MDA-MB-468 cells arrest in G1 and G2 following nocodazole and vincristine treatment. Cells treated with diluent (a), 100 nM paclitaxel (b), 1 μM nocodazole (c), or 100 nM vincristine (d) for 24 hours were stained with PI and subjected to flow cytometry. Numbers in each panel show mean ± SD of distributions inferred from PI staining of three to six separate experiments using ModFit.