MicroRNA miR-93 promotes tumor growth and angiogenesis by targeting integrin-β8

MicroRNA miR-24 enhances tumor invasion and metastasis by targeting PTPN9 and PTPRF to promote EGF signaling

MicroRNAs are known to play regulatory roles in gene expression associated with cancer development. We analyzed levels of the microRNA miR-24 in patients with breast carcinoma and found that miR-24 was higher in breast carcinoma samples than in benign breast tissues. We generated constructs expressing miR-24 and studied its functions using both in vitro and in vivo techniques. We found that the ectopic expression of miR-24 promoted breast cancer cell invasion and migration. In vivo experiments in mice indicated that the expression of miR-24 enhanced tumor growth, invasion into local tissues, metastasis to lung tissues and decreased overall mouse survival. In the miR-24-expressing cells and tumors, EGFR was highly phosphorylated, whereas expression of the phosphatases tyrosine-protein phosphatase non-receptor type 9 (PTPN9) and receptor-type tyrosine-protein phosphatase F (PTPRF) were repressed. We confirmed that miR-24 could directly target both PTPN9 and PTPRF. Consistent with this, we found that the levels of phosphorylated epidermal growth factor receptor (pEGFR) were higher whereas the levels of PTPN9 and PTPRF were lower in the patients with metastatic breast carcinoma. Ectopic expression of PTPN9 and PTPRF decreased pEGFR levels, cell invasion, migration and tumor metastasis. Furthermore, we found that MMP2, MMP11, pErk, and ADAM15 were upregulated, whereas TIMP2 was downregulated; all of which supported the roles of miR-24 in tumor invasion and metastasis. Our results suggest that miR-24 plays a key role in breast cancer invasion and metastasis. miR-24 could potentially be a target for cancer intervention.

Misprocessing and functional arrest of microRNAs by miR-Pirate: roles of miR-378 and miR-17

miRNAs (microRNAs) are short non-coding RNAs that can regulate gene expression in cancer development, which makes them valuable targets for therapeutic intervention. In the present study we report on an approach that can not only arrest the functions of mature miRNAs by binding to them, but it can also induce the ‘mis-processing’ of the target miRNA, producing a non-functional truncated miRNA. This approach involves generating an expression construct that produces an RNA fragment with 16 repeat sequences. The construct is named miR-Pirate (miRNA-interacting RNA-producing imperfect RNA and tangling endogenous miRNA). The transcript of the construct contained mismatches to the seed region, and thus it would not target the potential targets of the miRNA under study. The homology of the construct is sufficiently high, allowing the transcript to block miRNA functions. The functions of the construct were validated in cell cultures, in tumour formation assays and in transgenic mice stably expressing this construct. To explore the possibility of adopting this approach in gene therapy, we transfected cells with synthetic miR-Pirate and obtained the results we expected. The miR-Pirate, expressed by the construct or synthesized chemically, was found to be able to specifically pirate and silence a mature miRNA through its dual roles and thus could be clinically applied for miRNA intervention.

MicroRNA-145 is downregulated in glial tumors and regulates glioma cell migration by targeting connective tissue growth factor

Glioblastomas (GBM), the most common and aggressive type of malignant glioma, are characterized by increased invasion into the surrounding brain tissues. Despite intensive therapeutic strategies, the median survival of GBM patients has remained dismal over the last decades. In this study we examined the expression of miR-145 in glial tumors and its function in glioma cells. Using TCGA analysis and real-time PCR we found that the expression of miR-145/143 cluster was downregulated in astrocytic tumors compared to normal brain specimens and in glioma cells and glioma stem cells (GSCs) compared to normal astrocytes and neural stem cells. Moreover, the low expression of both miR-145 and miR-143 in GBM was correlated with poor patient prognosis. Transfection of glioma cells with miR-145 mimic or transduction with a lentivirus vector expressing pre-miR 145 significantly decreased the migration and invasion of glioma cells. We identified connective tissue growth factor (CTGF) as a novel target of miR-145 in glioma cells; transfection of the cells with this miRNA decreased the expression of CTGF as determined by Western blot analysis and the expression of its 3′-UTR fused to luciferase. Overexpression of a CTGF plasmid lacking the 3′-UTR and administration of recombinant CTGF protein abrogated the inhibitory effect of miR-145 on glioma cell migration. Similarly, we found that silencing of CTGF decreased the migration of glioma cells. CTGF silencing also decreased the expression of SPARC, phospho-FAK and FAK and overexpression of SPARC abrogated the inhibitory effect of CTGF silencing on cell migration. These results demonstrate that miR-145 is downregulated in glial tumors and its low expression in GBM predicts poor patient prognosis. In addition miR-145 regulates glioma cell migration by targeting CTGF which downregulates SPARC expression. Therefore, miR-145 is an attractive therapeutic target for anti-invasive treatment of astrocytic tumors.

Upregulation of miRNA-155 promotes tumour angiogenesis by targeting VHL and is associated with poor prognosis and triple-negative breast cancer

MicroRNA-155 (miR-155) is frequently up-regulated in various types of human cancer; however, its role in cancer angiogenesis remains unknown. Here, we demonstrate the role of miR-155 in angiogenesis through targeting von Hippel-Lindau tumour suppressor (VHL) in breast cancer. Ectopic expression of miR-155 induced whereas knockdown of miR-155 inhibited HUVEC network formation, proliferation, invasion, and migration. Furthermore, mammary fat pad xenotransplantation of ectopically expressed miR-155 resulted in extensive angiogenesis, proliferation, tumour necrosis, and recruitment of pro-inflammatory cells such as tumour associated macrophages. Expression of VHL abrogated these miR-155 effects. Moreover, miR-155 expression inversely correlates with VHL expression level and is associated with late stage, lymph node metastasis, and poor prognosis as well as triple-negative tumour in breast cancer. These findings indicate that miR-155 plays a pivotal role in tumour angiogenesis by downregulation of VHL, and provide a basis for miR-155-expressing tumours to embody an aggressive malignant phenotype, and therefore, miR-155 is an important therapeutic target in breast cancer.

Epithelial-to-mesenchymal(-like) transition as a relevant molecular event in malignant gliomas

Tumor dissemination and metastatic behavior account for the vast majority of cancer associated mortality. Epithelial tumors achieve this progressive state via epithelial-to-mesenchymal transition (EMT); however, the importance of this process in the neuroepithelial context is currently very controversially discussed. The review describes the current research status concerning EMT-like changes in malignant gliomas including the role of TWIST1, ZEB1/ZEB2 and SNAIl1/SNAIl2 as inducers for cell-invasiveness in GBMs. Furthermore, WNT/β-catenin signaling with its key-component FRIZZLED4 activating an EMT-like program in malignant gliomas and its relationship to the stem-like phenotype as well as discoveries on micro-RNA-level regulating the EMT-like process are discussed.

