MicroRNA-210: a unique and pleiotropic hypoxamir

The code of non-coding RNAs in lung fibrosis

The pathogenesis of pulmonary fibrosis is a complicated and complex process that involves phenotypic abnormalities of a variety of cell types and dysregulations of multiple signaling pathways. There are numerous genetic, epigenetic and post-transcriptional mechanisms that have been identified to participate in the pathogenesis of this disease. However, efficacious therapeutics developed from these studies have been disappointingly limited. In the past several years, a group of new molecules, i.e., non-coding RNAs (ncRNAs), has been increasingly appreciated to have critical roles in the pathological progression of lung fibrosis. In this review, we summarize the recent findings on the roles of ncRNAs in the pathogenesis of this disorder. We analyze the translational potential of this group of molecules in treating lung fibrosis. We also discuss challenges and future opportunities of studying and utilizing ncRNAs in lung fibrosis.

Dissecting the roles of Ephrin-A3 in malignant peripheral nerve sheath tumor by TALENs

Malignant peripheral nerve sheath tumor (MPNST) is a rare and aggressive soft tissue sarcoma for which effective treatments have not yet been established due to poor understanding of its pathogenesis. Our previous study indicated that miR-210-mediated Ephrin-A3 (EFNA3) promotion of proliferation and invasion of MPNST cells plays an important role in MPNST tumorigenesis and progression. The purpose of the present study was to further investigate the roles of EFNA3 in MPNST. Constructed transcription activator-like effector nucleases (TALENs) and lentiviral vectors were transfected into MPNST ST88-14 (NF1 wild-type) and sNF96.2 (NF1 mutant type) cell lines to obtain gain- and loss-of-function cell lines for the EFNA3 function study. The results showed that the knockout of ENFA3 increased cellular viability and invasiveness of the MPNST cells. However, the adhesion ability of MPNST cells was enhanced or inhibited when EFNA3 was overexpressed or knocked out, respectively. It was also observed that knockout of EFNA3 significantly decreased the expression of phosphorylated FAK (p-FAK) and the tumor necrosis factor α (TNF-α) compared to that in the control cells, yet the expression of phosphatidylinositol 3-kinase (PI3K), GTPase, integrins, vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1α (HIF-α) increased significantly. Inversely, overexpression of EFNA3 significantly increased the expression of p-FAK and TNF-α compared to that in the control cells, yet the expression of PI3K, GTPase, integrins, VEGF and HIF-α decreased significantly. The results indicated that EFNA3 serves as a tumor suppressor in MPNST cells and it may play a critical role in the focal adhesion kinase (FAK) signaling and VEGF-associated tumor angiogenesis pathway. These findings may not only facilitate the better understanding of MPNST pathogenesis, but also suggest EFNA3 as a promising target for MPNST treatment.

PLC-beta 1 regulates the expression of miR-210 during mithramycin-mediated erythroid differentiation in K562 cells

PLC-beta 1 (PLCβ1) inhibits in human K562 cells erythroid differentiation induced by mithramycin (MTH) by targeting miR-210 expression. Inhibition of miR-210 affects the erythroid differentiation pathway and it occurs to a greater extent in MTH-treated cells. Overexpression of PLCβ1 suppresses the differentiation of K562 elicited by MTH as demonstrated by the absence of γ-globin expression. Inhibition of PLCβ1 expression is capable to promote the differentiation process leading to a recovery of γ-globin gene even in the absence of MTH. Our experimental evidences suggest that PLCβ1 signaling regulates erythropoiesis through miR-210. Indeed overexpression of PLCβ1 leads to a decrease of miR-210 expression after MTH treatment. Moreover miR-210 is up-regulated when PLCβ1 expression is down-regulated. When we silenced PKCα by RNAi technique, we found a decrease in miR-210 and γ-globin expression levels, which led to a severe slowdown of cell differentiation in K562 cells and these effects were the same encountered in cells overexpressing PLCβ1. Therefore we suggest a novel role for PLCβ1 in regulating miR-210 and our data hint at the fact that, in human K562 erythroleukemia cells, the modulation of PLCβ1 expression is able to exert an impairment of normal erythropoiesis as assessed by γ-globin expression.

MicroRNAs in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating disease without effective treatment. Despite decades of research and the development of novel treatments, PAH remains a fatal disease, suggesting an urgent need for better understanding of the pathogenesis of PAH. Recent studies suggest that microRNAs (miRNAs) are dysregulated in patients with PAH and in experimental pulmonary hypertension. Furthermore, normalization of a few miRNAs is reported to inhibit experimental pulmonary hypertension. We have reviewed the current knowledge about miRNA biogenesis, miRNA expression pattern, and their roles in regulation of pulmonary artery smooth muscle cells, endothelial cells, and fibroblasts. We have also identified emerging trends in our understanding of the role of miRNAs in the pathogenesis of PAH and propose future studies that might lead to novel therapeutic strategies for the treatment of PAH.

miR-210 mediates vagus nerve stimulation-induced antioxidant stress and anti-apoptosis reactions following cerebral ischemia/reperfusion injury in rats

Vagus nerve stimulation (VNS) exerts neuroprotective effects against cerebral ischemia/reperfusion (I/R) injury and modulates redox status, potentially through the activity of miR-210, an important microRNA that is regulated by hypoxia-inducible factor and Akt-dependent pathways. The aim of this study was to determine the mechanisms of VNS- and miR-210-mediated hypoxic tolerance. Male Sprague-Dawley rats were preconditioned with a miR-210 antagomir (A) or with an antagomir control (AC), followed by middle cerebral artery occlusion and VNS treatment. The animals were divided into eight groups: sham I/R, I/R, I/R+AC, I/R+A, sham I/R+VNS, I/R+VNS, I/R+VNS+AC, and I/R+VNS+A. Activation of the endogenous cholinergic a7 nicotinic acetylcholine receptor (a7nAchR) pathway was identified using double immunofluorescence staining. miR-210 expression was measured by PCR. Behavioral outcomes, infarct volume, and neuronal apoptosis were observed at 24 h following reperfusion. Markers of oxidative stress were detected using ELISA. Rats treated with VNS showed increased miR-210 expression as well as decreased apoptosis and antioxidant stress responses compared with the I/R group; these rats also showed increased p-Akt protein expression and significantly decreased levels of cleaved caspase 3 in the ischemic penumbra, as measured by western blot and immunofluorescence analyses, respectively. Strikingly, the beneficial effects of VNS were attenuated following miR-210 knockdown. In conclusion, our results indicate that miR-210 is a potential mediator of VNS-induced neuroprotection against I/R injury. Our study highlights the neuroprotective potential of VNS, which, to date, has been largely unexplored. Since approved by the FDA in 1997, vagus nerve stimulation (VNS) has proven to be a safe and effective treatment for refractory epilepsy and resistant depression. Recent studies have found that VNS also provided neuroprotective effects against ischemic injury in a rat stroke model. We showed that miR-210 played an important role in the antioxidant stress and anti-apoptosis responses induced by VNS. This is the first report showing the effects of VNS at the mRNA level. Therefore, VNS represents a promising candidate treatment for ischemic stroke patients. Schematic view of the role of miR210 mediated in the protective effects of the VNS on the acute cerebral ischemia. VNS acts to activate neuronal and astrocytes a7nAchR , inhibits the apoptosis and oxidant stress responses possibly associated with increased Akt phosphorylation and miR210 expression.

miRNA-196b inhibits cell proliferation and induces apoptosis in HepG2 cells by targeting IGF2BP1

Background

Tumor hypoxia is one of the features of tumor microenvironment that contributes to chemoresistance. miRNAs have recently been shown to play important roles in tumorigenesis and drug resistance. Moreover, hypoxia also regulates the expression of a series of miRNAs. However, the interaction between chemoresistance, hypoxia and miRNAs has not been explored yet. The aim of this study is to understand the mechanisms activated/inhibited by miRNAs under hypoxia that induce resistance to chemotherapy-induced apoptosis.

Methods

TaqMan low-density array was used to identify changes in miRNA expression when cells were exposed to etoposide under hypoxia or normoxia. The effects of miR-196b overexpression on apoptosis and cell proliferation were studied in HepG2 cells. miR-196b target mRNAs were identified by proteomic analysis, luciferase activity assay, RT-qPCR and western blot analysis.

