2-Methoxyestradiol (2-MeOE2)

2-Methoxyestradiol exhibits the inhibitory activity of cellular proliferation in a breast carcinoma cell line MDA-MB-435 and an ovarian carcinoma cell line SK-OV-3 with IC50 of 1.38 μM and 1.79 μM, respectively. Furthermore, 2-Methoxyestradiol also inhibits cellular microtubule depolymerization in rat aortic smooth muscle A-10 cells with EC50 of 7.5 μM. ^[1] 2-Methoxyestradiol inhibits proliferation of MCF-7 and BM cells with IC50 of 52 μM and 8 μM. ^[2] In MDA-MB-231 cells, 2-Methoxyestradiol inhibits HIF-1-mediated transcriptional activation of target genes without affecting the transcription of HIF-1α itself. ^[3] A recent study shows that 2-Methoxyestradiol (0.5 μM), blocks TGF-β3-induced expression of collagen (Col) type I(αI), Col III(αI), plasminogen activator inhibitor (PAI) 1, connective tissue growth factor (CTGF), and α-smooth muscle actin (α-SMA). Moreover, 2-Methoxyestradiol ameliorates TGF-β3-induced Smad2/3 phosphorylation and nuclear translocation, and inhibits TGF-β3-induced activation of the PI3K/Akt/mTOR pathway. ^[4]

The sulforhodamine B (SRB) assay is used to evaluate the antiproliferative activity of 2-Methoxyestradiol in the MDA-MB-435 and SK-OV-3 cell lines. Cells a plated into 96-well plates and allowed to grow and attach for 24 hours followed by addition of 2-Methoxyestradiol or vehicle controls. The cells are incubated with drugs for 48 hours and then the cellular protein is fixed, stained, and concentration determined by absorbance at 560 nm. Log dose–response curves are constructed for each experiment and the IC50 for inhibition of proliferation determined.

In a 9L rat glioma (9L-V6R) rat model, 2-Methoxyestradiol significantly decreases HIF-1 activity and inhibits the tumor growth in a dose-dependent manner by 4-fold reduction for 60 mg/kg/day, and 23-fold reduction for 600 mg/kg/day, respectively. ^[5]