Human breast cancer cells are more sensitive to SAHA-mediated cell killing than normal cells. (A) Trypan blue exclusion assays of MCF7, MCF-10A, and fibroblast cells that had been treated for 48 hr with suberoylanilide hydroxamic acid (SAHA) at increasing concentrations. The bars represent standard deviations of three independent experiments. (B) Photographic pictures depicting phase-contrast imaging of MCF7, MCF-10A, and fibroblast cells after 48 hr treatment with dimethylsulfoxide (DMSO; control), or SAHA at 4 µM or 10 µM. The MCF7 cells with dark intensity appearing only after SAHA treatment were floating dead cells that increased in number as SAHA concentration increased. No floating dead cells were observed in MCF-10A or fibroblast cells after 48 hr treatment with SAHA at either 4 µM or 10 µM.