miR Cluster Research Articles

MiR18a and miR19a Recruit Specific Proteins for Splicing in Thyroid Cancer Cells.

Thyroid cancer is one of the most frequent types of endocrine cancers. In most cases, thyroid cancers are caused by deregulated miRNA expression, especially involving the miR17-92 cluster. miR17-92 transcription is altered in several different tumor types including lymphoma, leukemia, and of the breast and thyroid. As an intronic cluster, miR17-92 must be processed during splicing and therefore interaction between microprocessor and spliceosome machineries is of major importance in understanding its expression. We investigated the protein composition of spliceosomes assembled on pre-RNAs containing intronic miR18a and miR19a, components of the miR17-92 cluster, using mass spectrometry. Interestingly, we observed that proteins associated with intronic miR18a and miR19a are cell-specific, and are similar for both miRNAs analyzed. The only exception is the group of heterogeneous nuclear proteins that are commonly recruited by different cells. miRNA processing depends on cell-specific proteins and heterogeneous nuclear proteins have a general role in miRNA processing from introns.

Down-regulation of traditional oncomiRs in plasma of breast cancer patients.

Deregulated expression of microRNAs has the oncogenic or tumor suppressor function in cancer. Since miRNAs in plasma are highly stable, their quantification could contribute to more precise cancer diagnosis, prognosis and therapy prediction. We have quantified expression of seven oncomiRs, namely miR-17/92 cluster (miR-17, miR-18a, miR-19a and miR-20a), miR-21, miR-27a and miR-155, in plasma of 137 breast cancer (BC) patients. We detected down-regulation of six miRNAs in patients with invasive BC compared to controls; however, only miR-20a and miR-27a down-regulations were statistically significant. Comparing miRNA expression between early and advanced stages of BC, we observed statistically significant decrease of miR-17 and miR-19a. We identified down-regulation of miR-17 and miR-20a in patients with clinical parameters of advanced BC (lymph node metastasis, tumor grade 3, circulating tumor cells, higher Ki-67-related proliferation, hormone receptor negativity and HER2 amplification), when compared to controls. Moreover, decreased level of miR-17 was found from low to high grade. Therefore, miR-17 could represent an indicator of advanced BC. Down-regulated miR-27a expression levels were observed in all clinical categories regardless of tumor progression. Hence, miR-27a could be used as a potential diagnostic marker for BC. Our data indicates that any changes in miRNA expression levels in BC patients in comparison to controls could be highly useful for cancer-associated pathology discrimination. Moreover, dynamics of miRNA expression changes could be used for BC progression monitoring.

MiR-290 contributes to the low abundance of cyclin D1 protein in mouse embryonic stem cells.

Mouse miR-290 cluster miRNAs are expressed specifically in early embryos and embryonic germ cells. These miRNAs play critical roles in the maintenance of pluripotency and self-renewal. Here, we showed that Cyclin D1 is a direct target gene of miR-290 cluster miRNAs. Negative relationships between the expression of Cyclin D1 protein and miR-290 cluster miRNAs in pluripotent and non-pluripotent cells, as well as in differentiating CGR8 cells were observed. Inhibition of miR-290 cluster miRNAs could arrest cells at the G1 phase and slow down the cell proliferation in CGR8 mouse stem cells. Since miR-290 cluster miRNAs are the most dominant stem-cell-specific miRNAs, our results revealed an important cause for the absence of Cyclin D1 in mouse embryonic stem cells.

Abstract LB-325: Tumor suppressor effects of miR-17-92a cluster miRNAs on prostate cancer

