The class II HDAC4 was found to inhibit the expression of the proapoptotic p21/CDKN1A gene [13], the high expression levels of which may have a poor prognostic value in the GB mesenchymal subtype [54], and may promote radioresistance [55]; therefore, the general downregulation in GB of TCGA and REMBRANDT cohorts compared to LGG may probably be part of a homeostatic response to refrain tumor malignancy. Here, HDAC4 is linked to neoplasm.