breast stem cell marker-expressing cell population is enriched in mammospheres. MCF7-derived mammospheres were collected after 7 days in culture and dissociated. Adherent MCF7 and mammosphere-derived cells were stained for CD44 and CD24 breast stem cell markers and analyzed by flow cytometry (A) and immunostaining (B) for the CD44high/CD24low cell population. (C) Immunofluorescence depiction of CD44high/CD24low cell population was calculated manually, after acquiring several images from each cell type and counting the number of cells expressing the appropriate markers, compared to the total cell number. Results for flow cytometry represent means ± SE of 2 different mammosphere cultures. Results for immunostaining represent means ± SE of 3 different mammosphere cultures. Statistical significance was determined by the student’s t-test analysis: *p < 0.05.