BC-ER cells grew more slowly than BC-V cells in the presence of E2. (A, B) Cell cycle status of the BC-ER and BC-V cells. (A) Cells were treated with E2 for 16 hours before being analyzed by flow cytometry. (B) Cells were treated with E2 for 12 days. (C) The growth curve of the BC-ER and BC-V cells was plotted for 6 days of cell culture.