Fig. 1.

Identification of Label-Retaining Cells In Vitro. a Cytofluorimetric histograms illustrating dilution of Vybrant^® DiD in adherent human breast cancer cell cultures at passages 2, 4 and 6 of culture growth (P2, P4 and P6, respectively, where P = passage number). All cells were intensely positive immediately after staining (Day 0). Fluorescent dye was lost from rapidly proliferating cells to reveal a population of more slowly cycling label-retaining cells beyond passage 4. b Representative flow cytometry plots depicting Vybrant^® DiD negative (DiD−) and positive (DiD+) populations in adherent MCF-7 and MDA-MB-231 cultures at passage six post-staining. c Cytofluorimetrically determined percentage of Vybrant^® DiD-positive cells within adherent MCF-7 and MDA-MB-231 cultures over six consecutive passages of culture growth (n = 3). d Analysis of Vybrant^® DiD retention in MDA-MB-231 cultures in the presence and absence of mitomycin C (MMC) over six consecutive passages of culture growth (n = 3). e Fluorescent and phase-contrast image overlay of MCF-7 and MDA-MB-231 cultures at passage five post-staining (scale bar = 100 µm). White arrows indicate DiD+ cells (red). All graphical data are expressed as mean ± SEM