Abstract: PURPOSE  To investigate the effect and mechanism of the Genistein derivative 5,4’-Di-n-octoxyl-7-gem-difluoromethylene-genistein(DOdFMG) on the growth and apoptosis of  human breast cancer(MCF-7) cells line in vitro.and provide a molecular mechanism of this effect so as to find a new candidate for tumor chemotherapy.METHODS   Soft ager-colon assay was used to test colon formation inhibitory effect of MCF-7 by DOdFMG.PI stain flow cytometry(FCM) was used to analyse the apoptosis  after being treated with DOdFMG.Western blotting assay was used to detect the effect of DOdFMG on the CK2 and NF-κB protein expression level of breast cells.Results: DOdFMG significantly inhibited proliferation and growth of MCF-7 cells in dose-dependent manner.DOdFMG significantly induced apoptosis. Western-blotting analysis indicated that after exposures to DOdFMG3.0,10.0,30.0μmol/L for 24h,the protein expressions of CK2 were down-regulated by 12.50%,41.50%,67.30%，the protein expressions of NF-κB were down-regulated by 20.50%,51.47%,71.93% respectively in comparison with the control group.After MCF-7 cells were treated with DOdFMG at 30.0 μmol/L for 6,12 and 24 h,the protein expressions of CK2 were down-regulated by 27.73％,44.8％,65.2％，the protein expressions of NF-κB were down-regulated by 20.5%,49.83%,69.93%  respectively in comparison with the control group.These showed that the expressions of CK2，NF-κB were decreased in a time and dose-dependent manner  after treatment with various concentrations of DOdFMG..In comparison with the lead compound Gen,DOdFMG was more effective.CONCLUSION DOdFMG possesses a significant inhibitory effect on the cell proliferation and growth of human breast carcinoma cell(MCF-7) in vitro  DOdFMG significantly induced apoptosis of human breast cancer （MCF-7 ） cell line.The mechanism might be associate
d with down-regulation of ck2 and NF-κB.

Key words: breast cancer, Genistein, 5,4&rsquo, -Di-n-octoxyl-7-gem-Difluoromethylene-genistein, CK2