Effects of genistein and daidzein on membrane characteristics of HCT cells

Genistein and daidzein are two major isoflavonoids in soybeans. They have r eceived increasing attention because of their possible role in cancer preve ntion. In the present investigation, the human colon tumor (HCT) cell line was used to investigate the effect of isoflavonoids on cell growth with 3-( 4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide colorimetric ass ay. We found that genistein and/or daidzein could inhibit growth in HCT cel ls. The 50% inhibitory concentrations of genistein and daidzein were 15 and 40 mu M, respectively. Fluorescent polarization quasielastic light scatter ing, and circular dichroism were used to study the influence of isoflavonoi ds on membrane characteristics of HCT cells, including membrane fluidity, d ensity of cell surface charge, and membrane protein conformation. Membrane fluidity of HCT cells was obviously reduced by genistein, but not by daidze in. The effect of genistein was time and dose dependent. In addition, genis tein and daidzein could reduce the density of cell surface charge and incre ase the order of membrane protein conformation. All these changes may repre sent one of the mechanisms of the effect of isoflavonoids on growth inhibit ion, differentiation promotion, and transfer interference in a tumor cell l ine.