Ewing sarcoma is a cancer of bone and soft tissue in children driven by EWS::ETS fusion, most commonly EWS::FLI1. Because current cytotoxic chemotherapies are not improving the survival of those with metastatic or recurrent Ewing sarcoma cases, there is a need for novel and more effective targeted therapies. While EWS::FLI1 is the major driver of Ewing sarcoma, EWS::FLI1 has been difficult to target. A promising alternative approach is to identify and target the molecular vulnerabilities created by EWS::FLI1. Here we report that EWS::FLI1 induces the expression of Slit2, the ligand of Roundabout (Robo) receptors implicated in axon guidance and multiple other developmental processes. EWS::FLI1 binds to the Slit2 gene promoter and stimulates the expression of Slit2. Slit2 inactivates cdc42 and stabilizes the BAF chromatin remodeling complexes, enhancing EWS::FLI1 transcriptional output. Silencing of Slit2 strongly inhibited anchorage-dependent and anchorage-independent growth of Ewing sarcoma cells. Silencing of Slit2 receptors, Robo1 and Robo2, inhibited Ewing sarcoma growth as well. These results uncover a new role for Slit2 signaling in stimulating Ewing sarcoma growth and suggest that this pathway can be targeted therapeutically.

Angiogenesis is required for tumor growth. WT1, a protein that affects both mRNA transcription and splicing, has recently been shown to regulate expression of vascular endothelial growth factor (VEGF), one of the major mediators of angiogenesis. In the present study, we tested the hypothesis that WT1 is a key regulator of tumor angiogenesis in Ewing sarcoma. We expressed exogenous WT1 in the WT1-null Ewing sarcoma cell line, SK-ES-1, and we suppressed WT1 expression using shRNA in the WT1-positive Ewing sarcoma cell line, MHH-ES. Suppression of WT1 in MHH-ES cells impairs angiogenesis, while expression of WT1 in SK-ES-1 cells causes increased angiogenesis. Different WT1 isoforms result in vessels with distinct morphologies, and this correlates with preferential upregulation of particular VEGF isoforms. WT1-expressing tumors show increased expression of pro-angiogenic molecules such as VEGF, MMP9, Ang-1, and Tie-2, supporting the hypothesis that WT1 is a global regulator of angiogenesis. We also demonstrate that WT1 regulates the expression of a panel of pro-angiogenic molecules in Ewing sarcoma cell lines. Finally, we found that WT1 expression is correlated with VEGF expression, MMP9 expression, and microvessel density in samples of primary Ewing sarcoma. Thus, our results demonstrate that WT1 expression directly regulates tumor angiogenesis by controlling the expression of a panel of pro-angiogenic genes.

The diagnosis of Ewing sarcoma family of tumours (ESFT) is challenging, especially in adults and in extra-skeletal or visceral location. Several morphologic mimics with varied treatment options and prognosis confer diagnostic dilemmas. Application of ancillary diagnostic modalities in surgical pathology in clinical routine has enabled accurate diagnosis of ESFT in bone, soft tissues, and viscera.

Ewing sarcoma is an aggressive pediatric small round cell tumor that predominantly occurs in bone. Approximately 85% of Ewing sarcomas harbor the EWS/FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS/FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS/FLI binds the osteogenic transcription factor RUNX2 and prevents osteoblast differentiation. In this study, we investigated the role of another Runt-domain protein, RUNX3, in Ewing sarcoma. RUNX3 participates in mesenchymal-derived bone formation and is a context dependent tumor suppressor and oncogene. RUNX3 was detected in all Ewing sarcoma cells examined, whereas RUNX2 was detected in only 73% of specimens. Like RUNX2, RUNX3 binds to EWS/FLI via its Runt domain. EWS/FLI prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2. Stable suppression of RUNX3 expression in the Ewing sarcoma cell line A673 delayed colony growth in anchorage independent soft agar assays and reversed expression of EWS/FLI-responsive genes. These results demonstrate an important role for RUNX3 in Ewing sarcoma.

