To investigate the anti-proliferative effect ofrosiglitazone and its relationship to peroxisome proliferator-activated receptor γ(PPARγ)in human breast cancer cell lineMDA-MB-231 and evaluate the potential application value ofrosiglitazone for breast cancer therapy.METHoDS The cytostatic effect of rosiglitazone on MDA-MB-231 cellS was measured by the MTT assay.Cell-cyclekinetics.was assessed by flow cytometry.Apoptotic cells weredetermined by the TUNEL assay.MDA.MB-231 cells weretreated with rosiglitazone or in combination with the PPARyantagonist GW9662 to investigate the effect of rosiglitazone on cellproliferation and its relationship to PPARγ.RESUITS The results showed that rosiglitazone could inhibitgrowth of MDA-MB-231 cells in a dose-and time-dependentmanner with an IC50 value of 5.2 pmol/L at 24 h after the drugwas added into the culture.Cell cycle analysis showed that thepercentage of G0/G1 phase cells increased,S phase cells decreased,and cells were arrested in G1 phase with increasing concentrationsof rosiglitazone.Detectable signs of apoptotic cell death caused byrosiglitazone occurred at a concentration of 100 pmol/L and theapoptotic rate was(18±3)%.PPARγ selective antagonist GW9662could partially reverse the inhibitory effect of rosiglitazone onproliferation of MDA.MB-231 cells.CoNCLUSION It was concluded that rosiglitazone Can inhibitgrowth of MDA-MB-231 cells via PPARγ activation and a highconcentration of rosiglitazone can also induce MDA-MB-231 cellapoptosis.These results suggest that PPARv represents a putativemolecular target for chemopreventive therapy and rosiglitazonemay be effective in the treatment of breast cancer.