2-Methoxyestradiol, an Endogenous Estradiol Metabolite, Differentially Inhibits Granulosa and Endothelial Cell Mitosis: A Potential Follicular Antiangiogenic Regulator1

Abstract

2-Methoxyestradiol (2-ME) is an estradiol metabolite with antiangiogenic and antitumor activity. It is formed by granulosa cell (GC) catechol-O-methyltransferase activity and is present in the normal follicle at high concentrations. In this unique microenvironment, it may regulate selected cell types via autocrine and/or paracrine action. To assess the possibility that 2-ME or estradiol might exert differential mitotic and/or apoptotic effects on endothelial cells and GCs, we compared their actions on primary cultures of hormone- and/or growth factor-stimulated porcine GCs (pGCs) as well as two types of endothelial cells, primary cultures of porcine endothelial cells (pECs), and a spontaneously transformed rabbit endothelial vascular cell (REVC) line. The 2-ME, but not estradiol, dose dependently suppressed tritiated thymidine ((3)H-T) incorporation into epidermal growth factor (EGF)-stimulated REVCs and EGF/insulin (INS)-stimulated pECs. In contrast, 2-ME did not attenuate incorporation in FSH/INS-stimulated pGCs. It reduced incorporation by approximately 50% in EGF/INS-stimulated pGCs, indicating that responsiveness to 2-ME in normal cells can be modulated by hormone and growth factor treatment. Estradiol was not antimitotic to pGCs. As indicated by 4',6-diamido-2-phenylindole hydrochloride nuclear staining, estradiol was nonapoptotic in either cell type, and 2-ME significantly increased apoptosis of REVCs, but not of pGCs. In a cell migration assay, REVC movement was attenuated by 2-ME, but not by estradiol. In summary, the results show that antimitotic as well as proapoptotic responses to 2-ME vary with cell type and, in the case of pGC antimitotic activity, with the regulatory microenvironment. Thus, they provide a rationale for autocrine and/or paracrine action of 2-ME at its site of production in vivo, and they strongly support the concept of 2-ME as a candidate ovarian angiogenesis inhibitor.

Regulation of gene expression in endothelial cells: the role of human follicular fluid

“…In addition to pro-angiogenic molecules, negative regulators of angiogenesis were observed (Tempel et al 2000, Shang et al 2001, Grasselli et al 2003. The present work demonstrates that factors contained in follicular fluid regulate the transcription of angiogenesis-modulating genes in endothelial cells and thus could help to explain the temporal and spatial discrepancy between the high expression of VEGF and the restricted angiogenesis in the preovulatory follicle.…”

“…Experimental evidence suggests that granulosa cells are also the source of angiogenesis inhibitors, such as hyaluronic acid (Tempel et al 2000) and 2-methoxyestradiol (Shang et al 2001). However, detailed studies investigating the cascade of events controlling angiogenesis during folliculogenesis and corpus luteum formation in the human have not been reported.…”

2-MeOE2bisMATE and 2-EtE2bisMATE induce cell cycle arrest and apoptosis in breast cancer xenografts as shown by a novel ex vivo technique

“…One such compound is 2-methoxyestradiol, a natural metabolite of estradiol, which has demonstrated, in in vitro and in vivo models, anti-angiogenic and anti-proliferative activity [11][12][13][14][15][16]. However, phase I clinical trials for 2-MeOE2, dosed at 1600-3000 mg/day, have been terminated early due to extremely low drug plasma bioavailability [17].…”

Regulation of catechol O-methyltransferase expression in granulosa cells: a potential role for follicular arrest in polycystic ovary syndrome

“…Several reports have shown a strong inhibitory effect of 2-methoxyestradiol (2-ME 2 ), which is synthesized in the ovarian follicles and present in the follicular fluid, on granulosa cell proliferation in different assays (12)(13)(14). Shang et al (12) demonstrated an additional strong antiangiogenic impact of 2-ME 2 on ovarian angiogenesis, adding another facet to mediate the antifollicular effect of this compound.…”