Targeting the EWS::FLI1 Transcription Factor for Ewing Sarcoma: A Phase 1/2 Study of Trabectedin and Low Dose Irinotecan (SARC037)
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE322640 | GEO | 2026/03/02
REPOSITORIES: GEO
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Project description:The EWS::FLI1 transcription factor drives the growth of Ewing sarcoma (ES). Trabectedin above a threshold concentration reverses the activity of EWS::FLI1, which is potentiated in vivo by low dose irinotecan. This open label phase 1/2 trial of trabectedin with irinotecan enrolled 37 relapsed/refractory ES patients (SARC037; NCT04067115). The recommended phase 2 dose (RP2D) was trabectedin 1.0 mg/m2 over 1 hour (Day 1) and irinotecan 25 mg/m2 (Days 2 & 4) of 21-day cycle. Toxicities were manageable with >Grade 3 toxicities (>15%) of myelosuppression and ALT elevations at RP2D. The phase 2 objective response rate was 33% (39%, including RP2D phase 1 patients) and 6-month PFS was 48%. Transcriptional profiling demonstrated reversal of the EWS::FLI1 transcriptome in tumors from a subset of patients. Additional correlative objectives captured molecular profiling, ctDNA levels, and 18F-FLT PET avidity. The combination of trabectedin and irinotecan is active in ES and suppresses its driver, EWS::FLI1.
2026-03-02 | GSE322664 | GEO
Project description:The synthesis and processing of mRNA, from transcription to translation initiation, often requires splicing of intragenic material. The final mRNA composition varies based upon proteins that modulate splice site selection. EWS-FLI1 is an Ewing sarcoma (ES) oncogene with an interactome that we demonstrate to have multiple partners in spliceosomal complexes. We evaluate EWS-FLI1 upon post-transcriptional gene regulation using both exon array and RNA-seq. Genes that potentially regulate oncogenesis including CLK1, CASP3, PPFIBP1, and TERT validate as alternatively spliced by EWS-FLI1. EWS-FLI1 also alters splicing by directly binding to known splicing factors including DDX5, hnRNPK, and PRPF6. Reduction of EWS-FLI1 produces an isoform of g-TERT that has increased telomerase activity compared to WT TERT. The small molecule YK-4-279 is an inhibitor of EWS-FLI1 oncogenic function that disrupts specific protein interactions including DDX5 and RNA helicase A (RHA) that alters RNA splicing ratios. As such, YK-4-279 validates the splicing mechanism of EWS-FLI1 showing alternatively spliced gene patterns that significantly overlap with EWS-FLI1 reduction and WT human mesenchymal stem cells. Exon array analysis of 75 ES patient samples show similar isoform expression patterns to cell line models expressing EWS-FLI1, supporting the clinical relevance of our findings. These experiments establish systemic alternative splicing as an oncogenic process modulated by EWS-FLI1. EWS-FLI1 modulation of mRNA splicing may provide insight into the contribution of splicing towards oncogenesis, and reciprocally, EWS-FLI1 interactions with splicing proteins may inform the splicing code. Alternative splicing of RNA allows a limited number of coding regions in the human genome to produce proteins with diverse functionality. Alternative splicing has also been implicated as an oncogenic process. Identifying aspects of cancer cells that differentiate them from non-cancer cells remains an ongoing challenge and our research suggests that alternatively spliced mRNA and subsequent protein isoforms will provide new anti-cancer targets. We determined that the key oncogene of Ewing sarcoma (ES), EWS-FLI1, regulates alternative splicing in multiple cell line models. These experiments establish oncogenic aspects of splicing which are specific to cancer cells and thereby illuminate potentially oncogenic splicing shifts as well as provide a useful stratification mechanism for ES patients. We analyzed three models of EWS-FLI1 using Affymetrix GeneChip Human Exon 1.0 ST microarray: (i) Ewing's sarcoma TC32 wild-type cells expressing EWS-FLI1, and TC32 cells where EWS-FLI1 was reduced with a lentiviral shRNA; (ii) A673i, which has a doxycycline-inducible shRNA to reduce EWS-FLI1 expression, and wild-type EWS-FLI1 to screen for alternative splicing as measured by exon-specific expression changes; and (iii) human mesenchymal stem cells (hMSC), a putative cell of origin of Ewing's sarcoma, exogenously expressing EWS-FLI1, and hMSC wild-type cells without EWS-FLI1. Three biological replicates were included for each condition. The Bioconductor package "oligo" in the R programming language was used for normalization and background correction. Analysis was carried out using only core probesets, as defined by the manufacturer.
