Relative telomere length and telomerase activity varies by lineage within cultured strains. (A) Representative FACS analyses of CD227 and CD10 expression in 4th passage HMEC strains isolated from a 19 year old woman (240L) and a 91 year old woman (805P). FACS plots are shown as dot plots, at left are isotype antibody controls, and at right are the CD10 and CD227 stained samples. Luminal and myoepithelial lineages are identified as LEP and MEP, respectively. (B) Histogram of CD117 expression by flow cytometry analysis of isotope negative control staining (black lines) and CD117 expression (blue lines) from 4th passage HMEC strains 240L and 805P. Histograms of ratios of keratin (K)14 to K19 protein expression in FACS enriched lineages, MEP (CD117-/CD227-/CD10+), LEP (CD117-/CD227+/CD10-), cKit + (CD117+) and unsorted cells from 4th passage strains (C) 240L and (D) 805P (n = 500 cells/histogram). Insets show examples of FACS enriched cells stained to show K14 (red), K19 (green), and nuclei (blue). (E) RTL measurements in FACS enriched lineages strains 240L and 805P at 4th passage, (n = 4). * = P < 0.05, ** = P < 0.01, ***P < 0.001.