Abstract LB-157: Chromatin alterations induce C-MYC and BRD4 downregulation in pediatric sarcoma

Sarcoma accounts for 15% of all pediatric cancers diagnosed every year. Refractory patients have a poor prognosis with a 5-year survival rate of 10%, demonstrating the need for development of new therapeutic approaches. Epigenetic events, including DNA methylation and post-translational histone modifications (such as histone acetylation), are responsible for silencing tumor suppressor genes and overexpressing oncogenes. In sarcomas, a better understanding of epigenetic alterations is needed to develop new epigenetic targeted therapies. Several epigenetics drugs have demonstrated anticancer activity against sarcoma cell lines but the identification of a specific target is still missing. We demonstrated that targeting histone acetylation may represent a specific epigenetic mark in pediatric sarcomas. We identified that proscillaridin A, a newly defined epigenetic drug, has epigenetic and anticancer effects on osteosarcoma (U2OS) and rhabdomyosarcoma (RD) cell lines. Our findings show a decrease of histone 3 acetylation on specific lysine residues after a 48h-treatment with proscillaridin A at 5 nM, a clinically relevant dose. These effects correlate with downregulation of histone acetylation associated proteins such as bromodomain BRD4 and oncogene C-MYC. A 48h-treatment with proscillaridin A produces a G2/M block and a reduction in the clonogenic potential of both U2OS and RD cells with IC50 value of approximately 6 nM. Interestingly, remaining colonies of RD cells fully lost their abilities to growth after drug removal, suggesting a long-term epigenetic reprograming. We demonstrated that proscillaridin A epigenetic effects occurred through calcium signaling since its mechanism of action may be dependent on calcium-calmodulin kinase activity.These promising results illustrate the epigenetic and anticancer potential of proscillaridin A against pediatric sarcoma. Additional experiments are currently ongoing in order to further characterize the mechanism of action of proscillaridin A in vitro and in vivo. Citation Format: Elodie Da Costa, Gregory Armaos, Simon Jacques-Ricard, Annie Beaudry, Noel Raynal. Chromatin alterations induce C-MYC and BRD4 downregulation in pediatric sarcoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-157.