Induction of apoptosis by DATS treatment in human leukemia cells. (A) Following treatment with 20 μM of DATS for 12 and 48 h, U937 cell morphology was visualized using an inverted microscope. Magnification, ×200. (B and C) Cells grown under the same conditions as (A, U937) or cells (THP-1, HL60 and K562) treated with 20 μM of DATS for 48 h were fixed, stained with DAPI, and the nuclear morphology was then photographed under fluorescence using a blue filter. Magnification, ×400. (D) For analysis of DNA fragmentation, genomic DNA was extracted and then electrophoresed on a 1.0 % agarose gel, and then visualized by EtBr staining. Marker indicates a size marker of the DNA ladder.