IKBKB and breast cancer: Although the effect of IKKβ knockdown/overexpression on breast cancer bone metastasis that we observed in this study were limited to the osteotropic MDA-231 breast cancer cells used, it is tempting to speculate that over-expressing IKKβ would likely have increased the ability of parental MDA-231 to metastasise to bone after intra-cardiac injection in mice.