MicroRNAs in Ewing Sarcoma

The Landscape of microRNAs in Bone Tumor: A Comprehensive Review in Recent Studies

Cancer, the second greatest cause of mortality worldwide, frequently causes bone metastases in patients with advanced-stage carcinomas such as prostate, breast, and lung cancer. The existence of these metastases contributes to the occurrence of skeletal-related events (SREs), which are defined by excessive pain, pathological fractures, hypercalcemia, and spinal cord compression. These injurious incidents leave uncomfortably in each of the cancer patient's life quality. Primary bone cancers, including osteosarcoma (OS), chondrosarcoma (CS), and Ewing's sarcoma (ES), have unclear origins. MicroRNA (miRNA) expression patterns have been changed in primary bone cancers such as OS, CS, and ES, indicating a role in tumor development, invasion, metastasis, and treatment response. These miRNAs are persistent in circulation and exhibit distinct patterns in many forms of bone tumors, making them potential biomarkers for early detection and treatment of such diseases. Given their crucial regulatory functions in various biological processes and conditions, including cancer, this study aims to look at miRNAs' activities and possible contributions to bone malignancies, focusing on OS, CS, and ES. In conclusion, miRNAs are valuable tools for diagnosing, monitoring, and predicting OS, CS, and ES outcomes. Further research is required to fully comprehend the intricate involvement of miRNAs in these bone cancers and to develop effective miRNA-based treatments.

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.

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.

Overview of miR-106a Regulatory Roles: from Cancer to Aging

MicroRNAs (miRNAs) comprise a class of non-coding RNA with extensive regulatory functions within cells. MiR-106a is recognized for its super-regulatory roles in vital processes. Hence, the analysis of its expression in association with diseases has attracted considerable attention for molecular diagnosis and drug development. Numerous studies have investigated miR-106 target genes and shown that this miRNA regulates the expression of some critical cell cycle and apoptosis factors, suggesting miR-106a as an ideal diagnostic and prognostic biomarker with therapeutic potential. Furthermore, the reported correlation between miR-106a expression level and cancer drug resistance has demonstrated the complexity of its functions within different tissues. In this study, we have conducted a comprehensive review on the expression levels of miR-106a in various cancers and other diseases, emphasizing its target genes. The promising findings surrounding miR-106a suggest its potential as a valuable biomolecule. However, further validation assessments and overcoming existing limitations are crucial steps before its clinical implementation can be realized.

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.

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 Biological Function of MicroRNAs in Bone Tumors

Micro ribonucleic acids (miRNAs) are small endogenous noncoding RNAs molecules that regulate gene expression post-transcriptionally. A single miRNA is able to target hundreds of specific messenger RNA (mRNAs) by binding to the 3′-untranslated regions. miRNAs regulate different biological processes such as cell proliferation, differentiation and apoptosis. Altered miRNA expression is certainly related to the development of the most common human diseases, including tumors. Osteosarcoma (OS), Ewing’s Sarcoma (ES), and Chondrosarcoma (CS) are the most common primary bone tumors which affect mainly children and adolescents. A significant dysregulation of miRNA expression, in particular of mir-34, mir-21, mir-106, mir-143, and miR-100, has been revealed in OS, ES and CS. In this context, miRNAs can act as either tumor suppressor genes or oncogenes, contributing to the initiation and progression of bone tumors. The in-depth study of these small molecules can thus help to better understand their biological functions in bone tumors. Therefore, this review aims to examine the potential role of miRNAs in bone tumors, especially OS, ES and CS, and to suggest their possible use as potential therapeutic targets for the treatment of bone tumors and as biomarkers for early diagnosis.

