ActRIIA, activin-A type IIA receptor; BC, breast cancer; BM, bone metastases; BMD, bone mineral density; BMPs, bone morphogenetic proteins; BMSC, bone marrow stromal cells; BPs, bisphosphonates; BTA, bone targeting agents; BTM, bone turnover markers; Bone metastases; Bone targeting agents; CCR, chemokine-receptor; CRPC, castration-resistant PC; CXCL-12, C­X­C motif chemokine-ligand-12; CXCR-4, chemokine-receptor-4; DFS, disease-free survival; DKK1, dickkopf1; EBC, early BC; ECM, extracellular matrix; ET-1, endothelin-1; FDA, food and drug administration; FGF, fibroblast growth factor; GAS6, growth-arrest specific-6; GFs, growth factors; GnRH, gonadotropin-releasing hormone; HER-2, human epidermal growth factor receptor 2; HR, hormone receptor; IL, interleukin; LC, lung cancer; MAPK, mitogen-activated protein kinase; MCSF, macrophage colony-stimulating factor; MCSFR, MCSF receptor; MIP-1α, macrophage inflammatory protein-1 alpha; MM, multiple myeloma; MPC, malignant plasma cells; N-BPs, nitrogen-containing BPs; NF-κB, nuclear factor-κB; ONJ, osteonecrosis of the jaw; OS, overall survival; Osteotropic tumors; PC, prostate cancer; PDGF, platelet-derived growth factor; PFS, progression-free survival; PIs, proteasome inhibitors; PSA, prostate specific antigen; PTH, parathyroid hormone; PTH-rP, PTH related protein; QoL, quality of life; RANK-L, receptor activator of NF-κB ligand; RT, radiation therapy; SREs, skeletal-related events; SSEs, symptomatic skeletal events; Skeletal related events; TGF-ß, transforming growth factor ß; TK, tyrosine kinase; TKIs, TK inhibitors; TNF, tumornecrosis factor; VEGF, vascular endothelial growth factor; VEGFR, VEGF receptor; mTOR, mammalian target of rapamycin; non-N-BPs, non-nitrogen containing BPs; v-ATPase, vacuolar-type H+ ATPase