Abstract MicroRNAs in miR-17-92a cluster are transcribed from a polycistronic transcription unit C13orf25 that generates six mature miRNAs, miR-17, miR-18a, miR-19a, miR- 19b, miR-20a. These miRNAs are reported to be overexpressed in colon and lung cancers, however, we noted a loss of expression of all members of this miR cluster in prostate cancer tissues compared to uninvolved tissues and in aggressive prostate cancer cells. In this study, we show that replenishment of miR-17-92a cluster as a whole showed antiproliferative effects, reduced activation of AKT and MAP kinases, delayed tumorigenicity and reduced tumor growth. Analysis of the expression of mRNA targets showed reduced expression of cell cycle regulatory proteins cyclin D1 and SSH1; and LIMK1 and FGD4 of RhoGTPase signaling pathway through direct targeting. miR-17-92 cluster expression also inhibited EMT via reduced cell migration and expression of mesenchymal markers while elevating expression and surface localization of the epithelial marker E-Cadherin. miR-17-92a miRNAs improved sensitivity of androgen dependent LNCaP 104-S prostate cancer cells to anti-androgen drug Casodex, AKT inhibitor MK-2206 2HCl, and docetaxel. The androgen refractory PC-3 cells also showed increased sensitivity to docetaxel, MK-2206 2HCl and Aurora kinase inhibitor VX680 upon ectopic expression of miR-17-92a cluster miRNAs. RNA seq analysis of prostate cancer cells expressing miR-17-92a cluster revealed altered expression of a number of oncogenic and tumor suppressor mRNAs, and noncoding RNAs, which may have implications in the altered phenotype of these cells. Our data demonstrate a tumor suppressor effect of miR-17-92a cluster miRNAs in prostate cancer cells and restoration of expression of these miRNAs has a therapeutic benefit for both androgen-dependent and -independent prostate cancer cells. Note: This abstract was not presented at the meeting. Citation Format: Ratna Chakrabarti, Richard Ottman, Md Faqrul Hasan. Tumor suppressor effects of miR-17-92a cluster miRNAs on prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-325. doi:10.1158/1538-7445.AM2017-LB-325

195 Crispr/cas9 gene editing reveals novel tertiary constraints in clustered mirna processing

IntroductionMicroRNAs (miRNAs) play an important role in the cellular function. They often form families, with members sharing high sequence homology, a property that hampers miRNA research as there is a...

Micromanaging lupus nephritis: miR17-92 modulates TFH development and regulatory T cell activity

Abstract T follicular helper (TFH) cell provide crucial growth signals to germinal center (GC) B cells supporting antibody production. Tight control of TFH numbers maintains self-tolerance. Regulatory T (Treg) cells play a critical role in maintaining self-tolerance and controlling the magnitude of physiologic immune response. The Treg transcription factor forkhead box P3 (Foxp3) works in concert with other co-regulator molecules to determine suppressive phenotype of Treg. Compiling evidence show that aberrant TFH, GC responses and deficiencies of Treg are associated with systemic lupus erythematous and autoantibody production. We induce pristane nephropathy on T cell specific miR-17–92 knockout (miR-17–92−/−) mice. Mir17-92 T cell specific deficiency mitigates pristane induced-lupus nephropathy in mice. The mice showed less TFH cells, less GC B cells and lower autoantibody formation. Consistent with the reduction in autoantibody production, histological analysis revealed a lower mean renal histopathology score and less compliment deposition. We demonstrate that the miR17-92 cluster regulates TFH development by targeting Akt pathway. Moreover, miR17-92 mitigate the suppression function of Tregs by targeting Foxp3 co-regulators. Ectopic expression of miR17-92 downmodulates the suppression functions of Tregs and provides Tregs with partial effector activity via de-repression of cytokine genes. Our studies suggest that miR17-92 modulates lupus activity through critical regulation in TFH and Treg, unveiling the future therapeutic potential of microRNA manipulation in lupus nephritis.

A mouse model of MYCN-driven retinoblastoma reveals MYCN-independent tumor reemergence.

The most frequent focal alterations in human retinoblastoma are mutations in the tumor-suppressor gene retinoblastoma (RB) and amplification of the oncogene MYCN. Whether MYCN overexpression drives retinoblastoma has not been assessed in model systems. Here, we have shown that Rb inactivation collaborates strongly with MYCN overexpression and leads to retinoblastoma in mice. Overexpression of human MYCN in the context of Rb inactivation increased the expression of MYC-, E2F-, and ribosome-related gene sets, promoted excessive proliferation, and led to retinoblastoma with anaplastic changes. We then modeled responses to MYCN-directed therapy by suppressing MYCN expression in MYCN-driven retinoblastomas. Initially, MYCN suppression led to proliferation arrest and partial tumor regression with loss of anaplasia. However, over time, retinoblastomas reemerged, typically without reactivation of human MYCN or amplification of murine Mycn. A subset of returning retinoblastomas showed genomic amplification of a Mycn target gene encoding the miR cluster miR-17~92, while most retinoblastomas reemerged without clear genetic alterations in either Mycn or known Mycn targets. This Rb/MYCN model recapitulates key genetic driver alterations seen in human retinoblastoma and reveals the emergence of MYCN independence in an initially MYCN-driven tumor.

