BMI1 and diffuse intrinsic pontine glioma: Treatment of DIPG neurospheres with PTC-209 reduces BMI-1 protein levels and inhibited cell growth and neurosphere formation in a dose-dependent manner regardless of H3.1/H3.3K27 mutation status suggesting that (1) BMI-1 has an oncogenic role in DIPGs, required for tumor growth, and (2) BMI-1 is a valid therapeutic target for DIPG.