Recent studies have highlighted the strong potential of drugs targeting histone‐modifying enzymes for invasive cancer.44 Some of these drugs are currently in various stages of clinical trials.45 Entinostat/MS‐275, a HDAC inhibitor, was reported to inhibit angiogenesis and metastasis,46 as well as reverse EMT.47, 48 Entinostat/MS‐275 is currently used in multiple phase III clinical trials of breast cancer treatment. Here, HDAC9 is linked to breast cancer.