HIF-1α downregulates miR-17/20a directly targeting p21 and STAT3: a role in myeloid leukemic cell differentiation

miR-372 inhibits p62 in head and neck squamous cell carcinoma in vitro and in vivo

Here we showed that exogenous miR-372 expression and knockdown of p62 (sequestosome1 or SQSTM1), both increased migration of head and neck squamous cell carcinoma (HNSCC) cells. p62 induced phase II detoxification enzyme NADPH quinone oxidoreductase 1 (NQO1), which decreased ROS levels and cell migration. Also, miR-372 decreased p62 during hypoxia, thus increasing cell migration. Levels of miR-372 and p62 inversely correlated in human HNSCC tissues. Plasma levels of miR-372 was associated with advanced tumor stage and patient mortality. Both plasma and salivary miR-372 levels were decreased after tumor resection. We conclude that miR-372 decreases p62, thus increasing ROS and motility in HNSCC cells.

Hypoxia and Hypoxia-Inducible Factors in Leukemias

Despite huge improvements in the treatment of leukemia, the percentage of patients suffering relapse still remains significant. Relapse most often results from a small number of leukemic stem cells (LSCs) within the bone marrow, which are able to self-renew, and therefore reestablish the full tumor. The marrow microenvironment contributes considerably in supporting the protection and development of leukemic cells. LSCs share specific niches with normal hematopoietic stem cells with the niche itself being composed of a variety of cell types, including mesenchymal stem/stromal cells, bone cells, immune cells, neuronal cells, and vascular cells. A hallmark of the hematopoietic niche is low oxygen partial pressure, indeed this hypoxia is necessary for the long-term maintenance of hematopoietic stem/progenitor cells. Hypoxia is a strong signal, principally maintained by members of the hypoxia-inducible factor (HIF) family. In solid tumors, it has been well established that hypoxia triggers intrinsic metabolic changes and microenvironmental modifications, such as the stimulation of angiogenesis, through activation of HIFs. As leukemia is not considered a “solid” tumor, the role of oxygen in the disease was presumed to be inconsequential and remained long overlooked. This view has now been revised since hypoxia has been shown to influence leukemic cell proliferation, differentiation, and resistance to chemotherapy. However, the role of HIF proteins remains controversial with HIFs being considered as either oncogenes or tumor suppressor genes, depending on the study and model. The purpose of this review is to highlight our knowledge of hypoxia and HIFs in leukemic development and therapeutic resistance and to discuss the recent hypoxia-based strategies proposed to eradicate leukemias.

The progress of angiogenic factors in the development of leukemias

Angiogenic factors have been demonstrated to play important roles in modulating angiogenesis of solid tumors. Recently, accumulating studies extensively indicated that some angiogenic factors widely exist in malignant cells of hematologic malignancy, which regulated the expression of a number of genes that were involved in abnormal proliferation, differentiation and apoptosis of these cells. With deep research of angiogenic factors, its expression, function and regulatory mechanism were gradually elucidated, and some of them were related to the development and prognosis of leukemia, or provide more possible strategies for treatment of patients with leukemia. Herein, we summarize the progress in study of some important angiogenic factors and hematological malignancies.

Targeted Disruption of miR-17-92 Impairs Mouse Spermatogenesis by Activating mTOR Signaling Pathway

The miR-17-92 cluster and its 6 different mature microRNAs, including miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, and miR-92a, play important roles in embryo development, immune system, kidney and heart development, adipose differentiation, aging, and tumorigenicity. Currently, increasing evidence indicates that some members of miR-17-92 cluster may be critical players in spermatogenesis, including miR-17, miR-18a, and miR-20a. However, the roles and underlying mechanisms of miR-17-92 in spermatogenesis remain largely unknown. Our results showed that the targeted disruption of miR-17-92 in the testes of adult mice resulted in severe testicular atrophy, empty seminiferous tubules, and depressed sperm production. This phenotype is partly because of the reduced number of spermatogonia and spermatogonial stem cells, and the significantly increased germ cell apoptosis in the testes of miR-17-92-deficient mice. In addition, overactivation of the mammalian target of rapamycin signaling pathway and upregulation of the pro-apoptotic protein Bim, Stat3, c-Kit, and Socs3 were also observed in miR-17-92-deficient mouse testes, which might be, at least partially if not all, responsible for the aforementioned phenotypic changes in mutant testes. Taken together, these findings suggest that miR-17-92 is essential for normal spermatogenesis in mice.

