Pharmacological targeting of P300/CBP reveals EWS::FLI1-mediated senescence evasion in Ewing sarcoma.

Ewing sarcoma (ES) poses a significant therapeutic challenge due to the difficulty in targeting its main oncodriver, EWS::FLI1. We show that pharmacological targeting of the EWS::FLI1 transcriptional complex via inhibition of P300/CBP drives a global transcriptional outcome similar to direct knockdown of EWS::FLI1, and furthermore yields prognostic risk factors for ES patient outcome. We find that EWS::FLI1 upregulates LMNB1 via repetitive GGAA motif recognition and acetylation codes in ES cells and EWS::FLI1-permissive mesenchymal stem cells, which when reversed by P300 inhibition leads to senescence of ES cells. P300-inhibited senescent ES cells can then be eliminated by senolytics targeting the PI3K signaling pathway. The vulnerability of ES cells to this combination therapy suggests an appealing synergistic strategy for future therapeutic exploration.

Primary Ewing's Sarcoma of the Sternum in an Adult Male: A Rare Case Report.

Ewing's sarcoma, a rare primary bone malignancy primarily affecting adolescents and young adults, typically manifests in the pelvic bones and femur. Primary Ewing's sarcoma of the sternum is exceptionally rare, constituting less than 1% of cases. We present a case of a 34-year-old man with a 2-month history of anterior chest wall pain initially attributed to muscular spasm. Subsequently, the patient developed a palpable mass and imaging demonstrated a mid-lower sternal lesion with cortical destruction and soft tissue involvement, confirmed as Ewing's sarcoma on biopsy. In addition, a suspicious lesion was identified in the left distal tibia, which was histologically confirmed as a metastasis from the primary sternal sarcoma. Neoadjuvant chemotherapy preceded partial sternotomy with rib resection and reconstruction, achieving clear surgical margins. Postoperative evaluation showed shrinkage in the sternal lesion and near-resolution of the tibial metastasis. Subsequent chemotherapy cycles resulted in no evidence of the disease on the follow-up positron emission tomography scan. This case underscores the diagnostic challenges of primary sternal Ewing's sarcoma and emphasizes the importance of early recognition and comprehensive evaluation in managing such rare presentations.

Clinicopathological characteristics and genetic features of young and senior Ewing sarcoma patients.

BACKGROUND: Ewing sarcoma (EwS) is a highly malignant and heterogeneous tumor. Exploring clinicopathological characteristics and genetic features of EwS is critical for prognosis and treatment regimen. METHODS: Clinicopathological characteristics and genetic features of young (≤ 30y) and senior (> 30y) EwS patients were analyzed based on histology, phenotype, and next-generation sequencing (NGS) detection. RESULTS: The young group (18/36) presented nontypical EwS histological morphology, whereas the senior group (18/36) presented typical morphology. The prognosis of the young group was found to be worse compared with the senior group for patients without metastasis at the initial diagnosis. DNA- and RNA-based NGS was conducted on 20 extraosseous EwS patients. 16/20 samples demonstrated EWSR1-FLI1 fusion and 4/20 demonstrated EWSR1-ERG fusion. However, 13/16 EWSR1-FLI1fusions were detected both in DNA- and RNA-based NGS, 1/16 was detected only at the DNA level, and 2/16 were detected only at the RNA level. An analysis of the genetic profiles of the EWSR1-FLI1 cases revealed that the young group was inclined to couple with more copy number variations (CNV), such as CCND1, CDK4 amplification, and fusion variations, such as CHEK1-EWSR1, SLIT2-EWSR1, and EWSR1-FAM76B fusion. The senior group was more likely to have SNV or Indel mutations, such as EPHA3 and STAG2 mutations. Moreover, patients with more CNV abnormalities had a worse prognosis than those with predominantly SNP variants. In addition, compared with the senior group, the young group had significantly higher CyclinD1 protein expression. CONCLUSION: Clinicopathological characteristics and genetic features in young and senior EwS patients differed significantly. Targeting cell cycle dysregulation based on age subgroup may be a potential therapeutic strategy for Ewing sarcoma.