Abstract 141: The Microrna 17-92 Cluster in Neural Progenitor Cells is Required for Stroke-induced Neurogenesis and Gliogenesis

Background: Molecular mechanisms underlying stroke-induced neurogenesis have not been fully investigated. The microRNA 17-92 cluster (miR17-92) regulates proliferation and differentiation of adult neural progenitor cells (NPCs). The present study investigated whether the miR17-92 cluster in NPCs is required for stroke-induced neurogenesis. Methods and Results: Mice with inducible and conditional knockdown of the miR17-92 cluster in nestin lineage NPCs (nestin-CreER T2 /miR17-92 -/- , 17-92-cKO, n=9) and wild-type litters (WT, n=9) were treated by tamoxifen. Administration of tamoxifen resulted in more than 60% reduction of individual members of the miR-17-92 cluster (miR-17: 1.0 vs 0.4; miR-19a: 1.0 vs 0.3; miR-19b: 1.0 vs 0.2; miR-20a: 1.0 vs 0.4; miR-92a: 1.0 vs 0.4 fold in WT, p<0.05) in NPCs localized to the subventricular zone (SVZ). Two days after termination of tamoxifen treatment, these mice were subjected to permanent right middle cerebral artery occlusion (MCAO) and sacrificed 28 days post-MCAo. Compared to WT mice, 17-92-cKO mice exhibited significant (p<0.05) reduction of proliferation of NPCs measured by the number of Ki67 + cells (226±43 vs 471±100 cells/mm 2 ) and the number of DCX + neuroblasts (11±2% vs 24±4% ) in the ischemic SVZ. Cultured NPCs harvested from ischemic cKO mice showed significant (p<0.05) reduction of BrdU + cells (37±2% vs 61±4% WT , n=3/group), Tuj1 + neuroblasts (5±0.2% vs 9±0.4% ), GFAP + cells (33±3% vs 53±2% ), and NG2 + oligodendrocyte progenitor cells (OPCs, 3±0.1% vs 5±0.5%). These in vivo and in vitro data indicate that reduction of the miR17-92 cluster suppresses stroke-induced neurogenesis and gliogenesis. Western blot analysis showed that miR17-92 cKO significantly (p<0.05) increased and reduced a cytoskeleton-associated protein, Enigma homolog1 (ENH1, 1.6 vs 1.0 fold), and its down-stream transcription factor, inhibitor of differentiation1 (ID1, 1.0 vs 0.6 fold), respectively. ENH1 is a putative target of the miR17-92 cluster. Conclusion: Our data indicate that the miR17-92 cluster in adult nestin lineage NPCs is required for stroke-induced neurongenesis and gliogenesis, and that the miR17-92 cluster possibly targets ENH1/ID1 signaling.

Expression of oncogenic miR-17-92 and tumor suppressive miR-143-145 clusters in basal cell carcinoma and cutaneous squamous cell carcinoma

BackgroundA variety of cancers are associated with the expression of the oncogenic miR-17-92 cluster (Oncomir-1) and tumor suppressor miR-143-5p/miR-145-5p. Epidermal skin cancer has not been investigated for the expression of miR-17-92 and miR-143-145 clusters, despite being extensively studied regarding global microRNA profiles. The goal of this study was to investigate the expression and possible correlation of expression of miR17-92 and miR-143-145 cluster members in epidermal skin cancer. MethodsWe evaluated punch biopsies from patients with cutaneous squamous cell carcinoma (cSCC, n=15) and basal cell carcinoma (BCC, n=16), along with control specimens from non-lesional epidermal skin (n=16). Expression levels of the miR17-92 cluster (including miR-17-5p, miR-17-3p, miR-18a-3p, miR-18a-5p, miR-19a-3p, miR-19a-5p, miR-19b-3p, miR-19b-1-5p, miR-20a-3p, miR-20a-5p, miR-92a-3p, and miR-92a-5p) and the tumor-suppressive cluster miR-143-145 (including miR-143-5p and miR-145-5p) were detected by quantitative real-time reverse transcriptase polymerase chain reaction. ResultsWe noted a highly significant increased expression of the miR-17-92 members miR-17-5p, miR-18a-5p, miR19a-3p, and miR-19b-3p and tumor suppressor miR-143-5p (p<0.01) in cSCC. miR-145-5p had a significantly decreased expression (p<0.05) for in BCC. A correlation analysis revealed multiple correlating miRNA-pairs within and between the investigated clusters. ConclusionThis study marks the first evidence for the participation of members of the miR-17-92 cluster in cSCC and miR-143-145 cluster in BCC.

A MicroRNA Cluster miR-23-24-27 Is Upregulated by Aldosterone in the Distal Kidney Nephron Where it Alters Sodium Transport.

