Similar to the effects we reported after exposure of HCT116 colon cancer cells overexpressing miR-143 to 5-fluorouracil [12], exposure of MDA-MB-231 breast cancer cells to genistein induced cell growth suppression and induction of apoptosis, with down-regulation of ERK5, p-ERK5, NF-κB and Bcl-2 steady state levels. This evidence concerns the gene NFKB1 and breast cancer.