Current status and implications of microRNAs in ovarian cancer diagnosis and therapy

Ovarian cancer is the fifth most common cancer among women and causes more deaths than any other type of female reproductive cancer. Currently, treatment of ovarian cancer is based on the combination of surgery and chemotherapy. While recurrent ovarian cancer responds to additional chemotherapy treatments, the progression-free interval becomes shorter after each cycle, as chemo-resistance increases until the disease becomes incurable. There is, therefore, a strong need for prognostic and predictive markers to help optimize and personalize treatment in order to improve the outcome of ovarian cancer. An increasing number of studies indicate an essential role for microRNAs in ovarian cancer progression and chemo-resistance. MicroRNAs (miRNAs) are small endogenous non-coding RNAs (~22bp) which are frequently dysregulated in cancer. Typically, miRNAs are involved in crucial biological processes, including development, differentiation, apoptosis and proliferation. Two families of miRNAs, miR-200 and let-7, are frequently dysregulated in ovarian cancer and have been associated with poor prognosis. Both have been implicated in the regulation of epithelial-to-mesenchymal transition, a cellular transition associated with tumor aggressiveness, tumor invasion and chemo-resistance. Moreover, miRNAs also have possible implications for improving cancer diagnosis; for example miR-200 family, let-7 family, miR-21 and miR-214 may be useful in diagnostic tests to help detect ovarian cancer at an early stage. Additionally, the use of multiple target O-modified antagomirs (MTG-AMO) to inhibit oncogenic miRNAs and miRNA replacement therapy for tumor suppressor miRNAs are essential tools for miRNA based cancer therapeutics. In this review we describe the current status of the role miRNAs play in ovarian cancer and focus on the possibilities of microRNA-based therapies and the use of microRNAs as diagnostic tools.

Stress response of glioblastoma cells mediated by miR-17-5p targeting PTEN and the passenger strand miR-17-3p targeting MDM2

Tumor development not only destroys the homeostasis of local tissues but also the whole body, and thus the tumor cells have to face the body's defense system, a shortage of nutrition and oxygen, and chemotherapeutic drug treatment. In response to these stresses, tumor cells often alter gene expression and microRNA levels to facilitate survival. We have demonstrated that glioblastoma cells deprived of nutrition or treated with chemotherapeutics drugs expressed increased levels of miR-17. Ectopic transfection of miR-17 prolonged glioblastoma cell survival when the cells were deprived with nutrition or treated with chemotherapeutic drugs. Expression of miR-17 also promoted cell motility, invasion, and tube-like structure formation. We found that these phenotypes were the results of miR-17 targeting PTEN. As a consequence, HIF1α and VEGF were up-regulated. Ectopic expression of miR-17 was found to facilitate enrichment of stem-like tumor cells, since the cells became drug-resistant, showed increased capacity to form colonies and neurospheres, and expressed higher levels of CD133, a phenotype similar to ectopic expression of HIF1α. To further confirm the phenotypic property of stem cells, we demonstrated that glioblastoma cells transfected with miR-17 proliferated slower in different nutritional conditions by facilitating more cells staying in the G1 phase than the control cells. Finally, we demonstrated that miR-17 could repress MDM2 levels, resulting in decreased cell proliferation and drug-resistance. Our results added a new layer of functional mechanism for the well-studied miRNA miR-17.

Insulin-like growth factor-1 signaling regulates miRNA expression in MCF-7 breast cancer cell line

In breast carcinomas, increased levels of insulin-like growth factor 1 (IGF-1) can act as a mitogen to augment tumorigenesis through the regulation of MAPK and AKT signaling pathways. Signaling through these two pathways allows IGF-1 to employ mechanisms that favor proliferation and cellular survival. Here we demonstrate a subset of previously described tumor suppressor and oncogenic microRNAs (miRNAs) that are under the direct regulation of IGF-1 signaling. Additionally, we show that the selective inhibition of either the MAPK or AKT pathways prior to IGF-1 stimulation prevents the expression of previously described tumor suppressor miRNAs that are family and cluster specific. Here we have defined, for the first time, specific miRNAs under the direct regulation of IGF-1 signaling in the estrogen receptor positive MCF-7 breast cancer cell line and demonstrate kinase signaling as a modulator of expression for a small subset of microRNAs. Taken together, these data give new insights into mechanisms governing IGF-1 signaling in breast cancer.

Versican 3'-untranslated region (3'-UTR) functions as a ceRNA in inducing the development of hepatocellular carcinoma by regulating miRNA activity

This study was designed to explore the role of versican in the development of hepatocellular carcinoma (HCC). Ectopic expression of the versican 3'-untranslated region (3'-UTR) was studied as a competitive endogenous RNA for regulating miRNA functions. We used this approach to modulate the expression of versican and its related proteins in 3'-UTR transgenic mice and in the liver cancer cell line HepG2, stably transfected with the 3'-UTR or a control vector. We demonstrated that transgenic mice expressing the versican 3'-UTR developed HCC and increased expression of versican isoforms V0 and V1. HepG2 cells transfected with versican 3'-UTR displayed increased proliferation, survival, migration, invasion, colony formation, and enhanced endothelial cell growth, but decreased apoptosis. We found that versican 3'-UTR could bind to miRNAs miR-133a, miR-199a*, miR-144, and miR-431 and also interacted with CD34 and fibronectin. As a consequence, expression of versican, CD34, and fibronectin was up-regulated by ectopic transfection of the versican 3'-UTR, which was confirmed in HepG2 cells and in transgenic mice as compared with wild-type controls. Transfection with siRNAs targeting the versican 3'-UTR abolished the effects of the 3'-UTR. Taken together, these results demonstrate that versican V0 and V1 isoforms play important roles in HCC development and that versican mRNAs compete with endogenous RNAs in regulating miRNA functions.

miRNAs regulate expression and function of extracellular matrix molecules

MicroRNAs (miRNAs) are a family of small non-coding RNA molecules that are made up of 18-25 nucleotides that function in post-transcriptional gene regulation. The expression of miRNAs is highly conserved and essential in regulating many cellular processes including formation, maintenance and the remodelling of the extracellular matrix (ECM). In this review, we examine different ECM molecules and the miRNAs involved in regulating their abundance and how these changes influence cell phenotype. For example, miRNAs and their target messenger RNAs (mRNAs) are involved in cell adhesion, by regulating the synthesis and turnover of key ECM adhesion molecules and their receptors including cadherins, integrins and other non-integrin ECM receptors. Other miRNAs regulate the abundance of cytokines and growth factors which in turn stimulate cells to synthesize and secrete specialized ECMs. For example, miR-125a/b and miR-146a and their downstream target mRNAs influence the production of the epidermal growth factor family which has a significant impact on the nature of the ECM formed. miRNAs affect structural ECM proteins important in the assembly, composition and organization of the ECM. Proteins such as collagen, fibronectin, versican, and nephronectin are targeted by several miRNAs. miRNAs can also control the expression of proteins such as matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs), which are involved in ECM remodelling and are important for tissue development, cell motility and wound healing. It has become clear that many different miRNAs control the balance in ECM composition that determines normal tissue function and alterations in the expression of these miRNAs can lead to pathological consequences.

The intermediate filament vimentin mediates microRNA miR-378 function in cellular self-renewal by regulating the expression of the Sox2 transcription factor

MicroRNAs are short noncoding RNAs that are implicated in cell self- renewal and cancer development. We show that miR-378 is up-regulated in human cancers and found that tumor cells transfected with miR-378 acquired properties of tumor stem cells, including cell self-renewal. Overexpression of miR-378 enhanced cell survival and colony formation. Isolated from a single-cell colony, the miR-378-expressing cells formed tumors in nude mice at low cell densities. These cells expressed higher levels of miR-378 and formed more and larger spheres and colonies. We found that the miR-378-expressing cells contained a large number of side population cells and could undergo differentiation. Cells transfected with miR-378 expressed increased levels of Sox2. Expression of miR-378 and Sox2 was found correlated significantly in cancer cell lines and in cancer patient specimens. We also observed opposite levels of vimentin in the cancer cell lines and human breast carcinoma specimens. We further demonstrated that vimentin is a target of miR-378, and ectopic transfection of vimentin inhibited Sox2 expression, resulting in decreased cell survival. Silencing vimentin promoted Sox2 expression and cell survival. Our study demonstrates that miR-378 is a regulator of stem cell marker Sox2 by targeting vimentin, which may serve as a new tool in studying the role of stem cells in tumorigenesis.

