K. Szuhai, M. Ijszenga, D. de Jong
Apr 1, 2009
Clinical Cancer Research
Purpose: Ewing sarcoma is an aggressive sarcoma and is the second most common bone sarcoma in childhood. Disease-specific t(11;22) (∼85-90%), t(21;22) (∼5-10%), or rarer variant translocations with the involvement of chromosome 22 (∼5%) are present. At the gene level, the EWSR1 gene fuses with FLI1, ERG, or other ETS transcription factor family members. Thus far, no Ewing sarcoma has been identified with a fusion to transcription factors other than ETS. Experimental Design: Using molecular tools such as multicolor fluorescence in situ hybridization and array comparative genomic hybridization, a ring chromosome containing chromosomes 20 and 22 was identified in four Ewing sarcoma cases. The breakpoint was mapped with (fiber-) fluorescence in situ hybridization and reverse transcription-PCR followed by sequencing of the fusion partners. Results: Molecular karyotyping showed the translocation and amplification of regions of chromosomes 20q13 and 22q12. Cloning of the breakpoint showed an in-frame fusion between the EWSR1 and NFATc2 genes, resulting in loss of the NH2-terminal, calcineurin-dependent control region and an intact active domain of NFATc2 controlled by the transactivation domains of EWSR1. Conclusion: A new translocation involving EWSRI and NFATc2 was cloned. NFATc2 is a transcription factor that is not a member of the ETS family and functions in T-cell differentiation and immune response. Direct involvement of NFATc2 has not yet been observed in oncogenesis. We show that due to the shared sequence recognition of NFATc2 and the ETS family, shared transcriptional control is possible using activating protein complex 1.