Lung and bone metastases patterns in Ewing sarcoma: Chemotherapy improves overall survival.

Ewing sarcoma (ES) is a small round cell malignancy, mainly in the bone tissue, followed by the soft tissue. Lung metastases (LM) and bone metastases (BM) are the most common types of metastases. From 2010 to 2018, the Surveillance, Epidemiology, and End Results database diagnosed 242 cases of ES with LM, 186 cases of ES with BM, and 74 cases of ES with LM and BM. Univariate and multivariate logistic regression analyses were used to determine the risk factors for LM and/or BM, and Kaplan-Meier curves and Cox regression analysis were used to determine the prognostic factors for LM and/or BM. Tumor size ≥50 mm, N1 stage, BM, liver metastases, and surgical treatment were significantly correlated with LM; tumor size >100 mm, brain metastases, LM, surgical treatment, and chemotherapy were significantly correlated with BM; female, N1 stage, brain metastases, liver metastases, and surgical treatment were significantly correlated with LM and BM. Older age, BM, higher T stage, no surgical treatment, and no chemotherapy were harmful to the survival of ES patients with LM; older age, female, LM, and no chemotherapy were harmful to the survival of ES patients with BM; older age and no chemotherapy were harmful to the survival of ES patients with LM and BM. Larger tumor size, N1 stages, and organ metastases were significantly associated with ES patients with LM and/or BM. Chemotherapy is effective in improving the survival.

Knockdown of PRDX2 Inhibits the Proliferation, Growth, Migration, Invasion, and MMP9 Activity of Ewing's Sarcoma Cells Cultured In Vitro.

BACKGROUND: Ewing's sarcoma (ES) is the second most common malignant primary bone tumor in children and adolescents. Peroxiredoxin 2 (PRDX2) is an antioxidant enzyme. AIMS: Here, we investigated the role and mechanism of PRDX2 in the development of ES. METHODS AND RESULTS: PRDX2 expression was knocked down in A673 and RDES cells by specific siRNA interference (si-PRDX2). Knockdown of PRDX2 strongly inhibited the proliferation, growth, migration, invasion, and MMP9 activity and induces apoptosis of A673 and RDES cells. si-PRDX2 significantly inhibited the phosphorylation of Akt and the expression of cyclin D1. The transcription factor that might regulate PRDX2 transcription was predicted with the JASPAR and UCSC databases, and analyzed using dual-luciferase and Chromatin co-immunoprecipitation experiments. SNAI1 could activate the transcription of PRDX2 by binding to predicted promoter binding site. CONCLUSION: PRDX2 may be a potential therapeutic target for ES.

EWS-FLI1 and Activator Protein-1 (AP-1) Reciprocally Regulate Extracellular-Matrix Proteins in Ewing sarcoma Cells.

Ribonucleotide reductase (RNR) is the rate-limiting enzyme in the synthesis of deoxyribonucleotides and the target of multiple chemotherapy drugs, including gemcitabine. We previously identified that inhibition of RNR in Ewing sarcoma tumors upregulates the expression levels of multiple members of the activator protein-1 (AP-1) transcription factor family, including c-Jun and c-Fos, and downregulates the expression of c-Myc. However, the broader functions and downstream targets of AP-1, which are highly context- and cell-dependent, are unknown in Ewing sarcoma tumors. Consequently, in this work, we used genetically defined models, transcriptome profiling, and gene-set -enrichment analysis to identify that AP-1 and EWS-FLI1, the driver oncogene in most Ewing sarcoma tumors, reciprocally regulate the expression of multiple extracellular-matrix proteins, including fibronectins, integrins, and collagens. AP-1 expression in Ewing sarcoma cells also drives, concurrent with these perturbations in gene and protein expression, changes in cell morphology and phenotype. We also identified that EWS-FLI1 dysregulates the expression of multiple AP-1 proteins, aligning with previous reports demonstrating genetic and physical interactions between EWS-FLI1 and AP-1. Overall, these results provide novel insights into the distinct, EWS-FLI1-dependent features of Ewing sarcoma tumors and identify a novel, reciprocal regulation of extracellular-matrix components by EWS-FLI1 and AP-1.

