A, Changes in the expression of Wnt target genes in MMTV-Wnt1 mammary tumors harvested from mice on the standard diet (Std) and those receiving calcitriol (Cal). Relative mRNA expression of each gene is shown with the expression in tumors from mice on the standard diet (Std) normalized to 1 (n = 6–10; *, P < 0.05). B, Changes in the expression of Wnt target genes in CD49fhiEpCAMlow TIC-enriched cells treated with ethanol or calcitriol (1 nM) for 16 hrs. Relative mRNA expression of each gene is shown (n = 3; ***, P < 0.05). C, Effect of constitutively active β-catenin on calcitriol sensitivity of TICs. Spheroid formation by CD49fhiEpCamlow cells was assayed after treatment with vehicle (ethanol) or calcitriol (1 nM) following transduction with control or constitutively active β-catenin expressing lentiviruses (n = 5–6; P < 0.05). Values represent mean ± SEM.