MiR-93 enhances angiogenesis and metastasis by targeting LATS2

Here we report that miR-93, a miRNA in the miR-106B~25 cluster, a paralog of the miR-17-92 cluster, was significantly upregulated in human breast carcinoma tissues. We stably expressed miR-93 in the MT-1 human breast carcinoma cell line and found that tumors formed by the miR-93 cells contained more blood vessels than those formed by the control cells. Co-culture experiments indicated that the MT-1 cells displayed a high activity of adhesion with endothelial cells and could form larger and more tube-like structures with endothelial cells. Lung metastasis assays were performed in a mouse metastatic model, and it was found that expression of miR-93 promoted tumor cell metastasis to lung tissue. In cell culture, expression of miR-93 enhanced cell survival and invasion. We examined the potential target that mediated miR-93's effects and found that the large tumor suppressor, homology 2 (LATS2) was a target of miR-93. Higher levels of LATS2 were associated with cell death in the tumor mass. Silencing LATS2 expression promoted cell survival, tube formation and invasion, while ectopic expression of LATS2 decreased cell survival and invasion. These findings demonstrated that miR-93 promoted tumor angiogenesis and metastasis by suppressing LATS2 expression. Our results suggest that the inhibition of miR-93 function may be a feasible approach to repress tumor metastasis.

A human monoclonal antibody 264RAD targeting αvβ6 integrin reduces tumour growth and metastasis, and modulates key biomarkers in vivo

αvβ6 integrin expression is upregulated on a wide range of epithelial tumours, and is thought to play a role in modulating tumour growth. Here we describe a human therapeutic antibody 264RAD, which binds and inhibits αvβ6 integrin function. 264RAD cross-reacts with human, mouse and cynomolgus monkey αvβ6, and inhibits binding to all ligands including the latency-associated peptide of TGF-β. Screening across a range of integrins revealed that 264RAD also binds and inhibits the related integrin αvβ8, but not the integrins α5β1, αvβ3, αvβ5 and α4β1. In vitro 264RAD inhibited invasion of VB6 and Detroit 562 cells in a Matrigel invasion assay and αvβ6 mediated production of matrix metalloproteinase-9 in Calu-3 cells. It inhibited TGF-β-mediated activation of dermal skin fibroblasts by preventing local activation of TGF-β by NCI-H358 tumour cells in a tumour cell-fibroblast co-culture assay. In vivo 264RAD showed dose-dependent inhibition of Detroit 562 tumour growth, regressing established tumours when dosed at 20 mg/kg once weekly. The reduction in growth associated with 264RAD was related to a dose-dependent inhibition of Ki67 and phospho-ERK and a reduction of αvβ6 expression in the tumour cells, coupled to a reduction in fibronectin and alpha smooth muscle actin expression in stromal fibroblasts. 264RAD also reduced the growth and metastasis of orthotopic 4T1 tumours. At 20 mg/kg growth of both the primary tumour and the number of metastatic deposits in lung were reduced. The data support the conclusion that 264RAD is a potent inhibitor of αvβ6 integrin, with some activity against αvβ8 integrin, that reduces both tumour growth and metastasis.

A systematic review of microRNA in glioblastoma multiforme: micro-modulators in the mesenchymal mode of migration and invasion

Glioblastoma multiforme (GBM) is an incurable form of brain cancer with a very poor prognosis. Because of its highly invasive nature, it is impossible to remove all tumor cells during surgical resection, making relapse inevitable. Further research into the regulatory mechanism underpinning GBM pathogenesis is therefore warranted, and over the past decade, there has been an increased focus on the functional role of microRNA (miRNA). This systematic review aims to present a comprehensive overview of all the available literature on the expression profiles and function of miRNA in GBM. Here, we have reviewed 163 papers and identified 253 upregulated, 95 downregulated, and 17 disputed miRNAs with respect to expression levels; 85 % of these miRNAs have not yet been functionally characterized. A focus in this study has been 26 interesting miRNAs involved in the mesenchymal mode of migration and invasion, demonstrating the importance of miRNAs in the context of the cellular niche. Both oncogenic and tumor-suppressive miRNAs were found to affect target genes involved in cell migration, cytoskeletal rearrangement, invasiveness, and angiogenesis. Clearly, the distinct functional properties of these miRNAs need further investigation and might hold a great potential in future molecular therapies targeting GBM.

MicroRNA-106b-25 cluster expression is associated with early disease recurrence and targets caspase-7 and focal adhesion in human prostate cancer

The miR-106b-25 microRNA (miRNA) cluster is a candidate oncogene in human prostate cancer. Here, we report that miRNAs encoded by miR-106b-25 are upregulated in both primary tumors and distant metastasis. Moreover, increased tumor miR-106b expression was associated with disease recurrence and the combination of high miR-106b and low CASP7 (caspase-7) expressions in primary tumors was an independent predictor of early disease recurrence (adjusted hazard ratio=4.1; 95% confidence interval: 1.6-12.3). To identify yet unknown oncogenic functions of miR-106b, we overexpressed it in LNCaP human prostate cancer cells to examine miR-106b-induced global expression changes among protein-coding genes. The approach revealed that CASP7 is a direct target of miR-106b, which was confirmed by western blot analysis and a 3'-untranslated region reporter assay. Moreover, selected phenotypes induced by miR-106b knockdown in DU145 human prostate cancer cells did not develop when both miR-106b and CASP7 expression were inhibited. Further analyses showed that CASP7 is downregulated in primary prostate tumors and metastatic lesions across multiple data sets and is by itself associated with disease recurrence and disease-specific survival. Using bioinformatics, we also observed that miR-106b-25 may specifically influence focal adhesion-related pathways. This observation was experimentally examined using miR-106b-25-transduced 22Rv1 human prostate cancer cells. After infection with a miR-106b-25 lentiviral expression construct, 22Rv1 cells showed increased adhesion to basement membrane- and bone matrix-related filaments and enhanced soft agar growth. In summary, miR-106b-25 was found to be associated with prostate cancer progression and disease outcome and may do so by altering apoptosis- and focal adhesion-related pathways.

Guidance for life, cell death, and colorectal neoplasia by netrin dependence receptors

This review is focusing on a critical mediator of embryonic and postnatal development with multiple implications in inflammation, neoplasia, and other pathological situations in brain and peripheral tissues. These morphogenetic guidance and dependence processes are involved in several malignancies targeting the epithelial and immune systems including the progression of human colorectal cancers. We consider the most important findings and their impact on basic, translational, and clinical cancer research. Expected information can bring new cues for innovative, efficient, and safe strategies of personalized medicine based on molecular markers, protagonists, signaling networks, and effectors inherent to the Netrin axis in pathophysiological states.

