Hsa-mir-145 is the top EWS-FLI1-repressed microRNA involved in a positive feedback loop in Ewing's sarcoma

A logical model of Ewing sarcoma cell epithelial-to-mesenchymal transition supports the existence of hybrid cellular phenotypes

Ewing sarcoma (ES) is a highly aggressive pediatric tumor driven by the RNA-binding protein EWS (EWS)/friend leukemia integration 1 transcription factor (FLI1) chimeric transcription factor, which is involved in epithelial-mesenchymal transition (EMT). EMT stabilizes a hybrid cell state, boosting metastatic potential and drug resistance. Nevertheless, the mechanisms underlying the maintenance of this hybrid phenotype in ES remain elusive. Our study proposes a logical EMT model for ES, highlighting zinc finger E-box-binding homeobox 2 (ZEB2), miR-145, and miR-200 circuits that maintain hybrid states. The model aligns with experimental findings and reveals a previously unknown circuit supporting the mesenchymal phenotype. These insights emphasize the role of ZEB2 in the maintenance of the hybrid state in ES.

Oncomeric Profiles of microRNAs as New Therapeutic Targets for Treatment of Ewing's Sarcoma: A Composite Review

Ewing's sarcoma is a rare type of cancer that forms in bones and soft tissues in the body, affecting mostly children and young adults. Current treatments for ES are limited to chemotherapy and/or radiation, followed by surgery. Recently, microRNAs have shown favourable results as latent diagnostic and prognostic biomarkers in various cancers. Furthermore, microRNAs have shown to be a good therapeutic agent due to their involvement in the dysregulation of various molecular pathways linked to tumour progression, invasion, angiogenesis, and metastasis. In this review, comprehensive data mining was employed to explore various microRNAs that might have therapeutic potential as target molecules in the treatment of ES.

Ewing sarcoma from molecular biology to the clinic

In Europe, with an incidence of 7.5 cases per million, Ewing sarcoma (ES) is the second most common primary malignant bone tumor in children, adolescents and young adults, after osteosarcoma. Since the 1980s, conventional treatment has been based on the use of neoadjuvant and adjuvant chemotherapeutic agents combined with surgical resection of the tumor when possible. These treatments have increased the patient survival rate to 70% for localized forms, which drops drastically to less than 30% when patients are resistant to chemotherapy or when pulmonary metastases are present at diagnosis. However, the lack of improvement in these survival rates over the last decades points to the urgent need for new therapies. Genetically, ES is characterized by a chromosomal translocation between a member of the FET family and a member of the ETS family. In 85% of cases, the chromosomal translocation found is (11; 22) (q24; q12), between the EWS RNA-binding protein and the FLI1 transcription factor, leading to the EWS-FLI1 fusion protein. This chimeric protein acts as an oncogenic factor playing a crucial role in the development of ES. This review provides a non-exhaustive overview of ES from a clinical and biological point of view, describing its main clinical, cellular and molecular aspects.

Targeted Therapy for EWS-FLI1 in Ewing Sarcoma

Ewing sarcoma (EwS) is a rare and predominantly pediatric malignancy of bone and soft tissue in children and adolescents. Although international collaborations have greatly improved the prognosis of most EwS, the occurrence of macrometastases or relapse remains challenging. The prototypic oncogene EWS-FLI1 acts as an aberrant transcription factor that drives the cellular transformation of EwS. In addition to its involvement in RNA splicing and the DNA damage response, this chimeric protein directly binds to GGAA repeats, thereby modifying the transcriptional profile of EwS. Direct pharmacological targeting of EWS-FLI1 is difficult because of its intrinsically disordered structure. However, targeting the EWS-FLI1 protein complex or downstream pathways provides additional therapeutic options. This review describes the EWS-FLI1 protein partners and downstream pathways, as well as the related target therapies for the treatment of EwS.

Regulation of EWSR1-FLI1 Function by Post-Transcriptional and Post-Translational Modifications

Ewing sarcoma is the second most common bone tumor in childhood and adolescence. Currently, first-line therapy includes multidrug chemotherapy with surgery and/or radiation. Although most patients initially respond to chemotherapy, recurrent tumors become treatment refractory. Pathologically, Ewing sarcoma consists of small round basophilic cells with prominent nuclei marked by expression of surface protein CD99. Genetically, Ewing sarcoma is driven by a fusion oncoprotein that results from one of a small number of chromosomal translocations composed of a FET gene and a gene encoding an ETS family transcription factor, with ~85% of tumors expressing the EWSR1::FLI1 fusion. EWSR1::FLI1 regulates transcription, splicing, genome instability and other cellular functions. Although a tumor-specific target, EWSR1::FLI1-targeted therapy has yet to be developed, largely due to insufficient understanding of EWSR1::FLI1 upstream and downstream signaling, and the challenges in targeting transcription factors with small molecules. In this review, we summarize the contemporary molecular understanding of Ewing sarcoma, and the post-transcriptional and post-translational regulatory mechanisms that control EWSR1::FLI1 function.

The importance of fusion protein activity in Ewing sarcoma and the cell intrinsic and extrinsic factors that regulate it: A review

Accumulating evidence shows that despite clonal origins tumors eventually become complex communities comprised of phenotypically distinct cell subpopulations. This heterogeneity arises from both tumor cell intrinsic programs and signals from spatially and temporally dynamic microenvironments. While pediatric cancers usually lack the mutational burden of adult cancers, they still exhibit high levels of cellular heterogeneity that are largely mediated by epigenetic mechanisms. Ewing sarcomas are aggressive bone and soft tissue malignancies with peak incidence in adolescence and the prognosis for patients with relapsed and metastatic disease is dismal. Ewing sarcomas are driven by a single pathognomonic fusion between a FET protein and an ETS family transcription factor, the most common of which is EWS::FLI1. Despite sharing a single driver mutation, Ewing sarcoma cells demonstrate a high degree of transcriptional heterogeneity both between and within tumors. Recent studies have identified differential fusion protein activity as a key source of this heterogeneity which leads to profoundly different cellular phenotypes. Paradoxically, increased invasive and metastatic potential is associated with lower EWS::FLI1 activity. Here, we review what is currently understood about EWS::FLI1 activity, the cell autonomous and tumor microenvironmental factors that regulate it, and the downstream consequences of these activity states on tumor progression. We specifically highlight how transcription factor regulation, signaling pathway modulation, and the extracellular matrix intersect to create a complex network of tumor cell phenotypes. We propose that elucidation of the mechanisms by which these essential elements interact will enable the development of novel therapeutic approaches that are designed to target this complexity and ultimately improve patient outcomes.

