However, in terms of epigenetic mechanism, a recent study indicated that the promoter region of CD24, one of the cancer stem cell genes, is unmethylated in breast cancer cells regardless of mRNA levels, whereas the expression of other cancer stem cell genes including CD44, CD133, and Musashi–1 has an inverse correlation with DNA methylation, indicating that other epigenetic mechanisms are involved in the transcriptional regulation of CD24 [23]. This evidence concerns the gene CD24 and breast cancer.