The role of microRNAs in the osteogenic and chondrogenic differentiation of mesenchymal stem cells and bone pathologies

Mesenchymal stem cells (MSCs) have been identified in many adult tissues. MSCs can regenerate through cell division or differentiate into adipocytes, osteoblasts and chondrocytes. As a result, MSCs have become an important source of cells in tissue engineering and regenerative medicine for bone tissue and cartilage. Several epigenetic factors are believed to play a role in MSCs differentiation. Among these, microRNA (miRNA) regulation is involved in the fine modulation of gene expression during osteogenic/chondrogenic differentiation. It has been reported that miRNAs are involved in bone homeostasis by modulating osteoblast gene expression. In addition, countless evidence has demonstrated that miRNAs dysregulation is involved in the development of osteoporosis and bone fractures. The deregulation of miRNAs expression has also been associated with several malignancies including bone cancer. In this context, bone-associated circulating miRNAs may be useful biomarkers for determining the predisposition, onset and development of osteoporosis, as well as in clinical applications to improve the diagnosis, follow-up and treatment of cancer and metastases. Overall, this review will provide an overview of how miRNAs activities participate in osteogenic/chondrogenic differentiation, while addressing the role of miRNA regulatory effects on target genes. Finally, the role of miRNAs in pathologies and therapies will be presented.

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.

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.

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.

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.

Presence of the minor allele of microRNA205 rs3842530 polymorphism increases 18FDG uptake in patients with breast cancer via targeting VEGF

MicroRNAs (miRNAs) are regarded as key regulators of gene expression involved in the pathogenesis of various diseases. Numerous single nucleotide polymorphisms (SNPs) in miRNA genes have been found to be associated with human diseases by affecting the processing process of miRNAs. In the present study, patients with breast cancer underwent a PET scan, and the maximum standard uptake value (SUVmax)/partial volume‑corrected standard uptake value (SUVpvc) were determined in each individual. The samples were collected and genotyped for rs3842530. Statistical analysis was performed to evaluate the difference between the genotype groups. The results demonstrated that miR‑205 downregulated the expression of vascular endothelial growth factor (VEGF) by binding to its 3'untranslated region. The introduction of exogenous miRNA, which mimicked miR‑205, decreased the protein and mRNA expression levels of VEGF and, consistently, the suppression of endogenous miR‑205 resulted in an increase in the expression levels of VEGF. Furthermore, it was found that the expression of mature miR‑205 was markedly reduced by the presence of rs3842530. 18F‑fluorodeoxyglucose (18FDG) metabolism, including SUVmax and SUVpvc, are important parameters of PET, and dysregulation of the expression of VEGF has been reported to be associated with an altered 18FDG metabolism. In the present study, it was found that the presence of minor allele rs3842530 was correlated with increased SUVmax and SUVpvc, which may have been mediated by release of the physiologically inhibited expression of VEGF. Therefore, VEGF was a direct target of miR‑205, and the presence of rs3842530 compromised the expression of miR‑205, suggesting it is a promising biomarker for the metabolism of 18FDG.

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.

MiR-193b, downregulated in Ewing Sarcoma, targets the ErbB4 oncogene to inhibit anchorage-independent growth

Ewing Sarcoma is an aggressive, oncofusion-driven, malignant neoplasm of bone and soft tissue affecting predominantly children and young adults. Seeking to identify potential novel therapeutic targets/agents for this disease, our previous studies uncovered microRNAs regulated by EWS/Fli1, the most common oncofusion, with growth modulatory properties. In the present study, we sought to identify EWS/Fli1-repressed, growth suppressive, microRNAs potentially amenable to replacement in Ewing Sarcoma cells. Eight microRNAs (143, 153, 184, 193b, 195, 203, 206 and 223) were selected for evaluation as EWS/Fli1-repressed and underexpressed in Ewing Sarcoma cells, and reported to be growth suppressive in other pediatric or/and adult cancers. The selected miRs, and appropriate non-targeting controls, were introduced into two different Ewing Sarcoma cell lines (A673 and SK-ES-1), and effects on growth were examined using a high and low-density growth assay. MiR-193b was growth inhibitory in both assays and cell lines. In subsequent analyses, we found that stable overexpression of miR-193b also inhibits anchorage-independent growth in both A673 and SK-ES-1 cells. We further show that miR-193b negatively regulates expression of the ErbB4 oncogene in A673 and SK-ES-1 cells, and that depletion of ErbB4 is itself inhibitory to anchorage-independent growth in the same cell lines. Together, our studies show that the EWS/Fli1-repressed miR-193b is growth suppressive in Ewing Sarcoma, and identify ErbB4 as a target gene and candidate mediator of this growth suppression.

