Translational research with progesterone receptor modulator motivated by the use of levonorgestrel-releasing intrauterine system

The use of levonorgestrel-releasing intrauterine system (LNG-IUS) is effective for management of menorrhagic women with uterine myomas because of reduction in menorrhagia. However, the size of myomas during use of LNG-IUS increased in some but decreased in other instances. This prompted us to characterize the effects of progesterone (P4) on cultured leiomyoma cell growth. Treatment with P4 resulted in increase in epidermal growth factor (EGF) expression in cultured leiomyoma cells, whereas treatment with E2 augmented EGF-R expression in those cells. This indicates that P4 and E2 act in combination to stimulate myoma growth through induction of EGF/EGF-R expression. Bcl-2 expression in leiomyoma cells was up-regulated by P4. Furthermore, P4 augmented proliferating cell nuclear antigen expression in cultured leiomyoma cells but not in cultured normal myometrial cells. This fact let us to examine the effects of progesterone receptor modulator (PRM) on leiomyoma cell proliferation and apoptosis in comparison with normal myometrial cells. Our studies revealed that CDB-2914 inhibits the proliferation, stimulates apoptosis of cultured leiomyoma cells, and inhibits the expression of angiogenic factors (vascular endothelial growth factor and adrenomedullin) and their receptors in cultured leimyoma cells, without affecting those in cultured normal myometrial cells. We then evaluated the effects of CDB-2914 on extracellular matrix (ECM) components in cultured leiomyoma cells. CDB-2914 increased ECM metalloproteinase inducer, matrix metalloproteinase (MMP)-1, MMP-8 contents and decreased tissue inhibitors of MMP (TIMP)-1, TIMP-2 contents as well as type I and type III collagen contents in cultured leiomyoma cells, without comparable effects on cultured normal myometrial cells. These findings demonstrate that PRM not only inhibits the proliferation and stimulates apoptosis of cultured leiomyoma cells but also suppresses collagen synthesis in a cell-type specific manner. This is meaningful for understanding the molecular mechanism of the usefulness of PRM in the treatment of uterine fibroids.