Breast cancer cells themselves can acquire an osteoblast-like phenotype, by ectopically expressing bone matrix proteins such as bone sialoprotein (BSP), osteopontin (OPN), osteoprotegerin (OPG) and osteoblast-specific cadherins (Ibrahim et al. 2000, Kapoor et al. 2008, Tan et al. 2016). Here, SPP1 is linked to breast cancer.