Genetic module and miRNome trait analyses reflect the distinct biological features of endothelial progenitor cells from different anatomic locations

Background

Endothelial progenitor cells (EPCs) play a fundamental role in post-natal vascular repair, yet EPCs from different anatomic locations possess unique biological properties. The underlying mechanisms are unclear.

Results

EPCs from CB expressed abundant genes involved in cell cycle, hypoxia signalling and blood vessel development, correlating with the phenotypes that CB-EPCs proliferated more rapidly, migrated faster, and formed tubule structure more efficiently. smRNA-seq further deciphered miRNome patterns in EPCs isolated from CB or PB: 54 miRNAs were enriched in CB-EPCs, while another 50 in PB-EPCs. Specifically, CB-EPCs expressed more angiogenic miRNAs such as miR-31, while PB-EPCs possessed more tumor suppressive miRNAs including miR-10a. Knocking down miR-31 levels in CB-EPCs suppressed cell migration and microtubule formation, while overexpressing miR-31 in PB-EPCs helped to recapitulate some of CB-EPC functions.

Conclusions

Our results show the foundation for a more detailed understanding of EPCs from different anatomic sources. Stimulating the expression of angiogenic microRNAs or genes in EPCs of low activity (such as those from patients with cardiovascular diseases) might allow the development of novel therapeutic strategies.

Ergosterol peroxide isolated from Ganoderma lucidum abolishes microRNA miR-378-mediated tumor cells on chemoresistance

Due to an altered expression of oncogenic factors and tumor suppressors, aggressive cancer cells have an intrinsic or acquired resistance to chemotherapeutic agents. This typically contributes to cancer recurrence after chemotherapy. microRNAs are short non-coding RNAs that are involved in both cell self-renewal and cancer development. Here we report that tumor cells transfected with miR-378 acquired properties of aggressive cancer cells. Overexpression of miR-378 enhanced both cell survival and colony formation, and contributed to multiple drug resistance. Higher concentrations of chemotherapeutic drugs were needed to induce death of miR-378-transfected cells than to induce death of control cells. We found that the biologically active component isolated from Ganoderma lucidum could overcome the drug-resistance conferred by miR-378. We purified and identified the biologically active component of Ganoderma lucidum as ergosterol peroxide. We demonstrated that ergosterol peroxide produced greater activity in inducing death of miR-378 cells than the GFP cells. Lower concentrations of ergosterol peroxide were needed to induce death of the miR-378-transfected cells than in the control cells. With further clinical development, ergosterol peroxide represents a promising new reagent that can overcome the drug-resistance of tumor cells.

Current Progress on Understanding MicroRNAs in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is an aggressive grade IV astrocytoma with a 1-year median survival rate despite current treatment modalities. A thorough understanding of the vast genetic aberrations and signaling pathways involved in gliomagenesis as well as heterogeneous clinicopathological presentation remains elusive. The recent discovery of microRNAs (miRs) and their capability of simultaneously regulating multiple downstream genes may play a key role in explaining the complex mechanisms underlying GBM formation. miRs are 19 to 25 nucleotide non-protein-coding small RNA molecules involved in the suppression of mRNA translation. This review will summarize and discuss the most recent findings regarding miRs in GBM including downstream targets, functional effects, and therapeutic potentials. Specifically discussed miRs include miR-7, miR-9/miR-9*, miR-10a/miR-10a*/miR-10b, miR-15b, miR-17-92, miR-21, miR-26a, miR-34a, miR-93, miR-101, miR-124, miR-125a, miR-125b, miR-128, miR-137, miR-146b-5p, miR-153, miR-181a/miR-181b, miR-196a/miR-196b, miR-218, miR-221/miR-222, miR-296, miR-302-367, miR-326, miR-381, miR-451, and let-7a. In addition to gene regulatory roles, miRs have demonstrated significant diagnostic, prognostic, and therapeutic potential. These small molecules may both help in the understanding of GBM and in developing new therapeutic options.

An anti-let-7 sponge decoys and decays endogenous let-7 functions

The let-7 family contains 12 members, which share identical seed regions, suggesting that they may target the same mRNAs. It is essential to develop a means that can regulate the functions of all members. Using a DNA synthesis technique, we have generated an anti-let-7 sponge aiming to modulate the function of all members. We found that products of the anti-let-7 construct could bind and inactivate all members of the let-7 family, producing decoy and decay effects. To test the role of the anti-let-7 sponge, we stably expressed the anti-let-7 construct in two types of cells, the breast carcinoma cells MT-1 and the oldest and most commonly used human cervical cancer cell line, HeLa cells. We found that expression of anti-let-7 increased cell survival, invasion and adhesion, which corroborate with known functions of let-7 family members. We further identified a novel target site across all species of the let-7 family in hyaluronan synthase 2 (HAS2). HAS2 overexpression produced similar effects as the anti-let-7 sponge. Silencing HAS2 expression by siRNAs produced opposite effects to anti-let-7 on cell survival and invasion. The ability of anti-let-7 to regulate multiple members of the let-7 family allows us to observe their multiple functions using a single reagent. This approach can be applied to other family members with conserved sequences.

Differential gene expression in tamoxifen-resistant breast cancer cells revealed by a new analytical model of RNA-Seq data

Resistance to tamoxifen (Tam), a widely used antagonist of the estrogen receptor (ER), is a common obstacle to successful breast cancer treatment. While adjuvant therapy with Tam has been shown to significantly decrease the rate of disease recurrence and mortality, recurrent disease occurs in one third of patients treated with Tam within 5 years of therapy. A better understanding of gene expression alterations associated with Tam resistance will facilitate circumventing this problem. Using a next generation sequencing approach and a new bioinformatics model, we compared the transcriptomes of Tam-sensitive and Tam-resistant breast cancer cells for identification of genes involved in the development of Tam resistance. We identified differential expression of 1215 mRNA and 513 small RNA transcripts clustered into ERα functions, cell cycle regulation, transcription/translation, and mitochondrial dysfunction. The extent of alterations found at multiple levels of gene regulation highlights the ability of the Tam-resistant cells to modulate global gene expression. Alterations of small nucleolar RNA, oxidative phosphorylation, and proliferation processes in Tam-resistant cells present areas for diagnostic and therapeutic tool development for combating resistance to this anti-estrogen agent.

miR-93/106b and their host gene, MCM7, are differentially expressed in leiomyomas and functionally target F3 and IL-8

miR-93/106b and their host gene minichromosome maintenance complex component 7 (MCM7) reside at chr7q22, a region frequently rearranged in leiomyomas. We explored the expression of miR-93/106b in leiomyoma and paired myometrium (n = 63) from untreated and patients exposed to hormonal therapies (GnRH agonist, Depo-Provera, and oral contraceptives) from African-Americans and Caucasians and their regulatory functions in isolated paired (n = 15) leiomyoma and myometrial smooth muscle cells and the leiomyosarcoma cell line. At tissue level leiomyomas expressed significantly lower levels of miR-93 and elevated MCM7 as compared with myometrium with limited racial influence or hormonal exposure on their expression. Assessing the regulatory function of miR-93/106b through doxycycline-inducible lentiviral transduction in a microarray analysis, tissue factor (F3) and IL8 were identified as their possible targets. At the tissue level, leiomyomas expressed a significantly lower level of F3 and an elevated IL-8 level, which exhibited an inverse relationship with miR-93 but with limited racial or hormonal influences. The gain of function of miR-93/106b in leiomyoma smooth muscle cells, myometrial smooth muscle cells, and the leiomyosarcoma cell line dose dependently repressed F3 and IL8 through direct interactions with their respective 3'-untranslated region and indirectly through F3 repression inhibited IL8, CTGF, and PAI-1 expression, confirmed by using small interfering RNA silencing or factor Vlla (FVIIa) activation of F3, as well as reducing the rate of proliferation, while increasing caspase-3/7 activity. We concluded that differential expression of miR-93/106b and their direct and/or indirect regulatory functions on F3, IL8, CTGF, and PAI-1 expression, with key roles in inflammation and tissue turnover may be of significance in the outcome of leiomyoma growth and associated symptoms.

