Fig. 3

Resistant cell lines overcome epirubicin-induced G₂/M arrest. a–d Cells were synchronised by a double-thymidine block and treated with dimethyl sulphoxide or epirubicin at selection doses established for each resistant cell line: 25 nM epirubicin to MDA-MB-231, 30 nM epirubicin to MCF7, 15 nM epirubicin to SKBR3 and 15 nM epirubicin to ZR-75-1. Epirubicin concentration was increased to 100 nM for MCF7 and SKBR3 cells because G₂/M block was not observed at the lower doses of epirubicin. Cells were collected at 48 h, stained with propidium iodide and analysed by flow cytometry. Debris was gated out. GAPDH glyceraldehyde-3-phosphate dehydrogenase