Fig. 4

Estrogen stimulates proliferation of Brca1-deficient tumor cells. a, b Expression of Ki67 and Ck14 in p18^−/−;Brca1^MGKO (a) and BRCA1 mutant patient-derived xenograft (b) tumors treated with E2 or placebo was analyzed by immunostaining. The percentages of Ki67⁺ and/or Ck14⁺ cells were calculated from 4',6-diamidino-2-phenylindole (DAPI)⁺ tumor cells and quantitated in four randomly selected fields for each section of a tumor, and the results represent the mean ± SD of three individual tumors per group. c, d p18^−/−;Brca1^MGKO tumor cells were treated with DMSO or E2 for 24 h. The expression of p-RB was determined by western blot (c) and the bromodeoxyuridine (Brdu) incorporation was determined by fluorescence-activated cell sorting (FACS) (d). The percentages of Brdu-positive cells in (d) are indicated