DKK1 and breast cancer: In line with this, 1,25(OH)2D3 induces DKK1 expression and reduces β-catenin transcriptional activity in R7 murine breast cancer cells, and Vdr deletion and 1,25(OH)2D3 treatment increases and inhibits, respectively, the tumor expression of several Wnt/β-catenin target genes in breast cancer mouse models [101,102].