Although oestrogen receptor-positive breast cancer cell lines, MCF7 and T47D reliably metastasise from mouse mammary fat pads to mouse long bones in ~90% of animals when mice are supplemented with oestradiol, it is hypothesised that metastasis to bone is driven by the bone anabolic effects of oestradiol (Holen et al. 2016b), as IL-1B also affects bone turnover data obtained using these model systems would need to be interpreted with this in mind (Holen et al. 2016a). Here, IL1B is linked to breast cancer.