Nutrient deprivation-related OXPHOS/glycolysis interconversion via HIF-1α/C-MYC pathway in U251 cells

Although the Warburg effect is a dominant metabolic phenotype observed in cancers, the metabolic changes and adaptation occurring in tumors have been demonstrated to extend beyond the Warburg effect and thus considered a secondary effect to the transformation process of carcinogenesis, including nutritional deficiencies. However, the role of nutritional deficiencies in this metabolic reprogramming (e. g., oxidative phosphorylation (OXPHOS)/glycolysis interconversion) is not completely known yet. Here, we showed that under regular culture condition, the proliferation of U251 cells, but not other tumor cell lines, preferentially performed the Warburg effect and was remarkably inhibited by oxamic acid which can inhibit the activity of lactate dehydrogenase (LDH); whereas under serum starvation, glycolysis was depressed, tricarboxylic acid cycle (TCA) was enhanced, and the activity of OXPHOS was reinforced to maintain cellular ATP content in a high level, but interestingly, we observed a decreased expression of reactive oxygen species (ROS). Moreover, the upregulated activity of mitochondrial complex I was confirmed by Western blots and showed that the mitochondrial-related protein, NDUFA9, NDUFB8, ND1, and VDAC1 were remarkably increased after serum starved. Mechanistically, nutritional deficiencies could reduce hypoxia-inducible factor α (HIF-1α) protein expression to increase C-MYC protein level, which in turn increased nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) transcription to enhance the activity of OXPHOS, suggesting that metabolic reprogramming by the changes of microenvironment during the carcinogenesis can provide some novel therapeutic clues to traditional cancer treatments.

Cancer metabolism and the Warburg effect: the role of HIF-1 and PI3K

Cancer cells have been shown to have altered metabolism when compared to normal non-malignant cells. The Warburg effect describes a phenomenon in which cancer cells preferentially metabolize glucose by glycolysis, producing lactate as an end product, despite being the presence of oxygen. The phenomenon was first described by Otto Warburg in the 1920s, and has resurfaced as a controversial theory, with both supportive and opposing arguments. The biochemical aspects of the Warburg effect outline a strong explanation for the cause of cancer cell proliferation, by providing the biological requirements for a cell to grow. Studies have shown that pathways such as phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) as well as hypoxia inducible factor-1 (HIF-1) are central regulators of glycolysis, cancer metabolism and cancer cell proliferation. Studies have shown that PI3K signaling pathways have a role in many cellular processes such as metabolism, inflammation, cell survival, motility and cancer progression. Herein, the cellular aspects of the PI3K pathway are described, as well as the influence HIF has on cancer cell metabolism. HIF-1 activation has been related to angiogenesis, erythropoiesis and modulation of key enzymes involved in aerobic glycolysis, thereby modulating key processes required for the Warburg effect. In this review we discuss the molecular aspects of the Warburg effect with a particular emphasis on the role of the HIF-1 and the PI3K pathway.

MicroRNA-130a expression is decreased in Xinjiang Uygur patients with type 2 diabetes mellitus

AIMS

MicroRNAs play important roles in energy metabolism, insulin synthesis, insulin transport and the development of diabetes. This study aims to investigate the expression and effect of microRNA-130a in Uygur patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

Peripheral blood and omental adipose tissues were collected from individuals with normal glucose tolerance and patients with T2DM. The microRNA expression profile of peripheral blood was established by microarray analysis. The differentially expressed microRNAs and possible target genes were identified by bioinformatics analysis. MicroRNA-130a mimics and inhibitors were transfected into 3T3-L1 preadipocytes.

RESULTS

Our results showed that microRNA-130a expression level was significantly decreased in peripheral blood and omental adipose tissues of T2DM patients (P < 0.01). Peroxisome proliferator-activated receptors γ (PPARγ) were predicted as target genes of microRNA-130a. This prediction was verified by the results that PPARγ mRNA expression in omental adipose tissues of T2DM patients were significantly increased (P < 0.01). The glucose consumption level after microRNA-130a transfection was significantly decreased (P < 0.05). And, microRNA-130a mimics inhibited PPARγ expression at both mRNA and protein level, further suggesting that PPARγ is a target gene of microRNA-130a. Additionally, adiponectin, lipoprotein lipase, CCAAT enhancer binding protein α, and the downstream genes of PPARγ, were significantly decreased after microRNA-130a mimics transfection.

CONCLUSIONS

In conclusion, microRNA-130a is decreased in Uygur patients with T2DM and it may play a role in T2DM through targeting PPARγ.

MiR-20a-5p mediates hypoxia-induced autophagy by targeting ATG16L1 in ischemic kidney injury

AIMS

Autophagy is a cellular homeostatic mechanism activated under stress conditions and might act as protective response for cell survival in ischemic kidney injury. The micro RNA (miRNA) network may be critically involved in the regulation of autophagy. The aim of this study was to evaluate whether miRNA regulates autophagy in ischemic kidney injury and renal proximal tubular cells under hypoxic conditions.

MATERIALS AND METHODS

Ischemic kidney injury was performed by clamping bilateral renal pedicles for 60min in male mice. Human kidney proximal tubular (HK-2) cells were exposed to in vitro hypoxic conditions. ATG16L1 is essential for autophagosome formation. Bioinformatics analyses were used to select the candidate miRNA, miR-20a-5p, which potentially targets ATG16L1. Gain-of-function and loss-of-function methods were employed to evaluate the effects of miRNA on autophagy. Chromatin immunoprecipitation analysis and promoter luciferase reporter assays were used to evaluate the interaction of transcriptional factors with miRNA.

