MicroRNA-210: a unique and pleiotropic hypoxamir

High expression of miR-210 predicts poor survival in patients with breast cancer: a meta-analysis

BACKGROUND

Many microRNAs (miRNAs) exhibit altered expression levels in cancers, and they may be considered as valuable prognostic biomarkers for cancers. Here we aimed to summarize the recent advances in miR-210 involvement in human breast cancer and analyze the predicting role of miR-210 for survival.

METHODS

A meta-analysis was performed by searching PubMed, Cochrane Library, and Science Direct databases. Data were extracted from studies comparing survival in patients with breast cancer having higher expression of miR-210 with those having lower expression. Pooled hazard ratios (HRs) and 95% confidence intervals (CI) were calculated.

RESULTS

A total of 511 cases of breast cancer were involved for this global meta-analysis. For post-operational survival, the HR of higher miR-210 expression in breast cancer tissue was 3.39 (95% CI: 2.04-5.63, P<0.05), which could significantly predict poorer survival.

CONCLUSIONS

High expression of miR-210 might predict poor survival in patients with breast cancer.

Regulatory mechanisms and clinical perspectives of miRNA in tumor radiosensitivity

MicroRNA (miRNA) influences carcinogenesis at multiple stages and it can effectively control tumor radiosensitivity by affecting DNA damage repair, cell cycle checkpoint, apoptosis, radio-related signal transduction pathways and tumor microenvironment. MiRNA also efficiently modulates tumor radiosensitivity at multiple levels by blocking the two essential non-homologous end-joining repair and homologous recombination repair pathways in the DNA damage response. It interferes with four radio-related pathways in ionizing radiation, including the PI3-K/Akt, NF-κB, MAPK and TGFβ signaling pathways. Moreover, the regulatory effect of miRNA in radiosensitivity can be enhanced when interacting with various key molecules, including H2AX, BRCA1, ATM, DNA-PK, RAD51, Chk1, Cdc25A, p53, PLK1, HIF-1 and VEGF, which are involved in these processes. Therefore, thoroughly understanding the mechanism of miRNA in tumor radiosensitivity could assist in finding novel targets to improve the radiotherapeutic effects and provide new clinical perspectives and insights for developing effective cancer treatments.

On the Pro-Metastatic Stress Response to Cancer Therapies: Evidence for a Positive Co-Operation between TIMP-1, HIF-1α, and miR-210

In contrast to expectations in the past that tumor starvation or unselective inhibition of proteolytic activity would cure cancer, there is accumulating evidence that microenvironmental stress, such as hypoxia or broad-spectrum inhibition of metalloproteinases can promote metastasis. In fact, malignant tumor cells, due to their genetic and epigenetic instability, are predisposed to react to stress by adaptation and, if the stress persists, by escape and formation of metastasis. Recent recognition of the concepts of dynamic evolution as well as population and systems biology is extremely helpful to understand the disappointments of clinical trials with new drugs and may lead to paradigm-shifts in therapy strategies. This must be complemented by an increased understanding of molecular mechanism involved in stress response. Here, we review new roles of Hypoxia-inducible factor-1 (HIF-1), one transcription factor regulating stress response-related gene expression: HIF-1 is crucial for invasion and metastasis, independent from its pro-survival function. In addition, HIF-1 mediates pro-metastatic microenvironmental changes of the proteolytic balance as triggered by high systemic levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), typical for many aggressive cancers, and regulates the metabolic switch to glycolysis, notably via activation of the microRNA miR-210. There is preliminary evidence that TIMP-1 also induces miR-210. Such positive-regulatory co-operation of HIF-1α, miR-210, and TIMP-1, all described to correlate with bad prognosis of cancer patients, opens new perspectives of gaining insight into molecular mechanisms of metastasis-inducing evasion of tumor cells from stress.

