1 or CBL genes. It has been demonstrated that after this first genetic event, an additional somatic mutation or epigenetic modification is involved in disease progression. The available genetic and clinical data have enabled researchers to establish relationships between JMML and several clinical conditions, including Noonan syndrome, Ras-associated lymphoproliferative disease, and Moyamoya disease. Despite scientific progress and the development of more effective treatments, JMML is still a deadly disease: the 5-year survival rate is ~50%. Here, we report on recent research having led to a better understanding of the genetic and molecular mechanisms involved in JMML.

microRNA-22 promotes megakaryocyte differentiation through repression of its target, GFI1

Precise control of microRNA expression contributes to development and the establishment of tissue identity, including in proper hematopoietic commitment and differentiation, whereas aberrant expression of various microRNAs has been implicated in malignant transformation. A small number of microRNAs are upregulated in megakaryocytes, among them is microRNA-22 (miR-22). Dysregulation of miR-22 leads to various hematologic malignancies and disorders, but its role in hematopoiesis is not yet well established. Here we show that upregulation of miR-22 is a critical step in megakaryocyte differentiation. Megakaryocytic differentiation in cell lines is promoted upon overexpression of miR-22, whereas differentiation is disrupted in CRISPR/Cas9-generated miR-22 knockout cell lines, confirming that miR-22 is an essential mediator of this process. RNA-sequencing reveals that miR-22 loss results in downregulation of megakaryocyte-associated genes. Mechanistically, we identify the repressive transcription factor, GFI1, as the direct target of miR-22, and upregulation of GFI1 in the absence of miR-22 inhibits megakaryocyte differentiation. Knocking down aberrant GFI1 expression restores megakaryocytic differentiation in miR-22 knockout cells. Furthermore, we have characterized hematopoiesis in miR-22 knockout animals and confirmed that megakaryocyte differentiation is similarly impaired in vivo and upon ex vivo megakaryocyte differentiation. Consistently, repression of Gfi1 is incomplete in the megakaryocyte lineage in miR-22 knockout mice and Gfi1 is aberrantly expressed upon forced megakaryocyte differentiation in explanted bone marrow from miR-22 knockout animals. This study identifies a positive role for miR-22 in hematopoiesis, specifically in promoting megakaryocyte differentiation through repression of GFI1, a target antagonistic to this process.

Long non-coding RNA SNHG1 indicates poor prognosis and facilitates disease progression in acute myeloid leukemia

The role of long non-coding RNAs (lncRNAs) in acute myeloid leukemia (AML) is becoming increasingly questioned. Previous studies have reported that the lncRNA small nucleolar RNA host gene 1 (SNHG1) is involved in multiple human malignant tumors, while its expression and role in AML is still unexplored. Here, we show that SNHG1 is highly expressed in AML specimens from non-M3 patients, as well as AML cell lines. Meanwhile, upregulation of SNHG1 is correlated with poor prognosis. Notably, SNHG1 facilitates the proliferation and inhibits the apoptosis of AML cells in vitro Consistent with these findings, knockdown of SNHG1 significantly inhibits AML progression in an immunodeficient mouse model. Mechanistically, we found that an anti-tumor microRNA-101 (miR-101) is upregulated and its target genes are downregulated in AML cells after SNHG1 knockdown. Further investigations display that SNHG1 can serve as a competing endogenous RNA to inhibit miR-101. In conclusion, our data indicate that SNHG1 plays an important role in facilitating AML progression at least in part by negatively regulating miR-101, and provides a new target for treating AML.

Monocyte mobilisation, microbiota & mental illness

The gastrointestinal microbiome has emerged as a key player in regulating brain and behaviour. This has led to the strategy of targeting the gut microbiota to ameliorate disorders of the central nervous system. Understanding the underlying signalling pathways in which the microbiota impacts these disorders is crucial for the development of future therapeutics for improving CNS functionality. One of the major pathways through which the microbiota influences the brain is the immune system, where there is an increasing appreciation for the role of monocyte trafficking in regulating brain homeostasis. In this review, we will shed light on the role of monocyte trafficking as a relay of microbiota signals in conditions where the central nervous system is in disorder, such as stress, peripheral inflammation, ageing, traumatic brain injury, stroke, multiple sclerosis, Alzheimer's disease and Parkinson's disease. We also cover how the gastrointestinal microbiota is implicated in these mental illnesses. In addition, we aim to discuss how the monocyte system can be modulated by the gut microbiota to mitigate disorders of the central nervous system, which will lead to novel microbiota-targeted strategies.

