Abstract 1227: Oncofusion driven de novo enhancer assembly promotes malignancy in Ewing sarcomavia aberrant expression of the stereociliary protein LOXHD1

Abstract

Abstract Ewing sarcoma (EwS) is a highly aggressive tumor of bone and soft tissues that mostly affects children and adolescents. The pathognomonic oncofusion EWSR1-ETS (EWS-FLI1/EWS-ERG) transcription factors drive EwS by orchestrating an oncogenic transcription program through de novo enhancers. Pharmacological targeting of these oncofusions has been challenged by unstructured prion-like domains and common DNA binding motifs in the EWSR1 and ETS, respectively. Alternatively, identification and characterization of mediators and downstream targets of EWS-FLI1 dependent or independent function could offer novel therapeutic options. By integrative analysis of thousands of transcriptomic datasets representing pan-cancer cell lines, primary cancer, metastasis, and normal tissues, we have identified a 32 gene signature (ESS32) in EwS that could stratify EwS from pan-cancer. Of the ESS32, LOXHD1 - coding for a stereociliary protein was the most exquisite gene expressed in EwS. CRISPR-Cas9 mediated deletion or silencing of EWS-FLI1 bound upstream de novo enhancer elements in EwS cells led to the loss of LOXHD1 expression and altered the EWS-FLI1, MYC, and HIF1a pathway genes, resulting in decreased proliferation and invasion in vitro and in vivo. These observations open up new avenues for developing LOXHD1-targeted small molecules or cellular therapies for this deadly disease. Citation Format: Qu Deng, Ramakrishnan Natesan, Florencia Cidre-Aranz, Shehbeel Arif, Ying Liu, Reyaz Rasool, Pei Wang, Zvi Crammer, Margaret Chou, Chandan Kumar, Kristy Weber, Karin Eisinger, Nicolas Grillet, Thomas Grünewald, Irfan Asangani. Oncofusion driven de novo enhancer assembly promotes malignancy in Ewing sarcomavia aberrant expression of the stereociliary protein LOXHD1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1227.