Targeting the epigenetic readers in Ewing Sarcoma inhibits the oncogenic transcription factor EWS/Fli1
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Camille Jacques1,2, François Lamoureux1,2, Marc Baud’huin1,2,3, Lidia Rodriguez Calleja1,2, Thibaut Quillard1,2, Jérôme Amiaud1,2, Franck Tirode4, Françoise Rédini1,2, James E. Bradner5,6, Dominique Heymann1,2,3, Benjamin Ory1,2
1INSERM, UMR 957, Équipe Labellisée Ligue 2012, Nantes, France
2Physiopathologie de la Résorption Osseuse et Thérapie des Tumeurs Osseuses Primitives, Université de Nantes, Nantes Atlantique Universités, EA3822, Nantes, France
3Nantes University Hospital, Nantes, France
4Institut Curie, INSERM U830, Paris, France
5Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
6Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA
Benjamin Ory, e-mail: Benjamin.firstname.lastname@example.org
Keywords: Ewing Sarcoma, JQ1, bromodomain, epigenetic, EWS/Fli1
Received: December 17, 2015 Accepted: March 02, 2016 Published: March 19, 2016
Ewing Sarcoma is a rare bone and soft tissue malignancy affecting children and young adults. Chromosomal translocations in this cancer produce fusion oncogenes as characteristic molecular signatures of the disease. The most common case is the translocation t (11; 22) (q24;q12) which yields the EWS-Fli1 chimeric transcription factor. Finding a way to directly target EWS-Fli1 remains a central therapeutic approach to eradicate this aggressive cancer. Here we demonstrate that treating Ewing Sarcoma cells with JQ1(+), a BET bromodomain inhibitor, represses directly EWS-Fli1 transcription as well as its transcriptional program. Moreover, the Chromatin Immuno Precipitation experiments demonstrate for the first time that these results are a consequence of the depletion of BRD4, one of the BET bromodomains protein from the EWS-Fli1 promoter. In vitro, JQ1(+) treatment reduces the cell viability, impairs the cell clonogenic and the migratory abilities, and induces a G1-phase blockage as well as a time- and a dose-dependent apoptosis. Furthermore, in our in vivo model, we observed a tumor burden delay, an inhibition of the global vascularization and an increase of the mice overall survival. Taken together, our data indicate that inhibiting the BET bromodomains interferes with EWS-FLi1 transcription and could be a promising strategy in the Ewing tumors context.
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