FLT1 and melanoma: A comparative flow cytometry analysis of stem cell markers with the GFP content revealed that the GFPhigh melanosphere cell subset was enriched in cells expressing well established melanoma stem cell markers, including ABCB5 [19], CD271 (p75NTR), [20] and VEGFR1 [21]; a marker of neural crest stem cells, HNK1 (CD57) [22]; and Notch1, which is a common marker for many stem cell types [23] (Figure 2C).