[Treatment of pediatric bone tumors around the knee]. / Behandlung kniegelenksnaher Knochentumoren im Wachstumsalter.

Primary bone tumors are rare but more frequently seen during childhood and with predilection for the distal femur and proximal tibia. Therapy of benign tumors-if indicated-includes surgical resection in most cases, whereas malignant bone tumors such as osteo- and Ewing's sarcomas are treated with chemotherapy, wide resection and/or radiation therapy (Ewing's sarcoma). The reconstruction of emerging bone defects is significantly influenced by surgeon-related preferences and tumor-associated factors, respectively. Double-barrel vascularized fibula grafts or extracorporeally irradiated autografts in combination with a free fibula transplant are preferred biological reconstruction techniques around the knee joint. In cases in which the knee joint cannot be preserved, reconstruction is performed using tumor endoprostheses, but potentially emerging leg length discrepancies after resection of a potent physis must be taken into account. In considerably young patients, rotationplasty might represent a viable option with promising functional results.

Treatment differences and long-term outcomes in adults and children with Ewing sarcoma.

INTRODUCTION: Ewing sarcoma is an aggressive malignancy primarily affecting children and adolescents. Limited research is available on treatment practices, clinical course, and survival in adults. METHODS: A multi-institution retrospective cohort study of all adults (>18 years) and children (≤18 years) with Ewing sarcoma treated in British Columbia, Canada between January 01, 2000 and December 31, 2018. RESULTS: One-hundred seven individuals (66 adults, 41 children) were included in the analysis. 5-year OS was 58 % in adults and 75 % in children. For individuals with local disease, 5-year OS was 74 % in adults and 84 % in children. Adult status was associated with impaired PFS (HR, 1.8; 95 % CI, 1.0 - 3.1, p=0.04) and OS (HR, 1.8; 95 % CI, 0.9 - 3.5; p=0.088). A Charlson Comorbidity Index (CCI) ≥3 was associated with impaired survival in adults and children (HR, 3.9, 95 % CI, 2.0 - 7.5; p=<0.001); baseline CCIs were not significantly different between groups. Most adults (61/66; 92 %) and all children (41/41; 100 %) received systemic treatment with no significant difference in mean lines of therapy, treatment modalities or agents. Most children received interval-compressed chemotherapy (35/41; 85 %) compared to adults (19/61; 29 %; p=<0.001). Interval-compression was not significantly associated with improved survival in adults with local disease (HR, 0.51; 95 % CI 0.1 - 2.3; p=0.373). Children more often initiated treatment within 28 days of diagnosis (31/33; 94 %) compared to adults (41/64; 64 %, p=0.001). Treatment within 28 days was associated with improved survival in the entire cohort (HR, 2.04 95 % CI, 1.1 - 3.9; p = 0.03). This association was preserved in subanalysis of individuals with local disease (HR, 5.4; 95 % CI, 1.9 - 15; p = 0.001) and only adults (HR, 5.3, 95 % CI, 1.7 - 17; p = 0.005). DISCUSSION: Survival for adults with Ewing sarcoma is inferior to children despite similarities in presentation, tumour characteristics and treatments. Further studies on the value of interval-compression in adults are required. Timely initation of treatment should be a priority for this disease.

Ewing sarcoma among children 5 years of age or younger: Is it a different disease?