Loss of Ewing sarcoma EWS allele promotes tumorigenesis by inducing chromosomal instability in zebrafish

The Ewing sarcoma family of tumors expresses aberrant EWSR1- (EWS) fusion genes that are derived from chromosomal translocation. Although these fusion genes are well characterized as transcription factors, their formation leaves a single EWS allele in the sarcoma cells, and the contribution that the loss of EWS makes towards disease pathogenesis is unknown. To address this question, we utilized zebrafish mutants for ewsa and tp53. The zebrafish tp53(M214K)^w/m line and the ewsa^w/m, zygotic ewsa^m/m, and Maternal-Zygotic (MZ) ewsa^m/m lines all displayed zero to low incidence of tumorigenesis. However, when the ewsa and tp53 mutant lines were crossed with each other, the incidence of tumorigenesis drastically increased. Furthermore, 27 hour post fertilization (hpf) MZ ewsa^m/m mutant embryos displayed a higher incidence of aberrant chromosome numbers and mitotic dysfunction compared to wildtype zebrafish embryos. Consistent with this finding, tumor samples obtained from ewsa^m/m;tp53^w/m zebrafish displayed loss of heterozygosity (LOH) for the wildtype tp53 locus. These results suggest that wildtype Ewsa inhibits LOH induction, possibly by maintaining chromosomal stability. We propose that the loss of ewsa promotes tumorigenesis, and EWS deficiency may contribute to the pathogenesis of EWS-fusion-expressing sarcomas.

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.

Epigenetic regulation of SMARCB1 By miR-206, -381 and -671-5p is evident in a variety of SMARCB1 immunonegative soft tissue sarcomas, while miR-765 appears specific for epithelioid sarcoma. A miRNA study of 223 soft tissue sarcomas

Complete/partial loss of SMARCB1 nuclear-immunopositivity is characteristic of a certain subset of soft tissue sarcomas (STSs). Our previous work showed that oncomiRs-206,-381, and 671-5p could silence the SMARCB1 mRNA and protein expression and that they display significant overexpression in epithelioid sarcomas (ESs). MiR-765 was overexpressed too, but functionally was inactive in the silencing. In the current work, using quantitative PCR, we conducted a miRNA study of 51 ESs, 20 rhabdoid tumors (RTs), 20 synovial sarcomas (SSs), 15 malignant peripheral nerve sheath tumors (MPNSTs), 11 myoepithelial carcinomas (MECs), and 10 extraskeletal myxoid chondrosarcomas (EMCSs) with complete/partial loss of SMARCB1 nuclear immunostain, in contrast to controls (SMARCB1-immunopositive) of 96 STSs, 13 melanomas and 10 sarcomatoid carcinomas. The SMARCB1 genetic status of ESs was determined by MLPA and FISH. A subset of ESs (5/51) showed biallelic deletion of SMARCB1 with no overexpression of any miRNA, suggesting these tumors could be the counterpart of pediatric RT, at least genetically. Another subset (5/51) was genetically either intact or monoallelic deleted with at least threefold overexpression of one of miR-206,-381,-671-5p, suggesting epigenetic regulation only. 39/51 ESs had a biallelic deletion (>20% by FISH and/or by MLPA) but with overexpressed miR-206,-381, and 671-5p, suggesting intratumoral heterogeneity, i.e., both genetic and epigenetic regulation. At least threefold overexpression of one of miR-206,-381, and 671-5p was detected in all MPNSTs, EMCSs, SSs and 7 MCs. Except for ESs, four SSs and one MPNST, there was no event above threefold overexpression of miR-765 among all 195 tested tumors. Our results suggest a general role of miR-206,-381, and 671-5p in SMARCB1 gene silencing of ES, MC, EMCS, MPNST and SS. In the future, miR-765 could possibly be a diagnostic tool for ES because of its 97% specificity and 80% sensitivity. © 2016 Wiley Periodicals, Inc.

