ET-06 * PRECLINICAL TESTING OF THE HISTONE DEACETYLASE INHIBITOR, PANOBINOSTAT, IN A GENETICALLY ENGINEERED DIFFUSE INTRINSIC PONTINE GLIOMA MOUSE MODEL

Abstract

Diffuse Intrinsic Pontine Glioma (DIPG) is a type of incurable pediatric brain tumor with a dismal outcome. With overall survival of less than one year, and no therapeutic advancements over the last three decades, gaining a better understanding of how to treat these deadly tumors is crucial. Recent genomic analysis has revealed that nearly 80% of DIPGS harbor a K27M mutation in histone H3.3 (K27M H3.3) or histone H3.1 (K27M H3.1). In an effort to elucidate novel therapeutics to treat DIPG, we examined Panobinostat, a potent pan-histone deacetylase inhibitor (HDACi) currently in clinical trials for a variety of different cancers. HDACi are a promising new class of agents known to have multiple target effects. Panobinostat targets HDACs in Classes I, II and IV and can cause disruption of genes involved in cell cycle control, apoptosis, DNA damage repair, and differentiation. To determine the effect of Panobinostat on DIPG, we utilized cell lines derived from a genetically engineered DIPG mouse model driven by PDGF-B overexpression, p53 loss, and either K27M or WT H3.3. Our results indicate that Panobinostat is highly effective at low nanomolar concentrations (<50nM), decreasing proliferation and viability, and increasing apoptosis in a dose dependent manner. Furthermore, utilizing isogenic lines we found the sensitivity of DIPG cells to Panobinostat to be independent of their H3.3 mutational status and that both K27M H3.3 and WT H3.3 lines were equally susceptible to treatment. In conclusion, murine DIPG cell lines, both with and without the K27M H3.3 mutation, show high sensitivity to Panobinostat in vitro. We are currently investigating its efficacy in vivo with hopes of translation to the clinic as a new therapeutic avenue for DIPG.