Soy isoflavones sensitize cancer cells to radiotherapy

Soy isoflavones are dietary compounds isolated from soybeans, which are safe for human use and have mild anti-cancer properties. Soy isoflavones inhibit the activity of transcription factors and genes essential for tumor cell proliferation, invasion, and neovascularization, and it appears that soy isoflavones may enhance the effectiveness of conventional therapies against cancer. Soy isoflavones could be an effective complementary treatment given that they inhibit the survival signaling pathways of various cancer cells through altered activation of APE1/Ref-1, NF-κB, and HIF-1α, which are genes essential for tumor cell survival, tumor growth, and angiogenesis, thus making such cells more sensitive to radiotherapy. Studies in which soy isoflavones were given in conjunction with radiotherapy to prostate cancer patients suggest that soy isoflavones might also mitigate the adverse effects of radiation on normal tissues, probably by acting as antioxidants. These observations open new avenues for exploiting soy isoflavones as supplements to conventional therapies.