Ewing's Sarcoma: An Analysis of miRNA Expression Profiles and Target Genes in Paraffin-Embedded Primary Tumor Tissue

The molecular mechanism responsible for Ewing’s Sarcoma (ES) remains largely unknown. MicroRNAs (miRNAs), a class of small non-coding RNAs able to regulate gene expression, are deregulated in tumors and may serve as a tool for diagnosis and prediction. However, the status of miRNAs in ES has not yet been thoroughly investigated. This study compared global miRNAs expression in paraffin-embedded tumor tissue samples from 20 ES patients, affected by primary untreated tumors, with miRNAs expressed in normal human mesenchymal stromal cells (MSCs) by microarray analysis. A miRTarBase database was used to identify the predicted target genes for differentially expressed miRNAs. The miRNAs microarray analysis revealed distinct patterns of miRNAs expression between ES samples and normal MSCs. 58 of the 954 analyzed miRNAs were significantly differentially expressed in ES samples compared to MSCs. Moreover, the qRT-PCR analysis carried out on three selected miRNAs showed that miR-181b, miR-1915 and miR-1275 were significantly aberrantly regulated, confirming the microarray results. Bio-database analysis identified BCL-2 as a bona fide target gene of the miR-21, miR-181a, miR-181b, miR-29a, miR-29b, miR-497, miR-195, miR-let-7a, miR-34a and miR-1915. Using paraffin-embedded tissues from ES patients, this study has identified several potential target miRNAs and one gene that might be considered a novel critical biomarker for ES pathogenesis.

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.

Overexpression of miR‑199b‑5p inhibits Ewing's sarcoma cell lines by targeting CCNL1

MicroRNAs (miRNAs) are known to regulate the expression of a variety of genes, which are important in the development of several types of tumor, including Ewing's sarcoma (ES), at the post‑transcriptional level. Although previous studies have identified that the expression of miRNA‑199b‑5p was downregulated in various types of tumor, the expression levels of miR‑199b‑5p in ES cells remain to be elucidated. The mechanism underlying ES via the miRNA pathway remains to be elucidated. The present study demonstrated that miR‑199b‑5p was an important regulator in ES cells and its expression was downregulated in ES originated A673/TC252 cells. The ES cell lines, A673 and TC252, were transfected with an miR‑199b‑5p mimic to overexpress the levels of this miRNA. This forced expression of miR‑199b‑5p suppressed the cell proliferation and invasion, arrested cell cycle progression, and promoted cell apoptosis. Furthermore, CCNL1 was identified by bioinformatic software as a potential target gene of miR‑199b‑5p. Following this, the present study identified CCNL1 as a direct target of miR‑199b‑5p in ES cells. Taken together, the present study established a functional link between ES, miR‑199b‑5p and CCNL1, and suggested that miR‑199b‑5p acts as a tumor suppressor and may be of diagnostic and therapeutic importance for human ES.

Review of microRNA in osteosarcoma and chondrosarcoma

MicroRNAs (miRNAs) are small noncoding RNAs, which play a complex role in posttranscriptional gene expression and can theoretically be used as a diagnostic or prognostic tool, or therapeutic target for neoplasia. Despite advances in the diagnosis and treatment of skeletal sarcomas, including osteosarcoma and chondrosarcoma, much remains unknown regarding their underpinning molecular mechanisms. Given the recent increasing knowledge base of miRNA roles in neoplasia, both as oncogenes and tumor suppressor genes, this review will focus on the available literature regarding the expression profiles and potential roles of miRNA in skeletal sarcomas. Although this is an emerging field, miRNA profiling may be of use in clarifying competing diagnoses of skeletal sarcomas and possibly indicate patient risk of resistance to traditional chemotherapeutic agents. While detecting and targeting miRNAs is currently limited to experimental investigations, miRNA may be utilized for future clinical management of skeletal sarcomas.