INTRODUCTION: Children ≤5 years of age with Ewing's sarcoma (ES) possibly have a distinct disease biology, data on which are scarce. We evaluated clinical features, outcomes, and prognostic factors of ES among children with age ≤5 years. METHODS: Children with ES registered between 2003 and 2019 were included. Baseline clinical and treatment details were retrieved from medical records. Prognostic factors were identified using multivariable Cox regression. Clinical features and outcomes of children ≤5 years were compared with those greater than 5 years by chi-square and log-rank tests. Propensity score-matched (PSM) analysis was done to evaluate the impact of age on survival in the metastatic and localized subgroups. RESULTS: Out of the 859 patients, 86 (10%) were ≤5 years of age (median age 4 years, 60 males [69.8%]). The most common location was the extremities (37.2%), followed by thorax (27.9%) and head and neck (H&N) (22.1%); baseline metastases were seen in 25 patients (29.8%). The median event-free-survival (EFS) and overall survival (OS) were 25.6 and 68.7 months, respectively. Metastatic disease predicted inferior OS (hazard ratio [HR] = 2.54, p = .018) and EFS (HR = 2.47, p = .007], symptom duration ≤3 months predicted an inferior OS (HR = 2.17, p = .048). Compared to age greater than 5 years, younger children had more H&N and less pelvic primaries (p < .001) and lesser baseline metastases (p = .037). PSM analysis did not reveal any significant impact of age on OS in the metastatic (HR = 1.59, p = .29) or localized cohort (HR = 1.77, p = .09). CONCLUSIONS: Children with ES ≤5 years of age have a distinct favorable clinical presentation. However, age is not an independent prognostic factor for survival outcomes when adjusted for confounders.

Let it glow: Intraoperative visualization of pulmonary metastases using pafolacianine, a next-generation fluorescent agent, for young adults undergoing pulmonary metastasectomy.

A new generation of disease-specific molecular imaging agents is poised to revolutionize fluorescence-guided surgery. Pafolacianine has been approved for adult lung and ovarian cancers. We demonstrate a proof of concept for pediatric surgeons treating young adults with pulmonary metastatic sarcomas. Five successful fluorescence-guided pulmonary metastasectomy operations were performed in young adult patients with metastatic osteosarcoma or Ewing sarcoma following administration of pafolacianine. All osteosarcoma lesions identified using standard techniques were also markedly fluorescent in patients. Novel fluorescent molecular agents targeted to tumor-specific receptors have promise of increased sensitivity and specificity for detecting metastatic nodules and enhancing surgical clearance of disease.

Ewing sarcoma presenting in the lung: a case report.

BACKGROUND: Ewing sarcoma is a malignant round-cell tumor that primarily affects bones in children. It can also arise in extraosseous tissues, such as the lung, kidneys, and liver. The presentation symptoms of Ewing sarcoma may include cough, dyspnea, and chest pain. CASE PRESENTATION: This report details the history of a 15-year-old Syrian boy with a previous diagnosis of Hodgkin lymphoma who presented with chronic shoulder pain. Imaging studies revealed an 80 mm mass in the apex of the left lung, which was confirmed through histopathological examination to be Ewing sarcoma following a computed-tomography-guided biopsy. The patient received multiple cycles of chemotherapy and subsequently underwent surgical resection of the remaining mass. CONCLUSIONS: This case highlights the rare occurrence of Ewing sarcoma in the lung and the unusual clinical presentation of shoulder pain without other accompanying symptoms.

Prognostic factors and outcome of relapsed/progressive pediatric Ewing sarcoma: single-center 10-year experience.

