All together these results demonstrate that there are at least two sources of DKK1, one released by bone cells contributing to DKK1 levels in circulation and possibly exerting systemic pro-tumorigenic effects, and one from CAFs at tumor site, possibly affecting the local tumor microenvironment; abrogating DKK1 expression by either of the sources is sufficient to reduce tumor growth. This evidence concerns the gene DKK1 and neoplasm.