Genistein induces G₂ arrest in malignant B cells by decreasing IL-10 secretion

Chronic B cell malignancies are often chemoresistant and the development of new therapeutic modalities is a high priority. Many B cell malignancies have autocrine production of IL-10, which regulates B cell growth and differentiation. Here we demonstrate that the soy isoflavone genistein, a tyrosine kinase inhibitor, rapidly decreased IL-10 secretion followed by upregulation of IFNγ and inhibition of cell proliferation with predominantly G₂ arrest. The antiproliferative effects of genistein were reversed by the addition of exogenous IL-10. Genistein downregulated cdc25C and cdk1 as well as anti-apoptotic proteins survivin and Ian-5. After genistein withdrawal, the G₂M arrested cells reentered the cell cycle and underwent apoptosis, which was significantly augmented by fludarabine. We conclude that genistein can sensitize malignant B cells to the action of other chemotherapeutic agents by modulating the cytokine profile and controlling cell cycle progression.