The interaction between ETS transcription factor family members and microRNAs: A novel approach to cancer therapy

In cancer biology, ETS transcription factors promote tumorigenesis by mediating transcriptional regulation of numerous genes via the conserved ETS DNA-binding domain. MicroRNAs (miRNAs) act as posttranscriptional regulators to regulate various tumor-promoting or tumor-suppressing factors. Interactions between ETS factors and miRNAs regulate complex tumor-promoting and tumor-suppressing networks. This review discusses the progress of ETS factors and miRNAs in cancer research in detail. We focused on characterizing the interaction of the miRNA/ETS axis with competing endogenous RNAs (ceRNAs) and its regulation in posttranslational modifications (PTMs) and the tumor microenvironment (TME). Finally, we explore the prospect of ETS factors and miRNAs in therapeutic intervention. Generally, interactions between ETS factors and miRNAs provide fresh perspectives into tumorigenesis and development and novel therapeutic approaches for malignant tumors.

miR-214-3p Is Commonly Downregulated by EWS-FLI1 and by CD99 and Its Restoration Limits Ewing Sarcoma Aggressiveness

Simple Summary

Ewing’s sarcoma (EWS), the second most frequent primary tumor of bone in the pediatric population, is a very aggressive, undifferentiated mesenchymal malignancy with a high tendency to develop lung and/or bone metastasis. The prognosis of patients with metastasis remains dismal, and new strategies are needed to control the dissemination of EWS cells. EWS is driven by alterations induced by the EWS-FLI1 chimera which acts as an aberrant transcriptional factor that induces the complete reprograming of the gene expression. EWS cells are also characterized by high expression of CD99, a cell surface molecule that interacts with EWS-FLI1 to sustain EWS malignancy. This study shows that miR-214-3p is a common mediator of EWS-FLI1 and CD99, and we report that miR-214-3p acts as on oncosuppressor in EWS. MiR-214-3p is constitutively repressed in cell lines and clinical samples but is re-expressed after the silencing of EWS-FLI1 and/or CD99. The restoration of miR-214-3p limits EWS cell growth and migration and represses the expression of its target HMGA1, supporting the potential role of this miRNA as a marker of tumor aggressiveness.

Abstract

Ewing’s sarcoma (EWS), an aggressive pediatric bone and soft-tissue sarcoma, has a very stable genome with very few genetic alterations. Unlike in most cancers, the progression of EWS appears to depend on epigenetic alterations. EWS–FLI1 and CD99, the two hallmarks of EWS, are reported to severely impact the malignancy of EWS cells, at least partly by regulating the expression of several types of non-coding RNAs. Here, we identify miR-214-3p as a common mediator of either EWS-FLI1 or CD99 by in silico analysis. MiR-214-3p expression was lower in EWS cells and in clinical samples than in bone marrow mesenchymal stem cells, and this miRNA was barely expressed in metastatic lesions. Silencing of EWS-FLI1 or CD99 restored the expression of miR-214-3p, leading to a reduced cell growth and migration. Mechanistically, miR-214-3p restoration inhibits the expression of the high-mobility group AT-hook 1 (HMGA1) protein, a validated target of miR-214-3p and a major regulator of the transcriptional machinery. The decrease in HMGA1 expression reduced the growth and the migration of EWS cells. Taken together, our results support that the miR-214-3p is constitutively repressed by both EWS-FLI1 and CD99 because it acts as an oncosuppressor limiting the dissemination of EWS cells.

The Landscape of Regulatory Noncoding RNAs in Ewing's Sarcoma

Ewing’s sarcoma (ES) is a pediatric sarcoma caused by a chromosomal translocation. Unlike in most cancers, the genomes of ES patients are very stable. The translocation product of the EWS-FLI1 fusion is most often the predominant genetic driver of oncogenesis, and it is pertinent to explore the role of epigenetic alterations in the onset and progression of ES. Several types of noncoding RNAs, primarily microRNAs and long noncoding RNAs, are key epigenetic regulators that have been shown to play critical roles in various cancers. The functions of these epigenetic regulators are just beginning to be appreciated in ES. Here, we performed a comprehensive literature review to identify these noncoding RNAs. We identified clinically relevant tumor suppressor microRNAs, tumor promoter microRNAs and long noncoding RNAs. We then explored the known interplay between different classes of noncoding RNAs and described the currently unmet need for expanding the noncoding RNA repertoire of ES. We concluded the review with a discussion of epigenetic regulation of ES via regulatory noncoding RNAs. These noncoding RNAs provide new avenues of exploration to develop better therapeutics and identify novel biomarkers.

Targeting EYA3 in Ewing Sarcoma Retards Tumor Growth and Angiogenesis

EWSR1/FLI1, the most common fusion gene in Ewing sarcoma, upregulates expression of the Eyes Absent 3 (EYA3) transactivator-phosphatase protein. The purpose of this study was to investigate molecular and cellular mechanisms through which EYA3 might promote Ewing sarcoma tumor growth and to determine whether the EYA3 tyrosine phosphatase activity represents a viable therapeutic target. We used genetic and pharmacologic modulation of EYA3 in cell line-based xenografts to examine how loss of EYA3 tyrosine phosphatase activity affects tumor growth and angiogenesis. Molecular mechanisms were evaluated in vivo and in vitro through analyses of tumor tissue and multicellular tumor spheroids. Our results show that both loss of EYA3 in Ewing sarcoma cells and pharmacologic inhibition of the EYA3 tyrosine phosphatase activity inhibit tumor growth and tumor angiogenesis. EYA3 regulates levels of VEGFA in Ewing tumors, as well as promoting DNA damage repair and survival of Ewing sarcoma tumor cells. Target engagement is demonstrated in tumor tissue through elevated levels of the EYA3 substrate H2AX-pY142 upon loss of EYA3 or with Benzarone treatment. The efficacy of EYA3 tyrosine phosphatase inhibition in attenuating tumor growth and angiogenesis is corroborated in an Ewing sarcoma patient-derived tumor xenograft. Together, the results presented here validate EYA3 as a target for the development of novel Ewing sarcoma therapeutic strategies, and set the stage for evaluating the efficacy of combining the antiangiogenic and anti-cell survival effects of EYA3 inhibition with cytotoxic chemotherapy.

Selective inhibition of HDAC6 regulates expression of the oncogenic driver EWSR1-FLI1 through the EWSR1 promoter in Ewing sarcoma

Ewing sarcoma (EWS) is an aggressive bone and soft tissue tumor of children and young adults in which the principal driver is a fusion gene, EWSR1-FLI1. Although the essential role of EWSR1-FLI1 protein in the regulation of oncogenesis, survival, and tumor progression processes has been described in-depth, little is known about the regulation of chimeric fusion-gene expression. Here, we demonstrate that the active nuclear HDAC6 in EWS modulates the acetylation status of specificity protein 1 (SP1), consequently regulating the SP1/P300 activator complex binding to EWSR1 and EWSR1-FLI1 promoters. Selective inhibition of HDAC6 impairs binding of the activator complex SP1/P300, thereby inducing EWSR1-FLI1 downregulation and significantly reducing its oncogenic functions. In addition, sensitivity of EWS cell lines to HDAC6 inhibition is higher than other tumor or non-tumor cell lines. High expression of HDAC6 in primary EWS tumor samples from patients correlates with a poor prognosis in two independent series accounting 279 patients. Notably, a combination treatment of a selective HDAC6 and doxorubicin (a DNA damage agent used as a standard therapy of EWS patients) dramatically inhibits tumor growth in two EWS murine xenograft models. These results could lead to suitable and promising therapeutic alternatives for patients with EWS.

