A study was conducted to examine the role genistein played in growth factors'-such as protein tyrosine kinase and in thymidine incorporation into cancer cells. Genistein suppressed protein tyrosine kinase activity and the subsequent growth stimulatory incorporation of thymidine into cancer cells. The scientists speculated that genistein has potential value in the prevention and treatment of some tumors in vivo. An investigation into the effect of soy genistein on the growth and differentiation of human melanoma cells showed that genistein significantly inhibited cell growth. Some studies suggest that genistein may enhance the efficacy of certain chemotherapy regimens.
Soy protein contains several anticancer agents including genistein and other isoflavones.
In one study, a lower incidence of prostate cancer was shown in Chinese men who had higher amounts isoflavonoid phytoestrogens, daidzein, and equol within their prostatic fluids and in their blood plasma. The study concluded that the high concentrations of isoflavones present in the prostatic fluid of Asian men may protect them from prostate disease. Earlier in 1999, a study in the British Journal of Cancer reported an inhibitory effect of genistein and quercetin on the growth of tumors. Curcumin and genistein have both been shown to inhibit the growth of estrogen-positive human breast cancer cells induced by pesticides. When curcumin and genistein were added to breast cancer cells, a synergistic effect resulted in a total inhibition of cancer cell growth caused by pesticide-induced estrogenic activity.