HDAC9 and cancer: In fact, several reports has been shown that SAHA and other HDAC-inhibitors enhances tumor cell apoptosis through induction of proapoptotic proteins, such as Bim, Noxa and PUMA.37, 38 Therefore, it could not denied the possibility that induction of apoptosis, but not suppression of cancer stem cell, by HDAC inhibitor is mainly involved in these effects.