Results

Results showed that hypoxia down-regulated miR-196b expression that was induced by etoposide. miR-196b overexpression increased the etoposide-induced apoptosis and reversed the protection of cell death observed under hypoxia. By a proteomic approach combined with bioinformatics analyses, we identified IGF2BP1 as a potential target of miR-196b. Indeed, miR-196b overexpression decreased IGF2BP1 RNA expression and protein level. The IGF2BP1 down-regulation by either miR-196b or IGF2BP1 siRNA led to an increase in apoptosis and a decrease in cell viability and proliferation in normal culture conditions. However, IGF2BP1 silencing did not modify the chemoresistance induced by hypoxia, probably because it is not the only target of miR-196b involved in the regulation of apoptosis.

Conclusions

In conclusion, for the first time, we identified IGF2BP1 as a direct and functional target of miR-196b and showed that miR-196b overexpression reverses the chemoresistance induced by hypoxia. These results emphasize that the chemoresistance induced by hypoxia is a complex mechanism.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0349-6) contains supplementary material, which is available to authorized users.

The role of hypoxia-induced miR-210 in cancer progression

Prolonged hypoxia, the event of insufficient oxygen, is known to upregulate tumor development and growth by promoting the formation of a neoplastic environment. The recent discovery that a subset of cellular microRNAs (miRs) are upregulated during hypoxia, where they function to promote tumor development, highlights the importance of hypoxia-induced miRs as targets for continued investigation. miRs are short, non-coding transcripts involved in gene expression and regulation. Under hypoxic conditions, miR-210 becomes highly upregulated in response to hypoxia inducing factors (HIFs). HIF-1α drives miR-210’s overexpression and the resultant alteration of cellular processes, including cell cycle regulation, mitochondria function, apoptosis, angiogenesis and metastasis. Here we discuss hypoxia-induced dysregulation of miR-210 and the resultant changes in miR-210 protein targets that regulate cancer progression. Potential methods of targeting miR-210 as a therapeutic tool are also explored.

Posttranscriptional adaptations of the vascular endothelium to hypoxia

PURPOSE OF REVIEW

Remarkable new advances have been made in the field of posttranscriptional gene regulation over recent years. These include the revelation of noncoding RNAs, such as microRNAs, antisense transcripts and their interactions with RNA-binding proteins (RBPs) in the context of both health and disease settings, such as hypoxia. In particular, these discoveries bear much relevance to the field of vascular biology, which historically has focused upon transcriptional processes. Thus, the contributions of these posttranscriptional gene regulatory mechanisms to vascular and endothelial biology represent a newer concept that warrants discussion.

RECENT FINDINGS

Recent studies have revealed two emerging themes that are critical to endothelial/vascular biology and function. First is the functional integration between the microRNA pathway and the cellular hypoxic response, which, in addition to specific microRNAs, involves key components of the microRNA biogenesis machinery. A key concept here is the regulation of a master transcriptional programme through posttranscriptional mechanisms. The second major theme involves the dynamic interactions between RBPs, microRNAs and antisense RNAs. The condition-dependent collaborations and competitions between these different classes of posttranscriptional regulators reveal a critical layer of control for gene expression.

SUMMARY

Taken together, these findings bear significant diagnostic and therapeutic implications for vascular disease.

Role of secreted modular calcium-binding protein 1 (SMOC1) in transforming growth factor β signalling and angiogenesis

AIMS

Secreted modular calcium-binding protein 1 (SMOC1) is a matricellular protein that potentially interferes with growth factor receptor signalling. The aim of this study was to determine how its expression is regulated in endothelial cells and its role in the regulation of endothelial cell function.

METHODS AND RESULTS

SMOC1 was expressed by native murine endothelial cells as well as by cultured human, porcine, and murine endothelial cells. SMOC1 expression in cultured cells was increased by hypoxia via the down-regulation of miR-223, and SMOC1 expression was increased in lungs from miR-223-deficient mice. Silencing SMOC1 (small interfering RNA) attenuated endothelial cell proliferation, migration, and sprouting in in vitro angiogenesis assays. Similarly endothelial cell sprouting from aortic rings ex vivo as well as postnatal retinal angiogenesis in vivo was attenuated in SMOC1(+/-) mice. In endothelial cells, transforming growth factor (TGF)-β signalling via activin-like kinase (ALK) 5 leads to quiescence, whereas TGF-β signalling via ALK1 results in endothelial cell activation. SMOC1 acted as a negative regulator of ALK5/SMAD2 signalling, resulting in altered α2 integrin levels. Mechanistically, SMOC1 associated (immunohistochemistry, proximity ligation assay, and co-immunoprecipitation) with endoglin; an endothelium-specific type III auxiliary receptor for the TGF-β super family and the effects of SMOC1 down-regulation on SMAD2 phosphorylation were abolished by the down-regulation of endoglin.

CONCLUSION

These results indicate that SMOC1 is an ALK5 antagonist produced by endothelial cells that tips TGF-β signalling towards ALK1 activation, thus promoting endothelial cell proliferation and angiogenesis.

The crossroads of iron with hypoxia and cellular metabolism. Implications in the pathobiology of pulmonary hypertension

The pathologic hallmark of pulmonary arterial hypertension (PAH) is pulmonary vascular remodeling, characterized by endothelial cell proliferation, smooth muscle hypertrophy, and perivascular inflammation, ultimately contributing to increased pulmonary arterial pressures. Several recent studies have observed that iron deficiency in patients with various forms of PAH is associated with worsened clinical outcome. Iron plays a key role in many cellular processes regulating the response to hypoxia, oxidative stress, cellular proliferation, and cell metabolism. Given the potential importance of iron supplementation in patients with the disease and the broad cellular functions of iron, we review its role in processes that pertain to PAH.

Targeting of multiple myeloma-related angiogenesis by miR-199a-5p mimics: in vitro and in vivo anti-tumor activity

Multiple myeloma (MM) cells induce relevant angiogenic effects within the human bone marrow milieu (huBMM) by the aberrant expression of angiogenic factors. Hypoxia triggers angiogenic events within the huBMM and the transcription factor hypoxia-inducible factor-1α (HIF-1α) is over-expressed by MM cells. Since synthetic miR-199a-5p mimics negatively regulates HIF-1α, we here investigated a miRNA-based therapeutic strategy against hypoxic MM cells. We indeed found that enforced expression of miR-199a-5p led to down-modulated expression of HIF-1α as well as of other pro-angiogenic factors such as VEGF-A, IL-8, and FGFb in hypoxic MM cells in vitro. Moreover, miR-199a-5p negatively affected MM cells migration, while it increased the adhesion of MM cells to bone marrow stromal cells (BMSCs) in hypoxic conditions. Furthermore, transfection of MM cells with miR-199a-5p significantly impaired also endothelial cells migration and down-regulated the expression of endothelial adhesion molecules such as VCAM-1 and ICAM-1. Finally, we identified a hypoxia/AKT/miR-199a-5p loop as a potential molecular mechanism responsible of miR-199a-5p down-regulation in hypoxic MM cells. Taken together our results indicate that miR-199a-5p has an important role for the pathogenesis of MM and support the hypothesis that targeting angiogenesis via a miRNA/HIF-1α pathway may represent a novel potential therapeutical approach for this still lethal disease.

MicroRNA-687 Induced by Hypoxia-Inducible Factor-1 Targets Phosphatase and Tensin Homolog in Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion injury contributes to tissue damage and organ failure in clinical settings, but the underlying mechanism remains elusive and effective therapies are still lacking. Here, we identified microRNA 687 (miR-687) as a key regulator and therapeutic target in renal ischemia-reperfusion injury. We show that miR-687 is markedly upregulated in the kidney during renal ischemia-reperfusion in mice and in cultured kidney cells during hypoxia. MiR-687 induction under these conditions was mediated by hypoxia-inducible factor-1 (HIF-1). Upon induction in vitro, miR-687 repressed the expression of phosphatase and tensin homolog (PTEN) and facilitated cell cycle progression and apoptosis. Blockade of miR-687 preserved PTEN expression and attenuated cell cycle activation and renal apoptosis, resulting in protection against kidney injury in mice. Collectively, these results unveil a novel HIF-1/miR-687/PTEN signaling pathway in ischemia-reperfusion injury that may be targeted for therapy.

Direct detection of microRNA based on plasmon hybridization of nanoparticle dimers

We demonstrate the direct detection of microRNA-210, a biomarker for hypoxia-related diseases, in cellular RNA extracts and cell media using discrete actuatable plasmonic nanoparticle dimers.

