SOST and osteosarcoma: As a well-known negative regulator of bone formation (Zhang et al., 2016), sclerostin inhibits the proliferation and differentiation of cementoblasts (Bao et al., 2013) and osteoprogenitor cells including osteosarcoma cells (Zou, Zhang & Li, 2017) and human mesenchymal stem cells (Sutherland et al., 2004).