2015-03-31 | E-GEOD-65941 | biostudies-arrayexpress
Project description:The synthesis and processing of mRNA, from transcription to translation initiation, often requires splicing of intragenic material. The final mRNA composition varies based upon proteins that modulate splice site selection. EWS-FLI1 is an Ewing sarcoma (ES) oncogene with an interactome that we demonstrate to have multiple partners in spliceosomal complexes. We evaluate EWS-FLI1 upon post-transcriptional gene regulation using both exon array and RNA-seq. Genes that potentially regulate oncogenesis including CLK1, CASP3, PPFIBP1, and TERT validate as alternatively spliced by EWS-FLI1. EWS-FLI1 also alters splicing by directly binding to known splicing factors including DDX5, hnRNPK, and PRPF6. Reduction of EWS-FLI1 produces an isoform of g-TERT that has increased telomerase activity compared to WT TERT. The small molecule YK-4-279 is an inhibitor of EWS-FLI1 oncogenic function that disrupts specific protein interactions including DDX5 and RNA helicase A (RHA) that alters RNA splicing ratios. As such, YK-4-279 validates the splicing mechanism of EWS-FLI1 showing alternatively spliced gene patterns that significantly overlap with EWS-FLI1 reduction and WT human mesenchymal stem cells. Exon array analysis of 75 ES patient samples show similar isoform expression patterns to cell line models expressing EWS-FLI1, supporting the clinical relevance of our findings. These experiments establish systemic alternative splicing as an oncogenic process modulated by EWS-FLI1. EWS-FLI1 modulation of mRNA splicing may provide insight into the contribution of splicing towards oncogenesis, and reciprocally, EWS-FLI1 interactions with splicing proteins may inform the splicing code. Alternative splicing of RNA allows a limited number of coding regions in the human genome to produce proteins with diverse functionality. Alternative splicing has also been implicated as an oncogenic process. Identifying aspects of cancer cells that differentiate them from non-cancer cells remains an ongoing challenge and our research suggests that alternatively spliced mRNA and subsequent protein isoforms will provide new anti-cancer targets. We determined that the key oncogene of Ewing sarcoma (ES), EWS-FLI1, regulates alternative splicing in multiple cell line models. These experiments establish oncogenic aspects of splicing which are specific to cancer cells and thereby illuminate potentially oncogenic splicing shifts as well as provide a useful stratification mechanism for ES patients.
2015-03-31 | GSE65941 | GEO
Project description:Ewing sarcoma (ES) is characterized by EWS::FLI1 or EWS::ERG fusion proteins. Knowing that ion channels are involved in tumorigenesis, this work aimed to study the involvement of the KCNN1 gene, which encodes the SK1 potassium channel, in ES development. Bioinformatics analyses from databases were used to study KCNN1 expression in patients and cell lines. Molecular approaches and in vitro assays were used to study the transcriptional regulation of KCNN1 and its involvement in the regulation of ES cell proliferation. KCNN1 is overexpressed in ES patient biopsies, and its expression is inversely correlated with patient survival. EWS::FLI1, like EWS::ERG, promotes KCNN1 and SK1 expression, binding to GGAA microsatellites near the promoter of KCNN1 isoforms. KCNN1 is involved in the regulation of ES cell proliferation, with its silencing being associated with a slowing of the cell cycle, and its expression modulates membrane potential and therefore calcium flux. These results highlight that KCNN1 is a direct target of EWS::FLI1 and EWS::ERG and demonstrate that KCNN1 is involved in the regulation of intracellular calcium activity and ES cell proliferation, making it a promising therapeutic target in ES.
