KLK3 and neoplasm: In addition, protease secreted by tumor (urokinase-type plasminogen activator, prostate-specific antigen (PSA), and matrix metalloproteinases) promotes the release of osteoblast-induced growth factors, such as insulin-like growth factors, PDGF, and transforming growth factor β (TGF-β), which further enhances the differentiation of mesenchymal stem cells into osteoblasts [27].