Figure 2

Melanospheres contain a small subpopulation of quiescent/slow-cycling GFP^highlabel-retaining cells (LRCs) with a melanoma stem cell phenotype. A. Representative melanospheres (left panel, scale bar = 50 μm) formed by HBL-H2BGFP cells dividing at different rates, as reflected by differences in the GFP fluorescence intensity between dissociated melanosphere cells (right panel, scale bar = 20 μm). B. GFP^high melanosphere HBL cells cycle slower and incorporate less EdU than their GFP^low counterparts. C. These GFP^high cells overexpress stem cell surface markers. Histogram illustrating the ratio of expression of each marker in GFP^high cells to their own GFP^low controls, which were set at “1” and marked by the red interrupted line. D. Representative histograms of flow cytometry data for the surface ABCB5 marker in melanosphere HBL-H2BGFP cells. Upper histogram illustrates GFP (green) fluorescence distribution in total population. R1 is a region encompassing GFP negative (black lines) and GFP^low subset and R2 GFP^high subpopulation (shaded). Lower histograms show ABCB5 distribution between GFP^low and GFP^high (shaded) subpopulations. R3 is a boundary drawn around ABCB5^high cells within GFP^low subset and R4 within GFP^high subpopulation. Numbers indicate percentage of cells with a particular phenotype.