The epithelial sodium channel (ENaC) is expressed in the epithelial cells of the distal convoluted tubules, connecting tubules, and cortical collecting duct (CCD) in the kidney nephron. Under the regulation of the steroid hormone aldosterone, ENaC is a major determinant of sodium (Na+ ) and water balance. The ability of aldosterone to regulate microRNAs (miRs) in the kidney has recently been realized, but the role of miRs in Na+ regulation has not been well established. Here we demonstrate that expression of a miR cluster mmu-miR-23-24-27, is upregulated in the CCD by aldosterone stimulation both in vitro and in vivo. Increasing the expression of these miRs increased Na+ transport in the absence of aldosterone stimulation. Potential miR targets were evaluated and miR-27a/b was verified to bind to the 3'-untranslated region of intersectin-2, a multi-domain protein expressed in the distal kidney nephron and involved in the regulation of membrane trafficking. Expression of Itsn2 mRNA and protein was decreased after aldosterone stimulation. Depletion of Itsn2 expression, mimicking aldosterone regulation, increased ENaC-mediated Na+ transport, while Itsn2 overexpression reduced ENaC's function. These findings reinforce a role for miRs in aldosterone regulation of Na+ transport, and implicate miR-27 in aldosterone's action via a novel target. J. Cell. Physiol. 232: 1306-1317, 2017. © 2016 Wiley Periodicals, Inc.

The eutheria-specific miR-290 cluster modulates placental growth and maternal-fetal transport.

The vertebrate-specific ESCC microRNA family arises from two genetic loci in mammals: miR-290/miR-371 and miR-302. The miR-302 locus is found broadly among vertebrates, whereas the miR-290/miR-371 locus is unique to eutheria, suggesting a role in placental development. Here, we evaluate that role. A knock-in reporter for the mouse miR-290 cluster is expressed throughout the embryo until gastrulation, when it becomes specifically expressed in extraembryonic tissues and the germline. In the placenta, expression is limited to the trophoblast lineage, where it remains highly expressed until birth. Deletion of the miR-290 cluster gene (Mirc5) results in reduced trophoblast progenitor cell proliferation and a reduced DNA content in endoreduplicating trophoblast giant cells. The resulting placenta is reduced in size. In addition, the vascular labyrinth is disorganized, with thickening of the maternal-fetal blood barrier and an associated reduction in diffusion. Multiple mRNA targets of the miR-290 cluster microRNAs are upregulated. These data uncover a crucial function for the miR-290 cluster in the regulation of a network of genes required for placental development, suggesting a central role for these microRNAs in the evolution of placental mammals.