KEY FINDINGS

Increased expression of punctate LC3 and ATG16L1, autophagy-related proteins, and down-expression of miR-20a-5p were detected in kidneys after ischemic injury and in HK-2 cells under hypoxic conditions. 3'-untranslated region luciferase reporter assays indicated that miR-20a-5p targeted ATG16L1 messenger RNA. Over-expression of miR-20a-5p reduced the expression of LC3-II and ATG16L1 in HK-2 cells under hypoxic conditions, whereas antagomiR-20a reversed the inhibition. Using RNAi against hypoxia-inducible factor-1α (HIF-1α) in HK-2 cells, we confirmed the inhibitory binding of HIF-1α to miR-20a-5p.

SIGNIFICANCE

The signaling axis of HIF-1α, miR-20a-5p, and ATG16L1 in autophagic process might be a critical adapting mechanism for ischemic kidney injury.

The miR-124-prolyl hydroxylase P4HA1-MMP1 axis plays a critical role in prostate cancer progression

Collagen prolyl hydroxylases (C-P4HAs) are a family of enzymes involved in collagen biogenesis. One of the isoforms of P4HA, Prolyl 4-hydroxylase, alpha polypeptide I (P4HA1), catalyzes the formation of 4-hydroxyproline that is essential for the proper three-dimensional folding of newly synthesized procollagen chains. Here, we show the overexpression of P4HA1 in aggressive prostate cancer. Immunohistochemical analysis using tissue microarray demonstrated that P4HA1 expression was correlated with prostate cancer progression. Using in vitro studies, we showed that P4HA1 plays a critical role in prostate cancer cell growth and tumor progression. Expression profiling studies using P4HA1-modulated prostate cells suggested regulation of Matrix metalloprotease 1. The invasive properties of P4HA1 overexpressing cells were reversed by blocking MMP1. Our studies indicate P4HA1 copy number gain in a subset of metastatic prostate tumors and its expression is also regulated by microRNA-124. MiR-124 in turn is negatively regulated by transcriptional repressors EZH2 and CtBP1, both of which are overexpressed in aggressive prostate cancer. Chick chorioallantoic membrane (CAM) assay and mice xenograft investigations show that P4HA1 is required for tumor growth and metastasis in vivo. Our observations suggest that P4HA1 plays a critical role in prostate cancer progression and could serve as a viable therapeutic target.

The potential of plasma miRNAs for diagnosis and risk estimation of colorectal cancer

Circulating microRNAs (miRNAs) were recognized to be potential non-invasive biomarkers for colorectal cancer (CRC) detection and prediction. Meanwhile, the association of the expression of plasma miRNAs with the risk of CRC patients has rarely been analyzed. Therefore, we conducted this study to evaluate the value of plasma miRNAs for CRC diagnosis and risk estimation. Fasting blood samples from 100 CRC patients and 79 cancer-free controls were collected. Plasma miR-106a, miR-20a, miR-27b, miR-92a and miR-29a levels were detected by RT-qPCR. Sensitivity and specificity were employed to evaluate the diagnostic value of miRNAs for CRC. Univariate and multivariate logistic regression were employed to analyze the association between miRNAs expression and CRC risk. As results, miR-106a and miR-20a were elevated in the patients with CRC. The sensitivity of miR-106a was 74.00% and the specificity was 44.40%, while the cutoff value was 2.03. As for miR-20a, the sensitivity was 46.00% and specificity was 73.42% when employed 2.44 as cutoff value. High expression of plasma miR-106a increased CRC risk by 1.80 -fold. Plasma miR-106a and miR-20a may as noninvasive biomarkers for detecting the CRC. High expression of miR-106a associated with CRC risk.

Interactional role of microRNAs and bHLH-PAS proteins in cancer (Review)

MicroRNAs (miRNAs) are recognized as an emerging class of master regulators that regulate human gene expression at the post-transcriptional level and are involved in many normal and pathological cellular processes. Mammalian basic HLH (helix-loop-helix)-PER-ARNT-SIM (bHLH-PAS) proteins are heterodimeric transcriptional regulators that sense and respond to environmental signals (such as chemical pollutants) or to physiological signals (for instance hypoxia). In the normal state, bHLH-PAS proteins are responsible for multiple critical aspects of physiology to ensure the cell accurate homeostasis, but dysregulation of these proteins has been shown to contribute to carcinogenic events such as tumor initiation, promotion, and progression. Increasing epidemiological and experimental studies have shown that bHLH-PAS proteins regulate a panel of miRNAs, whereas some miRNAs also target bHLH-PAS proteins. The interaction between miRNAs and certain bHLH-PAS proteins [hypoxia-inducible factor (HIF) and aryl hydrocarbon receptor (AHR)] is relevant to many vital events associated with tumorigenesis. This review will summarize recent findings on the interesting and complicated underlying mechanisms that miRNAs interact with HIFs or AHR in tumors, hopefully to benefit the discovery of novel drug-interfering targets for cancer therapy.

