Trimethylation of lysine 27 on histone H3 (H3K27) alteration occurs in 80% of pediatric diffuse midline gliomas (pDIPGs) and is a driving event leading to tumor initiation and progression.137–140 The H3K27 alteration elevates the activity of histone deacetylases (HDACs), and HDAC inhibitors are a potent compound for the reduced survival of pDIPG cells.141,142 A clinical trial of the HDAC inhibitor panobinostat for the treatment of pDIPG is ongoing (NCT02717455). This evidence concerns the gene HDAC9 and diffuse midline glioma.