HDAC9 and cancer: It has been reported that HDAC inhibitors can promotemetastasis of solid tumors such as breast cancer.773,774 This can be explained by the fact that cell state transitions underlyingthe metastatic phenotypes require alterations of histone acetylation.11,445,775 Thus, HDAC inhibitors may adverselyperturb epigenetic programs, regulating cancer cell proliferationand metastasis.