MBRS-32. TOPOISOMERASE II β INDUCES NEURONAL, BUT NOT GLIAL, DIFFERENTIATION IN MEDULLOBLASTOMA

Abstract

BACKGROUNDWe previously reported that Gli3, which was a downstream molecule of Sonic Hedgehog signal, induced neuronal and/or glial differentiation in some types of medulloblastoma (desmoplastic/nodular medulloblastoma and medulloblastoma with extensive nodularity), and patients of medulloblastoma with neuronal differentiation showed favorable prognosis, but those with glial differentiation tended to show miserable prognosis (Miyahara H, Neuropathology, 2013). This time, we focused on Topoisomerase II β (Top2β), which was reported to induce neuronal differentiation and inhibit glial differentiation, and examined the expression of Top2β in medulloblastomas with neuronal and glial differentiations.METHODSWe assessed the expression of Top2β, NeuN, and GFAP using triple fluorescent immunostaining method in medulloblastoma samples with both neuronal and glial differentiations. Furthermore, the expression of Top2β, H3K4me2, and H3K27me3 were also assessed, because Top2βwas positively or negatively regulated by H3K4me2 and H3K27me3, respectively.RESULTSMany large nuclei in the nodules, in which differentiated cells were seen, was visualized by Top2β. The Top2β signals were seen in NeuN+ cells but not GFAP+ cells. H3K4me2 signals were visualized in Top2β+ large nuclei, but H3K27me3 and NeuN+ large nuclei were distributed independently.CONCLUSIONSThese results indicate that Top2β may be a molecule associated with neuronal, but not glial, differentiation of medulloblastoma cells. Drugs targeting histone modification enzymes such as EZH2 inhibitors are possible therapeutic targets as a differentiation-inducing therapy for medulloblastoma.