HDAC6 and glioblastoma: In GBM cells, the ratio of HDAC6 to p97/VCP is larger than normal, contributing to increase in aggrephagy, the 78 kDa glucose-regulated protein 78 (GRP78)-dependent ER stress tolerance, and TMZ resistance, which can be reversed in the presence of the HDAC6 inhibitor Tubastatin A [140].