Fig. 3

Proliferation and biomarker expression in breast tumor explants in response to estrogen (E2), progesterone (P4), or combined P4 + U0126 treatment. a Post surgery, breast tumors were dissected and prepared for tissue explant experiments. Tumors were cut into small fragments and placed on sponges soaked in tissue culture medium. Sections were treated with vehicle (ethanol), E2 (1 or 10 nM) or P4 (1 or 10 nM) for 48 h. Tissue sections were then fixed, embedded, and processed for Ki-67 IHC staining. The percent of Ki-67-positive cells were plotted (mean ± SE). Comparing the groups via one-way ANOVA, followed by TukeyHSD posttest, indicated that only the P4 (10 nM) treatment was significantly different from vehicle (P = 0.0061, n = 6 explants per treatment condition). b Breast tumor explants were treated with vehicle, estradiol (E2, 10 nM), progesterone (P4, 10 nM), or a combination of P4 and MAPK inhibitor U0126 (1 μM) for 2 h. Explants were fixed, paraffin embedded, and stained for phospho-Ser294 PR expression, and H-scores were plotted. c–f Representative tumor explant IHC images after staining for total ER, total PR, pSer-294 PR, and phospho-ERK1/2 expression