Different mechanisms of soy isoflavones in cell cycle regulation and inhibition of invasion.

Soy isoflavones, genistein, daidzein and glycitein, are thought to have beneficial effects on cancer prevention.We used cell cycle analysis, invasion assay and immunoblotting to determine the effects of genistein and glycitein on Jurkat T cells.Glycitein inhibited Jurkat cell invasion at a level comparable to the inhibition by genistein. Both genistein and glycitein down-regulated MMP-13 proteolytic activity by 60-70% and MMP-8 expression. Caffeine could block G2/M arrest by genistein, but was unable to block the inhibition of invasion by genistein and glycitein. We also demonstrated that glycitein inhibited proteintyrosine phosphorylation in Jurkat cells.We determined, for the first time, that glycitein inhibited Jurkat cell invasion, in part through the down-regulation of MMP-13 activity and MMP-8 expression. Our findings also suggest that soy isoflavones may utilize different mechanisms to exert their effects on cell cycle progression and invasiveness of Jurkat cells.