Figure 4

BC-ER cells exhibited much higher resistance than BC-V cells in the presence of E2. (A, B) The viability of BC-ER and BC-V cells after being exposed to four chemotherapeutic agents was determined by MTT assays. (A) Cells were pretreated with or without E2 for 16 hours before being exposed to chemotherapeutic agents. (B) Cells were pretreated with or without E2 for 12 days. The chemotherapeutic agents used in the MTT assays were paclitaxel, epirubicin, fluorouracil, and vinorelbine. Three concentrations were tested for each chemotherapeutic agent. (C, D) Cell death induced by chemotherapeutic agents was determined by PI dye exclusion assays. (C) Cells were pretreated with or without E2 for 16 hours before being exposed to chemotherapeutic agents. (D) Cells were pretreated with or without E2 for 12 days. The chemotherapeutic agents used in the PI dye exclusion assays were paclitaxel, fluorouracil, and vinorelbine. One concentration was tested for each anticancer drug.