CD44 and breast cancer: Breast cancer cell lines (MDA-MB-231, MDA-MB-468, MCF7 and T47D) and primary human breast cancer cells were labelled as described above and sorted into two populations CD44+/24lo/ESA+ (Stem-like cells) and CD44-/24hi/ESA- (Non stem-like cells) and according to cell cycle (Hoechst DNA profile) within the two populations into G0/1 and S/G2/M, and for comparison the whole cell population.