Context: Human uterine leiomyomas are very common smooth muscle cell tumors that occur in reproductive-age women and are the leading reason for performing hysterectomies. The present study was conducted to explore the potential mechanism behind the effects exerted by dominant negative estrogen receptors (DNERs) delivered by adenovirus to leiomyoma cells to ascertain the utility of DNERs as a novel strategy for treatment of uterine fibroids.

Objective and methods: We investigated the ability of DNER to affect estrogen response element (ERE) activity induced by wild type estrogen receptor (ER) by utilizing the adenovirus estrogen response element luciferase (Ad-ERE-luc) system in ELT3 cells and the effect of graded doses of DNER (10, 50, and 100 plaque forming units [pfu]/cell) on the expression of some selected genes controlling cultured human leiomyoma cell proliferation (cyclin D1, Cox2, PCNA, VEGF, EGF), apoptosis (Bcl2, Bax), estrogen metabolism (COMT), MMP₁, as well as progesterone receptors (A, B) were assessed using Western blot analysis. These genes are all regulated by estrogen and/or progesterone.

Results: DNER has the ability to suppress the ERE luc activity induced by wild type ER, p < .01 and significantly (p < .05) inverse the expression of all estrogen- and progesterone-regulated genes in this study.

Conclusions: These results suggest that interruption of the estrogen signaling pathway using DNER results in modulation of both estrogen- and progesterone-regulated genes that control leiomyoma cell apoptosis, proliferation, extracellular matrix formation, progesterone receptors, and estrogen metabolism, which might account for the DNER mechanism of action.