Stem cell-based delivery of Hypoxamir-210 to the infarcted heart: implications on stem cell survival and preservation of infarcted heart function

This study seeks to test our hypothesis that transgenic induction of miR-210 in mesenchymal stem cells (MSC) simulates the pro-survival effects of ischemic preconditioning (IPC) and that engraftment of (PC)MSC helps in the functional recovery of ischemic heart by miR-210 transfer to host cardiomyocytes through gap junctions. miR-210 expression in MSC was achieved by IPC or nanoparticle-based transfection of miR-210 plasmid ((miR)MSC) and functional recovery of the infarcted heart of rat transplanted with (PC)MSC or (miR)MSC was evaluated. Both (PC)MSC and (miR)MSC showed higher survival under lethal anoxia as compared to (non-PC)MSC and scramble-transfected MSC ((Sc)MSC) controls with concomitantly lower CASP8AP2 expression. Similarly, both (PC)MSC and (miR)MSC survived better and accelerated functional recovery of ischemic heart post-transplantation. To validate our hypothesis that MSC deliver miR-210 to host cardiomyocytes, in vitro co-culture between cardiomyocytes and (PC)MSC or (miR)MSC (using (non-PC)MSC or (Sc)MSC as controls) showed co-localization of miR-210 with gap-junctional connexin-43. miR-210 transfer to cardiomyocytes was blocked by heptanol pretreatment. Moreover, higher survival of cardiomyocytes co-cultured with (PC)MSC was observed with concomitant expression of CASP8AP2 as compared to cardiomyocytes co-cultured with (non-PC)MSC thus suggesting that miR-210 was translocated from MSC to protect host cardiomyocytes. Induction of miR-210 in MSC promoted their survival post-engraftment in the infarcted heart. Moreover, direct transfer of pro-survival miR-210 from (miR)MSC to host cardiomyocytes led to functional recovery of the ischemic heart.

microRNA-210 negatively regulates LPS-induced production of proinflammatory cytokines by targeting NF-κB1 in murine macrophages

Ligation of TLR4 with LPS in macrophages leads to the production of proinflammatory cytokines, which are central to eliminate viral and bacterial infection. However, uncontrolled TLR4 activation may contribute to pathogenesis of inflammatory diseases such as septic shock. In this study, we found microRNA-210 was induced in murine macrophages by LPS. Transfection of miR-210 mimics significantly inhibited LPS-induced production of inflammatory cytokines. In contrast, transfection of anti-miR-210 inhibitors increased LPS-induced expression of proinflammatory cytokines. Furthermore, we demonstrated that miR-210 targets NF-κB1. Therefore, our data identify miR-210 as a very important feedback negative regulator for LPS-induced production of proinflammatory cytokines.

MicroRNAs As Biomarkers For Clinical Features Of Lung Cancer

Each year about 1.4 million people die from lung cancer worldwide. Despite efforts in prevention, diagnosis and treatment, survival rate remains poor for this disease. This unfortunate situation is largely due to the fact that a high proportion of cases are diagnosed at advanced stages, highlighting the great need for identifying new biomarkers in order to improve early diagnosis and treatment. Recent studies on microRNAs have not only shed light on their involvement in tumor development and progression, but also suggested their potential utility as biomarkers for subtype diagnostics, staging and prediction of treatment response. This review article summarizes the impact of microRNAs on lung cancer biology, and highlights their role in the detection and classification of lung cancer as well as direct targets for drug development.

Preconditioning approach in stem cell therapy for the treatment of infarcted heart

Nearly two decades of research in regenerative medicine have been focused on the development of stem cells as a therapeutic option for treatment of the ischemic heart. Given the ability of stem cells to regenerate the damaged tissue, stem-cell-based therapy is an ideal approach for cardiovascular disorders. Preclinical studies in experimental animal models and clinical trials to determine the safety and efficacy of stem cell therapy have produced encouraging results that promise angiomyogenic repair of the ischemically damaged heart. Despite these promising results, stem cell therapy is still confronted with issues ranging from uncertainty about the as-yet-undetermined "ideal" donor cell type to the nonoptimized cell delivery strategies to harness optimal clinical benefits. Moreover, these lacunae have significantly hampered the progress of the heart cell therapy approach from bench to bedside for routine clinical applications. Massive death of donor cells in the infarcted myocardium during acute phase postengraftment is one of the areas of prime concern, which immensely lowers the efficacy of the procedure. An overview of the published data relevant to stem cell therapy is provided here and the various strategies that have been adopted to develop and optimize the protocols to enhance donor stem cell survival posttransplantation are discussed, with special focus on the preconditioning approach.