Systems Biology Analysis for Ewing Sarcoma

Ewing sarcoma (EwS) is a highly aggressive pediatric bone cancer that is defined by a somatic fusion between the EWSR1 gene and an ETS family member, most frequently the FLI1 gene, leading to expression of a chimeric transcription factor EWSR1-FLI1. Otherwise, EwS is one of the most genetically stable cancers. The situation when the major cancer driver is well known looks like a unique opportunity for applying the systems biology approach in order to understand the EwS mechanisms as well as to uncover some general mechanistic principles of carcinogenesis. A number of studies have been performed revealing the direct and indirect effects of EWSR1-FLI1 on multiple aspects of cellular life. Nevertheless, the emerging picture of the oncogene action appears to be highly complex and systemic, with multiple reciprocal influences between the immediate consequences of the driver mutation and intracellular and intercellular molecular mechanisms, including regulation of transcription, epigenome, and tumoral microenvironment. In this chapter, we present an overview of existing molecular profiling resources available for EwS tumors and cell lines and provide an online comprehensive catalogue of publicly available omics and other datasets. We further highlight the systems biology studies of EwS, involving mathematical modeling of networks and integration of molecular data. We conclude that despite the seeming simplicity, a lot has yet to be understood on the systems-wide mechanisms connecting the driver mutation and the major cellular phenotypes of this pediatric cancer. Overall, this chapter can serve as a guide for a systems biology researcher to start working on EwS.

The Optimal Outcome of Suppressing Ewing Sarcoma Growth in vivo With Biocompatible Bioengineered miR-34a-5p Prodrug

Being the second most common type of primary bone malignancy in children and adolescents, Ewing Sarcoma (ES) encounters the dilemma of low survival rate with a lack of effective treatments. As an emerging approach to combat cancer, RNA therapeutics may expand the range of druggable targets. Since the genome-derived oncolytic microRNA-34a (miR-34a) is down-regulated in ES, restoration of miR-34a-5p expression or function represents a new therapeutic strategy which is, however, limited to the use of chemically-engineered miRNA mimics. Very recently we have developed a novel bioengineering technology using a stable non-coding RNA carrier (nCAR) to achieve high-yield production of biocompatible miRNA prodrugs, which is a great addition to current tools for the assessment of RNA therapeutics. Herein, for the first time, we investigated the biochemical pharmacology of bioengineered miR-34a-5p prodrug (nCAR/miR-34a-5p) in the control of ES using human ES cells and xenograft mouse models. The bioengineered nCAR/miR-34a-5p was precisely processed to mature miR-34a-5p in ES cells and subsequently suppressed cell proliferation, attributable to the enhancement of apoptosis and induction of G2 cell cycle arrest through downregulation of SIRT-1, BCL-2 and CDK6 protein levels. Furthermore, systemic administration of nCAR/miR-34a-5p dramatically suppressed the ES xenograft tumor growth in vivo while showing biocompatibility. In addition, the antitumor effect of bioengineered nCAR/miR-34a-5p was associated with a lower degree of tumoral cell proliferation and greater extent of apoptosis. These findings demonstrate the efficacy of bioengineered miR-34a-5p prodrug for the treatment of ES and support the development of miRNA therapeutics using biocompatible bioengineered miRNA prodrugs.

Expression profile of MicroRNA: An Emerging Hallmark of Cancer

MicroRNA (miRNAs), a class of small, endogenous non-coding RNA molecules of about 21-24 nucleotides in length, have unraveled a new modulatory network of RNAs that form an additional level of posttranscriptional gene regulation by targeting messenger RNAs (mRNAs). These miRNAs possess the ability to regulate gene expression by modulating the stability of mRNAs, controlling their translation rates, and consequently regulating protein synthesis. Substantial experimental evidence established the involvement of miRNAs in most biological processes like growth, differentiation, development, and metabolism in mammals including humans. An aberrant expression of miRNAs has been implicated in several pathologies, including cancer. The association of miRNAs with tumor growth, development, and metastasis depicts their potential as effective diagnostic and prognostic biomarkers. Furthermore, exploitation of the role of different miRNAs as oncogenes or tumor suppressors has aided in designing several miRNA-based therapeutic approaches for treating cancer patients whose clinical trials are underway. In this review, we aim to summarize the biogenesis of miRNAs and the dysregulations in these pathways that result in various pathologies and in some cases, resistance to drug treatment. We provide a detailed review of the miRNA expression signatures in different cancers along with their diagnostic and prognostic utility. Furthermore, we elaborate on the potential employment of miRNAs to enhance cancer cell apoptosis, regress tumor progression and even overcome miRNA-induced drug resistance.

Signatures of circulating microRNA in four sarcoma subtypes

Background: Sarcomas are rare malignant tumors of mesenchymal origin. The discovery of circulating biomarkers with high diagnostic value could supplement diagnosis of this heterogenous group of tumors. The aim of this study was to identify the profiles of circulating miRNA (c-miRNAs) in four groups of common bone and soft tissue sarcomas.

Methods: At the time of diagnosis, blood samples were collected from 86 patients: 36 with locally advanced/unresectable/metastatic gastrointestinal stromal tumor (GIST) who received first-line treatment with imatinib; 16 with locally advanced osteosarcoma (OS); 26 with locally advanced synovial sarcoma (SS); and eight with locally advanced Ewing sarcoma (ES). In addition, samples were collected from 30 healthy controls. C-miRNAs were isolated using a miRCURY RNA Isolation Kit, followed by preparation of cDNA libraries and sequencing on the Ion Proton platform.

Results: Pair-wise comparisons identified 156 unique c-miRNAs (adjusted P-value < 0.05) showing significant dysregulation between controls and patients; of these, 24, 36, 42, and 99 differentiated controls from pretherapeutic OS, SS, ES, and GIST, respectively. Ten c-miRNAs were commonly altered in at least three sarcoma types. Receiver operating characteristic curves and area under the curve (ROC-AUC) analyses revealed that a four-miRNA diagnostic classifier was able to differentiate controls from ES, GIST, OS, and SS, with AUC-ROC values of 1, 0.97, 0.95, and 0.94, respectively.

Conclusions: Aberrant miRNA expression signatures were identified in serum from patients with four different sarcoma subtypes. Differences in miRNA expression profiles between sarcoma patients and healthy volunteers suggest that miRNAs may play a role in sarcoma development.

