The isoflavones in soy are likely to contribute to the historically low incidence of breast cancer among Asian women who consume traditional diets. The possible role of isoflavones in controlling the expression of p27^kip1 and p57^kip2 has not been previously explored. In this study, the ability of the isoflavone, genistein, to regulate the expression of p27^kip1 and p57^kip2 in breast cancer cells was evaluated.

The effects of genistein was examined on the expression of p27^kip1 and p57^kip2 at the mRNA level, using the MDA-MB 231 human breast cancer cell lines.

By genistein treatment, p27^kip1 mRNA increased significantly in comparison to the control group. In particular, p27^kip1 mRNA level in 10µM and 50µM genistein treatedgroups increased about two-folds more than the control. p57^kip2 mRNA was not different from control group. p57^kip2 mRNA decreased slightly only in the 50µM genistein treated-group. PPAR-γ mRNA level increased slightly according to the concentration-dependent manner of genistein, but it was not significantly different.

These results suggest that the up-regulated p27^kip1 by genistein might contribute to cancer prevention or inhibition.