The effects of fulvestrant, an estrogen receptor antagonist, on the proliferation, differentiation and mineralization of osteoprecursor cells

Fulvestrant is a novel type of endocrine treatment and is considered to be a potent inhibitor of breast cancer cell proliferation. Fulvestrant is reported to work by downregulating as well as degrading the estrogen receptor, leading to an inhibition of estrogen signaling through the estrogen receptor. The effects of various doses of fulvestrant for bone cells have not yet been fully investigated. In the present study, the effects of fulvestrant on osteoprecursor cells were evaluated. The effect on cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and protein measurement. Differentiation and mineralization were examined using an alkaline phosphatase activity (ALP) test and Alizarin red S staining. The protein expression of osteocalcin was evaluated using western blot analysis. Cultures grown in the presence of fulvestrant at concentrations of 0.1-10 μM did not show any significant change in cell proliferation. Cultures grown in the presence of fulvestrant showed a dose-dependent reduction in ALP activity, however, statistically significant differences were not achieved. Cultures grown in the presence of fulvestrant presented with a dose-dependent reduction in mineralization with a statistically significant difference at the 10 μM concentration. The use of fulvestrant may produce negative effects on the mineralization of osteoprecursor cells, while long-term use of fulvestrant may have detrimental effects on osteoblastic activity.