Tumor-forming ability of cancer cells and aggressiveness of various cancers has been associated with the presence of cells having stem-like phenotype.33,34 Activin-A has been shown to regulate expression of various stemness markers such as Nanog, Sox2, and Oct4 in various cells.35,36 Hence, to investigate whether activin-A expression affects stemness of breast cancer cells, we analyzed population of CD44high and CD24low cells. This evidence concerns the gene SOX2 and cancer.