Effects of D1 and D6 on the growth of human neuroblastoma and melanoma cell lines. (A), (B): Six NB cell lines were cultured in the presence of various concentrations (0-25 μM) of D1 (A) and D6 (B) or 0.1% DMSO (control cells) for 72 hours. Cell proliferation was measured by 3H-thymidine incorporation. Results, derived from three different experiments, are expressed as mean percentage of 3H-thymidine incorporation from quadruplicate wells as compared to that of control cells. Error bars represent 95% confidence intervals. (C) IC50 values obtained on the six NB cell lines and the six MM cell lines reported in the M&M section. (D) and (E): drug washout assays to assess the impact of D6 time exposure on cell proliferation in NB cells (D), MM cells and BJ fibroblasts (E). Cells were incubated with D6 for the indicated times and concentration and then washed and cultured in drug-free medium up to 72 hours. Cell proliferation was assessed by 3H-thymidine incorporation. Results are expressed as described above.