SOST and osteosarcoma: Osteocytes, in addition to osteoblasts, may act as a cell of origin for osteosarcoma.107 High levels of the osteocyte‐derived factor Sclerostin are also found in prostate cancer patients with osteoblastic bone metastasis.108, 109 Yet, whether Sclerostin contributes to the osteoblastic disease in these patients remains to be determined.