FLI1 promotes protein translation via the transcriptional regulation of MKNK1 expression

The disruption of protein translation machinery is a common feature of cancer initiation and progression, and drugs that target protein translation offer new avenues for therapy. The translation initiation factor, eukaryotic initiation factor 4E (eIF4E), is induced in a number of cancer cell lines and is one such candidate for therapeutic intervention. Friend leukemia integration 1 (FLI1) is a potent oncogenic transcription factor that promotes various types of cancer by promoting several hallmarks of cancer progression. FLI1 has recently been implicated in protein translation through yet unknown mechanisms. This study identified a positive association between FLI1 expression and mitogen-activated protein kinase (MAPK)-interacting serine/threonine kinase1 (MKNK1), the immediate upstream regulator of the eIF4E initiation factor. The short hairpin RNA (shRNA)-mediated silencing or overexpression of FLI1 in leukemic cell lines downregulated or upregulated MKNK1 expression, respectively. Promoter analysis identified a potent FLI1 binding site in the regulatory region of the MKNK1 promoter. In transient transfection experiments, FLI1 increased MKNK1 promoter activity, which was blocked by mutating the FLI1 binding site. FLI1 specifically affected the expression of MKNK1, but not that of MKNK2. The siRNA-mediated downregulation of MKNK1 downregulated the expression of survivin (BIRC5) and significantly suppressed cell proliferation in culture. FLI1 inhibitory compounds were shown to downregulate this oncogene through the suppression of MAPK/extracellular-regulated kinase (ERK) signaling and the subsequent activation of miR-145, leading to a lower MKNK1 expression and the suppression of leukemic growth. These results uncover a critical role for FLI1 in the control of protein translation and the importance of targeting its function and downstream mediators, such as MKNK1, for cancer therapy.

miRNA signatures in childhood sarcomas and their clinical implications

Progresses in multimodal treatments have significantly improved the outcomes for childhood cancer. Nonetheless, for about one-third of patients with Ewing sarcoma, rhabdomyosarcoma, or osteosarcoma steady remission has remained intangible. Thus, new biomarkers to improve early diagnosis and the development of precision-targeted medicine remain imperative. Over the last decade, remarkable progress has been made in the basic understanding of miRNAs function and in interpreting the contribution of their dysregulation to cancer development and progression. On this basis, this review focuses on what has been learned about the pivotal roles of miRNAs in the regulation of key genes implicated in childhood sarcomas.

The RNA binding protein EWS is broadly involved in the regulation of pri-miRNA processing in mammalian cells

The Ewing Sarcoma protein (EWS) is a multifaceted RNA binding protein (RBP) with established roles in transcription, pre-mRNA processing and DNA damage response. By generating high quality EWS-RNA interactome, we uncovered its specific and prevalent interaction with a large subset of primary microRNAs (pri-miRNAs) in mammalian cells. Knockdown of EWS reduced, whereas overexpression enhanced, the expression of its target miRNAs. Biochemical analysis revealed that multiple elements in target pri-miRNAs, including the sequences flanking the stem-loop region, contributed to high affinity EWS binding and sequence swap experiments between target and non-target demonstrated that the flanking sequences provided the specificity for enhanced pri-miRNA processing by the Microprocessor Drosha/DGCR8. Interestingly, while repressing Drosha expression, as reported earlier, we found that EWS was able to enhance the recruitment of Drosha to chromatin. Together, these findings suggest that EWS may positively and negatively regulate miRNA biogenesis via distinct mechanisms, thus providing a new foundation to understand the function of EWS in development and disease.

An Insight into the Roles of MicroRNAs and Exosomes in Sarcoma

Sarcomas are rare solid tumors, but at least one-third of patients with sarcoma die from tumor-related disease. MicroRNA (miRNA) is a noncoding RNA that regulates gene expression in all cells and plays a key role in the progression of cancers. Recently, it was identified that miRNAs are transferred between cells by enclosure in extracellular vesicles, especially exosomes. The exosome is a 100 nm-sized membraned vesicle that is secreted by many kinds of cells and contains miRNA, mRNA, DNA, and proteins. Cancer uses exosomes to influence not only the tumor microenvironment but also the distant organ to create a premetastatic niche. The progression of sarcoma is also regulated by miRNAs and exosomes. These miRNAs and exosomes can be targeted as biomarkers and treatments. In this review, we summarize the studies of miRNA and exosomes in sarcoma.

Identification of diterpenoid compounds that interfere with Fli-1 DNA binding to suppress leukemogenesis

The ETS transcription factor Fli-1 controls the expression of genes involved in hematopoiesis including cell proliferation, survival, and differentiation. Dysregulation of Fli-1 induces hematopoietic and solid tumors, rendering it an important target for therapeutic intervention. Through high content screens of a library of chemicals isolated from medicinal plants in China for inhibitors of a Fli-1 transcriptional reporter cells, we hereby report the identification of diterpenoid-like compounds that strongly inhibit Fli-1 transcriptional activity. These agents suppressed the growth of erythroleukemic cells by inducing apoptosis and differentiation. They also inhibited survival and proliferation of B-cell leukemic cell lines as well as primary B-cell lymphocytic leukemia (B-CLL) isolated from 7 patients. Moreover, these inhibitors blocked leukemogenesis in a mouse model of erythroleukemia, in which Fli-1 is the driver of tumor initiation. Computational docking analysis revealed that the diterpenoid-like compounds bind with high affinity to nucleotide residues in a pocket near the major groove within the DNA-binding sites of Fli-1. Functional inhibition of Fli-1 by these compounds triggered its further downregulation through miR-145, whose promoter is normally repressed by Fli-1. These results uncover the importance of Fli-1 in leukemogenesis, a Fli-1-miR145 autoregulatory loop and new anti-Fli-1 diterpenoid agents for the treatment of diverse hematological malignancies overexpressing this transcription factor.

Robust analysis of novel mRNA-lncRNA cross talk based on ceRNA hypothesis uncovers carcinogenic mechanism and promotes diagnostic accuracy in esophageal cancer

Background

ceRNAs have emerged as pivotal players in the regulation of gene expression and play a crucial role in the physiology and development of various cancers. Nevertheless, the function and underlying mechanisms of ceRNAs in esophageal cancer (EC) are still largely unknown.

Methods

In this study, profiles of DEmRNAs, DElncRNAs, and DEmiRNAs between normal and EC tumor tissue samples were obtained from the Cancer Genome Atlas database using the DESeq package in R by setting the adjusted P<0.05 and |log₂(fold change)|>2 as the cutoff. The ceRNA network (ceRNet) was initially constructed to reveal the interaction of these ceRNAs during carcinogenesis based on the bioinformatics of miRcode, miRDB, miRTarBase, and TargetScan. Then, independent microarray data of GSE6188, GSE89102, and GSE92396 and correlation analysis were used to validate molecular biomarkers in the initial ceRNet. Finally, a least absolute shrinkage and selection operator logistic regression model was built using an oncogenic ceRNet to diagnose EC more accurately.

Results

We successfully constructed an oncogenic ceRNet of EC, crosstalk of hsa-miR372-centered CADM2-ADAMTS9-AS2 and hsa-miR145-centered SERPINE1-PVT1. In addition, the risk-score model -0.0053*log₂(CADM2)+0.0168*log₂(SERPINE1)-0.0073*log₂(ADAMTS9-AS2)+0.0905*log₂(PVT1)+0.0047*log₂(hsa-miR372)-0.0193*log₂(hsa-miR145), (log₂[gene count]) could improve diagnosis of EC with an AUC of 0.988.

