HDAC9 and cancer: In cancer progression, there is increasing evidence that gene expression is governed by epigenetic changes of histones.[39, 40] Histone deacetylases (HDACs) are enzymes involved in the remodeling of the chromatin, which are aberrant in cancer.[41] Several classes of HDAC inhibitors (HDACi) have been found to have potent anticancer activities.[42] In our study, WYC‐209 induces melanoma TRC apoptosis via decondensing chromatin and to upregulate apoptotic‐related genes and DNA damage gene, similar to the action of HDACi.