BACKGROUND: Ewing sarcoma (ES) is the second most common primary malignant bone tumor in children and adolescents. Despite more intensive chemotherapy regimens and improved local control therapy, there is still a considerable rate of recurrent/progressive disease. METHODS: A retrospective study of 50 relapsed/progressive ES patients who were treated at the National Cancer Institute (NCI), Cairo University, during the period from 1st of January 2008 to the end of December 2018, to assess different prognostic variables and disease outcomes. RESULTS: Out of fifty eligible cases, 32 patients (64%) had disease recurrence, and 18 (36%) developed disease progression on treatment. The median follow-up period was 7.4 months. The median overall survival (OS) was 7.5 months, and the cumulative OS was 64% at 6 months and 32.6% at 1 year. The cumulative event-free survival (EFS) was 41.3% at 6 months and 22.3% at 1 year. Patients with disease recurrence had better OS and EFS than patients with disease progression (p = 0.019). Patients who underwent local control at relapse/progression had a significantly better outcome than patients who received chemotherapy only (p < 0.001). Recurrence > 2 years from initial diagnosis was the only independent predictor of better survival outcome. CONCLUSIONS: Patients with relapsing/progressive ES portended a poor outcome, with disease progression on treatment faring worse than relapse. Better outcome was observed in patients who experienced recurrence > 2 years after diagnosis, patients with disease recurrence rather than disease progression on treatment, and patients who underwent local control along with intensive chemotherapy.

Prion-like domain mediated phase separation of ARID1A promotes oncogenic potential of Ewing's sarcoma.

Liquid-liquid phase separation (LLPS) facilitates the formation of membraneless organelles within cells, with implications in various biological processes and disease states. AT-rich interactive domain-containing protein 1A (ARID1A) is a chromatin remodeling factor frequently associated with cancer mutations, yet its functional mechanism remains largely unknown. Here, we find that ARID1A harbors a prion-like domain (PrLD), which facilitates the formation of liquid condensates through PrLD-mediated LLPS. The nuclear condensates formed by ARID1A LLPS are significantly elevated in Ewing's sarcoma patient specimen. Disruption of ARID1A LLPS results in diminished proliferative and invasive abilities in Ewing's sarcoma cells. Through genome-wide chromatin structure and transcription profiling, we identify that the ARID1A condensate localizes to EWS/FLI1 target enhancers and induces long-range chromatin architectural changes by forming functional chromatin remodeling hubs at oncogenic target genes. Collectively, our findings demonstrate that ARID1A promotes oncogenic potential through PrLD-mediated LLPS, offering a potential therapeutic approach for treating Ewing's sarcoma.

Ceramide-induced cleavage of GPR64 intracellular domain drives Ewing sarcoma.

Ewing sarcoma is a cancer of bone and soft tissue in children and young adults primarily driven by the EWS-FLI1 fusion oncoprotein, which has been undruggable. Here, we report that Ewing sarcoma depends on secreted sphingomyelin phosphodiesterase 1 (SMPD1), a ceramide-generating enzyme, and ceramide. We find that G-protein-coupled receptor 64 (GPR64)/adhesion G-protein-coupled receptor G2 (ADGRG2) responds to ceramide and mediates critical growth signaling in Ewing sarcoma. We show that ceramide induces the cleavage of the C-terminal intracellular domain of GPR64, which translocates to the nucleus and restrains the protein levels of RIF1 in a manner dependent on SPOP, a substrate adaptor of the Cullin3-RING E3 ubiquitin ligase. We demonstrate that both SMPD1 and GPR64 are transcriptional targets of EWS-FLI1, indicating that SMPD1 and GPR64 are EWS-FLI1-induced cytokine-receptor dependencies. These results reveal the SMPD1-ceramide-GPR64 pathway, which drives Ewing sarcoma growth and is amenable to therapeutic intervention.

Extraskeletal Ewing Sarcoma Disguised as a Vascular Malformation.

Extraskeletal Ewing sarcoma (EES) is a rare entity, accounting for only 3% of lesions encountered in upper extremity. We present two paediatric patients, who were initially diagnosed with a vascular malformation based on clinical assessment and imaging. Final histopathology revealed Ewing sarcoma of soft tissue origin, confirmed by immunohistochemical analysis. Hand surgeons, who are routinely approached for a myriad of hand pathologies, should be wary and consider EES as a differential when treating such lesions. A multidisciplinary approach with an appropriate treatment algorithm can help in a speedy diagnosis, improving the long-term prognosis of the disease. Level of Evidence: Level V (Therapeutic).