Conclusion

We identified two novel pairs of ceRNAs in EC and its role of diagnosis. The pairs of hsa-miR372-centered CADM2-ADAMTS9-AS2 and hsa-miR145-centered SERPINE1-PVT1 were likely potential carcinogenic mechanisms of EC, and their joint detection could improve diagnostic accuracy.

MicroRNA‑34b promotes proliferation, migration and invasion of Ewing's sarcoma cells by downregulating Notch1

Ewing's sarcoma is the second most frequent bone and soft tissue sarcoma, which is commonly driven by the Ewing's sarcoma breakpoint region 1-friend leukemia integration 1 transcription factor (EWS-FLI1) fusion gene. Since microRNAs (miRs) can act as either oncogenes or tumor suppressor genes in human cancer, and miR-34b has been reported to act as a tumor suppressor, the role of miR-34b in Ewing's sarcoma was investigated in the present study. The results demonstrated that miR-34b expression levels were higher in tumor samples compared within normal tissue samples. Notably, miR-34b expression levels were significantly higher in EWS-FLI1-positive samples compared within EWS-FLI1-negative samples. The effects of miR-34b expression on cell proliferation, migration and invasion were also examined. miR-34b expression was inhibited using small interfering (si)RNA targeting the fusion gene. Transfection of a miR-34b precursor sequence into siRNA-treated tumor cells resulted in a significant increase in cell growth, migration and invasion compared within the control group. In addition, the adhesive ability was increased in the Ewing's sarcoma cell line RD-ES, but not A673, following miR-34b upregulation. Conversely, downregulation of miR-34b expression led to a significant decrease in cell growth, migration and invasion. Notch has previously been reported to serve either oncogenic or tumor suppressive roles in human cancer. The results indicated that Notch1 and its target genes, Hes family BHLH transcription factor 1 and Hes-related family BHLH transcription factor with YRPW motif 1, were suppressed by miR-34b directly In conclusion, EWS-FLI1 may modulate miR-34b expression directly or indirectly, and miR-34b potentially has an oncogenic role in Ewing's sarcoma by downregulating Notch1.

Ewing sarcoma

Ewing sarcoma is the second most frequent bone tumour of childhood and adolescence that can also arise in soft tissue. Ewing sarcoma is a highly aggressive cancer, with a survival of 70-80% for patients with standard-risk and localized disease and ~30% for those with metastatic disease. Treatment comprises local surgery, radiotherapy and polychemotherapy, which are associated with acute and chronic adverse effects that may compromise quality of life in survivors. Histologically, Ewing sarcomas are composed of small round cells expressing high levels of CD99. Genetically, they are characterized by balanced chromosomal translocations in which a member of the FET gene family is fused with an ETS transcription factor, with the most common fusion being EWSR1-FLI1 (85% of cases). Ewing sarcoma breakpoint region 1 protein (EWSR1)-Friend leukaemia integration 1 transcription factor (FLI1) is a tumour-specific chimeric transcription factor (EWSR1-FLI1) with neomorphic effects that massively rewires the transcriptome. Additionally, EWSR1-FLI1 reprogrammes the epigenome by inducing de novo enhancers at GGAA microsatellites and by altering the state of gene regulatory elements, creating a unique epigenetic signature. Additional mutations at diagnosis are rare and mainly involve STAG2, TP53 and CDKN2A deletions. Emerging studies on the molecular mechanisms of Ewing sarcoma hold promise for improvements in early detection, disease monitoring, lower treatment-related toxicity, overall survival and quality of life.

miR-130b directly targets ARHGAP1 to drive activation of a metastatic CDC42-PAK1-AP1 positive feedback loop in Ewing sarcoma

Ewing Sarcoma (ES) is a highly aggressive bone tumor with peak incidence in the adolescent population. It has a high propensity to metastasize, which is associated with dismal survival rates of approximately 25%. To further understand mechanisms of metastasis we investigated microRNA regulatory networks in ES. Our studies focused on miR-130b due to our analysis that enhanced expression of this microRNA has clinical relevance in multiple sarcomas, including ES. Our studies provide insights into a novel positive feedback network involving the direct regulation of miR-130b and activation of downstream signaling events contributing toward sarcoma metastasis. Specifically, we demonstrated miR-130b induces proliferation, invasion, and migration in vitro and increased metastatic potential in vivo. Using microarray analysis of ES cells with differential miR-130b expression we identified alterations in downstream signaling cascades including activation of the CDC42 pathway. We identified ARHGAP1, which is a negative regulator of CDC42, as a novel, direct target of miR-130b. In turn, downstream activation of PAK1 activated the JNK and AP-1 cascades and downstream transcriptional targets including IL-8, MMP1 and CCND1. Furthermore, chromatin immunoprecipitation of endogenous AP-1 in ES cells demonstrated direct binding to an upstream consensus binding site within the miR-130b promoter. Finally, small molecule inhibition of PAK1 blocked miR-130b activation of JNK and downstream AP-1 target genes, including primary miR-130b transcripts, and miR-130b oncogenic properties, thus identifying PAK1 as a novel therapeutic target for ES. Taken together, our findings identify and characterize a novel, targetable miR-130b regulatory network that promotes ES metastasis.

The role of miR-17-92 in the miRegulatory landscape of Ewing sarcoma

MicroRNAs serve to fine-tune gene expression and play an important regulatory role in tissue specific gene networks. The identification and validation of miRNA target genes in a 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 ectopic expression of the miRNA do not reliably predict regulation under physiological conditions. The chimeric oncoprotein EWS-FLI1 is the driving pathogenic force in Ewing sarcoma. MiR-17-92, one of the most potent oncogenic miRNAs, was recently reported to be among the top EWS-FLI1 activated miRNAs. Using a combination of AGO2 pull-down experiments by PAR-CLIP (Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation) and of RNAseq upon miRNA depletion by ectopic sponge expression, we aimed to identify the targetome of miR-17-92 in Ewing sarcoma. Intersecting both datasets we found an 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 specific sponge expression. Strikingly, approximately a quarter of these genes annotate to the TGFB/BMP pathway, the majority mapping downstream of SMAD signaling. Testing for SMAD phosphorylation, we identify quiet but activatable TGFB signaling and cell autonomous activity of the BMP pathway resulting in the activation of the stemness regulatory transcriptional repressors ID1 and ID3. Taken together, our findings shed light on the complex miRegulatory landscape of Ewing Sarcoma pointing miR-17-92 as a key node connected to TGFB/BMP pathway.

