In brief, cytokines or growth factors secreted by invading cancer cells (e.g., parathyroid hormone-related protein, PTHrP) act to stimulate osteoblasts to produce more receptor activator of nuclear factor kappa-B ligand (RANKL) and less osteoprotegerin (OPG), a decoy receptor for RANKL. This evidence concerns the gene TNFSF11 and cancer.