Fig. 2.

Multidrug-resistant cells are cross-resistant to disorazole. Cells were incubated with various concentrations of compounds for 72 h, and the total cell number was determined by Hoechst staining nuclei using an ArrayScan reader as described under Materials and Methods. MCF-7 cells (closed triangles) and MCF-7/MDR cells (open triangles). 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.