Figure 5

Assessment of the sensitivity of Topors^+/+ and Topors^-/- pMEFs to DNA-damaging agents and the microtubule-targeting drug vinblastine. A-C. Early passage Topors^+/+ (solid lines, triangles) and Topors^-/- (dotted lines, squares) pMEFs were exposed to increasing doses of ionizing radiation or incubated for 72 hours with increasing concentrations of topotecan or vinblastine. Anti-proliferative activity was determined using an MTT assay. Data represent means and standard deviations of 3-6 replicates. D. Representative cell cycle distributions observed 12 hours after vinblastine exposure, using propidium iodide staining and flow cytometry. The lower panel indicates mean and standard deviations of cell cycle distribution data obtained from two independent cell lines. Statistical analyses indicated no significant differences in mean values of cell cycle phases.