1. Overview of EWSR1-FLI1
- Genes involved:
- EWSR1 (Ewing Sarcoma Breakpoint Region 1) – chromosome 22q12
- FLI1 (Friend Leukemia Integration 1 transcription factor) – chromosome 11q24
- Fusion: t(11;22)(q24;q12) → EWSR1-FLI1 fusion gene
- Result: Oncogenic fusion protein acts as abnormal transcription factor, driving proliferation and blocking differentiation
2. Tumor Association
- Primary Tumor: Ewing Sarcoma family of tumors (ESFT)
- Rare, aggressive bone and soft tissue sarcomas
- Most common in children and adolescents (age 10–20)
- Diagnostic Marker:
- Detection of EWSR1-FLI1 fusion confirms Ewing Sarcoma
- FISH, RT-PCR, or next-generation sequencing can detect fusion
3. Mechanism of Oncogenesis
- Fusion protein functions:
- Acts as transcriptional activator/repressor
- Dysregulates cell cycle genes, growth factors, and survival pathways
- Promotes chromatin remodeling and aberrant gene expression
- Downstream effects:
- Upregulation of IGF1, NKX2.2, CCND1
- Inhibition of differentiation → uncontrolled growth
4. Clinical Implications
- Prognosis:
- Aggressive tumor; metastatic disease at diagnosis worsens prognosis
- Fusion type (e.g., type 1 vs type 2 EWSR1-FLI1 transcript) can influence survival
- Treatment:
- Multi-agent chemotherapy: VDC/IE (Vincristine, Doxorubicin, Cyclophosphamide / Ifosfamide, Etoposide)
- Surgery ± radiation for local control
- Targeted therapies: Investigational agents targeting EWS-FLI1 transcription or IGF1R pathway
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Monitoring:
- Imaging (MRI, CT, PET)
- Fusion transcript detection for minimal residual disease in research settings
5. Key Points for Pharmacy/Clinical Reference
- EWSR1-FLI1 is a pathognomonic driver fusion in Ewing Sarcoma
- Direct targeting is difficult; most therapies are cytotoxic chemotherapy
- Molecular detection guides diagnosis and may inform prognosis