Found in 40% of BC tumors [24], YB-1 is believed to promote the tumorigenesis of BC, since it has been shown to enhance mammosphere formation in vitro, and transcriptionally up-regulate the expressions of a large cassette of stem cell-associated proteins including CD44, CD49f (α6 integrin), c-Met, EGFR, Her-2, Cyclin D1, MDR-1, and p110α [22,25-28]. Here, CD44 is linked to breast cancer.