2-Methoxyestradiol, an Endogenous Estrogen Metabolite, Induces Apoptosis in Endothelial Cells and Inhibits Angiogenesis: Possible Role for Stress-Activated Protein Kinase Signaling Pathway and Fas Expression

Abstract

2-Methoxyestradiol (2-ME) is an endogenous metabolite of estradiol-17beta and the oral contraceptive agent 17-ethylestradiol. 2-ME was recently reported to inhibit endothelial cell proliferation. The current study was undertaken to explore the mechanism of 2-ME effects on endothelial cells, especially whether 2-ME induces apoptosis, a prime mechanism in tissue remodeling and angiogenesis. Cultured bovine pulmonary artery endothelial cells (BPAEC) exposed to 2-ME showed morphological (including ultrastructural) features characteristic of apoptosis: cell shrinkage, cytoplasmic and nuclear condensation, and cell blebbing. 2-ME-induced apoptosis in BPAEC was a time- and concentration-dependent process (EC50 = 0.45 +/- 0.09 microM, n = 8). Nucleosomal DNA fragmentation in BPAEC treated with 2-ME was identified by agarose gel electrophoresis (DNA ladder) as well as in situ nick end labeling. Under the same experimental conditions, estradiol-17beta and two of its other metabolites, estriol and 2-methoxyestriol (< or =10 microM), did not have an apoptotic effect on BPAEC. 2-ME activated stress-activated protein kinase (SAPK)/c-Jun amino-terminal protein kinase in BPAEC in a concentration-dependent manner. The activity of SAPK was increased by 170 +/- 27% and 314 +/- 22% over the basal level in the presence of 0.4 and 2 microM 2-ME (n = 3-6), respectively. The activation of SAPK was detected at 10 min, peaked at 20 min, and returned to basal levels at 60 min after exposure to 2-ME. Inhibition of SAPK/c-Jun amino-terminal protein kinase activation by basic fibroblast growth factor, insulin-like growth factor, or forskolin reduced 2-ME-induced apoptosis. Immunohistochemical analysis of BPAEC indicated that 2-ME up-regulated expression of both Fas and Bcl-2. In addition, 2-ME inhibited BPAEC migration (IC50 = 0.71 +/- 0.11 microM, n = 4) and basic fibroblast growth factor-induced angiogenesis in the chick chorioallantoic membrane model. Taken together, these results suggest that promotion of endothelial cell apoptosis, thereby inhibiting endothelial cell proliferation and migration, may be a major mechanism by which 2-ME inhibits angiogenesis.

Inhibition of MDA-MB-231 cell cycle progression and cell proliferation by C-2-substituted oestradiolmono- andbis-3-O-sulphamates

“…2-MeOE2 induces apoptosis and inhibits angiogenesis in many tumour models, indicating that this compound has considerable potential as an antitumour agent. [1][2][3][4][5][6][7][8][9][10][11] Previous studies from our group have shown that these sulphamoylated derivatives induce an irreversible G2-M arrest and inhibit proliferation of not only androgen receptor 1ve/2ve prostrate, ovarian, and breast cancer cells, but also cells resistant to conventional chemotherapeutic agents, such as adriamycin and cisplatin. 26,27 In all these studies, sulphamoylated derivatives of 2-MeOE2, 2-MeOE2-MATE, and 2-MeOE2bisMATE are significantly more potent at inducing cell cycle arrest and apoptosis than 2-MeOE2.…”

“…1-9 2-MeOE2 also inhibited the proliferation, migration, and invasion of capillary endothelial cells and angiogenesis in several in vitro and in vivo tumour models. 2,8,10 In addition, 2-MeOE2 inhibited tumour growth in murine xenograft models of MDA-MB-235 cells and H460 non-small cell lung carcinoma. 8,11 In a Gy/T-15 transgenic murine model of androgen-independent prostate cancer, 2-MeOE2 inhibited the progression of the tumour without toxic side effects.…”

“…[12][13][14] Although the exact mechanism by which 2-MeOE2 induces its antiangiogenic and antitumour effects is not known, several cellular responses, such as G2-M cell cycle arrest, caspase-3 activation, BCL-2 phosphorylation, increased expression of FAS and p53, downregulation of HIF-1, mitochondrial release of cytochrome c, and inhibition of tubulin polymerisation, have been reported. 4,5,9,10,[15][16][17][18][19][20][21] However, it has been shown that its antimitotic effects are mediated via inhibition of tubulin polymerisation by binding to the colchicine binding site on tubulin. 19,20 Because of the antiproliferative properties associated with 2-MeOE2, several analogues of 2-MeOE2 have been synthesised and tested for various biological activities.…”

In vitro and in vivo antitumor effect of 2‐methoxyestradiol on human melanoma

“…This observation might be important in the light of the inherent resistance of melanomas to drug-induced apoptosis. 38,39 Reports on the effects of 2ME 2 on the expression of apoptosis regulating proteins (e.g., p53 and Bcl-2) 16,24,26,29,36,40 suggest that 2ME 2 may have a potential to overcome apoptosis resistance of melanoma cells.…”

Ex vivoDetermination of an Estradiol Analogue-Induced Changes on Platelet Morphology and Angiogenic Biomarkers

“…Angiogenesis is a closely controlled biological process, which takes place during fetal development of blood vessels and wound healing (Folkman & Shing, 1992;Yue et al, 1997). It is also an essential requirement to enable tumor growth (Yue et al, 1997;Hall et al, 2013).…”