Therapeutic Potential of Modulating MicroRNA in Peripheral Artery Disease

Peripheral artery disease (PAD) produces significant disability attributable to lower extremity ischemia. Limited treatment modalities exist to ameliorate clinical symptoms in patients with PAD. Growing evidence links microRNAs to key processes that govern disease expression in PAD including angiogenesis, endothelial function, inflammation, vascular regeneration, vascular smooth muscle cell function, restenosis, and mitochondrial function. MicroRNAs have been identified in circulation and may serve as novel biomarkers in PAD. This article reviews the potential contribution of microRNA to key pathways of disease development in PAD that may lead to microRNA-based diagnostic and therapeutic approaches.

The hypoxia-inducible miR-429 regulates hypoxia-inducible factor-1α expression in human endothelial cells through a negative feedback loop

Hypoxia-inducible factors (HIFs) 1 and 2 are dimeric α/β transcription factors that regulate cellular responses to low oxygen. HIF-1 is induced first, whereas HIF-2 is associated with chronic hypoxia. To determine how HIF1A mRNA, the inducible subunit of HIF-1, is regulated during hypoxia, we followed HIF1A mRNA levels in primary HUVECs over 24 hours using quantitative PCR. HIF1A and VEGF A (VEGFA) mRNA, a transcriptional target of HIF-1, increased ∼ 2.5- and 8-fold at 2-4 hours, respectively. To determine how the mRNAs were regulated, we identified a microRNA (miRNA), miR-429, that destabilized HIF1A message and decreased VEGFA mRNA by inhibiting HIF1A. Target protector analysis, which interferes with miRNA-mRNA complex formation, confirmed that miR-429 targeted HIF1A message. Desferoxamine treatment, which inhibits the hydroxylases that promote HIF-1α protein degradation, stabilized HIF-1 activity during normoxic conditions and elevated miR-429 levels, demonstrating that HIF-1 promotes miR-429 expression. RNA-sequencing-based transcriptome analysis indicated that inhibition of miRNA-429 in HUVECs up-regulated 209 mRNAs, a number of which regulate angiogenesis. The results demonstrate that HIF-1 is in a negative regulatory loop with miR-429, that miR-429 attenuates HIF-1 activity by decreasing HIF1A message during the early stages of hypoxia before HIF-2 is activated, and this regulatory network helps explain the HIF-1 transition to HIF-2 during chronic hypoxia in endothelial cells.

Circulating biomarkers in renal cell carcinoma: the link between microRNAs and extracellular vesicles, where are we now?

Renal cell carcinoma (RCC) is a lethal urological cancer, with incidence and mortality rates increasing by 2-3% per decade. The lack of standard screening tests contributes to the fact that one-third of patients are diagnosed with locally invasive or metastatic disease. Moreover, 20-40% of RCC patients submitted to surgical nephrectomy will develop metastasis. MicroRNAs (miRNAs) are small non-coding RNAs responsible for gene regulation at a post-transcriptional level. It is accepted that they are deregulated in cancer and can influence tumor development. Thus, miRNAs are promising RCC biomarkers, since they can be detected using non-invasive methods. They are highly stable and easier to quantify in circulating biofluids. The elevated miRNA stability in circulating samples may be the consequence of their capacity to circulate inside of extracellular microvesicles (EMVs), for example, the exosomes. The EMVs are bilayered membrane vesicles secreted by all cell types. They can be released in the interstitial space or into circulating biofluids, which allows the travelling, binding and entrance of these vesicles in receptor cells. This type of cell communication can shuttle bioactive molecules between cells, allowing the horizontal transference of genetic material. In this review, we focus on circulating miRNAs (miR-210, miR-1233, miR-221, miR-15a, miR-451, miR-508, miR-378) in the biofluids of RCC patients and attempt to establish the diagnostic and prognostic accuracy, their synergic effects, and the pathways involved in RCC biology.

Enhanced miR-210 expression promotes the pathogenesis of endometriosis through activation of signal transducer and activator of transcription 3

STUDY QUESTION

What are the roles of the microRNA miR-210-an miRNA that is up-regulated in endometriotic cyst stromal cells (ECSCs)-in the pathogenesis of endometriosis?

SUMMARY ANSWER

Up-regulated miR-210 expression in ECSCs is involved in their proliferation, resistance to apoptosis and angiogenesis through signal transducer and activator of transcription (STAT) 3.

WHAT IS KNOWN ALREADY

In the pathogenesis of endometriosis, a number of roles for microRNAs (miRNAs) are becoming apparent.

STUDY DESIGN, SIZE, DURATION

ECSCs and normal endometrial stromal cells (NESCs) were isolated from ovarian endometriotic tissues (patients aged 24-40 years undergoing salpingo-oophorectomy or evisceration for the treatment of ovarian endometriotic cysts, n = 10) and the eutopic endometrial tissues without endometriosis (premenopausal patients aged 35-45 years undergoing hysterectomies for subserousal leiomyoma, n = 13), respectively.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used a global gene expression microarray technique to identify downstream targets of miR-210, and we assessed the functions of miR-210 in the pathogenesis of endometriosis by using the miR-210-transfected NESCs.

MAIN RESULTS AND THE ROLE OF CHANCE

Gene expression microarray analysis revealed that one of the key target molecules of miR-210 is STAT3. In the NESCs, in comparison to the control, miR-210 transfection resulted in the induction of cell proliferation (P < 0.0005), the production of vascular endothelial cell growth factor (VEGF) (P < 0.0005) and the inhibition of apoptosis (P < 0.05) through STAT3 activation [increased levels of mRNA (P < 0.0005), and protein (P < 0.005)]. In the ECSCs, inhibitors of STAT3 inhibited the cell proliferation and VEGF production (P < 0.05), and induced the apoptosis of these cells (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

The roles of aberrant miR-210 expression were investigated only in the stromal component of ectopic and eutopic endometrium. Control endometrial tissues were obtained from premenopausal patients who had subserosal leiomyoma and NESC gene expression patterns may be altered in these women. Furthermore, the effects of STAT3 inhibitors were evaluated only in ECSCs and not in NESCs.

WIDER IMPLICATIONS OF THE FINDINGS

The present findings indicate that miR-210 induces NESCs to differentiate into the endometriotic phenotype and we speculate that up-regulated miR-210 expression in ECSCs is involved in the creation of the endometriosis-specific cellular dysfunctions through epigenetic mechanisms. The data indicate that STAT3 inhibitors may be promising candidates for the treatment of endometriosis.

STUDY FUNDING/COMPETING INTERESTS

This work was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (no. 13237327 to K.N., no. 25861500 to Y.K. and no. 23592407 to H.N.). There are no conflicts of interest to declare.

The oncogenic MicroRNA Hsa-miR-155-5p targets the transcription factor ELK3 and links it to the hypoxia response

The molecular response to hypoxia is a critical cellular process implicated in cancer, and a target for drug development. The activity of the major player, HIF1α, is regulated at different levels by various factors, including the transcription factor ELK3. The molecular mechanisms of this intimate connection remain largely unknown. Whilst investigating global ELK3-chromatin interactions, we uncovered an unexpected connection that involves the microRNA hsa-miR-155-5p, a hypoxia-inducible oncomir that targets HIF1α. One of the ELK3 chromatin binding sites, detected by Chromatin Immuno-Precipitation Sequencing (ChIP-seq) of normal Human Umbilical Vein Endothelial Cells (HUVEC), is located at the transcription start site of the MIR155HG genes that expresses hsa-miR-155-5p. We confirmed that ELK3 binds to this promoter by ChIP and quantitative polymerase chain reaction (QPCR). We showed that ELK3 and hsa-miR-155-5p form a double-negative regulatory loop, in that ELK3 depletion induced hsa-miR-155-5p expression and hsa-miR-155-5p expression decreased ELK3 expression at the RNA level through a conserved target sequence in its 3'-UTR. We further showed that the activities of hsa-miR-155-5p and ELK3 are functionally linked. Pathway analysis indicates that both factors are implicated in related processes, including cancer and angiogenesis. Hsa-miR-155-5p expression and ELK3 depletion have similar effects on expression of known ELK3 target genes, and on in-vitro angiogenesis and wound closure. Bioinformatic analysis of cancer RNA-seq data shows that hsa-miR-155-5p and ELK3 expression are significantly anti-correlated, as would be expected from hsa-miR-155-5p targeting ELK3 RNA. Finally, hypoxia (0% oxygen) down-regulates ELK3 mRNA in a microRNA and hsa-miR-155-5p dependent manner. These results tie ELK3 into the hypoxia response pathway through an oncogenic microRNA and into a circuit implicated in the dynamics of the hypoxic response. This crosstalk could be important for the development of new treatments for a range of pathologies.

