The direct mechanism of GnRH antagonist cetrorelix acetate therapy for uterine leiomyomas: modulation of fibrosis

Abstract

OBJECTIVE: Uterine leiomyomata are hormonally-regulated tumors that can impact fertility and miscarriage. Gonadotropin releasing hormone antagonists (GnRHant) have been effective in decreasing the size of these tumors by over 30%. Hypothetically, GnRHant acts indirectly by decreasing gonadal hormone production. However, recent data demonstrates that GnRH receptors are expressed on leiomyomas. Since GnRHant treatment involves systemic exposure, we hypothesized that GnRHant could directly regulate leiomyoma proliferation and extracellular matrix (ECM) production. DESIGN: Laboratory study. MATERIALS AND METHODS: After IRB approval, proliferation studies were performed using immortalized human leiomyoma and patient-matched myometrial cells either untreated or treated with cetrorelix at concentrations ranging from 0.1μg/ml to 10μg/ml. We also isolated mRNA from treated and untreated leiomyoma cells for real time reverse transcriptase polymerase chain reaction analysis of collagen 1A1, versican and TGF-β3 expression. Wilcoxon sign rank test was used, with significance set at p<0.05. RESULTS: We have previously demonstrated the validity of our immortalized human leiomyoma model, and have demonstrated that ECM genes collagen 1A1, versican, and TGF-β3 were increased in both leiomyoma surgical samples and immortalized cells relative to patient-matched myometrium. In proliferation studies using cetrorelix at concentrations of 0.1μg/ml, 1μg/ml, and 10μg/ml, the cetrorelix had no significant impact on proliferation for treatment analyzed as early as 24 hours exposure to as long as 6 days exposure for either leiomyoma or patient-matched myometrial cells when compared to untreated cells. Analysis of ECM-related gene expression demonstrated decreased expression of collagen 1A1 (0.13 ± 0.07 fold), versican (0.23 ± 0.15 fold) and TGF-β3 (0.72 ± 0.26 fold) in leiomyoma cells treated with 1μg/ml cetrorelix compared with untreated cells. CONCLUSIONS: The discovery that the GnRHant cetrorelix regulates ECM rather than cell proliferation provides critical insight into the mechanism of leiomyoma regression induced by cetrorelix. Our results demonstrate that cetrorelix does not regulate cell proliferation at both high concentration and long exposure. However, expression of collagen 1A1, versican, and TGF-beta 3 was inhibited by cetrorelix treatment, suggesting that GnRHant can regulate gene expression and directly control the production of leiomyoma cell ECM components.