Targeting BET Bromodomains in Pre-Clinical Models of Burkitt Lymphoma

Background: Burkitt lymphoma (BL) is the most common NHL type in children. Although treatment for pediatric BL has improved significantly, there is an urgent need for novel therapies that reduce the toxicity of modern treatment regimens and improve on the dismal survival observed in the relapsed/refractory setting where only about 20-30% of patients survive their disease. Recent reports have implicated co-activation of c-Myc and PI3K in Burkitt lymphomagenesis. Genomic analysis of recurrent oncogenic mutations in BL have identified tonic B-cell receptor signaling and the over-expression of Myc induced microRNAs from the MIR17-92 family, e.g. mir17 and mir19, as possible mechanisms of PI3K activation in BL. Mir17 and mir19, have been implicated in Burkitt lymphomagenesis and their overexpression may be associated with a higher risk of relapse. The protein phosphatase and tensin homolog (PTEN) is a major regulator of PI3K pathway activation. MIR17-92 cluster members have been shown to target PTEN leading to increased PI3K activation. We have previously identified increased expression of mir17 and mir19 along with increased activation of AKT in cell line models of chemotherapy resistant BL suggesting a potential mechanism for increased resistance. BET bromodomains interact with chromatin and enhance transcriptional activation of numerous genes including c-Myc. Thus, BET bromodomains represent a promising target in BL. To investigate the effects of inhibition of c-Myc driven activation of the PI3K/AKT/mTOR pathway, we characterized the activity of the highly potent small molecule bromodomain inhibitor JQ1 in chemotherapy sensitive and resistant BL cell lines. Additionally, we analyzed the ability to enhance anti-lymphoma activity of PI3K/Akt/mTOR pathway inhibition in BL by the combination of BET bromodomain inhibition and targeted inhibition of the PI3K/AKT/mTOR pathway.Methods: The in vitro activity of JQ1 was investigated in the BL cell lines Raji, Raji 4RH (chemotherapy-rituximab resistant), Raji 8RH (rituximab resistant), Ramos, and Daudi. Cell Viability following exposure to JQ1 alone and in combination with the PI3K/mTOR inhibitor omipalisib (GSK458)) was analyzed using Cell-Titer Glo or Alamar Blue assays following 24, 48, and 72 hour exposure over a range of inhibitor concentrations. Induction of apoptosis was analyzed using western blotting for cleaved PARP. C-Myc expression following JQ1 exposure was determined by western blot following 48 hour JQ1 exposure. The effect of JQ1 exposure on the expression of c-Myc induced microRNA expression was determined by qRT-PCR in cells exposed to JQ1 for 48hours. Synergy of combination exposures was determined using CalcuSyn to generate combination index (CI) values.Results: In vitro exposure of BL cell lines to JQ1 for 24, 48, and 72 hours resulted in a significant dose and time dependent decrease in viable cells (72 hour IC50 values: Raji 0.12µM, Raji 4RH 1.7µM, Raji 8RH 0.7µM, Ramos 0.22µM and Daudi 4µM). There was an increase in cleaved PARP after 72 hour exposure indicating induction of apoptosis. While single agent effect was seen in the resistant Raji 4RH cell line, activity was noted to primarily occur at the higher end of the dosing. Western blot analysis demonstrated a reduction in c-Myc expression following exposure to JQ1 1µM for 24 hours (relative band intensity normalized to control: Raji=0.12, Raji 4RH=0.18, Raji 8RH=0.11). qPCR showed a reduction in Mir17 relative transcription levels after 48 hours of exposure to JQ1 2.5mM (relative expression compared to control: Raji=0.72, Raji 4RH=0.98, Raji 8RH=0.83, Ramos=0.57, Daudi=0.46). When combined with omipalisib, an increased effect on cell viability was noted. The combination effect was noted to be synergistic (CI<0.9) at multiple dose combinations while other combinations exhibited primarily additive effects.Conclusion: In vitro inhibition of BET bromodomains with JQ1 results in a decrease in c-Myc expression and a decrease in c-Myc dependent miR expression with impaired proliferation and induction of apoptosis in chemotherapy-sensitive and -resistant BL cell lines. Augmented, and in some cases synergistic, activity is also noted with dual inhibition of BET bromodomains and the PI3K/Akt/mTOR pathway in BL cell lines. DisclosuresNo relevant conflicts of interest to declare.

MiR Cluster 143/145 Directly Targets Nrl and Regulates Rod Photoreceptor Development.

Retinal histogenesis requires coordinated and temporal functioning of factors by which different cell types are generated from multipotent progenitors. Development of rod photoreceptors is regulated by multiple transcription factors, and Nrl is one of the major factors involved in their fate specification. Presence or absence of Nrl at the postnatal stages decides the generation of cone photoreceptors or other later retinal cells. This suggests the need for regulated expression of Nrl in order to accelerate the generation of other cell types during retinal development. We found that miR cluster 143/145, comprising miR-143 and miR-145, targets and imparts a posttranscriptional inhibition of Nrl. Expression of both miRNAs was differentially regulated during retinal development and showed least expression at PN1 stage in which most of the rod photoreceptors are generated. Downregulation of rod photoreceptor regulators and markers upon miR cluster 143/145 overexpression demonstrated that this cluster indeed negatively regulates rod photoreceptors. Further, we prove that Nrl positively regulates miR cluster 143/145, thus establishing a feedback loop regulatory mechanism. This may be one possible mechanism by which Nrl is posttranscriptionally regulated to facilitate the generation of other cell types in retina.

Multimodal tumor suppression by miR-302 cluster in melanoma and colon cancer

The miR-302 family is one of the main groups of microRNAs, which are highly expressed in embryonic stem cells (ESCs). Previous reports have indicated that miR-302 can reduce the proliferation rate of some cancer cells while compromising on their oncogenic potential at the same time without having the same effect on normal somatic cells. In this study we aimed to further investigate the role of the miR-302 cluster in multiple cancer signaling pathways using A-375 melanoma and HT-29 colorectal cancer cells. Our results indicate that the miR-302 cluster has the potential to modulate oncogenic properties of cancer cells through inhibition of proliferation, angiogenesis and invasion, and through reversal of the epithelial-to-mesenchymal transition (EMT) in these cells. We showed for the first time that overexpression of miR-302 cluster sensitized A-375 and HT-29 cells to hypoxia and also to the selective BRAF inhibitor vemurafenib. MiR-302 is a pleiotropically acting miRNA family which may have significant implications in controlling cancer progression and invasion. It acts through a reprogramming process, which has a global effect on a multitude of cellular pathways and events. We propose that reprogramming of cancer cells by epigenetic factors, especially miRNAs might provide an efficient tool for controlling cancer and especially for those with more invasive nature.

