phenotype, within population B, selects luminal progenitors. A) A representative dot plot showing the expression of each stem/progenitor cell marker in population B (Ep-CAMhigh/CD49f + population,gated red dots) as analyzed by flow cytometry, *numbers in brackets indicates average percentage (n = 10, mean ± SEM). Quadrants show positivity while rectangles show "stem/progenitor" marker positive population. B&C) Mammosphere formation measured by either number (b) or volume (C) of each stem/progenitor subpopulation, compared with the remaining bulk (rest) of population B (means ± S.E.M, n = 3). D) Number of colonies formed of each cell subpopulation from population B (means ± S.E.M, n = 2). Data in B, C &D are normalized to unfractionated population B, **indicate statistical significance (p < 0.05). E) Top) Representative image (x400,) of immunohistochemistry for estrogen receptor (nuclear, brown) in each cell subpopulation of population B compared with population C (Ep-CAMhigh/CD49fneg) cells as a positive control. Gills hematoxylin (nuclear, blue) was used as a counterstain. Bottom) Quantification of estrogen receptor positive cells in each subpopulation of population B. ALL = the subpopulation within population B that express all the three stem/progenitor markers simultaneously.