Figure 1

Cell cycle and morphological changes in response to paclitaxel treatment in breast cancer cell lines. Cells were treated with 100 nM paclitaxel for 0, 24, 48, or 72 hours and then stained with (a) propidium iodide or (b) aceto-orcein staining solution. Propidium iodide-stained cells were subjected to DNA analysis by flow cytometry. Morphology of orcein-stained chromatin was assessed by light microscopy. Arrowheads indicate typical chromatin condensation staining, and arrows indicate ring-like staining of mitotic cells. The flow cytometry data were analyzed at the time corresponding to the doubling time of each cell line (that is, after 24 hours of treatment for the MDA-MB-468 and MDA-MB-231 cells, and after 48 hours for the T47D and MCF-7 cells). The MDA-MB-468 and MDA-MB-231 cells could not be analyzed at 48 hours after treatment because of extremely low viability (<10%) at that time.