Dietary compounds galangin and myricetin suppress ovarian cancer cell angiogenesis

Galangin and myricetin are flavonoids isolated from vegetables and fruits which exhibit anti-proliferative activity in human cancer cells. In this study, their anti-angiogenic effects were investigated with in vitro (HUVEC) and in vivo (CAM) models, which showed that galangin and myricetin inhibited angiogenesis induced by OVCAR-3 cells. The molecular mechanisms through which galangin and myricetin suppress angiogenesis were also studied. It was observed that galangin and myricetin inhibited secretion of the key angiogenesis mediator vascular endothelial growth factor (VEGF) and decreased levels of p-Akt, p-70S6K and hypoxia-inducible factor-1α (HIF-1α) proteins in A2780/CP70 and OVCAR-3 cells. Transient transfection experiments showed that galangin and myricetin inhibited secretion of VEGF by the Akt/p70S6K/ HIF-1α pathway. Moreover, a novel pathway, p21/HIF-1α/VEGF, was found to be involved in the inhibitory effect of myricetin on angiogenesis in OVCAR-3 cells. These data suggest that galangin and myricetin might serve as potential anti-angiogenic agents in the prevention of ovarian cancers dependent on new blood vessel networks.

MicroRNA-20a regulates autophagy related protein-ATG16L1 in hypoxia-induced osteoclast differentiation

Autophagy and autophagy-related proteins (ATGs) play decisive roles in osteoclast differentiation. Emerging lines of evidence show the deregulation of miRNA in autophagic responses. However, the role of hypoxia and involvement of miRNA in osteoclast differentiation are unclear. In the present study, we demonstrate that hypoxia caused induction of autophagy and osteoclast differentiation markers in RAW264.7 cells stimulated with M-CSF and RANKL. In addition, miR-20a was significantly repressed during hypoxia and identified as the prime candidate involved in hypoxia-induced osteoclast differentiation. The results from dual luciferase reporter assay revealed that miR-20a directly targets Atg16l1 by binding to its 3'UTR end. Further, miR-20a transfection studies showed significant down regulation of autophagic proteins (LC3-II and ATG16L1) and osteoclast differentiation markers (Nfatc1, Traf6, and Trap) thus confirming the functional role of miR-20a under hypoxic conditions. Results of chromatin immunoprecipitation assay showed that HIF-1α binds to miRNA-20a. From miRNA Q-PCR results, we confirmed that shRNA HIF-1α knockdown significantly downregulated both autophagy (LC3, p62, Atg5, Atg12, Atg16l1, Atg7, Becn1, Atg9a) and osteoclast markers (Traf6, Nfatc1, Ctsk, cFos, Mmp9, Trap) in RAW264.7 cells. Thus, our findings suggest that the regulatory axis of HIF-1α-miRNA-20a-Atg16l1 might be a critical mechanism for hypoxia-induced osteoclast differentiation.

miR-199a-5p inhibits monocyte/macrophage differentiation by targeting the activin A type 1B receptor gene and finally reducing C/EBPα expression

miRNAs are short, noncoding RNAs that regulate expression of target genes at post-transcriptional levels and function in many important cellular processes, including differentiation, proliferation, etc. In this study, we observed down-regulation of miR-199a-5p during monocyte/macrophage differentiation of HL-60 and THP-1 cells, as well as human CD34(+) HSPCs. This down-regulation of miR-199a-5p resulted from the up-regulation of PU.1 that was demonstrated to regulate transcription of the miR-199a-2 gene negatively. Overexpression of miR-199a-5p by miR-199a-5p mimic transfection or lentivirus-mediated gene transfer significantly inhibited monocyte/macrophage differentiation of the cell lines or HSPCs. The mRNA encoding an ACVR1B was identified as a direct target of miR-199a-5p. Gradually increased ACVR1B expression level was detected during monocyte/macrophage differentiation of the leukemic cell lines and HSPCs, and knockdown of ACVR1B resulted in inhibition of monocyte/macrophage differentiation of HL-60 and THP-1 cells, which suggested that ACVR1B functions as a positive regulator of monocyte/macrophage differentiation. We demonstrated that miR-199a-5p overexpression or ACVR1B knockdown promoted proliferation of THP-1 cells through increasing phosphorylation of Rb. We also demonstrated that the down-regulation of ACVR1B reduced p-Smad2/3, which resulted in decreased expression of C/EBPα, a key regulator of monocyte/macrophage differentiation, and finally, inhibited monocyte/macrophage differentiation.

HypoxamiRs and cancer: from biology to targeted therapy

SIGNIFICANCE

Hypoxia is a hallmark of the tumor microenvironment and represents a major source of failure in cancer therapy.

