Trichostatin A is a potent and specific inhibitor of HDAC class I/II, with an IC50 value of 1.8 nM for HDAC. Trichostatin A (TSA) inhibits proliferation of eight breast carcinoma cell lines with mean±SD IC50 of 124.4±120.4 nM (range, 26.4-308.1 nM). HDAC inhibitory activity of Trichostatin A is similar in all cell lines with mean IC50 of 2.4±0.5 nM (range, 1.5-2.9 nM). Trichostatin A (330 nM) increases Gαs protein expression in human myometrial cells, but does not increase Gαs mRNA levels. Trichostatin A (20-75 nM) induces minimal cytotoxicity to adipose-derived stem cells (ADSCs), and enhances the osteogenic differentiation capacity of ADSCs. In addition, Trichostatin A (0, 10, 100, 500 nM) dose-dependently decreases HDAC class I/II activity.