Inducible overexpression of zebrafish microRNA-722 suppresses chemotaxis of human neutrophil like cells

Neutrophil migration is essential for battling against infections but also drives chronic inflammation. Since primary neutrophils are terminally differentiated and not genetically tractable, leukemia cells such as HL-60 are differentiated into neutrophil-like cells to study mechanisms underlying neutrophil migration. However, constitutive overexpression or inhibition in this cell line does not allow the characterization of the genes that affect the differentiation process. Here we apply the tet-on system to induce the expression of a zebrafish microRNA, dre-miR-722, in differentiated HL-60. Overexpression of miR-722 reduced the mRNA level of genes in the chemotaxis and inflammation pathways, including Ras-Related C3 Botulinum Toxin Substrate 2 (RAC2). Consistently, polarization of the actin cytoskeleton, cell migration and generation of the reactive oxygen species are significantly inhibited upon induced miR-722 overexpression. Together, zebrafish miR-722 is a suppressor for migration and signaling in human neutrophil like cells.

Non-coding RNA MFI2-AS1 promotes colorectal cancer cell proliferation, migration and invasion through miR-574-5p/MYCBP axis

Objective

Long non‐coding RNAs (lncRNAs) and microRNAs (miRNAs) play essential roles in the tumour progression. LncRNAs mostly act as competing endogenous RNAs (ceRNAs) by sponging miRNAs. This study aimed to study the association of a novel lncRNA MFI2‐AS1 with miR‐574‐5p/MYCBP axis in the development of colorectal cancer (CRC).

Methods

Ninety‐four CRC tissues and paired adjacent non‐tumour tissues were included in our study. The relative expression level of MFI2‐AS1 was detected, and its relationship with clinico‐pathological factors was analysed. Then, the CRC cells lines (LoVo and RKO) were transfected with MFI2‐AS1 siRNA, miR‐574‐5p mimics and inhibitors. Cell proliferation, migration, invasion, cell cycle distribution and DNA damage in response to different transfection conditions were examined. Dual‐luciferase reporter assay was performed to identify the target interactions between MFI2‐AS1 and miR‐574‐5p, miR‐574‐5p and MYCBP.

Results

LncRNA MFI2‐AS1 and MYCBP were up‐regulated in CRC tissues when compared with adjacent non‐tumour tissues. The expression levels of MFI2‐AS1 were significantly associated with tumour histological grade, lymph and distant metastasis, TNM stage and vascular invasion. Both MFI2‐AS1 siRNA and miR‐574‐5p mimics inhibited proliferation, migration and invasion in LoVo and RKO cells. The transfection of miR‐574‐5p inhibitor showed MFI2‐AS1 siRNA‐induced changes in CRC cells. Dual‐luciferase reporter assay revealed target interactions between MFI2‐AS1 and miR‐574‐5p, miR‐574‐5p and MYCBP.

Conclusions

These findings suggested that lncRNA MFI2‐AS1 and MYCBP have promoting effects in CRC tissues. LncRNA MFI2‐AS1 promoted CRC cell proliferation, migration and invasion through activating MYCBP and by sponging miR‐574‐5p.

In silico genome-wide miRNA-QTL-SNPs analyses identify a functional SNP associated with mastitis in Holsteins

Background

Single-nucleotide polymorphisms (SNPs) in microRNAs (miRNAs) and their target binding sites affect miRNA function and are involved in biological processes and diseases, including bovine mastitis, a frequent inflammatory disease. Our previous study has shown that bta-miR-2899 is significantly upregulated in the mammary gland tissue of mastitis-infected cow than that of healthy cows.