Structure-function based molecular relationships in Ewing's sarcoma

Ewing's Sarcoma Oncogene (ews) on chromosome 22q12 is encoding a ubiquitously expressed RNA-binding protein (EWS) with unknown function that is target of tumor-specific chromosomal translocations in Ewing's sarcoma family of tumors. A model of transcription complex was proposed in which the heterodimer Rpb4/7 binds to EAD, connecting it to Core RNA Pol II. The DNA-binding domain, provided by EFP, is bound to the promoter. Rpb4/7 binds RNA, stabilizing the transcription complex. The complex Rpb4/7 can stabilize the preinitiation complexes by converting the conformation of RNA Pol II. EWS may change its conformation, so that NTD becomes accessible. Two different mechanisms of interaction between EWS and RNA Pol II are proposed: (I) an intermolecular EWS-EWS interaction between two molecules, pushing conformation from “closed” to “open” state, or (II) an intramolecular interaction inside the molecule of EWS, pushing conformation of the molecule from “closed” to “open” state. The modified forms of EWS may interact with Pol II subunits hsRpb5 and hsRpb7. The EWS and EFPs binding partners are described schematically in a model, an attempt to link the transcription with the splicing. The proposed model helps to understand the functional molecular interactions in cancer, to find new partners and ways to treat cancer.

Variable expression of PIK3R3 and PTEN in Ewing Sarcoma impacts oncogenic phenotypes

Ewing Sarcoma is an aggressive malignancy of bone and soft tissue affecting children and young adults. Ewing Sarcoma is driven by EWS/Ets fusion oncoproteins, which cause widespread alterations in gene expression in the cell. Dysregulation of receptor tyrosine kinase signaling, particularly involving IGF-1R, also plays an important role in Ewing Sarcoma pathogenesis. However, the basis of this dysregulation, including the relative contribution of EWS/Ets-dependent and independent mechanisms, is not well understood. In the present study, we identify variable expression of two modifiers of PI3K signaling activity, PIK3R3 and PTEN, in Ewing Sarcoma, and examine the consequences of this on PI3K pathway regulation and oncogenic phenotypes. Our findings indicate that PIK3R3 plays a growth-promotional role in Ewing Sarcoma, but suggest that this role is not strictly dependent on regulation of PI3K pathway activity. We further show that expression of PTEN, a well-established, potent tumor suppressor, is lost in a subset of Ewing Sarcomas, and that this loss strongly correlates with high baseline PI3K pathway activity in cell lines. In support of functional importance of PTEN loss in Ewing Sarcoma, we show that re-introduction of PTEN into two different PTEN-negative Ewing Sarcoma cell lines results in downregulation of PI3K pathway activity, and sensitization to the IGF-1R small molecule inhibitor OSI-906. Our findings also suggest that PTEN levels may contribute to sensitivity of Ewing Sarcoma cells to the microtubule inhibitor vincristine, a relevant chemotherapeutic agent in this cancer. Our studies thus identify PIK3R3 and PTEN as modifiers of oncogenic phenotypes in Ewing Sarcoma, with potential clinical implications.

Therapy resistance mechanisms in Ewing's sarcoma family tumors

Ewing's sarcoma family tumors are aggressive small round cell malignancies that arise in bone or soft tissues in adolescents and young adults. The addition of chemotherapy to local control measures has remarkably improved the survival of patients with localized disease. However, metastatic tumors are often refractory to conventional chemotherapy and irradiation, and the outcome of patients with metastatic or recurrent disease remains dismal. Despite growing understanding of the molecular biology of this tumor and the discovery of new therapeutic targets such as the insulin growth factor-1 receptor, tumor resistance continues to be a formidable challenge. Numerous adaptive mechanisms have been identified which allow tumor cells to escape the cytotoxic effect of chemotherapeutic agents. This review focuses on these mechanisms in an effort to highlight opportunities for more effective disease control.