Epigenetic and genetic changes in soft tissue sarcomas: a review

Soft tissue sarcomas are a versatile group of tumors with a proposed origin from mesenchymal stem cells. During recent years, the molecular biologic mechanisms behind the histogenesis of these tumors have become clearer. In addition to translocations and other genomic changes, epigenetic mechanisms have been shown to be greatly involved in the histogenesis of sarcomas as well as other cancers. Even though the molecular mechanisms behind sarcomas appear to be more complex than previously expected, epigenetic mechanisms bring new opportunities and means for the treatment of these complex diseases.

miR-145 suppresses colorectal cancer cell migration and invasion by targeting an ETS-related gene

MicroRNA-45 (miR-145) has been demonstrated to be downregulated in various cancer types including colorectal cancer (CRC). However, the function of miR‑145 in CRC has not been clearly elucidated. In this study, we examined miR-145 expression by quantitative real‑time PCR (qRT‑PCR) in CRC cell lines as well as tumors and corresponding normal mucosa, and the results were correlated to the clinicopathological parameters. In addition, using computational algorithms we investigated putative miR‑145 targets. The role of miR‑145 was further examined in studies in vitro. In our study miR‑145 was significantly decreased in CRC tissues and cell lines compared with non‑cancerous colorectal mucosa, especially lymph node or distance metastasis cases. Based on computational algorithms, we assumed that ERG was directly modulated by miR‑145 in colorectal cancer cells. For the first time, we demonstrated that ERG was highly expressed in CRC tissues compared with normal ones by qRT‑PCR. The inverse correlation between the expression of miR‑145 and ERG was observed in CRC tissues. Dual‑Luciferase assays demonstrated the direct interaction between miR‑145 and 3'‑UTR of ERG mRNA. Ectopic expression of miR‑145 suppressed the proliferation and invasion ability of colorectal cancer cells, while ERG knockdown partially restored the tumor suppressive effect of miR‑145. These results suggested that miR‑145 might act as a tumor suppressor during the process of CRC malignant transformation by interacting with ERG.

Twenty Years on: What Do We Really Know about Ewing Sarcoma and What Is the Path Forward?

Ewing sarcoma (ES) is a highly aggressive bone and soft-tissue tumor with peak incidence among adolescents and young adults. Despite advances in local control and systemic chemotherapy, metastatic relapse after an initial clinical remission remains a significant clinical problem. In addition, metastasis at the time of presentation or at relapse continues to be the leading cause of death for patients diagnosed with ES. Since the discovery of the pathognomonic EWS-FLI1 fusion gene more than 20 years ago, much about the molecular and cellular biology of ES pathogenesis has been learned. In addition, more recent exploitation of advances in stem cell and developmental biology has provided key insights into the cellular origins of ES and the role of epigenetic deregulation in tumor initiation and maintenance. Nevertheless, the mechanisms that drive tumor relapse and metastasis remain largely unknown. These gaps in our knowledge continue to hamper the development of novel therapeutic strategies that may improve outcomes for patients with relapsed and metastatic disease. In this article we review the current status of ES biology research, highlighting areas of investigation that we consider to have the greatest potential to yield findings that will translate into clinically significant advances.

microRNA and Bone Cancer

MicroRNA molecules have a variety of roles in cellular development and proliferation processes, including normal osteogenesis. These effects are exerted through post-translational inhibition of target genes. Altered miRNA expression has been demonstrated in several cancers, both in the tumor tissue and in the peripheral circulation. This may influence carcinogenesis if the specific miRNA targets are encoded by tumor suppressor genes or oncogenes. To date, most research investigating the role of microRNAs and primary bone tumors has focused on osteosarcoma and Ewing sarcoma. Several microRNAs including the miR-34 family have been implicated in osteosarcoma tumorigenesis via effects on the Notch signaling pathway. Progression, invasion, and metastasis of osteosarcoma tumor cells is also influenced by microRNA expression. In addition, microRNA expression may affect the response to chemotherapy in osteosarcoma and thus hold potential for future use as either a prognostic indicator or a therapeutic target. The EWS-FLI1 fusion protein produced in Ewing sarcoma has been shown to induce changes in miRNA expression. MicroRNA expression profiling may have some potential for prediction of disease progression and survival in Ewing sarcoma. There is limited evidence to support a role for microRNAs in other primary bone tumors, either malignant or benign; however, early work is suggestive of involvement in chondrosarcoma, multiple osteochondromatosis, and giant cell tumors of bone.

Uterine leiomyosarcoma and endometrial stromal sarcoma have unique miRNA signatures

OBJECTIVE

To compare the microRNA (miRNA) profiles of uterine endometrial stromal sarcoma (ESS) and leiomyosarcoma (LMS), and to compare the miRNA signatures of primary and metastatic uterine LMS.

METHODS

Eight primary LMS, 9 primary ESS and 8 metastatic LMS were analyzed for miRNA profiles using TaqMan Human miRNA Array Cards. Findings for 20 differentially expressed miRNAs were validated in a series of 44 uterine sarcomas (9 primary uterine ESS, 17 primary uterine LMS, 18 metastatic LMS) using qPCR. Frizzled-6 protein expression was analyzed in 30 LMS (15 primary, 15 metastases). Frizzled-6 was silenced in SK-LMS-1 uterine LMS cells using siRNA and the effect on invasion, wound healing and matrix metalloproteinase-2 (MMP2) activity was assessed.

RESULTS

Ninety-four miRNAs were significantly differentially expressed in ESS and LMS, of which 76 were overexpressed in ESS and 18 overexpressed in LMS. Forty-nine miRNAs were differentially expressed in primary and metastatic LMS, of which 45 were overexpressed in primary LMS and 4 in metastases. Differential expression was confirmed for 10/20 miRNA analyzed using qPCR. Frizzled-6 silencing in SK-LMS-1 cells significantly inhibited cellular invasion, wound healing and MMP-2 activity.

CONCLUSIONS

Differential miRNA signatures of ESS and LMS provide novel data regarding transcriptional regulation in these cancers, based on which new potential diagnostic markers, prognostic biomarkers and therapeutic targets may be explored. Differences in miRNA profiles of primary and metastatic LMS may improve our understanding of disease progression in this aggressive malignancy.

Implications of miR cluster 143/145 as universal anti-oncomiRs and their dysregulation during tumorigenesis

Tumorigenesis is a multistep process, de-regulated due to the imbalance of oncogenes as well as anti-oncogenes, resulting in disruption of tissue homeostasis. In many cases the effect of oncogenes and anti-oncogenes are mediated by various other molecules such as microRNAs. microRNAs are small non-coding RNAs established to post-transcriptionally regulate more than half of the protein coding genes. miR cluster 143/145 is one such cancer-related microRNA cluster which is down-regulated in most of the cancers and is able to hinder tumorigenesis by targeting tumor-associated genes. The fact that they could sensitize drug-resistant cancer cells by targeting multidrug resistant genes makes them potent tools to target cancer cells. Their low levels precede events which lead to cancer progression and therefore could be considered also as biomarkers to stage the disease. Interestingly, evidence suggests the existence of several in vivo mechanisms by which this cluster is differentially regulated at the molecular level to keep their levels low in cancer. In this review, we summarize the roles of miR cluster 143/145 in cancer, their potential prognostic applications and also their regulation during tumorigenesis.