Combinatorial macrophage induced innate immunotherapy against Ewing sarcoma: Turning "Two Keys" simultaneously.

BACKGROUND: Macrophages play important roles in phagocytosing tumor cells. However, tumors escape macrophage phagocytosis in part through the expression of anti-phagocytic signals, most commonly CD47. In Ewing sarcoma (ES), we found that tumor cells utilize dual mechanisms to evade macrophage clearance by simultaneously over-expressing CD47 and down-regulating cell surface calreticulin (csCRT), the pro-phagocytic signal. Here, we investigate the combination of a CD47 blockade (magrolimab, MAG) to inhibit the anti-phagocytic signal and a chemotherapy regimen (doxorubicin, DOX) to enhance the pro-phagocytic signal to induce macrophage phagocytosis of ES cells in vitro and inhibit tumor growth and metastasis in vivo. METHODS: Macrophages were derived from human peripheral blood monocytes by granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF). Flow cytometry- and microscopy-based in-vitro phagocytosis assays were performed to evaluate macrophage phagocytosis of ES cells. Annexin-V assay was performed to evaluate apoptosis. CD47 was knocked out by CRISPR/Cas9 approach. ES cell-based and patient-derived-xenograft (PDX)-based mouse models were utilized to assess the effects of MAG and/or DOX on ES tumor development and animal survival. RNA-Seq combined with CIBERSORTx analysis was utilized to identify changes in tumor cell transcriptome and tumor infiltrating immune cell profiling in MAG and/or DOX treated xenograft tumors. RESULTS: We found that MAG significantly increased macrophage phagocytosis of ES cells in vitro (p < 0.01) and had significant effect on reducing tumor burden (p < 0.01) and increasing survival in NSG mouse model (p < 0.001). The csCRT level on ES cells was significantly enhanced by DOX in a dose- and time-dependent manner (p < 0.01). Importantly, DOX combined with MAG significantly enhanced macrophage phagocytosis of ES cells in vitro (p < 0.01) and significantly decreased tumor burden (p < 0.01) and lung metastasis (p < 0.0001) and extended animal survival in vivo in two different mouse models of ES (p < 0.0001). Furthermore, we identified CD38, CD209, CD163 and CD206 as potential markers for ES-phagocytic macrophages. Moreover, we found increased M2 macrophage infiltration and decreased expression of Cd209 in the tumor microenvironment of MAG and DOX combinatorial therapy treated tumors. CONCLUSIONS: By turning "two keys" simultaneously to reactivate macrophage phagocytic activity, our data demonstrated an effective and highly translatable alternative therapeutic approach utilizing innate (tumor associated macrophages) immunotherapy against high-risk metastatic ES.

Germline variants in patients diagnosed with pediatric soft tissue sarcoma.

BACKGROUND: While soft tissue sarcomas affect younger patients, few studies have assessed the distribution of underlying pathogenic germline variants. PATIENTS AND METHODS: We retrospectively identified all pediatric and young adult patients (0-22 years) at Haukeland University Hospital, Norway (1981-2019), through clinical and pathological records. We identified n = 46 eligible patients. From these 46 patients, adequate material representing normal tissue was available for n = 41 cases (n = 24 diagnosed with rhabdomyosarcoma, 9 with synovial sarcomas, 2 with Ewing sarcomas, and 6 without further classification), with matching tumor tissue for n = 40. Normal tissue samples were analyzed for germline pathogenic variants (PVs) by targeted sequencing of 360 cancer genes. RESULTS: Out of the 41 analyzed cases, we found PVs or likely PVs in 7 (17%). These variants were found in TP53, MUTYH, FANCC, DICER1, FANCA, MYO3A, and MYO5B. Supporting the causality of these PVs, four cases revealed loss of heterozygosity (LOH) of the wild-type allele in the tumor tissue, one patient with a PV in DICER1 had a second somatic variant in DICER1, and a patient with a PV in TP53 had the altered allele amplified in the tumor. For three out of five with available family history, a history of other cancers in relatives was recorded. Among genes with variants of uncertain significance, CHD1L was of particular interest, revealing a stop-gain and a missense variant. INTERPRETATION: A high fraction of young patients with soft tissue sarcoma harbor PVs. Among the genes affected, we substantiate a potential role of MYO5B and propose a potential role for MYO3A.

