Abstract: BACKGROUND AND AIM: To investigate the effects of thalidomide on the proliferation in breast cancer cell lines. MATERIALS AND METHODS: Establishing the solvent control against and different densities，different durations, in order to study the relation between time and efficacy, The growth rate among these groups was measured by MTT assay. The influence of thalidomide on apoptosis and cell cycle were detected in treated cells by FCM assay. RESULTS: The growth rates in these groups were different, thalidomide could inhibit the proliferation of MCF-7 and MDA-MB-231 from 10 μg/ml to 200 μg/ml. The peak inhibitory effect occurred after thalidomide treatment for 48 h. 100 μg/ml had the maximal inhibitory effect after 48 h. Apoptosis was found in the breast cancer cells in the second period of G1 in the DNA histogram of FCM. 100 μg/ml thalidomide treatment for 48 h, the MCF-7 cell apoptotic index could amount to 9.66％ and MDA-MB-231 cell to 11.18％, comparing with control groups, the difference was significant(P<0.01). CONCLUSION: Thalidomide could inhibit the proliferation and induce apoptosis of breast cancer cell lines MCF-7 and MDA-MB-231.

Key words: breast cancer, cell lines, thalidomide, proliferation, apoptosis