Hypoxia interferes with aryl hydrocarbon receptor pathway in hCMEC/D3 human cerebral microvascular endothelial cells

The expression of aryl hydrocarbon receptor (AhR) transcription factor was detected at transcript level in freshly isolated human brain microvessels and in the hCMEC/D3 human cerebral microvascular endothelial cell line. Recent studies have demonstrated that AhR pathway is able to crosstalk with other pathways such as hypoxia signaling pathway. Therefore, we used the hCMEC/D3 cell line to investigate the potential crosstalk between AhR and hypoxia signaling pathways. First, we performed two different hypoxia-like procedures in hCMEC/D3 cells; namely, exposition of cells to 150 μM deferoxamine or to glucose and oxygen deprivation for 6 h. These two procedures led to hypoxia-inducible factor (HIF)-1α and HIF-2α proteins accumulation together with a significant induction of the two well-known hypoxia-inducible genes VEGF and GLUT-1. Both HIF-1α and -2α functionally mediated hypoxia response in the hCMEC/D3 cells. Then, we observed that a 6 h exposure to 25 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin, a strong AhR ligand, up-regulated CYP1A1 and CYP1B1 expression, and that this effect was AhR dependent. Regarding AhR and hypoxia crosstalk, our experiments revealed that an asymmetric interference between these two pathways effectively occurred in hCMEC/D3 cells: hypoxia pathway interfered with AhR signaling but not the other way around. We studied the putative crosstalk of AhR and hypoxia pathways in hCMEC/D3 human cerebral microvascular endothelial cells. While hypoxia decreased the expression of the two AhR target genes CYP1A1 and CYP1B1, AhR activation results in no change in hypoxia target gene expression. This is the first sign of AhR and hypoxia pathway crosstalk in an in vitro model of the human cerebral endothelium.

CTGF increases vascular endothelial growth factor-dependent angiogenesis in human synovial fibroblasts by increasing miR-210 expression

Connective tissue growth factor (CTGF, a.k.a. CCN2) is inflammatory mediator and abundantly expressed in osteoarthritis (OA). Angiogenesis is essential for OA progression. Here, we investigated the role of CTGF in vascular endothelial growth factor (VEGF) production and angiogenesis in OA synovial fibroblasts (OASFs). We showed that expression of CTGF and VEGF in synovial fluid were higher in OA patients than in controls. Directly applying CTGF to OASFs increased VEGF production then promoted endothelial progenitor cells tube formation and migration. CTGF induced VEGF by raising miR-210 expression via PI3K, AKT, ERK, and nuclear factor-κB (NF-κB)/ELK1 pathways. CTGF-mediating miR-210 upregulation repressed glycerol-3-phosphate dehydrogenase 1-like (GPD1L) expression and PHD activity and subsequently promoted hypoxia-inducible factor (HIF)-1α-dependent VEGF expression. Knockdown of CTGF decreased VEGF expression and abolished OASF-conditional medium-mediated angiogenesis in vitro as well as angiogenesis in chick chorioallantoic membrane and Matrigel-plug nude mice model in vivo. Taken together, our results suggest CTGF activates PI3K, AKT, ERK, and NF-κB/ELK1 pathway, leading to the upregulation of miR-210, contributing to inhibit GPD1L expression and prolyl hydroxylases 2 activity, promoting HIF-1α-dependent VEGF expression and angiogenesis in human synovial fibroblasts.

Multi-omic integrated networks connect DNA methylation and miRNA with skeletal muscle plasticity to chronic exercise in Type 2 diabetic obesity

Epigenomic regulation of the transcriptome by DNA methylation and posttranscriptional gene silencing by miRNAs are potential environmental modulators of skeletal muscle plasticity to chronic exercise in healthy and diseased populations. We utilized transcriptome networks to connect exercise-induced differential methylation and miRNA with functional skeletal muscle plasticity. Biopsies of the vastus lateralis were collected from middle-aged Polynesian men and women with morbid obesity (44 kg/m(2) ± 10) and Type 2 diabetes before and following 16 wk of resistance (n = 9) or endurance training (n = 8). Longitudinal transcriptome, methylome, and microRNA (miRNA) responses were obtained via microarray, filtered by novel effect-size based false discovery rate probe selection preceding bioinformatic interrogation. Metabolic and microvascular transcriptome topology dominated the network landscape following endurance exercise. Lipid and glucose metabolism modules were connected to: microRNA (miR)-29a; promoter region hypomethylation of nuclear receptor factor (NRF1) and fatty acid transporter (SLC27A4), and hypermethylation of fatty acid synthase, and to exon hypomethylation of 6-phosphofructo-2-kinase and Ser/Thr protein kinase. Directional change in the endurance networks was validated by lower intramyocellular lipid, increased capillarity, GLUT4, hexokinase, and mitochondrial enzyme activity and proteome. Resistance training also lowered lipid and increased enzyme activity and caused GLUT4 promoter hypomethylation; however, training was inconsequential to GLUT4, capillarity, and metabolic transcriptome. miR-195 connected to negative regulation of vascular development. To conclude, integrated molecular network modelling revealed differential DNA methylation and miRNA expression changes occur in skeletal muscle in response to chronic exercise training that are most pronounced with endurance training and topographically associated with functional metabolic and microvascular plasticity relevant to diabetes rehabilitation.

MicroRNA-210 knockdown contributes to apoptosis caused by oxygen glucose deprivation in PC12 cells

It was previously demonstrated that microRNA-210 (miR-210) exhibited neuroprotective effects in a murine model of hypoxic-ischemic encephalopathy via inhibition of apoptosis. The aim of the present study was to further elucidate the effect of miR-210 on apoptosis in PC12 cells following transfection with miR-210 inhibitors and exposure to oxygen glucose deprivation (OGD). The expression levels of miR-210 were identified using reverse transcription-quantitative polymerase chain reaction analysis. Apoptosis was investigated using Annexin V-fluorescein isothiocyanate assays. Apoptosis-related protein expression levels were studied with western blot analysis. The results showed that the expression levels of miR-210 were upregulated in PC12 cells following a 4-h exposure to OGD, relative to those in normoxic control cells. miR-210 knockdown increased cell apoptosis by inducing caspase activity and regulating the balance between Bcl-2 and Bax levels. The present study demonstrated that miR-210 knockdown induced cell apoptosis using an ex vivo model of ischemic hypoxia (IH). Knockdown of miR-210 represents a potential novel therapeutic approach to combat neonatal IH.

Hypoxamirs and mitochondrial metabolism

SIGNIFICANCE

Chronic hypoxia can drive maladaptive responses in numerous organ systems, leading to a multitude of chronic mammalian diseases. Oxygen homeostasis is intimately linked with mitochondrial metabolism, and dysfunction in these systems can combine to form the backbone of hypoxic-ischemic injury in multiple tissue beds. Increased appreciation of the crucial roles of hypoxia-associated miRNA (hypoxamirs) in metabolism adds a new dimension to our understanding of the regulation of hypoxia-induced disease.

RECENT ADVANCES

Myriad factors related to glycolysis (e.g., aldolase A and hexokinase II), tricarboxylic acid cycle function (e.g., glutaminase and iron-sulfur cluster assembly protein 1/2), and apoptosis (e.g., p53) have been recently implicated as targets of hypoxamirs. In addition, several hypoxamirs have been implicated in the regulation of the master transcription factor of hypoxia, hypoxia-inducible factor-1α, clarifying how the cellular program of hypoxia is sustained and resolved.

CRITICAL ISSUES

Central to the discussion of metabolic change in hypoxia is the Warburg effect, a shift toward anaerobic metabolism that persists after normal oxygen levels have been restored. Many newly discovered targets of hypoxia-driven microRNA converge on pathways known to be involved in this pathological phenomenon and the apoptosis-resistant phenotype associated with it.

FUTURE DIRECTIONS

The often synergistic functions of miRNA may make them ideal therapeutic targets. The use of antisense inhibitors is currently being considered in diseases in which hypoxia and metabolic dysregulation predominate. In addition, exploration of pleiotripic miRNA functions will likely continue to offer unique insights into the mechanistic relationships of their downstream target pathways and associated hypoxic phenotypes.