Results

In the present study, we used a customized miRNAQTLsnp software and identified 5252 SNPs in 691 bovine pre-miRNAs, which are also located within the quantitative trait loci (QTLs) that are associated with mastitis and udder conformation-related traits. Using luciferase assay in the bovine mammary epithelial cells, we confirmed a candidate SNP (rs109462250, g. 42,198,087 G > A) in the seed region of bta-miR-2899 located in the somatic cell score (SCS)-related QTL (Chr.18: 33.9–43.9 Mbp), which affected the interaction of bta-miR-2899 and its putative target Spi-1 proto-oncogene (SPI1), a pivotal regulator in the innate and adaptive immune systems. Quantitative real-time polymerase chain reaction results showed that the relative expression of SPI1 in the mammary gland of AA genotype cows was significantly higher than that of GG genotype cows. The SNP genotypes were associated with SCS in Holstein cows.

Conclusions

Altogether, miRNA-related SNPs, which influence the susceptibility to mastitis, are one of the plausible mechanisms underlying mastitis via modulating the interaction of miRNAs and immune-related genes. These miRNA-QTL-SNPs, such as the SNP (rs109462250) of bta-miR-2899 may have implication for the mastitis resistance breeding program in Holstein cattle.

Electronic supplementary material

The online version of this article (10.1186/s12863-019-0749-5) contains supplementary material, which is available to authorized users.

MicroRNAs as regulators and effectors of hematopoietic transcription factors

Hematopoiesis is a highly-regulated development process orchestrated by lineage-specific transcription factors that direct the generation of all mature blood cells types, including red blood cells, megakaryocytes, granulocytes, monocytes, and lymphocytes. Under homeostatic conditions, the hematopoietic system of the typical adult generates over 10¹¹ blood cells daily throughout life. In addition, hematopoiesis must be responsive to acute challenges due to blood loss or infection. MicroRNAs (miRs) cooperate with transcription factors to regulate all aspects of hematopoiesis, including stem cell maintenance, lineage selection, cell expansion, and terminal differentiation. Distinct miR expression patterns are associated with specific hematopoietic lineages and stages of differentiation and functional analyses have elucidated essential roles for miRs in regulating cell transitions, lineage selection, maturation, and function. MiRs function as downstream effectors of hematopoietic transcription factors and as upstream regulators to control transcription factor levels. Multiple miRs have been shown to play essential roles. Regulatory networks comprised of differentially expressed lineage-specific miRs and hematopoietic transcription factors are involved in controlling the quiescence and self-renewal of hematopoietic stem cells as well as proliferation and differentiation of lineage-specific progenitor cells during erythropoiesis, myelopoiesis, and lymphopoiesis. This review focuses on hematopoietic miRs that function as upstream regulators of central hematopoietic transcription factors required for normal hematopoiesis. This article is categorized under: RNA in Disease and Development > RNA in Development Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

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 interplay between critical transcription factors and microRNAs in the control of normal and malignant myelopoiesis

Myelopoiesis is a complex process driven by essential transcription factors, including C/EBPα, PU.1, RUNX1, KLF4 and IRF8. Together, these factors are critical for the control of myeloid progenitor cell expansion and lineage determination in the development of granulocytes and monocytes/macrophages. MicroRNAs (miRNAs) are expressed in a cell type and lineage specific manner. There is increasing evidence that miRNAs fine-tune the expression of hematopoietic lineage-specific transcription factors and drive the lineage decisions of hematopoietic progenitor cells. In this review, we discuss recently discovered self-activating and feed-back mechanisms in which transcription factors and miRNAs interact during myeloid cell development. Furthermore, we delineate how some of these mechanisms are affected in acute myeloid leukemia (AML) and how disrupted transcription factor-miRNA interplays contribute to leukemogenesis.

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

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

MicroRNA, an Antisense RNA, in Sensing Myeloid Malignancies

Myeloid malignancies, including myelodysplastic syndromes and acute myeloid leukemia, are clonal diseases arising in hematopoietic stem or progenitor cells. In recent years, microRNA (miRNA) expression profiling studies have revealed close associations of miRNAs with cytogenetic and molecular subtypes of myeloid malignancies, as well as outcome and prognosis of patients. However, the roles of miRNA deregulation in the pathogenesis of myeloid malignancies and how they cooperate with protein-coding gene variants in pathological mechanisms leading to the diseases have not yet been fully understood. In this review, we focus on recent insights into the role of miRNAs in the development and progression of myeloid malignant diseases and discuss the prospect that miRNAs may serve as a potential therapeutic target for leukemia.