MicroRNAs mediate metabolic stresses and angiogenesis

MicroRNAs are short endogenous RNA molecules that are able to regulate (mainly inhibiting) gene expression at the post-transcriptional level. The MicroRNA expression profile is cell-specific, but it is sensitive to perturbations produced by stresses and diseases. Endothelial cells subjected to metabolic stresses, such as calorie restriction, nutrients excess (glucose, cholesterol, lipids) and hypoxia may alter their functionality. This is predictive for the development of pathologies like atherosclerosis, diabetes, and hypertension. Moreover, cancer cells can activate a resting endothelium by secreting pro-angiogenic factors, in order to promote neoangiogenesis, which is essential for tumor growth. Endothelial altered phenotype is mirrored by altered mRNA, microRNA, and protein expression, with a microRNA being able to control pathways by regulating the expression of multiple mRNAs. In this review we will consider the involvement of microRNAs in modulating the response of endothelial cells to metabolic stresses and their role in promoting or halting angiogenesis.

Hypoxia control to normalize pathologic angiogenesis: potential role for endothelial precursor cells and miRNAs regulation

Tumor microenvironment is a complex and highly dynamic milieu that provides very important clues on tumor development and progression mechanisms. Tumor-associated endothelial cells play a key role in stroma organization. They achieve tumor angiogenesis, a formation of tumor-associated (angiogenic) vessels mainly through sprouting from locally preexisting vessels and/or recruitment of bone marrow-derived endothelial progenitor cells. This process participates to supply nutritional support and oxygen to the growing tumor. Endothelial cells constitute the interface between circulating blood cells, tumor cells and the extracellular matrix, thereby controlling leukocyte recruitment, tumor cell behavior and metastasis formation. Hypoxia, a critical parameter of the tumor microenvironment, controls endothelial/tumor cell interactions and is the key to tumor angiogenesis development. Under hypoxic stress, tumor cells produce factors that promote angiogenesis, vasculogenesis, tumor cell motility, metastasis and cancer stem cell selection. Targeting tumor vessels is a therapeutic strategy that has lately been fast evolving from antiangiogenesis to vessel normalization as discussed in this review. We shall focus on the pivotal role of endothelial cells within the tumor microenvironment, the specific features and the part played by circulating endothelial precursors cells. Attention is stressed on their recruitment to the tumor site and their role in tumor angiogenesis where they are submitted to miRNAs-mediated de/regulation. Here the compensation of the tumor deregulated angiogenic miRNAs - angiomiRs - is emphasized as a potential therapeutic approach. The strategy is to over express anti-angiomiRs in the tumor angiogenesis site upon selective delivery by precursor endothelial cells as miRs carriers.

A genetic variant in the promoter region of miR-106b-25 cluster and risk of HBV infection and hepatocellular carcinoma

Background

MiR-106b-25 cluster, hosted in intron 13 of MCM7, may play integral roles in diverse processes including immune response and tumorigenesis. A single nucleotide polymorphism (SNP), rs999885, is located in the promoter region of MCM7.

Methods

We performed a case-control study including 1300 HBV-positive hepatocellular carcinoma (HCC) cases, 1344 HBV persistent carriers and 1344 subjects with HBV natural clearance to test the association between rs999885 and the risk of HBV persistent infection and HCC. We also investigated the genotype-expression correlation between rs999885 and miR-106b-25 cluster in 25 pairs of HCC and adjacent non-tumor liver tissues.

Results

Compared with the HBV natural clearance subjects carrying rs999885 AA genotype, those with AG/GG genotypes had a decreased risk of chronic HBV infection with an adjusted odds ratio (OR) of 0.79 [95% confidence intervals (CIs) = 0.67–0.93]. However, the AG/GG genotypes were significantly associated with an increased HCC risk in HBV persistent carriers (adjusted OR = 1.25, 95% CIs = 1.06–1.47). Expression analysis revealed that the expression level of miR-106b-25 cluster was significantly higher in AG/GG carriers than those in AA carriers in non-tumor liver tissues.

Conclusions

These findings indicate that the A to G base change of rs999885 may provide a protective effect against chronic HBV infection but an increased risk for HCC in HBV persistent carriers by altering the expression of the miR-106b-25 cluster.

Unraveling the global microRNAome responses to ionizing radiation in human embryonic stem cells

MicroRNAs (miRNA) comprise a group of short ribonucleic acid molecules implicated in regulation of key biological processes and functions at the post-transcriptional level. Ionizing radiation (IR) causes DNA damage and generally triggers cellular stress response. However, the role of miRNAs in IR-induced response in human embryonic stem cells (hESC) has not been defined yet. Here, by using system biology approaches, we show for the first time, that miRNAome undergoes global alterations in hESC (H1 and H9 lines) after IR. Interrogation of expression levels of 1,090 miRNA species in irradiated hESC showed statistically significant changes in 54 genes following 1 Gy of X-ray exposures; global miRNAome alterations were found to be highly temporally and cell line - dependent in hESC. Time-course studies showed that the 16 hr miRNAome radiation response of hESC is much more robust compared to 2 hr-response signature (only eight genes), and may be involved in regulating the cell cycle. Quantitative real-time PCR performed on some miRNA species confirms the robustness of our miRNA microarray platform. Positive regulation of differentiation-, cell cycle-, ion transport- and endomembrane system-related processes were predicted to be negatively affected by miRNAome changes in irradiated hESC. Our findings reveal a fundamental role of miRNAome in modulating the radiation response, and identify novel molecular targets of radiation in hESC.

Matched rabbit monoclonal antibodies against αv-series integrins reveal a novel αvβ3-LIBS epitope, and permit routine staining of archival paraffin samples of human tumors

The relationship between integrin expression and function in pathologies is often contentious as comparisons between human pathological expression and expression in cell lines is difficult. In addition, the expression of even integrins αvβ6 and αvβ8 in tumor cell lines is not comprehensively documented. Here, we describe rabbit monoclonal antibodies (RabMabs) against the extracellular domains of αv integrins that react with both native integrins and formalin fixed, paraffin embedded (FFPE) human tissues. These RabMabs, against αvβ3 (EM22703), αvβ5 (EM09902), αvβ6 (EM05201), αvβ8 (EM13309), and pan-αv (EM01309), recognize individual integrin chains in Western blots and in flow cytometry. EM22703 detected a ligand-induced binding site (LIBS), reporting an epitope enhanced by the binding of an RGD-peptide to αvβ3. αvβ8 was rarely expressed in human tumor specimens, and weakly expressed in non-small-cell lung carcinoma (NSCLC). However, ovarian carcinoma cell lines expressed αvβ8, as did some melanoma cells, whereas U87MG glioma lacked αvβ8 expression. We observed an unexpected strong expression of αvβ6 in tumor samples of invasive ductal breast adenoma, colorectal carcinoma (CRC), and NSCLC. αvβ3 was strongly expressed in some invasive NSCLC cohorts. Interestingly, PC3 prostate cell and human prostate tumors did not express αvβ3. The RabMabs stained plasma membranes in FFPE-immunohistochemistry (IHC) samples of tumor cell lines from lung, ovary, colon, prostate, squamous cell carcinoma of head and neck (SCCHN), breast, and pancreas carcinomas. The RabMabs are unique tools for probing αv integrin biology, and suggest that especially αvβ6 and αvβ8 biologies still have much to reveal.