RECENT ADVANCES

Recent work has generated extensive evidence that microRNAs (miRNAs) are significant components of the adaptive response to low oxygen in tumors. Induction of specific miRNAs, collectively termed hypoxamiRs, has become an accepted feature of the hypoxic response in normal and transformed cells.

CRITICAL ISSUES

Overexpression of miR-210, the prototypical hypoxamiR, is detected in most solid tumors, and it has been linked to adverse prognosis in many tumor types. Several miR-210 target genes, including iron-sulfur (Fe-S) cluster scaffold protein (ISCU) and glycerol-3-phosphate dehydrogenase 1-like (GPD1L), have been correlated with prognosis in an inverse fashion to miR-210, suggesting that their down- regulation by miR-210 occurs in vivo and contributes to tumor growth. Additional miRNAs are modulated by decreased oxygen tension in a more tissue-specific fashion, adding another level of complexity over the classic hypoxia-regulated gene network.

FUTURE DIRECTIONS

From a biological standpoint, hypoxamiRs are emerging modifiers of cancer cell response to the adaptive challenges of the microenvironment. From a clinical perspective, assessing the status of these miRNAs may contribute to a detailed understanding of hypoxia-induced mechanisms of resistance and/or to the fine-tuning of future hypoxia-modifying therapies.

The role of hypoxia and exploitation of the hypoxic environment in hematologic malignancies

Tumor hypoxia is a well-described phenomenon during the progression of solid tumors affecting cell signaling pathways and cell metabolism; however, its role in hematologic malignancies has not been given the same attention in the literature. Therefore, this review focuses on the comparative differences between solid and hematologic malignancies with emphasis on the role of hypoxia during tumorigenesis and progression. In addition, contribution of the bone marrow and angiogenic environment are also discussed. Insight is provided into the role of hypoxia in metastatic spread, stemness, and drug resistance in hematologic conditions. Finally, emerging therapeutic strategies such as small-molecule prodrugs and hypoxia-inducible factor (HIF) targeting approaches are outlined to combat hypoxic cells and/or adaptive mechanisms in the treatment of hematologic malignancies.

The Silencing Effect of microRNA miR-17 on p21 Maintains the Neural Progenitor Pool in the Developing Cerebral Cortex

Expansion of the neural progenitor pool in the developing cerebral cortex is crucial for controlling brain size, since proliferation defects have been associated with the pathogenesis of microcephaly in humans. Cell cycle regulators play important roles in proliferation of neural progenitors. Here, we show that the cyclin-dependent kinase inhibitor p21 (also called Cdkn1a and Cip1) negatively regulates proliferation of radial glial cells (RGCs) and intermediate progenitors (IPs) in the embryonic mouse cortex. MicroRNA-17 (miR-17) displays reciprocal expressions with p21 in the developing cortex. Opposite to p21, miR-17 promotes expansion of RGCs and IPs, as demonstrated by overexpressing miR-17 precursors and miR-17 sponges that can knock down the endogenous miR-17. Moreover, p21 is a putative target normally silenced by miR-17. Co-expression of miR-17 with p21 is sufficient to rescue the negative regulation of p21 on progenitor proliferation. Our results indicate a mechanism of controlling the neural progenitor pool, which is to suppress p21 by miR-17 in the developing cortex.

Concise review: genetic dissection of hypoxia signaling pathways in normal and leukemic stem cells

Adult hematopoiesis depends on rare multipotent hematopoietic stem cells (HSCs) that self-renew and give rise to progenitor cells, which differentiate to all blood lineages. The strict regulation of the fine balance between self-renewal and differentiation is essential for normal hematopoiesis and suppression of leukemia development. HSCs and progenitor cells are commonly assumed to reside within the hypoxic BM microenvironment, however, there is no direct evidence supporting this notion. Nevertheless, HSCs and progenitors do exhibit a hypoxic profile and strongly express Hif-1α. Although hypoxia signaling pathways are thought to play important roles in adult HSC maintenance and leukemogenesis, the precise function of Hif-dependent signaling in HSCs remains to be uncovered. Here we discuss recent gain-of-function and loss-of-function studies that shed light on the complex roles of hypoxia-signaling pathways in HSCs and their niches in normal and malignant hematopoiesis. Importantly, we comment on the current and often contrasting interpretations of the role of Hif-dependent signaling in stem cell functions.