Human EWS-FLI protein levels and neomorphic functions show a complex, function-specific dose-response relationship in Drosophila.

Ewing sarcoma (EwS) is a cancer that arises in the bones and soft tissues, typically driven by the Ewing's sarcoma breakpoint region 1-Friend leukemia virus integration 1 (EWS-FLI) oncogene. Implementation of genetically modified animal models of EwS has proved difficult largely owing to EWS-FLI's high toxicity. The EWS-FLI1FS frameshift variant that circumvents toxicity but is still able to perform key oncogenic functions provided the first study model in Drosophila. However, the quest for Drosophila lines expressing full-length, unmodified EWS-FLI remained open. Here, we show that EWS-FLI1FS's lower toxicity is owed to reduced protein levels caused by its frameshifted C-terminal peptide, and report new strategies through which we have generated Drosophila lines that express full-length, unmodified EWS-FLI. Using these lines, we have found that the upregulation of transcription from GGAA-microsatellites (GGAAµSats) presents a positive linear correlation within a wide range of EWS-FLI protein concentrations. In contrast, rather counterintuitively, GGAAµSats-independent transcriptomic dysregulation presents relatively minor differences across the same range, suggesting that GGAAµSat-dependent and -independent transcriptional upregulation present different kinetics of response with regards to changing EWS-FLI protein concentration. Our results underpin the functional relevance of varying EWS-FLI expression levels and provide experimental tools to investigate, in Drosophila, the effect of the EWS-FLI 'high' and 'low' states that have been reported and are suspected to be important for EwS in humans.

SETD8 inhibits apoptosis and ferroptosis of Ewing's sarcoma through YBX1/RAC3 axis.

Ewing's sarcoma (ES) represents a rare yet exceedingly aggressive neoplasm that poses a significant health risk to the pediatric and adolescent population. The clinical outcomes for individuals with relapsed or refractory ES are notably adverse, primarily attributed to the constrained therapeutic alternatives available. Despite significant advancements in the field, molecular pathology-driven therapeutic strategies have yet to achieve a definitive reduction in the mortality rates associated with ES. Consequently, there exists an imperative need to discover innovative therapeutic targets to effectively combat ES. To reveal the mechanism of the SETD8 (also known as lysine methyltransferase 5A) inhibitor UNC0379, cell death manners were analyzed with different inhibitors. The contributions of SETD8 to the processes of apoptosis and ferroptosis in ES cells were evaluated employing the histone methyltransferase inhibitor UNC0379 in conjunction with RNA interference techniques. The molecular regulatory mechanisms of SETD8 in ES were examined through the application of RNA sequencing (RNA-seq) and mass spectrometry-based proteomic analysis. Moreover, nude mouse xenograft models were established to explore the role of SETD8 in ES in vivo. SETD8, a sole nucleosome-specific methyltransferase that catalyzes mono-methylation of histone H4 at lysine 20 (H4K20me1), was found to be upregulated in ES, and its overexpression was associated with dismal outcomes of patients. SETD8 knockdown dramatically induced the apoptosis and ferroptosis of ES cells in vitro and suppressed tumorigenesis in vivo. Mechanistic investigations revealed that SETD8 facilitated the nuclear translocation of YBX1 through post-transcriptional regulatory mechanisms, which subsequently culminated in the transcriptional upregulation of RAC3. In summary, SETD8 inhibits the apoptosis and ferroptosis of ES cells through the YBX1/RAC3 axis, which provides new insights into the mechanism of tumorigenesis of ES. SETD8 may be a potential target for clinical intervention in ES patients.