MicroRNA target identification: lessons from hypoxamiRs

SIGNIFICANCE

MicroRNAs (miRNAs) are small noncoding RNAs that have emerged as key regulators of many physiological and pathological processes, including those relevant to hypoxia such as cancer, neurological dysfunctions, myocardial infarction, and lung diseases.

RECENT ADVANCES

During the last 5 years, miRNAs have been shown to play a role in the regulation of the cellular response to hypoxia. The identification of several bona fide targets of these hypoxamiRs has underlined their pleiotropic functions and the complexity of the molecular rules directing miRNA::target transcript pairing.

CRITICAL ISSUES

This review outlines the main in silico and experimental approaches used to identify the targetome of hypoxamiRs and presents new recent relevant methodologies for future studies.

FUTURE DIRECTIONS

Since hypoxia plays key roles in many pathophysiological conditions, the precise characterization of regulatory hypoxamiRs networks will be instrumental both at a fundamental level and for their future potential therapeutic applications.

Hypoxia-induced miR-210 modulates tissue response to acute peripheral ischemia

AIMS

Peripheral artery disease is caused by the restriction or occlusion of arteries supplying the leg. Better understanding of the molecular mechanisms underpinning tissue response to ischemia is urgently needed to improve therapeutic options. The aim of this study is to investigate hypoxia-induced miR-210 regulation and its role in a mouse model of hindlimb ischemia.

RESULTS

miR-210 expression was induced by femoral artery dissection. To study the role of miR-210, its function was inhibited by the systemic administration of a miR-210 complementary locked nucleic acid (LNA)-oligonucleotide (anti-miR-210). In the ischemic skeletal muscle, anti-miR-210 caused a marked decrease of miR-210 compared with LNA-scramble control, while miR-210 target expression increased accordingly. Histological evaluation of acute tissue damage showed that miR-210 inhibition increased both apoptosis at 1 day and necrosis at 3 days. Capillary density decrease caused by ischemia was significantly more pronounced in anti-miR-210-treated mice; residual limb perfusion decreased accordingly. To investigate the molecular mechanisms underpinning the increased damage triggered by miR-210 blockade, we tested the impact of anti-miR-210 treatment on the transcriptome. Gene expression analysis highlighted the deregulation of mitochondrial function and redox balance. Accordingly, oxidative damage was more severe in the ischemic limb of anti-miR-210-treated mice and miR-210 inhibition increased oxidative metabolism. Further, oxidative-stress resistant p66(Shc)-null mice displayed decreased tissue damage following ischemia.

INNOVATION

This study identifies miR-210 as a crucial element in the adaptive mechanisms to acute peripheral ischemia.

CONCLUSIONS

The physiopathological significance of miR-210 is context dependent. In the ischemic skeletal muscle it seems to be cytoprotective, regulating oxidative metabolism and oxidative stress.

Methods of quantifying microRNAs for hypoxia research: classic and next generation

SIGNIFICANCE

Recent evidence is uncovering the ever-increasing importance of microribonucleic acids (miRNAs) in the hypoxia response. In order to investigate the important roles that these small RNAs play, methods of quantification whether using classic single-gene methods or genome-wide technologies are necessary to obtain a global picture of the differential expression of miRNAs in hypoxia and their interplay with protein coding genes.

RECENT ADVANCES

Building on the groundwork of classic quantitative polymerase chain reaction (qPCR) and microarrays, the advent of next-generation sequencing technology has revolutionized how small RNAs can be detected and quantified on a genome-wide scale and without a priori knowledge of the small RNA sequence. This method delivers accurate and comprehensive data on the expression and sequence of all expressed small RNAs, and the data can be further combined with other sequencing modalities to better understand miRNAs via integrated genomic analyses.

CRITICAL ISSUES

Advancing technology has increased the need for better methods of sample and library preparation and for bioinformatics tools. Speed, cost, sample input, and analysis expertise remain the mainstay critical issues of small RNA sequencing.

FUTURE DIRECTIONS

Future hypoxia research will benefit from the application of genome-wide sequencing technologies. Analyses that combine genomic, transcriptomic, chromosome conformation, DNA/RNA-protein binding, and proteomics will help greatly advance hypoxia miRNA research.

MicroRNA-210 promotes proliferation and invasion of peripheral nerve sheath tumor cells targeting EFNA3

MicroRNA (miR) plays an important role in tumorigenesis including malignant peripheral nerve sheath tumor (MPNST). miR-210 downregulation is frequently observed in a variety of tumors. In this study, miR-210 was identified as downregulated in MPNST cells, and its potential target ephrin-A3 (EFNA3) was upregulated in them compared with neurofibroma cells using quantitative real-time (qRT)-PCR. Luciferase reporter assay further demonstrates that EFNA3 is a target of miR-210. Then it is confirmed that miR-210 can regulate EFNA3 mRNA and protein expression in MPNST ST88-14 (NF1 wild-type) and sNF96.2 (NF1 mutant type) cell lines. The functions of miR-210 in MPNST cells were investigated, and the results showed that overexpression of miR-210 increased cellular viability, colony formation, S phase percentage, and invasiveness of MPNST cells. Inversely, inhibition of miR-210 expression induced suppression of proliferation and invasion of MPNST cells. These results suggest that miR-210-mediated EFNA3 promotion of proliferation and invasion of MPNST cells plays an important role in MPNST tumorigenesis and progression. miR-210 and EFNA3 may be candidate novel therapeutic targets for MPNST.

The clinical significance and regulation mechanism of hypoxia-inducible factor-1 and miR-191 expression in pancreatic cancer

The aim of study was to discuss the correlation and regulatory mechanism of HIF-1 and miR-191 expression in pancreatic tumor. The association between the miR-191 and the clinicopathologic characteristics and the prognosis of pancreatic cancer was further explored. After hypoxic cultured for 6 and 12 h, qRT-PCR and Western blot were practiced to analyze the miR-191 and HIF-1 expression of MIA PaCa-2 and Aspac1 cells. We regulated the HIF-1 expression via plasmid and siRNA transfection to observe the alteration of HIF-1 and miR-191 expression. ChIP sequencing identified the binding sites of HIF-1 and miR-191. Dual luciferase assays were practiced to verify the binding sites. Immunohistochemical staining was practiced to analyze the expression of HIF-1, while qRT-PCR were done for investigating miR-191 in tumor tissues. Then, the association between the expression of them and the clinicopathologic characteristics and prognosis of pancreatic cancer were analyzed. After hypoxic cultured 12 h, the expression of HIF-1 protein, HIF-1mRNA and miR-191 of MIA PaCa-2 and AsPC-1 cells increased significantly (P < 0.05). After HIF-1 overexpressing plasmid transfected to the MIA PaCa-2 and AsPC-1 cells for 48 h, the expression of HIF-1 protein, HIF-1mRNA, and miR-191 upregulated significantly (P < 0.05). While after transfected the MIA PaCa-2 cells by HIF-1 siRNA, the significant decreasing of HIF-1 protein, HIF-1mRNA, and miR-191 expression were observed (P < 0.05). ChIP sequencing showed the protein synthesis of HIF-1 increased in hypoxia situation. Only the HRE5 (-1,169 bp, ChIP4) were significantly brighter in hypoxia in comparing with normoxic cells. In dual luciferase assays, after pGL3-miR-191 and HIF-1 overexpressing plasmid co-transfect the MIAPaCa-2 cells for 48 h, its relative expression of bioluminescence was higher than those co-transfected by mutant miR-191 vectors and HIF-1 overexpressing plasmid or by pGL3-miR-191 and HIF-1 empty plasmid. The expression of miR-191 closely associated with the tumor size, pTNM stage, lymph node metastasis, and perineural invasion (P < 0.05). Patients with higher expression of miR-191 were a risk factor for prognosis of pancreatic cancers. Expression of HIF-1 in pancreatic cancer cells increased under the condition of chronic hypoxia, which may bind to HRE2 in 5'flanking region of miR-191 and initiate transcription of miR-191. Expression of miR-191 was significantly higher in pancreatic tumor tissues. The expression of miR-191 closely associated with the tumor size, pTNM stage, lymph node metastasis and perineural invasion and poor prognosis of pancreatic cancer.

