For example, in our studies the CD44+/CD24− cells isolated from the MCF-7 breast cancer cell line consisted of only 0.1% of the analyzed cells while the subset of Hoechst 33342 excluding cells constituted 1.3% of the same population.(data not shown) Likewise, in MDA-MB-231 cells, CD44+/CD24− cells were >85% of the cell population while Hoechst 33342 excluding cells were less than 0.1% (data not shown). This evidence concerns the gene CD44 and breast cancer.