2024-11-04 | GSE229906 | GEO
Project description:Ewing sarcoma (ES) is an aggressive bone and soft tissue neoplasm, unique to humans, characterized by EWSR1/ETS rearrangements and whose cellular origin remains unclear. Expression of EWS-FLI1 in pediatric human mesenchymal stem cells (hMSCs) induced a transcriptional profile more resembling ES than its expression in adult hMSCs, but did not confer tumorigenic capacity. We have isolated human mesenchymal stem-like cells (hMSLCs) from experimental human embryonic stem cell (hESC)-derived teratomas. EWS-FLI1 expression in hMSLCs results in the acquisition of an ES signature through its preferential binding to microsatellites of intergenic and intronic regions. In hMSLCs, EWS-FLI1 directly regulates BRCA1 expression, although oncogene-expressing cells show defects in DNA damage repair (DDR). Xenografting in mice of EWS-FLI1-transduced hMSLCs resulted in the formation of tumors expressing characteristic ES markers. In summary, EWS-FLI1 enforces an aberrant transcriptome and endows in vivo transforming capacity when expressed in an undifferentiated early embryonic hMSC. Our approach represents an innovative experimental method for understanding critical aspects of the biology of developmental tumors, from leukemia to sarcomas, in which few (even single) genetic alterations are able to transform a fetal stem cell.
2025-01-31 | GSE272958 | GEO
Project description:Ewing sarcoma (ES) is an aggressive bone and soft tissue neoplasm, unique to humans, characterized by EWSR1/ETS rearrangements and whose cellular origin remains unclear. Expression of EWS-FLI1 in pediatric human mesenchymal stem cells (hMSCs) induced a transcriptional profile more resembling ES than its expression in adult hMSCs, but did not confer tumorigenic capacity. We have isolated human mesenchymal stem-like cells (hMSLCs) from experimental human embryonic stem cell (hESC)-derived teratomas. EWS-FLI1 expression in hMSLCs results in the acquisition of an ES signature through its preferential binding to microsatellites of intergenic and intronic regions. In hMSLCs, EWS-FLI1 directly regulates BRCA1 expression, although oncogene-expressing cells show defects in DNA damage repair (DDR). Xenografting in mice of EWS-FLI1-transduced hMSLCs resulted in the formation of tumors expressing characteristic ES markers. In summary, EWS-FLI1 enforces an aberrant transcriptome and endows in vivo transforming capacity when expressed in an undifferentiated early embryonic hMSC. Our approach represents an innovative experimental method for understanding critical aspects of the biology of developmental tumors, from leukemia to sarcomas, in which few (even single) genetic alterations are able to transform a fetal stem cell.
2025-01-31 | GSE272959 | GEO
Project description:A chimeric fusion between the RNA binding protein EWS and the ETS family transcription factor FLI1 (EWS-FLI1), created from a chromosomal translocation, is implicated in driving the majority of Ewing sarcomas (ES) by modulation of transcription and alternative splicing. The small molecule YK-4-279 inhibits EWS-FLI1 function and induces apoptosis. We tested 69 anti-cancer drugs in combination with YK-4-279 and found that vinca alkaloids exhibited synergy with YK-4-279 in five ES cell lines. The combination of YK-4-279 and vincristine reduced tumor burden and increased survival in mice bearing ES xenografts. We determined that independent drug-induced events converged to cause this synergistic therapeutic effect. YK-4-279 rapidly induced G2/M arrest, increased the abundance of cyclin B1, and decreased EWS-FLI1–mediated expression of microtubule-associated proteins, which rendered cells more susceptible to microtubule depolymerization by vincristine. YK-4-279 reduced the expression of the EWS-FLI1 target gene encoding ubiquitin ligase UBE2C, and this in part contributed to the increase in cyclin B1. Biochemical assays revealed that YK-4-279 also increased the abundance of proapoptotic isoforms of MCL1 and BCL2, presumably through inhibition of alternative splicing by EWS-FLI1, thus promoting cell death in response to vincristine. Thus a combination of vincristine and YK-4-279 might be therapeutically effective in ES patients.
