Breast cancer cells in bone promote osteolysis by inhibiting osteoblast differentiation [12, 13, 43, 47] and previous studies reported that inhibition of IKK-mediated NFκB activity in osteoblasts increased osteoblast differentiation in vitro and promoted bone formation in vivo [19, 21, 22, 24–26]. Here, NFKB1 is linked to breast cancer.