OBJECTIVETo study the inhibitig effects of genistein on the growth of human breast cancer cell lines in vitro and its mechanisms. METHORD: Human breast cancer cell lines both MCF-7(positive estrogen receptor, ER+) and MDA-MB-231 (negative estrogen receptor, ER-) were cultured in vitro. The proliferation of cells was measured with MTT methord and the growth curve was drawn with cell count. The estrogen receptor in cells was show with immunohistochemistry.

RESULTGenistein inhibited proliferation of MCF-7 and MDA-MB-231 cell lines and inhibition was dependent on dose within some concentration range, IC50 being 32.5 mumol.L-1 and 46.8 mumol.L-1 respectively. Genisteins antiproliferation of MCF-7 was stimulated by ectogenesis estrogen but proliferation of MDA-MB-231 inhibited by geinstein was not related to estrogen. The positive signs of ER in cellular nuclei of MCF-7 cell line fed with genistein at concentration of 30 mumol.L-1 were significantly weaker than these not fed with genistein.

CONCLUSIONGenistein obviously inhibits proliferation of both cell lines of MCF-7 and MDA-MB-231 in vitro and is dependent on dose. Genisteins antiproliferous effect on MCF-7 cell lines is stimulated by estrogen and this effect is related with ER, but genisteins inhibiting proliferation of MDA-MB-231 cell line is not through ER.