RepSox slows decay of CD34+ acute myeloid leukemia cells and decreases T cell immunoglobulin mucin-3 expression

Despite initial response to therapy, most acute myeloid leukemia (AML) patients relapse. To eliminate relapse-causing leukemic stem/progenitor cells (LPCs), patient-specific immune therapies may be required. In vitro cellular engineering may require increasing the "stemness" or immunogenicity of tumor cells and activating or restoring cancer-impaired immune-effector and antigen-presenting cells. Leukapheresis samples provide the cells needed to engineer therapies: LPCs to be targeted, normal hematopoietic stem cells to be spared, and cancer-impaired immune cells to be repaired and activated. This study sought to advance development of LPC-targeted therapies by exploring nongenetic ways to slow the decay and to increase the immunogenicity of primary CD34(+) AML cells. CD34(+) AML cells generally displayed more colony-forming and aldehyde dehydrogenase activity than CD34(-) AML cells. Along with exposure to bone marrow stromal cells and low (1%-5%) oxygen, culture with RepSox (a reprogramming tool and inhibitor of transforming growth factor-β receptor 1) consistently slowed decline of CD34(+) AML and myelodysplastic syndrome (MDS) cells. RepSox-treated AML cells displayed higher CD34, CXCL12, and MYC mRNA levels than dimethyl sulfoxide-treated controls. RepSox also accelerated loss of T cell immunoglobulin mucin-3 (Tim-3), an immune checkpoint receptor that impairs antitumor immunity, from the surface of AML and MDS cells. Our results suggest RepSox may reduce Tim-3 expression by inhibiting transforming growth factor-β signaling and slow decay of CD34(+) AML cells by increasing CXCL12 and MYC, two factors that inhibit AML cell differentiation. By prolonging survival of CD34(+) AML cells and reducing Tim-3, RepSox may promote in vitro immune cell activation and advance development of LPC-targeted therapies.

Dynamin 2 along with microRNA-199a reciprocally regulate hypoxia-inducible factors and ovarian cancer metastasis

Hypoxia-driven changes in the tumor microenvironment facilitate cancer metastasis. In the present study, we investigated the regulatory cross talk between endocytic pathway, hypoxia, and tumor metastasis. Dynamin 2 (DNM2), a GTPase, is a critical mediator of endocytosis. Hypoxia decreased the levels of DNM2. DNM2 promoter has multiple hypoxia-inducible factor (HIF)-binding sites and genetic deletion of them relieved hypoxia-induced transcriptional suppression. Interestingly, DNM2 reciprocally regulated HIF. Inhibition of DNM2 GTPase activity and dominant-negative mutant of DNM2 showed a functional role for DNM2 in regulating HIF. Furthermore, the opposite strand of DNM2 gene encodes miR-199a, which is similarly reduced in cancer cells under hypoxia. miR-199a targets the 3'-UTR of HIF-1α and HIF-2α. Decreased miR-199a expression in hypoxia increased HIF levels. Exogenous expression of miR-199a decreased HIF, cell migration, and metastasis of ovarian cancer cells. miR-199a-mediated changes in HIF levels affected expression of the matrix-remodeling enzyme, lysyloxidase (LOX). LOX levels negatively correlated with progression-free survival in ovarian cancer patients. These results demonstrate a regulatory relationship between DNM2, miR-199a, and HIF, with implications in cancer metastasis.

miR-17 regulates the proliferation and differentiation of the neural precursor cells during mouse corticogenesis

MicroRNAs (miRNAs) are endogenously expressed small, non-coding nucleotides that repress gene expression at the post-transcriptional level. In mammals, the developing brain contains a large, diverse group of miRNAs, which suggests that they play crucial roles in neural development. In the present study, we analyzed the miRNA expression patterns in the mouse cortex at various developmental stages. We found that miR-17 family miRNAs were highly expressed in the cortex during early developmental stages, and that their expression levels gradually decreased as the cortex developed. Further investigation revealed that the change in miR-17-5p expression occurred in the ventricular zone/sub-ventricular zone. In addition to promoting cell proliferation, miR-17-5p also influences the differentiation fate of neural precursor cells exposed to bone morphogenetic protein 2. Moreover, we show that these effects of miR-17-5p were mainly the result of regulating the bone morphogenetic protein signaling pathway by repressing expression of the bone morphogenetic protein type II receptor. Taken together, these findings suggest that miR-17 family members play a pivotal role in regulating cell activity during early development of the mouse cortex.

MicroRNAs as Haematopoiesis Regulators

The production of different types of blood cells including their formation, development, and differentiation is collectively known as haematopoiesis. Blood cells are divided into three lineages erythriod (erythrocytes), lymphoid (B and T cells), and myeloid (granulocytes, megakaryocytes, and macrophages). Haematopoiesis is a complex process regulated by several mechanisms including microRNAs (miRNAs). miRNAs are small RNAs which regulate the expression of a number of genes involved in commitment and differentiation of hematopoietic stem cells. Evidence shows that miRNAs play an important role in haematopoiesis; for example, myeloid and erythroid differentiation is blocked by the overexpression of miR-15a. miR-221, miR-222, and miR-24 inhibit the erythropoiesis, whereas miR-150 plays a role in B and T cell differentiation. miR-146 and miR-10a are downregulated in megakaryopoiesis. Aberrant expression of miRNAs was observed in hematological malignancies including chronic myelogenous leukemia, chronic lymphocytic leukemia, multiple myelomas, and B cell lymphomas. In this review we have focused on discussing the role of miRNA in haematopoiesis.

