Isoflavones and gamma irradiation inhibit cell growth in human salivary gland cells

We studied the effects of isoflavones and irradiation on cell cycle in a human salivary gland cell line (HSG). Genistein and a soy isoflavone conjugate (NS) inhibited DNA synthesis. Cells deconjugated the glucoside form of isoflavones in NS to the aglycones genistein and daidzein. NS, genistein and IR increased phosphorylation of p53 and p21CIP1 at serine 15 (phos-p53). Irradiation and NS also increased levels of p21CIP1. In a cologenic survival assay, cells in log phase growth had high radio-sensitivity with 2 Gy causing a reduction in survival (SF2 = 0.45). Conclusion: isoflavones and radiation may interact to sensitize cancer cells to radiation.