Stimulatory and inhibitory effects of genistein on human uterine leiomyoma cell proliferation are influenced by the concentration

Abstract

Due to dietary exposure of women to genistein, a soy-derived phytoestrogen, and the estrogen responsiveness of uterine leiomyomas ‘fibroids’, we evaluated the effects of genistein (0.001–50 µg/ml) on human uterine leiomyoma (UtLM) cells versus uterine smooth muscle cells (UtSMCs) in vitro. Light microscopy was used to determine the effects of genistein on cell morphology. Proliferation was assessed using a colorimetric assay and proliferating cell nuclear antigen (PCNA) immunocytochemistry. Flow cytometry was used to quantitate cells in the S-phase and those undergoing apoptosis. A fluorometric assay and confocal microscopy were used to detect caspase-3 activity and apoptotic bodies, respectively. In UtLM cells, low concentrations (≤1 µg/ml) of genistein stimulated proliferation, increased PCNA labeling and the percentage of cells in the S-phase, but this did not occur in UtSMCs. Higher concentrations (≥10 µg/ml) of genistein adversely affected the morphology, significantly inhibited proliferation, decreased PCNA labeling, increased caspase-3 activity and induced apoptosis in both cell types. Genistein’s effects are concentration-dependent in both cell lines. Lower concentrations elicit proliferative effects on UtLM cells only; whereas, higher concentrations alter morphology, inhibit proliferation, and increase caspase activity and apoptosis in both cell types, with the latter two effects being more extensive in UtSMCs.