FOXO3 and breast cancer: Consistent with this idea, we have shown previously that paclitaxel mediates its cytotoxic functions through FOXO3a,26, 27 which is an upstream negative regulator of FOXM1 expression and activity.10, 28, 29 Interestingly, our data also reveal that in response to paclitaxel, breast cancer cell lines undergo mitotic catastrophe, followed by cellular senescence and/or non-apoptotic cell death.