Inhibition of microRNA-495 Enhances Therapeutic Angiogenesis of Human Induced Pluripotent Stem Cells.

Therapeutic angiogenesis has emerged as a promising strategy to regenerate the damaged blood vessels resulting from ischemic diseases such as myocardial infarction (MI). However, the functional integration of implanted endothelial cells (ECs) in infarcted heart remains challenging. We herein develop an EC generation approach by inhibiting microRNA-495 (miR-495) in human induced pluripotent stem cells (hiPSCs) and assess the angiogenic potential for MI treatment. The anti-angiogenic miR-495 belonging to Dlk1-Dio3 miR cluster was identified through expression profiling and computational analysis. Loss-of-function experiments for miR-495 were performed using a lentiviral transfer of antisense sequence in hiPSCs. The pluripotency of hiPSCs was not impacted by the genetic modification. Induced with differentiation medium, miR-495 inhibition enhanced the expression of EC genes of hiPSCs, as well as the yield of ECs. Newly derived ECs displayed prominent angiogenic characteristics including tube formation, cell migration, and proliferation. Mechanistically, miR-495 mediated the expression of endothelial or angiogenic genes by directly targeting vascular endothelial zinc finger 1. After transplantation in immunodeficient MI mice, the derived ECs significantly increased neovascularization in the infarcted heart, prevented functional worsening, and attenuated expansion of infarct size. The functional integration of the implanted ECs into coronary networks was also enhanced by inhibiting miR-495. miR-495 represents a new target not only for promoting EC generation from hiPSCs but also for enhancing angiogenesis and engraftment of hiPSC-derived ECs in ischemic heart. Stem Cells 2017;35:337-350.

MiRNA in Macrophage Development and Function.

MicroRNAs (miRNAs) control cellular gene expression via primarily binding to 3' or 5' untranslated region of the target transcript leading to translational repression or mRNA degradation. In most cases, miRNAs have been observed to fine-tune the cellular responses and, therefore, act as a rheostat rather than an on/off switch. Transcription factor PU.1 is a master switch that controls monocyte/macrophage development from hematopoietic stem cells. Recent Advances: PU.1 induces a specific set of miRNAs while suppressing the miR17-92 cluster to regulate monocyte/macrophage development. In addition to development, miRNAs tightly control the macrophage polarization continuum from proinflammatory M1 or proreparative M2 by regulating expression of key transcription factors involved in the process of polarization. miRNAs are intricately involved with fine-tuning fundamental macrophage functions such as phagocytosis, efferocytosis, inflammation, tissue repair, and tumor promotion. Macrophages are secretory cells that participate in intercellular communication by releasing regulatory molecules and microvesicles (MVs). MVs are bilayered lipid membranes packaging a hydrophilic cargo, including proteins and nucleic acids. Macrophage-derived MVs carry functionally active miRNAs that suppress gene expression in target cells via post-transcriptional gene silencing, thus regulating cell function. In summary, miRNAs fine-tune several major facets of macrophage development and function. Such fine-tuning is critical in preventing exaggerated macrophage response to endogenous or exogenous stimuli. A critical role of miRNAs in the regulation of innate immune response and macrophage biology, including development, differentiation, and activation, has emerged. A clear understanding of such regulation on macrophage function remains to be elucidated. Antioxid. Redox Signal. 25, 795-804.

Systematic Review of Micro-RNA Expression in Pre-Eclampsia Identifies a Number of Common Pathways Associated with the Disease.

