Genistein modulates the anti-tumor activity of cisplatin in MCF-7 breast and HT-29 colon cancer cells.

The function of genistein (GEN) on tumor prevention and tumor promotion is discussed controversially. A possible interference of GEN with chemotherapy has been only rarely addressed so far. In this study, effects of GEN on the anti-tumor activity of cisplatin (CIS) were investigated in the presence and absence of estradiol (10(-10) M) in MCF-7 breast and HT-29 colon cancer cells. Cells were treated with graded concentrations of GEN (10(-4)-10(-6) M), E2, CIS and combinations. Cell growth, proliferation and apoptosis were determined as well as the expression level of PCNA, Ki67 and BCL-2 family members. CIS and GEN 10(-4) M inhibited cell growth and induced apoptosis in MCF-7 and HT-29 cells in the presence and absence of E2. Co-treatment with CIS and 10(-4)M GEN resulted in additive effects. In concentrations of 10(-5) and 10(-6) M, GEN stimulated cell growth in MCF-7 cells. It promoted proliferation, inhibited apoptosis and counteracted the anti-tumor activity of CIS in MCF-7 and HT-29 cells. Particularly the ability of CIS to induce apoptosis was antagonized. In ER alpha-positive MCF-7 cells, but not in ER alpha-negative HT-29 cells, E2 was able to neutralize the anti-CIS effects of GEN. Our data provide evidence that GEN in the absence of E2, a situation which occurs in postmenopausal women, directly affects the anti-tumor activity of cytostatic drugs like CIS. The exact molecular mechanism has to be investigated in future studies.