A soy-derived isoflavone and phytoestrogen with antineoplastic activity. Genistein binds to and inhibits protein-tyrosine kinase, thereby disrupting signal transduction and inducing cell differentiation. This agent also inhibits topoisomerase-II, leading to DNA fragmentation and apoptosis, and induces G2/M cell cycle arrest. Genistein exhibits antioxidant, antiangiogenic, and immunosuppressive activities.