CD44 and breast cancer: Based on the expression pattern of nucleostemin, CD44, CD24 and ALDH-1, the stemness character of the SKBR3 human breast cancer population is similar to that of the 10AT-Her2 cell population, whereas MCF-7 and MDA-MB-231 cells express significantly lower levels of nucleostemin and do not produce detectable levels of ALDH-1.