Fig. 1. Sensitivity of wild-type and mutant cell lines to paclitaxel and colcemid. Approximately 200 cells were added to replicate wells of a 24-well dish containing the indicated concentrations of paclitaxel (A) or colcemid (B) in ng/ml. The cells were allowed to grow for 7 days and then stained with methylene blue. Note that compared with wild-type (WT), mutant Tax 5-6 is resistant to paclitaxel but exhibits enhanced sensitivity to colcemid. In contrast, CV 2-8 is resistant to colcemid but more sensitive to paclitaxel. Tax 2-4 is dependent on paclitaxel for growth, while Tax 9-5 is only partially paclitaxel dependent. Strain 6H2 is a revertant of a colcemid-resistant cell line and has regained normal colcemid sensitivity.