The miR-106b-25 cluster targets Smad7, activates TGF-β signaling, and induces EMT and tumor initiating cell characteristics downstream of Six1 in human breast cancer

The role of TGF-β signaling in tumorigenesis is paradoxical: it can be tumor suppressive or tumor promotional, depending on context. The metastatic regulator, Six1, was recently shown to mediate this switch, providing a novel means to explain this elusive “TGF-β paradox”. Herein, we identify a mechanism by which Six1 activates the tumor promotional arm of TGF-β signaling, via its ability to upregulate the miR-106b-25 microRNA cluster, and further identify a novel function for this cluster of microRNAs. While expression of the miR-106b-25 cluster is known to overcome TGF-β-mediated growth suppression via targeting p21 and BIM, we demonstrate for the first time that this same cluster can additionally target the inhibitory Smad7 protein, resulting in increased levels of the TGF-β type I receptor (TβRI) and downstream activation of TGF-β signaling. We further show that the miR-106b-25 cluster is sufficient to induce an epithelial to mesenchymal transition and a tumor initiating cell phenotype, and that it is required downstream of Six1 to induce these phenotypes. Finally, we demonstrate a significant correlation between miR-106b, Six1, and activated TGF-β signaling in human breast cancers, and further show that high levels of miR-106b and miR-93 in breast tumors significantly predicts shortened time to relapse. These findings expand the spectrum of oncogenic functions of miR-106b-25, and may provide a novel molecular explanation, through the Six1 regulated miR-106b-25 cluster, by which TGF-β signaling shifts from tumor suppressive to tumor promoting.

The Non-coding 3′UTR of CD44 Induces Metastasis by Regulating Extracellular Matrix Functions

The importance of non-coding RNA transcripts in regulating microRNA (miRNA) functions, especially the 3′ untranslated region (UTR), has been revealed in recent years. Genes encoding the extracellular matrix normally produce large mRNA transcripts including the 3′UTR. How these large transcripts affect miRNA functions and how miRNAs modulate the extracellular matrix (ECM) protein expression are largely unknown. Here, we demonstrate that the over-expression of the CD44 3′UTR results in enhanced cell motility, invasion and cell adhesion in human breast carcinoma cell line MDA-MB-231. Furthermore, we found that expression of the CD44 3′UTR enhances metastasis in vivo. We hypothesized that the increased expression of the CD44 3′UTR affected miRNA binding and modulated synthesis of the extracellular matrix. Computational analysis indicated that miRNAs that interact with the CD44 3′UTR also have binding sites in other matrix encoding mRNA 3′UTRs, including collagen type 1α1 (Col1α1) repressed by miR-328 and fibronectin type 1 (FN1) repressed by miR-512-3p, miR-491 and miR-671. Protein analysis demonstrated that expression of CD44, Col1α1, and FN1 were synergistically up-regulated in vitro and in vivo upon transfection of the CD44 3′UTR. The non-coding 3′UTR of CD44 interacts with multiple miRNAs that target extracellular matrix properties and thus can be used to antagonize miRNA activities.

MicroRNA miR-199a-3p regulates cell proliferation and survival by targeting caveolin-2

Recent advances in the study of microRNAs indicate that they have an important role in regulating cellular activities such as proliferation, morphogenesis, apoptosis and differentiation by regulating the expression of various genes. MiR-199a-3p is highly expressed in hair follicles and in some tumor cells, suggesting its participation in tumor progression, but it is significantly underexpressed in hepatocellular carcinoma and in bladder cancer. The mechanism underlying these effects is not yet known. Here, we dissect the effects of miR-199a-3p on YPEN-1 endothelial cells, and MDA-MB-231 and MT-1 breast cancer cell lines. We found that expression of miR-199a-3p promotes proliferation and survival of endothelial cells as well as breast cancer cells. Remarkably, miR-199a-3p inhibited both endogenous caveolin-2 activity and exogenous caveolin-2 activity, which was confirmed by a reporter construct bearing the 3'-untranslated region of caveolin-2. However, overexpression of caveolin-2 completely counteracted the enhancement of miR-199a-3p-mediated activities on cell proliferation, survival and sensitivity of tumor cells to anticancer drugs. Our findings suggest that MiR-199a-3p targeting of caveolin-2 might have an important role in breast cancer tumor progression, making it a potential candidate for intervention in cancer.

MicroRNA-29b suppresses tumor angiogenesis, invasion, and metastasis by regulating matrix metalloproteinase 2 expression

Hepatocellular carcinoma (HCC) is a highly vascularized tumor with frequent intrahepatic metastasis. Active angiogenesis and metastasis are responsible for rapid recurrence and poor survival of HCC. We previously found that microRNA-29b (miR-29b) down-regulation was significantly associated with poor recurrence-free survival of HCC patients. Therefore, the role of miR-29b in tumor angiogenesis, invasion, and metastasis was further investigated in this study using in vitro capillary tube formation and transwell assays, in vivo subcutaneous and orthotopic xenograft mouse models, and Matrigel plug assay, and human HCC samples. Both gain- and loss-of-function studies showed that miR-29b dramatically suppressed the ability of HCC cells to promote capillary tube formation of endothelial cells and to invade extracellular matrix gel in vitro. Using mouse models, we revealed that tumors derived from miR-29b-expressed HCC cells displayed significant reduction in microvessel density and in intrahepatic metastatic capacity compared with those from the control group. Subsequent investigations revealed that matrix metalloproteinase-2 (MMP-2) was a direct target of miR-29b. The blocking of MMP-2 by neutralizing antibody or RNA interference phenocopied the antiangiogenesis and antiinvasion effects of miR-29b, whereas introduction of MMP-2 antagonized the function of miR-29b. We further disclosed that miR-29b exerted its antiangiogenesis function, at least partly, by suppressing MMP-2 expression in tumor cells and, in turn, impairing vascular endothelial growth factor receptor 2-signaling in endothelial cells. Consistently, in human HCC tissues and mouse xenograft tumors miR-29b level was inversely correlated with MMP-2 expression, as well as tumor angiogenesis, venous invasion, and metastasis.

CONCLUSION

miR-29b deregulation contributes to angiogenesis, invasion, and metastasis of HCC. Restoration of miR-29b represents a promising new strategy in anti-HCC therapy.

