Figure 5

Dose-dependent stimulation of luciferase activity by 17β-estradiol. MDA-MB-436 and 436.1 cells were transiently transfected with 0.4 or 10 ng of estrogen receptor plasmid (pHEGO-hyg) and incubated in the presence of ethanol or increasing amounts of 17β-estradiol. The total levels of luciferase seen with ethanol and varying levels 17β-estradiol in 436.1 cells are plotted in (A). The data from (A) was replotted in (B) as a percentage of the maximal activity with 10 nM 17β-estradiol, as described in the Materials and Methods section. To facilitate direct comparison of the position of the dose-response curves for the two cell lines, the data from (A) and that obtained with MDA-MB-436 cells with 0.4 ng ER (data not shown) is illustrated in panel (C). The data are representative of eight (436.1) and five (MDA-MB-436) experiments. (D) Whole cell lysates from ER-positive BT474 and MCF-7 breast cancer cells and transiently transfected MDA-MB-436 and 436.1 cells were analyzed by Western blot. The 58 kDa ER protein (arrow) was detected in ER-positive BT474 and MCF-7 cells, as well as both cell lines that were transfected with 10 and 100 ng of ER.