2017-09-14 | GSE103837 | GEO
Project description:There is a long-established connection between epigenetic reprogramming and the local function of the spliceosome. Recently the oncogenic potential of this connection has also been recognized. Recent work has demonstrated that EWS-FLI1 recruits the BRG1/BRM-associated factor (BAF) complex, however, the specific BAF subunits that interact with EWS-FLI1 and the role of the BAF complex in oncogenesis remains unknown. Within the BAF complex, the AT-rich interactive domain-containing protein 1A (ARID1A, BAF250a) gene encodes a central scaffold. EWS-FLI1 is a well-described transcriptional regulator that also has a role in modulating RNA splicing. While EWS-FLI1 alters the splicing of many mRNA isoforms, the role of splicing modulation in ES oncogenesis remains unknown. Here we report a direct connection between the EWS-FLI1-induced transcriptome and the EWS-FLI1 protein interactome to reveal a novel interaction with a specific isoform of ARID1A that has a direct impact on oncogenicity. We report a novel feed-forward cycle of EWS-FLI1 and ARID1A-L facilitating ES growth through splicing modulation and protein stability that may lead to improved cancer-specific drug targeting.
2019-08-30 | GSE115676 | GEO
Project description:There is a critical need in cancer therapeutics to identify targeted therapies that will improve outcomes and decrease toxicities compared to conventional, cytotoxic chemotherapy. Ewing sarcoma is a highly aggressive bone and soft tissue cancer that is caused by the EWS-FLI1 fusion protein. Although EWS-FLI1 is specific for cancer cells, and required for tumorigenesis, directly targeting this transcription factor has proven challenging. Consequently, targeting unique dependencies or key downstream mediators of EWS-FLI1 represent important alternative strategies. We used gene expression data derived from a genetically defined model of Ewing sarcoma to interrogate the Connectivity Map and identify a class of drugs, iron chelators, that downregulate a significant number of EWS-FLI1 target genes. We then identified ribonucleotide reductase M2 (RRM2), the iron-dependent subunit of ribonucleotide reductase (RNR), as one mediator of iron chelator toxicity in Ewing sarcoma cells. Inhibition of RNR in Ewing sarcoma cells led to apoptosis and cell death in vitro and attenuated tumor growth in vivo in a xenograft model. Additionally, we discovered that the sensitivity of Ewing sarcoma cells to inhibition or suppression of RNR is mediated, in part, by high levels of SLFN11, a protein that sensitizes cells to DNA damage. This work demonstrates a unique dependency of Ewing sarcoma cells on RNR and supports further exploration of clinically used inhibitors of RNR as a therapeutic approach in treating this cancer.
2016-12-01 | GSE79641 | GEO
Project description:CX-5461 is a G-quadruplex stabilizer that exhibits synthetic lethality in homologous recombination (HR) deficient models. In this multicentre Phase Ib trial in patients with solid tumors, 40 patients were treated across 10 dose levels (50 - 650 mg/m2) to determine the recommended phase II dose (RP2D), and evaluate safety, tolerability, pharmacokinetics. Defective HR was explored as a predictive biomarker. CX-5461 was generally well tolerated, with a RP2D of 475 mg/m2 d1, 8 and 15 every 4 weeks, and dose limiting toxicities of phototoxicity. Responses were observed in 10% of patients, primarily in patients with defective HR (ORR 14%). Reversion mutations in PALB2 and BRCA2 were detected on progression following initial response in germline carriers, confirming the underlying synthetic lethal mechanism. In vitro characterization of UV sensitization showed this toxicity is related to the CX-5461 chemotype, independent of G4 synthetic lethality. These results establish clinical proof-of-concept for this first-in class G4 stabilizer.
| EGAS00001006173 | EGA