Tectorigenin, an isoflavone of Pueraria thunbergiana Benth., induces differentiation and apoptosis in human promyelocytic leukemia HL-60 cells

Cytotoxic effects of six isoflavonoids, tectorigenin, glycitein, tectoridin , glycitin, 6"-O-xylosyltectoridin, and 6"-O-xylosylglycitin isolated from the flower of Pueraria thunbergiana BENTH. together with genistein, a known differentiation and apoptosis inducer, were examined. Among these isoflavo noids, tectorigenin and genistein exhibited cytotoxicity against various hu man cancer cells; glycitein showed only mild cytotoxicity. These results su ggest that the isoflavone structure and 5-hydroxyl group are crucial for th e cytotoxic properties and that glycosides are inactive. Moreover, tectorig enin induced differentiation of human promyelocytic leukemia HL-60 cells to granulocytes and monocytes/macrophages, and caused apoptotic changes of DN A in the cells, as did genistein. Tectorigenin also inhibited autophosphory lation of epidermal growth factor (EGF) receptor by EGF and decreased the e xpression of Bcl-2 protein, with less activity than genistein. From these r esults, tectorigenin may be a possible therapeutic agent for leukemia.