Cell lines with CD44+/CD24- subpopulation are highly invasive. (a) Matrigel invasion properties of breast cancer cell lines with or without CD44+/CD24- subpopulation. Number of cells invaded through matrigel to serum-free media for each cell line was set as one unit and relative invasion to media containing 10% fetal calf serum is shown. Mean and standard error of the mean is shown. Although invasion by TMD-231 and TMD-436 cells were higher than that of MDA-MB-231 and MDA-MB-436 cells, respectively, differences were not statistically significant. (b) Matrigel invasive properties of CD44+/CD24- and CD44+/CD24+ subpopulations of TMD-436 cells. P = 0.006.