Let-7a functions as a tumor suppressor in Ewing's sarcoma cell lines partly by targeting cyclin-dependent kinase 6

MicroRNAs play an important role in the development and progression of Ewing's sarcoma (ES). Especially, the expression of let-7a has been reported to be significantly downregulated in various cancers, and can affect the initiation and maintenance of tumor progression. However, the relative effects of let-7a on ES cells and relative mechanisms are largely unknown. In this study, we identified the underexpression of let-7a in human ES cells comparing with the human mesenchymal stem cells. Then, we sought to compensate for its loss through exogenous transfection with let-7a mimic into ES cell lines A673 and SK-ES-1. Restored let-7a expression inhibited cell proliferation, migration, as well as invasion; arrested cell cycle progression; and induced cell apoptosis of both cell lines. Moreover, bioinformatic prediction suggested that cyclin-dependent kinase 6 (CDK6), which is overexpressed and functions as an oncoprotein in ES cells, is a putative target gene of let-7a. Using mRNA and protein expression analysis and luciferase assays, we further identified the target role of CDK6. Finally, we found that restored CDK6 expression in ES cells that had been treated with let-7a mimic before could partly dampen let-7a-mediated tumor suppression. Taken together, our results showed that let-7a acted as a tumor suppressor in ES by targeting CDK6, and it may provide novel diagnostic and therapeutic options for human Ewing sarcoma clinical operation in future.

Genomics, personalized medicine, and pediatrics

Genomic discoveries are advancing biomedicine at an ever-increasing pace. Pediatrics is near the epicenter of these discoveries, which are revising our understanding of the genome and its function. Since the completion of the Human Genome Project in 2003, dramatic reductions in the cost of genotyping, and more recently sequencing, have permitted the study of the genomes of a great number of species as well as humans. These studies have led to insights on gene regulation and the complex interplay of factors responsible for normal development and biology. Study of single-gene disorders has greatly benefited from the genomics revolution and tests are now available for well over 2000 Mendelian conditions; availability of these tests are changing screening and diagnosis paradigms for rare conditions. Genomics is also yielding an increased understanding of common conditions such as diabetes, obesity, asthma, cancers, and mental health conditions. Personalized medicine, an approach to care in which an individual's genomic information is used to help tailor interventions to maximize health outcomes, is rapidly becoming a reality for a variety of conditions. Though challenges remain in translating new genomic insights into improved patient health, today's pediatricians and their patients will increasingly benefit from this watershed moment in the biological sciences.

SMARCB1 expression in epithelioid sarcoma is regulated by miR-206, miR-381, and miR-671-5p on Both mRNA and protein levels

Proximal type epithelioid sarcoma shares similarities with malignant rhabdoid tumor, including the lack of nuclear immunoreactivity of SMARCB1. Biallelic mutation of SMARCB1 has been convincingly established as the cause of loss of protein expression in rhabdoid tumor, but the cause in epithelioid sarcoma remains unknown. In our previous work, we demonstrated that DNA hypermethylation and post-translational modification mechanisms were not involved. In this current work, we explored the hypothesis that miRNAs regulate SMARCB1 gene expression in epithelioid sarcomas. In silico target prediction analysis revealed eight candidate miRNAs, and quantitative PCR-in 32 formalin-fixed, paraffin-embedded tumor samples comprising 30 epithelioid sarcomas and two malignant rhabdoid tumors-demonstrated significant (P < 0.001) overexpression of four miRNAs in epithelioid sarcomas: miR-206, miR-381, miR-671-5p, and miR-765. Two human tumors (fibrosarcoma and colon adenocarcinoma) and a normal cell line (human dermal fibroblast) with retained SMARCB1 expression were cultured for miRNA transient transfection (electroporation) experiments. SMARCB1 mRNA expression was analyzed by quantitative real-time PCR and immunostaining of SMARCB1 was performed to examine the effect of miRNAs transfections on both RNA and protein levels. Only three of the overexpressed miRNAs (miR-206, miR-381, and miR-671-5p) could silence the SMARCB1 mRNA expression in cell cultures; most effectively miR-206. Transfection of miR-206, miR-381, miR-671-5p, and some combination of them also eliminated SMARCB1 nuclear staining, demonstrating a strong effect on not only mRNA but also protein levels. Our results suggest loss of SMARCB1 protein expression in epithelioid sarcoma is due to the epigenetic mechanism of gene silencing by oncomiRs.