Ewing sarcoma (EWS) is a pediatric malignancy driven by the EWSR1-FLI1 fusion protein formed by the chromosomal translocation t(11; 22). The small molecule TK216 was developed as a first-in-class direct EWSR1-FLI1 inhibitor and is in phase II clinical trials in combination with vincristine for patients with EWS. However, TK216 exhibits anti-cancer activity against cancer cell lines and xenografts that do not express EWSR1-FLI1, and the mechanism underlying cytotoxicity remains unresolved. We apply a forward-genetics screening platform utilizing engineered hypermutation in EWS cell lines and identify recurrent mutations in TUBA1B, encoding ⍺-tubulin, that prove sufficient to drive resistance to TK216. Using reconstituted microtubule (MT) polymerization in vitro and cell-based chemical probe competition assays, we demonstrate that TK216 acts as an MT destabilizing agent. This work defines the mechanism of cytotoxicity of TK216, explains the synergy observed with vincristine, and calls for a reexamination of ongoing clinical trials with TK216.

The incidence of Ewing sarcoma varies according to race and ethnicity, and genetic susceptibility is known to affect disease risk. Apart from these factors, the etiology of Ewing sarcoma is largely unknown.

The prognosis of patients with Ewing sarcoma (ES) has improved over the course of the last decades. However, those patients suffering from metastatic and recurrent ES still have only poor chances of survival and require new therapeutic approaches. Interleukin-6 (IL6) is a pleiotropic cytokine expressed by immune cells and a great variety of cancer cells. It induces inflammatory responses, enhances proliferation and inhibits apoptosis in cancer cells, thereby promoting chemoresistance.

Metastatic spread is the single-most powerful predictor of poor outcome in Ewing sarcoma (ES). Therefore targeting pathways that drive metastasis has tremendous potential to reduce the burden of disease in ES. We previously showed that activation of the ERBB4 tyrosine kinase suppresses anoikis, or detachment-induced cell death, and induces chemoresistance in ES cell lines in vitro. We now show that ERBB4 is transcriptionally overexpressed in ES cell lines derived from chemoresistant or metastatic ES tumours. ERBB4 activates the PI3K-Akt cascade and focal adhesion kinase (FAK), and both pathways contribute to ERBB4-mediated activation of the Rac1 GTPase in vitro and in vivo. ERBB4 augments tumour invasion and metastasis in vivo, and these effects are blocked by ERBB4 knockdown. ERBB4 expression correlates significantly with reduced disease-free survival, and increased expression is observed in metastatic compared to primary patient-matched ES biopsies. Our findings identify a novel ERBB4-PI3K-Akt-FAK-Rac1 pathway associated with aggressive disease in ES. These results predict that therapeutic targeting of ERBB4, alone or in combination with cytotoxic agents, may suppress the metastatic phenotype in ES.

Among sarcomas, Ewing sarcoma (EWS) is characterized as a highly malignant type of bone tumor caused by the fusion of EWS RNA Binding Protein-1 (EWSR1)/ Friend leukemia integration 1 (FLI1) genes. The product of fusion gene gives rise to EWSR1/FLI1 which activates the activity of Eyes absent homolog 3 (EYA3) which causes tumor growth and angiogenesis. EYA3 is now considered as a therapeutic drug target for EWS . The study was designed to gather potential inhibitors for the EYA3 target using medicinal compounds.

Ewing sarcoma is a malignant pediatric bone and soft tissue tumor. Although the 5-year survival rate of localized disease approaches 75%, the prognosis of metastatic and/or therapy-resistant disease remains dismal despite the wide use of aggressive therapeutic strategies. We previously reported that high expression of glutathione S-transferase M4 (GSTM4) in primary tumors correlates with poor patient outcomes. GSTM4 is required for oncogenic transformation and mediates resistance to chemotherapeutic drugs in Ewing sarcoma cells. Here, we performed RNA-sequencing analyses of Ewing sarcoma cells and combined our results with publicly available datasets to demonstrate that GSTM4 is a major GST specifically expressed in Ewing sarcoma. Pharmacological inhibition of GSTM4 activity using a pan GST inhibitor, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol (NBDHEX), significantly limited cellular proliferation and oncogenic transformation of Ewing sarcoma cells. Moreover, combined use of NBDHEX and etoposide synergistically increased cytotoxicity, suggesting a role for GSTM4 as an inhibitor of apoptosis. Mechanistic studies revealed that GSTM4 limits apoptosis owing to its ability to interact with Apoptosis Signal-regulating Kinase 1 (ASK1) and inhibit signaling via the c-Jun N-terminal Kinase axis. To exploit our observation that GSTM4 expression is specifically up-regulated in Ewing sarcoma, we tested the effect of a GSTM4-activated anti-cancer agent, O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate or JS-K, on tumor growth and survival. We found that JS-K robustly decreased Ewing sarcoma cell viability and xenograft tumor growth and improved overall survival of xenograft mice. Our data suggest that GSTM4 is a novel therapeutic target for the treatment of high GSTM4-expressing Ewing sarcoma. Strategies that combine standard chemotherapy with agents that inhibit GSTM4, that are activated by GSTM4, or that block GSTM4/ASK1 interactions, can potentially be more specific and/or efficacious than standard therapeutic approaches.

