Abstract 4973: Long non-coding RNA promotes metastatic behavior in Ewing sarcoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Ewing sarcoma (ES) is a highly malignant bone and soft tissue tumor with a 20% 5-year survival rate for patients with metastatic disease. Further, even clinically localized tumors are not successfully treated with local therapy like surgery and radiation, indicative of sub-clinical dissemination at presentation, as noted by James Ewing in his original papers. Extensive research has led to better understanding of the molecular pathogenesis of the disease but few discoveries have been successfully translated into improving treatment of ES patients. Our aim is to identify and characterize novel genomic features that can be developed into therapeutic targets for metastatic ES. This study documents the importance of one such ES-specific long non-coding RNA (lncRNA) in invasion and metastasis. Expression data from over a hundred ES primary tumors were compared to normal adult tissues as well as other types of pediatric and adult cancers to identify ES-specific coding and non-coding RNA transcripts. One highly expressed lncRNA, AK057037, was exclusively associated with ES. Further characterization of the transcript using loss of function studies showed that this 2.6 kb, 7 exon, polyadenylated RNA was directly regulated by EWS-FLI1, the chimeric oncoprotein that is the hallmark of ES and a major driver of tumorigenesis. In vitro, knockdown of the lncRNA resulted in reduced invasiveness of ES cells. In vivo, cells over-expressing the transcript showed statistically significant increase in metastasis compared to controls. Downstream targets included cell adhesion molecules such as cadherins and extracellular matrix proteins. Immunoprecipitation (IP) showed binding of the lncRNA to its direct targets. Binding of the lncRNA to other regulatory proteins also affected more global changes including promoter methylation and subsequent modulation of the downstream targets. We conclude that this lncRNA is a highly specific and unique ES biomarker. It acts as an oncogene by promoting invasion and metastasis of ES cells by controlling expression of genes involved in these pathways. Understanding this additional regulation by non-coding RNAs will enable development of multi-modal therapies that may prove to be more effective in treating aggressive disease. Citation Format: Sheetal A. Mitra, Anirban P. Mitra, Jonathan D. Buckley, William A. May, Philipp Kapranov, Robert J. Arceci, Timothy J. Triche. Long non-coding RNA promotes metastatic behavior in Ewing sarcoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4973. doi:10.1158/1538-7445.AM2014-4973