PTN and prostate carcinoma: In accordance, COL1-PC3SFPR2 cells had a high expression of Pleiotrophin (Osteoblast Specific Factor-1, PTN), which is considered as a poor prognosis marker in prostate cancer patients with bone metastasis [61], but it is generally known as a secreted growth factor produced by osteoblasts during early osteogenic differentiation and angiogenesis [62].