DHMEQ induces apoptosis in ATL-derived cell lines. (A) Results of dose-response and time-course experiments. Relative levels of cell viability of DHMEQ-treated ATL-derived cell lines compared with those treated with DMSO. Mean and SD of triplicate experiments are presented. TL-Om1, MT-1, KK-1, and ST-1 are ATL-derived cell lines; K562, an uninfected cell line used as a control. □ indicates K562;▵, TL-Om1; ▪, MT-1; ○, KK-1; •, ST-1. (B) Induction of apoptosis by DHMEQ. Cells were treated with 10 μg/mL DHMEQ for indicated time periods and binding of FITC-conjugated annexin V was analyzed by flow cytometry. Representative results of 3 independent experiments are shown. (C) Hoechst 33342 staining of the cells. Cells were treated with DHMEQ (10 μg/mL) or DMSO (0.1%) for 24 hours and stained by Hoechst 33342. Original magnification, × 600. Objective lens = 60×/1.4.