We have shown previously that high expression levels of microsomal epoxide hydrolase (mEH) correlate with a poor prognosis of breast cancer patients receiving tamoxifen, suggesting that enhanced mEH expression could lead to antiestrogen resistance (Fritz et al. in J Clin Oncol 19:3-9, 2001). Thus, the purpose of this study was to gain insights into the role of mEH in hormone-responsive tissues. We analyzed biopsy samples of the endometrium by immunohistochemical staining, pointing to a regulation of mEH during the menstrual cycle: during the first half mEH expression was low, increased during the second half and reached highest levels during pregnancy. Additionally, the progesterone receptor (PR) positive human endometrial cell lines IKPRAB-36 (estrogene receptor α [ERα] negative) and ECC1-PRAB72 (ERα positive) were chosen to further investigate the hormonal regulation of mEH expression. Western Blot and quantitative RT-PCR analysis revealed an increase of mEH expression after treatment with medroxy-progesterone 17-acetate (MPA) in the ERα containing ECC1-PRAB72 cells. In contrast our results suggest that MPA had no influence on the mEH protein level in the ERα- IKPRAB-36 cells. In conclusion, mEH expression is regulated by progesterone in the presence of both PRs and ERα.

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doi.org/10.1007/s10735-010-9266-6, hdl.handle.net/1765/21221
Journal of Molecular Histology
Erasmus MC: University Medical Center Rotterdam

Popp, S., Abele, I., Buck, M., Stope, M., Blok, L., Hanifi-Moghaddam, P., … Knabbe, C. (2010). Microsomal epoxide hydrolase expression in the endometrial uterine corpus is regulated by progesterone during the menstrual cycle. Journal of Molecular Histology, 41(2-3), 111–119. doi:10.1007/s10735-010-9266-6