Regulation of microRNA expression and function by nuclear receptor signaling

MicroRNAs (miRNAs) are small non-coding RNA transcripts that affect various cellular pathways by serving as regulators of gene expression at the translational and transcriptional level. Nuclear receptors (NRs) are ligand-activated transcription factors that regulate gene transcription by binding to the promoter region or by interacting with other transcription factors. NRs can regulate miRNA expression either at the transcriptional level, or through posttranscriptional maturation by interacting with miRNA processing factors. This review will summarize recent advances in knowledge of the modulation of miRNA expression by NRs. Increased understanding of the molecular basis of miRNA expression may enable new therapeutic interventions that modulate miRNA activities through NR-mediated signaling.

MicroRNA expression profiles associated with development of drug resistance in Ehrlich ascites tumor cells

Multidrug resistance (MDR) poses a major obstacle to successful chemotherapeutic treatment of cancer, and often involves multiple genes, which may be regulated post-transcriptionally by microRNAs (miRNAs). The purpose of the present study was therefore to identify any resistance-associated changes in miRNA expression in a sensitive and five increasingly drug-resistant Ehrlich ascites tumor (EAT) cell lines, representing different steps in the development of resistance. We used an LNA-enhanced microarray platform to study the global miRNA expression profiles in the six murine EAT cell lines, and identified growth-, hypoxia-, and resistance-specific miRNA patterns. Among the differentially expressed miRNAs, we found the two clusters miR-183∼miR-96∼miR-182 and miR-200b∼miR-200a∼miR-429 as well as miR-141 to be consistently upregulated in the MDR cell lines, while miR-125b-5p and the two clusters miR-30d∼miR-30b and miR-23b∼miR-27b∼miR-24-1 were downregulated in most of the resistant EAT cells. Several of the target genes for these miRNAs-including Zeb1/Zeb2 and members of the Fox gene family-could contribute to the drug-resistant phenotype, although we did not find that the degree of resistance was directly correlated to any specific changes in miRNA expression. Probably, the observed miRNA expression patterns reflect the underlying genomic instability of the tumor cells, and further studies are needed to explore how the highly complex regulatory miRNA networks contribute to the development of MDR.

Gene expression and hypoxia in breast cancer

Hypoxia is a feature of most solid tumors and is associated with poor prognosis in several cancer types, including breast cancer. The master regulator of the hypoxic response is the Hypoxia-inducible factor 1α (HIF-1α). It is becoming clear that HIF-1α expression alone is not a reliable marker of tumor response to hypoxia, and recent studies have focused on determining gene and microRNA (miRNA) signatures for this complex process. The results of these studies are likely to pave the way towards the development of a robust hypoxia signature for breast and other cancers that will be useful for diagnosis and therapy. In this review, we outline the existing markers of hypoxia and recently identified gene and miRNA expression signatures, and discuss their potential as prognostic and predictive biomarkers. We also highlight how the hypoxia response is being targeted in the development of cancer therapies.

HIF induces human embryonic stem cell markers in cancer cells

Low oxygen levels have been shown to promote self-renewal in many stem cells. In tumors, hypoxia is associated with aggressive disease course and poor clinical outcomes. Furthermore, many aggressive tumors have been shown to display gene expression signatures characteristic of human embryonic stem cells (hESC). We now tested whether hypoxia might be responsible for the hESC signature observed in aggressive tumors. We show that hypoxia, through hypoxia-inducible factor (HIF), can induce an hESC-like transcriptional program, including the induced pluripotent stem cell (iPSC) inducers, OCT4, NANOG, SOX2, KLF4, cMYC, and microRNA-302 in 11 cancer cell lines (from prostate, brain, kidney, cervix, lung, colon, liver, and breast tumors). Furthermore, nondegradable forms of HIFα, combined with the traditional iPSC inducers, are highly efficient in generating A549 iPSC-like colonies that have high tumorigenic capacity. To test potential correlation between iPSC inducers and HIF expression in primary tumors, we analyzed primary prostate tumors and found a significant correlation between NANOG-, OCT4-, and HIF1α-positive regions. Furthermore, NANOG and OCT4 expressions positively correlated with increased prostate tumor Gleason score. In primary glioma-derived CD133 negative cells, hypoxia was able to induce neurospheres and hESC markers. Together, these findings suggest that HIF targets may act as key inducers of a dynamic state of stemness in pathologic conditions.

