MTT assays of viable cell numbers were performed after 120 h of culture in the presence of increasing concentrations of (A) BEZ, (B) MPA and (C) VPA as single drug treatments. Cells are designated as follows: SAOS2: orange, MG63: red, human MSCs: green. (D) Drug combinations of VPA (0.6 mM) with increasing concentrations BEZ and MPA (termed, V-BAP). Data shown as mean ± SEM (n=3 independent experiments) **P<0.01, ***P<0.001. Significant differences between both osteosarcoma cell lines and human MSCs have been indicated only.