MicroRNA-210 contributes to preeclampsia by downregulating potassium channel modulatory factor 1

Preeclampsia is a pregnancy-specific syndrome manifested by the onset of hypertension and proteinuria after the 20th week of gestation. Abnormal placenta development has been generally accepted as the initial cause of the disorder. Recently, microRNA-210 (miR-210) has been found to be upregulated in preeclamptic placentas compared with normal placentas, indicating a possible association of this small molecule with the placental pathology of preeclampsia. However, the function of miR-210 in the development of the placenta remains elusive. The aim of this study was to characterize the molecular mechanism of preeclampsia development by examining the role of miR-210. In this study, miR-210 and potassium channel modulatory factor 1 (KCMF1) expressions were compared in placentas from healthy pregnant individuals and patients with preeclampsia, and the role of miR-210 in trophoblast cell invasion via the downregulation of KCMF1 was investigated in the immortal trophoblast cell line HTR8/SVneo. The levels of KCMF1 were significantly lower in preeclamptic placenta tissues than in gestational week-matched normal placentas, which was inversely correlated with the level of miR-210. KCMF1 was validated as the direct target of miR-210 using real-time polymerase chain reaction, Western blotting, and dual luciferase assay in HTR8/SVneo cells. miR-210 inhibited the invasion of trophoblast cells, and this inhibition was abrogated by the overexpression of KCMF1. The inflammatory factor tumor necrosis factor-α could upregulate miR-210 while suppressing KCMF1 expression in HTR8/SVneo cells. This is the first report on the function of KCMF1 in human placental trophoblast cells, and the data indicate that aberrant miR-210 expression may contribute to the occurrence of preeclampsia by interfering with KCMF1-mediated signaling in the human placenta.

An Argonaute 2 switch regulates circulating miR-210 to coordinate hypoxic adaptation across cells

Complex organisms may coordinate molecular responses to hypoxia by specialized avenues of communication across multiple tissues, but these mechanisms are poorly understood. Plasma-based, extracellular microRNAs have been described, yet their regulation and biological functions in hypoxia remain enigmatic. We found a unique pattern of release of the hypoxia-inducible microRNA-210 (miR-210) from hypoxic and reoxygenated cells. This microRNA is also elevated in human plasma in physiologic and pathologic conditions of altered oxygen demand and delivery. Released miR-210 can be delivered to recipient cells, and the suppression of its direct target ISCU and mitochondrial metabolism is primarily evident in hypoxia. To regulate these hypoxia-specific actions, prolyl-hydroxylation of Argonaute 2 acts as a molecular switch that reciprocally modulates miR-210 release and intracellular activity in source cells as well as regulates intracellular activity in recipient cells after miR-210 delivery. Therefore, Argonaute 2-dependent control of released miR-210 represents a unique communication system that integrates the hypoxic response across anatomically distinct cells, preventing unnecessary activity of delivered miR-210 in normoxia while still preparing recipient tissues for incipient hypoxic stress and accelerating adaptation.

Towards a molecular basis of oligometastatic disease: potential role of micro-RNAs

Oligometastasis is a cancer disease state characterized by a limited number of metastatic tumors involving single or few organs and with biological properties that make them potentially amenable to locoregional antitumor therapy. Current clinical data show that they are potentially curable with surgical resection or/and radiotherapy. Yet, mechanisms of progression from primary tumor to oligometastasis, rather than to polymetastases, is lacking in detail. In the current review we focus on the role of micro-RNAs in the regulation of metastases development and the role they may play in the differentiation of oligometastatic from polymetastatic progression. We also discuss the analyses of metastatic samples from oligo-and polymetastatic patients, which suggest that oligometastasis is a distinct biologic entity regulated in part by micro-RNAs. In addition, a review of the known functions of oligometastatic-specific micro-RNAs suggest that they regulate multiple steps in the metastatic cascade, including epithelial–mesenchymal transition, tumor invasion, intravasation, distant vascular extravasation and proliferation in a distant organ. Understanding the role of micro-RNAs and their target genes in oligometastatic disease may allow for the development of targeted therapies to effectively conrol the spread of metastases.

MicroRNA expression profile in intrauterine hypoxia-induced pulmonary hypoplasia in rats

Hypoxia is necessary for fetal development; however, excess hypoxia is detrimental. The mechanisms underlying the effects of hypoxia on lung development remain unclear, although important roles of microRNAs (miRNAs) during lung development have recently been established. However, the effect on lung development at an miRNA expression level, following changes in oxygen tension, have not yet been studied. In the present study, pregnant rats were exposed to a fraction of inspired oxygen of 10.5 or 21% for two days on gestation day 19, following which the body weight, lung wet weight, radial alveolar count (RAC) and mean linear intercept (Lm) of the newborn pups were analyzed on postnatal day 1. To define the role of miRNAs during lung development following intrauterine hypoxia exposure, the miRNA expression pattern was profiled using a miRNA microarray. The newborn rats in the hypoxic group exhibited statistically significant decreases in body weight, lung weight and the RAC, as well as a marked increase in the Lm. A total of 69 miRNAs were identified to have significant changes in expression, including 55 upregulated and 14 downregulated miRNAs. Quantitative polymerase chain reaction was used to validate the microarray results of six selected miRNAs. Therefore, the results indicated that late gestation intrauterine hypoxia exposure may cause lung injury and miRNAs may play important roles in this process.

miR-210 promotes IPF fibroblast proliferation in response to hypoxia

Idiopathic pulmonary fibrosis (IPF) is characterized by the relentless spread of fibroblasts from scarred alveoli into adjacent alveolar units, resulting in progressive hypoxia and death by asphyxiation. Although hypoxia is a prominent clinical feature of IPF, the role of hypoxia as a driver of the progressive fibrotic nature of the disease has not been explored. Here, we demonstrate that hypoxia robustly stimulates the proliferation of IPF fibroblasts. We found that miR-210 expression markedly increases in IPF fibroblasts in response to hypoxia and that knockdown of miR-210 decreases hypoxia-induced IPF fibroblast proliferation. Silencing hypoxia-inducible factor (HIF)-2α inhibits the hypoxia-mediated increase in miR-210 expression and blocks IPF fibroblast proliferation, indicating that HIF-2α is upstream of miR-210. We demonstrate that the miR-210 downstream target MNT is repressed in hypoxic IPF fibroblasts and that knockdown of miR-210 increases MNT expression. Overexpression of MNT inhibits hypoxia-induced IPF fibroblast proliferation. Together, these data indicate that hypoxia potently stimulates miR-210 expression via HIF-2α, and high miR-210 expression drives fibroblast proliferation by repressing the c-myc inhibitor, MNT. In situ analysis of IPF lung tissue demonstrates miR-210 expression in a similar distribution with HIF-2α and the hypoxic marker carbonic anhydrase-IX in cells within the IPF fibrotic reticulum. Our results raise the possibility that a pathological feed-forward loop exists in the IPF lung, in which hypoxia promotes IPF fibroblast proliferation via stimulation of miR-210 expression, which in turn worsens hypoxia.

Multiple functions of hypoxia-regulated miR-210 in cancer

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression post-transcriptionally. miRNAs can be induced by a variety of stresses such as hypoxia, and are involved in diverse biological processes including differentiation, cell proliferation, cell death, and tumorigenesis. Hypoxia, a common feature of tumor microenvironment, can induce a number of miRNAs expression. miRNA-210 (miR-210) is one of the hypoxia-regulated-miRNAs, which has been investigated extensively in cancer. However, paradoxically opposing results were documented regarding whether it is an oncogene or a tumor suppressor, and whether it is a positive or negative prognostic biomarker. In the present review, we focus on the following investigations of miR-210: 1) its functions of as an oncogene, 2) its functions as a tumor suppressor, 3) its functions in mitochondrial metabolism, and finally, the diagnostic and prognostic value of miR-210 in cancer researches.

MicroRNA-382 induced by HIF-1α is an angiogenic miR targeting the tumor suppressor phosphatase and tensin homolog

Recent studies have revealed that microRNAs (miRs) play important roles in the regulation of angiogenesis. In this study, we have characterized miR-382 upregulation by hypoxia and the functional relevance of miR-382 in tumor angiogenesis. miRs induced by hypoxia in MKN1 human gastric cancer cells were investigated using miRNA microarrays. We selected miR-382 and found that the expression of miR-382 was regulated by HIF-1α. Conditioned media (CM) from MKN1 cells transfected with a miR-382 inhibitor (antagomiR-382) under hypoxic conditions significantly decreased vascular endothelial cell (EC) proliferation, migration and tube formation. Algorithmic programs (Target Scan, miRanda and cbio) predicted that phosphatase and tensin homolog (PTEN) is a target gene of miR-382. Deletion of miR382-binding sequences in the PTEN mRNA 3′-untranslated region (UTR) diminished the luciferase reporter activity. Subsequent study showed that the overexpression of miR-382 or antagomiR-382 down- or upregulated PTEN and its downstream target AKT/mTOR signaling pathway, indicating that PTEN is a functional target gene of miR-382. In addition, PTEN inhibited miR-382-induced in vitro and in vivo angiogenesis as well as VEGF secretion, and the inhibition of miR-382 expression reduced xenograft tumor growth and microvessel density in tumors. Taken together, these results suggest that miR-382 induced by hypoxia promotes angiogenesis and acts as an angiogenic oncogene by repressing PTEN.

