Abstract 2196: Novel and selective histone deacetylase (HDAC) 1 & 2 inhibitors enhance differentiation of neuroblastoma cells in combination with retinoic acid
Authors: Tamang David L. , Lurier Emily , Golonzhka Olga , Quayle Steven N. , Jones Simon S. , Yang Min 
Published: August 2015

Abstract
Neuroblastoma is an extra-cranial solid cancer arising from the neural crest and is among the most common cancers in infants less than 1 year of age (Park, JR et al., 2008). Approximately one child per 100,000 is diagnosed with neuroblastoma, resulting in 650 new cases each year in the United States. Half of the children with neuroblastoma have high risk disease and 20% - 50% of those children will fail to respond adequately to current therapies, illustrating a clear unmet medical need. Current treatment for high-risk disease is aggressive, including chemotherapy, surgery, radiation with stem cell transplant, anti-GD2/cytokine immunotherapy and retinoic acid (Yang, RK et. al., 2010; Cheung, NK et. al., 2012). Retinoic acid is a pro-differentiation agent that acts on neuroblastoma cells to slow growth and promote cell death. A gene expression pattern associated with retinoic acid induced neuroblastoma differentiation was recently identified (Hahn, CK et. al., 2008; Frumm, SM et. al., 2013), and it was further shown that inhibition of HDAC1/2 was able to induce a similar expression pattern.
In this work, we demonstrate that next generation selective and orally bioavailable HDAC1/2 inhibitors can induce gene expression changes in neuroblastoma cells consistent with differentiation. The action of HDAC1/2 inhibitors potently enhances the retinoic acid differentiation effect at sub-optimal concentrations of retinoic acid or HDAC inhibitor, as well as with intermittent (pulse) HDAC1/2 inhibition. Retinoic acid alone and in combination with HDAC1/2 inhibitors is able to slow cell proliferation in long term growth assays and alter morphology in a manner consistent with differentiation. The observed enhancement of differentiation by selective HDAC1/2 inhibitors occurs at concentrations below that required for cell death as evidenced by viability assays and caspase 3/7 activation. Acute toxicity is induced by elevated concentrations of HDAC1/2 inhibitors, and synergy is observed in combination with retinoic acid. Ongoing studies exploring global gene expression changes, ChIP-seq examining retinoic acid receptor and HDAC1/2 chromatin binding, and activity of the selective HDAC1/2 inhibitor in combination with retinoic acid in animal models of neuroblastoma will be discussed. Taken together, these findings support a role for selective HDAC1/2 inhibitors in combination with retinoic acid for the treatment of patients with high risk neuroblastoma.
Citation Format: David L. Tamang, Emily Lurier, Olga Golonzhka, Steven N. Quayle, Simon S. Jones, Min Yang. Novel and selective histone deacetylase (HDAC) 1 & 2 inhibitors enhance differentiation of neuroblastoma cells in combination with retinoic acid. [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 2196. doi:10.1158/1538-7445.AM2015-2196