Circulating microRNAs in patients with active pulmonary tuberculosis

Emerging evidence shows that microRNAs (miRNAs) play an important role in pathogen-host interactions. Circulating miRNAs have been repeatedly and stably detected in blood and hold promise to serve as molecular markers for diverse physiological and pathological conditions. To date, the relationship between circulating miRNAs and active pulmonary tuberculosis (TB) has not been reported. Using microarray-based expression profiling followed by real-time quantitative PCR validation, the levels of circulating miRNAs were compared between patients with active pulmonary tuberculosis and matched healthy controls. The receiver operating characteristic curve was used to evaluate the diagnostic effect of selected miRNA. Bioinformatic analysis was used to explore the potential roles of these circulating miRNAs in active pulmonary tuberculosis infection. Among 92 miRNAs significantly detected, 59 miRNAs were downregulated and 33 miRNAs were upregulated in the TB serum compared to their levels in the control serum. Interestingly, only two differentially expressed miRNAs were increased not only in the serum but also in the sputum of patients with active pulmonary tuberculosis compared to the levels for the healthy controls. Upregulated miR-29a could discriminate TB patients from healthy controls with reasonable sensitivity and specificity. A number of significantly enriched pathways regulated by these circulating miRNAs were predicted, and most of them were involved in acute-phase response, inflammatory response, and the regulation of the cytoskeleton. In all, for the first time our results revealed that a number of miRNAs were differentially expressed during active pulmonary tuberculosis infection, and circulating miR-29a has great potential to serve as a marker for the detection of active pulmonary tuberculosis infection.

Comparative studies of vertebrate Beta integrin genes and proteins: ancient genes in vertebrate evolution

Intregins are heterodimeric α- and β-subunit containing membrane receptor proteins which serve various cell adhesion roles in tissue repair, hemostasis, immune response, embryogenesis and metastasis. At least 18 α- (ITA or ITGA) and 8 β-integrin subunits (ITB or ITGB) are encoded on mammalian genomes. Comparative ITB amino acid sequences and protein structures and ITB gene locations were examined using data from several vertebrate genome projects. Vertebrate ITB genes usually contained 13-16 coding exons and encoded protein subunits with ~800 amino acids, whereas vertebrate ITB4 genes contained 36-39 coding exons and encoded larger proteins with ~1800 amino acids. The ITB sequences exhibited several conserved domains including signal peptide, extracellular β-integrin, β-tail domain and integrin β-cytoplasmic domains. Sequence alignments of the integrin β-cytoplasmic domains revealed highly conserved regions possibly for performing essential functions and its maintenance during vertebrate evolution. With the exception of the human ITB8 sequence, the other ITB sequences shared a predicted 19 residue α-helix for this region. Potential sites for regulating human ITB gene expression were identified which included CpG islands, transcription factor binding sites and microRNA binding sites within the 3'-UTR of human ITB genes. Phylogenetic analyses examined the relationships of vertebrate beta-integrin genes which were consistent with four major groups: 1: ITB1, ITB2, ITB7; 2: ITB3, ITB5, ITB6; 3: ITB4; and 4: ITB8 and a common evolutionary origin from an ancestral gene, prior to the appearance of fish during vertebrate evolution. The phylogenetic analyses revealed that ITB4 is the most likely primordial form of the vertebrate β integrin subunit encoding genes, that is the only β subunit expressed as a constituent of the sole integrin receptor 'α6β4' in the hemidesmosomes of unicellular organisms.

Glioblastoma angiogenesis and tumor cell invasiveness are differentially regulated by β8 integrin

Glioblastoma multiforme (GBM) is a highly invasive brain tumor that develops florid microvascular proliferation and hemorrhage. However, mechanisms that favor invasion versus angiogenesis in this setting remain largely uncharacterized. Here, we show that integrin β8 is an essential regulator of both GBM-induced angiogenesis and tumor cell invasiveness. Highly angiogenic and poorly invasive tumors expressed low levels of β8 integrin, whereas highly invasive tumors with limited neovascularization expressed high levels of β8 integrin. Manipulating β8 integrin protein levels altered the angiogenic and invasive growth properties of GBMs, in part, reflected by a diminished activation of latent TGFβs, which are extracellular matrix protein ligands for β8 integrin. Taken together, these results establish a role for β8 integrin in differential control of angiogenesis versus tumor cell invasion in GBM. Our findings suggest that inhibiting β8 integrin or TGFβ signaling may diminish tumor cell invasiveness during malignant progression and following antivascular therapies.

Repression of human activation induced cytidine deaminase by miR-93 and miR-155

Background

Activation Induced cytidine Deaminase (AID) targets the immunoglobulin genes of activated B cells, where it converts cytidine to uracil to induce mutagenesis and recombination. While essential for immunoglobulin gene diversification, AID misregulation can result in genomic instability and oncogenic transformation. This is classically illustrated in Burkitt's lymphoma, which is characterized by AID-induced mutation and reciprocal translocation of the c-MYC oncogene with the IgH loci. Originally thought to be B cell-specific, AID now appears to be misexpressed in several epithelial cancers, raising the specter that AID may also participate in non-B cell carcinogenesis.

Methods

The mutagenic potential of AID argues for the existence of cellular regulators capable of repressing inappropriate AID expression. MicroRNAs (miRs) have this capacity, and we have examined the publically available human AID EST dataset for miR complementarities to the human AID 3'UTR. In this work, we have evaluated the capacity of two candidate miRs to repress human AID expression in MCF-7 breast carcinoma cells.

Results

We have discovered moderate miR-155 and pronounced miR-93 complementary target sites encoded within the human AID mRNA. Luciferase reporter assays indicate that both miR-93 and miR-155 can interact with the 3'UTR of AID to block expression. In addition, over-expression of either miR in MCF-7 cells reduces endogenous AID protein, but not mRNA, levels. Similarly indicative of AID translational regulation, depletion of either miR in MCF-7 cells increases AID protein levels without concurrent increases in AID mRNA.

Conclusions

Together, our findings demonstrate that miR-93 and miR-155 constitutively suppress AID translation in MCF-7 cells, suggesting widespread roles for these miRs in preventing genome cytidine deaminations, mutagenesis, and oncogenic transformation. In addition, our characterization of an obscured miR-93 target site located within the AID 3'UTR supports the recent suggestion that many miR regulations have been overlooked due to the prevalence of truncated 3'UTR annotations.

A non-coding transcript of nephronectin promotes osteoblast differentiation by modulating microRNA functions

We investigated the roles of the non-coding transcripts and found that expression of a fragment containing the 3'-untranslated region (3'-UTR) of nephronectin in osteoblast progenitor cells MC3T3-E1 promoted cell differentiation dramatically. We hypothesized that the ectopically expressed 3'-UTR binds microRNAs and modulates their functions. β-Catenin and GSK3β were up-regulated in the 3'-UTR-transfected cells, contributing to the increased cell differentiation, through reduction of EGFR and ERK phosphorylation. Activator of GSK3β promoted differentiation, while inhibitor of GSK3β blocked differentiation. Our results indicate that the non-coding transcripts are important in regulating cell activities and may have potential application for modulating endogenous microRNA functions.

The microRNA cluster miR-106b~25 regulates adult neural stem/progenitor cell proliferation and neuronal differentiation

In adult mammals, neural stem cells (NSCs) generate new neurons that are important for specific types of learning and memory. Controlling adult NSC number and function is fundamental for preserving the stem cell pool and ensuring proper levels of neurogenesis throughout life. Here we study the importance of the microRNA gene cluster miR-106b~25 (miR-106b, miR-93, and miR-25) in primary cultures of neural stem/progenitor cells (NSPCs) isolated from adult mice. We find that knocking down miR-25 decreases NSPC proliferation, whereas ectopically expressing miR-25 promotes NSPC proliferation. Expressing the entire miR-106b~25 cluster in NSPCs also increases their ability to generate new neurons. Interestingly, miR-25 has a number of potential target mRNAs involved in insulin/insulin-like growth factor-1 (IGF) signaling, a pathway implicated in aging. Furthermore, the regulatory region of miR-106b~25 is bound by FoxO3, a member of the FoxO family of transcription factors that maintains adult stem cells and extends lifespan downstream of insulin/IGF signaling. These results suggest that miR-106b~25 regulates NSPC function and is part of a network involving the insulin/IGF-FoxO pathway, which may have important implications for the homeostasis of the NSC pool during aging.