BackgroundPre-eclampsia (PE) is a complex, multi-systemic condition of pregnancy which greatly impacts maternal and perinatal morbidity and mortality. MicroRNAs (miRs) are differentially expressed in PE and may be important in helping to understand the condition and its pathogenesis.MethodsCase-control studies investigating expression of miRs in PE were collected through a systematic literature search. Data was extracted and compared from 58 studies to identify the most promising miRs associated with PE pathogenesis and identify areas of methodology which could account for often conflicting results.ResultsSome of the most frequently differentially expressed miRs in PE include miR-210, miR-223 and miR-126/126* which associate strongly with the etiological domains of hypoxia, immunology and angiogenesis. Members of the miR-515 family belonging to the imprinted chromosome 19 miR cluster with putative roles in trophoblast invasion were also found to be differentially expressed. Certain miRs appear to associate with more severe forms of PE such as miR-210 and the immune-related miR-181a and miR-15 families. Patterns of miR expression may help pinpoint key pathways (e.g. IL-6/miR-223/STAT3) and aid in untangling the heterogeneous nature of PE. The detectable presence of many PE-associated miRs in antenatal circulatory samples suggests their usefulness as predictive biomarkers. Further progress in ascertaining the clinical value of miRs and in understanding how they might contribute to pathogenesis is predicated upon resolving current methodological challenges in studies. These include differences in diagnostic criteria, cohort characteristics, sampling technique, RNA isolation and platform-dependent variation in miR profiling.ConclusionReviewing studies of PE-associated miRs has revealed their potential as informants of underlying target genes and pathways relating to PE pathogenesis. However, the incongruity in results across current studies hampers their capacity to be useful biomarkers of the condition.

Abstract 1960: Identification of differentially expressed miRNAs of breast cancer among African American and European American women

Abstract African American (AA) women are more likely than European American (EA) women to be diagnosed with aggressive, estrogen receptor (ER) negative breast cancer. Differences in microRNA (miRNA) expression patterns have not been well studied as potential mechanisms underlying this racial disparity. In this study, we performed a whole-genome miRNA expression profiling in 58 (29 AA and 29 EA) fresh-frozen breast tumors, with clinical characteristics (e.g., ER status, histological grade, stage) comparable between AA and EA samples, and in 10 (5 AA and 5 EA) normal breast tissues obtained from women undergoing reduction mammoplasty, with pathology determined free from any abnormalities. Unsupervised hierarchical clustering showed that miRNA expression patterns clearly distinguish breast cancer from normal breast tissue. In tumors, a number of miRNAs are significantly differentially expressed, i.e., DEmiRs defined as &amp;gt;2-fold change in expression and FDR&amp;lt;0.05, between tumor subtypes and by race. We identified 61 DEmiRs between ER negative and ER positive breast tumors; of these, 14 miRNAs were differentially expressed regardless of race; 29 miRNAs were specific in EA tumors only; and 18 were in AA samples only. Specifically, the top most differentially expressed miRNAs from EA women include: several members of miR-17-92 cluster (miR-17,-18a,-19a, -20a), miR-508, -509,and -514a that are up-regulated, and miR-1, -133a, -133b, and -206, which are down-regulated, in ER negative compared to ER positive tumors. In AA women, however, up-regulated miRNAs include miR-105, -106b, -135b, and -520b; down-regulated ones include miR-216a, -217, -1303, and -378a. We also identified 14 DEmiRs between AA and EA tumor samples, with 5 miRNAs specific in ER- tumors, such as miR-9, -106b, and 9 miRNAs in ER+ tumors, such as miR-1, -133a, -133b, and -206. Further, several of these miRNAs, such as miR-17, miR-18a, miR-133a, miR-206, miR-9, have been shown to regulate various target genes involved in apoptosis, cell cycle, invasion, or angiogenesis. We also found that several miRNAs, such as miR-1, -133a, -216a, are associated with improved or reduced recurrence-free or overall survival. In summary, in this genome-wide miRNA expression profiling analysis by next generation sequencing, our results suggest that miRNA expression patterns may differ by tumor subtypes between AA and EA breast samples. These initial results will provide the basis for the functional analysis of the identified miRNAs, and findings could contribute to a better understanding of the biology of breast cancer disparities and more targeted preventative and therapeutic strategies. Citation Format: Zhihong Gong, Dan Wang, Allyson Espinal, Qiang Hu, Xuan Peng, Lara Sucheston-Campbell, Li Tang, Jo Freudenheim, Peter Shields, Carl Morrison, Steven Belinsky, Song Liu, Kitaw Demissie, Michael Higgins, Christine Ambrosone. Identification of differentially expressed miRNAs of breast cancer among African American and European American women. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1960.