Renal cell carcinoma development and miRNAs: a possible link to the EGFR pathway

Renal cell carcinoma (RCC) is the most common solid cancer of the adult kidney and the majority of RCC cases are detected accidentally. This reality and the nonexistence of a standard screening test contribute to the fact that one third of patients are diagnosed with local invasive disease or metastatic disease. miRNAs are a family of small ncRNAs that regulate gene expression and have been identified as key regulators in many biological processes including cell development, differentiation, apoptosis and proliferation. The EGF receptor signaling pathway is usually deregulated in cancer and it is suggested to have an important role in RCC. Further studies are needed to characterize deregulation of this pathway during RCC development. In this review we highlight some potential miRNAs that could be involved in the modulation of the EGF receptor pathway and consequently in RCC development.

Distinct microRNA expression signatures are associated with melanoma subtypes and are regulated by HIF1A

The complex genetic changes underlying metastatic melanoma need to be deciphered to develop new and effective therapeutics. Previously, genome-wide microarray analyses of human melanoma identified two reciprocal gene expression programs, including transcripts regulated by either transforming growth factor, beta 1 (TGFβ1) pathways, or microphthalmia-associated transcription factor (MITF)/SRY-box containing gene 10 (SOX10) pathways. We extended this knowledge by discovering that melanoma cell lines with these two expression programs exhibit distinctive microRNA (miRNA) expression patterns. We also demonstrated that hypoxia-inducible factor 1 alpha (HIF1A) is increased in TGFβ1 pathway-expressing melanoma cells and that HIF1A upregulates miR-210, miR-218, miR-224, and miR-452. Reduced expression of these four miRNAs in TGFβ1 pathway-expressing melanoma cells arrests the cell cycle, while their overexpression in mouse melanoma cells increases the expression of the hypoxic response gene Bnip3. Taken together, these data suggest that HIF1A may regulate some of the gene expression and biological behavior of TGFβ1 pathway-expressing melanoma cells, in part via alterations in these four miRNAs.

Effect of microRNA-210 on prognosis and response to chemotherapeutic drugs in pediatric acute lymphoblastic leukemia

Many studies have demonstrated that microRNA-210 (miR-210) expression is intensively upregulated in hypoxic states and differentially regulated in most types of cancer cells. However, the clinical significance of miR-210 and its effects on the response of leukemic cells to chemotherapeutic drugs in childhood acute lymphoblastic leukemia (ALL) remain unknown. In the current study, using real-time qRT-PCR to detect miR-210 expression in bone marrow samples from 114 children at initial diagnosis of ALL, we investigated the prognostic significance of miR-210 and determined its associations with common clinical characteristics and treatment outcome. We further examined its effect on the response to chemotherapeutic drugs in the Reh and RS4;11 cell lines. Results showed that miR-210 expression was significantly lower in patients suffering from relapse and induction failure than in other patients (P < 0.001). Using the receiver operating characteristic curve, 3.8243 was selected as the cut-off value of miR-210 expression in our test cohort (38 cases). A significantly poorer treatment outcome (P < 0.05) was found in the low-expression group and verified in the validation cohort (76 cases, P < 0.05). Patients with low expression of miR-210 and positive minimal residual disease at the end of induction had a much higher rate of relapse or induction failure (P = 0.001). Increasing/decreasing miR-210 expression using agomir/antagomir could enhance or reduce the response of Reh cells and RS4;11 cells to daunorubicin/dexamethasone/L-asparaginase and daunorubicin/dexamethasone/vincristine, respectively. In conclusion, miR-210 may be a good prognostic factor and a useful predictor of drug sensitivity, and is a potential therapeutic target for pediatric ALL.

Prognostic value of circulating microRNA-210 levels in patients with moderate to severe aortic stenosis

BACKGROUND

Circulating micro-RNAs have been proposed as a novel class of cardiovascular (CV) biomarkers, but whether they meet analytical requirements and provide additional information to establish risk indices have not been established. miR-210 levels are increased in subjects with low VO2 max, which is a recognized risk factor in patients with aortic stenosis (AS), and we hypothesized that circulating miR-210 levels may be increased in patients with AS and associated with a poor prognosis.

METHODS

We measured circulating miR-210 levels by real-time PCR in 57 patients with moderate to severe AS and in 10 age- and gender-matched healthy controls. The merit of miR-210 as a biomarker was assessed according to established criteria, including by comparing miR-210 levels with NT-proBNP and miR-22 levels, which is another miRNA biomarker candidate.

RESULTS

All patients and control subjects had miR-210 levels within the range of detection (Cq<35) and the analytical variability was low. Circulating miR-210 levels were 2.0±0.2 [mean±SEM] fold increased in AS patients compared to controls (p = 0.002), whereas miR-22 levels were not differently expressed in the AS patients (0.12±0.06 fold increase, p = 0.45). The increase in miR-210 levels in AS patients was comparable to the increment in NT-proBNP levels: [AUC] 0.82 (95% CI 0.70-0.90) vs. 0.85 (0.75-0.93), respectively, p = 0.71. During a median follow-up of 1287 days, 15 patients (26%) died. There was a significant association between higher circulating levels of miR-210 and increased mortality during follow-up: hazard ratio [supra- vs. inframedian levels] 3.3 (95% CI 1.1-10.5), p = 0.039. Adjusting for other risk indices in multivariate analysis did not attenuate the prognostic merit of circulating miR-210 levels.

CONCLUSION

Circulating miR-210 levels are increased in patients with AS and provide independent prognostic information to established risk indices. Analytical characteristics were also excellent supporting the potential of micro-RNAs as novel CV biomarkers.

Inactivation of von Hippel-Lindau increases ovarian cancer cell aggressiveness through the HIF1α/miR-210/VMP1 signaling pathway

The inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene not only results in tumor initiation, but also mediates tumor metastasis. However, the mechanisms by which VHL inactivation leads to metastasis have not yet been well defined. In this study, the silencing of VHL in 3AO and SKOV3 ovarian cancer cells was found to promote cell motility and to increase the expression of matrix metalloproteinase (MMP)2, MMP9, hypoxia-inducible factor 1-α (HIF-1α) and microRNA (miR)-210. The suppression of HIF-1α with its inhibitor 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) in VHL-silenced 3AO cells antagonized the pro-migratory activity induced by the VHL deficiency and reversed the upregulation of MMP2, MMP9, HIF-1α and miR-210; however, it had no obvious effect on the VHL protein level. The introduction of miR-210 inhibitor into VHL-silenced 3AO cells resulted in similar changes as those induced by YC-1. Furthermore, vacuole membrane protein 1 (VMP1) was found to be diminished by VHL silencing in a HIF-1α/miR-210-dependent manner. Taken together, our data demonstrate that the loss of VHL stimulates ovarian cancer cell migration by stabilizing HIF-1α, upregulating miR-210 and decreasing VMP1 expression. These results indicate that the aberrant signaling of the VHL/HIF-1α/miR-210/VMP1 pathway may be involved in ovarian cancer aggressiveness.

Integrated analysis of microRNA and mRNA expression and association with HIF binding reveals the complexity of microRNA expression regulation under hypoxia

BACKGROUND

In mammalians, HIF is a master regulator of hypoxia gene expression through direct binding to DNA, while its role in microRNA expression regulation, critical in the hypoxia response, is not elucidated genome wide. Our aim is to investigate in depth the regulation of microRNA expression by hypoxia in the breast cancer cell line MCF-7, establish the relationship between microRNA expression and HIF binding sites, pri-miRNA transcription and microRNA processing gene expression.

METHODS

MCF-7 cells were incubated at 1% Oxygen for 16, 32 and 48 h. SiRNA against HIF-1α and HIF-2α were performed as previously published. MicroRNA and mRNA expression were assessed using microRNA microarrays, small RNA sequencing, gene expression microarrays and Real time PCR. The Kraken pipeline was applied for microRNA-seq analysis along with Bioconductor packages. Microarray data was analysed using Limma (Bioconductor), ChIP-seq data were analysed using Gene Set Enrichment Analysis and multiple testing correction applied in all analyses.

