Comparison of the inhibitory effect of estriol on the proliferative effect of 17β-estradiol on TBNC cells. Cells of two GPR30 expressing TNBC cell lines (A) HCC1806, (B) HCC70 were stimulated with 10-9 M E2 or 10-8 M E2 in the absence or presence of 10-4 M E3. Cell number was evaluated using Alamar blue. ODs estimated in stimulated wells were divided by the average value of the control wells to give the relative cell number in % of control achieved under the indicated conditions. (c) p < 0.01 vs. control; (d) p < 0.001 vs. 10-9 M E2 w/o E3; (e) p < 0.01 vs. control; (f) p < 0.001 vs.10-8 M E2 w/o E3; (g) p < 0.01 vs. 10-9 M E2 w/o E3; (h) p < 0.05 vs. 10-8 M E2 w/o E3. Data are mean values and SE of three independent experiments with four replicates.