Abstract 2514: Second generation HDAC inhibitor, Quisinostat reinstates RD3 in neuroblastoma CSCs and promotes stem cell differentiation

Abstract

Abstract Recently, we characterized the adaptive stemness and extreme plasticity of neuroblastoma (NB) cancer stem cells (CSCs). Further, new to science, we defined the loss of retinal degeneration protein 3 (RD3) in high-risk NB and identified its novel tumor evolution stabilization function. Moreover our studies identified definitive contribution of HDACs in the evolution of progressive NB. Herein, we investigated the potential of pyrimidyl-hydroxamic acid HDAC inhibitor, Quisinostat in restoring RD3 and NB-CSCs differentiation. Well characterized CD133+-CD34+ human NB CSCs exposed to increasing concentrations (2.5, 5, 10, 100, 200nM, 1, 2, 4, 8μM) of quisinostat were examined for inhibition of HDACs (HDACs 1-11, QPCR analysis), transcriptional (QPCR) and translational (immunoblotting) restoration of RD3, CSCs cell viability (automated trypan exclusion assay) differentiation (real-time live cell imaging) and formation of organized tumorospheres (tumorosphere formation assay). Quisinostat inflicted complete inhibition of NB-CSCs cell viability at 100nM concentration and beyond. QPCR analysis revealed a dose-dependent inhibition of HDACs in NB CSCs with quisinostat. We observed a significant transcriptional/translational restoration of RD3 selectively at 100nM and above of quisinostat treatment. Live-cell imaging demonstrated a dose-dependent -loss of stemness behavior and -increased differentiation of NB CSCs with quisinostat treatment. Tumorosphere formation assay demonstrated complete inhibition of organized tumorospheres at/after 100nM treatment. These results imply that Quisinostat restores RD3 and promotes NB-CSCs differentiation. More importantly, selective dose-dependent specificity of HDAC inhibition by Quisinostatnt and, restoration of RD3 and regulation of stemness physiognomies at/above 100nM concentrations identifies that HDAC 7 could serve as a critical player in this setting. Taken together, these results for the first time identify the potential of quisinostat in the regulation of NB evolution and with further studies may serve as a potential drug deliverable in the treatment and cure of high-risk NB. Acknowledgements: Stephenson Cancer Center - Experimental Therapeutics Program, NIH COBRE 1P20GM103639-01. Citation Format: DINESH BABU SOMASUNDARAM, Natarajan Aravindan. Second generation HDAC inhibitor, Quisinostat reinstates RD3 in neuroblastoma CSCs and promotes stem cell differentiation. [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 2514.