In contrast, most of the high-grade tumors express low or decreased ERβ expression compared to low-grade gliomas, and this lower ERβ expression correlates with histological malignancy and poor survival of patients.15,19,25,40 Further, ERβ expression is downregulated or lost in several tumors including those of the breast, ovary, prostate, and colon.15,28,44,45 Our results suggest that HDAC-mediated epigenetic changes contribute to suppression of ERβ expression in GBM and HDACi such as panobinostat and romidepsin have the potential to enhance reexpression of ERβ. Here, HDAC9 is linked to glioblastoma.