FIG. 3.

Cell death induced by microtubule-disrupting agents is abrogated in mekk1^−/− cell lines. The CytoTox nonradioactive cytotoxicity assay kit from Promega was used for all cytotoxicity assays. Wild-type DT40, MC1, MC2, and MC3 cells (5 × 10⁴ per well) were plated on a 96-well plate. (A) In the vinblastine dose-response experiment, vinblastine was titrated into the wells at concentrations of 0 to 1 μM. (B) In the etoposide dose-response experiment, etoposide was titrated into the wells at concentrations of 781 nM, 3.13 μM, and 25 μM. Plates for both dose-response experiments were incubated for approximately 16 h at 37°C. The cytotoxicity assay was performed as described in Materials and Methods.