MicroRNAs in the pathobiology of sarcomas

Sarcomas are a rare and heterogeneous group of tumors. The last decade has witnessed extensive efforts to understand the pathobiology of many aggressive sarcoma types. In parallel, we have also begun to unravel the complex gene regulation processes mediated by microRNAs (miRNAs) in sarcomas and other cancers, discovering that microRNAs have critical roles in the majority of both oncogenic and tumor suppressor signaling networks. Expression profiles and a greater understanding of the biologic roles of microRNAs and other noncoding RNAs have considerably expanded our current knowledge and provided key pathobiological insights into many sarcomas, and helped identify novel therapeutic targets. The limited number of sarcoma patients in each sarcoma type and their heterogeneity pose distinct challenges in translating this knowledge into the clinic. It will be critical to prioritize these novel targets and choose those that have a broad applicability. A small group of microRNAs have conserved roles across many types of sarcomas and other cancers. Therapies that target these key microRNA-gene signaling and regulatory networks, in combination with standard of care treatment, may be the pivotal component in significantly improving treatment outcomes in patients with sarcoma or other cancers.

What Do We Know about the Role of miRNAs in Pediatric Sarcoma?

Non-coding RNAs have received a lot of attention in recent years, with especial focus on microRNAs (miRNAs), so much so that in the just over two decades since the first miRNA, Lin4, was described, almost 40,000 publications about miRNAs have been generated. Less than 500 of these focus on sarcoma, and only a fraction of those on sarcomas of childhood specifically, with some of these representing observational studies and others containing functionally validated data. This is a group of cancers for which prognosis is often poor and therapeutic options limited, and it is especially in these areas that strides in understanding the role of non-coding RNAs and miRNAs in particular are to be welcomed. This review deals with the main forms of pediatric sarcoma, exploring what is known about the diagnostic and prognostic profiles of miRNAs in these tumours and where novel therapeutic options might present themselves for further exploration.

Sequencing Overview of Ewing Sarcoma: A Journey across Genomic, Epigenomic and Transcriptomic Landscapes

Ewing sarcoma is an aggressive neoplasm occurring predominantly in adolescent Caucasians. At the genome level, a pathognomonic EWSR1-ETS translocation is present. The resulting fusion protein acts as a molecular driver in the tumor development and interferes, amongst others, with endogenous transcription and splicing. The Ewing sarcoma cell shows a poorly differentiated, stem-cell like phenotype. Consequently, the cellular origin of Ewing sarcoma is still a hot discussed topic. To further characterize Ewing sarcoma and to further elucidate the role of EWSR1-ETS fusion protein multiple genome, epigenome and transcriptome level studies were performed. In this review, the data from these studies were combined into a comprehensive overview. Presently, classical morphological predictive markers are used in the clinic and the therapy is dominantly based on systemic chemotherapy in combination with surgical interventions. Using sequencing, novel predictive markers and candidates for immuno- and targeted therapy were identified which were summarized in this review.

MicroRNAs as potential target in human bone and soft tissue sarcoma therapeutics

Sarcomas are highly aggressive heterogeneous tumors that are mesenchymal in origin. There have been vast advancements on identifying diagnostic markers for sarcomas including chromosomal translocations, but very little progress has been made to identify targeted therapies against them. The tumor heterogeneity, genetic complexity and the lack of drug studies make it challenging to recognize the potential targets and also accounts for the inadequate treatments in sarcomas. In recent years, microRNAs that are a part of small non-coding RNAs have shown promising results as potential diagnostic and prognostic biomarkers in multiple sarcoma types. This review focuses on the current knowledge of the microRNAs that are deregulated in sarcomas, and an insight on the strategies to target these microRNAs that are essential for developing improved therapies for various human sarcomas.

Pediatric cancer epigenome and the influence of folate

Despite improvement in clinical treatment of childhood cancer, it remains the leading cause of disease-related mortality in children with survivors often suffering from treatment-related toxicity and premature death. Because childhood cancer is vastly different from cancer in adults, a thorough understanding of the underlying molecular mechanisms specific to childhood cancer is essential. Although childhood cancer contains much fewer mutations, a subset of cancer subtypes has a higher frequency of mutations in gene encoding epigenetic regulators. Thus, in this review, we will focus on epigenetic deregulations in childhood cancers, the use of genome-wide analysis for cancer subtype classification, prediction of clinical outcomes and the influence of folate on epigenetic mechanisms.

The potential value of miR-1 and miR-374b as biomarkers for colorectal cancer

The mortality of colorectal cancer (CRC) is growing due to the unsatisfactory specificity and sensitivity of the existing screening methods. Previous studies have focused on the role of miRNAs as CRC biomarkers. However, few studies have examined the miRNA profiles at each stage. The objective of this study was to identify miRNAs that distinguish CRC patients from normal people to prevent the misdiagnosis of patients with certain stages of CRC. We performed miRNA profiling of 1547 human miRNAs by qRT-PCR in CRC patients with stage II and stage III disease. The statistical analyses showed that there were 96 miRNAs that were significantly dysregulated in CRC relative to normal tissues (P<0.05). There were 28 dysregulated miRNAs associated with separate or combined stages II and III disease. There were 25 downregulated miRNAs, including the following: miR-1, -145, -145*, -137, -363, -143, -4770, -490-5p, -9, -144*, -99a, -99b, -23b, -143*, -100, -768-3p, -24-1*, -125a-5p, -30e*, -574-3p, -126, let-7b, miR-1979, -374b, and -140-3p. We found an upregulation of miR-203, 182, and 96. Our results demonstrated that the expression of miR-1 and miR-374b was significantly decreased in each stage and may function as a biomarker of CRC. Furthermore, 20 miRNAs were dysregulated both in stage II disease without lymph node or distant metastasis and in stage II-III tumors but not in stage III tumors. Only miR-4794 was involved exclusively with stage II tumors, and there were 19 miRNAs that were dysregulated only in stage III disease with lymph node metastasis and in stage II-III disease. There were only 6 miRNAs that were uniquely dysregulated in stage III. Our results indicate that miRNA expression may be valuable in the clinic. However, large prospective studies are required to confirm the role of miRNAs. This study provides a new model for analyzing novel CRC biomarkers by considering more clinical factors.

MicroRNA expression and its clinical implications in Ewing's sarcoma

Ewing's sarcoma (EWS) is the second most common primary bone cancer, and is a predominant childhood malignant disease. Due to limited understanding of its pathogenesis and frequent occurrence of resistance to conventional types of treatment, its management remains difficult, and mortality is frequent. Development of EWS is a multistep process involving genetic and epigenetic alterations of protein-coding proto-oncogenes and tumour-suppressor genes. MicroRNAs (miRNAs) have recently been discovered as a new category of non-protein coding; small RNA molecules that regulate gene expression at the post-transcriptional level. Substantial numbers of deregulated miRNAs have been documented in EWS and their biological significance has been confirmed in multiple functional experiments. Several studies have confirmed involvement of miRNAs in various steps of EWS pathogenesis, from occurrence to metastasis. Functionally, miRNA dysregulation may promote cell-cycle progression, confer resistance to apoptosis, and enhance invasiveness and metastasis. These miRNAs have opened a novel field in cancer research with potential clinical utilization for screening, diagnosis, prognostics and prediction of response to treatment. Elucidating biological aspects of miRNA dysregulation may help better understand pathogenesis of EWS and promote development of miRNA directed-therapeutics against it.

