VDR and cancer: Given that CSCs are responsible for the initiation, metastasis, and drug resistance of cancers, and activation of the Wnt signaling pathway in CSCs is required for tumorigenesis and metastasis [5–8,12], we sorted MCF-7 stem cells by using fluorescence-activated cell sorting methods and the CD133 antibody to examine VDR expression and activation of Wnt/β-catenin signaling in MCF-7 cells.