The detection of chromosomal translocations has important implications in the diagnosis, prognosis and treatment of patients with cancer. Current approaches to translocation detection have significant shortcomings, including limited sensitivity and/or specificity, and difficulty in application to formalin-fixed paraffin-embedded (FFPE) clinical samples. We developed a new approach called antibody detection of translocations (ADOT) that avoids the shortcomings of current techniques. ADOT combines a transcriptional microarray-based approach with a novel antibody-based detection method. ADOT allows for the accurate and sensitive identification of translocations and provides exon-level information about the fusion transcript. ADOT can detect translocations in poor-quality unprocessed total ribonucleic acid (RNA). Furthermore, the technique is readily generalizable to detect any potential fusion transcript, including previously undescribed fusions. We demonstrate the feasibility of ADOT by examples in which both known and unknown Ewing sarcoma translocations are identified from cell lines, tumour xenografts and FFPE primary tumours. These results demonstrate that ADOT may be an effective approach for translocation analysis in clinical specimens with significant RNA degradation and may offer a novel diagnostic tool for translocation-based cancers.

The differential diagnosis of Ewing sarcoma and osteomyelitis can be challenging and can lead to delays in treatment with possibly devastating results. In this retrospective, small-cohort study we demonstrate, that the Fourier Transformed Infrared (FTIR) spectra of osteomyelitis bone tissue can be differentiated from Ewing sarcoma and normal bone tissue sampled outside tumour area. Significant differences in osteomyelitis samples can be seen in lipid and protein composition. Supervised learning using a quadratic discriminant analysis classifier was able to differentiate the osteomyelitis samples with high accuracy. FTIR spectroscopy, alongside routine radiological and histopathological methods, may offer an additional tool for the differential diagnosis of osteomyelitis and ES.

Ewing Family Tumors (Ewing Sarcoma and peripheral Primitive Neuroectodermal Tumor) are common bone and soft tissue malignancies of childhood, adolescence and young adulthood. Chromosomal translocation in these tumors produces fusion oncogenes of the EWS/ETS class, with EWS/FLI1 being by far the most common. EWS/ETS chimera are the only well established driver mutations in these tumors and they function as aberrant transcription factors. Understanding the downstream genes whose expression is modified has been a central approach to the study of these tumors. FOXM1 is a proliferation associated transcription factor which has increasingly been found to play a role in the pathogenesis of a wide range of human cancers. Here we demonstrate that FOXM1 is expressed in Ewing primary tumors and cell lines. Reduction in FOXM1 expression in Ewing cell lines results in diminished potential for anchorage independent growth. FOXM1 expression is enhanced by EWS/FLI1, though, unlike other tumor systems, it is not driven by expression of the EWS/FLI1 target GLI1. Thiostrepton is a compound known to inhibit FOXM1 by direct binding. We show that Thiostrepton diminishes FOXM1 expression in Ewing cell lines and this reduction reduces cell viability through an apoptotic mechanism. FOXM1 is involved in Ewing tumor pathogenesis and may prove to be a useful therapeutic target in Ewing tumors.

Despite multimodal therapy, the prognosis of patients with metastatic Ewing sarcoma (ES) remains poor, with new treatments urgently needed. The disialoganglioside GD2, a well-established tumor-associated antigen, is expressed in 40% to 90% of ES cells, making it a suitable therapeutic target. Here we report 3 cases with newly diagnosed, metastatic, GD2-positive ES or Ewing-like sarcoma treated with the anti-GD2 antibody dinutuximab beta in addition to standard chemotherapeutic regimens. Treatment was well-tolerated, and all patients achieved complete remission, without evidence of relapse. First-line anti-GD2 immunotherapy in patients with metastatic, GD2-positive ES or Ewing-like sarcoma represents a promising therapeutic option that warrants further clinical evaluation.