Dynamic regulation of circulating microRNA during acute exhaustive exercise and sustained aerobic exercise training

MicroRNAs (miRNAs) are intracellular mediators of essential biological functions. Recently, plasma-based 'circulating' miRNAs (c-miRNAs) have been shown to control cellular processes, but the c-miRNA response to human exercise remains unknown. We sought to determine whether c-miRNAs are dynamically regulated in response to acute exhaustive cycling exercise and sustained rowing exercise training using a longitudinal, repeated measures study design. Specifically, c-miRNAs involved in angiogenesis (miR-20a, miR-210, miR-221, miR-222, miR-328), inflammation (miR-21, miR-146a), skeletal and cardiac muscle contractility (miR-21, miR-133a), and hypoxia/ischaemia adaptation (miR-21, miR-146a, and miR-210) were measured at rest and immediately following acute exhaustive cycling exercise in competitive male rowers (n = 10, age = 19.1 ± 0.6 years) before and after a 90 day period of rowing training. Distinct patterns of c-miRNA response to exercise were observed and adhered to four major profiles: (1) c-miRNA up-regulated by acute exercise before and after sustained training (miR-146a and miR-222), (2) c-miRNA responsive to acute exercise before but not after sustained training (miR-21 and miR-221), (3) c-miRNA responsive only to sustained training (miR-20a), and (4) non-responsive c-miRNA (miR-133a, miR-210, miR-328). Linear correlations were observed between peak exercise levels of miR-146a and VO2max (r = 0.63, P = 0.003) and between changes in resting miR-20a and changes in VO2max (pre-training vs. post-training, r = 0.73; P = 0.02). Although future work is required, these results suggest the potential value of c-miRNAs as exercise biomarkers and their possible roles as physiological mediators of exercise-induced cardiovascular adaptation.

MicroRNAs as new maestro conducting the expanding symphony orchestra of regenerative and reparative medicine

The human genome encodes 1,048 microRNAs (miRNAs). These miRNAs regulate virtually all biological processes. Leaving ignominy on the significance miRNAs behind we are approaching a new era in tissue repair where an ever expanding orchestra of events that enable tissue repair and regeneration seems to be conducted by miRNAs as the maestro. microRNAs are emerging as molecular rheostats that fine-tune and switch regulatory circuits governing tissue repair. Key elements of tissue repair such as stem cell biology, inflammation, hypoxia-response, and angiogenesis are all under the sophisticated control of a network of specific mRNAs. Embryonic stem cells lacking miRNAs lose their "stemness." Manipulation of specific cellular miRNAs helps enhance reprogramming of somatic cells to an embryonic stem cell-like phenotype helping generate inducible pluripotent stem cells. Expression of miRNAs is subject to control by epigenetic factors. Such control influences the balance between proliferation and differentiation of stem cells. Angiomirs regulate various aspects of angiogenesis, such as proliferation, migration, and morphogenesis of endothelial cells. MiRNAs play a key role in resolution of inflammation. Hypoxia-inducible mRNAs or hypoxamirs suppress mitochondrial respiration, cause cell cycle arrest, and interfere with growth factor signaling. miRNA-210 is a good example in this category that impairs wound closure. As fine tools enabling specific and temporally controlled manipulation of cell-specific miRNAs emerge, miRNA-based therapies hold promise in facilitating tissue repair. Treatment of skin wounds has lower barriers because it lends itself to local delivery of miRNA mimics and antagonizing agents minimizing risks associated with systemic off-target toxicity.

Biomimetic high density lipoprotein nanoparticles for nucleic acid delivery

We report a gold nanoparticle-templated high density lipoprotein (HDL AuNP) platform for gene therapy that combines lipid-based nucleic acid transfection strategies with HDL biomimicry. For proof-of-concept, HDL AuNPs are shown to adsorb antisense cholesterylated DNA. The conjugates are internalized by human cells, can be tracked within cells using transmission electron microscopy, and regulate target gene expression. Overall, the ability to directly image the AuNP core within cells, the chemical tailorability of the HDL AuNP platform, and the potential for cell-specific targeting afforded by HDL biomimicry make this platform appealing for nucleic acid delivery.

