HDAC6 and glioblastoma: Recently, the transcription factor Specificity protein 1 (Sp1) was identified as a substrate of HDAC6; deacetylated Sp1 promotes the transcription of several oncogenes potentially related to TMZ resistance in GBM cells, and levels of both HDAC6 and deacetylated Sp1 were increased after long-term TMZ treatment [130].