Evidences are emerging that the prostate cancer stem cells may play important roles in resistance to castration37 and chemotherapy.31 Recently, it has been shown that mocetinostat induces cell cycle arrest and apoptosis in colon-cancer-initiating cells.12 Our data suggest that mocetinostat can efficiently induce apoptosis in the primary prostate cancer stem cells through a mechanism involving miR-31 and E2F6 (Figure 6). This evidence concerns the gene E2F6 and colonic neoplasm.