Synergetic regulatory networks mediated by oncogene-driven microRNAs and transcription factors in serous ovarian cancer

Although high-grade serous ovarian cancer (OVC) is the most lethal gynecologic malignancy in women, little is known about the regulatory mechanisms in the cellular processes that lead to this cancer. Recently, accumulated lines of evidence have shown that the interplay between transcription factors (TFs) and microRNAs (miRNAs) is critical in cellular regulation during tumorigenesis. A comprehensive investigation of TFs and miRNAs, and their target genes, may provide a deeper understanding of the regulatory mechanisms in the pathology of OVC. In this study, we have integrated three complementary algorithms into a framework, aiming to infer the regulation by miRNAs and TFs in conjunction with gene expression profiles. We demonstrated the utility of our framework by inferring 67 OVC-specific regulatory feed-forward loops (FFL) initiated by miRNAs or TFs in high-grade serous OVC. By analyzing these regulatory behaviors, we found that all the 67 FFLs are consistent in their regulatory effects on genes that are jointly targeted by miRNAs and TFs. Remarkably, we unveiled an unbalanced distribution of FFLs with different oncogenic effects. In total, 31 of the 67 coherent FFLs were mainly initiated by oncogenes. On the contrary, only 4 of the FFLs were initiated by tumor suppressor genes. These overwhelmingly observed oncogenic genes were further detected in a sub-network with 32 FFLs centered by miRNA let-7b and TF TCF7L1 to regulate cell differentiation. Closer inspection of 32 FFLs revealed that 75% of the miRNAs reportedly play functional roles in cell differentiation, especially when enriched in epithelial-mesenchymal transitions. This study provides a comprehensive pathophysiological overview of recurring coherent circuits in OVC that are co-regulated by miRNAs and TFs. The prevalence of oncogenic coherent FFLs in serous OVC suggests that oncogene-driven regulatory motifs could cooperatively act upon critical cellular processes such as cell differentiation in a highly efficient and consistent manner.

The signaling pathway of hypoxia inducible factor and its role in renal diseases

It is well-documented that hypoxia inducible factor (HIF) is a key mediator of tissue and cellular adaptation to hypoxia. HIF-target genes are also involved in cellular apoptosis and profibrotic mechanisms. The role of HIF in diseases is not consistent. It is a risk factor for tumor progression, whereas it plays a protective role against ischemic hypofusion. For renal diseases, it is not always a risk or protective factor. Many factors are involved in the pathogenesis of renal diseases. It is reported that HIF not only increases hypoxia tolerance, but also regulates a lot of signaling pathways. In the past decades, a number of studies were also conducted to explore the association between HIF and the risk of renal diseases. However, the role of HIF in the development of renal diseases was not entirely clear. In this study, the signal transduction pathways of HIF and its role in the pathogenesis of renal diseases were reviewed.

Regulation of the Hif-system by micro-RNA 17 and 20a - role during monocyte-to-macrophage differentiation

MiRNAs are a class of endogenous tiny RNAs that act as inhibitors of translation or promote RNA degradation by duplex-formation within the 3'-UTR of target mRNAs. They play an important role during a wide range of cellular processes by fine-tuning of gene expression. The differentiation of monocytes to macrophages plays a pivotal role in physiological as well as pathophysiological processes such as atherosclerosis. Monocytes which can be found in well-oxygenated blood migrate into areas with a high inflammation, such as the atherosclerotic plaque. There, they differentiate into macrophages. Interestingly, macrophages were found mainly at hypoxic sites of the plaque. Key regulators for the adaptation to hypoxia are the hypoxia-inducible factors (Hif). Therefore the aim of the present study was to investigate the regulation of the Hif-system by miRNAs during the process of monocyte differentiation. The present study shows that during the differentiation of monocytes into macrophages a dramatically change in the expression pattern of Hif-1α and Hif-2α took place. This was associated with a downregulation of microRNAs encoded by the miR-17-92 cluster. An in silico analysis of the 3'-UTR of Hif-α subunits for binding sites of miRNAs was performed using different miRNA databases in concert with a secondary structure prediction algorithm. This analysis revealed that both 3'-UTRs contain binding sites for miRNAs of the miR-17-92 cluster. Transfection of HeLa cells with miR-17 and miR-20a led to an inhibition of Hif-1α and -2α mRNA and protein expression and a lowered Hif DNA binding activity. Using a Luciferase-Reporter assay, it could be shown, that both Hif-α subunits are targeted by miR-17 and miR-20a. Furthermore, miR-overexpression in primary human macrophages demonstrates the important role of this microRNA-mediated regulation of the Hif-system for adaption of macrophages to hypoxia. In conclusion, the present study shows that the Hif-system is activated during monocyte-to-macrophage differentiation. This activation is in part mediated by a miRNA-dependent mechanism, which seems to be crucial for the adaption of macrophages to hypoxia.

