We also collected nine CD44+CD24− phenotype breast cancer cell line stem cells (MCF‐7‐S, T47D‐S, BT‐474‐s, SKBR3‐S, MDA‐MB‐453‐S, MDA‐MB‐468‐S, HCC‐38‐S, MDA‐MB‐231‐S and BT‐549‐S) and one CD44+CD24− phenotype mammary epithelial cell line stem cells (MCF‐10A‐S), which were serum‐free suspension cultured and then sorted by flow cytometry. This evidence concerns the gene CD44 and breast cancer.