In vitro activity: MTT assays using G-1 shows that, in SkBr3 cells, the proliferative effect induced by 100 nM G-1 is abolished in the presence of 1 μM estriol which acts as an antagonist of GPR30-dependent pathway. A cell-free transcription assay demonstrates that the antiestrogenic activity exhibited by estriol is because of interferring with estradiol-induced positive cooperative binding and receptor dimerization, binding of hER complexes to ERE, as well as reducing estradiol-dependent transcription in a dose-dependent manner. A recent study shows that estrogen (estrone, estradiol, and estriol) inhibits Alzheimers disease-associated low-order Aβ oligomer formation, and among them, estriol shows the strongest in vitro activity.

Cell Assay: For the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cells are cultured in plastic 96-well plates under 200 μL of growth medium and at an initial density of 10,000 cells per well. Cells are washed once they have attached and further incubated in medium containing 2.5% charcoal-stripped FBS with the indicated treatment. The medium is changed every 2 days (with treatment). Where applicable, 200 ng of the indicated plasmids are transfected every 2 days before treatments using Fugene6 Reagent, as recommended by the manufacturer. Following 6 days of incubation, the assay mixture (10µL per well) containing 1mg/mL 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is added to each well and incubated at 37 ◦C for 4 h in a 5% CO2 atmosphere. The yellow tetrazolium MTT, reduced by metabolically active cells, results in intracellular purple formazan, which is released after overnight incubation with 200 µL 1% sodium dodecyl sulfate in 0.01N HCL and quantified spectrophotometrically by reading absorbance at 570nm using an enzyme-linked immunosorbent assay plate reader.