We found that soluble factors such as β2-microglobulin (β2-M) and receptor activator of NF-κB ligand (RANKL) can drive PC and other human cancer cells to undergo epithelial-to-mesenchymal transition (EMT) and confer aggressive phenotypes including local invasion and distant metastases [6]–[12]. Here, TNFSF11 is linked to cancer.