HDAC9 and cancer: Overexpression of HDAC leads to the compaction of chromatin and repression of transcription [38], and thus, the use of different HDAC inhibitors (HDACi) (4-sodium phenylbutyrate (PBA), trichostatin A (TSA), or suberoylanilide hydroxamic acid (SAHA) have led to the discovery of HDAC-repressed miRNAs in cancer.