To demonstrate whether B7-H4 deficiency leads to breast cancer stem cell differentiation in vivo, SKBR3-KO, MCF7-OE and MDA-MB-231-OE cells were employed subcutaneous xenografting in nude mice at a limiting dilution to examine tumorigenicity, which is the gold standard assay that fulfills the criterion of CSCs. This evidence concerns the gene VTCN1 and breast carcinoma.