Both in vitro and in vivo studies have demonstrated the key role of IL-1B in this ‘vicious cycle’: In vitro co-culture of breast cancer cells (MDA-MB-231 or T47D) with bone cells (human bone marrow stromal cell HS5 or pre-osteoblast cell OB1) not only significantly increase the proliferation of these cells, but also significantly increased IL-1B expression and secretion form all of these cell types [4]. This evidence concerns the gene IL1B and breast cancer.