Suppression of deacetylase SIRT1 mediates tumor-suppressive NOTCH response and offers a novel treatment option in metastatic Ewing sarcoma

The developmental receptor NOTCH plays an important role in various human cancers as a consequence of oncogenic mutations. Here we describe a novel mechanism of NOTCH-induced tumor suppression involving modulation of the deacetylase SIRT1, providing a rationale for the use of SIRT1 inhibitors to treat cancers where this mechanism is inactivated because of SIRT1 overexpression. In Ewing sarcoma cells, NOTCH signaling is abrogated by the driver oncogene EWS-FLI1. Restoration of NOTCH signaling caused growth arrest due to activation of the NOTCH effector HEY1, directly suppressing SIRT1 and thereby activating p53. This mechanism of tumor suppression was validated in Ewing sarcoma cells, B-cell tumors, and human keratinocytes where NOTCH dysregulation has been implicated pathogenically. Notably, the SIRT1/2 inhibitor Tenovin-6 killed Ewing sarcoma cells in vitro and prohibited tumor growth and spread in an established xenograft model in zebrafish. Using immunohistochemistry to analyze primary tissue specimens, we found that high SIRT1 expression was associated with Ewing sarcoma metastasis and poor prognosis. Our findings suggest a mechanistic rationale for the use of SIRT1 inhibitors being developed to treat metastatic disease in patients with Ewing sarcoma.

MicroRNA-145: a potent tumour suppressor that regulates multiple cellular pathways

MicroRNAs are endogenous, small (18-25 nucleotides) non-coding RNAs, which regulate genes expression by directly binding to the 3'-untranslated regions of the target messenger RNAs. Emerging evidence shows that alteration of microRNAs is involved in cancer development. MicroRNA-145 is commonly down-regulated in many types of cancer, regulating various cellular processes, such as the cell cycle, proliferation, apoptosis and invasion, by targeting multiple oncogenes. This review aims to summarize the recent published literature on the role of microRNA-145 in regulating tumourigenesis and progression, and explore its potential for cancer diagnosis, prognosis and treatment.

The ets transcription factor Fli-1 in development, cancer and disease

Friend Leukemia Virus Induced erythroleukemia-1 (Fli-1), an ETS transcription factor, was isolated a quarter century ago through a retrovirus mutagenesis screen. Fli-1 has since been recognized to play critical roles in normal development and homeostasis. For example, it transcriptionally regulates genes that drive normal hematopoiesis and vasculogenesis. Indeed, Fli-1 is one of 10 key regulators of hematopoietic stem/progenitor cell maintenance and differentiation. Aberrant expression of Fli-1 also underlies a number of virally induced leukemias, including Friend virus-induced erythroleukemia and various types of human cancers, and it is the target of chromosomal translocations in childhood Ewing’s sarcoma. Abnormal expression of Fli-1 is important in the aetiology of auto-immune diseases such as Systemic Lupus Erythematosus (SLE) and Systemic Sclerosis (SSc). These studies establish Fli-1 as a strong candidate for drug development. Despite difficulties in targeting transcription factors, recent studies identified small molecule inhibitors for Fli-1. Here we review past and ongoing research on Fli-1 with emphasis on its mechanistic function in autoimmune disease and malignant transformation. The significance of identifying Fli-1 inhibitors and their clinical applications for treatment of disease and cancer with deregulated Fli-1 expression are discussed.

Differentially expressed miRNAs in Ewing sarcoma compared to mesenchymal stem cells: low miR-31 expression with effects on proliferation and invasion

Ewing sarcoma, the second most common bone tumor in children and young adults, is an aggressive malignancy with a strong potential to metastasize. Ewing sarcoma is characterised by translocations encoding fusion transcription factors with an EWSR1 transactivation domain fused to an ETS family DNA binding domain. microRNAs are post-transcriptional regulators of gene expression and aberrantly expressed microRNAs have been identified as tumor suppressors or oncogenes in most cancer types. To identify potential oncogenic and tumor suppressor microRNAs in Ewing sarcoma, we determined and compared the expression of 377 microRNAs in 40 Ewing sarcoma biopsies, 6 Ewing sarcoma cell lines and mesenchymal stem cells, the putative cellular origin of Ewing sarcoma, from 6 healthy donors. Of the 35 differentially expressed microRNAs identified (fold change >4 and q<0.05), 19 were higher and 16 lower expressed in Ewing sarcoma. In comparisons between Ewing sarcoma samples with EWS-FLI or EWS-ERG translocations, with differing dissemination characteristics and of primary samples and metastases no significantly differential expressed microRNAs were detected using various stringency criteria. For miR-31, the microRNA with lowest expression in comparison to mesenchymal stem cells, functional analyses were performed to determine its potential as a tumor suppressor in Ewing sarcoma. Two of four miR-31 transfected Ewing sarcoma cell lines showed a significantly reduced proliferation (19% and 33% reduction) due to increased apoptosis in one and increased length of G1-phase in the other cell line. All three tested miR-31 transfected Ewing sarcoma cell lines showed significantly reduced invasiveness (56% to 71% reduction). In summary, we identified 35 microRNAs differentially expressed in Ewing sarcoma and demonstrate that miR-31 affects proliferation and invasion of Ewing sarcoma cell lines in ex vivo assays.

MiR-125b inhibits cell biological progression of Ewing's sarcoma by suppressing the PI3K/Akt signalling pathway

OBJECTIVES

Increasing evidence has suggested the close relationship between microRNAs (miRNAs) dysregulation and the carcinogenesis of Ewing's sarcoma (ES), among of which miR-125b has been reported to be decreased in ES tissues recently. Strikingly, ectopic expression of miR-125b could suppress cell proliferation of ES cell line A673, suggesting the tumor suppressor role of miR-125b in ES. However, the other accurate mechanistic functions and relative molecule mechanisms are largely unknown.

MATERIALS AND METHODS

Herein, we completed a series of experiments to investigate the role of miR-125b in Ewing's sarcoma. We restored the expression of miR-125b in ES cell line A673 through transfection with miR-125b mimics. To further understand the role of miR-125b in ES, we detected the effects of miR-125b on the cell proliferation, migration and invasion, cell cycle as well as cell apoptosis.

RESULTS

We found that restored expression of miR-125b in ES cell line A673 inhibited cell proliferation, migration and invasion, arrested cell cycle progression, and induced cell apoptosis. Moreover, bioinformatic prediction suggested the oncogene, phosphoinositide-3-kinase catalytic subunit delta (PIK3CD), was a target gene of miR-125b in ES cells. Further quantitative RT-PCR and western blot assays identified over-expression of miR-125b suppressed the expression of PIK3CD mRNA and protein. PIK3CD participates in regulating the PI3K signaling pathway, which has been reported to play an important role in the development of ES. Suppression of PIK3CD down-regulated the expression of phospho-AKT and phospho-mTOR proteins and inhibited the biologic progression of A673 cells.

CONCLUSIONS

Collectively, these data suggest that miR-125b functions as a tumor suppressor by targeting the PI3K/Akt/mTOR signaling pathway, and may provide potential therapy strategy for ES patients by targeting miRNA expression.