A low concentration of genistein induces estrogen receptor-alpha and insulin-like growth factor-I receptor interactions and proliferation in uterine leiomyoma cells.
BACKGROUND
Previously, we found that genistein at low concentrations stimulates the growth of human uterine leiomyoma (LM) cells, but not uterine smooth muscle (myometrial) cells (SMC). The aim of this study was to understand the molecular mechanism whereby genistein causes hyperproliferation of LM cells.


METHODS
The effects of genistein at 1 microg/ml on LM cells and SMC were evaluated using estrogen response element gene reporter, real-time RT-PCR, western blot, immunoprecipitation and cell proliferation assays.


RESULTS
Elevated estrogen receptor (ER) transactivation, increased mRNA expression of early estrogen-responsive genes, progesterone receptor and insulin-like growth factor-I (IGF-I), and decreased protein levels of ER-alpha (ER alpha) were found in genistein-treated LM cells, but not SMC. Additionally, extracellular regulated kinase (ERK), Src homology/collagen (Shc) and ER alpha were transiently activated, and interactions between ER alpha and IGF-I receptor (IGF-IR) were rapidly induced by genistein in LM cells. Using ER antagonist ICI 182,780 and MAPK/ERK kinase (MEK) inhibitor PD98059, we found that these early events were inhibited and the proliferative effect of genistein on LM cells was abrogated.


CONCLUSIONS
ER alpha is involved in the transient activation of ERK/mitogen activated protein kinase (MAPK) by genistein via its early association with IGF-IR, leading to hyper-responsiveness of LM cells and confirming that ER signaling is enhanced by activation of ERK/MAPK in LM cells.
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Comparative Pathobiology Group, Cellular and Molecular Pathology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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Moore
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Castro
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Zheng
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Hermon
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Dixon
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D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D047628:Estrogen Receptor alpha / Q000096:biosynthesis / Q000502:physiology*; D047629:Estrogen Receptor beta / Q000096:biosynthesis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis; D007889:Leiomyoma / Q000503:physiopathology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D008954:Models, Biological; D009215:Myometrium / Q000187:drug effects / Q000502:physiology; D015688:Oncogene Protein pp60(v-src); D025941:Protein Interaction Mapping; D017526:Receptor, IGF Type 1 / Q000502:physiology*; D015533:Transcriptional Activation; D015854:Up-Regulation; D014594:Uterine Neoplasms / Q000503:physiopathology*
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D007334:Insulin-Like Growth Factor I; D019833:Genistein; D017526:Receptor, IGF Type 1; D015688:Oncogene Protein pp60(v-src); D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3