MicroRNA and target protein patterns reveal physiopathological features of glioma subtypes

Gliomas such as oligodendrogliomas (ODG) and glioblastomas (GBM) are brain tumours with different clinical outcomes. Histology-based classification of these tumour types is often difficult. Therefore the first aim of this study was to gain microRNA data that can be used as reliable signatures of oligodendrogliomas and glioblastomas. We investigated the levels of 282 microRNAs using membrane-array hybridisation and real-time PCR in ODG, GBM and control brain tissues. In comparison to these control tissues, 26 deregulated microRNAs were identified in tumours and the tissue levels of seven microRNAs (miR-21, miR-128, miR-132, miR-134, miR-155, miR-210 and miR-409-5p) appropriately discriminated oligodendrogliomas from glioblastomas. Genomic, epigenomic and host gene expression studies were conducted to investigate the mechanisms involved in these deregulations. Another aim of this study was to better understand glioma physiopathology looking for targets of deregulated microRNAs. We discovered that some targets of these microRNAs such as STAT3, PTBP1 or SIRT1 are differentially expressed in gliomas consistent with deregulation of microRNA expression. Moreover, MDH1, the target of several deregulated microRNAs, is repressed in glioblastomas, making an intramitochondrial-NAD reduction mediated by the mitochondrial aspartate-malate shuttle unlikely. Understanding the connections between microRNAs and bioenergetic pathways in gliomas may lead to identification of novel therapeutic targets.

Targeting miR-375 in gastric cancer

INTRODUCTION

Gastric cancer remains a major cancer burden in the world, with a poor 5-year survival rate. It is necessary to develop new effective therapeutic strategies to improve the long-term clinical outcome. MicroRNA (miRNA), a class of small non-coding RNA, has been identified as a key regulator of gene expression, and is implicated in the pathogenesis of gastric cancer.

AREAS COVERED

This review summarizes the role of miRNAs in gastric carcinogenesis, with an emphasis on the expression and function of miR-375 in gastric cancer and beyond. It also discusses the opportunities and challenges of miR-375 as a potential therapeutic target for gastric cancer. The genes targeted by miR-375, including JAK2 and 3'-phosphoinositide dependent protein kinase-1 (PDK1), are also candidates for gastric cancer therapy.

EXPERT OPINION

Although radical surgery and rational chemotherapy are still the main treatment for gastric cancer, targeting miRNAs, in combination with other conventional therapies, may serve as a promising therapy strategy to improve the clinical outcome.

miRNA expression profiling of mycosis fungoides

MicroRNAs (miRNAs) are small RNA species that regulate gene expression post-transcriptionally and are aberrantly expressed in many malignancies including lymphoma. However, the role of miRNAs in the pathogenesis of T-cell lymphoid malignancies is poorly understood. Previously we examined the miRNA profile of Sézary syndrome (Sz), a leukemia of skin-homing memory T cells. In this study we determined the complete miRNome of mycosis fungoides (MF), the most common type of cutaneous T cell lymphoma. The miRNA profile of skin biopsies from 19 patients with tumor stage MF and 12 patients with benign inflammatory dermatoses (eczema and lichen planus) were compared by microarray analysis. We identified 49 miRNAs that are differentially expressed in tumor stage MF compared to benign inflammatory dermatoses using ANOVA analysis (P < 0.05, Benjamini-Hochberg corrected). The majority of the differentially expressed miRNAs (30/49) were up-regulated in tumor stage MF. The most significant differentially expressed were miR-155 and miR-92a (both up-regulated in tumor stage MF), while miR-93 showed the highest up-regulation in tumor stage MF with a fold difference of 5.8. Differential expression of a selection of these miRNAs was validated by miRNA-Q-PCR on additional test groups (tumors and controls). None of the miRNAs up-regulated in tumor stage MF was previously shown to be up-regulated in Sz, and only 2 of the 19 miRNAs down-regulated in tumor stage MF were also down-regulated in Sz. Taken together this report is the first describing the miRNA signature of tumor stage MF.

Expression of CD44 3'-untranslated region regulates endogenous microRNA functions in tumorigenesis and angiogenesis

The non-coding 3'-untranslated region (UTR) plays an important role in the regulation of microRNA (miRNA) functions, since it can bind and inactivate multiple miRNAs. Here, we show the 3'-UTR of CD44 is able to antagonize cytoplasmic miRNAs, and result in the increased translation of CD44 and downstream target mRNA, CDC42. A series of cell function assays in the human breast cancer cell line, MT-1, have shown that the CD44 3'-UTR inhibits proliferation, colony formation and tumor growth. Furthermore, it modulated endothelial cell activities, favored angiogenesis, induced tumor cell apoptosis and increased sensitivity to Docetaxel. These results are due to the interaction of the CD44 3'-UTR with multiple miRNAs. Computational algorithms have predicted three miRNAs, miR-216a, miR-330 and miR-608, can bind to both the CD44 and CDC42 3'-UTRs. This was confirmed with luciferase assays, western blotting and immunohistochemical staining and correlated with a series of siRNA assays. Thus, the non-coding CD44 3'-UTR serves as a competitor for miRNA binding and subsequently inactivates miRNA functions, by freeing the target mRNAs from being repressed.

Expression of versican 3'-untranslated region modulates endogenous microRNA functions

Background

Mature microRNAs (miRNAs) are single-stranded RNAs that regulate post-transcriptional gene expression. In our previous study, we have shown that versican 3′UTR, a fragment of non-coding transcript, has the ability to antagonize miR-199a-3p function thereby regulating expression of the matrix proteins versican and fibronectin, and thus resulting in enhanced cell-cell adhesion and organ adhesion. However, the impact of this non-coding fragment on tumorigenesis is yet to be determined.

Methods and Findings

Using computational prediction confirmed with in vitro and in vivo experiments, we report that the expression of versican 3′UTR not only antagonizes miR-199a-3p but can also lower its steady state expression. We found that expression of versican 3′UTR in a mouse breast carcinoma cell line, 4T1, decreased miR-199a-3p levels. The decrease in miRNA activity consequently translated into differences in tumor growth. Computational analysis indicated that both miR-199a-3p and miR-144 targeted a cell cycle regulator, Rb1. In addition, miR-144 and miR-136, which have also been shown to interact with versican 3′UTR, was found to target PTEN. Expression of Rb1 and PTEN were up-regulated synergistically in vitro and in vivo, suggesting that the 3′UTR binds and modulates miRNA activities, freeing Rb1 and PTEN mRNAs for translation. In tumor formation assays, cells transfected with the 3′UTR formed smaller tumors compared with cells transfected with a control vector.

Conclusion

Our results demonstrated that a 3′UTR fragment can be used to modulate miRNA functions. Our study also suggests that miRNAs in the cancer cells are more susceptible to degradation, due to its interaction with a non-coding 3′UTR. This non-coding component of mRNA may be used retrospectively to modulate miRNA activities.