HDAC9 and hematologic disorder: HDAC inhibitors not only trigger cell differentiation, apoptosis, autophagy, and cell cycle arrest but also modulate immune reactions and inhibit angiogenesis in various hematologic malignancies and some solid tumors.620 It has been hypothesized that malignant cells are more vulnerable to epigenetic treatment, rendering the specificity and selectivity of malignant cells over normal cells.351 A number of HDAC inhibitors have been developed and demonstrated effective in treating hematologic malignancies.