A review is made of the clinical, diagnostic, therapeutic and survival characteristics of Ewing sarcoma (ES) of the oral cavity.

Interleukin-2 (IL-2) transgenic Ewing sarcoma cells can induce tumor specific T and NK cell responses and reduce tumor growth in vivo and in vitro. Nevertheless, the efficiency of this stimulation is not high enough to inhibit tumor growth completely. In addition to recognition of the cognate antigen, optimal T-cell stimulation requires signals from so-called co-stimulatory molecules. Several members of the tumor necrosis factor superfamily have been identified as co-stimulatory molecules that can augment antitumor immune responses. OX40 (CD134) and OX40 ligand (OX40L = CD252; also known as tumor necrosis factor ligand family member 4) is one example of such receptor/ligand pair with co-stimulatory function. In the present investigation, we generated OX40L transgenic Ewing sarcoma cells and tested their immunostimulatory activity in vitro. OX40L transgenic Ewing sarcoma cells showed preserved expression of Ewing sarcoma-associated (anti)gens including lipase member I, cyclin D1 (CCND1), cytochrome P450 family member 26B1 (CYP26B1), and the Ewing sarcoma breakpoint region 1-friend leukemia virus integration 1 (EWSR1-FLI1) oncogene. OX40L-expressing tumor cells showed a trend for enhanced immune stimulation against Ewing sarcoma cells in combination with IL-2 and stimulation of CD137. Our data suggest that inclusion of the OX40/OX40L pathway of co-stimulation might improve immunotherapy strategies for the treatment of Ewing sarcoma.

The globally low incidence of pediatric chest wall Ewing sarcoma (CWES) has limited prior studies of this disease to mostly small, single-institution reviews. Our objective was to assess incidence, demographics, treatment patterns, and long-term survival of this disease through a population-based analysis.

We report here on a case of Ewing sarcoma (ES) occurring in a child with neurofibromatosis type 1. The sarcoma had an EWSR1-ERG translocation as well as loss of the remaining wild-type allele of NF1. Loss of the NF1 wild-type allele in the tumor suggests that activation of the Ras pathway contributed to its evolution. Review of available public data suggests that secondary mutations in the Ras pathway are found in ∼3% of ESs. This case suggests that Ras pathway activation may play a role in tumor progression in a subset of ESs.

Ewing sarcoma (ES), the second most prevalent bone malignant tumor has no widely known prognostic biomarker. Earlier studies have suggested that chaperonin containing TCP1 complex 6A (CCT6A), which encodes a molecular protein chaperone, is involved in the pathogenesis of many cancers. However, there are no known reports providing clear evidence of its role in ES pathogenesis.

There is an imperious need for the development of novel therapeutics for the treatment of Ewing sarcoma, the second most prevalent solid bone tumour observed in children and young adolescents. Recently, a 4-nitrobenzofuroxan derivative, XI-006 (NSC207895) was shown to diminish MDM4 promoter activity in breast cancer cell lines. As amplification of MDM4 is frequently observed in sarcomas, this study examined the therapeutic potential of XI-006 for the treatment of Ewing and osteosarcoma. XI-006 treatment of Ewing and osteosarcoma cell lines (n = 11) resulted in rapid and potent apoptosis at low micro-molar concentrations specifically in Ewing sarcoma cell lines (48 hr IC50 0.099-1.61 μM). Unexpectedly, apoptotic response was not dependent on MDM4 mRNA/protein levels or TP53 status. Alkaline/neutral comet and γH2AX immunofluorescence assays revealed that the cytotoxic effects of XI-006 could not be attributed to the induction of DNA damage. RNA expression analysis revealed that the mechanism of action of XI-006 could be accredited to the inhibition of cell division and cycle regulators such as KIF20A and GPSM2. Finally, potent synergy between XI-006 and olaparib (PARP inhibitor) were observed due to the down-regulation of Mre11. Our findings suggest that XI-006 represents a novel therapeutic intervention for the treatment of Ewing sarcoma.