The autophagic tumor stroma model of cancer: Role of oxidative stress and ketone production in fueling tumor cell metabolism

A loss of stromal Cav-1 in the tumor fibroblast compartment is associated with early tumor recurrence, lymph-node metastasis, and tamoxifen-resistance, resulting in poor clinical outcome in breast cancer patients. Here, we have used Cav-1 (-/-) null mice as a pre-clinical model for this "lethal tumor micro-environment." Metabolic profiling of Cav-1 (-/-) mammary fat pads revealed the upregulation of numerous metabolites (nearly 100), indicative of a major catabolic phenotype. Our results are consistent with the induction of oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy. The two most prominent metabolites that emerged from this analysis were ADMA (asymmetric dimethyl arginine) and BHB (beta-hydroxybutyrate; a ketone body), which are markers of oxidative stress and mitochondrial dysfunction, respectively. Transcriptional profiling of Cav-1 (-/-) stromal cells and human tumor stroma from breast cancer patients directly supported an association with oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy, as well as ADMA and ketone production. MircoRNA profiling of Cav-1 (-/-) stromal cells revealed the upregulation of two key cancer-related miR's, namely miR-31 and miR-34c. Consistent with our metabolic findings, these miR's are associated with oxidative stress (miR-34c) or activation of the hypoxic response/HIF1a (miR-31), which is sufficient to drive authophagy/mitophagy. Thus, via an unbiased comprehensive analysis of a lethal tumor micro-environment, we have identified a number of candidate biomarkers (ADMA, ketones, and miR-31/34c) that could be used to identify high-risk cancer patients at diagnosis, for treatment stratification and/or for evaluating therapeutic efficacy during anti-cancer therapy. We propose that the levels of these key biomarkers (ADMA, ketones/BHB, miR-31, and miR-34c) could be (1) assayed using serum or plasma from cancer patients, or (2) performed directly on excised tumor tissue. Importantly, induction of oxidative stress and autophagy/mitophagy in the tumor stromal compartment provides a means by which epithelial cancer cells can directly "feed off" of stromal-derived essential nutrients, chemical building blocks (amino acids, nucleotides), and energy-rich metabolites (glutamine, pyruvate, ketones/BHB), driving tumor progression and metastasis. Essentially, aggressive cancer cells are "eating" the cancer-associated fibroblasts via autophagy/mitophagy in the tumor micro-environment. Lastly, we discuss that this "Autophagic Tumor Stroma Model of Cancer Metabolism" provides a viable solution to the "Autophagy Paradox" in cancer etiology and chemo-therapy.

E2F and microRNA regulation of angiogenesis

E2F family of transcription factors are best known for regulating genes involved in cell cycle control, cell proliferation, tumorigenesis, and apoptosis. Recent evidences have revealed their critical involvement in modulating cellular response to hypoxia and ischemia in a variety of physiological and pathological processes. Of particular interest are findings that E2Fs act as both regulators and targets of microRNAs that govern hypoxic/ischemic angiogenesis. This review focuses on the crosstalk between E2Fs and microRNAs that have been shown to participate in the regulation of angiogenesis, hypoxia response and ischemic disease.

Metastamirs: a stepping stone towards improved cancer management

MicroRNAs (miRNAs) are non-coding RNAs that regulate protein expression. Aberrant miRNA expression in cancer has been well documented; miRNAs can act as oncogenes or tumor-suppressor genes, depending on the cellular context and target genes that they regulate, and are involved in tumor progression and metastasis. The potential mechanisms by which miRNAs are involved in tumor aggressiveness include migration, invasion, cell proliferation, epithelial-to-mesenchymal transition, angiogenesis and apoptosis. MiRNAs are involved in various cellular pathways and an miRNA can elicit more than one biological effect in a given cell. Existing data show the potential clinical utility of miRNAs as prognostic and predictive markers for aggressive and metastatic cancers. The stability of miRNAs in formalin-fixed, paraffin-embedded tissues and body fluids is advantageous for biomarker discovery and validation. In addition, miRNAs can be extracted from small biopsy specimens, which is a further advantage. Finally, miRNAs are potential therapeutic agents for personalized cancer management.