RESULTS

Hypoxia time course microRNA sequencing data analysis identified 41 microRNAs significantly up- and 28 down-regulated, including hsa-miR-4521, hsa-miR-145-3p and hsa-miR-222-5p reported in conjunction with hypoxia for the first time. Integration of HIF-1α and HIF-2α ChIP-seq data with expression data showed overall association between binding sites and microRNA up-regulation, with hsa-miR-210-3p and microRNAs of miR-27a/23a/24-2 and miR-30b/30d clusters as predominant examples. Moreover the expression of hsa-miR-27a-3p and hsa-miR-24-3p was found positively associated to a hypoxia gene signature in breast cancer. Gene expression analysis showed no full coordination between pri-miRNA and microRNA expression, pointing towards additional levels of regulation. Several transcripts involved in microRNA processing were found regulated by hypoxia, of which DICER (down-regulated) and AGO4 (up-regulated) were HIF dependent. DICER expression was found inversely correlated to hypoxia in breast cancer.

CONCLUSIONS

Integrated analysis of microRNA, mRNA and ChIP-seq data in a model cell line supports the hypothesis that microRNA expression under hypoxia is regulated at transcriptional and post-transcriptional level, with the presence of HIF binding sites at microRNA genomic loci associated with up-regulation. The identification of hypoxia and HIF regulated microRNAs relevant for breast cancer is important for our understanding of disease development and design of therapeutic interventions.

Clear cell papillary renal cell carcinoma: micro-RNA expression profiling and comparison with clear cell renal cell carcinoma and papillary renal cell carcinoma

Clear cell papillary renal cell carcinoma (CCPRCC) is a low-grade renal neoplasm with morphological characteristics mimicking both clear cell renal cell carcinoma (CCRCC) and papillary renal cell carcinoma (PRCC). However, despite some overlapping features, their morphological, immunohistochemical, and molecular profiles are distinct. Micro-RNAs (miRNAs) are small noncoding RNAs that play a crucial role in regulating gene expression and are involved in various biological processes, including cancer development. To better understand the biology of this tumor, we aimed to analyze the miRNA expression profile of a set of CCPRCC using microarray and quantitative reverse transcription-polymerase chain reaction. A total of 15 cases diagnosed as CCPRCC were used in this study. Among the most differentially expressed miRNA in CCPRCC, we found miR-210, miR-122, miR-34a, miR-21, miR-34b*, and miR-489 to be up-regulated, whereas miR-4284, miR-1202, miR-135a, miR-1973, and miR-204 were down-regulated compared with normal renal parenchyma. To identify consensus of differentially regulated miRNA between CCPRCC, CCRCC, and PRCC, we additionally determined differential miRNA expression using 2 publically available microarray data sets from the NCBI Gene Expression Omnibus database (GSE41282 and GSE3798). This comparison revealed that the miRNA expression profile of CCPRCC shows some overlapping characteristics between CCRCC and PRCC. Moreover, CCPRCC lacks dysregulation of important miRNAs typically associated with aggressive behavior. In summary, we describe the miRNA expression profile of a relatively infrequent type of renal cancer. Our results may help in understanding the molecular underpinning of this newly recognized entity.

Targeting CSCs in tumor microenvironment: the potential role of ROS-associated miRNAs in tumor aggressiveness

Reactive oxygen species (ROS) have been widely considered as critical cellular signaling molecules involving in various biological processes such as cell growth, differentiation, proliferation, apoptosis, and angiogenesis. The homeostasis of ROS is critical to maintain normal biological processes. Increased production of ROS, namely oxidative stress, due to either endogenous or exogenous sources causes irreversible damage of bio-molecules such as DNA, proteins, lipids, and sugars, leading to genomic instability, genetic mutation, and altered gene expression, eventually contributing to tumorigenesis. A great amount of experimental studies in vitro and in vivo have produced solid evidence supporting that oxidative stress is strongly associated with increased tumor cell growth, treatment resistance, and metastasis, and all of which contribute to tumor aggressiveness. More recently, the data have indicated that altered production of ROS is also associated with cancer stem cells (CSCs), epithelial-to-mesenchymal transition (EMT), and hypoxia, the most common features or phenomena in tumorigenesis and tumor progression. However, the exact mechanism by which ROS is involved in the regulation of CSC and EMT characteristics as well as hypoxia- and, especially, HIF-mediated pathways is not well known. Emerging evidence suggests the role of miRNAs in tumorigenesis and progression of human tumors. Recently, the data have indicated that altered productions of ROS are associated with deregulated expression of miRNAs, suggesting their potential roles in the regulation of ROS production. Therefore, targeting ROS mediated through the deregulation of miRNAs by novel approaches or by naturally occurring anti-oxidant agents such as genistein could provide a new therapeutic approach for the prevention and/or treatment of human malignancies. In this article, we will discuss the potential role of miRNAs in the regulation of ROS production during tumorigenesis. Finally, we will discuss the role of genistein, as a potent anti-tumor agent in the regulation of ROS production during tumorigenesis and tumor development.

The Effect of miR-210 Up-regulation on Proliferation and Survival of Mouse Bone Marrow Derived Mesenchymal Stem Cell

BACKGROUND

Bone marrow derived mesenchymal stem cells (MSCs) are a population of multipotent progenitors which have the capacity of proliferation and differentiation into mesenchymal lineage cells. Hypoxia could promote the proliferation of MSCs. Micro-RNAs are endogenous RNAs that can play an important role in some processes such as proliferation and differentiation. MiR-210 could help for better proliferation of MSCs since this miRNA could activate HIF pathway. In current study we investigated if MSCs can preserve their differentiation and proliferation ability under normoxic conditions by upregulation of miR-210.

MATERIALS AND METHODS

MSCs isolated from C57 BL/6 mice by flushing it's femurs into the cell culture media. After 72 hours, MSCs which are plastic adherent cells were attached to the flask and non-adherent cells were removed. Subsequently, MSCs induced to differentiate into osteocytes and adipocytes with specific differentiation media in order to confirm their identity and multipotency. Then miR-210 was inserted in Lentiviruse vectors and affected MSCs. In each passage, the number and viability of cells were evaluated.

RESULTS

Comparison between miR-210 infected MSCs with control cells showed that miR-210 has ability to increase proliferation of MSCs significantly.

CONCLUSION

We showed that miR-210 has ability to induce proliferation of MSCs without any negative effect on their differentiation abilities. Further studies are needed for evaluation of probable effects of miR-210 mechanisms on MSCs proliferation.

Over-expression of microRNA-494 up-regulates hypoxia-inducible factor-1 alpha expression via PI3K/Akt pathway and protects against hypoxia-induced apoptosis

BACKGROUND

Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the key regulators of hypoxia/ischemia. MicroRNA-494 (miR-494) had cardioprotective effects against ischemia/reperfusion (I/R)-induced injury, but its functional relationship with HIF-1α was unknown. This study was undertaken to determine if miR-494 was involved in the induction of HIF-1α.

RESULTS

Quantitative RT-PCR showed that miR-494 was up-regulated to peak after 4 hours of hypoxia in human liver cell line L02. To investigate the role of miR-494, cells were transfected with miR-494 mimic or miR-negative control, followed by incubation under normoxia or hypoxia. Our results indicated that overexpression of miR-494 significantly induced the expression of p-Akt, HIF-1α and HO-1 determined by qRT-PCR and western blot under normoxia and hypoxia, compared to negative control (p < 0.05). While LY294002 treatment markedly abolished miR-494-inducing Akt activation, HIF-1α and HO-1 increase under both normoxic and hypoxic conditions (p < 0.05). Moreover, apoptosis detection using Annexin V indicated that overexpression of miR-494 significantly decreased hypoxia-induced apoptosis in L02 cells, compared to control (p < 0.05). MiR-494 overexpression also decreased caspase-3/7 activity by 1.27-fold under hypoxia in L02 cells.

CONCLUSIONS

Overexpression of miR-494 upregulated HIF-1α expression through activating PI3K/Akt pathway under both normoxia and hypoxia, and had protective effects against hypoxia-induced apoptosis in L02 cells. Thus, these findings suggested that miR-494 might be a target of therapy for hepatic hypoxia/ischemia injury.