Since mammosphere formation is reportedly dependent on the presence of CSC [9] and isolated mammospheres in this study showed an increase in cells expressing the CD44+/CD24- breast cancer stem cell (BCSC) phenotype, the ability of RU017 and RU018 to inhibit mammosphere formation suggested that these compounds have putative anti-CSC activity and may inhibit a signal transduction pathway which is essential in mammosphere formation. The gene discussed is CD44; the disease is breast carcinoma.