Long noncoding RNA EWSAT1-mediated gene repression facilitates Ewing sarcoma oncogenesis.

Chromosomal translocation that results in fusion of the genes encoding RNA-binding protein EWS and transcription factor FLI1 (EWS-FLI1) is pathognomonic for Ewing sarcoma. EWS-FLI1 alters gene expression through mechanisms that are not completely understood. We performed RNA sequencing (RNAseq) analysis on primary pediatric human mesenchymal progenitor cells (pMPCs) expressing EWS-FLI1 in order to identify gene targets of this oncoprotein. We determined that long noncoding RNA-277 (Ewing sarcoma-associated transcript 1 [EWSAT1]) is upregulated by EWS-FLI1 in pMPCs. Inhibition of EWSAT1 expression diminished the ability of Ewing sarcoma cell lines to proliferate and form colonies in soft agar, whereas EWSAT1 inhibition had no effect on other cell types tested. Expression of EWS-FLI1 and EWSAT1 repressed gene expression, and a substantial fraction of targets that were repressed by EWS-FLI1 were also repressed by EWSAT1. Analysis of RNAseq data from primary human Ewing sarcoma further supported a role for EWSAT1 in mediating gene repression. We identified heterogeneous nuclear ribonucleoprotein (HNRNPK) as an RNA-binding protein that interacts with EWSAT1 and found a marked overlap in HNRNPK-repressed genes and those repressed by EWS-FLI1 and EWSAT1, suggesting that HNRNPK participates in EWSAT1-mediated gene repression. Together, our data reveal that EWSAT1 is a downstream target of EWS-FLI1 that facilitates the development of Ewing sarcoma via the repression of target genes.

The impact of surgical excision in chest wall rhabdomyosarcoma: a report from the Children's Oncology Group.

AIMS: Rhabdomyosarcoma (RMS) is the most common soft tissue tumor of childhood. Patient age, size, histologic finding, and site of the tumor are primary determinants of prognosis in RMS. Chest wall RMS is a site in which the limitations of surgical excision are realized. We aim to determine the impact of surgical excision in chest wall RMS. METHODS: A retrospective chart review was conducted of all 130 pediatric patients enrolled in the Intergroup Rhabdomyosarcoma Study (IRS) with chest wall rhabdomyosarcoma from the first (I) through fourth (IV) IRS with follow-up to June 2005. Median follow-up was 12.1 years (4.6-27.2 years). RESULTS: There was a significant improvement in failure-free survival (FFS) and overall survival (OS) between the first IRS study, I, and IRS-IV. The estimated FFS and OS at 5 years in IRS I was 30% and 40%, respectively, compared to 68% and 78%, respectively, in IRS-IV (P = .03 and P = .05, respectively). There was no association between histologic finding or size and FFS or OS. However, all patients who presented without metastasis had an FFS and OS of 49% and 61%, respectively, compared with metastatic patients, 7% and 7%, respectively (P < .001). Five-year FFS of group I, II, and III patients was 52%, 52%, and 45%, respectively, and OS was 65%, 60%, and 59%, respectively. There was no significant difference in 5-year FFS or OS in patients who had a complete resection (group I), complete resection with positive microscopic margins (group II), or biopsy or partial resection only (group III). In groups I to III patients, the local and regional failure rate at 5 years is 25% and 6%, respectively. CONCLUSIONS: The most significant impact on outcome in chest wall RMS patients is metastatic disease at diagnosis. The locoregional failure rate is high but does not appear to impact survival. Alternative treatment strategies are needed for chest wall RMS, but aggressive surgical excision may not be necessary.