Abstract 492: Epigenetic suppression of miRNA-203 promotes Ewing sarcoma malignancy

Abstract

Abstract Ewing sarcoma (ES), a malignancy of bone and soft tissue that affects children and young adults, is characterized by early metastasis to lung and bone and by oncogenic ews/ets translocations. We previously observed the histone methyltransferase Enhancer of Zeste, Drosophila, Homolog 2 (EZH2) to be regulated by EWS-FLI1 and highly increased in ES. We hypothesized non-coding RNAs to contribute to epigenetic processes and malignancy of ES. Here we show by ChIP on chip analysis that EZH2 occupies promoter regions of putative tumor suppressor miRNAs, oncogenic miRNAs and differentiation-associated miRNAs in ES and investigated their functional relevance by miRNA mimic, RNA interference, and functional assays. We show that hsa-miR-203a-3p (miR-203), a promoter of epidermal differentiation and trigger to exit cell cycle, was found epigenetic silenced in ES. We not only observed miR-203 up-regulation in different ES lines after EZH2 knock down or treatment with the EZH2 inhibitors GSK126 but also after histone de-acetylase inhibition (HDACi) via Trichostatin A (TSA) as well as MS-275. Similarly, treatment of ES lines with the DNA-methylation inhibitor 5′-azacytidine resulted in a strong up-regulation of miR-203 in ES. On the other hand, de-regulated expression of miR-203 after transient transfection with a miR-203-mimic identified a feed back loop resulting in a down-regulation of EWS-FLI1 and EZH2 in ES cell lines as compared to controls. In functional assays we observed that an increased expression of miR-203 suppressed contact dependent as well as independent growth in ES. In addition, in vitro invasiveness was strongly impaired after over-expression of miR-203. Taken together, we demonstrate the essential need for epigenetic suppression of miR-203 expression in ES that otherwise would suppress critical features of ES malignancy such as contact independent growth and invasiveness of ES. These results further provide a rationale for epigenetic combination therapy directed to reverse miR-203 suppression. Citation Format: Tim Hensel, Esther Heid, Stephanie Plehm, Stefan Burdach, Günther H. Richter. Epigenetic suppression of miRNA-203 promotes Ewing sarcoma malignancy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 492. doi:10.1158/1538-7445.AM2015-492