KLK3 and prostate cancer: Osteoclast-derived proteinases and prostate cancer cells-secreted PSA and uPA activate transforming growth factor β (TGF-β), which may also promote osteolytic metastases (Josson et al., 2010[66]; Jin et al., 2011[63]) through induction of the proosteolytic gene expression in cancer cells, with PTHrP in the key position (Yin et al., 1999[141]; Kingsley et al., 2007[72]).