Mining mRNA microarray expression data for ependymoma (GSE64415, n = 209) showed that HDAC1, HDAC2, and HDAC3 mRNA expression levels were significantly upregulated in EPN compared to CNS tissues (i.e., whole brain GSE11882, n = 172; cerebellum GSE3526, n = 9), thus underlining a potential role for these enzymes in the development of this particular type of pediatric brain tumor (Figure S6). This evidence concerns the gene HDAC1 and ependymoma.