Effects of D1 and D6 on apoptosis in melanoma and neuroblastoma cells. (A) Melanoma cells (LB24) and normal fibroblasts (BJ) were incubated with solvent (control), or with 10 μM D1 and D6 for 24 hours, then stained by TUNEL assay. Apoptotic cells are visualized by red staining. Cell nuclei (blue) were stained with DAPI (bar, 100 μm). (B) Melanoma cells (LB24) and (C) Neuroblastoma cells (GI-LI-N) were incubated with 10 μM D1 and with 5 and 10 μM D6 for 24 and 48 hours. Apoptosis induction was determined as the percentage of Annexin-V positive cells. Columns: means; bars: SD. *, P < 0.05; **, P < 0.01; ***, P < 0.001 vs control levels.