This result is consistent with a previous study that demonstrated the capability of 100–200 self-renewable CD24−/CD44+-expressing breast cancer cells to initiate tumor growth in non-obese diabetic/severe combined immunodeficient (NOD/SCID) immunocompromised mice, whereas 20,000 of CD24+/CD44+-expressing cells failed to do so [28]. This evidence concerns the gene CD44 and breast cancer.