Abstract 1918: The role of miR17-92 in the miRegulatory landscape of Ewing sarcoma

Abstract MicroRNAs (miRNA) serve to fine-tune gene expression and thus play an important regulatory role in tissue specific gene networks. The identification and validation of miRNA target genes in a given tissue still poses a significant problem since the presence of a seed sequence in the 3′UTR of an mRNA and its expression modulation upon forced ectopic expression of the miRNA do not reliably predict regulation under physiological conditions. The chimeric oncoprotein EWS-FLI1 is the driving pathogenic force in ES. Recently, we reported on the EWS-FLI1 microRNA (miRNA) signature based on knockdown experiments in ES cell lines and on differential expression in primary tumors versus mesenchymal stem cells. Comparison of both datasets revealed the miR17-92 cluster to be the top EWS-FLI1 activated miRNA, which is one of the most potent oncogenic miRNAs. The whole cluster is among the small number of miRNAs down-regulated upon knockdown of EWS-FLI1 in multiple ES cell lines. We now report the use of a combination of AGO2 pull-down experiments by PAR-CLIP - to enrich and sequence RISC-associated RNAs - and of RNAseq upon miRNA depletion by ectopic sponge expression to identify the targetome of miR17-92 in Ewing sarcoma (ES) cells We found a significant enrichment of PAR-CLIP hits for members of the miR-17-92 cluster in the 3′UTRs of genes up-regulated in response to mir-17-92 but not miR9 and 10b specific sponge expression. Among them, we consistently identified known (i.e. CTGF, MXD1, CYLD1) and a multitude of so far unknown targets of the oncomir-1 cluster in ES in three PAR-CLIP experiments. Interestingly, approximately a quarter of these genes annotate to the TGFB/BMP pathway, the majority mapping downstream of SMAD signaling. Gene reporter assays using 3’UTRs of select novel candidate genes showed enhancement of luciferase activity upon transfection of a sponge specific to miR-17-92 and 20a, but not to unrelated miR-9 and 10b. Site directed mutagenesis of seed sequences in these 3’UTR confirmed the direct regulation of these genes by miR17-92. Current research focuses on the functional validation of TGFB pathway modulation by miR17-92. This study provides a paradigmatic approach to the comprehensive definition of the targetome for a defined group of miRNAs under physiological conditions. This study was supported by the 7th framework program of the European Commission (FP7-259348, “ASSET”) and the Austrian Science Fund FWF (24708-B21) Citation Format: Raphaela Schwentner, Maximilian Kauer, David Herrero-Martin, Heinrich Kovar. The role of miR17-92 in the miRegulatory landscape of Ewing sarcoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1918.

Distinct MicroRNA Expression Signatures of Porcine Induced Pluripotent Stem Cells under Mouse and Human ESC Culture Conditions.

It is well known that microRNAs play a very important role in regulating reprogramming, pluripotency and cell fate decisions. Porcine induced pluripotent stem cells (piPSCs) are now available for studying the pluripotent regulation network in pigs. Two types of piPSCs have been derived from human and mouse embryonic stem cell (ESC) culture conditions: hpiPSCs and mpiPSCs, respectively. The hpiPSCs were morphologically similar to human ESCs, and the mpiPSCs resembled mouse ESCs. However, our current understanding of the role of microRNAs in the development of piPSCs is still very limited. Here, we performed small RNA sequencing to profile the miRNA expression in porcine fibroblasts (pEFs), hpiPSCs and mpiPSCs. There were 22 differential expressed (DE) miRNAs down-regulated in both types of piPSCs compared with pEFs, such as ssc-miR-145-5p and ssc-miR-98. There were 27 DE miRNAs up-regulated in both types of piPSCs compared with pEFs. Among these up-regulated DE miRNAs in piPSCs, ssc-miR-217, ssc-miR-216, ssc-miR-142-5p, ssc-miR-182, ssc-miR-183 and ssc-miR-96-5p have much higher expression levels in mpiPSCs, while ssc-miR-106a, ssc-miR-363, ssc-miR-146b, ssc-miR-195, ssc-miR-497, ssc-miR-935 and ssc-miR-20b highly expressed in hpiPSCs. Quantitative stem-loop RT-PCR was performed to confirm selected DE miRNAs expression levels. The results were consistent with small RNA sequencing. Different expression patterns were observed for key miRNA clusters, such as the miR-17-92 cluster, the let-7 family, the miR-106a-363 cluster and the miR-182-183 cluster, in the mpiPSCs and hpiPSCs. Novel miRNAs were also predicted in this study, including a putative porcine miR-302 cluster: ssc_38503, ssc_38503 and ssc_38501 (which resemble human miR-302a and miR-302b) found in both types of piPSCs. The miR-106a-363 cluster and putative miR-302 cluster increased the reprogramming efficiency of pEFs. The study revealed significant differences in the miRNA signatures of hpiPSCs and mpiPSCs under different pluripotent states that were derived from different culture conditions. These differentially expressed miRNAs may play important roles in pluripotent regulation in pigs, and this information will facilitate the understanding of the mechanism of pluripotency in pigs.