MiR-17 partly promotes hematopoietic cell expansion through augmenting HIF-1α in osteoblasts

Background

Hematopoietic stem cell (HSC) regulation is highly dependent on interactions with the marrow microenvironment, of which osteogenic cells play a crucial role. While evidence is accumulating for an important role of intrinsic miR-17 in regulating HSCs and HPCs, whether miR-17 signaling pathways are also necessary in the cell-extrinsic control of hematopoiesis hereto remains poorly understood.

Methodology/Principal Findings

Using the immortalized clone with the characteristics of osteoblasts, FBMOB-hTERT, in vitro expansion, long-term culture initiating cell (LTC-IC) and non-obese diabetic/severe combined immunodeficient disease (NOD/SCID) mice repopulating cell (SRC) assay revealed that the ectopic expression of miR-17 partly promoted the ability of FBMOB-hTERT to support human cord blood (CB) CD34⁺ cell expansion and maintain their multipotency. It also seemed that osteoblastic miR-17 was prone to cause a specific expansion of the erythroid lineage. Conversely, deficient expression of miR-17 partly inhibited the hematopoietic supporting ability of FBMOB-hTERT. We further identified that HIF-1α is responsible for, at least in part, the promoted hematopoietic supporting ability of FBMOB-hTERT caused by miR-17. HIF-1α expression is markedly enhanced in miR-17 overexpressed FBMOB-hTERT upon interaction with CB CD34⁺ cells compared to other niche associated factors. More interestingly, the specific erythroid lineage expansion of CB CD34⁺ cells caused by osteoblastic miR-17 was abrogated by HIF-1α knock down.

Conclusion/Significance

Our data demonstrated that CB CD34⁺ cell expansion can be partly promoted by osteoblastic miR-17, and in particular, ectopic miR-17 can cause a specific expansion of the erythroid lineage through augmenting HIF-1α in osteoblasts.

MicroRNA-138 plays a role in hypoxic pulmonary vascular remodelling by targeting Mst1

Unbalanced apoptosis is a major cause of structural remodelling of vasculatures associated with PAH (pulmonary arterial hypertension), whereas the underlying mechanisms are still elusive. miRNAs (microRNAs) regulate the expression of several proteins that are important for cell fate, including differentiation, proliferation and apoptosis. It is possible that these regulatory RNA molecules play a role in the development of PAH. To test this hypothesis, we studied the effect of several miRNAs on the apoptosis of cultured PASMCs (pulmonary artery smooth muscle cells) and identified miR-138 to be an important player. miR-138 was expressed in PASMCs, and its expression was subjected to regulation by hypoxia. Expression of exogenous miR-138 suppressed PASMC apoptosis, prevented caspase activation and disrupted Bcl-2 signalling. The serine/threonine kinase Mst1, an amplifier of cell apoptosis, seemed to be a target of miR-138, and the activation of the Akt pathway was necessary for the anti-apoptotic effect of miR-138. Therefore the results of the present study suggest that miR-138 appears to be a negative regulator of PASMC apoptosis, and plays an important role in HPVR (hypoxic pulmonary vascular remodelling).

What a difference a hydroxyl makes: mutant IDH, (R)-2-hydroxyglutarate, and cancer

Mutations in metabolic enzymes, including isocitrate dehydrogenase 1 (IDH1) and IDH2, in cancer strongly implicate altered metabolism in tumorigenesis. IDH1 and IDH2 catalyze the interconversion of isocitrate and 2-oxoglutarate (2OG). 2OG is a TCA cycle intermediate and an essential cofactor for many enzymes, including JmjC domain-containing histone demethylases, TET 5-methylcytosine hydroxylases, and EglN prolyl-4-hydroxylases. Cancer-associated IDH mutations alter the enzymes such that they reduce 2OG to the structurally similar metabolite (R)-2-hydroxyglutarate [(R)-2HG]. Here we review what is known about the molecular mechanisms of transformation by mutant IDH and discuss their implications for the development of targeted therapies to treat IDH mutant malignancies.

Hypoxia-regulated target genes implicated in tumor metastasis

Hypoxia is an important microenvironmental factor that induces cancer metastasis. Hypoxia/hypoxia-inducible factor-1α (HIF-1α) regulates many important steps of the metastatic processes, especially epithelial-mesenchymal transition (EMT) that is one of the crucial mechanisms to cause early stage of tumor metastasis. To have a better understanding of the mechanism of hypoxia-regulated metastasis, various hypoxia/HIF-1α-regulated target genes are categorized into different classes including transcription factors, histone modifiers, enzymes, receptors, kinases, small GTPases, transporters, adhesion molecules, surface molecules, membrane proteins, and microRNAs. Different roles of these target genes are described with regards to their relationship to hypoxia-induced metastasis. We hope that this review will provide a framework for further exploration of hypoxia/HIF-1α-regulated target genes and a comprehensive view of the metastatic picture induced by hypoxia.