Fig. 3.

Disorazole C₁ resistance is reversible. Cells were incubated with various concentrations of compounds for 72 h, and the total number of HeLa (closed circles), HeLa/DZR (closed squares), and HeLa/DZR/Rev (open diamonds) cells was determined by Hoechst staining nuclei using an ArrayScan II reader as described under Materials and Methods. Each value was the mean of four determinations. Bars equal S.E.M. unless the value was less than the size of the symbol. A, disorazole C₁. B, vinblastine.