The cellular response to hypoxia: tuning the system with microRNAs

Adaptation to hypoxia is an essential cellular response controlled by the oxygen-sensitive master transcription factor hypoxia-inducible factor 1 (HIF-1). HIF-1 expression is also controlled by specific microRNAs and, in turn, controls the expression of other microRNAs, which fine-tune adaptation to low oxygen tension. In this issue of the JCI, Ghosh and colleagues identify a unique microRNA in hypoxic endothelial cells, miR424, that promotes HIF-1 stabilization and angiogenesis. The actions of this microRNA are considered in the context of the complex interactions that act to ensure optimal endothelial adaptation to this critical environmental condition.

Hypoxia-induced microRNA-424 expression in human endothelial cells regulates HIF-α isoforms and promotes angiogenesis

Adaptive changes to oxygen availability are critical for cell survival and tissue homeostasis. Prolonged oxygen deprivation due to reduced blood flow to cardiac or peripheral tissues can lead to myocardial infarction and peripheral vascular disease, respectively. Mammalian cells respond to hypoxia by modulating oxygen-sensing transducers that stabilize the transcription factor hypoxia-inducible factor 1α (HIF-1α), which transactivates genes governing angiogenesis and metabolic pathways. Oxygen-dependent changes in HIF-1α levels are regulated by proline hydroxylation and proteasomal degradation. Here we provide evidence for what we believe is a novel mechanism regulating HIF-1α levels in isolated human ECs during hypoxia. Hypoxia differentially increased microRNA-424 (miR-424) levels in ECs. miR-424 targeted cullin 2 (CUL2), a scaffolding protein critical to the assembly of the ubiquitin ligase system, thereby stabilizing HIF-α isoforms. Hypoxia-induced miR-424 was regulated by PU.1-dependent transactivation. PU.1 levels were increased in hypoxic endothelium by RUNX-1 and C/EBPα. Furthermore, miR-424 promoted angiogenesis in vitro and in mice, which was blocked by a specific morpholino. The rodent homolog of human miR-424, mu-miR-322, was significantly upregulated in parallel with HIF-1α in experimental models of ischemia. These results suggest that miR-322/424 plays an important physiological role in post-ischemic vascular remodeling and angiogenesis.

MicroRNAs in skin and wound healing

MicroRNAs (miRNAs) are small endogenous RNA molecules ∼22 nt in length. miRNAs are capable of posttranscriptional gene regulation by binding to their target messenger RNAs (mRNAs), leading to mRNA degradation or suppression of translation. miRNAs have recently been shown to play pivotal roles in skin development and are linked to various skin pathologies, cancer, and wound healing. This review focuses on the role of miRNAs in cutaneous biology, the various methods of miRNA modulation, and the therapeutic opportunities in treatment of skin diseases and wound healing.

Redox Pioneer: Professor Joseph Loscalzo

Dr. Joseph Loscalzo (M.D., 1978; Ph.D., 1977) is recognized here as a Redox Pioneer because he has published two articles in the field of antioxidant/redox biology that have been cited more than 1,000 times and 22 articles that have been cited more than 100 times. Dr. Loscalzo is known for his seminal contributions to our understanding of the vascular biology of nitric oxide. His initial discovery that the antiplatelet effects of organic nitrates are potentiated by thiols through a mechanism that involved metabolism to S-nitrosothiols was followed by the demonstration that S-nitrosothiols are formed endogenously through S-transnitrosation, stabilize nitric oxide, and facilitate the transport and transfer of nitric oxide between and within cells of the vessel wall. These properties led to the development of S-nitrosothiol-containing pharmacotherapies to treat disease states characterized by nitric oxide deficiency. Dr. Loscalzo's other scientific contributions include identifying the vascular functional consequences of genetic deficiencies of antioxidant enzymes that decrease nitric oxide bioavailability, collectively termed the "oxidative enzymopathies," and demonstrating the role of mitochondria in modulating the disulfide subproteome, and in redox signaling in hypoxia. He has received numerous awards and honors for his scientific contributions, including election to the Institute of Medicine of the National Academy of Sciences.