MicroRNA-22 controls interferon alpha production and erythroid maturation in response to infectious stress in mice

MicroRNA-22 (miR-22) is a highly conserved microRNA that can regulate cell proliferation, oncogenesis, and cell maturation, especially during stress. In hematopoietic stem cells (HSCs), miR-22 has been reported to be involved in the regulation of key self-renewal factors, including Tet2. Recent work demonstrates that miR-22 also participates in regulation of the interferon (IFN) response, and expression profiling studies suggest that it is variably expressed at different stages in erythroid differentiation. We thus hypothesized that miR-22 regulates maturation of erythroid progenitors during stress hematopoiesis through its interaction with IFN. We compared the blood and bone marrow of wild-type (WT) and miR-22-deficient mice at baseline and upon infectious challenge with systemic lymphochoriomeningitis (LCMV) virus. miR-22-deficient mice maintained platelet counts better than WT mice during infection, but they showed significantly reduced red blood cells and hemoglobin. Analysis of bone marrow progenitors demonstrated better overall survival and improved HSC homeostasis in infected miR-22-null mice compared with WT, which was attributable to a blunted IFN response to LCMV challenge in the miR-22-null mice. We found that miR-22 was expressed exclusively in stage II erythroid precursors and downregulated upon infection in WT mice. Our results indicate that miR-22 promotes the IFN response to viral infection and that it functions at baseline as a brake to slow erythroid differentiation and maintain adequate erythroid potential. Impaired regulation of erythrogenesis in the absence of miR-22 can lead to anemia during infection.

MicroRNAs and acute myeloid leukemia: therapeutic implications and emerging concepts

Acute myeloid leukemia (AML) is a deadly hematologic malignancy characterized by the uncontrolled growth of immature myeloid cells. Over the past several decades, we have learned a tremendous amount regarding the genetic aberrations that govern disease development in AML. Among these are genes that encode noncoding RNAs, including the microRNA (miRNA) family. miRNAs are evolutionarily conserved small noncoding RNAs that display important physiological effects through their posttranscriptional regulation of messenger RNA targets. Over the past decade, studies have identified miRNAs as playing a role in nearly all aspects of AML disease development, including cellular proliferation, survival, and differentiation. These observations have led to the study of miRNAs as biomarkers of disease, and efforts to therapeutically manipulate miRNAs to improve disease outcome in AML are ongoing. Although much has been learned regarding the importance of miRNAs in AML disease initiation and progression, there are many unanswered questions and emerging facets of miRNA biology that add complexity to their roles in AML. Moving forward, answers to these questions will provide a greater level of understanding of miRNA biology and critical insights into the many translational applications for these small regulatory RNAs in AML.

Specific Depletion of Leukemic Stem Cells: Can MicroRNAs Make the Difference?

For over 40 years the standard treatment for acute myeloid leukemia (AML) patients has been a combination of chemotherapy consisting of cytarabine and an anthracycline such as daunorubicin. This standard treatment results in complete remission (CR) in the majority of AML patients. However, despite these high CR rates, only 30–40% (<60 years) and 10–20% (>60 years) of patients survive five years after diagnosis. The main cause of this treatment failure is insufficient eradication of a subpopulation of chemotherapy resistant leukemic cells with stem cell-like properties, often referred to as “leukemic stem cells” (LSCs). LSCs co-exist in the bone marrow of the AML patient with residual healthy hematopoietic stem cells (HSCs), which are needed to reconstitute the blood after therapy. To prevent relapse, development of additional therapies targeting LSCs, while sparing HSCs, is essential. As LSCs are rare, heterogeneous and dynamic, these cells are extremely difficult to target by single gene therapies. Modulation of miRNAs and consequently the regulation of hundreds of their targets may be the key to successful elimination of resistant LSCs, either by inducing apoptosis or by sensitizing them for chemotherapy. To address the need for specific targeting of LSCs, miRNA expression patterns in highly enriched HSCs, LSCs, and leukemic progenitors, all derived from the same patients’ bone marrow, were determined and differentially expressed miRNAs between LSCs and HSCs and between LSCs and leukemic progenitors were identified. Several of these miRNAs are specifically expressed in LSCs and/or HSCs and associated with AML prognosis and treatment outcome. In this review, we will focus on the expression and function of miRNAs expressed in normal and leukemic stem cells that are residing within the AML bone marrow. Moreover, we will review their possible prospective as specific targets for anti-LSC therapy.

