Recombinant Wnt3A recapitulated the effect of CM in stimulating mammosphere colony formation in breast cancer cell lines (MCF7; p < 0.0001, MDA-MB-231_BH; p < 0.0001) (Fig. 2b), and inhibiting Wnt using recombinant human DKK1 (inhibitor of the Wnt co-receptor LRP520), or Vantictumab (therapeutic antibody to Frizzled receptors21) (Western blots showing reduction in protein levels of active β-catenin in Supplementary Fig. 2A), reversed the effect of CM on breast CSC colony formation in cell lines (MCF7; DKK1 p < 0.0001, Vantictumab p = 0.0432. This evidence concerns the gene DKK1 and breast cancer.