WIF1 and osteosarcoma: Consistent with a role in these tumors, reduction of in vitro and in vivo tumor growth and metastasis in osteosarcoma and fibrosarcoma respectively [25], [26] was achieved through ectopic expression of negative secreted modulators of the canonical Wnt pathway, such as of Wnt inhibitory factor 1 (WIF1) and the secreted Frizzled-related protein 3 (sFRP3; [27], [28]).