Interestingly, Hiraga et al. reported that bone-derived IGF-1 promotes bone metastasis and survival as well as proliferation of bone-metastatic breast cancer cells via an insulin-like growth factor 1 receptor (IGF-1R)/AKT/NFKB pathway independently of other bone-derived growth factors, such as TGFβ, fibroblast growth factor (FGF), or platelet-derived growth factor (PDGF) [70]. Here, IGF1R is linked to breast cancer.