MicroRNA-22-3p as a novel regulator and therapeutic target for autoimmune diseases

MicroRNAs (miRNAs) are a class of noncoding RNAs and have emerged as critical regulators of gene expression. Some miRNAs play important roles in regulating the function of the immune system and are involved in the pathogenesis of autoimmune diseases. Recent studies suggested that microRNA-22-3p (miR-22-3p) was able to regulate the function of several types of immune cells and may be involved in the development of autoimmune diseases. We systematically reviewed relevant literatures to provide a comprehensive review of the possible roles of miR-22-3p in autoimmune diseases. Published studies suggest that miR-22-3p can act as a novel regulator of autoimmune diseases via several pathways. More studies are needed to further elucidate the exact roles of miR-22-3p in autoimmune diseases. Treatment strategy targeting miR-22-3p is also a promising therapy for autoimmune diseases.

A Macro View of MicroRNAs: The Discovery of MicroRNAs and Their Role in Hematopoiesis and Hematologic Disease

MicroRNAs (MiRNAs) are a class of endogenously encoded ~22 nucleotide, noncoding, single-stranded RNAs that contribute to development, body planning, stem cell differentiation, and tissue identity through posttranscriptional regulation and degradation of transcripts. Given their importance, it is predictable that dysregulation of MiRNAs, which target a wide variety of transcripts, can result in malignant transformation. In this review, we explore the discovery of MiRNAs, their mechanism of action, and the tools that aid in their discovery and study. Strikingly, many of the studies that have expanded our understanding of the contributions of MiRNAs to normal physiology and in the development of diseases have come from studies in the hematopoietic system and hematologic malignancies, with some of the earliest identified functions for mammalian MiRNAs coming from observations made in leukemias. So, with a special focus on the hematologic system, we will discuss how MiRNAs contribute to differentiation of stem cells and how dysregulation of MiRNAs contributes to the development of malignancy, by providing examples of specific MiRNAs that function as oncogenes or tumor suppressors, as well as of defects in MiRNA processing. Finally, we will discuss the promise of MiRNA-based therapeutics and challenges for the future study of disease-causing MiRNAs.

The inhibition role of miR-22 in hepatocellular carcinoma cell migration and invasion via targeting CD147

BACKGROUND

Recently, miR-22 is identified as a tumor-suppressing microRNA in many human cancers. CD147 is a novel cancer-associated biomarker that plays an important role in the invasion and metastasis of malignant tumor. However, the involvement of miR-22 in CD147 regulation and hepatocellular carcinoma (HCC) progression and metastasis has not been investigated.

METHODS

We measured miR-22 expression level in 34 paired of HCC and matched normal tissues, HCC cell lines by real-time quantitative RT-PCR. Invasion assay, MTT proliferation assay and wound-healing assay were performed to test the invasion and proliferation of HCC cell after overexpression of miR-22. The effect of miR-22 on HCC in vivo was validated by murine xenograft model. The relationship of miR-22 and its target gene CD147 was also investigated.

RESULTS

We found that the expression of miR-22 in HCC tissues and cell lines were much lower than that in normal control, respectively. The expression of miR-22 was inversely correlated with HCC metastatic ability. Moreover, overexpression of miR-22 could significantly inhibit the HCC cell proliferation, migration and invasion in vitro and decrease HCC tumor growth in vivo. Finally, we found that miR-22 interacted with CD147 and decreased its expression, via a specific target site within the CD147 3'UTR by luciferase reporter assay. The expression of CD147 was inversely correlated with miR-22 expression in HCC tissues.

CONCLUSION

Our results suggested that miR-22 was downexpressed in HCC and inhibited HCC cell proliferation, migration and invasion through downregulating cancer-associated gene CD147 which may provide a new bio-target for HCC therapy.