Abstract: To explore the mechanisms of mifepristone on the proliferation and apoptosis of MCF-7 cells in vitro. Methods1.25，2.50，5.00，10.00，20.00 or 40.00mg/L MIF was added into 6 intervention groups and no MIF was added into the control group. Cellular morphological changes were observed under an inverted microscope, the apoptosis rate was measured by a flow cytometer, cell vigor was detected by methyl thiazolyl tetrazolium (MTT), and the expression levels of ER， PR， VEGF， bcl-2， Ki67， CerbB-2 and p53 were determined by immunohistochemistry. Results① Cell adherence was aequalis and in good condition in the control group and decreased in the intervention groups, also cell debris was increased in a dose-and time-dependent manner. ② The optical density significantly degraded in each intervention group(P＜0.01) in a dose- and time-dependent manner by MTT test. ③ The apoptosis rate was much higher in each intervention group than that in the control group (P＜0.01), which was also in a dose- and time-dependent manner(P＜0.01).　④　Expressions of VEGF, bcl-2, Ki67, CerbB-2 and p53 levels were statistically different between the 10.00 and 20.00mg/L groups and the 2.50 and 5.00mg/L groups (P＜0.01), but of ER and PR were not statistically different among each group. ⑤ Every apoptosis index had distinguishing differences and cell vigor had significantly degraded after the interventions(P＜0.01). Conclusions MIF can inhibit the growth of the breast cancer cell possibly by promoting apoptosis in dose- and time- dependent manners and inhibiting proliferation and growth of tumor micro-vessels.

Key words: Mifepristone, Breast neoplasms, Proliferation, Apoptosis, Immunohistochemistry